Silencing SLC52A2 promotes tertiary lymphoid structure formation and inhibits IL-17 pathway to ameliorate melanoma...

Tertiary lymphoid structure (TLS) correlates with improved prognosis in melanoma. The role of solute carrier family 52 member A2 (SLC52A2) in mediating this interplay and influencing melanoma progression remains unclear. Integrated bioinformatics analysis of melanoma datasets (GSE3189, GSE19234, GSE46801, GSE4587, GSE238207, GSE53223) were applied to identify TLS-associated candidate genes. Machine learning was performed to screen key genes validated in independent cohorts and clinical blood samples. In vitro functional assays and in vivo syngeneic models assessed the impact of SLC52A2 knockdown. TLS-related indicators were evaluated by immunohistochemistry, multiplex immunofluorescence (mIF), flow cytometry, and enzyme-linked immunosorbent assay. Furthermore, the downstream pathway of SLC52A2 was identified by bioinformatics analysis. CD8⁺ T cell depletion and pathway feedback experiments were conducted to validate mechanistic dependencies. Herein, SLC52A2 was identified as a key hub gene associated with TLSs. Silencing SLC52A2 significantly inhibited melanoma cell proliferation, migration, and invasion in vitro, and suppressed tumor growth in vivo, reducing Ki67 expression. SLC52A2 knockdown enhanced TLS formation, evidenced by increased CD4/CD20/CD68 infiltration, elevated CD3+/CD8+ T-cell infiltration with enhanced cytotoxic function (granzyme B⁺ and interferon-γ⁺), and upregulated TLS-organizing chemokines. mIF and quantitative TLS scoring confirmed significantly increased TLS abundance and maturity upon SLC52A2 silencing. Depletion of CD8⁺ T cells reversed both the TLS enhancement and the tumor-suppressive effects induced by SLC52A2 silencing. Mechanistically, interleukin (IL)- 17 signaling pathway was screened as the downstream pathway of SLC52A2. Experimentally, SLC52A2 knockdown reduced IL-17A/IL-17RA protein levels, and IL-17 receptor antagonist LY3509754 exhibited the anti-tumor role in vitro. Collectively, SLC52A2 drives melanoma progression by inhibiting TLS-mediated anti-tumor immunity and activating the IL-17 pathway, positioning SLC52A2 as a promising therapeutic target for melanoma.