Ehrlich, Lori A.

Abstract Myelodysplastic syndromes/neoplasms (MDSs) are heterogeneous stem cell malignancies characterized by poor prognosis and no curative therapies outside of allogeneic hematopoietic stem cell transplantation. Despite some recent approvals by the US Food and Drug Administration, (eg, luspatercept, ivosidenib, decitabine/cedazuridine, and imetelstat), there has been little progress in the development of truly transformative therapies for the treatment of patients with MDS. Challenges to advancing drug development in MDS are multifold but may be grouped into specific categories, including criteria for risk stratification and eligibility, response definitions, time-to-event end points, transfusion end points, functional assessments, and biomarker development. Strategies to address these challenges and optimize future clinical trial design for patients with MDS are presented here.

Abstract Purpose: The phosphatidylinositol 3-kinase/AKT/mammalian target of rapamycin (mTOR) pathway and the heat shock protein family are up-regulated in multiple myeloma and are both regulators of the cyclin D/retinoblastoma pathway, a critical pathway in multiple myeloma. Inhibitors of mTOR and HSP90 protein have showed in vitro and in vivo single-agent activity in multiple myeloma. Our objective was to determine the effects of the mTOR inhibitor rapamycin and the HSP90 inhibitor 17-allylamino-17-demethoxygeldanamycin (17-AAG) on multiple myeloma cells. Experimental Design: Multiple myeloma cell lines were incubated with rapamycin (0.1-100 nmol/L) and 17-AAG (100-600 nmol/L) alone and in combination. Results: In this study, we showed that the combination of rapamycin and 17-AAG synergistically inhibited proliferation, induced apoptosis and cell cycle arrest, induced cleavage of poly(ADP-ribose) polymerase and caspase-8/caspase-9, and dysregulated signaling in the phosphatidylinositol 3-kinase/AKT/mTOR and cyclin D1/retinoblastoma pathways. In addition, we showed that both 17-AAG and rapamycin inhibited angiogenesis and osteoclast formation, indicating that these agents target not only multiple myeloma cells but also the bone marrow microenvironment. Conclusions: These studies provide the basis for potential clinical evaluation of this combination for multiple myeloma patients.

Abstract Macrophage inflammatory protein–1α (MIP-1α) gene expression is abnormally regulated in multiple myeloma (MM) owing to imbalanced expression of the acute myeloid leukemia–1A (AML-1A) and AML-1B transcription factors. We hypothesized that the increased expression ratios of AML-1A to AML-1B also induced abnormal expression of other hematopoietic and bone-specific genes that contribute to the poor prognosis of MM patients with high levels of MIP-1α. We found that interleukin-3 (IL-3) was also induced by the imbalanced AML-1A and AML-1B expression in myeloma. IL-3 mRNA levels were increased in CD138+ purified myeloma cells with increased AML-1A–to–AML-1B expression from MM patients, and IL-3 protein levels were significantly increased in freshly isolated bone marrow plasma from MM patients (66.4 ± 12 versus 22.1 ± 8.2 pg/mL; P = .038). IL-3 in combination with MIP-1α or receptor activator of nuclear factor–kappa B ligand (RANKL) significantly enhanced human osteoclast (OCL) formation and bone resorption compared with MIP-1α or RANKL alone. IL-3 stimulated the growth of interleukin-6 (IL-6)–dependent and IL-6–independent myeloma cells in the absence of IL-6, even though IL-3 did not induce IL-6 expression by myeloma cells. These data suggest that increased IL-3 levels in the bone marrow microenvironment of MM patients with imbalanced AML-1A and AML-1B expression can increase bone destruction and tumor cell growth.