High levels of c-myc mRNA were observed in two human tumor cell lines, a giant cell carcinoma of the lung (C-Lu99) and a colon cancer (C1). The increased expression of c-myc in these cell lines, which was comparable with those in cell lines in which the c-myc gene is amplified, was not due to gene amplification. Run-on transcription revealed that the transcriptional rate of the c-myc gene was greatly increased in these cell lines
