ACTIN CYTOSKELETAL ORGANIZATION LOSS IN THE BENIGN-TO-MALIGNANT TUMOR TRANSITION IN CULTURED HUMAN COLONIC EPITHELIAL-CELLS

  • 1 January 1984
    • journal article
    • research article
    • Vol. 44  (7) , 3040-3050
Abstract
Culture methods were developed to allow the normal cellular migration of the cells comprising the colonic epithelium sheet to flatten into a patch on the surface of a Petri dish. Actin cytoskeletal organization was analyzed in such epithelial patches derived from several human colonic adenocarcinomas and adenomas. The actin cytoskeleton was visualized by fluorescence microscopy after the cells were stained with rhodamine-conjugated phalloidin. This drug has a very high affinity for actin filaments and a much lower affinity for monomeric actin. Actin organization was scored from 0 (no cables) to 5 points (extensive intercellular cable network). The phalloidin-stained actin in 7 adenocarcinomas had a predominantly granular fluorescence pattern with very little cable organization, scoring an average of 0.9 .+-. 0.8 (SD). Three established human colon carcinoma cell lines contained no cables by this analysis, scoring 0.0 .+-. 0.0. All 12 of the cultured adenomas had extensive actin cable networks, scoring an average of 4.3 .+-. 0.4. There was no statistical difference between adenomas of differing histopathology class and malignant potential. Cytoskeletons of plasminogen-activator-secreting late-stage preneoplastic cells from adenomas became disorganized by exposure to 12-O-tetradecanoyl-phorbol-13-acetate [TPA] or another tumor promoter, teleocidin B. They scored, respectively, average actin organization values of 0.0 .+-. 0.0 and 0.4 .+-. 0.6. Nonplasminogen-activator-secreting early-stage preneoplastic cells from less advanced benign tumors were unaffected by TPA or teleocidin B and retained extensive actin organization. Most, if not all, adenocarcinomas arise from preexisting preneoplastic adenomatous cells. Loss of actin organization appears to mark the transition of noninvasive benign colonic tumors to invasive malignant tumors in humans. This transition is mimicked in vitro by exposure of certain late-stage preneoplastic cells to a tumor promoter which induces secretion of a plasminogen activator.