The role of the insulin-like growth factor 1 receptor axis in multiple myeloma

Functional Investigation of IGF1R Mutations in Multiple Myeloma

High expression of the receptor tyrosine kinase (RTK) insulin-like growth factor-1 receptor (IGF1R) and RTK mutations are associated with high-risk/worse prognosis in multiple myeloma (MM). Combining the pIGF1R/pINSR inhibitor linsitinib with the proteasome inhibitor (PI) bortezomib seemed promising in a clinical trial, but IGF1R expression was not associated with therapy response. Because the oncogenic impact of IGF1R mutations is so far unknown, we investigated the functional impact of IGF1R mutations on survival signaling, viability/proliferation and survival response to therapy. We transfected four human myeloma cell lines (HMCLs) with IGF1RWT, IGF1RD1146N and IGF1RN1129S (Sleeping Beauty), generated CRISPR-Cas9 IGF1R knockouts in the HMCLs U-266 (IGF1RWT) and L-363 (IGF1RD1146N) and tested the anti-MM activity of linsitinib alone and in combination with the second-generation PI carfilzomib in seven HMCLs. IGF1R knockout entailed reduced proliferation. Upon IGF1R overexpression, survival signaling was moderately increased in all HCMLs and slightly affected by IGF1RN1129S in one HMCL, whereby the viability remained unaffected. Expression of IGF1RD1146N reduced pIGF1R-Y1135, especially under serum reduction, but did not impact downstream signaling. Linsitinib and carfilzomib showed enhanced anti-myeloma activity in six out of seven HMCL irrespective of the IGF1R mutation status. In conclusion, IGF1R mutations can impact IGF1R activation and/or downstream signaling, and a combination of linsitinib with carfilzomib might be a suitable therapeutic approach for MM patients potentially responsive to IGF1R blockade.

Growth and dormancy control of myeloma cells by mesenchymal stem cells

Bone marrow mesenchymal stem cells (MSCs) may have contrasting impacts on the progression of multiple myeloma (MM). Priming normal MSCs, by culturing them with MM cells, mimics the MSC-induced MM growth. We studied the contrasting effects of conditioned medium (CM) from unprimed or primed MSCs on growth of MM cells from newly diagnosed cases. We elucidated potential molecular pathways using global gene expression profiling and focused on the role of the mTOR2 component, RICTOR, as a novel mediator of dormancy in MM. Primed MSCs CM consistently increased proportions of proliferating cells and supported MM growth in 3-day (n = 20) and 10-day (n = 12) cultures, effects that were partially mediated through the IGF1 axis. In contrast, unprimed MSCs CM inhibited growth of MM cells in cases mainly from stages I/II MM. The genes most overexpressed in MM cells treated with primed MSCs CM were associated with cell cycle, DNA-damage repair, and proliferation; genes most overexpressed in MM cells treated with unprimed MSCs CM were associated with dormancy pathways including RICTOR (mTOR2 pathway), CXCR4, and BCL2. RICTOR protein level was induced by unprimed MSCs CM and was lower in KI67+ proliferating MM cells treated with primed MSCs CM. RICTOR was underexpressed in clinical relapse samples compared with baseline samples of the same patients. Inhibiting RICTOR expression in primary MM cells promoted their growth, and enforced expression of RICTOR in MM cell lines inhibited their growth. Our findings suggest that, after prolonged interactions with MM cells, bone marrow MSCs shift from MM-repressive to MM-permissive. AVAILABILITY OF DATA AND MATERIALS: Our institutional GEP data of MM cells from newly diagnosed patients used to show RICTOR expression have been deposited at Gene Expression Omnibus (GEO: GSE2658, https://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE2658).

Bone marrow stromal cells derived exosomal miR-10a and miR-16 may be involved in progression of patients with multiple myeloma by regulating EPHA8 or IGF1R/CCND1

