Down-regulation of pancreatic and duodenal homeobox-1 by somatostatin receptor subtype 5: a novel mechanism for inhibition of cellular proliferation and insulin secretion by somatostatin

Somatostatin (SST) is a regulatory peptide and acts as an endogenous inhibitory regulator of the secretory and proliferative responses of target cells. SST's actions are mediated by a family of seven transmembrane domain G protein-coupled receptors that comprise five distinct subtypes (SSTR1-5). SSTR5 is one of the major SSTRs in the islets of Langerhans. Homeodomain-containing transcription factor pancreatic and duodenal homeobox-1 (PDX-1) is essential for pancreatic development, β cell differentiation, maintenance of normal β cell functions in adults and tumorigenesis. Recent studies show that SSTR5 acts as a negative regulator for PDX-1 expression and that SSTR5 mediates somatostatin's inhibitory effect on cell proliferation and insulin expression/excretion through down-regulating PDX-1 expression. SSTR5 exerts its inhibitory effect on PDX-1 expression at both the transcriptional level by down-regulating PDX-1 mRNA and the post-translational level by enhancing PDX-1 ubiquitination. Identification of PDX-1 as a transcriptional target for SSTR5 may help in guiding the choice of therapeutic cancer treatments

Pancreatic cancer actionable genes in precision medicine and personalized surgery

Pancreatic ductal adenocarcinoma (PDAC) is a deadly cancer with an overall 5-year survival rate less than 5% due to the poor early diagnosis and lack of effective therapeutic options. The most effective therapy remains surgery, however post-operative survival could be enhanced with effective adjuvant therapy. The massive information gained from Omics techniques on PDAC at the beginning of the 21st century is a remarkable accomplishment. However, the information gained from the omics data, including next generation sequencing data, has yet to successfully affect care of patients suffering with PDAC. Therefore, we propose the development of an actionable genomic platform that matches a patient's PDAC clinically actionable genes with potential targeted adjuvant therapies. Using this platform, PDX1 has been identified as a potential actionable gene for PDAC, therefore, RNAi therapy, gene therapy and small inhibitory drugs, all targeting PDX1, serve as potential targeted adjuvant therapies. Preclinical studies support the hypothesis that identification of PDAC actionable genes could permit translation of a patient's genomic information into precision targeted adjuvant therapy for PDAC

Down-regulation of pancreatic and duodenal homeobox-1 by somatostatin receptor subtype 5: a novel mechanism for inhibition of cellular proliferation and insulin secretion by somatostatin.

Somatostatin (SST) is a regulatory peptide and acts as an endogenous inhibitory regulator of the secretory and proliferative responses of target cells. SST's actions are mediated by a family of seven transmembrane domain G protein-coupled receptors that comprise five distinct subtypes (SSTR1-5). SSTR5 is one of the major SSTRs in the islets of Langerhans. Homeodomain-containing transcription factor pancreatic and duodenal homeobox-1 (PDX-1) is essential for pancreatic development, β cell differentiation, maintenance of normal β cell functions in adults and tumorigenesis. Recent studies show that SSTR5 acts as a negative regulator for PDX-1 expression and that SSTR5 mediates somatostatin's inhibitory effect on cell proliferation and insulin expression/excretion through down-regulating PDX-1 expression. SSTR5 exerts its inhibitory effect on PDX-1 expression at both the transcriptional level by down-regulating PDX-1 mRNA and the post-translational level by enhancing PDX-1 ubiquitination. Identification of PDX-1 as a transcriptional target for SSTR5 may help in guiding the choice of therapeutic cancer treatments

SSTR5 P335L monoclonal antibody differentiates pancreatic neuroendocrine neuroplasms with different SSTR5 genotypes

