BATF3 is an AP-1 family transcription factor that serves as a master regulator of dendritic cell differentiation and anti-tumor immunity. Functionally, BATF3 controls the development of CD8α+ conventional dendritic cells (cDC1) and CD103+ dendritic cells 1, which are critical for cross-presenting antigens to CD8+ T cells and producing IL-12 in response to pathogens. BATF3 operates as a heterodimer with JUN family proteins to recognize DNA sequences and regulate target gene expression 1. Mechanistically, BATF3 forms part of a minimal transcriptional network with PU.1 and IRF8 that is sufficient to reprogram differentiated cells into functional antigen-presenting cells 23. This reprogramming induces cDC1-like transcriptional and epigenetic programs, restoring antigen presentation machinery and costimulatory molecules on tumor cells 3. Clinically, BATF3-dependent dendritic cells are essential for successful cancer immunotherapy. Radiation-induced anti-tumor immunity requires BATF3+ DC recruitment and activation 4, while BATF3+ DCs mediate therapy-elicited neutrophil responses critical for tumor control 5. In adoptive T cell therapy, BATF3 overexpression enhances CAR-T cell potency and programs transcriptional signatures correlating with positive clinical response 6. These findings establish BATF3 as a key target for in vivo cell reprogramming approaches in cancer immunotherapy 7.