Interaction with bone marrow stromal cells (BMSCs) has been suggested as an important mechanism for the progression of multiple myeloma (MM) cells, while exosomes are crucial mediators for cell-to-cell communication. The study was to investigate the miRNA profile changes in exosomes released by BMSCs of MM patients and explore their possible function roles.The microarray datasets of exosomal miRNAs in BMSCs were downloaded from the Gene Expression Omnibus database (GSE110271: 6 MM patients, 2 healthy donors; GSE78865: 4 donors and 2 MM patients; GSE39571: 7 MM patients and 4 controls). The differentially expressed miRNAs (DEMs) were identified using the LIMMA method. The target genes of DEMs were predicted by the miRwalk 2.0 database and the hub genes were screened by constructing the protein-protein interaction (PPI) network, module analysis and overlapping with the differentially expressed genes (DEGs) after overexpression or knockout of miRNAs.Three downregulated DEMs were found to distinguish MM from normal and MM-MGUS controls in the GSE39571 dataset; one downregulated and one upregulated DEMs (hsa-miR-10a) could differentiate MM from normal and MM-MGUS controls in the GSE110271-GSE78865 merged dataset. Furthermore, 11 downregulated (hsa-miR-16) and 1 upregulated DEMs were shared between GSE39571 and merged dataset when comparing MM with normal samples. The target genes were predicted for these 17 DEMs. PPI with module analysis showed IGF1R and CCND1 were hub genes and regulated by hsa-miR-16. Furthermore, EPHA8 was identified as a DEG that was downregulated in MM cells when the use of has-miR-10a mimics; while IGF1R, CCND1, CUL3, and ELAVL1 were also screened as DEGs that were upregulated in MM cells when silencing of hsa-miR-16.BMSCs-derived exosomal miR-10a and miR-16 may be involved in MM progression by regulating EPHA8 or IGF1R/CCND1/CUL3/ELAVL1, respectively. These exosomal miRNAs or genes may represent potential biomarkers for diagnosis of MM and prediction of progression and targets for developing therapeutic drugs.

The Association between Metabolic Syndrome and Multiple Myeloma

Multiple myeloma (MM) is a haematological malignancy arising from monoclonal proliferation of plasma cells in the bone marrow, resulting in the presence of paraproteins or M-protein in serum. The involvement of paraproteins produced by malignant plasma cells in the development of hyperlipidaemia and low-HDL cholesterol has been described, as has an association with MM and obesity, hypertension, and type 2 diabetes mellitus, and insulin resistance, that is, features of the metabolic syndrome (MS). There is an association between MS components, inflammatory cytokines, and the development of MM, and some drugs used in the treatment of MS such as statins and metformin may improve outcomes in MM.

The insulin-like growth factor system in multiple myeloma: diagnostic and therapeutic potential

Multiple myeloma (MM) is a highly heterogeneous plasma cell malignancy. The MM cells reside in the bone marrow (BM), where reciprocal interactions with the BM niche foster MM cell survival, proliferation, and drug resistance. As in most cancers, the insulin-like growth factor (IGF) system has been demonstrated to play a key role in the pathogenesis of MM. The IGF system consists of IGF ligands, IGF receptors, IGF binding proteins (IGFBPs), and IGFBP proteases and contributes not only to the survival, proliferation, and homing of MM cells, but also MM-associated angiogenesis and osteolysis. Furthermore, increased IGF-I receptor (IGF-IR) expression on MM cells correlates with a poor prognosis in MM patients. Despite the prominent role of the IGF system in MM, strategies targeting the IGF-IR using blocking antibodies or small molecule inhibitors have failed to translate into the clinic. However, increasing preclinical evidence indicates that IGF-I is also involved in the development of drug resistance against current standard-of-care agents against MM, including proteasome inhibitors, immunomodulatory agents, and corticoids. IGF-IR targeting has been able to overcome or revert this drug resistance in animal models, enhancing the efficacy of standard-of-care agents. This finding has generated renewed interest in the therapeutic potential of IGF-I targeting in MM. The present review provides an update of the impact of the different IGF system components in MM and discusses the diagnostic and therapeutic potentials.

The impact of MET, IGF-1, IGF1R expression and EGFR mutations on survival of patients with non-small-cell lung cancer

Introduction

To compare the efficacy of silver in situ hybridization (SISH) and immunohistochemistry (IHC) in detecting MET and IGF1R alterations and to investigate their prevalence and prognostic significance. A possible correlation between MET receptor expression, MET gene alterations and the two most frequent occurring EGFR gene mutations was also investigated.

Materials and methods

Stage I to IIIA tumors from 326 patients with NSCLC were immunohistochemically tested for protein expression of MET and IGF-1. Their cytoplasmic expression was compared with the gene copy number of the MET and IGF1Rgenes by SISH in paraffin-embedded, formalin-fixed material. Correlations were made with the immunohistochemical expression of two frequent EGFR mutations and clinicopathological variables. Univariate and multivariate survival analyses was used to evaluate the prognostic efficacy of the tested markers.

