Simple virus-free mouse models of COVID-19 pathologies and oral therapeutic intervention

The paucity of preclinical models that recapitulate COVID-19 pathology without requiring SARS-COV-2 adaptation and humanized/transgenic mice limits research into new therapeutics against the frequently emerging variants-of-concern. We developed virus-free models by C57BL/6 mice receiving oropharyngeal instillations of a SARS-COV-2 ribo-oligonucleotide common in all variants or specific to Delta/Omicron variants, concurrently with low-dose bleomycin. Mice developed COVID-19-like lung pathologies including ground-glass opacities, interstitial fibrosis, congested alveoli, and became moribund. Lung tissues from these mice and bronchoalveolar lavage and lung tissues from patients with COVID-19 showed elevated levels of hyaluronic acid (HA), HA-family members, an inflammatory signature, and immune cell infiltration. 4-methylumbelliferone (4-MU), an oral drug for biliary-spasm treatment, inhibits HA-synthesis. At the human equivalent dose, 4-MU prevented/inhibited COVID-19-like pathologies and long-term morbidity; 4-MU and metabolites accumulated in mice lungs. Therefore, these versatile SARS-COV-2 ribo-oligonucleotide oropharyngeal models recapitulate COVID-19 pathology, with HA as its critical mediator and 4-MU as a potential therapeutic for COVID-19.

Development of a Transparent Transgenic Zebrafish Cellular Phenotype Tg(6xNF-kB:EGFP); Casper(roy-/-, nacre-/-) to Study NF-kB Activity

NF-κB signaling has broad effects on cell survival, tissue growth, and proliferation activities. It controls many genes that are involved in inflammation and thus is a key player in many inflammatory diseases. The elevation of NF-κB activators is associated with elevated mortality, especially in cancer and cardiovascular diseases. The zebrafish has emerged as an important model for whole-organism in vivo modeling in translational research. In vertebrates, in-vivo spatial resolution is limited due to normal opacification of skin and subdermal structure. For in vivo imaging, skin transparency by blocking the pigmentation via chemical inhibition is required and the maintenance of this transparency is vital. The Casper(roy^-/-, nacre^-/-) mutant of zebrafish maintains this transparency throughout its life and serves as an ideal combination of sensitivity and resolution for in vivo stem cell analyses and imaging. We developed an NF-kB:GFP/Casper transparent transgenic zebrafish cellular phenotype to study inflammatory processes in vivo. We outline the experimental setup to generate a transparent transgenic NF-kB/Casper strain of zebrafish through the cross-breeding of Casper and NF-kB transgenic adult fish and have generated F01 in the form of heterozygous progeny. The transgenic F01 progeny was further inbred to generate heterozygous progenies from F1 to F4 generations. Furthermore, it continued to successfully develop the homozygous strain Tg(6xNF-kB:EGFP); Casper(roy^-/-, nacre^-/-) in the F05 generation. This novel strain of F05 generation showed 100% homozygosity in the transgenic transparent progeny of Tg(6xNF-kB:EGFP); Casper(roy^-/-, nacre^-/-). The strain has been confirmed by generating the F06 generation of homozygous progeny and again verified and validated for its homogeneity in the F07 generation. The newly developed novel transparent transgenic strain of the NF-kB reporter line has been coined as "Tg(6xNF-kB:EGFP); Casper(roy^-/-, nacre^-/-)gmc1". We have established a newly generated phenotype of transparent transgenic zebrafish for time-lapse in vivo confocal microscopy to study the cellular phenotype and pathologies at the cellular level over time. This will allow for quantifying the changes in the NF-kB functional activities over time and allow the comparison of control and cardiac-oncology experimental therapeutics. We validated the newly developed Tg(6xNF-kB:EGFP); Casper(roy^-/-, nacre^-/-)gmc1 homozygous strain of zebrafish by studying the inflammatory response to bacterial lipopolysaccharide (LPS) exposure, tolerance, and the inhibitory role of a potential novel drug candidate against LPS-induced inflammation. The results establish the unique application of newly developed strains by identifying hit and lead drug candidates for experimental therapeutics.

Abstract 1678: Overcoming treatment resistance in advanced bladder cancers using a neo-adjuvant combination with a natural product analog

Urinary bladder cancer (BC) is a common cancer worldwide, with approximately 573,278 new cases and 212,536 deaths arising annually. Tumors detected beyond the transitional zone of the bladder (advanced BC) account for most deaths. In advanced BC, tumor heterogeneity and resistance to successive chemotherapy regimens are major contributors to morbidity and mortality. Toxicity associated with the combination of Gemcitabine and Cisplatin (G+C) treatment limits the efficacy of chemotherapy. We tested the potential antitumor activity of a novel combination therapy involving a semisynthetic derivative of the pentacyclic triterpene (PTA) Ursolic Acid (N-methyl piperazine conjugated Ursolate, UA4) and Gemcitabine (Gem) in two Gem resistant BC cell lines developed in the laboratory. UA4 was synthesized from the PTA Ursolic Acid and Gem was purchased from LC-Labs. We tested the response to Gem and UA4 on naïve (WT) and Gem Resistant (GemR) cells. We generated Gem resistant BC cell lines HTB-4 (T24) and HTB-9 (5637) by repeated selection in increased Gem doses in vitro. The surviving cells were tested for a stable resistant phenotype. We measured the sensitivity to Gem and UA4 alone, and in adjuvant and neo-adjuvant combinations by colorimetric, cell counting, or clonogenic assays. The antitumor efficacy of UA4 and Gem were tested in vivo by xenograft studies on Fox N1-/- athymic mice (both sexes). The expression of markers associated with drug resistance was determined by qPCR, immunoblotting, and immunofluorescence studies. The 50% growth inhibition (IC50) dose in Gem treated cells increased significantly in 5637 and T24 GemR cells - 10-fold higher in GemR (100nM) than in WT cells (10 nM). Both WT and GemR cells showed equal sensitivity to UA4 (~5 µM). GemR cells showed elevated mRNA expression of a pyrimidine salvaging enzyme, cytidine deaminase (CDA), which degrades intracellular Gem, MRP2, and ENT1, all related to limiting intracellular drug availability. Tetrahydrouridine (THU), a competitive inhibitor of CDA, reduced the resistance significantly, indicating CDA as the principal mediator of resistance in GemR cells. Oral administration of UA4 was highly effective in reducing tumor growth of 5637 WT and GemR xenografts, whereas Gem (25mg/kg, 2x per week, i.p.) did not significantly reduce growth of GemR xenografts. Gem antitumor activity on 5637 WT tumors was predominantly due to apoptosis. Increased expression of autophagy markers, but not markers of apoptosis, was evident in vitro and in vivo treatments with UA4. Overall, treatment with UA4 was equally effective in decreasing viability in both WT and GemR advanced BC cells in vitro and reducing their tumor growth in vivo. Unlike Gem, UA4 did not induce significant levels of apoptosis but mainly autophagy-induced cell death. Ongoing studies indicate potential to use UA4 as an adjuvant or neo-adjuvant therapy in the treatment of advanced BC.

Citation Format: Juliette R. Seremak, Sunilkanth Bonigala, Kunj B. Gupta, Siva S. Panda, Bal L. Lokeshwar. Overcoming treatment resistance in advanced bladder cancers using a neo-adjuvant combination with a natural product analog [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1678.

Molecular Oncology of Bladder Cancer from Inception to Modern Perspective

Within the last forty years, seminal contributions have been made in the areas of bladder cancer (BC) biology, driver genes, molecular profiling, biomarkers, and therapeutic targets for improving personalized patient care. This overview includes seminal discoveries and advances in the molecular oncology of BC. Starting with the concept of divergent molecular pathways for the development of low- and high-grade bladder tumors, field cancerization versus clonality of bladder tumors, cancer driver genes/mutations, genetic polymorphisms, and bacillus Calmette-Guérin (BCG) as an early form of immunotherapy are some of the conceptual contributions towards improving patient care. Although beginning with a promise of predicting prognosis and individualizing treatments, "-omic" approaches and molecular subtypes have revealed the importance of BC stem cells, lineage plasticity, and intra-tumor heterogeneity as the next frontiers for realizing individualized patient care. Along with urine as the optimal non-invasive liquid biopsy, BC is at the forefront of the biomarker field. If the goal is to reduce the number of cystoscopies but not to replace them for monitoring recurrence and asymptomatic microscopic hematuria, a BC marker may reach clinical acceptance. As advances in the molecular oncology of BC continue, the next twenty-five years should significantly advance personalized care for BC patients.

Design, Synthesis, and Molecular Docking Studies of Curcumin Hybrid Conjugates as Potential Therapeutics for Breast Cancer

Curcumin (CUR) has received great attention over the past two decades due to its anticancer, anti-inflammatory, and antioxidant properties. Similarly, Dichloroacetate (DCA), an pyruvate dehydrogenase kinase 1 (PKD1) inhibitor, has gained huge attention as a potential anticancer drug. However, the clinical utility of these two agents is very limited because of the poor bioavailability and unsolicited side effects, respectively. We have synthesized fusion conjugates of CUR and DCA with an amino acids linker to overcome these limitations by utilizing the molecular hybridization approach. The molecular docking studies showed the potential targets of Curcumin-Modified Conjugates (CMCs) in breast cancer cells. We synthesized six hybrid conjugates named CMC1-6. These six CMC conjugates do not show any significant toxicity in a human normal immortalized mammary epithelial cell line (MCF10A) in vitro and C57BL/6 mice in vivo. However, treatment with CMC1 and CMC2 significantly reduced the growth and clonogenic survival by colony-formation assays in several human breast cancer cells (BC). Treatment by oral gavage of a transgenic mouse BC and metastatic BC tumor-bearing mice with CMC2 significantly reduced tumor growth and metastasis. Overall, our study provides strong evidence that CUR and DCA conjugates have a significant anticancer properties at a sub-micromolar concentration and overcome the clinical limitation of using CUR and DCA as potential anticancer drugs.

RAD51AP1 Loss Attenuates Colorectal Cancer Stem Cell Renewal and Sensitizes to Chemotherapy

DNA damage, induced by either chemical carcinogens or environmental pollutants, plays an important role in the initiation of colorectal cancer. DNA repair processes, however, are involved in both protecting against cancer formation, and also contributing to cancer development, by ensuring genomic integrity and promoting the efficient DNA repair in tumor cells, respectively. Although DNA repair pathways have been well exploited in the treatment of breast and ovarian cancers, the role of DNA repair processes and their therapeutic efficacy in colorectal cancer is yet to be appreciably explored. To understand the role of DNA repair, especially homologous recombination (HR), in chemical carcinogen-induced colorectal cancer growth, we unraveled the role of RAD51AP1 (RAD51-associated protein 1), a protein involved in HR, in genotoxic carcinogen (azoxymethane, AOM)-induced colorectal cancer. Although AOM treatment alone significantly increased RAD51AP1 expression, the combination of AOM and dextran sulfate sodium (DSS) treatment dramatically increased by several folds. RAD51AP1 expression is found in mouse colonic crypt and proliferating cells. RAD51AP1 expression is significantly increased in majority of human colorectal cancer tissues, including BRAF/KRAS mutant colorectal cancer, and associated with reduced treatment response and poor prognosis. Rad51ap1-deficient mice were protected against AOM/DSS-induced colorectal cancer. These observations were recapitulated in a genetically engineered mouse model of colorectal cancer (Apc^{Min /+} ). Furthermore, chemotherapy-resistant colorectal cancer is associated with increased RAD51AP1 expression. This phenomenon is associated with reduced cell proliferation and colorectal cancer stem cell (CRCSC) self-renewal. Overall, our studies provide evidence that RAD51AP1 could be a novel diagnostic marker for colorectal cancer and a potential therapeutic target for colorectal cancer prevention and treatment. IMPLICATIONS: This study provides first in vivo evidence that RAD51AP1 plays a critical role in colorectal cancer growth and drug resistance by regulating CRCSC self-renewal.

