Nelson S. Yee

Differential roles of PI3-kinase and Kit tyrosine 821 in Kit receptor-mediated proliferation, survival and cell adhesion in mast cells.

The pleiotropic effects of the Kit receptor system are mediated by Kit‐Ligand (KL) induced receptor autophosphorylation and its association with and activation of distinct second messengers, including phosphatidylinositol 3′‐kinase (PI3‐kinase), p21ras and mitogen‐activated protein kinase (MAPK). To define the role of PI3‐kinase, p21ras and MAPK in Kit‐mediated cell proliferation, survival and adhesion in bone marrow‐derived mast cells (BMMC), mutant Kit receptors were expressed in Wsh/Wsh BMMC lacking endogenous c‐kit expression. The introduction of both murine Kit(S) and KitL (isoform containing a four amino acid insert) into Wsh/Wsh BMMC restored KL‐induced proliferation, survival and adhesion to fibronectin, as well as activation of PI3‐kinase, p21ras and MAPK, and induced expression of c‐fos, junB, c‐myc and c‐myb mRNA. Substitution of tyrosine 719 in the kinase insert with phenylalanine (Y719F) abolished PI3‐kinase activation, diminished c‐fos and junB induction, and impaired KL‐induced adhesion of BMMC to fibronectin. In addition, the Y719F mutation had partial effects on p21ras activation, cell proliferation and survival, while MAP kinase activation was not affected. On the other hand, Y821F substitution impaired proliferation and survival without affecting PI3‐kinase, p21ras and MAPK activation, and induction of c‐myc, c‐myb, c‐fos and c‐jun mRNA, while KL‐induced cell adhesion to fibronectin remained intact. In agreement with a role for PI3‐kinase in Kit‐mediated cell adhesion, wortmannin blocked Kit‐mediated cell adhesion at concentrations known to specifically inhibit PI3‐kinase. We conclude, that association of Kit with p85PI3‐K, and thus with PI3‐kinase activity, is necessary for a full mitogenic as well as adhesive response in mast cells. In contrast, tyrosine 821 is essential for Kit‐mediated mitogenesis and survival, but not cell adhesion.

Locally Advanced, Unresectable Pancreatic Cancer: American Society of Clinical Oncology Clinical Practice Guideline

PURPOSE To provide evidence-based recommendations to oncologists and others for treatment of patients with locally advanced, unresectable pancreatic cancer. METHODS American Society of Clinical Oncology convened an Expert Panel of medical oncology, radiation oncology, surgical oncology, gastroenterology, palliative care, and advocacy experts and conducted a systematic review of the literature from January 2002 to June 2015. Outcomes included overall survival, disease-free survival, progression-free survival, and adverse events. RESULTS Twenty-six randomized controlled trials met the systematic review criteria. RECOMMENDATIONS A multiphase computed tomography scan of the chest, abdomen, and pelvis should be performed. Baseline performance status and comorbidity profile should be evaluated. The goals of care, patient preferences, psychological status, support systems, and symptoms should guide decisions for treatments. A palliative care referral should occur at first visit. Initial systemic chemotherapy (6 months) with a combination regimen is recommended for most patients (for some patients radiation therapy may be offered up front) with Eastern Cooperative Oncology Group performance status 0 or 1 and a favorable comorbidity profile. There is no clear evidence to support one regimen over another. The gemcitabine-based combinations and treatments recommended in the metastatic setting (eg, fluorouracil, leucovorin, irinotecan, and oxaliplatin and gemcitabine plus nanoparticle albumin-bound paclitaxel) have not been evaluated in randomized controlled trials involving locally advanced, unresectable pancreatic cancer. If there is local disease progression after induction chemotherapy, without metastasis, then radiation therapy or stereotactic body radiotherapy may be offered also with an Eastern Cooperative Oncology Group performance status ≤ 2 and an adequate comorbidity profile. If there is stable disease after 6 months of induction chemotherapy but unacceptable toxicities, radiation therapy may be offered as an alternative. Patients with disease progression should be offered treatment per the ASCO Metastatic Pancreatic Cancer Treatment Guideline. Follow-up visits every 3 to 4 months are recommended. Additional information is available at www.asco.org/guidelines/LAPC and www.asco.org/guidelines/MetPC and www.asco.org/guidelineswiki.

