title: PTPN6 expression is epigenetically regulated and influences survival and response to chemotherapy in high-grade gliomas.
abstract: The prognosis of high-grade glioma patients is poor, and the tumors are characterized by resistance to therapy. The aims of this study were to analyze the prognostic value of the expression of the protein tyrosine phosphatase non-receptor type 6 (PTPN6, also referred to as SHP1) in high-grade glioma patients, the epigenetic regulation of the expression of PTPN6, and the role of its expression in chemotherapy resistance in glioma-derived cells. PTPN6 expression was analyzed with immunohistochemistry in 89 high-grade glioma patients. Correlation between PTPN6 expression and overall survival was analyzed with Kaplan-Meier univariate analysis and Cox regression multivariate analysis. Differences in drug sensitivity to a panel of 16 chemotherapeutic drugs between PTPN6-overexpressing clones and control clones were analyzed in vitro with the fluorometric microculture cytotoxicity assay. Cell cycle analysis was done with Krishan staining and flow cytometry. Apoptosis was analyzed with a cell death detection ELISA kit as well as cleaved caspase-3 and caspase-9 Western blotting. Autophagy was analyzed with LC3B Western blotting. Methylation of the PTPN6 promoter was analyzed with bisulfite pyrosequencing, and demethylation of PTPN6 was done with decitabine treatment. The PTPN6 expression correlated in univariate analysis to poor survival for anaplastic glioma patients (p = 0.026). In glioma-derived cell lines, overexpression of PTPN6 caused increase resistance (p < 0.05) to the chemotherapeutic drugs bortezomib, cisplatin, and melphalan. PTPN6 expression did not affect bortezomib-induced cell cycle arrest, apoptosis, or autophagy. Low PTPN6 promoter methylation correlated to protein expression, and the protein expression was increased upon demethylation in glioma-derived cells. PTPN6 expression may be a factor contributing to poor survival for anaplastic glioma patients, and in glioma-derived cells, its expression is epigenetically regulated and influences the response to chemotherapy.
authors: Rudbeck Laboratory, Section of Oncology, Department of Radiology, Oncology and Radiation Sciences, Uppsala University, 751 85, Uppsala, Sweden, linda.sooman@onkologi.uu.se.
authors: Linda
authors: L
authors: Sooman
authors: Simon
authors: S
authors: Ekman
authors: Georgios
authors: G
authors: Tsakonas
authors: Archita
authors: A
authors: Jaiswal
authors: Sanjay
authors: S
authors: Navani
authors: Per-Henrik
authors: PH
authors: Edqvist
authors: Fredrik
authors: F
authors: Pontén
authors: Stefan
authors: S
authors: Bergström
authors: Mikael
authors: M
authors: Johansson
authors: Xuping
authors: X
authors: Wu
authors: Erik
authors: E
authors: Blomquist
authors: Michael
authors: M
authors: Bergqvist
authors: Joachim
authors: J
authors: Gullbo
authors: Johan
authors: J
authors: Lennartsson
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D017209:Apoptosis; D001343:Autophagy; D001897:Boronic Acids / Q000494:pharmacology; D000069286:Bortezomib; D001932:Brain Neoplasms / Q000188:drug therapy / Q000401:mortality*; D045744:Cell Line, Tumor; D019175:DNA Methylation; D044127:Epigenesis, Genetic; D005260:Female; D005910:Glioma / Q000188:drug therapy / Q000401:mortality*; D006801:Humans; D008297:Male; D008875:Middle Aged; D060787:Neoplasm Grading; D011379:Prognosis; D011401:Promoter Regions, Genetic; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6 / Q000235:genetics / Q000502:physiology*; D011719:Pyrazines / Q000494:pharmacology
chemical_list: D001897:Boronic Acids; D011719:Pyrazines; D000069286:Bortezomib; C509249:PTPN6 protein, human; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6