Zoledronic acid treatment of 5T2MM-bearing mice inhibits the development of myeloma bone disease: evidence for decreased osteolysis, tumor burden and angiogenesis, and increased survival

Zoledronic acid affects over-angiogenic phenotype of endothelial cells in patients with multiple myeloma

Therapeutic doses of zoledronic acid markedly inhibit in vitro proliferation, chemotaxis, and capillarogenesis of bone marrow endothelial cells of patients with multiple myeloma. Zoledronic acid also induces a sizeable reduction of angiogenesis in the in vivo chorioallantoic membrane assay. These effects are partly sustained by gene and protein inhibition of vascular endothelial growth factor and vascular endothelial growth factor receptor 2 in an autocrine loop. Mevastatin, a specific inhibitor of the mevalonate pathway, reverts the zoledronic acid antiangiogenic effect, indicating that the drug halts this pathway. Our results provide evidence of a direct antiangiogenic activity of zoledronic acid on multiple myeloma patient-derived endothelial cells due to at least four different mechanisms identified either in vitro or in vivo. Tentatively, we suggest that the zoledronic acid antitumoral activity in multiple myeloma is also sustained by antiangiogenesis, which would partly account for its therapeutic efficacy in multiple myeloma.

On the horizon: can bisphosphonates prevent bone metastases?

Skeletal complications of bone metastases increase the risk of death and undermine patients' functional independence and quality of life. Although bisphosphonates are integral in the treatment regimen of patients with metastatic bone disease and have demonstrated efficacy in delaying the onset and reducing the incidence of skeletal-related events, there is great interest in developing treatments to prevent metastasis to bone. Emerging evidence indicates that the potential benefits of bisphosphonate therapy extend beyond the treatment of metastatic bone lesions. Data from preclinical studies suggest that bisphosphonates may have antitumour activity and may prevent bone metastasis. The mechanisms of these antitumour effects are currently under investigation and may include induction of apoptosis, inhibition of tumour cell invasion and angiogenesis, and tumour growth reduction. Therefore, patients with early-stage disease may benefit from early bisphosphonate therapy, before bone metastasis develops, and investigations are ongoing to determine the clinical utility of bisphosphonates in this setting.

New developments of aminobisphosphonates: the double face of Janus

BACKGROUND

Bisphosphonate (BP) therapy has become a standard of therapy for patients with malignant bone disease. In vivo preclinical and preliminary clinical data indicate that BPs may prevent cancer treatment-induced bone loss and the onset of malignant bone disease in patients with early-stage cancer.

DESIGN

This review will describe the preclinical evidences of action of BPs on osteoclasts and tumor cells. In addition, the effects of principal BPs on skeletal disease progression in patients with breast cancer, prostate cancer, non-small-cell lung cancer and other cancers will be reported. The preliminary clinical data from retrospective trials on the effect of zoledronic acid (ZA) on survival will be described and the ongoing adjuvant phase III trial will be analyzed.

CONCLUSIONS

This review will describe the preliminary clinical evidences from prospective studies on the effect of ZA treatment on the prevention of bone metastasis.

Bisphosphonates in cancer therapy

Bisphosphonates are the standard of care in the treatment of malignant bone diseases, because of their ability to inhibit osteoclast-mediated bone destruction. We review here preclinical evidence that bisphosphonates also exert direct antitumour effects and antiangiogenic properties. Furthermore, we describe new insights on how bisphosphonates may act synergistically in combination with antineoplastic drugs or gammadelta T cells to exhibit antitumour activity. These findings reveal new exciting possibilities to fully exploit the antitumour potential of bisphosphonates in the clinical practice.

Angiogenesis inhibitors and the need for anti-angiogenic therapeutics

Angiogenesis is the formation of new blood vessels from pre-existing vessels to form capillary networks, which, among other diseases, such as diabetic retinopathy and macular degeneration, is particularly important for tumor growth and metastasis. Thus, depriving a tumor of its vascular supply by means of anti-angiogenic agents has been of great interest since its proposal in the 1970s. This review looks at the common angiogenic inhibitors (angiostatin, endostatin, maspin, pigment epithelium-derived factor, bevacizumab and other monoclonal antibodies, and zoledronic acid) and their current status in clinical trials.

Zoledronic Acid and Survival in Breast Cancer Patients with Bone Metastases and Elevated Markers of Osteoclast Activity

OBJECTIVE

Most breast cancer patients with bone metastases will receive bisphosphonate treatment. This post hoc analysis investigated whether early normalization of urinary N-telopeptide of type I collagen (NTX) levels during bisphosphonate therapy correlates with a long-term reduction in skeletal-related event (SRE) risk and mortality in patients with breast cancer.

METHODS

This was a retrospective subset analysis of a phase III randomized trial comparing i.v. zoledronic acid with pamidronate treatment in patients with bone metastases from breast cancer or multiple myeloma. Patients with breast cancer who had NTX assessments at baseline and at months 1 and 3 (n = 342) were classified as normal (NTX < 64 nmol/mmol creatinine) or elevated (NTX > or = 64 nmol/mmol creatinine). The relative risk for an SRE or death was estimated with Cox regression models.

RESULTS

Among the 328 evaluable patients treated with zoledronic acid, 196 patients (59.7%) had elevated baseline NTX, with 149 of those patients (76.0%) having normalized NTX levels and 31 patients (15.8%) having persistently elevated NTX levels at 3 months. The normalized NTX group had significantly lower risks for a first SRE, a first fracture or surgery to bone, or death than the group that had persistently elevated NTX levels.

CONCLUSIONS

These results suggest that early normalization of elevated baseline NTX while receiving zoledronic acid is associated with longer event-free and overall survival times compared with persistently elevated NTX. Further analyses in cancer patients with elevated marker levels are warranted to confirm the implications of these findings.

Immunomodulating role of bisphosphonates on human gamma delta T cells: an intriguing and promising aspect of their antitumour activity

Vgamma9Vdelta2 T cells have the ability to produce inflammatory cytokines involved in protective immunity against intracellular pathogens and tumours and to display strong cytolytic as well as bactericidal activities. This suggests a direct involvement of Vgamma9Vdelta2 T lymphocytes in immune control of cancer and infections. These observations have recently aided development of novel immunotherapeutic approaches aimed at Vgamma9Vdelta2 T cell activation. Nitrogen-containing bisphosphonates (N-BPs) play a crucial role in Vgamma9Vdelta2 T lymphocyte activation and in the acquisition of effector functions. The preliminary results of these innovative strategies are encouraging. Moreover, compelling evidence in the literature supports the hypothesis that the antitumour effect of bisphosphonates is exerted through direct as well as indirect mechanisms. An additional and not yet well explored mechanism by which N-BPs may display antineoplastic effect is related to their immunomodulatory properties. It is fascinating that N-BPs influence the immune system in various but interrelated ways, being able to enhance the innate and to promote the adaptive immune responses. For all these reasons, Vgamma9Vdelta2 T lymphocytes represent a particularly interesting target for immunotherapeutic protocols based on N-BP administration. All these unexpected effects of N-BPs on the immune system have opened new and intriguing possibilities of therapeutic use for these drugs.