Transient receptor potential channel TRPM8 is over-expressed and required for cellular proliferation in pancreatic adenocarcinoma

The roles of transient receptor potential (TRP) cation channels in pancreatic tumorigenesis are essentially unknown. Here, we focus on the TRP melastatin-subfamily (TRPM) members. Expression of the thermally regulated transmembrane Ca(2+)-permeable channel TRPM8 is consistently up-regulated in human pancreatic adenocarcinoma cell lines and tissues. TRPM8-deficient pancreatic cancer cells have reduced ability of proliferation and cell cycle progression with elevated levels of cyclin-dependent kinase inhibitors. These results indicate that TRPM8 is aberrantly over-expressed in pancreatic adenocarcinoma and required for cellular proliferation, and they support further investigation of the potential of TRPM8 as a clinical biomarker and therapeutic target in pancreatic adenocarcinoma.

Combined targeting of histone deacetylases and hedgehog signaling enhances cytoxicity in pancreatic cancer

Combined targeting of distinct cellular signaling mechanisms may improve the efficacy and reduce the toxicity of therapy in pancreatic cancer. Histone deacetylases (HDACs) control cellular functions through epigenetic modulation, and HDACs inhibitors suppress cell growth in pancreatic adenocarcinoma. The Hedgehog (Hh) pathway regulates the development of the pancreas, and aberrant Hh signaling promotes the initiation and progression of pancreatic neoplasia. We hypothesize that HDACs and the Hh pathway cooperatively interact to regulate cellular proliferation of the exocrine pancreas. A combination of the HDAC inhibitor SAHA and the Smoothened antagonist SANT-1 was evaluated for their ability to suppress growth of the Gemcitabine-resistant pancreatic adenocarcinoma cell lines Panc-1 and BxPC-3. The combination of SAHA and SANT-1 supra-additively suppressed cellular proliferation and colony formation. Flow cytometric and immunohistochemical analyses indicated that enhanced induction of apoptotic cell death, cell cycle arrest in G0/G1 phase, and ductal epithelial differentiation are involved. Cell death was associated with nuclear localization of survivin, increased bax expression, and activation of caspases 3 and 7. Consistent with the cell cycle arrest and cytodifferentiation, the cyclin-dependent kinase inhibitors p21waf and p27kip1 were upregulated, and cyclin D1 down-regulated. The potentiated anti-proliferative effect by the combination of SAHA and SANT-1 may involve cooperative suppression of the Hh pathway activity, as shown by the up-regulation of HHIP by SAHA, and enhanced repression of of Ptc-1 mRNA expression. In summary, we have developed a molecular target-based therapeutic approach that overcomes chemoresistance in pancreatic cancer cells by chemically inhibiting HDACs and Hh signaling in combination.

Mutation of RNA Pol III Subunit rpc2/polr3b Leads to Deficiency of Subunit Rpc11 and Disrupts Zebrafish Digestive Development

The role of RNA polymerase III (Pol III) in developing vertebrates has not been examined. Here, we identify a causative mutation of the second largest Pol III subunit, polr3b, that disrupts digestive organ development in zebrafish slim jim (slj) mutants. The slj mutation is a splice-site substitution that causes deletion of a conserved tract of 41 amino acids in the Polr3b protein. Structural considerations predict that the slj Pol3rb deletion might impair its interaction with Polr3k, the ortholog of an essential yeast Pol III subunit, Rpc11, which promotes RNA cleavage and Pol III recycling. We engineered Schizosaccharomyces pombe to carry an Rpc2 deletion comparable to the slj mutation and found that the Pol III recovered from this rpc2-Δ yeast had markedly reduced levels of Rpc11p. Remarkably, overexpression of cDNA encoding the zebrafish rpc11 ortholog, polr3k, rescued the exocrine defects in slj mutants, indicating that the slj phenotype is due to deficiency of Rpc11. These data show that functional interactions between Pol III subunits have been conserved during eukaryotic evolution and support the utility of zebrafish as a model vertebrate for analysis of Pol III function.

Targeted silencing of TRPM7 ion channel induces replicative senescence and produces enhanced cytotoxicity with gemcitabine in pancreatic adenocarcinoma

The transient receptor potential TRPM7 ion channel is required for cellular proliferation in pancreatic epithelia and adenocarcinoma. To elucidate the mechanism that mediates the function of TRPM7, we examined its role in survival of pancreatic cancer cells. RNA interference-mediated silencing of TRPM7 did not induce apoptotic cell death. TRPM7-deficient cells underwent replicative senescence with up-regulation of p16(CDKN2A) and WRN mRNA. The combination of anti-TRPM7 siRNA and gemcitabine produced enhanced cytotoxicity as compared to gemcitabine alone. Thus, TRPM7 is required for preventing senescence, and modulation of TRPM7 expression may help improve treatment response of pancreatic cancer by combining with apoptosis-inducing agents.

Clinicopathologic and molecular features of pancreatic adenocarcinoma associated with Peutz-Jeghers syndrome.