Results

In univariate analyses, high cytoplasmic MET expression showed a significant negative prognostic effect in adenocarcinoma patients (p = 0.026). MET gene to chromosome 7 ratio was a significant positive prognostic marker (p = 0.005), probably only due to the highly negative prognostic significance of chromosome 7 polysomy (p = 0.002). High IGF1R gene copy number was a negative prognostic marker for all NSCLC patients (p = 0.037). In the multivariate analysis, polysomy of chromosome 7 in tumor cells correlated significantly and independently with a poor prognosis (p = 0.011). In patients with adenocarcinoma, a high cytoplasmic MET expression was an independent negative prognostic marker (p = 0.013). In males a high IGF1R gene copy number to chromosome 15 count ratio was significantly and independently correlated to a poor prognosis (p = 0.018).

Conclusion

MET protein expression provides superior prognostic information compared with SISH. Polysomy of chromosome 7 is an independent negative prognostic factor in NSCLC patients. This finding has an important implication while examining genes located on chromosome 7 by means of SISH. High IGF1R gene copy number to chromosome 15 count ratio is an independent predictor of inferior survival in male patients with primary NSCLC.

Single-molecule analysis reveals widespread structural variation in multiple myeloma

Multiple myeloma (MM), a malignancy of plasma cells, is characterized by widespread genomic heterogeneity and, consequently, differences in disease progression and drug response. Although recent large-scale sequencing studies have greatly improved our understanding of MM genomes, our knowledge about genomic structural variation in MM is attenuated due to the limitations of commonly used sequencing approaches. In this study, we present the application of optical mapping, a single-molecule, whole-genome analysis system, to discover new structural variants in a primary MM genome. Through our analysis, we have identified and characterized widespread structural variation in this tumor genome. Additionally, we describe our efforts toward comprehensive characterization of genome structure and variation by integrating our findings from optical mapping with those from DNA sequencing-based genomic analysis. Finally, by studying this MM genome at two time points during tumor progression, we have demonstrated an increase in mutational burden with tumor progression at all length scales of variation.

A peculiar molecular profile of umbilical cord-mesenchymal stromal cells drives their inhibitory effects on multiple myeloma cell growth and tumor progression

Bone marrow-derived mesenchymal stromal cells (BM-MSCs) are under intensive investigation in preclinical models of cytotherapies against cancer, including multiple myeloma (MM). However, the therapeutic use of stromal progenitors holds critical safety concerns due to their potential MM-supporting activity in vivo. Here, we explored whether MSCs from sources other than BM, such as adipose tissue (AD-MSCs) and umbilical cord (UC-MSCs), affect MM cell growth in comparison to either normal (nBM-MSCs) or myelomatous marrow MSCs (MM-BM-MSCs). Results from both proliferation and clonogenic assays indicated that, in contrast to nBM- and MM-BM-MSCs, both AD and particularly UC-MSCs significantly inhibit MM cell clonogenicity and growth in vitro. Furthermore, when co-injected with UC-MSCs into mice, RPMI-8226 MM cells formed smaller subcutaneous tumor masses, while peritumoral injections of the same MSC subtype significantly delayed the tumor burden growing in subcutaneous plasmocytoma-bearing mice. Finally, both microarrays and ELISA revealed different expression of several genes and soluble factors in UC-MSCs as compared with other MSCs. Our data suggest that UC-MSCs have a distinct molecular profile that correlates with their intrinsic anti-MM activity and emphasize the UCs as ideal sources of MSCs for future cell-based therapies against MM.

The IGF-1 receptor inhibitor picropodophyllin potentiates the anti-myeloma activity of a BH3-mimetic

