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In pancreatic cancer, the robust fibroinflammatory stroma contributes to immune suppression and renders tumors hypoxic, altering intratumoral metabolic pathways and leading to poor survival. One metabolic enzyme activated during hypoxia is lactate dehydrogenase A (LDHA). As a result of its promiscuous activity under hypoxia, LDHA produces L-2 hydroxyglutarate (L-2HG), an epigenetic modifier, that regulates the tumor transcriptome. However, the role of L-2HG in remodeling the pancreatic tumor microenvironment is not known. Here we used mass spectrometry to detect L-2HG in serum samples from patients with pancreatic cancer, comprising tumor cells as well as stromal cells. Both hypoxic pancreatic tumors as well as serum from patients with pancreatic cancer accumulated L-2HG as a result of promiscuous activity of LDHA. This abnormally accumulated L-2HG led to H3 hypermethylation and altered gene expression, which regulated a critical balance between stemness and differentiation in pancreatic tumors. Secreted L-2HG inhibited T-cell proliferation and migration, suppressing antitumor immunity. In a syngeneic orthotopic model of pancreatic cancer, inhibition of LDH with GSK2837808A decreased L-2HG, induced tumor regression, and sensitized tumors to anti-PD1 therapy. In conclusion, hypoxia-mediated promiscuous activity of LDH produces L-2HG in pancreatic tumor cells, regulating the stemness-differentiation balance and contributing to immune evasion. Targeting LDH can be developed as a potential therapy to sensitize pancreatic tumors to checkpoint inhibitor therapy.Significance:This study shows that promiscuous LDH activity produces L-2HG in pancreatic tumor and stromal cells, modulating tumor stemness and immune cell function and infiltration in the tumor microenvironment.

ITRAQ table

RNA seq data file after treatment of MIA-PACA2 cells with L-2HG

Pancreatic ductal adenocarcinoma (PDAC) is considered to be a highly immunosuppressive and heterogenous neoplasm. Despite improved knowledge regarding the genetic background of the tumor and better understanding of the tumor microenvironment, immune checkpoint inhibitor therapy (targeting CTLA4, PD1, PDL1) has not been very successful against PDAC. The robust desmoplastic stroma, along with an extensive extracellular matrix (ECM) that is rich in hyaluronan, plays an integral role in this immune evasion. Hexosamine biosynthesis pathway (HBP), a shunt pathway of glycolysis, is a metabolic node in cancer cells that can promote survival pathways on the one hand and influence the hyaluronan synthesis in the ECM on the other. The rate-limiting enzyme of the pathway, glutamine-fructose amidotransferase 1 (GFAT1), uses glutamine and fructose 6-phosphate to eventually synthesize uridine diphosphate N-acetylglucosamine (UDP-GlcNAc). In the current manuscript, we targeted this glutamine-utilizing enzyme by a small molecule glutamine analog (6-diazo-5-oxo-l-norleucine [DON]). Our results showed that DON decreased the self-renewal potential and metastatic ability of tumor cells. Further, treatment with DON decreased hyaluronan and collagen in the tumor microenvironment, leading to an extensive remodeling of the ECM and an increased infiltration of CD8(+) T cells. Additionally, treatment with DON sensitized pancreatic tumors to anti-PD1 therapy, resulting in tumor regression and prolonged survival.

Endoplasmic reticulum (ER) stress and the unfolded protein response (UPR) signaling have been shown to be dysregulated in multiple cancer types. Glucose regulatory protein 78 (GRP78), the master regulator of the UPR, plays a role in proliferation, invasion, and metastasis in cancer. Cancer stem cells (CSCs) make up a crucial component of the tumor heterogeneity in pancreatic cancer, as well as other cancers. “Stemness” in pancreatic cancer defines a population of cells within the tumor that have increased therapeutic resistance as well as survival advantage. In the current study, we investigated how GRP78 was responsible for maintaining “stemness” in pancreatic cancer thereby contributing to its aggressive biology. We determined that GRP78 downregulation decreased clonogenicity and self-renewal properties in pancreatic cancer cell lines in vitro. In vivo studies resulted in delayed tumor initiation frequency, as well as smaller tumor volume in the shGRP78 groups. Additionally, downregulation of GRP78 resulted in dysregulated fatty acid metabolism in pancreatic tumors as well as the cells. Further, our results showed that shGRP78 dysregulates multiple transcriptomic and proteomic pathways that involve DNA damage, oxidative stress, and cell death, that were reversed upon treatment with a ROS inhibitor, N-acetylcysteine. This study thus demonstrates for the first time that the heightened UPR in pancreatic cancer may be responsible for maintenance of the “stemness” properties in these cells that are attributed to aggressive properties like chemoresistance and metastasis.

Pancreatic adenocarcinoma (PDAC) claims more than 90% of the patients diagnosed with the disease owing to its aggressive biology that is manifested by high rate of tumor recurrence. Aberrant upregulation in the transcriptional activity of proteins involved in self-renewal like Sox2, Oct4 and Nanog is instrumental in these recurrence phenomena. In cancer, Sox2 is aberrantly “turned-on” leading to activation of downstream genes those results in relapse of the tumor. Molecular mechanisms that regulate the activity of Sox2 in PDAC are not known. In the current study, we have studied the how glycosylation of Sox2 by O-GlcNAc transferase (OGT) can affect its transcriptional activity and thus regulate self-renewal in cancer. Methods: RNA-Seq analysis of CRISPR-OGTi PDAC cells indicated a deregulation of differentiation and self-renewal pathways in PDAC. Pancreatic tumor burden following inhibition of OGT in vivo was done by using small molecule inhibitor, OSMI, on subcutaneous implantation of PDAC cells. Sox2 activity assay was performed by Dual Luciferase Reporter Assay kit. Results: Our study shows for the first time that in PDAC, glycosylation of Sox2 by OGT stabilizes it in the nucleus. Site directed mutagenesis of this site (S246A) prevents this modification. We further show that inhibition of OGT delayed initiation of pancreatic tumors by inhibition of Sox2. We also show that targeting OGT in vivo with a small molecule-inhibitor OSMI, results in decreased tumor burden in PDAC. Conclusion: Understanding this mechanism of SOX2 regulation by its glycosylation is expected to pave the way for development of novel therapy that has the potential to eradicate the cells responsible for tumor-recurrence.

