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.

Colonic ketogenesis, a microbiota-regulated process, contributes to blood ketones and protects against colitis in mice

Ketogenesis is considered to occur primarily in liver to generate ketones as an alternative energy source for non-hepatic tissues when glucose availability/utilization is impaired. 3-Hydroxy-3-methylglutaryl-CoA synthase-2 (HMGCS2) mediates the rate-limiting step in this mitochondrial pathway. Publicly available databases show marked down-regulation of HMGCS2 in colonic tissues in Crohn's disease and ulcerative colitis. This led us to investigate the expression and function of this pathway in colon and its relevance to colonic inflammation in mice. Hmgcs2 is expressed in cecum and colon. As global deletion of Hmgcs2 showed significant postnatal mortality, we used a conditional knockout mouse with enzyme deletion restricted to intestinal tract. These mice had no postnatal mortality. Fasting blood ketones were lower in these mice, indicating contribution of colonic ketogenesis to circulating ketones. There was also evidence of gut barrier breakdown and increased susceptibility to experimental colitis with associated elevated levels of IL-6, IL-1β, and TNF-α in circulation. Interestingly, many of these phenomena were mostly evident in male mice. Hmgcs2 expression in colon is controlled by colonic microbiota as evidenced from decreased expression in germ-free mice and antibiotic-treated conventional mice and from increased expression in a human colonic epithelial cell line upon treatment with aqueous extracts of cecal contents. Transcriptomic analysis of colonic epithelia from control mice and Hmgcs2-null mice indicated an essential role for colonic ketogenesis in the maintenance of optimal mitochondrial function, cholesterol homeostasis, and cell-cell tight-junction organization. These findings demonstrate a sex-dependent obligatory role for ketogenesis in protection against colonic inflammation in mice.

The Transcription Factor RXRα in CD11c+ APCs Regulates Intestinal Immune Homeostasis and Inflammation

APCs such as dendritic cells and macrophages play a pivotal role in mediating immune tolerance and restoring intestinal immune homeostasis by limiting inflammatory responses against commensal bacteria. However, cell-intrinsic molecular regulators critical for programming intestinal APCs to a regulatory state rather than an inflammatory state are unknown. In this study, we report that the transcription factor retinoid X receptor α (RXRα) signaling in CD11c+ APCs is essential for suppressing intestinal inflammation by imparting an anti-inflammatory phenotype. Using a mouse model of ulcerative colitis, we demonstrated that targeted deletion of RXRα in CD11c+ APCs in mice resulted in the loss of T cell homeostasis with enhanced intestinal inflammation and increased histopathological severity of colonic tissue. This was due to the increased production of proinflammatory cytokines that drive Th1/Th17 responses and decreased expression of immune-regulatory factors that promote regulatory T cell differentiation in the colon. Consistent with these findings, pharmacological activation of the RXRα pathway alleviated colitis severity in mice by suppressing the expression of inflammatory cytokines and limiting Th1/Th17 cell differentiation. These findings identify an essential role for RXRα in APCs in regulating intestinal immune homeostasis and inflammation. Thus, manipulating the RXRα pathway could provide novel opportunities for enhancing regulatory responses and dampening colonic inflammation.

Targeting hyaluronic acid synthase-3 (HAS3) for the treatment of advanced renal cell carcinoma

BACKGROUND

Hyaluronic acid (HA) promotes cancer metastasis; however, the currently approved treatments do not target HA. Metastatic renal carcinoma (mRCC) is an incurable disease. Sorafenib (SF) is a modestly effective antiangiogenic drug for mRCC. Although only endothelial cells express known SF targets, SF is cytotoxic to RCC cells at concentrations higher than the pharmacological-dose (5-µM). Using patient cohorts, mRCC models, and SF combination with 4-methylumbelliferone (MU), we discovered an SF target in RCC cells and targeted it for treatment.

METHODS

We analyzed HA-synthase (HAS1, HAS2, HAS3) expression in RCC cells and clinical (n = 129), TCGA-KIRC (n = 542), and TCGA-KIRP (n = 291) cohorts. We evaluated the efficacy of SF and SF plus MU combination in RCC cells, HAS3-transfectants, endothelial-RCC co-cultures, and xenografts.

RESULTS

RCC cells showed increased HAS3 expression. In the clinical and TCGA-KIRC/TCGA-KIRP cohorts, higher HAS3 levels predicted metastasis and shorter survival. At > 10-µM dose, SF inhibited HAS3/HA-synthesis and RCC cell growth. However, at ≤ 5-µM dose SF in combination with MU inhibited HAS3/HA synthesis, growth of RCC cells and endothelial-RCC co-cultures, and induced apoptosis. The combination inhibited motility/invasion and an HA-signaling-related invasive-signature. We previously showed that MU inhibits SF inactivation in RCC cells. While HAS3-knockdown transfectants were sensitive to SF, ectopic-HAS3-expression induced resistance to the combination. In RCC models, the combination inhibited tumor growth and metastasis with little toxicity; however, ectopic-HAS3-expressing tumors were resistant.

CONCLUSION

HAS3 is the first known target of SF in RCC cells. In combination with MU (human equivalent-dose, 0.6-1.1-g/day), SF targets HAS3 and effectively abrogates mRCC.

Upregulation of the EGFR/MEK1/MAPK1/2 signaling axis as a mechanism of resistance to antiestrogen‑induced BimEL dependent apoptosis in ER+ breast cancer cells

The epidermal growth factor receptor (EGFR) is commonly upregulated in multiple cancer types, including breast cancer. In the present study, evidence is provided in support of the premise that upregulation of the EGFR/MEK1/MAPK1/2 signaling axis during antiestrogen treatment facilitates the escape of breast cancer cells from BimEL‑dependent apoptosis, conferring resistance to therapy. This conclusion is based on the findings that ectopic BimEL cDNA overexpression and confocal imaging studies confirm the pro‑apoptotic role of BimEL in ERα expressing breast cancer cells and that upregulated EGFR/MEK1/MAPK1/2 signaling blocks BimEL pro‑apoptotic action in an antiestrogen‑resistant breast cancer cell model. In addition, the present study identified a pro‑survival role for autophagy in antiestrogen resistance while EGFR inhibitor studies demonstrated that a significant percentage of antiestrogen‑resistant breast cancer cells survive EGFR targeting by pro‑survival autophagy. These pre‑clinical studies establish the possibility that targeting both the MEK1/MAPK1/2 signaling axis and pro‑survival autophagy may be required to eradicate breast cancer cell survival and prevent the development of antiestrogen resistance following hormone treatments. The present study uniquely identified EGFR upregulation as one of the mechanisms breast cancer cells utilize to evade the cytotoxic effects of antiestrogens mediated through BimEL‑dependent apoptosis.

Genetic Deletion of LRP5 and LRP6 in Macrophages Exacerbates Colitis-Associated Systemic Inflammation and Kidney Injury in Response to Intestinal Commensal Microbiota

Extraintestinal manifestations are common in inflammatory bowel disease and involve several organs, including the kidney. However, the mechanisms responsible for renal manifestation in inflammatory bowel disease are not known. In this study, we show that the Wnt-lipoprotein receptor-related proteins 5 and 6 (LRP5/6) signaling pathway in macrophages plays a critical role in regulating colitis-associated systemic inflammation and renal injury in a murine dextran sodium sulfate-induced colitis model. Conditional deletion of the Wnt coreceptors LRP5/6 in macrophages in mice results in enhanced susceptibility to dextran sodium sulfate colitis-induced systemic inflammation and acute kidney injury (AKI). Furthermore, our studies show that aggravated colitis-associated systemic inflammation and AKI observed in LRP5/6^LysM mice are due to increased bacterial translocation to extraintestinal sites and microbiota-dependent increased proinflammatory cytokine levels in the kidney. Conversely, depletion of the gut microbiota mitigated colitis-associated systemic inflammation and AKI in LRP5/6^LysM mice. Mechanistically, LRP5/6-deficient macrophages were hyperresponsive to TLR ligands and produced higher levels of proinflammatory cytokines, which are associated with increased activation of MAPKs. These results reveal how the Wnt-LRP5/6 signaling in macrophages controls colitis-induced systemic inflammation and AKI.

