Poster Presentation 36th Lorne Cancer Conference 2024

Exploiting the dna damage response to develop personalised treatments for high-risk sarcoma in children (#250)

Larissa Volken 1 2 , Gabor Tax 1 2 , Jie Mao 1 , Roxanna Cadiz 1 , Muhammad Rishfi 3 , Emmy Dolman 1 2 4 , Emmy Fleuren 1 2
  1. Children's Cancer Institute, Lowy Cancer Research Centre, UNSW Sydney, Kensington, New South Wales, Australia
  2. School of Clinical Medicine, UNSW Medicine & Health, UNSW Sydney, Kensington, New South Wales, Australia
  3. Department of Biomolecular Medicine, Faculty of Medicine & Health Sciences, University, Belgium; Cancer Research Institute Ghent (CRIG), Ghent , Belgium
  4. Princess Maxima Center for Pediatric Oncology , Utrecht, Netherlands

Background Outcomes for children with the most aggressive forms of sarcoma are dismal, and the currently applied multimodal treatment regiments are often associated with side effects and life-long health issues. Consequently, precision medicine is the ongoing focus to further improve the outcome and quality of life for children with high-risk sarcomas. The DNA damage landscape harbours molecular characteristics some tumours rely on. Aim We aim to unravel the DNA damage landscape of sarcoma and exploit the link with sensitivity to inhibitors of the DNA damage response (DDR). Methods DDR encompasses all intra- and intercellular signalling pathways that deal with DNA damage to maintain genome integrity. DNA damage response inhibitors targeting the ATR, ATM, and non-homologous end-joining (NHEJ) signalling cascades were tested as single agents and in combination. In vitro effects on cell viability were tested using a panel of sarcoma cell lines, including cell lines derived from high-risk sarcoma patients participating in the Zero childhood cancer precision medicine program with available tumour molecular profiling data. Next, further validation studies were performed to evaluate effects on target inhibition, single- and double-strand DNA break markers, cell proliferation and apoptosis. Results Replication stress will lead to the recruitment of ATR and activation of its downstream targets CHK1 and WEE1 resulting in fork stabilization and G2-M checkpoint activation. Inhibitors of the ATR signalling cascade including ATR inhibitors Berzosertib and Elimusertib, CHK1 inhibitors Prexasertib and LY2880070, and WEE1 inhibitor Adavosertib were most effective with IC50 and LC50 values below plasma concentrations achievable in patients. Highest efficacy was observed in Ewing Sarcoma (ES), where we identified a shift from high replication stress to double strand break signals upon treatment. Interestingly, we found that vertical suppression of the ATR signalling cascade by combining drugs targeting two distinct key players (i.e., ATR + CHK1, ATR + WEE1, CHK1 + WEE1) resulted in strong synergism with high overall efficacy in ES. Conclusion Dual targeting the DDR pathway has potential as a new treatment strategy for Ewing patients. Next, combinations will be further validated in vitro and in vivo to compare and prove their advantages over standard chemotherapeutics.