Brief report p16INK4a and p15INK4b gene methylations in plasma cells from monoclonal gammopathy of undetermined significance

p15INK4b and p16INK4a proteins are cell cycle regulators involved in the inhibition of G1 phase progression. High frequency of methylation of both genes has been reported in multiple myeloma (MM), but it remains to be determined how and when these alterations contribute to tumorigenesis. Monoclonal gammopathy of undetermined significance (MGUS) represents an early disease stage in a fraction of MMs. Plasma cells from 33 patients with MGUS and 33 patients with MM were isolated and analyzed for p15INK4b and p16INK4a methylation by methylation-specific polymerase chain reaction. Selective methylation was found in 19% for p16INK4a, 36% for p15INK4b, and 6.5% for both genes in MGUS, and frequencies were similar in MM suggesting that methylation of these genes is an early event, not associated with transition from MGUS to MM. p15INK4b and p16INK4a gene methylation might contribute to immortalization of plasma cells rather than malignant transformation in the natural history of MM. (Blood. 2001;98:244-246)