Molecular and biological role of CD40 in multiple myeloma

Targeted therapies in multiple myeloma

Increasing knowledge of the biology of multiple myeloma led the way for the development of novel drugs that have changed the management of the disease. New treatments target not only to the malignant plasma cell but also target the interactions of myeloma cells with their microenvironment. Several preclinical studies have identified potential targets and drugs are developed that act on pathways crucial for myeloma cell survival, proliferation, migration and drug resistance. The identification of active agents in the laboratory is followed by rationally designed clinical studies that validate these drugs, either as single agents or in combinations with other active drugs. These novel agents may be either small molecules or monoclonal antibodies targeting receptors, kinase activity of receptors or key molecules within critical pathways, intracellular maintenance mechanisms and immune modulation.

Human anti-CD40 antagonist antibody triggers significant antitumor activity against human multiple myeloma

Monoclonal antibodies (mAb) directed against lineage-specific B-cell antigens have provided clinical benefit for patients with hematologic malignancies, but to date no antibody-mediated immunotherapy is available for multiple myeloma. In the present study, we assessed the efficacy of a fully human anti-CD40 mAb CHIR-12.12 against human multiple myeloma cells. CHIR-12.12, generated in XenoMouse mice, binds to CD138-expressing multiple myeloma lines and freshly purified CD138-expressing cells from >80% multiple myeloma patients, as assessed by flow cytometry. Importantly, CHIR-12.12 abrogates CD40L-induced growth and survival of CD40-expressing patient multiple myeloma cells in the presence or absence of bone marrow stromal cells (BMSC), without altering constitutive multiple myeloma cell proliferation. Immunoblotting analysis specifically showed that PI3-K/AKT, nuclear factor-kappaB (NF-kappaB), and extracellular signal-regulated kinase activation induced by CD40L (5 mug/mL) was inhibited by CHIR-12.12 (5 mug/mL). Because CD40 activation induces multiple myeloma cell adhesion to both fibronectin and BMSCs, we next determined whether CHIR-12.12 inhibits this process. CHIR-12.12 decreased CD40L-induced multiple myeloma cell adhesion to fibronectin and BMSCs, whereas control human IgG1 did not. Adhesion of multiple myeloma cells to BMSCs induces interleukin-6 (IL-6) and vascular endothelial growth factor (VEGF) secretion, and treatment of multiple myeloma cells with CD40L further enhanced adhesion-induced cytokine secretion; conversely, CHIR-12.12 blocks CD40L-enhanced IL-6 and VEGF secretion in cocultures of multiple myeloma cells with BMSCs. Finally, CHIR-12.12 triggered lysis of multiple myeloma cells via antibody-dependent cellular cytotoxicity (ADCC) but did not induce ADCC against CD40-negative multiple myeloma cells, confirming specificity against CD40-expressing multiple myeloma cells. These results provide the preclinical rationale for clinical trials of CHIR-12.12 to improve patient outcome in multiple myeloma.

Mechanisms by which SGN-40, a humanized anti-CD40 antibody, induces cytotoxicity in human multiple myeloma cells: clinical implications

CD40 is expressed on B-cell malignancies, including human multiple myeloma (MM) and a variety of carcinomas. We examined the potential therapeutic utility of SGN-40, the humanized anti-CD40 monoclonal antibody, for treating human MM using MM cell lines and patient MM cells (CD138(++), CD40(+)). SGN-40 (0.01-100 micro g/ml) induces modest cytotoxicity in MM cell lines and patient MM cells. In the presence of de novo protein synthesis inhibitor cycloheximide, SGN-40 significantly induced apoptosis in Dexamethasone (Dex)-sensitive MM.1S and Dex-resistant MM.1R cells and in patient MM cells. SGN-40-mediated cytotoxicity is associated with up-regulation of cytotoxic ligands of the tumor necrosis factor family (Fas/FasL, tumor necrosis factor-related apoptosis-inducing ligand, and tumor necrosis factor alpha). SGN-40 treatment also induces a down-regulation of CD40 dependent on an endocytic pathway. Consequently, pretreatment of MM cells with SGN-40 blocked sCD40L-mediated phosphatidylinositol 3'-kinase/AKT and nuclear factor kappaB activation. Importantly, pretreatment of MM.1S and MM.1R cells with SGN-40 inhibited proliferation triggered by interleukin 6 (IL-6) but not by insulin-like growth factor-I. In addition, SGN-40 pretreatment of MM.1S cells blocked the ability of IL-6 to protect against Dex-induced inhibition of DNA synthesis. This was associated with a 2-4-fold reduction of IL-6 receptor at protein and mRNA levels in SGN-40-treated MM.1S cells and patient MM cells. Taken together, these results provide the preclinical rationale for the evaluation of SGN-40 as a potential new therapy to improve patient outcome in MM.