Multiplicity of transforming growth factors in human malignant effusions

Abstract

Human malignant effusions were found to contain transforming growth factor (TGF) activity capable of stimulating anchorage independent growth of nontransformed rodent fibroblasts. Bio-Gel P-60 chromatography of acid-ethanol extracts demonstrated the presence of three populations of TGF activities in 57% of malignant effusions. Two activities were similar to those of TGF alpha and TGF beta as judged by their size (Mr approximately equal to 6,000 and approximately equal to 25,000, respectively), biological activity (ability to stimulate anchorage independent growth of NRK fibroblasts in the absence or presence of epidermal growth factor, respectively), and capacity to competitively inhibit binding of 125I-labeled epidermal growth factor to A-431 membranes and 125I-TGF beta to baby hamster kidney fibroblasts, respectively. In addition a third factor which stimulated anchorage independent growth of nontransformed rodent fibroblast and human colonic epithelial cells was also recovered following Bio-Gel P-60 chromatography of extracts from several cytology positive human malignant effusions of patients with colonic and breast carcinoma as well as other malignancies. The latter malignant effusion related transforming growth factor was not present in benign or cytology negative effusions. Malignant effusion related TGF factor was inactivated by sulfhydryl reducing agents, heat, and trypsin treatment but was stable in 1% acetic acid and ethanol. Partial purification was accomplished by chromatography of an acid-ethanol extract on Bio-Gel P-60 followed by high performance liquid chromatography with C18-mu Bondapak to yield a nearly pure protein with apparent molecular weights of 64,000 by sodium dodecyl sulfate-polacrylamide gel electrophoresis when run in nonreducing conditions and 32,000 when run in reducing conditions. Malignant effusion related TGF was able to stimulate anchorage independent growth of nontransformed fibroblasts in the absence of other growth factors. It did not competitively inhibit binding of 125I-labeled epidermal growth factor, 125I-TGF beta, or 125I-labeled platelet derived growth factor. Therefore, this factor isolated from human malignant effusions may be distinct from previously described transforming growth factors. Collectively these observations indicate that human malignant effusions contain a multiplicity of transforming growth factors. It is possible that the malignant effusion related transforming growth factors play a role or reflect the metastatic growth properties of various tumors.