title: Expression of CD74 in high grade gliomas: a potential role in temozolomide resistance.
abstract: Temozolomide (TMZ) is the most effective chemotherapeutic agent for glioblastoma (GBM). Resistance to this methylating agent is linked to DNA repair enzyme O6-methylguanine-DNA methyltransferase (MGMT). However, in recent studies MGMT status was not completely accurate as a predictor of TMZ response in GBM, suggesting other mechanisms of resistance. As part of an effort aimed at discovery of genes involved in TMZ resistance in GBM, the expression of CD74 was evaluated in GBM patient samples and the influence of CD74 on TMZ response was evaluated in GBM tumor models. Reverse transcription-polymerase-chain reaction (RT-PCR) demonstrated differential expression of CD74 mRNA among the GBM xenografts; 8 of 20 (40%) expressed CD74 mRNA. In a preliminary evaluation of whether CD74 expression might influence TMZ response, CD74 mRNA expression levels were inversely associated with in vivo TMZ resistance in 20 GBM xenograft lines (median survival 122 vs. 62.5 days; r = -0.48, P = 0.032). In follow up to this observation, CD74 shRNA knock down in U87 cells significantly suppressed in vitro proliferation and increased TMZ sensitivity as compared to a non-specific control shRNA. Consistent with an effect on proliferation and survival, silencing of CD74 by shRNA was associated with reduced Akt and Erk1/2 activation in response to stimulation by CD74 ligand macrophage-migration inhibition factor (MIF). Lastly, expression of CD74 protein was assessed in patient samples [nine anaplastic astrocytoma (AA), and 62 GBM] by immunohistochemistry, and appreciable expression was observed in 28% of samples. Collectively, these findings suggest that CD74 is expressed in a subset of high grade gliomas and may contribute to TMZ resistance.
authors.affiliation: Department of Radiation Oncology, Mayo Clinic, Rochester, MN 55905, USA. kitange.gaspar@mayo.edu
authors.forename: Gaspar J
authors.initials: GJ
authors.lastname: Kitange
authors.forename: Brett L
authors.initials: BL
authors.lastname: Carlson
authors.forename: Mark A
authors.initials: MA
authors.lastname: Schroeder
authors.forename: Paul A
authors.initials: PA
authors.lastname: Decker
authors.forename: Bruce W
authors.initials: BW
authors.lastname: Morlan
authors.forename: Wenting
authors.initials: W
authors.lastname: Wu
authors.forename: Karla V
authors.initials: KV
authors.lastname: Ballman
authors.forename: Caterina
authors.initials: C
authors.lastname: Giannini
authors.forename: Jann N
authors.initials: JN
authors.lastname: Sarkaria
mesh_terms: D000818:Animals; D000944:Antigens, Differentiation, B-Lymphocyte / Q000096:biosynthesis*; D000970:Antineoplastic Agents / Q000494:pharmacology; D015153:Blotting, Western; D001932:Brain Neoplasms / Q000235:genetics / Q000378:metabolism*; D003606:Dacarbazine / Q000031:analogs & derivatives / Q000494:pharmacology; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D020869:Gene Expression Profiling; D055785:Gene Knockdown Techniques; D005910:Glioma / Q000235:genetics / Q000378:metabolism*; D000949:Histocompatibility Antigens Class II / Q000096:biosynthesis*; D006801:Humans; D007150:Immunohistochemistry; D051379:Mice; D008819:Mice, Nude; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000077204:Temozolomide; D014162:Transfection; D023041:Xenograft Model Antitumor Assays
chemical_list: D000944:Antigens, Differentiation, B-Lymphocyte; D000970:Antineoplastic Agents; D000949:Histocompatibility Antigens Class II; C045084:invariant chain; D003606:Dacarbazine; D000077204:Temozolomide