Myeloma bone disease and proteasome inhibition therapies

Bone disease is one of the most debilitating manifestations of multiple myeloma. A complex interdependence exists between myeloma bone disease and tumor growth, creating a vicious circle of extensive bone destruction and myeloma progression. Proteasome inhibitors have recently been shown to promote bone formation in vitro and in vivo. Preclinical studies have demonstrated that proteasome inhibitors, including bortezomib, which is the first-in-class such agent, stimulate osteoblast differentiation while inhibiting osteoclast formation and bone resorption. Clinical studies are confirming these observations. Bortezomib counteracts the abnormal balance of osteoclast regulators (receptor activator of nuclear factor-κB ligand and osteoprotegerin), leading to osteoclast inhibition and decreased bone destruction, as measured by a reduction in markers of bone resorption. In addition, bortezomib stimulates osteoblast function, possibly through the reduction of dickkopf-1, leading to increased bone formation, as indicated by the elevation in bone-specific alkaline phosphatase and osteocalcin. The effect of bortezomib on bone disease is thought to be direct and not only a consequence of the agent's antimyeloma properties, making it an attractive agent for further investigation, as it may combine potent antimyeloma activity with beneficial effects on bone. However, the clinical implication of these effects requires prospective studies with specific clinical end points.

The effect of novel anti-myeloma agents on bone metabolism of patients with multiple myeloma

Immunomodulatory drugs (IMiDs) and bortezomib have been recently used in the management of patients with both newly diagnosed and relapsed/refractory multiple myeloma. Except of their direct anti-myeloma effect, these agents also alter the interactions between myeloma cells and marrow microenvironment. Several recent studies have investigated their potential effect on myeloma bone disease. Preclinical studies have demonstrated that IMiDs reduce osteoclast formation and function in vitro. Clinical studies have confirmed that thalidomide reduces markers of bone resorption, while lenalidomide induces osteoclast arrest in myeloma patients. However, IMiDs seem to have no effect on osteoblast exhaustion present in myeloma. The proteasome inhibitor bortezomib restores abnormal bone remodeling through the inhibition of osteoclast function and the increase in osteoblast differentiation and activity in vitro. In myeloma patients, bortezomib reduces biochemical markers of bone resorption and normalizes the RANKL/osteoprotegerin ratio, while at the same time increases bone formation markers reducing levels of dickkopf-1 protein. Whether these effects are direct and not only a consequence of the agents' antimyeloma activity is not totally clear. This review summarizes all available data for these attractive agents that combine potent anti-myeloma activity with beneficial effects on bone and may alter the way of management of myeloma-related bone disease.

Inhibition of p38alpha mitogen-activated protein kinase prevents the development of osteolytic bone disease, reduces tumor burden, and increases survival in murine models of multiple myeloma

The bone microenvironment plays a critical role in supporting the growth and survival of multiple myeloma as well as in the development of osteolytic bone disease. Signaling through p38alpha mitogen-activated protein kinase (MAPK) mediates synthesis of multiple myeloma cell growth factors, and its inhibition reduces proliferation in vitro. However, it is unclear whether targeting p38alpha MAPK prevents multiple myeloma growth and the development of bone disease in vivo. In this study, we determined whether SCIO-469, a selective p38alpha MAPK inhibitor, inhibits multiple myeloma growth and prevents bone disease in the 5T2MM and 5T33MM models. SCIO-469 decreased constitutive p38alpha MAPK phosphorylation of both 5T2MM and 5T33MM cells in vitro. This was associated with decreased DNA synthesis and an induction of apoptosis when the cells were cultured with bone marrow stromal cells. Treatment of C57Bl/KaLwRij mice bearing 5T33MM cells with SCIO-469 inhibited p38alpha MAPK phosphorylation and was associated with a significant decrease in serum paraprotein, an almost complete reduction in tumor cells in the bone marrow, a decrease in angiogenesis, and a significant increase in disease-free survival. Injection of 5T2MM murine myeloma cells into C57Bl/KaLwRij mice resulted in myeloma bone disease characterized by increased osteoclast occupation of the bone surface, reduced cancellous bone, and the development of osteolytic bone lesions. Treatment of 5T2MM-injected mice with SCIO-469 reduced this development of bone disease. Together, these data show that targeting p38alpha MAPK with SCIO-469 decreases myeloma burden in vivo, in addition to preventing the development of myeloma bone disease.

Apomine, an inhibitor of HMG-CoA-reductase, promotes apoptosis of myeloma cells in vitro and is associated with a modulation of myeloma in vivo

Apomine, a novel 1,1 bisphosphonate ester, increases the rate of degradation of HMG-CoA reductase, inhibiting the mevalonate pathway and thereby blocking cholesterol biosynthesis. We have investigated whether Apomine can induce myeloma cell apoptosis in vitro and modulate myeloma disease in vivo. Apomine induced a dose-dependent increase in apoptosis in NCI H929, RPMI 8226 and JJN-3 human myeloma cells. Apomine, unlike the bisphosphonate, alendronate, had no measurable effect on osteoclastic bone resorption in vitro. To investigate the effect of Apomine in vivo, 5T2MM murine myeloma cells were injected into C57BL/KaLwRij mice. After 8 weeks all animals had a serum paraprotein and were treated with Apomine (200 mg/kg), or vehicle, for 4 weeks. Animals injected with 5T2MM cells and treated with vehicle developed osteolytic bone lesions, reduced cancellous bone area, decreased bone mineral density (BMD) and increased osteoclast number. Apomine caused a decrease in serum paraprotein and a decrease in tumor burden. Apomine inhibited the development of osteolytic lesions and prevented the tumor-induced decreases in BMD. Apomine had no effect on osteoclast number in contrast to what had been seen previously with the bisphosphonate, zoledronic acid, suggesting that these are direct effects of Apomine on myeloma cells. This demonstrates that Apomine is able to promote myeloma cell apoptosis in vitro and inhibit the development of multiple myeloma and lytic bone disease in vivo. The use of bisphosphonate esters such as Apomine represents a novel therapeutic approach in the treatment of myeloma and, indirectly, the associated bone disease.

