Inhibition of enhancer of zeste homolog 2 (EZH2) expression is associated with decreased tumor cell proliferation, migration, and invasion in endometrial cancer cell lines.

OBJECTIVE: To investigate the impact of enhancer of zeste homolog 2 (EZH2) expression on endometrial cancer cell line behavior. MATERIALS AND METHODS: Enhancer of zeste homolog 2 expression levels were compared between the nonmalignant endometrial cell line T-HESC and 3 endometrial cancer cell lines, ECC-1, RL95-2, and HEC1-A. Stable EZH2 knockdown cell lines were created, and the impact on cellular proliferation, migration, and invasion were determined. Fluorescent activated cell sorting was used to examine effects of EZH2 silencing on cell cycle progression. Enhancer of zeste homolog 2 expression in endometrial cancer tissue specimens was examined using immunohistochemistry. Comparison of differences between control and short-hairpin EZH2 cell lines was performed using the Student t test and the Fischer exact test. RESULTS: Enhancer of zeste homolog 2 protein expression was increased in all 3 cancer cell lines and human endometrial cancer tissue specimens relative to control. RNA interference of EZH2 expression in ECC-1, RL95-2, and HEC1-A significantly decreased cell proliferation, migration, and invasion. Down-regulation of EZH2 expression resulted in a significant increase in the proportion of cells arrested in the G2/M phase. RNA interference of EZH2 expression was associated with an increase in the expression of Wnt pathway inhibitors sFRP1 and DKK3 and a concomitant decrease in ß-catenin. Enhancer of zeste homolog 2 expression in human tissue samples was significantly associated with increased stage, grade, depth of invasion, and nodal metastasis. CONCLUSIONS: Enhancer of zeste homolog 2 expression is associated with tumor cell proliferation, migration, and invasion in 3 endometrial cancer cell lines as well as with increased stage, grade, depth of invasion, and nodal metastasis in human cancer tissue specimens. Further investigation into this potential therapeutic target is warranted.

Diagnosing colorectal medullary carcinoma: interobserver variability and clinicopathological implications.

Colorectal medullary carcinoma, recognized by the World Health Organization as a distinct histologic subtype, is commonly regarded as a specific entity with an improved prognosis and unique molecular pathogenesis. A fundamental but as yet unaddressed question, however, is whether it can be diagnosed reproducibly. In this study, by analyzing 80 colorectal adenocarcinomas whose dominant growth pattern was solid (thus encompassing medullary carcinoma and its mimics), we provided a detailed description of the morphological spectrum from "classic medullary histology" to nonmedullary poorly differentiated histologies and demonstrated significant overlapping between categories. By assessing a selected subset (n=30) that represented the spectrum of histologies, we showed that the interobserver agreement for diagnosing medullary carcinoma by using 2010 World Health Organization criteria was poor; the κ value among 5 gastrointestinal pathologists was only 0.157 (95% confidence interval, 0.127-0.263; P=.001). When we arbitrarily classified the entire cohort into "classic" and "indeterminate" medullary tumors (group 1, n=19; group 2, n=26, respectively) and nonmedullary poorly differentiated tumors (group 3, n=35), groups 1 and 2 were more likely to exhibit mismatch repair protein deficiency than group 3 (P<.001); however, improved survival could not be detected in either group compared with group 3. Our findings suggest that the diagnosis of medullary carcinoma, as currently applied, may only serve as a morphological descriptor indicating an increased likelihood of mismatch-repair deficiency. Additional evidence including a more objective classification system is needed before medullary carcinoma can be regarded as a distinct entity with prognostic relevance. Until such evidence becomes available, caution should be exercised when making this diagnosis, as well as when comparing results across different studies.