Connectivity mapping-based identification of pharmacological inhibitor targeting HDAC6 in aggressive pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) remains highly lethal due to limited therapeutic options and expensive/burdensome drug discovery processes. Utilizing genomic-data-driven Connectivity Mapping (CMAP) to identify a drug closer to real-world PC targeting may improve pancreatic cancer (PC) patient outcomes. Initially, we mapped CMAP data to gene expression from 106 PC patients, identifying nine negatively connected drugs. These drugs were further narrowed down using a similar analysis for PC cell lines, human tumoroids, and patient-derived xenografts datasets, where ISOX emerged as the most potent agent to target PC. We used human and mouse syngeneic PC cells, human and mouse tumoroids, and in vivo mice to assess the ability of ISOX alone and in combination with 5FU to inhibit tumor growth. Global transcriptomic and pathway analysis of the ISOX-LINCS signature identified HDAC 6/cMyc as the target axis for ISOX. Specifically, we discovered that genetic and pharmacological targeting of HDAC 6 affected non-histone protein cMyc acetylation, leading to cMyc instability, thereby disrupting PC growth and metastasis by affecting cancer stemness. Finally, KrasG12D harboring tumoroids and mice responded effectively against ISOX and 5FU treatment by enhancing survival and controlling metastasis incidence. Overall, our data validate ISOX as a new drug to treat advanced PC patients without toxicity to normal cells. Our study supports the clinical utility of ISOX along with 5FU in future PC clinical trials.

A Novel HOXA10-Associated 5-Gene-Based Prognostic Signature for Stratification of Short-term Survivors of Pancreatic Ductal Adenocarcinoma

PURPOSE

Despite the significant association of molecular subtypes with poor prognosis in patients with pancreatic ductal adenocarcinoma (PDAC), few efforts have been made to identify the underlying pathway(s) responsible for this prognosis. Identifying a clinically relevant prognosis-based gene signature may be the key to improving patient outcomes.

EXPERIMENTAL DESIGN

We analyzed the transcriptomic profiles of treatment-naïve surgically resected short-term survivor (STS) and long-term survivor (LTS) tumors (GSE62452) for expression and survival, followed by validation in several datasets. These results were corroborated by IHC analysis of PDAC-resected STS and LTS tumors. The mechanism of this differential survival was investigated using CIBERSORT and pathway analyses.

RESULTS

We identified a short-surviving prognostic subtype of PDAC with a high degree of significance (P = 0.018). One hundred thirty genes in this novel subtype were found to be regulated by a master regulator, homeobox gene HOXA10, and a 5-gene signature derived from these genes, including BANF1, EIF4G1, MRPS10, PDIA4, and TYMS, exhibited differential expression in STSs and a strong association with poor survival. This signature was further associated with the proportion of T cells and macrophages found in STSs and LTSs, demonstrating a potential role in PDAC immunosuppression. Pathway analyses corroborated these findings, revealing that this HOXA10-driven prognostic signature is associated with immune suppression and enhanced tumorigenesis.

CONCLUSIONS

Overall, these findings reveal the presence of a HOXA10-associated prognostic subtype that can be used to differentiate between STS and LTS patients of PDAC and inform on the molecular interactions that play a role in this poor prognosis.

MUC16 promotes triple-negative breast cancer lung metastasis by modulating RNA-binding protein ELAVL1/HUR

BACKGROUND

Triple-negative breast cancer (TNBC) is highly aggressive with an increased metastatic incidence compared to other breast cancer subtypes. However, due to the absence of clinically reliable biomarkers and targeted therapy in TNBC, outcomes are suboptimal. Hence, there is an urgent need to understand biological mechanisms that lead to identifying novel therapeutic targets for managing metastatic TNBC.

METHODS

The clinical significance of MUC16 and ELAVL1 or Hu antigen R (HuR) was examined using breast cancer TCGA data. Microarray was performed on MUC16 knockdown and scramble TNBC cells and MUC16-associated genes were identified using RNA immunoprecipitation and metastatic cDNA array. Metastatic properties of MUC16 were evaluated using tail vein experiment. MUC16 and HuR downstream pathways were confirmed by ectopic overexpression of MUC16-carboxyl-terminal (MUC16-Cter), HuR and cMyc as well as HuR inhibitors (MS-444 and CMLD-2) in TNBC cells.

RESULTS

MUC16 was highly expressed in TNBC and correlated with its target HuR. Depletion of MUC16 showed decreased invasion, migration, and colony formation abilities of human and mouse TNBC cells. Mice injected with MUC16 depleted cells were less likely to develop lung metastasis (P = 0.001). Notably, MUC16 and HuR were highly expressed in the lung tropic TNBC cells and lung metastases. Mechanistically, we identified cMyc as a HuR target in TNBC using RNA immunoprecipitation and metastatic cDNA array. Furthermore, MUC16 knockdown and pharmacological inhibition of HuR (MS-444 and CMLD-2) in TNBC cells showed a reduction in cMyc expression. MUC16-Cter or HuR overexpression models indicated MUC16/HuR/cMyc axis in TNBC cell migration.

CONCLUSIONS

Our study identified MUC16 as a TNBC lung metastasis promoter that acts through HuR/cMyc axis. This study will form the basis of future studies to evaluate the targeting of both MUC16 and HuR in TNBC patients.

Mucins as Potential Biomarkers for Early Detection of Cancer

Early detection significantly correlates with improved survival in cancer patients. So far, a limited number of biomarkers have been validated to diagnose cancers at an early stage. Considering the leading cancer types that contribute to more than 50% of deaths in the USA, we discuss the ongoing endeavors toward early detection of lung, breast, ovarian, colon, prostate, liver, and pancreatic cancers to highlight the significance of mucin glycoproteins in cancer diagnosis. As mucin deregulation is one of the earliest events in most epithelial malignancies following oncogenic transformation, these high-molecular-weight glycoproteins are considered potential candidates for biomarker development. The diagnostic potential of mucins is mainly attributed to their deregulated expression, altered glycosylation, splicing, and ability to induce autoantibodies. Secretory and shed mucins are commonly detected in patients' sera, body fluids, and tumor biopsies. For instance, CA125, also called MUC16, is one of the biomarkers implemented for the diagnosis of ovarian cancer and is currently being investigated for other malignancies. Similarly, MUC5AC, a secretory mucin, is a potential biomarker for pancreatic cancer. Moreover, anti-mucin autoantibodies and mucin-packaged exosomes have opened new avenues of biomarker development for early cancer diagnosis. In this review, we discuss the diagnostic potential of mucins in epithelial cancers and provide evidence and a rationale for developing a mucin-based biomarker panel for early cancer detection.

Elevated PAF1-RAD52 axis confers chemoresistance to human cancers

Cisplatin- and gemcitabine-based chemotherapeutics represent a mainstay of cancer therapy for most solid tumors; however, resistance limits their curative potential. Here, we identify RNA polymerase II-associated factor 1 (PAF1) as a common driver of cisplatin and gemcitabine resistance in human cancers (ovarian, lung, and pancreas). Mechanistically, cisplatin- and gemcitabine-resistant cells show enhanced DNA repair, which is inhibited by PAF1 silencing. We demonstrate an increased interaction of PAF1 with RAD52 in resistant cells. Targeting the PAF1 and RAD52 axis combined with cisplatin or gemcitabine strongly diminishes the survival potential of resistant cells. Overall, this study shows clinical evidence that the expression of PAF1 contributes to chemotherapy resistance and worse clinical outcome for lethal cancers.

Distinct tumor architectures for metastatic colonization of the brain

Brain metastasis is a dismal cancer complication, hinging on the initial survival and outgrowth of disseminated cancer cells. To understand these crucial early stages of colonization, we investigated two prevalent sources of cerebral relapse, triple-negative (TNBC) and HER2+ breast cancer (HER2BC). We show that these tumor types colonize the brain aggressively, yet with distinct tumor architectures, stromal interfaces, and autocrine growth programs. TNBC forms perivascular sheaths with diffusive contact with astrocytes and microglia. In contrast, HER2BC forms compact spheroids prompted by autonomous extracellular matrix components and segregating stromal cells to their periphery. Single-cell transcriptomic dissection reveals canonical Alzheimer's disease-associated microglia (DAM) responses. Differential engagement of tumor-DAM signaling through the receptor AXL suggests specific pro-metastatic functions of the tumor architecture in both TNBC perivascular and HER2BC spheroidal colonies. The distinct spatial features of these two highly efficient modes of brain colonization have relevance for leveraging the stroma to treat brain metastasis.

Small molecule inhibitor against onco-mucins disrupts Src/FosL1 axis to enhance gemcitabine efficacy in pancreatic ductal adenocarcinoma

Mucin MUC4 is an aberrantly expressed oncogene in pancreatic ductal adenocarcinoma (PDAC), yet no pharmacological inhibitors have been identified to target MUC4. Here, we adapted an in silico screening method using the Cancer Therapeutic Response Database (CTRD) to Identify Small Molecule Inhibitors against Mucins (SMIMs). We identified Bosutinib as a candidate drug to target oncogenic mucins among 126 FDA-approved drugs from CTRD screening. Functionally, Bosutinib treatment alone/and in combination with gemcitabine (Gem)/5' fluorouracil (5FU) reduced in vitro viability, migration, and colony formation in multiple PDAC cell lines as well as human PDAC organoid prolifertaion and growth and in vivo xenograft growth. Further, biochemical and molecular analyses showed that Bosutinib exhibited these functional effects by downregulating MUC4 mucin at both transcript and translation levels in a dose- and time-dependent manner. Mechanistically, global transcriptome analysis in PDAC cells upon treatment with Bosutinib revealed disruption of the Src-ERK/AKT-FosL1 pathway, leading to decreased expression of MUC4 and MUC5AC mucins. Taken together, Bosutinib is a promising, novel, and highly potent SMIMs to target MUC4/MUC5AC mucins. This mucin-targeting effect of Bosutinib can be exploited in the future with cytotoxic agents to treat mucinous tumors.

