title: Transketolase-like 1 ectopic expression is associated with DNA hypomethylation and induces the Warburg effect in melanoma cells.
abstract: BACKGROUND
  The metabolism of cancer cells is often reprogrammed by dysregulation of metabolic enzymes. Transketolase-like 1 (TKTL1) is a homodimeric transketolase linking the pentose-phosphate pathway with the glycolytic pathway. It is generally silenced at a transcriptional level in somatic tissues. However, in human cancers its expression is associated with the acquisition of a glycolytic phenotype (the Warburg effect) by cancer cells that contributes to the progression of malignant tumors. In melanoma, defective promoter methylation results in the expression of genes and their products that can affect the tumor cell's phenotype including the modification of immune and functional characteristics. The present study evaluates the role of TKTL1 as a mediator of disease progression in melanoma associated with a defective methylation phenotype.
  
  
  METHODS
  The expression of TKTL1 in metastatic melanoma tumors and cell lines was analysed by qRT-PCR and immunohistochemistry. The promoter methylation status of TKTL1 in melanoma cells was evaluated by quantitative methylation specific PCR. Using qRT-PCR, the effect of a DNA demethylating agent 5-aza-2'-deoxycytidine (5aza) on the expression of TKTL1 was examined. Biochemical and molecular analyses such as glucose consumption, lactate production, invasion, proliferation and cell cycle progression together with ectopic expression and siRNA mediated knockdown were used to investigate the role of TKTL1 in melanoma cells.
  
  
  RESULTS
  Expression of TKTL1 was highly restricted in normal adult tissues and was overexpressed in a subset of metastatic melanoma tumors and derived cell lines. The TKTL1 promoter was activated by hypomethylation and treatment with 5aza induced TKTL1 expression in melanoma cells. Augmented expression of TKTL1 in melanoma cells was associated with a glycolytic phenotype. Loss and gain of function studies revealed that TKTL1 contributed to enhanced invasion of melanoma cells.
  
  
  CONCLUSIONS
  Our data provide evidence for an important role of TKTL1 in aerobic glycolysis and tumor promotion in melanoma that may result from defective promoter methylation. This epigenetic change may enable the natural selection of tumor cells with a metabolic phenotype and thereby provide a potential therapeutic target for a subset of melanoma tumors with elevated TKTL1 expression.
authors.affiliation: Ludwig Institute for Cancer Research, Melbourne-Austin Branch, Heidelberg, VIC, 3084, Australia.|Olivia Newton-John Cancer Research Institute, Heidelberg, VIC, 3084, Australia.|Department of Medicine, University of Melbourne, Melbourne, VIC, 3010, Australia.|School of Cancer Medicine, Latrobe University, Melbourne, VIC, 3086, Australia.|School of Medicine and the Gallipoli Medical Research Foundation, The University of Queensland, Brisbane, QLD 4120, Australia.
authors.forename: Aparna
authors.initials: A
authors.lastname: Jayachandran
authors.affiliation: Ludwig Institute for Cancer Research, Melbourne-Austin Branch, Heidelberg, VIC, 3084, Australia.
authors.forename: Pu-Han
authors.initials: PH
authors.lastname: Lo
authors.affiliation: Ludwig Institute for Cancer Research, Melbourne-Austin Branch, Heidelberg, VIC, 3084, Australia.|ACRF Chemical Biology Division, The Walter and Eliza Hall Institute of Medical Research, Parkville, Melbourne, 3052, Australia.|Department of Medical Biology, University of Melbourne, Parkville, Melbourne, 3010, Australia.
authors.forename: Anderly C
authors.initials: AC
authors.lastname: Chueh
authors.affiliation: Ludwig Institute for Cancer Research, Melbourne-Austin Branch, Heidelberg, VIC, 3084, Australia.|Olivia Newton-John Cancer Research Institute, Heidelberg, VIC, 3084, Australia.|Department of Medicine, University of Melbourne, Melbourne, VIC, 3010, Australia.
authors.forename: Prashanth
authors.initials: P
authors.lastname: Prithviraj
authors.affiliation: Ludwig Institute for Cancer Research, Melbourne-Austin Branch, Heidelberg, VIC, 3084, Australia.|Olivia Newton-John Cancer Research Institute, Heidelberg, VIC, 3084, Australia.
authors.forename: Ramyar
authors.initials: R
authors.lastname: Molania
authors.affiliation: Ludwig Institute for Cancer Research, Melbourne-Austin Branch, Heidelberg, VIC, 3084, Australia.|Olivia Newton-John Cancer Research Institute, Heidelberg, VIC, 3084, Australia.
authors.forename: Mercedes
authors.initials: M
authors.lastname: Davalos-Salas
authors.affiliation: Ludwig Institute for Cancer Research, Melbourne-Austin Branch, Heidelberg, VIC, 3084, Australia.|Department of Medicine, University of Melbourne, Melbourne, VIC, 3010, Australia.
authors.forename: Matthew
authors.initials: M
authors.lastname: Anaka
authors.affiliation: Ludwig Institute for Cancer Research, Melbourne-Austin Branch, Heidelberg, VIC, 3084, Australia.|Olivia Newton-John Cancer Research Institute, Heidelberg, VIC, 3084, Australia.
authors.forename: Marzena
authors.initials: M
authors.lastname: Walkiewicz
authors.affiliation: Ludwig Institute for Cancer Research, Melbourne-Austin Branch, Heidelberg, VIC, 3084, Australia.|Olivia Newton-John Cancer Research Institute, Heidelberg, VIC, 3084, Australia.|Department of Medicine, University of Melbourne, Melbourne, VIC, 3010, Australia.|School of Cancer Medicine, Latrobe University, Melbourne, VIC, 3086, Australia.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Cebon
authors.affiliation: Ludwig Institute for Cancer Research, Melbourne-Austin Branch, Heidelberg, VIC, 3084, Australia. andreas.behren@onjcri.org.au.|Olivia Newton-John Cancer Research Institute, Heidelberg, VIC, 3084, Australia. andreas.behren@onjcri.org.au.|Department of Medicine, University of Melbourne, Melbourne, VIC, 3010, Australia. andreas.behren@onjcri.org.au.|School of Cancer Medicine, Latrobe University, Melbourne, VIC, 3086, Australia. andreas.behren@onjcri.org.au.|Cancer Immuno-biology Laboratory, Olivia Newton-John Cancer Research Institute, Level 5, Olivia Newton-John Cancer and Wellness Centre, 145 Studley Road, Heidelberg, VIC, 3084, Australia. andreas.behren@onjcri.org.au.
authors.forename: Andreas
authors.initials: A
authors.lastname: Behren
mesh_terms: D001374:Azacitidine / Q000031:analogs & derivatives / Q000494:pharmacology; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D019175:DNA Methylation / Q000187:drug effects; D000077209:Decitabine; D044127:Epigenesis, Genetic; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006019:Glycolysis; D006801:Humans; D008545:Melanoma / Q000235:genetics* / Q000378:metabolism; D009361:Neoplasm Invasiveness; D009362:Neoplasm Metastasis; D011401:Promoter Regions, Genetic / Q000187:drug effects; D014174:Transketolase / Q000235:genetics* / Q000378:metabolism; D015854:Up-Regulation
chemical_list: D000077209:Decitabine; C505431:TKTL1 protein, human; D014174:Transketolase; D001374:Azacitidine