CDKN2/p16/MTS1 Gene Methylation Analysis in Neuroblastomas

Objective To investigate whether the hypermethylation of p16 gene is present or not.Method The methylation pattern at 5′ CpG island of p16 gene was analyzed by PCR combined with methylation sensitive restriction endonuclease enzymes Hpa Ⅱ、Sac Ⅱ and FnuDⅡ in the normal tissue in 5 cases and 14 primary tumors and in 2 of which metastatic tumors were available.Results 5′ CpG island methylation occured in 4/14 primary tumors and 1/2 metastatic tumors.no methylation occured in the normal tissue in 5 cases,no homozygous deletions occured in neuroblastomas since all tumor DNA undigested displayed specific bands after PCR amplification.Methylation scattered from stage Ⅱ to stage Ⅳ,both the primary and metastatic DNA display methylation in one Ⅳ stage patient.This indicated that methylation occured prior to metastasis and methylation of CpG island was early event of this tumorigenesis.Conclusions De novo 5′ CpG island methylation of p16 gene is an important and common mode of inactivation for this negative regulator of cell cycle in neuroblastomas.