Fig. 6: The phagocytosis of ferroptotic tumor cells is dependent on the interaction of SAPE-OOH and TLR2.

a The phagocytosis was observed by immunohistochemistry of F4/80-labeled and  H&E stained tumor sections. Red arrows: F4/80-positive cells. @: macrophages containing multiple nuclei. Enlarged: images in dashed frames. Scale = 100 μM (black) and 10 μM (white). b The protein expressions of the indicated proteins in tumor tissues. Each immunoblot represents three biological animals, and representative blotting results are shown. c PI staining of 4T1 cells treated with RSL3 (1 μM, 6 h) or SAPE-OOH (2.5 μM, 6 h). Data are mean ± SEM (n = 3 independent biologically cell cultures). d Phagocytosis of 4T1 cells treated with RSL3 or SAPE-OOH. Data are mean ± SEM (n = 3 independent biologically cell cultures). e THP-1 cells pretreated with SMU-Z1 (1 μM) and CU-CPT22 (10 μM) for 24 h. Phagocytosis of 4T1 cells treated with RSL3. Data are mean ± SEM (n = 5 independent biologically cell cultures). f L1210 cells (previously treated with RSL3 (5 μM, 6 h) or SAPE-OOH (10 μM, 6 h) were injected into the peritoneum of WT or Tlr2 KO mice. Total peritoneal cells were harvested and labeled with F4/80 before the in vivo phagocytosis was assessed by flow cytometry. Data are mean ± SEM (n = 5 independent biologically cell cultures). g Graphic abstract: SAPE-OOH on ferroptotic cell surfaces acts as an eat-me signal and navigates phagocytosis by targeting TLR2 on macrophages. All data represent mean ± SEM. ^*P < 0.05, ^**P < 0.01 and ^***P < 0.001, by one-way ANOVA with LSD post hoc test.