Researchers reported a mechanism by which tumors may resist anti–PD-1 therapy despite high PD-L1 expression. In the study, DDB1 was implicated in driving PD-L1 into nuclei, where the authors describe downstream effects that support resistance to immune checkpoint blockade. The findings add to the evolving understanding of checkpoint biology beyond surface PD-L1 and suggest that intracellular PD-L1 localization could be a determinant of treatment failure in subsets of patients. The work also frames new potential targets within the PD-L1 trafficking machinery. For translational teams, the report provides a biologically grounded rationale to explore biomarkers that capture not just PD-L1 presence but where it functions, potentially guiding patient selection and combination strategies.