RESUMO
Ribonucleotide reductase catalyzes the rate limiting step of deoxyribonucleotide formation, a crucially important step in DNA synthesis and repair. The regulatory subunit M1 of ribonucleotide reductase (RRM1) is the necessary part of the RR function and controls substrate specificity and global on/off enzyme activity. Despite recent research progress, the role of RRM1 in lung cancer sensitivity to chemotherapeutics remains to be elucidated. This study was to investigate the relationship between polymorphisms of the RRM1 gene and sensitivity to platinum-based chemotherapy in non-small cell lung cancer (NSCLC). Genomic DNA samples from 214 NSCLC patients treated with platinum-based chemotherapy were used to determine the RRM1 promoter allelotypes. The RR37CC-RR524TT was the most frequent allelotype (38.50%), followed by RR37AC-RR524CT (26.76%) and RR37CC-RR524CT (14.95%). The average response rate for chemotherapy was 44.4%. The response rates to the treatment regimens in the RR37CC-RR524TT, RR37AC-RR524CT and RR37CC-RR524CT allelotypes were 43.9%, 52.6%, and 51.6%, respectively. The response rates to therapy among patients with RRM1 (-)524 allelotypes were significantly different (p=0.046), whereas that among patients with RRM1 (-)37 allelotypes were not significant. Further analysis showed that the response rate in the patients with RR524CT allelotype (52.3%) was the highest, compared with that with RR37CC-RR524TT allelotype (43.9%, p=0.28), or the Others (RR524CC and RR37AC-RR524TT, 30.2%, p=0.02). Our results suggest that the RR524CT allelotype may be associated with an increased sensitivity to platinum-based chemotherapy in NSCLC. Further research on determining RR524CT as a clinical marker for predicting response to platinum-based therapy in NSCLC patients is warranted.
Assuntos
Carcinoma Pulmonar de Células não Pequenas/tratamento farmacológico , Carcinoma Pulmonar de Células não Pequenas/genética , Resistencia a Medicamentos Antineoplásicos/genética , Neoplasias Pulmonares/tratamento farmacológico , Neoplasias Pulmonares/genética , Polimorfismo Genético , Proteínas Supressoras de Tumor/genética , Adulto , Idoso , Biomarcadores Farmacológicos/metabolismo , Carcinoma Pulmonar de Células não Pequenas/patologia , Feminino , Testes Genéticos , Humanos , Neoplasias Pulmonares/patologia , Masculino , Pessoa de Meia-Idade , Estadiamento de Neoplasias , Compostos de Platina/uso terapêutico , Ribonucleosídeo Difosfato Redutase , Proteínas Supressoras de Tumor/metabolismoRESUMO
BACKGROUND: Aberrant DNA methylation plays a key role in human carcinogenesis. 5-aza-2'-deoxycytidine inhibits DNA methylation and induces the expression of genes putatively silenced by promoter methylation in vitro. There are few studies of the biological and clinical significance of 5-aza-2'-deoxycytidine in human hepatocellular carcinoma. This study explored the mechanism of 5-aza-2'-deoxycytidine targeting transcriptional repressor complexes affecting global gene expression in hepatocellular carcinoma cell line. METHODS: High density oligonucleotide gene expression microarrays were used to examine the effects of 5-aza-2'-deoxycytidine treatments on human hepatocellular carcinoma cell line SMMC-7721. The 5' ends of the genes upregulated or downregulated in this manner were compared with BLAST database to determine whether they might have promoter CpG islands. Flow cytometry was used to detect stages of the cell cycle and apoptosis of SMMC-7721 after being treated with 5-aza-2'-deoxycytidine. RESULTS: Data obtained 3 days after 4 days of treatment with 5-aza-2'-deoxycytidine showed that more genes were induced in tumorigenic cells including genes that function in cell proliferation, differentiation, regulation of transcription, and cytokine signalling. Approximately 30% of induced genes did not have CpG islands within their 5' regions, suggesting that some genes activated by 5-aza-2'-deoxycytidine may not result from the direct inhibition of promoter methylation. This phenomenon may contribute to a number of upregulated genes involving regulation of transcription in the treated cell. Results showed that 100 micromol/L 5-aza-2'-deoxycytidine blocked cell cycle at S/G2-M phase increasing rate of apoptosis. Notably, we found differential expression of molecular action in the methylation although DNA methyltransferases did not show significant difference in the treated cell line. CONCLUSION: 5-aza-2'-deoxycytidine could restore some silenced genes expression independently of DNA methylation inhibition and expression of DNA methyltransferases.
