Actin architecture of cultured human thyroid cancer cells: predictor of differentiation?
The actin cytoskeleton is important for cell structure and motility. A disordered actin architecture has been correlated with a high metastatic potential in melanoma, fibrosarcoma, and colon cancer models. Thyrotropin is known to induce growth and differentiation in cultured thyroid cells, whereas the carcinogenic phorbol ester 12-O-tetradecanoylphorbol 13-acetate (TPA) causes dedifferentiation and malignant transformation in many cell lines. We therefore assessed the effect of thyrotropin and TPA on the actin architecture of FTC-133 human follicular thyroid cancer cells in continuous culture. Staining of filamentous actin with rhodamine phalloidin showed that 1 mU/ml or 30 mU/ml thyrotropin-induced actin polymerization was detectable at 1 hour but more notable at 24 hours. Similarly TPA (0.008 to 10 mumol/L) caused rapid actin fiber disruption and redistribution to the cell periphery. Secondary antibody staining for alpha-actinin, a protein that binds and crosslinks actin, was more prominent after treatment with thyrotropin but decreased after TPA. These findings indicate that the actin cytoskeleton has a dynamic response to trophic factors. Thyrotropin promoted actin polymerization, but TPA caused depolymerization. These effects may correlate with cellular alpha-actinin levels. Actin architecture may therefore reflect the state of differentiation of thyroid tumor cells.
Demeure
M J
MJ
Surgical Service Veterans Administration Medical Center, San Francisco, CA 94121.
Hughes-Fulford
M
M
Goretzki
P E
PE
Duh
Q Y
QY
Clark
O H
OH
D008841:Actin Cytoskeleton / Q000378:metabolism / Q000648:ultrastructure; D000199:Actins / Q000378:metabolism*; D002454:Cell Differentiation; D005544:Forecasting; D006801:Humans; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013964:Thyroid Neoplasms / Q000378:metabolism* / Q000473:pathology / Q000648:ultrastructure; D013972:Thyrotropin / Q000494:pharmacology; D013997:Time Factors; D014407:Tumor Cells, Cultured / Q000187:drug effects
D000199:Actins; D013972:Thyrotropin; D013755:Tetradecanoylphorbol Acetate