Therapy of relapsed and refractory multiple myeloma

HDAC6-Selective Inhibitor Overcomes Bortezomib Resistance in Multiple Myeloma

Although multiple myeloma (MM) patients benefit from standard bortezomib (BTZ) chemotherapy, they develop drug resistance, resulting in relapse. We investigated whether histone deacetylase 6 (HDAC6) inhibitor A452 overcomes bortezomib resistance in MM. We show that HDAC6-selective inhibitor A452 significantly decreases the activation of BTZ-resistant markers, such as extracellular signal-regulated kinases (ERK) and nuclear factor kappa B (NF-κB), in acquired BTZ-resistant MM cells. Combination treatment of A452 and BTZ or carfilzomib (CFZ) synergistically reduces BTZ-resistant markers. Additionally, A452 synergizes with BTZ or CFZ to inhibit the activation of NF-κB and signal transducer and activator of transcription 3 (STAT3), resulting in decreased expressions of low-molecular-mass polypeptide 2 (LMP2) and LMP7. Furthermore, combining A452 with BTZ or CFZ leads to synergistic cancer cell growth inhibition, viability decreases, and apoptosis induction in the BTZ-resistant MM cells. Overall, the synergistic effect of A452 with CFZ is more potent than that of A452 with BTZ in BTZ-resistant U266 cells. Thus, our findings reveal the HDAC6-selective inhibitor as a promising therapy for BTZ-chemoresistant MM.

HDAC6‑selective inhibitor synergistically enhances the anticancer activity of immunomodulatory drugs in multiple myeloma

Nonselective histone deacetylase (HDAC) inhibitors have therapeutic effects, but exhibit dose‑limiting toxicities in patients with multiple myeloma (MM). The present study investigated the interaction between the HDAC6 inhibitor, A452, and immunomodulatory drugs (IMiDs) on dexamethasone (Dex)‑sensitive and ‑resistant MM cells compared with the current clinically tested HDAC6 inhibitor, ACY‑1215. It was shown that the combination of the HDAC6‑selective inhibitor, A452, with either of the IMiDs tested (lenalidomide or pomalidomide) led to the synergistic inhibition of cell growth, a decrease in the viability of MM cells and in an increase in the levels of apoptosis. Furthermore, enhanced cell death was associated with the inactivation of AKT and extracellular signal‑regulated kinase (ERK)1/2. Of note, A452 in combination with IMiDs induced synergistic MM cytotoxicity without altering the expression of cereblon and thereby, the synergistic downregulation of IKAROS family zinc finger (IKZF)1/3, c‑Myc and interferon regulatory factor 4 (IRF4). Furthermore, combined treatment with A452 and IMiDs induced the synergistic upregulation of PD‑L1. More importantly, this combination treatment was effective in the Dex‑resistant MM cells. Overall, the findings of this study indicate that A452 is more effective as an anticancer agent than ACY‑1215. Taken together, these findings suggest that a combination of the HDAC6‑selective inhibitor, A452, and IMiDs may prove to be beneficial in the treatment of patients with MM.

Microvessel Density as a Surrogate Prognostic Marker in Patients with Multiple Myeloma: A Meta-Analysis

BACKGROUND/AIMS

Bone marrow (BM) angiogenesis is considered a hallmark of multiple myeloma (MM) development and progression, and can be quantified with the use of microvessel density (MVD). The purpose of this study is to provide a review and a meta-analysis of the current literature regarding the prognostic value of MVD in the overall survival (OS) of MM patients.

METHODS

MEDLINE was screened for studies evaluating the OS of MM patients with regard to their MVD count in BM trephine. The pooled hazard ratio (HR) and its associated 95% confidence interval (CI) among MM patients with a high and low MVD count was the primary end point. Secondary outcomes included odds ratios (OR) for 12-, 36-, and 60-month survival.

RESULTS

Ten eligible trials were identified for the analysis of the primary end point and 9 for the secondary end points. Pooled HR for OS was 1.85 (95% CI: 1.25-2.73, p = 0.002). The pooled OR of survival were 1.59 (95% CI: 1.02-2.46, p = 0.04) at 12 months, 2.90 (95% CI: 1.68-5.03, p = 0.0001) at 36 months, and 3.42 (95% CI: 2.41-4.85, p < 0.00001) at 60 months, in favor of the low MVD group.

CONCLUSION

This meta-analysis provides persuasive evidence that MVD has significant impact on the clinical outcome of MM patients.

