Contribution of Proteomics in Transplantation: Identification of Injury and Rejection Markers

Solid organ transplantation saves thousands of lives suffering from end-stage diseases. Although early transplants experienced acute organ injury, medical breakthroughs, such as tissue typing, and use of immunosuppressive agents have considerably improved graft survival. However, the overall incidence of allograft injury and chronic rejection remains high. Often the clinical manifestations of organ injury or rejection are nonspecific and late. Current requirement for successful organ transplantation is the identification of reliable, accurate, disease-specific, noninvasive methods for the early diagnosis of graft injury or rejection. Development of noninvasive techniques is important to allow routine follow-ups without the discomfort and risks associated with a graft biopsy. Multiple biofluids have been successfully tested for the presence of potential proteomic biomarkers; these include serum, plasma, urine, and whole blood. Kidney transplant research has provided significant evidence to the potential of proteomics-based biomarkers for acute and chronic kidney rejection, delayed graft function, early detection of declining allograft health. Multiple proteins have been implicated as biomarkers; however, recent observations implicate the use of similar canonical pathways and biofunctions associated with graft injury/rejection with altered proteins as potential biomarkers. Unfortunately, the current biomarker studies lack high sensitivity and specificity, adding to the complexity of their utility in the clinical space. In this review, we first describe the high-throughput proteomics technologies and then discuss the outcomes of proteomics profiling studies in the transplantation of several organs. Existing literature provides hope that novel biomarkers will emerge from ongoing efforts and guide physicians in delivering specific therapies to prolong graft survival.

Single-cell RNA sequencing reveals peripheral blood mononuclear immune cell landscape associated with operational tolerance in a kidney transplant recipient

Operational tolerance (OT) after kidney transplantation is defined as stable graft acceptance without the need for immunosuppression therapy. However, it is not clear which cellular and molecular pathways are driving tolerance in these patients. In this first-of-its-kind pilot study, we assessed the immune landscape associated with OT using single-cell analyses. Peripheral mononuclear cells from a kidney transplant recipient with OT (Tol), 2 healthy individuals (HC), and a kidney transplant recipient with normal kidney function on standard-of-care immunosuppression (SOC) were evaluated. The immune landscape of the Tol was drastically different from that of SOC and emerged closer to the profile of HC. TCL1A+ naive B cells and LSGAL1+ regulatory T cells (Tregs) were in higher proportions in Tol. We were unable to identify the Treg subcluster in SOC. The ligand-receptor analysis in HC and Tol identified interactions between B cells, and Tregs that enhance the proliferation and suppressive function of Tregs. SOC reported the highest proportion of activated B cells with more cells in the G2M phase. Our single-cell RNA sequencing study identified the mediators of tolerance; however, it emphasizes the requirement of similar investigations on a larger cohort to reaffirm the role of immune cells in tolerance.

European Society for Organ Transplantation Consensus Statement on Biomarkers in Liver Transplantation

Currently, one-year survival following liver transplantation (LT) exceeds 90% in large international registries, and LT is considered definitive treatment for patients with end-stage liver disease and liver cancer. Recurrence of disease, including hepatocellular carcinoma (HCC), significantly hampers post-LT outcomes. An optimal approach to immunosuppression (IS), including safe weaning, may benefit patients by mitigating the effect on recurrent diseases, as well as reducing adverse events associated with over-/under-IS, including chronic kidney disease (CKD). Prediction of these outcome measures-disease recurrence, CKD, and immune status-has long been based on relatively inaccurate clinical models. To address the utility of new biomarkers in predicting these outcomes in the post-LT setting, the European Society of Organ Transplantation (ESOT) and International Liver Transplant Society (ILTS) convened a working group of experts to review literature pertaining to primary disease recurrence, development of CKD, and safe weaning of IS. Summaries of evidence were presented to the group of panelists and juries to develop guidelines, which were discussed and voted in-person at the Consensus Conference in Prague November 2022. The consensus findings and recommendations of the Liver Working Group on new biomarkers in LT, clinical applicability, and future needs are presented in this article.

MYB sustains hypoxic survival of pancreatic cancer cells by facilitating metabolic reprogramming

Extensive desmoplasia and poor vasculature renders pancreatic tumors severely hypoxic, contributing to their aggressiveness and therapy resistance. Here, we identify the HuR/MYB/HIF1α axis as a critical regulator of the metabolic plasticity and hypoxic survival of pancreatic cancer cells. HuR undergoes nuclear-to-cytoplasmic translocation under hypoxia and stabilizes MYB transcripts, while MYB transcriptionally upregulates HIF1α. Upon MYB silencing, pancreatic cancer cells fail to survive and adapt metabolically under hypoxia, despite forced overexpression of HIF1α. MYB induces the transcription of several HIF1α-regulated glycolytic genes by directly binding to their promoters, thus enhancing the recruitment of HIF1α to hypoxia-responsive elements through its interaction with p300-dependent histone acetylation. MYB-depleted pancreatic cancer cells exhibit a dramatic reduction in tumorigenic ability, glucose-uptake and metabolism in orthotopic mouse model, even after HIF1α restoration. Together, our findings reveal an essential role of MYB in metabolic reprogramming that supports pancreatic cancer cell survival under hypoxia.

Dynamics of age- versus therapy-related clonal hematopoiesis in long-term survivors of pediatric cancer

We present the first comprehensive investigation of clonal hematopoiesis (CH) in 2,860 long-term survivors of pediatric cancer with a median follow-up time of 23.5 years. Deep-sequencing over 39 CH-related genes reveals mutations in 15% of the survivors, significantly higher than the 8.5% in 324 community controls. CH in survivors is associated with exposures to alkylating agents, radiation, and bleomycin. Therapy-related CH shows significant enrichment in STAT3, characterized as a CH-gene specific to Hodgkin lymphoma survivors, and TP53. Single-cell profiling of peripheral blood samples revealed STAT3 mutations predominantly present in T-cells and contributed by SBS25, a mutational signature associated with procarbazine exposure. Serial-sample tracking reveals that larger clone size is a predictor for future expansion of age-related CH clones, while therapy-related CH remains stable decades post-treatment. These data depict the distinct dynamics of these CH subtypes and support the need for longitudinal monitoring to determine the potential contribution to late effects.

Biphasic transcriptional and posttranscriptional regulation of MYB by androgen signaling mediates its growth control in prostate cancer

MYB, a proto-oncogene, is overexpressed in prostate cancer (PCa) and promotes its growth, aggressiveness, and resistance to androgen-deprivation therapy. Here, we examined the effect of androgen signaling on MYB expression and delineated the underlying molecular mechanisms. Paralleling a dichotomous effect on growth, low-dose androgen induced MYB expression at both transcript and protein levels, whereas it was suppressed in high-dose androgen-treated PCa cells. Interestingly, treatment with both low- and high-dose androgen transcriptionally upregulated MYB by increasing the binding of androgen receptor to the MYB promoter. In a time-course assay, androgen induced MYB expression at early time points followed by a sharp decline in high-dose androgen-treated cells due to decreased stability of MYB mRNA. Additionally, profiling of MYB-targeted miRNAs demonstrated significant induction of miR-150 in high-dose androgen-treated PCa cells. We observed a differential binding of androgen receptor on miR-150 promoter with significantly greater occupancy recorded in high-dose androgen-treated cells than those treated with low-dose androgen. Functional inhibition of miR-150 relieved MYB suppression by high-dose androgen, while miR-150 mimic abolished MYB induction by low-dose androgen. Furthermore, MYB-silencing or miR-150 mimic transfection suppressed PCa cell growth induced by low-dose androgen, whereas miR-150 inhibition rescued PCa cells from growth repression by high-dose androgen. Similarly, we observed that MYB silencing suppressed the expression of androgen-responsive, cell cycle-related genes in low-dose androgen-treated cells, while miR-150 inhibition increased their expression in cells treated with high-dose androgen. Overall, these findings reveal novel androgen-mediated mechanisms of MYB regulation that support its biphasic growth control in PCa cells.