Synopsis of a roundtable on validating novel therapeutics for multiple myeloma

PURPOSE

With the identification of new molecular targets and pathways, many new therapeutic approaches are being identified for potential application in the treatment of multiple myeloma. New chemical compounds and biologics have been developed against molecular targets with substantial scientific evidence that these targets are involved in myeloma development, progression, or relapse. To safely and rapidly bring these advances to bear on the disease, new preclinical models in cells and animals need to be established, as well as prioritization and standardization in current preclinical and clinical validation. An experts' roundtable was convened in November 2005 to discuss shortcomings in current preclinical models and discuss what models are needed to best validate therapeutics and combinations of therapies for multiple myeloma.

CONCLUSIONS

This exciting event brought together experts in compound validation, preclinical development, and experts in multiple myeloma from academic institutions and the pharmaceutical and biotechnology industries. The goals were to evaluate an algorithm for therapeutic validation and discuss in vitro modeling for target discovery, animal models for preclinical development, and models for testing drug combinations.

An Osteoprotegerin-like Peptidomimetic Inhibits Osteoclastic Bone Resorption and Osteolytic Bone Disease in Myeloma

Multiple myeloma is a B-cell malignancy characterized by the uncontrolled growth of plasma cells in the bone marrow and the development of osteolytic bone disease. Myeloma cells express the receptor activator of nuclear factor kappaB ligand (RANKL), induce RANKL expression in the bone marrow, and down-regulate expression of the decoy receptor osteoprotegerin, thereby promoting bone resorption. Targeting this system in myeloma has clear therapeutic potential. However, osteoprotegerin also binds tumor necrosis factor-related apoptosis inducing ligand (TRAIL) and prevents TRAIL-induced apoptosis of myeloma cells. Whether or not osteoprotegerin can bind TRAIL and prevent apoptosis in vivo and the relative importance of osteoprotegerin binding to TRAIL and RANKL are unclear. In the present study, we have investigated the ability of an osteoprotegerin-like peptidomimetic (OP3-4), designed to block the RANKL/RANK interaction, to inhibit osteoclastic bone resorption and TRAIL-induced apoptosis in vitro and myeloma bone disease in vivo. OP3-4 inhibited osteoclast formation (P < 0.01) and bone resorption (P < 0.01) in vitro. However, OP3-4 had no effect on TRAIL-induced apoptosis of RPMI 8226 myeloma cells. Treatment of 5T2MM myeloma-bearing mice with OP3-4 decreased osteoclast number and the proportion of bone surface covered by osteoclasts (P < 0.05). Treatment also prevented the tumor-induced decrease in cancellous bone area and the development of osteolytic lesions (P < 0.05). OP3-4 also reduced tumor burden when compared with the control (P < 0.05). These data suggest that OP3-4 and the selective inhibition of RANKL, but not TRAIL activity, are effective in preventing myeloma bone disease and offer a novel therapeutic approach to treating this aspect of myeloma. [Cancer Res 2007;67(1):202-8].

Molecular mechanisms of action of bisphosphonates: current status

PURPOSE

Bisphosphonates are currently the most important class of antiresorptive agents used in the treatment of metabolic bone diseases, including tumor-associated osteolysis and hypercalcemia. These compounds have high affinity for calcium ions and therefore target bone mineral, where they are internalized by bone-resorbing osteoclasts and inhibit osteoclast function.

EXPERIMENTAL DESIGN

This article reviews the pharmacology of bisphosphonates and the relationship between chemical structure and antiresorptive potency. We also describe new insights into their intracellular molecular mechanisms of action, methods for assessing the effects of bisphosphonates on protein prenylation, and their potential as direct antitumor agents.

RESULTS

Nitrogen-containing bisphosphonates act intracellularly by inhibiting farnesyl diphosphate synthase, an enzyme of the mevalonate pathway, thereby preventing prenylation of small GTPase signaling proteins required for normal cellular function. Inhibition of farnesyl diphosphate synthase also seems to account for their antitumor effects observed in vitro and for the activation of gamma,delta T cells, a feature of the acute-phase response to bisphosphonate treatment in humans. Bisphosphonates that lack a nitrogen in the chemical structure do not inhibit protein prenylation and have a different mode of action that seems to involve primarily the formation of cytotoxic metabolites in osteoclasts.

CONCLUSIONS

Bisphosphonates are highly effective inhibitors of bone resorption that selectively affect osteoclasts in vivo but could also have direct effects on other cell types, such as tumor cells. After >30 years of clinical use, their molecular mechanisms of action on osteoclasts are finally becoming clear but their exact antitumor properties remain to be clarified.

Neridronate inhibits angiogenesis in vitro and in vivo

The effects of the amino-bisphosphonate neridronate on endothelial cell functions involved in angiogenesis, namely, proliferation and morphogenesis on Matrigel were tested in vitro, whereas its effects on angiogenesis were studied in vivo, by using the chick embryo chorioallantoic membrane (CAM) assay. In vitro, neridronate inhibited endothelial cell proliferation in a dose-dependent fashion, peaking at 30 microM. At the same concentration, neridronate inhibited fibroblast growth factor-2 (FGF-2)-induced capillary-like tube formation in the morphogenesis assay on Matrigel. In vivo, when tested in the CAM assay, neridronate again displayed the capability to inhibit FGF-2-induced angiogenesis. Overall, these results suggest that anti-angiogenesis by neridronate could be used to treat a wide spectrum of angiogenesis-dependent diseases, including certain chronic inflammatory diseases and cancer.

Antibody-based inhibition of DKK1 suppresses tumor-induced bone resorption and multiple myeloma growth in vivo

Dickkopf-1 (DKK1), a soluble inhibitor of Wnt signaling secreted by multiple myeloma (MM) cells contributes to osteolytic bone disease by inhibiting the differentiation of osteoblasts. In this study, we tested the effect of anti-DKK1 therapy on bone metabolism and tumor growth in a SCID-rab system. SCID-rab mice were engrafted with primary MM cells expressing varying levels of DKK1 from 11 patients and treated with control and DKK1-neutralizing antibodies for 4 to 6 weeks. Whereas bone mineral density (BMD) of the implanted myelomatous bone in control mice was reduced during the experimental period, the BMD in mice treated with anti-DKK1 increased from pretreatment levels (P < .001). Histologic examination revealed that myelomatous bones of anti-DKK1-treated mice had increased numbers of osteocalcin-expressing osteoblasts and reduced number of multinucleated TRAP-expressing osteoclasts. The bone anabolic effect of anti-DKK1 was associated with reduced MM burden (P < .04). Anti-DKK1 also significantly increased BMD of the implanted bone and murine femur in nonmyelomatous SCID-rab mice, suggesting that DKK1 is physiologically an important regulator of bone remodeling in adults. We conclude that DKK1 is a key player in MM bone disease and that blocking DKK1 activity in myelomatous bones reduces osteolytic bone resorption, increases bone formation, and helps control MM growth.

