Inhibition of the MDM2 E3 Ligase induces apoptosis and autophagy in wild-type and mutant p53 models of multiple myeloma, and acts synergistically with ABT-737

MDMX enhances radiosensitivity in lung adenocarcinoma and squamous cell carcinoma by inhibiting P53-mediated autophagy

OBJECTIVE

Radioresistance is a common cause of poor radiation therapy effectiveness for non-small cell lung cancer. Finding molecular targets or methods to enhance radiosensitivity or overcome radioresistance is crucial. This study aimed to investigate the effects of MDMX on modulating radiosensitivity in lung adenocarcinoma (LUAD) and squamous cell carcinoma (LUSC).

METHODS

The expression of MDMX and its correlation with radiotherapy response were analyzed in 101 LUAD and LUSC patient samples. LUAD and LUSC cell lines (A549, SK-MES-1) and their radioresistant counterparts (A549R, SK-MES-1R) were used to assess the effects of MDMX and P53 on radiosensitivity through autophagy by using molecular assays and animal models.

RESULTS

The expression of MDMX was decreased, but the autophagy was enhanced in radioresistant LUAD and LUSC cells. Overexpression of MDMX inhibited P53 activity, leading to autophagy suppression and increasing radiosensitivity. In contrast, P53 upregulation counteracted the effects of MDMX, resulting in increasing autophagy and radioresistance. The higher MDMX expression was associated with improved radiotherapy response and prolonged overall survival in LUAD and LUSC cells. The 5-year survival rate was 93.62% in the low MDMX expression group and 98.11% in the high MDMX expression group (P < 0.01).

CONCLUSION

MDMX enhances LUAD and LUSC radiosensitivity by downregulating P53-mediated autophagy. High MDMX expression correlated with better clinical outcomes, suggesting that MDMX could be a potential biomarker for predicting radiotherapy response and prognosis in LUAD and LUSC patients.

Ubiquitination regulates autophagy in cancer: simple modifications, promising targets

Autophagy is an important lysosomal degradation process that digests and recycles bio-molecules, protein or lipid aggregates, organelles, and invaded pathogens. Autophagy plays crucial roles in regulation of metabolic and oxidative stress and multiple pathological processes. In cancer, the role of autophagy is dual and paradoxical. Ubiquitination has been identified as a key regulator of autophagy that can influence various steps in the autophagic process, with autophagy-related proteins being targeted for ubiquitination, thus impacting cancer progression and the effectiveness of therapeutic interventions. This review will concentrate on mechanisms underlying autophagy, ubiquitination, and their interactions in cancer, as well as explore the use of drugs that target the ubiquitin-proteasome system (UPS) and ubiquitination process in autophagy as part of cancer therapy.

Advancements in MDM2 inhibition: Clinical and pre-clinical investigations of combination therapeutic regimens

Cancer cells often depend on multiple pathways for their growth and survival, resulting in therapeutic resistance and the limited effectiveness of treatments. Combination therapy has emerged as a favorable approach to enhance treatment efficacy and minimize acquired resistance and harmful side effects. The murine double minute 2 (MDM2) protein regulates cellular proliferation and promotes cancer-related activities by negatively regulating the tumor suppressor protein p53. MDM2 aberrations have been reported in a variety of human cancers, making it an appealing target for cancer therapy. As a result, several small-molecule MDM2 inhibitors have been developed and are currently being investigated in clinical studies. Nevertheless, it has been shown that the inhibition of MDM2 alone is inadequate to achieve long-term suppression of tumor growth, thus prompting the need for further investigation into combination therapeutic strategies. In this review, possible clinical and preclinical MDM2 combination inhibitor regimens are thoroughly analyzed and discussed. It provides a rationale for combining MDM2 inhibitors with other therapeutic approaches in the management of cancer, taking into consideration ongoing clinical trials that evaluate the combination of MDM2 inhibitors. The review explores the current status of MDM2 inhibitors in combination with chemotherapy or targeted therapy, as well as promising approach of combining MDM2 inhibitors with immunotherapy. In addition, it investigates the function of PROTACs as MDM2 degraders in cancer treatment. A comprehensive examination of these combination regimens highlights the potential for advancing MDM2-inhibitor therapy and improving clinical outcomes for cancer patients and establishes the foundation for future research and development in this promising area of study.

