Patient-Derived Models of Cancer in the NCI PDMC Consortium: Selection, Pitfalls, and Practical Recommendations

For over a century, early researchers sought to study biological organisms in a laboratory setting, leading to the generation of both in vitro and in vivo model systems. Patient-derived models of cancer (PDMCs) have more recently come to the forefront of preclinical cancer models and are even finding their way into clinical practice as part of functional precision medicine programs. The PDMC Consortium, supported by the Division of Cancer Biology in the National Cancer Institute of the National Institutes of Health, seeks to understand the biological principles that govern the various PDMC behaviors, particularly in response to perturbagens, such as cancer therapeutics. Based on collective experience from the consortium groups, we provide insight regarding PDMCs established both in vitro and in vivo, with a focus on practical matters related to developing and maintaining key cancer models through a series of vignettes. Although every model has the potential to offer valuable insights, the choice of the right model should be guided by the research question. However, recognizing the inherent constraints in each model is crucial. Our objective here is to delineate the strengths and limitations of each model as established by individual vignettes. Further advances in PDMCs and the development of novel model systems will enable us to better understand human biology and improve the study of human pathology in the lab.

Micelle-Formulated Juglone Effectively Targets Pancreatic Cancer and Remodels the Tumor Microenvironment

Pancreatic cancer remains a formidable challenge due to limited treatment options and its aggressive nature. In recent years, the naturally occurring anticancer compound juglone has emerged as a potential therapeutic candidate, showing promising results in inhibiting tumor growth and inducing cancer cell apoptosis. However, concerns over its toxicity have hampered juglone's clinical application. To address this issue, we have explored the use of polymeric micelles as a delivery system for juglone in pancreatic cancer treatment. These micelles, formulated using Poloxamer 407 and D-α-Tocopherol polyethylene glycol 1000 succinate, offer an innovative solution to enhance juglone's therapeutic potential while minimizing toxicity. In-vitro studies have demonstrated that micelle-formulated juglone (JM) effectively decreases proliferation and migration and increases apoptosis in pancreatic cancer cell lines. Importantly, in-vivo, JM exhibited no toxicity, allowing for increased dosing frequency compared to free drug administration. In mice, JM significantly reduced tumor growth in subcutaneous xenograft and orthotopic pancreatic cancer models. Beyond its direct antitumor effects, JM treatment also influenced the tumor microenvironment. In immunocompetent mice, JM increased immune cell infiltration and decreased stromal deposition and activation markers, suggesting an immunomodulatory role. To understand JM's mechanism of action, we conducted RNA sequencing and subsequent differential expression analysis on tumors that were treated with JM. The administration of JM treatment reduced the expression levels of the oncogenic protein MYC, thereby emphasizing its potential as a focused, therapeutic intervention. In conclusion, the polymeric micelles-mediated delivery of juglone holds excellent promise in pancreatic cancer therapy. This approach offers improved drug delivery, reduced toxicity, and enhanced therapeutic efficacy.

Targeting the RNA-Binding Protein HuR in Cancer

The RNA-binding protein human antigen R (HuR) is a well-established regulator of gene expression at the posttranscriptional level. Its dysregulation has been implicated in various human diseases, particularly cancer. In cancer, HuR is considered "active" when it shows increased subcellular localization in the cytoplasm, in addition to its normal nuclear localization. Cytoplasmic HuR plays a crucial role in stabilizing and enhancing the translation of prosurvival mRNAs that are involved in stress responses relevant to cancer progression, such as hypoxia, radiotherapy, and chemotherapy. In general, due to HuR's abundance and function in cancer cells compared with normal cells, it is an appealing target for oncology research. Exploiting the principles underlying HuR's role in tumorigenesis and resistance to stressors, targeting HuR has the potential for synergy with existing and novel oncologic therapies. This review aims to explore HuR's role in homeostasis and cancer pathophysiology, as well as current targeting strategies, which include silencing HuR expression, preventing its translocation and dimerization from the nucleus to the cytoplasm, and inhibiting mRNA binding. Furthermore, this review will discuss recent studies investigating the potential synergy between HuR inhibition and traditional chemotherapeutics.

Repurposing the FDA-approved anthelmintic pyrvinium pamoate for pancreatic cancer treatment: study protocol for a phase I clinical trial in early-stage pancreatic ductal adenocarcinoma

BACKGROUND

Recent reports of the utilisation of pyrvinium pamoate (PP), an FDA-approved anti-helminth, have shown that it inhibits pancreatic ductal adenocarcinoma (PDAC) cell growth and proliferation in-vitro and in-vivo in preclinical models. Here, we report about an ongoing phase I open-label, single-arm, dose escalation clinical trial to determine the safety and tolerability of PP in PDAC surgical candidates.

METHODS AND ANALYSIS

In a 3+3 dose design, PP is initiated 3 days prior to surgery. The first three patients will be treated with the initial dose of PP at 5 mg/kg orally for 3 days prior to surgery. Dose doubling will be continued to a reach a maximum of 20 mg/kg orally for 3 days, if the previous two dosages (5 mg/kg and 10 mg/kg) were tolerated. Dose-limiting toxicity grade≥3 is used as the primary endpoint. The pharmacokinetic and pharmacodynamic (PK/PD) profile of PP and bioavailability in humans will be used as the secondary objective. Each participant will be monitored weekly for a total of 30 days from the final dose of PP for any side effects. The purpose of this clinical trial is to examine whether PP is safe and tolerable in patients with pancreatic cancer, as well as assess the drug's PK/PD profile in plasma and fatty tissue. Potential implications include the utilisation of PP in a synergistic manner with chemotherapeutics for the treatment of pancreatic cancer.

ETHICS AND DISSEMINATION

This study was approved by the Thomas Jefferson Institutional Review Board. The protocol number for this study is 20F.041 (Version 3.1 as of 27 October 2021). The data collected and analysed from this study will be used to present at local and national conferences, as well as, written into peer-reviewed manuscript publications.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov: NCT05055323.

Increased glucose availability sensitizes pancreatic cancer to chemotherapy

Pancreatic Ductal Adenocarcinoma (PDAC) is highly resistant to chemotherapy. Effective alternative therapies have yet to emerge, as chemotherapy remains the best available systemic treatment. However, the discovery of safe and available adjuncts to enhance chemotherapeutic efficacy can still improve survival outcomes. We show that a hyperglycemic state substantially enhances the efficacy of conventional single- and multi-agent chemotherapy regimens against PDAC. Molecular analyses of tumors exposed to high glucose levels reveal that the expression of GCLC (glutamate-cysteine ligase catalytic subunit), a key component of glutathione biosynthesis, is diminished, which in turn augments oxidative anti-tumor damage by chemotherapy. Inhibition of GCLC phenocopies the suppressive effect of forced hyperglycemia in mouse models of PDAC, while rescuing this pathway mitigates anti-tumor effects observed with chemotherapy and high glucose.

A Novel 3DNA® Nanocarrier effectively delivers payloads to pancreatic tumors

INTRODUCTION

Standard-of-care systemic chemotherapies for pancreatic ductal adenocarcinoma (PDAC) currently have limited clinical benefits, in addition to causing adverse side effects in many patients. One factor known to contribute to the poor chemotherapy response is the poor drug diffusion into PDAC tumors. Novel treatment methods are therefore drastically needed to improve targeted delivery of treatments. Here, we evaluated the efficacy of the 3DNA® Nanocarrier (3DNA) platform to direct delivery of therapeutics to PDAC tumors in vivo.

MATERIALS AND METHODS

A panel of PDAC cell lines and a patient tissue microarray were screened for established tumor-specific proteins to identify targeting moieties for active targeting of the 3DNA. NRG mice with or without orthotopic MIA PaCa-2-luciferase PDAC tumors were treated intraperitoneally with 100 μl of fluorescently labeled 3DNA.

RESULTS

Folic acid and transferrin receptors were significantly elevated in PDAC compared to normal pancreas. Accordingly, both folic acid- and transferrin-conjugated 3DNA treatments significantly increased delivery of 3DNA specifically to tumors in comparison to unconjugated 3DNA treatment. In the absence of tumors, there was an increased clearance of both folic acid-conjugated 3DNA and unconjugated 3DNA, compared to the clearance rate in tumor-bearing mice. Lastly, delivery of siLuciferase by folic acid-conjugated 3DNA in an orthotopic model of luciferase-expressing PDAC showed significant and prolonged suppression of luciferase protein expression and activity.

CONCLUSION

Our study progresses the 3DNA technology as a reliable and effective treatment delivery platform for targeted therapeutic approaches in PDAC.

Abstract 5530: A community led approach to addressing disparities in pancreatic cancer care for Native Americans in Oregon

Pancreatic adenocarcinoma (PDAC) is the third leading cause of cancer-related deaths in the United States (US). Due to unique barriers facing Native Americans (NA) patients, this underrepresented population has worse outcomes and increased mortality. In Oregon, NAs have nearly double the PDAC incidence rate compared to the general US population. Oregon Health & Science University (OHSU) is a leader in PDAC care and research, yet NAs remain underrepresented in pancreatic cancer research at OHSU, and across the country. This highlights the need for a focused and comprehensive research program that collaborates with local tribal communities to identify specific issues and barriers that can be addressed to improve patient care in the NA population. We hypothesize that if we establish a workflow that strengthens existing relationships with tribal communities and leverages established OHSU infrastructure and expertise, we can directly address the unmet need of understanding, preventing and treating PDAC for NA individuals in our local communities. This includes increasing enrollment of NAs in PDAC clinical trials and developing a genetic registry that could help both depict genetic underpinnings that predispose NA individuals to PDAC and potentially guide therapeutic approaches. To build trust within NA communities, we initiated collaborations with Oregon tribes to develop culturally appropriate programs guided by NA community members. Through OHSU’s Northwest Native American Center of Excellence, we developed a close relationship with the Confederated Tribes of Warm Springs. Together with our institution’s Community Outreach, Research, and Engagement (CORE) team, we are working with the Confederated Tribes of Warm Springs to better understand provider and NA community member attitudes towards and barriers to clinical trial participation. We will incorporate these perceptions into a tribe-specific program that describes the multi-faceted facilitators and barriers that inform decision-making. Moreover, we are implementing a patient navigator program to help NA patients overcome clinical trial barriers by providing culturally appropriate patient education, reimbursement for travel-associated expenses, local administration of chemotherapy, and telehealth capabilities. Future work includes co-implementing strategies for tribes to review incoming research requests with the goal of implementing a system to promote awareness and enrollment of NAs in PDAC clinical research. This system will be then be utilized to establish the first NA PDAC tissue registry to identifying gene-environment interactions and unique genetic alterations that may predispose NA individuals to PDAC. Overall, this collaborative work will create a roadmap for engagement and a conscientious process to provide awareness and the best in class treatment for NA individuals with PDAC.

