Axl Is a Potential Cancer Prognostic Marker for the Migration and Invasion of Nasopharyngeal Carcinoma

Background. The Axl receptor tyrosine kinase has been demonstrated to be elevated and activated in many human cancers including liver, lung, breast, and pancreatic cancer. Its high expression has been considered as a cancer biomarker for predicting poor prognosis and increased invasiveness/metastasis. Objectives. The aim of the study was to investigate the clinical significance of Axl in nasopharyngeal carcinoma (NPC) and its role in cell migration and invasion. Material and Methods. We detected Axl expression in 86 collected NPC tissues and 20 collected normal nasopharyngeal epithelial tissues using quantitative reverse transcription polymerase chain reaction (qRT-PCR) and immunohistochemical staining. Axl was knocked down by a specific shRNA in NPC cell lines, 5-8F and 6-10B. Transwell assays were used to determine NPC cell migration and invasion. Results. The expressions of Axl mRNA and protein in NPC tissues were significantly higher than those in normal nasopharyngeal epithelial tissues (p < 0.05, respectively). The positive expression of Axl was significantly correlated with distant metastasis and high TNM stage in NPC (p < 0.05, respectively). Furthermore, Axl positive expression was correlated with a worse overall survival of NPC patients (p < 0.05). Multivariate Cox repression analysis indicated that Axl was an independent factor for predicting overall survival of NPC patients (p < 0.05). In vitro studies found that Axl knockdown significantly reduced the number of migrated and invaded 5-8F and 6-10B cells (p < 0.05, respectively). Conclusions. The positive expression of Axl is correlated with the poor clinicopathological features in NPC. Furthermore, Axl is an independent prognostic marker for predicting overall survival of NPC patients. Functionally, Axl may facilitate tumour progression by promoting NPC cell migration and invasion.