Small-molecule correctors and stabilizers to target p53.

The tumor suppressor p53 is the most frequently mutated protein in human cancer and tops the list of high-value precision oncology targets. p53 prevents initiation and progression of cancer by inducing cell-cycle arrest and various forms of cell death. Tumors have thus evolved ways to inactivate p53, mainly by TP53 mutations or by hyperactive p53 degradation. This review focuses on two types of p53 targeting compounds, MDM2 antagonists and mutant p53 correctors. MDM2 inhibitors prevent p53 protein degradation, while correctors restore tumor suppressor activity of p53 mutants by enhancing thermodynamic stability. Herein we explore both novel and repurposed p53 targeting compounds, discuss their mode of action, and examine the challenges in advancing them to the clinic.

Synthetic Design and Biological Evaluation of New p53-MDM2 Interaction Inhibitors Based on Imidazoline Core.

The use of p53-MDM2 inhibitors is a prospective strategy in anti-cancer therapy for tumors expressing wild type p53 protein. In this study, we have applied a simple approach of two-step synthesis of imidazoline-based alkoxyaryl compounds, which are able to efficiently inhibit p53-MDM2 protein-protein interactions, promote accumulation of p53 and p53-inducible proteins in various cancer cell lines. Compounds 2l and 2k cause significant upregulation of p53 and p53-inducible proteins in five human cancer cell lines, one of which possesses overexpression of MDM2.

Therapeutic potential of p53 reactivation in prostate cancer: Strategies and opportunities.

Metastatic prostate cancer (mCaP) remains one of the leading causes of cancer-related death in men worldwide. Androgen receptor (AR) drives the progression of most of the mCaP, and hence the androgen deprivation therapy (ADT) is the first-line treatment of choice for mCaP. Although the responses of ADT and next-generation AR inhibitors initially improve the disease burden, the responses of this combinatorial drug therapy varied widely due to molecular alteration in mCaP patients. In addition to the altered AR signaling, loss of potent tumor-suppressor protein p53 exhibits poor outcomes. p53 influences cell plasticity and is frequently lost in more aggressive prostate cancer (CaP) with neuroendocrine differentiation. Loss of p53 antagonizes the effect of AR inhibitors and enhances the proliferation rate of CaP cells. Considering the important role of p53 inactivation in cancer development, restoration of wild-type p53 function by p53-reactivating compounds developed with different approaches, seems to be an attractive therapeutic strategy for prostate cancer therapy. In this review, we discuss the therapeutic potential of these compounds with a particular focus on the pharmacological rescue of p53 in mCaP. In addition, we also highlight the challenges and new opportunities of p53-targeted therapy for the future.

Antiangiogenic and antitumoral activity of LQFM126 prototype against B16F10 melanoma cells.

Inhibition of mouse double minute 2 homolog (MDM2)-p53 interaction and reactivation of p53 signaling have been explored as effective anticancer therapeutic strategy. The potent and specific antitumor activity shown by Nutlins, first class of MDM2-p53 inhibitors discovered, has made these compounds potential antitumor candidates. To this end, we synthesized Nutlin-1 and Nutlin-2 analogs through molecular simplification and selected the compound with the most efficient antitumoral activity. Cytotoxicity of Nutlin-2 analog LQFM126 on B16F10 melanoma cells induced intense cytoplasmic vacuolization, reduction of cell size, chromatin condensation, cytoplasmic degeneration and nuclear fragmentation. LQFM126 antiproliferative effects mediated cell cycle retention in G0/G1 phase and increased the levels of cell cycle regulatory proteins p21 and p27. This Nutlin analog increased mitochondrial membrane potential, activated caspase-8, -9 and -3/7 and reduced VEGF levels in B16F10 cells. Therefore, LQFM126 promoted alterations suggestive of apoptosis, G0/G1 cell cycle arrest and suppression of angiogenesis through modulation of VEGF expression in B16F10 cells. Additionally, LQFM126 was classified as UN GHS category 4 (LD50 > 300-2000 mg/kg), suggesting it has low acute systemic toxicity. LQFM126 can be a promising prototype for anticancer therapy.