Abstract LB133: EGFR upregulation in breast cancer cells: A key mechanism of escape from antiestrogen induced death, autophagy, and senescence

EGFR is upregulated commonly in multiple cancer types, including breast cancer. However, the multiple role(s) of EGFR in breast cancer are not fully elucidated. In this study, we characterized a unique antiestrogen resistant breast cancer subline and provide compelling data that upregulation of the EGFR/MEK1/MAPK1/2 signaling axis during antiestrogen treatment facilitated escape from senescence, autophagy, and BimEL-dependent apoptosis. Our studies were conducted with the antiestrogen resistant TR5 cell line established by our laboratory, using a step-wise drug selection with the antiestrogen 4-hydroxytamoxifen (4-OHT) of the estrogen receptor α (ER+) MCF-7 breast cancer cells. A preliminary microarray comparing mRNA expression between 4-OHT-selected TR5 cells and MCF-7 parent cells identified upregulation of the epidermal growth factor receptor (EGFR). Western blot showed a greater than 5-fold upregulation of EGFR expression and downregulation of estrogen receptor alpha (ERα) compared to the levels in MCF-7 and T47-D (antiestrogen sensitive). Selective inhibition of EGFR, phosphorylated at Tyr 1068, was achieved with erlotinib. Inhibition blocked MEK1/MAPK1/2 signaling, which was also upregulated in 4-OHT selected TR5 cells, with detectable increases in the pro-apoptotic BH3 protein BimEL, and a fifty percent reduction in cell viability. However, a high number of cells survived erlotinib therapy due to autophagy induction determined to be cytoprotective. Autophagy induction was identified by analyzing the expression/turnover of autophagy proteins LC3-II and p62, a standard approach to ascertain autophagy levels in cells. Further, erlotinib treatment induced a 2-fold increase in the number of senescent cells in the surviving population. Senescent cells were identified by β-galactosidase staining of erlotinib-treated cells utilizing confocal microscopy. Interestingly, blockade of autophagy with the lysosomotrophic compound chloroquine enhanced the senescence cell population, suggesting that either autophagy blocked senescence induction or lysosome impairment increased senescence. Mechanistically, we have identified phosphorylated AMP-activated protein kinase (pAMPK) as being elevated under conditions of erlotinib treatment, and reduced in 4-OHT-selected TR5 cells relative to MCF-7 parent cells. This correlation supports the hypothesis that pAMPK was downregulated during 4-OHT selection of TR5 cells by elevated EGFR/MEK/MAPK1/2 signaling to allow surviving cells escape senescence induction and/or anti-proliferative autophagy. Overall we propose that EGFR mediated downregulation of pAMPK is a major regulatory pathway in breast cancer cells surviving endocrine treatment. Our current studies are dissecting the role of EGFR-mediated AMPK regulation with somatic cell-based studies and pharmacological intervention.

Citation Format: Mackenzie L. Hagan, Michael McGrath, Carol Joseph, Allison Lewis, John R. Barrett, Muthusamy Thangaraju, David Gewirtz, Patricia V. Schoenlein. EGFR upregulation in breast cancer cells: A key mechanism of escape from antiestrogen induced death, autophagy, and senescence [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr LB133.

Netrin-1 Overexpression Induces Polycystic Kidney Disease: A Novel Mechanism Contributing to Cystogenesis in Autosomal Dominant Polycystic Kidney Disease

Despite recent advances in understanding the pathogenesis of polycystic kidney disease (PKD), the underlying molecular mechanisms involved in cystogenesis are not fully understood. This study describes a novel pathway involved in cyst formation. Transgenic mice overexpressing netrin-1 in proximal tubular cells showed increased production and urinary excretion of netrin-1. Although no cysts were detectable immediately after birth, numerous small cysts were evident by the age of 4 weeks, and disease was accelerated along with age. Surprisingly, cyst formation in the kidney was restricted to male mice, with 80% penetrance. However, ovariectomy induced kidney cyst growth in netrin-1-overexpressing female mice. Cyst development in males was associated with albuminuria and polyuria and increased cAMP excretion in netrin-1 transgenic mice. Netrin-1 overexpression significantly increased extracellular signal-regulated kinase and focal adhesion kinase phosphorylation and vimentin expression. Interestingly, p53 expression was increased but in an inactive form. Furthermore, netrin-1 expression was increased in cystic epithelia and urine of various rodent models of PKD. siRNA-mediated suppression of netrin-1 significantly reduced cyst growth and improved kidney function in netrin-1 transgenic mice and in two genetic animal models of PKD. Together, these data demonstrate that netrin-1 up-regulation induced cyst formation in autosomal dominant PKD.

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.

Activation of Transcription Factor 4 in Dendritic Cells Controls Th1/Th17 Responses and Autoimmune Neuroinflammation

Dendritic cells (DCs) are professional APCs that play a crucial role in initiating robust immune responses against invading pathogens while inducing regulatory responses to the body's tissues and commensal microorganisms. A breakdown of DC-mediated immunological tolerance leads to chronic inflammation and autoimmune disorders. However, cell-intrinsic molecular regulators that are critical for programming DCs to a regulatory state rather than to an inflammatory state are not known. In this study, we show that the activation of the TCF4 transcription factor in DCs is critical for controlling the magnitude of inflammatory responses and limiting neuroinflammation. DC-specific deletion of TCF4 in mice increased Th1/Th17 responses and exacerbated experimental autoimmune encephalomyelitis pathology. Mechanistically, loss of TCF4 in DCs led to heightened activation of p38 MAPK and increased levels of proinflammatory cytokines IL-6, IL-23, IL-1β, TNF-α, and IL-12p40. Consistent with these findings, pharmacological blocking of p38 MAPK activation delayed experimental autoimmune encephalomyelitis onset and diminished CNS pathology in TCF4^ΔDC mice. Thus, manipulation of the TCF4 pathway in DCs could provide novel opportunities for regulating chronic inflammation and represents a potential therapeutic approach to control autoimmune neuroinflammation.

Lactate-Dependent Regulation of Immune Responses by Dendritic Cells and Macrophages

For decades, lactate has been considered an innocuous bystander metabolite of cellular metabolism. However, emerging studies show that lactate acts as a complex immunomodulatory molecule that controls innate and adaptive immune cells’ effector functions. Thus, recent advances point to lactate as an essential and novel signaling molecule that shapes innate and adaptive immune responses in the intestine and systemic sites. Here, we review these recent advances in the context of the pleiotropic effects of lactate in regulating diverse functions of immune cells in the tissue microenvironment and under pathological conditions.

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.

Selenomethionine (Se-Met) Induces the Cystine/Glutamate Exchanger SLC7A11 in Cultured Human Retinal Pigment Epithelial (RPE) Cells: Implications for Antioxidant Therapy in Aging Retina

Oxidative damage has been identified as a major causative factor in degenerative diseases of the retina; retinal pigment epithelial (RPE) cells are at high risk. Hence, identifying novel strategies for increasing the antioxidant capacity of RPE cells, the purpose of this study, is important. Specifically, we evaluated the influence of selenium in the form of selenomethionine (Se-Met) in cultured RPE cells on system xc- expression and functional activity and on cellular levels of glutathione, a major cellular antioxidant. ARPE-19 and mouse RPE cells were cultured with and without selenomethionine (Se-Met), the principal form of selenium in the diet. Promoter activity assay, uptake assay, RT-PCR, northern and western blots, and immunofluorescence were used to analyze the expression of xc-, Nrf2, and its target genes. Se-Met activated Nrf2 and induced the expression and function of xc- in RPE. Other target genes of Nrf2 were also induced. System xc- consists of two subunits, and Se-Met induced the subunit responsible for transport activity (SLC7A11). Selenocysteine also induced xc- but with less potency. The effect of Se-met on xc- was associated with an increase in maximal velocity and an increase in substrate affinity. Se-Met increased the cellular levels of glutathione in the control, an oxidatively stressed RPE. The Se-Met effect was selective; under identical conditions, taurine transport was not affected and Na+-coupled glutamate transport was inhibited. This study demonstrates that Se-Met enhances the antioxidant capacity of RPE by inducing the transporter xc- with a consequent increase in glutathione.

The Wnt-β-Catenin-IL-10 Signaling Axis in Intestinal APCs Protects Mice from Colitis-Associated Colon Cancer in Response to Gut Microbiota

Loss of immune tolerance to gut microflora is inextricably linked to chronic intestinal inflammation and colitis-associated colorectal cancer (CAC). The LRP5/6 signaling cascade in APCs contributes to immune homeostasis in the gut, but whether this pathway in APCs protects against CAC is not known. In the current study, using a mouse model of CAC, we show that the LRP5/6-β-catenin-IL-10 signaling axis in intestinal CD11c⁺ APCs protects mice from CAC by regulating the expression of tumor-promoting inflammatory factors in response to commensal flora. Genetic deletion of LRP5/6 in CD11c⁺ APCs in mice (LRP5/6^ΔCD11c) resulted in enhanced susceptibility to CAC. This is due to a microbiota-dependent increased expression of proinflammatory factors and decreased expression of the immunosuppressive cytokine IL-10. This condition could be improved in LRP5/6^ΔCD11c mice by depleting the gut flora, indicating the importance of LRP5/6 in mediating immune tolerance to the gut flora. Moreover, mechanistic studies show that LRP5/6 suppresses the expression of tumor-promoting inflammatory factors in CD11c⁺ APCs via the β-catenin-IL-10 axis. Accordingly, conditional activation of β-catenin specifically in CD11c⁺ APCs or in vivo administration of IL-10 protected LRP5/6^ΔCD11c mice from CAC by suppressing the expression of inflammatory factors. In summary, in this study, we identify a key role for the LRP5/6-β-catenin-IL-10 signaling pathway in intestinal APCs in resolving chronic intestinal inflammation and protecting against CAC in response to the commensal flora.

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.

Molecular targeting of renal cell carcinoma by an oral combination

The 5-year survival rate of patients with metastatic renal cell carcinoma (mRCC) is <12% due to treatment failure. Therapeutic strategies that overcome resistance to modestly effective drugs for mRCC, such as sorafenib (SF), could improve outcome in mRCC patients. SF is terminally biotransformed by UDP-glucuronosyltransferase-1A9 (A9) mediated glucuronidation, which inactivates SF. In a clinical-cohort and the TCGA-dataset, A9 transcript and/or protein levels were highly elevated in RCC specimens and predicted metastasis and overall-survival. This suggested that elevated A9 levels even in primary tumors of patients who eventually develop mRCC could be a mechanism for SF failure. 4-methylumbelliferone (MU), a choleretic and antispasmodic drug, downregulated A9 and inhibited SF-glucuronidation in RCC cells. Low-dose SF and MU combinations inhibited growth, motility, invasion and downregulated an invasive signature in RCC cells, patient-derived tumor explants and/or endothelial-RCC cell co-cultures; however, both agents individually were ineffective. A9 overexpression made RCC cells resistant to the combination, while its downregulation sensitized them to SF treatment alone. The combination inhibited kidney tumor growth, angiogenesis and distant metastasis, with no detectable toxicity; A9-overexpressing tumors were resistant to treatment. With effective primary tumor control and abrogation of metastasis in preclinical models, the low-dose SF and MU combinations could be an effective treatment option for mRCC patients. Broadly, our study highlights how targeting specific mechanisms that cause the failure of “old” modestly effective FDA-approved drugs could improve treatment response with minimal alteration in toxicity profile.

