title: Partial characterization of a glucocorticoid suppressible mitogenic activity secreted from a rat hepatoma cell line hypersensitive to the antiproliferative effects of glucocorticoids.
abstract: We have previously shown that glucocorticoids suppress the proliferation of Fu5 hepatoma cells and have selected subclones which are either hypersensitive (BDS1) or resistant (EDR3) to the antiproliferative effects of dexamethasone, a synthetic glucocorticoid. BDS1 cells externalize a glucocorticoid suppressible mitogenic activity (denoted GSM) which stimulated [3H]thymidine incorporation in quiescent, serum-starved Balb/c 3T3 cells. Glucocorticoid treatment of BDS1 cells reduced the secreted levels of GSM activity by approximately 20-fold in comparison to untreated cells. The GSM activity was constitutively secreted from a glucocorticoid receptor minus variant (EDR3) demonstrating that the suppression of this mitogenic activity is a new glucocorticoid hormone response which required a functional receptor. GSM activity was sensitive to sulfhydryl reducing agents or trypsin, stable to heat and acid treatments and fractionated in gel filtration columns with a native molecular weight of approximately Mr 30,000. The persistence of this size for mitogenic activity after electrophoretic fractionation in nonreducing sodium dodecyl sulfate-poly-acrylamide gels suggested that the GSM activity is comprised of a single protein. Total secreted protein isolated from untreated BDS1, but not dexamethasone-treated BDS1, stimulated 3T3 cells to grow in transformed-appearing large colonies in soft agar and to display multiple layering and elongated spindle-like morphology on solid substratum. The addition of both insulin and EGF to conditioned medium protein isolated from glucocorticoid-treated BDS1 cells restored full induction of 3T3 cell anchorage-independent growth while insulin restored full and EGF partial mitogenic stimulation of these fibroblasts. These results suggest that the GSM activity acts in a pathway common to that of insulin or EGF in fibroblasts.
authors.affiliation: Department of Molecular and Cell Biology, University of California, Berkeley 94720.
authors.forename: P W
authors.initials: PW
authors.lastname: Cook
authors.forename: C P
authors.initials: CP
authors.lastname: Edwards
authors.forename: T
authors.initials: T
authors.lastname: Haraguchi
authors.forename: G L
authors.initials: GL
authors.lastname: Firestone
mesh_terms: D000818:Animals; D006528:Carcinoma, Hepatocellular / Q000378:metabolism*; D002448:Cell Adhesion / Q000187:drug effects; D002460:Cell Line; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D003470:Culture Media; D004247:DNA / Q000096:biosynthesis; D003907:Dexamethasone / Q000378:metabolism / Q000494:pharmacology*; D005347:Fibroblasts / Q000378:metabolism; D005796:Genes; D006131:Growth Inhibitors / Q000494:pharmacology*; D006133:Growth Substances / Q000096:biosynthesis*; D008113:Liver Neoplasms; D008114:Liver Neoplasms, Experimental / Q000378:metabolism*; D051379:Mice; D008807:Mice, Inbred BALB C; D008970:Molecular Weight; D009363:Neoplasm Proteins / Q000096:biosynthesis; D051381:Rats; D011965:Receptors, Glucocorticoid / Q000235:genetics; D014407:Tumor Cells, Cultured / Q000378:metabolism*
chemical_list: D003470:Culture Media; D006131:Growth Inhibitors; D006133:Growth Substances; D009363:Neoplasm Proteins; D011965:Receptors, Glucocorticoid; D003907:Dexamethasone; D004247:DNA