Chemokine-mucinome interplay in shaping the heterogeneous tumor microenvironment of pancreatic cancer

Pancreatic cancer (PC) is exemplified by a complex immune-suppressive, fibrotic tumor microenvironment (TME), and aberrant expression of mucins. The constant crosstalk between cancer cells, cancer-associated fibroblasts (CAFs), and the immune cells mediated by the soluble factors and inflammatory mediators including cytokines, chemokines, reactive oxygen species (ROS) promote the dynamic temporal switch towards an immune-escape phenotype in the neoplastic cells and its microenvironment that bolsters disease progression. Chemokines have been studied in PC pathogenesis, albeit poorly in the context of mucins, tumor glycocalyx, and TME heterogeneity (CAFs and immune cells). With correlative analysis from PC patients' transcriptome data, support from available literature, and scientific arguments-based speculative extrapolations in terms of disease pathogenesis, we have summarized in this review a comprehensive understanding of chemokine-mucinome interplay during stromal modulation and immune-suppression in PC. Future studies should focus on deciphering the complexities of chemokine-mediated control of glycocalyx maturation, immune infiltration, and CAF-associated immune suppression. Knowledge extracted from such studies will be beneficial to mechanistically correlate the mucin-chemokine abundance in serum versus pancreatic tumors of patients, which may aid in prognostication and stratification of PC patients for immunotherapy.

Muc16 depletion diminishes KRAS-induced tumorigenesis and metastasis by altering tumor microenvironment factors in pancreatic ductal adenocarcinoma

MUC16, membrane-bound mucin, plays an oncogenic role in pancreatic ductal adenocarcinoma (PDAC). However, the pathological role of MUC16 in the PDAC progression, tumor microenvironment, and metastasis in cooperation with KrasG12D and Trp53R172H mutations remains unknown. Deletion of Muc16 with activating mutations KrasG12D/+ and Trp53R172H/+ in mice significantly decreased progression and prolonged overall survival in KrasG12D/+; Trp53R172H/+; Pdx-1-Cre; Muc16-/- (KPCM) and KrasG12D/+; Pdx-1-Cre; Muc16-/- (KCM), as compared to KrasG12D/+; Trp53R172H/+; Pdx-1-Cre (KPC) and KrasG12D/+; Pdx-1-Cre (KC) mice, respectively. Muc16 knockout pancreatic tumor (KPCM) displays decreased tumor microenvironment factors and significantly reduced incidence of liver and lung metastasis compared to KPC. Furthermore, in silico data analysis showed a positive correlation of MUC16 with activated stroma and metastasis-associated genes. KPCM mouse syngeneic cells had significantly lower metastatic and endothelial cell binding abilities than KPC cells. Similarly, KPCM organoids significantly decreased the growth rate compared to KPC organoids. Interestingly, RNA-seq data revealed that the cytoskeletal proteins Actg2, Myh11, and Pdlim3 were downregulated in KPCM tumors. Further knockdown of these genes showed reduced metastatic potential. Overall, our results demonstrate that Muc16 alters the tumor microenvironment factors during pancreatic cancer progression and metastasis by changing the expression of Actg2, Myh11, and Pdlim3 genes.

MUC16 Promotes Liver Metastasis of Pancreatic Ductal Adenocarcinoma by Upregulating NRP2-Associated Cell Adhesion

Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal types of cancer, as it commonly metastasizes to the liver resulting in an overall poor prognosis. However, the molecular mechanism involved in liver metastasis remains poorly understood. Here, we aimed to identify the MUC16-mediated molecular mechanism of PDAC-liver metastasis. Previous studies demonstrated that MUC16 and its C-terminal (Cter) domain are involved in the aggressiveness of PDAC. In this study, we observed MUC16 and its Cter expression significantly high in human PDAC tissues, PDAC organoids, and metastatic liver tissues, while no expression was observed in normal pancreatic tissues using IHC and immunofluorescence (IFC) analyses. MUC16 knockdown in SW1990 and CD18/HPAF PDAC cells significantly decreased the colony formation, migration, and endothelial/p-selectin binding. In contrast, MUC16-Cter ectopic overexpression showed significantly increased colony formation and motility in MiaPaCa2 pancreatic cancer cells. Interestingly, MUC16 promoted cell survival and colonization in the liver, mimicking an ex vivo environment. Furthermore, MUC16 enhanced liver metastasis in the in vivo mouse model. Our integrated analyses of RNA-sequencing suggested that MUC16 alters Neuropilin-2 (NRP2) and cell adhesion molecules in pancreatic cancer cells. Furthermore, we identified that MUC16 regulated NRP2 via JAK2/STAT1 signaling in PDAC. NRP2 knockdown in MUC16-overexpressed PDAC cells showed significantly decreased cell adhesion and migration. Overall, the findings indicate that MUC16 regulates NRP2 and induces metastasis in PDAC.

IMPLICATIONS

This study shows that MUC16 plays a critical role in PDAC liver metastasis by mediating NRP2 regulation by JAK2/STAT1 axis, thereby paving the way for future therapy efforts for metastatic PDAC.

Abstract 1489: MicroRNA-1 targets CXCR4/FOXM1/RRM2 axis regulating small cell lung cancer growth and metastasis

Small cell lung cancer (SCLC) is a high-grade neuroendocrine metastatic lung cancer subtype having a universal relapse and poor prognosis. Limited or extensive-stage SCLC patients have limited therapeutic options due to a lack of potential drug targets. In the quest for novel therapeutic molecules, we performed micro-RNA sequencing from the serum samples and also analyzed bulk RNA-sequencing data from tumors of SCLC patients. We found a consistent downregulation of miR-1 in SCLC. These results were recapitulated in SCLC cell lines and tumor tissues compared to their matched normal. To assess the therapeutic potential of miR-1, we overexpressed miR-1 in SCLC cell lines that translated into decreased cell growth and oncogenic signaling. Mechanistic studies revealed that CXCR4 is a direct target for miR-1 in SCLC. Intracardiac injection of SCLC cell lines in the mouse models showed that overexpression of miR-1 decreases the distant organ metastasis, whereas miR-1 sponging potentiates aggressiveness and metastasis. Furthermore, we identified FOXM1-RRM2 as a unique downstream target of the miR-1/CXCR4 axis involved in the growth and metastasis of SCLC. Our results showed that FOXM1 directly binds to the promoter site of RRM2 and regulates its activity. Overexpression of miR-1 decreases the expression and activity of FOXM1-RRM2 through CXCR4 that reduces cell growth and metastasis. Taken together, our results suggest that miR-1 decreases SCLC metastasis by targeting the CXCR4/FOXM1-RRM2 axis and has a high potential for the development of novel SCLC therapies.

Citation Format: Parvez Khan, Jawed A. Siddiqui, Shailendra Kumar Maurya, Tamara Mirzapoiazova, Ranjana Kanchan, Ramakanth Chirravuri Venkata, Pranita Atri, Wemin Tang, NaveenKumar Perumal, Prakash Kshirsagar, Mahek Fatima, Md Arafat Khan, Sanjib Chaudhary, Asad Ur Rehman, Imayavaramban Lakshmanan, Sidharth Mahapatra, Prakash Kulkarni, Apar Kishor Ganti, Maneesh Jain, David Oupicky, Ravi Salgia, Surinder Kumar Batra, Mohd Wasim Nasser. MicroRNA-1 targets CXCR4/FOXM1/RRM2 axis regulating small cell lung cancer growth and metastasis [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 1489.

Abstract 2431: A novel role of MUC5AC/CD44v6/c-Met axis in breast cancer brain metastasis

Brain metastasis (BrM) is one of the leading causes of mortality in breast cancer (BC). Although BrM is associated with all BC subtypes, but it is more prevalent in triple-negative and HER2+ BC patients. Recent advancements in the multimodality treatment of primary BC have prolonged patient survival, which has in turn increased the incidence of BrM. Due to the lack of understanding of BC-BrM, there is no reliable biomarker and effective therapeutic strategy. In this regard, using publicly available databases and RNA-Seq analysis, we observed that secretory mucin MUC5AC is significantly upregulated in BC brain metastatic cell lines and tissues compared to their respective control. We validated these observations in brain-seeking BC (BSBC) cell lines and brain metastatic tissues at protein levels. Interestingly, we found that the MUC5AC levels were significantly increased in the serum of CNS metastatic patients relative to healthy donors and BC patients. Our functional studies revealed that silencing of MUC5AC in BSBC cell lines showed a significant decrease in cell adhesion, migration, brain metastatic potential, and increased survival of mice. Exploring the molecular mechanism further revealed that MUC5AC interacts with CD44v6 and c-Met and deletion of MUC5AC demonstrated a decrease in the expression of c-MET and CD44v6. Furthermore, pharmacological targeting of MUC5AC through c-Met inhibitor reduces the expression of CD44v6 and MUC5AC, suggesting that c-Met inhibitors could be used as a novel therapeutics for targeting MUC5AC and thereby attenuating BC brain metastasis. Altogether, our study demonstrates that MUC5AC/CD44v6/c-Met axis could be used as a novel approach to prevent breast cancer brain metastasis.

Citation Format: Shailendra Kumar Maurya, Jawed A. Siddiqui, Shailendra K. Gautama, Ranjana K. Kanchan, Ramesh Pothuraju, Gopalakrishnan Natarajan, Pranita Atri, Ramakanth C. Venkata, Rakesh Bhatia, Parvez Khan, Asad Ur Rehmana, Sanjib Chaudhary, Naveenkumar Perumal, Sidharth Mahapatra, Hitendra S. Chand, Maneesh Jain, Juan A. Santamaria-Barriab, Diana M. Cittelly, Surinder K. Batra, Mohd W. Nasser. A novel role of MUC5AC/CD44v6/c-Met axis in breast cancer brain metastasis [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 2431.

