INTERLEUKIN-2 EXERTS AUTOCRINE STIMULATION ON MURINE T-CELL LEUKEMIA GROWTH

As it has been suggested that an autocrine mechanism may control tumou r cell growth, in this work cells from a spontaneous murine T lymphocy te leukaemia (LB) expressing the interleukin-2 receptor (IL-2R) (CD25) were evaluated in vitro for IL-2-mediated autocrine growth. Cells gre w readily in culture and proliferation was enhanced by the addition of recombinant IL-2 but inhibited by monoclonal antibodies against eithe r IL-2 or IL-2 receptor, in the absence of exogenous IL-2. Cyclosporin A also inhibited LB cell growth. However, when exogenous IL-2 was add ed together with cyclosporin A, cell proliferation proved similar to c ontrols. Using reverse transcription polymerase chain reaction (PCR), mRNA for IL-2 was found to be present in tumour cells. Our findings su pport the hypothesis that LB tumour cell proliferation is mediated by an autocrine pathway involving endogenous IL-2 generation, despite the fact that these cells are not dependent on exogenous IL-2 to grow in culture.