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Tyrosinase in melanoma inhibits anti-tumor activity of PD-1 deficient T cells

ABSTRACT: Melanoma is one of the most commonly diagnosed malignancies and serves as a model for studying immunotherapy. The B16 melanoma model is characterized by low T cell infiltration in the tumor, and blocking the PD-1 pathway shows no significant anti-tumor activity, mirroring melanoma patients with a cold tumor immunophenotype. Therefore, understanding the molecular basis that prevents T cell-mediated anti-tumor activity in B16 melanoma is of great significance. In this study, we generated Tyr knockout B16 melanoma cells using CRISPR/Cas9 and discovered that tyrosinase in melanoma significantly inhibits the anti-tumor activity of T cells. Tyrosinase deficiency significantly increases T-cell infiltration and activation within the tumor. Single-cell RNA sequencing reveals an altered cold tumor immunophenotype in tyrosinase-deficient B16 melanoma. In wild-type mice, T cells in tyrosinase-deficient tumors express elevated levels of PD-1 and Foxp3. However, strikingly, in PD-1 deficient mice, the loss of tyrosinase in B16 melanoma unleashes the anti-tumor activity of PD-1 deficient T cells. This enhanced anti-tumor activity is explained by significantly increased tumor T cell infiltration accompanied by reduced frequencies of Tregs in PD-1 knockout mice. Targeting tyrosinase may enhance the anti-tumor efficacy of PD-1 blockade in cold tumors, offering a novel strategy to render cold tumors responsive to immunotherapy. Clinically, higher levels of tyrosinase expression in human melanoma are associated with a poorer prognosis, indicating that our findings could potentially improve the efficacy of immunotherapy in melanoma patients.

ORGANISM(S): Mus musculus

PROVIDER: GSE273734 | GEO | 2025/04/28

REPOSITORIES: GEO

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			Action	DRS
		Other
	GSE273734_Combined_GRIS-BD_Experiment_4-TAG_FKDL210224395-1a_1_RSEC_MolsPerCell.csv.gz	Csv
	GSE273734_GRIS-BD_Experiment_4-TAG_FKDL210224395-1a_1_Sample_Tag_Calls.csv.gz	Csv

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Project description:Dietary tyrosine regulating melanoma progression has been well-recognized. However, whether tyrosine-based melanin anabolism contributes to pulmonary and cerebral organotropic colonization of melanoma remains elusive. Furthermore, how to inhibit multi-organ metastasis by interfering tyrosinase activity of melanoma cells and function of immunocytes needs to be designed and validated. Patients derived melanoma cells and mouse B16 melanoma cells with different pigment were employed in this investigation. Tyrosine content dynamics in tumors and multiple organs during the melanoma progression were monitored, and tyrosine-based melanin synthesis ability of melanoma cells derived from multi-organ were detected. Additionally, we also adopted the RNA-seq, flowcytometry, real-time PCR and composite metastasis mouse model to analyze organotropic colonization and to design therapeutic strategies. B16 melanoma cells with high activity of tyrosinase and sensitivity of tyrosine utilization for melanin synthesis (Tyr-H cells) easily colonized in the lung, while B16 melanoma cells without above characteristics (Tyr-L cells) exhibited potent proliferation in the brain. Mechanistically, Tyr-H cells recruited and trained neutrophils and macrophages to build up the pulmonary metastatic niche dependent on highly secreted CXCL1 and CXCL2 and an excess melanosome accumulation-induced cell death. Tyr-L cells enhanced PD-L1 expression in tumor-infiltrated macrophages when they are progressing in the brain. Accordingly, intervention of tyrosinase activity (2-Ethoxybenzamide or hydroquinone), together with inhibitors to phagocytosis (GSK343) or chemotaxis (SB225002) suppress organotropic colonization and significantly improve the survival of immune checkpoint blockade (PD1 antibody) treated melanoma bearing mice. The heterogeneity of melanoma cells in utilization of tyrosine is associated with organotropic colonization, providing the basis for developing strategies to combat melanoma and prevent their metastasis.

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Tyrosinase in melanoma inhibits anti-tumor activity of PD-1 deficient T cells

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