Chronic exposure to excess iron promotes EMT and cancer via p53 loss in pancreatic cancer

Based on the evidence that hemochromatosis, an iron-overload disease, drives hepatocellular carcinoma, we hypothesized that chronic exposure to excess iron, either due to genetic or environmental causes, predisposes an individual to cancer. Using pancreatic cancer as our primary focus, we employed cell culture studies to interrogate the connection between excess iron and cancer, and combined in vitro and in vivo studies to explore the connection further. Ferric ammonium citrate was used as an exogenous iron source. Chronic exposure to excess iron induced epithelial-mesenchymal transition (EMT) in normal and cancer cell lines, loss of p53, and suppression of p53 transcriptional activity evidenced from decreased expression of p53 target genes (p21, cyclin D1, Bax, SLC7A11). To further extrapolate our cell culture data, we generated EL-Kras^G12D (EL-Kras) mouse (pancreatic neoplastic mouse model) expressing Hfe^+/+and Hfe^−/− genetic background. p53 target gene expression decreased in EL-Kras/Hfe^−/− mouse pancreas compared to EL-Kras/Hfe^+/+ mouse pancreas. Interestingly, the incidence of acinar-to-ductal metaplasia and cystic pancreatic neoplasms (CPN) decreased in EL-Kras/Hfe^−/− mice, but the CPNs that did develop were larger in these mice than in EL-Kras/Hfe^+/+ mice. In conclusion, these in vitro and in vivo studies support a potential role for chronic exposure to excess iron as a promoter of more aggressive disease via p53 loss and SLC7A11 upregulation within pancreatic epithelial cells.

Wasf3 Deficiency Reveals Involvement in Metastasis in a Mouse Model of Breast Cancer

The WASF3 gene has been implicated in cancer cell movement, invasion, and metastasis by regulating genetic pathways important in these processes. Invasion and metastasis assays, however, are largely centered on xenograft models in immune-compromised mice. To facilitate analysis of the role of WASF3 in the spontaneous development of cancer cell metastasis, we generated a Wasf3 null strain by deleting exons 4 and 5, which encode essential motifs for Wasf3 function. On exposure to cre-recombinase a stop codon is generated immediately downstream in exon 6. Using a cytomegalovirus (CMV)-cre strain, Wasf3 constitutively was inactivated, which led to viable mice with no visible morphologic or behavioral abnormalities. There was no abnormal development or function of the mouse mammary gland in the Wasf3 null mice and brain development was normal. In the mouse mammary tumor virus (MMTV)-driven polyoma middle-T oncogene strain, which shows early onset breast cancer development and metastasis, Wiskott-Aldrich syndrome protein family member 3 (Wasf3) is up-regulated in metastatic lesions. When this oncogene was introduced onto the Wasf3-null background, although metastasis was observed in these mice, there was a reduction in the number and size of metastatic lesions in the lungs. These data provide evidence for a role in WASF3 in the development of metastasis in a spontaneous model of breast cancer.

Abstract 3681: RAD51AP1 is a novel therapeutic target for cancer prevention and treatment

Although much progress has been made in recent years in its treatment and prevention, cancer is still the second leading cause of death in the United States. Surgical removal of the tumor is not possible in all cancer types; therefore, chemotherapy and radiation therapy have become the standard course of treatment and are often the only option for more late stage and metastatic tumors. Unfortunately, chemotherapy and radiation therapy resistance are the greatest challenge for physicians trying to eradicate disease, prevent tumor recurrence, and inhibit distant metastasis. This resistance is derived from a heterogeneous population of cells within the tumor known as cancer stem cells (CSCs). CSCs are able to maintain a higher capacity for self-renewal due to a more efficient DNA repair system. CSCs are actively cycling, therefore, the repair mechanism of homologous recombination (HR) plays a significant role in repairing double-stranded DNA breaks that inevitably accumulate. Several studies have examined the link between efficient DNA repair and CSC self-renewal and found that proteins involved in HR repair are elevated in many human cancers. RAD51-associated protein 1 (RAD51AP1), which is responsible for the successful resolution of HR during DNA repair, is overexpressed in wide variety of human cancers. The present study sought to determine the functional role of RAD51AP1 in CSC self-renewal and its relevance to cancer growth and progression and also drug resistance. Our studies provide evidence that RAD51AP1 plays a critical role in CSC self-renewal and maintenance in breast, lung, and colon cancers. To determine the functional role of RAD51AP1 in cancer growth and progression, we generated genetically engineered mouse (GEM) models in breast and lung in WT (Rad51ap1+/+) and Rad51ap1-knockout (KO, Rad51ap1-/-) background and found that Rad51ap1 deletion significantly delayed the time of tumor formation and distant metastasis, which in turn increase the overall survival. Rad51ap1 inactivation in human breast and lung cancer cell lines, significantly reduced tumor growth in xenograft mouse model. This findings are also recapitulated in mouse mammary tumor cell lines (AT3 and 4T1). We also investigated the functional role of RAD51AP1 on colon cancer growth and progression using AOM/DSS and Apcmin/+ models of colon cancer and found that smaller tumor burden in KO mice compared to WT suggesting that Rad51ap1 may have a significant role in tumor growth. Taken together, these data demonstrate that RAD51AP1 plays a critical role in CSC growth and self-renewal in many human cancers and RAD51AP1 could be a novel therapeutic target for cancer prevention and treatment.

Citation Format: Allison E. Bridges, Pragya Rajpurohit, Parth Patel, Nagendra Singh, Putter D. Prasad, Muthusamy Thangaraju. RAD51AP1 is a novel therapeutic target for cancer prevention and treatment [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 3681.

Abstract LB-040: SIRT1 requires for mammary stem cell self-renewal and maintenance

In spite of the many advances in cancer diagnosis and treatment, breast cancer remains a devastating disease among women worldwide. Although the critical role of estrogen (E2) in breast cancer has been unequivocally established and antiestrogens have been successfully used to treat this disease, there are about 2.6 million women in the United States who are continue to suffer from this disease. Further, approximately 80% of breast cancers are initially E2-dependent and respond well to antiestrogens, but many of them develop resistance and become unresponsive to antiestrogen therapy. Despite through investigation, the molecular mechanisms underlying this loss of responsiveness to antiestrogen therapy and the precise signaling molecules that impart E2-induced mitogenic signaling have not been fully understood. This gap in knowledge constitutes a significant impediment in effective prevention and treatment of this disease. Thus, the purpose of this study is to identify the precise signaling processes that impart E2 signaling and the molecular mechanisms underlying the resistance to hormonal therapy in breast cancer. In this study, we found that SIRT1, a type III histone deacetylase (HDAC), plays a critical role in E2-induced tumor growth as well as chemoresistance in human breast cancer cells. Functional inactivation of this gene abolished E2-induced tumor growth and made it more susceptible to hormonal- and chemotherapy-induced growth arrest and apoptosis. Additionally, our study showed that mammary stem-cells require Sirt1 for self-renewal and maintenance in the undifferentiated-state. Interestingly, mammary gland specific Sirt1-knockdown significantly reduced breast tumor growth and metastasis in syngeneic and genetically engineered mouse (GEM) models of breast cancer by limiting breast cancer stem cell (BCSC) self-renewal. RNA-seq analysis provided evidence that Sirt1 deletion is associated with significantly reduced expression of genes involved in BCSC self-renewal, tumor growth and metastasis, and drug resistance. Treatment of GEM mouse models of breast cancer with SIRT1 inhibitor reduced tumor growth with increased overall survival. Altogether, our study provides strong evidence that SIRT1 is a key regulator of E2-induced tumor growth signaling, and a potential modifier of drug resistance. Functional inactivation of this gene will effectively block mammary tumor development and circumvent drug resistance, which in turn could significantly increase the disease-free survival.

Citation Format: Utkarsh Parwal, Parth Patel, Sabarish Ramachandran, Rajneesh Pathania, Allison Bridges, Pragya Rajpurohit, Puttur D. Prasad, Muthusamy Thangaraju. SIRT1 requires for mammary stem cell self-renewal and maintenance [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 LB-040.

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.

Metabolic Reprogramming by MYCN Confers Dependence on the Serine-Glycine-One-Carbon Biosynthetic Pathway

MYCN amplification drives the development of neuronal cancers in children and adults. Given the challenge in therapeutically targeting MYCN directly, we searched for MYCN-activated metabolic pathways as potential drug targets. Here we report that neuroblastoma cells with MYCN amplification show increased transcriptional activation of the serine-glycine-one-carbon (SGOC) biosynthetic pathway and an increased dependence on this pathway for supplying glucose-derived carbon for serine and glycine synthesis. Small molecule inhibitors that block this metabolic pathway exhibit selective cytotoxicity to MYCN-amplified cell lines and xenografts by inducing metabolic stress and autophagy. Transcriptional activation of the SGOC pathway in MYCN-amplified cells requires both MYCN and ATF4, which form a positive feedback loop, with MYCN activation of ATF4 mRNA expression and ATF4 stabilization of MYCN protein by antagonizing FBXW7-mediated MYCN ubiquitination. Collectively, these findings suggest a coupled relationship between metabolic reprogramming and increased sensitivity to metabolic stress, which could be exploited as a strategy for selective cancer therapy. SIGNIFICANCE: This study identifies a MYCN-dependent metabolic vulnerability and suggests a coupled relationship between metabolic reprogramming and increased sensitivity to metabolic stress, which could be exploited for cancer therapy.See related commentary by Rodriguez Garcia and Arsenian-Henriksson, p. 3818.

