EVI1 Inhibits Apoptosis Induced by Antileukemic Drugs via Upregulation of CDKN1A/p21/WAF in Human Myeloid Cells

Abstract

Overexpression of ecotropic viral integration site 1 (EVI1) is associated with aggressive disease in acute myeloid leukemia (AML). Despite of its clinical importance, little is known about the mechanism through which EVI1 confers resistance to antileukemic drugs. Here, we show that a human myeloid cell line constitutively overexpressing EVI1 after infection with a retroviral vector (U937_EVI1) was partially resistant to etoposide and daunorubicin as compared to empty vector infected control cells (U937_vec). Similarly, inducible expression of EVI1 in HL-60 cells decreased their sensitivity to daunorubicin. Gene expression microarray analyses of U937_EVI1 and U937_vec cells cultured in the absence or presence of etoposide showed that 77 and 419 genes were regulated by EVI1 and etoposide, respectively. Notably, mRNA levels of 26 of these genes were altered by both stimuli, indicating that EVI1 regulated genes were strongly enriched among etoposide regulated genes and vice versa. One of the genes that were induced by both EVI1 and etoposide was CDKN1A/p21/WAF, which in addition to its function as a cell cycle regulator plays an important role in conferring chemotherapy resistance in various tumor types. Indeed, overexpression of CDKN1A in U937 cells mimicked the phenotype of EVI1 overexpression, similarly conferring partial resistance to antileukemic drugs.

The oncogeneEVI1enhances transcriptional and biological responses of human myeloid cells toall-transretinoic acid

“…30 To address the question whether EVI1 would modulate the ATRA responses not only of its own and the RARb, but of a larger number of genes, RNA was extracted from 3 independent replicate cultures of U937_EVI1 and control U937_vec cells treated with 1 mM ATRA or an equivalent amount of its solvent DMSO for 24 h. Gene expression microarray analysis revealed that 453 genes were induced and 240 repressed by ATRA, and 44 genes were up-and 67 down-regulated by EVI1 at a false discovery rate (FDR) 63 of 0.05 (Fig 1A, B; Tables S1A, B). Genes were considered to exhibit an EVI1 modulated ATRA response if they fulfilled the following stringent criteria: the factor by which EVI1 significantly altered their expression in the presence of ATRA was equal to or greater than 2, and equal to or greater than the square of the factor by which EVI1 changed their mRNA levels in the absence of ATRA (see Materials and Methods for details).…”

“…19 Analogously, experimental expression of Evi1 effected development of an MDS like disease, 20 and coexpression with other oncogenes such as HoxA9 C Meis1 or AML1 D171N caused AML 21,22 in murine bone marrow transplantation models. In vitro, EVI1 stimulated cell proliferation and inhibited differentiation and apoptosis in some experimental models, 12,16,20,[23][24][25][26][27][28][29][30][31] but elicited the opposite effects in others. 20,[31][32][33][34][35][36][37][38][39] This suggests that the fate of EVI1 overexpressing cells is influenced by lineage, maturation stage, cooperating molecular events, and/or environmental stimuli, and raises the possibility that it may be amenable to pharmacological modulation.…”

p21WAF1 modulates drug-induced apoptosis and cell cycle arrest in B-cell precursor acute lymphoblastic leukemia

“…T-ALL cells exhibit increased apoptotic characteristics compared with BCP-ALL cells following exposure to cytotoxic drugs While p21 WAF1 induction has been demonstrated to inhibit apoptosis in various cancer histotypes with a range of sensitivity to cytotoxic stimuli, [5][6][7][8][10][11][12][13][14]28,42 the anti-apoptotic role of p21 WAF1 in p53-functional, chemotherapy-sensitive hematopoietic cells has still not been fully elucidated. We assessed the in vitro apoptotic responses of T-ALL and BCP-ALL PDXs and cell lines following exposure to etoposide or vorinostat.…”

“…10,11,13,28 One study used a p53 expressing leukemia cell line (HL-60), and here the disruption of p21 WAF1 function did not appreciably sensitize the cells to cytarabine. 48 The study herein is the first to report on the anti-apoptotic role of p21 WAF1 in a BCP-lineage leukemia cell line that was previously shown to have an intact p53 response to DNA damaging agents.…”

“…10,11 Conversely, overexpression of p21 WAF1 in a range of leukemia and lymphoma cell lines conferred some resistance to cytarabine or etoposide. 10,12,13 However, in a recent study deletion of cdkn1a in a murine Em-Myc lymphoma model did not sensitize lymphoma cells to histone deacetylase inhibitor (HDAC)-induced apoptosis, 14 highlighting that questions remain over the proposed strength of the anti-apoptotic role of p21 WAF1 in hematopoietic cells.…”