Prognostic significance of O ⁶-methylguanine DNA methyltransferase and p57 methylation in patients with diffuse large B-cell lymphomas

To evaluate whether promoter methylation is related to responsiveness for chemotherapy or clinical outcome, we performed an association analysis between methylation and clinical outcomes. Patients with nodal diffuse large B-cell lymphomas (DLBCL) at a single institute (n=44) were studied for methylation of tumor-related genes, MGMT, p15 ^INK4B, p16 ^INK4A, p16 ^INK4A, Mad2, TMS1/ASC, CASP8, and GSTP1. The clinical behavior of DLBCL after chemotherapy was followed up and analyzed. Hypermethylation of promoters of MGMT, p15 ^INK4B, p16 ^INK4A, p16 ^INK4A, Mad2, and TMS1/ASC genes was observed in 52.3%, 31.8%, 54.5%, 47.7%, 50%, and 2.3% of the cases, respectively. Methylation of CASP8 and GSTP1 genes was not observed. Promoter methylation was not related to chemo-responsiveness, disease-free survival, and progress of disease after chemotherapy. However, in overall survival analyses, MGMT methylation (p<0.05) and responsiveness to chemotherapy (p<0.01) were significant prognostic factors in patients with DLBCL. In the low-risk group, patients with p57 methylation showed longer overall survival than patients without p57 methylation (p=0.02) and all patients with p57 methylation were alive during follow-up. Our results demonstrate that aberrant promoter methylation of MGMT and p57 is an additional biological marker for predicting increased overall survival in patients with DLBCL.