Neuropilin 2 Drives Tumor Lymphangiogenesis in Oral Squamous Cell Carcinoma

Abstract

Oral squamous cell carcinoma (OSCC) is the sixth most common cancer worldwide. The majority (67%) of patients with this aggressive cancer already exhibit local or distant metastases at the time of initial diagnosis. Understanding the molecular mechanisms that regulate OSCC progression and metastasis is paramount to developing novel therapeutic strategies for this disease. Enhanced tumor‐associated lymphangiogenesis correlates with increased lymph node metastasis and adversely affects prognosis in OSCC. Neuropilin 2 (NRP2) is an endothelial cell membrane receptor that binds the lymphangiogenic factors, VEGF‐C and VEGF‐D, in complex with VEGFR3 to stimulate the sprouting of lymphatic vessels during developmental lymphangiogenesis. However, once vessels are properly guided and patterned, NRP2 expression is downregulated and not upregulated until times of need such as during inflammation‐, ischemia‐, or cancer‐related neovascularization. Our hypothesis is that NRP2 plays a role in OSCC progression and metastasis. Results from immunohistochemical staining demonstrate that normal human and mouse oral mucosa are devoid of NRP2 expression. Conversely, NRP2 is upregulated in the epithelium in late stages of oral dysplasia and in OSCC and its associated endothelium. Several human OSCC cell lines express NRP2 in vitro and in vivo when implanted orthotopically in the tongue of immunodeficient mice. In fact, NRP2 expression levels in the cancer cells correlate with the degree of tumor‐associated lymphatic vessel density within the tumors. OSCC mouse intralingual isografts show reduced tumor angiogenesis and lymphangiogenesis in adult syngeneic Nrp2‐deficient mice compared to Nrp2‐intact littermates. Taken together, our data suggest that NRP2 may be useful as a late‐stage marker of oral epithelial dysplasia and highlight the importance of the NRP2 axis in effective tumor neovascularization in OSCC. Our ongoing studies using the 4NQO carcinogenesis model in mutant mice lacking Nrp2 specifically in epithelial cells will further elucidate the role of NRP2 in OSCC tumorigenesis.