Citation Format: Claymore Kills First, Grace A. McCarthy, Charles D. Lopez, Brett C. Sheppard, Jackilen Shannon, Jonathan R. Brody. A community led approach to addressing disparities in pancreatic cancer care for Native Americans in Oregon. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5530.

Strategies for the Management of Patients with Pancreatic Cancer with PARP Inhibitors

A subset of patients with pancreatic adenocarcinomas (PDAC) harbor mutations that are exploitable in the context of DNA-damage response and repair (DDR) inhibitory strategies. Between 8-18% of PDACs harbor specific mutations in the DDR pathway such as BRCA1/2 mutations, and a higher prevalence exists in high-risk populations (e.g., Ashkenazi Jews). Herein, we will review the current trials and data on the treatment of PDAC patients who harbor such mutations and who appear sensitive to platinum and/or poly ADP ribose polymerase inhibitor (PARPi) based therapies due to a concept known as synthetic lethality. Although this current best-in-class precision treatment shows clinical promise, the specter of resistance limits the extent of therapeutic responses. We therefore also evaluate promising pre-clinical and clinical approaches in the pipeline that may either work with existing therapies to break resistance or work separately with combination therapies against this subset of PDACs.

Nanoparticle-Based Follistatin Messenger RNA Therapy for Reprogramming Metastatic Ovarian Cancer and Ameliorating Cancer-Associated Cachexia

This study presents the first messenger RNA (mRNA) therapy for metastatic ovarian cancer and cachexia-induced muscle wasting based on lipid nanoparticles that deliver follistatin (FST) mRNA predominantly to cancer clusters following intraperitoneal administration. The secreted FST protein, endogenously synthesized from delivered mRNA, efficiently reduces elevated activin A levels associated with aggressive ovarian cancer and associated cachexia. By altering the cancer cell phenotype, mRNA treatment prevents malignant ascites, delays cancer progression, induces the formation of solid tumors, and preserves muscle mass in cancer-bearing mice by inhibiting negative regulators of muscle mass. Finally, mRNA therapy provides synergistic effects in combination with cisplatin, increasing the survival of mice and counteracting muscle atrophy induced by chemotherapy and cancer-associated cachexia. The treated mice develop few nonadherent tumors that are easily resected from the peritoneum. Clinically, this nanomedicine-based mRNA therapy can facilitate complete cytoreduction, target resistance, improve resilience during aggressive chemotherapy, and improve survival in advanced ovarian cancer.

The RNA-Binding Protein HuR Posttranscriptionally Regulates the Protumorigenic Activator YAP1 in Pancreatic Ductal Adenocarcinoma

Yes-associated protein 1 (YAP1) is indispensable for the development of mutant KRAS-driven pancreatic ductal adenocarcinoma (PDAC). High YAP1 mRNA is a prognostic marker for worse overall survival in patient samples; however, the regulatory mechanisms that mediate its overexpression are not well understood. YAP1 genetic alterations are rare in PDAC, suggesting that its dysregulation is likely not due to genetic events. HuR is an RNA-binding protein whose inhibition impacts many cancer-associated pathways, including the "conserved YAP1 signature" as demonstrated by gene set enrichment analysis. Screening publicly available and internal ribonucleoprotein immunoprecipitation (RNP-IP) RNA sequencing (RNA-Seq) data sets, we discovered that YAP1 is a high-confidence target, which was validated in vitro with independent RNP-IPs and 3' untranslated region (UTR) binding assays. In accordance with our RNA sequencing analysis, transient inhibition (e.g., small interfering RNA [siRNA] and small-molecular inhibition) and CRISPR knockout of HuR significantly reduced expression of YAP1 and its transcriptional targets. We used these data to develop a HuR activity signature (HAS), in which high expression predicts significantly worse overall and disease-free survival in patient samples. Importantly, the signature strongly correlates with YAP1 mRNA expression. These findings highlight a novel mechanism of YAP1 regulation, which may explain how tumor cells maintain YAP1 mRNA expression at dynamic times during pancreatic tumorigenesis.

Limited nutrient availability in the tumor microenvironment renders pancreatic tumors sensitive to allosteric IDH1 inhibitors

Nutrient-deprived conditions in the tumor microenvironment (TME) restrain cancer cell viability due to increased free radicals and reduced energy production. In pancreatic cancer cells a cytosolic metabolic enzyme, wild-type isocitrate dehydrogenase 1 (wtIDH1), enables adaptation to these conditions. Under nutrient starvation, wtIDH1 oxidizes isocitrate to generate α-ketoglutarate (αKG) for anaplerosis and NADPH to support antioxidant defense. In this study, we show that allosteric inhibitors of mutant IDH1 (mIDH1) are potent wtIDH1 inhibitors under conditions present in the TME. We demonstrate that low magnesium levels facilitate allosteric inhibition of wtIDH1, which is lethal to cancer cells when nutrients are limited. Furthermore, the Food & Drug Administration (FDA)-approved mIDH1 inhibitor ivosidenib (AG-120) dramatically inhibited tumor growth in preclinical models of pancreatic cancer, highlighting this approach as a potential therapeutic strategy against wild-type IDH1 cancers.

Disparities in Electronic Screening for Cancer-Related Psychosocial Distress May Promote Systemic Barriers to Quality Oncologic Care

BACKGROUND

Screening for cancer-related psychosocial distress is an integral yet laborious component of quality oncologic care. Automated preappointment screening through online patient portals (Portal, MyChart) is efficient compared with paper-based screening, but unstudied. We hypothesized that patient access to and engagement with EHR-based screening would positively correlate with factors associated with digital literacy (eg, age, socioeconomic status).

METHODS

Screening-eligible oncology patients seen at our Comprehensive Cancer Center from 2014 through 2019 were identified. Patients with active Portals were offered distress screening. Portal and screening participation were analyzed via multivariable logistic regression. Household income in US dollars and educational attainment were estimated utilizing zip code and census data.

RESULTS

Of 17,982 patients, 10,279 (57%) had active Portals and were offered distress screening. On multivariable analysis, older age (odds ratio [OR], 0.97/year; P<.001); male gender (OR, 0.89; P<.001); Black (OR, 0.47; P<.001), Hawaiian/Pacific Islander (OR, 1.54; P=.007), and Native American/Alaskan Native race (OR, 0.67; P=.04); Hispanic ethnicity (OR, 0.76; P<.001); and Medicare (OR, 0.59; P<.001), Veteran's Affairs/military (OR, 0.09; P<.01), Medicaid (OR, 0.34; P<.001), or no insurance coverage (OR, 0.57; P<.001) were independently associated with lower odds of being offered distress screening; increasing income (OR, 1.05/$10,000; P<.001) and educational attainment (OR, 1.03/percent likelihood of bachelor's degree or higher; P<.001) were independently associated with higher odds. In patients offered electronic screening, participation rate was 36.6% (n=3,758). Higher educational attainment (OR, 1.01; P=.03) was independently associated with participation, whereas Black race (OR, 0.58; P=.004), Hispanic ethnicity (OR, 0.68; P=.01), non-English primary language (OR, 0.67; P=.03), and Medicaid insurance (OR, 0.78; P<.001) were independently associated with nonparticipation.

CONCLUSIONS

Electronic portal-based screening for cancer-related psychosocial distress leads to underscreening of vulnerable populations. At institutions using electronic distress screening workflows, supplemental screening for patients unable or unwilling to engage with electronic screening is recommended to ensure efficient yet equal-opportunity distress screening.

Abstract 3191: Tumor intrinsic HuR promotes stroma activation in pancreatic cancer

Background: One of the factors contributing to poor prognosis of pancreatic ductal adenocarcinoma (PDAC) is thought to be the characteristically dense stroma and heterogeneous tumor microenvironment. The PDAC stroma involves multiple players, including cancer associated fibroblasts (CAFs) and pancreatic stellate cells (PSCs). These stromal cells, when activated, promote extensive fibrosis in PDAC, which is associated with poor prognosis and chemoresistance.

We have previously established that the RNA-binding protein Human Antigen R (HuR, ELAVL1) facilitates PDAC progression. In a tumor microarray of matched normal and malignant patient tissues, we found high active (i.e. cytoplasmic) HuR staining in 80% of PDAC tumors, while low or absent in adjacent normal tissues (n=80). Moreover, in both the orthotopic and the genetically engineered mouse models of PDAC, active HuR staining in tumors was dramatically higher than in normal pancreas. Pancreas-specific overexpression of HuR in a transgenic mouse model did not initiate tumorigenesis, but did increase fibrosis compared to control mice. We hypothesize that tumor intrinsic HuR regulates transcripts that are needed for tumor cells to activate the surrounding stroma.

Methods: MiaPaCa-2 or PANC-1 human PDAC cells, either HuR-proficient or CRISPR-mediated knocked-out, were used in an orthotopic model where cells were injected into the tail of the pancreas. Both NRG and athymic mice were used. Resulting tumors underwent immunohistochemistry, immunofluorescence, or RNA-sequencing. Secreted proteins from cells in 2D culture were analyzed using a cytokine array.

Results: HuR knockout tumors showed a decrease in CAF and PSC markers (i.e. podoplanin, alpha-SMA, desmin; &gt;55% decrease, p&lt;0.05), as well as a decrease in collagen deposition (56% decrease, p=0.0004). Additionally, HuR expression in tumors positively correlated with collagen abundance (p= 0.0002).

RNA sequencing of PDAC tumors at various times during tumor development found that gene expression of stroma-activating ligands was significantly downregulated in HuR knockout tumors (e.g. TGFb, CCL2, PDGFA; -0.8&lt;log2FC&lt;-3.6, 0.0009&lt;padj&lt;2^-57). Moreover, we found a significant decrease of these stroma-activating ligands in conditioned media obtained from HuR knockout compared to wild type (e.g. PDGFAA, PTX3, CCL2; &gt;50% decrease, p&lt;0.0001).

Conclusions: We found inhibition of HuR led to a robust decrease in stroma activation (i.e. lack of collagen, CAFs, and PSCs). To our knowledge, this is the first report of PDAC tumor intrinsic HuR having an extrinsic effect on neighboring stromal cells. Specifically, we found loss of HuR results in a decrease of secreted stroma-activating ligands, likely to be the cause of the decreased fibrosis in HuR knockout tumors. With evidence that fibrosis is associated with poor survival rates and chemoresistance, inhibiting HuR may sensitize tumors to standard of care therapy.

Citation Format: Grace A. McCarthy, Jennifer M. Finan, Aditi Jain, Roberto DiNiro, Aaron Grossberg, Jonathan R. Brody. Tumor intrinsic HuR promotes stroma activation in pancreatic cancer [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 3191.