Differential expression profile of CXC-receptor-2 ligands as potential biomarkers in pancreatic ductal adenocarcinoma

The discovery of early detection markers of pancreatic cancer (PC) disease is highly warranted. We analyzed the expression profile of different CXC-receptor-2 (CXCR2) ligands in PC cases for the potential of biomarker candidates. Analysis of different PDAC microarray datasets with matched normal and pancreatic tumor samples and next-generation sequenced transcriptomics data using an online portal showed significantly high expression of CXCL-1, 3, 5, 6, 8 in the tumors of PC patients. High CXCL5 expression was correlated to poor PC patient survival. Interestingly, mRNA and protein expression analysis of human PC cell lines showed higher CXCL2, 3, and 5 expressions in cell lines derived from metastatic sites than primary tumors. Furthermore, we utilized immunohistochemistry (IHC) to evaluate the expression of CXCR2 ligands in the human PC tumors and observed positive staining for CXCL1, 3, and 8 with a higher average IHC composite score of CXCL3 in the PC tissue specimens than the normal pancreas. We also observed an increase in the expression of mouse CXCL1, 3, and 5 in the pre-cancerous lesions of tumors and metastasis tissues derived from the PDX-cre-LSL-Kras^G12D mouse model. Together, our data suggest that different CXCR2 ligands show the potential of being utilized as a diagnostic biomarker in PC patients.

Mucin 5AC Serves as the Nexus for β-Catenin/c-Myc Interplay to Promote Glutamine Dependency During Pancreatic Cancer Chemoresistance

BACKGROUND & AIMS

A major clinical challenge for patients with pancreatic cancer (PC) is metabolic adaptation. Neoplastic cells harboring molecular perturbations suffice for their increased anabolic demand and nucleotide biosynthesis to acquire chemoresistance. The mucin 5AC expressed de novo in malignant pancreas promotes cancer cell stemness and is significantly associated with poor patient survival. Identification of MUC5AC-associated drivers of chemoresistance through metabolic alterations may facilitate the sculpting of a new combinatorial regimen.

METHODS

The contributions of MUC5AC to glutaminolysis and gemcitabine resistance were examined by The Cancer Genome Atlas data analysis, RNA sequencing, and immunohistochemistry analysis on pancreatic tissues of KrasG12D;Pdx1-Cre (KC) and KrasG12D;Pdx1-Cre;Muc5ac-/- mice. These were followed by metabolite flux assays as well as biochemical and xenograft studies on MUC5AC-depleted human and murine PC cells. Murine and human pancreatic 3-dimensional tumoroids were used to evaluate the efficacy of gemcitabine in combination with β-catenin and glutaminolysis inhibitors.

RESULTS

Transcriptional analysis showed that high MUC5AC-expressing human and autochthonous murine PC tumors exhibit higher resistance to gemcitabine because of enhanced glutamine use and nucleotide biosynthesis. Gemcitabine treatment led to MUC5AC overexpression, resulting in disruption of E-cadherin/β-catenin junctions and the nuclear translocation of β-catenin, which increased c-Myc expression, with a concomitant rise in glutamine uptake and glutamate release. MUC5AC depletion and glutamine deprivation sensitized human PC cells to gemcitabine, which was obviated by glutamine replenishment in MUC5AC-expressing cells. Coadministration of β-catenin and glutaminolysis inhibitors with gemcitabine abrogated the MUC5AC-mediated resistance in murine and human tumoroids.

CONCLUSIONS

The MUC5AC/β-catenin/c-Myc axis increases the uptake and use of glutamine in PC cells, and cotargeting this axis along with gemcitabine may improve therapeutic efficacy in PC.

Disruption of FDPS/Rac1 axis radiosensitizes pancreatic ductal adenocarcinoma by attenuating DNA damage response and immunosuppressive signalling

Background

Radiation therapy (RT) has a suboptimal effect in patients with pancreatic ductal adenocarcinoma (PDAC) due to intrinsic and acquired radioresistance (RR). Comprehensive bioinformatics and microarray analysis revealed that cholesterol biosynthesis (CBS) is involved in the RR of PDAC. We now tested the inhibition of the CBS pathway enzyme, farnesyl diphosphate synthase (FDPS), by zoledronic acid (Zol) to enhance radiation and activate immune cells.

Methods

We investigated the role of FDPS in PDAC RR using the following methods: in vitro cell-based assay, immunohistochemistry, immunofluorescence, immunoblot, cell-based cholesterol assay, RNA sequencing, tumouroids (KPC-murine and PDAC patient-derived), orthotopic models, and PDAC patient's clinical study.

Findings

FDPS overexpression in PDAC tissues and cells (P < 0.01 and P < 0.05) is associated with poor RT response and survival (P = 0.024). CRISPR/Cas9 and pharmacological inhibition (Zol) of FDPS in human and mouse syngeneic PDAC cells in conjunction with RT conferred higher PDAC radiosensitivity in vitro (P < 0.05, P < 0.01, and P < 0.001) and in vivo (P < 0.05). Interestingly, murine (P = 0.01) and human (P = 0.0159) tumouroids treated with Zol+RT showed a significant growth reduction. Mechanistically, RNA-Seq analysis of the PDAC xenografts and patients-PBMCs revealed that Zol exerts radiosensitization by affecting Rac1 and Rho prenylation, thereby modulating DNA damage and radiation response signalling along with improved systemic immune cells activation. An ongoing phase I/II trial (NCT03073785) showed improved failure-free survival (FFS), enhanced immune cell activation, and decreased microenvironment-related genes upon Zol+RT treatment.

Interpretation

Our findings suggest that FDPS is a novel radiosensitization target for PDAC therapy. This study also provides a rationale to utilize Zol as a potential radiosensitizer and as an immunomodulator in PDAC and other cancers.

Funding

National Institutes of Health (P50, P01, and R01).

MiR-212-3p functions as a tumor suppressor gene in group 3 medulloblastoma via targeting nuclear factor I/B (NFIB)

Haploinsufficiency of chromosome 17p and c-Myc amplification distinguish group 3 medulloblastomas which are associated with early metastasis, rapid recurrence, and swift mortality. Tumor suppressor genes on this locus have not been adequately characterized. We elucidated the role of miR-212-3p in the pathophysiology of group 3 tumors. First, we learned that miR-212-3p undergoes epigenetic silencing by histone modifications in group 3 tumors. Restoring its expression reduced cancer cell proliferation, migration, colony formation, and wound healing in vitro and attenuated tumor burden and improved survival in vivo. MiR-212-3p also triggered c-Myc destabilization and degradation, leading to elevated apoptosis. We then isolated an oncogenic target of miR-212-3p, i.e. NFIB, a nuclear transcription factor implicated in metastasis and recurrence in various cancers. Increased expression of NFIB was confirmed in group 3 tumors and associated with poor survival. NFIB silencing reduced cancer cell proliferation, migration, and invasion. Concurrently, reduced medullosphere formation and stem cell markers (Nanog, Oct4, Sox2, CD133) were noted. These results substantiate the tumor-suppressive role of miR-212-3p in group 3 MB and identify a novel oncogenic target implicated in metastasis and tumor recurrence.

Differential gene expression-based connectivity mapping identified novel drug candidate and improved Temozolomide efficacy for Glioblastoma

BACKGROUND

Glioblastoma (GBM) has a devastating median survival of only one year. Treatment includes resection, radiation therapy, and temozolomide (TMZ); however, the latter increased median survival by only 2.5 months in the pivotal study. A desperate need remains to find an effective treatment.

METHODS

We used the Connectivity Map (CMap) bioinformatic tool to identify candidates for repurposing based on GBM's specific genetic profile. CMap identified histone deacetylase (HDAC) inhibitors as top candidates. In addition, Gene Expression Profiling Interactive Analysis (GEPIA) identified HDAC1 and HDAC2 as the most upregulated and HDAC11 as the most downregulated HDACs. We selected PCI-24781/abexinostat due to its specificity against HDAC1 and HDAC2, but not HDAC11, and blood-brain barrier permeability.

RESULTS

We tested PCI-24781 using in vitro human and mouse GBM syngeneic cell lines, an in vivo murine orthograft, and a genetically engineered mouse model for GBM (PEPG - PTENflox/+; EGFRvIII+; p16Flox/- & GFAP Cre +). PCI-24781 significantly inhibited tumor growth and downregulated DNA repair machinery (BRCA1, CHK1, RAD51, and O6-methylguanine-DNA- methyltransferase (MGMT)), increasing DNA double-strand breaks and causing apoptosis in the GBM cell lines, including an MGMT expressing cell line in vitro. Further, PCI-24781 decreased tumor burden in a PEPG GBM mouse model. Notably, TMZ + PCI increased survival in orthotopic murine models compared to TMZ + vorinostat, a pan-HDAC inhibitor that proved unsuccessful in clinical trials.

CONCLUSION

PCI-24781 is a novel GBM-signature specific HDAC inhibitor that works synergistically with TMZ to enhance TMZ efficacy and improve GBM survival. These promising MGMT-agnostic results warrant clinical evaluation.

Mucin Expression and Splicing Determine Novel Subtypes and Patient Mortality in Pancreatic Ductal Adenocarcinoma

PURPOSE

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive malignancy demonstrating aberrant and progressive expression of mucins. The contribution of individual mucins has been extensively investigated in PDAC; however, comprehensive mucin profiling including splice variants in PDAC tumors has not been reported.

EXPERIMENTAL DESIGN

Using publicly available RNA sequencing (RNA-seq) datasets, we assess the expression of mucin family members and their splice variants (SV) in PDAC tumor samples for the first time. Mucin SVs that are correlated with PDAC patient survival are validated in a cohort of patient tumor samples. Further, we use computational methods to derive novel pancreatic tumor subtypes using mucin expression signatures and their associated activated pathways.

RESULTS

Principal component analysis identified four novel mucin-based PDAC subtypes. Pathway analysis implicated specific biological signatures for each subtype, labeled (i) immune activated, (ii) progressive, (iii) pancreatitis-initiated, and (iv) anti-inflammatory/PanIN-initiated. Assessing mucin SVs, significantly longer survival is observed with higher expression of 4 MUC1 and 1 MUC13 SVs, whereas patients expressing 2 MUC4 and 1 MUC16 SVs had shorter survival. Using a whole-transcriptome correlation, a three-gene panel, including ESRP2, PTK6, and MAGEH1, is designated to assess PDAC tumor sample cellularity by PCR. One MUC4 SV and one MUC13 SV are quantified in a separate PDAC patient cohort, and their effects on survival are experimentally validated.

