The three isoforms of TGF-beta expressed in mammals are functionally interchangeable in most in vitro assay systems, but they have distinctive activities on certain cells. To identify specific functional regions of the TGF-betas as well as to identify receptor components critical for TGF-beta action, we are utilizing colon carcinoma cells where the activities of TGF-beta1 on inhibition of growth are several hundred-fold more potent than that of TGF-beta2. To define specific regions of the TGF-beta molecule responsible for these differences in activities, we developed a system for expression and purification of recombinant TGF-betas engineered to have either mutations or substitutions of homologous regions of different isoforms, based on the 3-dimensional structure of TGF-beta. Using colorectal carcinoma cells which show selectivity for TGF-beta 1 and 3, we have identified another region of the molecule (amino acids 69-73) which may be involved in isoform-specific receptor binding. We have also demonstrated, using assays which measure in vitro binding to the soluble TGF-beta type II and III receptors and to the TGF-beta latency-associated protein (LAP), specific regions of the ligands which interact with these proteins. In a related aspect of this problem, we are attempting to characterize the expression of TGF-beta receptors on the colon carcinoma cells and to identify possible down-stream signalling intermediates. These studies are important both in identifying the specific elements of the receptor binding system which mediate isoform-specific effects, and in identifying putative signalling intermediates, the deletion or mutation of which would result in loss of TGF-beta responsiveness. It is proposed that such intermediates will have tumor-suppressor-like activity.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Intramural Research (Z01)
Project #
1Z01CP005051-17
Application #
5201457
Study Section
Project Start
Project End
Budget Start
Budget End
Support Year
17
Fiscal Year
1995
Total Cost
Indirect Cost
Name
Division of Cancer Epidemiology and Genetics
Department
Type
DUNS #
City
State
Country
United States
Zip Code