[Microsatellite alterations on chromosome 9p21-22 in sporadic colorectal cancer]

To study whether alteration of p16 plays an important role in the development of colorectal carcinomas and the relationship between the molecular changes of 9p21-22 chromosome subregion in sporadic colorectal cancers.

To detect microsatellite instability (MSI) and loss of heterozygosity (LOH) by PCR, denatured-polyacrylamide gel-electrophoresis and silver staining (microsatellite DNA-PCR-silver staining method) and to compare the results with the clinopathological parameters.

Between MSI positive and negative cases and the clinopathological findings, some evidences found in the MSI positive group were as follows: (1) tendency towards younger patients (usually < 50 years in age, P < 0.05); (2) more frequently seen in mucoid carcinomas (P < 0.01).

Microsatellite DNA-PCR-silver staining method is very sensitive in detecting even a tiny change of a single base. MSI occured in the selected microsatellite loci of different subregions and different chromosomes might be different in significance, therefore, a right choice of the suitable loci for studying the microsatellite changes is important. Since the frequency of loss of heterozygosity at 9p21-22 is low (merely 8.42%), it is considered that p16 is not closely associated with the development of sporadic colorectal cancer.