The ABT-analogous 737, 263 and 199 are BH3 mimetics showing potent anti-myeloma (MM) activity, but only on defined molecular subgroups of MM patients presenting a Bcl-2high/Mcl-1low profile. IGF-1 is a major survival factor in MM regulating the expression of Bcl-2 proteins and might therefore be a resistance factor to these ABT-analogous. We first show that IGF-1 protected human MM cell lines (HMCLs) against ABT-737. Concurrently, the IGF-1 receptor inhibitor picropodophyllin (PPP) synergistically sensitized HMCL, primary human MM and murine 5T33MM cells to ABT-737 and ABT-199 by further decreasing cell viability and enhancing apoptosis. Knockdown of Bcl-2 by shRNA protected MM cells to ABT-737, while Mcl-1 shRNA sensitized the cells. PPP overcame the Bcl-2 dependency of ABT-737, but failed to completely overcome the protective effect of Mcl-1. In vivo, co-treatment of 5T33MM bearing mice significantly decreased tumor burden and prolonged overall survival both in a prophylactic and therapeutic setting. Interestingly, proteasome inhibitor resistant CD138- 5T33MM cells were more sensitive to ABT-737, whereas PPP alone targeted the CD138+ cells more effectively. After co-treatment, both subpopulations were targeted equally. Together, the combination of an IGF-1R inhibitor and an ABT-analogue displays synergistic anti-myeloma activity providing the rational for further (pre)clinical testing.

The association of diabetes and anti-diabetic medications with clinical outcomes in multiple myeloma

Background:

Insulin/insulin-like growth factor-1 signalling may underlie the promoting effect of type 2 diabetes on cancer. This study examined the association of diabetes, including steroid-induced diabetes (SID), and the impact of anti-diabetic medication on clinical outcomes of multiple myeloma (MM).

Methods:

A retrospective review was conducted of 1240 MM patients. Overall survival (OS) and MM disease status prior to death were analysed.

Results:

Diabetic patients had a significantly shorter OS than non-diabetic patients (median: 65.4 vs 98.7 months). In multivariate analysis, SID was a significant predictor of decreased OS, along with age, comorbidity, MM stage, and cytogenetic abnormalities. Analyzing only the diabetic MM patients, Cox regression showed that metformin predicted an increased OS, whereas use of insulin/analogues predicted a decreased OS. Competing risk analysis showed that DM was associated with increased cumulative incidence of death with progressive MM. Among the diabetics, multivariate regression showed that insulin/analogues were associated with increased, but metformin with decreased death with progressive MM. Potential immortal time bias was evaluated by landmark analyses.

Conclusions:

DM, SID in particular, is associated with poor clinical outcomes in MM. Insulin/analogues are associated with poor outcomes, whereas metformin is associated with improved outcomes. No conclusion about causal relationships can be made at this time. Managing hyperglycaemia with non-insulin regimens should be investigated in randomised trials.

Cancer, physical activity, and exercise

This review examines the relationship between physical activity and cancer along the cancer continuum, and serves as a synthesis of systematic and meta-analytic reviews conducted to date. There exists a large body of epidemiologic evidence that conclude those who participate in higher levels of physical activity have a reduced likelihood of developing a variety of cancers compared to those who engage in lower levels of physical activity. Despite this observational evidence, the causal pathway underlying the association between participation in physical activity and cancer risk reduction remains unclear. Physical activity is also a useful adjunct to improve the deleterious sequelae experienced during cancer treatment. These deleterious sequelae may include fatigue, muscular weakness, deteriorated functional capacity, and many others. The benefits of physical activity during cancer treatment are similar to those experienced after treatment. Despite the growing volume of literature examining physical activity and cancer across the cancer continuum, a number of research gaps exist. There is little evidence on the safety of physical activity among all cancer survivors, as most trials have selectively recruited participants. The specific dose of exercise needed to optimize primary cancer prevention or symptom control during and after cancer treatment remains to be elucidated.

Biology and bioinformatics of myeloma cell

Multiple myeloma (MM) is a plasma cell disorder that occurs in about 10% of all hematologic cancers. The majority of patients (99%) are over 50 years of age when diagnosed. In the bone marrow (BM), stromal and hematopoietic stem cells (HSCs) are responsible for the production of blood cells. Therefore any destruction or/and changes within the BM undesirably impacts a wide range of hematopoiesis, causing diseases and influencing patient survival. In order to establish an effective therapeutic strategy, recognition of the biology and evaluation of bioinformatics models for myeloma cells are necessary to assist in determining suitable methods to cure or prevent disease complications in patients. This review presents the evaluation of molecular and cellular aspects of MM such as genetic translocation, genetic analysis, cell surface marker, transcription factors, and chemokine signaling pathways. It also briefly reviews some of the mechanisms involved in MM in order to develop a better understanding for use in future studies.

