Tumor Cells-Derived FGF-2 Promotes Lymphangiogenesis as a Prognostic Marker in OSCC.

Background: The "cold" tumor microenvironment of oral squamous cell carcinoma (OSCC), where tumor-associated lymphatic vessels play a critical role in the transport of immune cells, is associated with a poor prognosis. However, the effect of tumor-induced lymphangiogenesis on CD8+ T cell infiltration and its role in the formation of the tumor immune microenvironment remain unclear.

Methods: We analyzed the prognostic significance of several lymphangiogenesis factors in OSCC with The Cancer Genome Atlas dataset, and confirmed the impact of fibroblast growth factor-2 (FGF-2) on prognosis in tissue specimens. Subsequently, we investigated the effects of FGF-2 on the proliferation, migration, and tube formation capacities of lymphatic endothelial cells, and CD8+ T cell infiltration through in vivo and in vitro experiments. Survival analysis was performed by Kaplan-Meier analysis and log-rank tests. The hazard ratio was calculated by Cox proportional hazards model.

Results: Patients with high FGF-2 levels and increased numbers of peritumoral lymphatic vessels were associated with a worse prognosis. Furthermore, we demonstrated that tumor cell-derived FGF-2 promoted lymphangiogenesis by regulating the FGFR1/PTEN/AKT axis and increased the secretion of CXCL9 to recruit and egress CD8+ T cells via neo-lymphatic vessels. PD-166866, an inhibitor of FGFR1, suppressed lymphangiogenesis and the secretion of CXCL9 to increase CD8+ T cell infiltration and inhibit tumor progression.

Conclusions: Our data suggest that FGF-2 is a significant prognostic factor that induces lymphangiogenesis and affects intratumoral CD8+ T cells, contributing to the formation of a "cold" tumor microenvironment in OSCC. FGF-2/FGFR1 could serve as an effective target for improving the prognosis of OSCC.