Abstract 2353: Biphasic regulation of MYB by androgen signaling mediates its growth-promoting and repressive effects in prostate cancer cells

Prostate cancer is the most frequently diagnosed malignancy affecting millions of men worldwide. It is also the second leading cause of cancer-related death in American men. Androgen signaling plays a central role in prostate cancer development but results in growth inhibition at high doses. Mechanisms underlying such biphasic effect of androgens are not well understood. We recently identified MYB as an aberrantly expressed gene in prostate cancer cells, which promoted their growth and aggressive behavior. We also observed that MYB induced ligand-independent activation of androgen receptor (AR) and influenced its binding to selective target genes to promote castration-resistance. The goal of the present study was to examine the regulatory crosstalk between MYB and AR in prostate cancer cells. We observed that while MYB had no significant effect on AR expression, androgen (dihydrotestosterone, DHT) treatment resulted in a dose-dependent biphasic regulation of MYB at both transcript and protein levels correlating with its effect on the growth of prostate cancer cells. Interestingly, we observed that the treatment of prostate cancer cells with either low (1 nM) or high (100 nM) doses of DHT enhanced the transcriptional activity of MYB promoter. In silico analysis identified two potential androgen-responsive elements (AREs) in MYB promoter and AR bound more efficiently to the proximal sequence as determined by chromatin immunoprecipitation (ChIP). In a time-course experiment, we observed that both low and high doses of DHT increased MYB transcript and protein levels at early time points, which decreased sharply after 12 h in high dose DHT-treated prostate cancer cells. RNA stability assay following treatment with actinomycin D (inhibitor of transcription) showed decreased MYB mRNA half-life in prostate cancer cells at late time points when treated with high dose DHT. Profiling of MYB-targeted miRNAs showed significantly greater induction of miR-150 in high-dose DHT-treated prostate cancer cells than those treated with low-dose DHT. Two AREs were predicted in the 1000 bp upstream sequence of miR-150 transcription start site and AR binding was confirmed by ChIP assay. Functional inhibition of miR-150 using anti-miR relieved MYB suppression by high-dose DHT and promoted the growth of prostate cancer cells. Further, transfection of prostate cancer cells by miR-150 mimic reduced endogenous MYB levels and led to repression of growth of prostate cancer cells. Overall, our findings reveal a novel mechanism of MYB regulation that mediates, at least in part, the biphasic effect of androgens on the growth of prostate cancer cells.

Citation Format: Srijan Acharya, Shashi Anand, Mohammad Aslam Khan, Haseeb Zubair, Sanjeev Kumar Srivastava, Seema Singh, Ajay Pratap Singh. Biphasic regulation of MYB by androgen signaling mediates its growth-promoting and repressive effects in prostate cancer cells [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 2353.

Abstract 499: Accelerated clonal hematopoiesis in survivors of childhood cancer: A report for the St. Jude Lifetime Cohort Study

Survivors of childhood cancer are at risk for a spectrum of adverse outcomes including hematological malignancies and cardiovascular diseases, which in other populations have been associated with clonal hematopoiesis (CH), an age-related clonal expansion of hematopoietic stem cells. Here we present the first comprehensive CH analysis including 2,872 pediatric cancer survivors from the St. Jude Lifetime Cohort (median follow-up of 26 years from cancer diagnosis; median age of 31 years at blood draw) using deep sequencing (10,000 ×) over 39 CH genes on DNA derived from peripheral blood. As a comparison group, 324 age-, sex- and race/ethnicity-frequency-matched community controls (median age of 35 years at blood draw) were also analyzed. To detect rare CH variants, a machine-learning approach was applied, which characterized true variants as outliers in a genomic context-specific error profile. Digital droplet PCR validation was performed for 543 variants (323 positive [allele frequency: median 0.003, range 0.001 to 0.255] and 220 negative) out of 1,450 putative variants. The 907 untested variants were inferred using the 543 experimentally validated variants’ status as a training set. Analyses considered mutation status by the 555 positive variants and clinical data including age, sex, and detailed cancer treatment exposures. CH was detected in 15% (95% Confidence Interval (CI): 13.7 to 16.3) of survivors and 8.6% (95% CI: 5.6 to 11.7) of controls in an age-dependent manner: 10.6% (survivors) vs. 6.3% (controls) for ages in year 18 - 29; 13.5% vs. 5.8% for 30 - 39; 26.3% vs. 13.2% for 40 - 49; 28.1% vs. 17.2% for > 50. We also observed that the alterations in DNMT3A, TP53, STAT3, KRAS and TET2 became more prevalent as the survivors aged: combined proportion for the 5 genes, 61% for ages in year < 30; 72% for 30 - 40; 77% for 40 - 50; 87% for > 50. Analysis of longitudinal samples available for 73 survivors with 180 time points (median interval 4.6 years [range: 2.07 to 8.0 years]) confirmed that clones with these gene mutations had a higher growth rate than those without (p=0.034), suggesting fitness advantages in hematopoietic stem cell context. Multivariable analysis adjusted for treatment indicated that CH development is associated with cumulative dose of alkylating agents (Odds Ratio (OR) for 1st tertile 1.77 [95% CI: 1.22 to 2.57], 2nd tertile 2.72 [95% CI: 1.83 to 4.04], and 3rd tertile 2.92 [95% CI: 2.03 to 4.02], relative to the unexposed) and estimated radiotherapy-dose to active bone marrow (OR for 1st tertile 0.98 [95% CI: 0.68 to 1.40], 2nd tertile 1.06 [0.77 to 1.47], and 3rd tertile 1.57 [1.15 to 2.14], relative to the unexposed), supporting the hypothesis that CH development in survivors is primarily driven by prior therapy. This study identified accelerated CH development in pediatric cancer survivors, which may represent an important genomic biomarker predictive of future adverse health risks.

Citation Format: Kohei Hagiwara, Zhaoming Wang, Haseeb Zubair, John Easton, Heather L. Mulder, Xiaotu Ma, Kristen K. Ness, Zhenghong Li, Daniel A. Mulrooney, Carmen L. Wilson, Yutaka Yasui, Melissa M. Hudson, Leslie L. Robison, Jinghui Zhang. Accelerated clonal hematopoiesis in survivors of childhood cancer: A report for the St. Jude Lifetime Cohort Study [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 499.

Abstract 2351: MYB plays an essential role in the hypoxic survival of pancreatic cancer cells via its impact on metabolic reprogramming

Pancreatic ductal adenocarcinoma exhibits high degree of intratumoral hypoxia due to its unique histopathological features contributing to its extremely aggressive nature and unusual chemoresistance. It is however not yet very clear what drives and sustains the growth of pancreatic cancer cells under an adverse hypoxic tumor microenvironment. Previously we reported that MYB was overexpressed in pancreatic cancer cells and supported the tumorigenicity and metastatic progression of pancreatic cancer cells. Here, we examined the role of MYB in hypoxic survival of pancreatic cancer cells. We found that the silencing of MYB expression in pancreatic cancer cells severely reduced their growth under hypoxia whereas its forced overexpression promoted hypoxic survival. We also observed that MYB was upregulated under hypoxia and its silencing was associated with a reduced accumulation of hypoxia inducible factor-1 α (HIF1α). Additionally, we confirmed HIF1α as a direct transcriptional target of MYB and its transcripts level and promoter activity correlated positively with MYB expression under both normoxia and hypoxia. Interestingly, restoration of HIF1α expression in MYB-silenced cells was not sufficient to rescue their survival under hypoxia. MYB knockdown pancreatic cancer cells failed to optimally reprogram their metabolism under hypoxia to meet their energetic and biosynthetic demands despite restored HIF1α overexpression. Specifically, MYB knockdown cells exhibited a large decrease in intracellular glucose and several metabolic intermediates of glycolysis, TCA cycle, and amino acid metabolism, whereas glycogenolysis and pentose phosphate pathway metabolites were increased. MYB silencing also altered the expression of several metabolic genes, including established hypoxia-responsive gene targets. MYB co-occupied the promoter regions of GLUT3, HK2, PFKL, ENO2, and MCT4 with HIF1α and its silencing reduced HIF1α binding to these promoters despite its forced overexpression. We also confirmed MYB interaction with HIF1α and p300 and demonstrated enhanced recruitment of p300 to these gene promoters in MYB-overexpressing pancreatic cancer cells. Altogether, our studies suggest that MYB acts as major regulator of metabolic reprogramming and HIF1α signaling and thus acts as an important driver of hypoxic survival of pancreatic cancer cells.

Citation Format: Shashi Anand, Mohammad Aslam Khan, Haseeb Zubair, Sarabjeet Kour Sudan, Kunwar Somesh Vikramdeo, Sachin Kumar Deshmukh, Shafquat Azim, Sanjeev Kumar Srivastava, Seema Singh, Ajay Pratap Singh. MYB plays an essential role in the hypoxic survival of pancreatic cancer cells via its impact on metabolic reprogramming [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 2351.

MYB interacts with androgen receptor, sustains its ligand-independent activation and promotes castration resistance in prostate cancer

BACKGROUND

Aberrant activation of androgen receptor signalling following castration therapy is a common clinical observation in prostate cancer (PCa). Earlier, we demonstrated the role of MYB overexpression in androgen-depletion resistance and PCa aggressiveness. Here, we investigated MYB-androgen receptor (AR) crosstalk and its functional significance.