Abstract 3935: The polymeric fluoropyrimidine CF10 overcomes limitations of 5-FU in pancreatic ductal adenocarcinoma cells through increased replication stress

Pancreatic ductal adenocarcinoma (PDA) is a lethal disease that will soon become the second leading cause of cancer deaths in the US. Beside surgery, current therapies have narrow clinical benefits for this devastating disease, and in the majority of cases, only improve survival by a few months. Moreover, systemic toxicities are a harsh reality of these treatments. FOLFIRINOX is the drug regimen of choice, one component of which is 5-Fluorouracil (5-FU) which causes serious gastrointestinal and hematopoietic toxicities and is vulnerable to resistance due, in part, to thymidylate synthase (TS) overexpression. The Gmeiner lab has pioneered the development of polymeric fluoropyrimidines, named F10 and CF10, which unlike 5-FU, are in principle completely converted to the TS inhibitory metabolite FdUMP, without generating appreciable levels of ribonucleotides that cause systemic toxicities and while displaying much stronger anti-cancer activity. Here, we further confirm the potency of CF10 and investigate enhancement of its efficacy through combination with inhibitors targeting replication stress, a hallmark of PDA cells. We show that, consistent with our previous studies in PDA cells, CF10 is much more potent as a single agent than 5-FU, by an average 308x fold, and was effective in the nM range (GI50 range 3.13 - 336 nM) in 5 PDA cell lines tested. We also found that CF10 induces increased replication stress as assessed by phosphorylation of ATR, which appears as early as 8 hours after treatment and increases in intensity over 48 hours, consistent with the kinetics of FdU being released from CF10 and incorporated into DNA, a process requiring several hours. Importantly, phosphorylation of ATR induced by CF10 was significantly higher than with 5-FU. This is especially striking because compounds for this assay were used at their IC50 concentrations, with for example MiaPaCA2 cells being exposed to 899 time more 5-FU than CF10, yet at this concentration 5-FU induced less ATR phosphorylation. Further, we find that the activity of CF10, but not 5-FU can be enhanced through combination with inhibitors of ATR and Wee1 that regulate the S and G2 damage checkpoints. Our results indicate CF10 has potential to supersede the established benefit of 5-FU in PDA treatment and indicate novel combination approaches that may be beneficial compared to well-established regimens used currently for 5-FU.

Citation Format: Roberto DiNiro, Alex O. Haber, Kang J. Jeong, Soon Y. Park, Gordon B. Mills, William H. Gmeiner, Jonathan R. Brody. The polymeric fluoropyrimidine CF10 overcomes limitations of 5-FU in pancreatic ductal adenocarcinoma cells through increased replication stress [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 3935.

Abstract 2597: Inhibition of BARD1-PLK1 axis enhances PARP inhibitor/platinum sensitivity in homologous repair proficient pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive cancer with a grim prognosis. Though the overall 5-year survival rates have recently improved to 10%, there is still an unmet need for better therapies. PARP inhibitors (PARPi)/platinum therapies have demonstrated clinical efficacy in BRCA1/2 mutated PDAC and has recently led to the FDA approval of PARPi (olaparib) in the maintenance setting, offering the best personalized treatment approach for such patients. Although promising, the benefits of these therapeutic strategies are currently limited to only a few patients. We have recently established that BARD1 (BRCA1- Associated-Ring-Domain-1), the main binding partner of BRCA1 in regulating homologous recombination repair is upregulated in PDAC cells exposed to PARPi/platinum compounds, by a post-transcriptional RNA binding mechanism. We therefore hypothesized that inhibition of BARD1 will sensitize cells to these agents. We found that inhibition of BARD1 (both by siRNA/shRNA and CRISPR-KO) not only sensitized the cells to olaparib or oxaliplatin but enhanced DNA damage in cells, as analyzed by comet assays and γ-H2AX immunofluorescence staining. BARD1 inhibition led to a decrease in homologous repair efficiency of cells as analyzed by the well established pDRGFP assay. To further understand BARD1 dependent downstream signaling, we performed comparative transcriptomic analysis of BARD1 silenced cells compared to scramble control. RNA seq analysis revealed modulation of several cell cycle checkpoints and DNA damage response pathways. Notably, through gene set enrichment analysis (GSEA), we found that silencing BARD1 causes de-enrichment of pathway regulating Polo-Like-Kinase-1 (PLK1, a serine/threonine kinase) activity (p-val=0.05, FDR=0.07). PLK1 is frequently upregulated in PDAC cells and promotes progression of cells through mitosis. Based on these results, we found that a PLK1 specific inhibitor (onvansertib) synergized with olaparib to reduce cell survival of homologous repair proficient (HR-P) PDAC cells. Importantly, the mechanism of drug synergy involved induction of apoptosis and DNA damage, as assessed by cleaved caspase-3 and γ-H2AX protein analysis. These results are suggestive of targeting the BARD1-PLK1 axis in order to enhance sensitivity of PARPi/platinums in HR proficient cells. Our ongoing and future studies are aimed at understanding the interaction of BARD1 and PLK1 in PDAC cells and analyze the effects of onvansertib and olaparib on tumor growth in vivo. Accomplishment of these studies will establish novel therapeutic targets and synthetic lethal combinations that have not been explored yet for deadly pancreatic cancers, ultimately benefiting patient survival in the long run.

Citation Format: Carolyn Coats, Anoohya Arkala, Eric Londin, Avinoam Nevler, Jonathan R. Brody, Charles J. Yeo, Aditi Jain. Inhibition of BARD1-PLK1 axis enhances PARP inhibitor/platinum sensitivity in homologous repair proficient pancreatic ductal adenocarcinoma [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 2597.

Abstract 1811: Dithiazanine Iodide suppresses mitochondrial function to strongly inhibit pancreatic ductal adenocarcinoma growth in-vitro and in-vivo, producing a marked increase in survival

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive recalcitrant cancer with a uniquely austere tumor microenvironment (TME). It is hypovascularized, hypoxic, and poor in nutrients. These features, which are critical due to the increased energetic demand in continuously replicating cancer cells, drive metabolic reprograming to support the continued activity. Thus leading to a vulnerability in the form of energy restriction - a vulnerability further exacerbated by the nutrient-poor pancreatic cancer TME. We have recently shown mitochondrial inhibition to have great potential in in-vitro inhibition of PDAC cells. Since repurposing of FDA-approved drugs holds great promise in terms of faster and safer drug development, we selected to investigate the effect of mitochondrial inhibition on pancreatic cancer cells through assessment of the previously FDA-approved antimicrobial Dithiazanine Iodide (CDI). CDI is a fluorescent, orally bioavailable, small molecule. In-vitro, it has been previously shown to preferentially localize to the mitochondria, bind proteins and nucleic acids, and have a yet to be discerned inhibitory effect on the electron transport chain. We demonstrated CDI had low IC50s (30-300 nM) in multiple PDAC and other GI cancer cell lines. In an agnostic, unbiased manner, we assessed metabolomic and transcriptomic perturbations caused by CDI. These revealed a profound 92% decrease in the abundance of mitochondrial-encoded transcripts (P&lt;0.05), decreased mitochondrial beta-oxidation, and a reduction in the ATP/ADP ratio. We have therefore hypothesized that the anti-cancer effects of CDI may be related to disruption of mitochondrial processes and we proceeded to characterize its mechanism of action. CDI treatment reduced protein expression of electron transport chain complexes I, II, III, and IV. Treatment with CDI in hypoglycemic conditions resulted in a 3-4 fold increase in sensitivity (P&lt;0.05) and ATP quantification showed a marked &gt;90% decrease in cellular ATP (P&lt;0.05). Furthermore, mitochondria-depleted PDAC cell lines were 4-fold more resistant to CDI treatment (P&lt;0.05). In-vivo, oral CDI treatment resulted in a 2-fold decrease in mouse xenograft tumor growth compared to gemcitabine treatment. RNA-sequencing from the in-vivo samples showed a 60% reduction in the abundance of mitochondrial-encoded transcripts (P&lt;0.05). Examination of the mitochondrial sequences revealed the existence of putative G-Quadruplex sequences. Fluorescence shift and stop-PCR assays confirmed CDI to be a G-Quadruplex binder of mitochondrial sequences.

Citation Format: Avinoam Nevler, Christopher W. Schultz, Aditi Jain, Saed Khalilieh, Grace McCarthy, Harish Lavu, Wilbur Bowne, Charles J. Yeo, Jonathan R. Brody. Dithiazanine Iodide suppresses mitochondrial function to strongly inhibit pancreatic ductal adenocarcinoma growth in-vitro and in-vivo, producing a marked increase in survival [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 1811.

Abstract 3137: Elucidating the role of RNA-binding proteins in pancreatic cancer extracellular vesicle crosstalk

Many solid tumors, including pancreatic ductal adenocarcinoma (PDAC) tumors, rely on pro-tumorigenic intercellular paracrine signaling during tumor progression. Extensive work has been done to understand paracrine signaling via cytokines, chemokines, and metabolites secreted from tumor cells, but only recent studies have begun to investigate the role of extracellular vesicles (EVs) and their cargoes in the tumor microenvironment. Studies have illustrated the ability of PDAC-derived EVs to activate and recruit pancreatic stellate cells in the tumor microenvironment; however, no work has been done in vivo to determine whether this EV uptake occurs within tumors. Additionally, little mechanistic work has been done to understand the functional consequences of EV cargo within recipient cells.

Based on transcriptomic and proteomic analysis of PDAC patient-derived EVs, mRNAs and RNA-binding proteins (RBPs) are enriched within EVs. Our lab focuses on the role of RBPs in PDAC, and thus, we will utilize enhanced crosslinking immunoprecipitation to identify the RBPs within PDAC EVs and evaluate their impact on the EV transcriptome. We have successfully isolated and characterized EVs via size exclusion chromatography isolation paired with western blotting for classical EV markers, fluorescent nanoparticle tracking analysis, and transmission electron microscopy. We have also demonstrated that we can identify mRNA cargoes that are bound and unbound by RBPs. Additionally, we have optimized PKH67 labeling and detection of PDAC EVs to assess specific and preferential uptake in vitro. Further, we are establishing the validated PalmGRET bioluminescent reporter in our patient derived cell lines to track PDAC EVs in a pancreatic orthotopic mouse model. Utilizing this method, we intend to identify cell types in the microenvironment that are importing PDAC EVs and perform functional studies to understand how these cells are impacted by EV signaling.

These studies will elucidate which cells in the PDAC tumor microenvironment import PDAC EVs, as well as interrogate the mechanistic role of PDAC EV crosstalk. This work will further characterize the role of RBPs in PDAC and begin to evaluate their role in a cell extrinsic manner.

Citation Format: Jennifer M. Finan, Roberto Di Niro, Randall Armstrong, Jonathan R. Brody. Elucidating the role of RNA-binding proteins in pancreatic cancer extracellular vesicle crosstalk [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 3137.

