Deletion of the mRNA stability factor ELAVL1 (HuR) in pancreatic cancer cells disrupts the tumor microenvironment integrity

Stromal cells promote extensive fibrosis in pancreatic ductal adenocarcinoma (PDAC), which is associated with poor prognosis and therapeutic resistance. We report here for the first time that loss of the RNA-binding protein human antigen R (HuR, ELAVL1) in PDAC cells leads to reprogramming of the tumor microenvironment. In multiple in vivo models, CRISPR deletion of ELAVL1 in PDAC cells resulted in a decrease of collagen deposition, accompanied by a decrease of stromal markers (i.e. podoplanin, α-smooth muscle actin, desmin). RNA-sequencing data showed that HuR plays a role in cell-cell communication. Accordingly, cytokine arrays identified that HuR regulates the secretion of signaling molecules involved in stromal activation and extracellular matrix organization [i.e. platelet-derived growth factor AA (PDGFAA) and pentraxin 3]. Ribonucleoprotein immunoprecipitation analysis and transcription inhibition studies validated PDGFA mRNA as a novel HuR target. These data suggest that tumor-intrinsic HuR supports extrinsic activation of the stroma to produce collagen and desmoplasia through regulating signaling molecules (e.g. PDGFAA). HuR-deficient PDAC in vivo tumors with an altered tumor microenvironment are more sensitive to the standard of care gemcitabine, as compared to HuR-proficient tumors. Taken together, we identified a novel role of tumor-intrinsic HuR in its ability to modify the surrounding tumor microenvironment and regulate PDGFAA.

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.

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.

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; >55% decrease, p<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<log2FC<-3.6, 0.0009<padj<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; >50% decrease, p<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.

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).

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.

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.

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.

Vertical transmission of Kaposi's sarcoma

AIDS related Kaposi's sarcoma is commonly seen in homosexual men, only occasionally in men and women with heterosexually acquired HIV, and extremely rarely in children. The case of an HIV infected mother and her vertically infected child who both developed visceral Kaposi's sarcoma is reported. It is proposed that the putative Kaposi's sarcoma agent may also be transmitted vertically.

The changing clinical features of HIV-1 infection in the United Kingdom

Despite advances in antimicrobial and anti-retroviral treatment in the past decade, the natural history of HIV-1 infection remains largely unchanged. Clinical monitoring has led to the introduction of effective prophylaxis of Pneumocystis carinii pneumonia and has facilitated the early detection and treatment of opportunistic infections. Pneumocystis carinii pneumonia now makes up a smaller proportion of first AIDS defining diagnoses than before prophylaxis was introduced. The proportion made up by more unusual opportunistic infections and malignancies, that occur later in the course of the disease, is growing. Late stage HIV disease--which is now complicated by infections with organisms of low pathogenicity, often combined with systemic Kaposi's sarcoma or lymphoma--presents major problems in clinical management. Further changes in the clinical features of HIV-1 infection may be expected in the future as more effective antimicrobial and anti-retroviral treatments are developed.

A women-only clinic for HIV, genitourinary medicine and substance misuse

OBJECTIVE

To evaluate a multidisciplinary women-only clinic (WOC) providing HIV testing, HIV follow-up, genitourinary screening and a substance misuse service. The clinic is designed to attract women who are at risk of acquiring sexually transmitted infections, including HIV, yet are not using existing medical services.

DESIGN

A questionnaire survey and review of the case notes of women attending the WOC during the first seven months (April to October 1991) and comparison with a mixed-sex, daytime genitourinary clinic (John Hunter Clinic), and a HIV out-patients clinic (Kobler Centre) all within St Stephen's Clinic.

RESULTS

One hundred and twenty-nine women attended the WOC over the seven month period and 113 completed a questionnaire. The main reasons for attendance included a preference to be seen by a female doctor and staff, the presence of female patients in the waiting area, and the greater convenience of an evening clinic. In the absence of the WOC over half the patients (56%) indicated that they would not have attended a genitourinary medicine (GUM) clinic. The WOC attracted significantly more new patients than in the JHC (31.5% vs 15% p < 0.001). One hundred and four women (81%) were screened for genitourinary infection. Compared with the JHC there were significantly more cases of genital warts (33.9% vs 16.1% p < 0.001) and candidosis (41.5% vs 22.3% p < 0.001). A greater number of HIV tests were also performed (19% vs 9% p < 0.01). Sixteen (12.4%) women were HIV positive. Their attendance record at both first appointment (88% vs 64% p < 0.05) and subsequent follow-up appointments (81% vs 43% p < 0.05) was significantly higher than a comparable group of women seen by the same doctor (FB) in the Kobler Centre. The women also saw the health adviser more frequently. Although the number of injecting drug users was small (eight), all women currently injecting drugs entered a detoxification programme.

CONCLUSION

The WOC has become an established and popular service at St Stephen's. Women not previously using medical services are attending. The multidisciplinary nature of the clinic encourages a wider use of medical and paramedical services. Attendance record for HIV positive women has improved significantly. Whether these factors will lead to improved standards of sexual health will require a longer period of audit. Seventy-nine per cent of women indicated they would use a family planning service if available. An integrated family planning clinic was introduced after the audit period.