Abstract: Composition and methods for affecting cell proliferation, metabolism or sensitization, including the potentiation of proteasome inhibitor therapy for the treatment of disease caused by deregulation of ubiquitin-proteasome systems, in a cell or subject. The composition includes a compound in combination with a ubiquitin-proteasome inhibitor. In one embodiment, the compound has the formula C42H35N5O3 and the ubiquitin-protease inhibitor is a proteasome inhibitor or an inhibitor of another component of the ubiquitin-proteasome pathway such as an E3 ubiquitin ligase. In one embodiment of the method, the compound is administered to a cell or subject and a therapeutically effective amount of a ubiquitin-protease inhibitor is also administered. In another embodiment, the compound is administered to a cell or subject to inhibit cell proliferation. In yet another embodiment, the compound is administered to a cell or subject to increase, or augment, glucose utilization.