Regulation of cellular sphingosine-1-phosphate by sphingosine kinase 1 and sphingosine-1-phopshate lyase determines chemotherapy resistance in gastroesophageal cancer.
BACKGROUND
Resistance to chemotherapy is common in gastroesophageal cancer. Mechanisms of resistance are incompletely characterised and there are no predictive biomarkers in clinical practice for cytotoxic drugs. We used new cell line models to characterise novel chemotherapy resistance mechanisms and validated them in tumour specimens to identify new targets and biomarkers for gastroesophageal cancer.


METHODS
Cell lines were selected for resistance to oxaliplatin, cisplatin and docetaxel and gene expression examined using Affymetrix Exon 1.0 ST arrays. Leads were validated by qRT-PCR and HPLC of tumour metabolites. Protein expression and pharmacological inhibition of lead target SPHK1 was evaluated in independent cell lines, and by immunohistochemistry in gastroesophageal cancer patients.


RESULTS
Genes with differential expression in drug resistant cell lines compared to the parental cell line they were derived from, were identified for each drug resistant cell line. Biological pathway analysis of these gene lists, identified over-represented pathways, and only 3 pathways - lysosome, sphingolipid metabolism and p53 signalling- were identified as over-represented in these lists for all three cytotoxic drugs investigated. The majority of genes differentially expressed in chemoresistant cell lines from these pathways, were involved in metabolism of glycosphingolipids and sphingolipids in lysosomal compartments suggesting that sphingolipids might be important mediators of cytotoxic drug resistance in gastroeosphageal cancers . On further investigation, we found that drug resistance (IC50) was correlated with increased sphingosine kinase 1(SPHK1) mRNA and also with decreased sphingosine-1-phosphate lysase 1(SGPL1) mRNA. SPHK1 and SGPL1 gene expression were inversely correlated. SPHK1:SGPL1 ratio correlated with increased cellular sphingosine-1-phosphate (S1P), and S1P correlated with drug resistance (IC50). High SPHK1 protein correlated with resistance to cisplatin (IC50) in an independent gastric cancer cell line panel and with survival of patients treated with chemotherapy prior to surgery but not in patients treated with surgery alone. Safingol a SPHK1 inhibitor, was cytotoxic as a single agent and acted synergistically with cisplatin in gastric cancer cell lines.


