In a mouse model of breast cancer, tumor cells use their production of leukotriene B4 (LTB4) to activate peroxisome proliferator‐activated receptor α (PPARα) on B cells, which results in the induction of differentiation of tumor‐evoked regulatory B cells (tBregs).[33] Deletion of the PPARα gene on B cells inhibits the tBregs generation. The gene discussed is PPARA; the disease is breast carcinoma.