Immunohistochemistry for hMLH1 and hMSH2: A Practical Test for DNA Mismatch Repair-Deficient Tumors

Abstract

Inactivation of deoxyribonucleic acid (DNA) mismatch repair genes, most commonly human mutL homologue 1 (hMLH1) or human mutS homologue 2 (hMSH2), is a recently described alternate pathway in cancer development and progression. The resulting genetic instability is characterized by widespread somatic mutations in tumor DNA, and is termed high-frequency microsatellite instability (MSI-H). Although described in a variety of tumors, mismatch repair deficiency has been studied predominantly in colorectal carcinoma. Most MSI-H colorectal carcinomas are sporadic, but some occur in patients with hereditary nonpolyposis colorectal cancer (HNPCC), and are associated with germline mutations in mismatch repair genes. Until now, the identification of MSI-H cancers has required molecular testing. To evaluate the role of immunohistochemistry as a new screening tool for mismatch repair-deficient neoplasms, the authors studied the expression of hMLH1 and hMSH2, using commercially available monoclonal antibodies, in 72 formalin-fixed, paraffin-embedded tumors that had been tested previously for microsatellite instability. They compared immunohistochemical patterns of 38 MSI-H neoplasms, including 16 cases from HNPCC patients with known germline mutations in hMLH1 or hMSH2, with 34 neoplasms that did not show microsatellite instability. Thirty-seven of 38 MSI-H neoplasms were predicted to have a mismatch repair gene defect, as demonstrated by the absence of hMLH1 and/or hMSH2 expression. This included correspondence with all 16 cases with germline mutations. All 34 microsatellite-stable cancers had intact staining with both antibodies. These findings clearly demonstrate that immunohistochemistry can discriminate accurately between MSI-H and microsatellite-stable tumors, providing a practical new technique with important clinical and research applications.

Reduced Fhit expression is associated with mismatch repair deficiency in human advanced colorectal carcinoma

“…In addition, it was reported that sporadic CRCs with MSI were more frequent in the poorly differentiated phenotype (Ward et al, 2001). In our study, the ratio of poorly differentiated CRCs was high compared with previous reports (Kinzler and Vogelstein, 1996;Marcus et al, 1999;Ward et al, 2001). Therefore, high frequency of abnormal MMR protein expression might be mainly due to the different distributions of histological differentiation.…”

“…MMR deficiency is present in 10 -15% of sporadic CRCs (Kinzler and Vogelstein, 1996), and is the underlying cause of more than 90% of HNPCC (Peltomaki and Vasen, 1997). Previous studies demonstrated that immunohistochemical analysis of the expression of Mlh1 and Msh2 could be an accurate and rapid screening procedure for the identification of MMR gene alterations (Thibodeau et al, 1996;Marcus et al, 1999). We found abnormal Mlh1 or Msh2 expression in 21 of the 52 (46%) CRCs using immunohistochemical methods.…”

“…This frequency of abnormal MMR protein expression was more frequent than that observed in CRC by other investigators (Kinzler and Vogelstein, 1996). In the assessment of MMR protein expression, we used almost the same criteria used by other groups (Marcus et al, 1999;Ward et al, 2001). In addition, it was reported that sporadic CRCs with MSI were more frequent in the poorly differentiated phenotype (Ward et al, 2001).…”

“…Most sporadic CRCs with MSI have been demonstrated to be caused by somatic hypermethylation of the MLH1 promoter region, resulting in the downregulation of MLH1 gene expression (Herman et al, 1998). Recent data have revealed that immunohistochemistry is an accurate screening technique to identify MMR deficient tumours (Thibodeau et al, 1996;Marcus et al, 1999).…”

Cytoplasmic phospholipase A2 alpha overexpression in stromal cells is correlated with angiogenesis in human colorectal cancer

“…We also assessed microsatellite instability by immunohistochemical evaluation of hMLH1 and hMSH2 protein expression. This method was shown to be sensible and specific 27 (anti-human MLH1 monoclonal antibody, clone G168-728, 1/70, BD Pharmigen, and anti-human MSH2 monoclonal antibody, clone FE-11, 1/100, oncogene research products). Indeed, a loss of hMLH1 or hMSH2 protein expression was observed in all the carcinomas with microsatellite instability and in none of the others.…”