1,25-Dihydroxyvitamin D3 Enhances the Apoptotic Activity of MDM2 Antagonist Nutlin-3a in Acute Myeloid Leukemia Cells Expressing Wild-type p53

Abstract

The tumor suppressor p53 is often referred to as "the guardian of the genome" because of its central role in the cellular response to oncogenic stress and prevention of tumor development. Mutations of p53 in acute myeloid leukemia (AML) are rare but resistance to chemotherapy has been reported because of the deregulation of the p53 signaling and differentiation pathways. It is known that the interaction of the vitamin D metabolite 1,25-dihydroxyvitamin D 3 (1,25D) with its functional vitamin D receptor leads to differentiation, G 1 arrest, and increased cell survival in p53-null AML cells. However, there are no reports on the effect of 1,25D in leukemia cells expressing wild-type p53. Here, we examine vitamin D signaling in AML cells MOLM-13 and OCI-AML3 expressing wild-type p53 in the presence and absence of the MDM2 antagonist nutlin-3. We find that 1,25D alone induces monocytic differentiation in these cell lines similar to that seen in p53-null AML cells, suggesting that the presence of wild-type p53 is compatible with activation of vitamin D signaling. Combination of nutlin-3a with 1,25D accelerated programmed cell death, likely because of enhanced nutlin-induced upregulation of the proapoptotic PIG-6 protein and downregulation of antiapoptotic BCL-2, MDMX, human kinase suppressor of Ras 2, and phosphorylated extracellular signal-regulated kinase 2.

Tumor suppressor p53 status does not determine the differentiation-associated G1cell cycle arrest induced in leukemia cells by 1,25-dihydroxyvitamin D3and antioxidants

“…We have previously shown that 1,25D can induce differentiation of p53wt as well as p53null AML cells, 29 but the effect of the vitamin D-based "differentiation cocktail" was not previously investigated. Values are the mean ± sD (n = 3).…”

“…34,35 These data seem to nicely complement our recent study using wild-type p53 cells that focused on the effects of 1,25D on cell survival in relation to p53 expression. 29 We showed there that in AML cell lines with endogenous p53wt, exposure to 1,25D enhances the apoptotic activity of the MDM2 antagonist nutlin 3a, which stabilizes the protein levels of p53, and that the pro-apoptotic effect of the combination of 1,25D with nutlin3a was most likely due to the upregulation of PIG-6 and/or the downregulation of one or more of the survival proteins BCL-2, MDMX, hKSR2 or ERK1/2 activated by phosphorylation. 29 The observation noted in that study that activated ERK1/2 is downregulated by the 1,25D-nutlin 3a combination is reminiscent of the finding here that 1,25D combination with antioxidants, especially carnosic acid in combination with the p38 inhibitor also reduce the levels of activated ERK1/2 (Fig.…”

Hematological Malignancy

“…A combination of nutlin-3a with 1,25(OH) 2 D 3 enhanced apoptosis in wild-type p53 expressing MOLM-13 and OCI-AML3 cells in vitro by suppressing anti-apoptitic protein BCL-2 and p90RSK and by inducing the pro-apoptotic protein PIG-6 [153].…”

Vitamin D and Acute Myeloid Leukemia

“…It was recently shown that vitamin D alone induced monocytic differentiation of two wild-type p53 AML cell lines as well as a p53-null AML cells. Combination of a small molecule inhibitor (nutlin-3a) of p53-MDM2 interaction and vitamin D accelerated programmed cell death (Thompson, Andreeff et al 2010). Interestingly, MDM2 levels dropped significantly in the presence of vitamin D 3 , possibly contributing to the apoptotic effect.…”