Abstract
Malignant melanoma is the most commonly diagnosed skin cancer associated with a high rate of metastasis. Low-stage melanoma is easily treated, but metastatic malignant melanoma is an extremely treatment-resistant malignancy with low survival rates. The application of recombinant human tumor necrosis factor-related apoptosis-inducing ligand (rhTRAIL) for the treatment of metastatic malignant melanoma holds considerable promise because of its selective proapoptotic activity towards cancer cells and not nontransformed cells. Unfortunately, the clinical utilization of rhTRAIL has been terminated due to the resistance of many cancer cells to undergo apoptosis in response to rhTRAIL. However, rhTRAIL-resistance can be abrogated through the cotreatment with compounds derived from 'Mother Nature' such as quercetin that can modulate cellular components responsible for rhTRAIL-resistance. Here, we show that rhTRAIL-resistant malignant melanomas are sensitized by quercetin. Quercetin action is manifested by the upregulation of rhTRAIL-binding receptors DR4 and DR5 on the surface of cancer cells and by increased rate of the proteasome-mediated degradation of the antiapoptotic protein FLIP. Our data provide for a new efficient and nontoxic treatment of malignant melanoma.