Multimodal imaging analysis of tumor progression and bone resorption in a murine cancer model

OBJECTIVE

This study evaluates the use of multimodal imaging to qualitatively and quantitatively measure tumor progression and bone resorption in a xenotransplanted tumor model of human neuroblastoma.

METHODS

Human neuroblastoma cells expressing a luciferase reporter gene were injected into the femur of nu/nu mice. Tumor progression with and without zoledronic acid treatment was monitored using radiographs, D-luciferin-induced luminescence, micro-computer tomography (CT) and micro-magnetic resonance imaging (MRI).

RESULTS

We observed a gradual increase in D-luciferin-based bioluminescence concomitant with detectable osteolytic lesions. Tumor growth was inhibited (P=0.003-0.07) with zoledronic acid treatment. Micro-CT analysis in vivo provided a method to quantify bone loss, and its prevention by zoledronic acid. High-resolution MRI images allowed the observation of tumor cells within the bone marrow cavity, as well as distant metastasis.

CONCLUSION

Multimodal imaging allows to measure tumor growth and bone resorption simultaneously in vivo and also proved useful in the detection distant metastasis.

Advances in the management of myeloma bone disease

Multiple myeloma is the second most common adult haematological malignancy. One of the major clinical features is the development of a unique osteolytic bone disease, characterised by progressive and devastating bone destruction, bone pain, pathological fractures and hypercalcaemia. Bisphosphonates, inhibitors of osteoclastic bone resorption, are the standard therapy for myeloma-induced bone disease. However, as our understanding of the molecular mechanisms involved in the development of myeloma bone disease increases, new molecular targets have been identified for the treatment of this devastating bone disease.

Myeloma bone disease: pathogenetic mechanisms and clinical assessment

Bone disease in multiple myeloma (MM) leads to progressive devastation of the skeleton and is the most severe cause of morbidity. Its pathogenetic mechanisms are not fully defined, though the current evidence points to hyperactivation of osteoclasts (OC) in presence of a major defect of bone repairing in erosion sites due to osteoblast (OB) impairment. Bone resorption, however, is promoted by early OB, namely stromal cells that respond to chronic stimulation by myeloma cells by enhancing marrow levels of RANKL and other osteoclastogenic factors and thus accelerating the maturation of OC progenitors. In myeloma bone disease (MBD), OBs are systematically defeated by a number of inhibiting effects induced by the malignant clone within the marrow microenvironment. Thus, MBD primarily affects the OB lineage, particularly in overt MM, where serum markers of osteoblastogenesis, such as osteocalcin and osteoprotegerin, are extremely low in contrast with their slight increase in inactive MM. These markers, in association with others of bone turnover (RANKL, MIP-1alpha, type I collagen telopeptides such as NTX and CTX) may be used in the clinical assessment of MBD as well as to monitor the efficacy of bisphosphonate in delaying the progressive skeletal destruction.

Mechanisms of disease: Preclinical reports of antineoplastic synergistic action of bisphosphonates

For patients with malignant bone disease, bisphosphonate therapy is the standard treatment. Preclinical and preliminary clinical data suggest that bisphosphonates have direct or indirect antitumor effects: they affect growth-factor release, cancer-cell adhesion, invasion and viability, angiogenesis, and apoptosis of cancer cells. These effects might be enhanced through co-administration with chemotherapy agents, biological agents, or both. We survey the biochemical pathways and molecular targets of bisphosphonates, and discuss the molecular mechanisms of these antitumor effects, as well as the documented antineoplastic preclinical effects of bisphosphonates used in combination with cytotoxic and biological drugs. Moreover, the positive interactions between bisphosphonates and farnesyltransferase inhibitors, KIT receptor tyrosine kinase inhibitors (e.g. imatinib mesylate) and cyclo-oxygenase-2 inhibitors are discussed in relation to their potential synergistic and additive effects. We briefly discuss identification of new molecular targets of bisphosphonates from genomic and proteomic analysis, and highlight the cellular consequences of drug-related enzyme inhibition.

Fibroblast activation protein (FAP) is upregulated in myelomatous bone and supports myeloma cell survival

The microenvironment plays a critical role in facilitating cancer progression and metastasis. We previously demonstrated the ability of osteoclasts to support primary myeloma plasma cell (MM PC) growth. Our study on the role of the bone marrow (BM) microenvironment in myeloma, using global gene expression profiling, has identified fibroblast activation protein (FAP) as one of 28 genes significantly overexpressed in cocultured osteoclasts. Because FAP has been previously implicated in tumorigenesis and shown to be selectively expressed by the reactive stroma of epithelial tumours, we focused our study on the role of this serine protease in myeloma. Using quantitative polymerase chain reaction amplification, we demonstrated upregulation of FAP by cocultured osteoclasts and mesenchymal stem cells, and in whole myelomatous human bone in SCID-hu mice. Immunohistochemical analysis of myelomatous bone sections revealed FAP expression by osteoclasts, osteogenic cells, fibrotic stroma and certain adipocytes and vascular endothelial cells. FAP was not expressed in PCs by all these methods. Inhibition of FAP expression with the use of small-interference RNA reduced MM PC survival in cocultures. Our results indicate that FAP is critical for the interaction of MM cells with the BM microenvironment--a potential therapeutic target in myeloma.

The phenotypic plasticity of myeloma plasma cells as expressed by dedifferentiation into an immature, resilient, and apoptosis-resistant phenotype

PURPOSE

We previously showed the ability of osteoclasts to support myeloma plasma cell survival and proliferation in vivo and ex vivo. The aim of the current study was to investigate osteoclast-induced phenotypic changes associated with long-term survival of myeloma cells in coculture.

EXPERIMENTAL DESIGN

CD138-selected myeloma plasma cells from 16 patients were cocultured with human osteoclasts for up to 20 weeks.

