p53 abnormalities and potential therapeutic targeting in multiple myeloma

Exploring the role of histone deacetylase and histone deacetylase inhibitors in the context of multiple myeloma: mechanisms, therapeutic implications, and future perspectives

Histone deacetylase inhibitors (HDACis) are a significant category of pharmaceuticals that have developed in the past two decades to treat multiple myeloma. Four drugs in this category have received approval from the U.S. Food and Drug Administration (FDA) for use: Panobinonstat (though canceled by the FDA in 2022), Vorinostat, Belinostat and Romidepsin. The efficacy of this group of drugs is attributed to the disruption of many processes involved in tumor growth through the inhibition of histone deacetylase, and this mode of action leads to significant anti-multiple myeloma (MM) activity. In MM, inhibition of histone deacetylase has many downstream consequences, including suppression of NF-κB signaling and HSP90, upregulation of cell cycle regulators (p21, p53), and downregulation of antiapoptotic proteins including Bcl-2. Furthermore, HDACis have a variety of direct and indirect oxidative effects on cellular DNA. HDAC inhibitors enhance normal immune function, thereby decreasing the proliferation of malignant plasma cells and promoting autophagy. The various biological effects of inhibiting histone deacetylase have a combined or additional impact when used alongside other chemotherapeutic and targeted drugs for multiple myeloma. This helps to decrease resistance to treatment. Combination treatment regimens that include HDACis have become an essential part of the therapy for multiple myeloma. These regimens incorporate drugs from other important classes of anti-myeloma agents, such as immunomodulatory drugs (IMiDs), conventional chemotherapy, monoclonal antibodies, and proteasome inhibitors. This review provides a comprehensive evaluation of the clinical efficacy and safety data pertaining to the currently approved histone deacetylase inhibitors, as well as an explanation of the crucial function of histone deacetylase in multiple myeloma and the characteristics of the different histone deacetylase inhibitors. Moreover, it provides a concise overview of the most recent developments in the use of histone deacetylase inhibitors for treating multiple myeloma, as well as potential future uses in treatment.

Clarifying the molecular mechanism of tomentosin‑induced antiproliferative and proapoptotic effects in human multiple myeloma via gene expression profile and genetic interaction network analysis

Multiple myeloma (MM) is an aggressive B cell malignancy. Substantial progress has been made in the therapeutic context for patients with MM, however it still represents an incurable disease due to drug resistance and recurrence. Development of more effective or synergistic therapeutic approaches undoubtedly represents an unmet clinical need. Tomentosin is a bioactive natural sesquiterpene lactone extracted by various plants with therapeutic properties, including anti-neoplastic effects. In the present study, the potential antitumor activity of tomentosin was evaluated on the human RPMI-8226 cell line, treated with increasing tomentosin concentration for cytotoxicity screening. The data suggested that both cell cycle arrest and cell apoptosis could explain the antiproliferative effects of tomentosin and may result in the inhibition of RPMI-8226 cell viability. To assess differentially expressed genes contributing to tomentosin activity and identify its mechanism of action, a microarray gene expression profile was performed, identifying 126 genes deregulated by tomentosin. To address the systems biology and identify how tomentosin deregulates gene expression in MM from a systems perspective, all deregulated genes were submitted to enrichment and molecular network analysis. The Protein-Protein Interaction (PPI) network analysis showed that tomentosin in human MM induced the downregulation of genes involved in several pathways known to lead immune-system processes, such as cytokine-cytokine receptor interaction, chemokine or NF-κB signaling pathway, as well as genes involved in pathways playing a central role in cellular neoplastic processes, such as growth, proliferation, migration, invasion and apoptosis. Tomentosin also induced endoplasmic reticulum stress via upregulation of cyclic AMP-dependent transcription factor ATF-4 and DNA damage-inducible transcript 3 protein genes, suggesting that in the presence of tomentosin the protective unfolded protein response signaling may induce cell apoptosis. The functional connections analysis executed using the Connectivity Map tool, suggested that the effects of tomentosin on RPMI-8226 cells might be similar to those exerted by heat shock proteins inhibitors. Taken together, these data suggested that tomentosin may be a potential drug candidate for the treatment of MM.

Targeting the methyltransferase SETD8 impairs tumor cell survival and overcomes drug resistance independently of p53 status in multiple myeloma

Background

Multiple myeloma (MM) is a malignancy of plasma cells that largely remains incurable. The search for new therapeutic targets is therefore essential. In addition to a wide panel of genetic mutations, epigenetic alterations also appear as important players in the development of this cancer, thereby offering the possibility to reveal novel approaches and targets for effective therapeutic intervention.

