CHARACTERIZATION OF MUTATED TRANSFORMING GROWTH FACTOR-BETA-S WHICH POSSESS UNIQUE BIOLOGICAL PROPERTIES

Transforming growth factor-beta (TGF-beta) is a potent regulator of cell growth and differentiation. On the basis of the crystal structure df TGF-beta 2, we have designed and synthesized two mutant TGF-beta s, TGF-beta 1(71 Trp) and TGF-beta 1(Delta 69-73). Although both of these molecules inhibited the growth of Mv1Lu mink lung epithelial cells and LS1034 colorectal cancer cells, which are affected equally by TGF-beta 1 and TGF-beta 2, TGF-beta 1(Delta 69-73) was much less potent than TGF-beta 1 or TGF-beta 1(71 Trp) at inhibiting the growth of LS513 colorectal cancer cells which are growth-inhibited by TGF-beta 1 but not TGF-beta 2. Both TGF-beta 1 (71 Trp) and TGF-beta 1(Delta 69-73) increased levels of mRNAs for fibronectin and plasminogen activator inhibitor with Mv1Lu cells, whereas only TGF-beta 1(71 Trp) and not TGF-beta 1(Delta 69-73) up-regulated the mRNA level of carcinoembryonic antigen in LS513 cells. The expression level of carcinoembryonic antigen mRNA in LS1034 cells was not altered by either wild-type or mutant TGF-Ps. Receptor labeling experiments demonstrated that TGF-beta 1(71 Trp) bound with high affinity to the cell-surface receptors of Mv1Lu, LS1034, and LS513 cells while TGF-beta 1(Delta 69-73) bound effectively to the receptors of Mv1Lu and LS1034 cells but much less to the receptors on LS513 cells. In contrast, binding of TGF-beta 1(71 Trp) and TGF-beta 1(Delta 69-73) to endoglin and the type II receptor of human umbilical vein endothelial cells (HUVECs) was similar to TGF-beta 1, not TGF-beta 2. These results demonstrate the feasibility of synthesizing TGF-beta mutants with unique biological properties.