Abstract 3494: Characterizing the relationship between genotype and phenotype in DNA damage response-altered pancreatic cancer models

Alterations in DNA damage response (DDR) proteins are prevalent across cancers and present unique opportunities for the therapeutic induction of synthetic lethality (i.e., two gene deficiencies in the same pathway synergize to kill tumor cells). In pancreatic adenocarcinoma, patients harboring alterations in DDR genes, such as in homology-directed repair (HDR), comprise the 10-20% of patients that may benefit from the recent FDA approval of Olaparib, a poly (ADP-ribose) polymerase inhibitor that disrupts non-homologous end joining (NHEJ). Despite being the best-in-class targeted therapy for DDR-altered pancreatic cancers, a subset of patients fails to respond to Olaparib and those that initially respond eventually go on to develop resistance. The mechanisms underlying resistance are poorly elucidated but suggest that some patients harboring DDR-altered tumors are HDR-proficient or revert to HDR-proficiency during therapy, bypassing the second gene deficiency requisite for synthetic lethal induction with targeted therapy (e.g., Olaparib). Utilizing patient-derived models of cancer, we are actively investigating DDR-altered, pancreatic tumor cell lines and exploring the relationship between DDR-alterations and HDR-deficiency with three goals: [1] To evaluate the prevalence of HDR-proficiency in BRCA-altered tumors, [2] to understand the extent to which patient-derived models of cancer are concordant and predictive of clinical outcomes, and [3] to identify novel therapeutic strategies for resistant patients. So far, we have observed HDR-proficiency by functional assays (e.g., RAD51 foci formation) in DDR-altered patient-derived cell lines that corresponds with poor response to Olaparib in vitro, and resistance to platinum therapy clinically. Whereas DDR-altered HDR-deficient lines had greater sensitivity to Olaparib and platinum therapy. These early data suggest that measures of HDR by functional assay may be more predictive of clinical therapeutic responses than the use of genetic signatures alone.

Citation Format: James R. Carroll, Jason M. Link, Jonathan R. Brody. Characterizing the relationship between genotype and phenotype in DNA damage response-altered pancreatic cancer models [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 3494.

Disparities in pancreatic cancer care and research in Native Americans: Righting a history of wrongs

Disparities in pancreatic cancer incidence and outcomes exist in Native American populations. These disparities are multifactorial, difficult to quantify, and are influenced by historical, socioeconomic, and health care structural factors. The objective of this article was to assess these factors and offer a call to action to overcome them. The authors reviewed published data on pancreatic cancer in Native American populations with a focus on disparities in incidence, outcomes, and research efforts. The historical context of the interactions between Native Americans and the United States health care system was also analyzed to form actionable items to build trust and collaboration. The incidence of pancreatic cancer in Native Americans is higher than that in the general US population and has the worst survival of any major racial or ethnic group. These outcomes are influenced by a patient population with often poor access to high-quality cancer care, historical trauma potentially leading to reduced care utilization, and a lack of research focused on etiologies and comorbid conditions that contribute to these disparities. A collaborative effort between nontribal and tribal leaders and cancer centers is key to addressing disparities in pancreatic cancer outcomes and research. More population-level studies are needed to better understand the incidence, etiologies, and comorbid conditions of pancreatic cancer in Native Americans. Finally, a concerted, focused effort should be undertaken between nontribal and tribal entities to increase the access of Native Americans to high-quality care for pancreatic cancer and other lethal malignancies.

HuR Plays a Role in Double-Strand Break Repair in Pancreatic Cancer Cells and Regulates Functional BRCA1-Associated-Ring-Domain-1(BARD1) Isoforms

Human Antigen R (HuR/ELAVL1) is known to regulate stability of mRNAs involved in pancreatic ductal adenocarcinoma (PDAC) cell survival. Although several HuR targets are established, it is likely that many remain currently unknown. Here, we identified BARD1 mRNA as a novel target of HuR. Silencing HuR caused a >70% decrease in homologous recombination repair (HRR) efficiency as measured by the double-strand break repair (pDR-GFP reporter) assay. HuR-bound mRNAs extracted from RNP-immunoprecipitation and probed on a microarray, revealed a subset of HRR genes as putative HuR targets, including the BRCA1-Associated-Ring-Domain-1 (BARD1) (p < 0.005). BARD1 genetic alterations are infrequent in PDAC, and its context-dependent upregulation is poorly understood. Genetic silencing (siRNA and CRISPR knock-out) and pharmacological targeting of HuR inhibited both full length (FL) BARD1 and its functional isoforms (α, δ, Φ). Silencing BARD1 sensitized cells to olaparib and oxaliplatin; caused G2-M cell cycle arrest; and increased DNA-damage while decreasing HRR efficiency in cells. Exogenous overexpression of BARD1 in HuR-deficient cells partially rescued the HRR dysfunction, independent of an HuR pro-oncogenic function. Collectively, our findings demonstrate for the first time that BARD1 is a bona fide HuR target, which serves as an important regulatory point of the transient DNA-repair response in PDAC cells.

Psychosocial distress is dynamic across the spectrum of cancer care and requires longitudinal screening for patient-centered care

PURPOSE

Screening for cancer-related psychosocial distress is recommended for patients with cancer; however, data on the long-term prevalence of distress and its natural history in survivors are scarce, preventing recommendations for screening frequency and duration. We sought to evaluate longitudinal distress in cancer patients.

METHODS

We evaluated longitudinal distress screening data for patients with cancer treated or surveilled at our institution from 2010 to 2018. Anxiety, depression, insurance/financial, family, memory, and strength-related distress were separately assessed and analyzed. Multivariable logistic regression was utilized to evaluate factors associated with distress subtypes.

RESULTS

In 5660 patients, distress was the highest at diagnosis for anxiety, depression, financial, and overall distress. On multivariable analysis, factors independently associated with distress at diagnosis included younger age, female gender, disease site/stage, payor, and income, varying by subtype-specific analyses. Severe distress in at least one subtype persisted in over 30% of survivors surveyed through 10 years after diagnosis. Over half of patients with initially severe distress at diagnosis improved within 12 months; however, distress worsened in 20-30% of patients with moderate, low, and no initial distress, regardless of the distress subtype.

CONCLUSION

Psychosocial distress in cancer survivors is a long-lasting burden with implications for quality of life and oncologic outcomes. Severe distress remains prevalent through 10 years after diagnosis in survivors receiving continued care at cancer centers and results from both persistent and new sources of distress in a variety of psychosocial domains. Longitudinal distress screening is an invaluable tool for providing comprehensive patient-centered cancer care and is recommended to detect new or recurrent distress in cancer survivors.

The FDA-Approved Anthelmintic Pyrvinium Pamoate Inhibits Pancreatic Cancer Cells in Nutrient-Depleted Conditions by Targeting the Mitochondria

Pancreatic ductal adenocarcinoma (PDAC) is a lethal aggressive cancer, in part due to elements of the microenvironment (hypoxia, hypoglycemia) that cause metabolic network alterations. The FDA-approved antihelminthic pyrvinium pamoate (PP) has previously been shown to cause PDAC cell death, although the mechanism has not been fully determined. We demonstrated that PP effectively inhibited PDAC cell viability with nanomolar IC50 values (9-93 nmol/L) against a panel of PDAC, patient-derived, and murine organoid cell lines. In vivo, we demonstrated that PP inhibited PDAC xenograft tumor growth with both intraperitoneal (IP; P < 0.0001) and oral administration (PO; P = 0.0023) of human-grade drug. Metabolomic and phosphoproteomic data identified that PP potently inhibited PDAC mitochondrial pathways including oxidative phosphorylation and fatty acid metabolism. As PP treatment reduced oxidative phosphorylation (P < 0.001), leading to an increase in glycolysis (P < 0.001), PP was 16.2-fold more effective in hypoglycemic conditions similar to those seen in PDAC tumors. RNA sequencing demonstrated that PP caused a decrease in mitochondrial RNA expression, an effect that was not observed with established mitochondrial inhibitors rotenone and oligomycin. Mechanistically, we determined that PP selectively bound mitochondrial G-quadruplexes and inhibited mitochondrial RNA transcription in a G-quadruplex-dependent manner. This subsequently led to a 90% reduction in mitochondrial encoded gene expression. We are preparing to evaluate the efficacy of PP in PDAC in an IRB-approved window-of-opportunity trial (IND:144822).

Gemcitabine-loaded microbubble system for ultrasound imaging and therapy

Ultrasound imaging presents many positive attributes, including safety, real-time imaging, universal accessibility, and cost. However, inherent difficulties in discrimination between soft tissues and tumors prompted development of stabilized microbubble contrast agents. This presents the opportunity to develop agents in which drug is entrapped in the microbubble shell. We describe preparation and characterization of theranostic poly(lactide) (PLA) and pegylated PLA (PEG-PLA) shelled microbubbles that entrap gemcitabine, a commonly used drug for pancreatic cancer (PDAC). Entrapping 6 wt% gemcitabine did not significantly affect drug activity, microbubble morphology, or ultrasound contrast activity compared with unmodified microbubbles. In vitro microbubble concentrations yielding ≥ 500nM entrapped gemcitabine were needed for complete cell death in MIA PaCa-2 PDAC drug sensitivity assays, compared with 62.5 nM free gemcitabine. In vivo administration of gemcitabine-loaded microbubbles to xenograft MIA PaCa-2 PDAC tumors in athymic mice was well tolerated and provided substantial tumoral image enhancement before and after destructive ultrasound pulses. However, no significant differences in tumor growth were observed among treatment groups, in keeping with the in vitro observation that much higher doses of gemcitabine are required to mirror free gemcitabine activity. STATEMENT OF SIGNIFICANCE: The preliminary results shown here are encouraging and support further investigation into increased gemcitabine loading. Encapsulation of gemcitabine within polylactic acid (PLA) microbubbles does not damage its activity towards pancreatic cancer (pancreatic ductal adenocarcinoma, PDAC) cells. Excellent imaging and evidence of penetration into the highly desmoplastic PDAC tumors is demonstrated. Microbubble destruction was confirmed in vivo, showing that elevated mechanical index shatters the microbubbles for enhanced delivery. The potential to slow PDAC growth in vivo is shown, but higher gemcitabine concentrations are required. Current efforts are directed at increasing drug loading by inclusion of drug-carrying nanoparticles for effective in vivo treatment.

Stromal-Derived Extracellular Vesicles Suppress Proliferation of Bone Metastatic Cancer Cells Mediated By ERK2

Bone is a common site of cancer metastasis, including cancers such as breast, prostate, and multiple myeloma. Disseminated tumor cells (DTC) shed from a primary tumor may travel to bone and can survive undetected for years before proliferating to form overt metastatic lesions. This period of time can be defined as metastatic latency. Once in the metastatic microenvironment, DTCs engage in intercellular communication with surrounding stromal cells, which can influence cancer cell survival, proliferation, and ultimately disease progression. The role of the surrounding tumor microenvironment in regulating DTC fate is becoming increasingly recognized. We have previously shown that in the bone microenvironment, osteoblasts are "educated" by interactions with breast cancer cells, and these "educated" osteoblasts (EO) produce soluble factors that regulate cancer cell proliferation. In this study, we provide evidence indicating that EOs produce small extracellular vesicles (sEV) that suppress breast cancer proliferation, in part through regulation of ERK1/2 signaling. In addition, using EdU-incorporation assays and propidium iodide staining we demonstrate that exposure to EO-derived sEVs decreases breast cancer cell entry to S-phase of cell cycle. We also have evidence that particular microRNAs, including miR-148a-3p, are enriched in EO-derived sEVs, and that miR-148a-3p is capable of regulating breast cancer proliferation. IMPLICATIONS: These findings underscore the importance of sEV-mediated communication in the earlier stages of cancer progression, and suggest that EO-derived sEVs may be one mechanism by which the bone microenvironment suppresses breast cancer cell proliferation.

