TIG3 - A Novel Inhibitor of Breast Cancer Cell Proliferation

摘要

The mechanism of inhibition of cancer cell proliferation by vitamin A is poorly understood because many of the targets that mediate the retinoid- dependent growth suppression are not known. We have recently identified a novel retinoid-responsive gene target, TIG3, that we believe may be a key player in mediating the retinoid-dependent suppression of tumor cell proliferation. Understanding the mechanism of TIG3 action may provide insights that lead to innovative new anti-breast cancer therapies. Exploiting this potential requires that we understand how TIG3 inhibits cell proliferation - the major goal of this proposal: (Specific Aim 1) Subcellular location plays a major role in determining function, and knowing location provides clues about function. Therefore, our first goal is to localize TIG3 in breast cancer cells; (Specific Aim 2) Most proteins contain distinct functional domains, some responsible for localization and others for function. We hypothesize that TIG3 is divided into distinct functional domains that are important for growth suppression. We are testing this hypothesis; (Specific Aim 3) The TIG3 amino acid sequence/structure reveals no obvious catalytic functional domains, suggesting that TIG3 acts by modulating the function of other proteins. A major goal of the study is to identify these targets. During the first year we have: (1) constructed a plasmid-based TIG3 expression systems and used it to express TIG3 in cells; (2) identified a perinuclear localization of TIG3 in cells; (3) demonstrated that the TIG3 carboxy-terminal hydrophobic domain guides appropriate subcellular localization; (4) shown that the TIG3 carboxy-terminal tail is required for optimal cell killing; and (5) constructed an adenovirus expression system that permits efficient TIG3 expression for biochemical studies.