Iris Breitkreutz

Immunomodulatory drug lenalidomide (CC-5013, IMiD3) augments anti-CD40 SGN-40-induced cytotoxicity in human multiple myeloma: Clinical implications

SGN-40, a humanized immoglobulin G1 (IgG1) anti-CD40 monoclonal antibody, mediates cytotoxicity against human multiple myeloma (MM) cells via suppression of interleukin (IL)-6-induced proliferative and antiapoptotic effects as well as antibody-dependent cell-mediated cytotoxicity (ADCC). Here, we studied the clinical significance of an immunomodulatory drug lenalidomide on SGN-40-induced cytotoxicity against CD138(+)CD40(+) MM lines and patient MM cells. Pretreatment with lenalidomide sensitized MM cells to SGN-40-induced cell death. Combined lenalidomide and SGN-40 significantly induced MM apoptosis, evidenced by enhanced cleavage of caspase-3/8/poly(ADP-ribose)polymerase and increased sub-G(0) cells, compared with either single agent at the same doses. Pretreatment of effector cells with lenalidomide augmented SGN-40-induced MM cell lysis, associated with an increased number of CD56(+)CD3(-) natural killer (NK) cells expressing CD16 and LFA-1. Importantly, pretreatment with lenalidomide or lenalidomide and SGN-40 markedly enhanced NK-cell-mediated lysis of autologous patient MM cells triggered by SGN-40. Lenalidomide also up-regulated CD40L on CD56(+)CD3(-) NK cells, facilitating IL-2-mediated activation of NK cells. In addition, lenalidomide induced the CD56(dim) NK subset, which are more potent mediators of ADCC against target MM cells than the CD56(bright) NK subset. Finally, pretreatment of both effector and target MM cells with lenalidomide markedly enhanced SGN-40-mediated ADCC against CD40-expressing MM cells. These studies, therefore, show that the addition of lenalidomide to SGN-40 enhances cytotoxicity against MM cells, providing the framework for combined lenalidomide and SGN-40 in a new treatment paradigm to both target MM cells directly and induce immune effectors against MM.

Thalidomide in induction treatment increases the very good partial response rate before and after high-dose therapy in previously untreated multiple myeloma

Thalidomide as part of initial treatment of multiple myeloma improves pre- and post-transplant response by increasing the proportion of patients achieving a very good partial response. In the prospective phase 3 HOVON-50/GMMG-HD3 trial, patients randomized to TAD (thalidomide, doxorubicin, dexamethasone) had a significantly higher response rate (at least PR) after induction compared with patients randomized to VAD (vincristine, adriamycin, dexamethasone, 72% vs. 54%, p<0.001). Complete remission (CR) and very good partial remission (VGPR) were also higher after TAD. After High Dose melphalan 200mg/m2 response was comparable in both arms, 76% and 79% respectively. However, CR plus VGPR were significantly higher in the patients randomized to TAD (49% vs. 32%, p<0.001). CTC grade 3–4 adverse events were similar in both arms.

Prevention of venous thromboembolism with low molecular-weight heparin in patients with multiple myeloma treated with thalidomide and chemotherapy

Prevention of venous thromboembolism with low molecular-weight heparin in patients with multiple myeloma treated with thalidomide and chemotherapy

Targeting PKC: a novel role for beta-catenin in ER stress and apoptotic signaling

Targeting protein kinase C (PKC) isoforms by the small molecule inhibitor enzastaurin has shown promising preclinical activity in a wide range of tumor cells. We further delineated its mechanism of action in multiple myeloma (MM) cells and found a novel role of beta-catenin in regulating growth and survival of tumor cells. Specifically, inhibition of PKC leads to rapid accumulation of beta-catenin by preventing the phosphorylation required for its proteasomal degradation. Microarray analysis and small-interfering RNA (siRNA)-mediated gene silencing in MM cells revealed that accumulated beta-catenin activates early endoplasmic reticulum stress signaling via eIF2alpha, C/EBP-homologous protein (CHOP), and p21, leading to immediate growth inhibition. Furthermore, accumulated beta-catenin contributes to enzastaurin-induced cell death. Sequential knockdown of beta-catenin, c-Jun, and p73, as well as overexpression of beta-catenin or p73 confirmed that accumulated beta-catenin triggers c-Jun-dependent induction of p73, thereby conferring MM cell apoptosis. Our data reveal a novel role of beta-catenin in endoplasmic reticulum (ER) stress-mediated growth inhibition and a new proapoptotic mechanism triggered by beta-catenin on inhibition of PKC isoforms. Moreover, we identify p73 as a potential novel therapeutic target in MM. Based on these and previous data, enzastaurin is currently under clinical investigation in a variety of hematologic malignancies, including MM.

GF-15, a novel inhibitor of centrosomal clustering, suppresses tumor cell growth in vitro and in vivo

In contrast to normal cells, malignant cells are frequently aneuploid and contain multiple centrosomes. To allow for bipolar mitotic division, supernumerary centrosomes are clustered into two functional spindle poles in many cancer cells. Recently, we have shown that griseofulvin forces tumor cells with supernumerary centrosomes to undergo multipolar mitoses resulting in apoptotic cell death. Here, we describe the characterization of the novel small molecule GF-15, a derivative of griseofulvin, as a potent inhibitor of centrosomal clustering in malignant cells. At concentrations where GF-15 had no significant impact on tubulin polymerization, spindle tension was markedly reduced in mitotic cells upon exposure to GF-15. Moreover, isogenic cells with conditional centrosome amplification were more sensitive to GF-15 than parental controls. In a wide array of tumor cell lines, mean inhibitory concentrations (IC(50)) for proliferation and survival were in the range of 1 to 5 μmol/L and were associated with apoptotic cell death. Importantly, treatment of mouse xenograft models of human colon cancer and multiple myeloma resulted in tumor growth inhibition and significantly prolonged survival. These results show the in vitro and in vivo antitumor efficacy of a prototype small molecule inhibitor of centrosomal clustering and strongly support the further evaluation of this new class of molecules.

