Faculty Bibliography

Myeloma cells are highly dependent on the unfolded protein response to assemble folded immunoglobulins correctly. Therefore, targeting protein handling within a myeloma cell by inhibiting the aminopeptidase enzyme system, which catalyses the hydrolysis of amino acids from the proteins NH2 terminus, represents a therapeutic approach. CHR-2797, a novel aminopeptidase inhibitor, is able to inhibit proliferation and induce growth arrest and apoptosis in myeloma cells, including cells resistant to conventional chemotherapeutics. It causes minimal inhibition of bone marrow stromal cell (BMSC) proliferation but is able to overcome the microenvironmental protective effects, inhibiting the proliferation of myeloma cells bound to BMSCs and the increase in vascular endothelial growth factor levels seen when myeloma cells and BMSCs are bound together. Additive and synergistic effects are seen with bortezomib, melphalan, and dexamethasone. Apoptosis occurs via both caspase-dependent and non-caspase-dependent pathways with an increase in Noxa, cleavage of Mcl-1, and activation of the unfolded protein response. Autophagy is also seen. CHR-2797 causes an up-regulation of genes involved in the proteasome/ubiquitin pathway, as well as aminopeptidases, and amino acid deprivation response genes. In conclusion, inhibiting protein turnover using the aminopeptidase inhibitor CHR-2797 results in myeloma cell apoptosis and represents a novel therapeutic approach that warrants further investigation in the clinical setting.

Bortezomib (Velcade) is a boron containing molecule which reversibly inhibits the proteasome, an intracellular organelle which is central to the breakdown of ubiquinated proteins and consequently crucial for normal cellular homeostasis. Phase II clinical trials demonstrate it is effective for the treatment of relapsed refractory myeloma, and a phase III trial comparing bortezomib to dexamethasone in second/third line treatment showed superiority in progression free and overall survival. It is administered intravenously in the outpatient setting on days 1, 4, 8 and 11 of a 21-day cycle and regular monitoring for side effects is essential. It is currently approved for the treatment of multiple myeloma patients who have received at least one prior therapy and who have already undergone or are unsuitable for transplantation. Given the strength of this data the UK Myeloma Forum and British Committee for Standards in Haematology believe that bortezomib should be available for prescription by UK haematologists according to its licensed indication in patients with relapsed myeloma.

Blastoid morphology is a rare presenting feature of myeloma which is frequently seen in patients with extramedullary myeloma and is associated with poor clinical outcome. Cell cycle active agents can be effective as treatment for aggressive myeloma and their activity enhanced by using them in combination with the anti-angiogenic agent thalidomide. DT-PACE is an example of such a regimen which we have used to treat 26 relapsed and or refractory patients with extramedullary/blastoid myeloma. The overall response rate (complete response/PR) was 59%, but despite these initial good responses, patients had a short progression free survival (PFS) and overall survival (OS). A subgroup of patients who proceeded to autologous stem cell transplant (ASCT) have a trend towards a better PFS and OS when compared with the group receiving chemotherapy alone (PFS = 10 vs. 3 months P = 0.273 and OS 10 vs. 7 months P = 0.235). Interestingly of the group who received ASCT consolidation three patients remain alive beyond 18 months. In conclusion, the clinical outcome of this group of cases is poor even when treated with the intensive regimen DT-PACE; however, a subgroup can do well if DT-PACE is consolidated by ASCT.

RNA interference (RNAi) has been shown to be a valuable tool to specifically target gene expression in a number of organisms becoming an indispensable weapon in the arsenal in functional genomics. In this study, we demonstrate that streptolysin-O (SLO) reversible permeabilisation is an efficient method to deliver small interfering RNAs (siRNAs) to hard-to-transfect human myeloma cell lines. We used published, pre-validated siRNAs for ERK2 and non-silencing siRNA control. We transfected siRNAs into human myeloma cell lines using SLO reversible permeabilisation method. Flow cytometry and western blot analysis were performed to assess the effect of SLO on transfection efficiency and ERK2 knockdown. These experiments demonstrate that SLO reversible permeabilisation method is an efficient and easy-to-use method to deliver siRNAs into human myeloma cell lines. Optimised SLO permeabilisation method showed to transfect >80% of JIM-3, H929, RPMI8226 and U266 cells, with minimal effect on cell viability (<10%) and cell cycle. Equally important, SLO permeabilisation induced a substantial knockdown of ERK2 at the protein level. These studies demonstrate that reversible SLO permeabilisation can successfully be applied to hard-to-transfect human myeloma cell lines to effectively silence genes.

Multiple myeloma is the second most common haematological malignancy. It is becoming increasingly manageable with conventional and high-dose chemotherapy but there remains a critical need to develop both new drugs and combinations to improve long-term outcomes. Novel biological therapies that specifically target myeloma cells and/or their microenvironmental interactions are being developed that are highly effective, both as single agents and as combinations. Chief among these new agents are the proteasome inhibitor, bortezomib, and the immunomodulatory agents, thalidomide and lenalidomide. These drugs show improved single agent activity that is enhanced in combination. However, many drugs that are being developed in this setting may only have limited single agent activity, but combination use with these and other agents represents a very exciting way of targeting important pathogenic pathways crucial in myeloma development. This represents a challenge for both drug development and clinical trial evaluation, which has the potential to revolutionise the clinical management of myeloma and a paradigm for drug development in other diseases.

