Μοριακή Και Γενετική Ανάλυση Του Ηπατοκυτταρικού Καρκίνου Και Συσχέτιση Με Ιούς Της Ηπατίτιδας

Abstract

Hepatocellular carcinoma (HCC) is the most common primary cancer of the liver. The disease has a dismal five-year survival rate of less than 5%. While a number of etiologic factors have been identified, the elucidation of their mechanistic roles in hepatocarcinogenesis has only recently begun. Clearly in some parts of the world viral and chemical carcinogenic components are involved, with the subsequent inactivation of the p53 tumor suppressor gene. This gene has become the center of intensive study ever since it became apparent that slightly more than 50% of human cancers contain mutations in its sequence. p53 activity has been linked to tumor suppression, cell cycle control, DNA repair, stress responses, cell senescence, genomic stability and apoptotic cell death. Interestingly, in hepatocellular carcinoma, the p53 mutational spectra present geographical distribution. The discovery of instability of microsatellite repeats (MIN) and its linkage to hereditary non polyposis colon cancer opened new chapters in tumor biology and in clinical management of patients with heightened cancer susceptibility. Over the past six years, the scope of MIN has been expanded to encompass a unique form of genomic instability broadly involved in the genesis of cancer, not limited to hereditary non polyposis colon cancer. MIN is caused by a failure of the mismatch repair system to repair specific errors that occur during the replication of DNA.The aim of the present study was to examine microsatellite instability and p53 mutations in correlation with infection by hepatitis Β and C viruses in hepatocellular carcinoma. HBV sequences were amplified using polymerase chain reaction in tumor tissues. The entire coding sequence along with the splicing sites of the p53 gene was analyzed, using an automated sequencer, from microdissected HCC surgical specimens of 27 patients from Greece. Mutations were found in 5 of the 27 tumors (18.5%), including mutations in exons 5 and 8, which encompass the conserved hydrophobic midregion of the protein that is required for the sequence-specific binding to DNA. Our data support the view that the abnormalities mentioned could lead to malignant transformation of selected subclones. Three of these are missense mutations and two insertions, one of the latter has not been previously reported. No mutations were detected at the hot-spot codon 249, which has been linked by in vitro and in vivo studies with the dietary consumption of aflatoxins. A correlation between p53 mutations and advanced tumor grade was found. Furthermore, p53 mutations were detected in 26% of samples infected by HBV or HCV (5/19), while no mutation was found in the remaining 8 samples not infected by either of these viruses. Specifically, p53 mutations were found in 26.67% of HCCs infected by HBV and in 40% infected by HCV, while 3/5 mutant samples have indications of dual infection. Our results indicate a possible relationship between hepatitis viruses, especially HCV and p53 mutations in liver cancer. Additionally a possible polymorphism...