High RAC3 expression levels are required for induction and maintaining of cancer cell stemness

MILENI SOARES MACHADO; MARÍA CECILIA LIRA; ELBA SUSANA VÁZQUEZ; LAURA CAROLINA PANELO; MARÍA FERNANDA RUBIO; ALEJANDRO JORGE URTREGER; FELIPE MARTIN JAWORSKI; FRANCISCO DAMIÁN ROSA; MÓNICA ALEJANDRA COSTAS

Cdad Autonoma de Buenos Aires

Congreso; Segunda Reunión Conjunta de Sociedades de BioCiencias; 2017

Sociedad Argentina de Investigación Clínica (SAIC)

RAC3 is a transcription coactivator, usually overexpressed in several tumors and required to maintain the pluripotency in normal stem cells. Although its involvement in tumor development has been amply investigated its potential role inducing or maintaining cancer cell stemness has not been determined. In this work we studied the association between RAC3 overexpression and cancer cell stemness and the capacity of this protein to induce cancer stem properties in non tumoral cells. We performed in vitro and in vivo experiments using two strategies: by overexpressing RAC3 in the non tumoral cell line HEK293 by transfection with a RAC3 expression vector and by silencing RAC3 in the human colorectal epithelial cell line HCT116 with a specific shRAC3. Furthermore, we analyzed public repository microarrays data from 19 human colorectal tumors in different developmental stages. In the microarrays analysis, we found that RAC3 overexpression was mainly associated to early and advanced stages of colon cancer, involving increased expression of RAC3, Vimentin, cMYC, OCT4 and Nanog mRNA. In turn, RAC3 silencing in HCT116 induced diminished tumoral properties and cancer stem cells (CSC) as determined by Hoechst efflux, tumorspheres and clonogenic growth, which correlated with decreased Nanog and OCT4 expression. Moreover, RAC3 overexpression was mainly associated to CD133+ side population. In non tumoral cells, RAC3 overexpression induced tumoral transformation; mesenchymal phenotype, migration, invasion, metalloproteinases production, proliferation under low serum, clonogenic tumorspheres growth, OCT4 and Nanog expression. Moreover, these transformed cells generated tumors in vivo. Our results demonstrate that RAC3 is associated to cancer stem phenotype not only maintaining the stemness in cancer cells, but also inducing cancer stem like cells by overexpression in non tumoral cells.