Abstract 274: Neuropilin-2 is upregulated during EMT in lung cancer.

Abstract

Abstract Neuropilins (NRP1 and NRP2) are high affinity receptors for the class-3 semaphorins, cell guidance molecules involved in tissue development, immune responses, angiogenesis and cancer. Semaphorins can inhibit proliferation, affect cell protrusion, spreading and adhesion, and trigger migratory responses often in a repulsive manner depending on the cellular context.However, neuropilins can also serve as receptors for galectin-1 and growth promoting factors including VEGF, PlGF, EGF and TGFβ. We previously cloned the SEMA3F gene from chromosome 3p21.3, which undergoes homozygous deletion and frequent loss of heterozygosity in lung cancer. We found that SEMA3F levels were inversely correlated with tumor aggressiveness in human lung cancer and confirmed its tumor suppressor activity in experimental xenograft models. We subsequently discovered that SEMA3F is directly downregulated by ZEB1, a transcription factor involved in the epithelial to mesenchymal transition (EMT). In the present study, we asked whether NRP2, the SEMA3F-specific receptor, was also regulated during the EMT process.TGFβ, a physiologic EMT inducer, rapidly increased NRP2 expression in NSCLC cell lines. Mechanistically, this increase resulted primarily from enhanced translation with some contribution from increased mRNA levels. However, TGFβ did not stabilize NRP2 mRNA or protein. Furthermore, we found out that a substantial amount of protein at the cell surface directly depended on the presence of TGFβ in the tumor microenvironment. The pathways regulating NRP2 induction include ERK1/2 and Akt but are Smad independent. In addition, forced expression of ZEB1 also induced NRP2. Conversely, ZEB1 inhibition reduced NRP2 upregulation by TGFβ. Importantly, inhibiting NRP2 affected TGFβ-induced morphologic changes, migration and ERK1/2 activation. Interestingly, some EMT target genes were also affected by NRP2 knockdown. Preliminary data in xenograft models indicate that NRP2 inhibition counteracts tumor growth-promoting effects of TGFβ .In a lung tumor tissue microarray, we observed that higher tumor grades were characterized by positive staining for NRP2 and negative staining for E-cadherin while lower tumor grades often presented the opposite profile. Since NRP2 is the highest affinity receptor for SEMA3F, our results suggest that loss of SEMA3F coupled with increased NRP2 would facilitate the binding of growth factors to NRP2 to further promote EMT and metastasis. Therefore, targeting NRP2 could be an important therapeutic approach against EMT in lung cancer. Citation Format: Patrick Nasarre, Joelle Roche, Vincent A. Potiron, Joyce Nair-Menon, Robert M. Gemmill, Harry A. Drabkin. Neuropilin-2 is upregulated during EMT in lung cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 274. doi:10.1158/1538-7445.AM2013-274