title: O6-Methylguanine-DNA methyltransferase is a novel negative effector of invasion in glioblastoma multiforme.
abstract: The dismal prognosis of glioblastoma multiforme (GBM) is mostly due to the high propensity of GBM tumor cells to invade. We reported an inverse relationship between GBM angiogenicity and expression of the DNA repair protein O(6)-methylguanine-DNA methyltransferase (MGMT), which has been extensively characterized for its role in resistance to alkylating agents used in GBM treatment. In the present study, given the major role of angiogenesis and invasion in GBM aggressiveness, we aimed to investigate the relationship between MGMT expression and GBM invasion. Stable overexpression of MGMT in the U87MG cell line significantly decreased invasion, altered expression of invasion-related genes, decreased expression of α(5)β(1) integrin and focal adhesion kinase, and reduced their spindle-shaped morphology and migration compared with the empty vector control. Conversely, short hairpin RNA-mediated stable knockdown of MGMT or its pharmacologic depletion in the MGMT-positive T98G cell line were required for increased invasion. The inverse relationship between MGMT and invasion was further validated in primary GBM patient-derived cell lines. Using paraffin-embedded tumors from patients with newly diagnosed GBM (n = 59), tumor MGMT promoter hypermethylation (MGMT gene silencing) was significantly associated with increased immunohistochemical expression of the proinvasive matricellular protein secreted protein acidic and rich in cysteine (SPARC; P = 0.039, χ(2) test). Taken together, our findings highlight for the first time the role of MGMT as a negative effector of GBM invasion. Future studies are warranted to elucidate the role of SPARC in the molecular mechanisms underlying the inverse relationship between MGMT and GBM invasion and the potential use of MGMT and SPARC as biomarkers of GBM invasion.
authors.affiliation: The Research Institute of the McGill University Health Centre, 1625 Pine Avenue West, Montreal, Quebec, H3G 1A4, Canada.
authors.forename: Manik
authors.initials: M
authors.lastname: Chahal
authors.forename: Bassam
authors.initials: B
authors.lastname: Abdulkarim
authors.forename: Yaoxian
authors.initials: Y
authors.lastname: Xu
authors.forename: Marie-Christine
authors.initials: MC
authors.lastname: Guiot
authors.forename: Jacob C
authors.initials: JC
authors.lastname: Easaw
authors.forename: Nicolas
authors.initials: N
authors.lastname: Stifani
authors.forename: Siham
authors.initials: S
authors.lastname: Sabri
mesh_terms: D001932:Brain Neoplasms / Q000201:enzymology* / Q000235:genetics / Q000473:pathology*; D045744:Cell Line, Tumor; D002465:Cell Movement; D048430:Cell Shape; D004789:Enzyme Activation; D051416:Focal Adhesion Protein-Tyrosine Kinases / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic; D055785:Gene Knockdown Techniques; D005909:Glioblastoma / Q000201:enzymology* / Q000235:genetics / Q000473:pathology*; D006801:Humans; D007150:Immunohistochemistry; D009361:Neoplasm Invasiveness; D019853:O(6)-Methylguanine-DNA Methyltransferase / Q000172:deficiency / Q000378:metabolism*; D015676:Osteonectin / Q000378:metabolism; D010641:Phenotype; D034741:RNA, Small Interfering / Q000378:metabolism
chemical_list: D015676:Osteonectin; D034741:RNA, Small Interfering; D019853:O(6)-Methylguanine-DNA Methyltransferase; D051416:Focal Adhesion Protein-Tyrosine Kinases