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The introduction of the Immunomodulatory drugs (IMiDs) and proteasome inhibitors, used either as a single-agent or combined with classic anti-myeloma therapies, has improved the outcome for patients with relapsed myeloma. However, there is currently no generally accepted standard treatment for relapsed/refractory myeloma patients, partly because of the absence of trials comparing the efficacy of the novel agents in relapsed/refractory myeloma. Choice of a new treatment regimen depends on both patient and disease-specific characteristics. A lenalidomide-based regimen is the first choice in patients with neuropathy, while bortezomib has the highest efficacy in patients with renal insufficiency and is not associated with increased risk of thromboembolism. A second autologous stem cell transplantation (auto-SCT) can be applied in patients with a progression-free period of ≥ 18-24 months after the first auto-SCT. In high-risk relapse such as occurring early after auto-SCT consolidation with allogeneic SCT can be considered. In this review we provide an overview of the various salvage regimens and give recommendations for treatment of patients with relapsed/refractory myeloma in different clinical settings., (Copyright © 2010 Elsevier Ltd. All rights reserved.)

The effects of the combination of simvastatin and lenalidomide were analyzed in myeloma. Myeloma cell lines and patient myeloma cells were incubated with different concentrations of lenalidomide, simvastatin, or the combination. Co exposure to simvastatin and lenalidomide resulted in a synergistic reduction of cell viability in myeloma cells. This effect was due to induction of apoptosis and inhibition of proliferation. The combination augmented induction of caspase-8 cleavage and enhanced down-regulation of pStat3. Mevalonate and GGOH abrogated the synergy between lenalidomide and simvastatin. These data provide a rationale for the clinical evaluation of lenalidomide and simvastatin in patients with myeloma.

In vitro statins induce apoptosis in myeloma and lymphoma cells in a dose-and time-dependent way. In combination with dexamethasone and doxorubicin, statins have a chemo-sensitizing effect. Twenty-eight patients with relapsed myeloma or lymphoma were treated with a dose-escalating regimen of simvastatin for 7 days followed by VAD in myeloma patients and CHOP in lymphoma patients. The maximum tolerated dose was 15 mg/kg/day simvastatin. The most frequently reported side-effects were fatigue, gastrointestinal CTC grade 1-2 and neutropenic fever. The dose-limiting toxicity was neutropenic sepsis and grade 3 gastrointestinal side effects. High-dose simvastatin given immediately prior to chemotherapy is safe and tolerable up to a dose of 15 mg/kg/day.

Insight into the mechanisms of primary or acquired drug resistance of (hematological) malignancies is critical for the development of new treatment strategies. This review will focus on Bcl-2 and the mevalonate pathway as targets for reversal of drug resistance in multiple myeloma. The Bcl-2 protein is highly expressed in myeloma patients and in vitro studies have shown its role in the regulation of chemosensitivity, which makes Bcl-2 an attractive target for treatment. Statins are widely used for the treatment of hypercholesteremia. Several in vitro studies have shown that statins may also kill hematological malignant cells including myeloma cells. We found that lovastatin induced apoptosis in myeloma and lymphoma cells by inhibition of geranylgeranylation and subsequent down regulation of Mcl-1, probably the most important anti-apoptotic protein in myeloma. Phase 1 and 2 studies have been performed with Bcl-2 antisense oligonucleotides and high dose simvastatin in combination with chemotherapy in heavily pre-treated myeloma patients. Encouraging results from these studies may provide the framework for the future application of new treatment strategies for myeloma.

Purpose: Prenylation is essential for membrane localization and participation of proteins in various signaling pathways. This study examined the role of farnesylated and geranylgeranylated proteins in the regulation of myeloma cell proliferation., Experimental Design: Antiproliferative and apoptotic effects of various modulators of farnesylated and geranylgeranylated proteins were investigated in myeloma cells., Results: Depletion of geranylgeranylpyrophosphate inhibited myeloma cell proliferation through accumulation of cells in G(1) phase of the cell cycle and loss of cells in S phase. In contrast, depletion of farnesylpyrophosphate had no or only minor effects. Furthermore, inhibition of geranylgeranyl transferase I activity was more effective in reducing myeloma cell growth when compared with inhibition of farnesyl transferase activity. This indicates that protein geranylgeranylation is important for myeloma cell proliferation and cell cycle progression through G(1). Geranylgeranylated target proteins involved in the control of proliferation include GTPases, such as Rac-1, Cdc42, and RhoA. Inhibition of Rho, Rac, and Cdc42 GTPases by toxin B reduced proliferation, without affecting cell viability, whereas specific inhibition of Rho GTPases by C3 exoenzyme was without effect. This suggests a role for Rac and/or Cdc42 GTPases in myeloma cell growth. Rac-1 activity was found in all myeloma cell lines and was suppressed by the depletion of intracellular pools of geranylgeranylpyrophosphate, whereas interleukin-6 rapidly induced Rac-1 activation. Furthermore, dominant-negative Tat-Rac-1 reduced myeloma cell proliferation, whereas constitutively active Tat-Rac-1 enhanced proliferation., Conclusion: These results indicate that protein geranylgeranylation is essential for myeloma cell proliferation and suggest that Rac-1 is a regulator of myeloma cell growth.

Purpose: Prenylation is essential for membrane localization and participation of proteins in various signaling pathways. The following study was conducted to examine the importance of protein farnesylation and geranylgeranylation for the regulation of lymphoma cell survival and proliferation., Experimental Design: Lymphoma cells were treated with the beta-hydroxy-beta-methylglutaryl-CoA reductase inhibitor lovastatin, which inhibits protein farnesylation and geranylgeranylation by the depletion of intracellular pools of farnesylpyrophosphate and geranylgeranylpyrophosphate. In addition, farnesyl transferase and geranylgeranyl transferase activities were specifically inhibited by FTI-277 and GGTI-298, respectively., Results: Only inhibition of geranylgeranylation by lovastatin led to reduction of cell viability in lymphoma cell lines and purified tumor cells from lymphoma patients in a time- and dose-dependent way. Reduction in the number of viable cells was mediated by both induction of apoptosis and inhibition of proliferation. In addition, GGTI-298 was more effective in induction of apoptosis and inhibition of proliferation than FTI-277. Apoptosis induced by inhibition of protein geranylgeranylation was associated with a reduction of Mcl-1 protein levels, collapse of the mitochondrial transmembrane potential, and caspase-3 activation. Inhibition of proliferation resulted from the induction of G(1) arrest. Furthermore, lovastatin at low concentrations sensitized lymphoma cells to dexamethasone, including cells resistant to this drug., Conclusion: These results indicate that protein geranylgeranylation is critical for the regulation of lymphoma tumor cell survival and proliferation and that pharmacological agents such as lovastatin or geranylgeranyl transferase inhibitors, alone or in combination with other drugs, may be useful in the treatment of lymphoma.