title: Density-dependent induction of 92-kd type IV collagenase activity in cultures of A431 human epidermoid carcinoma cells.
abstract: We examined the in vitro regulation of the production of two type IV collagenases, MMP-2 and MMP-9, by A431 human epidermoid carcinoma cells. The A431 cells were cultured under sparse or confluent conditions. The addition of transforming growth factor-beta (TGF-beta) or phorbolester-TPA to sparse cultures induced low levels of MMP-9 secretion, whereas in confluent cultures only TGF-beta produced this effect. Neither treatment altered the level of constitutive secretion of MMP-2. Treatment of sparse, actively growing cultures but not confluent stationary cultures with both TGF-beta and TPA produced synergistic induction of MMP-9 but did not affect MMP-2. A431 cells were grown as discrete large monolayer colonies. Radiolabeling with [3H]leucine or [3H]thymidine followed by autoradiography revealed that all the A431 cells in the colonies were metabolically active and only those on the periphery were dividing. Only these dividing A431 cells stained positive by anti-MMP-9 antibodies. Our results demonstrate that the synergistic induction of MMP-9 secretion in A431 cells occurs subsequent to stimulation by external signals in only noncontact-inhibited dividing tumor cells. These regulatory mechanisms may account for the in vivo finding that many proteinases are localized at the invasion front of a neoplasm where tumor cells are dividing and accessible to various environmental signals.
authors.affiliation: Department of Cell Biology, University of Texas M.D. Anderson Cancer Center, Houston 77030.
authors.forename: B
authors.initials: B
authors.lastname: Xie
authors.forename: C D
authors.initials: CD
authors.lastname: Bucana
authors.forename: I J
authors.initials: IJ
authors.lastname: Fidler
mesh_terms: D002294:Carcinoma, Squamous Cell / Q000201:enzymology* / Q000473:pathology*; D002452:Cell Count; D002455:Cell Division; D017364:Collagenases / Q000096:biosynthesis*; D004357:Drug Synergism; D004790:Enzyme Induction; D006801:Humans; D020780:Matrix Metalloproteinase 9; D009361:Neoplasm Invasiveness; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D016212:Transforming Growth Factor beta / Q000494:pharmacology*; D014407:Tumor Cells, Cultured
chemical_list: D016212:Transforming Growth Factor beta; D017364:Collagenases; D020780:Matrix Metalloproteinase 9; D013755:Tetradecanoylphorbol Acetate