Inhibition of antibody-complement-mediated killing of tumor cells by hormones.

ABSTRACT

Line 1, a chemically induced guinea pig hepatoma, is susceptible to killing by anti-Forssman immunoglobulin M antibody and guinea pig complement. When these tumor cells are pretreated at 37 degrees with 10(-4) to 10(-11) M concentrations of the polypeptide hormone insulin, with the catecholamine L-epinephrine-HCl, or with the glucocorticoid steroids hydrocortisone sodium succinate or prednisolone sodium succinate, the cells show a marked reduction in their suseptibility to killing by antibody and guinea pig complement; pretreatment at 0 degrees is ineffective. Similar results were obtained with another antigenically distinct guinea pig hepatoma (line 10) when tested with anti-Forssman immuno-globulin M or specific antitumor antibodies and human complement. The ability of the hormones to render the cells resistant is dependent on time, temperature, and hormone concentration. The effect of hormone treatment is maximal between 30 and 60 min and is reversible within 4 hr even in the continued presence of hormone. Treatment of line 1 cells with up to 10,000-fold greater concentrations of the less biologically active or inactive analogs, DL-epinephrine, beta-estradiol, testosterone, or proinsulin has no effect on the susceptibility of the cells to killing by antibody and guinea pig complement. The effect of hormone treatment is not due to a direct inactivation of bound or fluid-phase complement components by the hormones or to a decrease in the ability of the cells to bind complement-fixing antibody.

ABSTRACT

PIP Various aspects of hormone treatment of tumor cells are reported; it is shown that following treatment with certain hormones, the cells are less susceptible to killing by antibody and complement. The diethylnitrosamine-induced guinea pig hepatoma, designated Line 1, is susceptible to killing by anti-Forssman immunoglobulin M (IgM) antibody and guinea pig complement (GPC) but not by specific antitumor antibody and GPC. The antigenetically distinct Line 10 hepatoma, when sensitized with either antibody, is susceptible to killing by human complement (HUC) but not by GPC. Strain 2 of Servall-Wright male guinea pigs were used. 2 antigenetically distinct diethylnitrosamine-induced hepatic tumors (ascites form), Lines 1 and 10, passed in Strain 2 guinea pigs, were collected and suspended in RPMI 1640-20% FCS. Toxicity assays were performed in VBS-gel. The hormones used were hydrocortisone sodium succinate, prednisolone sodium succinate, NSC9151, bovine insulin, L-epinephrine methyl ether HC1, DL-epinephrine, beta-estradiol, testosterone, pork insulin, chicken insulin, pork proinsulin, pork DAA insulin, and the A and B chains of pork insulin. Tumor cells were cultured in 10-ml volumes of RPMI 1640-20% FCS in plastic Petri dishes. After incubation, cell cultures were washed 5 times in VBS-gel and tested for their susceptibility to killing by antibody and complement. Rabbit antiserum to sheep Forssman antigen was prepared and stored at -20 degrees until used. Tumor specific rabbit Antilines 1 and 10 antisera were prepared and similarly stored. Results of tests show that Line 1 tumor cells incubated in a medium containing the polypeptide hormone, insulin, the catecholamine, L-epinephrine HCl, or the glucocorticoid steroids, hydrocortisone sodium succinate, or prednisolone sodium succinate were rendered resistant to killing byanti-Forssman IgM antibody and GPC. This effect was dependent on hormone concentration, temperature, and time. Effects were reversible. Similar results were obtianed with Line 10 cells under attack by specific antitumor and HUC or anti-Forssman antibodies. Less physiologically active analogs of the hormones did not have this effect. Tumor cells showed maximum resistance within 30-60 minutes of exposure to the hormones and reverted to the sensitive state within 4 hours. Resistance of the cells to killing was observed at 37 degrees but not at 0 degrees. It is concluded that the effect of hormone treatment was not due to a direct inactivation of bound or fluid-phase complement components by the hormones or to a decrease in the ability of the cells to bind complement-fixing antibody.