EPIDERMAL GROWTH-FACTOR BINDING AND PROTEIN-KINASE-C ACTIVITIES IN HUMAN-BREAST CANCER CELL-LINES - POSSIBLE QUANTITATIVE RELATIONSHIP

  • 1 June 1986
    • journal article
    • research article
    • Vol. 46  (6) , 2720-2725
Abstract
Quantitative polyacrylamide gel electrophoresis analysis of Ca2+, phospholipid-dependent protein kinase (PKC) of human mammary tumor cell lines (MCF-7, ZR-75, T-47-D, MDA-MB-231, BT-20, and HBL-100) revealed that 80% of the total cellular PKC resided in the cytosol. The tumor cells with no detectable levels of estrogen receptors (MDA-MB-231, HBL-100, and BT-20 cells) exhibited significantly larger (P < 0.001) cytosolic PKC activities than those cells that contained estrogen receptors (MCF-7, T-47-D, and ZR-75 cells). In addition, in estrogen receptor-negative cell lines, relatively high levels of specific low-affinity (apparent Kd=700 pM) epidermal growth factor (EGF) binding activities were found as compared with estrogen receptor-positive cells with significantly (P < 0.001) lower levels of specific high-affinity (apparent Kd=90 pM) EGF binding. A significant positive correlation (P < 0.01) was observed between the number of EGF receptor (R5=0.50) and/or the EGF receptor dissociation constants (R5=0.78) with the cytosolic PKC activity levels. These data indicate that, in human breast cells, a positive relationship may exist between PKC activity, estrogen, and EGF receptors.