In situ detection of c-myc mRNA in adenocarcinomas, adenomas, and mucosa of human colon.

We used a sensitive RNA:RNA in situ hybridization technique to study steady-state levels of c-myc proto-oncogene mRNA in primary human colon adenocarcinomas, villous adenomas, and normal mucosa samples. Frozen tissue sections, fixed in 4% buffered paraformaldehyde, were hybridized to 35S-labeled anti-sense transcripts of a c-myc clone and processed for autoradiography. The specificity of the hybridization was controlled by using 35S-labeled plasmid transcripts as a negative control, while RNA preservation in the tissue sample was assessed by using 35S-labeled anti-sense transcripts of a murine 28S rRNA clone. c-myc RNA was detectable in all the carcinomas (eight) and villous adenomas (four), but steady-state levels varied from high to low in different tumors with similar histology. Low levels of c-myc RNA were detected in epithelial stem cells of some of the normal mucosa samples (five). No genetic alterations of the c-myc locus were found by Southern analysis of DNAs extracted from the carcinomas.