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

ROSA, FRANCISCO D; CELÍA, ALEJANDRO; VIRGINILLIO, M; COSTAS, MÓNICA A; LIRA, MARÍA CECILIA; AZURMENDI, PABLO; SAMBRESQUI, A; SALAZAR, CECILIA; PANELO, LAURA C; PAZ, L; PALMITANO, JB; RUBIO, MARÍA FERNANDA

Mar del Plata

Congreso; LXI REUNIÓN ANUAL DE LA SOCIEDAD ARGENTINA DE INVESTIGACIÓN CLÍNICA (SAIC); 2016

Sociedad Argentina de Investigación Clínica (SAIC)

Colorectal cancer CRC is one of the most commonly diagnosed cancers with high prevalence. Our group studies the role of RAC3 coactivator in tumor development and previously demonstrated that RAC3 overexpression contributes to cell proliferation, inhibition of apoptosis and autophagy. The aim of this study was to evaluate the RAC3 expression levels in different CRC cell lines and determine their sensitivity to chemotherapeutic drugs. The expression levels of RAC3 were determined by qPCR and Western blot in three human CRC cell lines HT29, HCT116 and LoVo. RAC3 expression was higher in HT29> HCT116> LoVo (44> 9.6> 1-fold respect LoVo by qPCR). Once characterized the RAC3 expression levels, we studied sensitivity to drugs used to treat CRC such as 5-fluorouracil (5FU 0-200 mM) and oxaliplatin (Oxa 0-100 mM). Cell viability was determined by crystal violet 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 LoVo 0.62±0.2 mM;5FU:EC50 HCT116 4.5±0.6 mM, LoVo: 0.62±0.2 mM, HT29 did not respond to treatment with 5FU in the doses used. We observed that LoVo were more sensitive to treatment with these drugs. To study whether sensitivity observed in the different CRC lines was due to the expression levels of RAC3, the HCT116 cell line was transfected with a shRNA for RAC3 (shRAC3) and performed qPCR to validate the knockdown efficiency (shRAC3 0.08-fold respect HCT116 control). Compared to the control, the shRAC3-transfected group displayed significantly decreased viability (5FU:control 4.5±0.6 mM vs shRAC3 2.4±0.2 mM and Oxa:control 0.6±0.3 mM vs shRAC3 0.18±0.1 mM). In conclusion, our results show that the expression levels of RAC3 influence sensitivity to chemotherapeutic drugs. Therefore, the knowing of the RAC3 expression levels in tumoral samples could be probably important in order to design new improved therapeutic strategies.