PARP1 and ovarian cancer: To delineate the contributions of DSB repair pathways (MMEJ, NHEJ and HR) to eccDNA biogenesis, we systematically knocked down key pathway‐specific factors in SKOV3 ovarian cancer cells: LIG3 and POLQ for MMEJ, KU80 and DNA‐PKcs for NHEJ, RAD51 for HR, and PARP1 as an upstream regulator of DNA repair (Figure 2A,B).