New interleukin-15 superagonist (IL-15SA) significantly enhances graft-versus-tumor activity.

Interleukin-15 (IL-15) is a potent cytokine that increases CD8+ T and NK cell numbers and function in experimental models. However, obstacles remain in using IL-15 therapeutically, specifically its low potency and short in vivo half-life. To help overcome this, a new IL-15 superagonist complex comprised of an IL-15N72D mutation and IL-15RαSu/Fc fusion (IL-15SA, also known as ALT-803) was developed. IL-15SA exhibits a significantly longer serum half-life and increased in vivo activity against various tumors. Herein, we evaluated the effects of IL-15SA in recipients of allogeneic hematopoietic stem cell transplantation. Weekly administration of IL-15SA to transplant recipients significantly increased the number of CD8+ T cells (specifically CD44+ memory/activated phenotype) and NK cells. Intracellular IFN-γ and TNF-α secretion by CD8+ T cells increased in the IL-15SA-treated group. IL-15SA also upregulated NKG2D expression on CD8+ T cells. Moreover, IL-15SA enhanced proliferation and cytokine secretion of adoptively transferred CFSE-labeled T cells in syngeneic and allogeneic models by specifically stimulating the slowly proliferative and nonproliferative cells into actively proliferating cells.We then evaluated IL-15SA\u27s effects on anti-tumor activity against murine mastocytoma (P815) and murine B cell lymphoma (A20). IL-15SA enhanced graft-versus-tumor (GVT) activity in these tumors following T cell infusion. Interestingly, IL-15 SA administration provided GVT activity against A20 lymphoma cells in the murine donor leukocyte infusion (DLI) model without increasing graft versus host disease. In conclusion, IL-15SA could be a highly potent T- cell lymphoid growth factor and novel immunotherapeutic agent to complement stem cell transplantation and adoptive immunotherapy

Mcl-1 Inhibition Modulates ERK-Mediated Resistance in Multiple Myeloma

Novel multiple myeloma (MM) treatments have significantly improved over the previous several decades, primarily on account of targeting bone marrow microenvironment (BMM) pathways. However, drug resistance and patient relapse remain major clinical problems. The role of BMM in the upregulation of anti-apoptotic protein Mcl-1 is well documented. The Mcl-1 protein plays a critical role in the progression and acquired drug resistance in MM. The regulation of Mcl-1, a protein characterized by a short half-life, from transcription to degradation is crucial for understanding its role in cell survival. The GSK3β and Erk play important role in the stability of Mcl-1. Also, overexpression of phospho Erk is associated with the acquired resistance. In this study, we investigated Mcl-1 regulation, focusing on transcriptional and post-translational modifications and their impact on protein stability in Mcl-1 inhibitor ( KS18) treated cells. The small molecule inhibitor KS18 induces Mcl-1Ser159/Thr163 phosphorylation and ubiquitination resulting in a sharp decline in Mcl-1 protein levels. Furthermore, we assessed the effects of the KS18 in a combination with ERK inhibitors on cell viability and found that blocking the Mcl-1 stabilization mechanism improves the effectiveness and potency of KS18. Furthermore, we compared KS18 to different classes of chemotherapeutic agents, such as GSK3β/α inhibitor (LY209031), ERK inhibitor (SEH77272), MEK inhibitor (PD18435), and Akt inhibitor (AZD5363). Interestingly, we found KS18 more potent than other agents. Combined, our results propose a strong rationale for novel combination therapies using selective KS18 and ERK inhibitors, which have the potential to markedly improve the outcome of MM treatment. This may also address one of the major clinical problems, drug resistance, and enhance the use of existing drugs

Development of Novel Dual Inhibitor of Chemokine Receptor 4 and Mcl-1 Against Multiple Myeloma

