New species of hybridizable nuclear RNA in breast cancer cells.

Abstract

Summary The rapidly labeled nRNA in normal mammary cells and in transplantable breast cancer cells of mice and rats were compared by the techniques of RNA-DNA hybridization and hybridization-competition. The RNA9s from the normal and neoplastic cell types showed similar reactivity toward DNA9s from various species and reacted with them in proportion to known genetic relatedness. The specificity of the competition reaction between breast cancer RNA- 3 H and homologous DNA was shown by the competition of heterologous RNA from various species in proportion to the known relatedness of the DNA9s from which they were transcribed. While the unlabeled breast cancer RNA9s competed with RNA- 3 H from breast cancer cells to 92 to 94% of the theoretical value for identical RNA populations, unlabeled normal mammary RNA competed to only approximately 50 to 65% of this value. Unlabeled RNA from breast cancer cells competed completely with labeled RNA from normal mammary cells. These findings indicate that these breast cancer cells synthesize species of nuclear RNA which either are not formed by normal mammary cells or are present in nonneoplastic mammary cells in undetectably low concentrations.