Expression of IL-2 receptors in human melanoma cells

Melanoma cells can secrete several cytokines and express various cell surface molecules, such as the intercellular adhesion molecule ICAM-1, class II histocompatibility antigens, and the CALLA antigen, typically found in cells of the immune system. We have investigated the possible expression of interleukin-2 (IL-2) receptors in melanoma using monoclonal antibodies specific for the p55/alpha chain (TAC antigen) and the p75/beta subunit. Flow cytometric analysis of cultured melanoma cells showed the presence of low levels of the TAC antigen and of the beta chain on the surface of several cell lines. Similar results were obtained in vivo by immunohistochemistry on cryosections prepared from cutaneous and ocular melanoma explants. Positive staining was observed for the alpha chain of the IL-2 receptor in a high percentage of tumour cells. The beta chain could also be detected, although in a limited number of specimens. Analysis of RNA from melanoma cell lines by Northern blot showed the presence of typical 4 Kb transcripts for the p75 subunit, while low-abundance message for the p55 chain could be detected using combined reverse transcription/polymerase chain reaction analysis. Together, these results suggest that melanoma cells may express high affinity receptors for IL-2.