Tanespimycin and bortezomib combination treatment in patients with relapsed or relapsed and refractory multiple myeloma: results of a phase 1/2 study

Therapeutic Targeting of Hypoxia-Inducible Factors in Cancer

In the realm of cancer therapeutics, targeting the hypoxia-inducible factor (HIF) pathway has emerged as a promising strategy. This study delves into the intricate web of HIF-associated mechanisms, exploring avenues for future anticancer therapies. Framing the investigation within the broader context of cancer progression and hypoxia response, this article aims to decipher the pivotal role played by HIF in regulating genes influencing angiogenesis, cell proliferation, and glucose metabolism. Employing diverse approaches such as HIF inhibitors, anti-angiogenic therapies, and hypoxia-activated prodrugs, the research methodologically intervenes at different nodes of the HIF pathway. Findings showcase the efficacy of agents like EZN-2968, Minnelide, and Acriflavine in modulating HIF-1α protein synthesis and destabilizing HIF-1, providing preliminary proof of HIF-1α mRNA modulation and antitumor activity. However, challenges, including toxicity, necessitate continued exploration and development, as exemplified by ongoing clinical trials. This article concludes by emphasizing the potential of targeted HIF therapies in disrupting cancer-related signaling pathways.

Combination therapy with HSP90 inhibitors and piperlongumine promotes ROS-mediated ER stress in colon cancer cells

Colon cancer is a major cause of cancer-related death. Despite recent improvements in the treatment of colon cancer, new strategies to improve the overall survival of patients are urgently needed. Heat shock protein 90 (HSP90) is widely recognized as a promising target for treating various cancers, including colon cancer. However, no HSP90 inhibitor has been approved for clinical use due to limited efficacy. In this study, we evaluated the antitumor activities of HSP90 inhibitors in combination with piperlongumine in colon cancer cells. We show that combination treatment with HSP90 inhibitors and piperlongumine displayed strong synergistic interaction in colon cancer cells. These agents synergize by promoting ER stress, JNK activation, and DNA damage. This process is fueled by oxidative stress, which is caused by the accumulation of reactive oxygen species. These studies nominated piperlongumine as a promising agent for HSP90 inhibitor-based combination therapy against colon cancer.

Hypoxia-Inducible Factor-1: A Novel Therapeutic Target for the Management of Cancer, Drug Resistance, and Cancer-Related Pain

Hypoxia-inducible factor-1 (HIF-1) is a key transcription factor that regulates the transcription of many genes that are responsible for the adaptation and survival of tumor cells in hypoxic environments. Over the past few decades, tremendous efforts have been made to comprehensively understand the role of HIF-1 in tumor progression. Based on the pivotal roles of HIF-1 in tumor biology, many HIF-1 inhibitors interrupting expression, stabilization, DNA binding properties, or transcriptional activity have been identified as potential therapeutic agents for various cancers, yet none of these inhibitors have yet been successfully translated into clinically available cancer treatments. In this review, we briefly introduce the regulation of the HIF-1 pathway and summarize its roles in tumor cell proliferation, angiogenesis, and metastasis. In addition, we explore the implications of HIF-1 in the development of drug resistance and cancer-related pain: the most commonly encountered obstacles during conventional anticancer therapies. Finally, the current status of HIF-1 inhibitors in clinical trials and their perspectives are highlighted, along with their modes of action. This review provides new insights into novel anticancer drug development targeting HIF-1. HIF-1 inhibitors may be promising combinational therapeutic interventions to improve the efficacy of current cancer treatments and reduce drug resistance and cancer-related pain.

Heat shock proteins: Biological functions, pathological roles, and therapeutic opportunities

The heat shock proteins (HSPs) are ubiquitous and conserved protein families in both prokaryotic and eukaryotic organisms, and they maintain cellular proteostasis and protect cells from stresses. HSP protein families are classified based on their molecular weights, mainly including large HSPs, HSP90, HSP70, HSP60, HSP40, and small HSPs. They function as molecular chaperons in cells and work as an integrated network, participating in the folding of newly synthesized polypeptides, refolding metastable proteins, protein complex assembly, dissociating protein aggregate dissociation, and the degradation of misfolded proteins. In addition to their chaperone functions, they also play important roles in cell signaling transduction, cell cycle, and apoptosis regulation. Therefore, malfunction of HSPs is related with many diseases, including cancers, neurodegeneration, and other diseases. In this review, we describe the current understandings about the molecular mechanisms of the major HSP families including HSP90/HSP70/HSP60/HSP110 and small HSPs, how the HSPs keep the protein proteostasis and response to stresses, and we also discuss their roles in diseases and the recent exploration of HSP related therapy and diagnosis to modulate diseases. These research advances offer new prospects of HSPs as potential targets for therapeutic intervention.

Targeting Heat-Shock Protein 90 in Cancer: An Update on Combination Therapy

Heat-shock protein 90 (HSP90) is an important molecule chaperone associated with tumorigenesis and malignancy. HSP90 is involved in the folding and maturation of a wide range of oncogenic clients, including diverse kinases, transcription factors and oncogenic fusion proteins. Therefore, it could be argued that HSP90 facilitates the malignant behaviors of cancer cells, such as uncontrolled proliferation, chemo/radiotherapy resistance and immune evasion. The extensive associations between HSP90 and tumorigenesis indicate substantial therapeutic potential, and many HSP90 inhibitors have been developed. However, due to HSP90 inhibitor toxicity and limited efficiency, none have been approved for clinical use as single agents. Recent results suggest that combining HSP90 inhibitors with other anticancer therapies might be a more advisable strategy. This review illustrates the role of HSP90 in cancer biology and discusses the therapeutic value of Hsp90 inhibitors as complements to current anticancer therapies.

secDrug: a pipeline to discover novel drug combinations to kill drug-resistant multiple myeloma cells using a greedy set cover algorithm and single-cell multi-omics

Multiple myeloma, the second-most common hematopoietic malignancy in the United States, still remains an incurable disease with dose-limiting toxicities and resistance to primary drugs like proteasome inhibitors (PIs) and Immunomodulatory drugs (IMiDs).We have created a computational pipeline that uses pharmacogenomics data-driven optimization-regularization/greedy algorithm to predict novel drugs ("secDrugs") against drug-resistant myeloma. Next, we used single-cell RNA sequencing (scRNAseq) as a screening tool to predict top combination candidates based on the enrichment of target genes. For in vitro validation of secDrugs, we used a panel of human myeloma cell lines representing drug-sensitive, innate/refractory, and acquired/relapsed PI- and IMiD resistance. Next, we performed single-cell proteomics (CyTOF or Cytometry time of flight) in patient-derived bone marrow cells (ex vivo), genome-wide transcriptome analysis (bulk RNA sequencing), and functional assays like CRISPR-based gene editing to explore molecular pathways underlying secDrug efficacy and drug synergy. Finally, we developed a universally applicable R-software package for predicting novel secondary therapies in chemotherapy-resistant cancers that outputs a list of the top drug combination candidates with rank and confidence scores.Thus, using 17AAG (HSP90 inhibitor) + FK866 (NAMPT inhibitor) as proof of principle secDrugs, we established a novel pipeline to introduce several new therapeutic options for the management of PI and IMiD-resistant myeloma.

