A comparison of melphalan transport in human breast cancer cells and lymphocytes in vitro.

Evidence is presented that melphalan uptake by MCF-7 human breast cancer cells and peripheral blood lymphocytes from normal human subjects is an active process involving 2 amino acid carriers. Quantitative differences were observed in drug transport between the 2 cell types. Cell/medium distribution ratios of melphalan at equilibrium conditions were approx. 4-fold higher in breast cancer cells than in lymphocytes. The transport capacity, Vmax, for both carrier systems was at least 50-fold greater in MCF-7 cells than in lymphocytes, whereas the Michaelis constants were similar. These findings, in part, provide a rational basis for the use of melphalan in the chemotherapy of breast cancer.