RESULTS

Precultured cells were typically CD45(low/intermediate) CD38(high) CD138(high), CD19(-)CD34(-). After >6 weeks, the phenotype of cocultured myeloma cells consistently shifted to cells expressing CD45(intermediate/high) CD19(low) CD34(low). Expression of CD38 and CD138 were reduced to subpopulations with CD38(intermediate) and CD138(low) levels. Morphologically, cocultured plasma cells became plasmablastic. Blocking interleukin-6 activity did not affect the immature phenotype of myeloma cells. The effect of dexamethasone on myeloma cells cultured alone or in cocultures at baseline and after 6 weeks of coculture was determined. When baseline myeloma cells were cultured alone, dexamethasone significantly increased the percentage of apoptotic cells over the spontaneous rate. Conversely, myeloma cells recovered from cocultures had high survival rates and were resistant to dexamethasone-induced apoptosis. Long-term coculture of normal CD34-expressing hematopoietic stem cells (HSC) resulted in loss of CD34 expression, suggesting a common mechanism for osteoclast-induced myeloma and HSC plasticity.

CONCLUSIONS

This study indicates that myeloma cells have plasticity expressed by their ability to reprogram, dedifferentiate, and acquire autonomous survival properties.

Selective inhibition of Rab prenylation by a phosphonocarboxylate analogue of risedronate induces apoptosis, but not S-phase arrest, in human myeloma cells

Bisphosphonates (BPs) are widely used in the treatment of osteolytic bone disease associated with multiple myeloma, and have been demonstrated to exert antitumor effects both in vitro and in vivo. However, the precise molecular mechanisms involved in the direct antitumor effects of BPs in vitro are not known. Nitrogen-containing BPs, such as risedronate (RIS), act by inhibiting protein prenylation. A phosphonocarboxylate analogue of RIS, 3-PEHPC, has previously been shown in osteoclasts and macrophages to specifically inhibit prenylation of Rab GTPases. The aim of this study was to identify the molecular targets of RIS and 3-PEHPC in human myeloma cells and to determine the cellular effects of selective inhibition of Rab prenylation by 3-PEHPC as compared to nonspecific inhibition of protein prenylation by RIS in human myeloma cells. RIS dose-dependently inhibited prenylation of both Rap1A and Rab6, whereas 3-PEHPC only inhibited Rab6 prenylation. Both RIS and 3-PEHPC dose-dependently increased apoptosis in human myeloma cells. RIS induced an accumulation of cells in the S-phase of the cell cycle, associated with inhibition of DNA replication. In contrast, 3-PEHPC did not cause cell-cycle arrest. Furthermore, geranylgeraniol could prevent inhibition of prenylation, induction of apoptosis, and cell-cycle arrest in response to RIS, but not inhibition of Rab prenylation and apoptosis induced by 3-PEHPC, consistent with specific inhibition of Rab geranylgeranyl transferase by 3-PEHPC. In conclusion, our studies demonstrate that selective inhibition of Rab prenylation induces apoptosis, but not S-phase arrest, thus identifying distinct molecular pathways that mediate the antimyeloma effect of nitrogen-containing BPs.

Zoledronate inhibits proliferation and induces apoptosis of imatinib-resistant chronic myeloid leukaemia cells

Although imatinib mesylate has revolutionized the treatment of chronic myeloid leukaemia (CML), resistance to the drug, manifesting as relapse after an initial response or persistence of disease, remains a therapeutic challenge. In order to overcome this, alternative or additional targeting of signaling pathways downstream of Bcr-Abl may provide the best option for improving clinical response. Bisphosphonates, such as zoledronate, have been shown to inhibit the oncogenicity of Ras, an important downstream effector of Bcr-Abl. In this study, we show that zoledronate is equally effective in inhibiting the proliferation and clonogenicity of both imatinib-sensitive and -resistant CML cells, regardless of their mechanism of resistance. This is achieved by the induction of S-phase cell cycle arrest and apoptosis, through the inhibition of prenylation of Ras and Ras-related proteins by zoledronate. The combination of imatinib and zoledronate also augmented the activity of either drug alone and this occurred in imatinib-resistant CML cells as well. Since zoledronate is already available for clinical use, these results suggest that it may be an effective addition to the armamentarium of drugs for the treatment of CML.

HTLV-1 Tax transgenic mice develop spontaneous osteolytic bone metastases prevented by osteoclast inhibition

One in 20 carriers of human T-cell leukemia virus type 1 (HTLV-1) will develop adult T-cell leukemia/lymphoma (ATL), a disease frequently associated with hypercalcemia, bone destruction, and a fatal course refractory to current therapies. Overexpression of the HTLV-1-encoded Tax oncoprotein under the human granzyme B promoter causes large granular lymphocytic leukemia/lymphomas in mice. We found that Tax+ mice spontaneously developed hypercalcemia, high-frequency osteolytic bone metastases, and enhanced osteoclast activity. We evaluated Tax tumors for the production of osteoclast-activating factors. Purification of Tax+ tumor cells and nonmalignant tumor-infiltrating lymphocytes demonstrated that each of these populations expressed transcripts for distinct osteoclast-activating factors. We then evaluated the effect of osteoclast inhibition on tumor formation. Mice doubly transgenic for Tax and the osteoclast inhibitory factor, osteoprotegerin, were protected from osteolytic bone disease and developed fewer soft-tissue tumors. Likewise, osteoclast inhibition with bone-targeted zoledronic acid protected Tax+ mice from bone and soft-tissue tumors and prolonged survival. Tax+ mice represent the first animal model of high-penetrance spontaneous osteolytic bone metastasis and underscore the critical role of nonmalignant host cells recruited by tumor cells in the process of cancer progression and metastasis.

Zoledronic-acid-induced circulating level modifications of angiogenic factors, metalloproteinases and proinflammatory cytokines in metastatic breast cancer patients

BACKGROUND

To evaluate the modifications of circulating angiogenic factors, metalloproteinases and acute-phase cytokines after the first single zoledronic acid (ZA) intravenous infusion.

EXPERIMENTAL DESIGN

Eighteen consecutive breast cancer patients with bone metastases were evaluated for circulating levels of vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), metalloproteinase 1 (MMP-1), metalloproteinase 2 (MMP-2), interleukins 1beta, 6 and 8 (IL-1beta, IL-6, IL-8), interferon gamma, tumor necrosis factor alpha (TNF-alpha) and transforming growth factor beta1 just before and 2 and 7 days after ZA infusion.

