| Primary Hepatocellular carcinoma(HCC) is one of the most common and malignant tumor in Asia and Africa. Although great progress has been made in treatment of HCC with half century's great efforts, the effect of HCC treatment is still unsatisfactory with the limits of surgical resection, radiotherapy, chemotherapy as well as highly malignant behaviors of tumor cells. Therefore, It is urgent to put more efforts to do further research for the molecular carcinogenesis mechanism and to find out the ideal target gene which controls tumor cells proliferation and migration. Just like other tumors, the development of HCC is a complex process involving many genes and factors. The phosphorylation level of protein tyrosine, precisely regulated by PTKs and PTPs, plays an important role in the cellular signal transduction and cell cycle progression. As many PTKs are encoded by pro-oncogenes, it has been postulated that some of PTPs may act as tumor suppressor gene for a long time. But this assumption is not testified until the discovery of PTEN tumor suppressor gene.Since characterized and cloned seperately by Jing Li, Peter A. Steck and DaMing Li. in 1997, PTEN has been found to be inactivated by point mutations or homozygous deletions in many malignant tumors such as glioblastoma, prostate carcinoma, breast carcinoma and Cowden's disease. And it attracted much enthusiasm from scientists in different countries and was immediately designated as a second "star molecule" subsequent to p53. Although much work has been done on the498±~t~relationships between PTEN gene and some tumors such as endometrial carcinoma, glioblastoma, prostate carcinoma, breast carcinoma and melanoma and so on, there are few reports on the relationship between PTEN mutation and HCC. And so far, to our knowledge there is no report concerning PTEN expression during the development of HCC and effect of PTEN transfection on the biological behaviors of liver tumor cells.In this report, we aim to determine whether PTEN is a candidate gene of I Oq loss of heterozygosity in hepatocellular carcinoma, and to investigate the exact role of PTEN in the development of HCC by the widely recognized methods such as PCR-SSCP, Northern Blot, Western Blot, Immuno-histochemistry and stable gene transfection. During the research, we screened a panel of human primary HCC tissues with respect to the presence of mutations and PTEN mRNA and protein expression levels. It was shown that five kinds of novel point mutations of PTEN in HCC samples used were identified by PCR-SSCP and DNA sequencing methods. Among them, two cases of base substitutions were found in exon 4(13 bp of downstream of exon 4 5-flanking region, 89031 C—*T) and lead to a amino acid residue substitution of R84K, while the other 4 cases of point mutations all localized in the intron region including 1 case of G—*T in exon 4-intron region (67 bp downstream of exon 4 3 '-end, 89125 G—'T) of PTEN tumor suppressor gene genomic DNA, 1 case of T—~A in exon6-intron region (58 bp downstream of exon 6 3'-end, 110285 T—~A) and 2 cases of point mutations in intron 7-exon 8 region(29 bp upstream of exon 8 5 '-end, 118833 C—'~T and 82 bp upstream of exon 8 5'-end, 118780 A—'C). No mutation of PTEN was detected in the 5 kinds of hepatocellular cells examined.As to the expression levels, The average value of PTEN mRNA in HCC were lower than in paired para-carcinoma liver tissues (p <0.05). The low mRNA expression levels of the 5.5 kb and 4.4 kb transcript were significantly associated with serum AFP value, presence of tumor thrombus, state of satellite lesion and histological grading(p <0.05). However no significant relationship was found with age, serum HIBsAg status, tumor size, histological pattern, cirrhosis, fibrocapsule (p 0.05). The low mRNA expression level of the 2.4 kb transcript in HCC was significantly598 M±~ki~associated with serum HBsAg status, presence of tumor thrombus and satellite lesions (p <0.05), and also...
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