Deferiprone: Pan-selective Histone Lysine Demethylase Inhibition Activity and Structure Activity Relationship Study

Deferiprone (DFP) is a hydroxypyridinone-derived iron chelator currently in clinical use for iron chelation therapy. DFP has also been known to elicit antiproliferative activities, yet the mechanism of this effect has remained elusive. We herein report that DFP chelates the Fe2+ ion at the active sites of selected iron-dependent histone lysine demethylases (KDMs), resulting in pan inhibition of a subfamily of KDMs. Specifically, DFP inhibits the demethylase activities of six KDMs - 2A, 2B, 5C, 6A, 7A and 7B - with low micromolar IC50s while considerably less active or inactive against eleven KDMs - 1A, 3A, 3B, 4A-E, 5A, 5B and 6B. The KDM that is most sensitive to DFP, KDM6A, has an IC50 that is between 7- and 70-fold lower than the iron binding equivalence concentrations at which DFP inhibits ribonucleotide reductase (RNR) activities and/or reduces the labile intracellular zinc ion pool. In breast cancer cell lines, DFP potently inhibits the demethylation of H3K4me3 and H3K27me3, two chromatin posttranslational marks that are subject to removal by several KDM subfamilies which are inhibited by DFP in cell-free assay. These data strongly suggest that DFP derives its anti-proliferative activity largely from the inhibition of a sub-set of KDMs. The docked poses adopted by DFP at the KDM active sites enabled identification of new DFP-based KDM inhibitors which are more cytotoxic to cancer cell lines. We also found that a cohort of these agents inhibited HP1-mediated gene silencing and one lead compound potently inhibited breast tumor growth in murine xenograft models. Overall, this study identified a new chemical scaffold capable of inhibiting KDM enzymes, globally changing histone modification profiles, and with specific anti-tumor activities.

Alcohol-induced ketonemia is associated with lowering of blood glucose, downregulation of gluconeogenic genes, and depletion of hepatic glycogen in type 2 diabetic db/db mice

Alcoholic ketoacidosis and diabetic ketoacidosis are life-threatening complications that share the characteristic features of high anion gap metabolic acidosis. Ketoacidosis is attributed in part to the massive release of ketone bodies (e.g., β-hydroxybutyrate; βOHB) from the liver into the systemic circulation. To date, the impact of ethanol consumption on systemic ketone concentration, glycemic control, and hepatic gluconeogenesis and glycogenesis remains largely unknown, especially in the context of type 2 diabetes. In the present study, ethanol intake (36% ethanol- and 36% fat-derived calories) by type 2 diabetic db/db mice for 9 days resulted in significant decreases in weight gain (∼19.5% ↓) and caloric intake (∼30% ↓). This was accompanied by a transition from macrovesicular-to-microvesicular hepatic steatosis with a modest increase in hepatic TG (∼37% ↑). Importantly, ethanol increased systemic βOHB concentration (∼8-fold ↑) with significant decreases in blood glucose (∼4-fold ↓) and plasma insulin and HOMA-IR index (∼3-fold ↓). In addition, ethanol enhanced hepatic βOHB content (∼5-fold ↑) and hmgcs2 mRNA expression (∼3.7-fold ↑), downregulated key gluconeogenic mRNAs (e.g., Pcx, Pck1, and G6pc), and depleted hepatic glycogen (∼4-fold ↓). Furthermore, ethanol intake led to significant decreases in the mRNA/protein expression and allosteric activation of glycogen synthase (GS) in liver tissues regardless of changes in the phosphorylation of GS, GSK-3β, or Akt. Together, our findings suggest that ethanol-induced ketonemia may occur in concomitance with significant lowering of blood glucose concentration, which may be attributed to suppression of gluconeogenesis in the setting of glycogen depletion in type 2 diabetes.

Canonical Wnt Signaling in CD11c+ APCs Regulates Microbiota-Induced Inflammation and Immune Cell Homeostasis in the Colon

Aberrant Wnt/β-catenin signaling occurs in several inflammatory diseases, including inflammatory bowel disease and inflammatory bowel disease-associated colon carcinogenesis. However, its role in shaping mucosal immune responses to commensals in the gut remains unknown. In this study, we investigated the importance of canonical Wnt signaling in CD11c⁺ APCs in controlling intestinal inflammation. Using a mouse model of ulcerative colitis, we demonstrated that canonical Wnt signaling in intestinal CD11c⁺ APCs controls intestinal inflammation by imparting an anti-inflammatory phenotype. Genetic deletion of Wnt coreceptors, low-density lipoprotein receptor-related proteins 5 and 6 (LRP5/6) in CD11c⁺ APCs in LRP5/6^ΔCD11c mice, resulted in enhanced intestinal inflammation with increased histopathological severity of colonic tissue. This was due to microbiota-dependent increased production of proinflammatory cytokines and decreased expression of immune-regulatory factors such as IL-10, retinoic acid, and IDO. Mechanistically, loss of LRP5/6-mediated signaling in CD11c⁺ APCs resulted in altered microflora and T cell homeostasis. Furthermore, our study demonstrates that conditional activation of β-catenin in CD11c⁺ APCs in LRP5/6^ΔCD11c mice resulted in reduced intestinal inflammation with decreased histopathological severity of colonic tissue. These results reveal a mechanism by which intestinal APCs control intestinal inflammation and immune homeostasis via the canonical Wnt-signaling pathway.

Iron Overload Accelerates the Progression of Diabetic Retinopathy in Association with Increased Retinal Renin Expression

Diabetic retinopathy (DR) is a leading cause of blindness among working-age adults. Increased iron accumulation is associated with several degenerative diseases. However, there are no reports on the status of retinal iron or its implications in the pathogenesis of DR. In the present study, we found that retinas of type-1 and type-2 mouse models of diabetes have increased iron accumulation compared to non-diabetic retinas. We found similar iron accumulation in postmortem retinal samples from human diabetic patients. Further, we induced diabetes in HFE knockout (KO) mice model of genetic iron overload to understand the role of iron in the pathogenesis of DR. We found increased neuronal cell death, vascular alterations and loss of retinal barrier integrity in diabetic HFE KO mice compared to diabetic wildtype mice. Diabetic HFE KO mouse retinas also exhibited increased expression of inflammation and oxidative stress markers. Severity in the pathogenesis of DR in HFE KO mice was accompanied by increase in retinal renin expression mediated by G-protein-coupled succinate receptor GPR91. In light of previous reports implicating retinal renin-angiotensin system in DR pathogenesis, our results reveal a novel relationship between diabetes, iron and renin-angiotensin system, thereby unraveling new therapeutic targets for the treatment of DR.

GPR81, a Cell-Surface Receptor for Lactate, Regulates Intestinal Homeostasis and Protects Mice from Experimental Colitis

At mucosal sites such as the intestine, the immune system launches robust immunity against invading pathogens while maintaining a state of tolerance to commensal flora and ingested food Ags. The molecular mechanisms underlying this phenomenon remain poorly understood. In this study, we report that signaling by GPR81, a receptor for lactate, in colonic dendritic cells and macrophages plays an important role in suppressing colonic inflammation and restoring colonic homeostasis. Genetic deletion of GPR81 in mice led to increased Th1/Th17 cell differentiation and reduced regulatory T cell differentiation, resulting in enhanced susceptibility to colonic inflammation. This was due to increased production of proinflammatory cytokines (IL-6, IL-1β, and TNF-α) and decreased expression of immune regulatory factors (IL-10, retinoic acid, and IDO) by intestinal APCs lacking GPR81. Consistent with these findings, pharmacological activation of GPR81 decreased inflammatory cytokine expression and ameliorated colonic inflammation. Taken together, these findings identify a new and important role for the GPR81 signaling pathway in regulating immune tolerance and colonic inflammation. Thus, manipulation of the GPR81 pathway could provide novel opportunities for enhancing regulatory responses and treating colonic inflammation.

Promoter Methylation Modulates Indoleamine 2,3-Dioxygenase 1 Induction by Activated T Cells in Human Breast Cancers

Triple-negative breast cancer (TNBC) cells are modulated in reaction to tumor-infiltrating lymphocytes. However, their specific responses to this immune pressure are unknown. In order to address this question, we first used mRNA sequencing to compare the immunophenotype of the TNBC cell line MDA-MB-231 and the luminal breast cancer cell line MCF7 after both were cocultured with activated human T cells. Despite similarities in the cytokine-induced immune signatures of the two cell lines, MDA-MD-231 cells were able to transcribe more IDO1 than MCF7 cells. The two cell lines had similar upstream JAK/STAT1 signaling and IDO1 mRNA stability. However, using a series of breast cancer cell lines, IFNγ stimulated IDO1 protein expression and enzymatic activity only in ER^-, not ER⁺, cell lines. Treatment with 5-aza-deoxycytidine reversed the suppression of IDO1 expression in MCF7 cells, suggesting that DNA methylation was potentially involved in IDO1 induction. By analyzing several breast cancer datasets, we discovered subtype-specific mRNA and promoter methylation differences in IDO1, with TNBC/basal subtypes exhibiting lower methylation/higher expression and ER⁺/luminal subtypes exhibiting higher methylation/lower expression. We confirmed this trend of IDO1 methylation by bisulfite pyrosequencing breast cancer cell lines and an independent cohort of primary breast tumors. Taken together, these findings suggest that IDO1 promoter methylation regulates anti-immune responses in breast cancer subtypes and could be used as a predictive biomarker for IDO1 inhibitor-based immunotherapy. Cancer Immunol Res; 5(4); 330-44. ©2017 AACR.

