Introduction
Decades after the discovery that p53 plays a central role in the human body’s defence against cancer, the development of effective therapeutic strategies to target mutant p53 cancers still remains an unmet need in oncology. Several compounds, including APR-246, have been developed that target mutant p53 protein and restore wild-type p53 function in cancer cells. APR-246 is the most advanced in terms of clinical development, with ongoing Phase Ib/II trials in solid and haematological malignancies. Currently, little is known about potential mechanisms of resistance to reactivating mutant p53, and there has been no proteome-wide analysis of APR-246 off-target activities to date.
Method
Using oesophageal cancer as a model, this study employed a multiomics approach, combining genome-wide CRISPR/Cas9 loss-of-function and gain-of-function screens with whole-cell proteomics to identify novel mechanisms that govern cellular resistance and sensitivity to APR-246. To broaden the validity of our screening approaches, we are mining data from the Cancer Therapeutics Response Portal to compare APR-246 activity in over 800 cancer cell lines to other anti-cancer agents in order to uncover additional mechanisms of action.
Results
From the knockout screen we have identified multiple genes involved in folate and formate metabolic pathways to regulate cellular response to APR-246 in vitro. Additionally, results from the proteomics screen have identified novel protein targets for APR-246, including metabolic enzymes associated with the folate cycle. Consistent with these findings, altering folate and formate concentrations alters sensitivity to APR-246. Thus, we have identified new potential strategies to target mutant p53 cancers in combination with APR-246, and potential biomarkers that could help guide the use of APR-246 in the clinic.