ARRB1 Regulates Metabolic Reprogramming to Promote Glycolysis in Stem Cell-Like Bladder Cancer Cells

Simple Summary

Bladder cancer (BC) ranks second in incidence and mortality among all genitourinary cancers. The high recurrence of BC is attributed to the presence of cancer stem cells (CSCs), which are the driving force behind tumor growth. Increasing evidence suggests that stem cells exhibit a distinct metabolic program compared to differentiated cells. Understanding their metabolic preference for maintaining stem cell properties is essential for developing novel therapeutics targeting CSCs. The current work shows for the first time that the scaffold protein β-arrestin1 (ARRB1) functions as a metabolic switch regulating the metabolic reprogramming of CSC-like cells towards glycolysis by regulating the mitochondrial pyruvate carrier MPC1 and glucose transporter GLUT1. The balance between glycolysis and oxidative phosphorylation plays a crucial role in regulating the fate of stem cells. Our findings will potentially open new therapeutic avenues for targeting bladder cancer cells and/or the CSC-like cells within aggressive bladder tumors.

Abstract

β-arrestin 1 (ARRB1) is a scaffold protein that regulates signaling downstream of G protein-coupled receptors (GPCRs). In the current work, we investigated the role of ARRB1 in regulating the metabolic preference of cancer stem cell (CSC)-like cells in bladder cancer (BC). We show that ARRB1 is crucial for spheroid formation and tumorigenic potential. Furthermore, we measured mitochondrial respiration, glucose uptake, glycolytic rate, mitochondrial/glycolytic ATP production and fuel oxidation in previously established ARRB1 knock out (KO) cells and corresponding controls. Our results demonstrate that depletion of ARRB1 decreased glycolytic rate and induced metabolic reprogramming towards oxidative phosphorylation. Mechanistically, the depletion of ARRB1 dramatically increased the mitochondrial pyruvate carrier MPC1 protein levels and reduced the glucose transporter GLUT1 protein levels along with glucose uptake. Overexpression of ARRB1 in ARRB1 KO cells reversed the phenotype and resulted in the upregulation of glycolysis. In conclusion, we show that ARRB1 regulates the metabolic preference of BC CSC-like cells and functions as a molecular switch that promotes reprogramming towards glycolysis by negatively regulating MPC1 and positively regulating GLUT1/ glucose uptake. These observations open new therapeutic avenues for targeting the metabolic preferences of cancer stem cell (CSC)-like BC cells.

Targeting Mitochondrial Metabolism in Prostate Cancer with Triterpenoids

Metabolic reprogramming is a hallmark of malignancy. It implements profound metabolic changes to sustain cancer cell survival and proliferation. Although the Warburg effect is a common feature of metabolic reprogramming, recent studies have revealed that tumor cells also depend on mitochondrial metabolism. Due to the essential role of mitochondria in metabolism and cell survival, targeting mitochondria in cancer cells is an attractive therapeutic strategy. However, the metabolic flexibility of cancer cells may enable the upregulation of compensatory pathways, such as glycolysis, to support cancer cell survival when mitochondrial metabolism is inhibited. Thus, compounds capable of targeting both mitochondrial metabolism and glycolysis may help overcome such resistance mechanisms. Normal prostate epithelial cells have a distinct metabolism as they use glucose to sustain physiological citrate secretion. During the transformation process, prostate cancer cells consume citrate to mainly power oxidative phosphorylation and fuel lipogenesis. A growing number of studies have assessed the impact of triterpenoids on prostate cancer metabolism, underlining their ability to hit different metabolic targets. In this review, we critically assess the metabolic transformations occurring in prostate cancer cells. We will then address the opportunities and challenges in using triterpenoids as modulators of prostate cancer cell metabolism.

G protein βγ translocation to the Golgi apparatus activates MAPK via p110γ-p101 heterodimers

The Golgi apparatus (GA) is a cellular organelle that plays a critical role in the processing of proteins for secretion. Activation of G protein-coupled receptors at the plasma membrane (PM) induces the translocation of G protein βγ dimers to the GA. However, the functional significance of this translocation is largely unknown. Here, we study PM-GA translocation of all 12 Gγ subunits in response to chemokine receptor CXCR4 activation and demonstrate that Gγ9 is a unique Golgi-translocating Gγ subunit. CRISPR-Cas9-mediated knockout of Gγ9 abolishes activation of extracellular signal-regulated kinase 1 and 2 (ERK1/2), two members of the mitogen-activated protein kinase family, by CXCR4. We show that chemically induced recruitment to the GA of Gβγ dimers containing different Gγ subunits activates ERK1/2, whereas recruitment to the PM is ineffective. We also demonstrate that pharmacological inhibition of phosphoinositide 3-kinase γ (PI3Kγ) and depletion of its subunits p110γ and p101 abrogate ERK1/2 activation by CXCR4 and Gβγ recruitment to the GA. Knockout of either Gγ9 or PI3Kγ significantly suppresses prostate cancer PC3 cell migration, invasion, and metastasis. Collectively, our data demonstrate a novel function for Gβγ translocation to the GA, via activating PI3Kγ heterodimers p110γ-p101, to spatiotemporally regulate mitogen-activated protein kinase activation by G protein-coupled receptors and ultimately control tumor progression.

The Role of β-Arrestins in Regulating Stem Cell Phenotypes in Normal and Tumorigenic Cells

β-Arrestins (ARRBs) are ubiquitously expressed scaffold proteins that mediate inactivation of G-protein-coupled receptor signaling, and in certain circumstances, G-protein independent pathways. Intriguingly, the two known ARRBs, β-arrestin1 (ARRB1) and β-Arrestin2 (ARRB2), seem to have opposing functions in regulating signaling cascades in several models in health and disease. Recent evidence suggests that ARRBs are implicated in regulating stem cell maintenance; however, their role, although crucial, is complex, and there is no universal model for ARRB-mediated regulation of stem cell characteristics. For the first time, this review compiles information on the function of ARRBs in stem cell biology and will discuss the role of ARRBs in regulating cell signaling pathways implicated in stem cell maintenance in normal and malignant stem cell populations. Although promising targets for cancer therapy, the ubiquitous nature of ARRBs and the plethora of functions in normal cell biology brings challenges for treatment selectivity. However, recent studies show promising evidence for specifically targeting ARRBs in myeloproliferative neoplasms.

Promotion of epithelial hyperplasia by interleukin-8-CXCR axis in human prostate

BACKGROUND

The clinical manifestation of benign prostatic hyperplasia (BPH) is causally linked to the inflammatory microenvironment and proliferation of epithelial and stromal cells in the prostate transitional zone. The CXC-chemokine interleukin-8 (IL-8) contributes to inflammation. We evaluated the expression of inflammatory cytokines in clinical specimens, primary cultures, and prostatic lineage cell lines. We investigated whether IL-8 via its receptor system (IL-8 axis) promotes BPH.

METHODS

The messenger RNA and protein expression of chemokines, including components of the IL-8 axis, were measured in normal prostate (NP; n = 7) and BPH (n = 21), urine (n = 24) specimens, primary cultures, prostatic lineage epithelial cell lines (NHPrE1, BHPrE1, BPH-1), and normal prostate cells (RWPE-1). The functional role of the IL-8 axis in prostate epithelial cell growth was evaluated by CRISPR/Cas9 gene editing. The effect of a combination with two natural compounds, oleanolic acid (OA) and ursolic acid (UA), was evaluated on the expression of the IL-8 axis and epithelial cell growth.

RESULTS

Among the 19 inflammatory chemokines and chemokine receptors we analyzed, levels of IL-8 and its receptors (CXCR1, CXCR2), as well as, of CXCR7, a receptor for CXCL12, were 5- to 25-fold elevated in BPH tissues when compared to NP tissues (P ≤ .001). Urinary IL-8 levels were threefold to sixfold elevated in BPH patients, but not in asymptomatic males and females with lower urinary tract symptoms (P ≤ .004). The expression of the IL-8 axis components was confined to the prostate luminal epithelial cells in both normal and BPH tissues. However, these components were elevated in BPH-1 and primary explant cultures as compared to RWPE-1, NHPrE1, and BHPrE1 cells. Knockout of CXCR7 reduced IL-8, and CXCR1 expression by 4- to 10-fold and caused greater than or equal to 50% growth inhibition in BPH-1 cells. Low-dose OA + UA combination synergistically inhibited the growth of BPH-1 and BPH primary cultures. In the combination, the drug reduction indices for UA and OA were 16.4 and 7852, respectively, demonstrating that the combination was effective in inhibiting BPH-1 growth at significantly reduced doses of UA or OA alone.

CONCLUSION

The IL-8 axis is a promotor of BPH pathogenesis. Low-dose OA + UA combination inhibits BPH cell growth by inducing autophagy and reducing IL-8 axis expression in BPH-epithelial cells.

RAD51AP1 Deficiency Reduces Tumor Growth by Targeting Stem Cell Self-Renewal

RAD51-associated protein 1 (RAD51AP1) plays an integral role in homologous recombination by activating RAD51 recombinase. Homologous recombination is essential for preserving genome integrity and RAD51AP1 is critical for D-loop formation, a key step in homologous recombination. Although RAD51AP1 is involved in maintaining genomic stability, recent studies have shown that RAD51AP1 expression is significantly upregulated in human cancers. However, the functional role of RAD51AP1 in tumor growth and the underlying molecular mechanism(s) by which RAD51AP1 regulates tumorigenesis have not been fully understood. Here, we use Rad51ap1-knockout mice in genetically engineered mouse models of breast cancer to unravel the role of RAD51AP1 in tumor growth and metastasis. RAD51AP1 gene transcript was increased in both luminal estrogen receptor-positive breast cancer and basal triple-negative breast cancer, which is associated with poor prognosis. Conversely, knockdown of RAD51AP1 (RADP51AP1 KD) in breast cancer cell lines reduced tumor growth. Rad51ap1-deficient mice were protected from oncogene-driven spontaneous mouse mammary tumor growth and associated lung metastasis. In vivo, limiting dilution studies provided evidence that Rad51ap1 plays a critical role in breast cancer stem cell (BCSC) self-renewal. RAD51AP1 KD improved chemotherapy and radiotherapy response by inhibiting BCSC self-renewal and associated pluripotency. Overall, our study provides genetic and biochemical evidences that RAD51AP1 is critical for tumor growth and metastasis by increasing BCSC self-renewal and may serve as a novel target for chemotherapy- and radiotherapy-resistant breast cancer. SIGNIFICANCE: This study provides in vivo evidence that RAD51AP1 plays a critical role in breast cancer growth and metastasis by regulating breast cancer stem cell self-renewal.

A Novel Splice Variant of HYAL-4 Drives Malignant Transformation and Predicts Outcome in Patients with Bladder Cancer

PURPOSE

Poor prognosis of patients with muscle-invasive bladder cancer that often metastasizes drives the need for discovery of molecular determinants of bladder cancer progression. Chondroitin sulfate proteoglycans, including CD44, regulate cancer progression; however, the identity of a chondroitinase (Chase) that cleaves chondroitin sulfate from proteoglycans is unknown. HYAL-4 is an understudied gene suspected to encode a Chase, with no known biological function. We evaluated HYAL-4 expression and its role in bladder cancer.