CONCLUSIONS

Altogether, we demonstrate the unique expression pattern of mucins, four mucin-based PDAC subtypes, and the contribution of MUC1, MUC4, and MUC16 SVs in PDAC patient survival.

Protein Phosphatase 2A as a Therapeutic Target in Small Cell Lung Cancer

Protein phosphatase 2A (PP2A), a serine/threonine phosphatase involved in the regulation of apoptosis, proliferation, and DNA-damage response, is overexpressed in many cancers, including small cell lung cancer (SCLC). Here we report that LB100, a small molecule inhibitor of PP2A, when combined with platinum-based chemotherapy, synergistically elicited an antitumor response both in vitro and in vivo with no apparent toxicity. Using inductively coupled plasma mass spectrometry, we determined quantitatively that sensitization via LB100 was mediated by increased uptake of carboplatin in SCLC cells. Treatment with LB100 alone or in combination resulted in inhibition of cell viability in two-dimensional culture and three-dimensional spheroid models of SCLC, reduced glucose uptake, and attenuated mitochondrial and glycolytic ATP production. Combining LB100 with atezolizumab increased the capacity of T cells to infiltrate and kill tumor spheroids, and combining LB100 with carboplatin caused hyperphosphorylation of the DNA repair marker γH2AX and enhanced apoptosis while attenuating MET signaling and invasion through an endothelial cell monolayer. Taken together, these data highlight the translational potential of inhibiting PP2A with LB100 in combination with platinum-based chemotherapy and immunotherapy in SCLC.

Dual blockade of EGFR and CDK4/6 delays head and neck squamous cell carcinoma progression by inducing metabolic rewiring

Despite preclinical success, monotherapies targeting EGFR or cyclin D1-CDK4/6 in Head and Neck squamous cell carcinoma (HNSCC) have shown a limited clinical outcome. Here, we aimed to determine the combined effect of palbociclib (CDK4/6) and afatinib (panEGFR) inhibitors as an effective strategy to target HNSCC. Using TCGA-HNSCC co-expression analysis, we found that patients with high EGFR and cyclin D1 expression showed enrichment of gene clusters associated with cell-growth, glycolysis, and epithelial to mesenchymal transition processes. Phosphorylated S6 (p-S6), a downstream effector of EGFR and cyclin D1-CDK4/6 signalling, showed a progressive increase from normal oral tissues to leukoplakia and frank malignancy, and associated with poor outcome of the patients. This increased p-S6 expression was drastically reduced after combination treatment with afatinib and palbociclib in the cell lines and mouse models, suggesting its utiliy as a prognostic marker in HNSCC. Combination treatment also reduced the cell growth and induced cell senescence via increasing reactive oxygen species with concurrent ablation of glycolytic and tricarboxylic acid cycle intermediates. Finally, our findings in sub-cutaneous and genetically engineered mouse model (K14-CreERtam;LSL-KrasG12D/+;Trp53R172H/+) studies showed a significant reduction in the tumor growth and delayed tumor progression after combination treatment. This study collectively demonstrates that dual targeting may be a critical therapeutic strategy in blocking tumor progression via inducing metabolic alteration and warrants clinical evaluation.

BIOL-07. MIR-212 FUNCTIONS AS A TUMOR SUPPRESSOR GENE IN GROUP 3 MEDULLOBLASTOMA VIA TARGETING NUCLEAR FACTOR I/B (NFIB)

Medulloblastoma (MB), the most frequent malignant pediatric brain tumor is subdivided into four primary subgroups, i.e. wingless-type (WNT), sonic hedgehog (SHH), group 3, and group 4. Haploinsufficiency of chromosome 17p13.3 and c-myc amplification distinguish high-risk group 3 tumors, which are associated with rapid metastasis, recurrence and early mortality. We sought to identify the role of miR-212, which resides on chromosome 17p13.3, in the pathophysiology of group 3 MB. RNA expression analyses revealed dramatically reduced levels of miR-212 in group 3 tumors and cell lines mainly through epigenetic silencing via histone modifications (deacetylation). Restoring in vitro miR-212 expression reduced tumor cell proliferation, colony formation, wound healing, migration and invasion with decreased p-AKT and p-ERK levels in group 3 MB cell lines. Interestingly, a shift in differential c-myc phosphorylation (from serine-62 to threonine-58) was also discovered with miR-212 expression, resulting in reduced total c-myc levels, concurrent with elevated cellular apoptosis. In turn, pro-apoptotic binding partners of c-myc, i.e. Bin-1 and P19ARF, were upregulated in these cells. These findings were recapitulated in stable inducible miR-212 expressing tumor cells. Using a combination of transcriptomic data and a dual luciferase assay, we isolated an important oncogenic target of miR-212, i.e, NFIB, a nuclear transcription factor implicated in metastasis and recurrence. Increased expression of NFIB was confirmed in group 3 tumors, with poor survival shown in high NFIB-expressing patients. As prior, transient NFIB silencing in vitro reduced not only tumor cell proliferation, colony formation, wound healing, migration and invasion, but also medullosphere formation along with decreased expression of stem cell markers (Nanog, Oct4, Sox2, CD133), confirming its role in tumor recurrence possibly via augmenting tumor stemness. Taken together, these results substantiate the tumor suppressive role of miR-212 in group 3 MB and provide a potential new oncogenic target implicated in tumor recurrence, NFIB.

BIOL-06. MIR-1253 POTENTIATES CISPLATIN RESPONSE IN PEDIATRIC GROUP 3 MEDULLOBLASTOMA BY REGULATING FERROPTOSIS

Medulloblastoma (MB), the most common malignant pediatric brain tumor and a leading cause of childhood mortality, is stratified into four primary subgroups, i.e. SHH (sonic hedgehog), WNT (wingless), and non-SHH/WNT groups 3 and 4, the latter representing high-risk MB. Haploinsufficiency of 17p13.3, which houses the tumor suppressor gene miR-1253, characterizes high-risk tumors. Despite improvements in targeted therapies, a limited proportion of these patients survive the disease. Capitalizing on the tumor suppressive properties of miRNAs as adjuncts to chemotherapy provides a promising alternative to current therapeutic strategies. In this study, we explored the potentiating effects of miR-1253 on cisplatin cytotoxicity in group 3 MB. First, in silico and in vitro analyses revealed an upregulation of ABCB7, a mitochondrial iron transporter and putative target of miR-1253, in MB cell lines and group 3 MB tumors. Overexpression of miR-1253 resulted in downregulation of ABCB7 and GPX4, a critical ferroptosis regulator, which consequently increased labile mitochondrial iron pool and, in turn, mitochondrial ROS (mtROS). Complementarily, we demonstrated, using CRISPR knockdown of ABCB7, ferroptosis induction with downregulation of GPx4 expression, liberation of free iron, mtROS generation and lipid peroxidation. Cisplatin is reported as an inducer of both apoptosis and ferroptosis-mediated cancer cell death. Therapeutically, the combination of miR-1253 and cisplatin led to an additive effect on cell viability, colony formation, apoptosis, and ROS generation. In turn, treatment with mtROS inhibitor (MnTBAP) and ferroptosis inhibitor (Ferrostatin) lead to partial recovery from the cytotoxic effects of this combination therapy. These studies identify an miR-1253-induced ferroptosis pathway targeting the ABCB7/GPX4/mtROS axis in group 3 MB. They further provide proof-of-concept in using miR-based therapeutics to augment treatment efficacy of current chemotherapeutics in the treatment of high-risk tumors.

ST6GalNAc-I promotes lung cancer metastasis by altering MUC5AC sialylation

Lung cancer (LC) is the leading cause of cancer-related mortality. However, the molecular mechanisms associated with the development of metastasis are poorly understood. Understanding the biology of LC metastasis is critical to unveil the molecular mechanisms for designing targeted therapies. We developed two genetically engineered LC mouse models Kras^G12D/+ ; Trp53^R172H/+ ; Ad-Cre (KPA) and Kras^G12D/+ ; Ad-Cre (KA). Survival analysis showed significantly (P = 0.0049) shorter survival in KPA tumor-bearing mice as compared to KA, suggesting the aggressiveness of the model. Our transcriptomic data showed high expression of N-acetylgalactosaminide alpha-2, 6-sialyltransferase 1 (St6galnac-I) in KPA compared to KA tumors. ST6GalNAc-I is an O-glycosyltransferase, which catalyzes the addition of sialic acid to the initiating GalNAc residues forming sialyl Tn (STn) on glycoproteins, such as mucins. Ectopic expression of species-specific p53 mutants in the syngeneic mouse and human LC cells led to increased cell migration and high expression of ST6GalNAc-I, STn, and MUC5AC. Immunoprecipitation of MUC5AC in the ectopically expressing p53^R175H cells exhibited higher affinity toward STn. In addition, ST6GalNAc-I knockout (KO) cells also showed decreased migration, possibly due to reduced glycosylation of MUC5AC as observed by low STn on the glycoprotein. Interestingly, ST6GalNAc-I KO cells injected mice developed less liver metastasis (P = 0.01) compared to controls, while colocalization of MUC5AC and STn was observed in the liver metastatic tissues of control mice. Collectively, our findings support the hypothesis that mutant p53^R175H mediates ST6GalNAc-I expression, leading to the sialyation of MUC5AC, and thus contribute to LC liver metastasis.