Chaperone-assisted E3 ligase CHIP: A double agent in cancer

The carboxy-terminus of Hsp70-interacting protein (CHIP) is a ubiquitin ligase and co-chaperone belonging to Ubox family that plays a crucial role in the maintenance of cellular homeostasis by switching the equilibrium of the folding-refolding mechanism towards the proteasomal or lysosomal degradation pathway. It links molecular chaperones viz. HSC70, HSP70 and HSP90 with ubiquitin proteasome system (UPS), acting as a quality control system. CHIP contains charged domain in between N-terminal tetratricopeptide repeat (TPR) and C-terminal Ubox domain. TPR domain interacts with the aberrant client proteins via chaperones while Ubox domain facilitates the ubiquitin transfer to the client proteins for ubiquitination. Thus, CHIP is a classic molecule that executes ubiquitination for degradation of client proteins. Further, CHIP has been found to be indulged in cellular differentiation, proliferation, metastasis and tumorigenesis. Additionally, CHIP can play its dual role as a tumor suppressor as well as an oncogene in numerous malignancies, thus acting as a double agent. Here, in this review, we have reported almost all substrates of CHIP established till date and classified them according to the hallmarks of cancer. In addition, we discussed about its architectural alignment, tissue specific expression, sub-cellular localization, folding-refolding mechanisms of client proteins, E4 ligase activity, normal physiological roles, as well as involvement in various diseases and tumor biology. Further, we aim to discuss its importance in HSP90 inhibitors mediated cancer therapy. Thus, this report concludes that CHIP may be a promising and worthy drug target towards pharmaceutical industry for drug development.

Overview of Ferroptosis and Synthetic Lethality Strategies

Ferroptosis, a term first proposed in 2012, is iron-dependent, non-apoptotic regulatory cell death induced by erastin. Ferroptosis was originally discovered during synthetic lethal screening for drugs sensitive to RAS mutant cells, and is closely related to synthetic lethality. Ferroptosis sensitizes cancer stem cells and tumors that undergo epithelial−mesenchymal transition and are resistant to anticancer drugs or targeted therapy. Therefore, ferroptosis-inducing molecules are attractive new research targets. In contrast, synthetic lethal strategies approach mechanisms and genetic abnormalities that cannot be directly targeted by conventional therapeutic strategies, such as RAS mutations, hypoxia, and abnormalities in the metabolic environment. They also target the environment and conditions specific to malignant cells, have a low toxicity to normal cells, and can be used in combination with known drugs to produce new ones. However, the concept of synthetic lethality has not been widely adopted with ferroptosis. In this review, we surveyed the literature on ferroptosis-related factors and synthetic lethality to examine the potential therapeutic targets in ferroptosis-related molecules, focusing on factors related to synthetic lethality, discovery methods, clinical application stages, and issues in drug discovery.

Geldanamycin-Derived HSP90 Inhibitors Are Synthetic Lethal with NRF2

Activating mutations in KEAP1-NRF2 are frequently found in tumors of the lung, esophagus, and liver, where they are associated with aggressive growth, resistance to cancer therapies, and low overall survival. Despite the fact that NRF2 is a validated driver of tumorigenesis and chemotherapeutic resistance, there are currently no approved drugs which can inhibit its activity. Therefore, there is an urgent clinical need to identify NRF2-selective cancer therapies. To this end, we developed a novel synthetic lethal assay, based on fluorescently labeled isogenic wild-type and Keap1 knockout cell lines, in order to screen for compounds which selectively kill cells in an NRF2-dependent manner. Through this approach, we identified three compounds based on the geldanamycin scaffold which display synthetic lethality with NRF2. Mechanistically, we show that products of NRF2 target genes metabolize the quinone-containing geldanamycin compounds into more potent HSP90 inhibitors, which enhances their cytotoxicity while simultaneously restricting the synthetic lethal effect to cells with aberrant NRF2 activity. As all three of the geldanamycin-derived compounds have been used in clinical trials, they represent ideal candidates for drug repositioning to target the currently untreatable NRF2 activity in cancer.

Network Pharmacology Approach Uncovering Pathways Involved in Targeting Hsp90 Through Curcumin and Epigallocatechin to Control Inflammation

AIMS

To fetch pathways involved in targetting Hsp90 through Curcumin and Epigallocatechin through Network pharmacological approach.

BACKGROUND

Hsp90 is a molecular chaperone involved in stabilizing inflammatory protein which may lead to chronic diseases. The herbal compounds Curcumin and Epigallocatechin processing antiinflammatory properties are known to follow a common pathway and control the expression of Hsp90.

OBJECTIVE

To collect the gene targets of Hsp90, Curcumin and Epigallocatechin in order to understand protein-protein interactions of gene targets by constructing the interactome to identify the hub proteins. Hub proteins docking was performed with curcumin and epigallocatechin. Finally, hub proteins involvement with various human diseases were identified.

METHODS

The gene targets of Hsp90, Curcumin and Epigallocatechin were obtained from there respective databases. Protein-protein interactions of Pkcδ-Nrf2 and Tlr4 pathway gene targets were collected from String database. Protein interaction network was constructed and merged to get intercession network in cytoscape and Cluego was used to predict the disease related target genes. Docking of ligands to target proteins was carried out using Autodock vina tool.

RESULT

The main key regulators of Curcumin and Epigallocatechin were identified particularly from Pkcδ-Nrf2 and Tlr4 pathway.

CONCLUSION

The combined action of Curcumin and Epigallocatechin can reduce the expression of Hsp90 eventually controlling the inflammation.

Bortezomib promotes apoptosis of multiple myeloma cells by regulating HSP27

The aim of the present study was to investigate the effect of bortezomib on heat shock protein 27 (HSP27) in multiple myeloma (MM) and provide a potential new target for clinical treatment. Peripheral blood was collected from 50 normal subjects and 50 patients with newly diagnosed MM and the expression of HSP27 was detected by ELISA. The changes of HSP27 after conventional vincristine, doxorubicin and dexamethasone (VAD) chemotherapy, and bortezomib plus VAD were compared. The effect of bortezomib on U266 cell proliferation and apoptosis was detected using a Cell Counting Kit‑8 assay and Annexin V‑FITC/propidium iodide double staining with flow cytometry. The content of HSP27 following bortezomib treatment was determined by ELISA. Western blot analysis and reverse transcription‑quantitative PCR were used to detect the mRNA and protein expression of HSP27, Bax and Bcl‑2. HSP27 expression was increased in patients with MM compared with healthy control subjects, and the expression was increased as the cancer progressed (P<0.05). Compared with the VAD chemotherapy group, the bortezomib plus VAD chemotherapy regimen significantly inhibited the expression of HSP27 (P<0.05), and the content of HSP27 was decreased in patients in which treatment was effective compared to those patients that exhibited disease progression (P<0.05). The efficacy of the treatment regimes was not associated with age or gender. Compared with the control group, bortezomib or OGX‑427 (HSP27 inhibitor) treatment inhibited U266 cell proliferation, promoted U266 cell apoptosis (P<0.05) and significantly decreased HSP27 expression (P<0.05). Furthermore, the expression of HSP27 and Bcl‑2 was significantly decreased, while the expression of Bax was increased by bortezomib and OGX‑427 (P<0.05). There was no significant difference between the bortezomib and OGX‑427 group in the in vitro analysis. HSP27 was positively correlated with Bcl‑2 expression and negatively correlated with Bax expression in U266 cells. In conclusion, bortezomib promotes the apoptosis of MM cells, potentially by downregulating the expression of HSP27, providing a potential novel target for the clinical treatment of multiple myeloma.

