[Study on the p53 gene mutation and microsatellite instability of gastric carcinoma]

To observe the relationship between p53 gene mutation and microsatellite instability (MSI) of the preoperative staging of gastric carcinoma by endoscopic ultrasonography(EUS).

A total of 73 cases of gastric carcinoma were taken for the preoperative staging with EUS. Silver staining PCR-SSCP method was used to detect mutations in exons 5, 6, 7, 8 of p53 gene and MSI at 4 loci on chromosomes 2, 5, 17 in the 73 paraffin-embedded biopsy specimens, and the relationship between them was studied further.

The overall mutated rate of p53 gene was 54.8%, with 6.8%, 15.1%, 19.2% and 13.7% in exons 5 to 8, respectively. Analysis of the relation of the mutation with the preoperative staging by EUS showed that it was significantly higher in T3(64.3%) and T4(67.9%) than in T1(0) or T2(25.0%)(P<0.05), and it was 67.6% in cases with lymph node metastasis, which was significantly higher than that without metastasis (41.7%)(P<0.05). The overall detective rate of MSI was 37.0%. The detective rate of MSI had no relation with the depth of invasion, which was 40.0%, 33.3%, 39.3% and 34.5% at T1 to T4 stages (P<0.05), respectively, but it was significantly higher in cases with lymph node metastasis(51.4%) than those without metastasis(22.2%)(P<0.05). Although the detective rate of MSI showed an increasing trend in the mutated cases of p53 gene as compared with the no mutation cases, there was no relationship between MSI and p53 gene mutation (P<0.05).

These results suggest that the gene mutation of p53 and MSI may represent the different mechanisms of carcinogenesis. They can reflect the cytobiologic malignant behavior of gastric carcinoma in varying degrees, which may be of reference significance in analysing the prognosis of the patients in clinics.