<qa>  What is the antiproliferative activity of ZD 1839?Overexpresssion of EGFR andor TGF-alpha is frequent in human breast cancer and has been correlated in many cases with poor prognostic features. Inhibition of the EGFR pathway has been proposed as a potential therapeutic modality in advanced breast cancer. The antiproliferative activity of ZD 1839 in combination with cytotoxic drugs, such as docetaxel was evaluated in breast cancer cell lines ZR-75-1 and MCF-10A ras that coexpress EGFR and TGF-alpha. Combination treatment demonstrated dose dependent supra-additive growth inhibition and markedly enhanced apoptotic cell death. 