METHODS

Interaction and co-localization of MYB and AR were examined by co-immunoprecipitation and immunofluorescence analyses, respectively. Protein levels were measured by immunoblot analysis and enzyme-linked immunosorbent assay. The role of MYB in ligand-independent AR transcriptional activity and combinatorial gene regulation was studied by promoter-reporter and chromatin immunoprecipitation assays. The functional significance of MYB in castration resistance was determined using an orthotopic mouse model.

RESULTS

MYB and AR interact and co-localize in the PCa cells. MYB-overexpressing PCa cells retain AR in the nucleus even when cultured under androgen-deprived conditions. AR transcriptional activity is also sustained in MYB-overexpressing cells in the absence of androgens. MYB binds and promotes AR occupancy to the KLK3 promoter. MYB-overexpressing PCa cells exhibit greater tumorigenicity when implanted orthotopically and quickly regain growth following castration leading to shorter mice survival, compared to those carrying low-MYB-expressing prostate tumours.

CONCLUSIONS

Our findings reveal a novel MYB-AR crosstalk in PCa and establish its role in castration resistance.

Abstract 5070: LIN28A-mediated repression of Let-7a is involved in resistin-induced STAT3 upregulation in breast cancer cells and supports growth and stemness properties

Breast cancer (BC) is the most frequently diagnosed malignancy and continues to be the second leading cause of cancer-related death in women in the United States. Dysregulation of Let-7 family microRNAs is observed in BC and associated with disease pathogenesis. Previously, we reported a significant increase in serum levels of resistin in BC patients as compared to the healthy individuals. Moreover, this increase was significantly greater in BC patients of African American background as compared to those of European descent. We also demonstrated that treatment of BC cells with resistin promoted their growth, aggressiveness, stemness and chemoresistance by inducing the expression and activation of STAT3. Here we present data to show that resistin induces STAT3 expression in BC cells in a LIN28A and Let-7a-dependent manner. Treatment of BC cells with resistin led to the most significant decrease in the expression of Let-7a among other Let-7 family members. Furthermore, resistin treatment also induced the expression of LIN28A at both transcript and protein levels and its silencing abrogated resistin-mediated Let-7a suppression. Let-7a restoration or LIN28A silencing abolished the resistin-induced growth, clonogenicity and sphere-forming ability of BC cells. Restoration of Let-7a suppressed the expression of several genes associated with growth, survival and stemness. Ingenuity Pathway Analysis suggested STAT3 as a putative central node associated with Let-7a-mediated gene regulation. Immunoblot analysis confirmed that Let-7a restoration dramatically suppressed basal as well as resistin-induced STAT3 expression. STAT3 regulation by Let-7a was further confirmed 3'UTR-reporter assay. Taken together, our findings demonstrate a novel resistin/LIN28A/Let-7a/STAT3 signaling axis regulating the growth and stemness phenotypes of BC cells.

Citation Format: Sachin Kumar Deshmukh, Sanjeev K. Srivastava, Haseeb Zubair, Ajay P. Singh, Seema Singh. LIN28A-mediated repression of Let-7a is involved in resistin-induced STAT3 upregulation in breast cancer cells and supports growth and stemness properties [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5070.

Modulation of the tumor microenvironment by natural agents: implications for cancer prevention and therapy

The development of cancer is not just the growth and proliferation of a single transformed cell, but its surrounding environment also coevolves with it. Indeed, successful cancer progression depends on the ability of the tumor cells to develop a supportive tumor microenvironment consisting of various types of stromal cells. The interactions between the tumor and stromal cells are bidirectional and mediated through a variety of growth factors, cytokines, metabolites, and other biomolecules secreted by these cells. Tumor-stromal crosstalk creates optimal conditions for the tumor growth, metastasis, evasion of immune surveillance, and therapy resistance, and its targeting is being explored for clinical management of cancer. Natural agents from plants and marine life have been at the forefront of traditional medicine. Numerous epidemiological studies have reported the health benefits imparted on the consumption of certain fruits, vegetables, and their derived products. Indeed, a significant majority of anti-cancer drugs in clinical use are either naturally occurring compounds or their derivatives. In this review, we describe fundamental cellular and non-cellular components of the tumor microenvironment and discuss the significance of natural compounds in their targeting. Existing literature provides hope that novel prevention and therapeutic approaches will emerge from ongoing scientific efforts leading to the reduced tumor burden and improve clinical outcomes in cancer patients.

Co-targeting of CXCR4 and hedgehog pathways disrupts tumor-stromal crosstalk and improves chemotherapeutic efficacy in pancreatic cancer

Pancreatic cancer (PC) remains a therapeutic challenge because of its intrinsic and extrinsic chemoresistance mechanisms. Here, we report that C-X-C motif chemokine receptor 4 (CXCR4) and hedgehog pathways cooperate in PC chemoresistance via bidirectional tumor-stromal crosstalk. We show that when PC cells are co-cultured with pancreatic stellate cells (PSCs) they are significantly more resistant to gemcitabine toxicity than those grown in monoculture. We also demonstrate that this co-culture-induced chemoresistance is abrogated by inhibition of the CXCR4 and hedgehog pathways. Similarly, the co-culture-induced altered expression of genes in PC cells associated with gemcitabine metabolism, antioxidant defense, and cancer stemness is also reversed upon CXCR4 and hedgehog inhibition. We have confirmed the functional impact of these genetic alterations by measuring gemcitabine metabolites, reactive oxygen species production, and sphere formation in vehicle- or gemcitabine-treated monocultures and co-cultured PC cells. Treatment of orthotopic pancreatic tumor-bearing mice with gemcitabine alone or in combination with a CXCR4 antagonist (AMD3100) or hedgehog inhibitor (GDC-0449) displays reduced tumor growth. Notably, we show that the triple combination treatment is the most effective, resulting in nearly complete suppression of tumor growth. Immunohistochemical analysis of Ki67 and cleaved caspase-3 confirm these findings from in vivo imaging and tumor measurements. Our findings provide preclinical and mechanistic evidence that a combination of gemcitabine treatment with targeted inhibition of both the CXCR4 and hedgehog pathways improves outcomes in a PC mouse model.

Proteomic Analysis of MYB-Regulated Secretome Identifies Functional Pathways and Biomarkers: Potential Pathobiological and Clinical Implications

Earlier we have shown important roles of MYB in pancreatic tumor pathobiology. To better understand the role of MYB in the tumor microenvironment and identify MYB-associated secreted biomarker proteins, we conducted mass spectrometry analysis of the secretome from MYB-modulated and control pancreatic cancer cell lines. We also performed in silico analyses to determine MYB-associated biofunctions, gene networks, and altered biological pathways. Our data demonstrated significant modulation (p < 0.05) of 337 secreted proteins in MYB-silenced MiaPaCa cells, whereas 282 proteins were differentially present in MYB-overexpressing BxPC3 cells, compared to their respective control cells. Alteration of several phenotypes such as cellular movement, cell death and survival, inflammatory response, protein synthesis, etc. was associated with MYB-induced differentially expressed proteins (DEPs) in secretomes. DEPs from MYB-silenced MiaPaCa PC cells were suggestive of the downregulation of genes primarily associated with glucose metabolism, PI3K/AKT signaling, and oxidative stress response, among others. DEPs from MYB-overexpressing BxPC3 cells suggested the enhanced release of proteins associated with glucose metabolism and cellular motility. We also observed that MYB positively regulated the expression of four proteins with potential biomarker properties, i.e., FLNB, ENO1, ITGB1, and INHBA. Mining of publicly available databases using Oncomine and UALCAN demonstrated that these genes are overexpressed in pancreatic tumors and associated with reduced patient survival. Altogether, these data provide novel avenues for future investigations on diverse biological functions of MYB, specifically in the tumor microenvironment, and could also be exploited for biomarker development.

Dysregulation of metabolic enzymes in tumor and stromal cells: Role in oncogenesis and therapeutic opportunities

Altered cellular metabolism is a hallmark of cancer. Metabolic rewiring in cancer cells occurs due to the activation of oncogenes, inactivation of tumor suppressor genes, and/or other adaptive changes in cell signaling pathways. Furthermore, altered metabolism is also reported in tumor-corrupted stromal cells as a result of their interaction with cancer cells or due to their adaptation in the dynamic tumor microenvironment. Metabolic alterations are associated with dysregulation of metabolic enzymes and tumor-stromal metabolic crosstalk is vital for the progressive malignant journey of the tumor cells. Therefore, several therapies targeting metabolic enzymes have been evaluated and/or are being investigated in preclinical and clinical studies. In this review, we discuss some important metabolic enzymes that are altered in tumor and/or stromal cells, and focus on their role in supporting tumor growth. Moreover, we also discuss studies carried out in various cancers to target these metabolic abnormalities for therapeutic exploitation.