Small-molecule MDM2 inhibitor LQFM030-induced apoptosis in p53-null K562 chronic myeloid leukemia cells.

Our group designed and synthesized the N-phenyl-piperazine LQFM030 [1-(4-((1-(4-chlorophenyl)-1H-pyrazol-4-yl)methyl) piperazin-1-yl) ethanone], a small molecule derived from molecular simplification of the Nutlin-1, an inhibitor of the human homologue of murine double minute 2 (MDM2) protein that is expressed in several types of cancer. To better investigate the effects of LQFM030 regarding the p53 mutation status, this study investigated the antiproliferative activity of LQFM030 against the p53-null K562 leukemia cells as well as the cell death pathways involved. In addition, the effects of LQFM030 on the levels of the p53/MDM2 complex were also carried out using 3T3 cells as a p53 wild-type model. Our data suggest that LQFM030 triggered apoptosis in K562 cells via different mechanisms including cell cycle arrest, caspase activation, reduction of mitochondrial activity, decrease in MDM2 expression, and transcriptional modulation of MDMX, p73, MYC, and NF-ĸB. Additionally, it promoted effects in p53/MDM2 binding in p53 wild-type 3T3 cells. Therefore, LQFM030 has antiproliferative effects in cancer cells by a p53 mutation status-independent manner with different signaling pathways. These findings open new perspectives to the treatment of leukemic cells considering the resistance development associated with cancer treatment with conventional cytotoxic drugs.

MDM2 antagonists as a novel treatment option for acute myeloid leukemia: perspectives on the therapeutic potential of idasanutlin (RG7388).

Acute myeloid leukemia (AML) is a clonal heterogenous malignancy of the myeloid cells with a poor prognosis lending itself to novel treatment strategies. TP53 is a critical tumor suppressor and plays an essential role in leukemogenesis. Although TP53 is relatively unusual in de novo AML, inactivation of wild-type p53 (WT-p53) is a common event. Murine double minute 2 (MDM2) is a key negative regulator of p53 and its expression; inhibition of MDM2 is postulated to reactivate WT-p53 and its tumor suppressor functions. Nutlins were the first small molecule inhibitors that bind to MDM2 and target its interaction with p53. RG7388 (idasanutlin), a second-generation nutlin, was developed to improve upon the potency and toxicity profile of earlier nutlins. Preliminary data from early phase trials and ongoing studies suggest clinical response with RG7388 (idasanutlin) both in monotherapy and combination strategies in AML. We herein briefly discuss currently approved therapies in AML and review the clinical data for RG7388 (idasanutlin) and MDM2 inhibition as novel treatment strategies in AML. We further describe efficacy and toxicity profile data from completed and ongoing trials of RG7388 (idasanutlin) and other MDM2-p53 inhibitors in development. Many targeted therapies have been approved recently in AML, with a focus on the older and unfit population for intensive induction therapy and in relapsed/refractory disease. The "nutlins", including RG7388 (idasanutlin), merit continued investigation in such settings.

LQFM030 reduced Ehrlich ascites tumor cell proliferation and VEGF levels.

