Detection of human lung epithelial cell growth factors produced by a lung carcinoma cell line: use in culture of primary solid lung tumors.
Serum-free medium conditioned for 72 h by a human bronchioloalveolar carcinoma of lung, A549-1, stimulated the colony formation of normal human bronchial epithelial cells, newly cultured cells from human solid lung tumors, and established human lung tumor cell lines, including A549-1 cells themselves. This activity was concentration dependent and was stable to acid. Growth factors in A549-1 conditioned medium (CM) supported culture of solid lung tumors; primary cell cultures were obtained from nine of 10 solid lung tumors of non-small cell origin and from one small cell tumor using A549-1 CM. In addition, three cell lines have been established to date from these primary cultures. Gel filtration of concentrated A549-1 CM on Biogel P-10 separated the growth promoting activity into four regions of apparent Mr 70,000, 12,000, 8,000, and 6,000, and two broad regions of apparent Mr 3000-5000. All but the 12,000 Mr fraction contained activity which competed for specific binding of epidermal growth factor (EGF) to A431 cell membranes. CM was superior to both EGF and TGF alpha in stimulating growth of normal and neoplastic lung cells. EGF also was inhibitory to tumor cells while TGF alpha stimulated both normal and tumor cell growth. TGF beta was also found in CM but inhibited normal and neoplastic lung epithelial cell growth. Of other substances tested, ILGF-I stimulated colony formation. The results suggest that autocrine factors may be important in non-small cell lung tumor cell growth and that differences in response to EGF and TGF alpha may provide the basis for selective culturing of normal and neoplastic lung epithelial cells.