Addition of nab-paclitaxel to gemcitabine offers a survival benefit of only 6 weeks over gemcitabine alone at a cost of increased toxicity in PDAC. The goal of the present study is to evaluate the efficacy of Minnelide, a water-soluble prodrug of triptolide, in combination with the standard of care regimen for chemotherapy with the added advantage of reducing the doses of these drugs to minimize toxicity. Pancreatic cancer cell lines were implanted subcutaneously or orthotopically in athymic nude or C57BL/6J mice. Subsequently, animals were randomized and received saline or minnelide or full dose chemotherapy or low dose chemotherapy or minnelide in combination with low dose chemotherapy. Our results show that a combination of low doses of Minnelide with Gemcitabine + nab-paclitaxel significantly inhibited tumor progression and increased the survival of tumor-bearing mice in comparison with conventional chemotherapy alone. Moreover, combination therapy significantly reduced cancer-related morbidity by decreasing ascites and metastasis and effectively targeted both cancer and the associated stroma. In vitro studies with a combination of low doses of triptolide and paclitaxel significantly decreased the cell viability, increased apoptosis and led to significantly increased M-phase cell cycle arrest in various pancreatic cancer cell lines as compared to either drug alone. Our results show that Minnelide synergizes with conventional chemotherapy leading to a significant reduction in the doses of these toxic drugs, all the while achieving better efficacy in the treatment of PDAC. This combination effectively targeted both the cancer and the associated stromal components of pancreatic cancer.

Metabolic rewiring is an integral part of tumor growth. Among metabolic pathways, the Mevalonic-Acid-Pathway (MVAP) plays a key role in maintaining membrane architecture through cholesterol synthesis, thereby affecting invasiveness. In the current study, we show for the first time that CD133Hi pancreatic tumor initiating cells (TIC) have increased expression of MVAP enzymes, cholesterol-content and Caveolin expression. Further, we show that CD133 in these cells is localized in the lipid-rafts (characterized by Cav-1-cholesterol association). Disruption of lipid-rafts by either depleting Cav-1 or by inhibiting MVAP by lovastatin decreased metastatic-potential and chemoresistance in CD133Hi cells while not affecting the CD133lo cells. Additionally, disruption of lipid-raft results in deregulation of FAK-signaling, decreasing invasiveness in pancreatic-TICs. Furthermore, this also inhibits ABC-transporter activity resulting in sensitizing TICs to standard chemotherapeutic agents. Repurposing existing drugs for new clinical applications is one of the safest and least resource intensive approaches to improve therapeutic options. In this context, our study is extremely timely as it shows that targeting lipid-rafts with statins can sensitize the normally resistant pancreatic TICHi-cells to standard chemotherapy and decrease metastasis, thereby defining a novel strategy for targeting the TICHi-PDAC.

In pancreatic cancer, the robust fibroinflammatory stroma contributes to immune suppression and renders tumors hypoxic, altering intratumoral metabolic pathways and leading to poor survival. One metabolic enzyme activated during hypoxia is lactate dehydrogenase A (LDHA). As a result of its promiscuous activity under hypoxia, LDHA produces L-2 hydroxyglutarate (L-2HG), an epigenetic modifier, that regulates the tumor transcriptome. However, the role of L-2HG in remodeling the pancreatic tumor microenvironment is not known. Here we used mass spectrometry to detect L-2HG in serum samples from patients with pancreatic cancer, comprising tumor cells as well as stromal cells. Both hypoxic pancreatic tumors as well as serum from patients with pancreatic cancer accumulated L-2HG as a result of promiscuous activity of LDHA. This abnormally accumulated L-2HG led to H3 hypermethylation and altered gene expression, which regulated a critical balance between stemness and differentiation in pancreatic tumors. Secreted L-2HG inhibited T-cell proliferation and migration, suppressing antitumor immunity. In a syngeneic orthotopic model of pancreatic cancer, inhibition of LDH with GSK2837808A decreased L-2HG, induced tumor regression, and sensitized tumors to anti-PD1 therapy. In conclusion, hypoxia-mediated promiscuous activity of LDH produces L-2HG in pancreatic tumor cells, regulating the stemness-differentiation balance and contributing to immune evasion. Targeting LDH can be developed as a potential therapy to sensitize pancreatic tumors to checkpoint inhibitor therapy. Significance: This study shows that promiscuous LDH activity produces L-2HG in pancreatic tumor and stromal cells, modulating tumor stemness and immune cell function and infiltration in the tumor microenvironment.

