Michael Kline

Isolation of an mRNA encoding a soluble form of the human interleukin-6 receptor

Soluble forms of the interleukin (IL)-2, IL-4 and IL-7 receptors which lack the transmembrane domain have been described. IL-6 is a growth factor important in the final differentiation of B-cells into plasma cells and in the pathogenesis of multiple myeloma. To determine whether the receptor for IL-6 may exist as a soluble molecule, RNA was analysed from the transformed B-cell lines U266, CESS and Daudi, from bone marrow from two myeloma patients, and from normal leukocytes. Using polymerase chain reaction, oligonucleotide primers which flank the transmembrane domain were selected to generate a 339 bp fragment. All samples produced equivalent amounts of the expected 339 bp fragment plus a smaller 245 bp fragment except Daudi which exhibited virtual absence of both. Sequence analysis of the smaller fragments from each of the five samples demonstrated the deletion of the entire transmembrane region from codons 356 (G-TG) to 387 (AG-G). The boundaries of this deletion were identical in all cases. Partial sequence analysis of the ligand-binding domain for U266 demonstrated identical sequences for the membrane-bound and soluble forms of the IL-6 receptor cDNAs. In summary, an mRNA which encodes a soluble form of the IL-6 receptor is expressed in both normal and myeloma cells.

Induction of a Chronic Disease State in Patients With Smoldering or Indolent Multiple Myeloma by Targeting Interleukin 1β-Induced Interleukin 6 Production and the Myeloma Proliferative Component

OBJECTIVE To conduct in vitro studies as well as a phase 2 clinical trial in patients with smoldering or indolent multiple myeloma to determine if interleukin 1 (IL-1) inhibitors can delay or prevent active myeloma. PATIENTS AND METHODS Stromal cells were cocultured with IL-1beta-expressing myeloma cells in the presence of dexamethasone, IL-1 receptor antagonist (IL-1Ra), or both. Levels of interleukin 6 (IL-6) and of apoptosis were also quantified. Between November 19, 2002, and May 24, 2007, 47 patients were enrolled in the study and subsequently treated with IL-1Ra. In 25 (53%) of the 47 study patients, low-dose dexamethasone (20 mg/wk) was added. The primary end point was progression-free survival (PFS). RESULTS In vitro, IL-1Ra was superior to dexamethasone at inhibiting IL-6 production; maximal IL-6 inhibition and apoptosis induction were achieved by addition of both IL-1Ra and dexamethasone. In the clinical trial, 3 patients achieved a minor response to IL-1Ra alone; 5 patients achieved a partial response and 4 patients a minor response after addition of dexamethasone. Seven patients showed a decrease in the plasma cell labeling index that paralleled a decrease in high-sensitivity C-reactive protein (hs-CRP) levels. The median overall PFS was 37.5 months. The median PFS for patients without (n=12) or with (n=35) a greater than 15% decrease in 6-month vs baseline hs-CRP levels was 6 months and more than 3 years, respectively (P=.002). Disease stability was maintained in 8 patients who received therapy for more than 4 years. CONCLUSION In patients with smoldering or indolent multiple myeloma who were at risk of progression to active myeloma, treatment with IL-1 inhibitors decreased the myeloma proliferative rate and hs-CRP levels in those who responded, leading to a chronic disease state and an improved PFS. TRIAL REGISTRATION clinicaltrials.gov identifier: NCT00635154.

ABT-737, an inhibitor of Bcl-2 family proteins, is a potent inducer of apoptosis in multiple myeloma cells

Disruption of pathways leading to programmed cell death plays a major role in most malignancies, including multiple myeloma (MM). ABT-737 is a BH3 mimetic small-molecule inhibitor that binds with high affinity to Bcl-2 and Bcl-xL, preventing the sequestration of proapoptotic molecules and shifting the cell survival/apoptosis balance toward apoptosis induction. In this study, we show that ABT-737 is cytotoxic to MM cell lines, including those resistant to conventional therapies, and primary tumor cells. Flow cytometric analysis of intracellular levels of Bcl-2 family proteins demonstrates a clear inversion of the Bax/Bcl-2 ratio leading to induction of apoptosis. Activation of the mitochondrial apoptosis pathway was indicated by mitochondrial membrane depolarization and caspase cleavage. Additionally, several signaling pathways known to be important for MM cell survival are disrupted following treatment with ABT-737. The impact of ABT-737 on survival could not be overcome by the addition of interleukin-6, vascular endothelial growth factor or insulin-like growth factor, suggesting that ABT-737 may be effective in preventing the growth and survival signals provided by the microenvironment. These data indicate that therapies targeting apoptotic pathways may be effective in MM treatment and warrant clinical evaluation of ABT-737 and similar drugs alone or in combination with other agents in the setting of MM.

