Therapeutic approaches to myeloma bone disease: an evolving story

Bone disease is a major morbidity factor in patients with multiple myeloma and significantly affects their overall survival. A complex interplay between malignant plasma cells and other marrow cells results in the generation of a microenvironment capable of enhancing both tumor growth and bone destruction. Bisphosphonates have consistently reduced the incidence of skeletal-related events in patients with multiple myeloma and other osteotropic tumors as well. However, their use is burdened with side-effects, including the risks of osteonecrosis of the jaw and kidney failure, suggesting that they should be discontinued after prolonged administration. New molecular targets of cell cross-talk in myeloma bone marrow are therefore under intensive investigation and new drugs are being explored in preclinical and clinical studies of myeloma bone disease. Compounds targeting osteoclast activation pathways, such as receptor activator of nuclear factor-κB/receptor activator of nuclear factor-κB ligand/osteoprotegerin, B-cell activating factor, mitogen-activated protein kinase and macrophage inflammatory protein-1α/chemokine receptor for macrophage inflammatory protein-1α axes, or soluble agents that improve osteoblast differentiation by modulating specific inhibitors such as Dickkopf-1 and transforming growth factor-β, as well as novel approaches of cytotherapy represent a new generation of promising drugs for the treatment of myeloma bone disease.     

Molecular crosstalk between the proteasome,aggresomes and autophagy: Translational potential and clinical implications

Targeting the ubiquitin+proteasome protein degradation pathway with the therapeutic agent bortezomib has significantly improved the survival of cancer patients but drug resistance inevitably develops. Aggresomes and the autophagy pathway serve as compensatory protein-clearance mechanisms that eradicate potentially toxic proteins to promote resistance to proteasome inhibitors and, hence, tumor survival. Pre-clinical evidence has emerged to demonstrate active crosstalk between these protein degradation pathways and has revealed novel therapeutic targets and strategies. Translational research and clinical trials are now focused on these pathways to prevent the emergence of drug resistance, enhance apoptosis and further improve the survival of cancer patients.