Pancreatic adenocarcinoma is a devastating disease with an abysmal survival rate of 9%. A robust fibro-inflammatory and desmoplastic stroma, characteristic of pancreatic cancer, contribute to the challenges in developing viable therapeutic strategies in this disease. Apart from constricting blood vessels and preventing efficient drug delivery to the tumor, the stroma also contributes to the aggressive biology of cancer along with its immune-evasive microenvironment. In this study, we show that in pancreatic tumors, the developing stroma increases tumor initiation frequency in pancreatic cancer cells in vivo by enriching for CD133 + aggressive “stem-like” cells. Additionally, the stromal fibroblasts secrete IL6 as the major cytokine, increases glycolytic flux in the pancreatic tumor cells, and increases lactate efflux in the microenvironment via activation of the STAT signaling pathway. We also show that the secreted lactate favors activation of M2 macrophages in the tumor microenvironment, which excludes CD8 + T cells in the tumor. Our data additionally confirms that the treatment of pancreatic tumors with anti-IL6 antibody results in tumor regression as well as decreased CD133 + population within the tumor. Furthermore, inhibiting the lactate efflux in the microenvironment reduces M2 macrophages, and makes pancreatic tumors more responsive to anti-PD1 therapy. This suggests that stromal IL6 driven metabolic reprogramming plays a significant role in the development of an immune-evasive microenvironment. In conclusion, our study shows that targeting the metabolic pathways affected by stromal IL6 can make pancreatic tumors amenable to checkpoint inhibitor therapy.

Cancer is a major health problem. Most of the treatments exhibit systemic toxicity, as they are not targeted or specific to cancerous cells and tumors. Adenoviruses are very promising gene delivery vectors and have immense potential to deliver targeted therapy. Here, we review a wide range of strategies that have been tried, tested, and demonstrated to enhance the specificity of oncolytic viruses towards specific cancer cells. A combination of these strategies and other conventional therapies may be more effective than any of those strategies alone.

2-hydroxyglutarate (2-HG) has gained considerable importance in glioma and blood cancers that have mutations in the IDH1/2 gene. In the current study we show for the first time that pancreatic tumors produce 2HG in the absence of IDH1/2 mutation. Our study shows that hypoxic pancreatic tumors that have activated lactate dehydrogenase (LDH) activity, produce the L-isoform of 2HG.Metabolic mass spectrometric analysis along with chiral derivatization showed that pancreatic cancer cells as well as stromal cells secrete the L-isomeric form of 2-hydroxyglutarate (L-2HG) when exposed to hypoxic environment. Serum analysis of human pancreatic cancer patients also showed similar accumulation of L-2HG. Our results showed that this abnormally accumulated L-2HG regulates self-renewal by increasing expression of genes associated with stemness (Sox-2, CD133) and by decreasing expression of differentiation genes (Pdx-1, HB9, NKX6.1). Further analysis showed that secreted L-2HG mediates cross talk with immune T-cells and hampers their proliferation and migration thereby suppressing the anti-tumor immunity. In vivo targeting of LDH enzyme with inhibitor (GSK2837808A) showed decrease in L-2HG as well as subsequent tumor regression and sensitization to immune-checkpoint therapy.Present study shows for the first time that hypoxia mediated accumulation of L-2HG drives self-renewal in pancreatic cancer by shifting critical balance of gene expression towards stemness and promotes immune suppression by impairing T cell activation in this disease. Additionally, it indicates that targeting LDH can sensitize pancreatic tumors to anti-PD1 therapy by decreasing L-2HG and reverting their immune evasive function.

Chemoresistance is a major therapeutic challenge that plays a role in the poor statistical outcomes in pancreatic cancer. Unfolded protein response (UPR) is one of the homeostasis mechanisms in cancer cells that have been correlated with chemoresistance in a number of cancers including pancreatic cancer. In this study, we show that modulating glucose regulatory protein 78 (GRP78), the master regulator of the UPR, can have a profound effect on multiple pathways that mediate chemoresistance. Our study showed for the first time that silencing GRP78 can diminish efflux activity of ATP-binding cassette (ABC) transporters, and it can decrease the antioxidant response resulting in an accumulation of reactive oxygen species (ROS). We also show that these effects can be mediated by the activity of specificity protein 1 (SP1), a transcription factor overexpressed in pancreatic cancer. Thus, inhibition of SP1 negatively affects the UPR, deregulates the antioxidant response of NRF2, as well as ABC transporter activity by inhibiting GRP78-mediated ER homeostasis. Sp1 and NRF2 have been classified as nononcogene addiction genes and thus are imperative to understanding the molecular mechanism of resistance. These finding have huge clinical relevance as both Sp1 and GRP78 are overexpressed in pancreatic cancer patients and increased expression of these proteins is indicative of poor prognosis. Understanding how these proteins may regulate chemoresistance phenotype of this aggressive cancer may pave the way for development of efficacious therapy for this devastating disease.

Resident fibroblasts that contact tumor epithelial cells (TEC) can become irreversibly activated as cancer-associated-fibroblasts (CAF) that stimulate oncogenic signaling in TEC. In this study, we evaluated the cross-talk between CAF and TEC isolated from tumors generated in a mouse model of KRAS/mut p53-induced pancreatic cancer (KPC mice). Transcriptomic profiling conducted after treatment with the anticancer compound Minnelide revealed deregulation of the TGFβ signaling pathway in CAF, resulting in an apparent reversal of their activated state to a quiescent, nonproliferative state. TEC exposed to media conditioned by drug-treated CAFs exhibited a decrease in oncogenic signaling, as manifested by downregulation of the transcription factor Sp1. This inhibition was rescued by treating TEC with TGFβ. Given promising early clinical studies with Minnelide, our findings suggest that approaches to inactivate CAF and prevent tumor–stroma cross-talk may offer a viable strategy to treat pancreatic cancer. Significance: In an established mouse model of pancreatic cancer, administration of the promising experimental drug Minnelide was found to actively deplete reactive stromal fibroblasts and to trigger tumor regression, with implications for stromal-based strategies to attack this disease. Cancer Res; 78(5); 1321–33. ©2018 AACR.