Traditional and Novel Mechanisms of Heat Shock Protein 90 (HSP90) Inhibition in Cancer Chemotherapy Including HSP90 Cleavage

HSP90 is a molecular chaperone that increases the stability of client proteins. Cancer cells show higher HSP90 expression than normal cells because many client proteins play an important role in the growth and survival of cancer cells. HSP90 inhibitors mainly bind to the ATP binding site of HSP90 and inhibit HSP90 activity, and these inhibitors can be distinguished as ansamycin and non-ansamycin depending on the structure. In addition, the histone deacetylase inhibitors inhibit the activity of HSP90 through acetylation of HSP90. These HSP90 inhibitors have undergone or are undergoing clinical trials for the treatment of cancer. On the other hand, recent studies have reported that various reagents induce cleavage of HSP90, resulting in reduced HSP90 client proteins and growth suppression in cancer cells. Cleavage of HSP90 can be divided into enzymatic cleavage and non-enzymatic cleavage. Therefore, reagents inducing cleavage of HSP90 can be classified as another class of HSP90 inhibitors. We discuss that the cleavage of HSP90 can be another mechanism in the cancer treatment by HSP90 inhibition.

Spotlight on 17-AAG as an Hsp90 inhibitor for molecular targeted cancer treatment

Hsp90 is a ubiquitous chaperone with important roles in the organization and maturation of client proteins that are involved in the progression and survival of cancer cells. Multiple oncogenic pathways can be affected by inhibition of Hsp90 function through degradation of its client proteins. That makes Hsp90 a therapeutic target for cancer treatment. 17-allylamino-17-demethoxy-geldanamycin (17-AAG) is a potent Hsp90 inhibitor that binds to Hsp90 and inhibits its chaperoning function, which results in the degradation of Hsp90's client proteins. There have been several preclinical studies of 17-AAG as a single agent or in combination with other anticancer agents for a wide range of human cancers. Data from various phases of clinical trials show that 17-AAG can be given safely at biologically active dosages with mild toxicity. Even though 17-AAG has suitable pharmacological potency, its low water solubility and high hepatotoxicity could significantly restrict its clinical use. Nanomaterials-based drug delivery carriers may overcome these drawbacks. In this paper, we review preclinical and clinical research on 17-AAG as a single agent and in combination with other anticancer agents. In addition, we highlight the potential of using nanocarriers and nanocombination therapy to improve therapeutic effects of 17-AAG.

Targeting Proteotoxic Stress in Cancer: A Review of the Role that Protein Quality Control Pathways Play in Oncogenesis

Despite significant advances in cancer diagnostics and therapeutics the majority of cancer unfortunately remains incurable, which has led to continued research to better understand its exceptionally diverse biology. As a result of genomic instability, cancer cells typically have elevated proteotoxic stress. Recent appreciation of this functional link between the two secondary hallmarks of cancer: aneuploidy (oxidative stress) and proteotoxic stress, has therefore led to the development of new anticancer therapies targeting this emerging “Achilles heel” of malignancy. This review highlights the importance of managing proteotoxic stress for cancer cell survival and provides an overview of the integral role proteostasis pathways play in the maintenance of protein homeostasis. We further review the efforts undertaken to exploit proteotoxic stress in multiple myeloma (as an example of a hematologic malignancy) and triple negative breast cancer (as an example of a solid tumor), and give examples of: (1) FDA-approved therapies in routine clinical use; and (2) promising therapies currently in clinical trials. Finally, we provide new insights gleaned from the use of emerging technologies to disrupt the protein secretory pathway and repurpose E3 ligases to achieve targeted protein degradation.

The effects of bortezomib on the ovariectomy applied rat uterus: A histopathological, stereological, and immunohistochemical study

Objective(s):

In this study, potential protective effects of Bortezomib (Bort), as a proteasome inhibitor, were investigated on the uterus of ovariectomized rats by histological, morphometric and immunohistochemical methods.

Materials and Methods:

In this study, 18 Sprague dawley strain female rats (12 weeks old, 250-300 g body weight) were used. Animals in the control group (Cont, n=6) were not exposed to any treatment. Ovariectomy was performed on the experimental groups. They (n=12) were divided into ovariectomy (Ovt, n=6) and Bortezomib (Bort, n=6) subgroups. Twelve weeks later, the rats were perfused. Then, uterine tissues were removed and examined by morphometrical, and light and electron microscopy methods. In addition, immunoreactivity of nuclear factor-kappa (NF-κB) was evaluated.

Results:

Morphometric and histopathological evaluations showed that Bort was effective in the uterus and protects the layer structures and the cells.

Conclusion:

In the light of these findings, we suggest that for proteasome inhibitor particularly Bort is thought to be useful through proteasome inhibition and NF-κB pathway.

HSF1 Is Essential for Myeloma Cell Survival and A Promising Therapeutic Target

Purpose: Myeloma is a plasma cell malignancy characterized by the overproduction of immunoglobulin, and is therefore susceptible to therapies targeting protein homeostasis. We hypothesized that heat shock factor 1 (HSF1) was an attractive therapeutic target for myeloma due to its direct regulation of transcriptional programs implicated in both protein homeostasis and the oncogenic phenotype. Here, we interrogate HSF1 as a therapeutic target in myeloma using bioinformatic, genetic, and pharmacologic means.Experimental Design: To assess the clinical relevance of HSF1, we analyzed publicly available patient myeloma gene expression datasets. Validation of this novel target was conducted in in vitro experiments using shRNA or inhibitors of the HSF1 pathway in human myeloma cell lines and primary cells as well as in in vivo human myeloma xenograft models.Results: Expression of HSF1 and its target genes were associated with poorer myeloma patient survival. ShRNA-mediated knockdown or pharmacologic inhibition of the HSF1 pathway with a novel chemical probe, CCT251236, or with KRIBB11, led to caspase-mediated cell death that was associated with an increase in EIF2α phosphorylation, CHOP expression and a decrease in overall protein synthesis. Importantly, both CCT251236 and KRIBB11 induced cytotoxicity in human myeloma cell lines and patient-derived primary myeloma cells with a therapeutic window over normal cells. Pharmacologic inhibition induced tumor growth inhibition and was well-tolerated in a human myeloma xenograft murine model with evidence of pharmacodynamic biomarker modulation.Conclusions: Taken together, our studies demonstrate the dependence of myeloma cells on HSF1 for survival and support the clinical evaluation of pharmacologic inhibitors of the HSF1 pathway in myeloma. Clin Cancer Res; 24(10); 2395-407. ©2018 AACRSee related commentary by Parekh, p. 2237.

