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Multiple myeloma (MM) is preceded by the asymptomatic pre-malignant state, monoclonal gammopathy of undetermined significance (MGUS). Although MGUS patients may remain stable for years, they are at increased risk of progressing to MM. A better understanding of the relevant molecular changes underlying the transition from an asymptomatic to symptomatic disease state is urgently needed. Our studies show for the first time that the CD147 molecule (extracellular matrix metalloproteinase inducer) may be having an important biological role in MM. We first demonstrate that CD147 is overexpressed in MM plasma cells (PCs) vs normal and pre-malignant PCs. Next, functional studies revealed that the natural CD147 ligand, cyclophilin B, stimulates MM cell growth. Moreover, when MM patient PCs displaying bimodal CD147 expression were separated into CD147(bright) and CD147(dim) populations and analyzed for proliferation potential, we discovered that CD147(bright) PCs displayed significantly higher levels of cell proliferation than did CD147(dim) PCs. Lastly, CD147-silencing significantly attenuated MM cell proliferation. Taken together, these data suggest that the CD147 molecule has a key role in MM cell proliferation and may serve as an attractive target for reducing the proliferative compartment of this disease.

DNA double-strand breaks (DSBs) are deleterious lesions that can lead to chromosomal anomalies, genomic instability and cancer. The histone protein H2AX has an important role in the DNA damage response (DDR) and the presence of phospho-H2AX (γH2AX) nuclear foci is the hallmark of DSBs. We hypothesize that ongoing DNA damage provides a mechanism by which chromosomal abnormalities and intratumor heterogeneity are acquired in malignant plasma cells (PCs) in patients with multiple myeloma (MM). Therefore, we assessed PCs from patients with the premalignant condition, monoclonal gammopathy of undetermined significance (MGUS) and MM, as well as human MM cell lines (HMCLs) for evidence of DSBs. γH2AX foci were detected in 2/5 MGUS samples, 37/40 MM samples and 6/6 HMCLs. Notably, the DSB response protein 53BP1 colocalized with γH2AX in both MM patient samples and HMCLs. Treatment with wortmannin decreased phosphorylation of H2AX and suggests phosphoinositide (PI) 3-kinases and/or PI3-kinase-like family members underlie the presence of γH2AX foci in MM cells. Taken together, these data imply that ongoing DNA damage intensifies across the disease spectrum of MGUS to MM and may provide a mechanism whereby clonal evolution occurs in the monoclonal gammopathies.

Survivin is a member of the inhibitor of apoptosis protein (IAP) family and functions both as an apoptosis inhibitor and a regulator of cell division. Survivin overexpression is common in many human tumors and correlates with survival in large cell non-Hodgkin's lymphoma. To evaluate this molecule as a potential therapeutic target in large-cell lymphoma, we evaluated the effect of survivin inhibition both in vitro and in vivo. Using an antisense oligonucleotide (ASO) approach, cell growth was significantly inhibited in the DoHH2, RL and HT lymphoma cell lines. In a lymphoma xenograft model, the development of tumors as well as the growth of established tumors was inhibited in the survivin ASO-treated mice compared to controls. To assess the efficacy of the survivin ASO in combination with other biological agents, we combined the survivin ASO with an anti-CD20 monoclonal antibody, rituximab. The effect of survivin ASO and rituximab in combination was additive in vitro. In vivo, however, suppression of tumor growth with the combination was not significantly superior to controls. We conclude that inhibition of survivin expression is an attractive therapeutic strategy in aggressive non-Hodgkin's lymphomas, and that combining survivin ASO with rituximab may enhance the efficacy of this approach.