EXPERIMENTAL DESIGN

In clinical specimens, HYAL-4 wild-type (Wt) and V1 expression was evaluated by RT-qPCR, IHC, and/or immunoblotting; a novel assay measured Chase activity. Wt and V1 were stably expressed or silenced in normal urothelial and three bladder cancer cell lines. Transfectants were analyzed for stem cell phenotype, invasive signature and tumorigenesis, and metastasis in four xenograft models, including orthotopic bladder.

RESULTS

HYAL-4 expression, specifically a novel splice variant (V1), was elevated in bladder tumors; Wt expression was barely detectable. V1 encoded a truncated 349 amino acid protein that was secreted. In bladder cancer tissues, V1 levels associated with metastasis and cancer-specific survival with high efficacy and encoded Chase activity. V1 cleaved chondroitin-6-sulfate from CD44, increasing CD44 secretion. V1 induced stem cell phenotype, motility/invasion, and an invasive signature. CD44 knockdown abrogated these phenotypes. V1-expressing urothelial cells developed angiogenic, muscle-invasive tumors. V1-expressing bladder cancer cells formed tumors at low density and formed metastatic bladder tumors when implanted orthotopically.

CONCLUSIONS

Our study discovered the first naturally-occurring eukaryotic/human Chase and connected it to disease pathology, specifically cancer. V1-Chase is a driver of malignant bladder cancer and potential predictor of outcome in patients with bladder cancer.

Atypical chemokine receptors in tumor cell growth and metastasis

Atypical chemokine receptors (ACKRs) are seven-transmembrane cell surface protein receptors expressed in immune cells, normal mesenchymal cells, and several tumor cells. As of this writing, six ACKRs have been characterized by diverse activities. They bind both cysteine-cysteine (CC) type and cysteine-X-cysteine (CXC)-type chemokines, either alone, or together with a ligand bound-functional G-protein coupled (typical) chemokine receptor. The major structural difference between ACKRs and typical chemokine receptors is the substituted DRYLAIV amino acid motif in the second intracellular loop of the ACKR. Due to this substitution, these receptors cannot bind Gαi-type G-proteins responsible for intracellular calcium mobilization and cellular chemotaxis. Although initially characterized as non-signaling transmembrane receptors (decoy receptors) that attenuate ligand-induced signaling by GPCRs, studies of all ACKRs have shown ligand-independent and ligand-dependent transmembrane signaling in both non-tumor and tumor cells. The precise function and mechanism of the differential expression of ACKRs in many tumors are not understood well. The use of antagonists of ACKRs ligands has shown limited antitumor potential; however, depleting ACKR expression resulted in a reduction in experimental tumor growth and metastasis. The ACKRs represent a unique class of transmembrane signaling proteins that regulate growth, survival, and metastatic processes in tumor cells, affecting multiple pathways of tumor growth. Therefore, closer investigations of ACKRs have a high potential for identifying therapeutics which affect the intracellular signaling, preferentially via the ligand-independent mechanism.

Abstract 123A: The critical role of interleukin-8 chemokine axis in the development of benign prostatic hyperplasia (BPH)

Benign prostatic hyperplasia (BPH), a non-malignant proliferative disease of the prostate, has a global incidence of over 210 million men aged 50 years or older. BPH is essentially a non-cancerous (non-malignant tumor) with significant morbidity. The severity varies from mild urinary retention to severe lower urinary tract symptoms (LUTS) accounting for greater than 50% of hospital visits for difficulty with urination, retention, and pain, and close to 40% of the prostate surgeries. BPH strongly associates with prostate volume that begins to increase in men aged 40 or higher. We investigated the role of chemokine and chemokine receptors in three immortalized cell lines and primary cultures derived from fresh BPH tissue following transurethral resection of the prostate. We analyzed the levels of chemokines and chemokine receptors secreted in the culture medium and in the mRNA from cells by qPCR, western blotting and Cytokine arrays. The epithelial identity of primary cultures was established by analyzing cytokeratin expression. Two natural products isolated from Allspice were identified that inhibit the growth of BPH cultures. A cell line identified as the BPH progenitor, a BPH intermediary cell line and a cell line with frank BPH features secreted a large excess of chemokine, predominantly CXCL-VIII or Interleukin-8 (IL-8). Unusually high amount of IL-8 was secreted by BPH progenitor cells and intermediate cells as compared to a stable normal prostate cell line (RWPE1) derived from the peripheral zone of the prostate, which did not secrete any IL-8 or express its receptor. The investigation found that expression of CXC receptors CXCR1, CXCR2 and an IL-8 inducible CXCR (CXCR7) was absent in progenitor cells and in intermediate cells, but was highly expressed in the cell line derived from BPH tissue and more significantly, in primary cultures of BPH tissue. Further, primary cultures and progenitor cells expressed high levels of immune stimulatory factors indicating PMN and monocyte infiltration leading to potential chronic inflammation of the transitional zone of the prostate. The natural products from Allspice inhibited all members of the IL-8 axis and proliferation, suggesting their potential preventative potential for BPH. These results demonstrate how a novel chemokine axis is likely to enhance pathogenesis of BPH and suggest several avenues to control the abnormal growth of prostate in aging male.

Note: This abstract was not presented at the meeting.

Citation Format: Diandra K. Smith, Natasha Venugopal, Martha K. Terris, Bal L. Lokeshwar. The critical role of interleukin-8 chemokine axis in the development of benign prostatic hyperplasia (BPH) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 123A.

Abstract 5069: Breast cancer prevention by triterpenoids from allspice

Breast cancer ranks second as a lethal cancer in women. Although survival following initial diagnosis is ~ 100% in first five years, cancer progression and mortality is imminent in subsequent years. The slow progression to the lethal form of breast cancer has prompted development of multiple avenues to delay the progression, metastasis and mortality using potent prevention strategies, including the use of nutraceuticals. Oleanolic acid (OA) and ursolic acid (UA) are two triterpenoids found in edible plant parts-fruits and seeds with potent cancer preventive, and selective cytotoxic activities against multiple cancers including breast cancer. We conducted cytotoxic assays of the combination of OA and UA. We found the combination has enhanced efficacy as compared to OA or UA alone. The combination of OA and UA and UA alone caused cell death by increased autophagy but not apoptosis in both MCF7 and MB231 human breast cancer cells. Further analysis revealed increased autopagosomes and autophagic flux, inhibition of either process reduced cytotoxicity, indicating cytotoxic autophagy is the primary mechanism of their action. Therefore, a combination of OA and UA with conventional therapies could enhance their therapeutic efficacy while limiting systemic toxicities of existing therapies.

Citation Format: Jie Gao, Kenza Mamouni, Georgios Kallifatidis, Siva Panda, Muthusamy Thangaraju, Bal L. Lokeshwar. Breast cancer prevention by triterpenoids from allspice [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 5069.

β-Arrestins Regulate Stem Cell-Like Phenotype and Response to Chemotherapy in Bladder Cancer

β-Arrestins are classic attenuators of G-protein-coupled receptor signaling. However, they have multiple roles in cellular physiology, including carcinogenesis. This work shows for the first time that β-arrestins have prognostic significance for predicting metastasis and response to chemotherapy in bladder cancer. β-Arrestin-1 (ARRB1) and β-arrestin-2 (ARRB2) mRNA levels were measured by quantitative RT-PCR in two clinical specimen cohorts (n = 63 and 43). The role of ARRBs in regulating a stem cell-like phenotype and response to chemotherapy treatments was investigated. The consequence of forced expression of ARRBs on tumor growth and response to Gemcitabine in vivo were investigated using bladder tumor xenografts in nude mice. ARRB1 levels were significantly elevated and ARRB2 levels downregulated in cancer tissues compared with normal tissues. In multivariate analysis only ARRB2 was an independent predictor of metastasis, disease-specific-mortality, and failure to Gemcitabine + Cisplatin (G+C) chemotherapy; ∼80% sensitivity and specificity to predict clinical outcome. ARRBs were found to regulate stem cell characteristics in bladder cancer cells. Depletion of ARRB2 resulted in increased cancer stem cell markers but ARRB2 overexpression reduced expression of stem cell markers (CD44, ALDH2, and BMI-1), and increased sensitivity toward Gemcitabine. Overexpression of ARRB2 resulted in reduced tumor growth and increased response to Gemcitabine in tumor xenografts. CRISPR-Cas9-mediated gene-knockout of ARRB1 resulted in the reversal of this aggressive phenotype. ARRBs regulate cancer stem cell-like properties in bladder cancer and are potential prognostic indicators for tumor progression and chemotherapy response.

The andean anticancer herbal product BIRM causes destabilization of androgen receptor and induces caspase-8 mediated-apoptosis in prostate cancer

BIRM is an anticancer herbal formulation from Ecuador. Previous study established its antitumor and antimetastatic activity against prostate cancer models. The activity of BIRM against human prostate cancer (PCa) cells was investigated to uncover its mechanism of antitumor activity. In androgen receptor (AR)-expressing PCa cells BIRM was 2.5-fold (250%) more cytotoxic in presence of androgen (DHT) compared to cells grown in the absence of DHT. In AR-positive cells (LAPC-4 and LNCaP) BIRM caused a dose and time-dependent down-regulation of AR and increased apoptosis. Exposing cells to BIRM did not affect the synthesis of AR and AR promoter activity but increased degradation of AR via proteasome-pathway. BIRM caused destabilization of HSP90-AR association in LAPC-4 cells. It induced apoptosis in PCa cells by activation of caspase-8 via death receptor and FADD-mediated pathways. A synthetic inhibitor of Caspase-8 cleavage (IETD-CHO) aborted BIRM-induced apoptosis. The effect of BIRM on AKT-mediated survival pathway in both AR+ and AR- negative (PC-3 and DU145) showed decreased levels of p-AKTser 473 in all PCa cell lines. BIRM dosed by oral gavage in mice bearing PC-3ML tumors showed selective efficacy on tumor growth; before tumors are established but limited efficacy when treated on existing tumors. Moreover, BIRM inhibited the LNCaP tumor generated by orthotropic implantation into dorsal prostate of nude mice. Partial purification of BIRM by liquid-liquid extraction and further fractionation by HPLC showed 4-fold increased specific activity on PCa cells. These results demonstrate a mechanistic basis of anti-tumor activity of the herbal extract BIRM.

Designing a broad-spectrum integrative approach for cancer prevention and treatment

Targeted therapies and the consequent adoption of "personalized" oncology have achieved notable successes in some cancers; however, significant problems remain with this approach. Many targeted therapies are highly toxic, costs are extremely high, and most patients experience relapse after a few disease-free months. Relapses arise from genetic heterogeneity in tumors, which harbor therapy-resistant immortalized cells that have adopted alternate and compensatory pathways (i.e., pathways that are not reliant upon the same mechanisms as those which have been targeted). To address these limitations, an international task force of 180 scientists was assembled to explore the concept of a low-toxicity "broad-spectrum" therapeutic approach that could simultaneously target many key pathways and mechanisms. Using cancer hallmark phenotypes and the tumor microenvironment to account for the various aspects of relevant cancer biology, interdisciplinary teams reviewed each hallmark area and nominated a wide range of high-priority targets (74 in total) that could be modified to improve patient outcomes. For these targets, corresponding low-toxicity therapeutic approaches were then suggested, many of which were phytochemicals. Proposed actions on each target and all of the approaches were further reviewed for known effects on other hallmark areas and the tumor microenvironment. Potential contrary or procarcinogenic effects were found for 3.9% of the relationships between targets and hallmarks, and mixed evidence of complementary and contrary relationships was found for 7.1%. Approximately 67% of the relationships revealed potentially complementary effects, and the remainder had no known relationship. Among the approaches, 1.1% had contrary, 2.8% had mixed and 62.1% had complementary relationships. These results suggest that a broad-spectrum approach should be feasible from a safety standpoint. This novel approach has potential to be relatively inexpensive, it should help us address stages and types of cancer that lack conventional treatment, and it may reduce relapse risks. A proposed agenda for future research is offered.

