RESUMO
Objective: The reverse of chemoresistance and the improvement of sensitivity to chemotherapeutic agents of colorectal cancer cells have great clinical significance and the mechanism underlying the drug resistance is still unclear. REG Iα was reported to be upregulated in colorectal cancer tissues, but the roles of chemoresistance are still unclear. Materials and Methods: The expression of REG Iα in colorectal cancer cell lines was assessed by quantitative real-time polymerase chain reaction (Q-PCR). The expression of REG Iα in HCT116 and LOVO cells was knockdown by siRNA. The cell viability and IC50 (half maximal inhibitory concentration) values were analyzed by the CCK8 assay. The proportion of apoptosis and cell cycles were analyzed by flow cytometry. The migration potency of HCT116 and LOVO cells was analyzed by cell migration assay. The protein level of Cyclin D1, CDK4 (cyclin-dependent kinase 4), Bax and Bcl-2 were analyzed by western blot. Results: Knockdown of REG Iα enhances the sensitivity to 5-Fu of colorectal cancer cells. REG Iα knockdown promoted the cell apoptosis of HCT116 and LOVO under the 5-Fu treatment. The cell migration and cycle of colorectal cancer cells was also inhibited by REG Iα knockdown. We also found that REG Iα knockdown induced cell cycle arrest and cell apoptosis by Cyclin D1/CDK4 pathway and BAX/BCL-2 pathways. Conclusions: Knockdown of REG Iα enhances the sensitivity to 5-Fu of colorectal cancer cells via cyclin D1/CDK4 pathway and BAX/BCL-2 pathways.
Assuntos
Neoplasias Colorretais/tratamento farmacológico , Ciclina D1/metabolismo , Quinase 4 Dependente de Ciclina/metabolismo , Fluoruracila/farmacologia , Litostatina/antagonistas & inibidores , Proteínas Proto-Oncogênicas c-bcl-2/metabolismo , Proteína X Associada a bcl-2/metabolismo , Antimetabólitos Antineoplásicos/farmacologia , Apoptose , Ciclo Celular , Movimento Celular , Proliferação de Células , Neoplasias Colorretais/metabolismo , Neoplasias Colorretais/patologia , Ciclina D1/genética , Quinase 4 Dependente de Ciclina/genética , Resistencia a Medicamentos Antineoplásicos , Regulação Neoplásica da Expressão Gênica , Humanos , Litostatina/genética , Litostatina/metabolismo , Proteínas Proto-Oncogênicas c-bcl-2/genética , Células Tumorais Cultivadas , Proteína X Associada a bcl-2/genéticaRESUMO
REG (Regenerating gene) Ialpha protein functions as a growth factor for gastrointestinal cancer cells, and its mRNA expression is strongly associated with a poor prognosis in gastrointestinal cancer patients. We here demonstrated that PPARgamma-agonist thiazolidinediones (TZDs) inhibited cell proliferation and REG Ialpha protein/mRNA expression in gastrointestinal cancer cells. TZDs inhibited the REG Ialpha gene promoter activity, via its cis-acting element which lacked PPAR response element and could not bind to PPARgamma, in PPARgamma-expressing gastrointestinal cancer cells. The inhibition was reversed by co-treatment with a specific PPARgamma-antagonist GW9662. Although TZDs did not inhibit the REG Ialpha gene promoter activity in PPARgamma-non-expressing cells, PPARgamma overexpression in the cells recovered their inhibitory effect. Taken together, TZDs inhibit REG Ialpha gene transcription through a PPARgamma-dependent pathway. The TZD-induced REG Ialpha mRNA reduction was abolished by cycloheximide, indicating the necessity of novel protein(s) synthesis. TZDs may therefore be a candidate for novel anti-cancer drugs for patients with gastrointestinal cancer expressing both REG Ialpha and PPARgamma.