Tumor-initiating cells (TIC) have been implicated in pancreatic tumor initiation, progression, and metastasis. Among different markers that define this cell population within the tumor, the CD133+ cancer stem cell (CSC) population has reliably been described in these processes. CD133 expression has also been shown to functionally promote metastasis through NF-κB activation in this population, but the mechanism is unclear. In the current study, overexpression of CD133 increased expression and secretion of IL1β (IL1B), which activates an autocrine signaling loop that upregulates NF-κB signaling, epithelial–mesenchymal transition (EMT), and cellular invasion. This signaling pathway also induces CXCR4 expression, which in turn is instrumental in imparting an invasive phenotype to these cells. In addition to the autocrine signaling of the CD133 secreted IL1β, the tumor-associated macrophages (TAM) also produced IL1β, which further activated this pathway in TICs. The functional significance of the TIC marker CD133 has remained elusive for a very long time; the current study takes us one step closer to understanding how the downstream signaling pathways in these cells regulate the functional properties of TICs. Implications: This study demonstrates the important role of tumor- and macrophage-derived IL1β stimulation in pancreatic cancer. IL1 signaling is increased in cells with CD133 expression, leading to increased NF-kB activity, EMT induction, and invasion. Increased invasiveness via IL1β stimulation is mediated by the upregulation of CXCR4 expression. The study highlights the importance of IL1-mediated signaling in TICs. Mol Cancer Res; 16(1); 162–72. ©2017 AACR.

Pancreatic tumors are renowned for their extremely hypoxic centers, resulting in upregulation of a number of hypoxia mediated signaling pathways including cell proliferation, metabolism and cell survival. Previous studies from our laboratory have shown that Minnelide, a water-soluble pro-drug of triptolide (anti-cancer compound), decreases viability of cancer cells in vitro as well as in vivo. However, its mechanism of action remain elusive. In the current study we evaluated the effect of Minnelide, on hypoxia mediated oncogenic signaling as well as stemness in pancreatic cancer. Minnelide has just completed Phase 1 trial against GI cancers and is currently awaiting Phase 2 trials. Our results showed that upon treatment with triptolide, HIF-1α protein accumulated in pancreatic cancer cells even though hypoxic response was decreased in them. Our studies showed even though HIF-1α is accumulated in the treated cells, there was no decrease in HIF-1 binding to hypoxia response elements. However, the HIF-1 transcriptional activity was significantly reduced owing to depletion of co-activator p300 upon treatment with triptolide. Further, treatment with triptolide resulted in a decreased activity of Sp1 and NF-kB the two major oncogenic signaling pathway in pancreatic cancer along with a decreased tumor initiating cell (TIC) population in pancreatic tumor.

Presence of quiescent, therapy evasive population often described as cancer stem cells (CSC) or tumor initiating cells (TIC) is often attributed to extreme metastasis and tumor recurrence. This population is typically enriched in a tumor as a result of microenvironment or chemotherapy induced stress. The TIC population adapts to this stress by turning on cell cycle arrest programs that is a “fail-safe” mechanism to prevent expansion of malignant cells to prevent further injury. Upon removal of the “stress” conditions, these cells restart their cell cycle and regain their proliferative nature thereby resulting in tumor relapse. Growth Arrest Specific 5 (GAS5) is a long-non-coding RNA that plays a vital role in this process. In pancreatic cancer, CD133+ population is a typical representation of the TIC population that is responsible for tumor relapse. In this study, we show for the first time that emergence of CD133+ population coincides with upregulation of GAS5, that reprograms the cell cycle to slow proliferation by inhibiting GR mediated cell cycle control. The CD133+ population further routed metabolites like glucose to shunt pathways like pentose phosphate pathway, that were predominantly biosynthetic in spite of being quiescent in nature but did not use it immediately for nucleic acid synthesis. Upon inhibiting GAS5, these cells were released from their growth arrest and restarted the nucleic acid synthesis and proliferation. Our study thus showed that GAS5 acts as a molecular switch for regulating quiescence and growth arrest in CD133+ population, that is responsible for aggressive biology of pancreatic tumors.

Presence of quiescent, therapy evasive population often described as cancer stem cells (CSC) or tumor initiating cells (TIC) is often attributed to extreme metastasis and tumor recurrence. This population is typically enriched in a tumor as a result of microenvironment or chemotherapy induced stress. The TIC population adapts to this stress by turning on cell cycle arrest programs that is a “fail-safe” mechanism to prevent expansion of malignant cells to prevent further injury. Upon removal of the “stress” conditions, these cells restart their cell cycle and regain their proliferative nature thereby resulting in tumor relapse. Growth Arrest Specific 5 (GAS5) is a long-noncoding RNA that plays a vital role in this process. In pancreatic cancer, CD133+ population is a typical representation of the TIC population that is responsible for tumor relapse. In this study, we show for the first time that emergence of CD133+ population coincides with upregulation of GAS5, that reprograms the cell cycle to slow proliferation by inhibiting GR mediated cell cycle control. The CD133+ population further routed metabolites like glucose to shunt pathways like pentose phosphate pathway, that were predominantly biosynthetic in spite of being quiescent in nature but did not use it immediately for nucleic acid synthesis. Upon inhibiting GAS5, these cells were released from their growth arrest and restarted the nucleic acid synthesis and proliferation. Our study thus showed that GAS5 acts as a molecular switch for regulating quiescence and growth arrest in CD133+ population, that is responsible for aggressive biology of pancreatic tumors.

