Deregulation of folate pathway gene expression correlates with poor prognosis in acute leukemia
Authors: Organista-Nava, Jorge; Gomez-Gomez, Yazmin; Del Moral-Hernandez, Oscar; Illades-Aguiar, Berenice; Gomez-Santamaria, Jazmin; Rivera-Ramirez, Ana Bertha; Saavedra-Herrera, Monica Virginia; Jimenez-Lopez, Marco Antonio; Leyva-Vazquez, Marco Antonio
The present study analyzed the mRNA expression levels of genes involved in the transport and metabolism of methotrexate (MTX) (RFC1, ABCC1, ABCB1, GGH, FPGS, ATIC, TS, MTHFR, MTRR, MS and MTHFD1) in patients with acute leukemia (AL). The expression levels of the examined genes were analyzed by reverse transcription quantitative polymerase chain reaction (RT-qPCR) in patients with AL (ALL:50/AML:19) and 66 healthy individuals. The mRNA expression levels of RFC1, MS, MTRR, MTHFR and ABCB1 were decreased (P<0.05), while those of GGH, FPGS, TS and MTHFD1 (P<0.05) were overexpressed in patients with AL. Patients with high mRNA levels of GGH (OR=4.28, 95% CI=1.29-14.14), TS (OR=7.14, 95% CI 1.84-27.81), MTHFR (OR=4.81, 95% CI=1.31-17.64), ABCB1 (OR=4.61, 95% CI=1.33-15.97) and ABCC1 (OR=5.50, 95% CI=1.12-27.06) had a higher chance of relapse. Interestingly, high mRNA levels of RFC1 are a protective factor in the risk of AL relapse (OR=0.22, 95% 0.06-0.80). The results of the present study indicated that deregulation of folate pathway gene expression is associated with poor prognosis in AL and that the expression levels of these markers could serve as novel molecular targets for the treatment of patients with AL.
Epigenetic regulation of human gamma-glutamyl hydrolase activity in acute lymphoblastic leukemia cells
AMERICAN JOURNAL OF HUMAN GENETICS
Authors: Cheng, Qing; Cheng, Cheng; Crews, Kristine R.; Ribeiro, Raul C.; Pui, Ching-Hon; Relling, Mary V.; Evans, William E.
gamma-Glutamyl hydrolase (GGH) catalyzes degradation of the active polyglutamates of natural folates and the antifolate methotrexate (MTX). We found that GGH activity is directly related to GGH messenger RNA expression in acute lymphoblastic leukemia (ALL) cells of patients with a wild-type germline GGH genotype. We identified two CpG islands (CpG1 and CpG2) in the region extending from the GGH promoter through the first exon and into intron 1 and showed that methylation of both CpG islands in the GGH promoter (seen in leukemia cells from similar to 15% of patients with non-hyperdiploid B-lineage ALL) is associated with significantly reduced GGH mRNA expression and catalytic activity and with significantly higher accumulation of MTX polyglutamates (MTXPG(4-7)) in ALL cells. Furthermore, methylation of CpG1 was leukemia-cell specific and had a pronounced effect on GGH expression, whereas methylation of CpG2 was common in leukemia cells and normal leukocytes but did not significantly alter GGH expression. These findings indicate that GGH activity in human leukemia cells is regulated by epigenetic changes, in addition to previously recognized genetic polymorphisms and karyotypic abnormalities, which collectively determine interindividual differences in GGH activity and influence MTXPG accumulation in leukemia cells.