Pancreatic cancer is increasingly prevalent and almost uniformly fatal. Studies of the molecular genetics of sporadic and hereditary cases of pancreatic cancer as well as the molecular biology of pancreatic development may advance our understanding of the mechanism underlying pathogenesis of this malignancy. Based on a case of pancreatic adenocarcinoma in a patient with Peutz-Jeghers syndrome (PJS), the clinicopathologic features and molecular genetics of pancreatic tumors associated with this hereditary cancer syndrome are reviewed. Particular emphasis is placed on the developmental roles and biochemical functions of STK11/LKB1, the gene mainly responsible for PJS. Modeling pancreatic cancer in animal models such as the mouse and zebrafish will further our understanding of the pathogenesis of this important disease, and the studies derived from these model organisms can be potentially applied for developing novel preventive and therapeutic strategies.

Zebrafish as a model for pancreatic cancer research.

Elucidation of basic mechanisms that regulate pancreatic organogenesis may help define molecular pathways involved in the development of exocrine pancreas cancer. The zebrafish has emerged as a powerful model for genetic dissection of the mechanisms underlying vertebrate organogenesis including formation of the pancreas. Unique properties of zebrafish enable genetic and embryological analyses not feasible using other vertebrate model organisms. The optical clarity of the zebrafish embryos allows visual detection of markers for pancreatic morphogenesis and cytodifferentiation by whole mount immunohistochemistry and RNA in situ hybridization. This feature, coupled with the accessibility of the externally fertilized zebrafish embryo and the small size and fecundity of adult zebrafish, facilitates large-scale forward genetic screens using chemical or insertional mutagenesis techniques. Furthermore, these properties allow high throughput studies that target functions of known genes via antisense or enforced expression studies. Together, such studies are predicted to identify novel genes, or known genes essential for pancreas development. Work in zebrafish is predicted to complement research performed using other vertebrate model organisms, and may help identify markers that define early stages of pancreatic tumorigenesis as well as potential targets for therapy.

TRPM8 ion channel is aberrantly expressed and required for preventing replicative senescence in pancreatic adenocarcinoma: Potential role of TRPM8 as a biomarker and target

Pancreatic adenocarcinoma is mostly fatal and generally resistant to conventional treatments, such that effective therapies with tolerable side effects are desperately needed. Ion channels including the transient receptor potential (TRP) channels have been implicated in human malignancies, but their roles in pancreatic cancer were mostly unknown. Recent identification of the melastatin-subfamily members of the TRP family of ion channels, and their functions in pancreatic epithelia and adenocarcinoma, is expected to provide a new perspective to understanding the mechanism underlying pancreatic tumorigenesis. In this report, we present the clinical and pathological features of a mini-series of patients with pancreatic adenocarcinoma, which aberrantly exhibits immunoreactivity against the TRPM8 channel. We have recently demonstrated the proliferative role of TRPM8 channel in pancreatic cancer cells. Here, we present evidence that RNA interference-mediated silencing of TRPM8 induces replicative senescence in pancreatic adenocarcinoma cells. This suggests that the aberrantly expressed TRPM8 channel may contribute to pancreatic tumorigenesis by preventing oncogene-induced senescence, and targeted inhibition of TRPM8 may enhance tumor sensitivity to therapeutics. Based on these observations, we hypothesize that the TRPM8 ion channel plays a crucial role in the growth and progression of pancreatic neoplasia during tumorigenesis. We propose that TRPM8 can be exploited as a clinical biomarker and as a therapeutic target for developing personalized therapy in pancreatic adenocarcinoma.

Roles of TRPM8 Ion Channels in Cancer: Proliferation, Survival, and Invasion

The goal of this article is to provide a critical review of the transient receptor potential melastatin-subfamily member 8 (TRPM8) in cancers, with an emphasis on its roles in cellular proliferation, survival, and invasion. The TRPM8 ion channels regulate Ca2+ homeostasis and function as a cellular sensor and transducer of cold temperature. Accumulating evidence has demonstrated that TRPM8 is aberrantly expressed in a variety of malignant solid tumors. Clinicopathological analysis has shown that over-expression of TRPM8 correlates with tumor progression. Experimental data have revealed important roles of TRPM8 channels in cancer cells proliferation, survival, and invasion, which appear to be dependent on the cancer type. Recent reports have begun to reveal the signaling mechanisms that mediate the biological roles of TRPM8 in tumor growth and metastasis. Determining the mechanistic roles of TRPM8 in cancer is expected to elucidate the impact of thermal and chemical stimuli on the formation and progression of neoplasms. Translational research and clinical investigation of TRPM8 in malignant diseases will help exploit these ion channels as molecular biomarkers and therapeutic targets for developing precision cancer medicine.