HYPERMETHYLATION OF A 5'-CPG ISLAND OF P16 IS A FREQUENT EVENT IN NON-HODGKINS-LYMPHOMA

Hypermethylation of a 5' CpG island of p16 gene has been recently desc ribed as a possible way of inactivation of this tumor suppressor gene, alternative to deletions and mutations. We have investigated if hyper methylation of a 5' CpG island of pie occurs in non-Hodgkin's lymphoma (NHL) and normal lymphoid tissue. A total of 82 NHLs were examined fo r p16 methylation by Southern blot and PCR analysis. Hypermethylation was detected in approximately 20% of B cell lymphomas of both low and high grade and in 15% of T cell NHL. The highest rate of pie gene meth ylation in tumors was found among MALT (mucosa-associated lymphoid tis sue) lymphomas in which the percentage of cases with p16 gene methylat ion reached 67%. However, normal lymphoid tissue was always unmethylat ed at p16 locus. These results indicate that p16 gene methylation is a frequent event in NHLs, mainly in MALT lymphomas, and suggest that it could be an important mechanism of inactivation of this gene.