Neuropilin 2 Receptor is Necessary for Tumorigenesis and Angiogenesis in Oral Squamous Cell Carcinoma

Introduction

Oral squamous cell carcinoma (OSCC) is the most common cancer in the oral cavity with a 5-year survival rate of only 38% in metastatic cases. OSCC dissemination is correlated with enhanced tumor lymphan- giogenesis. 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. Recently, our laboratory identified NRP2 as a novel target in OSCC and its associated vascula- ture in human patient biopsies, human OSCC xenografts, and mouse carcinogenesis models of OSCC. We also found correlation between NRP2 expression and lymphatic vessel density in human OSCC xenografts in immunodeficient mice. Our hypothesis is that NRP2 plays a key role in OSCC tumorigenesis and tumor angiogenesis and lymphangio- gesis.

Methods/Results

To study the role of Nrp2 in the tumor microenvironment, luciferase-labeled, syngeneic Nrp2-expressing mouse OSCC cells were implanted in the tongue of C57Bl/6 wildtype and Nrp2-deficient littermate. Although there was no significant difference in tumor incidence (WT=5/5; KO=4/5) or average tumor biolumines- cence between the groups after one week of tumor growth in vivo, histological examination revealed a 46% and 74% reduction in tumor angiogenesis and lymphangiogenesis, respectively, in Nrp2deficient mice compared to wild- type controls. Next, to characterize the role of Nrp2 in keratinocytes during tumorigenesis, K14Cre^ERT;Nrp2-floxed (Nrp2iKO) mice were treated with 4-Hydroxytamoxifen to induce Cre activity to delete the Nrp2 gene. Nrp2iKO and control (K14-Cre or Nrp2-floxed) mice were given 4-NQO carcinogen in the drinking water for 16 weeks to generate premalignant lesions and OSCC. To date, 86% of control mice have developed tumors while only 38% of Nrp2iKO mice have developed tumors. Histological examination will be compared between the groups.

Conclusion

Our data draw attention to the essential role of Nrp2 in both carcinoma cells and tumor endothelium in OSCC.