Abstract P5-07-12: RAD51AP1 is a novel prognostic marker and therapeutic target for breast cancer

Background: Ionizing radiation is one of the most effective therapeutic strategies for the treatment of breast cancer and is considered as a more appropriate therapy for patients with high-risk of recurrence. Despite substantial benefits are achievable with this treatment, especially for ductal carcinoma and early invasive cancer, the critical barrier in using this treatment strategy is that tumor cells develop radioresistance, which in turn progress into advanced invasive cancer. Breast cancer stem cells (BCSCs), a subpopulation of cells within the tumor with a characteristic feature of self-renewal, play a critical role radioresistance and treatment failure. BCSCs exhibit increased DNA repair activity by increasing RAD51AP1 for their prolonged survival and to evade from the radiation therapy. We explored the expression profile of RAD51AP1 in BCSCs, human normal and various subtypes of breast tumor tissues and cell lines and response to chemo- and radiation- therapy.

Methods: Gene expression (RNA and protein) profile was assessed using semi-quantitative and real-time PCR (qPCR) and western blot analyses. RAD51AP1 expression and its prognostic value in large cohort of human samples were analyzed by TCGA, GOBO, and Kaplan-Meier plotter integrative bioinformatics interface analyses. Breast cancer stem cell (BCSC) status was analyzed by FACS using CD24 and CD49f cell surface marker. Cell death was analyzed by propidium iodide (PI) stained cell cycle analysis.

Results: We found that tumor propagating CD49f+CD24+ cells activate RAD51AP1 more promptly than non-tumorigenic CD49f-CD24- cells and confer chemo- and radiation- therapy resistance. RAD51AP1 inactivation facilitates chemo- and radiation- therapy response by depleting CD49f+CD24+ cells with significant activation of apoptotic cell death signaling. RAD51AP1 expression was significantly higher in BC, especially in the basal triple-negative and HER2-positive BC subtype, than in normal mammary tissue. Further, RAD51AP1 expression is highest in grade III histological tumor types and negatively associated to overall disease-free survival. RAD51AP1 levels across different BC cell lines showed that triple-negative breast cancer (TNBC) cell lines expressed highest level of this gene than other sub types.

Conclusion:Overall, our findings provide evidence that BCSCs utilize DNA repair signaling for their self-renewal and RAD51AP1 play a critical role in BCSC self-renewal and maintenance. Further, RAD51AP1 expression profile can be used as a prognostic marker to monitor disease progression and chemotherapy response.

Citation Format: Thangaraju M, Kolhe RB, Pathania R. RAD51AP1 is a novel prognostic marker and therapeutic target for breast cancer [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P5-07-12.

Increased Retinal Expression of the Pro-Angiogenic Receptor GPR91 via BMP6 in a Mouse Model of Juvenile Hemochromatosis

PURPOSE

Hemochromatosis, an iron-overload disease, occurs as adult and juvenile types. Mutations in hemojuvelin (HJV), an iron-regulatory protein and a bone morphogenetic protein (BMP) coreceptor, underlie most of the juvenile type. Hjv(-/-) mice accumulate excess iron in retina and exhibit aberrant vascularization and angiomas. A succinate receptor, GPR91, is pro-angiogenic in retina. We hypothesized that Hjv(-/-) retinas have increased BMP signaling and increased GPR91 expression as the basis of angiomas.

METHODS

Expression of GPR91 was examined by qPCR, immunofluorescence, and Western blot in wild-type and Hjv(-/-) mouse retinas and pRPE cells. Influence of excess iron and BMP6 on GPR91 expression was investigated in ARPE-19 cells, and wild-type and Hjv(-/-) pRPE cells. Succinate was used to activate GPR91 and determine the effects of GPR91 signaling on VEGF expression. Signaling of BMP6 was studied by the expression of Smad1/5/8 and pSmad4, and the BMP-target gene Id1. The interaction of pSmad4 with GPR91 promoter was studied by ChIP.

RESULTS

Expression of GPR91 was higher in Hjv(-/-) retinas and RPE than in wild-type counterparts. Unexpectedly, BMP signaling was increased, not decreased, in Hjv(-/-) retinas and RPE. Bone morphogenetic protein 6 induced GPR91 in RPE, suggesting that increased BMP signaling in Hjv(-/-) retinas was likely responsible for GPR91 upregulation. Exposure of RPE to excess iron and succinate as well as BMP6 and succinate increased VEGF expression. Bone morphogenetic protein 6 promoted the interaction of pSmad4 with GPR91 promoter in RPE.

CONCLUSIONS

G-protein-coupled receptor 91 is a BMP6 target and Hjv deletion enhances BMP signaling in retina, thus underscoring a role for excess iron and hemochromatosis in abnormal retinal vascularization.

Homeostatic PPARα Signaling Limits Inflammatory Responses to Commensal Microbiota in the Intestine

Dietary lipids and their metabolites activate members of the peroxisome proliferative-activated receptor (PPAR) family of transcription factors and are critical for colonic health. The PPARα isoform plays a vital role in regulating inflammation in various disease settings, but its role in intestinal inflammation, commensal homeostasis, and mucosal immunity in the gut are unclear. In this study, we demonstrate that the PPARα pathway in innate immune cells orchestrates gut mucosal immunity and commensal homeostasis by regulating the expression of IL-22 and the antimicrobial peptides RegIIIβ, RegIIIγ, and calprotectin. Additionally, the PPARα pathway is critical for imparting regulatory phenotype in intestinal macrophages. PPARα deficiency in mice led to commensal dysbiosis in the gut, resulting in a microbiota-dependent increase in the expression of inflammatory cytokines and enhanced susceptibility to intestinal inflammation. Pharmacological activation of this pathway decreased the expression of inflammatory cytokines and ameliorated colonic inflammation. Taken together, these findings identify a new important innate immune function for the PPARα signaling pathway in regulating intestinal inflammation, mucosal immunity, and commensal homeostasis. Thus, the manipulation of the PPARα pathway could provide novel opportunities for enhancing mucosal immunity and treating intestinal inflammation.

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.

Deletion of LRP5 and LRP6 in dendritic cells enhances antitumor immunity

The tumor microenvironment (TME) contains high levels of the Wnt family of ligands, and aberrant Wnt-signaling occurs in many tumors. Past studies have been directed toward how the Wnt signaling cascade regulates cancer development, progression and metastasis. However, its effects on host antitumor immunity remain unknown. In this report, we show that Wnts in the TME condition dendritic cells (DCs) to a regulatory state and suppress host antitumor immunity. DC-specific deletion of Wnt co-receptors low-density lipoprotein receptor-related protein 5 and 6 (LRP5/6) in mice markedly delayed tumor growth and enhanced host antitumor immunity. Mechanistically, loss of LRP5/6-mediated signaling in DCs resulted in enhanced effector T cell differentiation and decreased regulatory T cell differentiation. This was due to increased production of pro-inflammatory cytokines and decreased production of IL-10, TGF-β1 and retinoic acid (RA). Likewise, pharmacological inhibition of the Wnts' interaction with its cognate co-receptors LRP5/6 and Frizzled (Fzd) receptors had similar effects on tumor growth and effector T cell responses. Moreover, blocking Wnt-signaling in DCs resulted in enhanced capture of tumor-associated antigens and efficient cross-priming of CD8⁺ T cells. Hence, blocking the Wnt pathway represents a potential therapeutic to overcome tumor-mediated immune suppression and augment antitumor immunity.

Abstract 1005: Dual targeting of MEK/MAPK1/2 and pro-survival autophagy to optimize antiestrogen treatment toward the eradication of antiestrogen resistant breast cancer

In past studies, we showed that pro-survival autophagy mediates resistance to antiestrogen-induced apoptosis and facilitates the emergence of antiestrogen resistant breast cancer cells (Sammadar et al., Molecular Cancer Ther. 9, 2008). We also identified the pro-apoptotic BimEL protein as a key death effector of antiestrogen treatment and determined that BimEL pro-apoptotic activity is abrogated by a MEK1/MAPK1/2-dependent phosphorylation (Periyasamy-Thandavan et al., Breast Cancer Res. 14, 2012). In this study, we tested the hypothesis that the MEK1/MAPK1/2/BimEL signaling node simultaneously regulates antiestrogen- induced pro-survival autophagy and apoptosis in ER+ breast cancer cells. In our approach, we utilized T47-D and MCF-7 breast cancer cells and modulated the activity of MEK1/MAPK1/2/ BimEL expression with U0126, a small molecule inhibitor of MEK1, BimEL cDNA over-expression, or siRNA targeting under a variety of endocrine treatments. We also conducted studies in the presence or absence of the pan-caspase inhibitor ZVAD-fmk so that autophagy levels/function could be analyzed independent of effects mediated by BimEL-dependent caspase activation. Autophagic flux was measured by comparing the levels of lipidated LC3II in cell populations undergoing the different treatments in the presence or absence of chloroquine (CQ), a lysosomotropic agent that prevents autolysosomal turnover. These studies determined that: 1) dephosphorylated BimEL significantly attenuates autophagic flux, but primarily as a consequence of BimEL-induced caspase-activation; (2) BimEL-dependent apoptotic death induced in antiestrogen-treated ER+ breast cancer cells by MEK1 inhibition is not dependent on autophagy; and (3) agents that selectively target autophagy (i.e. CQ and spautin) enhance apoptosis induced by MEK1 blockade in breast cancer cells undergoing endocrine treatment. Based on these pre-clinical in vitro studies, we postulate that the eradication of antiestrogen resistant breast cancer will require the targeting of MEK1/MAPK1/2 to activate BimEL and pro-survival autophagy to eradicate cells surviving BimEL-dependent apoptosis.

