RESUMO
Resveratrol (RES), a polyphenol compound with antiproliferative properties, has been previously evaluated for its beneficial effects against a variety of tumour cells. The current study elucidated the means by which RES enhances the antiproliferative effects of cisplatin (CIS) on MCF7 cells, focusing on the inhibitory effects on DNA repair of doublestrand breaks (DSBs). Chemoresistant MCF7 cells (MCF7R) were generated by continuous exposure to low concentrations of CIS (10 µM CISIC40) during 5 passages, with the IC50 value increasing ~3fold. Using an MTT assay, we estimated the changes in IC50 for CIS in MCF7, T47D, MDAMB231 and MCF7R cells in the presence of RES. The relative transcript level of Nbs1, Mre11 and Rad50 genes was assessed using RTqPCR analysis. Rad51 and H2AX [pSer139] protein expression was determined by western blot analysis. RES at 50 and 100 µM significantly enhanced the antiproliferative effects of CIS in both MCF7 and MCF7R cells, decreasing the IC50 values for CIS to onetenth and onesixth, respectively. A total of 100 µM RES decreased the relative transcript levels of homologous recombination (HR) initiation complex components and the Rad51 protein level in MCF7 and MCF7R cells. After 48 h of CIS DNA damage, the levels of Rad51 protein increased, but this effect was inhibited by 100 µM RES. RES also maintained serine 139 phosphorylation of histone H2AX, suggesting that RES prevents the repair of DSBs. It was observed that RES exerts an antagonistic effect over CIS on the activation of Rad51 and sustained phosphorylation of H2AX. The results suggest that RES in combination with DNA damagebased therapy has potential as a strategy to overcome resistance and provide much safer and more effective treatment for breast cancer.
Assuntos
Neoplasias da Mama/genética , Cisplatino/farmacologia , Regulação para Baixo , Resistencia a Medicamentos Antineoplásicos/efeitos dos fármacos , Rad51 Recombinase/genética , Estilbenos/farmacologia , Neoplasias da Mama/tratamento farmacológico , Neoplasias da Mama/metabolismo , Linhagem Celular Tumoral , Feminino , Perfilação da Expressão Gênica , Regulação Neoplásica da Expressão Gênica/efeitos dos fármacos , Histonas/metabolismo , Humanos , Células MCF-7 , Fosforilação/efeitos dos fármacos , Rad51 Recombinase/metabolismo , ResveratrolRESUMO
It is well known that vitamin A and its receptors protect against cancer development and that Retinoid Acid Receptor ß (RARß) is epigenetically silenced during tumoral progression. Cervical Cancer (CC) has been causally linked to high risk human papillomavirus (HR-HPV) infection. However, host factors are important in determining the outcome of persistent HR-HPV infection as most cervical precancerous lesions containing HR-HPVs do not progress to invasive carcinomas. Increasing evidence suggests that low diet in vitamin A and their receptors participate in the development of CC. The aim of this study has been to investigate the effects of abated RARß expression in the development of cervical premalignant lesions in 4 month-old conditional mice (RARß(L-/L-)). Results demonstrated the development of spontaneous squamous metaplasia, inflammatory infiltrate, enhanced mitotic activity, loss of cell differentiation, as well as decreased apoptosis and p16(INK4a) protein levels in RARß(L-/L-) mice cervix. All these changes are hallmarks of moderate dysplasia. Importantly, our results suggest that the low expression of RARß, may induce the down regulation of p16(INK4a), chronic inflammation and decreased apoptosis and may be involved in vulnerability to HR-HPV and early stage cervical carcinogenesis.