Paclitaxel is currently used in the treatment of ovarian, breast, gastric, colorectal, lung and recurrent cervical cancer. Initial studies on the mechanism of action of paclitaxel have demonstrated that this drug alters microtubule assembly, by inhibiting microtubule depolymerization and changing microtubule dynamics. Although treatment of various tumor cells with paclitaxel induces apoptosis, but early paclitaxel-targeted proteins is not yet known. We tried to search paclitaxel-targeted proteins and to investigate its functions.

The effects of paclitaxel on HeLa cervical cancer cell growth were evaluated by cell proliferation assay, DAPI stain, and FACS analysis. We performed proteome analysis including 2-DE and MALDI-TOF-MS in nontreated-and paclitaxel-treated HeLa cells, as a result, we identified TACC3 protein that is down-regulated with paclitaxel treatment. We tried to characterize TACC3 functions through in vitro treatment of paclitaxel or RNAi technique.

Paclitaxel- and TACC3 siRNA-treated cells are unable to proceed normally through the cell cycle and are arrested in G2/M phase and reveal apoptotic morphology. TACC3 levels after paclitaxel treatment decreased as a time- and dose- dependent manner both mRNA and protein levels. We confirmed that the role of TACC3 down-regulation for microtubule stabilization was similar to that of paclitaxel. Also, TACC3 is expressed at high levels in various cancer cells and tumor tissues.

This study is proposed that the TACC3 protein may be participated in microtubule formation as an oncoprotein during mitosis and be regulated by paclitaxel as a novel target.