Deletion, Point Mutation And Promotor Methylation Of P16 And P15 Genes In Acute Lymphocytic Leukemia

Objective To investigate the homozygous deletion, the point mutation of exon2 and the methylation in promoter CpC islands of p16 and p15 genes in 29 Chinese acute lymphocytic leukemia(ALL) patients. And to discuss the inactivation mechanism of MTS genes in Chinese ALL. Methods To get peripheral blood from 29 ALL patients and extract DNA from leukocytes using phenol/chloroform method, design the primers for detecting the exon2 of p16 and p15 genes, the primers are designed to discriminate between methylated and unmethylated alleles following bisulfite treatment and to discriminate between DNA modified by bisulfite and that had not been modified. To analyse the deletions and point mutations of exon2 and methylation variations in promoter CpG islands of p16 and p15 genes by PCR(polymerase chain reaction), PCR-SSCP(PCR-single strand conformational polymorphism) and MSP(methylation-specific PCR) methods. Results In these ALL samples, no homozygous deletion of p16 exonl is detected, the homozygous deletion rate of p16 exon2 is 27.6% (8/29), and that of p15 exon2 is 6.9%(2/29); the point mutation rate of p15 exon2 is 17.2%(5/29) and no point mutation of p16 exon2 is found; the methylation rate of the promoter CpG islands of p16 gene is 13.8(4/29), and that of p15 gene is 27.6(8/29). Conclusions There are three ways of inactivation mechanism of p16 and p15 genes in ALL: homozygous deletion, point mutation and promoter methylation. Each mechamism plays an important role and is related to the progression of ALL. Although no point mutation of p!6 gene is found in these 29 Chinese ALL patients, we can't conclude that it is not one of the inactivation mechanism. We will make further study of the point mutation of p!6 by enlarging the specimen.