RESUMO
BACKGROUND: Previously, MDR1 T-129C polymorphism, encoding multidrug resistant transporter MDR1/P-glycoprotein, was reported to be predictive of poorly-differentiated colorectal adenocarcinomas. Here, VEGF T-1498C, C-634G and C-7T polymorphisms, encoding vascular endothelial growth factor (VEGF), were investigated in terms of their association with differentiation grade. METHODS: VEGF genotypes were determined by TaqMan(R) MGB probe based polymerase chain reaction and evaluated were confirmed by direct sequencing in 36 Japanese patients. RESULTS: VEGF T-1498C, but not C-634G or C-7T, was predictive of poorly-differentiated ones, and thereby a poor prognosis (p = 0.064 for genotype, p = 0.037 for allele), and this effect can be explained by that on VEGF expression. Treatment of a colorectal adenocarcinoma cell line, HCT-15, with sodium butyrate, a typical differentiating agent, resulted in an increase of alkaline phosphatase activity and MDR1 mRNA expression, but in a decrease of VEGF mRNA expression. The transfection of VEGF small interfering RNA (siRNA) induced the expression of MDR1 mRNA to 288-332% of the control level, whereas MDR1 siRNA had no effect on VEGF mRNA expression. CONCLUSIONS: VEGF T-1498C polymorphism is also a candidate marker predictive of poorly-differentiated colorectal adenocarcinomas, but further investigations with a large number of patients should be addressed to draw a conclusion.
Assuntos
Adenocarcinoma/genética , Transformação Celular Neoplásica/genética , Neoplasias Colorretais/genética , Fator A de Crescimento do Endotélio Vascular/genética , Subfamília B de Transportador de Cassetes de Ligação de ATP , Membro 1 da Subfamília B de Cassetes de Ligação de ATP/metabolismo , Adulto , Idoso , Fosfatase Alcalina/metabolismo , Povo Asiático/genética , Butiratos/farmacologia , Linhagem Celular Tumoral , Transformação Celular Neoplásica/efeitos dos fármacos , Transformação Celular Neoplásica/metabolismo , Feminino , Humanos , Japão , Masculino , Pessoa de Meia-Idade , Polimorfismo de Nucleotídeo Único , RNA Mensageiro/metabolismo , RNA Interferente PequenoRESUMO
The expression level of MDR1 mRNA was evaluated in colorectal adenocarcinomas and adjacent noncancerous colorectal tissues obtained from 21 Japanese patients. It was lower in the former than in the latter (p=0.012), suggesting its down-regulation as a consequence of malignant transformation of colorectal tissues, possibly with the suppression of differentiation. Relatively lower expression was suggested in moderately-differentiated colorectal adenocarcinomas than well-differentiated ones, but there was no statistical difference (p=0.111). MDR1 mRNA up-regulation was found in a colorectal adenocarcinoma cell line, HCT-15, after treatment with two typical differentiating agents, sodium butyrate and all-trans retinoic acid, suggesting its involvement in the cellular events, resulting in differentiation without malignant transformation. MDR1 T-129C, but not G2677A,T and C3435T, was associated with the lower expression of MDR1 mRNA both in colorectal adenocarcinomas (p=0.040) and adjacent noncancerous colorectal tissues (p=0.023), possibly being an useful invasive marker predicting poorly-differentiated colorectal adenocarcinomas and thereby the poor prognosis of the patients, especially when no extra biopsy samples will be obtained. Further investigations with relatively large number of patients should be undertaken to confirm these preliminary results.