Mammalian START-like phosphatidylinositol transfer proteins - Physiological perspectives and roles in cancer biology.

PtdIns and its phosphorylated derivatives, the phosphoinositides, are the biochemical components of a major pathway of intracellular signaling in all eukaryotic cells. These lipids are few in terms of cohort of unique positional isomers, and are quantitatively minor species of the bulk cellular lipidome. Nevertheless, phosphoinositides regulate an impressively diverse set of biological processes. It is from that perspective that perturbations in phosphoinositide-dependent signaling pathways are increasingly being recognized as causal foundations of many human diseases - including cancer. Although phosphatidylinositol transfer proteins (PITPs) are not enzymes, these proteins are physiologically significant regulators of phosphoinositide signaling. As such, PITPs are conserved throughout the eukaryotic kingdom. Their biological importance notwithstanding, PITPs remain understudied. Herein, we review current information regarding PITP biology primarily focusing on how derangements in PITP function disrupt key signaling/developmental pathways and are associated with a growing list of pathologies in mammals.

Restoration of PITPNA in Type 2 diabetic human islets reverses pancreatic beta-cell dysfunction.

Defects in insulin processing and granule maturation are linked to pancreatic beta-cell failure during type 2 diabetes (T2D). Phosphatidylinositol transfer protein alpha (PITPNA) stimulates activity of phosphatidylinositol (PtdIns) 4-OH kinase to produce sufficient PtdIns-4-phosphate (PtdIns-4-P) in the trans-Golgi network to promote insulin granule maturation. PITPNA in beta-cells of T2D human subjects is markedly reduced suggesting its depletion accompanies beta-cell dysfunction. Conditional deletion of Pitpna in the beta-cells of Ins-Cre, Pitpnaflox/flox mice leads to hyperglycemia resulting from decreasing glucose-stimulated insulin secretion (GSIS) and reducing pancreatic beta-cell mass. Furthermore, PITPNA silencing in human islets confirms its role in PtdIns-4-P synthesis and leads to impaired insulin granule maturation and docking, GSIS, and proinsulin processing with evidence of ER stress. Restoration of PITPNA in islets of T2D human subjects reverses these beta-cell defects and identify PITPNA as a critical target linked to beta-cell failure in T2D.

Porphyrins to restrict progression of pancreatic cancer by stabilizing KRAS G-quadruplex: In silico, in vitro and in vivo validation of anticancer strategy.

KRAS, a frequently mutated G-quadruplex forming proto-oncogene is responsible for almost every type of cancer which can form a parallel G-quadruplex structure in the promoter region. G-quadruplex structure is one of the most important drug targets for modern cancer therapy for their unique structure and specificity. Here, we have screened several synthetic porphyrin-based compounds as potential KRAS G-quadruplex stabilizing ligands, using molecular modeling and docking studies. Two novel porphyrins: Porphyrin-1(Cobalt containing) and Porphyrin-2 (Palladium containing) evidenced high affinity towards KRAS-promoter/G-quadruplex. As KRAS mutation is prevalent in pancreatic cancer, the efficacy of these ligands against human pancreatic ductal carcinoma cell line PANC-1 and MiaPaCa2 were examined. Both the Porphyrins exhibited significant cytotoxicity and block metastasis by inhibiting Epithelial to messenchymal transition. In vivo studies confirmed both porphyrin compounds to be effective against EAC tumors along with significantly low toxicity against normal Swiss albino mice. The expression of KRAS gene in porphyrin-treated PANC-1, MiaPaCa2 and tumor-derived EAC cells were drastically reduced at both protein and RNA levels. Thus interaction of porphyrin-based ligands with G-quadruplex DNA at the promoter region of KRAS, might be utilized as a target for anticancer therapeutic strategy.

Determination of p16 overexpression as an indicator of human papillomavirus infection in oral dysplasia and carcinoma.

CONTEXT: Oral and pharyngeal cancer, grouped together, is the sixth most common cancer in the world. In the past few years, human papillomavirus (HPV) infection has been suggested as a risk factor for oral cancer apart from traditional risk factors such as smoking, tobacco, and alcohol consumption. AIMS: The aim of this study was to determine HPV status of the tumors using polymerase chain reaction (HPV-DNA PCR) and p16 immunostaining and to correlate p16 overexpression as an indicator of HPV-associated oral dysplasia and carcinoma. SETTINGS AND DESIGN: A prospective study was conducted in fifty cases of suspected oral cancer. MATERIALS AND METHODS: PCR Amplification of extracted HPV-DNA was done for HPV-DNA status in fresh tissue of suspected oral cancer cases. Histomorphological features of the cases were analyzed, and p16 immunohistochemistry was performed on the same specimen after making paraffin blocks to study p16 overexpression. STATISTICAL ANALYSIS USED: Chi-square test was used to analyze the differences between discrete variables. RESULTS: 5/6 (83.3%) HPV-DNA-positive cases were positive for p16 expression, whereas 26/44 (59.09%) p16-positive cases which were negative for HPV-DNA. Sensitivity and specificity of p16 as a surrogate marker for HPV-DNA were found to be 83.3% and 40%, respectively. CONCLUSIONS: p16 immunostaining is a good first-line assay for eliminating HPV-negative cases from additional analysis, but other causes of p16 overexpression in oral tumorigenesis related to tobacco consumption in keratinizing squamous cell carcinoma needs to be explored further.