Multiple Myeloma: Bioinformatic Analysis for Identification of Key Genes and Pathways

Multiple myeloma (MM) is a hematological malignancy in which monoclonal plasma cells multiply in the bone marrow and monoclonal immunoglobulins are overproduced in older people. Several molecular and cytogenetic advances allow scientists to identify several genetic and chromosomal abnormalities that cause the disease. The comprehension of the pathophysiology of MM requires an understanding of the characteristics of malignant clones and the changes in the bone marrow microenvironment. This study aims to identify the central genes and to determine the key signaling pathways in MM by in silico approaches. A list of 114 differentially expressed genes (DEGs) is important in the prognosis of MM. The DEGs are collected from scientific publications and databases (https://www.ncbi.nlm.nih.gov/). These data are analyzed by Search Tool for the Retrieval of Interacting Genes/Proteins (STRING) software (https://string-db.org/) through the construction of protein-protein interaction (PPI) networks and enrichment analysis of the Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways, by CytoHubba, AutoAnnotate, Bingo Apps plugins in Cytoscape software (https://cytoscape.org/) and by DAVID database (https://david.ncifcrf.gov/). The analysis of the results shows that there are 7 core genes, including TP53; MYC; CDND1; IL6; UBA52; EZH2, and MDM2. These top genes appear to play a role in the promotion and progression of MM. According to functional enrichment analysis, these genes are mainly involved in the following signaling pathways: Epstein-Barr virus infection, microRNA pathway, PI3K-Akt signaling pathway, and p53 signaling pathway. Several crucial genes, including TP53, MYC, CDND1, IL6, UBA52, EZH2, and MDM2, are significantly correlated with MM, which may exert their role in the onset and evolution of MM.

Roles of Cullin-RING Ubiquitin Ligases in Cardiovascular Diseases

Maintenance of protein homeostasis is crucial for virtually every aspect of eukaryotic biology. The ubiquitin-proteasome system (UPS) represents a highly regulated quality control machinery that protects cells from a variety of stress conditions as well as toxic proteins. A large body of evidence has shown that UPS dysfunction contributes to the pathogenesis of cardiovascular diseases. This review highlights the latest findings regarding the physiological and pathological roles of cullin-RING ubiquitin ligases (CRLs), an essential player in the UPS, in the cardiovascular system. To inspire potential therapeutic invention, factors regulating CRL activities are also discussed.

Where We Stand With Precision Therapeutics in Myeloma: Prosperity, Promises, and Pipedreams

Multiple myeloma remains an incurable disease despite numerous novel agents being approved in the last decade. Furthermore, disease behavior and susceptibility to current treatments often vary drastically from patient to patient. To date there are no approved therapies in myeloma that are targeted to specific patient populations based on genomic or immunologic findings. Precision medicine, using biomarkers descriptive of a specific tumor's biology and predictive of response to appropriate agents, may continue to push the field forward by expanding our treatment arsenal while refining our ability to expose patients to only those treatments likely to be efficacious. Extensive research efforts have been carried out in this endeavor including the use of agents targeting Bcl2 and the RAS/MAPK and PI3K/AKT/mTOR pathways. Thus far, clinical trials have yielded occasional successes intermixed with disappointments, reflecting significant hurdles which still remain including the complex crosstalk between oncogenic pathways and the nonlinear genetic development of myeloma, prone to cultivating sub-clones with distinctive mutations. In this review, we explore the landscape of precision therapeutics in multiple myeloma and underscore the degree to which research efforts have produced tangible clinical results.

