HAF, hepatoma aggregation factor produced by Streptomyces sp. strain No. A-6143

We searched for a new cell aggregation factor for hepatoma AH109A cells, and found one we called HAF in the culture filtrate of Streptomyces sp. strain No. A-6143 isolated from a soil sample. HAF was purified by salting-out with ammonium sulfate. DEAE-cellulose column chromatography, gel filtration on Sephadex G-100, and hydroxylapatite column chromatography, HAF was glycoprotein which had a molecular weight of about 73,000. HAF was stable from pH 6 to 8 at 37 degrees C and up to 40 degrees C at pH 8.0 and the aggregation activity of HAF was maximum around pH 8 at 30 degrees C. The activity was not influenced by some saccharides, but it was inhibited by EDTA and EGTA: moreover HAF activity was restored by the addition of calcium ions. HAF aggregated hepatoma AH136B and COS-7 cells as well as hepatoma AH109A cells, but it was inert to other cancer cells and human erythrocytes. These properties proved that HAF is completely different from other aggregation factors for cancer cells so far reported.