LYMPHOTOXIN GENE-EXPRESSION BY MELANOCYTES AND MELANOMA CELL-LINES AND PERSISTENCE OF UNSPLICED MESSENGER-RNA

Human melanoma cell lines express many different cytokines [1], includ ing lymphotoxin (LT), the production of which has been considered to b e restricted to cells of the lymphocytic lineage in response to cell a ctivation. LT expression by melanomas is constitutive and characterize d by the presence of two mRNAs. In the present paper we report an anal ysis of the origin of the two LT-specific transcripts in four human me lanoma cell lines at different stages of progression and in four melan ocytic cell lines. Reverse transcription-polymerase chain reaction (RT -PCR) performed with primers lying in the first and fourth exons and h ybridization with intron probes showed a spliced and a full-unspliced LT mRNA. This pattern was also displayed by one out of four melanocyte cell lines. Western blot analysis indicated that LT RNA is properly t ranslated to a 23-25 kDa protein and immunocytochemistry showed its lo calization within the cytoplasm and on the cell membrane.