Aberrant methylation of the M-type phospholipase A2 receptor gene in leukemic cells

Abstract

BackgroundThe M-type phospholipase A2 receptor (PLA2R1) plays a crucial role in several signaling pathways and may act as tumor-suppressor. This study examined the expression and methylation of the PLA2R1 gene in Jurkat and U937 leukemic cell lines and its methylation in patients with myelodysplastic syndrome (MDS) or acute leukemia.MethodsSites of methylation of the PLA2R1 locus were identified by sequencing bisulfite-modified DNA fragments. Methylation specific-high resolution melting (MS-HRM) analysis was then carried out to quantify PLA2R1 methylation at 5`-CpG sites identified with differences in methylation between healthy control subjects and leukemic patients using sequencing of bisulfite-modified genomic DNA.ResultsExpression of PLA2R1 was found to be completely down-regulated in Jurkat and U937 cells, accompanied by complete methylation of PLA2R1 promoter and down-stream regions; PLA2R1 was re-expressed after exposure of cells to 5-aza-2´-deoxycytidine. MS-HRM analysis of the PLA2R1 locus in patients with different types of leukemia indicated an average methylation of 28.9% ± 17.8%, compared to less than 9% in control subjects. In MDS patients the extent of PLA2R1 methylation significantly increased with disease risk. Furthermore, measurements of PLA2R1 methylation appeared useful for predicting responsiveness to the methyltransferase inhibitor, azacitidine, as a pre-emptive treatment to avoid hematological relapse in patients with high-risk MDS or acute myeloid leukemia.ConclusionsThe study shows for the first time that PLA2R1 gene sequences are a target of hypermethylation in leukemia, which may have pathophysiological relevance for disease evolution in MDS and leukemogenesis.

Repression of PLA2R1 by c-MYC and HIF-2alpha promotes cancer growth

“…Interestingly, PLA2R1 has recently been shown to be repressed by DNA methylation in leukemic cells [32] pointed out a potential mechanism by which the VHL-HIF2α-MYC pathway might regulate PLA2R1 expression in RCC.…”

“…Confirming this hypothesis, c-MYC binds PLA2R1 genomic regions closed to PLA2R1 transcription start site and its forced expression represses PLA2R1 expression. C-MYC is known to repress transcription by recruiting various repressive complexes including the DNA methyl transferases (DNMT), the enzymes that methylate the CpG [30, 31] and PLA2R1 has recently been found to be methylated,[32] suggesting that c-MYC might exert its repressive activity through induction of PLA2R1 DNA methylation. Indeed, inhibiting the DNMT in cells expressing low levels of PLA2R1 is sufficient to restore PLA2R1 expression.…”

Nouveaux rôles physiopathologiques pour le récepteur PLA2R1 dans le cancer et la glomérulonéphrite extramembraneuse

“…[22]. Chez certains patients atteints de leucémie, et dans des lignées tumorales lymphocytaires (Jurkat, U937) et mammaires (MDAMB-453, Cama1, BT20), cette perte d'expression semble être la conséquence d'un contrôle épigénétique via une hyperméthylation du promoteur [23]. Lorsque PLA2R1 est réintroduit par une approche virale dans des lignées tumorales mammaires, il induit leur apoptose [24].…”

Identification and Quantification of Heterogeneously-methylated DNA Fragments Using Epiallele-sensitive Droplet Digital Polymerase Chain Reaction (EAST-ddPCR)

“…PLA2R1 was shown to play a crucial role in several anti-tumour and anti-inflammatory responses including apoptosis, replicative-and stress-induced senescence, and inhibition of cell transformation (7,(15)(16)(17)(18). The discovery of PLA2R1 promoter hypermethylation connected with lowered PLA2R1 expression in leukemic cells indicated a tumour-suppressive role of this receptor (19). The observed PLA2R1 promoter methylation was not restricted to leukemia, but also observed in breast cancer cell lines (20) and in clear cell renal cell carcinomas (21) and is also present in prostate cancer cell lines as shown in this study.…”