Complement Dependent Inhibition of RNA Synthesis in Malignant Melanoma Cells 1

Abstract

The RNA synthesis of human melanoma cells in suspension is estimated by the uptake of tritiated uridine (³HU) after incubation with autologous, homologous serum from other patients with malignant melanoma and normal control serum with active and inactivated added complement. The total amount of labelled precursor incorporated is determined by extracting the acid/alcohol soluble material, dissolving the final precipitate in a solvent and mixing with scintillation fluid. Each pot is then counted in a Packard-3 liquid scintillation counter. The pulses recorded reveal the rate of RNA synthesis in the cells after incubation with the tested sera and inversely indicate the extent of the cytotoxic action exerted by serum antibodies upon the target cells in the presence of active complement. A test is positive when the uptake of ³HU in a pot containing the precipitate of autologous and/or homologous action is at least 20 per cent less than the average pulses for the control pots.

Tumor cell suspensions from 44 melanoma patients were tested against their own sera, against the sera from other melanoma patients and against sera from normal healthy individuals. Autologous cytotoxic effect was recorded in 11 cases (approximately 30 per cent of the cases). Homologous positivity was displayed in 5 cases. Cytotoxic action, being quantitatively determined, diminished with the spread of the disease.