Purpose: Although many articles have been published regarding chromosomal instability (CI) and microsatellite instability (MI) in endometrial adenocarcinoma, the relationship between prognostic factors and the biological mechanisms accounting for genetic instability in these tumors has not yet been precisely defined. To do that, it will be necessary to clarify the molecular mechanisms involved in endometrial carcinogenesis.
Experimental design: Tissue samples from 43 human primary endometrioid endometrial adenocarcinomas (EACs) were analyzed for CI and MI status using comparative genomic hybridization and 11 microsatellite loci, respectively. Methylation status of the promoter of MLH1 was also determined. We analyzed all three of these parameters in relation to each other and to clinicopathological factors.
Results: Sixty-five percent of the EACs we examined had detectable CI. Frequent copy number gains were seen at 1q25-41 (23%), 8q11.1-q21.1 (23%), 8q21.3-qter (21%); 28% of these tumors exhibited high-frequency MI (MSI-H); Methylation of the MLH1 promoter was observed in 92% of EACs with MSI-H. Southern blotting showed amplification of MYCN in one tumor, which has been documented for the first time in a primary human EAC.
Conclusions: MSI-H was correlated with histological grade, International Federation of Gynecologists and Obstetricians (FIGO) stage, myometrial invasion, and lymphonode metastasis. Our comparative genomic hybridization results demonstrated that the number of chromosomes involved in genomic alterations in EACs was distinctively fewer than those in other types of tumor. The carcinogenetic process leading to EAC appears to be highly complex; for example, MI and CI may act synergistically, whereas CI and/or MI are likely to be linked with tumor heterogeneity.