DIFFERENTIATION OF CA2-SENSITIVE AND RESISTANT CELL-LINES OF HUMAN LUNG-CANCER, SBC-3( SIGNALING BETWEEN ADRIAMYCIN)

Changes in cytosolic concentrations of Ca2+ ([Ca2+](c)) were monitored in a cell line of human small-cell lung cancer, SBC-3, and an adriamy cin(ADM)-resistant subline of SBC-3 (SBC-3/ADM) by a digital image ana lyzing technique using Fura-2. Adding ADM to the bathing solution (20 mu M at a final concentration) caused a gradual increase in the [Ca2+] , to reach a maximum plateau level of 600 nM in SBC-3 cells having hig her sensitivity for ADM, whereas it induced little, if any, effect on SBC-3/ADM cells. In some SBC-3 cells, [Ca2+](c) fluctuated spontaneous ly in diverse manners in the absence of any agent: frequency, amplitud e, and shape of the fluctuations were different in individual cells. S timulation of the SBC-3 cells with 10 mM NaF, a G-protein activator, c aused various types of [Ca2+](c) dynamics. These results are compatibl e with a view that the ADM-induced increase in [Ca2+](c) may play a ca rdinal role in the establishment of chemoresistance to ADM.