Suppression of Tumor Growth In vivo by the Mitocan α-tocopheryl Succinate Requires Respiratory Complex II
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Purpose: Vitamin E analogues are potent novel anticancer drugs. The purpose of this study was to elucidate the cellular target by which these agents, represented by a-tocopoheryl succinate (a-TOS), suppress tumors in vivo, with the focus on the mitochondrial complex II (CII). Experimental Design: Chinese hamster lung fibroblasts with functional, dysfunctional, and reconstituted CII were transformed using H-Ras. The cells were then used to form xenografts in immunocompromized mice, and response of the cells and the tumors to a-TOS was studied. Results: The CII-functional and CII-reconstituted cells, unlike their CII-dysfunctional counterparts, responded to a-TOS by reactive oxygen species generation and apoptosis execution. Tumors derived from these cell lines reciprocated their responses to a-TOS. Thus, growth of CII-functional and CII-reconstituted tumors was strongly suppressed by the agent, and this was accompanied by high level of apoptosis induction in the tumor cells. On the other hand, a-TOS did not inhibit the CII-dysfuntional tumors. Conclusions: We document in this report a novel paradigm, according to which the mitochondrial CII, which rarely mutates in human neoplasias, is a plausible target for anticancer drugs from the group of vitamin E analogues, providing support for their testing in clinical trials.
Clinical Cancer Research
Copyright 2009 AACR. This is the author-manuscript version of the paper. Reproduced in accordance with the copyright policy of the publisher. Please refer to the journal link for access to the definitive, published version.