Vitamin B12 deficiency presenting as pseudo-thrombotic microangiopathy: a case report and literature review

Pseudo-thrombotic microangiopathy (pseudo-TMA) is a recognized, yet uncommon, clinical presentation of vitamin B12 deficiency. Patients with pseudo-TMA present with microangiopathic hemolytic anemia (MAHA), thrombocytopenia and schistocytes. They are often misdiagnosed as thrombotic thrombocytopenia purpura (TTP) and receive unnecessary therapy. Here, we report a case of a 60-year-old male who presented with thrombocytopenia and normocytic normochromic anemia. Anemia work-up was remarkable for severe B12 deficiency (<60 pg/mL) and a positive non-immune hemolysis panel. Peripheral smear was reviewed and showed anisocytes, poikilocytes, schistocytes and hypersegmented neutrophils. Vitamin B12 replacement (1000 mcg IM daily) was started, ADAMTS13 activity was sent and daily plasmapheresis was initiated. Over the next 3 days, the patient’s hemoglobin and platelets were stable and the hemolysis panel showed gradual improvement. On day 4, ADAMTS13 activity results came back normal at 61%. Accordingly, plasmapheresis was discontinued, parenteral B12 replacement was continued and that resulted in gradual improvement and eventually cessation of hemolysis and normalization of hemoglobin and platelets. In this patient, parietal cell autoantibodies were positive and so the diagnosis of pernicious anemia was made. Patients with severe vitamin B12 deficiency may present with features mimicking TTP such as MAHA, thrombocytopenia and schistocytosis. An early and accurate diagnosis of pseudo-TMA has a critical clinical impact with respect to administering the correct treatment with vitamin B12 replacement and avoiding, or shortening the duration of, unnecessary therapy with plasmapheresis.

Hypoxia alters the release and size distribution of extracellular vesicles in pancreatic cancer cells to support their adaptive survival

Pancreatic tumors are highly desmoplastic and poorly-vascularized, and therefore must develop adaptive mechanisms to sustain their survival under hypoxic condition. Extracellular vesicles (EV) play vital roles in pancreatic tumor pathobiology by facilitating intercellular communication. Here we studied the effect of hypoxia on the release of EVs and examined their role in adaptive survival of pancreatic cancer (PC) cells. Hypoxia promoted the release of EV in PC cell lines, MiaPaCa and AsPC1, wherein former exhibited a far greater induction. Moreover, a time-dependent, measurable and significant increase was recorded for small EV (SEV) in both the cell lines with only minimal induction observed for medium (MEV) and large EVs (LEV). Similarly, noticeable changes in size distribution of SEV were also recorded with a shift toward smaller average size under extreme hypoxia. Thrombospondin (apoptotic bodies marker) was exclusively detected on LEVs, while Arf6 (microvesicles marker) was mostly present on MEV with some expression in LEV as well. However, CD9 and CD63 (exosome markers) were expressed in both SEV and MEVs with a decreased expression recorded under hypoxia. Among all subfractions, SEV was the most bioactive in promoting the survival of hypoxic PC cells and hypoxia-inducible factor-1α stabilization was involved in heightened EV release under hypoxia and for their potency to promote hypoxic cell survival. Altogether, our findings provide a novel mechanism for the adaptive hypoxic survival of PC cells and should serve as the basis for future investigations on broader functional implications of EV.

Abstract 2609: A novel MYB-AR cross-talk promoting castration-resistance in prostate cancer

Progression of prostate cancer from castration-sensitive to castration-resistant disease is a complex process, which likely involves multiple genetic and epigenetic alterations. Here we report a novel mechanism where MYB acts as a novel binding partner of AR enabling its ligand-independent activation to support castration resistance in prostate cancer. MYB and AR interact and co-localize with each other predominantly in the nuclei. Androgen-depletion or enzalutamide treatment does not interfere with MYB-AR interaction, and MYB-overexpressing prostate cancer cells retain AR in the nucleus even when cultured under androgen-deprived condition. Transcriptional activity of KLK3 (an androgen-responsive gene encoding PSA) promoter is increased in MYB-overexpressing cells, while sustained under androgen-depleted condition. In silico analysis identifies a MYB-binding region in KLK3 promoter in close proximity to the AR binding site, and MYB is shown to cooperatively promote AR binding to the KLK3 promoter. MYB-overexpressing prostate cancer cells exhibit greater tumorigenicity when implanted orthotopically and quickly regain growth following castration leading to the poorer survival of mice, compared to those carrying low MYB-expressing prostate tumors. Together, these findings establish a novel and significant role of MYB-AR cross-talk in prostate cancer, which could be exploited for its therapeutic management.

Citation Format: Sanjeev Kumar Srivastava, Haseeb Zubair, Girijesh K. Patel, Mohammad Aslam Khan, Sachin Kumar Deshmukh, Seema Sing, Joel Andrews, Bin Wang, James E. Carter, Ajay Pratap Singh. A novel MYB-AR cross-talk promoting castration-resistance in prostate cancer [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 2609.

Abstract 5158: Hypoxia alters the release and size distribution of extracellular vesicles in pancreatic cancer cells to support their adaptive survival

Pancreatic tumors are characterized by poor vasculature and fibrous stromal tissue networksthat create an extensive hypoxic tumor microenvironment. Extracellular vesicles (EVs) play important roles in pancreatic tumor pathobiology by supporting inter-cellular communications. They arebroadly classified into three subtypes: exosomes (Exo; 30-150 nm), microvesicles (MVs; 100 nm-1 µm) and apoptotic bodies (Abs; 1-5 µm), according to their cellular origin. Here, we studied the effect of hypoxic stress on the release kinetics and size distribution of EVs in pancreatic cancer cells. Further, we also investigated the role of different EV subtypes in adaptive survival of pancreatic cancer cells under hypoxia.Our data demonstrated that under hypoxic conditions, pancreatic cancer cells (MiaPaCa and AsPC1) shed greater amount of EVs with most noticeable changes recorded for the small size EVs. Moreover, all EVs (small, moderate, large) showed a shift towards reduced size depending upon the extent of hypoxia. When examined for subtype-specific markers, we observed mixed profiles. Thrombospondin (marker for Abs) and Arf6 (marker for MVs) were exclusively detected in large and moderate size fractions, respectively, under both normoxia and hypoxia. However, CD9 (marker for Exo) was detected in both small and moderate size EVs under hypoxia. Furthermore, in release kinetics studies we observed cyclic increases in accumulation of EV subtypes under hypoxic conditions. In addition, our data demonstrated that EVs from hypoxic cancer cells promoted survival of cancer cells under hypoxia,with small EVs being the most active. Altogether, our findings establish that hypoxia alters shedding of EVs in supporting adaptive survival of pancreatic cancer cells; associated differences could possibly be exploited for effective cancer management.

Citation Format: Mary C. Patton, Haseeb Zubair, Mohammad Aslam Khan, Seema Singh, Ajay P. Singh. Hypoxia alters the release and size distribution of extracellular vesicles in pancreatic cancer cells to support their adaptive survival [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 5158.

Abstract 1911: Bi-directional cross-talk of pancreatic cancer and stellate cells, mediated through CXCR4 and hedgehog pathways, promotes chemoresistance via its effect on gemcitabine metabolism, ROS detoxification and cancer stemness

Mounting evidence suggests that tumor-stromal interactions play a key role in pancreatic cancer (PC) pathogenesis and chemoresistance. We previously demonstrated that CXCL12, a chemokine secreted by activated pancreatic stellate cells (PSCs), promoted PC chemoresistance upon binding to its receptor CXCR4. Furthermore, activation of CXCL12/CXCR4 pathway in PC cells (PCCs) also increased the expression and secretion of sonic hedgehog (SHH), which is a known inducer of PSCs thus establishing a bi-directional tumor-stromal crosstalk. Here we present data to support that dual targeting of CXCL12/CXCR4 and hedgehog pathways is effective in improving therapeutic outcome in PC by diminishing multiple chemoresistance mechanisms. Monoculture of PCCs (MiaPaCa and Colo357) or coculture of PCCs and PSCs were treated with gemcitabine in the presence and absence of CXCR4 antagonist (AMD3100) and hedgehog inhibitor (GDC-0449). The data demonstrated that PCCs in coculture had better survival against gemcitabine treatment as compared to those grown in monoculture and inhibition of CXCL12/CXCR4 and hedgehog pathways abrogated this co-culture-induced chemoresistance. In further mechanistic studies, we identified co-culture-induced changes in gene expression and confirmed their functional significance in chemoresistance. Our data established important roles of genes associated with gemcitabine metabolism, ROS detoxification and stemness in PC chemoresistance. Inhibition of CXCL12/CXCR4 and hedgehog pathways led to increase in gemcitabine-mediated ROS production, enhanced accumulation of active gemcitabine metabolite (gemcitabine tri-phosphate) and reduced stemness in cocultured PCCs. Finally, we examined the efficacy of our dual targeting approach in vivo in an orthotopic mouse model of pancreatic cancer by treating the mice with gemcitabine alone or in combination with AMD3100 and/or GDC-0449. Our data demonstrated that mice treated with gemcitabine along with AMD3100 and/or GDC-0449 had significantly greater reduction in tumor growth as compared to those treated with gemcitabine only. Studies are ongoing in additional pancreatic tumor models. Together, these findings provide strong evidence in support of a novel combination therapy for pancreatic cancer treatment.