Heat shock protein-guided dual-mode CT/MR imaging of orthotopic hepatocellular carcinoma tumor

Au@PEI-Gd-AAG NP nanoprobes hold enormous promise for highly efficient tumor diagnosis and dual-mode CT/T₁ positive MR imaging.

A phase I/II study of KW-2478, an Hsp90 inhibitor, in combination with bortezomib in patients with relapsed/refractory multiple myeloma

Background:

KW-2478 is a novel non-ansamycin Hsp90 inhibitor with modest single-agent activity in relapsed/refractory myeloma but which shows synergistic antimyeloma activity with bortezomib (BTZ) in preclinical studies. This study determined the safety, preliminary clinical activity, and pharmacokinetics of KW-2478, an Hsp90 inhibitor, in combination with BTZ in patients with relapsed/refractory multiple myeloma (MM).

Methods:

Phase I dose escalation determined the recommended phase II dose (RP2D) of KW-2478 plus BTZ, which was then used during phase II.

Results:

The maximum tolerated dose was not reached during phase I and the RP2D was KW-2478 175 mg m⁻² plus BTZ 1.3 mg m⁻² on days 1, 4, 8, and 11 every 3 weeks. In the efficacy evaluable phase I/II population treated at the RP2D (n=79), the objective response rate was 39.2% (95% confidence interval: 28.4–50.9%), clinical benefit rate 51.9% (40.4–63.3%), median progression-free survival 6.7 (5.9-not reached (NR)) months, and median duration of response 5.5 (4.9-NR) months. In the phase I/II safety population (n=95), the most frequently observed treatment-related grade 3/4 adverse events were diarrhoea, fatigue, and neutropenia (each in 7.4% of patients), and nausea and thrombocytopenia (each in 5.3%).

Conclusions:

KW-2478 plus BTZ was well tolerated with no apparent overlapping toxicity in patients with relapsed/refractory MM. The antimyeloma activity of KW-2478 in combination with BTZ as scheduled in this trial appeared relatively modest; however, the good tolerability of the combination would support further exploration of alternate dosing schedules and combinations.

A lowered 26S proteasome activity correlates with mantle lymphoma cell lines resistance to genotoxic stress

Background

Mantle cell lymphoma (MCL) is a B-cell hemopathy characterized by the t(11;14) translocation and the aberrant overexpression of cyclin D1. This results in an unrestrained cell proliferation. Other genetic alterations are common in MCL cells such as SOX11 expression, mutations of ATM and/or TP53 genes, activation of the NF-κB signaling pathway and NOTCH receptors. These alterations lead to the deregulation of the apoptotic machinery and resistance to drugs. We observed that among a panel of MCL cell lines, REC1 cells were resistant towards genotoxic stress. We studied the molecular basis of this resistance.

Methods

We analyzed the cell response regarding apoptosis, senescence, cell cycle arrest, DNA damage response and finally the 26S proteasome activity following a genotoxic treatment that causes double strand DNA breaks.

Results

MCL cell lines displayed various sensitivity/resistance towards genotoxic stress and, in particular, REC1 cells did not enter apoptosis or senescence after an etoposide treatment. Moreover, the G2/M cell cycle checkpoint was deficient in REC1 cells. We observed that three main actors of apoptosis, senescence and cell cycle regulation (cyclin D1, MCL1 and CDC25A) failed to be degraded by the proteasome machinery in REC1 cells. We ruled out a default of the βTrCP E3-ubiquitine ligase but detected a lowered 26S proteasome activity in REC1 cells compared to other cell lines.

Conclusion

The resistance of MCL cells to genotoxic stress correlates with a low 26S proteasome activity. This could represent a relevant biomarker for a subtype of MCL patients with a poor response to therapies and a high risk of relapse.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-017-3530-z) contains supplementary material, which is available to authorized users.

The Role of Intracellular Signaling Pathways in the Pathogenesis of Multiple Myeloma and Novel Therapeutic Approaches

The introduction of novel agents, such as bortezomib, thalidomide, and lenalidomide, into daily practice has dramatically improved clinical outcomes and prolonged survival of patients with multiple myeloma (MM). However, despite these advanced clinical benefits, MM remains an incurable hematological malignancy. Therefore, development of new agents and novel therapeutic strategies is urgently needed. Recent advances toward understanding the mechanism of myeloma cell growth and drug resistance in the bone marrow milieu have provided clues for the development of next-generation agents aimed at improving patient outcomes. In this review article, we discuss new possible agents for the treatment of MM based on recent advances in the understanding of signaling pathways in myeloma cells.

Sensitization of multidrug-resistant human cancer cells to Hsp90 inhibitors by down-regulation of SIRT1

The effectiveness of Hsp90 inhibitors as anticancer agents was limited in multidrug-resistant (MDR) human cancer cells due to induction of heat shock proteins (Hsps) such as Hsp70/Hsp27 and P-glycoprotein (P-gp)-mediated efflux. In the present study, we showed that resistance to Hsp90 inhibitors of MDR human cancer cells could be overcome with SIRT1 inhibition. SIRT1 knock-down or SIRT1 inhibitors (amurensin G and EX527) effectively suppressed the resistance to Hsp90 inhibitors (17-AAG and AUY922) in several MDR variants of human lymphoblastic leukemia and human breast cancer cell lines. SIRT1 inhibition down-regulated the expression of heat shock factor 1 (HSF1) and subsequently Hsps and facilitated Hsp90 multichaperone complex disruption via hyperacetylation of Hsp90/Hsp70. These findings were followed by acceleration of ubiquitin ligase CHIP-mediated mutant p53 (mut p53) degradation and subsequent down-regulation of P-gp in 17-AAG-treated MDR cancer cells expressing P-gp and mut p53 after inhibition of SIRT1. Therefore, combined treatment with Hsp90 inhibitor and SIRT1 inhibitor could be a more effective therapeutic approach for Hsp90 inhibitor-resistant MDR cells via down-regulation of HSF1/Hsps, mut p53 and P-gp.

Advances in targeted therapy for the treatment of patients with relapsed/refractory multiple myeloma

The development of proteasome inhibitors (PIs) and immunomodulatory drugs has significantly improved outcomes for patients with relapsed/refractory multiple myeloma (RRMM); however, not all patients benefit from treatment with these agents and some patients can become drug refractory over time. Due to the largely incurable nature of multiple myeloma, the development of newer agents is ongoing and includes new oral PIs (ixazomib), immunotherapies (e.g., CD38- or SLAMF7-targeted antibodies), and small molecules. This review provides an overview of the advances in targeted therapy for patients with RRMM, including recently approved agents, with a focus on monotherapy and combined targeted therapies.