Citation Format: Mathew Manning, Suchreet Takhar, Sudharsan Periyasamy-Thandavan, Michael Cheng, Thomas Barrett, William Hill, Darren Browning, Muthusamy Thangaraju, Meghan McGee-Lawrence, Patricia V. Schoenlein. Dual targeting of MEK/MAPK1/2 and pro-survival autophagy to optimize antiestrogen treatment toward the eradication of antiestrogen resistant breast cancer. [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 1005. doi:10.1158/1538-7445.AM2015-1005

Abstract LB-142: Functional role of DNA methyltransferase1 (DNMT1) in regulation of mammary stem/progenitor and cancer stem cells

Tumor propagation is the hallmark feature of the cancer stem/tumor propagating cells. Several genetic and epigenetic components are involved in regulation of this process; however, DNA methylation provides a potential epigenetic mechanism for the cellular memory, which needed to preserve the tumorigenic potential through repeated cell divisions. Further, DNA methylation plays a critical role in stem/progenitor cell maintenance wherein the DNMT proteins get enriched in undifferentiated cells and thereby it retains the regenerative capacity while suppressing differentiation. However, the precise role of DNMTs in maintaining stem/progenitor and tumorigenic phenotype in constantly replenished organ, like mammary glands and mammary tumor is not yet known. Here we show that Dnmt1 is required for mammary gland outgrowth and terminal end bud development and that mammary-gland specific Dnmt1 deletion in mice leads to significant reduction in mammary stem/progenitor cell formation. Interestingly, Dnmt1 deletion almost completely abolishes Neu-Tg- and C3(1)-SV40-Tg- driven mammary tumor formation and metastasis. This phenomenon is associated with significant reduction in cancer stem cell (CSC) formation. Similar observations were also recapitulated using pharmacological inhibitors of Dnmts in Neu-Tg mice. To unravel the cause of tumorigenicity of tumor propagating cells, we used genome-wide methylation and RNA sequence approach and find that DNA methylation plays a vital role in regulation of abnormal self-renewal by hypermethylating genes that are involved in development and cell commitment pathways; thereby leading to immortality and autonomous growth to the tumor propagating cells. Overall, our studies provide the first in vivo evidence that DNMT1 is indispensable for mammary stem, progenitor and cancer stem cell formation and that functional inactivation of this gene drastically reduces mammary tumor formation even in the aggressive triple-negative breast cancer subtype. Furthermore, we identified ISL1 as a functional target of DNMT1 in tumor progenitor cells, and stable expression of ISL1 induces apoptosis in cancer stem cells. Thus, DNMT1 specific inhibitors could have a great impact on eradication of cancer stem cells and associated disease recurrence, and ISL1 hypermethylation status could be used as a prognostic marker for early breast cancer diagnosis.

Citation Format: Rajneesh Pathania, Sabarish Ramachandran, Puttur Prasad, Vadivel Ganapathy, Muthusamy Thangaraju. Functional role of DNA methyltransferase1 (DNMT1) in regulation of mammary stem/progenitor and cancer stem 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 LB-142. doi:10.1158/1538-7445.AM2015-LB-142

Curcumin inhibits PhIP induced cytotoxicity in breast epithelial cells through multiple molecular targets

Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), found in cooked meat, is a known food carcinogen that causes several types of cancer, including breast cancer, as PhIP metabolites produce DNA adduct and DNA strand breaks. Curcumin, obtained from the rhizome of Curcuma longa, has potent anticancer activity. To date, no study has examined the interaction of PhIP with curcumin in breast epithelial cells. The present study demonstrates the mechanisms by which curcumin inhibits PhIP-induced cytotoxicity in normal breast epithelial cells (MCF-10A). Curcumin significantly inhibited PhIP-induced DNA adduct formation and DNA double stand breaks with a concomitant decrease in reactive oxygen species (ROS) production. The expression of Nrf2, FOXO targets; DNA repair genes BRCA-1, H2AFX and PARP-1; and tumor suppressor P16 was studied to evaluate the influence on these core signaling pathways. PhIP induced the expression of various antioxidant and DNA repair genes. However, co-treatment with curcumin inhibited this expression. PhIP suppressed the expression of the tumor suppressor P16 gene, whereas curcumin co-treatment increased its expression. Caspase-3 and -9 were slightly suppressed by curcumin with a consequent inhibition of cell death. These results suggest that curcumin appears to be an effective anti-PhIP food additive likely acting through multiple molecular targets.

DNMT1 is essential for mammary and cancer stem cell maintenance and tumorigenesis

Mammary stem/progenitor cells (MaSCs) maintain self-renewal of the mammary epithelium during puberty and pregnancy. DNA methylation provides a potential epigenetic mechanism for maintaining cellular memory during self-renewal. Although DNA methyltransferases (DNMTs) are dispensable for embryonic stem cell maintenance, their role in maintaining MaSCs and cancer stem cells (CSCs) in constantly replenishing mammary epithelium is unclear. Here we show that DNMT1 is indispensable for MaSC maintenance. Furthermore, we find that DNMT1 expression is elevated in mammary tumors, and mammary gland-specific DNMT1 deletion protects mice from mammary tumorigenesis by limiting the CSC pool. Through genome-scale methylation studies, we identify ISL1 as a direct DNMT1 target, hypermethylated and downregulated in mammary tumors and CSCs. DNMT inhibition or ISL1 expression in breast cancer cells limits CSC population. Altogether, our studies uncover an essential role for DNMT1 in MaSC and CSC maintenance and identify DNMT1-ISL1 axis as a potential therapeutic target for breast cancer treatment.

IFNγ Induces DNA Methylation-Silenced GPR109A Expression via pSTAT1/p300 and H3K18 Acetylation in Colon Cancer

Short-chain fatty acids, metabolites produced by colonic microbiota from fermentation of dietary fiber, act as anti-inflammatory agents in the intestinal tract to suppress proinflammatory diseases. GPR109A is the receptor for short-chain fatty acids. The functions of GPR109A have been the subject of extensive studies; however, the molecular mechanisms underlying GPR109A expression is largely unknown. We show that GPR109A is highly expressed in normal human colon tissues, but is silenced in human colon carcinoma cells. The GPR109A promoter DNA is methylated in human colon carcinoma. Strikingly, we observed that IFNγ, a cytokine secreted by activated T cells, activates GPR109A transcription without altering its promoter DNA methylation. Colon carcinoma grows significantly faster in IFNγ-deficient mice than in wild-type mice in an orthotopic colon cancer mouse model. A positive correlation was observed between GPR109A protein level and tumor-infiltrating T cells in human colon carcinoma specimens, and IFNγ expression level is higher in human colon carcinoma tissues than in normal colon tissues. We further demonstrated that IFNγ rapidly activates pSTAT1 that binds to the promoter of p300 to activate its transcription. p300 then binds to the GPR109A promoter to induce H3K18 hyperacetylation, resulting in chromatin remodeling in the methylated GPR109A promoter. The IFNγ-activated pSTAT1 then directly binds to the methylated but hyperacetylated GPR109 promoter to activate its transcription. Overall, our data indicate that GPR109A acts as a tumor suppressor in colon cancer, and the host immune system might use IFNγ to counteract DNA methylation-mediated GPR109A silencing as a mechanism to suppress tumor development.

Canonical wnt signaling in dendritic cells regulates Th1/Th17 responses and suppresses autoimmune neuroinflammation

Breakdown in immunological tolerance to self-Ags or uncontrolled inflammation results in autoimmune disorders. Dendritic cells (DCs) play an important role in regulating the balance between inflammatory and regulatory responses in the periphery. However, factors in the tissue microenvironment and the signaling networks critical for programming DCs to control chronic inflammation and promote tolerance are unknown. In this study, we show that wnt ligand-mediated activation of β-catenin signaling in DCs is critical for promoting tolerance and limiting neuroinflammation. DC-specific deletion of key upstream (lipoprotein receptor-related protein [LRP]5/6) or downstream (β-catenin) mediators of canonical wnt signaling in mice exacerbated experimental autoimmune encephalomyelitis pathology. Mechanistically, loss of LRP5/6-β-catenin-mediated signaling in DCs led to an increased Th1/Th17 cell differentiation but reduced regulatory T cell response. This was due to increased production of proinflammatory cytokines and decreased production of anti-inflammatory cytokines such as IL-10 and IL-27 by DCs lacking LRP5/6-β-catenin signaling. Consistent with these findings, pharmacological activation of canonical wnt/β-catenin signaling delayed experimental autoimmune encephalomyelitis onset and diminished CNS pathology. Thus, the activation of canonical wnt signaling in DCs limits effector T cell responses and represents a potential therapeutic approach to control autoimmune neuroinflammation.

