A Simple and Useful Method for Simultaneous Screening of Elevated Levels of Expression of a Variety of Oncogenes in Malignant Cells

Abnormal expression of various oncogenes has been implicated in the development of many malignant tumors. Although RNA blotting methods have been used to measure abnormal expression, they involve the time‐consuming process of individually labeling the oncogene probes. To simplify this process we have attempted to develop a new method, termed simultaneous screening, which is based on the synthesis of radiolabeled cDNA corresponding to the mRNA population of malignant cells and on hybridization with various oncogene probes, immobilized on a membrane filter. This method circumvents the time‐consuming process of the prevailing RNA blotting methods and is also sensitive enough to detect accurately a five‐ to ten‐fold level of expression of rare mRNA (∼10 copies per cell). Overexpression of ten oncogenes was detected in a variety of malignant cells and mitogen‐stimulated cells with this method. These results suggest that our simultaneous screening method can be used to examine the overexpression of oncogenes.