MBRS-72. MiR-212 FUNCTIONS AS A TUMOR SUPPRESSOR GENE IN GROUP 3 MEDULLOBLASTOMA VIA TARGETING NUCLEAR FACTOR I/B (NFIB)

Medulloblastoma (MB), the most frequent malignant pediatric brain tumor is divided into four primary subgroups, i.e. wingless-type (WNT), sonic hedgehog (SHH), group 3, and group 4. Haploinsufficiency of chromosome 17p13.3 and c-myc amplification distinguish high-risk group 3 tumors and are associated with rapid recurrence and early mortality. We sought to identify the role of miR-212, which resides on chromosome 17p13.3, in the pathophysiology of group 3 medulloblastoma. RNA expression analyses revealed dramatically reduced levels of miR-212 in group 3 tumors and cell lines mainly through epigenetic silencing via histone modification (deacetylation). Restoring in vitro expression reduced tumor cell proliferation with decreased p-AKT and p-ERK levels, colony formation, migration and invasion in group 3 MB. Interestingly, a shift in differential c-myc phosphorylation (from serine-62 to threonine-58) was noted, resulting in reduced total c-myc levels, concurrent with elevated cellular apoptosis. In turn, pro-apoptotic binding partners of c-myc, i.e. Bin-1 and P19^ARF, were upregulated in these cells. A dual luciferase assay confirmed direct targeting of miR-212 to NFIB, a nuclear transcription factor implicated in metastasis and recurrence. Concurrently, increased expression of NFIB was confirmed in group 3 MB tumors with poor survival in high NFIB-expressing patients. Transient NFIB silencing in vitro reduced tumor cell proliferation, migration and invasion, and medullosphere formation along with a reduction in stem cell markers (Nanog, Oct4, Sox2, CD133) and the multi-drug resistance maker, ABCG2. Taken together, these results substantiate the tumor suppressive role of miR-212 in group 3 medulloblastomas and provide a potential new therapeutic target, NFIB.

MBRS-13. MiR-1253 POTENTIATES CISPLATIN RESPONSE IN PEDIATRIC MEDULLOBLASTOMA BY REGULATING FERROPTOSIS

Despite improvements in targeted therapies, few group 3 medulloblastoma patients survive long-term. Haploinsufficiency of 17p13.3 is a hallmark of these high-risk tumors; included within this locus is miR-1253, which has tumor suppressive properties in medulloblastoma. Therapeutic strategies capitalizing on the anti-neoplastic properties of miRNAs can provide promising adjuncts to chemotherapy. In this study, we explored the potentiation of miR-1253 on cisplatin cytotoxicity in group 3 MB. Overexpression of miR-1253 sensitized group 3 MB cell lines to cisplatin, leading to a pronounced downregulation in cell viability and induction of apoptosis. Cisplatin is reported as an inducer of both apoptosis and ferroptosis-mediated cancer cell death. In silico analysis revealed an upregulation of several ABC transporters in high-risk MB tumors. When compared to cell lines overexpressing miR-1253, the ABC transporter ABCB7, which regulates both apoptosis and ferroptosis, was revealed as a putative target of miR-1253 with poor survival that may facilitate its chemosensitizing effects by modulating mitochondrial ROS and HIF1α-driven NFκB signaling. We observed high expression of ABCB7 and GPX4, ferroptosis regulators, in MB patients with poor overall survival. MiR-1253 negatively regulated the expression of ABCB7 in Group 3 MB cell lines and induced cytoplasmic ROS and mitochondrial O2-, suggesting ROS-mediated induction of ferroptosis through regulation of ABCB7 and GPX4. Treatment with ROS and ferroptosis inhibitors rescued miR-1253 transfected cells treated with cisplatin. We conclude that miR-1253 induced ROS and potentiated the ferroptotic effects of cisplatin via targeting miR-1253/ABCB7/GPX4/mtROS axis.

Differential mutation spectrum and immune landscape in African Americans versus Whites: A possible determinant to health disparity in head and neck cancer

African Americans (AA) with Head and Neck Squamous Cell Carcinoma (HNSCC) have a worse disease prognosis than White patients despite adjusting for socio-economic factors, suggesting the potential biological contribution. Therefore, we investigated the genomic and immunological components that drive the differential tumor biology among race. We utilized the cancer genome atlas and cancer digital archive of HNSCC patients (1992-2013) for our study. We found that AA patients with HNSCC had a higher frequency of mutation compared to Whites in the key driver genes-P53, FAT1, CASP8 and HRAS. AA tumors also exhibited lower intratumoral infiltration of effector immune cells (CD8+, γδT, resting memory CD4+ and activated memory CD4+ T cells) with shorter survival than Whites. Unsupervised hierarchical clustering of differentially expressed genes demonstrated distinct gene clusters between AA and White patients with unique signaling pathway enrichments. Connectivity map analysis identified drugs (Neratinib and Selumetinib) that target aberrant PI3K/RAS/MEK signaling and may reduce racial disparity in therapy response.

Secretory Mucin 5AC Promotes Neoplastic Progression by Augmenting KLF4-Mediated Pancreatic Cancer Cell Stemness

Secreted mucin 5AC (MUC5AC) is the most abundantly overexpressed member of the mucin family during early pancreatic intraepithelial neoplasia stage I (PanIN-I) of pancreatic cancer. To comprehend the contribution of Muc5ac in pancreatic cancer pathology, we genetically ablated it in an autochthonous murine model (KrasG12D; Pdx-1cre, KC), which mirrors the early stages of pancreatic cancer development. Neoplastic onset and the PanIN lesion progression were significantly delayed in Muc5ac knockout (KrasG12D; Pdx-1 cre; Muc5ac-/-, KCM) animals with a 50% reduction in PanIN-2 and 70% reduction in PanIN-3 lesions compared with KC at 50 weeks of age. High-throughput RNA-sequencing analysis from pancreatic tissues of KCM animals revealed a significant decrease in cancer stem cell (CSC) markers Aldh1a1, Klf4, EpCAM, and CD133. Furthermore, the silencing of MUC5AC in human pancreatic cancer cells reduced their tumorigenic propensity, as indicated by a significant decline in tumor formation frequency by limiting dilution assay upon subcutaneous administration. The contribution of MUC5AC in CSC maintenance was corroborated by a significant decrease in tumor burden upon orthotopic implantation of MUC5AC-depleted pancreatic cancer cells. Mechanistically, MUC5AC potentiated oncogenic signaling through integrin αvβ5, pSrc (Y416), and pSTAT3 (Y705). Phosphorylated STAT3, in turn, upregulated Klf4 expression, thereby enriching the self-renewing CSC population. A strong positive correlation of Muc5ac with Klf4 and pSTAT3 in the PanIN lesions of KC mouse pancreas reinforces the crucial involvement of MUC5AC in bolstering the CSC-associated tumorigenic properties of Kras-induced metaplastic cells, which leads to pancreatic cancer onset and progression. SIGNIFICANCE: This study elucidates that de novo expression of MUC5AC promotes cancer cell stemness during Kras-driven pancreatic tumorigenesis and can be targeted for development of a novel therapeutic regimen.

CXCR3 and Cognate Ligands are Associated with Immune Cell Alteration and Aggressiveness of Pancreatic Ductal Adenocarcinoma

PURPOSE

The cytokine milieu in pancreatic ductal adenocarcinoma (PDAC) promotes tumor progression and immune suppression, contributing to the dismal prognosis of patients with PDAC. The roles of many of these cytokines, however, have not been thoroughly investigated in PDAC.

EXPERIMENTAL DESIGN

PDAC microarray and The Cancer Genome Atlas datasets were analyzed to identify cytokines and cognate receptors overexpressed in PDAC and associated with survival. Pathway and CIBERSORT analyses were used to elucidate potential mechanisms of altered patient survival. Comparative analysis of cytokine expression in KPC (K-ras^G12D; TP53^R172H; Pdx-1cre) and KC (K-ras^G12D; Pdx-1cre) PDAC models and multicolor immunofluorescence (IF) staining of human PDAC-resected samples were used to validate these findings.

RESULTS

CXCL9 and CXCL10 were among the most highly overexpressed cytokines by bioinformatics analyses, while their receptor, CXCR3, was significantly overexpressed by IHC analysis. Higher CXCR3 ligand expression was associated with shorter overall survival, while high CXCR3 expression was associated with better survival. The CXCR3 ligands, CXCL4, 9, and 10, were overexpressed in KPC compared with KC mice. Pathway analysis of CXCR3- and CXCR3 ligand-associated genes showed that CXCR3 is a marker of antitumor immunity, while its ligands may promote immunosuppression. CIBERSORT and IF studies of PDAC tissues demonstrated that high CXCR3 expression was associated with increased CD8⁺ T-cell and naïve B-cell signatures and loss of plasma cell signatures. CXCR3 ligand expression was associated with increased CD8⁺ T-cell signatures and loss of natural killer-cell signatures.

CONCLUSIONS

CXCR3 ligands are overexpressed in PDAC and are associated with poor survival likely related to alterations in tumor immune infiltrate/activity.

Abstract 6194: Evaluation of the differential expression profile of CXC-receptor-2 ligands for potential biomarker candidates in pancreatic ductal adenocarcinoma

The major complexity of pancreatic cancer (PC) cases is late clinical presentation and metastasis at the time of detection. Achievement of significant clinical advancement in the treatment of PC disease needs extensive research efforts to discover early detection markers of this disease. In this study, we wanted to analyze the expression profile of different CXC-receptor 2 (CXCR2) ligands, well documented in the literature for their role in inflammation, in pancreatic ductal adenocarcinoma (PDAC) cases for the potential of biomarker candidates. With this perspective, we utilized different online portals to evaluate mRNA expression of different CXCR2 ligands CXCL1-3 and 5-8 in PDAC tumors in comparison with the normal pancreas. Analysis of GEO PDAC microarray dataset, GSE15471 containing 39 pancreatic tumors with corresponding matched normal samples, showed significantly higher expression of CXCL-3,5,6,8 in pancreatic tumors in comparison with their matched normal tissue. Similarly, analysis of next-generation sequenced transcriptomics data on MiPanda portal showed higher expression of CXCL-1,3,5,6,8 in pancreatic tumors of 417 PC patients in comparison with the normal pancreas. Interestingly, only CXCL5 ligand showed association with patient survival data based on the mRNA, miRNA, or lncRNA expression on Oncolnc-TCGA portal. PC patients with lower CXCL5 expression showed significantly higher survival in comparison with patients with higher CXCL5 expression. Next, we evaluated the expression pattern of CXCR2 ligands CXCL1, 3, and 8 in the human PC tissue specimens and using pancreatic tissues derived from disease progression mouse model of PDX-cre-LSL-KRASG12D. Immunohistochemical (IHC) analysis revealed positive staining for CXCL1, and 3 in both in the ducts and the stroma of the human PC tumors and normal pancreas specimens. However, in normal pancreas, the expression was localized only to the acinar cell compartment and pancreatic ducts were negative for expression. Overall the average composite score of CXCL3 IHC was higher in the PC tissue specimens versus the normal pancreas. Furthermore, we observed an increase in the expression of mCXCL1, 3, and 5 in the pre-cancerous lesions of tumors and metastasis derived from PDX-cre-LSL-KrasG12D. However, unlike the human tissues the normal murine pancreas was negative for the expression of mCXCL1 and 5. Lastly, mRNA expression analysis of nine different human PC cell lines showed higher CXCL2, 3, and 5 in cell lines derived from metastatic sites in comparison with cell lines derived from primary tumors. Our observations resonated with CXCL5 protein levels in these cell lines. In conclusion, our data suggest that among different CXCR2 ligands, CXCL5 shows the potential of being used as a biomarker in PC patients.

