Transforming growth factor beta induces anchorage-independent growth of NRK fibroblasts via a connective tissue growth factor-dependent signaling pathway.
Connective tissue growth factor (CTGF) is a M(r)38,000 cysteine-rich peptide, the synthesis and secretion of which are selectively induced by transforming growth factor beta (TGF-beta). The relationship of CTGF to TGF-beta action on fibroblastic cells is not well understood. TGF-beta has the unique ability to stimulate the growth of normal fibroblasts in soft agar, a property of transformed cells. We have investigated whether CTGF can substitute for TGF-beta or whether CTGF action is essential for TGF-beta to stimulate anchorage-independent growth (AIG) of NRK fibroblasts. Our studies demonstrate that CTGF cannot induce AIG of NRK fibroblasts. However, CTGF synthesis and action are essential for the TGF-beta-induced AIG of NRK fibroblasts. Anti-CTGF antibodies specifically block TGF-beta-induced AIG but have no effect on platelet-derived growth factor or epidermal growth factor-induced growth in monolayer cultures and do not cross-react with platelet-derived growth factor or TGF-beta. Clones of NRK fibroblasts that express an antisense CTGF gene (NRK-ASCTGF), which blocks the expression of the endogenous CTGF gene, do not respond to TGF-beta in the AIG assay. The growth and morphology of the cells (NRK-ASCTGF) in monolayer culture are unaltered from the parent NRK cell line. The addition of recombinant CTGF to the NRK-ASCTGF clones in the presence of TGF-beta restores the AIG response of the cells. These studies demonstrate that the TGF-beta stimulation of NRK fibroblast AIG is dependent on events induced via the synergistic action of CTGF-dependent and CTGF-independent signaling pathways.
Kothapalli
D
D
Department of Cell Biology and Anatomy, University of Miami School of Medicine, Florida 33136, USA.
Frazier
K S
KS
Welply
A
A
Segarini
P R
PR
Grotendorst
G R
GR
D000818:Animals; D002448:Cell Adhesion / Q000502:physiology; D002455:Cell Division / Q000187:drug effects*; D002460:Cell Line; D055513:Connective Tissue Growth Factor; D016373:DNA, Antisense / Q000494:pharmacology; D005347:Fibroblasts; D006133:Growth Substances / Q000235:genetics / Q000494:pharmacology / Q000502:physiology*; D017874:Immediate-Early Proteins; D036341:Intercellular Signaling Peptides and Proteins; D008934:Mitogens / Q000502:physiology; D051381:Rats; D011994:Recombinant Proteins / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D016212:Transforming Growth Factor beta / Q000494:pharmacology*
C526316:CCN2 protein, rat; D016373:DNA, Antisense; D006133:Growth Substances; D017874:Immediate-Early Proteins; D036341:Intercellular Signaling Peptides and Proteins; D008934:Mitogens; D011994:Recombinant Proteins; D016212:Transforming Growth Factor beta; D055513:Connective Tissue Growth Factor