Observation On The Biological Charateristics Of Glioma Cells Transfected With P16 Gene

Recently, the activation of oncogene and the inactivation of tumor suppressor gene have been known as one of the mechanisms of tumorgenesis. So far, more than one hundred kinds of oncogenes have been found, but of which only a few tumor suppressor genes. Most of suppressor genes involved in the regulation of cell proliferation and maintain of the stability of cell heredity. Mutation of tumor suppressor genes such as Rb, p53, p16 and PTEN has been reported correlating with the development of human glioma. Homozygous deletion of p16 gene occurred in glioma cells, with the deletion rate reaching as high as 85%. Transfection of p16 cDNA into the p16-deficient tumor cells effectively inhibited tumor cell proliferation in vivo and in vitro. These results strongly suggest that p16 gene deletion or mutation play a pivotal role in glioma genesis, and p16 gene therapy has a promising future in treatment of patients with glioma. But, until now it is not fully clear that how p16 gene suppress the growth of the p16- gene -transfected tumor cells, and whether the p1 6-gene-transfection effects the expression of other oncogenes or tumor suppressor genes.Some undifferentiation cells aberrate from noble cells to form glioma. One of the possible reasons of this 揳tavistic heredity?is that the activation of oncogene and inactivation of tumor suppressor gene. At present, it has been proved that these undifferentiation cells may be transformed to mature cells by the inductors such as RA, HMBA and SB. Moreover, the effects of these inductors were validated by regulating the expression of oncogene and tumor suppressor gene. Combination of restoration of tumor suppressor gene with application of inductors may be a promising therapeutics for glioma. Dexamethasone is a frequently-used drug in treatment of glioma and it can alleviate edema around the tumor. Although it was found that dexamethasone induces the cells of neuroblastoma to mature, there is a question about the effect of dexamethasone on glioma.The substitutive short of tumor suppressor gene was validated to play an important role in treatment of cancer in laboratory. Although this therapeutics is available in clinic, it can not be a substitute for radiotherapy and chemotherapy. So, many researchers investigate the relationship between the substitutive short of tumor suppressor gene and other therapeutics. Generally speaking, p16 gene increases cancerV7~c4~radiosensitivity, but there is a controversy about relationship between p16 gene and chemosensitivity.Section I The effects of exogenous p16 gene on proliferation ofHuman glioma cells and its mechanismThe p16 gene mutation is very common in human glioma. The transcription product of p16 gene ,p16 protein, acting as a negative factor of cell proliferation ,plays a very important role in tumor formation and development. To explore the effect of p16 gene on the growth of glioma cell line and its mechanism as well as the possibility of application of exogenous p16 gene for gene therapy for human glioma. p16 gene recombinant expression vector plasmid(pcDNA3-p16) was constructed by subcloning a p16 cDNA into the pcDNA3 vector at the sites of BamH I and Xho I and then transfected into the glioma cell line (SHG-44) by using liposome. The transfected SHG-44 cells was selected by G4 18 . The positive clones are confirmed to have integration and expression of exogenous p16 gene by PCR detecting p16 gene DNA, and by Western blot and immuohistochemistry detecting p16 protein. We also assessed cell growth properties and cell cycle patern by flow cytometr of SHG-44-p 16, SHG-44-vect ( transfected with pcDNA3) and SHG-44. The percentage of G1 phase, S phase and G2/M phase in SHG-44-p16 was 61.35?.97, 24.65?.87 and 14.00?.88; in SHG-44-vect was 36.35?.99, 41.08?.07 and 22.75?.47; in SHG-44 was 35.53?.98, 42.70?.34 and 21.55?.79. The growth of those cells transfected with p16 gene were markedly suppressed compared with their control cells. The inhibitory rate of growth was 84.27%. The...