Citation Format: Sugandha Saxena, Abhilasha Purohit, Evie Ehrhorn, Pranita Atri, Caitlin Molczyk, Michelle Varney, Rakesh K. Singh. Evaluation of the differential expression profile of CXC-receptor-2 ligands for potential biomarker candidates in pancreatic ductal adenocarcinoma [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 6194.

Abstract 6072: MUC16-Cter cleavage increases the metastatic potential in pancreatic cancer

Pancreatic cancer (PC) is one of the most lethal malignant tumors. Several membrane-bound mucins are overexpressed in PC, including MUC16. The role and molecular mechanism of MUC16 mucin, particularly carboxyl-terminal domain (MUC16-Cter) in metastasis of pancreatic cancer, are poorly understood. Therefore, we hypothesize that the “MUC16-Cter domain plays a vital role in facilitating metastasis in pancreatic cancer”. Here, we knockout MUC16 in Capan 1 PC cells and overexpressed MUC16-Cter (F114AA) domain in MiaPaCa2 PC cells to study its functional impact in PC. Capan-1 MUC16 knockout cells displayed a significant decrease in colony-forming by in vitro tumorigenicity assay, endothelial binding, and P-selectin binding ability compared to control cells. Whereas, MUC16-Cter domain overexpressed MiaPaCa2 cells showed a significant increase in colony formation as compared to vector control cells. These results suggest that MUC16 plays a role in promoting in vitro tumorigenicity and facilitating intravasation and circulation of PC cell by interacting with endothelial cells during the metastatic spread of PC cells. Interestingly, we observed that chemotherapeutic drug (gemcitabine) induces MUC16-Cter cleavage in PC cells. We generated a genetically engineered mouse model Muc16-/- with KrasG12D, Trp53R172H/+, Pdx1-Cre (KPCM) background to study the role of Muc16 in PC tumorigenesis and metastasis with existing KPC model. KPCM showed decreased the early onset of cancer formation compared to KPC. Further, the Kaplan Meier test showed an increased survival rate in Muc16 -/- with KPC background as compared to KPC mice. EMT markers showed decreased expression in KPCM compared to KPC tumors. KPCM cells showed a significant decreased in migratory potential, endothelial, and P-selectin binding ability KPC PC cells. In conclusion, our in vitro and in vivo findings confirm that MUC16 and its Cter domain might play an essential role during the PC tumorigenesis and metastasis. Therefore, targeting MUC16-Cter might be an ideal therapeutic strategy for inhibiting tumorigenesis and metastasis of PC.

Citation Format: Saravanakumar Marimuthu, Imayavaramban Lakshmanan, Sakthivel Muniyan, Pranita Atri, Maneesh Jain, Moorthy P. Ponnusamy, Surinder K. Batra. MUC16-Cter cleavage increases the metastatic potential in pancreatic cancer [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 6072.

MiR-1253 exerts tumor-suppressive effects in medulloblastoma via inhibition of CDK6 and CD276 (B7-H3)

Of the four primary subgroups of medulloblastoma, the most frequent cytogenetic abnormality, i17q, distinguishes Groups 3 and 4 which carry the highest mortality; haploinsufficiency of 17p13.3 is a marker for particularly poor prognosis. At the terminal end of this locus lies miR-1253, a brain-enriched microRNA that regulates bone morphogenic proteins during cerebellar development. We hypothesized miR-1253 confers novel tumor-suppressive properties in medulloblastoma. Using two different cohorts of medulloblastoma samples, we first studied the expression and methylation profiles of miR-1253. We then explored the anti-tumorigenic properties of miR-1253, in parallel with a biochemical analysis of apoptosis and proliferation, and isolated oncogenic targets using high-throughput screening. Deregulation of miR-1253 expression was noted, both in medulloblastoma clinical samples and cell lines, by epigenetic silencing via hypermethylation; specific de-methylation of miR-1253 not only resulted in rapid recovery of expression but also a sharp decline in tumor cell proliferation and target gene expression. Expression restoration also led to a reduction in tumor cell virulence, concomitant with activation of apoptotic pathways, cell cycle arrest and reduction of markers of proliferation. We identified two oncogenic targets of miR-1253, CDK6 and CD276, whose silencing replicated the negative trophic effects of miR-1253. These data reveal novel tumor-suppressive properties for miR-1253, i.e., (i) loss of expression via epigenetic silencing; (ii) negative trophic effects on tumor aggressiveness; and (iii) downregulation of oncogenic targets.

A Comparative Analysis of Survival and Funding Discrepancies in Cancers With High Mortality

OBJECTIVE

Comparative analyses of survival and funding statistics in cancers with high mortality were performed to quantify discrepancies and identify areas for intervention.

BACKGROUND

Discrepancies in research funding may contribute to stagnant survival rates in pancreatic ductal adenocarcinoma (PDAC).

METHODS

The Surveillance, Epidemiology, and End Results database was queried for survival statistics. Funding data were obtained from the National Cancer Institute (NCI). Clinical trial data were obtained from www.clinicaltrials.gov. Cancers with high mortality were included for analyses.

RESULTS

Since 1997, PDAC has received lesser funding ($1.41 billion) than other cancers such as breast ($10.52 billion), prostate ($4.93 billion), lung ($4.80 billion), and colorectal ($4.50 billion). Similarly, fewer clinical trials have been completed in PDAC (n = 608) compared with breast (n = 1904), lung (n = 1629), colorectal (n = 1080), and prostate (n = 1055) cancer. Despite this, since 1997, dollars invested in PDAC research produced a greater return on investment with regards to 5-year overall survival (5Y-OS) compared with breast, prostate, uterine, and ovarian cancer. Incremental cost-effectiveness analysis demonstrates that millions (liver, non-Hodgkin lymphoma, and melanoma) and billions (colorectal and lung) of dollars were required for each additional 1% increase in 5Y-OS compared with PDAC. Funding of research towards early diagnosis of PDAC has decreased by 19% since 2007. For nearly all cancers, treatment-related research receives the highest percentage of NCI funding.

CONCLUSIONS

Funding of PDAC research is significantly less than other cancers, despite its higher mortality and greater potential to improve 5Y-OS. Increased awareness and lobbying are required to increase funding, promote research, and improve survival.

Analysis of associations of CXCR3 ligands with immune microenvironment and aggressiveness in murine and human pancreatic ductal adenocarcinoma

762

Background: The complex milieu of cytokines within pancreatic ductal adenocarcinoma (PDAC) promotes tumor progression and immune suppression thereby contributing to the dismal prognosis of patients with PDAC. However, the roles of many cytokines, including CXCR3 ligands, in PDAC have not been thoroughly investigated. Methods: Bioinformatics analyses of PDAC microarray and TCGA datasets were used to identify cytokines overexpressed in PDAC, their association with patient survival as well as the expression of cognate cytokine receptors. Comparative analysis of cytokine expression in KrasLSL-G12D-P53LSL-R172H-Pdx1-Cre (KPC) and KrasLSL-G12D-Pdx1-Cre (KC) murine PDAC models were used to validate these findings. Pathway and CIBERSORT analyses were employed to determine mechanistic basis of altered survival associated with cytokines of interest. Results: Of the 149 cytokines analyzed, CXCR3 ligands CXCL9 and CXCL10 were highly and consistently overexpressed in PDAC datasets. Concurrently, CXCL9, CXCL10 and PF4 were overexpressed in the aggressive KPC murine model compared to the indolent KC model. CXCR3 showed robust expression in PDAC in microarray, TCGA and IHC analyses. Interestingly, high expression of CXCR3 ligands was associated with shorter overall survival (p = 0.04 for CXCL9, 10 and 11 and p = 0.02 for PF4) while high expression of CXCR3 was associated with increased overall survival (p = 0.03). Pathway analysis of genes correlated with CXCR3 and/or its ligands showed that CXCR3 ligands may promote T-cell exhaustion (p < 0.001). Finally, CIBERSORT analysis of TCGA data demonstrated that high CXCR3 expression was associated with increased CD8 T-cell and naïve B-cell signatures and loss of plasma cells signatures. High CXCR3 ligand expression was associated with increased CD8 T-cell, and M1 macrophage, and loss of NK-cell signatures(p < 0.05). Conclusions: CXCR3 ligands are overexpressed in PDAC and are associated with poor survival, likely related to alterations in tumor immune infiltrate/activity and may represent targets to augment anti-tumor immunity.

Presence and structure-activity relationship of intrinsically disordered regions across mucins

Many members of the mucin family are evolutionarily conserved and are often aberrantly expressed and glycosylated in various benign and malignant pathologies leading to tumor invasion, metastasis, and immune evasion. The large size and extensive glycosylation present challenges to study the mucin structure using traditional methods, including crystallography. We offer the hypothesis that the functional versatility of mucins may be attributed to the presence of intrinsically disordered regions (IDRs) that provide dynamism and flexibility and that the IDRs offer potential therapeutic targets. Herein, we examined the links between the mucin structure and function based on IDRs, posttranslational modifications (PTMs), and potential impact on their interactome. Using sequence-based bioinformatics tools, we observed that mucins are predicted to be moderately (20%-40%) to highly (>40%) disordered and many conserved mucin domains could be disordered. Phosphorylation sites overlap with IDRs throughout the mucin sequences. Additionally, the majority of predicted O- and N- glycosylation sites in the tandem repeat regions occur within IDRs and these IDRs contain a large number of functional motifs, that is, molecular recognition features (MoRFs), which directly influence protein-protein interactions (PPIs). This investigation provides a novel perspective and offers an insight into the complexity and dynamic nature of mucins.

