Extracellular matrix (ECM) proteins and their cell surface receptors called integrins are known to play an important role in the growth, differentiation, migration, metastasis, and invasion of cancer cells. A number of studies have shown that decreases in expression of fibronectin (FN) and its receptor alpha5, Beta1 intergrin, are associated with increased malignancy in mouse transformed fibroblasts, human neuroblastoma and carcinoma of breast, colon and pancreas. In contrast, when alpha5,Beta1 integrin was overexpressed in tumorigenic Chinese hamster ovary cells, they became nontumorigenic. A limited number of studies have also suggested that interaction between ECM and integrins may modulate growth factor action. We have observed that the expression of FN and its receptor alpha5 subunit is cell cycle-dependent indicating the involvement of growth factors in the control of their expression and their possible involvement in regulating cell cycle progression. These observations have led to the hypothesis that growth factors control the expression of FN and alpha5 Beta1 integrin which in turn modulate the expression and function of growth factors and their receptors to maintain growth regulatory and tumorigenic phenotypes of human cancer cells. The following specific aims are designed to test this hypothesis. 1. Characterization of the roles of FN and alpha5 Beta1 integrin in conferring the phenotypes of human cancer cells (breast carcinoma MCF-7 cells, prostate carcinoma PC-3 cells, colon carcinoma Geo cells, lung carcinoma A549 cells, fibrosarcoma HT1080 cells and glioblastoma U138 cells) with respect to their proliferation, mitogenesis, attachment, cloning efficiency in soft agar, invasion in Matrigel, and in vivo tumorigenicity using controlled antisense and/or sense expression techniques. 2. Determination of the roles of FN and alpha5 Beta1 integrin in modulating the expression and function of growth factors and their receptors using FN and alpha5 subunit antisense and alpha5, subunit sense transfected cells. 3. Determination of the effect of cell cycle and growth factors on the expression of FN and alpha5 subunit at transcriptional and post- transcriptional levels in these cancer cells. Completion of this project should benefit the assessment of using FN and alpha5 Beta1 integrin as novel targets for tumor prevention and anti- cancer therapy.
