THE EFFECT OF TAMOXIFEN ON ESTABLISHED HUMAN COLORECTAL-CANCER CELL-LINES IN-VITRO

The purpose of this study was to evaluate the effect of the anti-estro genic tamoxifen (Tx) on the growth of human colorectal cancer cells. M ethods: Serial concentrations (0.005 mu M, 0.05 mu M, 0.5 mu M, 5 mu M , and 50 mu M) of the anti-estrogenic tamoxifen (Tx) were added and an alyzed for their effect on the growth of established human colorectal cancer cells. HT-29 and SW-620 colon cancer cells and SW-1463 rectal c ancer cells were rested in both serum-free media and serum-containing media (10% fetal calf serum). COLO-205 colon cancer and SW-837 rectal cancer cells were only tested in 10% fetal calf serum-containing media . Cell growth was measured with the hexosaminidase assay and was compa red among the different groups. Cells were analyzed for estrogen, rece ptors using enzyme immunoassay. Results: In serum-free media, Tx inhib ited the growth of HT-29 (P=.05) and SW-620 (P=.01) colon cancer cells at all concentrations tested Results: In serum-containing media, Tx i nhibited (P=.04) the growth of the SW-837 rectal cancer cells at all c oncentrations and SW-1463 (P=.05) rectal cancer cells at the concentra tions of 0.05 mu M and 0.5 mu M Tx. The inhibition of cell growth in H T-29, SW-620 and SW-1463 line was greater (P<.001) under serum-free me dia conditions Estrogen receptors were not detected in any of the cell lines tested. Conclusions: Hormonal manipulation with colo-rectal can cers is possible, but the effect of Tx on the growth of colon cancer c ells differs from the effect on rectal cancer cells under various cond itions. The mechanism of inhibition is not clear yet, and further stud ies are warranted before any clinical implications can be postulated.