Synergistic Cytotoxic Activity of Recombinant TRAIL Plus the Non-Genotoxic Activator of the p53 Pathway Nutlin-3 in Acute Myeloid Leukemia Cells

Abstract

To potentiate the response of acute myeloid leukemia (AML) to TRAIL cytotoxicity, we have adopted a strategy of combining nutlin-3, a potent non-genotoxic activator of the p53 pathway, with recombinant TRAIL. The rationale for using such a combination was that deletions and/or mutations of the p53 gene occur in only 5-10% of AML and that TRAIL and nutlin-3 activate the extrinsic and intrinsic pathways of apoptosis, respectively. TRAIL induced a rapid increase of apoptosis when added to OCI M4-type and MOLM M5-type AML cells, carrying a wild-type p53, as well as to NB4 M3-type AML, carrying a mutated p53. On the other hand, the small molecule activator of the p53 pathway nutlin-3 induced p53 accumulation, cell cycle arrest and a slow progressive increase of apoptosis in OCI and MOLM but not in NB4. Of note, nutlin-3 up-regulated the surface expression of TRAIL-R2 and synergized with TRAIL in inducing apoptosis in OCI and MOLM as well as in primary M4-type and M5-type AML blasts, but not in NB4 cells. Moreover, while nutlin-3 up-regulated the expression of cyclin dependent kinase inhibitor p21, a p53-target gene mediating cell cycle block and showing anti-apoptotic activity, the simultaneous addition of TRAIL plus nutlin-3 induced the caspase-dependent cleavage of p21. The relevance of p21 down-regulation for sensitizing AML cells to apoptosis was underscored in knocking-down experiments with small interfering RNAs. Our data suggest that the combined treatment of nutlin-3 plus TRAIL might offer a novel therapeutic strategy for AML.

The therapeutic potential of p53 reactivation by nutlin-3a in ALK+ anaplastic large cell lymphoma with wild-type or mutated p53

“…33,46 Our data provide evidence that such therapeutic strategies can be improved by incorporation of agents such as nutlin-3a, in agreement with others. 47,48 Recent studies have shown that nutlin-3a, at very high concentrations, usually 420-30 mM, can inhibit the growth of cancer cells with deleted p53, or harbouring a nonfunctional, mt p53 gene, although the exact mechanism is incompletely understood. 35,36 It seems, depending on the in vitro system, that activation of other partners of Mdm2, including p73 or E2F1, may be involved in this phenomenon.…”

miR-34a Induces the Downregulation of BothE2F1andB-MybOncogenes in Leukemic Cells

“…wild-type (p53 wt ) status (3)(4)(5)(6)(7)(8)(9). However, because p53 mediates different cellular functions, such as in particular cell-cycle arrest and apoptosis (3) the critical molecular determinants mediating/modulating the therapeutic activity of Nutlin-3 in leukemic cells are not completely understood.…”

Nutlin-3 Downregulates the Expression of the Oncogene TCL1 in Primary B Chronic Lymphocytic Leukemic Cells

“…Interestingly, unlike solid tumors, mutations and/or deletions of p53 in hematologic malignancies have been detected in less than 20% of patients at diagnosis, mostly in patients with 17p monosomy, which is often associated with TP53 mutation of the second allele (12). Of note, recent studies have shown that Nutlin-3, used alone or in combination with chemotherapeutic drugs, effectively increases the degree of apoptosis in different hematopoietic malignancies (13)(14)(15), including B-CLL (16)(17)(18)(19). In spite of these studies, the potential mechanisms of action of Nutlin-3 are still not completely understood.…”