The invention features screening assays for compounds that are potentially useful for treating or preventing a proliferative disease. The assays are based on contacting a candidate compound with a cell containing a nucleic acid including a HER2 regulatory element and a reporter sequence. In addition, the invention features compounds identified by the assays of the invention. The invention further features compounds structurally related to those identified by the screening assays. Finally, the invention features methods of treating or preventing a proliferative disease using the compounds of the invention.