Elevated Serum B-Lymphocyte Stimulator Levels in Patients With Familial Lymphoproliferative Disorders

PURPOSE Serum B-lymphocyte stimulator (BLyS) levels have been found to be elevated in a number of immune disease models. Therefore, we sought to establish whether BLyS levels were elevated in patients with B-cell lymphoproliferative disorders and to determine whether elevated BLyS levels correlated with clinical characteristics of the disease. PATIENTS AND METHODS Specimens were collected from the peripheral blood of individuals diagnosed with B-cell chronic lymphocytic leukemia (B-CLL; n = 70) or from age- and sex-matched patients seen at the same institution (n = 41). Serum BLyS levels were determined by enzyme-linked immunosorbent assay, and sequencing of the BLyS promoter was performed by conventional methods and confirmed by restriction fragment length polymorphism analysis. RESULTS We found that elevated BLyS levels were more common in patients with familial B-CLL than individuals with sporadic B-CLL or normal controls. Because of this association, we sequenced the BLyS promoter in patients with B-CLL and normal controls and identified a polymorphic site, -871 C/T. We found that the wild-type sequence was significantly underrepresented in patients with familial B-CLL (4%) compared with patients with sporadic B-CLL (30%; P = .01) or controls (24%; P = .04). Furthermore, using a luciferase reporter under control of the BLyS promoter containing either a C or a T at position -871, we found that the reporter construct containing a T at -871 had a 2.6-fold increase in activity (P = .004). CONCLUSION Our data suggest serum BLyS levels are elevated in patients with familial B-CLL and that elevated BLyS levels correlate with the presence of a T at -871 in the BLyS promoter.

R-(-)-gossypol (AT-101) activates programmed cell death in multiple myeloma cells.

OBJECTIVE Bcl-2 family proteins play a critical role in malignancies by regulating the balance between cell survival and apoptosis. R-(-)-gossypol (AT-101) is a small molecule that mimics the BH3 domain of cellular Bcl-2 inhibitors and interferes with the function of prosurvival Bcl-2 proteins. We examined the cytotoxicity of AT-101 in the context of multiple myeloma, a fatal hematological malignancy. MATERIALS AND METHODS Multiple myeloma cell lines and primary cells obtained from multiple myeloma patients were used to investigate the effects of AT-101. Cell viability, apoptosis, and apoptosis pathways were examined using conventional viability assays, flow cytometry, and immunoblots. RESULTS AT-101 was not only cytotoxic to conventional multiple myeloma cell lines, but was also effective against drug-resistant cell lines and primary multiple myeloma patient cells. Furthermore, AT-101 decreased proliferation of multiple myeloma cell lines in the presence of marrow stromal cells, indicating that this drug may overcome the protective effect of the microenvironment that is important for multiple myeloma cell proliferation and survival. Apoptosis was activated via the mitochondrial pathway in multiple myeloma cell lines treated with AT-101 as demonstrated by an increased Bax to Bcl-2 ratio, mitochondrial membrane depolarization, and caspase activation. Finally, our studies demonstrated that AT-101 exhibits potent synergy with dexamethasone, a valuable therapeutic for multiple myeloma. CONCLUSION These data suggest that the activity of AT-101 may be highly relevant to multiple myeloma disease biology and may represent an option for treatment of patients with this disease.

Contrast in cytokine expression between patients with monoclonal gammopathy of undetermined significance or multiple myeloma.

We investigated whether differences in IL-6 and IL-1β expression could be detected in monoclonal plasma cells from patients with MGUS or MM. Expression of IL-6 and IL-1β in bone marrow cells was determined using cell sorting to enrich for plasma cells followed by reverse transcriptase/polymerase chain reaction (RT/PCR). Nineteen patients (six MGUS, two primary amyloid (AL), 11 MM) were studied. IL-6 mRNA expression was detectable in the sorted CD38+/CD45− plasma cell populations from 0/6 MGUS, 0/2 AL and 5/11 MM patients. All five MM patients with autocrine IL-6 expression demonstrated an elevated plasma cell labeling index. IL-1β mRNA was detectable in the sorted CD38+/CD45− plasma cell populations from 1/6 MGUS, 0/2 AL and 10/11 MM patients. In situ hybridization (ISH) confirmed that the IL-1β producing cells were plasma cells. In conclusion, autocrine production of IL-6 parallels a high labeling index and aberrant expression of IL-1β correlates with the diagnosis of MM. Follow-up of IL-1β-positive MGUS patients will determine whether aberrant expression of IL-1β will predict those MGUS patients that will eventually progress to MM.

Thymoglobulin targets multiple plasma cell antigens and has in vitro and in vivo activity in multiple myeloma

Multiple myeloma is characterized by the proliferation of clonal plasma cells that have a heterogeneous expression of various cell surface markers, precluding successful use of monoclonal antibodies for therapeutic targeting of the tumor cell. Thymoglobulin (rabbit-derived polyclonal anti-thymocyte globulin), by virtue of its method of preparation, contains antibodies against several B-cell and plasma cell antigens and offers an attractive option for immunotherapy of myeloma. Here, we demonstrate potent anti-myeloma activity of the rabbit anti-thymocyte globulin preparation Thymoglobulin in vitro and in vivo in an animal model of myeloma. Thymoglobulin was able to induce dose- and time-dependent apoptosis of several myeloma cell lines, including those resistant to conventional anti-myeloma agents. Importantly, the anti-myeloma activity was preserved even when myeloma cells were grown with different cytokines demonstrating the ability to overcome microenvironment-mediated resistance. Thymoglobulin induced apoptosis of freshly isolated primary myeloma cells from patients. Using a competitive flow cytometric analysis, we were able to identify the potential antigen targets for Thymoglobulin preparation. Finally, in a plasmacytoma mouse model of myeloma, Thymoglobulin delayed the tumor growth in a dose-dependent manner providing convincing evidence for continued evaluation of this agent in the clinic in patients with myeloma, either alone or in combination with other agents.