Cell Survival and Cell Death at the Intersection of Autophagy and Apoptosis: Implications for Current and Future Cancer Therapeutics

Autophagy and apoptosis are functionally distinct mechanisms for cytoplasmic and cellular turnover. While these two pathways are distinct, they can also regulate each other, and central components of the apoptosis or autophagy pathway regulate both processes directly. Furthermore, several upstream stress-inducing signaling pathways can influence both autophagy and apoptosis. The crosstalk between autophagy and apoptosis has an integral role in pathological processes, including those related to cancer, homeostasis, and aging. Apoptosis is a form of programmed cell death, tightly regulated by various cellular and biochemical mechanisms, some of which have been the focus of drug discovery efforts targeting cancer therapeutics. Autophagy is a cellular degradation pathway whereby cells recycle macromolecules and organelles to generate energy when subjected to stress. Autophagy can act as either a prodeath or a prosurvival process and is both tissue and microenvironment specific. In this review we describe five groups of proteins that are integral to the apoptosis pathway and discuss their role in regulating autophagy. We highlight several apoptosis-inducing small molecules and biologics that have been developed and advanced into the clinic and discuss their effects on autophagy. For the most part, these apoptosis-inducing compounds appear to elevate autophagy activity. Under certain circumstances autophagy demonstrates cytoprotective functions and is overactivated in response to chemo- or radiotherapy which can lead to drug resistance, representing a clinical obstacle for successful cancer treatment. Thus, targeting the autophagy pathway in combination with apoptosis-inducing compounds may be a promising strategy for cancer therapy.

High cell density increases glioblastoma cell viability under glucose deprivation via degradation of the cystine/glutamate transporter xCT (SLC7A11)

The cystine/glutamate transporter system x_c ^- consists of the light-chain subunit xCT (SLC7A11) and the heavy-chain subunit CD98 (4F2hc or SLC3A2) and exchanges extracellular cystine for intracellular glutamate at the plasma membrane. The imported cystine is reduced to cysteine and used for synthesis of GSH, one of the most important antioxidants in cancer cells. Because cancer cells have increased levels of reactive oxygen species, xCT, responsible for cystine-glutamate exchange, is overexpressed in many cancers, including glioblastoma. However, under glucose-limited conditions, xCT overexpression induces reactive oxygen species accumulation and cell death. Here we report that cell survival under glucose deprivation depends on cell density. We found that high cell density (HD) down-regulates xCT levels and increases cell viability under glucose deprivation. We also found that growth of glioblastoma cells at HD inactivates mTOR and that treatment of cells grown at low density with the mTOR inhibitor Torin 1 down-regulates xCT and inhibits glucose deprivation-induced cell death. The lysosome inhibitor bafilomycin A1 suppressed xCT down-regulation in HD-cultured glioblastoma cells and in Torin 1-treated cells grown at low density. Additionally, bafilomycin A1 exposure or ectopic xCT expression restored glucose deprivation-induced cell death at HD. These results suggest that HD inactivates mTOR and promotes lysosomal degradation of xCT, leading to improved glioblastoma cell viability under glucose-limited conditions. Our findings provide evidence that control of xCT protein expression via lysosomal degradation is an important mechanism for metabolic adaptation in glioblastoma cells.

Helping the Released Guardian: Drug Combinations for Supporting the Anticancer Activity of HDM2 (MDM2) Antagonists

The protein p53, known as the "Guardian of the Genome", plays an important role in maintaining DNA integrity, providing protection against cancer-promoting mutations. Dysfunction of p53 is observed in almost every cancer, with 50% of cases bearing loss-of-function mutations/deletions in the TP53 gene. In the remaining 50% of cases the overexpression of HDM2 (mouse double minute 2, human homolog) protein, which is a natural inhibitor of p53, is the most common way of keeping p53 inactive. Disruption of HDM2-p53 interaction with the use of HDM2 antagonists leads to the release of p53 and expression of its target genes, engaged in the induction of cell cycle arrest, DNA repair, senescence, and apoptosis. The induction of apoptosis, however, is restricted to only a handful of p53wt cells, and, generally, cancer cells treated with HDM2 antagonists are not efficiently eliminated. For this reason, HDM2 antagonists were tested in combinations with multiple other therapeutics in a search for synergy that would enhance the cancer eradication. This manuscript aims at reviewing the recent progress in developing strategies of combined cancer treatment with the use of HDM2 antagonists.

