ERBB2 and neoplasm: Although trastuzumab induced very marginal levels of apoptosis in both cell lines (Fig. 4), cetuximab and trastuzumab did not show effects on the cell growth and proliferation of CF41.Mg and CMT-U334 cells, both of which express low levels of HER-2 and EGFR (Figs. 2 and 3), These results are in agreement with human studies showing that the direct anti-cancer effects of cetuximab and trastuzumab were not observed in tumor cells expressing low levels of EGFR and HER-2, respectively [19, 30].