CONCLUSIONS
Agents that inhibit SPHK1 or S1P could overcome cytotoxic drug resistance in gastroesophageal cancer. There are several agents in early phase human trials including Safingol that could be combined with chemotherapy or used in patients progressing after chemotherapy.
School of Medicine and Dentistry, University of Aberdeen, Aberdeen Royal Infirmary, Foresterhill Healthcare Campus, Foresterhill, Aberdeen, AB25 2ZG, Scotland, UK.
Kasia
K
Matula
School of Medicine and Dentistry, University of Aberdeen, Aberdeen Royal Infirmary, Foresterhill Healthcare Campus, Foresterhill, Aberdeen, AB25 2ZG, Scotland, UK.
Elaina
E
Collie-Duguid
School of Medicine and Dentistry, University of Aberdeen, Aberdeen Royal Infirmary, Foresterhill Healthcare Campus, Foresterhill, Aberdeen, AB25 2ZG, Scotland, UK.|Department of Pathology, University of Aberdeen, Aberdeen Royal Infirmary, Foresterhill Healthcare Campus, Foresterhill, Aberdeen, AB25 2ZG, Scotland, UK.
Graeme
G
Murray
School of Medicine and Dentistry, University of Aberdeen, Aberdeen Royal Infirmary, Foresterhill Healthcare Campus, Foresterhill, Aberdeen, AB25 2ZG, Scotland, UK.
Khyati
K
Parikh
Department of Pathology, Maastricht University Medical Center, Maastricht, The Netherlands.
Heike
H
Grabsch
Cancer Science Institute of Singapore National University of Singapore, Singapore, Singapore.
Patrick
P
Tan
School of Medicine and Dentistry, University of Aberdeen, Aberdeen Royal Infirmary, Foresterhill Healthcare Campus, Foresterhill, Aberdeen, AB25 2ZG, Scotland, UK.
Salina
S
Lalwani
School of Medicine and Dentistry, University of Aberdeen, Aberdeen Royal Infirmary, Foresterhill Healthcare Campus, Foresterhill, Aberdeen, AB25 2ZG, Scotland, UK.
Roberta
R
Garau
School of Medicine and Dentistry, University of Aberdeen, Aberdeen Royal Infirmary, Foresterhill Healthcare Campus, Foresterhill, Aberdeen, AB25 2ZG, Scotland, UK.
Yuhan
Y
Ong
School of Medicine and Dentistry, University of Aberdeen, Aberdeen Royal Infirmary, Foresterhill Healthcare Campus, Foresterhill, Aberdeen, AB25 2ZG, Scotland, UK.|Department of Gastroenterology, University of Aberdeen, Aberdeen Royal Infirmary, Foresterhill Healthcare Campus, Foresterhill, Aberdeen, AB25 2ZG, Scotland, United Kingdom.
Gillian
G
Bain
School of Medicine and Dentistry, University of Aberdeen, Aberdeen Royal Infirmary, Foresterhill Healthcare Campus, Foresterhill, Aberdeen, AB25 2ZG, Scotland, UK.|Department of Oncology, University of Aberdeen, Aberdeen Royal Infirmary, Foresterhill Healthcare Campus, Foresterhill, Aberdeen, AB25 2ZG, Scotland, UK.
Asa-Dahle
AD
Smith
School of Medicine and Dentistry, University of Aberdeen, Aberdeen Royal Infirmary, Foresterhill Healthcare Campus, Foresterhill, Aberdeen, AB25 2ZG, Scotland, UK.|Department of Gastroenterology, University of Aberdeen, Aberdeen Royal Infirmary, Foresterhill Healthcare Campus, Foresterhill, Aberdeen, AB25 2ZG, Scotland, United Kingdom.
Gordon
G
Urquhart
Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, SC, USA.
Jacek
J
Bielawski
School of Medicine and Dentistry, University of Aberdeen, Aberdeen Royal Infirmary, Foresterhill Healthcare Campus, Foresterhill, Aberdeen, AB25 2ZG, Scotland, UK.
Michael
M
Finnegan
Division of Cancer Research, School of Medicine, University of Dundee, Mailbox 4, Level 7 Ninewells Hospital and Medical School, Dundee, DD1 9SY, Scotland, UK. r.petty@dundee.ac.uk.
Russell
R
Petty
D000446:Aldehyde-Lyases / Q000096:biosynthesis / Q000235:genetics*; D000970:Antineoplastic Agents / Q000627:therapeutic use; D045744:Cell Line, Tumor; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D004938:Esophageal Neoplasms / Q000188:drug therapy / Q000235:genetics* / Q000378:metabolism; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007150:Immunohistochemistry; D008246:Lysophospholipids / Q000096:biosynthesis / Q000235:genetics*; D008297:Male; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000096:biosynthesis / Q000235:genetics*; D012334:RNA, Neoplasm / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D015398:Signal Transduction; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000096:biosynthesis / Q000235:genetics; D013274:Stomach Neoplasms / Q000188:drug therapy / Q000235:genetics* / Q000378:metabolism; D000099157:Sphingosine Kinase
D000446:Aldehyde-Lyases; D000970:Antineoplastic Agents; D008246:Lysophospholipids; D017853:Phosphotransferases (Alcohol Group Acceptor); D012334:RNA, Neoplasm; D013110:Sphingosine; D000099157:Sphingosine Kinase; C060506:sphingosine 1-phosphate; C022649:sphingosine 1-phosphate lyase (aldolase)