Selecting the optimal parameters for sonoporation of pancreatic cancer in a pre-clinical model

Pancreatic ductal adenocarcinoma (PDAC) is one of the deadliest cancers in the modern world, in part due to poor delivery of chemotherapeutics. Sonoporation can be used to enhance the efficacy of standard of care therapies for PDAC. Using xenograft models of PDAC we investigate sonoporation using four ifferent ultrasound contrast agents (UCAs) and two ultrasound regimens to identify the ideal parameters to increase therapeutic efficacy. MIA-PaCa2 xenografts in over 175 immunodeficient mice were treated with gemcitabine and paclitaxel and subjected to low or high power ultrasound (60 and 200 mW/cm² respectively) in conjunction with one of four different UCAs. The UCAs investigated were Definity®, SonoVue®, Optison™ or Sonazoid™. Tumor volumes, vascularity, hemoglobin, and oxygenation were measured and compared to controls. High power treatment in conjunction with Sonazoid sonoporation led to significantly smaller tumors when started early (tumors ~50mm³; p = .0105), while no UCAs significantly increased efficacy in the low power cohort. This trend was also found in larger tumors (~250mm³) where all four UCA agents significantly increased therapeutic efficacy in the high power group (p < .01), while only Definity and SonoVue increased efficacy in the low power cohort (p < .03). Overall, the higher power ultrasound treatment modality was more consistently effective at decreasing tumor volume and increasing vascularity characteristics. In conclusion, Sonazoid was the most consistently effective UCA at decreasing tumor volume and increasing vascularity. Thus, we are pursuing a larger phase II clinical trial to validate the increased efficacy of sonoporation in conjunction with chemotherapy in PDAC patients.

AraC-FdUMP[10] Is a Next-Generation Fluoropyrimidine with Potent Antitumor Activity in PDAC and Synergy with PARG Inhibition

AraC-FdUMP[10] (CF10) is a second-generation polymeric fluoropyrimidine that targets both thymidylate synthase (TS), the target of 5-fluorouracil (5-FU), and DNA topoisomerase 1 (Top1), the target of irinotecan, two drugs that are key components of FOLFIRNOX, a standard-of-care regimen for pancreatic ductal adenocarcinoma (PDAC). We demonstrated that F10 and CF10 are potent inhibitors of PDAC cell survival (in multiple cell lines including patient-derived lines) with IC₅₀s in the nanomolar range and are nearly 1,000-fold more potent than 5-FU. The increased potency of CF10 relative to 5-FU correlated with enhanced TS inhibition and strong Top1 cleavage complex formation. Furthermore, CF10 displayed single-agent activity in PDAC murine xenografts without inducing weight loss. Through a focused drug synergy screen, we identified that combining CF10 with targeting the DNA repair enzyme, poly (ADP-ribose) glycohydrolase, induces substantial DNA damage and apoptosis. This work moves CF10 closer to a clinical trial for the treatment of PDAC. IMPLICATIONS: CF10 is a promising polymeric fluoropyrimidine with dual mechanisms of action (i.e., TS and Top1 inhibition) for the treatment of PDAC and synergizes with targeting of DNA repair. VISUAL OVERVIEW: http://mcr.aacrjournals.org/content/molcanres/19/4/565/F1.large.jpg.

Improved Antitumor Activity of the Fluoropyrimidine Polymer CF10 in Preclinical Colorectal Cancer Models through Distinct Mechanistic and Pharmacologic Properties

Chemotherapy regimens that include 5-fluorouracil (5-FU) are central to colorectal cancer treatment; however, risk/benefit concerns limit 5-FU's use, necessitating development of improved fluoropyrimidine (FP) drugs. In our study, we evaluated a second-generation nanoscale FP polymer, CF10, for improved antitumor activity. CF10 was more potent than the prototype FP polymer F10 and much more potent than 5-FU in multiple colorectal cancer cell lines including HCT-116, LS174T, SW480, and T84D. CF10 displayed improved stability to exonuclease degradation relative to F10 and reduced susceptibility to thymidine antagonism due to extension of the polymer with arabinosyl cytidine. In colorectal cancer cells, CF10 strongly inhibited thymidylate synthase (TS), induced Top1 cleavage complex formation and caused replication stress, while similar concentrations of 5-FU were ineffective. CF10 was well tolerated in vivo and invoked a reduced inflammatory response relative to 5-FU. Blood chemistry parameters in CF10-treated mice were within normal limits. In vivo, CF10 displayed antitumor activity in several colorectal cancer flank tumor models including HCT-116, HT-29, and CT-26. CF10's antitumor activity was associated with increased plasma levels of FP deoxynucleotide metabolites relative to 5-FU. CF10 significantly reduced tumor growth and improved survival (84.5 days vs. 32 days; P < 0.0001) relative to 5-FU in an orthotopic HCT-116-luc colorectal cancer model that spontaneously metastasized to liver. Improved survival in the orthotopic model correlated with localization of a fluorescent CF10 conjugate to tumor. Together, our preclinical data support an early-phase clinical trial of CF10 for treatment of colorectal cancer.

Combined Targeting of PARG and Wee1 Causes Decreased Cell Survival and DNA Damage in an S-Phase-Dependent Manner

The DNA damage response (DDR) pathway sets the stage for tumorigenesis and provides both an opportunity for drug efficacy and resistance. Therapeutic approaches to target the DDR pathway include aiming to increase the efficacy of cytotoxic chemotherapies and synergistic drug strategies to enhance DNA damage, and hence cell death. Here, we report the first preclinical evaluation of a novel synergistic approach by using both genetic and small-molecule inhibition methods of silencing the DDR-related protein, poly (ADP-ribose) glycohydrolase (PARG), and the checkpoint kinase inhibitor, Wee1, in pancreatic ductal adenocarcinoma (PDAC) and colorectal carcinoma cells in vitro and in vivo. Mechanistically, we demonstrate that coinhibition of PARG and Wee1 synergistically decreased cell survival and increased DNA damage in an S-phase-dependent manner. IMPLICATIONS: In preclinical models, we demonstrate the efficacy and mechanism of action of targeting both PARG and Wee1 in PDAC and colorectal carcinoma cells. VISUAL OVERVIEW: http://mcr.aacrjournals.org/content/molcanres/19/2/207/F1.large.jpg.

Abstract B45: A feedback gene regulatory mechanism between YAP1 and the RNA-binding protein, Human Antigen R (HuR), in pancreatic cancer cells: Implications for a context-dependent pancreatic cancer cell survival network

Pancreatic ductal adenocarcinoma (PDAC) is the third-leading cause of cancer-related death in the U.S. In roughly 95% of cases, gain-of-function mutations in KRAS combine with loss of tumor suppressors to progress preinvasive neoplasms (PanINs) to late-stage ductal adenocarcinoma. Two important facilitators of KRAS function, Human Antigen R (HuR) and Yes-associated protein 1 (YAP1), are both highly overexpressed in PDAC. HuR is an RNA-binding protein that facilitates gene expression through the stabilization and increased translation of target prosurvival mRNAs upon stress. YAP1 is a transcriptional coactivator, which associates with a number of transcription factor families to sense and upregulate targets that lead to tumor growth and cellular crosstalk. While the functions of HuR and YAP1 are well known, the events that lead to their overexpression and regulation are poorly understood.

Our previous work has shown that overexpression of cytoplasmic HuR correlates strongly with tumor staging. Low levels of HuR correspond to early PanINs with staining steadily increasing in late-stage PanIN lesions and gross overexpression in invasive adenocarcinoma. Conversely, YAP1 overexpression seems to be most critical for initial development and expansion of the tumor cells, while it converts to a maintenance role once PDAC is fully developed. Ongoing studies will address whether the temporal regulation of these proteins could explain their overexpression patterns in pancreatic pathologic stages as they relate to cooperating with KRAS activity.

YAP1 was first identified as a HuR target via ribonucleoprotein-immunoprecipitation assays in which HuR-bound mRNAs were run on a whole-transcriptome microarray. YAP1 mRNA was significantly bound to HuR as compared to the IgG isotype control (13.2-fold) and was in line with previously established mRNA targets (WEE1, 3.2-fold; PIM1, 13.9-fold). YAP1 mRNA bound to HuR is abolished when treated with a known HuR inhibitor, pyrvinium pamoate, even in the presence of an established HuR stressor (i.e., oxaliplatin). Actinomycin D chase assays demonstrated that YAP1 mRNA stability is significantly dependent on HuR proficiency. We validated that both YAP1 mRNA and protein expression levels are dependent on HuR via real-time quantitative PCR and Western blot analysis. Impact of YAP1 transcriptional activity was evaluated both by measuring total expression of canonical YAP targets (i.e., CTGF and CYR61) and by using a TEAD reporter construct (i.e., 8xGTIIC). Surprisingly, we found that RNA silencing of YAP1 significantly reduced HuR mRNA and protein expression, as well as established HuR targets, WEE1 and PIM1. Treatment with small-molecule inhibitors verteporfin and CA3, which target the interface of YAP1’s transcription-factor binding domain, recapitulated these effects in a dose- and time-dependent manner. We are currently cloning HuR’s promoter region into a luciferase reporter in order to evaluate the impact of YAP1 on HuR transcriptional expression.

Citation Format: Samantha Z. Brown, Christopher W. Schultz, Avinoam Nevler, Tianyun Li, Aditi Jain, Raymond O’Neil, Wei Jiang, Eric Londin, Dan A. Dixon, Liang Xu, Charles J. Yeo, Jonathan R. Brody. A feedback gene regulatory mechanism between YAP1 and the RNA-binding protein, Human Antigen R (HuR), in pancreatic cancer cells: Implications for a context-dependent pancreatic cancer cell survival network [abstract]. In: Proceedings of the AACR Special Conference on the Hippo Pathway: Signaling, Cancer, and Beyond; 2019 May 8-11; San Diego, CA. Philadelphia (PA): AACR; Mol Cancer Res 2020;18(8_Suppl):Abstract nr B45.

A Phase I/II Study of Veliparib (ABT-888) in Combination with 5-Fluorouracil and Oxaliplatin in Patients with Metastatic Pancreatic Cancer

PURPOSE

Up to 17% of patients with pancreatic ductal adenocarcinoma (PDAC) harbor pathogenic (germline or somatic) mutations in a homologous recombination, DNA damage response and repair (HR-DDR) gene, such as BRCA1/2, or PALB2. Platinum-based chemotherapy, or treatment with PARP inhibitors are of particular benefit in these patients. However, there may be even greater benefit when platinums and PARP inhibitors are combined.

