Abstract
This study explored the expression of sphingosine kinase 2 (SPHK2) and microRNA miR-19a-3p (miR-19a-3p) in patients with Hypopharyngeal squamous cell carcinoma (HSCC) together with pathways affecting HSCC invasion and metastasis. Quantitative real-time polymerase chain reaction (qRT-PCR) and Western blotting (WB) were performed to assess the differential expression of SPHK2 and miR-19a-3p in patients with HSCC lymph node metastasis (LNM). Immunohistochemical (IHC) results were analyzed together with clinical information to evaluate their clinical significance. Subsequently, the functional effects of SPHK2 overexpression and knockdown on FaDu cells were evaluated in in vitro experiments. We performed in vivo experiments using nude mouse to assess the effects of SPHK2 knockdown on tumor formation, growth and LNM. Finally, we explored upstream and downstream signaling pathways associated with SPHK2 in HSCC. SPHK2 was significantly elevated in HSCC patients with LNM and survival was lower in patients with enhanced SPHK2 expression (P < 0.05). We also demonstrated that SPHK2 overexpression accelerated the proliferation, migration, and invasion. Using animal models, we further verified that SPHK2 deletion abrogated tumor growth and LNM. In terms of mechanism, we found that miR-19a-3p was significantly reduced in HSCC patients with LNM and was negatively associated with SPHK2. MiR-19a-3p and SPHK2 could regulate tumor proliferation and invasion through the PI3K/AKT axis. SPHK2 was found to contribute significantly to both LNM and HSCC patient prognosis and was shown to be an independent risk factor for LNM and staging in HSCC patients. The miR-19a-3p/SPHK2/PI3K/AKT axis was found to contribute to the development and outcome of HSCC.