in MDA-MB-231 cells and increased in MCF-7 cells after treatment with the same dose of lycopene for 48 h (27). Betacarotene has already been reported as a chemopreventive against colon adenocarcinoma cell lines, and distinct effects were also reported on differentiated cell lines (15). All cell lines used in the present study have peculiarities. MCF-7 is a breast cancer cell line positive for estrogen receptor (ER), while MDA-MB-231 is negative. MDA-MB235 cells originated external to breast tissue, although they are considered breast cancer (28-30). These data confirm that characteristics of cell properties can be determinant for the type of response of cells to carotenoids. Our study presents many differences in the response of cell lines to the treatment. The viability of the cells treated with lycopene was time-dependent in MCF-7 and MDA-MB231 cells, an effect not observed in MDA-MB-235 cells. MCF-7 cells showed reduction of viability, more intensive after 96 h, reaching 25% without differences in the doses. After 48 h of exposure, the minimal inhibitory concentration was 2.5 μM, and the reduction reached 20% at the higher dose (10 μM). In parallel, a similar study showed that MCF7 cell line treated with lycopene did not present a dosedependent effect after 72 h of the treatment. This study also showed that despite its effect on MCF-7 viability, lycopene does not act on the MCF-10 cell line, reinforcing the importance of cell type in carotenoid action (31).