Figure 2.

Tumor-opsonizing antibodies can drive regression of metastases only when CD47 is disrupted. (A) (i) Human clinical CD47 blockade in solid tumors compared to our main design of a suitable preclinical model (mouse). Anti-CD47 monotherapies show no efficacy, motivating a combination with tumor-opsonizing antibodies (e.g., Cetuximab in colorectal cancer). Anti-Tyrp1 monotherapy also showed no efficacy against human melanoma. Two distinct approaches are taken in our model. (ii) Anti-Tyrp1 opsonization of established wild-type (WT) B16F10 melanoma metastases does not significantly affect lung tumor burden on day 14 after tail-vein inoculation with 2 × 10⁵ B16F10 cells. Tumors are allowed to establish, and mice are then tail-vein injected with anti-Tyrp1 (250 µg dosing) on days 4, 5, 7, 9, 11, and 13. Mice are sacrificed and organs are surveyed for B16F10 metastases. Results are illustrative of three independent experiments (n = 5 per group, mean ± s.e.m., n.s. not significant for p > 0.05, unpaired t-test). (B) CD47-deleted lung metastases require anti-Tyrp1 for significant suppression. (i) Mice are tail-vein injected with 2 × 10⁵ CD47 KO B16F10 cells on day 0 and later treated by tail-vein injections of anti-Tyrp1 (75 µg dosing). Mice are sacrificed and organs are surveyed for metastases, but only the lung shows nodules. Representative images from untreated controls or anti-Tyrp1 treatment. (ii) Tumor area on both sides of lung lobes were quantified, showing significant suppression by anti-Tyrp1 (n = 5 per group, mean ± s.e.m.; * p < 0.05, ** p < 0.01, **** p < 0.0001, one-way ANOVA, uncorrected Fisher’s LSD). (iii) Exponential-type growth (as power law: Area = A₀ t^B: A₀,_ctrl = 0.0019, A₀,_tx = 0.0087, B_ctrl = 4.1, B_tx = 3.0). (iv) CD47 deletion does not affect tumor growth relative to WT (Area = A₀ e^k*t, where A₀ = 0.05, k = 0.45).