Immunohistochemical staining of hMLH1 and hMSH2 reflects microsatellite instability status in ovarian carcinoma.
ABSTRACT Microsatellite instability is due to defects in the family of DNA repair genes, primarily hMLH1 and hMSH2, which can be detected by immunohistochemical staining. However, it is unclear whether immunohistochemical staining can accurately predict microsatellite instability status. We sought here to evaluate the sensitivity, specificity, and predictive values of immunostaining for the expression of the DNA mismatch-repair genes hMLH1 or hMSH2 in predicting microsatellite instability in ovarian carcinoma. Tissue microarrays with specimens from 322 women with primary ovarian carcinoma were stained with antibodies to hMLH1 and hMSH2; cases in which either hMLH1 or hMSH2 were negative were analyzed for microsatellite instability with the five-marker panel recommended by the National Cancer Institute (BAT26, BAT25, D5S346, D2S123, and D17S250). Microsatellite instability was also analyzed in another 19 cases selected at random in which both hMLH1 and hMSH2 were positive. Tumors with instability at two or more of the five NCI markers were considered to have a high level of microsatellite instability; tumors showing instability at only one marker were considered microsatellite instability-low; and tumors in which no markers exhibited microsatellite instability were considered microsatellite stable. We found that negative staining for hMLH1 protein (five cases) or hMSH2 protein (two cases) was associated with high level of microsatellite instability. The sensitivity and specificity of immunohistochemical staining for hMLH1 were 62 and 100% and those of hMSH2 alone were 25 and 100%. Combining loss of expression of both hMLH1 and hMSH2 led to sensitivity, specificity, and positive and negative predictive values of 87, 100, 100, and 95%. These results suggest that use of a two-molecule panel (hMLH1 and hMSH2) can accurately determine the microsatellite instability status of patients with ovarian cancer.
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ABSTRACT: Recently, the National Cancer Institute (NCI) established criteria for determination of microsatellite instability (MSI) in colorectal tumors. Although the best panel of markers for ovarian tumors is not known, we evaluated epithelial ovarian cancers for MSI based on the NCI recommendations. One hundred and nine ovarian tumors were analyzed for MSI by gel analysis of paired germ-line and tumor DNA. PCR amplification was performed using the panel of five microsatellite markers recommended by the NCI (BAT25, BAT26, D5S346, D2S123, and D17S250) and nine additional markers picked based on their genomic location (NME1, D10S197, D11S904, D13S175, DXS981, DXS6800, DXS6807, AR, and D3S1611). Tumors were characterized on the basis of: high-frequency MSI (MSI-H) if two or more of the five NCI markers showed instability or there was instability at 30% or more of all markers tested; or low-frequency MSI (MSI-L) if only one of the five NCI markers showed instability or <30% of all of the markers. All of the other tumors were considered microsatellite stable. On the basis of the NCI markers, 12 (11%) tumors demonstrated MSI-H, and 8 (7%) additional tumors had MSI-L. When all of the 14 markers were considered together, 13 (12%) tumors demonstrated MSI-H (based on 30% or more unstable loci), and 26 (24%) tumors had MSI-L. A single tumor identified to have MSI-H based upon all of the markers tested would have been classified as MSI-L based upon the NCI markers alone. Inclusion of an additional dinucleotide marker (NME1) to the NCI panel allowed detection of all of the tumors with MSI-H using only six markers. MSI-H occurs in approximately 12% of invasive ovarian tumors. For optimal detection of microsatellite instability in ovarian cancer, an additional marker (NME1) may be required, along with the five recommended by the NCI.Cancer Research 07/2001; 61(11):4371-4. · 8.65 Impact Factor
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ABSTRACT: The role of the replication error-positive (RER+) phenotype in the development of specific subtypes of sporadic ovarian carcinomas was examined by screening for the presence of microsatellite instability (MI) in 47 tumors. The overall frequency of ovarian MI was 17% only. However, MI occurred in 50% of the ovarian endometrioid-type tumors, which was significantly more often than in all the other histological subtypes combined (8%). Five of the 8 RER+ tumors exhibited most marked type I instability, possibly representing a different mechanism than for the remaining type 2 tumors. The cDNA of the mutation suppression gene hMSH2, the gene most often associated with MI, was screened for alterations in 8 MI-positive and 5 MI-negative ovarian tumors. Only 3 changes were found. Complete loss of hMSH2 mRNA expression was detected in I tumor, while another expressed only an abnormal transcript containing a deletion of exon 3. One additional RER+ serous adenocarcinoma contained a rare polymorphism with a non-conservative amino acid change. One of 8 RER+ tumors showed loss of heterozygosity at the hMSH2 loci. Genetic instability, caused in part by alterations in the hMSH2 gene, may play an important role in the sporadic endometrioid subtype of ovarian tumors. Other mutator-phenotype genes may be responsible for the remaining cases of RER+ ovarian tumors.International Journal of Cancer 01/1996; 64(6):361-6. · 6.20 Impact Factor
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ABSTRACT: The phenotypic variability of epithelial ovarian neoplasms correlates with a diversity of changes at the molecular level. Invasive serous and undifferentiated ovarian carcinomas are characterized by p53 mutations with p53 protein accumulation, extensive loss of genetic material of chromosome 17 and complex changes on many other chromosomes, e.g. amplification of oncogenes. These alterations are seen only in a minority of mucinous and endometrioid carcinomas, mainly in advanced stages. Overexpression of bcl-2 is seen most frequently in endometrioid carcinomas (ca. 90% of cases), which in addition show microsatellite instability in around a third of the cases, as has been described in endometrioid endometrial carcinomas. KRAS mutations are characteristic for mucinous LMP tumors and mucinous carcinomas (40-50% of cases) and are also found in a third of serous LMP tumors. In addition, serous LMP tumors show mild microsatellite instability in 30%. However, complex chromosomal aberrations are never seen in these neoplasms.Histology and histopathology 02/1999; 14(1):269-77. · 2.28 Impact Factor