Pancreatic ductal adenocarcinoma (PDAC) is considered to be a highly immunosuppressive and heterogenous neoplasm. Despite improved knowledge regarding the genetic background of the tumor and better understanding of the tumor microenvironment, immune checkpoint inhibitor therapy (targeting CTLA-4, PD-1, PD-L1) has not been very successful against PDAC.The robust desmoplastic stroma, along with an extensive extracellular matrix (ECM) that is rich in hyaluronan, plays an integral role in this immune evasion. Hexosamine biosynthesis pathway (HBP), a shunt pathway of glycolysis, is a metabolic node in cancer cells that can promote survival pathways on one hand and influence the hyaluronan synthesis in the ECM on the other. The rate-limiting enzyme of the pathway, glutamine-fructose amidotransferase (GFAT1), uses glutamine and fructose 6-phosphate to eventually synthesize UDP-GlcNAc.In the current manuscript, we target this glutamine-utilizing enzyme by a small molecule glutamine analog (6-diazo-5-oxo-L-norleucine or DON). Our results show that DON decreases the self-renewal potential and metastatic ability of tumor cell. Further, treatment with DON results in a decrease in hyaluronan and collagen in the tumor microenvironment, leading to an extensive remodeling of the ECM. this in turn, increases CD8+ cytotoxic T-cells infiltration, and makes the tumors tumors more amenable and sensitive to anti-PD1 therapy.

Porcine circovirus type 2 (PCV2), a small, single-stranded circular DNA virus and the causative agent of porcine circovirus associated disease (PCVAD), was first observed in the mid-1990s in pigs with a post-weaning wasting disease. In 2006 the number of PCVAD cases greatly increased, marking it as an important viral pathogen for the United States (US) swine industry. PCV2 vaccines were introduced to the US in 2006 in response to widespread outbreaks of PCVAD. These vaccines were effective in preventing disease, but did not eliminate virus from the animals. In 2006, prior to vaccine use, a study of PCV2 prevalence in pig herds across the US was performed in conjunction with the US National Animal Health Monitoring System. In 2012, 6 years after widespread PCV2 vaccination, this study was repeated. Since the introduction of PCV2 vaccines in 2006, viral presence and viral loads have greatly decreased, and a genotypic shift dominated by PCV2b has occurred. Antibody levels have decreased in the pig population, but approximately 95% of sites continue to be antibody-positive. Widespread vaccination has controlled PCVAD and decreased PCV2 prevalence to the point that viremia is not detected on many sites. Thus, continued vaccination may lead to PCV2 elimination in the national herd over time.

Background: Pancreatic adenocarcinoma (PDAC) is an extremely immunosuppressive and heterogenous neoplasm for which immune checkpoint inhibitor therapy has not been very successful. Hexosamine biosynthesis pathway (HBP), a shunt pathway of glycolysis, is a metabolic node in cancer cells that can promote survival pathways on one hand and also influence the extracellular matrix in the tumor microenvironment. Our study aims to sensitize pancreatic cancer to anti PD-1 therapy by targeting the HBP pathway. Methods: 6-Diazo-5-oxo L-norleucine or DON was used as a GFAT inhibitor. Tetracycline-inducible GFAT knockout cell lines were made using S2-VP10 as the parent cell line. Results: High-dose monotherapy of DON (1mg/kg/3days a week) caused significant decrease in tumor volume in immunocompetent KPC mice along with significant reduction in metastasis and circulating tumor cells. Circulating tumor cells (CTCs) were also found to be significantly reduced in DON-treated mice as compared to control, leading to reduced metastasis. Combination of low-dose DON (0.5mg/kg/3 days a week) with low-dose anti PD-1 (100 μgX3 times) caused an impressive reduction in tumor volume along with an increase in survival in KPC tumor-bearing mice. Flow-based analysis of tumor cells show a significant influx of CD8+ T cells along with an increase in M1 polarization of macrophages. Survival study of CD8 knockout mice (CD8KO), orthotopically implanted with KPC and fibroblast cells, show that at low doses DON loses its anticancer effect in absence of CD8 as demonstrated by decrease in survival in CD8KO mice as compared to tumor-bearing wild-type mice. Conclusion: Novel therapeutic strategies that can make PDAC more amenable to immune therapy are urgently needed. In this context, our study is extremely timely as it targets specific metabolic pathways in cancer cells to overcome immune resistance and sensitize the tumor to anti-PD1 therapy. Citation Format: Nikita S. Sharma, Vineet K. Gupta, Vanessa Garrido, Roey Hadad, Brittany Durden, Kousik Kesh, Anthony Ferrantella, Bhuwan Giri, Vikas Dudeja, Ashok Saluja, Sulagna Banerjee. Targeting tumor-intrinsic metabolic node in pancreatic cancer causes tumor regression, remodels extracellular matrix, and sensitizes to anti-PD1 therapy [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Advances in Science and Clinical Care; 2019 Sept 6-9; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2019;79(24 Suppl):Abstract nr B03.