Bioactive natural products for chemoprevention and treatment of castration-resistant prostate cancer

Prostate cancer (PCa), a hormonally-driven cancer, ranks first in incidence and second in cancer related mortality in men in most Western industrialized countries. Androgen and androgen receptor (AR) are the dominant modulators of PCa growth. Over the last two decades multiple advancements in screening, treatment, surveillance and palliative care of PCa have significantly increased quality of life and survival following diagnosis. However, over 20% of patients initially diagnosed with PCa still develop an aggressive and treatment-refractory disease. Prevention or treatment for hormone-refractory PCa using bioactive compounds from marine sponges, mushrooms, and edible plants either as single agents or as adjuvants to existing therapy, has not been clinically successful. Major advancements have been made in the identification, testing and modification of the existing molecular structures of natural products. Additionally, conjugation of these compounds to novel matrices has enhanced their bio-availability; a big step towards bringing natural products to clinical trials. Natural products derived from edible plants (nutraceuticals), and common folk-medicines might offer advantages over synthetic compounds due to their broader range of targets, as compared to mostly single target synthetic anticancer compounds; e.g. kinase inhibitors. The use of synthetic inhibitors or antibodies that target a single aberrant molecule in cancer cells might be in part responsible for emergence of treatment refractory cancers. Nutraceuticals that target AR signaling (epigallocatechin gallate [EGCG], curcumin, and 5α-reductase inhibitors), AR synthesis (ericifolin, capsaicin and others) or AR degradation (betulinic acid, di-indolyl diamine, sulphoraphane, silibinin and others) are prime candidates for use as adjuvant or mono-therapies. Nutraceuticals target multiple pathophysiological mechanisms involved during cancer development and progression and thus have potential to simultaneously inhibit both prostate cancer growth and metastatic progression (e.g., inhibition of angiogenesis, epithelial-mesenchymal transition (EMT) and proliferation). Given their multi-targeting properties along with relatively lower systemic toxicity, these compounds offer significant therapeutic advantages for prevention and treatment of PCa. This review emphasizes the potential application of some of the well-researched natural compounds that target AR for prevention and therapy of PCa.

Combined Inhibition of DNMT and HDAC Blocks the Tumorigenicity of Cancer Stem-like Cells and Attenuates Mammary Tumor Growth

Recently, impressive technical advancements have been made in the isolation and validation of mammary stem cells and cancer stem cells (CSC), but the signaling pathways that regulate stem cell self-renewal are largely unknown. Furthermore, CSCs are believed to contribute to chemo- and radioresistance. In this study, we used the MMTV-Neu-Tg mouse mammary tumor model to identify potential new strategies for eliminating CSCs. We found that both luminal progenitor and basal stem cells are susceptible to genetic and epigenetic modifications, which facilitate oncogenic transformation and tumorigenic potential. A combination of the DNMT inhibitor 5-azacytidine and the HDAC inhibitor butyrate markedly reduced CSC abundance and increased the overall survival in this mouse model. RNA-seq analysis of CSCs treated with 5-azacytidine plus butyrate provided evidence that inhibition of chromatin modifiers blocks growth-promoting signaling molecules such as RAD51AP1 and SPC25, which play key roles in DNA damage repair and kinetochore assembly. Moreover, RAD51AP1 and SPC25 were significantly overexpressed in human breast tumor tissues and were associated with reduced overall patient survival. In conclusion, our studies suggest that breast CSCs are intrinsically sensitive to genetic and epigenetic modifications and can therefore be significantly affected by epigenetic-based therapies, warranting further investigation of combined DNMT and HDAC inhibition in refractory or drug-resistant breast cancer. Cancer Res; 76(11); 3224-35. ©2016 AACR.

β-Arrestin-2 Counters CXCR7-Mediated EGFR Transactivation and Proliferation

The atypical 7-transmembrane chemokine receptor, CXCR7, transactivates the EGFR leading to increased tumor growth in several tumor types. However, the molecular mechanism of CXCR7 ligand-independent EGFR transactivation is unknown. We used cDNA knock-in, RNAi and analysis of mitogenic signaling components in both normal prostate epithelial cells and prostate cancer cells to decipher the proliferation-inducing mechanism of the CXCR7-EGFR interaction. The data demonstrate that CXCR7-induced EGFR transactivation is independent of both the release of cryptic EGFR ligands (e.g., AREG/amphiregulin) and G-protein-coupled receptor signaling. An alternate signaling mechanism involving β-arrestin-2 (ARRB2/β-AR2) was examined by manipulating the levels of β-AR2 and analyzing changes in LNCaP cell growth and phosphorylation of EGFR, ERK1/2, Src, and Akt. Depletion of β-AR2 in LNCaP cells increased proliferation/colony formation and significantly increased activation of Src, phosphorylation of EGFR at Tyr-1110, and phosphorylation/activation of ERK1/2 compared with that with control shRNA. Moreover, β-AR2 depletion downregulated the proliferation suppressor p21. Stimulation of β-AR2-expressing cells with EGF resulted in rapid nuclear translocation of phosphorylated/activated EGFR. Downregulation of β-AR2 enhanced this nuclear translocation. These results demonstrate that β-AR2 is a negative regulator of CXCR7/Src/EGFR-mediated mitogenic signaling.

IMPLICATIONS

This study reveals that β-AR2 functions as a tumor suppressor, underscoring its clinical importance in regulating CXCR7/EGFR-mediated tumor cell proliferation. Mol Cancer Res; 14(5); 493-503. ©2016 AACR.

A multi-targeted approach to suppress tumor-promoting inflammation

Cancers harbor significant genetic heterogeneity and patterns of relapse following many therapies are due to evolved resistance to treatment. While efforts have been made to combine targeted therapies, significant levels of toxicity have stymied efforts to effectively treat cancer with multi-drug combinations using currently approved therapeutics. We discuss the relationship between tumor-promoting inflammation and cancer as part of a larger effort to develop a broad-spectrum therapeutic approach aimed at a wide range of targets to address this heterogeneity. Specifically, macrophage migration inhibitory factor, cyclooxygenase-2, transcription factor nuclear factor-κB, tumor necrosis factor alpha, inducible nitric oxide synthase, protein kinase B, and CXC chemokines are reviewed as important antiinflammatory targets while curcumin, resveratrol, epigallocatechin gallate, genistein, lycopene, and anthocyanins are reviewed as low-cost, low toxicity means by which these targets might all be reached simultaneously. Future translational work will need to assess the resulting synergies of rationally designed antiinflammatory mixtures (employing low-toxicity constituents), and then combine this with similar approaches targeting the most important pathways across the range of cancer hallmark phenotypes.

Abstract 4993: β-arrestin-2 regulates CXCR7-mediated EGFR transactivation and tumor cell proliferation in prostate cancer cells

We have previously shown that the chemokine receptor CXCR7 trans-activates the epidermal growth factor receptor (EGFR) and is implicated in prostate tumor growth. However, the molecular mechanisms of CXCR7 mediated EGFR-trans-activation are not known. In the present work we show that CXCR7 induced EGFR transactivation is independent of EGF-like ligands such as amphiregulin and heparin-bound EGF. Importantly, treatment with pertussis toxin, a known G-protein inhibitor, had no effect on EGFR phosphorylation, indicating that G-protein signaling was not involved in CXCR7 mediated EGFR transactivation. Since CXCR7 is known to signal through β-arrestin-2 in its ligand dependent manner, we evaluated the role of β-arrestin-2 in CXCR7 induced EGFR trans-activation in prostate cancer cells. We used shRNA to stably down regulate β-arrestin-2 in LNCaP cells to evaluate the role of β-arrestin-2 in CXCR7 mediated induction of EGFR and downstream mitogenic signaling such as ERK1/2 and the phosphoinositide 3-kinase/Akt pathway. Interestingly, down regulation of β-arrestin-2 significantly induced phosphorylation of EGFR at Y1110 and Y1068 along with the phosphorylation/activation of ERK and AKT and an induction of proliferation/colony formation in prostate tumor cells. Moreover, shRNA mediated down regulation of β-arrestin-2 resulted in a decrease of p21 which is in accordance with the observed increased proliferation rate. The results of our study suggest that β-arrestin-2 is crucial negative regulator of CXCR7/EGFR signaling and underscore the importance of β-arrestin-2 in regulation of CXCR7/EGFR mediated tumor cell proliferation.

Citation Format: Georgios Kallifatidis, Daniel Munoz, Rajendra K. Singh, Bal L. Lokeshwar. β-arrestin-2 regulates CXCR7-mediated EGFR transactivation and tumor cell proliferation in prostate cancer cells. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4993. doi:10.1158/1538-7445.AM2015-4993

Polyphenol-rich extract of Pimenta dioica berries (Allspice) kills breast cancer cells by autophagy and delays growth of triple negative breast cancer in athymic mice

Bioactive compounds from edible plants have limited efficacy in treating advanced cancers, but they have potential to increase the efficacy of chemotherapy drugs in a combined treatment. An aqueous extract of berries of Pimenta dioica (Allspice) shows promise as one such candidate for combination therapy or chemoprevention. An aqueous extract of Allspice (AAE) was tested against human breast cancer (BrCa) cells in vitro and in vivo. AAE reduced the viability and clonogenic growth of several types of BrCa cells (IC50 ≤ 100 μg/ml) with limited toxicity in non-tumorigenic, quiescent cells (IC50 >200 μg/ml). AAE induced cytotoxicity in BrCa was inconsistent with apoptosis, but was associated with increased levels of autophagy markers LC3B and LC3B-positive puncta. Silencing the expression of autophagy related genes (ATGs) prevented AAE-induced cell death. Further, AAE caused inhibition of Akt/mTOR signaling, and showed enhanced cytotoxicity when combined with rapamycin, a chemotherapy drug and an inhibitor of mTOR signaling. Oral administration (gavage) of AAE into athymic mice implanted with MDA-MB231 tumors inhibited tumor growth slightly but not significantly (mean decrease ~ 14%, p ≥ 0.20) if mice were gavaged post-tumor implant. Tumor growth showed a significant delay (38%) in tumor palpability and growth rate (time to reach tumor volume ≥ 1,000 mm3) when mice were pre-dosed with AAE for two weeks. Analysis of tumor tissues showed increased levels of LC3B in AAE treated tumors, indicating elevated autophagic tumor cell death in vivo in treated mice. These results demonstrate antitumor and chemo-preventive activity of AAE against BrCa and potential for adjuvant to mTOR inhibition.