Resistance to current cancer therapies has forced scientists to investigate new avenues of therapy distinct from those aimed at single targets, to strategies based on targeting families of proteins, on which cancers rely for their ability to survive stress. Two such protein families are the heat shock proteins (HSP), especially the HSP90 family, and proteins involved in mediating the unfolded protein response (UPR). HSP90 stabilises key survival factors in cancer cells including AKT, ERB2 and HIF1alpha, which alone makes HSP90 inhibitors extremely interesting as potential therapies. In addition targeting HSP90 can destabilise the UPR inducing cell death. A broad range of cancer-types rely on the UPR to correctly fold key signalling proteins properly, as well as to allow the cell to cope with the hypoxic environment associated with tumour development. These associations suggest that a range of tumours may be targeted using HSP90 inhibitors and that the development of specific inhibitors of the UPR may be of interest. In this article, based on work in multiple myeloma, we highlight the importance of targeting multiple signalling pathways simultaneously, using the UPR and heat shock proteins as examples, as a means of effectively killing cancer cells.

A venous thromboembolism (VTE) with the subsequent risk of pulmonary embolism is a major concern in the treatment of patients with multiple myeloma with thalidomide. The susceptibility to developing a VTE in response to thalidomide therapy is likely to be influenced by both genetic and environmental factors. To test genetic variation associated with treatment related VTE in patient peripheral blood DNA, we used a custom-built molecular inversion probe (MIP)-based single nucleotide polymorphism (SNP) chip containing 3404 SNPs. SNPs on the chip were selected in "functional regions" within 964 genes spanning 67 molecular pathways thought to be involved in the pathogenesis, treatment response, and side effects associated with myeloma therapy. Patients and controls were taken from 3 large clinical trials: Medical Research Council (MRC) Myeloma IX, Hovon-50, and Eastern Cooperative Oncology Group (ECOG) EA100, which compared conventional treatments with thalidomide in patients with myeloma. Our analysis showed that the set of SNPs associated with thalidomide-related VTE were enriched in genes and pathways important in drug transport/metabolism, DNA repair, and cytokine balance. The effects of the SNPs associated with thalidomide-related VTE may be functional at the level of the tumor cell, the tumor-related microenvironment, and the endothelium. The clinical trials described in this paper have been registered as follows: MRC Myeloma IX: ISRCTN68454111; Hovon-50: NCT00028886; and ECOG EA100: NCT00033332.

PURPOSE/OBJECTIVE:Deletions of chromosome 1 have been described in 7% to 40% of cases of myeloma with inconsistent clinical consequences. CDKN2C at 1p32.3 has been identified in myeloma cell lines as the potential target of the deletion. We tested the clinical impact of 1p deletion and used high-resolution techniques to define the role of CDKN2C in primary patient material. EXPERIMENTAL DESIGN/METHODS:We analyzed 515 cases of monoclonal gammopathy of undetermined significance (MGUS), smoldering multiple myeloma (SMM), and newly diagnosed multiple myeloma using fluorescence in situ hybridization (FISH) for deletions of CDKN2C. In 78 myeloma cases, we carried out Affymetrix single nucleotide polymorphism mapping and U133 Plus 2.0 expression arrays. In addition, we did mutation, methylation, and Western blotting analysis. RESULTS:By FISH we identified deletion of 1p32.3 (CDKN2C) in 3 of 66 MGUS (4.5%), 4 of 39 SMM (10.3%), and 55 of 369 multiple myeloma cases (15%). We examined the impact of copy number change at CDKN2C on overall survival (OS), and found that the cases with either hemizygous or homozygous deletion of CDKN2C had a worse OS compared with cases that were intact at this region (22 months versus 38 months; P = 0.003). Using gene mapping we identified three homozygous deletions at 1p32.3, containing CDKN2C, all of which lacked expression of CDKN2C. Cases with homozygous deletions of CDKN2C were the most proliferative myelomas, defined by an expression-based proliferation index, consistent with its biological function as a cyclin-dependent kinase inhibitor. CONCLUSIONS:Our results suggest that deletions of CDKN2C are important in the progression and clinical outcome of myeloma.

We have used global protein expression analysis to characterize the pathways of dexamethasone-mediated apoptosis and resistance in myeloma. Analysis of MM.1S cells by two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) identified a series of proteins that were up- and downregulated following dexamethasone treatment. Downregulated proteins included proteins involved in cell survival and proliferation, whereas upregulated proteins were involved in post-translational modification, protein folding and trafficking. A comparison with published gene expression studies identified FK binding protein 5 (FKBP5) (also known as FKBP51), a key regulatory component of the Hsp90-steroid-receptor complex to be increased at the mRNA and protein level postdexamethasone exposure. Quantitative real time polymerase chain reaction and 2D-PAGE analysis of the dexamethasone resistant cell line MM.1R demonstrated no increase in FKBP5, consistent with its association with dexamethasone-mediated apoptosis. Western blot analysis of FKBP5 and other members of the Hsp90-receptor complex showed an increase in FKBP5 whilst FKBP4 (also known as FKBP52) and Hsp90 expression remained constant. No changes were observed in MM.1R. In conclusion, we demonstrated that following steroid receptor signalling, the cell carries out a number of adaptive responses prior to cell death. Interfering with these adaptive responses may enhance the myeloma killing effect of dexamethasone.