Molecular Insights into Endometrial Cancer in Mice.

Pluripotent, very small embryonic-like stem cells (VSELs) and the 'progenitors' endometrial stem cells (EnSCs) along with associated molecular changes in endometrial cancer, that developed seven months after neonatal exposure to estradiol in one of the sixty mice, were studied in the present study. Endocrine disruption affected both endometrium and myometrium, there was accumulation of endometrial fluid and significant hyperplasia. Disrupted endometrial-myometrial junction resulted in mobilization of myometrial cells into endometrium and epithelial and stromal cells into myometrium suggestive of adenomyosis. Markers specific for VSELs/ EnSCs (OCT-4, NANOG, SSEA-1, SCA-1, c-KIT) showed increased expression in uterine sections and marked upregulation of corresponding transcripts (Oct-4A, Oct-4, Sox-2, Nanog, Sca-1, c-Kit) was noted in RNA extracted from both uterine tissue and stem cells enriched from endometrial fluid. Hormonal receptors (ER-α, ER-β, PR, FSHR) were upregulated in both tumor sections and in endometrial fluid. ER-β and FSHR (Fshr3) expression was prominent suggesting a major role in endometrial cancer. Cancer cells showed global hypomethylation (reduced expression of 5-methyl cytosine), reduced expression of tumor suppressor gene (PTEN) and increased expression of cancer stem cells marker (CD166) which suggested dysregulation and aberrant oncogenic events. Increased expression of PCNA, Ki67, SOX-9 suggested excessive proliferation and hyperplasia which are predominant signs of endometrial cancer. Results suggest that VSELs increase in numbers and possibly transform into cancer stem cells (co-express CD166 and OCT-4) in endometrial cancer. Expression of OCT-4, CD133, ALDHA1 and CD166 in side-population cells from human endometrial cancer samples suggests a possible role of VSELs in human endometrial cancer as well.