Abstract 3336: The heterotypic interaction between CXCR7 and EGFR is an alternative proliferation mechanism in breast cancer

Introduction: CXCR7 is selectively over expressed in Breast Cancer (BrCa), suggesting its potential importance in BrCa development and function. CXCR7 is the latest CXC-chemokine receptor implicated in BrCa growth. Although it is endogenously over expressed in BrCa, the CXCR7 mechanism of tumor growth enhancement is still vaguely described. BrCa is a heterogeneous disease in several ways. An investigation of the interaction of CXCR7 with EGFR will help determine the relative contribution and consequence of such interaction in BrCa cell proliferation and progression.

Results: CXCR7 is expressed predominantly in Estrogen Receptor positive (ER+) BrCa cells, MCF7 and BT474, and was absent in common ER- BrCa cells. CXCR7 was expressed unevenly in normal breast and ER+ cancer tissues. Depletion of CXCR7 in BrCa cells by RNAi decreased cell proliferation and caused cell cycle arrest, with significant changes in cell cycle-associated proteins. Addition, depletion, and rescue of CXCR7-ligand, SDF-1a, had no significant effect on cell proliferation or phosphorylation of ERK1/2. Depletion of CXCR7 led to inhibition of EGF-mediated phosphorylation of EGFR at Tyrosine 1110 and ERK1/2 phosphorylation. We examined whether CXCR7 regulates BrCa proliferation through interaction with EGFR or by activating other potential targets of MAP-kinase activation and found that CXCR7 complexes with EGFR, as demonstrated by co-immunoprecipitation followed by immunoblotting and with proximity ligation assays, using the Duo-link fluorescence technique. Investigation of whether CXCR7-EGFR interaction is direct or indirect, led to test potential translocation of fluorescent β-Arrestin-2 from the plasma membrane to the cytoplasm. SDF-1a addition to MCF7 cells, over expressing β-Arrestin-2-EGFP, induced minimal movement of β-Arrestin-2-EGFP over a 30 min window, whereas EGF addition induced re-arrangement of β-Arrestin-2-EGFP localization. When CXCR7 was down-regulated by siRNA, the beta-ARR2-EGFP rearrangement was significantly reduced, suggesting this CXCR7-EGFR interaction is facilitated by β-Arrestin-2.

Conclusion: Our results demonstrate a heterotypic interaction between CXCR7 and EGFR in breast cancer independent of SDF-1a. Recent studies remind us that seventy percent of breast cancers are ER+ even at the metastatic stage, making the expression of CXCR7 clinically relevant. The innate heterogeneity of BrCa makes it clear that proliferation mechanisms change and may be altered during cancer progression, so that CXCR7 and other receptors may step in to support proliferation. These results demonstrate the important role of CXCR7 in breast cancer growth and progression.

Citation Format: Nicole Salazar, Daniel Muñoz, Rajendra K. Singh, Bal L. Lokeshwar. The heterotypic interaction between CXCR7 and EGFR is an alternative proliferation mechanism in breast cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3336. doi:10.1158/1538-7445.AM2014-3336

The chemokine receptor CXCR7 interacts with EGFR to promote breast cancer cell proliferation

Background

Recent advances have revealed a significant contribution of chemokines and their receptors in tumor growth, survival after chemotherapy, and organ-specific metastasis. The CXC chemokine receptor-7 (CXCR7) is the latest chemokine receptor implicated in cancer. Although over expressed in breast cancer cell lines and tumor tissues, its mechanism of action in breast cancer (BrCa) growth and metastasis is unclear. Studies in other cancers have implicated CXCR7 in cell proliferation, anti-apoptotic activity and cell-cell adhesion. The present study was initiated to examine the pattern of CXCR7 expression and its role in regulation of growth signaling in breast cancer.

Methods

The contribution of CXCR7 in BrCa cell proliferation was investigated in representative cell lines using real time quantitative PCR (q-PCR), proliferation assays, immunohistochemistry and immunoblotting. Phenotypic changes were examined after CXCR7 specific cDNA and siRNA transfection and expression levels were monitored by q-PCR. Further, the association of CXCR7 with epidermal growth factor receptor (EGFR) and modulation of its activity were investigated by western blotting, immunofluorescence, and in-situ proximity ligation assays in human BrCa cells and tissues.

Results

CXCR7 was expressed in both, estrogen receptor (ER) positive and negative BrCa cell lines. CXCR7 was also expressed unevenly in normal breast tissues and to a much higher extent in ER + cancer tissues. Depletion of CXCR7 in MCF7 BrCa cells by RNA interference decreased proliferation and caused cell cycle arrest. Further, proximity ligation assay (PLA) revealed colocalization of CXCR7 with EGFR in cancer tissues and cancer cell lines. CXCR7 depletion reduced levels of phospho-EGFR at Tyrosine1110 after EGF-stimulation and also reduced phosphorylation of ERK1/2, indicating a potentially direct impact on mitogenic signaling in MCF7 cells. Using siRNA to knockdown β-arrestin2 in cells with EGFR over expression we were able to nearly deplete the CXCR7-EGFR colocalization events, suggesting that β-arrestin2 acts as a scaffold to enhance CXCR7 dependent activation of EGFR after EGF stimulation.

Conclusions

These results demonstrate coupling of CXCR7 with EGFR to regulate proliferation of BrCa cells and suggest an important ligand-independent role of CXCR7 in BrCa growth. Thus, the CXCR7-EGFR axis is a promising target for breast cancer therapy.

Electronic supplementary material

The online version of this article (doi:10.1186/1476-4598-13-198) contains supplementary material, which is available to authorized users.

Abstract C210: Atypical chemokine receptor 3/CXCR7 and EGFR interact to control breast cancer growth

Introduction: Breast cancer (BrCa) is a major burden for women in the US, ranking second in both incidence and cancer related deaths. Many studies comparing cancer vs. normal gene expression have identified CXCR7 as being preferentially expressed in several different cancer types, including breast cancer. CXCR7 is the latest CXC-chemokine receptor implicated in breast cancer growth. The chemokine receptor CXCR7 is an atypical G-protein coupled receptor, in that it does not bind G-proteins as GPCRs do. It is so atypical, that convention by HUGO has recently changed the name of CXCR7 to ACKR3, atypical chemokine receptor 3.

Methods: We used the database Oncomine to confirm the correlation of CXCR7 with breast cancer at both mRNA and tissue level. We also show functional expression of CXCR7 on relevant human breast cancer cell lines and tissue. To identify the mechanism of function of CXCR7 in BrCa we studied its interaction with EGFR and beta-arrestin2 (beta-ARR2), which are relevant partners important in the mitogenic growth cascade. We used a proximity ligation assay (PLA) to visualize CXCR7-EGFR co-localization both in cell culture and in human normal and breast cancer tissue. To visualize interaction with beta-ARR2, we used live cell confocal microscopy.

Results: CXCR7 was over-expressed in ER-α positive BrCa cells, compared to normal breast epithelial cells. ER-negative cells also expressed CXCR7, however, at lower levels. Depletion of CXCR7 in MCF-7 BrCa cells by RNAi decreased cell proliferation and caused cell cycle arrest. Since CXCR7 is an atypical G-protein coupled receptor where ligand activation does not elicit conventional intracellular signaling, we hypothesized that CXCR7 regulates BrCa proliferation through interaction with EGFR or activation of other potential targets of the MAP-kinase pathway. CXCR7 depletion reduced site-specific phosphorylation of EGFR at Tyrosine 1110 after EGF-stimulation. CXCR7 depletion also reduced phosphorylation of ERK-1/2, indicating a potentially direct interaction with mitogenic signaling in MCF-7 cells. We found EGFR and CXCR7 co-localize as demonstrated by confocal microscopy, with increased co-localization after EGF stimulation. To clarify whether CXCR7-EGFR interaction is direct or indirect, we analyzed the role beta-ARR2 plays in this transactivation. SDF1 addition to MCF7 cells over expressing beta-ARR2-EGFP induced minimal movement of beta-ARR2-EGFP over a 30 min window. EGF addition induced an obvious shift of beta-ARR2-EGFP localization. When CXCR7 was down-regulated by siRNA, there was decreased rearrangement of beta-ARR2-EGFP after EGF stimulation, suggesting this CXCR7-EGFR interaction is beta-ARR2 mediated.

Conclusion: These data demonstrate significant molecular interactions between two cell surface receptors that have high clinical significance. The impact of this work may potentially lead to better treatment strategies based on cell surface targets.

Citation Information: Mol Cancer Ther 2013;12(11 Suppl):C210.

Citation Format: Nicole Salazar, Daniel Muñoz, Bal L. Lokeshwar. Atypical chemokine receptor 3/CXCR7 and EGFR interact to control breast cancer growth. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr C210.

Medicinal properties of the Jamaican pepper plant Pimenta dioica and Allspice

The Caribbean tropical tree, Pimenta dioica has been used for a variety of human endeavors, such as in perfumery industry, food spice, as a natural pesticide, and in folk medicine. Discovered in Jamaica during the voyages of Christopher Columbus, the dried unripe berries of P. dioica also known as Allspice can be found in all continents with unique names in over 50 languages. Systematic investigation of aromatic constituents of Pimenta leaves and its unripe berries, Allspice, have resulted in discovery of many and novel aromatic compounds, mostly glycosides and polyphenols that show antibacterial, hypotensive, anti-neuralgic and analgesic properties. Recent studies have shown two of the known compounds isolated from Allspice, Eugenol and Gallic acid have selective antiproliferative and anti-tumor properties on human cancer cells and their animal models. New characterization of novel compounds such as Ericifolin from the aqueous extract of Allspice berries show potent anti-prostate cancer and anti-breast cancer properties that can be verified in vitro as well as in vivo. Considering its purity, mostly available as "organically grown" berries, availability at low cost, wide acceptance in culinary delights of many cultures world-wide, Allspice may have an additional space in most households, in their medicine cabinets.

Chemokines and chemokine receptors as promoters of prostate cancer growth and progression

Prostate cancer (CaP) is estimated to be first in incidence among cancers, with more than 240,000 new cases in 2012 in the United States. Chemokines and their receptors provide survival, proliferation, and invasion characteristics to CaP cells in both primary sites of cancer and metastatic locations. The emerging data demonstrate that many chemokines and their receptors are involved in the multistep process of CaP, leading to metastasis, and, further, that these factors act cooperatively to enhance other mechanisms of tumor cell survival, growth, and metastasis. Changes of chemokine receptor cohorts may be necessary to activate tumor-promoting signals. Chemokine receptors can activate downstream effectors, such as mitogen-activated protein kinases, by complex mechanisms of ligand-dependent activation of cryptic growth factors; guanosine triphosphate-binding, protein-coupled activation of survival kinases; or transactivation of other receptors such as ErbB family members. We describe vanguard research in which more than the classic view of chemokine receptor biology was clarified. Control of chemokines and inhibition of their receptor activation may add critical tools to reduce tumor growth, especially in chemo-hormonal refractory CaP that is both currently incurable and the most aggressive form of the disease, accounting for most of the more than 28,000 annual deaths.

