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Aberrant Activation of the Kynurenine Pathway in Gliomas Increases Polymerase Kappa Expression and Promotes Genomic Instability and Chemoresistance
Author(s) -
Bostian April,
Maddukuri Leena,
Reed Megan,
Savenka Tatsiana,
Hartman Jessica,
Davis Lauren,
Pouncey Dakota,
Miller Grover,
Eoff Robert
Publication year - 2016
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.30.1_supplement.1052.5
Subject(s) - aryl hydrocarbon receptor , genome instability , cancer research , kynurenine pathway , aryl hydrocarbon receptor nuclear translocator , biology , kynurenine , glioma , dna damage , transcription factor , gene , dna , genetics , tryptophan , amino acid
Glioblastoma multiforme (GBM) is the most malignant primary brain tumor and has a median survival time of 12 months, due in large part to poor responses to chemo‐ and radio‐therapy. These tumors exhibit high levels of DNA damage response activation before treatment and this likely plays a role in the inherent chemo‐ and radio‐resistance of GBM. Y‐family polymerases aid cells in bypassing genotoxic damage, but they are mis‐regulated in many cancers. Over‐expression of the Y‐family enzyme human polymerase kappa (hpol κ), which is up‐regulated in GBM patients, has been linked to an increase in genomic instability. The factors promoting over‐expression of hpol κ in GBM are unknown, but previous work implicates the aryl hydrocarbon receptor (AhR) in the regulation of hpol k levels. Up‐regulation of the AhR pathway through aberrant production of the endogenous ligand kynurenine is associated with malignant progression and shorter survival in glioma patients. We tested the hypothesis that the AhR signaling pathway transcriptionally regulates hpol κ levels in gliomas using in vitro cell culture models. Exposure to the AhR agonist 3‐methylcholanthrene increases hpol κ protein and mRNA levels 2–3‐fold in GBM cells. Furthermore, when the enzyme tryptophan 2,3‐dioxygenase (TDO), which is responsible for aberrant kynurenine production in gliomas, is inhibited by the small molecule 680C91, hpol κ expression decreased 20–60% in three GBM cell lines. We then examined the idea that stimulation of hpol k expression by the AhR pathway contributes to the inherent genomic instability seen in gliomas. Supporting our hypothesis, TDO inhibition leads to a decrease in spontaneous micronuclei formation in three GBM cell lines (33.6% DMSO to 12.9% 10 μM 680C91 in T98G cells; 12.3% DMSO to 8.7% 10 μM 680C91 in U87MG; and 25.3% DMSO to 20.1% 10 μM 680C91 in A172 cells). Additionally, treatment with an AhR antagonist also decreases micronuclei formation in T98G cells (33.6% DMSO to 17.2% 10 μM CH‐223191), as does knock down of hpol κ expression (25.5% for scr siRNA to 19.7% hpol κ). Furthermore, we performed epistasis assays which supported our hypothesis that TDO activity, AhR signaling, and hpol κ expression act in the same pathway to promote genomic instability in gliomas. Moreover, we found that TDO inhibition also significantly increases sensitivity of the T98G cells to various concentrations (10 – 100 μM) of cisplatin. Our study reveals how activation of AhR signaling could impact replication dynamics in gliomas and may provide insight into the mechanisms leading to the genomic instability and chemoresistance often inherent to this disease. Support or Funding Information This work was supported by NIH grant CA 183895 (to R.L.E.).