Figure 1. Anti-SIRPα monotherapy efficacy in orthotopic syngeneic tumor models.

(A) Primary tumor volume and (B) lung metastasis count in the 4T1 triple-negative breast orthotopic tumor model (0.25 × 10⁶ cells injected in the mammary fat gland) of mice treated i.p. with a control mAb (black, n = 7), P84 (red, n = 8), or MY1-G1 (blue, n = 6) anti-SIRPα antagonist mAbs at 10 mg/kg 3 times from day 4 to day 18. (C) Tumor-infiltrating frequencies among live cells and peripheral leukocyte phenotype modification after treatment with P84 (red, n = 7) or control (black, n = 9) mAbs 15 days after tumor implantation. (D) Same protocols and symbols as in A, but a surgical resection of the primary tumor was performed 13 days after tumor implantation and the survival of mice (n = 7 per group) was analyzed. (E) Survival of WT (black, n = 23) and SIRPα mutant (purple, n = 11) untreated mice injected on day 0 in the pleural cavity with AK7 mesothelioma tumor cells (3 × 10⁶). Some WT mice were also treated i.p. with the MY-1-mG1 anti-SIRPα mAb (blue, n = 16) from day 4 to day 32 at 10 mg/kg 3 times a week. Three independent experiments were performed. (F) Cured-SIRPα mutant mice from the AK7 model were rechallenged i.p. with a new load of 3 × 10⁶ AK7 cells (n = 6). The same injection was performed in untreated WT mice as control (n = 7). *P < 0.05; **P < 0.01; ***P < 0.005, compared with control group; ^#P < 0.05 for P84 and MY-1 comparison, unpaired Mann-Whitney U test or log-rank for survival.