The effect of bortezomib on expression of inflammatory cytokines and survival in a murine sepsis model induced by cecal ligation and puncture

PURPOSE

Although the proteasome inhibitor known as bortezomib can modulate the inflammatory process through the nuclear factor-kappa B signaling pathway, the immunomodulatory effect of pre-incubated bortezomib has not been fully evaluated for inflammation by infectious agents. Therefore, we evaluated the effect of bortezomib on the expression of inflammatory cytokines and mediators in macrophage cell lines and on survival in a murine peritonitis sepsis model.

MATERIALS AND METHODS

Bortezomib was applied 1 hr before lipopolysaccharide (LPS) stimulation in RAW 264.7 cells. The cecal ligation and puncture (CLP) experiments were performed in C57BL/6J mice.

RESULTS

Pre-incubation with bortezomib (25 nM or 50 nM) prior to LPS (50 ng/mL or 100 ng/mL) stimulation significantly recovered the number of viable RAW 264.7 cells compared to those samples without pre-incubation. Bortezomib decreased various inflammatory cytokines as well as nitric oxide production in LPS-stimulated cells. The 7-day survival rate in mice that had received bortezomib at 0.01 mg/kg concentration 1 hr prior to CLP was significantly higher than in the mice that had only received a normal saline solution of 1 mL 1 hr prior to CLP. In addition, the administration of bortezomib at 0.01 mg/kg concentration 1 hr before CLP resulted in a significant decrease in inflammation of the lung parenchyma. Collectively, pretreatment with bortezomib showed an increase in the survival rate and changes in the levels of inflammatory mediators.

CONCLUSION

These results support the possibility of pretreatment with bortezomib as a new therapeutic target for the treatment of overwhelming inflammation, which is a characteristic of severe sepsis.

Vorinostat in combination with lenalidomide and dexamethasone in patients with relapsed or refractory multiple myeloma

The addition of vorinostat to lenalidomide/dexamethasone represents a novel combination therapy in multiple myeloma (MM), informed by laboratory studies suggesting synergy. This was a phase I, multicenter, open-label, non-randomized, dose-escalating study in patients with relapsed or relapsed and refractory MM. Clinical evaluation, electrocardiogram, laboratory studies and adverse events were obtained and assessed. The maximum-tolerated dose was not reached owing to a non-occurrence of two dose-limiting toxicities per six patients tested at any of the dosing levels. Patients tolerated the highest dose tested (Level 5) and this was considered the maximum administered dose: at 400 mg vorinostat on days 1-7 and 15-21, 25 mg lenalidomide on days 1-21 and 40 mg dexamethasone on days 1, 8, 15 and 22, per 28-day cycle. Drug-related adverse events were reported in 90% of patients serious adverse experiences were reported in 45% of the patients and 22% of all patients had adverse experiences considered, possibly related to study drug by the investigators. A confirmed partial response or better was reported for 14/30 patients (47%) evaluable for efficacy, including 31% of patients previously treated with lenalidomide. Vorinostat in combination with lenalidomide and dexamethasone proved tolerable with appropriate supportive care, with encouraging activity observed.

Current and emerging treatment options for patients with relapsed myeloma

Multiple myeloma (MM) is a neoplastic disorder. It results from proliferation of clonal plasma cells in bone marrow with production of monoclonal proteins, which are detectable in serum or urine. MM is clinically characterized by destructive bone lesions, anemia, hypercalcemia and renal insufficiency. Its prognosis is severe, with a median survival after diagnosis of approximately 3 years due to frequent relapses. Treatments for patients with relapsed/refractory MM include hematopoietic cell transplantation, a rechallenge using a previous chemotherapy regimen or a trial of a new regimen. The introduction of new drugs such as thalidomide, lenalidomide and bortezomib has markedly improved MM outcomes. When relapse occurs, the clinician's challenge is to select the optimal treatment for each patient while balancing efficacy and toxicity. Patients with indolent relapse can be first treated with a 2-drug or a 3-drug combination. Patients with more aggressive relapse often require therapy with a combination of multiple active agents. Autologous stem cell transplantation should be considered as salvage therapy at first relapse for patients who have cryopreserved stem cells early in the disease course. The aim of this review is to provide an overview on the pharmacological and molecular action of treatments used for patients with relapsed/refractory multiple myeloma.

