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Ruhul Amin A.R.M.,Case Western Reserve University | Ruhul Amin A.R.M.,Emory University | Thakur V.S.,Case Western Reserve University | Gupta K.,Case Western Reserve University | And 4 more authors.
Oncogene | Year: 2013

p53 is essential for the cellular responses to DNA damage that help to maintain genomic stability. However, the great majority of human cancers undergo disruption of the p53-network. Identification and characterization of molecular components important in both p53-dependent and-independent apoptosis might be useful in developing novel therapies for cancers. In the complete absence of p53, cells treated with N-(phosphonacetyl)-L-aspartate (PALA) continue to synthesize DNA slowly and eventually progress through S-phase, suffering severe DNA damage that in turn triggers apoptosis, whereas cells with functional p53 undergo growth arrest. In this study, we investigated apoptotic signaling in response to PALA and the role of p53 expression in this pathway. We found that treatment of cells lacking p53 with PALA induced TAp73, Noxa and Bim and inactivation of these proteins with dominant-negative plasmids or small interfering RNAs significantly inhibited apoptosis, suggesting that PALA-induced apoptosis was mediated via TAp73-dependent expression of Noxa and Bim. However, PALA treatment inhibited the expression of ΔNp73 only in cells lacking p53 but not in cells expressing p53. In addition, PALA treatment inhibited Bcl-2, and overexpression of Bcl-2 significantly inhibited PALA-induced apoptosis. Moreover, expression of p53 in these cells protected them from PALA-induced apoptosis by activating p21, sustaining the expression of ΔNp73 and inhibiting the induction of Noxa and Bim. Taken together, our study identifies novel but opposing roles for the p53 and TAp73 in the induction of Noxa and Bim and regulation of apoptosis. Our data will help to develop strategies to eliminate cancer cells lacking p53 while protecting normal cells with wild-type p53. © 2013 Macmillan Publishers Limited All rights reserved.

Thakur V.S.,Case Western Reserve University | Ruhul Amin A.R.M.,Case Western Reserve University | Ruhul Amin A.R.M.,Emory University | Paul R.K.,Case Western Reserve University | And 7 more authors.
Cancer Letters | Year: 2010

The tumor suppressor protein p53 plays a key role in regulation of negative cellular growth in response to EGCG. To further explore the role of p53 signaling and elucidate the molecular mechanism, we employed colon cancer HCT116 cell line and its derivatives in which a specific transcriptional target of p53 is knocked down by homologous recombination. Cells expressing p53 and p21 accumulate in G1 upon treatment with EGCG. In contrast, same cells lacking p21 traverse through the cell cycle and eventually undergo apoptosis as revealed by TUNEL staining. Treatment with EGCG leads to induction of p53, p21 and PUMA in p21 wild-type, and p53 and PUMA in p21-/- cells. Ablation of p53 by RNAi protects p21-/- cells, thus indicating a p53-dependent apoptosis by EGCG. Furthermore, analysis of cells lacking PUMA or Bax with or without p21 but with p53 reveals that all the cells expressing p53 and p21 survived after EGCG treatment. More interestingly, cells lacking both PUMA and p21 survived ECGC treatment whereas those lacking p21 and Bax did not. Taken together, our results present a novel concept wherein p21-dependent growth arrest pre-empts and protects cells from otherwise, in its absence, apoptosis which is mediated by activation of pro-apoptotic protein PUMA. Furthermore, we find that p53-dependent activation of PUMA in response to EGCG directly leads to apoptosis with out requiring Bax as is the case in response to agents that induce DNA damage. p21, thus can be used as a molecular switch for therapeutic intervention of colon cancer. © 2010 Elsevier Ireland Ltd.