AIMS: This study reports the biological properties of LQFM030 in vivo, a molecular simplification of the compound nutlin-1. MAIN METHODS: Ehrlich ascites tumor (EAT)-bearing mice were treated intraperitoneally with LQFM030 (50, 75 or 150mg/kg) for 10days to determine changes in ascites tumor volume, body weight, cytotoxicity and angiogenesis. Moreover, flow cytometric expression of p53 and p21 proteins and caspase-3/7, -8 and -9 activation were investigated in EAT cells from mice treated. Acute oral systemic toxicity potential of LQFM030 in mice was also investigated using an alternative method. KEY FINDINGS: Treatment of EAT-bearing mice with LQFM030 resulted in a marked decline in tumor cell proliferation and the vascular endothelial growth factor (VEGF) levels along with enhanced survival of the mice. Apoptotic tumor cell death was detected through p53 and p21 modulation and increase of caspase-3/7, -8 and -9 activity. LQFM030 also showed orally well tolerated, being classified in the UN GHS category 5 (LD50>2000-5000mg/Kg). SIGNIFICANCE: LQFM030 seems to be a promising antitumor candidate for combinatory therapy with typical cytotoxic compounds, reducing the toxicity burden while allowing a superior anticancer activity. Moreover, these data also open new perspectives for LQFM030 as an antiangiogenic agent for treatment of diseases involving VEGF overexpression.

p53-Mdm2 Interaction Inhibitors as Novel Nongenotoxic Anticancer Agents.

BACKGROUND: Cancer is a major global health problem with high mortality rate. Most of the clinically used anticancer agents induce apoptosis through genotoxic stress at various stages of cell cycle and activation of p53. Acting as a tumor suppressor, p53 plays a vital role in preventing tumor development. Tumor suppressor function of p53 is effectively antagonized by its direct interaction with murine double minute 2 (Mdm2) proteins via multiple mechanisms. Thus, p53-Mdm2 interaction has been found to be an important target for the development of novel anticancer agents. Currently, nutlin, spirooxindole, isoquilinone and piperidinone analogues inhibiting p53-Mdm2 interaction are found to be promising in the treatment of cancer. OBJECTIVE: The current review focused to scrutinize the structural aspects of p53-Mdm2 interaction inhibitors. METHODS: The present study provides a detailed collection of published information on different classes of inhibitors of p53-Mdm2 interaction as potential anticancer agents. The review highlighted the structural aspects of various reported p53-Mdm2 inhibitors for optimization. RESULTS: In the last few years, different classes of inhibitors of p53-Mdm2 have been designed and developed, and seven such compounds are being evaluated in clinical trials as new anticancer drugs. Further, to explore the role of p53 protein as a potential target for anticancer drug development, in this review, the mechanism of Mdm2 mediated inactivation of p53 and recent developments on p53- Mdm2 interactions inhibitors are discussed. CONCLUSION: Agents designed to block the p53-Mdm2 interaction may have a therapeutic potential for the treatment of a subset of human cancers retaining wild-type p53. We review herein the recent advances in the design and development of potent small molecules as p53-Mdm2 inhibitors.

Induction of apoptosis in Ehrlich ascites tumour cells via p53 activation by a novel small-molecule MDM2 inhibitor - LQFM030.

OBJECTIVE: The activation of the p53 pathway through the inhibition of MDM2 has been proposed as a novel therapeutic strategy against tumours. A series of cis-imidazoline analogues, termed nutlins, were reported to displace the recombinant p53 protein from its complex with MDM2 by binding to MDM2 in the p53 pocket, and exhibited an antitumour activity both in vitro and in vivo. Thus, the purpose of this study was to evaluate the antitumour properties of LQFM030 (2), a nutlin analogue created by employing the strategy of molecular simplification. METHODS: LQFM030 (2) cytotoxicity was evaluated in Ehrlich ascites tumour (EAT) cells, p53 wild type, by the trypan blue exclusion test, and the mechanisms involved in EAT cell death were investigated by light and fluorescence microscopy, flow cytometry, real-time PCR and Western blotting. KEY FINDINGS: Our results demonstrate that LQFM030 has dose-dependent antiproliferative activity and cytotoxic activity on EAT cells, induces the accumulation of p53 protein and promotes cell cycle arrest and apoptosis. p53 gene transcription was unaffected by LQFM030 (2); however, MDM2 mRNA increased and MDM2 protein decreased. CONCLUSIONS: These results suggest that the small-molecule p53 activator LQFM030 (2) has the potential for further development as a novel cancer therapeutic agent.