Characterization and Regulation of Corticotropin-Releasing Factor in the Human Hepatoma NPLC-KC Cell Line

Abstract

Corticotropin-releasing factor (CRF) has a broad distribution throughout the brain and periphery and has been shown to be present in certain human tumors. We have identified a human hepatoma cell line, NPLC-KC, that contains and secretes immunoreactive CRF (irCRF). Cyclohexyl-silica extracted supernatant from these cells displaced iodinated human CRF (hCRF) in our CRF radioimmunoassay in a manner parallel to the hCRF standard, stimulated release of ACTH from cultured primary rat anterior pituitary cells in a dose-responsive manner. In addition, multiple bioactive and immunoreactive forms of CRF were secreted from these cells as determined by gel permeation chromatography. To determine if irCRF secretion and synthesis could be modulated in the NPLC-KC cells, we tested the ability of factors and hormones to regulate CRF release from and synthesis in these cells. Phorbol 12-myristate 13-acetate (PMA) and forskolin stimulated irCRF release and synthesis, implicating calcium/phospholipid- and cAMP-dependent protein kinases in the regulation of these cells. The cytokine, interleukin-1, was a potent secretagogue of irCRF and this was effect-additive with the increase observed with forskolin, but not with PMA. The glucocorticoid dexamethasone exhibited negative regulation of both basal and stimulated secretion and synthesis of irCRF from the NPLC-KC cell line. Thus, the control of irCRF production by the NPLC-KC human hepatoma cell line exhibits distinct similarities to regulation of CRF in the rat hypothalamus. This cell line should therefore be useful for studying regulation of the synthesis, processing and secretion of mammalian CRF in vitro.