Microsatellite instability in early gastric cancer

Battista, Pasquale; Palmirotta, Raffaele; Vitullo, Paola; Verı̀, Maria Concetta; Colalongo, Cristiano; Luciana, Rigoli; Fedele, Fabiola; Caruso, Rosario Alberto; Inferrera, C; Romano, Ferdinando; Mariani–Costantini, Renato; Frati, Luigi; Cama, Alessandro

doi:10.3892/ijo.10.1.65

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“…MSI is a phenotypic indicator of defective DNA MMR and is detected in tumors from HNPCC patients, as well as in a low percentage of various sporadic cancers, such as colon, endometrial, and stomach cancer (Aaltonen et al 1993;Han et al 1993;Ionov et al 1993;Thibodeau et al 1993;Burks et al 1994;Duggan et al 1994;Keller et al 1995;Akiyama et al 1996;Caduff et al 1996;Battista et al 1997;Gurin et al 1999). In CRC, several phenotypes of MSI have been defined: MSI-H (MSI in 130% of loci examined), MSI-L (MSI in !30% loci examined), and MSS (microsatellite stable, showing no instability at any site) (Boland et al 1998).…”

Section: Introductionmentioning

confidence: 99%

The Frequency of Hereditary Defective Mismatch Repair in a Prospective Series of Unselected Colorectal Carcinomas

Cunningham

Kim

Christensen

et al. 2001

The American Journal of Human Genetics

301

205

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A comprehensive analysis of somatic and germline mutations related to DNA mismatch-repair (MMR) genes can clarify the prevalence and mechanism of inactivation in colorectal carcinoma (CRC). In the present study, 257 unselected patients referred for CRC resection were examined for evidence of defective DNA MMR. In particular, we sought to determine the frequency of hereditary defects in DNA MMR in this cohort of patients. MMR status was assessed by testing of tumors for the presence or absence of hMLH1, hMSH2, and hMSH6 protein expression and for microsatellite instability (MSI). Of the 257 patients, 51 (20%) had evidence of defective MMR, demonstrating high levels of MSI (MSI-H) and an absence of either hMLH1 (n=48) or hMSH2 (n=3). All three patients lacking hMSH2, as well as one patient lacking hMLH1, also demonstrated an absence of hMSH6. DNA sequence analysis of the 51 patients with defective MMR revealed seven germline mutations-four in hMLH1 (two truncating and two missense) and three in hMSH2 (all truncating). A detailed family history was available for 225 of the 257 patients. Of the seven patients with germline mutations, only three had family histories consistent with hereditary nonpolyposis colorectal cancer. Of the remaining patients who had tumors with defective MMR, eight had somatic mutations in hMLH1. In addition, hypermethylation of the hMLH1 gene promoter was present in 37 (88%) of the 42 hMLH1-negative cases available for study and in all MSI-H tumors that showed loss of hMLH1 expression but no detectable hMLH1 mutations. Our results suggest that, although defective DNA MMR occurs in approximately 20% of unselected patients presenting for CRC resection, hereditary CRC due to mutations in the MMR pathway account for only a small proportion of patients. Of the 257 patients, only 5 (1.9%) appear to have unequivocal evidence of hereditary defects in MMR. The epigenetic (nonhereditary) mechanism of hMLH1 promoter hypermethylation appears to be responsible for the majority of the remaining patients whose tumors are characterized by defective DNA MMR.

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