Varying oncomodulin mRNA abundance in developing placenta and solid tumors.

An antisense RNA probe complementary to rat oncomodulin mRNA has been prepared by run-off transcription. Blots of RNA isolated from tumors arising from both a chemically-induced hepatoma or virally transformed sarcomas, when probed with this antisense RNA, identified a common single hybridizable RNA of approx. 750 nucleotides, corresponding in size to that found in blots of RNA from rat placenta. Quantitative densitometry of dot blot autoradiographs allowed for relative measurements of oncomodulin mRNA in the various tumors. The increased sensitivity of detection afforded by the antisense probe permitted the measurement of oncomodulin mRNA in the developing placenta, which was not possible using DNA probes. In both tumors and placenta, a plot of mRNA versus protein revealed a direct relationship suggesting transcriptional control of oncomodulin abundance.