Conventional therapy and approach to management

Inhibition of pathologic immunoglobulin-free light chain production by small interfering RNA molecules

OBJECTIVE

Morbidity and mortality occurring in patients with multiple myeloma, AL amyloidosis, and light chain deposition disease can result from the pathologic deposition of monoclonal immunoglobulin light chains (LCs) in kidneys and other organs. To reduce synthesis of such components, therapy for these disorders typically has involved antiplasma cell agents; however, this approach is not always effective and can have adverse consequences. We have investigated another means to achieve this objective; namely, RNA interference.

MATERIALS AND METHODS

SP2/O mouse myeloma cells were stably transfected with a construct encoding a λ6 LC (Wil) under control of the cytomegalovirus promoter, while λ2-producing myeloma cell line RPMI 8226 was purchased from the American Type Culture Collection (Manassas, VA, USA). Both were treated with small interfering RNA directed specifically to the V, J, or C portions of the molecules and then analyzed by enzyme-linked immunosorbent assay, flow cytometry, and real-time polymerase chain reaction.

RESULTS

Transfected cells were found to constitutively express detectable quantities of messenger RNA and protein Wil and, after exposure to small interfering RNAs, an ∼ 40% reduction in messenger RNA and LC production was evidenced at 48 hours. An even greater effect was seen with the 8226 cells.

CONCLUSIONS

Our results have shown that RNA interference can markedly reduce LC synthesis and provide the basis for testing the therapeutic potential of this strategy using in vivo experimental models of multiple myeloma.

Targeting MEK/MAPK signal transduction module potentiates ATO-induced apoptosis in multiple myeloma cells through multiple signaling pathways

We demonstrate that blockade of the MEK/ERK signaling module, using the small-molecule inhibitors PD184352 or PD325901 (PD), strikingly enhances arsenic trioxide (ATO)–induced cytotoxicity in human myeloma cell lines (HMCLs) and in tumor cells from patients with multiple myeloma (MM) through a caspase-dependent mechanism. In HMCLs retaining a functional p53, PD treatment greatly enhances the ATO-induced p53 accumulation and p73, a p53 paralog, cooperates with p53 in caspase activation and apoptosis induction. In HMCLs carrying a nonfunctional p53, cotreatment with PD strikingly elevates the (DR4 + DR5)/(DcR1 + DcR2) tumor necrosis factor (TNF)–related apoptosis-inducing ligand (TRAIL) receptors ratio and caspase-8 activation of ATO-treated cells. In MM cells, irrespective of p53 status, the combined PD/ATO treatment increases the level of the proapoptotic protein Bim (PD-mediated) and decreases antiapoptotic protein Mcl-1 (ATO-mediated). Moreover, Bim physically interacts with both DR4 and DR5 TRAIL receptors in PD/ATO-treated cells, and loss of Bim interferes with the activation of both extrinsic and intrinsic apoptotic pathways in response to PD/ATO. Finally, PD/ATO treatment induces tumor regression, prolongs survival, and is well tolerated in vivo in a human plasmacytoma xenograft model. These preclinical studies provide the framework for testing PD325901 and ATO combination therapy in clinical trials aimed to improve patient outcome in MM.

Risk Stratification of Patients with Newly Diagnosed Multiple Myeloma: Optimizing Treatment Based on Pretreatment Characteristics

Marked clinical and biologic heterogeneity exists in multiple myeloma (MM). Over the years, many prognostic factors have been identified and several prognostic systems have been proposed. The integration of data from international groups including patients treated with common modalities such as chemotherapy and high-dose therapy culminated in the International Staging System. Recently, genetic information has also been shown to include powerful prognostic factors across different treatment modalities. These advances have facilitated categorization of patients into different risk groups, particularly a subset of patients at high risk with short survival times after current standard therapy. The expanding armamentarium of effective treatments in MM also means that it is now possible to select treatments for patients based on their risk categories. This review will summarize the important prognostic factors identified to date, how they can be used to identify patients at high risk, and their clinical utility in relation to treatment optimization at diagnosis.

Multiple myeloma: diagnosis and treatment

Major advances have occurred in our understanding of the biology of multiple myeloma (MM) and in its treatment in the past decade. New diagnostic criteria have been developed, and an international Staging System has replaced the Durle-Salmon Staging System. It is now possible to classify MM as standard risk or high risk on the basis of specific Independent prognostic factors. The role of single and double autologous stem cell transplantation has been clarified by randomized trials. Most importantly, thalidomide, bortezomib, and lenalidomide have emerged as new active agents and are being incorporated rapidly into the treatment of both newly diagnosed and relapsed MM. The current approach to the diagnosis, prognosis, and management of MM is reviewed.