The highest level of CYP1A1 mRNA was found in both breast cancer cell lines: MCF-7 (RA = 2.04 ± 0.43) and MDA-MB-231(RA = 1.86 ± 0.30) used in our screening; similarly the highest level of CYP1A1 protein was found in these lines (Fig. 2). This evidence concerns the gene CYP1A1 and breast carcinoma.