Citation Format: Mohammad Aslam Khan, Girijesh K. Patel, Sanjeev K. Srivastava, Sumit Arora, Haseeb Zubair, James Elliot Carter, Bin Wang, Seema Singh, Moh’d Khushman, Ajay P. Singh. Bi-directional cross-talk of pancreatic cancer and stellate cells, mediated through CXCR4 and hedgehog pathways, promotes chemoresistance via its effect on gemcitabine metabolism, ROS detoxification and cancer stemness [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 1911.

Addressing the pitfalls when designing intervention studies to discover and validate biomarkers of habitual dietary intake

INTRODUCTION

Dietary exposure monitoring within populations is reliant on self-reported measures such as Food Frequency Questionnaires and diet diaries. These methods often contain inaccurate information due to participant misreporting, non-compliance and bias. Urinary metabolites derived from individual foods could provide additional objective indicators of dietary exposure. For biomarker approaches to have utility it is essential that they cover a wide-range of commonly consumed foods and the methodology works in a real-world environment.

OBJECTIVES

To test that the methodology works in a real-world environment and to consider the impact of the major sources of likely variance; particularly complex meals, different food formulations, processing and cooking methods, as well as the dynamics of biomarker duration in the body.

METHODS

We designed and tested a dietary exposure biomarker discovery and validation strategy based on a food intervention study involving free-living individuals preparing meals and collecting urine samples at home. Two experimental periods were built around three consecutive day menu plans where all foods and drinks were provided (n = 15 and n = 36).

RESULTS

The experimental design was validated by confirming known consumption biomarkers in urinary samples after the first menu plan. We tested biomarker performance with different food formulations and processing methods involving meat, wholegrain, fruits and vegetables.

CONCLUSION

It was demonstrated that spot urine samples, together with robust dietary biomarkers, despite major sources of variance, could be used successfully for dietary exposure monitoring in large epidemiological studies.

Hydroxytyrosol Induces Apoptosis and Cell Cycle Arrest and Suppresses Multiple Oncogenic Signaling Pathways in Prostate Cancer Cells

SCOPE

Hydroxytyrosol (HT), a polyphenol from olives, is a potential anticancer agent. This study was designed to evaluate the anticancer activity of HT against prostate cancer cells, and the mechanism thereof.

METHODS AND RESULTS

Treatment of LNCaP and C4-2 prostate cancer cells with HT resulted in a dose-dependent inhibition of proliferation. This was in contrast to HT's ineffectiveness against normal prostate epithelial cells RWPE1 and PWLE2, suggesting cancer-cell-specific effect. HT induced G1/S cell cycle arrest, with inhibition of cyclins D1/E and cdk2/4 and induction of inhibitory p21/p27. HT also induced apoptosis, as confirmed by flow cytometry, caspase activation, PARP cleavage, and BAX/Bcl-2 ratio. It inhibited the phosphorylation of Akt/STAT3, and induced cytoplasmic retention of NF-κB, which may explain its observed effects. Finally, HT inhibited androgen receptor (AR) expression and the secretion of AR-responsive prostate-specific antigen.

CONCLUSION

Castration-resistant prostate cancers retain AR signaling and are often marked by activated Akt, NF-κB, and STAT3 signaling. Our results establish a pleiotropic activity of HT against these oncogenic signaling pathways. Combined with its nontoxic effects against normal cells, our results support further testing of HT for prostate cancer therapy.

Molecular Drivers of Pancreatic Cancer Pathogenesis: Looking Inward to Move Forward

Pancreatic cancer (PC) continues to rank among the most lethal cancers. The consistent increase in incidence and mortality has made it the seventh leading cause of cancer-associated deaths globally and the third in the United States. The biggest challenge in combating PC is our insufficient understanding of the molecular mechanism(s) underlying its complex biology. Studies during the last several years have helped identify several putative factors and events, both genetic and epigenetic, as well as some deregulated signaling pathways, with implications in PC onset and progression. In this review article, we make an effort to summarize our current understanding of molecular and cellular events involved in the pathogenesis of pancreatic malignancy. Specifically, we provide up-to-date information on the genetic and epigenetic changes that occur during the initiation and progression of PC and their functional involvement in the pathogenic processes. We also discuss the impact of the tumor microenvironment on the molecular landscape of PC and its role in aggressive disease progression. It is envisioned that a better understanding of these molecular factors and the mechanisms of their actions can help unravel novel diagnostic and prognostic biomarkers and can also be exploited for future targeted therapies.

Resistin potentiates chemoresistance and stemness of breast cancer cells: Implications for racially disparate therapeutic outcomes

Breast cancer (BC) continues to be the most frequently diagnosed cancer in American women, which disproportionately affects women of African-American (AA) descent. Previously, we reported greater serum levels of resistin in AA BC patients relative to Caucasian-American (CA) patients, and established its role in growth and aggressiveness of breast tumor cells. Here we have investigated the role of resistin in BC-chemoresistance. MDA-MB-231 and MDA-MB-468 BC cells of CA and AA origin, respectively, were incubated with resistin prior to doxorubicin treatment. Our data suggest that resistin conferred chemoresistance to both BC cell lines; however, the effect on AA cells was more profound. Furthermore, the resistin-induced doxorubicin-resistance was shown to occur due to suppression of apoptosis. Resistin treatment also affected the stemness of BC cells, as suggested by reduced cell surface expression of CD24, induced expression of CD44 and ALDH1, and increased capability of cells to form mammospheres. Mechanistic studies revealed that resistin-induced chemoresistance, apoptosis and stemness of BC cells were mediated through STAT3 activation. Taken together, our findings provide novel insight into the role of resistin in BC biology, and strengthen its role in racially disparate clinical outcomes.

Cancer Chemoprevention by Phytochemicals: Nature's Healing Touch

Phytochemicals are an important part of traditional medicine and have been investigated in detail for possible inclusion in modern medicine as well. These compounds often serve as the backbone for the synthesis of novel therapeutic agents. For many years, phytochemicals have demonstrated encouraging activity against various human cancer models in pre-clinical assays. Here, we discuss select phytochemicals—curcumin, epigallocatechin-3-gallate (EGCG), resveratrol, plumbagin and honokiol—in the context of their reported effects on the processes of inflammation and oxidative stress, which play a key role in tumorigenesis. We also discuss the emerging evidence on modulation of tumor microenvironment by these phytochemicals which can possibly define their cancer-specific action. Finally, we provide recent updates on how low bioavailability, a major concern with phytochemicals, is being circumvented and the general efficacy being improved, by synthesis of novel chemical analogs and nanoformulations.

Exosomes confer chemoresistance to pancreatic cancer cells by promoting ROS detoxification and miR-155-mediated suppression of key gemcitabine-metabolising enzyme, DCK

Background:

Chemoresistance is a significant clinical problem in pancreatic cancer (PC) and underlying molecular mechanisms still remain to be completely understood. Here we report a novel exosome-mediated mechanism of drug-induced acquired chemoresistance in PC cells.

Methods:

Differential ultracentrifugation was performed to isolate extracellular vesicles (EVs) based on their size from vehicle- or gemcitabine-treated PC cells. Extracellular vesicles size and subtypes were determined by dynamic light scattering and marker profiling, respectively. Gene expression was examined by qRT-PCR and/or immunoblot analyses, and direct targeting of DCK by miR-155 was confirmed by dual-luciferase 3′-UTR reporter assay. Flow cytometry was performed to examine the apoptosis indices and reactive oxygen species (ROS) levels in PC cells using specific dyes. Cell viability was determined using the WST-1 assay.

Results:

Conditioned media (CM) from gemcitabine-treated PC cells (Gem-CM) provided significant chemoprotection to subsequent gemcitabine toxicity and most of the chemoresistance conferred by Gem-CM resulted from its EVs fraction. Sub-fractionation grouped EVs into distinct subtypes based on size distribution and marker profiles, and exosome (Gem-Exo) was the only sub-fraction that imparted chemoresistance. Gene expression analyses demonstrated upregulation of SOD2 and CAT (ROS-detoxifying genes), and downregulation of DCK (gemcitabine-metabolising gene) in Gem-Exo-treated cells. SOD/CAT upregulation resulted, at least in part, from exosome-mediated transfer of their transcripts and they suppressed basal and gemcitabine-induced ROS production, and partly promoted chemoresistance. DCK downregulation occurred through exosome-delivered miR-155 and either the functional suppression of miR-155 or restoration of DCK led to marked abrogation of Gem-Exo-mediated chemoresistance.

