[A study on the changes of DCC and MCC genes in colorectal carcinoma and adenoma]

Both deleted in colorectal carcinoma (DCC) and mutated in colorectal carcinomas (MCC) genes are newly found tumour suppresser genes in colorectal carcinomas. In this study mutations of DCC gene and loss of heterozygosity (LOH) of MCC gene were detected with Southern blot and PCR methods respectively. The study consisted of 30 cases of colorectal adenoma (10 with mild, 10 with moderate and 10 with severe dysplasia) and 33 cases of colorectal carcinomas (13 highly, 10 moderately and 10 poorly differentiated, meanwhile 9 in Dukes A, 10 in B and 14 in C stage). Their paired normal colorectal mucosa served as control. The results were as follows: mutation of DCC was not found in any specimen with normal mucosa or with adenoma of mild and moderate dysplaaia, while it was found in one if those with severe dysplasia. Mutation of DCC was, however, found in 7 of the 33 specimens with carcinoma and there was a correlation between the positive rate and the differentiation or staging of the carcinoma. LOH of MCC was not found in normal mucosa, but it was found in 2/10, 3/10 and 4/10 of the adenoma specimens with mild, moderate and severe dysplasia respectively. 18/33 of the carcinoma specimens was found to have LOH of MCC and there was also a correlation between the positive rate and the differentiation or staging of the carcinoma. These results suggest that the frequency of multiple gene changes increase with poor differentiation and increased staging of colorectal carcinoma.