Loss of p73 gene expression in lymphoid leukemia cell lines is associated with hypermethylation

The expression of the p73 gene and the methylation status was examined in 6 1 acute lymphoblastic leukemia (ALL) cell lines and lymphocytes from seven healthy individuals. p73 mRNA was not expressed in 19 (31.1%) of 61 ALL cel l lines, including 11 (31.4%) of 35 B-precursor ALL cell lines, 2 (16.7%) o f 12 B-ALL/Burkitt lymphoma (BL) cell lines (totally 27.7% of B-lineage cel l lines). 6 (42.9%) of 14 T-ALL cell lines, and expressed in all of normal lymphocytes, by reverse transcriptase-polymerase chain reaction (RT-PCR). R estriction-enzyme related PCR (REP) and methylation-specific PCR (MSP) reve aled that the cell lines lacking p73 mRNA expression were hypermethylated. In contrast, normal lymphocytes and most cell lines that expressed detectab le p73 mRNA were not hypermethylated with the exception of five cell lines. Furthermore, bisulfite genomic sequencing confirmed the results obtained b y REP and MSP. Our results suggest that p73 inactivation may be involved in the pathogenesis of both T- and B-ALLs, and that hypermethylation is the p redominant mechanism of inactivation of the p73 gene in ALL. (C) 2001 Elsev ier Science Ltd. All rights reserved.