You can use cisplatin drug for your breast cancer cells.
or you can use Taxol
Taxol (paclitaxel, PAC) is a diterpene with antitumor activity against a variety of human neoplasms. PAC cytotoxicity is thought to derive mainly from a stabilization of microtu-bules as a result of enhanced tubulin polymerization that leads to an accumulation of cells in G 2 /M phase of cell cycle.
Article Evaluation of the Apoptotic and Antiproliferative Activities...