RESULTS

The MMP-2 basal value showed a statistically significant decrease 48 h after ZA (p = 0.01), being at 7 days higher than the day 2 value (p = 0.03). The VEGF basal value showed a statistically significant decrease 48 h after ZA infusion (p = 0.03), increasing above the basal level at 7 days (p = 0.07). The bFGF basal level almost significantly decreased 2 days after infusion (p = 0.06), being at 7 days higher than the basal value (p = 0.09). Comparing the day 2 values with basal ones, the linear regression model showed a significant positive correlation between IL-8 and bFGF (p = 0.02), IL-8 and TNF-alpha (p < 0.0001), bFGF and TNF-alpha (p = 0.01), MMP-1 and TNF-alpha (p = 0.02).

CONCLUSIONS

ZA could exert an antiangiogenic activity and inhibition of tumor cell bone invasiveness by a transient reduction of VEGF, bFGF and MMP-2 circulating levels after infusion.

Enhanced tumor regression and tissue repair when zoledronic acid is combined with ifosfamide in rat osteosarcoma

The efficacy of zoledronic acid (ZOL), with or without the anticancer drug ifosfamide (IFO), was tested on primary bone tumor growth using a rat-transplantable model of osteosarcoma. The effects on bone remodeling and tumor growth were analyzed by radiography, micro-computed tomography (micro-CT), and histological staining. The in vitro effects of ZOL were studied by proliferation, apoptosis, and cell cycle analyses on the osteosarcoma cells OSRGA compared to rat primary osteoblasts. Treatment with ZOL was effective in preventing the formation of osteolytic lesions that developed in bone sites and in reducing the local tumor growth, as compared to the untreated rats. The combination of ZOL and IFO was more effective than each agent alone in preventing tumor recurrence, improving tissue repair, and increasing bone formation as revealed by the analysis of trabecular architecture. In vitro studies demonstrated that ZOL was more potent against the OSRGA cell line than osteoblasts (with a half-maximal inhibitory effect on proliferation seen at 0.2 and 20 microM, respectively), the ZOL-induced inhibition of OSRGA proliferation being due to cell cycle arrest in S-phase. No effect on OSRGA apoptosis could be observed in vitro, as assessed by Hoechst staining and caspase-1 and -3 activation. In situ cell death was determined by TUNEL staining on tumor tissue sections. No significant difference in TUNEL-positive cells could be observed between ZOL-treated and -untreated rats. This is the first report of the anti-bone resorption and antitumoral activities of zoledronic acid in a rat model of osteosarcoma, and its beneficial association with an antitumoral chemotherapeutic drug in preventing tumor recurrence.

The bisphosphonate zoledronic acid inhibits the development of plasmacytoma induced in BALB/c mice by intraperitoneal injection of pristane

OBJECTIVES

Bisphosphonates (BPs) are mostly used in the palliative care of myeloma-associated osteolytic lesions. Recent studies have suggested that BPs may also exert direct antitumor effects on myeloma cells. We have investigated the effect of the potent bisphosphonate, zoledronic acid (ZOL), on the development of pristane (2,6,10,14-tetramethylpentadecane)-induced plasmacytoma (PCT) in six-week-old BALB/c mice.

METHODS

Different groups of pristane-treated mice also received ZOL (100 microg/kg) commencing after the development of PCT or ZOL (20 microg/kg) from the first day. Control groups received pristane alone, ZOL alone (20 microg/kg), or phosphate-buffered saline. The study was terminated on day 300, and the remaining mice were autopsied and abdominal tissues were examined histologically for PCT.

RESULTS AND CONCLUSIONS

Statistical analysis revealed a significant delay in PCT development in the group receiving pristane plus ZOL (20 microg/kg) from the first day compared to the groups receiving pristane alone and pristane combined with ZOL (100 microg/kg) after the appearance of PCT (Log-rank, P = 0.0001 and 0.0001; respectively). Kaplan-Meier analysis revealed a significant difference in survival between the group treated with pristane alone and the groups receiving pristane plus ZOL (20 microg/kg) from the first day or ZOL (100 microg/kg) after the appearance of PCT (Log-rank, P = 0.016 and 0.023; respectively). These results indicate a direct anti-tumor effect of ZOL in pristane-induced PCT development BALB/c mice, which may contribute to their significantly increased survival. This hypothesis should now be further investigated in clinical trials.

Bisphosphonates and Cancer-Induced Bone Disease: Beyond Their Antiresorptive Activity: Figure 1

Bisphosphonates are primarily known for their ability to inhibit osteoclast-mediated bone resorption. They are an indispensable part of therapy for patients with cancers that cause osteolysis. However, there is now a growing body of evidence from preclinical research showing that bisphosphonates also exhibit antitumor activity, both in vitro and in vivo. They can affect molecular mechanisms of tumor cell adhesion, invasion, and proliferation; reinforce the effects of cytotoxic agents in a synergistic manner; and exhibit antiangiogenic and immunomodulatory effects. These preclinical findings reveal exciting ways of optimizing bisphosphonate therapy in oncology to fully exploit their antitumor potential.

Myeloma bone disease: pathophysiology and management

Bone disease is a major feature of multiple myeloma. Myeloma-induced bone destruction is the result of an increased activity of osteoclasts, which is not accompanied by a comparable increase of osteoblast function. Recent studies have revealed that new molecules such as the receptor activator of nuclear factor-kappa B (RANK), its ligand (RANKL), osteoprotegerin (OPG), and macrophage inflammatory protein-1alpha are implicated in osteoclast activation and differentiation, while proteins such as dickkopf-1 inhibit osteoblastic bone formation. These new molecules seem to interfere not only with the biology of myeloma bone destruction but also with tumour growth and survival, creating novel targets for the development of new antimyeloma treatment. Currently, bisphosphonates play a major role in the management of myeloma bone disease. Clodronate, pamidronate and zoledronic acid are the most effective bisphosphonates in symptomatic myeloma patients. Biochemical markers of bone remodeling have been used in an attempt to identify patients more likely to benefit from early treatment with bisphosphonates. Furthermore, using microarray techniques, myeloma patients may be subdivided into molecular subgroups with certain clinical characteristics, such as propensity for lytic lesions that may need early prophylactic treatment. Recent phase I studies with recombinant OPG and monoclonal antibodies to RANKL appear promising.

