HIGH RAC3 EXPRESSION LEVELS ARE REQUIRED FOR INDUCTION AND MAINTAINING OF CANCER CELL STEMNESS.

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

Buenos Aires

Congreso; REUNIÓN CONJUNTA DE SOCIEDADES DE BIOCIENCIAS; 2017

SAIC

RAC3 is a transcription coactivator, usually overexpressedin several tumors and required to maintain thepluripotency in normal stem cells. Although its involvementin tumor development has been amply investigatedits potential role inducing or maintaining cancer cellstemness has not been determined.In this work we studied the association between RAC3overexpression and cancer cell stemness and the capacityof this protein to induce cancer stem properties in nontumoral cells.We performed in vitro and in vivo experiments using twostrategies: by overexpressing RAC3 in the non tumoralcell line HEK293 by transfection with a RAC3 expressionvector and by silencing RAC3 in the human colorectalepithelial cell line HCT116 with a specific shRAC3. Furthermore,we analysed public repository microarraysdata from 19 human colorectal tumors in different developmentalstages.In the microarrays analysis, we found that RAC3 overexpressionwas mainly associated to early and advancedstages of colon cancer (p≤0,05), involving increasedexpression of RAC3, Vimentin, cMYC, OCT4and Nanog mRNA (p≤0,05). In turn, RAC3 silencing inHCT116 induced diminished tumoral properties and cancerstem cells (CSC) as determined by Hoechst efflux,tumorspheres and clonogenic growth (p≤0,01), whichcorrelated with decreased Nanog and OCT4 expression(p≤0,05). Moreover, RAC3 overexpression was mainlyassociated to CD133+ side population (p≤0,05). In nontumoral cells, RAC3 overexpression induced tumoraltransformation; mesenchymal phenotype, migration,invasion, metalloproteinases production (p≤0,05), proliferationunder low serum (p≤0,05), clonogenic tumorspheresgrowth (p≤0,05), OCT4 and Nanog expression(p≤0,05). Moreover, these transformed cells generatedtumors in vivo.Our results demonstrate that RAC3 is associated to cancerstem phenotype not only maintaining the stemness incancer cells, but also inducing cancer stem like cells byoverexpression in non tumoral cells.