Transforming growth factor beta stimulates mammary adenocarcinoma cell invasion and metastatic potential.
The experimental metastatic potential of 13762NF mammary adenocarcinoma clone MTLn3 was tested after pretreatment in serum-free medium containing transforming growth factor (TGF) beta 1 at 0-5000 pg/ml. Lung colonies were measured 2 weeks after inoculation in syngeneic F344 rats, and a bell-shaped dose-response curve with 2- to 3-fold increase in number of surface lung metastases was seen. Maximal enhancement occurred at the 50 pg/ml dose level. The effect was specific because addition of neutralizing anti-TGF-beta antibody blocked the stimulatory activity at all levels of TGF-beta 1 pretreatment, but when antibody was given alone, neutralizing anti-TGF-beta antibody had no effect on untreated cells. Increased metastatic potential appears to be from an increased propensity of cells to extravasate as tested in the membrane invasion culture system. MTLn3 cells penetrated reconstituted basement-membrane barriers 2- to 3.5-fold more than did untreated control cells, depending upon length of TGF-beta 1 exposure. Increased invasive potential is apparently due, in part, to a 2- to 6-fold increase in type IV collagenolytic (gelatinolytic) and a 2.4-fold increase in heparanase activity. TGF-beta 1 treatment of MTLn3 cells did not alter their growth rate or morphology in the presence of serum; however, growth was inhibited in serum-free medium. Likewise, adhesion to human umbilical vein endothelial cell monolayers or to immobilized reconstituted basement membrane or fibronectin matrices was unchanged. These results suggest that TGF-beta 1 may modulate metastatic potential of mammary tumor cells by controlling their ability to break down and penetrate basement-membrane barriers.
Welch
D R
DR
Division of Chemotherapy, Glaxo Research Laboratories, Research Triangle Park, NC 27709.
Fabra
A
A
Nakajima
M
M
D000230:Adenocarcinoma / Q000473:pathology*; D000818:Animals; D000906:Antibodies; D002460:Cell Line; D005260:Female; D008325:Mammary Neoplasms, Experimental / Q000473:pathology*; D009361:Neoplasm Invasiveness; D009362:Neoplasm Metastasis; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology; D051381:Rats; D011916:Rats, Inbred F344; D016212:Transforming Growth Factor beta / Q000494:pharmacology*; D014407:Tumor Cells, Cultured / Q000166:cytology / Q000187:drug effects
D000906:Antibodies; D010982:Platelet-Derived Growth Factor; D016212:Transforming Growth Factor beta