Elevating pancreatic cystic lesion stratification: Current and future pancreatic cancer biomarker(s)

Pancreatic ductal adenocarcinoma (PDAC) is an incredibly deadly disease with a 5-year survival rate of 9%. The presence of pancreatic cystic lesions (PCLs) confers an increased likelihood of future pancreatic cancer in patients placing them in a high-risk category. Discerning concurrent malignancy and risk of future PCL progression to cancer must be carefully and accurately determined to improve survival outcomes and avoid unnecessary morbidity of pancreatic resection. Unfortunately, current image-based guidelines are inadequate to distinguish benign from malignant lesions. There continues to be a need for accurate molecular and imaging biomarker(s) capable of identifying malignant PCLs and predicting the malignant potential of PCLs to enable risk stratification and effective intervention management. This review provides an update on the current status of biomarkers from pancreatic cystic fluid, pancreatic juice, and seromic molecular analyses and discusses the potential of radiomics for differentiating PCLs harboring cancer from those that do not.

Abstract 65: Gel-forming mucin MUC5AC as the nexus for cell-adhesion molecules governing pancreatic cancer aggressiveness and chemoresistance

Background: Pancreatic cancer (PC) ranks as the third leading cause of cancer-related deaths in the U.S. Poor prognosis of this malignancy stems from propensity for early metastasis and resistance to chemotherapeutic drugs. Tumor-associated extracellular matrix (ECM) plays a key role in impeding drug penetration and regulating tumor aggressiveness by modulating the cell-adhesion molecules and cytoskeletal rearrangement. Heavily glycosylated secreted mucin MUC5AC, one of the most differentially expressed molecule in PC, is associated with poor prognosis of PC patients. We hypothesize, MUC5AC, with the virtue of its gel forming property, promotes tumor-associated ECM deposition that impedes intratumoral drug delivery. Further, abrogation of MUC5AC decreases PC cell aggressiveness and chemoresistance by acting as an interacting nexus for multiple cell-surface mechanotransducers.

Results: RNA sequencing and immunohistochemical analysis revealed significant decrease in profibrotic factors like fibronectin, collagen and α-smooth muscle actin in the pancreatic sections of KCM (KrasG12D; Pdx1-Cre; Muc5ac-/-) mice as compared to KC (KrasG12D; Pdx1-Cre) mice along PC progression. Second harmonic generation imaging revealed less cross-linked collagen organization in KCM as compared to KC. Further, decrease in invasive precursor lesions (p&lt;0.01) and Ki67-positive proliferative cells were observed in KCM mice pancreas. Orthotopic transplantation of human PC cells showed decreased tumor weight (p&lt;0.05) and metastatic incidences upon MUC5AC knock-down (KD). A global mechanistic insight using gene set enrichment analysis from RNA seq. data suggested significant downregulation in genes involved in cell-adhesion, cell-migration and ECM organization in the KCM mice. Among the cell-adhesion molecules, MUC5AC was found to interact with E-cadherin and CD44 on the surface of human PC cells and mouse-derived organoids. Furthermore, MUC5AC expressing cells showed high expression of integrin αvβ5 and pSrc/ pSTAT3 activation. Additionally, MUC5AC-KD cells and organoids from KCM mouse pancreas exhibited greater apoptotic propensity with lesser nuclear localization of β-catenin upon gemcitabine treatment as compared to control. Pharmacologic inhibition of β-catenin nuclear localization sensitized the MUC5AC expressing cells and organoids to gemcitabine.

Conclusion: Our results indicate that gel-forming mucin MUC5AC serves as key node for cell-cell and cell-matrix interactions thereby leading to bidirectional pro-tumorigenic signaling in PC. While, MUC5AC may disrupt E-cadherin-based intercellular junctions to promote transcriptional activation of β-catenin and thereby chemoresistance in PC cells; it also aggravates PC progression and desmoplasia via integrin-mediated mechanosensing.

Citation Format: Koelina Ganguly, Shiv Ram Krishn, Rahat Jahan, Pranita Atri, Satyanarayana Rachagani, Sanchita Rauth, Huang Xi, Yongfeng Lu, Surinder Batra, Sukhwinder Kaur. Gel-forming mucin MUC5AC as the nexus for cell-adhesion molecules governing pancreatic cancer aggressiveness and chemoresistance [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 65.

Abstract 4804: Pre-clinical development of ISOX; A novel therapy for pancreatic cancer identified utilizing system biology approach(s)

Background: Pancreatic Cancer (PC) remains one of the most common causes of cancer-related deaths. The low survival percentage in patients can be attributed primarily to ineffective therapeutic targeting and lack of new potent therapies. Over the years the conventional one target at a time approach for drug development has failed to achieve promising survival and better approaches are needed. Large-scale genomic database connectivity map (CMAP), a collection of perturbagen profiles from &gt;2800 drugs is a potential tool to identify effective therapies for PC by identifying novel drugs that essentially reverse the global gene signature originating due to malignant PC. Considering this information, we hypothesize that “a big data approach using CMAP will lead to the identification of novel drugs for highly lethal PC.”

Methods and Results: To generate a meta-gene signature for PC, GEO data for PC cases (N=106) and normal samples (N=68) was extracted, normalized & assessed for differential gene expression using R Bioconductor. Drugs specific to this gene signature across various datasets were identified using CMAP and the top hit ISOX chosen for further assessment. Considering the high mutational heterogeneity of PC, a five-cell line panel with diverse mutations was chosen for the validation studies. Cell line-based assessment for changes to proliferation using MTT and motility using matrigel assisted invasion showed the high potency of ISOX with an IC50 of 2.4nM-1.4µM & up to 90% reduction in invasion supporting initial hypothesis. It was further supported by the 48% induction of apoptosis. Molecular mechanism of ISOX was further assessed using an RNA-seq on ISOX treated PC cell lines followed by ingenuity pathway analyses. Gene ontology pathway analysis indicated SHH-WNT, PI3K-mTOR-AKT, and EGFR signaling as key pathways affected by ISOX. Further, 60% loss of viability was observed in pancreatic tumor organoids at 500nM of ISOX. Furthermore, about 10 fold statistically significant (p-value = 0.014) reduction in tumor weight at 50 mg/kg of ISOX both alone and in combination with 50 mg/kg 5FU (p-value=0.02) was observed in orthotopic mice models.

Conclusion: Our data suggest that ISOX is a potential new therapeutic for PC. In future, we aim to evaluate the potency of newly identified drug in both transgenic mouse models of PC as well as clinical phase I studies.

Citation Format: Pranita Atri, Parthasarathy Seshacharyulu, Satyanaryana Rachagani, Palanisamy Nallasamy, Sanchita Rauth, Garima Kaushik, Koelina Ganguly, Dario Ghersi, Moorthy P. Ponnusamy, Sukhwinder Kaur, Surinder K. Batra. Pre-clinical development of ISOX; A novel therapy for pancreatic cancer identified utilizing system biology approach(s) [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 4804.

Trefoil factor(s) and CA19.9: A promising panel for early detection of pancreatic cancer

Background

Trefoil factors (TFF1, TFF2, and TFF3) are small secretory molecules that recently have gained significant attention in multiple studies as an integral component of pancreatic cancer (PC) subtype-specific gene signature. Here, we comprehensively investigated the diagnostic potential of all the member of trefoil family, i.e., TFF1, TFF2, and TFF3 in combination with CA19.9 for detection of PC.

Methods

Trefoil factors (TFFs) gene expression was analyzed in publicly available cancer genome datasets, followed by assessment of their expression in genetically engineered spontaneous mouse model (GEM) of PC (KrasG12D; Pdx1-Cre (KC)) and in human tissue microarray consisting of normal pancreas adjacent to tumor (NAT), precursor lesions (PanIN), and various pathological grades of PC by immunohistochemistry (IHC). Serum TFFs and CA19.9 levels were evaluated via ELISA in comprehensive sample set (n = 362) comprised of independent training and validation sets each containing benign controls (BC), chronic pancreatitis (CP), and various stages of PC. Univariate and multivariate logistic regression and receiver operating characteristic curves (ROC) were used to examine their diagnostic potential both alone and in combination with CA19.9.

Findings

The publicly available datasets and expression analysis revealed significant increased expression of TFF1, TFF2, and TFF3 in human PanINs and PC tissues. Assessment of KC mouse model also suggested upregulated expression of TFFs in PanIN lesions and early stage of PC. In serum analyses studies, TFF1 and TFF2 were significantly elevated in early stages of PC in comparison to benign and CP control group while significant elevation in TFF3 levels were observed in CP group with no further elevation in its level in early stage PC group. In receiver operating curve (ROC) analyses, combination of TFFs with CA19.9 emerged as promising panel for discriminating early stage of PC (EPC) from BC (AUC_{TFF1+TFF2+TFF3+CA19.9} = 0.93) as well as CP (AUC_{TFF1+TFF2+TFF3+CA19.9} = 0.93). Notably, at 90% specificity (desired for blood-based biomarker panel), TFFs combination improved CA19.9 sensitivity by 10% and 25% to differentiate EPC from BC and CP respectively. In an independent blinded validation set, the combination of TFFs and CA19.9 (AUC_{TFF1+TFF2+TFF3+CA19.9} = 0.82) also improved the overall efficacy of CA19.9 (AUC_CA19.9 = 0.66) to differentiate EPC from CP proving unique biomarker capabilities of TFFs to distinguish early stage of this deadly lethal disease.

Interpretation

In silico, tissue and serum analyses validated significantly increased level of all TFFs in precursor lesions and early stages of PC. The combination of TFFs enhanced sensitivity and specificity of CA19.9 to discriminate early stage of PC from benign control and chronic pancreatitis groups.

