[Mutation and amplification of RIT1 gene in hepatocellular carcinoma].

OBJECTIVE: To explore the mutation and amplification of RIT1 gene and their correlation with carcinogenesis of hepatocellular carcinoma (HCC). METHODS: The polymerase chain reactioindirect sequencing method was used for detecting the mutations in the sequence of all 6 exons in the RIT1 gene of 50 HCC tissues and paratumor tissues. And the amplification of RIT1 gene was examined by fluorescence quantitative polymerase chain reaction method. RESULTS: A nucleotide 241 G --> C substitution in exon 5 of RIT1 gene was detected in one patient's HCC tissue, but not in paratumor tissue; this 241 G --> C substitution leads to Glu81Gln amino acid alteration in the conservative domain binding GTP. A nucleotide G --> C substitution in 5'-UTR (-21 bp from initial codon) was detected in all of the 50 HCC tissues and paratumor tissues, and 2- to 297-fold amplification of RIT1 gene was detected in 11 of 43 qualified cases, the amplification frequency being 25.6%. CONCLUSION: Gene amplification is one of the main activating ways of RIT1 gene in HCC, and its amplification might be correlated with HCC carcinogenesis, while point mutation might be not.

[Amplification of RIT1 in hepatocellular carcinoma and its clinical significance].

BACKGROUND & OBJECTIVE: Previous study has demonstrated that high frequent gain of 1q was detected in hepatocellular carcinoma (HCC), 1q21-22 was identified as the minimum overlapping amplified region and might contain the candidate oncogenes involved in HCC. RIT1 gene is located in 1q21.3 region and is a member of Ras subfamily. RIT1 protein is similar to Ras protein in molecular structure and functions. It was speculated that RIT1 gene might be a candidate oncogene in HCC. So, the amplification of RIT1 gene was examined in HCC and was linked with the clinical indicators in this study to explore the possible functions of RIT1 gene in HCC development and progression. METHODS: The fluorescence quantitative polymerase chain reaction(FQ-PCR) method was established successfully. The number of RIT1 gene DNA copies was examined in the tumor tissues and its paratumor tissues from 43 patients with HCC by PE ABI 7000 Sequence Detector. The ratio of the number of RIT1 gene DNA copies between the tumor tissue and its paratumor tissue represented the extent of amplification of RIT1 gene DNA. RESULTS: RIT1 gene DNA was amplified in 11 cases (25.6%)among 43 patients. The mean survival time (15 months) of the RIT1 gene-amplification group is significantly shorter than that (34 months) of the non-amplification group (P = 0.0009); furthermore, the pathological grade and the extent of liver cirrhosis were significantly different between the RIT1 gene-amplification group and the non-amplification group (P< 0.01). CONCLUSION: The amplification of RIT1 gene might be one of the activation ways in HCC and might play an important role in HCC development and progression.