Myeloma cells (5TMM) and their interactions with the marrow microenvironment

Myeloma is a deadly B-cell neoplasm, characterized by the monoclonal proliferation of plasma cells, the development of osteolytic lesions, and the induction of angiogenesis. Myeloma cells are predominantly localized in the marrow where they receive the appropriate survival and proliferation signals. To reach or spread over the marrow, the myeloma cells need to migrate from the vascular to the extravascular compartment of the marrow. A process called "homing". In this review, the steps of the homing scheme, analyzed in the 5TMM model, will be described. These murine models originated from spontaneously developed myeloma in elderly mice and have since been propagated by intravenous injection of myeloma cells into young syngeneic mice. These models resemble the human condition closely. The different studies reported here demonstrate that adhesion of 5TMM cells to marrow endothelial cells is partially mediated by CD44v10 and to stromal cells by CD44v6. The 5TMM cells migrate to the marrow through the effects of MCP-1, laminin-1, and IGF-1. Once past the marrow endothelium, they invade the extravascular compartment of the marrow by secreting MMP-9 and uPA. When they have settled in the marrow, they become susceptible to the effects of IGF-1, which stimulates the cells to proliferate and produce VEGF. Furthermore, studies targeting the marrow with inhibitors will be highlighted. These studies show that the 5TMM models are useful for unraveling basic biological processes and for identifying new therapeutic targets.

Bisphosphonates: preclinical review

Bisphosphonates effectively inhibit osteoclast-mediated bone resorption and are integral in the treatment of benign and malignant bone diseases. The evolution of bisphosphonates over the past 30 years has led to the development of nitrogen-containing bisphosphonates (N-BPs), which have a mechanism of action different from that of the nonnitrogen-containing bisphosphonates. Studies conducted over the past decade have elucidated the mechanism of action and pharmacologic properties of the N-BPs. N-BPs exert their effects on osteoclasts and tumor cells by inhibiting a key enzyme in the mevalonate pathway, farnesyl diphosphate synthase, thus preventing protein prenylation and activation of intracellular signaling proteins such as Ras. Recent evidence suggests that N-BPs also induce production of a unique adenosine triphosphate analogue (Apppi) that can directly induce apoptosis. Our increased understanding of the pharmacologic effects of bisphosphonates is shedding light on the mechanisms by which they exert antitumor effects. As a result of their biochemical effects on protein prenylation, N-BPs induce caspase-dependent apoptosis, inhibit matrix metalloproteinase activity, and downregulate alpha(v)beta(3) and alpha(v)beta(5) integrins. In addition, zoledronic acid (Zometa; Novartis Pharmaceuticals Corp.; East Hanover, NJ and Basel, Switzerland) exerts synergistic antitumor activity when combined with other anticancer agents. Zoledronic acid also inhibits tumor cell adhesion to the extracellular matrix and invasion through Matrigel trade mark and has antiangiogenic activity. A growing body of evidence from animal models demonstrates that zoledronic acid and other bisphosphonates can reduce skeletal tumor burden and prevent metastasis to bone. Further studies are needed to fully elucidate these biochemical mechanisms and to determine if the antitumor potential of bisphosphonates translates to the clinical setting.

Osteoclasts enhance myeloma cell growth and survival via cell-cell contact: a vicious cycle between bone destruction and myeloma expansion

Multiple myeloma (MM) expands in the bone marrow and causes devastating bone destruction by enhancing osteoclastic bone resorption in its vicinity, suggesting a close interaction between MM cells and osteoclasts (OCs). Here, we show that peripheral blood mononuclear cell-derived OCs enhanced growth and survival of primary MM cells as well as MM cell lines more potently than stromal cells, and that OCs protected MM cells from apoptosis induced by serum depletion or doxorubicin. OCs produced osteopontin (OPN) and interleukin 6 (IL-6), and adhesion of MM cells to OCs increased IL-6 production from OCs. In addition, IL-6 and OPN in combination enhanced MM cell growth and survival. However, the effects of OCs on MM cell growth and survival were only partially suppressed by a simultaneous addition of anti–IL-6 and anti-OPN antibodies and were completely abrogated by inhibition of cellular contact between MM cells and OCs. These results demonstrate that OCs enhance MM cell growth and survival through a cell-cell contact-mediated mechanism that is partially dependent on IL-6 and OPN. It is suggested that interactions of MM cells with OCs augment MM growth and survival and, thereby, form a vicious cycle, leading to extensive bone destruction and MM cell expansion.

Multifunctional role of matrix metalloproteinases in multiple myeloma: a study in the 5T2MM mouse model

Matrix metalloproteinases (MMPs) are known to play a role in cell growth, invasion, angiogenesis, metastasis, and bone degradation, all important events in the pathogenesis of cancer. Multiple myeloma is a B-cell cancer characterized by the proliferation of malignant plasma cells in the bone marrow, increased angiogenesis, and the development of osteolytic bone disease. The role of MMPs in the development of multiple myeloma is poorly understood. Using SC-964, a potent inhibitor of several MMPs (MMP-2, -3, -8, -9, and -13), we investigated the role of MMPs in the 5T2MM murine model. Reverse transcriptase-polymerase chain reaction demonstrated the presence of mRNA for MMP-2, -8, -9, and -13 in 5T2MM-diseased bone marrow. Mice bearing 5T2MM cells were given access to food containing SC-964. The concentration of SC-964 measured in the plasma of mice after 11 days of treatment was able to inhibit MMP-9 activity in gelatin zymography. Treatment of 5T2MM-bearing mice resulted in a significant reduction in tumor burden, a significant decrease in angiogenesis, and partially protective effect against the development of osteolytic bone disease. The direct role of MMPs in these different processes was confirmed by in vitro experiments. All these results support the multifunctional role of MMPs in the development of multiple myeloma.

Bisphosphonates: new therapeutic agents for the treatment of bone tumors

Bisphosphonates (BPs) have been used successfully for many years to reduce the skeletal complications associated with the benign and malignant bone diseases that are characterized by enhanced osteoclastic bone resorption. Until recently, it was thought that the clinical efficacy of BPs in the treatment of cancer patients with bone metastases was purely a result of the inhibition of osteoclast-mediated bone resorption. However, recent studies have demonstrated that BPs inhibit the growth, attachment and invasion of cancer cells in culture and promote their apoptosis. These results suggest that BPs are also anti-cancer agents, raising the possibility that BPs could inhibit cancer-cell colonization in visceral organs. However, results from clinical trials are conflicting, and whether BPs possess anti-cancer effects or not remains controversial.

