Celastrol enhanced CD8+T cell immunity in melanoma by targeting SHP2 and upregulating MHC-I

Celastrol (CEL) has demonstrated promising anti-cancer properties, yet its specific mechanisms against melanoma remain insufficient. This study investigated the CEL's anti-tumor effects and determined its potential mechanisms in the regulation of MHC-I expression in melanoma. In addition, we also tested its efficacy in sensitizing immune checkpoint inhibitors (ICIs) to melanoma.

CEL's anti-tumor activity was evaluated in B16F10 melanoma-bearing C57BL/6 mice across five groups (control, CEL 0.5 mg/kg, CEL 1 mg/kg, CEL 2 mg/kg, and ICIs), the tumor volume, histopathology, and body weight were assessed. Mechanistic insights were obtained through network pharmacology and RNA sequencing in B16F10 cells. Differential gene and pathway analysis were validated using qRT-PCR, Western blotting, and flow cytometry. CD8+T cell activation and cytotoxicity were analyzed in co-culture with CEL-pretreated B16F10 cells using flow cytometry and ELISA. CEL's interaction with potential targets was determined by molecular docking, surface plasmon resonance (SPR), and siRNA. The synergistic effect of CEL combined with ICIs was confirmed in B16F10-bearing C57BL/6 mice, and tumor-infiltrating T cells were assessed by flow cytometry across four groups (control, CEL, ICIs, CEL+ICIs).

CEL exhibited a significant anti-tumor effect in B16F10 melanoma-bearing mice. Mechanistically, CEL-pretreated B16F10 cells notably enhanced CD8+T cell activation and promoted IFNγ and TNFα secretion, leading to B16F10 cell death. CEL upregulated MHC-I expression through activation of the JAK/STAT1 pathway in B16F10 cells. The binding assay revealed that CEL interacted with SHP2, with an affinity of 37.93 μM. When SHP2 was silenced in B16F10 cells by siRNA, CEL failed to induce MHC-I upregulation. Moreover, CEL combined with ICIs produced superior antitumor efficacy compared to ICIs alone, which was accompanied by increased CD8+T cell infiltration in melanoma.

CEL enhanced CD8+T cell immunity by upregulating MHC-I expression in melanoma cells, these effects were at least partially through targeting SHP2 and activating JAK/STAT1 pathway. CEL might be a novel sensitizer for ICIs in melanoma.