Conditioned media of carcinoma cells cultured in hypoxic microenvironment stimulate angiogenesis in vitro; relationship to basic fibroblast growth factor.

Conditioned media (CM) harvested from human pulmonary squamous cell carcinoma (QG56), pulmonary small cell carcinoma (QG90) and gastric adenocarcinoma (MKN28) cultivated under hypoxic conditions (3% oxygen), enhanced the angiogenic activity in vitro more than those obtained under normoxic cultivation (20% oxygen). The total length of the tube structures formed by bovine capillary endothelial cells (BCEs) in the CM cultured at 3% oxygen was about 1.5 (QG56 and MKN28) or 1.9 (QG90) times longer than that at 20% oxygen. Tube formation was diminished by the preincubation of CM with anti-basic fibroblast growth factor (bFGF) IgG. After performing the fractionations of the CM and the crude extracts of cell lysates cultured using a heparin-Sepharose column, the mitogenic activity in the CM from all cancer cells at 3% oxygen was about twice that of CM at 20% oxygen, while it decreased in the cell lysates at 3% oxygen to about 40% of those at 20% oxygen. This mitogenic activity of BCEs in the CM from all cancer cells was almost totally suppressed by anti-bFGF IgG, but not with anti-vascular endothelial growth factor IgG. Hypoxia is an important factor in tumor angiogenesis by bFGF or bFGF-like molecule(s) derived from tumour cells.