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 3 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 5 freshly excised nonneoplastic human kidneys and 1 human lung stimulated soft agar growth of SW-13 cells as well. None of the 9 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 MW of 20,000-22,000 and was clearly separable from transforming growth factors reported previously which stimulate colony formaton by nontransformed mouse fibroblast AKR-2B and rat NRK kidney cells. The major peaks of SW-13, NRK and AKR-2B activity could be separated by high-performance liquid chromatography. This SW-13 activity induce irreversible anchorage-independent growth of SW-13 cells and increase in DNA synthesis as measured by [3H]-thymidine incorporation.