The presence of quiescent, therapy-resistant population of tumor cells is often attributed to extreme metastasis and tumor recurrence. This population, often described as cancer stem cells (CSCs), or tumor-initiating cells (TICs), is enriched in a tumor as a result of microenvironmental (hypoxia) or chemotherapeutic stress. In pancreatic cancer, CD133+ cells have been described as a representation of this aggressive TIC population and are most responsible for tumor relapse in patients. This population adapts to stress by turning on mechanisms to halt cell cycle progression. Upon removal of the stress, these cells restart their cell cycle and regain their proliferative nature. Growth Arrest Specific 5 (GAS5) is a long noncoding RNA critical for this process and is overexpressed in PDAC. 13C-Glucose labeling was used for glucose flux assay to track the use of glucose and other metabolites in CD133+ and CD133- populations of pancreatic cancer cells. CD133+/- cell populations were sorted with magnetic sorting or flow cytometry sorting techniques. Lentiviral stable transfection of human CD133 cDNA in MIA PaCa-2 cell line was used to obtain a CD133 overexpressing cell line. siGAS5 and siSOX2 were used to knock down genes in CD133Hi cell lines. Glucocorticoid receptor (GR) activity was assessed using GRE dual luciferase assay system (Qiagen). MTT-based assay was used for proliferation and BrDU incorporation assay was used for measure of nucleic acid synthesis. Fluorescent in situ hybridization using human GAS5 RNA probe (Stellaris) was used to visualize GAS5 localization in human PDAC vs. normal adjacent FFPE samples as well as xenograft FFPE samples. Our results show for the first time that the emergence of CD133+ population coincides with upregulation of GAS5, which reprograms cell cycle to slow proliferation by inhibiting GR-mediated cell cycle control. The CD133+ population further routed glucose through the pentose phosphate pathway, a predominantly biosynthetic pathway, in spite of being quiescent in nature. However, this did not result in immediate nucleic acid synthesis. Upon inhibiting GAS5, these cells were released from growth arrest and restarted nucleic acid synthesis and proliferation. Additionally, this study shows that GAS5 regulates cell cycle through GR, which it is known to bind and inhibit. CD133Hi cells with high GAS5 expression had low GR activity, and stimulation of these cells with dexamethasone was able to increase cell proliferation. Our study thus shows that GAS5 acts as a molecular switch for regulating quiescence and growth arrest in CD133+ population, allowing these cells to overcome chemical and environmental stressors and leading to the aggressive nature of pancreatic tumors. Citation Format: Nikita S. Sharma, Brittany C. Durden, Prisca Gnamlin, Vineet K. Gupta, Kousik Kesh, Vanessa T. Garrido, Ashok Saluja, Sulagna Banerjee. Long noncoding RNA growth arrest specific 5 (GAS5) as a proliferation «brake» in aggressive population of CD133+ cells responsible for recurrence in PDAC [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Advances in Science and Clinical Care; 2019 Sept 6-9; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2019;79(24 Suppl):Abstract nr B17.

Pancreatic cancer is among the 3rdleading cause of cancer related deaths in the United States along with a 5-year survival rate of 7%. The aggressive biology of the disease is responsible for such dismal outcome and is manifested by an increase in self-renewal capacity of the cancer cells, which leads to an increased rate of tumor-recurrence, contributing to poor prognosis. Transcription factor SOX2 maintains a critical balance between differentiation and “stemness” and is thus tightly regulated within a cell. In cancer, SOX2 is aberrantly “turned-on” leading to activation of self-renewal pathways in cancer. Regulation of Sox2 in cancer is poorly understood. In the current study, we show for the first time that in pancreatic cancer, Sox2 is modified by addition of O-GlcNAc moiety, catalyzed by OGT (O-GlcNAc Transferase) at S246. This activates Sox2 transcriptional activity by stabilizing the protein in the nucleus. A CRISPR-OGT knockout in pancreatic cancer cell line S2VP10 resulted in a delayed tumor initiation. We further showed that mutation of this site (S246A) prevents the modification of Sox2 and its downstream activity. Our study also demonstrated that targeting OGTin vivowith a small molecule inhibitor OSMI, results in decreased tumor burden, delayed tumor progression and a decreased expression of SOX2 in pancreatic cancer cells. Our study highlights for the first time that that the O-GlcNAc transferase dependent SOX2 glycosylation has a profound effect on the transcriptional activity of SOX2 and is instrumental in determining self-renewal in pancreatic cancer.SignificanceOur study highlights for the first time that that the O-GlcNAc transferase dependent SOX2 glycosylation determines self-renewal in pancreatic cancer which is responsible for tumor initiation.

Endoplasmic reticulum (ER) stress initiates an important mechanism for cell adaptation and survival, named the unfolded protein response (UPR). Severe or chronic/prolonged UPR can breach the threshold for survival and lead to cell death. There is a fundamental gap in knowledge on the molecular mechanism of how chronic ER stress is stimulated and leads to cell death in pancreatic ductal adenocarcinoma (PDAC). Our study shows that downregulating specificity protein 1 (Sp1), a transcription factor that is overexpressed in pancreatic cancer, activates UPR and results in chronic ER stress. In addition, downregulation of Sp1 results in its decreased binding to the ER stress response element present in the promoter region of Grp78, the master regulator of ER stress, thereby preventing homeostasis. We further show that inhibition of Sp1, as well as induction of ER stress, leads to lysosomal membrane permeabilization (LMP), a sustained accumulation of cytosolic calcium, and eventually cell death in pancreatic cancer.

Tumor-initiating cells (TICs) have been implicated in pancreatic tumor initiation, progression, and metastasis. Among different markers that define this cell population within the tumor, the CD133+ cancer stem cell (CSC) population has reliably been described in these processes. CD133 expression has also been shown to functionally promote metastasis through NF-κB activation in this population but, the mechanism is unclear. In the current study, overexpression of CD133 increased expression and secretion of IL-1β (IL1B), which activates an autocrine signaling loop that upregulates NF-κB signaling, epithelial-mesenchymal transition (EMT), and cellular invasion. This signaling pathway also induces CXCR4 expression, which in turn is instrumental in imparting an invasive phenotype to these cells. In addition to the autocrine signaling of the CD133 secreted IL-1β, the tumor-associated macrophages (TAMs) also produced IL-1β, that further activated this pathway in TICs. The functional significance of the TIC marker CD133 has remained elusive for a very long time; the current study takes us one step closer to understanding how the downstream signaling pathways in these cells regulate the functional properties of tumor-initiating cells.

