Promoter hypermethylation contributes to TIMP 3 down‐regulation in high stage endometrioid endometrial carcinomas

Aims Expression of tissue inhibitor of metalloproteinases‐3 ( TIMP ‐3) has been found to be decreased in several types of cancer by promoter gene hypermethylation. However, little is known regarding the silencing effect of TIMP 3 promoter hypermethylation on gene and protein expression in endometrial carcinomas and its prognostic significance.Methods and resultsTIMP 3 promoter hypermethylation and gene copy number variations were evaluated using a methylation‐specific multiplex ligation‐dependent probe amplification approach in 60 cases of endometrioid endometrial carcinomas. TIMP 3 expression was also evaluated at the transcript and protein levels. Loss of TIMP ‐3 protein expression was found in 44 (73%) of 60 carcinomas. Promoter hypermethylation was identified in 25% (15 of 60); was more frequent in stages II – IV (55%, six of 11) than in stage I (18%, nine of 49; P  =   0.021); and was found more commonly in tumours with deep myometrial invasion. MLH 1 and TIMP 3 promoters were hypermethylated simultaneously in the same group of tumours ( P  <   0.001). A correlation between TIMP 3 methylation and microsatellite instability ( MSI ) was found ( P  =   0.005). TIMP 3 copy number changes were frequently a loss (35%), whereas a gain was detected in only 5%.ConclusionsTIMP 3 promoter hypermethylation was associated with high stage endometrioid endometrial tumours with extrauterine spread. Nevertheless, promoter hypermethylation and loss of heterozygosity are not the only mechanisms for TIMP 3 inactivation.