Cisplatin is used as first-line chemotherapy treatment for patients diagnosed with various types of malignancies, such as leukemia, lymphomas, breast, testicular, ovarian, head and neck, non-small lung, cervical cancers, and sarcomas. However, our recent study provided evince on the activation of DNA repair genes in p53 wild-type of breast, non-small lung and liver cancer, but not in mutated triple-negative breast cancer or p53 deficient myeloid leukemia.
RNA- and ChIP-Seq, cellular technics (toxicity, confocal immunostaining, western blot, real-time PCR) we found p53 wild-type interaction with EP300 at the promoters of PARP1, BRCA1 and RAD51.
RNA-Seq data confirmed that pharmacological inhibition of ATM/ATR, EP300 and transient silencing of p53 prevent overexpression of genes contributing to nucleotide excision repair (GO:0006289), double-strand break repair via homologous recombination (GO:0000724) and nonhomologous end joining (GO:0006303) and DNA damage response, signal transduction by p53 class mediator resulting in cell cycle arrest (GO:0006977). This was not observed in p53 single-nucleotide or deletion mutants. Since transcription of majority of genes involved in DNA repair is controlled by cell cycle progression via E2F activity, we paid attention to p53 interaction with chromatin upon cisplatin treatment. ChIP-Seq data confirmed the enrichment of approximately 1200 genomic locations, where only 7% overlapped with E2F1, but 22% with EP300 peaks. Prediction of target genes linked p53 enriched regions with genes assigned to nucleotide-excision repair and DNA damage recognition (GO:0000715). Cisplatin caused p53 co-localization with EP300 in the nuclei, but E2F1 silencing restrained the enrichment of both proteins on chromatin. Pharmacological inhibition of ATR/ATM, EP300 and p53 silencing considerably increased cisplatin cytotoxicity. The same effect of EP300 inhibitors on cisplatin cytotoxicity was observed in cisplatin-resistant p53 wild-type breast and non-small lung cancers.
ATM/ATR-p53/E2F1/EP300 pathway allows cells to increase resistance to cisplatin. Addition of EP300 inhibitors may improve cisplatin-based chemotherapies of p53 wild-type cancers and improve chemotherapy outcome.
The authors.
National Center for Research and Development (LIDER/22/0122/L-10/18/NCBR/2019) and Ministry of Education and Science (IDUB-60/2021).
All authors have declared no conflicts of interest.