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.

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.

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.

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).

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.

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.

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 4441: Functional and clinical implications of an INDEL within the HuR regulatory region of the mitotic kinase inhibitor WEE1

The RNA-binding protein Human Antigen R (HuR) is upregulated in pancreatic ductal adenocarcinoma (PDA), where it promotes tumorigenesis via its mRNA pro-survival targets. PDA cells exposed to DNA damage upregulate the mitotic inhibitor kinase, WEE1, in a HuR-dependent manner to induce cell cycle arrest and facilitate drug-resistance (1). Herein, we further evaluate a 56 base-pair (bp) region within WEE1's 3'UTR (labeled WEE1.3UTR) where HuR binds and stabilizes expression. Within this regulatory site, we observed that a 10-thymidine (T) track contains frequent polymorphisms (mean allele frequency 8.67%) of thymidine insertions (i.e, an INDEL). Using a combined approach of Sanger sequencing and a more sensitive capillary-electrophoresis (CE) assay, we screened this region in various cancer cell lines and patient samples. Results revealed three distinct alleles between individual cohorts: the wild-type (10-T, 56 bps), a 1-T insertion (11-T, 57 bps), and a 2-T insertion (12-T, 58 bps). Luciferase reporter constructs were subcloned with the HuR regulatory region embedded in the WEE1.3'UTR. In response to stress, constructs with the wild-type allele reported a higher level of expression compared to the 11-T and 12-T alleles (p&lt;0.01). Complementary RNA-binding protein immunoprecipitation (RNP-IP) assays validated the enhanced binding of HuR to the wild-type construct as compared to the others. Collectively, these data suggest that HuR's regulation of WEE1 is impaired when 11-Ts or 12-Ts are present. Electrophoretic mobility shift assay (EMSA) experiments will investigate HuR's physical interaction by quantifying the relative affinity of the protein to each variant transcript, by itself and in direct competition with each other. To investigate the clinical implication of these findings, we sequenced (via Sanger and CE) a cohort of resected patient tumor samples (n=99), and found a significant enrichment for individuals homozygous for 12-T among those with a unique, Lynch-like familial history of cancer (odds ratio 2.4-6.9, p&lt;0.05). We postulate that the addition of the INDEL in the WEE1.3UTR disrupts the association of HuR, and therefore, the functional upregulation of the WEE1 transcript in response to the stressful PDA microenvironment. Thus, a dysregulated G2/M checkpoint could result in accumulated DNA-damage and eventually promote PDA tumorigenesis. Paradoxically, the disruption of the HuR-WEE1 axis may render PDA cells more sensitive to genotoxic agents, thus providing a potential therapeutic window for patients screened for the polymorphism.

Reference: 1. Lal et al., Cancer Res 2014;74(4):1128-40.

Citation Format: Samantha Z. Brown, Avinoam Nevler, Henry T. Thomsett, Shruti Lal, Mahsa Zarei, Fernando Blanco, Joseph A. Cozzitorto, Alexis L. Norris-Kirby, Charles J. Yeo, Jordan M. Winter, James R. Eshleman, Jonathan R. Brody. Functional and clinical implications of an INDEL within the HuR regulatory region of the mitotic kinase inhibitor WEE1 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4441.