Results

Here, we show that a higher expression of the lysine methyltransferase SETD8, which is responsible for the mono-methylation of histone H4 at lysine 20, is an adverse prognosis factor associated with a poor outcome in two cohorts of newly diagnosed patients. Primary malignant plasma cells are particularly addicted to the activity of this epigenetic enzyme. Indeed, the inhibition of SETD8 by the chemical compound UNC-0379 and the subsequent decrease in histone H4 methylation at lysine 20 are highly toxic in MM cells compared to normal cells from the bone marrow microenvironment. At the molecular level, RNA sequencing and functional studies revealed that SETD8 inhibition induces a mature non-proliferating plasma cell signature and, as observed in other cancers, triggers an activation of the tumor suppressor p53, which together cause an impairment of myeloma cell proliferation and survival. However, a deadly level of replicative stress was also observed in p53-deficient myeloma cells treated with UNC-0379, indicating that the cytotoxicity associated with SETD8 inhibition is not necessarily dependent on p53 activation. Consistent with this, UNC-0379 triggers a p53-independent nucleolar stress characterized by nucleolin delocalization and reduction of nucleolar RNA synthesis. Finally, we showed that SETD8 inhibition is strongly synergistic with melphalan and may overcome resistance to this alkylating agent widely used in MM treatment.

Conclusions

Altogether, our data indicate that the up-regulation of the epigenetic enzyme SETD8 is associated with a poor outcome and the deregulation of major signaling pathways in MM. Moreover, we provide evidences that myeloma cells are dependent on SETD8 activity and its pharmacological inhibition synergizes with melphalan, which could be beneficial to improve MM treatment in high-risk patients whatever their status for p53.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13148-021-01160-z.

Omega-3 Fatty Acids DHA and EPA Reduce Bortezomib Resistance in Multiple Myeloma Cells by Promoting Glutathione Degradation

Multiple myeloma (MM) is a hematological malignancy that exhibits aberrantly high levels of proteasome activity. While treatment with the proteasome inhibitor bortezomib substantially increases overall survival of MM patients, acquired drug resistance remains the main challenge for MM treatment. Using a combination treatment of docosahexaenoic acid (DHA) or eicosapentaenoic acid (EPA) and bortezomib, it was demonstrated previously that pretreatment with DHA/EPA significantly increased bortezomib chemosensitivity in MM cells. In the current study, both transcriptome and metabolome analysis were performed to comprehensively evaluate the underlying mechanism. It was demonstrated that pretreating MM cells with DHA/EPA before bortezomib potently decreased the cellular glutathione (GSH) level and altered the expression of the related metabolites and key enzymes in GSH metabolism, whereas simultaneous treatment only showed minor effects on these factors, thereby suggesting the critical role of GSH degradation in overcoming bortezomib resistance in MM cells. Moreover, RNA-seq results revealed that the nuclear factor erythroid 2-related factor 2 (NRF2)-activating transcription factor 3/4 (ATF3/4)-ChaC glutathione specific gamma-glutamylcyclotransferase 1 (CHAC1) signaling pathway may be implicated as the central player in the GSH degradation. Pathways of necroptosis, ferroptosis, p53, NRF2, ATF4, WNT, MAPK, NF-κB, EGFR, and ERK may be connected to the tumor suppressive effect caused by pretreatment of DHA/EPA prior to bortezomib. Collectively, this work implicates GSH degradation as a potential therapeutic target in MM and provides novel mechanistic insights into its significant role in combating bortezomib resistance.

Mutational analysis of p53 gene in cervical cancer and useful polymorphic variants in exons 3 and 4

Background

Factors contributing to the pathogenesis and progression of cervical cancer include poor attitude to screening and health intervention, late presentation, among others. Mutations in p53 gene have been attributed to several cancer cases. The present study was designed to find relationships between the mutation patterns in p53 gene and cervical carcinoma staging. Such knowledge could contribute to early diagnosis of cervical cancer.

Results

From the sequence analysis of p53 gene fragment isolated by polymerase chain reactions (PCR), nineteen (19) polymorphic variants were identified. Missense mutations occurred in 47% of the samples, 32% were silent mutations, 16% were frameshift mutations and 5% nonsense mutations. Socio-biological characteristics of the study participants revealed that 60% have husbands with multiple sexual partners and that only 23.3% of the participants have ever had the Papanicolaou (Pap) smear test prior to diagnosis, whilst 20% were unaware of the screening test.

Conclusions

Increased severity of cervical carcinoma staging as revealed from the histopathological analysis was found to be associated with accumulation of higher levels of mutations in the p53 gene. Molecular analysis of p53 gene mutations may prove useful as a screening biomarker for cervical cancer.

Progressive multifocal leukoencephalopathy in multiple myeloma. A literature review and lessons to learn

Progressive multifocal leukoencephalopathy (PML) is a rare opportunistic infection with high mortality rate usually seen in the context of immunosuppression. Although cases have been reported largely in patients with HIV/AIDS, following the use of monoclonal antibodies and occasionally in haematological malignancies, there is no review to date of patients with smouldering or treated myeloma who developed PML. Here, we conducted a literature search of PML cases in patients with multiple myeloma (MM), analyse patient and disease characteristics and describe the possible mechanisms that could lead to the development of PML. The lack of data and case reports until 2010 may indicate that PML in MM is underdiagnosed. Simultaneously, with an expanding field of new therapeutic options, patients with MM live longer, albeit continually immunosuppressed, and at risk of opportunistic infections. Emerging new treatments for PML in the horizon render the need to look out for this complication mandatory, and more case reports are needed to enrich our knowledge in this field.

