Breast cancer cell motility is promoted by 14-3-3γ

Purpose Pseudopodia are actin-rich ventral protrusions associated with cell motility and cancer cell invasion. We previously applied our established method of using excimer laser cell etching to isolate pseudopodial proteins from MDA-MB-231 breast cancer cells. We later identified 14-3-3 gamma as an oncogenic molecule among 46 candidate proteins that are specific to pseudopodia. The present study aimed to determine the function of 14-3-3 gamma in the motility of breast cancer cells. Methods MDA-MB-231 cells were cultured on 3-mu m porous membranes and double stained to localize 14-3-3 gamma and phalloidin in pseudopodia using confocal imaging. We assessed pseudopodia numbers and length, as well as migration and wound healing in MDA-MB-231 cells with knockdown and forced expression of 14-3-3 gamma to determine 14-3-3 gamma involvement in cell motility. We also immunohistochemically analyzed 14-3-3 gamma in human breast cancer tissues with high-grade lymphatic invasion. Results We specifically located 14-3-3 gamma in pseudopodia of MDA-MB-231 cells. Knockdown and forced expression of 14-3-3 gamma, respectively, decreased and increased pseudopodial formation and elongation. Migration and wound healing assays also showed that 14-3-3 gamma knockdown and forced expression, respectively, decreased and increased the number of underside cells and acellular areas in MDA-MB-231 breast cancer cells. More 14-3-3 gamma was expressed in sites of lymphatic invasion, than in the center and periphery of human breast cancer tissues. Conclusion The role of 14-3-3 gamma in breast cancer invasiveness might be to promote cell motility. Inhibition of 14-3-3 gamma could, therefore, become a novel target of therapy to prevent invasion and metastasis in patients with breast cancers expressing 14-3-3 gamma.