Background: Somatostatin receptor type 5 (SSTR5) P335L is a hypofunctional, single nucleotide polymorphism of SSTR5 with implications in the diagnostics and therapy of pancreatic neuroendocrine neoplasms. The purpose of this study is to determine whether a SSTR5 P335L-specific monoclonal antibody could sufficiently differentiate pancreatic neuroendocrine neoplasms (PNENs) with different SSTR5 genotypes. Methods: Cellular proliferation rate, SSTR5 mRNA level, and SSTR5 protein level were measured by performing MTS assay, a quantitative reverse transcription polymerase chain reaction study, Western blot analysis, and immunohistochemistry, respectively. SSTR5 genotype was determined with the TaqMan SNP Genotyping assay (Applied Biosystems, Foster City, CA). Results: We found that the SSTR5 analogue RPL-1980 inhibited cellular proliferation of CAPAN-1 cells more than that of PANC-1 cells. Only PANC-1 (TT) cells, but not CAPAN-1 (CC) cells expressed SSTR5 P335L. In 29 white patients with PNENs, 38% had a TT genotype for SSTR5 P335L, 24% had a CC genotype for WT SSTR5, and 38% hada CT genotype for both SSTR5 P335L and WT SSTR5. Immunohistochemistry using SSTR5 P335L monoclonal antibody detected immunostaining signals only from the neuroendocrine specimens with TT and CT genotypes, but not those with CC genotypes. Conclusion: A SSTR5 P335L monoclonal antibody that specifically recognizes SSTR5 P335L but not WT SSTR5 could differentiate PNENs with different SSTR5 genotypes, thereby providing a potential tool for the clinical diagnosis of PNEN. © 2011 Published by Mosby, Inc

Repurposing metformin, simvastatin and digoxin as a combination for targeted therapy for pancreatic ductal adenocarcinoma

Patients with pancreatic adenocarcinoma (PDAC) have a 5-year survival rate of 8%, the lowest of any cancer in the United States. Traditional chemotherapeutic regimens, such as gemcitabine- and fluorouracil-based regimens, often only prolong survival by months. Effective precision targeted therapy is therefore urgently needed to substantially improve survival. In an effort to expedite approval and delivery of targeted therapy to patients, we utilized a platform to develop a novel combination of FDA approved drugs that would target pancreaticoduodenal homeobox1 (PDX1) and baculoviral inhibitor of apoptosis repeat-containing 5 (BIRC5) utilizing super-promoters of the target genes to interrogate an FDA approved drug library. We identified and selected metformin, simvastatin and digoxin (C3) as a novel combination of FDA approved drugs, which were shown to effectively target PDX1 and BIRC5 in human PDAC tumors in mice with no toxicity

PDX-1 Is a Therapeutic Target for Pancreatic Cancer, Insulinoma and Islet Neoplasia Using a Novel RNA Interference Platform

<div><p>Pancreatic and duodenal homeobox-1 (PDX-1) is a transcription factor that regulates insulin expression and islet maintenance in the adult pancreas. Our recent studies demonstrate that PDX-1 is an oncogene for pancreatic cancer and is overexpressed in pancreatic cancer. The purpose of this study was to demonstrate that PDX-1 is a therapeutic target for both hormonal symptoms and tumor volume in mouse models of pancreatic cancer, insulinoma and islet neoplasia. Immunohistochemistry of human pancreatic and islet neoplasia specimens revealed marked PDX-1 overexpression, suggesting PDX-1 as a “drugable” target within these diseases. To do so, a novel RNA interference effector platform, bifunctional shRNA^PDX-1, was developed and studied in mouse and human cell lines as well as in mouse models of pancreatic cancer, insulinoma and islet neoplasia. Systemic delivery of bi-shRNA^humanPDX-1 lipoplexes resulted in marked reduction of tumor volume and improved survival in a human pancreatic cancer xenograft mouse model. bi-shRNA^mousePDX-1 lipoplexes prevented death from hyperinsulinemia and hypoglycemia in an insulinoma mouse model. shRNA^mousePDX-1 lipoplexes reversed hyperinsulinemia and hypoglycemia in an immune-competent mouse model of islet neoplasia. PDX-1 was overexpressed in pancreatic neuroendocrine tumors and nesidioblastosis. These data demonstrate that PDX-1 RNAi therapy controls hormonal symptoms and tumor volume in mouse models of pancreatic cancer, insulinoma and islet neoplasia, therefore, PDX-1 is a potential therapeutic target for these pancreatic diseases.</p> </div

Systemic bi-shRNA^mousePDX-1 lipoplexes prevent death from severe hyperinsulinemia and hypoglycemia in an insulinoma SCID mouse model.

<p>Glucose levels A and C corresponding to insulin levels B and D were acquired from the β TC-6 mice treated with bi-shRNAi^mousePDX-1 or shRNAi^mousePDX-1, respectively. In each figure a-d, the dash line represents control group data and the dash-dot line represents treatment group data. Islet cells expressing PDX-1, insulin, PP, PCNA, p27, cyclin E and CdK4 were shown by IHC and islet cell apoptosis was shown by TUNEL assay, as indicated by arrows (×200) (e). Mouse survival after three treatment cycles of either empty vector or bi-shRNAi^mousePDX-1 and empty vector or shRNAi^mousePDX-1 was evaluated and compared using Kaplan-Meier in SPSS (f).</p