Altered expression of hMLH1 and hMSH2 protein in endometrial carcinomas with microsatellite instability.
Microsatellite instability (MI) has been observed in approximately 20% of presumably sporadic cases of uterine endometrioid carcinoma (UEC). A previous mutational analysis of the 4 known DNA mismatch repair genes (hMSH2, hMLHI, hPMS1, and hPMS2) on a small number of Ml-positive tumors detected mutations in only 2 of 8 cases, both in hMSH2. To further explore the underlying cause of MI in UEC, we analyzed the protein expression of hMSH2 and hMLHI in UEC of known MI status. Formalin-fixed, paraffin-embedded archival tissue from 21 UECs was analyzed by immunoperoxidase staining with monodonal antibodies against hMLH1 and hMSH2 protein. Tumors were evaluated for presence of nuclear staining by 3 investigators. Lack of nuclear hMLHI staining was found in 7 of 13 carcinomas with MI, but in none of 8 carcinomas without MI (Fischer's exact, 0.018). Lack of nuclear hMSH2 staining was found in 3 of the MI-positive cases, but none of the MI-negative cases (not statistically significant). Taken together, lack of nuclear staining of either hMLH1 or hMSH2 was found in 9 of 13 cases with MI and in none of 8 cases without MI (Fischer's exact, 0.005). We conclude that MI in sporadic UEC appears to be associated with lack of expression of either hMLH1 or hMSH2, suggesting that inactivation of these genes may be responsible for MI in most MI-positive sporadic UECs.
Staebler
A
A
Department of Pathology, Johns Hopkins Medical Institutions, Baltimore, MD, USA.
Lax
S F
SF
Ellenson
L H
LH
D048868:Adaptor Proteins, Signal Transducing; D020137:Base Pair Mismatch; D018269:Carcinoma, Endometrioid / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D002352:Carrier Proteins; D002467:Cell Nucleus / Q000378:metabolism / Q000473:pathology; D004268:DNA-Binding Proteins; D016889:Endometrial Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D005260:Female; D006801:Humans; D007124:Immunoenzyme Techniques; D018895:Microsatellite Repeats / Q000235:genetics*; D000070957:MutL Protein Homolog 1; D051718:MutS Homolog 2 Protein; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism*; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*
D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; C501486:MLH1 protein, human; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins; C497172:MSH2 protein, human; D000070957:MutL Protein Homolog 1; D051718:MutS Homolog 2 Protein