Targeting p53-MDM2 Interaction Using Small Molecule Inhibitors and the Challenges Needed to be Addressed

MDM2 protein is the core negative regulator of p53 that maintains the cellular levels of p53 at a low level in normal cells. Mutation of the TP53 gene accounts for 50% of all human cancers. In the remaining malignancies with wild-type TP53, p53 function is inhibited through other mechanisms. Recently, synthetic small molecule inhibitors have been developed which target a small hydrophobic pocket on MDM2 to which p53 normally binds. Given that MDM2-p53 antagonists have been undergoing clinical trials for different types of cancer, this review illustrates different aspects of these new cancer targeted therapeutic agents with the focus on the major advances in the field. It emphasizes on the p53 function, regulation of p53, targeting of the p53-MDM2 interaction for cancer therapy, and p53-dependent and -independent effects of inhibition of p53-MDM2 interaction. Then, representatives of small molecule MDM2-p53 binding antagonists are introduced with a focus on those entered into clinical trials. Furthermore, the review discusses the gene signatures in order to predict sensitivity to MDM2 antagonists, potential side effects and the reasons for the observed hematotoxicity, mechanisms of resistance to these drugs, their evaluation as monotherapy or in combination with conventional chemotherapy or with other targeted therapeutic agents. Finally, it highlights the certainly intriguing questions and challenges which would be addressed in future studies.

High impact of miRNA-4521 on FOXM1 expression in medulloblastoma

Medulloblastoma, an embryonal tumor of the cerebellum/fourth ventricle, is one of the most frequent malignant brain tumors in children. Although genetic variants are increasingly used in treatment stratification, survival of high-risk patients, characterized by leptomeningeal dissemination, TP53 mutation or MYC amplification, is still poor. FOXM1, a proliferation-specific oncogenic transcription factor, is deregulated in various solid tumors, including medulloblastoma, and triggers cellular proliferation, migration and genomic instability. In tissue samples obtained from medulloblastoma patients, the significant upregulation of FOXM1 was associated with a loss of its putative regulating microRNA, miR-4521. To understand the underlying mechanism, we investigated the effect of miR-4521 on the expression of the transcription factor FOXM1 in medulloblastoma cell lines. Transfection of this microRNA reduced proliferation and invasion of several medulloblastoma cell lines and induced programmed cell death through activation of caspase 3/7. Further, downstream targets of FOXM1 such as PLK1 and cyclin B1 were significantly reduced thus affecting the cell cycle progression in medulloblastoma cell lines. In conclusion, a restoration of miRNA-4521 may selectively suppress the pathophysiological effect of aberrant FOXM1 expression and serve as a targeted approach for medulloblastoma therapy.

Deregulation and Targeting of TP53 Pathway in Multiple Myeloma

Multiple Myeloma (MM) is an incurable disease characterized by a clonal evolution across the course of the diseases and multiple lines of treatment. Among genomic drivers of the disease, alterations of the tumor suppressor TP53 are associated with poor outcomes. In physiological situation, once activated by oncogenic stress or DNA damage, p53 induces either cell-cycle arrest or apoptosis depending on the cellular context. Its inactivation participates to drug resistance in MM. The frequency of TP53 alterations increases along with the progression of the disease, from 5 at diagnosis to 75% at late relapses. Multiple mechanisms of regulation lead to decreased expression of p53, such as deletion 17p, TP53 mutations, specific microRNAs overexpression, TP53 promoter methylations, and MDM2 overexpression. Several therapeutic approaches aim to target the p53 pathway, either by blocking its interaction with MDM2 or by restoring the function of the altered protein. In this review, we describe the mechanism of deregulation of TP53 in MM, its role in MM progression, and the therapeutic options to interact with the TP53 pathway.

Pharmacokinetic-Pharmacodynamic Model of Neutropenia in Patients With Myeloma Receiving High-Dose Melphalan for Autologous Stem Cell Transplant

High-dose melphalan (HDM) is part of the conditioning regimen in patients with multiple myeloma (MM) receiving autologous stem cell transplantation (ASCT). However, individual sensitivity to melphalan varies, and many patients experience severe toxicities. Prolonged severe neutropenia is one of the most severe toxicities and contributes to potentially life-threatening infections and failure of ASCT. Granulocyte-colony stimulating factor (G-CSF) is given to stimulate neutrophil proliferation after melphalan administration. The aim of this study was to develop a population pharmacokinetic/pharmacodynamic (PK/PD) model capable of predicting neutrophil kinetics in individual patients with MM undergoing ASCT with high-dose melphalan and G-CSF administration. The extended PK/PD model incorporated several covariates, including G-CSF regimen, stem cell dose, hematocrit, sex, creatinine clearance, p53 fold change, and race. The resulting model explained portions of interindividual variability in melphalan exposure, therapeutic effect, and feedback regulation of G-CSF on neutrophils, thus enabling simulation of various doses and prediction of neutropenia duration.

