Interestingly, the observation that PARP inhibition in HR deficient cells can still lead to synthetic lethality but may not be necessarily accompanied by SSB accumulation has led to the conclusion that PARP1 must also be actively implicated in the Alt-NHEJ repair process, which is believed to take place in HR- and/or NHEJ-defective cancer cells [94]. Here, PARP1 is linked to cancer.