PARP1 and sarcoma: Furthermore, PARP1 regulates NHEJ (Non-homologous end joining) (Couto et al., 2011; Caron et al., 2019), and its inhibitors, such as olaparib, also cause DNA damage (McMahon et al., 2016) and are used in sarcomas in combination with DNA damaging agents, such as ionizing radiation (IR) (Lee et al., 2013).