Conclusions:

Together, these findings establish a novel role of exosomes in mediating the acquired chemoresistance of PC.

Biological basis of cancer health disparities: resources and challenges for research

Last few decades have witnessed remarkable progress in our understanding of cancer initiation and progression leading to refinement of prevention and treatment approaches. Although these advances have improved the survival of cancer patients in general, certain racial/ethnic groups have benefited only partially. Footprints of cancer-associated racial disparities are very much evident in cancers of the prostate, breast, cervical, colorectal, endometrium, liver and lung. These health inequalities are mostly attributed to socioeconomic differences among races, but there is a growing realization that these may actually be due to inherent biological differences as well. Indeed, significant data now exist to support the biological basis of racial disparities in cancer, warranting basic research investigations, using appropriate tools and model systems. In this article, we have aimed to succinctly review the literature supporting the biological bases of racial disparities in cancer, along with available resources, databases and model systems that will be of interest to researchers. Moreover, we have highlighted the specific areas that need attention in terms of development of resources and/or tools, and discuss the opportunities and challenges in basic biological research in cancer health disparities.

Gemcitabine triggers angiogenesis-promoting molecular signals in pancreatic cancer cells: Therapeutic implications

Pancreatic tumor microenvironment (TME) is characterized by poor tumor-vasculature and extensive desmoplasia that together contribute to poor response to chemotherapy. It was recently shown that targeting of TME to inhibit desmoplasiatic reaction in a preclinical model resulted in increased microvessel-density and intratumoral drug concentration, leading to improved therapeutic response. This approach; however, failed to generate a favorable response in clinical trial. In that regard, we have previously demonstrated a role of gemcitabine-induced CXCR4 signaling as a counter-defense mechanism, which also promoted invasiveness of pancreatic cancer (PC) cells. Here, we investigated the effect of gemcitabine on endothelial cell phenotype. Gemcitabine-treatment of human-umbilical-vein-endothelial-cells (HUVECs) did not promote the growth of HUVECs; however, it was induced when treated with conditioned media from gemcitabine-treated (Gem-CM) PC cells due to increased cell-cycle progression and apoptotic-resistance. Moreover, treatment of HUVECs with Gem-CM resulted in capillary-like structure (CLS) formation and promoted their ability to migrate and invade through extracellular-matrix. Gemcitabine-treatment of PC cells induced expression of various growth factors/cytokines, including IL-8, which exhibited greatest upregulation. Further, IL-8 depletion in Gem-CM diminished its potency to promote angiogenic phenotypes. Together, these findings suggest an indirect effect of gemcitabine on angiogenesis, which, in light of our previous observations, may hold important clinical significance.

Glucose Metabolism Reprogrammed by Overexpression of IKKε Promotes Pancreatic Tumor Growth

Aberrant expression of the kinase IKKε in pancreatic ductal adenocarcinoma (PDAC) has been associated with poor prognosis. In this study, we define a pathobiologic function for IKKε in reprogramming glucose metabolism and driving progression in PDAC. Silencing IKKε in PDAC cells, which overexpressed it endogenously, was sufficient to reduce malignant cell growth, clonogenic potential, glucose consumption, lactate secretion, and expression of genes involved in glucose metabolism, without impacting the basal oxygen consumption rate. IKKε silencing also attenuated c-Myc in a manner associated with diminished signaling through an AKT/GSK3β/c-MYC phosphorylation cascade that promoted MYC nuclear accumulation. In an orthotopic mouse model, IKKε-silenced PDAC exhibited a relative reduction in glucose uptake, tumorigenicity, and metastasis. Overall, our findings offer a preclinical mechanistic rationale to target IKKε to improve the therapeutic management of PDAC in patients. Cancer Res; 76(24); 7254-64. ©2016 AACR.

Abstract 1519: Myb-regulated gene networks and signaling pathways in pancreatic cancer

The MYB proto-oncogene (a cellular progenitor of v-Myb oncogene) encodes an oncogenic transcription factor that regulates the expression of a wide array of genes responsible for different cellular functions. We have recently identified MYB as a key driver of pancreatic cancer (PC) pathogenesis. Our findings demonstrated that MYB was overexpressed in majority of PC tissues and cell lines, while remained undetectable in normal pancreatic cells. In addition, MYB overexpression was shown to be associated with pancreatic tumor growth and metastasis. To gain further insight into the molecular mechanisms involved in MYB-potentiated effects in PC cells, we conducted Next-Generation Sequencing of transcriptome of control and MYB-silenced MiaPaCa cells on an Illumina HiSeq 2500 platform. By keeping a cut-off of fold change &gt; 1.5 and p ≤ 0.05, we identified a total of 774 genes to be differentially expressed in MYB-altered MiaPaCa cells. Out of these, 485 genes were downregulated, while 289 genes exhibited upregulated expression. The differentially-regulated genes were subsequently analyzed for functions and cellular pathways alterations using Ingenuity Pathway Analysis (IPA) software. The top three networks to be affected in MYB knockdown PC cells included i) RNA post-transcriptional modifications, molecular transport, RNA trafficking, ii) cellular assembly and organization, cancer, and, iii) cell cycle, DNA replication, recombination and repair. These networks are centered on splicing factors, EGFR and NF-κB complex, respectively. IPA predicted pancreatic adenocarcinoma signaling as one of the most significantly affected canonical pathway upon MYB-silencing. Altogether, our findings identify novel MYB-regulated gene networks and signaling pathways in PC and thus suggest potential molecular mechanisms involved in mediating MYB action in pancreatic tumorigenesis.

Citation Format: Shafquat Azim, Sanjeev K. Srivastava, Arun Bhardwaj, Haseeb Zubair, Mohammad Aslam Khan, Seema Singh, Ajay P. Singh. Myb-regulated gene networks and signaling pathways in pancreatic cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1519.

Abstract 2799: Exosomes from hypoxic pancreatic cancer cells confer resistance to subsequent hypoxia insult

Pancreatic cancer (PC) remains one of the leading causes of cancer-associated deaths in the US due to its highly aggressive nature and lack of effective treatments. Pancreatic tumors are characterized by a dense, desmoplastic reaction and poor vasculature leading to reduced oxygen levels within the tumor microenvironment. It is believed that this encounter of pancreatic tumor cells to intratumoral hypoxic condition is a major cause of their persistent survival under a variety of stresses, increased aggressiveness and therapeutic-resistance. However, underlying molecular mechanisms responsible for PC's adaptation to hypoxia (along with enhanced growth and aggressiveness) remain elusive. In this study, we examined the role of exosomes, which are nanoscale biological vesicles with a lipid bilayer membrane, in imparting survival benefit to PC cells. For this, we first examined the effect of conditioned media (CM) from PC cells cultured under hypoxic (0.1% O2, H-CM) or normoxic (21% O2, N-CM) conditions on the growth of fresh PC cells cultured under hypoxic (0.1% O2) conditions. We found that H-CM conferred significant survival benefit to cancer cells under hypoxia as compared to N-CM. Thereafter, we isolated exosomes from N-CM (N-exo) or H-CM (H-exo) and used them to treat pancreatic cancer cells under hypoxic culture conditions. We observed that H-exo imparted a significantly higher survival advantage to cancer cells under hypoxia as compared to N-exo. Interestingly, protein quantification indicated the presence of higher levels of exosomes from cells cultured under hypoxic conditions as compared to those grown in normoxic environment. Western blot analysis with anti-CD9 and anti-CD63 antibodies confirmed enrichment of exosomes. Moreover, Dynamic Light Scattering-based size distribution suggested that H-exo were smaller in size compared to N-exo. Further studies are underway to identify the molecular determinants in exosomes responsible for inducing growth-promoting effects under hypoxia. Overall, our data provides the first evidence that hypoxic PC cells secrete exosomes that enhance survivability under hypoxic conditions.

Citation Format: Mary C. Patton, Haseeb Zubair, Girijesh K. Patel, Seema Singh, Ajay P. Singh. Exosomes from hypoxic pancreatic cancer cells confer resistance to subsequent hypoxia insult. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2799.