Development of Novel Epoxyketone-Based Proteasome Inhibitors as a Strategy To Overcome Cancer Resistance to Carfilzomib and Bortezomib

Over the past 15 years, proteasome inhibitors (PIs), namely bortezomib, carfilzomib (Cfz) and ixazomib, have significantly improved the overall survival and quality-of-life for multiple myeloma (MM) patients. However, a significant portion of MM patients do not respond to PI therapies. Drug resistance is present either de novo or acquired after prolonged therapy through mechanisms that remain poorly defined. The lack of a clear understanding of clinical PI resistance has hampered the development of next-generation PI drugs to treat MM patients who no longer respond to currently available therapies. Here, we designed and synthesized novel epoxyketone-based PIs by structural modifications at the P1' site. We show that a Cfz analog, 9, harboring a hydroxyl substituent at its P1' position was highly cytotoxic against cancer cell lines displaying de novo or acquired resistance to Cfz. These results suggest that peptide epoxyketones incorporating P1'-targeting moieties may have the potential to bypass resistance mechanisms associated with Cfz and to provide additional clinical options for patients resistant to Cfz.

Ubiquitin-activating enzyme inhibition induces an unfolded protein response and overcomes drug resistance in myeloma

Three proteasome inhibitors have garnered regulatory approvals in various multiple myeloma settings; but drug resistance is an emerging challenge, prompting interest in blocking upstream components of the ubiquitin-proteasome pathway. One such attractive target is the E1 ubiquitin-activating enzyme (UAE); we therefore evaluated the activity of TAK-243, a novel and specific UAE inhibitor. TAK-243 potently suppressed myeloma cell line growth, induced apoptosis, and activated caspases while decreasing the abundance of ubiquitin-protein conjugates. This was accompanied by stabilization of many short-lived proteins, including p53, myeloid cell leukemia 1 (MCL-1), and c-MYC, and activation of the activating transcription factor 6 (ATF-6), inositol-requiring enzyme 1 (IRE-1), and protein kinase RNA-like endoplasmic reticulum (ER) kinase (PERK) arms of the ER stress response pathway, as well as oxidative stress. UAE inhibition showed comparable activity against otherwise isogenic cell lines with wild-type (WT) or deleted p53 despite induction of TP53 signaling in WT cells. Notably, TAK-243 overcame resistance to conventional drugs and novel agents in cell-line models, including bortezomib and carfilzomib resistance, and showed activity against primary cells from relapsed/refractory myeloma patients. In addition, TAK-243 showed strong synergy with a number of antimyeloma agents, including doxorubicin, melphalan, and panobinostat as measured by low combination indices. Finally, TAK-243 was active against a number of in vivo myeloma models in association with activation of ER stress. Taken together, the data support the conclusion that UAE inhibition could be an attractive strategy to move forward to the clinic for patients with relapsed and/or refractory multiple myeloma.

Dose and Schedule Determine Distinct Molecular Mechanisms Underlying the Efficacy of the p53-MDM2 Inhibitor HDM201