In vitro study comparing the efficacy of the water-soluble HSP90 inhibitors, 17-AEPGA and 17-DMAG, with that of the non‑water-soluble HSP90 inhibitor, 17-AAG, in breast cancer cell lines

Heat shock protein (HSP)90 has emerged as an important target in cancer therapeutics. Diverse HSP90 inhibitors are under evaluation. The aim of the present study was to investigate the growth inhibitory effects of the newly developed water-soluble HSP90 inhibitors, 17-[2-(Pyrrolidin-1-yl)ethyl]amino-17-demethoxygeldanamycin (17-AEPGA) and 17-dimethylaminoethylamino-17-demethoxygeldanamycin (17-DMAG), compared to that of the non-water-soluble HSP90 inhibitor, 17-allylamino-17-demethoxygeldanamycin (17-AAG). The anti-proliferative effects of the 3 drugs on the human breast cancer cell lines, MCF-7, SKBR-3 and MDA-MB-231, were examined in vitro. In addition, tumor progression factors, including human epidermal growth factor receptor 2 (HER2), epidermal growth factor receptor 1 (EGFR1) and insulin-like growth factor type 1 receptor (IGF1R), as well as apoptotic markers were analysed. We found a time- and dose-dependent effect in all the tested cell lines. The effects of 17-AEPGA and 17-DMAG were equal or superior to those of 17-AAG. The 50% growth inhibition concentration was <2 µM for the water-soluble compounds following 72 h of exposure. The significant inhibition of HER2, EGFR1 and IGF1R protein expression was already evident at the concentration of 1 µM. Apoptosis was examined by caspase-3 and poly(ADP-ribose) polymerase (PARP) assay at the concentration of 1 µM of the inhibitors. HSP70 was upregulated, but HSP27 expression was not affected. Our data indicate that 17-AEPGA and 17-DMAG are highly active in breast cancer cell lines and may help to overcome the delivery issues associated with the use of 17-AAG.

Development of Heat Shock Protein (Hsp90) Inhibitors To Combat Resistance to Tyrosine Kinase Inhibitors through Hsp90-Kinase Interactions

Heat shock protein 90 (Hsp90) is a ubiquitous chaperone of all of the oncogenic tyrosine kinases. Many Hsp90 inhibitors, alone or in combination, have shown significant antitumor efficacy against the kinase-positive naïve and mutant models. However, clinical trials of these inhibitors are unsuccessful due to insufficient clinical benefits and nonoptimal safety profiles. Recently, much progress has been reported on the Hsp90-cochaperone-client complex, which will undoubtedly assist in the understanding of the interactions between Hsp90 and its clients. Meanwhile, Hsp90 inhibitors have shown promise against patients' resistance caused by early generation tyrosine kinase inhibitors (TKIs), and at least 13 Hsp90 inhibitors are being reevaluated in the clinic. In this regard, the objectives of the current perspective are to summarize the structure and function of the Hsp90-cochaperone-client complex, to analyze the structural and functional insights into the Hsp90-client interactions to address several existing unresolved problems with Hsp90 inhibitors, and to highlight the preclinical and clinical studies of Hsp90 inhibitors as an effective treatment against resistance to tyrosine kinase inhibitors.

Mechanisms of Drug Resistance in Relapse and Refractory Multiple Myeloma

Multiple myeloma (MM) is a hematological malignancy that remains incurable because most patients eventually relapse or become refractory to current treatments. Although the treatments have improved, the major problem in MM is resistance to therapy. Clonal evolution of MM cells and bone marrow microenvironment changes contribute to drug resistance. Some mechanisms affect both MM cells and microenvironment, including the up- and downregulation of microRNAs and programmed death factor 1 (PD-1)/PD-L1 interaction. Here, we review the pathogenesis of MM cells and bone marrow microenvironment and highlight possible drug resistance mechanisms. We also review a potential molecular targeting treatment and immunotherapy for patients with refractory or relapse MM.

The 26S proteasome is a multifaceted target for anti-cancer therapies

Proteasomes play a critical role in the fate of proteins that are involved in major cellular processes, including signal transduction, gene expression, cell cycle, replication, differentiation, immune response, cellular response to stress, etc. In contrast to non-specific degradation by lysosomes, proteasomes are highly selective and destroy only the proteins that are covalently labelled with small proteins, called ubiquitins. Importantly, many diseases, including neurodegenerative diseases and cancers, are intimately connected to the activity of proteasomes making them an important pharmacological target. Currently, the vast majority of inhibitors are aimed at blunting the proteolytic activities of proteasomes. However, recent achievements in solving structures of proteasomes at very high resolution provided opportunities to design new classes of small molecules that target other physiologically-important enzymatic activities of proteasomes, including the de-ubiquitinating one. This review attempts to catalog the information available to date about novel classes of proteasome inhibitors that may have important pharmacological ramifications.

Ganetespib: research and clinical development

Under stressful conditions, the heat shock protein 90 (HSP90) molecular chaperone protects cellular proteins (client proteins) from degradation via the ubiquitin-proteasome pathway. HSP90 expression is upregulated in cancers, and this contributes to the malignant phenotype of increased proliferation and decreased apoptosis and maintenance of metastatic potential via conservation of its client proteins, including human epidermal growth factor receptor 2, anaplastic lymphoma kinase, androgen receptor, estrogen receptor, Akt, Raf-1, cell cycle proteins, and B-cell lymphoma 2 among others. Hence, inhibition of HSP90 leads to the simultaneous degradation of its many clients, thereby disrupting multiple oncogenic signaling cascades. This has sparked tremendous interest in the development of HSP90 inhibitors as an innovative anticancer strategy. Based on the wealth of compelling data from preclinical studies, a number of HSP90 inhibitors have entered into clinical testing. However, despite enormous promise and anticancer activity reported to date, none of the HSP90 inhibitors in development has been approved for cancer therapy, and the full potential of this class of agents is yet to be realized. This article provides a review on ganetespib, a small molecule HSP90 inhibitor that is currently under evaluation in a broad range of cancer types in combination with other therapeutic agents with the hope of further enhancing its efficacy and overcoming drug resistance. Based on our current understanding of the complex HSP90 machinery combined with the emerging data from these key clinical trials, ganetespib has the potential to be the first-in-class HSP90 inhibitor to be approved as a new anticancer therapy.

NKG2D and DNAM-1 Ligands: Molecular Targets for NK Cell-Mediated Immunotherapeutic Intervention in Multiple Myeloma

A pivotal strategy to improve NK cell-mediated antitumor activity involves the upregulation of activating ligands on tumor cells. Enhancement of NK cell-mediated recognition of multiple myeloma cells was reported by us and others showing increased surface expression of NKG2D and DNAM-1 ligands on tumor cells following treatment with a number of chemotherapeutic agents, such as genotoxic drugs or inhibitors of proteasome, histone deacetylases, GSK3, and HSP-90. These compounds have the capability to affect tumor survival but also to activate specific transduction pathways associated with the upregulation of different NK cell activating ligands on the tumor cells. Here, we will summarize and discuss the molecular pathways whereby these drugs can regulate the expression of NK cell activating ligands in multiple myeloma cells.