Deep sequencing and in silico analyses identify MYB-regulated gene networks and signaling pathways in pancreatic cancer

We have recently demonstrated that the transcription factor MYB can modulate several cancer-associated phenotypes in pancreatic cancer. In order to understand the molecular basis of these MYB-associated changes, we conducted deep-sequencing of transcriptome of MYB-overexpressing and -silenced pancreatic cancer cells, followed by in silico pathway analysis. We identified significant modulation of 774 genes upon MYB-silencing (p < 0.05) that were assigned to 25 gene networks by in silico analysis. Further analyses placed genes in our RNA sequencing-generated dataset to several canonical signalling pathways, such as cell-cycle control, DNA-damage and -repair responses, p53 and HIF1α. Importantly, we observed downregulation of the pancreatic adenocarcinoma signaling pathway in MYB-silenced pancreatic cancer cells exhibiting suppression of EGFR and NF-κB. Decreased expression of EGFR and RELA was validated by both qPCR and immunoblotting and they were both shown to be under direct transcriptional control of MYB. These observations were further confirmed in a converse approach wherein MYB was overexpressed ectopically in a MYB-null pancreatic cancer cell line. Our findings thus suggest that MYB potentially regulates growth and genomic stability of pancreatic cancer cells via targeting complex gene networks and signaling pathways. Further in-depth functional studies are warranted to fully understand MYB signaling in pancreatic cancer.

Mobilization of Intracellular Copper by Gossypol and Apogossypolone Leads to Reactive Oxygen Species-Mediated Cell Death: Putative Anticancer Mechanism

There is compelling evidence that serum, tissue and intracellular levels of copper are elevated in all types of cancer. Copper has been suggested as an important co-factor for angiogenesis. It is also a major metal ion present inside the nucleus, bound to DNA bases, particularly guanine. We have earlier proposed that the interaction of phenolic-antioxidants with intracellular copper leads to the generation of reactive oxygen species (ROS) that ultimately serve as DNA cleaving agents. To further validate our hypothesis we show here that the antioxidant gossypol and its semi-synthetic derivative apogossypolone induce copper-mediated apoptosis in breast MDA-MB-231, prostate PC3 and pancreatic BxPC-3 cancer cells, through the generation of ROS. MCF10A breast epithelial cells refractory to the cytotoxic property of these compounds become sensitized to treatment against gossypol, as well as apogossypolone, when pre-incubated with copper. Our present results confirm our earlier findings and strengthen our hypothesis that plant-derived antioxidants mobilize intracellular copper instigating ROS-mediated cellular DNA breakage. As cancer cells exist under significant oxidative stress, this increase in ROS-stress to cytotoxic levels could be a successful anticancer approach.

Distribution of nodal lymphomas in a referral hospital of Mangalore city

CONTEXT

The distribution of different types of lymphoma varies across geographic regions.

AIMS

The present study was done to understand the occurrence of nodal lymphomas in a referral hospital of Mangalore city.

SETTINGS AND DESIGN

Descriptive study.

SETTING

The present study was conducted on 95 lymph node biopsy specimens, received in a referral hospital of Mangalore city.

MATERIALS AND METHODS

All cases of nodal lymphoma diagnosed between January 2007 and June 2010 in a referral hospital of Mangalore were selected for the study. The patients age and clinical details were obtained. Immunophenotyping was done for all cases of NHL and selected cases of HL. IPI score for NHL was noted and correlated with the outcome.

STATISTICAL ANALYSIS USED

Chi square test was used.

RESULTS

Out of the total 95 cases of nodal lymphoma 37 (39%) were HL while 58 (61%) were NHL. Classical HL was diagnosed in 35 cases (37%) while 2 cases (2%) were diagnosed NLPHL. B cell lymphoma formed 72% of NHL. Follicular lymphoma accounted for 28% of all NHL. T cell lymphoma formed 28% of NHL.

CONCLUSIONS

In conclusion the following points are significant about the distribution of lymphomas in a referral hospital of Mangalore city. The incidence of NSHL is higher while national data suggests MCHL as the most common subtype. The incidence of FL as well as T cell NHL is much higher when compared to national incidence. The epidemiological factors for this high frequency (either genetic or environmental) needs to be studied further.

A comprehensive biological insight of trinuclear copper(II)-tin(IV) chemotherapeutic anticancer drug entity: in vitro cytotoxicity and in vivo systemic toxicity studies

Cisplatin (cis-diamminedichloroplatinum(II), CDDP) causes severe systemic toxicity, which limits its application in cancer treatment. Nevertheless, incorporation of endogenously present essential metal ions (copper) in anticancer drug regimes in a heterometallic ligand scaffold can substantially modulate the toxic effects of non-essential metals (platinum), thereby reducing unwanted toxic side effects. A chiral l-tryptophan derived [bis(1,2-diaminobenzene) copper(II)] chloride complex [CuSn2(Trp)] was previously synthesized by us as an active chemotherapeutic agent. Furthermore, we have explored CuSn2(Trp) induced in vitro cytotoxicity in a panel of human cancer cell lines and in vivo acute and systemic toxicities in healthy female Rattus norvegicus (Wistar) rats. MTT assay showed that CuSn2(Trp) exhibits strong anticancer potency against ovarian (PA-1) and prostate carcinomas (PC-3) but lower potency towards liver (HepG2) and breast carcinomas (MCF-7). Further, flow cytometric analysis demonstrated that CuSn2(Trp) kills PA-1 cells dose-dependently after 48 h treatment. Fluorescence microscopy and western blotting revealed that the plausible mechanism behind CuSn2(Trp) cytotoxicity was apoptosis, which was substantiated by cleavage of caspase-3 and poly-(ADP-ribose) polymerase (PARP). Furthermore, it has lower toxicity than CDDP in rats as evident from its eight fold (98.11 mg kg(-1)) more medial lethal dose (LD50) than CDDP (12 mg kg(-1)). Besides, the safety profile of CuSn2(Trp) was also established and no measurable DNA damage, nephrotoxicity, hepatotoxicity and neurotoxicity were observed when assessed as a function of oxidative stress markers in contrast to CDDP at equivalent lower doses. Our findings are of high importance in the context of further in vivo cancer studies on the CuSn2(Trp) drug entity.

Insights into the Role of microRNAs in Pancreatic Cancer Pathogenesis: Potential for Diagnosis, Prognosis, and Therapy

Pancreatic cancer is a highly lethal malignancy and a fourth leading cause of cancer-related death in the United States. Poor survival of pancreatic cancer patients is largely because of its asymptomatic progression to advanced stage against which no effective therapy is currently available. Over the years, we have developed significant knowledge of molecular progression of pancreatic cancer and identified several genetic and epigenetic aberrations to be involved in its etiology and aggressive behavior. In that regard, recent lines of evidence have suggested important roles of microRNAs (miRNAs/miRs) in pancreatic cancer pathogenesis. microRNAs belonging to a family of small, noncoding RNAs are able to control diverse biological processes due to their ability to regulate gene expression at the posttranscriptional level. Accordingly, dysregulation of miRNAs can lead to several disease conditions, including cancer. There is a long list of microRNAs that exhibit aberrant expression in pancreatic cancer and serve as key microplayers in its initiation, progression, metastasis, and chemoresistance. These findings have suggested that microRNAs could be exploited as novel biomarkers for diagnostic and prognostic assessments of pancreatic cancer and as targets for therapy. This book chapter describes clinical problems associated with pancreatic cancer, roles that microRNAs play in various aspects of pancreatic cancer pathogenesis, and envision opportunities for potential use of microRNAs in pancreatic cancer management.

The prooxidant action of dietary antioxidants leading to cellular DNA breakage and anticancer effects: implications for chemotherapeutic action against cancer

Plant-derived dietary antioxidants have attracted considerable interest in recent past for their ability to induce apoptosis and regression of tumors in animal models. While it is believed that the antioxidant properties of these agents may contribute to lowering the risk of cancer induction by impeding oxidative injury to DNA, it could not account for apoptosis induction and chemotherapeutic observations. In this article, we show that dietary antioxidants can alternatively switch to a prooxidant action in the presence of transition metals such as copper. Such a prooxidant action leads to strand breaks in cellular DNA and growth inhibition in cancer cells. Further, the cellular DNA breakage and anticancer effects were found to be significantly enhanced in the presence of copper ions. Moreover, inhibition of antioxidant-induced DNA strand breaks and oxidative stress by Cu(I)-specific chelators bathocuproine and neocuproine demonstrated the role of endogenous copper in the induction of the prooxidant mechanism. Since it is well established that tissue, cellular, and serum copper levels are considerably elevated in various malignancies, such a prooxidant cytotoxic mechanism better explains the anticancer activity of dietary antioxidants against cancer cells.

Molecular Targets of Honokiol: A Promising Phytochemical for Effective Cancer Management

Honokiol is a bioactive, biphenolic phytochemical, present in the aerial parts of plants classified under the genus Magnolia. It has been an important constituent of Asian traditional medicine and is used against many ailments. Honokiol possesses potent antioxidative, anti-inflammatory, antiangiogenic, and anticancer activities by targeting a variety of signaling molecules. Consequently, there has been immense interest in exploring its utility as a novel chemopreventive and therapeutic agent against several malignancies. In this chapter, we review the structure-function relationship of honokiol and its derivative compounds, the impact of honokiol on various phenotypes associated with cancer progression and metastasis, and its prominent molecular targets and pharmacokinetics. Clearly, the available data generate significant interest in this novel phytochemical and emerging information continues to provide strong support for its potential applicability in cancer management.

