title: MGMT immunoexpression in aggressive pituitary adenoma and carcinoma.
abstract: Recent case reports have documented the efficacy of temozolomide therapy in some aggressive pituitary adenomas and pituitary carcinomas resistant to multimodality therapy. Evidence suggests that low O6-methylguanine-DNA methyltransferase (MGMT) immunoexpression correlates with response to temozolomide chemotherapy. Herein, we aimed to study MGMT immunoexpression in a spectrum of pituitary tumors, indolent, aggressive and malignant. A literature review of the use of temozolomide in pituitary tumors was also performed. Immunohistochemistry for MGMT was performed on 60 pituitary tumors identified in the Mayo Clinic Tissue Registry and the consultation files of one of us (BWS). The group included 30 pituitary carcinomas (15 ACTH, 10 PRL, 1 FSH/LH, 1 TSH, 1 silent subtype 3 and 2 null cell). Tissue from recurrences was available in 17 cases. In addition, 30 functionally different pituitary adenomas were studied, including 15 invasive and 15 non-invasive adenomas. Overall, 32 cases of pituitary tumors (54%) demonstrated low MGMT immunoexpression. This included 17 of 30 (57%) carcinomas, 9 of 15 (60%) invasive adenomas, and 6 of 15 cases (40%) of non-invasive pituitary adenomas. There was no significant change in MGMT immunoexpression between primary and recurrent tumors. Prolactin-producing carcinomas had the highest proportion of tumors (80%) with low expression. A significant proportion of pituitary adenomas and carcinomas demonstrate low MGMT immunoexpression. In an effort to anticipate the likelihood of a temozolomide response, all cases of aggressive pituitary tumors should be assessed for MGMT expression.
authors.affiliation: Department of Anatomical Pathology and Cytopathology, Royal Brisbane and Women's Hospital and Gold Coast Hospital, Queensland, Australia.
authors.forename: Queenie
authors.initials: Q
authors.lastname: Lau
authors.forename: Bernd
authors.initials: B
authors.lastname: Scheithauer
authors.forename: Kalman
authors.initials: K
authors.lastname: Kovacs
authors.forename: Eva
authors.initials: E
authors.lastname: Horvath
authors.forename: Luis V
authors.initials: LV
authors.lastname: Syro
authors.forename: Ricardo
authors.initials: R
authors.lastname: Lloyd
mesh_terms: D000328:Adult; D000368:Aged; D018906:Antineoplastic Agents, Alkylating / Q000627:therapeutic use; D015254:DNA Modification Methylases / Q000378:metabolism*; D045643:DNA Repair Enzymes / Q000378:metabolism*; D003606:Dacarbazine / Q000031:analogs & derivatives / Q000627:therapeutic use; D006801:Humans; D007150:Immunohistochemistry; D007165:Immunosuppression Therapy; D008297:Male; D010911:Pituitary Neoplasms / Q000188:drug therapy / Q000276:immunology*; D000077204:Temozolomide; D025521:Tumor Suppressor Proteins / Q000378:metabolism*
chemical_list: D018906:Antineoplastic Agents, Alkylating; D025521:Tumor Suppressor Proteins; D003606:Dacarbazine; D015254:DNA Modification Methylases; C515491:MGMT protein, human; D045643:DNA Repair Enzymes; D000077204:Temozolomide