Targeting MEK1/2 blocks osteoclast differentiation, function and cytokine secretion in multiple myeloma

Osteolytic bone disease in multiple myeloma (MM) is associated with upregulation of osteoclast (OCL) activity and constitutive inhibition of osteoblast function. The extracellular signal‐regulated kinase 1/2 (ERK1/2) pathway mediates OCL differentiation and maturation. We hypothesized that inhibition of ERK1/2 could prevent OCL differentiation and downregulate OCL function. It was found that AZD6244, a mitogen‐activated or extracellular signal‐regulated protein kinase (MEK) inhibitor, blocked OCL differentiation and formation in a dose‐dependent manner, evidenced by decreased αVβ3‐integrin expression and tartrate‐resistant acid phosphatase positive (TRAP+) cells. Functional dentine disc cultures showed inhibition of OCL‐induced bone resorption by AZD6244. Major MM growth and survival factors produced by OCLs including B‐cell activation factor (BAFF) and a proliferation‐inducing ligand (APRIL), as well as macrophage inflammatory protein (MIP‐1α), which mediates OCL differentiation and MM, were also significantly inhibited by AZD6244. In addition to ERK inhibition, NFATc1 (nuclear factor of activated T‐cells, cytoplasmic, calcineurin‐dependent 1) and c‐fos were both downregulated, suggesting that AZD6244 targets a later stage of OCL differentiation. These results indicate that AZD6244 inhibits OCL differentiation, formation and bone resorption, thereby abrogating paracrine MM cell survival in the bone marrow microenvironment. The present study therefore provides a preclinical rationale for the evaluation of AZD6244 as a potential new therapy for patients with MM.

Retraction: Fatty acid synthase is a novel therapeutic target in multiple myeloma

Okawa, Y., Hideshima, T., Ikeda, H., Raje, N., Vallet, S., Kiziltepe,T., Yasui, H., Enatsu, S., Pozzi, S., Breitkreutz, I., Cirstea, D., Santo, L.,Richardson, P. & Anderson, K.C. (2008) Fatty acid synthase is a novel therapeutic target in multiple myeloma. British Journal of Haematology, 141, 659–671.

Thalidomide in multiple myeloma--clinical trials and aspects of drug metabolism and toxicity.

Background: After the tragic events in the early 1960s, thalidomide has re-emerged as therapeutic for multiple myeloma (MM). It was first approved for the treatment of erythema nodosum leprosum, and is now under evaluation for hematologic and non-hematologic disorders. Its complex mechanism of action is not fully understood; however extensive preclinical studies in MM have revealed its antiangiogenic and immunomodulatory properties. Objective: In this review, we focus on the importance and toxicity of thalidomide in todays clinical use. Methods: Key preclinical and clinical trials available as well as data on the pharmacokinetics and pharmacodynamics of thalidomide in humans are summarized. Conclusions: Thalidomide is widely used as first-line treatment and in relapsed/refractory MM. The most common side effects are fatigue, constipation and peripheral neuropathy, and careful monitoring is required to avoid fetal exposure.

Dose-intensified bendamustine followed by autologous peripheral blood stem cell support in relapsed and refractory multiple myeloma with impaired bone marrow function

Therapeutic options in heavily pretreated relapsed/refractory multiple myeloma patients are often very limited because of impaired bone marrow function. Bendamustine is effective in multiple myeloma and has a favourable toxicity profile. We hypothesized that dose‐intensified bendamustine (180 mg/m2, day 1 and 2) followed by autologous blood stem cell support (ASCS) would improve bone marrow function with low post‐transplant toxicity in patients with severely impaired haematopoiesis. We analyzed 28 consecutive myeloma patients, with a median of three prior lines of therapy (range 2–7), who had relapsed from the last treatment with very limited bone marrow function and were therefore ineligible for conventional chemotherapy, novel agents or trial enrolment. Dose‐intensified bendamustine with ASCS improved haematopoiesis as reflected by increased platelet counts (median 40/nl vs 94/nl, p = 0.0004) and white blood cell counts (3.0/nl vs 4.8/nl, p = 0.02) at day +100. The median time until engraftment of platelets (>50/nl) was 11 days (0–24 days) and of white cell counts (>1.0/nl) 0 days (0–24 days). At least, a minimal response was achieved in 36% of patients. The disease stabilization rate was 50% while the median progression‐free survival rate was limited to 2.14 months. Most importantly, patients were once again eligible for alternative treatments including enrolment into clinical trials. We conclude that dose‐intensified bendamustine followed by ASCS is safe and feasible for multiple myeloma patients with very limited bone marrow reserve. Copyright

Targeted treatments to improve stem cell outcome: Old and new drugs

Thalidomide, lenalidomide and bortezomib have been approved for the treatment of relapsed or refractory multiple myeloma in the recent years. These agents are now being increasingly integrated into therapeutic regimens for newly diagnosed patients. First data are available on the promising activity of these novel agents in induction therapy, as well as maintenance treatment to improve outcome after stem cell transplantation. Whether these early results will lead to prolonged overall survival and thereby ultimately redefine the role of stem cell transplantation in first-line treatment of multiple myeloma will be one of the most important questions to be answered in the coming years.