Colorectal carcinomas from Middle East. Molecular and tissue microarray analysis of genomic instability pathways

ABSTRACT

To evaluate the overall incidence of microsatellite instability [MSI], hereditary non polyposis colorectal cancer, and tumor supressor gene [TP53] mutations in Saudi colorectal carcinomas. We studied the MSI pathway in Saudi colorectal cancers [CRC] from 179 unselected patients using 2 methods: MSI by polymerase chain reaction, and immunohistochemistry detection of mutL homologs 1 and mutS homologs 2 proteins. The TP53 mutations were studied by sequencing exons 5, 6, 7, and 8. Of the 150 colorectal carcinomas analyzed for MSI, 16% of the tumors showed high level instability [MSI-H], 19.3% had low-level instability [MSI-L] and the remaining 64% tumors were stable. Survival of the MSI-H group was better as compared to the MSI-L or microsatellite stable group [p=0.0217]. In the MSI-H group, 48% were familial MSI tumors, which could be attributable to the high incidence of consanguinity in the Saudi population. The TP53 mutations were found in 24% of the cases studied. A high proportion of familial MSI cases and a lower incidence of TP53 mutations are some of the hallmarks of the Saudi colorectal carcinomas, which need to be explored further