Flow cytometric quantitation of C-myc and P53 proteins in bovine papillomavirus type 1-transformed primary mouse...

Bovine papillomavirus type 1 (BPV-1)-transformed mouse fibroblast cell lines were analyzed via flow cytometry (FCM) for expression of p53 and c-myc proteins along with their DNA content. In comparison to the nontransformed control cell line, significantly elevated levels of both the p53 and the c-myc protein were present in some but not all of the transformed cell lines. Quantitation of p53 and c-myc proteins in cell lines containing BPV-1 DNA revealed that the tumorigenic cell lines expressed higher levels of both the p53 (P = 0.0034; Mann-Whitney U test) and the c-myc protein (P = 0.0039; Mann-Whitney U test) as compared to the nontumorigenic cell lines. On average, at least 9,000-10,000 p53 or c-myc protein molecules per cell were detected in the transformed tumorigenic cell lines. These results show that quantitative FCM can be reliably used to detect very low levels (3,000 molecules per cell) of specific protein, and FCM is a useful tool to study the virus-induced changes in the levels of nuclear proteins within a cell population and in tumorigenesis.