In vitro killing of tumor cells by macrophage factors obtained from cancer patients and normal donors.

Macrophages obtained from cancer patients as well as normal volunteers secrete products that are cytotoxic to malignant but not normal cells. The susceptibility of the target cells varies considerably. These macrophage products have the following characteristics: 1) They are strongly absorbable to cellulose nitrate membrane filter materials. 2) They are quantitatively elutable with dilute hydrochloric acid. 3) They are relatively stable over a wide range of temperatures. 4) They are nondialyzable. When these macrophage products were subjected to polyacrylamide gel electrophoresis, it was found that the tumoricidal products secreted by the macrophages obtained from normal donors and cancer patients could be resolved into 8-10 protein bands, which were qualitatively identical. However, the products obtained from the macrophages of cancer patients differed quantitatively from the products obtained from the normal donor's macrophages. Utilizing column chromatography, the products secreted by the macrophages of cancer patients and normal donors were further purified. Eleven protein fractions with tumoricidal properties were recovered. In 7 of the 11 fractions, the cytotoxic capacity of the products secreted by the cancer patients' macrophages was equivalent to that of the normal donors. One fraction (MW 25,000) isolated from the cancer patients' macrophage supernatants was more cytotoxic than the macrophage product obtained from normal donors. In contrast, a second fraction (MW 45,000) isolated from the cancer patients' macrophage supernatants was less cytotoxic than the normal donors' macrophage products.