Abstract B50: MEK inhibitors mount a two-pronged attack to kill estrogen receptor positive (ER+) breast cancer cells undergoing hormonal therapy: Attenuated autophagy and induction of apoptosis

In a recent study, we identified the dephosphorylated form of BimEL as a key death effector of antiestrogen treatment of ER+ breast cancer cells and further showed that MEK1/MAPK1/2 blockade was required to produce high levels of dephosphorylated BimEL, particularly under conditions of insulin like growth factor 1 (IGF1) stimulation (Periyasamy-Thandavan et al., Breast Cancer Res. 14, 2012). Studies by others have identified MEK1/MAPK1/2 activation as essential to autophagy, a catabolic process induced by multiple stresses including ROS, ceramide accumulation, and nutrient deprivation. Autophagy induction results in autophagosome formation, trafficking of damaged proteins and mitochondria to the autophagosomes, and ultimately fusion with the lysosomes resulting in autolysosome formation. The autolysosome and its contents are degraded by the hydrolytic enzymes of the lysosome. Of particular interest to antiestrogen treatment of breast cancer, we and others have shown that pro-survival autophagy facilitates the emergence of antiestrogen resistant breast cancer cells. Thus, we are keenly interested in how MEK1/MAPK1/2 signaling affects pro-survival autophagy and if MEK blockade would be an effective approach toward blocking pro-survival autophagy in ER+ breast cancer cells undergoing hormonal treatment. In this study, we hypothesized that the requirement of MEK1/MAPK1/2 for pro-survival autophagy is due, in part, to its role in blocking the intracellular accumulation of dephosphorylated BimEL. To test this hypothesis, we modulated the expression of dephosphorylated BimEL with either a BimEL cDNA expression vector, siRNA targeting of BimEL, or MEK1 blockade with the small molecule inhibitor U0126 and determined the levels of the autophagic flux in ER+ breast cancer cells undergoing antiestrogen treatment. The determination of autophagic flux was made by comparing the levels of two proteins involved in autophagy -the LC3 /Atg8 and p62 (SQSTM1) proteins- in cell populations undergoing the different treatments in the presence or absence of chloroquine (CQ). The lipidated form of LC3, designated LC3II, is typically increased in cells undergoing autophagy, facilitates the formation of the mature autophagosomal membranes, and is subsequently degraded in the autolysosome. The p62 protein is required for the delivery of ubiquitinated protein complexes to the autophagosome and is degraded along with the ubiquitinated complex of proteins. CQ is a lysosomotrophic agent routinely used in autophagic flux assays because it blocks the turnover of autolysosomes with accumulation of LC3 II and p62, allowing the total levels of LC3II and p62 to be ascertained under all treatment conditions. These studies showed that siRNA targeting of BimEL increased basal and tamoxifen-induced autophagy in ER+ MCF-7 breast cancer cells. In contrast, the overexpression of dephosphorylated BimEL led to an increase in LC3 II and p62 levels due to a significant attenuation of autophagic flux (approximately 50%) in antiestrogen-treated cell populations. Current studies are focused on the mechanism of BimEL-mediated blockade of pro-survival autophagy, with the long term goal of optimizing this “downstream effector” function of MEK1/MAPK1/2 blockade in ER+ breast cancer cells for improved therapeutic outcome.

Citation Format: S. Takhar, M. Manning, A. Eason, M. Dix, S. Periyasamy-Thandavan, R. Padi, E. Bieberich, W. Hill, D. Browning, V. Ganapathy, M. Thangaraju, P. V. Schoenlein. MEK inhibitors mount a two-pronged attack to kill estrogen receptor positive (ER+) breast cancer cells undergoing hormonal therapy: Attenuated autophagy and induction of apoptosis. [abstract]. In: Proceedings of the AACR Special Conference on RAS Oncogenes: From Biology to Therapy; Feb 24-27, 2014; Lake Buena Vista, FL. Philadelphia (PA): AACR; Mol Cancer Res 2014;12(12 Suppl):Abstract nr B50. doi: 10.1158/1557-3125.RASONC14-B50

Abstract 2461: SLC5A8: A strategic target for advanced metastatic breast cancer

Despite intense efforts and great advances in cancer research, breast cancer remains the leading cause of death among women worldwide. Most breast cancer-related deaths are not due to cancer at the primary site, but rather due to metastasis, a process in which cancer cells spread from the primary site to distant secondary sites like lung, bones and brain. However, the molecular mechanism by which tumor cells invade from primary tumor site to distant metastasis has not been identified. Recently, we identified a tumor suppressor SLC5A8, which is not only prevent the mammary tumor incidence but also blocks tumor-metastasis by inactivating several metastasis-deriving molecules. SLC5A8, a transporter for small-chain fatty acids (SCFA) and monocarboxylates, is silenced in more than 10 different types of cancers including breast cancer. In breast cancer, irrespective of estrogen-receptor status SLC5A8 is inactivated in more than 90% of breast tumor tissues and in breast cancer cell lines. Ectopic expression of SLC5A8 in human breast cancer cells leads to translocation of the anti-apoptotic protein survivin to the plasma membrane through protein-protein interaction, thereby depleting nuclear survivin level. Further, tetracycline-inducible SLC5A8 expression in human breast cancer cells significantly reduced mammary tumor growth. In addition, functional inactivation of SLC5A8 in human immortalized normal mammary epithelial cells by lentivirus expressing shRNA showed differential regulation of genes that are involved in cellular transformation, oncogenesis, epithelial-mesenchymal-transition (EMT) and tumor metastasis. This is a totally unexpected finding and represents first of its kind for a plasma membrane transporter where mere expression itself, independent of its substrates, leads to tumor suppression. Reinforcing our findings further, deletion of Slc5a8 in mice is associated with increased stem/progenitor cells and mammary gland hyperplasia. By crossing the Slc5a8-null mice with spontaneous mouse mammary tumor mice, we observed increased cancer-initiating stem cells, early onset of mammary tumor formation and increased incidence of lung metastasis. More fascinatingly, mammary gland-specific overexpression of Slc5a8 or induction of endogenous Slc5a8 expression efficiently protects mice from breast cancer and associated lung metastasis resulting in extended life-span. Overall, our study provide a strong mechanism based evidence that SLC5A8 is a novel tumor suppressor in the mammary epithelium and it could be used as a potential new therapeutic target for treatment of breast cancer.

Citation Format: Sabarish Ramachandran, Rajneesh Pathania, Ravi N. Padia, Selvakumar Elangovan, Veena Coothankandaswamy, Puttur D. Prasad, Vadivel Ganapathy, Muthusamy Thangaraju. SLC5A8: A strategic target for advanced metastatic 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 2461. doi:10.1158/1538-7445.AM2014-2461

Abstract 3928: Genetic deletion or pharmacologic blockade of the amino acid transporter Slc6a14 in mice suppresses breast cancer induced by Polyoma middle T oncogene

Tumor cells have an increased need for amino acids. Mammalian cells cannot synthesize essential amino acids; they must obtain these amino acids via specific transporters. Glutamine, though a non-essential amino acid, is critical for tumor cells (glutamine addiction). Entry of amino acids into tumor cells is enhanced by upregulation of specific transporters. If we can interfere with the entry of amino acids into tumor cells, we should be able to starve these cells to death. If the transporters that are specifically induced in tumor cells are identified, blockade of the induced transporters would constitute a logical strategy for cancer treatment. Mammalian cells express ∼40 amino acid transporters, expressed in different combinations and in a cell type-specific manner. Among them, SLC6A14 is unique in that it transports all essential amino acids as well as glutamine, and is expressed only at low levels in normal tissues, but induced in colon cancer and in ER+ breast cancer. Tumor cells in these cancers upregulate SLC6A14 to meet their increased demand for essential amino acids and glutamine, indicating that SLC6A14 drives their “glutamine addiction.” We have now established the potential of this transporter as a drug target for breast cancer treatment using genetic and pharmacologic approaches. For this, we first generated Slc6a14-/- mouse. The Slc6a14 gene is located on X chromosome. Deletion of the gene is not lethal and there is no overt phenotype in hemizygous males (-/y) or in homozygous females (-/-). We then examined the progression of breast cancer in Polyoma middle T antigen (Py-MT) Tg mouse on Slc6a14+/+ and Slc6a14-/- background. Deletion of Slc6a14 markedly suppressed breast cancer and lung metastasis induced by the Py-MT oncogene. We have also identified -methyl-L-tryptophan (-MLT) as a selective blocker of Slc6a14. We investigated the consequences of pharmacologic blockade of Slc6a14 on Py-MT-induced breast cancer with oral administration of -MLT (1 mg/ml in drinking water). The blocker was able to suppress breast cancer to a marked extent. Py-MT-induced breast tumors showed robust upregulation of Slc6a14; however, the tumors also showed upregulation of Slc7a5/Slc3a2, another amino acid transporter. Therefore, we examined the interaction of -MLT with Slc7a5/Slc3a2 and found that while -MLT is a blocker of Slc6a14, it is a transportable substrate for Slc7a5/Slc3a2, demonstrating that only the function of Slc6a14 is selectively blocked by -MLT. We conclude that blockade of Slc6a14 is a viable strategy for treatment of certain specific subtypes of breast cancer (e.g., ER-positive) that are associated with upregulation of the transporter.

