DDX21 and cancer: Our study suggests that the use of PARPi as a cancer therapeutic can be expanded to further types of cancers and that DDX21 localization can potentially be used as a prognostic factor and as a biomarker for response to PARPi.<h4>Significance</h4>Currently, there are no reliable biomarkers for response to PARPi outside of homologous recombination deficiency.