Such cross-inhibition may potentiate cancer cell death, as in the case of rucaparib and PARP/H6PD inhibition, but may also be detrimental for combination therapy with niraparib and nucleoside analogs such as gemcitabine due to cross-inhibition of DCK required for their activation (Knezevic et al. 2016). Here, PARP1 is linked to cancer.