Activation of p53 by inhibitors of the p53-MDM2 interaction is being pursued as a therapeutic strategy in p53 wild-type cancers. Here, we report distinct mechanisms by which the novel, potent, and selective inhibitor of the p53-MDM2 interaction HDM201 elicits therapeutic efficacy when applied at various doses and schedules. Continuous exposure of HDM201 led to induction of p21 and delayed accumulation of apoptotic cells. By comparison, high-dose pulses of HDM201 were associated with marked induction of PUMA and a rapid onset of apoptosis. shRNA screens identified PUMA as a mediator of the p53 response specifically in the pulsed regimen. Consistent with this, the single high-dose HDM201 regimen resulted in rapid and marked induction of PUMA expression and apoptosis together with downregulation of Bcl-xL in vivo Knockdown of Bcl-xL was identified as the top sensitizer to HDM201 in vitro, and Bcl-xL was enriched in relapsing tumors from mice treated with intermittent high doses of HDM201. These findings define a regimen-dependent mechanism by which disruption of MDM2-p53 elicits therapeutic efficacy when given with infrequent dosing. In an ongoing HDM201 trial, the observed exposure-response relationship indicates that the molecular mechanism elicited by pulse dosing is likely reproducible in patients. These data support the clinical comparison of daily and intermittent regimens of p53-MDM2 inhibitors.Significance: Pulsed high doses versus sustained low doses of the p53-MDM2 inhibitor HDM201 elicit a proapoptotic response from wild-type p53 cancer cells, offering guidance to current clinical trials with this and other drugs that exploit the activity of p53. Cancer Res; 78(21); 6257-67. ©2018 AACR.

Cross Talk Networks of Mammalian Target of Rapamycin Signaling With the Ubiquitin Proteasome System and Their Clinical Implications in Multiple Myeloma

Multiple myeloma (MM) is the second most common hematological malignancy and results from the clonal amplification of plasma cells. Despite recent advances in treatment, MM remains incurable with a median survival time of only 5-6years, thus necessitating further insights into MM biology and exploitation of novel therapeutic approaches. Both the ubiquitin proteasome system (UPS) and the PI3K/Akt/mTOR signaling pathways have been implicated in the pathogenesis, and treatment of MM and different lines of evidence suggest a close cross talk between these central cell-regulatory signaling networks. In this review, we outline the interplay between the UPS and mTOR pathways and discuss their implications for the pathophysiology and therapy of MM.

Identification of the APC/C co-factor FZR1 as a novel therapeutic target for multiple myeloma

Multiple Myeloma (MM) is a haematological neoplasm characterised by the clonal proliferation of malignant plasma cells in the bone marrow. The success of proteasome inhibitors in the treatment of MM has highlighted the importance of the ubiquitin proteasome system (UPS) in the pathogenesis of this disease. In this study, we analysed gene expression of UPS components to identify novel therapeutic targets within this pathway in MM. Here we demonstrate how this approach identified previously validated and novel therapeutic targets. In addition we show that FZR1 (Fzr), a cofactor of the multi-subunit E3 ligase complex anaphase-promoting complex/cyclosome (APC/C), represents a novel therapeutic target in myeloma. The APC/C associates independently with two cofactors, Fzr and Cdc20, to control cell cycle progression. We found high levels of FZR1 in MM primary cells and cell lines and demonstrate that expression is further increased on adhesion to bone marrow stromal cells (BMSCs). Specific knockdown of either FZR1 or CDC20 reduced viability and induced growth arrest of MM cell lines, and resulted in accumulation of APC/C^Fzr substrate Topoisomerase IIα (TOPIIα) or APC/C^Cdc20 substrate Cyclin B. Similar effects were observed following treatment with proTAME, an inhibitor of both APC/C^Fzr and APC/C^Cdc20. Combinations of proTAME with topoisomerase inhibitors, etoposide and doxorubicin, significantly increased cell death in MM cell lines and primary cells, particularly if TOPIIα levels were first increased through pre-treatment with proTAME. Similarly, combinations of proTAME with the microtubule inhibitor vincristine resulted in enhanced cell death. This study demonstrates the potential of targeting the APC/C and its cofactors as a therapeutic approach in MM.

