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Microsatellite instability analysis in hereditary non-polyposis colon cancer using the Bethesda consensus panel of microsatellite markers in the absence of proband normal tissue

BackgroundHereditary non-polyposis colon cancer (HNPCC) is an autosomal dominant syndrome predisposing to the early development of various cancers including those of colon, rectum, endometrium, ovarium, small bowel, stomach and urinary tract. HNPCC is caused by germline mutations in the DNA mismatch repair genes, mostly hMSH2 or hMLH1.In this study, we report the analysis for genetic counseling of three first-degree relatives (the mother and two sisters) of a male who died of colorectal adenocarcinoma at the age of 23. The family fulfilled strict Amsterdam-I criteria (AC-I) with the presence of extracolonic tumors in the extended pedigree. We overcame the difficulty of having a proband post-mortem non-tumor tissue sample for MSI testing by studying the alleles carried by his progenitors.MethodsTumor MSI testing is described as initial screening in both primary and metastasis tumor tissue blocks, using the reference panel of 5 microsatellite markers standardized by the National Cancer Institute (NCI) for the screening of HNPCC (BAT-25, BAT-26, D2S123, D5S346 and D17S250). Subsequent mutation analysis of the hMLH1 and hMSH2 genes was performed.ResultsThree of five microsatellite markers (BAT-25, BAT-26 and D5S346) presented different alleles in the probands tumor as compared to those inherited from his parents. The tumor was classified as high frequency microsatellite instability (MSI-H). We identified in the HNPCC family a novel germline missense (c.1864C>A) mutation in exon 12 of hMSH2 gene, leading to a proline 622 to threonine (p.Pro622Thr) amino acid substitution.ConclusionThis approach allowed us to establish the tumor MSI status using the NCI recommended panel in the absence of probands non-tumor tissue and before sequencing the obligate carrier. According to the Human Gene Mutation Database (HGMD) and the International Society for Gastrointestinal Hereditary Tumors (InSiGHT) Database this is the first report of this mutation.

HNA-1a, HNA-1b and HNA-1c gene frequencies in Argentineans.

Human neutrophil antigens (HNA) are polymorphic structures located in the neutrophil membrane. The neutrophil-specific antigens HNA-1a (NA1), 1b (NA2) and 1c (SH) are well-recognized allotypic forms of FcgammaRIIIb and the most frequent targets of neutrophil alloantibodies. The aim of this study was to determine the gene frequencies of the neutrophil-specific antigens belonging to the HNA-1 system in blood donors and Toba Amerindians from Rosario, Argentina. Two hundred and eighteen unrelated healthy Argentinean blood donors and Toba Amerindians from Rosario were typed for HNA-1a, HNA-1b and HNA-1c using polymerase chain reaction with sequence-specific primers. For the Argentinean blood donors, the HNA-1a and HNA-1b gene frequencies were 0.44 and 0.56 and for the Amerindians Toba were 0.77 and 0.23, respectively. The HNA-1c antigen is present in 4.7% (gene frequency=0.023) of the blood donors but in none of the Amerindian individuals. The present data showed that the HNA-1 allele frequencies in the major population and the Toba Amerindians from Rosario are similar to those described in European and others distant Amerindians populations, respectively.