Decreased expression levels of RAC3 coactivator sensitizes colorectal cancer cells to the effect of chemotherapeutic drugs

LIRA, M C; ROSA, F D; PANELO L.C.; AZURMENDI P; CELÍA A. F.; PAZ L.; SAMBRESQUI A; VIRGINILLO M; PALMITANO J; SALAZAR C; COSTAS M A; RUBIO M F

Mar del Plata, Buenos Aires

Congreso; LXI Reunión Anual SAIC; 2016

Sociedad Argentina de Investigación Clìnica

Colorectal cancer (CRC) is one of the most commonly diagnosedcancers with high prevalence. Our group studies the roleof RAC3 coactivator in tumor development and previously demonstratedthat RAC3 overexpression contributes to cell proliferation,inhibition of apoptosis and autophagy. The aim of this studywas to evaluate the RAC3 expression levels in different CRC celllines and determine their sensitivity to chemotherapeutic drugs.The expression levels of RAC3 were determined by qPCR andWestern blot in three human CRC cell lines (HT29, HCT116 andLoVo). RAC3 expression was higher in HT29> HCT116> LoVo(44> 9.6> 1-fold respect LoVo by qPCR). Once characterizedthe RAC3 expression levels, we studied sensitivity to drugs usedto treat CRC such as 5-fluorouracil (5FU 0-200 mM) and oxaliplatin(Oxa 0-100 mM). Cell viability was determined by crystalviolet staining and the EC50 was calculated for each cell type(Oxa: EC50 HT29 0.85±0.2 mM, HCT116 0.6±0.3 mM and LoVo0.05±0.02 mM; 5FU: EC50 HCT116 4.5±0.6 mM, LoVo 0.62±0.2mM, HT29 did not respond to treatment with 5FU in the dosesused). We observed that Lovo were more sensitive to treatmentwith these drugs. To study whether sensitivity observed in thedifferent CRC lines was due to the expression levels of RAC3,the HCT116 cell line was transfected with an shRNA for RAC3(shRAC3) and performed qPCR to validate the knockdown efficiency(shRAC3 0.08-fold respect HCT116 control). Comparedto the control, the shRAC3-transfected group displayed significantlydecreased viability (5FU: control 4.5±0.6 mM vs shRAC32.4±0.2 mM and Oxa: control 0.6±0.3 mM vs shRAC3 0.18±0.1mM). In conclusion, our results show that the expression levels ofRAC3 influence sensitivity to chemotherapeutic drugs. Therefore ,the knowing of the RAC3 expression levels in tumoral samplescould be probably important in order to design new improvedtherapeutic strategies.