Effect of hormones on the killing by antibody and complement of tumor cells treated with proteolytic enzymes.

Line-10 guinea pig hepatoma cells are normally resistant to killing by antibody plus GPC but they are susceptible to killing by antibody plus HuC. Pretreatment of the cells with selected proteolytic enzymes renders the cells susceptible to killing by antibody plus GPC, whereas pretreatment with polypeptide, catecholamine, or steroid hormones renders the cells more resistant to killing by antibody plus HuC. Hormone pretreated tumor cells incubated with proteolytic enzymes remained resistant to antibody-GPC-mediated killing. Enzyme-pretreated cells incubated with hormones were either sensitive or resistant to antibody-GPC-mediated killing depending on the enzyme used to pretreat the cells, the enzyme concentration, the hormone class, and the specificity of the antibody used to sensitize the cells. The enzyme pretreated cells were able to bind amounts of hormone sufficient to render the cells resistant to humoral immune killing. These results suggest that the hormones exert their effects on certain areas of the tumor cell membrane rather than having a generalized effect on the cells. It is postulated that proteins, along with complex lipids, participate in the mechanism whereby tumor cells resist humoral immune killing.