Abstract 5299: Separate functions of caspase-3 in cell migration and apoptosis

Abstract

Abstract The cysteine protease function of caspase-3 in the execution phase of apoptosis is well known. However, even though subverting apoptosis is beneficial for tumor development and survival, some tumors maintain high expression levels of caspase-3 in positive correlation with malignancy. Here we show that caspase-3 expression is positively correlated with tumor cell migration and invasion. Furthermore, the enhanced migration and invasion is protease-independent and is specifically conferred by the inactive precursor form of caspase-3. Ectopic expression of caspase-3 in the MCF7 cell line, which is caspase-3 deficient and showed low migration ability, enhanced wound healing and chemotaxis. In contrast, shRNA reducing the expression of caspase-3 in the 5637 cell line, which expressed a high level of caspase-3 and high migration ability, hampered wound healing, chemotaxis, and matrigel invasion. Use of a caspase cysteine protease inhibitor or site directed mutagenesis of caspase-3 either rendering the ectopically expressed precursor form non-processable or inactivating the cysteine protease site did not diminish the caspase-3-dependent increase of cell migration. In addition, only reconstitution of the MCF7 cell line with the wild-type or non-processable precursor form of caspase-3 enhanced cell migration. Ectopic expression of the p17 or p12 fragment alone, the cysteine protease active p17 and p12 fragments together, or the cysteine protease inactive p17 fragment and p12 fragment together did not enhance cell migration. Fluorescence microscopy showed the enrichment of the non-processable mutant of caspase-3 in the leading edge of cells under experimental conditions of wound healing. In summary, the precursor form of caspase-3 induces cell migration by a protease-independent mechanism. This indentifies a new role for caspase-3 in tumor metastasis and represents a novel target for cancer therapeutics. Since the current evidence indicates that the role of caspase-3 in apoptosis and the role in migration are functionally separate, it is conceivable to design a molecule that disrupts the metastasis-inducing function of caspsase-3 while preserving the apoptosis-inducing function. We are currently investigating proteins that associate with caspase-3 under experimental conditions of caspase-3-dependent migration. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 5299.