Epithelial tissue-derived growth factor-like polypeptides.

Abstract

SW-13 cells, derived from a human adenocarcinoma of the adrenal cortex, formed only a few small colonies when suspended in soft agar at low cell densities. The number and size of colonies increased dramatically following stimulation with serum-free medium conditioned by SW-13 cells, indicating the possibility of autostimulation in these malignant cells. Evidence is presented suggesting that SW-13 cells form progressively growing soft agar colonies upon stimulation by epithelial tissue-derived growth factor-like polypeptides. Both acid-ethanol extracts and conditioned media from three human carcinoma cell lines (A431, D562, and A549) caused similar increases in colony number and size of SW-13 cells. Extracts from 26 of 32 freshly excised human carcinomas and five freshly excised nonneoplastic human kidneys and one human lung stimulated soft agar growth of SW-13 cells as well. None of the nine extracts from nonepithelial human solid malignant tumors stimulated SW-13 cells. However, a benign nonepithelial tumor (uterine leiomyoma) caused a low level of soft agar growth of SW-13 cells. Cell extract from A204 human sarcoma cells and both conditioned medium and acid-ethanol cell extract from A375 human melanoma cells lacked SW-13 activity, whereas medium conditioned by A204 cells stimulated soft agar growth of SW-13 cells. Chemical and physical treatment data indicated that the epithelial tissue-derived growth factor-like substances are acid- and heat-stable polypeptides with disulfide bonds. The major peak of this activity had an apparent molecular weight of 20,000 to 22,000 and was clearly separable from transforming growth factors reported previously which stimulate colony formation by nontransformed mouse AKR-2B and rat NRK cells. The major peaks of SW-13, NRK, and AKR-2B activity could be separated by high-performance liquid chromatography. This SW-13 activity induced irreversible anchorage-independent growth of SW-13 cells and an increase in DNA synthesis as measured by [3H]thymidine incorporation.