Studies On Deletions And Mutations Of FHIT--a Candidate Tumor Suppressor Gene In Primary Gastric And Hepatocelluar Cacinoma

Objective To investigate the homozygous deletion and point mutation of exon5 and exon8 of FHIT-a candidate tumor suppressor gene gastric carcinoma and hepatocellular carcinoma (HCC).And To construct the DNA fragment clone of FHIT exon8. Methods We collected 26 surgical samples of gastric carcinoma and 20 surgical samples of HCC,and all these samples were diagnosed by pathology.DNA was extracted from these tissues.The method of polymerase chain reaction(PCR) was set up to analyze the homozygous deletion of exon5 and exon8 of FHJT.The method of polymerase chain reaction single-strand confirmation polymorphism (PCR-SSCP) was set up to analyze the point mutation of exon5 and exon8 of FHIT. The pBK-FHIT was constructed by inserting the DNA of FHIT exon 8 into pBK-CMVResults In the 26 samples of gastric carcinoma, homozygous deletion of FHIT exon5 was detected in 3 cases with a deletion rate of I 1.5%,and homozygous deletion of FHIT exon8 was detected in 4 cases with a deletion rate of I 5.4%.The 3 cases which lost exon5 also lost exon8.So the total deletion rate of FHIT was 15.4%.But,in the 20 samples of HCC, homozygous deletion of FHJT exon5 was detected in 2 cases with a deletion rate of 10%,and homozygous deletion of FHIT exon8 was detected in 6 cases with a deletion rate of 30%. one of 2 cases which lost exon5 also lost exon8.So the total deletion rate of FHJT in HCC was 35%(7/20).In all 10 normal lymphocytes,there were not deletion and point mutation of FHIT. In the 22 samples of gastric carcinoma and 13 samples of HCC in which there were not homozygous deletion of FHIT exon5 and exon8,there were not point mutation of Fl-ITT exon5 and exon8. The restriction mapping of recombinant DNA showed that the restrictive endonuclease sites were identical with the original design. The DNA fragment of insert is 193 bp, which is of the same length with the span 2 between two primers designed by us. Conclusion The results suggest that the abnomal FHIT was only detected in cancer tissues;that the homozygous deletion of F~T exon5 and exon8 may not be a major way of inactivation of FHIT gene in garstric carcinoma, but other inactivation ways can not be excluded;that the homozygous deletion of FHJT exon5 and exon8(especial exon8) may be a major way of inactivation of FHIT gene. The results also suggested that the point mutation of FHIT exon5 and exon8 may not be a major way of inactivation of FHIT gene in garstric carcinoma and HCC.And we successfully constructed the FHIT exon8 clone.This results provide a solid foundations for further investigation of FHIT.