Autologous stem cell transplantation normalizes abnormal bone remodeling and sRANKL/osteoprotegerin ratio in patients with multiple myeloma

The osteoprotegerin (OPG)/receptor activator of NF-kappa B ligand (RANKL) system has a major role in the pathogenesis of bone disease in myeloma (MM). The effect of autologous stem cell transplantation (ASCT) on bone turnover in MM was evaluated in 51 patients (35M/16F). Markers of bone resorption (NTX, TRACP-5b), bone formation (bone-alkaline phosphatase (bALP), osteocalcin), OPG and sRANKL were measured pre- and every month post-ASCT. The median follow-up period was 12 months. Four patients were transplanted in CR, 44 were transplanted in PR and three patients had progressive/resistant disease. All patients received bisphosphonates both pre- and post-ASCT. At baseline the majority of patients had increased NTX, TRACP-5b levels, and sRANKL/OPG ratio, while markers of bone formation were strongly suppressed. ASCT produced a significant reduction of sRANKL/OPG ratio, with a concomitant decrease of NTX, and TRACP-5b levels, starting the second month post-ASCT. Bone formation markers, osteocalcin and bALP, started to increase after the 9th and 11th month post-ASCT, respectively, while the increase of OPG preceded this. These results provide biochemical evidence that ASCT normalizes the abnormal bone resorption in MM patients possibly through the decrease of RANKL/OPG ratio, while bone formation requires a longer period to return to normal.

Multiple myeloma biology: lessons from the 5TMM models

Multiple myeloma (MM) is a B cell neoplasm characterized by the monoclonal proliferation of plasma cells in the bone marrow, the development of osteolytic lesions and the induction of angiogenesis. These different processes require three-dimensional interactions, with both humoral and cellular contacts. The 5TMM models are suitable models to study these interactions. These murine models originate from spontaneously developed myeloma in elderly mice, which are propagated by in vivo transfer of the myeloma cells into young syngeneic mice. In this review we report on studies performed in the 5TMM models with special emphasis on the homing of the myeloma cells, the characterization of the migrating and proliferating clone and the identification of the isotype switch variants. The bone marrow microenvironment was further targeted with osteoprotegerin (OPG) to block the RANK/RANKL/OPG system and with potent bisphosphonates. Both treatments resulted in a significant protection against myeloma-associated bone disease, and they decreased myeloma disease, as evidenced by a lower tumor load and an increased survival of the mice. These different studies demonstrate the strength of these models, not only in unraveling basic biological processes but also in the testing of potentially new therapeutic targets.

Advances in Biology and Therapy of Multiple Myeloma

Even during this past year, further advances have been made in understanding the molecular genetics of the disease, the mechanisms involved in the generation of myeloma-associated bone disease and elucidation of critical signaling pathways as therapeutic targets. New agents (thalidomide, Revimid, Velcade) providing effective salvage therapy for end-stage myeloma, have broadened the therapeutic armamentarium markedly.

As evidenced in Section I by Drs. Kuehl and Bergsagel, five recurrent primary translocations resulting from errors in IgH switch recombination during B-cell development in germinal centers involve 11q13 (cyclin D1), 4p16.3 (FGFR3 and MMSET), 6p21 (cyclin D3), 16q23 (c-maf), and 20q11 (mafB), which account for about 40% of all myeloma tumors.

Based on gene expression profiling data from two laboratories, the authors propose 5 multiple myeloma (MM) subtypes defined by the expression of translocation oncogenes and cyclins (TC molecular classification of MM) with different prognostic implications. In Section II, Drs. Barillé-Nion and Bataille review new insights into osteoclast activation through the RANK Ligand/OPG and MIP-1 chemokine axes and osteoblast inactivation in the context of recent data on DKK1. The observation that myeloma cells enhance the formation of osteoclasts whose activity or products, in turn, are essential for the survival and growth of myeloma cells forms the basis for a new treatment paradigm aimed at reducing the RANKL/OPG ratio by treatment with RANKL inhibitors and/or MIP inhibitors.

In Section III, Dr. Fenton reviews apoptotic pathways as they relate to MM therapy. Defects in the mitochrondrial intrinsic pathway result from imbalances in expression levels of Bcl-2, Bcl-XL and Mcl-1. Mcl-1 is a candidate target gene for rapid induction of apoptosis by flavoperidol. Antisense oglionucleotides (ASO) lead to the rapid induction of caspace activity and apoptosis, which was potentiated by dexamethasone. Similar clinical trials with Bcl-2 ASO molecules alone and in combination with doxorubicin and dexamethasone or thalidomide showed promising results.

The extrinsic pathway can be activated upon binding of the ligand TRAIL. OPG, released by osteoblasts and other stromal cells, can act as a decoy receptor for TRAIL, thereby blocking its apoptosis-inducing activity. MM cells inhibit OPG release by stromal cells, thereby promoting osteoclast activation and lytic bone disease (by enhancing RANKL availability) while at the same time exposing themselves to higher levels of ambient TRAIL. Thus, as a recurring theme, the relative levels of pro- versus anti-apoptotic molecules that act in a cell autonomous manner or in the milieu of the bone marrow microenvironment determine the outcome of potentially lethal signals.

In Section IV, Dr. Barlogie and colleagues review data on single and tandem autotransplants for newly diagnosed myeloma. CR rates of 60%–70% can be reached with tandem transplants extending median survival to ~7 years. Dose adjustments of melphalan in the setting of renal failure and age &gt; 70 may be required to reduce mucositis and other toxicities in such patients, especially in the context of amyloidosis with cardiac involvement.

In Total Therapy II the Arkansas group is evaluating the role of added thalidomide in a randomized trial design. While data are still blinded as to the contribution of thalidomide, the overriding adverse importance of cytogenetic abnormalities, previously reported for Total Therapy I, also pertain to this successor trial. In these two-thirds of patients without cytogenetic abnormalities, Total Therapy II effected a doubling of the 4-year EFS estimate from 37% to 75% (P &lt; .0001) and increased the 4-year OS estimate from 63% to 84% (P = .0009).

The well-documented graft-vs-MM effect of allotransplants can be more safely examined in the context of non-myeloablative regimens, applied as consolidation after a single autologous transplant with melphalan 200 mg/m2, have been found to be much better tolerated than standard myeloablative conditioning regimens and yielding promising results even in the high-risk entity of MM with cytogenetic abnormalities.

For previously treated patients, the thalidomide congener Revimid and the proteasome inhibitor Velcade both are active in advanced and refractory MM (~30% PR).

Gene expression profiling (GEP) has unraveled distinct MM subtypes with different response and survival expectations, can distinguish the presence of or future development of bone disease, and, through serial investigations, can elucidate mechanisms of actions of new agents also in the context of the bone marrow microenvironment. By providing prognostically relevant distinction of MM subgroups, GEP should aid in the development of individualized treatment for MM.