Physical Poster + E-Poster Presentation 34th Lorne Cancer Conference 2022

Characterising therapy-induced senescence to identify novel targeting approaches in high-grade serous ovarian cancer. (#235)

Madeleine R Tancock 1 , Keefe T Chan 2 3 , Rick B Pearson 1 2 3
  1. Department of Biochemistry and Molecular Biology, , Monash University,, Clayton, , VIC, , Australia
  2. Sir Peter MacCallum Department of Oncology, , University of Melbourne, , Melbourne, , VIC, , Australia
  3. Division of Cancer Research,, Peter MacCallum Cancer Centre, , Melbourne, , VIC, , Australia

Background

Cellular senescence, a cell state characterised by growth arrest, morphological, and phenotypic changes, can be induced prematurely by DNA damage in normal cells. DNA-damaging chemotherapeutic agents have also been shown to induce senescence in cancer cells, termed therapy-induced senescence (TIS). Unlike cellular senescence in normal cells, TIS proliferative arrest in cancer cells is increasingly becoming recognised as being reversible and a potential mechanism of disease relapse. This is particularly relevant in high-grade serous ovarian cancer (HGSOC), where 70% of patients experience disease relapse within three years of initial treatment and have poor 5-year survival rates (20-30%). We hypothesise that understanding TIS in HGSOC will facilitate identifying novel approaches to target TIS and treat HGSOC.

Methods

Human HGSOC cell lines (OVCAR-3, OVCAR-4, OVCAR-8) and mouse HGSOC cell lines (ID8NF1-/-, ID8PTEN-/-) were exposed to the standard-of-care drug cisplatin (CP) and a novel ribosome-directed drug CX-5461 (CX) developed by our laboratory. TIS biomarkers were assessed: cell cycle arrest, senescence-associated beta-galactosidase (SA-b-gal) activity, DNA damage response, and senescence-associated heterochromatin. Live cell imaging was performed on TIS HGSOC cells exposed to the senolytic agent ABT-263 and apoptosis was measured using a caspase 3/7 dye. Characterisation of gene expression changes between TIS and proliferating cancer cells was performed via RNA-seq. 

Results and Conclusion

Both cisplatin and CX-5461 induced hallmarks of TIS in HGSOC cells, including persistent activation of the DNA damage response pathway and gene expression signatures consistent with engagement of an inflammatory phenotype. These cells have the potential to be selectively killed by ABT-263. Subtleties in the TIS phenotype may inform the future development of approaches to target TIS in HGSOC.