The effects of COL-3 and lLetrozole on cell growth and death in three human breast cancer cell lines

421 As part of a larger collaborative study, experiments were designed to evaluate the in vitro effects of Letrozole (Novartis) (an aromatase inhibitor), COL-3 (CollaGenex) (a protease inhibitor) and the combination of the two drugs on the human breast cancer cell lines MCF-7, MBA-MB-231 and MDA-MB-435 obtained from the ATCC (new evidence suggests that MDA-MB-435 is derived from a melanoma, J. Ellison et. al., J Clin Pathol: Mol Pathol 2002; 55: 294-299). The MCF-7 cell line is an estrogen receptor positive cell line and the MDA-MB-435 and MDA-MB-231 cell lines are estrogen receptor negative. Preliminary experiments were performed to determine the optimal growth inhibitory dose of each drug (125μg/ml and 10μg/ml, respectively) and the doubling time of each cell line. During the log phase portion of growth, the MDA-MB-435 cells had a doubling time of 23.44 hours, the MDA-MB-231 cells doubled every 39.90 hours, and the MCF-7 cells showed a much slower doubling time of 60.44 hours. Cellular proliferation experiments were performed for each cell line using 104 cells/well. The combination of COL-3 and letrozole and COL-3 alone statistically inhibited cell growth when compared to controls for all three cell lines. Letrozole alone statistically inhibited cell growth for the MCF-7 and MDA-MB 435 cell lines. However, experiments to determine if apoptosis was responsible for the observed inhibition of growth showed only the MDA-MB-435 cells in the combination of drugs to have a statistically significant increase in cytoplasmic histone-associated-DNA fragments when compared to the cells grown in just medium. The results of these studies will eventually be combined with in vivo studies using the same cell lines in SCID mice in hopes of improving the treatment for human breast cancer.