Appropriate expression and function of the transcription factor p53 is required for effective tumour suppression and the prevention of cancer. This is evident by the high mutational rate of p53 (~50%) found across the spectrum of human cancers. p53 is activated by diverse cellular stresses, including activation of oncogenes, accumulation of reactive oxygen species and DNA damage. Once activated, p53 can initiate a range of cellular tumour suppressive responses, such as apoptotic cell death, cell cycle arrest, cell cycle senescence and various DNA repair processes. However, it remains unknown which of these many p53-induced processes are critical for tumour suppression.
To address this question, we aim to characterise the response of a range of human tumour-derived cell lines of different cell origins containing wild-type (wt) p53 to p53 activation and to determine the cellular factors which govern the nature of their response.
In our experiments, we use the non-genotoxic p53 activator, nutlin-3a (an inhibitor of MDM2, the critical negative regulator of p53), to induce a p53 response and then measure p53 pathway activation. Cell cycling was assessed by flow cytometry using DAPI staining for DNA content. Apoptotic cell death was measured by flow cytometry using staining with Annexin-V plus propidium iodide. Cellular senescence was assessed using staining for senescence associated β-galactosidase.
We found that the different human tumour-derived cell lines undergo only one main p53-mediated cellular response upon nutlin-3a treatment in a dose-dependent manner. This research will be the foundation to further investigate and determine what causes cells to commit to different responses following p53 activation.