Use of multicolor fluorescence in situ hybridization to detect deletions in clinical tissue sections

A variety of laboratory methods are available for the detection of deletions of tumor suppressor genes and losses of their proteins. The clinical utility of fluorescence in situ hybridization (FISH) for the identification of deletions of tumor suppressor genes has previously been limited by difficulties in the interpretation of FISH signal patterns. The first deletion FISH assays using formalin-fixed paraffin-embedded tissue sections had to deal with a significant background level of signal losses affecting nuclei that are truncated by the cutting process of slide preparation. Recently, more efficient probe designs, incorporating probes adjacent to the tumor suppressor gene of interest, have increased the accuracy of FISH deletion assays so that true chromosomal deletions can be readily distinguished from the false signal losses caused by sectioning artifacts. This mini-review discusses the importance of recurrent tumor suppressor gene deletions in human cancer and reviews the common FISH methods being used to detect the genomic losses encountered in clinical specimens. The use of new probe designs to recognize truncation artifacts is illustrated with a four-color PTEN FISH set optimized for prostate cancer tissue sections. Data are presented to show that when section thickness is reduced, the frequency of signal truncation losses is increased. We also provide some general guidelines that will help pathologists and cytogeneticists run routine deletion FISH assays and recognize sectioning artifacts. Finally, we summarize how recently developed sequence-based approaches are being used to identify recurrent deletions using small DNA samples from tumors.

Successful Autologous Hematopoietic Stem Cell Transplantation Followed by Bortezomib Maintenance in a Patient with Relapsed CD138-low Multiple Solitary Plasmacytomas Harboring a 17p Deletion

Solitary bone plasmacytoma (SBP) tends to progress to multiple myeloma (MM); however, progression to multiple solitary plasmacytomas (MSP) is rare. We report a case of CD138-low MSP with 17p deletion in a patient with relapsed SBP. 17p deletion is associated with a poor outcome in patients with MM, and the low expression of CD138 in myeloma cells is associated with drug resistance and a poor prognosis. The patient was successfully treated with bortezomib plus dexamethasone induction therapy and autologous hematopoietic stem cell transplantation followed by bortezomib maintenance therapy. Consequently, bortezomib treatment was stopped and a stringent complete response has been maintained.

The role of p53 in cancer drug resistance and targeted chemotherapy

Cancer has long been a grievous disease complicated by innumerable players aggravating its cure. Many clinical studies demonstrated the prognostic relevance of the tumor suppressor protein p53 for many human tumor types. Overexpression of mutated p53 with reduced or abolished function is often connected to resistance to standard medications, including cisplatin, alkylating agents (temozolomide), anthracyclines, (doxorubicin), antimetabolites (gemcitabine), antiestrogenes (tamoxifen) and EGFR-inhibitors (cetuximab). Such mutations in the TP53 gene are often accompanied by changes in the conformation of the p53 protein. Small molecules that restore the wild-type conformation of p53 and, consequently, rebuild its proper function have been identified. These promising agents include PRIMA-1, MIRA-1, and several derivatives of the thiosemicarbazone family. In addition to mutations in p53 itself, p53 activity may be also be impaired due to alterations in p53s regulating proteins such as MDM2. MDM2 functions as primary cellular p53 inhibitor and deregulation of the MDM2/p53-balance has serious consequences. MDM2 alterations often result in its overexpression and therefore promote inhibition of p53 activity. To deal with this problem, a judicious approach is to employ MDM2 inhibitors. Several promising MDM2 inhibitors have been described such as nutlins, benzodiazepinediones or spiro-oxindoles as well as novel compound classes such as xanthone derivatives and trisubstituted aminothiophenes. Furthermore, even naturally derived inhibitor compounds such as a-mangostin, gambogic acid and siladenoserinols have been discovered. In this review, we discuss in detail such small molecules that play a pertinent role in affecting the p53-MDM2 signaling axis and analyze their potential as cancer chemotherapeutics.

p53 Deletion promotes myeloma cells invasion by upregulating miR19a/CXCR5

P53 deletion has been identified as one of the few factors that defined high risk and poor prognosis in MM. It has been reported p53 deletion is associated with resistance to chemotherapy and organ infiltrations of MM. However, p53 deletion in the migration and dissemination of MM cells has not been totally elucidated. In this research, first, we investigated whether p53 is associated with migration of MM cells. We found that p53 regulates the migration of NCI-H929 cells with wild-type p53 but not U266 cells with mutated-type p53. Next, we investigated the related mechanism by which p53 regulates the migration. We found that down-regulation of p53 reduced adhesion of NCI-H929 cells to the BM stroma via decreased expression of E-cadherin and increased EMT-regulating proteins. Further study have identified the miR-19a/CXCR5 pathway as a candidate p53-induced migration mechanism. In conclusion, we have demonstrated for the first time the critical value of p53 deletion in MM cell migration and dissemination, as well as the acquisition of an EMT-like phenotype. Our research provides new insights into the function of p53 in migration of MM and suggests p53/miRNA19a/CXCR5 may provide potentially therapeutic targets for the treatment of myeloma with p53 deletion.