Paradoxical effect of lenalidomide on cytokine/growth factor profiles in multiple myeloma

Background:

Lenalidomide is an active immunomodulatory and antiproliferative agent in multiple myeloma. However, the molecular mechanisms driving these activities are not yet fully elucidated. Therefore, we investigated the modulation of the cytokine/growth factor patterns of myeloma cells under LEN treatment.

Methods:

Lenalidomide effect on myeloma cell proliferation was investigated in a myeloma cell line collection (n=23) by ³H-thymidine incorporation. Modulation of the cytokine/growth factor patterns of myeloma cells under LEN treatment was analysed by real-time quantitative PCR.

Results:

Lenalidomide inhibits the proliferation of two-thirds of myeloma cell lines independently of their genetic background. We demonstrated that LEN increased TNF-α and IL-8 inflammatory cytokines and insulin-like growth factor-1 (IGF-1) growth factor in both sensitive and resistant myeloma cells to LEN.

Conclusion:

Lenalidomide favours a uniform TNF-α and IL-8 inflammatory and IGF-1 secretory profile of myeloma cells, an observation that raises important questions for therapeutic approaches incorporating the agent.

Lack of correlation between angiogenic cytokines and serum insulin-like growth factor-1 in patients with multiple myeloma

There are many growth factors influencing the expansion of multiple myeloma (MM). Angiogenesis is a process that may enhance MM growth, in various manners. Among them, insulin-like growth factor-1 (IGF-1) is a major factor, acting in many levels. The aim of the study was to measure serum levels of IGF-1 in newly diagnosed MM patients and to correlate them with clinical stage of the disease and with markers of angiogenesis, such as vascular endothelial growth factor (VEGF), hepatocyte growth factor (HGF), and interleukin-6 and 15 (IL-6 and IL-15). Serum levels of the above factors were measured, by ELISA, in 57 newly diagnosed MM patients and in 20 healthy controls. There was no difference in serum levels of IGF-1 in MM patients and in controls, contrary to angiogenic factors, which were higher in MM patients (p < 0.001). Similarly, IGF-1 did not correlate with clinical stage of the disease nor the other angiogenic factors, which also correlated with each other (p < 0.001). Serum IGF-1 concentrations are not influenced in MM patients. Therefore, although it is a proliferation cytokine, it cannot be used as marker of disease activity.

DNA methylation in multiple myeloma is weakly associated with gene transcription

Previous studies have now demonstrated that both genic and global hypomethylation characterizes the multiple myeloma (MM) epigenome. Whether these methylation changes are associated with global and corresponding increases (or decreases) in transcriptional activity are poorly understood. The purpose of our current study was to correlate DNA methylation levels in MM to gene expression. We analyzed matching datasets generated by the GoldenGate methylation BeadArray and Affymetrix gene expression platforms in 193 MM samples. We subsequently utilized two independent statistical approaches to identify methylation-expression correlations. In the first approach, we used a linear correlation parameter by computing a Pearson correlation coefficient. In the second approach, we discretized samples into low and high methylation groups and then compared the gene expression differences between the groups. Only methylation of 2.1% and 25.3% of CpG sites on the methylation array correlated to gene expression by Pearson correlation or the discretization method, respectively. Among the genes with methylation-expression correlations were IGF1R, DLC1, p16, and IL17RB. In conclusion, DNA methylation may directly regulate relatively few genes and suggests that additional studies are needed to determine the effects of genome-wide methylation changes in MM.

Fas apoptosis inhibitory molecule is upregulated by IGF-1 signaling and modulates Akt activation and IRF4 expression in multiple myeloma

Multiple myeloma (MM) is an incurable malignancy of terminally differentiated B-lymphoid cells. Here, we investigate the role of Fas apoptosis inhibitory molecule (FAIM) in MM. We demonstrate that insulin-like growth factor 1 (IGF-1) treatment upregulated FAIM expression in MM cells in a dose-dependent manner. Silencing of FAIM expression attenuates Akt signaling downstream of IGF-1 and compromises the viability of MM cells. We further showed that IGF-1 stimulation of MM cells leads to enhanced expression of IRF4, a known 'addictive' factor for MM. This upregulation of IRF4 expression by IGF-1 treatment of MM cells is abrogated when FAIM expression is silenced or Akt activation is inhibited. Thus, FAIM modulates IGF-1-induced Akt activation and IRF4 expression and has a role in MM cell survival. Consistent with these findings, FAIM expression is shown to be higher in plasma cells of symptomatic MM patients compared with normal individuals or patients with premalignant conditions. Moreover, a higher level of FAIM expression is shown to correlate with poorer survival outcomes of newly diagnosed MM patients treated with stem cell transplantation or relapsed MM patients treated in clinical trials with Bortezomib. Thus taken together, our study reveals a novel, as well as clinically relevant role for FAIM in MM.

