A method for treating, preventing or ameliorating breast cancer is provided by administering a synergistic amount of digitoxin and either actein or an extract of black cohosh comprising triterpene glycosides, and optionally another chemopreventive agent which may be paclitaxel. Methods for treating or preventing a neoplasia using a synergistic combination, and compositions of a synergistic combination of a cardiac glycoside and either actein or an extract of black cohosh comprising triterpene glycosides, and optionally another chemopreventive agent which may be a taxane are also provided. The compositions may also be used in a method for modulating Na+K+ATPase activity. In addition, a method for inhibiting the progression or development of breast cancer in vivo by administering either actein or an extract of black cohosh comprising triterpene glycosides and optionally at least one other chemoprotective agent is provided.