Small molecule CP-31398 induces reactive oxygen species-dependent apoptosis in human multiple myeloma

Reactive oxygen species (ROS) are normal byproducts of a wide variety of cellular processes. ROS have dual functional roles in cancer cell pathophysiology. At low to moderate levels, ROS act as signaling transducers to activate cell proliferation, migration, invasion, and angiogenesis. In contrast, high levels of ROS induce cell death. In multiple myeloma (MM), ROS overproduction is the trigger for apoptosis induced by several anticancer compounds, including proteasome inhibitors. However, no drugs for which oxidative stress is the main mechanism of action are currently used for treatment of MM in clinical situations. In this study, we demonstrate that the p53-activating small molecule CP-31398 (CP) effectively inhibits the growth of MM cell lines and primary MM isolates from patients. CP also suppresses the growth of MM xenografts in mice. Mechanistically, CP was found to induce intrinsic apoptosis in MM cells via increasing ROS production. Interestingly, CP-induced apoptosis occurs regardless of the p53 status, suggesting that CP has additional mechanisms of action. Our findings thus indicate that CP could be an attractive candidate for treatment of MM patients harboring p53 abnormalities; this satisfies an unmet clinical need, as such individuals currently have a poor prognosis.

The therapeutic potential of cell cycle targeting in multiple myeloma

Proper cell cycle progression through the interphase and mitosis is regulated by coordinated activation of important cell cycle proteins (including cyclin-dependent kinases and mitotic kinases) and several checkpoint pathways. Aberrant activity of these cell cycle proteins and checkpoint pathways results in deregulation of cell cycle progression, which is one of the key hallmarks of cancer. Consequently, intensive research on targeting these cell cycle regulatory proteins identified several candidate small molecule inhibitors that are able to induce cell cycle arrest and even apoptosis in cancer cells. Importantly, several of these cell cycle regulatory proteins have also been proposed as therapeutic targets in the plasma cell malignancy multiple myeloma (MM). Despite the enormous progress in the treatment of MM the past 5 years, MM still remains most often incurable due to the development of drug resistance. Deregulated expression of the cyclins D is observed in virtually all myeloma patients, emphasizing the potential therapeutic interest of cyclin-dependent kinase inhibitors in MM. Furthermore, other targets have also been identified in MM, such as microtubules, kinesin motor proteins, aurora kinases, polo-like kinases and the anaphase promoting complex/cyclosome. This review will provide an overview of the cell cycle proteins and checkpoint pathways deregulated in MM and discuss the therapeutic potential of targeting proteins or protein complexes involved in cell cycle control in MM.

Precision Medicine in Myeloma: Challenges in Defining an Actionable Approach

Recently, large sequencing studies have provided insights into the mutational landscape of multiple myeloma (MM), identifying actionable mutations and giving a precious opportunity for exploring new targeted therapies. The main goal of precision medicine, matching patients with the right drug, seems to be closer than ever. However, no targeted therapies in MM are approved yet. Several clinical trials testing targeted drugs and enrolling patients with MM are currently ongoing and will provide predictive biomarkers that might support clinical decision making. In this review, we evaluate the evidence supporting the implementation of precision medicine in MM and we discuss the challenges that should be dealt with in this imminent and promising new era.

Additional-structural-chromosomal aberrations are associated with inferior clinical outcome in patients with hyperdiploid multiple myeloma: a single-institution experience

Multiple myeloma is cytogenetically heterogeneous and a hyperdiploid karyotype is considered currently to have standard risk. In this study, we investigated the clinical impact of additional-structural-chromosomal aberrations assessed by chromosome analysis in 284 patients with a hyperdiploid karyotype that were subdivided into four groups based on the complexity of additional-structural-chromosomal aberrations: group 1, no additional-structural-chromosomal aberrations (n=35); group 2, one additional-structural-chromosomal aberration (n=46); group 3, two additional-structural-chromosomal aberrations (n=39); group 4, ≥three additional-structural-chromosomal aberrations (n=164). Clinicopathological data among these groups showed no differences, except patients in group 1 had higher hemoglobin (P=0.031) and albumin (P=0.045) levels. The median follow-up was 55 months (range, 3-221). The median overall survival of patients in groups 1-4 was negatively correlated with the number of the additional-structural-chromosomal aberrations: 98, 76, 61, and 48 months, respectively (P<0.0001). In group 4, CKS1B gain, RB1, or TP53 deletions had no additional impact on overall survival; however, trisomy 3 or 15 conferred a much better overall survival, and monosomy 13 and 14 predicted a worse outcome. In addition, the overall survival of patients in groups 3 and 4 was similar to a subset of high-risk multiple myeloma cases (n=21) (P=0.387). About 192 (67.6%) patients who received stem cell transplantation did not show improved overall survival compared with non-stem cell transplantation patients (n=92; P=0.142) overall; however, they did show significantly improved overall survival in patients with refractory disease in group 4 (P=0.0084). Multivariate analysis showed that two or more additional-structural-chromosomal aberrations (P<0.0001), stages (P=0.02 and P=0.002) and relapsed disease (P=0.009) negatively impacted the overall survival. We conclude that hyperdiploid karyotypes in multiple myeloma are associated with additional-structural-chromosomal aberrations and a greater number of additional-structural-chromosomal aberrations predicts poorer clinical outcome. A hyperdiploid karyotype with ≥2 additional-structural-chromosomal aberrations at chromosomal level should be considered an independent high-risk factor.