Targeting the neddylation pathway in cells as a potential therapeutic approach for diseases

The ubiquitin-proteasome system (UPS) is an important system that regulates the balance of intracellular proteins, and it is involved in the regulation of multiple vital biological processes. The approval of bortezomib for relapsed and refractory multiple myeloma has proven that agents targeting the UPS have the potential to be effective treatment strategies for diseases. Among of all of the components of the UPS, cullin-RING ligases (CRLs) are the focus of research. CRLs are the largest family of ubiquitin E3 ligases and they play a critical role in substrate binding. CRL activity is modulated by many pathways in which neddylation modification is the essential process for cullin activation. Thus, targeting the neddylation pathway of cullins could indirectly affect CRL activity, thereby interfering with substrate protein ubiquitination. In addition to cullin proteins, there are some other target proteins of neddylation, such as p53, mouse double minute 2, and epidermal growth factor receptor. For target proteins, neddylation modification mainly causes functions changes, not degradation. In addition, the level of neddylation is also closely related to disease development and prognosis. In this review, we summarize the research on some target proteins and active target agents of neddylation pathways, and explore the role of neddylation in disease therapy. We came to the conclusion that conducting research on neddylation may be a potential approach to discover some novel targets and agents that could be effective without serious side effects.

Constitutional mutation in CDKN2A is associated with long term survivorship in multiple myeloma: a case report

Background

Multiple Myeloma is a cancer of plasma cells associated with significantly reduced survival. Long term survivorship from myeloma is very rare and despite advances in its treatment the disease is generally considered incurable. We report a patient diagnosed with myeloma carrying a germline mutation of a tumour suppressor gene who has effectively been cured.

Case presentation

A 36-year-old woman was diagnosed with IgG lambda myeloma in 1985. She was treated with melphalan chemotherapy followed by high-dose melphalan and autologous stem cell rescue and since remained in complete remission despite not having received any additional therapy. After eliciting a prior history of multiple primary melanomas and breast cancer, she was tested for and shown to be a carrier for a germline mutation in CDKN2A.

Conclusions

This is the second case report of germline mutation of CDKN2A being associated with myeloma. CDKN2A is a stabiliser of p53. Long term survivorship after high dose DNA damaging chemotherapy with melphalan in this patient is compatible with an increased chemo-sensitivity due to impairment of the DNA repair pathway.

Therapeutics targeting Bcl-2 in hematological malignancies

Members of the B-cell lymphoma 2 (BCL-2) gene family are attractive targets for cancer therapy as they play a key role in promoting cell survival, a long-since established hallmark of cancer. Clinical utility for selective inhibition of specific anti-apoptotic Bcl-2 family proteins has recently been realized with the Food and Drug Administration (FDA) approval of venetoclax (formerly ABT-199/GDC-0199) in relapsed chronic lymphocytic leukemia (CLL) with 17p deletion. Despite the impressive monotherapy activity in CLL, such responses have rarely been observed in other B-cell malignancies, and preclinical data suggest that combination therapies will be needed in other indications. Additional selective antagonists of Bcl-2 family members, including Bcl-X_L and Mcl-1, are in various stages of preclinical and clinical development and hold the promise of extending clinical utility beyond CLL and overcoming resistance to venetoclax. In addition to direct targeting of Bcl-2 family proteins with BH3 mimetics, combination therapies that aim at down-regulating expression of anti-apoptotic BCL-2 family members or restoring expression of pro-apoptotic BH3 family proteins may provide a means to deepen responses to venetoclax and extend the utility to additional indications. Here, we review recent progress in direct and selective targeting of Bcl-2 family proteins for cancer therapy and the search for rationale combinations.

Crosstalk and Interplay between the Ubiquitin-Proteasome System and Autophagy

Proteolysis in eukaryotic cells is mainly mediated by the ubiquitin (Ub)-proteasome system (UPS) and the autophagylysosome system (hereafter autophagy). The UPS is a selective proteolytic system in which substrates are recognized and tagged with ubiquitin for processive degradation by the proteasome. Autophagy is a bulk degradative system that uses lysosomal hydrolases to degrade proteins as well as various other cellular constituents. Since the inception of their discoveries, the UPS and autophagy were thought to be independent of each other in components, action mechanisms, and substrate selectivity. Recent studies suggest that cells operate a single proteolytic network comprising of the UPS and autophagy that share notable similarity in many aspects and functionally cooperate with each other to maintain proteostasis. In this review, we discuss the mechanisms underlying the crosstalk and interplay between the UPS and autophagy, with an emphasis on substrate selectivity and compensatory regulation under cellular stresses.

