Genetic Identification of SEMA3F as an Antilymphangiogenic Metastasis Suppressor Gene in Head and Neck Squamous Carcinoma

Abstract

Head and neck squamous cell carcinomas (HNSCC) often metastasize to locoregional lymph nodes, and lymph node involvement represents one of the most important prognostic factors of poor clinical outcome. HNSCC are remarkably lymphangiogenic and represent a clear example of a cancer that utilizes the lymphatic vasculature for malignant dissemination; however, the molecular mechanisms underlying lymphangiogenesis in HNSCC is still poorly understood. Of interest, we found that an axon guidance molecule, Semaphorin 3F (SEMA3F), is among the top 1% underexpressed genes in HNSCC, and that genomic loss of SEMA3F correlates with increased metastasis and decreased survival. SEMA3F acts on its co-receptors, plexins and neuropilins, among which neuropilin-2 (NRP2) is highly expressed in lymphatic endothelial cells (LECs) but not in oral epithelium and most HNSCCs. We show that recombinant SEMA3F promotes LEC collapse and potently inhibits lymphangiogenesis in vivo. By reconstituting all possible plexin and neuropilin combinations, we found that SEMA3F acts through multiple receptors, but predominantly requires NRP2 to signal in LECs. Using orthotopic HNSCC metastasis mouse models, we provide direct evidence that SEMA3F re-expression diminishes lymphangiogenesis and lymph node metastasis. Furthermore, analysis of a large tissue collection revealed that SEMA3F is progressively lost during HNSCC progression, concomitant with increased tumor lymphangiogenesis. SEMA3F is localized to 3p21, an early and frequently deleted locus in HNSCC and many other prevalent human malignancies. Thus, SEMA3F may represent an antilymphangiogenic metastasis suppressor gene widely lost during cancer progression, hence serving as a prognostic biomarker and an attractive target for therapeutic intervention to halt metastasis.

Tumor lymphangiogenesis and new drug development

“…Further endogeneous factors with anti-lymphangiogenic activity have been described, such as vasohibin [99], TGF-b [100] and semaphorins [101,102]. Interestingly, Tcells, respectively T-cell derived cytokines, have also emerged as inhibitors of lymphangiogenesis.…”

The role of the semaphorins in cancer

“…60 Sema3F also functions as a potent inhibitor of lymphangiogenesis, a process that is critical for the metastatic spread of some types of solid tumors such as head and neck tumors or breast cancer tumors. 103,203 Recently it was suggested that sema3F may also be able to inhibit angiogenesis through competition with VEGF-A for binding to neuropilin-1, a receptor to which full length sema3F binds with low affinity as compared to its affinity to neuropilin-2 and which seems unable to convey sema3F signals. 100,204 However, cleavage with furin like pro-protein convertases at the sema3F C-terminus was found to result in an increase in its affinity to neuropilin-1 enabling it to compete effectively with VEGF-A for binding to neuropilin-1.…”

Tumor-associated Lymphatic Endothelial Cells Promote Lymphatic Metastasis By Highly Expressing and Secreting SEMA4C

“…Plexins A1-A4 have been described as transducers of antiangiogenic signals conveyed by class-3 semaphorins such as sema3F, while the SEMA4D-PlexinB1 has been known as a potent inducer of angiogenesis and is associated with poor prognosis in various solid tumors (15,16). Angiogenesis and lymphangiogenesis intersect in the regulation of tumor microenvironment, and several recent studies also suggested that semaphorins may affect lymphangiogenesis (17,18). Nevertheless, the knowledge about the role of the semaphorin-mediated regulation of tumor lymphangiogenesis is still limited.…”