Citation Format: Babu Ellappan, Yangzom D. Bhutia, Muthusamy Thangaraju, Puttur D. Prasad, Vadivel Ganapathy. Genetic deletion or pharmacologic blockade of the amino acid transporter Slc6a14 in mice suppresses breast cancer induced by Polyoma middle T oncogene. [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 3928. doi:10.1158/1538-7445.AM2014-3928

Abstract 4106: Curcumin inhibit PhIP induced cytotoxicity by inhibiting ROS production, DNA strand breaks and DNA adducts formation in MCF 10A cells

PhIP is a known food carcinogen found in well done meat which causes several cancers including breast cancer. PhIP metabolites produce DNA adduct and DNA strand breaks. Curcumin, obtained from the rhizome of Curcuma longa, has potent anticancer activity. So far none of the study demonstrates the inhibition of PhIP induced cytotoxicity by the co-treatment of Curcumin in normal breast epithelial cells in vitro. Therefore, we developed a model system using the MCF 10A normal breast epithelial cells to study the PhIP cytotoxicity and if cells are co-cultured with Curcumin and PhIP how it affects. Consequently, the core signaling pathways have been explored to evaluate the efficacy of Curcumin. In this study, the effectiveness of Curcumin was investigated in MCF 10A cells along with PhIP. The cytotoxic ability was detected with MTT assay, ROS activation by DCF, the influence of the cell cycle was checked with flow cytometry, DNA damage by comet assay, DNA adduct formation by anti-PhIP DNA primary, and apoptosis by Annexin-V-FITC staining. The influence of the core signaling pathways was evaluated by RT PCR and/or Western blotting which included Nrf2 (GSR, GPX, NQO1), FOXO (Catalase, GADD45, PRDX3) targets; DNA repair genes/proteins BRCA1, H2AFX and PARP-1; and tumor suppressor P16 gene expression. PhIP cytotoxicity induced the expression of various antioxidant and DNA repair genes on MCF-10A cells but co-treatment of Curcumin retained its expression level similar to untreated groups. Additionally, Curcumin co- treatment increased the expression level of tumor suppressor expression gene P-53. Expression of antioxidants genes was induced by PhIP whereas Curcumin significantly suppress the PhIP induced ROS activation, DNA strand breaks and DNA adduct formation and consequently inhibited the cell death. In conclusion, Curcumin appears to be effective to inhibit P450 mediated ROS production and PhIP-DNA adducts which consequently reduces DNA damage.

Citation Format: Ashok K. Jain, Abhilash Samykutty, Carissa L. Jackson, Muthusamy Thangaraju, Darren D. Browning. Curcumin inhibit PhIP induced cytotoxicity by inhibiting ROS production, DNA strand breaks and DNA adducts formation in MCF 10A cells. [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 4106. doi:10.1158/1538-7445.AM2014-4106

The niacin/butyrate receptor GPR109A suppresses mammary tumorigenesis by inhibiting cell survival

GPR109A, a G-protein-coupled receptor, is activated by niacin and butyrate. Upon activation in colonocytes, GPR109A potentiates anti-inflammatory pathways, induces apoptosis, and protects against inflammation-induced colon cancer. In contrast, GPR109A activation in keratinocytes induces flushing by activation of Cox-2-dependent inflammatory signaling, and the receptor expression is upregulated in human epidermoid carcinoma. Thus, depending on the cellular context and tissue, GPR109A functions either as a tumor suppressor or a tumor promoter. However, the expression status and the functional implications of this receptor in the mammary epithelium are not known. Here, we show that GPR109A is expressed in normal mammary tissue and, irrespective of the hormone receptor status, its expression is silenced in human primary breast tumor tissues, breast cancer cell lines, and in tumor tissues of three different murine mammary tumor models. Functional expression of this receptor in human breast cancer cell lines decreases cyclic AMP production, induces apoptosis, and blocks colony formation and mammary tumor growth. Transcriptome analysis revealed that GPR109A activation inhibits genes, which are involved in cell survival and antiapoptotic signaling, in human breast cancer cells. In addition, deletion of Gpr109a in mice increased tumor incidence and triggered early onset of mammary tumorigenesis with increased lung metastasis in MMTV-Neu mouse model of spontaneous breast cancer. These findings suggest that GPR109A is a tumor suppressor in mammary gland and that pharmacologic induction of this gene in tumor tissues followed by its activation with agonists could be an effective therapeutic strategy to treat breast cancer.

Transporters and receptors for short-chain fatty acids as the molecular link between colonic bacteria and the host

The mutually beneficial relationship between colonic bacteria and the host has been recognized but the molecular aspects of the relationship remain poorly understood. Dietary fiber is critical to this relationship. The short-chain fatty acids acetate, propionate and butyrate, generated by bacterial fermentation of dietary fiber, serve as messengers between colonic bacteria and the host. The beneficial effects of these bacterial metabolites in colon include, but are not limited to, suppression of inflammation and prevention of cancer. Recent studies have identified the plasma membrane transporter SLC5A8 and the cell-surface receptors GPR109A and GPR43 as essential for the biologic effects of short-chain fatty acids in colon. These three proteins coded by the host genome provide the molecular link between colonic bacteria and the host.

Sodium-coupled vitamin C transporter (SVCT2): expression, function, and regulation in intervertebral disc cells

BACKGROUND CONTEXT

Vitamin C (ascorbic acid [AA]) is essential for the synthesis of collagen and also acts as an antioxidant in the intervertebral disc (IVD). However, there is very little information currently available on the identity of the transporter that facilitates AA entry into IVD cells and the factors that mediate the transport process.

PURPOSE

To investigate the expression of the two known isoforms of Na+ -coupled vitamin C transporter, SVCT1 and SVCT2, in IVD cells and its regulation by insulin-like growth factor 1 (IGF-1) and the steroid hormone dexamethasone.

STUDY DESIGN

To identify the expression and functional activity of the sodium-dependent vitamin C transporter (SVCT) in the IVD.

METHODS

Uptake studies were carried out with rabbit annulus fibrosis and nucleus pulposus cells in 24-well plates using [14C]-AA. To characterize SVCT transporter, uptake was done in the presence and absence of Na+ in the uptake buffer. Time dependency, Na+ activation kinetics, saturation kinetics, and substrate selectivity studies were performed. Regulatory studies were performed in the presence of IGF-1 and the steroid hormone dexamethasone. Gene expression was analyzed by quantitative polymerase chain reaction.

RESULTS

Our real-time polymerase chain reaction results showed the presence of SVCT2 but not SVCT1 in IVD cells. Uptake of vitamin C in IVD cells is Na+ dependent and saturable. The Michaelis constant for the process is 96±11 μM. The activation of vitamin C uptake by Na+ exhibits a sigmoidal relationship, indicating involvement of more than one Na+ in the activation process. The uptake system does not recognize any other water-soluble vitamin as a substrate. Immunocytochemical analysis shows robust expression of SVCT2 protein in IVD cells. The growth factors IGF-1 and the steroid hormone dexamethasone upregulate the expression of SVCT2 in IVD cells.

CONCLUSIONS

Our studies demonstrate that the active SVCT2 is expressed in IVD cells and that the expression of this transporter is regulated by growth factors IGF-1 and dexamethasone.

Abstract 1725: HDAC inhibition induces Bim expression and apoptosis in breast cancer cells undergoing paclitaxel or antiestrogen treatment

Paclitaxel functions by preventing microtubule degradation, leading to mitotic arrest and apoptotic death. Of particular interest, paclitaxel-induced death in breast cancer cells is dependent, in part, on the levels of BimEL, a pro-apoptotic member of the Bcl-2 family of proteins. In addition, our recent studies demonstrated that BimEL is required for 4-hydroxytamoxifen-induced apoptosis of estrogen receptor positive (ER+) MCF-7 breast cancer cells [Breast Cancer Res. 2012 Mar 19;14(2):R52]. In contrast, we demonstrated low-level BimEL expression in ER+ T47D breast cancer cells that do not undergo antiestrogen-induced apoptosis. Thus, low-level BimEL expression in ER+ breast cancer may predict a poor apoptotic threshold which ultimately would facilitate the development of acqured resistance to paclitaxel, as well as antiestrogen therapy. Based on the ability of HDAC inhibitors to increase the transcription of pro-apoptotic genes, we hypothesized that the HDAC inhibitor suberoylanilide hydroxamic acid (SAHA) would increase BimEL expression in T47D breast cancer cells and induce a robust apoptotic response to paclitaxel chemotherapy and antiestrogen treatment. In this study, we now demonstrate that SAHA does significantly up-regulate BimEL expression in T47D cells, as well as in MCF-7 cells. Concomitant with BimEL upregulation, SAHA sensitizes T47D and MCF-7 cells to paclitaxel-induced apoptosis. Similarly, SAHA sensitizes T-47D cells to antiestrogen-induced apoptosis, while augmenting the level of antiestrogen-induced apoptosis in MCF-7 cells. These studies indicate that the pro-apoptotic protein BimEL is required for SAHA-induced sensitization of breast cancer cells to paclitaxel and/or antiestrogen-induced apoptosis. Currently, siRNA studies are being conducted to determine if BimEL is a key death effector in response to SAHA treatment and if the increased death from SAHA and paclitaxel or SAHA and antiestrogens is synergistic or additive. Our results provide strong support for the use of HDAC inhibitors when designing novel combination therapies to reduce the emergence of acquired resistance in breast cancer cells undergoing chemo- or antihormonal therapy.

Acknowledgement: this work was supported by teh MCG foundation and NIHRO1 CA121438 to P.V.S.

Citation Format: Aric Berning, Alexander Eason, Nathan Gilley, Suchreet Takhar, Sally ElShafey, Muthusamy Thangaraju, Patricia V. Schoenlein. HDAC inhibition induces Bim expression and apoptosis in breast cancer cells undergoing paclitaxel or antiestrogen treatment. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1725. doi:10.1158/1538-7445.AM2013-1725