RNA Polymerase I Inhibition with CX-5461 as a Novel Therapeutic Strategy to Target MYC in Multiple Myeloma

Dysregulation of MYC is frequently implicated in both early and late myeloma progression events, yet its therapeutic targeting has remained a challenge. Among key MYC downstream targets is ribosomal biogenesis, enabling increases in protein translational capacity necessary to support the growth and self-renewal programmes of malignant cells. We therefore explored the selective targeting of ribosomal biogenesis with the small molecule RNA polymerase (pol) I inhibitor CX-5461 in myeloma. CX-5461 induced significant growth inhibition in wild-type (WT) and mutant TP53 myeloma cell lines and primary samples, in association with increases in downstream markers of apoptosis. Moreover, Pol I inhibition overcame adhesion-mediated drug resistance and resistance to conventional and novel agents. To probe the TP53-independent mechanisms of CX-5461, gene expression profiling was performed on isogenic TP53 WT and knockout cell lines and revealed reduction of MYC downstream targets. Mechanistic studies confirmed that CX-5461 rapidly suppressed both MYC protein and MYC mRNA levels. The latter was associated with an increased binding of the RNA-induced silencing complex (RISC) subunits TARBP2 and AGO2, the ribosomal protein RPL5, and MYC mRNA, resulting in increased MYC transcript degradation. Collectively, these studies provide a rationale for the clinical translation of CX-5461 as a novel therapeutic approach to target MYC in myeloma.

P53-MDM2 Pathway: Evidences for A New Targeted Therapeutic Approach in B-Acute Lymphoblastic Leukemia

The tumor suppressor p53 is a canonical regulator of different biological functions, like apoptosis, cell cycle arrest, DNA repair, and genomic stability. This gene is frequently altered in human tumors generally by point mutations or deletions. Conversely, in acute lymphoblastic leukemia (ALL) genomic alterations of TP53 are rather uncommon, and prevalently occur in patients at relapse or with poor prognosis. On the other hand, p53 pathway is often compromised by the inactivation of its regulatory proteins, as MDM2 and ARF. MDM2 inhibitor molecules are able to antagonize p53-MDM2 interaction allowing p53 to exert tumor suppressor transcriptional regulation and to induce apoptotic pathways. Recent preclinical and clinical studies propose that MDM2 targeted therapy represents a promising anticancer strategy restoring p53 dependent mechanisms in ALL disease. Here, we discussed the use of new small molecule targeting p53 pathways as a promising drug target therapy in ALL.

Outcomes in patients with multiple myeloma with TP53 deletion after autologous hematopoietic stem cell transplant

TP53 gene deletion is associated with poor outcomes in multiple myeloma (MM). We report the outcomes of patients with MM with and without TP53 deletion who underwent immunomodulatory drug (IMiD) and/or proteasome inhibitor (PI) induction followed by autologous hematopoietic stem cell transplant (auto-HCT). We identified 34 patients with MM and TP53 deletion who underwent IMiD and/or PI induction followed by auto-HCT at our institution during 2008-2014. We compared their outcomes with those of control patients (n = 111) with MM without TP53 deletion. Median age at auto-HCT was 59 years in the TP53-deletion group and 58 years in the control group (P = 0.4). Twenty-one patients (62%) with TP53 deletion and 69 controls (62%) achieved at least partial remission before auto-HCT (P = 0.97). Twenty-three patients (68%) with TP53 deletion and 47 controls (42%) had relapsed disease at auto-HCT (P = 0.01). Median progression-free survival was 8 months for patients with TP53 deletion and 28 months for controls (P < 0.001). Median overall survival was 21 months for patients with TP53 deletion and 56 months for controls (P < 0.001). On multivariate analysis of both groups, TP53 deletion (hazard ratio 3.4, 95% confidence interval 1.9-5.8, P < 0.001) and relapsed disease at auto-HCT (hazard ratio 2.0, 95% confidence interval 1.2-3.4, P = 0.008) were associated with a higher risk of earlier progression. In MM patients treated with PI and/or IMiD drugs, and auto-HCT, TP53 deletion and relapsed disease at the time of auto-HCT are independent predictors of progression. Novel approaches should be evaluated in this high-risk population. Am. J. Hematol. 91:E442-E447, 2016. © 2016 Wiley Periodicals, Inc.

