DIFFERENTIAL MESSENGER-RNA LEVELS OF C-MYC, C-FOS AND MHC CLASS-I IN SEVERAL CLONES OF A MURINE FIBROSARCOMA

We have evaluated the relationship between MHC class-I, c-myc and c-fos proto-oncogene expression in several clones of a methylcholanthrene-induced fibrosarcoma (GR9) which originated in a BALB/c mouse. These clones represent a heterogeneous population and differ markedly with regard to H-2 class-I cell-surface expression, local tumor growth, NK sensitivity and metastatic potential. In the present study we show that cell-surface expression of MHC class-I antigens correlates inversely with levels of c-myc mRNA transcripts. On the other hand, mRNA levels of c-fos are correlated directly with the amount of mRNA of MHC class I. Treatment of the B9 clone with gamma interferon increased mRNA transcription and surface expression of H-2 class-I antigens, while c-myc transcription was simultaneously down-regulated. In contrast, c-fos mRNA levels remained unaltered.