Therapeutic potential of cladribine in combination with STAT3 inhibitor against multiple myeloma

Background

Cladribine or 2-chlorodeoxyadenosine (2-CDA) is a well-known purine nucleoside analog with particular activity against lymphoproliferative disorders, such as hairy cell leukemia (HCL). Its benefits in multiple myeloma (MM) remain unclear. Here we report the inhibitory effects of cladribine on MM cell lines (U266, RPMI8226, MM1.S), and its therapeutic potential in combination with a specific inhibitor of the signal transducer and activator of transcription 3 (STAT3).

Methods

MTS-based proliferation assays were used to determine cell viability in response to cladribine. Cell cycle progression was examined by flow cytometry analysis. Cells undergoing apoptosis were evaluated with Annexin V staining and a specific ELISA to quantitatively measure cytoplasmic histone-associated DNA fragments. Western blot analyses were performed to determine the protein expression levels and activation.

Results

Cladribine inhibited cell proliferation of MM cells in a dose-dependent manner, although the three MM cell lines exhibited a remarkably different responsiveness to cladribine. The IC50 of cladribine for U266, RPMI8226, or MM1.S cells was approximately 2.43, 0.75, or 0.18 μmol/L, respectively. Treatment with cladribine resulted in a significant G1 arrest in U266 and RPMI8226 cells, but only a minor increase in the G1 phase for MM1.S cells. Apoptosis assays with Annexin V-FITC/PI double staining indicated that cladribine induced apoptosis of U266 cells in a dose-dependent manner. Similar results were obtained with an apoptotic-ELISA showing that cladribine dramatically promoted MM1.S and RPMA8226 cells undergoing apoptosis. On the molecular level, cladribine induced PARP cleavage and activation of caspase-8 and caspase-3. Meanwhile, treatment with cladribine led to a remarkable reduction of the phosphorylated STAT3 (P-STAT3), but had little effect on STAT3 protein levels. The combinations of cladribine and a specific STAT3 inhibitor as compared to either agent alone significantly induced apoptosis in all three MM cell lines.

Conclusions

Cladribine exhibited inhibitory effects on MM cells in vitro. MM1.S is the only cell line showing significant response to the clinically achievable concentrations of cladribine-induced apoptosis and inactivation of STAT3. Our data suggest that MM patients with the features of MM1.S cells may particularly benefit from cladribine monotherapy, whereas cladribine in combination with STAT3 inhibitor exerts a broader therapeutic potential against MM.

Molecular target characterization and antimyeloma activity of the novel, insulin-like growth factor 1 receptor inhibitor, GTx-134

PURPOSE

Therapeutic strategies that target insulin-like growth factor 1 receptor (IGF-1R) hold promise in a wide variety of cancers including multiple myeloma (MM). In this study, we describe GTx-134, a novel small-molecule inhibitor of IGF-1R and insulin receptor (IR) and characterized its antitumor activity in preclinical models of MM.

EXPERIMENTAL DESIGN

The activity of GTx-134 as a single agent and in combination was tested in MM cell lines and primary patient samples. Downstream effector proteins and correlation with apoptosis was evaluated. Cytotoxcity in bone marrow stroma coculture experiments was assessed. Finally, the in vivo efficacy was evaluated in a human myeloma xenograft model.

RESULTS

GTx-134 inhibited the growth of 10 of 14 myeloma cell lines (<5 μmol/L) and induced apoptosis. Sensitivity to GTx-134 correlated with IGF-1R signal inhibition. Expression of MDR-1 and CD45 were associated with resistance to GTx-134. Coculture with insulin-growth factor-1 (IGF-1) or adherence to bone marrow stroma conferred modest resistance, but did not overcome GTx-134-induced cytotoxicity. GTx-134 showed in vitro synergies when combined with dexamethasone or lenalidomide. Further, GTx-134 enhanced the activity of PD173074, a fibroblast growth factor receptor 3 (FGFR3) inhibitor, against t(4;14) myeloma cells. Therapeutic efficacy of GTx-134 was shown against primary cells and xenograft tumors. Although dysregulation of glucose homeostasis was observed in GTx-134-treated mice, impairment of glucose tolerance was modest.