Ribonucleotide Reductase Catalytic Subunit M1 (RRM1) as a Novel Therapeutic Target in Multiple Myeloma

Purpose: To investigate the biological and clinical significance of ribonucleotide reductase (RR) in multiple myeloma.Experimental Design: We assessed the impact of RR expression on patient outcome in multiple myeloma. We then characterized the effect of genetic and pharmacologic inhibition of ribonucleotide reductase catalytic subunit M1 (RRM1) on multiple myeloma growth and survival using siRNA and clofarabine, respectively, in both in vitro and in vivo mouse xenograft models.Results: Newly diagnosed multiple myeloma patients with higher RRM1 expression have shortened survival. Knockdown of RRM1 triggered significant growth inhibition and apoptosis in multiple myeloma cells, even in the context of the bone marrow microenvironment. Gene expression profiling showed upregulation of DNA damage response genes and p53-regulated genes after RRM1 knockdown. Immunoblot and qRT-PCR analysis confirmed that γ-H2A.X, ATM, ATR, Chk1, Chk2, RAD51, 53BP1, BRCA1, and BRCA2 were upregulated/activated. Moreover, immunoblots showed that p53, p21, Noxa, and Puma were activated in p53 wild-type multiple myeloma cells. Clofarabine, a purine nucleoside analogue that inhibits RRM1, induced growth arrest and apoptosis in p53 wild-type cell lines. Although clofarabine did not induce cell death in p53-mutant cells, it did trigger synergistic toxicity in combination with DNA-damaging agent melphalan. Finally, we demonstrated that tumor growth of RRM1-knockdown multiple myeloma cells was significantly reduced in a murine human multiple myeloma cell xenograft model.Conclusions: Our results therefore demonstrate that RRM1 is a novel therapeutic target in multiple myeloma in the preclinical setting and provide the basis for clinical evaluation of RRM1 inhibitor, alone or in combination with DNA-damaging agents, to improve patient outcome in multiple myeloma. Clin Cancer Res; 23(17); 5225-37. ©2017 AACR.

Selenium nanoparticles: potential in cancer gene and drug delivery

In recent decades, colloidal selenium nanoparticles have emerged as exceptional selenium species with reported chemopreventative and therapeutic properties. This has sparked widespread interest in their use as a carrier of therapeutic agents with results displaying synergistic effects of selenium with its therapeutic cargo and improved anticancer activity. Functionalization remains a critical step in selenium nanoparticles' development for application in gene or drug delivery. In this review, we highlight recent developments in the synthesis and functionalization strategies of selenium nanoparticles used in cancer drug and gene delivery systems. We also provide an update of recent preclinical studies utilizing selenium nanoparticles in cancer therapeutics.

Myelodysplastic syndromes: advantages of a combined cytogenetic and molecular diagnostic workup

In this study we present a new diagnostic workup for the myelodysplastic syndromes (MDS) including FISH, aCGH, and somatic mutation assays in addition to the conventional cytogenetics (CC). We analyzed 61 patients by CC, FISH for chromosome 5, 7, 8 and PDGFR rearrangements, aCGH, and PCR for ASXL1, EZH2, TP53, TET2, RUNX1, DNMT3A, SF3B1 somatic mutations. Moreover, we quantified WT1 and RPS14 gene expression levels, in order to find their possible adjunctive value and their possible clinical impact. CC analysis showed 32% of patients with at least one aberration. FISH analysis detected chromosomal aberrations in 24% of patients and recovered 5 cases (13.5%) at normal karyotype (two 5q- syndromes, one del(7) case, two cases with PDGFR rearrangement). The aGCH detected 10 "new" unbalanced cases in respect of the CC, including one with alteration of the ETV6 gene. After mutational analysis, 33 patients (54%) presented at least one mutation and represented the only marker of clonality in 36% of all patients. The statistical analysis confirmed the prognostic role of CC either on overall or on progression-free-survival. In addition, deletions detected by aCGH and WT1 over-expression negatively conditioned survival. In conclusion, our work showed that 1) the addition of FISH (at least for chr. 5 and 7) can improve the definition of the risk score; 2) mutational analysis, especially for the TP53 and SF3B1, could better define the type of MDS and represent a "clinical warning"; 3) the aCGH use could be probably applied to selected cases (with suboptimal response or failure).