Proline-mediated proteasomal degradation of the prostate-specific tumor suppressor NKX3.1

Reduced expression of the homeodomain transcription factor NKX3.1 is associated with prostate cancer initiation and progression. NKX3.1 turnover requires post-translational modifications including phosphorylation and ubiquitination. Here, we demonstrate the existence of a non-canonical mechanism for NKX3.1 turnover that does not require ubiquitination. Using a structure-function approach, we have determined that the conserved, C-terminal 21-amino acid domain of NKX3.1 (C21) is required for this novel ubiquitin-independent degradation mechanism. Addition of C21 decreased half-life of enhanced green fluorescence protein (EGFP) by 5-fold, demonstrating that C21 constitutes a portable degron. Point mutational analyses of C21 revealed that a conserved proline residue (Pro-221) is central to degron activity, and mutation to alanine (P221A) increased NKX3.1 half-life >2-fold. Proteasome inhibition and in vivo ubiquitination analyses indicated that degron activity is ubiquitin-independent. Evaluating degron activity in the context of a ubiquitination-resistant, lysine-null NKX3.1 mutant (NKX3.1(KO)) confirmed that P221A mutation conferred additional stability to NKX3.1. Treatment of prostate cancer cell lines with a C21-based peptide specifically increased the level of NKX3.1, suggesting that treatment with degron mimetics may be a viable approach for NKX3.1 restoration.

Suberoylanilide hydroxamic acid as a radiosensitizer through modulation of RAD51 protein and inhibition of homology-directed repair in multiple myeloma

Histone deacetylase inhibitors (HDI) have shown promise as candidate radiosensitizers for many types of cancers. However, the mechanisms of action are not well understood, and whether they could sensitize multiple myeloma (MM) to radiation therapy is unclear. In this study, we show that suberoylanilide hydroxamic acid (SAHA) at low concentrations has minimal cytotoxic effects, yet can significantly increase radiosensitivity of MM cells. SAHA seems to block RAD51 protein response to ionizing radiation, consistent with an inhibitory effect on the formation of RAD51 focus in irradiated MM cells. These effects of SAHA on RAD51 focus are independent of cell-cycle distribution changes. Furthermore, we show that SAHA selectively inhibits the homology-directed repair (HDR) pathway. The results of this study suggest that SAHA, a recently approved HDI in clinical trials for malignancies, at lower concentrations may act as a radiosensitizer via disruption of the RAD51-dependent HDR pathway.

European perspective on multiple myeloma treatment strategies: update following recent congresses

The management of multiple myeloma has undergone profound changes over the recent past as a result of advances in our understanding of the disease biology as well as improvements in treatment and supportive care strategies. Notably, recent years have seen a surge in studies incorporating the novel agents thalidomide, bortezomib, and lenalidomide into treatment for different disease stages and across different patient groups. This article presents an update to a previous review of European treatment practices and is based on discussions during an expert meeting that was convened to review novel agent data published or presented at medical meetings until the end of 2011 and to assess their impact on treatment strategies.

Synthetic lethal screen identifies NF-κB as a target for combination therapy with topotecan for patients with neuroblastoma

Background

Despite aggressive multimodal treatments the overall survival of patients with high-risk neuroblastoma remains poor. The aim of this study was to identify novel combination chemotherapy to improve survival rate in patients with high-risk neuroblastoma.

Methods

We took a synthetic lethal approach using a siRNA library targeting 418 apoptosis-related genes and identified genes and pathways whose inhibition synergized with topotecan. Microarray analyses of cells treated with topotecan were performed to identify if the same genes or pathways were altered by the drug. An inhibitor of this pathway was used in combination with topotecan to confirm synergism by in vitro and in vivo studies.

Results

We found that there were nine genes whose suppression synergized with topotecan to enhance cell death, and the NF-κB signaling pathway was significantly enriched. Microarray analysis of cells treated with topotecan revealed a significant enrichment of NF-κB target genes among the differentially altered genes, suggesting that NF-κB pathway was activated in the treated cells. Combination of topotecan and known NF-κB inhibitors (NSC 676914 or bortezomib) significantly reduced cell growth and induced caspase 3 activity in vitro. Furthermore, in a neuroblastoma xenograft mouse model, combined treatment of topotecan and bortezomib significantly delayed tumor formation compared to single-drug treatments.

Conclusions

Synthetic lethal screening provides a rational approach for selecting drugs for use in combination therapy and warrants clinical evaluation of the efficacy of the combination of topotecan and bortezomib or other NF-κB inhibitors in patients with high risk neuroblastoma.