Growth stimulating activity of lung extract on lung-colonizing colon 26 clones and its partial characterization

The effects of lung tissue extract on the cell growth of eight colon 26 tumor clones, four highly and four poorly lung-colonizing clones, were examined in vitro. Addition of lung extract to serum-free medium stimulated the growth of all four of the highly lung-colonizing clones and one of the poorly lung-colonizing clones, but it had minimal effect on the other three poorly lung-colonizing clones. These results indicate that the lung extract contains a growth stimulating activity; it selectively stimulated some of the colon 26 clones including highly lung-colonizing ones. The growth stimulating activity was not dialyzable, was partially destroyed by heating at 56 degrees C or 80 degrees C for 30 min and completely destroyed by trypsin. These results suggest that the activity resides in a protein. Gel filtration chromatography of lung extract on Sephacryl S-200 revealed that the active component was eluted in a molecular weight range of 90,000-120,000.