Ericifolin: a novel antitumor compound from allspice that silences androgen receptor in prostate cancer

Silencing of androgen receptor (AR) signaling is a specific and effective mechanism to cure cancer of the prostate (CaP). In this study, the isolation and characterization of a compound from the aromatic berries of Pimenta dioica (allspice) that silences AR is presented. Potential antitumor activities of an aqueous allspice extract (AAE) and a compound purified from the extract were tested on CaP cells. AAE inhibited tumor cell proliferation and colony formation (50% growth inhibition ∼40-85 µg/ml) but not the viability of quiescent normal fibroblasts or non-tumorigenic prostate cells. In tumor cells, AAE inhibited cell cycle progression at G1/S, induced apoptosis or autophagy. Apoptosis was by caspase-dependent poly (ADP ribose) polymerase cleavage. A caspase-independent, apoptosis-inducing factor-mediated mechanism of apoptosis caused cell death in castration-resistant AR-positive or AR-negative CaP cells, such as CWR22RV1, PC-3 or DU145 cells. Treatment with AAE decreased the levels of AR messenger RNA (mRNA), protein and silenced AR activity in AR-positive cells. AR depletion was due to inhibition of AR promoter activity and mRNA stability. Delayed tumor growth (~55%) without measurable systemic toxicity was observed in LNCaP tumor-bearing mice treated with AAE by oral or intraperitoneal routes. LNCaP tumor tissues from AAE-treated mice revealed increased apoptosis as a potential mechanism of antitumor activity of AAE. The chemical identity of bioactive compound in AAE was established through multistep high-performance liquid chromatography fractionation, mass and Nuclear Magnetic Resonance spectroscopies. The compound, eugenol 5-O-β-(6'-galloylglucopyranoside) or ericifolin (EF), showed antiproliferative, pro-apoptosis and anti-AR transcription activities. These results demonstrate a potential use of AAE and EF against prostate cancer.

Effect of Wnt-1 induced signaling protein-2 (Wisp-2/CCN5) on angiogenesis and invasion in prostate cancer

164

Background: The Wnt-Induced Signaling Protein-2 (Wisp-2/CCN5) is a secreted protein implicated in modification of extracellular matrix, invasion, and angiogenesis. The regulation of Wisp-2 and its function in CaP is poorly explored although it is highly expressed in advanced CaP cells. We discovered recently that a pro-inflammatory chemokine, Interleukin-8 (IL-8) strongly modulates Wisp2 expression in CaP cells. Since chronic inflammation is thought to be significant in CaP metastasis and IL-8 is a major effecter of inflammatory pathway, we investigated the physiological consequence of Wisp-2 modulation in CaP cells. Methods: Quantitative PCR was used to determine the expression of Wisp-2 mRNA and other mRNA in prostate epithelial and cancer cells. Wisp-2 mediated-VEGF secretion was determined by ELISA and endothelial tube formation assay using human vascular endothelial cells. Invasive activity and their attributes were determined using gelatin-zymography for matrix metalloproteinases (MMPs), Matrigel invasion assay and chemotaxis assay. Results: Wisp2 RNA was strongly expressed in two highly metastatic CaP cell lines, DU145 and PC-3 and moderately in less invasive LAPC4 and LNCaP cells. Constitutive autocrine expression or external addition of IL-8 increased Wisp-2 mRNA by ≥15.2 times in LNCaP, and 7.4 times in LAPC4 cells. Depleting Wisp-2 by RNA interference caused 82% reduction of Wisp2 in DU145, and 75% in PC-3. Depletion of Wisp2 did not affect cell proliferation in DU145 and PC3 but it reduced expression of VEGF mRNA by 64% in DU145 and 43% in PC3. Secreted VEGF protein in cultures of DU145 and PC-3 cells showed a decrease of 62% in DU145 and 30% in PC3. Condition medium of Wisp-2 depleted DU145 cell cultures showed 20% decrease in proliferation and vessel formation activity in HUVEC cells. Further, Wisp-2 depletion in DU145 cells resulted in significant decrease in chemoinvasion activity (28%) and secretion of MMP-9 (25%). Conclusions: These results show that Wisp2 is down stream effector of IL-8 and is an important modulator, affecting extracellular matrix to stimulate angiogenesis and invasiveness in CaP cells. Suppression of Wisp-2 in CaP may reduce their metastatic potential.

Abstract P5-07-01: Defining the mechanism of breast cancer growth by chemokine receptor CXCR7 and Epidermal Growth Factor Receptor coupling interaction

Introduction: Breast cancer (BrCa) ranks second in both incidence and cancer deaths for women in the USA. Recent advances have revealed a significant contribution of chemokines and their receptors in tumor growth, survival after chemotherapy, and organ-specific metastasis. CXCR7 is the latest CXC-chemokine receptor implicated in BrCa growth. It is endogenously over expressed in BrCa, but its mechanism of tumor growth enhancement is still not clearly defined. CXCR7 heterodimerizes with CXCR4 and binds to SDF-1 (CXCL12) and CXCL11. No direct ligand mediated physiological action has been implicated for CXCR7 in BrCa other than facilitating CXCR4-mediated cell motility, however, studies in other cancers have implicated CXCR7 in cell proliferation, anti-apoptotic activity and cell-cell adhesion. The expression pattern of CXCR7 in BrCa tissues and its potential contribution in BrCa cell proliferation and survival were investigated in representative BrCa cell lines using knock down and knock-in experiments.

Results: CXCR7 was only expressed in ER-α positive BrCa cells (e.g., MCF-7) and was not found in BrCa cells with known metastatic potential (MDA-MB231 and SKBr3). Depletion of CXCR7 in MCF-7 BrCa cells by both siRNA and shRNA decreased cell proliferation and caused cell cycle arrest. Since CXCR7 is an atypical G-protein coupled receptor where ligand activation does not elicit conventional intracellular signaling, we hypothesized that CXCR7 regulates BrCa proliferation through interaction with EGFR or activating other potential targets of MAP-kinase activation. CXCR7 depletion reduced site-specific phosphorylation of EGFR at Tyrosine 1110 after EGF-stimulation. CXCR7 depletion also reduced phosphorylation of ERK-1/2, indicating a potentially direct interaction with mitogenic signaling in MCF-7 cells. We tested for direct interaction of CXCR7 with EGFR by co-immunoprecipitation and immunofluorescence studies. We found EGFR and CXCR7 co-immunoprecipitate and co-localize as demonstrated by confocal microscopy. Interestingly, our results also demonstrate CXCR7 and EGFR are co-localized before EGF stimulation. Further corroboration of CXCR7-EGFR interaction was established using the proximity ligation assay (PLA) technique that allowed us to visualize CXCR7-EGFR co-localization both in cell culture and in human normal and breast cancer tissue.

Conclusion: This data demonstrates an important role for CXCR7 in BrCa growth and explores the mechanism of action of direct coupling of EGFR with CXCR7.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P5-07-01.

Achyranthes aspera (Apamarg) leaf extract inhibits human pancreatic tumor growth in athymic mice by apoptosis

ETHNOPHARMACOLOGICAL RELEVANCE

Achyranthes aspera (Family Amaranthacea) is used for cancer therapy by ayurvedic medical practitioners in India. However, due to the non formal nature of its use, there are no systematic studies validating its medicinal properties. Thus, it's utility as an anti cancer agent remains anecdotal. Earlier, we demonstrated A. aspera to exhibit time and dose-dependent preferential cytotoxicity to cultured human pancreatic cancer cells. In this report we validate in vivo anti tumor properties of A. aspera.

MATERIALS AND METHODS

The in vivo anti tumor activity of leaf extract (LE) was tested by intraperitoneal (IP) injections into athymic mice harboring human pancreatic tumor subcutaneous xenograft. Toxicity was monitored by recording changes in behavioral, histological, hematological and body weight parameters.

RESULTS

Dosing LE to athymic mice by I.P. injection for 32 days showed no adverse reactions in treated mice. Compared to the control set, IP administration of LE to tumor bearing mice significantly reduced both tumor weight and volume. Gene expression analysis using Real time PCR methods revealed that LE significantly induced caspase-3 mRNA (p<0.001) and suppressed expression of the pro survival kinase Akt-1 (p<0.05). TUNEL assay and immunohistochemistry confirmed apoptosis induction by activation of caspase-3 and inhibiting Akt phosphorylation in treated sets. These results are in agreement with RT PCR data.

CONCLUSION

Taken together, these data suggest A. aspera to have potent anti cancer property.

Abstract 576: Novel compounds from Allspice (Pimenta dioica) inhibit breast cancer growth by autophagy induction

Background: Breast Cancer (BrCa) ranks second as cause of cancer death in women, causing 40,000 deaths in 2010. Recent studies have shown that novel plant-derived compounds used as dietary chemopreventive agents prolong survival and reduce breast cancer deaths. Lack of mechanism of action and limited bioavailability are the leading concerns for adopting natural dietary compounds as chemopreventive or adjuvant therapeutic agents against breast and other cancers. We identified several likely anti-cancer compounds from water extract of Allspice, the unripe berries of Pimenta dioica (Jamaican pepper). The compounds limit the growth of breast cancer cells by novel mechanism and may synergize with main-stream cancer therapeutics. Methods: An aqueous extract of Certified-organic Allspice (AAE) was prepared and a solution of suitable strength was tested on several BrCa cell lines (MCF-7, T47D, MDA-MB231, SKBr3) for potential inhibition of proliferation, autophagy and estrogen-receptor inactivation using commonly used analytical techniques. Potential effect on estrogen receptor levels and transcriptional activities were determined using quantitative-real time PCR, promoter luciferase assay and immunoblotting. Results: AAE reduced the viability and clonogenic growth of BrCa cells (IC50α100μg/ml) with limited activity (50% less toxicity in quiescent cells). AAE induced cell-death was only associated with several characteristics of autophagy, including increase in acidic vesicular organelle content, levels of GFP-LC3-positive puncta, and LC3-II protein level. Knockdown of ATG-7 gene expression by siRNA partially prevented AAE-induced cell death by 40%. Autophagy was induced by Endoplasmic reticulum (ER) stress but not changes in ATP levels. Further, AAE caused inhibition of mTOR signaling pathway and enhanced cytotoxicity combined with mTOR inhibitor, rapamycin. Furthermore, AAE reduced Estrogen Receptor-α protein as well mRNA levels in ERα positive-BrCa cell lines MCF-7 and T47D. The decrease in ERα protein level was only partially rescued by proteasome inhibitor MG132, indicating AAE accelerates ERα protein degradation. Activity based purification combined with chemical identification strategies resulted in identification of one compound Ericifolin, and several compounds in a highly enriched fraction exhibiting same properties as that of AAE. Conclusion: We showed the anti-cancer effects of aqueous extract of Allspice on BrCa cells, which includes anti-proliferation by inducting autophagy after AAE treatment and ERα downregulation which has promising clinical application for BrCa treatment. [Grant Support: R01 CA156776-01and Sylvester Cancer Center (BLL)].

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 576. doi:1538-7445.AM2012-576

Abstract 5589: An aqueous extract of Allspice (berries of Pimenta dioica) inhibits breast cancer growth through autophagy by targeting the estrogen receptor

Background: Breast cancer (BrCa) ranks second as cause of cancer deaths in women. However, &gt;90% of BrCa patients survive &gt;5 years after diagnosis, thus providing an chance to prevent clinical progression and metastasis. Several chemopreventive agents are currently under investigation, however, no single agent is highly effective. Dietary agents offer an advantage for long-term, well tolerated and personalized treatment for chemoprevention. With this goal, we investigated anticancer effects of an aqueous extract of a common spice, the unripe berries of Pimenta dioica (Allspice).

Methods: An aqueous exact of Allspice was prepared, lyophilized and a solution of suitable strength was tested on several BrCa cell lines (MCF-7, MDA-MB231, SKBr3) for potential inhibition of clonogenic growth, autophagy and estrogen-receptor inactivation using commonly used analytical techniques. Potential effect on estrogen receptor (ERα) levels and transcriptional activities were determined using quantitative-real time PCR and western blotting.

