Studies On The Expression And Mechanisms Of P16～(INK4a)gene In Human Pancreatic Adenocarcinoma

Pancreatic carcinoma related symptoms occur late in disease progression. Consequently, surgical intervention remains palliative in the majority of patients. The prognoses of pancreatic cancer patients are miserable even after radical surgery, and adjuvant therapy is necessary to improve the surgical results. P16, encoded by p 1 6INK4a gene, is tight- binding and inhibitory protein for cyclin-dependent kinase 4 to induce G 1 arrest of the cell cycle. p16 INK4a gene deletion is frequently identified in human pancreas cancer. The impaired gene function of p16 might be a major factor of the uncontrolled proliferation and malignancy of pancreas cancer cells. In this study, first, we studied human primary tumor tissues neighboring normal tissues and cell lines for the alterations f 16 LNK4a so as to clarigy the role of P16 protein in pancreatic adenocarcinoma. Second, we investigated the effect of retroviral p16 expression vector for pancreas cancer cell proliferation to clarify whether the vector might be a promising mode to assist the surgical therapy for pancreas cancer. By immunohistochemistry, We found the expression level of P16 of pancreatic adenocarcinoma was much lower than that of benign disease and normal tissues (P<0.0 1), but there was no differences in that of different histopathologic grade and clinical stage. Northern blot showed some tissues without P16 protein expression expressed p16 INK4a mRNA. We studied 3 human pancreatic cell carcinoma lines, and found that Patu8902 revealed homozygous deletion of ~16 INK4a exon II and SW 1990 had a quite low expression of P16 protein. Then We used the retroviral p16 expression vector pL-p 16-SN, which inserting p16 cDNA to a vector containing w + transcription and processing elements replication- incompetent infectious virus, to transfect pancreas cancer cell lines. Thereafter, we assessed the activity of pL-p 16-SN to induce p16 gene mRNA expression in Patu8902-p16 and to control cell proliferation. By 3 nowcytometric stUdies, Patu89o2 and swl99o cell was arrested at G,-G,and Gz-M stage after pL-p16-SN trallsfection. The cell proliferation wassignificanly suPPressed by pL-pl6-SN compared with the control grouP(P<0.0l). These data indicate that the dysfunction of pl6 INK4a gene inpancreatic carcinoma is frequently, and pL-pl6-SN has the potential toinduce pl6 gene expression and control pancreas cancer cell proliferation.And it suggest that the retroviral pl6 expression vector pL-pl6-SN mightbe a possible method of gene theraPy to improve the surgical theraPeuticresults for pancreas cancer.