Aberrant expression of the S1P regulating enzymes, SPHK1 and SGPL1, contributes to a migratory phenotype in OSCC mediated through S1PR2.

Sathya Narayanan Patmanathan,Wenbin Wei,Federico Torta,Steven P Johnson,Maha Hafez Ibrahim,Markus R Wenk,Deron R Herr,Paul G Murray,Suthashini Panja Bernam,Pradeep Narayanaswamy,Lee Fah Yap,Sook Ling Lai,Ian C Paterson,Victor Lopes

doi:10.1038/srep25650

Abstract

Oral squamous cell carcinoma (OSCC) is a lethal disease with a 5-year mortality rate of around 50%. Molecular targeted therapies are not in routine use and novel therapeutic targets are required. Our previous microarray data indicated sphingosine 1-phosphate (S1P) metabolism and signalling was deregulated in OSCC. In this study, we have investigated the contribution of S1P signalling to the pathogenesis of OSCC. We show that the expression of the two major enzymes that regulate S1P levels were altered in OSCC: SPHK1 was significantly upregulated in OSCC tissues compared to normal oral mucosa and low levels of SGPL1 mRNA correlated with a worse overall survival. In in vitro studies, S1P enhanced the migration/invasion of OSCC cells and attenuated cisplatin-induced death. We also demonstrate that S1P receptor expression is deregulated in primary OSCCs and that S1PR2 is over-expressed in a subset of tumours, which in part mediates S1P-induced migration of OSCC cells. Lastly, we demonstrate that FTY720 induced significantly more apoptosis in OSCC cells compared to non-malignant cells and that FTY720 acted synergistically with cisplatin to induce cell death. Taken together, our data show that S1P signalling promotes tumour aggressiveness in OSCC and identify S1P signalling as a potential therapeutic target.

Highlights

Oral squamous cell carcinoma (OSCC) remains a major world health issue and is prevalent in India and South East Asia
As we showed that the sphingosine rheostat and S1PR expression are deregulated in OSCC, we examined the cytotoxicity of FTY720 on two OSCC cell lines (H357 and H400), one immortalised normal keratinocyte (HaCaT) and two normal oral fibroblasts (NHOF4 and NHOF6) using MTT assays
We show that the expression of SPHK1 is upregulated in OSCC, results that are consistent with previous reports in a variety of cancer types[27], including other head and neck carcinomas[4,15,16]

Summary

Introduction

Oral squamous cell carcinoma (OSCC) remains a major world health issue and is prevalent in India and South East Asia. The balance between S1P and its metabolic precursors, ceramide and sphingosine, the so called sphingosine rheostat, regulates cell fate with a shift towards ceramide inducing cell growth arrest and apoptosis, whereas S1P production promotes cell survival[6]. The effects of S1P are largely due to the binding to one or more of a family of five G-protein coupled receptors, termed S1PR1-57, which stimulate multiple signalling cascades[8]. The cancer-promoting effects of S1P result from alterations in S1PR expression[9,11,13,14]. In addition to modulating the S1PRs, FTY720 can inhibit SPHK1 activity[21] and activate the tumour suppressor, protein serine/threonine phosphatase type 2A (PP2A)[22]. Due to the pleiotropic properties of the drug, FTY720 can inhibit proliferation and migration of a variety of cancer cell lines, and promote their apoptosis and chemo-sensitivity. FTY720 inhibits tumour growth, angiogenesis and metastasis in vivo[23]

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Results

Conclusion