Role of SphK1/S1P/S1PR1 Signaling Pathway in the Progression of Vocal Fold Leukoplakia of Patients With Laryngeal Reflux.

Background: Vocal fold leukoplakia (VFL) has a risk of malignant transformation, and the underlying mechanisms remain defined. It was assumed that laryngopharyngeal reflux (LPR) may contribute to the occurrence of VFL. Studies showed that sphingosine kinase 1 (Sphk1) was highly expressed in the gastroesophageal reflux-related gastrointestinal tumors. This study aimed to investigate the effects of Sphk1 on the transformation of VFL in LPR patients.

Materials and methods: Fifteen VFL patients with or without LPR were enrolled in this cohort study based on the results of pathology, reflux finding score (RFS)/reflux symptom index (RSI), and a Pepsin test. VFL lesion diagnosis from surgery or biopsy tissues was confirmed by clinical pathologists. The clinical characteristics of LPR and nonLPR groups were compared. Levels of Sphk1/sphingosine-1-phosphate (S1P)/sphingosine-1-phosphate receptor 1 (S1PR1), inflammatory markers, and cell-proliferative protein were measured using immunohistochemistry (IHC) and quantitative polymerase chain reactions (qPCR). Cell proliferation pathway-related proteins phosphorylated AKT (p-AKT) and phosphorylated ERK (p-ERK) were detected by western blot.

Results: There were no significant differences in age, sex, smoking, alcohol consumption, and the underlying diseases between patients with LPR and without LPR. RFS/RSI values of patients with LPR were significantly higher than those without LPR. SphK1 messenger RNA (mRNA) and protein expressions were increased with elevated levels of inflammatory-responsive biomarkers in the VFL tissues of patients with LPR. S1P and S1PR1 consecutively initiated the intracellular AKT and ERK signaling cascades, the latter of which is closely related to cell proliferation.

Conclusion: The proliferation of VFL patients with LPR was significantly higher than those without LPR. SphK1/S1P/S1PR1 signaling pathway molecules of VFL patients with LPR were dramatically elevated compared with patients without LPR. Sphk1 may promote malignant transformation of VFL in patients with LPR.