MSI status modulates the value of some molecular markers in colorectal tumors

 A. Colomer, N. Erill, M. Verdú, R. Román, A Vidal, X. Puig.

BIOPAT. Biopatologia Molecular, SL. Barcelona, Spain.


LOH 17p/TP53 and LOH 18q/DCC have been related to prognosis of colorectal adenocarcinomas. Since MSI-H tumors have a minor rate of TP53 mutations and rarely present allelic deletions, we intended to study these molecular features in a series of 197 primary tumors previously categorized for MSI status. Eighteen tumors out of 181 (10%) exhibited MSI-H. p53 alterations were approached by a combination of IHC (PAb 1801) and PCR-SSCP/sequencing (exons 4-8), that evidenced a decrease of TP53 mutations (from 70% to 50%) in tumors with unstable phenotype. Analysis of LOH 17p/TP53 locus (p53CA) and 18q (D18S55,58, 61,64,69) showed a high tendency for MSS tumors with nodal involvement to loose both allelic regions. The correlation of LOH 17p and 18q results with pathological data corroborated the impact of these markers in tumoral staging (TNM). As conclusions, we support the idea of including 17p and 18q allelic losses into the panel of prognostic markers for colorectal tumors, and outline the convenience of previously categorize them for MSI status.

Abstract in:

J Mol Diagn 2002; 4: 251 (S2)