Abstract 1961: Gaps in the armor: Targeting HuR to sensitize pancreatic cancer

HuR is an RNA binding protein involved in a coordinated cellular response to stressors. Upon insults such as chemotherapy or radiation treatment, 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 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. Previously published data also demonstrated that reduction of HuR in xenografts with a DOX-inducible shRNA system caused a 3.6 fold decrease in tumor size. HuR reduction was also shown to potentiate a PARP-inhibitor (olaparib) treatment from a 5.6-fold reduction alone to 9.3-fold reduction in tumor size when combined with shHuR, demonstrating the role of HuR in drug resistance. The aim of our current study was: A) to target HuR directly using nanoparticle delivery of siRNA against HuR; and B) to use the FDA approved small molecule pyrvinium pamoate (PP) to inhibit HuR's translocation and sensitize PDA cells to concurrent therapies. Using 3DNA, a 60nm nanoparticle composed of a sphere of crosslinked DNA, we have successfully delivered siRNA against HuR in vivo utilizing targeting moieties against receptors known to be overexpressed on the surface of PDA cells: EGFR, folic acid receptor, and transferrin receptor. Bi-weekly IP treatment of siHuR bound to 3DNA was safe and effective at extending life in a xenograft model as indicated by Kaplan Meier analysis (p=0.01). We are currently testing siHuR-3DNA dendrimer therapy's ability to sensitize PDA cells to oxaliplatin or olaparib in vivo. We are also investigating the use of PP to target HuR's localization. PP has previously been shown in bladder cancer to inhibit the translocation of HuR in vitro and in vivo. We have reproduced this finding in PDA cells, and have shown impressive drug potency with IC50s as low as 38nM in 2D cultures and 16nM in a 3D mouse PDA organoid model. Combination index (CI) values determine drugs interactions where 1 is additive, &lt;1 is synergistic and &gt;1 is antagonistic. We have determined that PP can enhance therapies such as gemcitabine (CI of 0.55), olaparib (CI of 0.40) and palbociclib (CI of 0.37) in vitro, and are currently validating these findings in vivo. Taken together, our data demonstrate that HuR inhibition via 3DNA delivery of siHuR and/or PP treatment can sensitize PDA cells to chemotherapy and targeted therapies. By inhibiting a resistance driver (HuR) in pancreatic cancer we aim to improve current therapies for this devastating disease.

Citation Format: Christopher W. Schultz, Kevin O'Hayer, Teena Dhir, Oloruntoba Bolaji, Kathryn M. Bormes, Samantha Z. Brown, Henry Thomsett, Saswati Chand, Aditi Jain, Wei Jiang, Grace McCarthy, Charles J. Yeo, Austin Goetz, Avinoam Nevler, Jonathan R. Brody, Jordan M. Winter, Ranjan Preet, Dan Dixon, Jessica Bowers, Kelly Rhodes, Robert Getts. Gaps in the armor: Targeting HuR to sensitize pancreatic cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1961.

Elevated HuR in Pancreas Promotes a Pancreatitis-Like Inflammatory Microenvironment That Facilitates Tumor Development

Human antigen R (ELAVL1; HuR) is perhaps the best-characterized RNA-binding protein. Through its overexpression in various tumor types, HuR promotes posttranscriptional regulation of target genes in multiple core signaling pathways associated with tumor progression. The role of HuR overexpression in pancreatic tumorigenesis is unknown and led us to explore the consequences of HuR overexpression using a novel transgenic mouse model that has a >2-fold elevation of pancreatic HuR expression. Histologically, HuR-overexpressing pancreas displays a fibroinflammatory response and other pathological features characteristic of chronic pancreatitis. This pathology is reflected in changes in the pancreatic gene expression profile due, in part, to genes whose expression changes as a consequence of direct binding of their respective mRNAs to HuR. Older mice develop pancreatic steatosis and severe glucose intolerance. Elevated HuR cooperated with mutant K-rasG12D to result in a 3.4-fold increase in pancreatic ductal adenocarcinoma (PDAC) incidence compared to PDAC presence in K-rasG12D alone. These findings implicate HuR as a facilitator of pancreatic tumorigenesis, especially in the setting of inflammation, and a novel therapeutic target for pancreatitis treatment.

Schwannoma of the pancreas: a report of two cases and a review of the literature

Schwannoma of the pancreas is a rare neoplasm. It generally affects older adults (average age, 60 yr). The sex incidence is equal. These tumors vary considerably in size and approximately two-thirds are partially cystic, which can cause clinical confusion with epithelial neoplasms. Histologically, they are typical schwannomas, with Antoni A and Antoni B areas, and they do not cause undue diagnostic problems once adequate tissue is examined histologically.