Global methylation and promoter-specific methylation of the P16, SOCS-1, E-cadherin, P73 and SHP-1 genes and their expression in patients with multiple myeloma during active disease and remission

Tumor suppressor gene promoter CpG island methylation is a well-recognized mechanism in cancer pathogenesis, but its role in multiple myeloma (MM) is controversial. The present study investigated the methylation status and expression of P16, suppressor of cytokine signaling 1 (SOCS-1), P73, E-cadherin and Src homology region 2 domain-containing phosphatase 1 (SHP-1), as well as global methylation in patients with MM during active disease and remission. Bone marrow samples were obtained from 43 patients at the Multiple Myeloma Clinic, Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán (Mexico City, Mexico) during active disease and remission. Methylation-specific polymerase chain reaction and ELISA were performed on bisulfite-treated or untreated DNA to determine promoter-specific or genomic methylation, respectively. Gene expression was measured using reverse-transcription polymerase chain reaction. The results indicated that SOCS-1 methylation occurred more frequently during active disease than remission [29 vs. 3.2% (P=0.021)] and was associated with more advanced forms of the disease [international staging system (ISS) 3, 16.67% vs. ISS 1, 8.3% (P=0.037)]. SHP-1 methylation during active disease was associated with a lower probability of survival at 39-month follow up (median), 52.5 vs. 87.5% (P=0.025). The percentage of methylation was associated with active disease at remission, but this was not significant. Global hypomethylation at remission was a negative predictor factor for overall survival (OS). The results indicated that methylated P16, SOCS-1 and SHP-1 were associated with clinical variables of poor prognosis in MM, likewise the persistence of global hypomethylation at remission. The negative impact on OS of global hypomethylation at remission must be confirmed in a larger sample. Future studies are necessary to investigate whether patients with global hypermethylation at remission should receive more aggressive treatments to improve their OS.