Pancreatic cancer cells undergo extensive metabolic reprogramming to fulfil the demands of metabolic nutrients to fuel their rapid proliferation. This results in abnormal accumulation of various metabolites which causes both metabolic and nonmetabolic dysregulation and potential transformation to malignancy and therefore termed as “oncometabolites”. Hypoxia is a major hallmark of pancreatic tumors which associated with increase in self-renewal. The present study investigates the role of Hypoxia mediated altered oncometabolite in regulating self-renewal in pancreatic cancer. GC-mass spectrometric analysis of pancreatic cancer cells under hypoxia showed significant accumulation of 2-hydroxyglutarate (2-HG) both in cells and culture supernatant. Further analysis of hypoxic cells showed selective accumulation L- enantiomer form. Self-renewal requires critical balance between stemness and differentiation. Present study showed for the first time that L-2-HG regulates self-renewal by increasing expression of genes associated with stemness (Sox-2, CD133) and by decreasing expression of differentiation genes (PdX-1, HB9, NKX6.1). Further analysis showed that L-2-HG mediated epigenetic changes regulates these self-renewal gens in pancreatic cancer. Our results indicated that hypoxia mediated metabolic changes results in accumulation of L-2-HG which upregulate self-renewal by shifting critical balance of gene expression towards stemness in pancreatic cancer which contribute to chemoresistance and metastasis in Pancreatic cancer. Citation Format: Vineet K. Gupta, Nikita Sharma, Kousik Kesh, Roey Hadad, Vikas Dudeja, Ashok Saluja, Sulagna Banerjee. Hypoxia promote self-renewal in pancreatic cancer by modulating L-2-Hydroxyglutarate level [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 5284.

Background: Pancreatic Cancer is an extremely aggressive disease with a bad outcome owing to its late detection, high rate of metastasis and self-renewal post-surgical and chemotherapeutic intervention. In cancer the balance between differentiation and self-renewal is tightly regulated by SOX2. Over expression of SOX2, as in pancreatic cancer, can tilt the balance towards self-renewal and thus increase the population of these undifferentiated “stem cells”. Methods: A CRISPR based OGT knockout kit was purchased from Origene and a knockout cell line was generated with S2VP10 cells. For the tumor initiation studies OGTi (OGT knockout cells) were implanted subcutaneously at a limiting dilution from 500,000 cells to 500 cells. Site directed mutagenesis was performed using theQuick-change Lightning from Agilent. Results: In the current study we show for the first time that SOX2 undergoes a type of post translational modification known as O GlcNAcylation. We also show for the first time that in humans this modification happens at Serine 246 and mutating this particular site via a side directed mutagenesis leads to a loss of O GlcNAcylation of SOX2.O GlcNAc modification of SOX2 further leads to its activation which then leads to its stabilization in the nucleus. A CRISPR-OGT knockout in pancreatic cancer cell line S2VP10 resulted in a delayed tumor initiation. We further showed that mutation of this site (S246A) prevents the modification of Sox2 and its downstream activity. Our study also demonstrated that targeting OGT in vivo with a small molecule inhibitor OSMI, results in decreased tumor burden, delayed tumor progression and a decreased expression of SOX2 in pancreatic cancer cells. Conclusion: Our study highlights for the first time that the O-GlcNAc transferase dependent SOX2 glycosylation has a profound effect on the transcriptional activity of SOX2 and is instrumental in determining self-renewal in pancreatic cancer which can be targeted therapeutically. Citation Format: Nikita S. Sharma, Vineet K. Gupta, Patricia Dauer, Roey Hadad, Kousik K. kesh, Vikas Dudeja, Ashok Saluja, Sulagna Banerjee. O GlcNAcylation of SOX2 regulates its tumor initiation properties in pancreatic 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 4498.

Castration-resistant prostate cancer (CRPC) arises from a failure of standard-of-care androgen deprivation (AD) therapy to suppress emergence of castration-resistant variants from the original AD-responsive prostate cancer (ADPC). Identification of molecular drivers of AD-resistance and CRPC emergence is critical for developing curative therapies. Comparative transcriptomic analysis of parental ADPC cells and their acutely-emergent CRPC counterparts, developed in our laboratory, identified two distinct and novel redox-regulated pathways in mediating castration resistance. The redox-protective protein thioredoxin-1 (TRX1) was elevated under AD in CRPC cells, but not ADPC cells. TRX1 inhibition, via shRNA or the Phase-I approved TRX1 inhibitor PX-12 (not tested in prostate cancer), elevated ROS levels and induced cell death in androgen-deprived CRPC cells and reduced xenograft tumor formation in castrate in vivo models. Unexpectedly, TRX1 inhibition also elevated androgen receptor (AR) levels under AD, and AR depletion mitigated both TRX1 inhibition-mediated ROS production and loss of viability. Our results suggest maintaining AR expression in CRPC induces oxidative stress that requires redox-protective adaptations (such as elevated TRX1) to avoid AD-induced cell death. In contrast to TRX1, we found GC1a, the main subunit of the nitric oxide receptor, soluble guanylate cyclase (sGC), was decreased in CRPC relative to ADPC. Treatment with sGC agonists, including an FDA-approved anti-hypertensive agent, led to reduction in castrate-resistant tumor burden in xenograft models. Tumor suppression was significantly correlated to the extent by which sGC signaling was stimulated in the treated animals. Our preliminary findings indicate sGC signaling is inhibitory to CRPC and that oxidation of the sGC complex is likely to be an important mechanism of signal dampening in CRPC. Our research points to a ROS duality in CRPC, comprising oxidation-mediated inhibition of anti-tumor signaling alongside a concomitant vulnerability to oxidative stress, requiring enhanced redox-protective mechanisms that could serve as novel avenues for therapeutic intervention in CRPC.