Misfolded proteins: from little villains to little helpers in the fight against cancer

The application of cytostatic drugs targeting the high proliferation rates of cancer cells is currently the most commonly used treatment option in cancer chemotherapy. However, severe side effects and resistance mechanisms may occur as a result of such treatment, possibly limiting the therapeutic efficacy of these agents. In recent years, several therapeutic strategies have been developed that aim at targeting not the genomic integrity and replication machinery of cancer cells but instead their protein homeostasis. During malignant transformation, the cancer cell proteome develops vast aberrations in the expression of mutated proteins, oncoproteins, drug- and apoptosis-resistance proteins, etc. A complex network of protein quality-control mechanisms, including chaperoning by heat shock proteins (HSPs), not only is essential for maintaining the extravagant proteomic lifestyle of cancer cells but also represents an ideal cancer-specific target to be tackled. Furthermore, the high rate of protein synthesis and turnover in certain types of cancer cells can be specifically directed by interfering with the proteasomal and autophagosomal protein recycling and degradation machinery, as evidenced by the clinical application of proteasome inhibitors. Since proteins with loss of their native conformation are prone to unspecific aggregations and have proved to be detrimental to normal cellular function, specific induction of misfolded proteins by HSP inhibitors, proteasome inhibitors, hyperthermia, or inducers of endoplasmic reticulum stress represents a new method of cancer cell killing exploitable for therapeutic purposes. This review describes drugs - approved, repurposed, or under investigation - that can be used to accumulate misfolded proteins in cancer cells, and particularly focuses on the molecular aspects that lead to the cytotoxicity of misfolded proteins in cancer cells.

Heat shock proteins in multiple myeloma

Heat shock proteins are molecular chaperones with a central role in protein folding and cellular protein homeostasis. They also play major roles in the development of cancer and in recent years have emerged as promising therapeutic targets. In this review, we discuss the known molecular mechanisms of various heat shock protein families and their involvement in cancer and in particular, multiple myeloma. In addition, we address the current progress and challenges in pharmacologically targeting these proteins as anti-cancer therapeutic strategies.

Hsp90 inhibitor as a sensitizer of cancer cells to different therapies (review)

Hsp90 is a molecular chaperone that maintains the structural and functional integrity of various client proteins involved in signaling and many other functions of cancer cells. The natural inhibitors, ansamycins influence the Hsp90 chaperone function by preventing its binding to client proteins and resulting in their proteasomal degradation. N- and C-terminal inhibitors of Hsp90 and their analogues are widely tested as potential anticancer agents in vitro, in vivo as well as in clinical trials. It seems that Hsp90 competitive inhibitors target different tumor types at nanomolar concentrations and might have therapeutic benefit. On the contrary, some Hsp90 inhibitors increased toxicity and resistance of cancer cells induced by heat shock response, and through the interaction of survival signals, that occured as side effects of treatments, could be very effectively limited via combination of therapies. The aim of our review was to collect the data from experimental and clinical trials where Hsp90 inhibitor was combined with other therapies in order to prevent resistance as well as to potentiate the cytotoxic and/or antiproliferative effects.

Inhibition of HSP90 by AT13387 delays the emergence of resistance to BRAF inhibitors and overcomes resistance to dual BRAF and MEK inhibition in melanoma models

Emergence of clinical resistance to BRAF inhibitors, alone or in combination with MEK inhibitors, limits clinical responses in melanoma. Inhibiting HSP90 offers an approach to simultaneously interfere with multiple resistance mechanisms. Using the HSP90 inhibitor AT13387, which is currently in clinical trials, we investigated the potential of HSP90 inhibition to overcome or delay the emergence of resistance to these kinase inhibitors in melanoma models. In vitro, treating vemurafenib-sensitive cells (A375 or SK-MEL-28) with a combination of AT13387 and vemurafenib prevented colony growth under conditions in which vemurafenib treatment alone generated resistant colonies. In vivo, when AT13387 was combined with vemurafenib in a SK-MEL-28, vemurafenib-sensitive model, no regrowth of tumors was observed over 5 months, although 2 of 7 tumors in the vemurafenib monotherapy group relapsed in this time. Together, these data suggest that the combination of these agents can delay the emergence of resistance. Cell lines with acquired vemurafenib resistance, derived from these models (A375R and SK-MEL-28R) were also sensitive to HSP90 inhibitor treatment; key clients were depleted, apoptosis was induced, and growth in 3D culture was inhibited. Similar effects were observed in cell lines with acquired resistance to both BRAF and MEK inhibitors (SK-MEL-28RR, WM164RR, and 1205LuRR). These data suggest that treatment with an HSP90 inhibitor, such as AT13387, is a potential approach for combating resistance to BRAF and MEK inhibition in melanoma. Moreover, frontline combination of these agents with an HSP90 inhibitor could delay the emergence of resistance, providing a strong rationale for clinical investigation of such combinations in BRAF-mutated melanoma.

Current treatment landscape for relapsed and/or refractory multiple myeloma

Recent developments in the treatment of multiple myeloma have led to improvements in response rates and to increased survival; however, relapse is inevitable in almost all patients. Recurrence of myeloma is typically more aggressive with each relapse, leading to the development of treatment-refractory disease, which is associated with a shorter survival. Several phase II and III trials have demonstrated the efficacy of recently approved agents in the setting of relapsed and/or refractory multiple myeloma, including immunomodulatory agents, such as lenalidomide and pomalidomide, and proteasome inhibitors, such as bortezomib and carfilzomib. Currently, however, there is no standard treatment for patients with relapsed and/or refractory disease. This Review discusses the current treatment landscape for patients with relapsed and/or refractory multiple myeloma and highlights disease-related and patient-related factors--such as pre-existing comorbidities or toxicities--that are important considerations for clinicians when selecting an appropriate treatment regimen.

Phase I dose-escalation studies of SNX-5422, an orally bioavailable heat shock protein 90 inhibitor, in patients with refractory solid tumours

BACKGROUND

Orally administered SNX-5422, a novel, selective prodrug of the Heat shock protein 90 (Hsp90) inhibitor SNX-2112, was investigated in two sequential phase I studies to determine the safety, maximum tolerated doses (MTDs) and pharmacokinetic profile of SNX-5422.

METHODS

Using a dose-escalation design, 3-6 adults with advanced solid tumours received SNX-5422 every-other-day (QOD) or once-daily (QD) 3weeks on/1week off or QD continuously, with disease assessments every 8 weeks. Single-dose and steady-state pharmacokinetic parameters of SNX-2112 were determined.