Disruption of C1galt1 Gene Promotes Development and Metastasis of Pancreatic Adenocarcinomas in Mice

BACKGROUND & AIMS

Pancreatic ductal adenocarcinomas (PDACs) produce higher levels of truncated O-glycan structures (such as Tn and sTn) than normal pancreata. Dysregulated activity of core 1 synthase glycoprotein-N-acetylgalactosamine 3-β-galactosyltransferase 1 (C1GALT1) leads to increased expression of these truncated O-glycans. We investigated whether and how truncated O-glycans contributes to the development and progression of PDAC using mice with disruption of C1galt1.

METHODS

We crossed C1galt1 floxed mice (C1galt1^loxP/loxP) with Kras^G12D/+; Trp53^R172H/+; Pdx1-Cre (KPC) mice to create KPCC mice. Growth and progression of pancreatic tumors were compared between KPC and KPCC mice; pancreatic tissues were collected and analyzed by immunohistochemistry; immunofluorescence; and Sirius red, alcian blue, and lectin staining. We used the CRISPR/Cas9 system to disrupt C1GALT1 in human PDAC cells (T3M4 and CD18/HPAF) and levels of O-glycans were analyzed by lectin blotting, mass spectrometry, and lectin pulldown assay. Orthotopic studies and RNA sequencing analyses were performed with control and C1GALT1 knockout PDAC cells. C1GALT1 expression was analyzed in well-differentiated (n = 36) and poorly differentiated (n = 23) PDAC samples by immunohistochemistry.

RESULTS

KPCC mice had significantly shorter survival times (median 102 days) than KPC mice (median 200 days) and developed early pancreatic intraepithelial neoplasias at 3 weeks, PDAC at 5 weeks, and metastasis at 10 weeks compared with KPC mice. Pancreatic tumors that developed in KPCC mice were more aggressive (more invasive and metastases) than those in KPC mice, had a decreased amount of stroma, and had increased production of Tn. Poorly differentiated PDAC specimens had significantly lower levels of C1GALT1 than well-differentiated PDACs. Human PDAC cells with knockout of C1GALT1 had aberrant glycosylation of MUC16 compared with control cells and increased expression of genes that regulate tumorigenesis and metastasis.

CONCLUSIONS

In studies of KPC mice with disruption of C1galt1, we found that loss of C1galt1 promotes development of aggressive PDACs and increased metastasis. Knockout of C1galt1 leads to increased tumorigenicity and truncation of O-glycosylation on MUC16, which could contribute to increased aggressiveness.

Cigarette Smoke Induces Stem Cell Features of Pancreatic Cancer Cells via PAF1

BACKGROUND & AIMS

Cigarette smoking is a major risk factor for pancreatic cancer. Aggressive pancreatic tumors contain cancer cells with stem cell features. We investigated whether cigarette smoke induces stem cell features in pancreatic cancer cells.

METHODS

Kras^G12D; Pdx1-Cre mice were exposed to cigarette smoke or clean air (controls) for up to 20 weeks; pancreata were collected and analyzed by histology, quantitative reverse transcription polymerase chain reaction, and confocal immunofluorescence microscopy. HPNE and Capan1 cells were exposed to cigarette smoke extract (CSE), nicotine and nicotine-derived carcinogens (NNN or NNK), or clean air (controls) for 80 days and evaluated for stem cell markers and features using flow cytometry-based autofluorescence, sphere formation, and immunoblot assays. Proteins were knocked down in cells with small interfering RNAs. We performed RNA sequencing analyses of CSE-exposed cells. We used chromatin immunoprecipitation assays to confirm the binding of FOS-like 1, AP-1 transcription factor subunit (FOSL1) to RNA polymerase II-associated factor (PAF1) promoter. We obtained pancreatic ductal adenocarcinoma (PDAC) and matched nontumor tissues (n = 15) and performed immunohistochemical analyses.

RESULTS

Chronic exposure of HPNE and Capan1 cells to CSE caused them to increase markers of stem cells, including autofluorescence and sphere formation, compared with control cells. These cells increased expression of ABCG2, SOX9, and PAF1, via cholinergic receptor nicotinic alpha 7 subunit (CHRNA7) signaling to mitogen-activated protein kinase 1 and FOSL1. CSE-exposed pancreatic cells with knockdown of PAF1 did not show stem cell features. Exposure of cells to NNN and NNK led to increased expression of CHRNA7, FOSL1, and PAF1 along with stem cell features. Pancreata from Kras^G12D; Pdx1-Cre mice exposed to cigarette smoke had increased levels of PAF1 mRNA and protein, compared with control mice, as well as increased expression of SOX9. Levels of PAF1 and FOSL1 were increased in PDAC tissues, especially those from smokers, compared with nontumor pancreatic tissue. CSE exposure increased expression of PHD-finger protein 5A, a pluripotent transcription factor and its interaction with PAF1.

CONCLUSIONS

Exposure to cigarette smoke activates stem cell features of pancreatic cells, via CHRNA7 signaling and FOSL1 activation of PAF1 expression. Levels of PAF1 are increased in pancreatic tumors of humans and mice with chronic cigarette smoke exposure.

Abstract 1909: NR4A2 role in head and neck cancer: Mechanistic and functional analysis

Background: Nuclear receptor related 1 protein (NURR1/NR4A2) is a transcription factor that mediates numerous functions in differentiation/development, maintenance and metabolism. In cancer cells, NR4A2 promotes proliferation, migration, transformation and chemo-resistance in many cancers. Here, we explore the role of NR4A2 in head and neck squamous cell cancers (HNC) tumorigenesis and define its target genes. Methods: NR4A2 expression was determined by immunohistochemistry (IHC) and in publically available databases (Oncomine, TCGA). NR4A2 was knockedout/knockdown by CRISPR or shRNA. Coimmunoprepitation and reverse chromatin immunoprecipitation were done to study the interaction between EGFR/STAT3. ChIPSeq analysis was done by using Illumina NextSeq 500 Genome Analyzer and integrated with microarray (HPV+/- patients) to identify the true target genes of NR4A2 using BETA Software and validated by PCR/qPCR. Results: IHC and database analysis demonstrated overexpression of NR4A2 in HNC patients. NR4A2 was significantly overexpressed in HPV+ HNC patients, SCC47 and SCC104 cell lines. Functionally, CRISPR/shRNA knockout/knockdown of NR4A2 in cell lines significantly decreased colonogenicity, proliferation and migration. Expression of NR4A2 was positively correlated with EGFR expression (R2=0.92), and EGF treatment (100ng/ml; 24-48h) induced NR4A2 (~2 fold) expression coupled with epithelial to mesenchymal transition in SCC1 and SCC10B cells (HPV-). We also observed EGF mediated NR4A2 induction was abrogated by panEGFR inhibitor (afatinib) with concomitant decrease in STAT3 expression. Physical interaction between EGFR and STAT3 with EGF treatment regulated NR4A2 expression. Whole genome integration of ChIPseq and microarray demonstrates 9% (2015) and 23% (3002) of the enriched up and down-regulated target genes, respectively were canonically regulated in HPV+ HNC. ChIP PCR validation indicates enrichment of NR4A2 in some of the target genes, wnt10, p53, cxcl13, cln10 and hoxb8 in HPV+ cells. Conclusions: Our data indicate overexpression of NR4A2 in HNC, and its positive correlation with EGFR expression. We also noted the physical interaction between EGFR and STAT3 which functionally attribute the NR4A2 expression. Integration and validation data showed the differential enrichment of NR4A2 target genes in HPV+/- cell lines which suggest its possible discriminatory role in HNC pathogenesis which needs to be confirmed.

Citation Format: Sanjib Chaudhary, Ramesh Pothuraju, Pranita Atri, Satyanarayana Rachagani, Surinder K. Batra, Muzafar A. Macha. NR4A2 role in head and neck cancer: Mechanistic and functional analysis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1909.

Abstract 50: Elucidating the role of MUC5AC-MET axis in breast cancer brain metastasis

Metastasis of breast cancer (BC) is the leading cause of mortality in American women. In particular, brain metastasis is a significant clinical problem present in 30-40% of triple receptor negative (TN) and epidermal growth factor receptor 2 (HER2) positive BC patients. These patients also have the worst prognosis of all breast cancers in women. Due to advances in clinical management at both the diagnostic and therapeutic levels, the lifespan or overall survival of these patients has increased, but the manifestation of brain metastasis at later stages of the disease remains an unfortunate burden for these patients. In addition, the blood-brain barrier (BBB) poses an additional hurdle for treatment of BC brain metastases, because the majority of chemotherapeutic drugs fail to cross the BBB. Furthermore, there is no single targeted therapy available for TNBC patients with brain metastasis, and thus there is an urgent requirement to discover novel biomarkers and therapeutics to address BC brain metastasis. In this regard, using a bioinformatics approach, we observed that several mucins, including MUC5AC, are significantly up-regulated in brain metastases of BC compared to primary tumors. However, we found the secretory mucin MUC5AC protein to be substantially high in brain-seeking BC (BSBC) cell lines and metastatic brain tissues. We also observed that knockdown of MUC5AC reduced proliferation and metastatic potential in these cell lines. Furthermore, we observed that MUC5AC colocalizes with activated MET receptor. MUC5AC knockdown in BSBC cell lines reduced MET activation and its downstream targets FAK and paxillin. Interestingly, MET and FAK inhibition using pharmacological inhibitors led to substantial decrease in MUC5AC expression. Overall, these studies suggest that MUC5AC-MET axis may regulate breast cancer brain metastasis. Understanding the MUC5AC-MET axis could be a novel approach for the development of better prognosis and prevention of life-threatening and treatment-resistant breast cancer brain metastasis.

Citation Format: Mohd W. Nasser, Shailendra K. Gautam, Ranjana Kanchan, Pranita Atri, Jawed Siddiqui, Rakesh Bhatia, Joseph Carmicheal, Dario Ghersi, Sukhwinder Kaur, Siddharth Mahapatra, Maneesh Jain, Surinder K. Batra. Elucidating the role of MUC5AC-MET axis in breast cancer brain metastasis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 50.