Plant polyphenol induced cell death in human cancer cells involves mobilization of intracellular copper ions and reactive oxygen species generation: a mechanism for cancer chemopreventive action

SCOPE

Anticancer polyphenolic nutraceuticals from fruits, vegetables, and spices are generally recognized as antioxidants, but can be prooxidants in the presence of copper ions. We earlier proposed a mechanism for such activity of polyphenols and now we provide data in multiple cancer cell lines in support of our hypothesis.

METHODS AND RESULTS

Through multiple assays, we show that polyphenols luteolin, apigenin, epigallocatechin-3-gallate, and resveratrol are able to inhibit cell proliferation and induce apoptosis in different cancer cell lines. Such cell death is prevented to a significant extent by cuprous chelator neocuproine and reactive oxygen species scavengers. We also show that normal breast epithelial cells, cultured in a medium supplemented with copper, become sensitized to polyphenol-induced growth inhibition.

CONCLUSION

Since the concentration of copper is significantly elevated in cancer cells, our results strengthen the idea that an important anticancer mechanism of plant polyphenols is mediated through intracellular copper mobilization and reactive oxygen species generation leading to cancer cell death. Moreover, this prooxidant chemopreventive mechanism appears to be a mechanism common to several polyphenols with diverse chemical structures and explains the preferential cytotoxicity of these compounds toward cancer cells.

DNA damage and DNA-protein cross-linking induced in rat intestine by the water disinfection by-product potassium bromate

The genotoxic effects of potassium bromate (KBrO3), a food additive and water disinfection by-product, on the small intestine of rats are reported here. Adult male rats were given a single oral dose of KBrO3 (100 mg kg(-1) body weight) and sacrificed 12, 24, 48, 96 and 168 h after this treatment while control animals were not given KBrO3. Administration of KBrO3 caused a significant increase in DNA damage when analyzed by the comet assay which suggests the induction of DNA strand breaks. This was also shown by colorimetric assay of nucleotides formed upon DNA degradation. KBrO3 treatment also resulted in increased formation of DNA-protein cross-links in the intestine. The maximum changes in these parameters were 48 h after administration of KBrO3 after which recovery took place. Thus, a single oral dose of KBrO3 exerts genotoxic effects in the intestine of rats, possibly through the mechanism of oxidative DNA damage.

Apogossypolone, derivative of gossypol, mobilizes endogenous copper in human peripheral lymphocytes leading to oxidative DNA breakage

Gossypol is a polyphenolic aldehyde that is produced in the cotton plant. Since long it has been reported to possess antiproliferative activity against a variety of cancer cell lines as well as tumor regression in animal models. However, the toxicity of gossypol does not permit it to be an effective antitumor agent. One of the derivatives of gossypol to show promising results is apogossypolone. For example, it has been shown to specifically target tumor growth in hepatocellular carcinoma xenograft in nude mice without causing any damage to normal tissue. Using human peripheral lymphocytes, in this paper we show that both gossypol and its semi-synthetic derivative apogossypolone cause oxidative DNA breakage in these cells through the mobilization of endogenous copper ions. Such cellular DNA breakage is inhibited by copper specific chelator but nor by iron or zinc chelating agents. Similar results are obtained with isolated nuclei indicating that chromatin bound copper is mobilized in this reaction. Further, apogossypolone showed enhanced DNA breakage and increased oxidative stress in whole lymphocytes as compared with gossypol indicating that this is possibly the result of greater permeability of apogossypolone. It is well established that tissue, cellular and serum copper levels are considerably elevated in various malignancies. Therefore, cancer cells may be subject to greater electron transfer between copper ions and gossypol/apogossypolone to generate reactive oxygen species responsible for DNA cleavage. This may account for the preferential cytotoxicity of apogossypolone towards tumor cells.

Oral administration of copper to rats leads to increased lymphocyte cellular DNA degradation by dietary polyphenols: implications for a cancer preventive mechanism

To account for the observed anticancer properties of plant polyphenols, we have earlier proposed a mechanism which involves the mobilization of endogenous copper ions by polyphenols leading to the generation of reactive oxygen species (ROS) that serve as proximal DNA cleaving agents and lead to cell death. Over the last decade we have proceeded to validate our hypothesis with considerable success. As a further confirmation of our hypothesis, in this paper we first show that oral administration of copper to rats leads to elevated copper levels in lymphocytes. When such lymphocytes with a copper overload were isolated and treated with polyphenols EGCG, genistein and resveratrol, an increased level of DNA breakage was observed. Further, preincubation of lymphocytes having elevated copper levels with the membrane permeable copper chelator neocuproine, resulted in inhibition of polyphenol induced DNA degradation. However, membrane impermeable chelator of copper bathocuproine, as well as iron and zinc chelators were ineffective in causing such inhibition in DNA breakage, confirming the involvement of endogenous copper in polyphenol induced cellular DNA degradation. It is well established that serum and tissue concentrations of copper are greatly increased in various malignancies. In view of this fact, the present results further confirm our earlier findings and strengthen our hypothesis that an important anticancer mechanism of plant polyphenols could be the mobilization of intracellular copper leading to ROS-mediated cellular DNA breakage. In this context, it may be noted that cancer cells are under considerable oxidative stress and increasing such stress to cytotoxic levels could be a successful anticancer approach.

Soy isoflavone genistein induces cell death in breast cancer cells through mobilization of endogenous copper ions and generation of reactive oxygen species

SCOPE

Worldwide geographical variation in cancer incidence indicates a correlation between dietary habits and cancer risk. Epidemiological studies have suggested that populations with high isoflavone intake through soy consumption have lower rates of breast, prostate, and colon cancer. Isoflavone genistein in soybean is considered a potent chemopreventive agent against cancer. Although several mechanisms have been proposed, a clear anticancer action mechanism of genistein is still not known.

METHODS AND RESULTS

Here, we show that the cytotoxic action of genistein against breast cancer cells involves mobilization of endogenous copper. Further, whereas the copper specific chelator neocuproine is able to inhibit the apoptotic potential of genistein, the molecules which specifically bind iron (desferroxamine mesylate) and zinc (histidine) are relatively ineffective in causing such inhibition. Also, genistein-induced apoptosis in these cells is inhibited by scavengers of reactive oxygen species (ROS) implicating ROS as effector elements leading to cell death.

CONCLUSIONS

As copper levels are known to be considerably elevated in almost all types of cancers, in this proof-of-concept study we show that genistein is able to target endogenous copper leading to prooxidant signaling and consequent cell death. We believe that such a mechanism explains the anticancer effect of genistein as also its preferential cytotoxicity towards cancer cells.

The antioxidant ascorbic acid mobilizes nuclear copper leading to a prooxidant breakage of cellular DNA: implications for chemotherapeutic action against cancer

PURPOSE

Ascorbic acid is an essential micronutrient and is considered to have an antioxidant function in living systems. For the past several decades, ascorbic acid has been the subject of considerable interest as an anticancer agent. Several studies have shown that ascorbic acid is cytotoxic to a variety of cancer cells, whereas normal cells are relatively resistant to such cytotoxic action. In this study, we propose a putative molecular mechanism that accounts for the preferential cytotoxicity of ascorbic acid against cancer cells.

METHODS

Standard and lysed version of alkaline single-cell gel electrophoresis (Comet assay); ferrous oxidation-xylenol orange (FOX) assay.

RESULTS

We show that ascorbic acid acts as a prooxidant and leads to oxidative DNA breakage in lymphocytes and lymphocyte nuclei. Scavengers of reactive oxygen species were able to inhibit ascorbic acid-induced DNA breakage, suggesting the involvement of reactive oxygen species in this reaction. We further show that such DNA breakage is inhibited by both iron and copper chelators in cells, whereas in nuclei, similar inhibition was achieved only by copper chelators, indicating an important role of chromatin-bound copper in the prooxidant cellular DNA breakage by ascorbic acid.

CONCLUSION

We propose that the copper-dependent cellular redox status is an important element in the cytotoxic action of ascorbic acid against cancer cells. It is well established that cellular copper levels are considerably elevated in various malignancies. Therefore, cancer cells may be more subject to electron transfer between copper and ascorbate to generate reactive oxygen species. In light of these observations and those in literature, in this paper we explain that the preferential cytotoxicity of ascorbic acid against cancer cells is the result of elevated copper levels in such cells. Further, this study identifies nuclear copper as a novel molecular target for cytotoxic action of ascorbic acid, which has implications for its chemotherapeutic properties against cancer.