This study documents the ability of substrata material derived from well but not poorly differentiated colon carcinoma cells to alter the biological characteristics of a separate colon carcinoma cell line (MOSERsf). To assess changes induced by the presence of these substrata, MOSERsf cells were screened for (a) morphological features, (b) secretion of carcinoembryonic antigen (CEA), (c) alteration of urokinase levels, and (d) sensitivity to the growth-inhibitory peptide transforming growth factor β. Morphologically, MOSERsf cells grown on plastic displayed a rounded shape and could be detached by agitation. Subculturing of these cells onto substrata laid down by well differentiated (mature) colon carcinoma cells resulted in cell attachment and spreading. These changes did not manifest themselves when cells were plated on material derived from poorly differentiated (primitive) colon cells.
Conditioned medium from MOSERsf cells grown on plastic or on colon-derived material from the well and poorly differentiated colon cells were compared for CEA levels. Substrata derived from undifferentiated cells were without effect on assayable CEA (substrata absent, 1.4 ng/ml/106 cells/72 h; substrata present, 1.4–1.7 ng/ml/106 cells/72 h). However, growth of MOSERsf cells on material deposited by well differentiated colon cells resulted in a 3-fold increase in the level of CEA.
Spent medium was also analyzed for urokinase. A high level of the protease (20.3 ng/ml/106 cells/72 h) was expressed by MOSERsf cells. The concentration of the enzyme was reduced by over 50% when MOSERsf cells were propagated on substrata laid down by well differentiated cells.
An enhanced sensitivity to the growth-retarding effects of transforming growth factor β was seen with certain substrata. On plastic, transforming growth factor β inhibited proliferation of MOSERsf cells with a median effective concentration of 0.65 ng/ml. However, on substrata from mature but not primitive cells, MOSERsf cells exhibited an increased sensitivity to the peptide (median effective concentration, 0.16 ng/ml).
Colon-derived material obtained from both well differentiated and poorly differentiated colon carcinoma cells was compared after [35S]methionine metabolic labeling. More [35S]methionine was incorporated into the material from the “mature” colon cells. The substrata could also be distinguished by quantitative differences in a number of high molecular weight proteins. Immunofluorescence of colon-deposited material revealed the presence of laminin and fibronectin.
This work was supported by NIH Grant CA34432.