The expression of DNA mismatch repair genes and detection of DNA ploidy in young patients with colorectal carcinoma

Abstract

OBJECTIVE: To investigate the clinicopathologic characters and carcinogentic pathways of young (age < 36) colorectal carcinomas (CRCs) in Guangzhou, China. METHODS: Immunohistochemistry and flow cytometry methods were used to detect the expression of hMSH(2) and hMLH(1), status of DNA ploidy in 63 cases of young CRCs from Guangzhou, China, and analyze their correlations with patient's clinicopathological characters. RESULTS: Of the 63 young CRCs studied, forty-four (69.8%) tumors were non-mucinous carcinomas, thirty-nine (61.9%) patients were in Dukes' C or D stage. Of the 59 CRCs which were successfully detected by immunohistochemistry and flow cytometry, ten (16.9%) CRCs lost either hMSH(2) or hMLH(1) and showed DNA diploid or near-diploid, while twenty-six (44.1%) had aneuploid DNA content and all with the normal expression of hMSH(2) and hMLH(1). In addition, there existed a significant percentage (23/59, 39%) of young CRCs showing no loss of either of these two mismatch repair proteins and having a diploid or near diploid DNA content. CONCLUSION: The overall percentage of young CRCs in Guangzhou is significantly higher than those in Caucasian predominant countries and about seventy percent of young CRCs in Guangzhou are conventional carcinomas. 39% of young CRCs in Guangzhou showed no evidence of either chromosomal instability or microsatellite instability carcinogentic pathway, indicating that there must be at least a third pathway which triggers the CRCs in these special subgroups of young patients in Guangzhou, China.