CONCLUSIONS

These studies support the potential therapeutic efficacy of GTx-134 in MM. Further, they provide a rationale for clinical application in combination with established antimyeloma treatments and novel targeted therapies.

Widespread deregulation of phosphorylation-based signaling pathways in multiple myeloma cells: opportunities for therapeutic intervention

Multiple myeloma (MM) is a neoplasm of plasma cell origin that is largely confined to the bone marrow (BM). Chromosomal translocations and other genetic events are known to contribute to deregulation of signaling pathways that lead to transformation of plasma cells and progression to malignancy. However, the tumor stroma may also provide trophic support and enhance resistance to therapy. Phosphorylation of proteins on tyrosine, serine and threonine residues plays a pivotal role in cell growth and survival. Therefore, knowing the status of phosphorylation-based signaling pathways in cells may provide key insights into how cell growth and survival is promoted in tumor cells. To provide a more comprehensive molecular analysis of signaling disruptions in MM, we conducted a kinome profile comparison of normal plasma cells and MM plasma cells as well as their surrounding cells from normal BM and diseased BM. Integrated pathway analysis of the profiles obtained reveals deregulation of multiple signaling pathways in MM cells but also in surrounding bone marrow blood cells compared to their normal counterparts. The deregulated kinase activities identified herein, which include the mTOR (mammalian target of rapamycin)/p70S6K and ERK1/2 (extracellular signal-regulated kinases 1 and 2) pathways, are potential novel molecular targets in this lethal disease.

The serine/threonine kinase Pim-2 is a novel anti-apoptotic mediator in myeloma cells

Bone marrow stromal cells (BMSCs) and osteoclasts (OCs) confer multiple myeloma (MM) cell survival through elaborating factors. We demonstrate herein that IL-6 and TNF family cytokines, TNFα, BAFF and APRIL, but not IGF-1 cooperatively enhance the expression of the serine/threonine kinase Pim-2 in MM cells. BMSCs and OCs upregulate Pim-2 expression in MM cells largely via the IL-6/STAT3 and NF-κB pathway, respectively. Pim-2 short interfering RNA reduces MM cell viability in cocultures with BMSCs or OCs. Thus, upregulation of Pim-2 appears to be a novel anti-apoptotic mechanism for MM cell survival. Interestingly, the mammalian target of rapamycin inhibitor rapamycin further suppresses the MM cell viability in combination with the Pim-2 silencing. The Pim inhibitor (Z)-5-(4-propoxybenzylidene) thiazolidine-2, 4-dione and the PI3K inhibitor LY294002 cooperatively enhance MM cell death. The Pim inhibitor suppresses 4E-BP1 phosphorylation along with the reduction of Mcl-1 and c-Myc. Pim-2 may therefore become a new target for MM treatment.

The microenvironment and molecular biology of the multiple myeloma tumor

Multiple myeloma (MM) is a deadly plasma cell cancer that resides in the bone marrow (BM). Numerous studies have demonstrated the involvement of the BM microenvironment supporting tumor growth, angiogenesis, bone disease and drug resistance. Reciprocal interactions between the different components of the BM microenvironment and the MM cells are necessary to regulate migration, differentiation, proliferation and survival of the malignant plasma cells. In this review we focus on the interactions and molecular mechanisms by which the BM microenvironment exert these effects. Better understanding of these interactions and the study of the epigenetic changes that tumor cells undergo are necessary in order to improve current treatments and for the discovery of new therapies that may eventually lead to a potential cure.

The effects of forodesine in murine and human multiple myeloma cells

Multiple myeloma (MM) is the second most commonly diagnosed hematological malignancy, characterized by a monoclonal proliferation of malignant cells in the bone marrow. Despite recent advances in treatment strategies, MM remains incurable and new therapeutical targets are needed. Recently forodesine, a purine nucleoside phosphorylase inhibitor, was found to induce apoptosis in leukemic cells of chronic lymphocytic leukemia patients by increasing the dGTP levels. We therefore tested whether forodesine was able to inhibit proliferation and/or induce apoptosis in both murine and human MM cells through a similar pathway. We found that after 48 hours of treatment with forodesine there was a slight dGTP increase in 5T33MM and RPMI-8226 MM cells associated with partial inhibition of proliferation and a limited induction of apoptosis. When investigating the pathways leading to cell cycle arrest and apoptosis, we observed an upregulation of p27, caspase 3, and BIM. We can conclude that forodesine has some effects on MM cells but not as impressive as the known effects in leukemic cells. Forodesine might be however potentiating towards other established cytotoxic drugs in MM.

