Detection of the ras p21 gene product in human leukemias by flow cytometry

To date, the detection of oncogene products in human neoplasms has relied primarily upon immunoblot analysis of specimen homogenates. Herein are reported the results of a study using flow cytometry to evaluate the expression of the ras p21 gene product in both fresh and cryopreserved specimens of human acute leukemias. Cell lines known to express ras p21 were used as positive controls and normal peripheral blood was used as a negative control. Intensity of staining for ras p21 (Ip21) was expressed as the ratio of the peak channel numbers of the peak generated by staining with anti-ras p21 to the peak obtained by staining with an isotype control. Using this method, 21 out of 32 clinical specimens of acute leukemia were found to express ras p21 in elevated amounts compared to normal peripheral blood. Flow cytometry appears to be a practical method for routine screening of clinical specimens for the expression of oncogene products on individual cells rather than cell homogenates.