Ruhul Amin A.R.M.,Case Western Reserve University | Ruhul Amin A.R.M.,Emory Winship Cancer Institute | Thakur V.S.,Case Western Reserve University | Gupta K.,Case Western Reserve University | And 6 more authors.
Molecular Cancer Therapeutics | Year: 2010

A great majority of human cancers encounter disruption of the p53 network. Identification and characterization of molecular components important in both p53-dependent and p53-independent apoptosis might be useful in developing novel therapies. Previously, we reported that concanavalin A (Con A) induced p73-dependent apoptosis of cells lacking functional p53. In the present study, we investigated the mechanism and role of p53 in protection from apoptosis induced by Con A. Treatment with Con A resulted in apoptosis of p53-null ovarian cancer, SKOV3, or Li-Fraumeni syndrome, MDAH041 (041), cells. However, their isogenic pairs, SKP53 and TR9-7, expressing wild-type p53 were much less sensitive and were protected by G1 arrest. Inhibition of p53 function rendered these cells sensitive to Con A. Con A-induced apoptosis was accompanied by upregulation of forkhead box O1a (FOXO1a) and Bcl-2-interacting mediator (Bim), which were strongly inhibited after p53 expression and rescued after p53 ablation. Moreover, ablation of Bim by short hairpin RNA protected cells from apoptosis. Taken together, our study suggests that Con A induces apoptosis of cells lacking p53 by activating FOXO1a-Bim signaling and that expression of p53 protects these cells by inducing G1 arrest and by downregulating the expression of both FOXO1a and Bim, identifying a novel cross-talk between FOXO1a and p53 transcription factors. ©2010 AACR.

Agency: Department of Health and Human Services | Branch: | Program: SBIR | Phase: Phase II | Award Amount: 853.20K | Year: 2011

DESCRIPTION (provided by applicant): Though AML is one of the most common forms of leukemia in adults; the 5 year survival is less than 20-50% in adults and significantly lowers in the elderly. The remarkable success in treating one relatively uncommon subset of AML, acute promyelocytic leukemia (APL), with all trans- retinoic acid (ATRA) illustrates the great promise for differentiation therapy. Utilizing ATRA, the presumed cure of 75-85% of patients is possible but only for this rare AML subset. ATRA's remarkable success stems from the fact that AML is a disease characterized by the arrest of differentiation of immature myeloid cells. ATRA overcomes this block in differentiation by forcing leukemic cells to mature. After leukemic cells undergo terminal differentiation, they lose their ability to proliferate. We have recently found that a plant-derived alkaloid holds promise as an AML therapeutic for non-APL leukemia due to its ability to induce potent AML differentiation. The major aims of this phase II project are to perform preclinical efficacy and toxicity studies in order to develop our optimized form of this plant-derived alkaloid into a clinical agent. As differentiation therapies are able to treat leukemia without the necessity for overt cytotoxicity,this work has the potential to lead to much needed more efficacious, less toxic, and better tolerated therapy for patients with AML. PUBLIC HEALTH RELEVANCE: This project is highly relevant to public health as its main objective is to develop a novel therapeutic regimen for patients with Acute Myeloid Leukemia that is both efficacious and has low toxicity. As current AML therapeutics has poor efficacy and high toxicities, there is a significant need for new therapies and therapeutic approaches for AML.

Gupta K.,Case Western Reserve University | Stefan T.,Case Western Reserve University | Ignatz-Hoover J.,Case Western Reserve University | Moreton S.,Case Western Reserve University | And 6 more authors.
Cancer Research | Year: 2016

1,25-dihydroxyvitamin D3 (1,25D), the biologically active form of vitamin D, is widely considered a promising therapy for acute myeloid leukemia (AML) based on its ability to drive differentiation of leukemic cells. However, clinical trials have been disappointing in part to dose-limiting hypercalcemia. Here we show how inhibiting glycogen synthase kinase 3 (GSK3) can improve the differentiation response of AML cells to 1,25D-mediated differentiation. GSK3 inhibition in AML cells enhanced the differentiating effects of low concentrations of 1,25D. In addition, GSK3 inhibition augmented the ability of 1,25D to induce irreversible growth inhibition and slow the progression of AML in mouse models. Mechanistic studies revealed that GSK3 inhibition led to the hyperphosphorylation of the vitamin D receptor (VDR), enabling an interaction between VDR and the coactivator, SRC-3 (NCOA3), thereby increasing transcriptional activity. We also found that activation of JNK-mediated pathways in response to GSK3 inhibition contributed to the potentiation of 1,25D-induced differentiation. Taken together, our findings offer a preclinical rationale to explore the repositioning of GSK3 inhibitors to enhance differentiation-based therapy for AML treatment. © 2016 American Association for Cancer Research.

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