PATIENTS AND METHODS

We performed a single-arm, open-label, phase I/II study of the PARP inhibitor, veliparib, with 5-fluorouracil (no 5FU bolus) and oxaliplatin (FOLFOX) for patients with metastatic PDAC. Thirty-one patients were enrolled in a phase I dose escalation of veliparib (40 mg to 250 mg twice a day, days 1-7 of each 14-day cycle), to identify the recommended phase II dose (RP2D) of veliparib for the combination. Another 33 patients were enrolled in two parallel phase II trials to assess the objective response rate (ORR) in untreated or in previously treated patients. If available, germline or somatic testing was collected to identify pathogenic HR-DDR mutations.

RESULTS

The combination of veliparib and FOLFOX was tolerable at a RP2D of veliparib of 200 mg twice a day. The primary endpoint for both phase II cohorts was met, and the ORR overall was 26%. There was greater activity in platinum-naïve patients, and those who harbored a pathogenic HR-DDR mutation. Specifically, the ORR of HR-DDR mutated, platinum-naïve patients was 57%.

CONCLUSIONS

The combination of veliparib and FOLFOX was safe for patients with metastatic PDAC and showed promising activity particularly in patients with platinum-naïve disease that harbors a pathogenic HR-DDR mutation.

A step towards personalizing next line therapy for resected pancreatic and related cancer patients: A single institution's experience

Background:

There is a lack of precision medicine in pancreatic ductal adenocarcinoma (PDA) and related cancers, and outcomes for patients with this diagnosis remain poor despite decades of research investigating this disease. Therefore, it is necessary to explore novel therapeutic options for these patients who may benefit from personalized therapies.

Objective:

Molecular profiling of hepatopancreaticobiliary malignancies at our institution, including but not limited to PDA, was initiated to assess the feasibility of incorporating molecular profiling results into patient oncological therapy planning.

Methods:

All eligible patients from Thomas Jefferson University (TJU) with hepatopancreaticobiliary tumors including PDA, who agreed to molecular testing profiling, were prospectively enrolled in a registry study from December 2014 to September 2017 and their tumor samples were tested to identify molecular markers that can be used to guide therapy options in the future. Next generation sequencing (NGS) and protein expression in tumor samples were tested at CLIA-certified laboratories. Prospective clinicopathologic data were extracted from medical records and compiled in a de-identified fashion.

Results:

Seventy eight (78) patients were enrolled in the study, which included 65/78 patients with PDA (local and metastatic) and out of that subset, 52/65 patients had surgically resected PDA. Therapy recommendations were generated based on molecular and clinicopathologic data for all enrolled patients. NGS uncovered actionable alterations in 25/52 surgically resected PDAs (48%) which could be used to guide therapy options in the future. High expression of three proteins, TS (p ¼ 0.005), ERCC1 (p = 0.001), and PD-1 (p = 0.04), was associated with reduced recurrence-free survival (RFS), while TP53 mutations were correlated with longer RFS (p = 0.01).

Conclusions:

The goal of this study was to implement a stepwise strategy to identify and profile resected PDAs at our institution. Consistent with previous studies, approximately half of patients with resected PDA harbor actionable mutations with possible targeted therapeutic implications. Ongoing studies will determine the clinical value of identifying these mutations in patients with resected PDA.

ATM Dysfunction in Pancreatic Adenocarcinoma and Associated Therapeutic Implications

Pancreatic ductal adenocarcinoma (PDAC) remains one of the most lethal solid malignancies with very few therapeutic options to treat advanced or metastatic disease. The utilization of genomic sequencing has identified therapeutically relevant alterations in approximately 25% of PDAC patients, most notably in the DNA damage response and repair (DDR) genes, rendering cancer cells more sensitive to DNA-damaging agents and to DNA damage response inhibitors, such as PARP inhibitors. ATM is one of the most commonly mutated DDR genes, with somatic mutations identified in 2% to 18% of PDACs and germline mutations identified in 1% to 34% of PDACs. ATM plays a complex role as a cell-cycle checkpoint kinase, regulator of a wide array of downstream proteins, and responder to DNA damage for genome stability. The disruption of ATM signaling leads to downstream reliance on ATR and CHK1, among other DNA-repair mechanisms, which may enable exploiting the inhibition of downstream proteins as therapeutic targets in ATM-mutated PDACs. In this review, we detail the function of ATM, review the current data on ATM deficiency in PDAC, examine the therapeutic implications of ATM alterations, and explore the current clinical trials surrounding the ATM pathway.

Targeting homologous recombination addicted tumors: challenges and opportunities

Recent advances in next generation sequencing (NGS) and molecular subtyping of tumors have opened the door to clinically available targeted therapies. Although the treatment of many solid tumors still rely on a steady regimen of non-targeted chemotherapeutic agents, it is becoming increasingly more apparent that certain tumors with defects in DNA damage repair (DDR) genes may be exquisitely sensitive to DNA damaging agents or therapies targeting key elements of this pathway such PARP1, ATR, or ATM. Still, for tumors with DDR defects the challenges are multi-fold including: (I) identifying these tumors in patients in time for a window of opportunity of treatment; (II) ensuring that these tumors are still reliant or addicted to this pathway; and (III) making sure these tumors are matched with the precise treatment option. Herein, we will discuss the opportunities, challenges, and future of targeting a subset of DDR-defective tumors.

Overall survival in patients with pancreatic cancer receiving matched therapies following molecular profiling: a retrospective analysis of the Know Your Tumor registry trial

BACKGROUND

About 25% of pancreatic cancers harbour actionable molecular alterations, defined as molecular alterations for which there is clinical or strong preclinical evidence of a predictive benefit from a specific therapy. The Know Your Tumor (KYT) programme includes US patients with pancreatic cancer and enables patients to undergo commercially available multi-omic profiling to provide molecularly tailored therapy options and clinical trial recommendations. We sought to determine whether patients with pancreatic cancer whose tumours harboured such actionable molecular alterations and who received molecularly matched therapy had a longer median overall survival than similar patients who did not receive molecularly matched therapy.

METHODS

In this retrospective analysis, treatment history and longitudinal survival outcomes were analysed in patients aged 18 years or older with biopsy-confirmed pancreatic cancer of any stage, enrolled in the KYT programme and who received molecular testing results. Since the timing of KYT enrolment varied for each patient, the primary outcome measurement of median overall survival was calculated from the initial diagnosis of advanced disease until death. We compared median overall survival in patients with actionable mutations who were treated with a matched therapy versus those who were not treated with a matched therapy.

FINDINGS

Of 1856 patients with pancreatic cancer who were referred to the KYT programme between June 16, 2014, and March 31, 2019, 1082 (58%) patients received personalised reports based on their molecular testing results. Actionable molecular alterations were identified in 282 (26%) of 1082 samples. Among 677 patients for whom outcomes were available, 189 had actionable molecular alterations. With a median follow-up of 383 days (IQR 214-588), those patients with actionable molecular alterations who received a matched therapy (n=46) had significantly longer median overall survival than did those patients who only received unmatched therapies (n=143; 2·58 years [95% CI 2·39 to not reached] vs 1·51 years [1·33-1·87]; hazard ratio 0·42 [95% CI 0·26-0·68], p=0·0004). The 46 patients who received a matched therapy also had significantly longer overall survival than the 488 patients who did not have an actionable molecular alteration (2·58 years [95% CI 2·39 to not reached] vs 1·32 years [1·25-1·47]; HR 0·34 [95% CI 0·22-0·53], p<0·0001). However, median overall survival did not differ between the patients who received unmatched therapy and those without an actionable molecular alteration (HR 0·82 [95% CI 0·64-1·04], p=0·10).

INTERPRETATION

These real-world outcomes suggest that the adoption of precision medicine can have a substantial effect on survival in patients with pancreatic cancer, and that molecularly guided treatments targeting oncogenic drivers and the DNA damage response and repair pathway warrant further prospective evaluation.

FUNDING

Pancreatic Cancer Action Network and Perthera.

Effect of Hypercapnia, an Element of Obstructive Respiratory Disorder, on Pancreatic Cancer Chemoresistance and Progression

BACKGROUND

Chronic obstructive respiratory disorders (ORDs) are linked to increased rates of cancer-related deaths. Little is known about the effects of hypercapnia (elevated CO₂) on development of pancreatic ductal adenocarcinoma (PDAC) and drug resistance.

STUDY DESIGN

Two PDAC cell lines were exposed to normocapnic (5% CO₂) and hypercapnic (continuous/intermittent 10% CO₂) conditions, physiologically similar to patients with active ORD. Cells were assessed for proliferation rate, colony formation, and chemo-/radiotherapeutic efficacy. In a retrospective clinical study design, patients with PDAC who had undergone pancreatic resection between 2002 and 2014 were reviewed. Active smokers were excluded to remove possible smoking-related protumorigenic influence. Clinical data, pathologic findings, and survival end points were recorded. Kaplan-Meier and Cox regression analyses were performed.

RESULTS

Exposure to hypercapnia resulted in increased colony formation and proliferation rates in vitro in both cell lines (MIA-PaCa-2: 111% increase and Panc-1: 114% increase; p < 0.05). Hypercapnia exposure induced a 2.5-fold increase in oxaliplatin resistance (p < 0.05) in both cell lines and increased resistance to ionizing radiation in MIA-PaCa-2 cells (p < 0.05). Five hundred and seventy-eight patients were included (52% were male, median age was 68.7 years [interquartile range 60.6 to 76.8 years]). Cox regression analysis, assessing TNM staging, age, sex, and ORD status, identified ORD as an independent risk factor for both overall survival (hazard ratio 1.64; 95% CI, 1.2 to 2.3; p < 0.05) and disease-free survival (hazard ratio 1.68; 95% CI, 1.06 to 2.67).

CONCLUSIONS

PDAC cells exposed to hypercapnic environments, which is common in patients with ORD, showed tumor proliferation, radioresistance, and chemoresistance. Patients with a history of ORD had a worse overall prognosis, suggesting that hypercapnic conditions play a role in the development and progression of PDAC and stressing the need for patient-tailored care.