Novel strategies to target the ubiquitin proteasome system in multiple myeloma

Multiple myeloma (MM) is a hematological malignancy characterized by the accumulation of plasma cells in the bone marrow (BM). The success of the proteasome inhibitor bortezomib in the treatment of MM highlights the importance of the ubiquitin proteasome system (UPS) in this particular cancer. Despite the prolonged survival of MM patients, a significant amount of patients relapse or become resistant to therapy. This underlines the importance of the development and investigation of novel targets to improve MM therapy. The UPS plays an important role in different cellular processes by targeted destruction of proteins. The ubiquitination process consists of enzymes that transfer ubiquitin to proteins targeting them for proteasomal degradation. An emerging and promising approach is to target more disease specific components of the UPS to reduce side effects and overcome resistance. In this review, we will focus on different components of the UPS such as the ubiquitin activating enzyme E1, the ubiquitin conjugating enzyme E2, the E3 ubiquitin ligases, the deubiquitinating enzymes (DUBs) and the proteasome. We will discuss their role in MM and the implications in drug discovery for the treatment of MM.

How I treat high-risk myeloma

The treatment of patients with myeloma has dramatically changed over the past decade due in part to the development of new agents and myeloma-specific targets. Despite these advancements, a group for whom the long-term benefit remains less clear are patients with genetically or clinically defined high-risk myeloma. In order to successfully treat these patients, it is important to first identify these patients, treat them with aggressive combination therapy, and employ the use of aggressive long-term maintenance therapy. Future directions include the use of new immune-based treatments (antibodies or cellular-based therapies) as well as target-driven approaches. Until these treatment approaches are better defined, this review will provide a potential treatment approach for standard- and high-risk myeloma that can be followed using agents and strategies that are currently available with the goal of improving progression-free and overall survival for these patients today.

Therapeutic targeting of Bcl-2 family for treatment of B-cell malignancies

The BCL2 gene was discovered nearly 30 years ago, launching a field of scientific inquiry and medical research with the potential for delivering transformational therapeutics. Revealed by its involvement in chromosomal translocations of B-cell lymphomas, BCL2 is the founding member of a family of cell survival genes that endow cells with long life spans and provide protection from a myriad of cellular stresses, including chemotherapy. Anti-apoptotic Bcl-2 family members are commonly overexpressed in a variety of human malignancies through a diversity of genetic and epigenetic mechanisms. Here, we review therapeutic strategies for targeting Bcl-2 family members with an emphasis on B-cell malignancies, providing insights into their current promise and remaining challenges.

Emerging Therapeutic Strategies for Overcoming Proteasome Inhibitor Resistance

The debut of the proteasome inhibitor bortezomib (Btz; Velcade®) radically and immediately improved the treatment of multiple myeloma (MM), an incurable malignancy of the plasma cell. Therapeutic resistance is unavoidable, however, and represents a major obstacle to maximizing the clinical potential of the drug. To address this challenge, studies have been conducted to uncover the molecular mechanisms driving Btz resistance and to discover new targeted therapeutic strategies and combinations that restore Btz activity. This review discusses the literature describing molecular adaptations that confer Btz resistance with a primary disease focus on MM. Also discussed are the most recent advances in therapeutic strategies that overcome resistance, approaches that include redox-modulating agents, murine double minute 2 inhibitors, therapeutic monoclonal antibodies, and new epigenetic-targeted drugs like bromodomain and extra terminal domain inhibitors.