Multiple myeloma (MM) is a neoplastic plasma-cell disorder. This is characterized by clonal proliferation of malignant plasma cells in the bone-marrow (BM) microenvironment, monoclonal protein in blood or urine, and associated organ dysfunction. The treatment options approved by FDA are immune-modulatory agents, proteasome inhibitors, and autologous stem cell transplantation (ASCT). Unfortunately, MM remains uniformly fatal owing to intrinsic or acquired drug resistance and the median survival time is 3 to 5 years. Thus, there is a great need for novel strategies to combat MM. The intimate relationship of myeloma cells to BM microenvironment is “hallmark of myeloma”. The homing of MM cells to the BM, mediated by the chemokine stromal cell-derived factor-1α (SDF-1α) and its receptor CXCR4 has important functional sequelae. The BM microenvironment constituting cells secrete chemokines, cytokines, and growth factors such as interleukin 6 (IL6), vascular endothelial growth factor (VEGF), SDF-1α, and tumor necrosis factor α (TNFα) etc. These growth factors either secreted by MM or BM microenvironment cells (e.g. stromal cells) contribute in activation of several signaling pathways including nuclear factor-κB (NF-κB); phosphatidylinositol 3-kinase (PI3K)-Akt; Ras-Raf-MAPK kinase (MEK)-extracellular signal regulated kinase (ERK); and the Janus kinase 2 (JAK2)-signal transducer and activator of transcription 3 (STAT3). Activation of these pathways has been associated with increased expression of several anti-apoptotic proteins such as Bcl-2, Bcl-xL, Mcl-1, and XIAP. Collectively, these discoveries highlight that interaction of MM cells to BM microenvironment not only promote growth, survival and migration of MM cells, but also confer resistance to conventional chemotherapy. We hypothesized that an agent capable of inhibiting the migration of myeloma cells to bone marrow and suppressing the expression of survival protein Mcl-1 would be a better option for MM treatment.We have synthesized a novel dual inhibitor of CXCR4 and Mcl-1. Our data suggests that this molecule inhibits the expression of CXCR4 and Mcl-1 and survival of MM cells

Autophagy and Apoptosis: Current Challenges of Treatment and Drug Resistance in Multiple Myeloma

Over the past two decades, the natural history of multiple myeloma (MM) has evolved dramatically, owing primarily to novel agents targeting MM in the bone marrow microenvironment (BMM) pathways. However, the mechanisms of resistance acquisition remain a mystery and are poorly understood. Autophagy and apoptosis are tightly controlled processes and play a critical role in the cell growth, development, and survival of MM. Genetic instability and abnormalities are two hallmarks of MM. During MM progression, plasma malignant cells become genetically unstable and activate various signaling pathways, resulting in the overexpression of abnormal proteins that disrupt autophagy and apoptosis biological processes. Thus, achieving a better understanding of the autophagy and apoptosis processes and the proteins that crosslinked both pathways, could provide new insights for the MM treatment and improve the development of novel therapeutic strategies to overcome resistance. This review presents a sufficient overview of the roles of autophagy and apoptosis and how they crosslink and control MM progression and drug resistance. Potential combination targeting of both pathways for improving outcomes in MM patients also has been addressed

Molecular Imaging Reveals Skeletal Engraftment Sites of Transplanted Bone Marrow Cells

Molecular imaging holds great promise for the in vivo study of cell therapy. Our hypothesis was that multimodality molecular imaging can identify the initial skeletal engraftment sites post-bone marrow cell transplantation. Utilizing a standard mouse model of bone marrow (BM) transplantation, we introduced a combined bioluminescence (BLI) and positron emission tomography (PET) imaging reporter gene into mouse bone marrow cells. Bioluminescence imaging was used for monitoring serially the early in vivo BM cell engraftment/expansion every 24 h. Significant cell engraftment/expansion was noted by greatly increased bioluminescence about 1 week posttransplant. Then PET was applied to acquire three-dimensional images of the whole-body in vivo biodistribution of the transplanted cells. To localize cells in the skeleton, PET was followed by computed tomography (CT). Co-registration of PET and CT mapped the sites of BM engraftment. Multiple, discrete BM cell engraftment sites were observed. Taken together, this multimodality approach may be useful for further in vivo characterization of various therapeutic cell types