S100A4/non-muscle myosin II signaling regulates epithelial-mesenchymal transition and stemness in uterine carcinosarcoma.

Uterine carcinosarcoma (UCS) represents a true example of cancer associated with epithelial-mesenchymal transition (EMT), which exhibits cancer stem cell (CSC)-like traits. Although S100A4 is an inducer of EMT, little is known about its involvement in UCS tumorigenesis. Herein, we focused on the functional role of S100A4 during development of UCS. Expression of S100A4 and molecules associated with its function were also examined in 35 UCS cases. In endometrial carcinoma cell lines, S100A4 promoter activity and mRNA levels were significantly increased by the transfection of NF-κB/p65, independent of a putative κB-binding site in the promoter. Cells stably overexpressing S100A4 showed enhancement of CSC properties, along with decreased cell proliferation and acceleration of cell migration. These phenotypes were abrogated in S100A4-knockdown cells. A combination of S100A4 antibody-mediated co-immunoprecipitation and shotgun proteomics analysis revealed that S100A4 strongly interacted with non-muscle myosin II (NMII) heavy chains, including myosin 9 and myosin 14. Specific inhibition of NMII by blebbistatin phenocopied S100A4 overexpression and induced a fibroblast-like morphology. In clinical samples, S100A4 score was significantly higher in sarcomatous as compared with carcinomatous components of UCS, and was positively correlated with ALDH1, Slug, and vimentin scores, and inversely with Ki-67 labeling indices. These findings suggest that an S100A4/NMII-related signaling cascade may contribute to the establishment and maintenance of EMT/CSC properties, along with changes in cell proliferation and migration capability. These events may be initiated in carcinomatous components in UCS and lead to divergent sarcomatous differentiation.