RESULTS

In total, 56 patients were enrolled: QOD 3 weeks on/1 week off, n=36; QD 3weeks on/1 week off, n=17; QD continuous, n=3. Doses ranged from 4 to 133mg/m(2) QOD and 50 to 89 mg/m(2) QD. The MTDs were defined as 100mg/m(2) QOD and 67 mg/m(2) QD, respectively, with diarrhoea being dose-limiting on both 3 weeks on/1 week off schedules. Overall, treatment-related adverse events were mainly low grade, including diarrhoea (64%), nausea (39%), fatigue (28%), and vomiting (28%). Reversible grade 1-3 nyctalopia (night blindness) was reported by four patients (dose: 50-89mg/m(2) QD; 100mg/m(2) QOD). Exposure was generally linear, though greater than dose-proportional. Of 32 evaluable patients on QOD dosing, there was one durable complete response (prostate cancer), one confirmed (HER2+breast cancer) and one unconfirmed partial response (adrenal gland cancer). Three patients (QOD schedule) had stable disease for ⩾ 6 months.

CONCLUSIONS

The dose and schedule recommended for further study with SNX-5422 is 100mg/m(2) QOD 3 weeks on/1 week off based on improved tolerability and preliminary evidence of clinical activity.

Beyond BRAF: where next for melanoma therapy?

In recent years, melanoma has become a poster-child for the development of oncogene-directed targeted therapies. This approach, which has been exemplified by the development of small-molecule BRAF inhibitors and the BRAF/MEK inhibitor combination for BRAF-mutant melanoma, has brought new hope to patients. Despite these successes, treatment failure seems near inevitable in the majority of cases—even in individuals treated with the BRAF/MEK inhibitor doublet. In the current review, we discuss the future of combination strategies for patients with BRAF-mutant melanoma as well as the emerging therapeutic options for patients with NRAS-mutant and BRAF/NRAS-wild-type melanoma. We also outline some of the newest developments in the in-depth personalisation of therapy that should allow melanoma treatment to continue shaping the field precision cancer medicine.

Change or die: targeting adaptive signaling to kinase inhibition in cancer cells

Small molecule kinase inhibitors have proven enormously successful at delivering impressive responses in patients with cancers as diverse as chronic myeloid-leukemia, melanoma, breast cancer and small cell lung cancer. Despite this, resistance is commonplace and most patients ultimately fail therapy. One emerging observation is the rapid rewiring of signaling that occurs across multiple cancer types when driver oncogene function is inhibited. These adaptive signaling changes seem critical in delivering some of the earliest survival signals that allow small numbers of cells to evade therapy. In this commentary we review the mechanisms that contribute to the robustness of signaling networks within cancer cells and suggest new therapeutic strategies to limit treatment failure.

Novel targeted agents in the treatment of multiple myeloma

New, next-generation targeted treatment strategies are required to improve outcomes in patients with multiple myeloma (MM). Monoclonal antibodies, cell signaling inhibitors, and selective therapies targeting the bone marrow microenvironment have demonstrated encouraging results with generally manageable toxicity in therapeutic trials of patients with relapsed and refractory disease, each critically informed by preclinical studies. A combination approach of these newer agents with immunomodulators and/or proteasome inhibitors as part of a treatment platform seems to improve the efficacy of anti-MM regimens, even in heavily pretreated patients. Future studies are required to better understand the complex mechanisms of drug resistance in MM.

Small molecule inhibitors in acute myeloid leukemia: from the bench to the clinic

Many patients with acute myeloid leukemia will eventually develop refractory or relapsed disease. In the absence of standard therapy for this population, there is currently an urgent unmet need for novel therapeutic agents. Targeted therapy with small molecule inhibitors represents a new therapeutic intervention that has been successful for the treatment of multiple tumors (e.g., gastrointestinal stromal tumors, chronic myelogenous leukemia). Hence, there has been great interest in generating selective small molecule inhibitors targeting critical pathways of proliferation and survival in acute myeloid leukemia. This review highlights a selective group of intriguing therapeutic agents and their presumed targets in both preclinical models and in early human clinical trials.

Novel agents and new therapeutic approaches for treatment of multiple myeloma

This review summarizes the therapeutic strategies and the drugs actually in development for the management of myeloma patients. Multiple myeloma is caused by the expansion of monoclonal plasma cells and secretion of M-protein (immunoglobulins, Bence Jones protein and free light chains). Multiple myeloma still remains an incurable disease with a high incidence rate in the elderly, despite the introduction of several new therapeutic agents (bortezomib, lenalidomide and thalidomide) which have changed its natural history. The high heterogeneity of this disease leads to large differences in clinical responses to treatments. Thus, the choice of the best treatment is a difficult issue. However, the introduction of new drugs has made it possible to achieve high response rates and good quality responses with long-term disease control. Interactions between tumor cells and their bone marrow microenvironment play a pivotal role in the development, maintenance, and progression of myeloma, inducing also drug resistance. These knowledges have improved treatment options, leading to the approval of new drugs which not only target the malignant cell itself, but also its microenvironment. These agents are in preclinical/early clinical evaluation and they appear to further improve disease control, but their use is still not approved outside of clinical trials.

Meta-analysis of the efficacy and safety of bortezomib re-treatment in patients with multiple myeloma

INTRODUCTION

Bortezomib is administered for a finite course; thus, patients might remain sensitive to bortezomib-based therapy at relapse. We report a meta-analysis of bortezomib-based retreatment in relapsed/refractory myeloma.

PATIENTS AND METHODS

A systematic literature review identified studies of bortezomib-based retreatment in relapsed/refractory myeloma. Proportions of bortezomib-refractory patients and additional prognostic factors were extracted and used in weighted stratified analyses of TTP and OS. Random-effect pooled estimates were calculated for overall response rate (ORR) and rates of common AEs.

RESULTS

Twenty-three studies (n = 1051 patients) were identified. Bortezomib was administered intravenously in all studies. Across studies in which data were available, pooled, weighted average ORR was 39.1% (95% confidence interval, 30.8%-47.4%), and pooled, weighted average median TTP and OS were 7.5 and 16.6 months, respectively. Patients with fewer previous therapies (≤ 4) and relapsed (not refractory) patients achieved higher ORRs, of 43.4% and 57.2%, respectively. Random-effects meta-regression analysis confirmed that relapsed patients were associated with a higher ORR by 28 to 41 percentage points versus refractory patients. In relapsed patients, median TTP and OS were 8.5 and 19.7 months, respectively. Common Grade 3/4 AEs included thrombocytopenia (35%), neutropenia (15%), anemia (14%), pneumonia (10%), and peripheral neuropathy (3%).

CONCLUSION

Based on these findings, bortezomib retreatment is well tolerated and appears efficacious in relapsed patients. In an era of new and emerging treatment options for relapsed and/or refractory myeloma, these data indicate that bortezomib retreatment might be a highly effective option in previously treated patients.

Heat shock protein 90 inhibitors in the treatment of cancer: current status and future directions

INTRODUCTION

Heat shock protein 90 (HSP90) serves as a critical facilitator for oncogene addiction. There has been augmenting enthusiasm in pursuing HSP90 as an anticancer strategy. In fact, since the initial serendipitous discovery that geldanamycin (GM) inhibits HSP90, the field has rapidly moved from proof-of-concept clinical studies with GM derivatives to novel second-generation inhibitors.