HDAC inhibition synergistically enhances alkylator-induced DNA damage responses and apoptosis in multiple myeloma cells

Histone deacetylase (HDAC) inhibitors induce chromatin destabilization. We sought to determine whether HDAC inhibition may amplify alkylator-induced mitotic cell death in multiple myeloma (MM) cells. The combination of SNDX-275, a class I HDAC inhibitor, with melphalan, showed a powerful synergism on growth inhibition with the combination index ranged from 0.27 to 0.75 in MM1.S and RPMI8226 cells. Their combinations as compared with either agent alone promoted much more caspase-dependent apoptosis. Flow cytometry analysis showed that SNDX-275 had minimal effects on cell cycle progression of MM1.S cells, but clearly increased the percentage of S phase in RPMI8226 cells associated with an upregulation in p21(waf1) and a reduction in cyclin D1 and E2F1. Melphalan alone significantly arrested both MM1.S and RPMI8226 cells at S phase and enhanced expression of p53 and p21(waf1). Furthermore, studies on DNA damage response revealed that phospho-histone H2A.X (gammaH2A.X), a hall marker of DNA double strand break, along with phosphorylated CHK1 (P-CHK1) and CHK2 (P-CHK2) was dramatically induced by SNDX-275 or melphalan. The increase in gammaH2A.X and P-CHK1 was considerably higher on combination than either agent alone. These molecular changes correlated well with the significant increase in mitotic catastrophe. Our data indicate that SNDX-275 synergistically enhances melphalan-induced apoptosis in MM cells via intensification of DNA damage, suggesting that SNDX-275 in combination with melphalan may be a novel therapeutic strategy for MM.

IGF-1 suppresses Bim expression in multiple myeloma via epigenetic and posttranslational mechanisms

Insulin-like growth factor-1 (IGF-1) is an important growth and survival factor in multiple myeloma (MM). Here, we demonstrate that IGF-1 induces significant down-regulation of the proapoptotic BH3-only protein Bim in MM cells. Reduced Bim levels by RNA interference (RNAi) protected cells from drug-induced cell death. The IGF-1-mediated down-regulation of Bim was the result of (1) reduced transcription by activation of the Akt pathway and inactivation of the transcription factor FoxO3a, (2) increased proteasome-mediated degradation of the Bim extra-long protein by activation of the mitogen-activated protein kinase pathway, and (3) epigenetic regulation of both the Bim and the FoxO3a promoter. Treatment of cells with the histone deacetylase inhibitor LBH589 resulted in a clear up-regulation in the expression of Bim. Furthermore, the methylation inhibitor 5-aza-2'deoxycytidine (decitabine) significantly increased the effects of LBH589. On IGF-1 treatment, the Bim promoter region was found to be unmethylated, whereas chromatin immunoprecipitation analysis of the IGF-1-treated cells showed both a reduced histone H3 tail Lys9 (H3K9) acetylation and an increased H3K9 dimethylation, which contributed actively to its silencing. These data identify a new mechanism in the IGF-1-dependent survival of MM cells and emphasize the need for IGF-1-targeted drug therapy.

Physical activity and hematologic cancer prevention

This chapter presents the epidemiologic evidence on the association between physical activity and hematologic cancers and related hypothesized biologic mechanisms. Some preliminary indications of a protective role for physical activity for non-Hodgkin's lymphoma, leukemia, multiple myeloma, and Hodgkin's lymphoma exist, but the level of epidemiologic evidence is still insufficient to make any definitive conclusions regarding the nature of these associations. Several plausible biologic mechanisms underlying the possible associations between physical activity and hematologic cancers have been proposed, including enhancement of immune function, reduction in obesity, improvement of antioxidant defense systems, impact on metabolic hormones, and anti-inflammatory effects. Future studies should improve the estimation of physical activity by using more reliable, valid, and comprehensive measurement tools, assessing all components of physical activity (type, intensity, and time period), and conducting intervention studies to evaluate the effect of physical activity on various biomarkers of cancer in order to provide further insight into plausible biologic mechanisms underlying the possible association between physical activity and hematologic cancers.