Methylation status of multidrug resistance (mdr1) gene and its correlation with expression of mdr1 gene in patients with hematologic malignancies / 中国实验血液学杂志

ABSTRACT

To investigate the correlation between methylation and expression of multidrug resistance (mdr1) gene, restriction endonuclease HpaII combined with competitive PCR technique was used to quantitatively detect the methylation status of two CCGG sites located at -110 and -50 bp (region I and II) up to the transcription start site in mdr1 promoter in 54 AL and 9 MM patients. Semi-quantitative RT-PCR was used to detect the expression level of mdr1 gene. The results showed that inverse correlation between methylation rate of either region or total methylation rate and expression of mdr1 gene was observed. The correlation in the region I (r = -0.64) was closer than that in the region II (r = -0.4). High expression rate of mdr1 ascended significantly in low methylation group (n = 36) (P < 0.001). In comparison with chemotherapy sensitive group (n = 8), the methylation rate in refractory AL patients (n = 16) was lower (P = 0.05) in the region I, P < 0.05 in the region II and total regions. Comparing with the untreated patients (n = 36), the methylation rate in the region I and total methylation rate were lower in the patients with chemotherapy (n = 14) (P < 0.05). The methylation rate in the region II was also decreased after chemotherapy, however, no statistical significance was shown (P > 0.05). Increased mdr1 expression level accompanying with decreased methylation rate after chemotherapy was found, although no significant difference was shown (P = 0.06). It is concluded that the expression level of mdr1 gene was associated with the methylation status of CCGG in -110 and -50 bp upstream to the transcription start site, especially the -110 site. In both the patients treated with chemotherapy and the refractory patients, the methylation level of mdr1 gene decreased relatively. The rising expression of mdr1 gene after chemotherapy was associated with the decrease of methylation level.