Understanding and targeting the disease-related RNA binding protein human antigen R (HuR)

Altered gene expression is a characteristic feature of many disease states such as tumorigenesis, and in most cancers, it facilitates cancer cell survival and adaptation. Alterations in global gene expression are strongly impacted by post-transcriptional gene regulation. The RNA binding protein (RBP) HuR (ELAVL1) is an established regulator of post-transcriptional gene regulation and is overexpressed in most human cancers. In many cancerous settings, HuR is not only overexpressed, but it is "overactive" as denoted by increased subcellular localization within the cytoplasm. This dysregulation of HuR expression and cytoplasmic localization allows HuR to stabilize and increase the translation of various prosurvival messenger RNA (mRNAs) involved in the pathogenesis of numerous cancers and various diseases. Based on almost 20 years of work, HuR is now recognized as a therapeutic target. Herein, we will review the role HuR plays in the pathophysiology of different diseases and ongoing therapeutic strategies to target HuR. We will focus on three ongoing-targeted strategies: (1) inhibiting HuR's translocation from the nucleus to the cytoplasm; (2) inhibiting the ability of HuR to bind target RNA; and (3) silencing HuR expression levels. In an oncologic setting, HuR has been demonstrated to be critical for a cancer cell's ability to survive a variety of cancer relevant stressors (including drugs and elements of the tumor microenvironment) and targeting this protein has been shown to sensitize cancer cells further to insult. We strongly believe that targeting HuR could be a powerful therapeutic target to treat different diseases, particularly cancer, in the near future. This article is categorized under: RNA in Disease and Development > RNA in Disease NRA Turnover and Surveillance > Regulation of RNA Stability Translation > Translation Regulation.

Outcomes in Patients With Pancreatic Adenocarcinoma With Genetic Mutations in DNA Damage Response Pathways: Results From the Know Your Tumor Program

PURPOSE

Up to 25% of pancreatic adenocarcinomas (PDACs) harbor mutations in the homologous recombination DNA damage response (HR-DDR) pathway. Although known to affect responsiveness to DNA-damaging chemotherapy, the prognostic relevance of these mutations is unclear and outcomes in patients with PDAC who harbor HR-DDR mutations beyond BRCA1/2 remain unexplored.

METHODS

We evaluated 820 patients with PDAC enrolled in the Know Your Tumor program for whom we had collected comprehensive genomic testing results and longitudinal clinical outcomes. Patients were categorized as having resected versus advanced disease, and as having received platinum-based therapy versus being platinum naïve. Tumor genomic profiles were categorized as HR-DDR mutated (HR-DDRmut) or proficient (pHR-DDR) on the basis of the presence of pathogenic mutations of somatic or germline origin in BRCA1/2 or PALB2 (group 1); ATM/ATR/ATRX (group 2); or BAP1, BARD1, BRIP1, CHEK1/2, RAD50/51/51B, or FANCA/C/D2/E/F/G/L (group 3). Overall survival was measured from the date of diagnosis until death.

RESULTS

Median overall survival (mOS) was similar in all resected patients irrespective of exposure to platinum-based therapy, whereas for platinum-treated patients with advanced disease, mOS was significantly longer for HR-DDRmut versus pHR-DDR (2.37 years v 1.45 years, respectively). Of importance, no difference was identified in platinum-naïve patients. mOS in patients with mutations in all three HR-DDRmut groups was greater than that for pHR-DDR patients, but this difference was lost in platinum-naïve patients.

CONCLUSION

Patients with advanced HR-DDRmut have improved mOS when treated with platinum-based therapy compared with pHR-DDR patients. In platinum-naïve patients, there is no mOS difference, which suggests that HR-DDR status has no pure prognostic value. These findings support the need to test all patients with advanced PDAC to ensure that HR-DDRmut patients receive the benefit of treatment with platinum-based therapy.

Poly (ADP) Ribose Glycohydrolase Can Be Effectively Targeted in Pancreatic Cancer

Patients with metastatic pancreatic ductal adenocarcinoma (PDAC) have an average survival of less than 1 year, underscoring the importance of evaluating novel targets with matched targeted agents. We recently identified that poly (ADP) ribose glycohydrolase (PARG) is a strong candidate target due to its dependence on the pro-oncogenic mRNA stability factor HuR (ELAVL1). Here, we evaluated PARG as a target in PDAC models using both genetic silencing of PARG and established small-molecule PARG inhibitors (PARGi), PDDX-01/04. Homologous repair-deficient cells compared with homologous repair-proficient cells were more sensitive to PARGi in vitro. In vivo, silencing of PARG significantly decreased tumor growth. PARGi synergized with DNA-damaging agents (i.e., oxaliplatin and 5-fluorouracil), but not with PARPi therapy. Mechanistically, combined PARGi and oxaliplatin treatment led to persistence of detrimental PARylation, increased expression of cleaved caspase-3, and increased γH2AX foci. In summary, these data validate PARG as a relevant target in PDAC and establish current therapies that synergize with PARGi. SIGNIFICANCE: PARG is a potential target in pancreatic cancer as a single-agent anticancer therapy or in combination with current standard of care.

The Sustained Induction of c-MYC Drives Nab-Paclitaxel Resistance in Primary Pancreatic Ductal Carcinoma Cells

Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive disease with limited and, very often, ineffective medical and surgical therapeutic options. The treatment of patients with advanced unresectable PDAC is restricted to systemic chemotherapy, a therapeutic intervention to which most eventually develop resistance. Recently, nab-paclitaxel (n-PTX) has been added to the arsenal of first-line therapies, and the combination of gemcitabine and n-PTX has modestly prolonged median overall survival. However, patients almost invariably succumb to the disease, and little is known about the mechanisms underlying n-PTX resistance. Using the conditionally reprogrammed (CR) cell approach, we established and verified continuously growing cell cultures from treatment-naïve patients with PDAC. To study the mechanisms of primary drug resistance, nab-paclitaxel-resistant (n-PTX-R) cells were generated from primary cultures and drug resistance was verified in vivo, both in zebrafish and in athymic nude mouse xenograft models. Molecular analyses identified the sustained induction of c-MYC in the n-PTX-R cells. Depletion of c-MYC restored n-PTX sensitivity, as did treatment with either the MEK inhibitor, trametinib, or a small-molecule activator of protein phosphatase 2a. IMPLICATIONS: The strategies we have devised, including the patient-derived primary cells and the unique, drug-resistant isogenic cells, are rapid and easily applied in vitro and in vivo platforms to better understand the mechanisms of drug resistance and for defining effective therapeutic options on a patient by patient basis.

Abemaciclib Is Effective Against Pancreatic Cancer Cells and Synergizes with HuR and YAP1 Inhibition

Mutation or promoter hypermethylation of CDKN2A is found in over 90% of pancreatic ductal adenocarcinomas (PDAC) and leads to loss of function of cell-cycle inhibitors p16 (INK4A) and p14 (ARF) resulting in unchecked proliferation. The CDK4/6 inhibitor, abemaciclib, has nanomolar IC₅₀s in PDAC cell lines and decreases growth through inhibition of phospho-Rb (pRb), G₁ cell-cycle arrest, apoptosis, and the senescent phenotype detected with β-galactosidase staining and relevant mRNA elevations. Daily abemaciclib treatments in mouse PDAC xenograft studies were safe and demonstrated a 3.2-fold decrease in tumor volume compared with no treatment (P < 0.0001) accompanying a decrease in both pRb and Ki67. We determined that inhibitors of HuR (ELAVL1), a prosurvival mRNA stability factor that regulates cyclin D1, and an inhibitor of Yes-Associated Protein 1 (YAP1), a pro-oncogenic, transcriptional coactivator important for CDK6 and cyclin D1, were both synergistic with abemaciclib. Accordingly, siRNA oligonucleotides targeted against HuR, YAP1, and their common target cyclin D1, validated the synergy studies. In addition, we have seen increased sensitivity to abemaciclib in a PDAC cell line that harbors a loss of the ELAVL1 gene via CRISP-Cas9 technology. As an in vitro model for resistance, we investigated the effects of long-term abemaciclib exposure. PDAC cells chronically cultured with abemaciclib displayed a reduction in cellular growth rates (GR) and coresistance to gemcitabine and 5-fluorouracil (5-FU), but not to HuR or YAP1 inhibitors as compared with no treatment controls. We believe that our data provide compelling preclinical evidence for an abemaciclib combination-based clinical trial in patients with PDAC. IMPLICATIONS: Our data suggest that abemaciclib may be therapeutically relevant for the treatment in PDAC, especially as part of a combination regimen inhibiting YAP1 or HuR.

Abstract 3058: Recharacterizing the FDA approved drug pyrvinium pamoate as a clinically relevant HuR inhibitor in pancreatic ductal adenocarcinoma

HuR is an RNA binding protein involved in a coordinated cellular survival response to stressors. Upon insults such as chemotherapy, HuR translocates from the nucleus to the cytoplasm where it binds the 3’UTR of target mRNAs. HuR’s interaction with target mRNAs leads to the upregulation of target genes and ultimately treatment resistance. This is particularly relevant in the case of pancreatic ductal adenocarcinoma (PDA). PDA is highly resistant to radiotherapy and standard chemotherapy such as FOLFIRINOX or gemcitabine/nab-paclitaxel. Using a tumor microarray (TMA), we found 79% of patient tumor samples (n=70) were positive for active cytoplasmic HuR, while little to no cytoplasmic localization was detected in normal tissue. In addition, HuR CRISPR knockout cell lines have a xenograft lethal phenotype. The aim of our current study is to target HuR by re-purposing the anti-helminthic, FDA approved small molecule pyrvinium pamoate (PP) to inhibit HuR’s translocation and sensitize PDA cells to concurrent therapies. PP has been shown in bladder cancer to inhibit the translocation of HuR in vitro and in vivo. We have reproduced this in multiple PDA cell lines and have shown impressive drug potency with IC50s as low as 38nM in 2D cultures of PDA cell lines and PDX lines and 16nM in a 3D mouse PDA organoid model. We have demonstrated that inhibition of HuR translocation is likely to occur through secondary effectors AMPK and CDK1. We have also demonstrated that PP’s inhibition of HuR function may be through direct inhibition of target binding. In comparison to other published HuR inhibitors PP inhibits the binding of HuR to targets more potentlt with nanomolar IC50’s. We confirmed this work through HuR RNA Immunoprecipitation experiments and determined that PP inhibited the ability of HuR to bind target mRNA. We generated HuR deficient CRISPR lines to and demonstrated that lack of HuR sensitizes PDA cells to various therapeutics, an effect which is exacerbated in physiologically relevant low glucose settings. We next demonstrated that PP can synergize with several therapeutics including the CDK4/6 inhibitors Abemaciclib and Palbociclib in PDA cells and that this synergy is increased in low glucose setting. This synergistic effect is ameliorated in HuR deficient CRISPR cell lines, indicating that PP achieves this synergistic potential through the inhibition of HuR. We performed targeted phosphoproteomics and found that PP robustly inhibited critical mTOR pathway members as well as validating previous reports that it can inhibit the WNT pathway. Finally, we have demonstrated that PP has a dose dependent effect on PDA tumor growth in vivo with IP and PO dosing regimens. This work supports the recharacterization of PP as a potentially effective therapeutic agent for the treatment of PDA. Early phase clinical trials of PP in human subjects are being planned for 2019.