Results: AAE reduced the viability and clonogenic growth of BrCa cells (IC50≈ 100μg/ml). Importantly, AAE was selectively effective against proliferating cells but not quiescent cells. In addition to cytotoxicity, AAE reduced ERα in an estrogen-dependent BrCa cell line, MCF-7. ERα protein levels were significantly decreased in AAE treated MCF7 cells (IC50≈ 100μg/ml). The decrease in ERα protein level by AAE was not rescued by MG132, a proteasome inhibitor, treatment indicating, it is likely due to AAE effect on ERα synthesis and not turnover. We did not detect AAE induced apoptosis in MCF-7 cells as confirmed by several assays. However AAE induced the expressions of autophagy-related proteins, microtubule-associated protein 1 light chain 3 (LC3).

Conclusion: We demonstrate anti-proliferative and anti-ERα activity of the aqueous extract of Allspice, a highly aromatic and delectable culinary additive world over. The cytotoxicity of this anticancer agent encompassed multiple pathways, including autophagy and ERα down modulation. These results, if found corroborative using studies in vivo models, should provide a strong rationale to test as an anti-cancer agent in breast cancer. [Grant Support: 1R01AT003544 (BLL)]

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5589. doi:10.1158/1538-7445.AM2011-5589

Abstract 5159: Wnt signaling protein (Wisp2/CCN5) stimulates angiogenesis and invasion in prostate cancer

Introduction: Angiogenesis and invasion are essential attributes of metastatic cancer cells. The Wnt-Induced Signaling Protein-2 (Wisp-2 /CCN5) is a secreted protein implicated in modification of extracellular matrix, invasion, and angiogenesis. The regulation of Wisp-2 and its function in CaP is poorly explored although it is highly expressed in advanced CaP cells. We discovered recently that a pro-inflammatory chemokine, Interleukin-8 (IL-8) strongly modulates Wisp2 expression in CaP cells. Since chronic inflammation is thought to be significant in CaP metastasis and IL-8 is a major effecter of inflammatory pathway, we investigated the physiological consequence of Wisp-2 modulation in CaP cells.

Hypothesis; Wisp-2 is a down-stream effector of IL-8 induced angiogenesis and invasion, and is essential for metastatic progression of prostate cancer.

Methods: Quantitative PCR (qPCR) was used to determine the expression of Wisp-2 mRNA and other mRNA in prostate epithelial and cancer cells (e.g. RWPE-1, LNCaP, LAPC-4, DU145, and PC3). Wisp-2 mediated-VEGF secretion was determined by ELISA and endothelial tube formation assay using human vascular endothelial cells (HUVEC cells). Invasive activity and their attributes were determined using gelatin-zymography for matrix metalloproteinases (MMPs), Matrigel invasion assay and chemotaxis assay.

Results: Wisp2 RNA was strongly expressed in two highly metastatic CaP cell lines, DU145 and PC-3 and moderately in less invasive LAPC4 and LNCaP cells. Constitutive autocrine expression or external addition of IL-8 increased Wisp-2 mRNA by ≥15.2 times in LNCaP, and 7.4 times in LAPC4 cells. Depleting Wisp-2 by RNA interference caused 82% reduction of Wisp2 in DU145, and 75% in PC-3. Depletion of Wisp2 did not affect cell proliferation in DU145 and PC3 but it reduced expression of VEGF mRNA by 64% in DU145 and 43% in PC3. Secreted VEGF protein in cultures of DU145 and PC-3 cells showed a decrease of 62% in DU145 and 30% in PC3. Condition medium of Wisp-2 depleted DU145 cell cultures showed 20% decrease in proliferation and vessel formation activity in HUVEC cells. Further, Wisp-2 depletion in DU145 cells resulted in significant decrease in chemo-invasion activity (28%) and secretion of MMP-9 (25%).

Conclusions: These results show that Wisp2 is down stream effector of IL-8 and is an important modulator, affecting extracellular matrix to stimulate angiogenesis and invasiveness in CaP cells. Suppression of Wisp-2 in CaP may reduce their metastatic potential.

(Grant Support; VA MERIT Review, VA5312.01 (BLL))

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5159. doi:10.1158/1538-7445.AM2011-5159

Abstract 1128: Interleukin-8 increases CXCR7 by non-cononical activation of NF-kb pathway in prostate cancer

Background & Objectives: IL-8 is a pro-inflammatory chemokine that promotes tumor growth, motility, invasion and angiogenesis in many cancers via activation of two receptors, CXCR1 and CXCR2. CXCR7 is a receptor for CXCL11 and CXCL12 and it interacts with CXCR4 all of which are highly elevated and are implicated in metastatic progression of prostate and other cancers. We showed recently that although CXCR7 does not invoke the classical G-protein coupled receptor activation pathway, it promotes tumor growth, angiogenesis, survival and invasion, in a ligand-independent pathway. Further, we reported that IL-8 up-regulates CXCR7 expression via an unknown mechanism. We hypothesized that IL-8 induces CXCR7 expression by activating NF-kB pathway as the CXCR7 promoter has several NF-KB binding sites. Further, many pro-inflammatory chemokines are the part of NF-kB pathway and known to exert their biological effects through the activation of one or more chemokine receptors.

Methods: All studies were conducted on prostate epithelial (RWPE-1) or tumor cell lines (LNCaP & PC-3). Quantitation of mRNA and protein expressions was performed by Q-PCR, western blotting and flow cytometry. Lipofectamine protocol was used for siRNA & plasmid DNA transfections. Transcription activity was quantitated by Luciferase-reporter activity using Dual-Glo™ Luciferase assay. Matrigel-coated invasion chambers were used to measure basement-membrane invasion activity.

Results & Conclusions: Addition of exogenous IL-8 or constitutive production by IL-8 cDNA transfection in RWPE-1 or LNCaP cultures increased CXCR7 mRNA expression by 4-20-folds respectively. Exogenous IL-8 addition increased CXCR7 mRNA within 15 min, maximizing at 4 h. IL-8 induced CXCR7 expression was significantly abolished by either CXCR1 or CXCR2 non-peptide antagonists, repertaxin & SB 225002, suggesting the requirement for both IL-8 receptors to increase CXCR7 transcription. Furthermore, IL-8 induced CXCR7 expression was inhibited when cells were treated with parthenolide (NF-κB inhibitor) or transfected with NF-kb super-suppressor, prior to IL-8 treatment, indicating effective blocking of NF-kB activation antagonized IL-8 induced CXCR7 mRNA and protein up-regulation. IL-8 induces NF-κB transcription and p65 activation in a time-dependent manner in prostate cells as detected by promoter luciferase activity & western blotting. IL-8 induces IκBα phosphorylation followed by degradation and p65 translocation in non tumorigenic, RWPE-1 cells. Moreover, PC-3 cells transfected with CXCR7 cDNA increased their invasive potential measured by invasion through the matrigel coated invasion chambers. Our data indicate that IL-8 induced CXCR7 expression responsible for prostate cancer invasion and mediates its effect in NF-κB dependent pathway [Grant Support; NIH R01AT003544, VA MERIT Review, VA5312.01 (BLL)].

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1128. doi:10.1158/1538-7445.AM2011-1128

Abstract 5572: An aqueous extract of allspice (Pimenta dioica) suppresses androgen receptor expression and prostate cancer growth

Background and objective: The aromatic berries of the Jamaican plant Pimenta dioica called Allspice are used in many cuisines for their delectable flavor and as folk remedies for variety of ailments. Despite a rich source of antioxidants the use of Allspice as cancer preventive or anticancer agent has not been reported. Potential anti-cancer activity of an Aqueous Allspice extract (AAE) was tested on prostate cancer (CaP) cells and on tumor models.

Methods: AAE was prepared from dried, unripe berries of P. dioica (Certified Organic, Oregon Spices, OR) in water and the extract was lyophilized before testing for biological activity. We tested AAE on growth, survival; response to androgen on human androgen sensitive (AR+) CaP cells (LNCaP, LAPC-4) and in LNCaP xenograft tumors in athymic-nude mice. We used colorimetric MTT-cell survival assay, colony-forming assays, bioluminescence reporter assays, Q-PCR and western blotting to delineate the molecular mechanism of tumor suppressive action of AAE.

Results: AAE inhibited tumor cell proliferation (IC50∼100ug/ml) and clonogenic growth (IC50∼40ug/ml) of AR+ CaP cells. AAE was selectively toxic to tumor cells and less toxic to non-tumorigenic cells. AAE blocked cell cycle progression from G1 to S by decreasing cyclin D1, phosphorylated Rb, CDK4 and increased P21 and P27 in AR+ CaP cells. AAE induced apoptosis in LNCaP cells was mediated by intrinsic apoptotic pathway via depolarization of mitochondria, activation of caspase 9, caspase 3/7, cleaved PARP levels, increase in pro-apoptotic protein Bax, decrease in anti-apoptotic protein BID and release of cytochrome C from mitochondria. Importantly, AAE treated AR+ CaP cells showed significant decrease in AR protein level (IC50 50µg/ml) and the proteosome inhibitor MG132 did not rescue the AR protein level decrease by AAE. Transcriptional analysis of androgen receptor (AR) in AR+ CaP cells showed rapid decrease in AR and PSA expression by AAE. Moreover, treatment of LNCaP tumor bearing mice with AAE (100mg/kg, IP, 2x/w) significantly delayed the tumor growth (58%), prolonged the survival period with no systemic toxicity. Ex vivo analyses of LNCaP tumor tissue showed increased apoptosis (70%) in AAE treated mice compared to tissue from vehicle control, with 44% decrease in IGF-1 levels in serum of treated animals. A chemical analysis showed that the major component present on AAE was polyphenol (37% w/v) and devoid of alkaloids and other bioactive compounds.

Conclusion: We identified an anticancer product from a New World plant commonly used in cuisines world-over. This extract suppressed the androgen receptor activity in AR+ CaP cells. These studies demonstrate potential use of AAE as a chemotherapeutic or chemopreventive agent against prostate cancer (Funds: NIH1R01 AT 003544 and VA MERIT Grant # 5312.01)

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5572. doi:10.1158/1538-7445.AM2011-5572

The IL-8-regulated chemokine receptor CXCR7 stimulates EGFR signaling to promote prostate cancer growth

The proinflammatory chemokine receptor CXCR7 that binds the ligands CXCL11 and CXCL12 (SDF-1a) is elevated in a variety of human cancers, but its functions are not understood as it does not elicit classical chemokine receptor signaling. Here we report that the procancerous cytokine IL-8 (interleukin-8) upregulates CXCR7 expression along with ligand-independent functions of CXCR7 that promote the growth and proliferation of human prostate cancer cells (CaP cells). In cell culture, ectopic expression or addition of IL-8 selectively increased expression of CXCR7 at the level of mRNA and protein production. Conversely, suppressing IL-8 signaling abolished the ability of IL-8 to upregulate CXCR7. RNAi-mediated knockdown of CXCR7 in CaP cells caused multiple antitumor effects, including decreased cell proliferation, cell-cycle arrest in G(1) phase, and decreased expression of proteins involved in G(1) to S phase progression. In contrast, addition of the CXCR7 ligand SDF-1a and CXCL11 to CaP cells did not affect cell proliferation. Over expression of CXCR7 in normal prostate cells increased their proliferation in a manner associated with increased levels of phospho-EGFR (epidermal growth factor receptor; pY1110) and phospho-ERK1/2. Notably, coimmunoprecipitation studies established a physical association of CXCR7 with EGFR, linking CXCR7-mediated cell proliferation to EGFR activation. Consistent with these findings, CXCR7-depleted CaP tumors grew more slowly than control tumors, expressing decreased tumor-associated expression of VEGF, cyclin D1, and p-EGFR. Together, these results reveal a novel mechanism of ligand-independent growth promotion by CXCR7 and its coregulation by the proinflammatory factor IL-8 in prostate cancer.

