PCR-SSCP-DNA sequencing method in detecting PTEN gene mutation and its significance in human gastric cancer

Abstract

To discuss the possible effect of PTEN gene mutations on occurrence and development of gastric cancer. Fifty-three gastric cancer specimens were selected to probe PTEN gene mutations in genome of gastric cancer and paracancerous tissues using PCR-SSCP-DNA sequencing method based on microdissection and to observe the protein expression by immunohistochemistry technique. PCR-SSCP-DNA sequencing indicated that 4 kinds of mutation sites were found in 5 of 53 gastric cancer specimens. One kind of mutation was found in exons. AA-TCC mutation was located at 40 bp upstream of 3' lateral exon 7 (115946 AA-TCC). Such mutations led to terminator formation in the 297th codon of the PTEN gene. The other 3 kinds of mutation were found in introns, including a G-C point mutation at 91 bp upstream of 5' lateral exon 5(90896 G-C), a T-G point mutation at 24 bp upstream of 5' lateral exon 5 (90963 T-G), and a single base A mutation at 7 bp upstream of 5' lateral exon 5 (90980 A del). The PTEN protein expression in gastric cancer and paracancerous tissues detected using immunohistochemistry technique indicated that the total positive rate of PTEN protein expression was 66% in gastric cancer tissue, which was significantly lower than that (100%) in paracancerous tissues (P < 0.005). PTEN gene mutation and expression may play an important role in the occurrence and development of gastric cancer.