Mutational landscape reflects the biological continuum of plasma cell dyscrasias

We subjected 90 patients covering a biological spectrum of plasma cell dyscrasias (monoclonal gammopathy of undetermined significance (MGUS), amyloid light-chain (AL) amyloidosis and multiple myeloma) to next-generation sequencing (NGS) gene panel analysis on unsorted bone marrow. A total of 64 different mutations in 8 genes were identified in this cohort. NRAS (28.1%), KRAS (21.3%), TP53 (19.5%), BRAF (19.1%) and CCND1 (8.9%) were the most commonly mutated genes in all patients. Patients with non-myeloma plasma cell dyscrasias showed a significantly lower mutational load than myeloma patients (0.91±0.30 vs 2.07±0.29 mutations per case, P=0.008). KRAS and NRAS exon 3 mutations were significantly associated with the myeloma cohort compared with non-myeloma plasma cell dyscrasias (odds ratio (OR) 9.87, 95% confidence interval (CI) 1.07–90.72, P=0.043 and OR 7.03, 95% CI 1.49–33.26, P=0.014). NRAS exon 3 and TP53 exon 6 mutations were significantly associated with del17p cytogenetics (OR 0.12, 95% CI 0.02–0.87, P=0.036 and OR 0.05, 95% CI 0.01–0.54, P=0.013). Our data show that the mutational landscape reflects the biological continuum of plasma cell dyscrasias from a low-complexity mutational pattern in MGUS and AL amyloidosis to a high-complexity pattern in multiple myeloma. Our targeted NGS approach allows resource-efficient, sensitive and scalable mutation analysis for prognostic, predictive or therapeutic purposes.

MicroRNA expression patterns and target prediction in multiple myeloma development and malignancy

Epigenetic changes have emerged as key causes in the development and progression of multiple myeloma (MM). In this study, global microRNA (miRNA) expression profiling were performed for 27 MM (19 specimens and 8 cell lines) and 3 normal controls by microarray. miRNA-targets were identified by integrating the miRNA expression profiles with mRNA expression profiles of the matched samples (unpublished data). Two miRNAs were selected for verification by RT-qPCR (miR-150-5p and miR-4430). A total of 1791 and 8 miRNAs were over-expressed and under-expressed, respectively in MM compared to the controls (fold change ≥2.0; p < 0.05). The miRNA-mRNA integrative analysis revealed inverse correlation between 5 putative target genes (RAD54L, CCNA2, CYSLTR2, RASGRF2 and HKDC1) and 15 miRNAs (p < 0.05). Most of the differentially expressed miRNAs are involved in survival, proliferation, migration, invasion and drug resistance in MM. Some have never been described in association with MM (miR-33a, miR-9 and miR-211). Interestingly, our results revealed 2 miRNAs, which are closely related to B cell differentiation (miR-150 and miR-125b). For the first time, we suggest that miR-150 might be potential negative regulator for two critical cell cycle control genes, RAD54L and CCNA2, whereas miR-125b potentially target RAS and CysLT signaling proteins, namely RASGRF2 and CYSLTR2, respectively. This study has enhanced our understanding on the pathobiology of MM and opens up new avenues for future research in myelomagenesis.

Molecular Mechanisms of p53 Deregulation in Cancer: An Overview in Multiple Myeloma

The p53 pathway is inactivated in the majority of human cancers. Although this perturbation frequently occurs through the mutation or deletion of p53 itself, there are other mechanisms that can attenuate the pathway and contribute to tumorigenesis. For example, overexpression of important p53 negative regulators, such as murine double minute 2 (MDM2) or murine double minute 4 (MDM4), epigenetic deregulation, or even alterations in TP53 mRNA splicing. In this work, we will review the different mechanisms of p53 pathway inhibition in cancer with special focus on multiple myeloma (MM), the second most common hematological malignancy, with low incidence of p53 mutations/deletions but growing evidence of indirect p53 pathway deregulation. Translational implications for MM and cancer prognosis and treatment are also reviewed.

Small interfering RNA-mediated silencing of nicotinamide phosphoribosyltransferase (NAMPT) and lysosomal trafficking regulator (LYST) induce growth inhibition and apoptosis in human multiple myeloma cells: A preliminary study

Multiple myeloma (MM) is a malignancy of B lymphocytes or plasma cells. Our array-based comparative genomic hybridization findings revealed chromosomal gains at 7q22.3 and 1q42.3, where nicotinamide (NAM) phosphoribosyltransferase (NAMPT) and lysosomal trafficking regulator (LYST) genes are localized, respectively. This led us to further study the functions of these genes in myeloma cells. NAMPT is a key enzyme involved in nicotinamide adenine dinucleotide salvage pathway, and it is frequently overexpressed in human cancers. In contrast, little is known about the function of LYST in cancer. The expression of LYST is shown to affect lysosomal size, granule size, and autophagy in human cells. In this study, the effects of small interfering RNA (siRNA)-mediated silencing of NAMPT and LYST on cell proliferation and apoptosis were evaluated in RPMI 8226 myeloma cells. Transfection efficiencies were determined by quantitative real time reverse transcriptase PCR. Cell proliferation was determined using MTT assay, while apoptosis was analyzed with flow cytometry using Annexin V-fluorescein isothiocyanate/propidium iodide assay. The NAMPT protein expression in siRNA-treated cells was estimated by enzyme-linked immunosorbent assay. Our results showed that NAMPT and LYST were successfully knockdown by siRNA transfection (p < 0.05). NAMPT or LYST gene silencing significantly inhibited cell proliferation and induced apoptosis in RPMI 8226 cells (p < 0.05). Silencing of NAMPT gene also decreased NAMPT protein levels (p < 0.01). Our study demonstrated that NAMPT and LYST play pivotal roles in the molecular pathogenesis of MM. This is the first report describing the possible functions of LYST in myelomagenesis and its potential role as a therapeutic target in MM.