Chemically modified non-antimicrobial tetracyclines are multifunctional drugs against advanced cancers

Metastatic cancers account for more than 90% of cancer mortality. The metastasis of all cancers is critically mediated by enzymes that degrade extracellular matrix. Aggressive tumors are characterized by an imbalance between enzymes that degrade ECM and endogenous inhibitors of the enzymes. Matrix metalloproteinases (MMPs) make up the majority of ECM degrading enzymes implicated in cancer metastasis. The potent MMP inhibitory activities of tetracyclines, especially their chemically modified analogs, combined with their relatively well tolerated pharmacological profile, led several researchers to investigate their anticancer potential in a variety of cancers, including melanoma, lung, breast and prostate cancers. Chemically modified non-antibiotic tetracyclines (CMTs or COL) were tested using tumors of prostate, breast and melanomas. Some of these CMTs, notably, CMT-3 and CMT-308 significantly inhibited not only invasive potential and MMP activity, but also inhibited cell proliferation by inducing cell cycle arrest and apoptosis. CMT-3 and CMT-308 were significantly more potent than doxycycline or minocycline in inhibiting tumor cell-derived MMPs and inducing apoptosis in vitro and in vivo. CMT-3 (COL-3) showed potent inhibition of tumor growth in xenografts and in bone metastatic models of prostate cancer. Similar results were also reported in melanoma and breast cancer models. The mechanism by which CMTs kill tumor cells is via generation of hydroxyl free radicals ([OH](-)) which permeate and depolarize mitochondria, which in turn activates caspase mediated apoptosis. Analysis of tumor tissues from CMT-3 treated rats demonstrated reduction in angiogenesis and increase in apoptosis; both emerged as mechanisms of CMT action. These observations led to testing the efficacy of CMT-3 in human clinical trials against several types of cancer with significant outcomes, which are described in the next chapter of this issue.

Role of Chemokines and Chemokine Receptors in Prostate Cancer Development and Progression

Prostate cancer (PC) is the second leading cause of cancer deaths in men in America and Western Europe. Epidemiological studies suggest that prostate cancer incidences increased in last few years in Asian. The causes or consequences of increasing trend of prostate cancer incidence are not completely known. Emerging evidences suggest that among the many risk factors, inflammation is the major risk factor for developing prostate cancer and its progression to metastasis. It is proposed that exposure to environmental factors such as infectious agents, dietary agents and saturated lipids leads to injury of the prostate due to chronic inflammation and regenerative risk factor lesions referred to as proliferative inflammatory atrophy (PIA). These phenomena predominantly control by a number of proinflammatory macro molecules such as chemokines, and their receptors. Some recent studies suggest that many of these pro-inflammatory chemokines and their receptors are the products of protooncogenes in many cancers including that of the prostate. This review will focus on the current biology of chemokines and chemokine receptors in prostate cancer. An understanding of this axis may enable researchers to develop targeted strategies for prostate cancer.

CXC receptor-1 silencing inhibits androgen-independent prostate cancer

The CXC receptor-1 (CXCR1) is a coreceptor for interleukin-8 (IL-8) and is expressed on both normal and tumor cells. The function of CXCR1 in prostate cancer was investigated by silencing its expression, using RNA interference. We established stable cell colonies of PC-3 cells, depleted of CXCR1, using lentiviral plasmids (pLK0.1puro) generating small hairpin RNA (shRNA) against CXCR1 mRNA. Stable shRNA transfectants (PLK1-PLK5) that express significantly reduced CXCR1 mRNA (>or=90% down) and protein (>or=43% down) or vector-only transfectants (PC-3V) were characterized. PLK cells showed reduced cell proliferation (down, >or=66%), due to cell cycle arrest at G(1)-S phase, decreases in Cyclin D1, CDK4, phosphorylated Rb, and extracellular signal-regulated kinase 1/2 levels compared with those in PC-3V cells. CXCR1 depletion lead to increases in spontaneous apoptosis by mitochondria-mediated intrinsic mechanism and increases in proapoptotic proteins (BAD, 40%; BAX, 12%), but decreases in antiapoptotic proteins (BCL2, down 38%; BCL(xL), 20%). PLK2 cells grew as slow-growing tumors (decrease of 54%), compared with that of PC3V tumors in athymic mice. Ex vivo analyses of PLK2 tumor tissues showed reduced expression of Cyclin D1 and vascular endothelial growth factor, and increased apoptosis activity. Other IL-8-expressing prostate cancer cell lines also exhibited similar phenotypes when CXCR1 was depleted by CXCR1 shRNA transfection. In contrast to these cells, CXCR1 depletion had little effect on IL-8 ligand-deficient LNCaP cells. RNA interference rescue using mutated CXCR1 plasmids reversed the silencing effect of PLK2, thus demonstrating the specificity of phenotypic alteration by CXCR1 shRNA. These studies establish that CXCR1 promotes IL-8-mediated tumor growth.

Depletion of intrinsic expression of Interleukin-8 in prostate cancer cells causes cell cycle arrest, spontaneous apoptosis and increases the efficacy of chemotherapeutic drugs

Background

The progression of all cancers is characterized by increased-cell proliferation and decreased-apoptosis. The androgen-independent prostate cancer (AIPC) is the terminal stage of the disease. Many chemokines and cytokines are suspects to cause this increased tumor cell survival that ultimately leads to resistance to therapy and demise of the host. The AIPC cells, but not androgen-responsive cells, constitutively express abundant amount of the pro-inflammatory chemokine, Interleukin-8 (IL-8). The mechanism of IL-8 mediated survival and therapeutic resistance in AIPC cells is unclear at present. The purpose of this report is to show the pervasive role of IL-8 in malignant progression of androgen-independent prostate cancer (AIPC) and to provide a potential new therapeutic avenue, using RNA interference.

Results

The functional consequence of IL-8 depletion in AIPC cells was investigated by RNA interference in two IL-8 secreting AIPC cell lines, PC-3 and DU145. The non-IL-8 secreting LNCaP and LAPC-4 cells served as controls. Cells were transfected with RISC-free siRNA (control) or validated-pool of IL-8 siRNA. Transfection with 50 nM IL-8 siRNA caused >95% depletion of IL-8 mRNA and >92% decrease in IL-8 protein. This reduction in IL-8 led to cell cycle arrest at G₁/S boundary and decreases in cell cycle-regulated proteins: Cyclin D1 and Cyclin B1 (both decreased >50%) and inhibition of ERK1/2 activity by >50%. Further, the spontaneous apoptosis was increased by >43% in IL-8 depleted cells, evidenced by increases in caspase-9 activation and cleaved-PARP. IL-8 depletion caused significant decreases in anti-apoptotic proteins, BCL-2, BCL-xL due to decrease in both mRNA and post-translational stability, and increased levels of pro-apoptotic BAX and BAD proteins. More significantly, depletion of intracellular IL-8 increased the cytotoxic activity of multiple chemotherapeutic drugs. Specifically, the cytotoxicity of Docetaxel, Staurosporine and Rapamycin increased significantly (>40% at IC₅₀ dose) in IL-8 depleted cells as compared to that in C-siRNA transfected cells.

Conclusion

These results show the pervasive role of IL-8 in promoting tumor cell survival, and resistance to cytotoxic drugs, regardless of the cytotoxic mechanism of antiproliferative drugs, and point to potential therapeutic significance of IL-8 depletion in men with AIPC.

Epigenetic regulation of HYAL-1 hyaluronidase expression. identification of HYAL-1 promoter

HYAL-1 (hyaluronoglucosaminidase-1) belongs to the hyaluronidase family of enzymes that degrade hyaluronic acid. HYAL-1 is a marker for cancer diagnosis and a molecular determinant of tumor growth, invasion, and angiogenesis. The regulation of HYAL-1 expression is unknown. Real time reverse transcription-PCR using 11 bladder and prostate cancer cells and 69 bladder tissues showed that HYAL-1 mRNA levels are elevated 10-30-fold in cells/tissues that express high hyaluronidase activity. Although multiple transcription start sites (TSS) for HYAL-1 mRNA were detected in various tissues, the major TSS in many tissues, including bladder and prostate, was at nucleotide 27274 in the cosmid clone LUCA13 (AC002455). By analyzing the 1532 base sequence 5' to this TSS, using cloning and luciferase reporter assays, we identified a TACAAA sequence at position -31 and the minimal promoter region between nucleotides -93 and -38. Mutational analysis identified that nucleotides -73 to -50 (which include overlapping binding consensus sites for SP1, Egr-1, and AP-2), bases C(-71) and C(-59), and an NFkappaB-binding site (at position -15) are necessary for promoter activity. The chromatin immunoprecipitation assay identified that Egr-1, AP-2, and NFkappaB bind to the promoter in HYAL-1-expressing cells, whereas SP1 binds to the promoter in non-HYAL-1-expressing cells. 5-Aza-2'-deoxycytidine treatment, bisulfite DNA sequencing, and methylation-specific PCR revealed that HYAL-1 expression is regulated by methylation at C(-71) and C(-59); both Cs are part of the SP1/Egr-1-binding sites. Thus, HYAL-1 expression is epigenetically regulated by the binding of different transcription factors to the methylated and unmethylated HYAL-1 promoter.

Osteopontin and interleukin-8 expression is independently associated with prostate cancer recurrence

PURPOSE

Lack of reliable biomarkers limits accurate prediction of prostate-specific antigen biochemical recurrence (disease progression) in prostate cancer. The two inflammatory chemokines, osteopontin and interleukin-8 (IL-8), are associated with tumor angiogenesis and metastasis. We investigated whether osteopontin and IL-8 expression in prostate cancer correlates with disease progression.

EXPERIMENTAL DESIGN

Archival prostatectomy specimens (n = 103) were obtained from patients with minimum 72-month follow-up. Osteopontin and IL-8 expression was evaluated by immunohistochemistry and graded for intensity and the area. Association of osteopontin and IL-8 staining with biochemical recurrence was evaluated by univariate and multivariate models.

RESULTS

In tumor cells, osteopontin and IL-8 staining was higher in the recurred group (203.2 +/- 78.4; 181.1 +/- 89.3) than in the nonrecurred group (122.7 +/- 76.6; 96.4 +/- 85.6; P < 0.001). Higher osteopontin and IL-8 staining was also observed in benign areas adjacent to tumor in the recurred group, than in nonrecurred group. In univariate analysis, except age, all preoperative and postoperative variables and osteopontin and IL-8 staining scores were significantly associated with biochemical recurrence (P < 0.05). In multivariate analysis, margin status and osteopontin staining independently associated with biochemical recurrence within 72 months. Osteopontin, either alone or with IL-8 and seminal vesicle invasion, was a significant variable in predicting biochemical recurrence within 24 months. Osteopontin and IL-8 staining predicted recurrence with high sensitivity (75.5%; 73.6%) and specificity (76%; 70.6%).

CONCLUSION

In prostatectomy specimens, osteopontin expression is independently associated with biochemical recurrence. Both osteopontin and IL-8 may be predictors of early disease progression.