Pancreatic cancer remains a significant health burden associated with limited patient survival and poses a major therapeutic challenge. Among cancer cells, Cancer stem cells (CSCs) are instrumental in inducing chemoresistance and metastasis in pancreatic cancer. CD133 has been identified as a CSC surface marker in several malignancies including pancreatic cancer. However, the functional role of CD133 in CSCs still not clear. The present study investigates the role of caveolar lipid raft integrity in functional properties of CD133+ CSCs. Current study showed first time that CD133 localizes to caveolar lipid rafts in pancreatic cancer cells, and associates with Caveolin1 (Cav-1) and cholesterol to form an integral signaling complex which drives the downstream processes of chemoresistance and metastasis. Further analysis showed that the integrity of the lipid-raft is crucial for maintenance of the functional properties of pancreatic CSCs, and its disruption leads to increased chemo-sensitivity to chemotherapeutic compound paclitaxel both in vitro as well as in vivo. Additionally, disruption of lipid raft results in decreased invasiveness and metastatic ability of the cells by deregulation of FAK signaling. The study also reveals that pancreatic cancer cells that lack the CSC population marker, CD133, did not respond to lipid raft disruption. Our results indicated that targeting the lipid-raft integrity in pancreatic cancer can specifically eradicate the CD133+ CSCs in pancreatic tumors, leading to a better prognosis for the disease. Citation Format: Vineet K. Gupta, Nikita S. Sharma, Kousik Kesh, Patrcia Dauer, Alice Nomura, Bhuwan Giri, Vikas Dudeja, Ashok Saluja, Sulagna Banerjee. Lipid raft integrity is essential for metastasis and chemoresistance properties of CD133+ cancer stem cells in pancreatic cancer [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 3551.

Recent advances in diagnostics and better understanding of molecular mechanism underlying breast cancer has let to the better therapeutic options and disease outcome for majority of breast cancer patients. However, ~10 - 20% of all breast cancers often referred to as “triple negative” as they lack expression of the estrogen (ER), progesterone (PR), and human epidermal growth factor 2 (HER2) receptors convey a poor prognosis due in part to a lack of targeted therapies. The aim of the current study is to evaluate whether triptolide and its water soluble analog Minnelide is effective against triple negative breast cancer cells. We have previously shown that triptolide/Minnelide not only reduces tumor growth in various cancer models but it also regulates epithelial -mesenchymal transition (EMT), an important mechanism underlying metastasis. In our preliminary findings using three triple negative breast cancer (TNBC) cell lines, MDA-MB-231, MDA-MB-468, and MDA-MB-157, we demonstrate that triptolide not only inhibits the proliferation of TNBC cells but also regulates the protein levels of EMT markers including β-Catenin and Vimentin. In order to elucidate the mechanism underlying triptolide mediated inhibition of cellular proliferation and regulation of EMT markers in TNBC cells, we identified Src kinase and Aurora kinase A as two new targets for triptolide action in TNBC cells. By targeting Src and Aurora kinase, triptolide disrupts the integrity of focal adhesion structures and reduces cell spreading via regulating FAK activity. Our preliminary findings regarding potential use of triptolide/Minnelide in TNBC based on in vitro experiments are promising. However, considering the complex pathophysiology of breast cancer and other biological factors playing role in a disease setting, in-vivo experiments to test the efficacy of Minnelide in relevant mouse models for mammary cancers are currently underway. Citation Format: Mahendra K. Singh, Soham Shah, Nikita Satish Sharma, Bhuwan Giri, Sulagna Banerjee, Ashok Saluja. Evaluation of Minnelide as potential targeted therapy for triple negative breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5119. doi:10.1158/1538-7445.AM2017-5119

296 Background: Pancreatic cancer is an aggressive disease. The current chemotherapy only marginally increases the survival of patients with PDAC. Hence there is an urgent need for novel therapies. We have shown that minnelide, a pro-drug of triptolide which is currently in phase I trials, when administered intra-peritoneally is very effective against pancreatic cancer in multiple animal models. In the current study we evaluated the efficacy of oral minnelide against pancreatic cancer, alone or in combination with standard therapy in PDAC. Methods: Xenograft, subcutaneous and orthotopic models were established using S2-VP10 and MIA PaCa-2 cell lines. Minnelide was used in doses ranging from 0.15-0.6 mg/kg/day either oral or i.p. and standard chemotherapy was gemcitabine 250 mg/kg/week + nab-paclitaxel 25 mg/kg/week. The tumor burden was compared between various treatment groups. Results: Minnelide i.p significantly decreased tumor mass in MIA PaCa-2 derived tumors and oral administration had equipotent effects. In the S2-VP10 model, combination of low doses of orally administered minnelide with gemcitabine + nab-paclitaxel was significantly more effective in decreasing the tumor burden leading to an increased survival of tumor bearing mice when compared with either therapy alone (p < 0.05). Combination therapy significantly reduced cancer-related morbidity by decreasing ascites and metastasis. Conclusions: Oral administration of minnelide is effective against pancreatic cancer at doses which have been shown to be safe in phase I clinical trial. Oral minnelide has great potential to emerge as novel therapy for pancreatic cancer.