AREAS COVERED

The authors highlight the current status of the second-generation HSP90 inhibitors in clinical development. Herein, the authors note the lessons learned from the completed clinical trials of first- and second-generation inhibitors and describe various assays attempting to serve for a more rational implementation of these agents to cancer treatment. Finally, the authors discuss the future perspectives for this promising class of agents.

EXPERT OPINION

The knowledge gained thus far provides perhaps only a glimpse at the potential of HSP90 for which there is still much work to be done. Lessons from the clinical trials suggest that HSP90 therapy would advance at a faster pace if patient selection and tumor pharmacokinetics of these drugs were better understood and applied to their clinical development. It is also evident that combining HSP90 inhibitors with other potent anticancer therapies holds great promise not only due to synergistic antitumor activity but also due to the potential of prolonging or preventing the development of drug resistance.

Evaluating melanoma drug response and therapeutic escape with quantitative proteomics

The evolution of cancer therapy into complex regimens with multiple drugs requires novel approaches for the development and evaluation of companion biomarkers. Liquid chromatography-multiple reaction monitoring mass spectrometry (LC-MRM) is a versatile platform for biomarker measurement. In this study, we describe the development and use of the LC-MRM platform to study the adaptive signaling responses of melanoma cells to inhibitors of HSP90 (XL888) and MEK (AZD6244). XL888 had good anti-tumor activity against NRAS mutant melanoma cell lines as well as BRAF mutant cells with acquired resistance to BRAF inhibitors both in vitro and in vivo. LC-MRM analysis showed HSP90 inhibition to be associated with decreased expression of multiple receptor tyrosine kinases, modules in the PI3K/AKT/mammalian target of rapamycin pathway, and the MAPK/CDK4 signaling axis in NRAS mutant melanoma cell lines and the inhibition of PI3K/AKT signaling in BRAF mutant melanoma xenografts with acquired vemurafenib resistance. The LC-MRM approach targeting more than 80 cancer signaling proteins was highly sensitive and could be applied to fine needle aspirates from xenografts and clinical melanoma specimens (using 50 μg of total protein). We further showed MEK inhibition to be associated with signaling through the NFκB and WNT signaling pathways, as well as increased receptor tyrosine kinase expression and activation. Validation studies identified PDGF receptor β signaling as a potential escape mechanism from MEK inhibition, which could be overcome through combined use of AZD6244 and the PDGF receptor inhibitor, crenolanib. Together, our studies show LC-MRM to have unique value as a platform for the systems level understanding of the molecular mechanisms of drug response and therapeutic escape. This work provides the proof-of-principle for the future development of LC-MRM assays for monitoring drug responses in the clinic.

Molecularly targeted therapies in multiple myeloma

Multiple myeloma (MM) is a hematological malignancy that remains incurable because most patients will eventually relapse or become refractory to the treatments. Although the treatments have improved, the major problem in MM is the resistance to therapy. Novel agents are currently in development for the treatment of relapsed/refractory MM, including immunomodulatory drugs, proteasome inhibitors, monoclonal antibodies, cell signaling targeted therapies, and strategies targeting the tumor microenvironment. We have previously reviewed in detail the contemporary immunomodulatory drugs, proteasome inhibitors, and monoclonal antibodies therapies for MM. Therefore, in this review, we focused on the role of molecular targeted therapies in the treatment of relapsed/refractory multiple myeloma, including cell signaling targeted therapies (HDAC, PI3K/AKT/mTOR, p38 MAPK, Hsp90, Wnt, Notch, Hedgehog, and cell cycle) and strategies targeting the tumor microenvironment (hypoxia, angiogenesis, integrins, CD44, CXCR4, and selectins). Although these novel agents have improved the therapeutic outcomes for MM patients, further development of new therapeutic agents is warranted.

New drugs and novel mechanisms of action in multiple myeloma in 2013: a report from the International Myeloma Working Group (IMWG)

Treatment in medical oncology is gradually shifting from the use of nonspecific chemotherapeutic agents toward an era of novel targeted therapy in which drugs and their combinations target specific aspects of the biology of tumor cells. Multiple myeloma (MM) has become one of the best examples in this regard, reflected in the identification of new pathogenic mechanisms, together with the development of novel drugs that are being explored from the preclinical setting to the early phases of clinical development. We review the biological rationale for the use of the most important new agents for treating MM and summarize their clinical activity in an increasingly busy field. First, we discuss data from already approved and active agents (including second- and third-generation proteasome inhibitors (PIs), immunomodulatory agents and alkylators). Next, we focus on agents with novel mechanisms of action, such as monoclonal antibodies (MoAbs), cell cycle-specific drugs, deacetylase inhibitors, agents acting on the unfolded protein response, signaling transduction pathway inhibitors and kinase inhibitors. Among this plethora of new agents or mechanisms, some are specially promising: anti-CD38 MoAb, such as daratumumab, are the first antibodies with clinical activity as single agents in MM. Moreover, the kinesin spindle protein inhibitor Arry-520 is effective in monotherapy as well as in combination with dexamethasone in heavily pretreated patients. Immunotherapy against MM is also being explored, and probably the most attractive example of this approach is the combination of the anti-CS1 MoAb elotuzumab with lenalidomide and dexamethasone, which has produced exciting results in the relapsed/refractory setting.

A phase 1, dose-escalation, pharmacokinetic and pharmacodynamic study of BIIB021 administered orally in patients with advanced solid tumors

PURPOSE

BIIB021 is the first oral, synthetic, non-geldanamycin-based HSP90 inhibitor that showed activity in preclinical models at low nanomolar concentrations. We performed a phase 1 trial of BIIB021 administered to subjects with advanced solid tumors.

EXPERIMENTAL DESIGN

Sixty patients received BIIB021 capsules orally on days 1, 4, 8, 11, 15, and 18 of each course in schedule 1, and on days 1, 4, 8, 11, 15, 18, 22, and 25 of each course in schedule 2. The treatment schedules were repeated every 28 days. In addition to determining the MTD, we evaluated pharmacokinetics of BIIB021 and pharmacodynamic effects of BIIB021 [Hsp70, HER2 extracellular domain (HER2-ECD)].

RESULTS

The MTD was 700 mg twice weekly when BIIB021 was dosed for 3 weeks out of each 4-week course. The MTD for continuous dosing regimen was established at 600 mg twice weekly. Gastrointestinal (nausea, vomiting), hot flashes, and neurologic (dizziness) events characterize the safety profile of BIIB021 dosed twice weekly, with events mostly mild or moderate. Plasma exposure to BIIB021 was dose-dependent. Cmax occurred at approximately 90 minutes and t1/2 was approximately 1 hour across dosing cohorts of 25 to 800 mg BIIB021 twice weekly. The biologic activity of BIIB021 was demonstrated in serum, PBMCs, and tumor tissue. Hsp70 levels were increased (>150% from baseline) and serum HER2-ECD was significantly decreased (>15% inhibition from baseline).

CONCLUSIONS

BIIB021 twice weekly, given with or without the 1 of 4-week rest period was tolerated in subjects with advanced solid tumors at doses that are pharmacodynamically active.