Citation Format: Christopher W. Schultz, Teena Dhir, Samantha Z. Brown, Saswati Chand, Wei Jiang, Grace A. McCarthy, Alex O. Haber, Charles J. Yeo, Austin Goetz, Avinoam Nevler, Oloruntoba Bolaji, Jonathan R. Brody. Recharacterizing the FDA approved drug pyrvinium pamoate as a clinically relevant HuR inhibitor in pancreatic ductal adenocarcinoma [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 3058.

Abstract LB-117: Increased peripheral glucose levels restores chemotherapeutic efficacy in a mouse model of pancreatic cancer

Pancreatic cancer is the third leading cause of cancer-related death in the United States. The 5-year survival rate is less than 10% and less than 5% for patients with metastatic disease due to the lack of effective therapy. Therefore, searching for novel therapies or strategies to improve existing therapies is a high priority in the field. The pancreatic cancer microenvironment comprises the majority of the tumor mass, and is characterized by a dense, fibrotic stroma, high interstitial fluid pressure and diminished vascularity. This creates a large nutrient gradient, such that pancreatic cancers must adapt to severely austere conditions to survive. We previously demonstrated that the harsh, nutrient-deprived conditions directly resulted in aggressive pancreatic cancer biology and chemotherapy resistance, in part due to activation of a stress response protein, HuR (ELAVL1). It also followed that higher blood glucose levels (e.g., diabetics) correlated with longer disease-free survival in pancreatic cancer patients who received gemcitabine after tumor resection. Herein, we extend this line of investigation in an in vivo mouse model of pancreatic cancer. First, we induced moderate hyperglycemia using a single dose of streptozotocin (120 mg/kg), which destroys beta islets in the pancreas. Blood glucose levels were titrated to a “non-toxic” level (~300 mg/dL) through daily injections of long-acting insulin, glargine. In a second independent model, we induced mild hyperglycemia by adding dextrose to the drinking water (30% dextrose). In both models, blood glucose levels and body weights were measured weekly, and mice were examined for the signs of distress. Interestingly, low-dose gemcitabine treatment, 50 mg/kg twice per week, significantly inhibited PDA xenograft growth under moderate and mild hyperglycemia. However, gemcitabine had no benefit in euglycemic mice with especially low levels of glucose in the xenograft microenvironment. These results demonstrate that chemotherapeutic efficacy may be potentially enhanced through forced induction of hyperglycemia in patients receiving chemotherapy.

Citation Format: Ali Vaziri-Gohar, Imran Khokhar, George Titomihelakis, Jonathan R. Brody, Jordan M. Winter. Increased peripheral glucose levels restores chemotherapeutic efficacy in a mouse model of 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 LB-117.

Abstract 4764: A global transcriptome analysis of pancreatic cancer cells distinguishes between acute and acquired PARP inhibitor resistance mechanisms

Pancreatic ductal adenocarcinoma (PDAC) is the 3rd leading cause of cancer related deaths in the U.S. Recent advances in understanding RNA biology in PDAC have shed light on post-transcriptional regulation of genes and pathways through RNA binding proteins (RBP). Our lab has demonstrated that HuR, an RBP, is overexpressed in PDAC cells and stabilizes pro-survival mRNAs. Additionally, our work and others have demonstrated that this level of gene regulation can support drug resistance in PDAC cells. A synthetic lethal strategy employing Poly-ADP ribose polymerase inhibitors (PARPi) in a subset of patients with DNA repair deficient pancreatic cancers has been gaining interest. However, the success of PARPi is often hindered by the emergence of drug resistance in patients who initially respond. We have published that short-term PARPi treatment of PDAC cells causes activation of HuR where it stabilizes a DNA repair enzyme, PAR-glycohydrolase, and mediates acute PARPi resistance. In this study, we generated olaparib acquired resistant pancreatic cancer cells in vitro and acquired pancreatic patient derived xenograft cell lines (pre- and post PARPi) to understand acute versus acquired resistant mechanism(s). In characterising the acquired resistant model of PARPi resistance, we found that these cells are &gt;20 fold more resistant to olaparib and platinums and &gt;5 fold resistant to other PARPi like rucaparib and veliparib, compared to parental cells. No cross resistance was seen with other chemotherapeutics like gemcitabine. Additionally, we also found acquired resistant cells lost PARP-1 protein expression compared to parental cells. Bioinformatic analyses on HuR-RNA immunoprecipitation-microarray (RIP-microarray) data from acutely treated olaparib cells show enrichment of pro-survival mRNAs. Interestingly, these mRNAs are significantly downregulated in acquired resistant cells compared to control cells (i.e., negative log2 fold changes, p&lt;0.001) in differential expression of HuR and HuR established targets. Interestingly, upregulated gene transcripts in these samples belong to pathways that negatively regulate biosynthetic and metabolic processes, and hence may represent pathways to target. Further, in vitro analyses show that parental PDAC cells are sensitive to combined inhibition of PARP and HuR but acquired resistant cells fail to respond to HuR inhibition. In conclusion, HuR mediates acute resistance to PARPi in PDAC cells and HuR inhibitor therapy could enhance PARPi therapy immediately, yet is most likely not useful in the setting of acquired- resistance. Future studies will explore genetic alterations and novel HuR-independent pathways in PARPi acquired resistant cells. Finally, we have begun a line of investigation of combining PARPi therapy with HuR inhibitors in an effort to optimize upfront therapeutic efficacy

Citation Format: Aditi Jain, Matthew McCoy, Lebaron A. Agostini, Yuriy Gusev, Subha Madhavan, Michael Pishvaian, Sankar Addya, Eric Londin, Maria R. Gurevich, Chani Stossel, Talia Golan, Charles J. Yeo, Jonathan R. Brody. A global transcriptome analysis of pancreatic cancer cells distinguishes between acute and acquired PARP inhibitor resistance mechanisms [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 4764.

A Pilot Trial of Molecularly Tailored Therapy for Patients with Metastatic Pancreatic Ductal Adenocarcinoma

Purpose: Despite the wide adoption of tumor molecular profiling, there is a dearth of evidence linking molecular biomarkers for treatment selection to prediction of treatment outcomes in patients with metastatic pancreatic cancer. We initiated a pilot study to test the feasibility of designing a larger phase II trial of molecularly tailored treatment for metastatic pancreatic cancer.

Methods: Our study aimed to assess the feasibility of following a treatment algorithm based on the expression of three published predictive markers of response to chemotherapy: ribonucleotide reductase catalytic subunit M1 (for gemcitabine); excision repair cross-complementation group 1 (for platinum agents); and thymidylate synthase (for 5-fluorouracil) in patients with untreated, metastatic pancreatic cancer. Results of the tumor biopsy analysis were used to assign patients to one of seven doublet regimens. Key secondary objectives included response rate (RR), disease control rate (DCR), progression-free survival (PFS), and overall survival (OS).

Results: Between December 2012 and March 2015, 30 patients were enrolled into the study. Ten patients failed screening primarily due to inadequate tumor tissue availability. Of the remaining 20 patients, 19 were assigned into 6 different chemotherapy doublets, and achieved an RR of 28%, with a DCR rate of 78%. The median PFS and OS were 5.78 and 8.21 months, respectively.

Conclusions: The incorporation of biomarkers into a treatment algorithm is feasible and resulted in a PFS and OS similar to other doublet therapies for patients with metastatic pancreatic cancer. Based on the results from this pilot study, a larger phase II randomized trial of molecularly targeted therapy versus physicians' choice of standard of care has been initiated in the second-line setting (NCT02967770).

Corrigendum: Metabolic Dependencies in Pancreatic Cancer

[This corrects the article DOI: 10.3389/fonc.2018.00617.].

Abstract A101: IDO2 host genetic status influences progression and radiotherapy response in pancreatic ductal adenocarcinoma

Sporadic pancreatic ductal adenocarcinoma (PDAC) develops into a lethal disease that has remained refractory to different treatment approaches including recent advances in cancer immunotherapy. Variations in host genetic status affecting the inflammatory microenvironment can impact cancer susceptibility, malignant progression and clinical outcomes. In this study, we present genetic evidence from mouse and human genetic studies supporting a role for IDO2, an immunometabolic modifier of B cell-mediated autoimmune responses, in promoting pancreatic ductal adenocarcinoma (PDAC). In an established transgenic mouse model of KRAS-induced pancreatic cancer, IDO2 genetic inactivation markedly reduced malignant progression. In retrospective clinical analyses of PDAC patients (N=200), the biallelic occurrence of either of two inactivating polymorphisms in the IDO2 coding region trended with favorable disease-free survival. In PDAC tissues, an inactive IDO2 host genotype corresponded with changes in expression of genes involved in tryptophan catabolism and immune modulation, along with a reduced neutrophil to lymphocyte ratio. Notably, subset analysis revealed a striking association of inactive IDO2 status with improved disease-free survival in patients who had received adjuvant radiotherapy, a treatment modality that has been highly debated due to its variable efficacy in patients. Accordingly, our findings suggest that host IDO2 genetic status may offer a simple incisive marker to stratify PDAC patients who stand to gain the most from adjuvant radiotherapy, addressing the long-standing debate of its benefits.

Citation Format: George C. Prendergast, Avinoam Nevler, Alexander J. Muller, Erika Sutanto-Ward, James B. DuHadaway, Kei Nagatomo, Eric Londin, Kevin O'Hayer, Joseph A. Cozzitorto, Harish Lavu, Theresa P. Yeo, Mark Curtis, Tatiana Villatoro, Benjamin E. Leiby, Jordan M. Winter, Charles J. Yeo, Jonathan R. Brody. IDO2 host genetic status influences progression and radiotherapy response in pancreatic ductal adenocarcinoma [abstract]. In: Proceedings of the Fourth CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; Sept 30-Oct 3, 2018; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2019;7(2 Suppl):Abstract nr A101.

Precious Data: Interim Report from the Jefferson Pancreas Tumor Registry

Purpose: The Jefferson Pancreas Tumor Registry (JPTR) is a voluntary hospital-based registry of persons with pancreas and related periampullary cancers, premalignant lesions, and nonaffected family members (NAFMs). The ultimate goals of the JPTR are to provide a link between family history, gene mutations, and precision medicine therapy, and to identify high-risk NAFMs for potential surveillance screening.

Methods: The JPTR is an Institutional Review Board approved longitudinal epidemiological study housed in the Department of Surgery at Thomas Jefferson University Hospital. Individuals who met the eligibility criteria and signed informed consent provide information on hereditary conditions, family history of cancers, environmental exposures, and occupational risk factors. Data are collected using a self-administered questionnaire, the electronic medical record, and the molecular analysis of tumor specimens.

Results: Established in 2008, >725 persons have enrolled in the JPTR. The cohort is mostly composed of sporadic pancreas cancer, with 13% of enrollees having familial pancreas cancer and a control group comprising nonaffected persons. Data from the registry have been utilized to inform clinical studies, molecular investigations, and to shed light on and gain insight into the lived experience of persons with these conditions.

Conclusion: The JPTR contains precious qualitative data and is an invaluable repository of information about persons with pancreatic and related tumors.