I propose to continue to study the mechanisms of growth, differentiation, and adhesion control of human colon carcinoma cells. Since perturbation of such biological processes is the hallmark of malignant transformation, a better understanding of these processes in colon carcinoma may lead to better management and control of this highly refractory and malignant disease. The control of growth, differentiation, and adhesion are complex biological processes which are very poorly understood in normal cells, and even less is known about the control of these processes in colon carcinoma. However, polypeptide growth factors, adhesion molecules, and adhesion receptors are known to be key players in this realm of biological control. Several new hypotheses have originated from my R29 work. They are: 1) Transforming growth factor (TGF)-beta1 works in concert with the adhesion molecules fibronectin and laminin in regulating cellular adhesion, proliferation, and differentiation. 2) The induction of the expression of adhesion molecules and adhesion receptors by TGF-beta1 is a tightly coupled event. 3) Protein kinase C (PKC) is functionally involved in the postreceptor or intracellular mechanism of action of TGF-beta1. Accordingly, the Specific Aims are proposed to test these hypotheses using a human colon carcinoma cell line that is highly sensitive to TGF-beta1. I will identify and characterize the adhesion receptors that are under the control of TGF-beta1, fibronectin, and laminin. The use of fibronectin and laminin antisense expression vectors, and anti- fibronectin and anti-laminin antibodies in blocking experiments are also proposed to determine the regulation of the expression of these adhesion molecules and their receptors at the cellular level and the functional role of fibronectin and laminin in the cellular responses to TGF-beta1. Finally, by using a combination of antisense PKC expression vectors and PKC enzyme inhibitors, I propose to test the functional role of PKC in TGF-beta1 action.