Reactivation of wild-type and mutant p53 by tryptophanolderived oxazoloisoindolinone SLMP53-1, a novel anticancer small-molecule

Restoration of the p53 pathway, namely by reactivation of mutant (mut) p53, represents a valuable anticancer strategy. Herein, we report the identification of the enantiopure tryptophanol-derived oxazoloisoindolinone SLMP53-1 as a novel reactivator of wild-type (wt) and mut p53, using a yeast-based screening strategy. SLMP53-1 has a p53-dependent anti-proliferative activity in human wt and mut p53R280K-expressing tumor cells. Additionally, SLMP53-1 enhances p53 transcriptional activity and restores wt-like DNA binding ability to mut p53R280K. In wt/mut p53-expressing tumor cells, SLMP53-1 triggers p53 transcription-dependent and mitochondrial apoptotic pathways involving BAX, and wt/mut p53 mitochondrial translocation. SLMP53-1 inhibits the migration of wt/mut p53-expressing tumor cells, and it shows promising p53-dependent synergistic effects with conventional chemotherapeutics. In xenograft mice models, SLMP53-1 inhibits the growth of wt/mut p53-expressing tumors, but not of p53-null tumors, without apparent toxicity. Collectively, besides the potential use of SLMP53-1 as anticancer drug, the tryptophanol-derived oxazoloisoindolinone scaffold represents a promissing starting point for the development of effective p53-reactivating drugs.

Targeting Intrinsic and Extrinsic Vulnerabilities for the Treatment of Multiple Myeloma

Multiple myeloma (MM) is a malignant plasma cell disorder, clinically characterized by osteolytic lesions, immunodeficiency, and renal disease. Over the past decade, MM therapy is significantly improved by the introduction of novel therapeutics such as immunomodulatory agents (thalidomide, lenalidomide, and pomalidomide), proteasome inhibitors (bortezomib, carfilzomib, and ixazomib), monoclonal antibodies (daratumumab and elotuzumab), histone deacetylase (HDAC) inhibitors (Panobinostat). The clinical success of these agents has clearly identified vulnerabilities intrinsic to the MM cell, as well as targets that emanate from the tumor microenvironment. Despite these significant improvements, MM remains incurable due to the development of drug resistance. This perspective will discuss more recent strategies which take advantage of multiple targets within the proteome recycling pathway, chromatin remodeling, and disruption of nuclear export. In addition, we will review the development of strategies designed to block opportunistic survival signaling that occurs between the MM cell and the tumor microenvironment including strategies for inhibiting myeloma-induced immune suppression. It has become clear that MM tumors continue to evolve on therapy leading to drug resistance. It will be important to understand the emerging drug resistant mechanisms and additional vulnerabilities that occur due to the development of clinical resistance. J. Cell. Biochem. 118: 15-25, 2017. © 2016 Wiley Periodicals, Inc.

Plasmodium meets AAV-the (un)likely marriage of parasitology and virology, and how to make the match

The increasing use of screening technologies in malaria research has substantially expanded our knowledge on cellular factors hijacked by the Plasmodium parasite in the infected host, including those that participate in the clinically silent liver stage. This rapid gain in our understanding of the hepatic interaction partners now requires a means to validate and further disentangle parasite-host networks in physiologically relevant liver model systems. Here, we outline seminal work that contributed to our present knowledge on the intrahepatic Plasmodium host factors, followed by a discussion of surrogate models of mammalian livers or hepatocytes. We finally describe how Adeno-associated viruses could be engineered and used as hepatotropic tools to dissect Plasmodium-host interactions, and to deliberately control these networks for antimalaria vaccination or therapy.

Touch and go: nuclear proteolysis in the regulation of metabolic genes and cancer

The recruitment of transcription factors to promoters and enhancers is a critical step in gene regulation. Many of these proteins are quickly removed from DNA after they completed their function. Metabolic genes in particular are dynamically regulated and continuously adjusted to cellular requirements. Transcription factors controlling metabolism are therefore under constant surveillance by the ubiquitin–proteasome system, which can degrade DNA‐bound proteins in a site‐specific manner. Several of these metabolic transcription factors are critical to cancer cells, as they promote uncontrolled growth and proliferation. This review highlights recent findings in the emerging field of nuclear proteolysis and outlines novel paradigms for cancer treatment, with an emphasis on multiple myeloma.

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.