Humberto Uribe

MGMT immunoexpression predicts responsiveness of pituitary tumors to temozolomide therapy

Temozolomide, an alkylating imidazol tetrazine derivative, inhibits DNA replication and is used successfully in the management of patients with gliomas and other malignancies [5, 12]. Recent studies showed the drug to be eVective in patients with pituitary carcinoma and aggressive pituitary adenoma [1, 2, 7, 10, 14]. We reported the case of a 46-year-old man with an aggressive, prolactin (PRL) secreting pituitary tumor [4, 13]. Temozolomide treatment caused marked clinical improvement, reduction in blood PRL levels, and tumor shrinkage [13]. Morphologically, the treated tumor showed necrosis, hemorrhage, Wbrosis and neuronal transformation. Mitotic activity and Ki-67 labeling were signiWcantly decreased [4]. Based on these dramatic clinical, laboratory, imaging and morphologic changes, temozolomide was given to a 41-year-old man with an aggressive silent subtype 2 corticotroph pituitary adenoma. Neither clinical improvement nor tumor shrinkage was observed. No morphologic diVerences were seen between the preand posttreatment tumors. The cytotoxic eVect of the temozolomide depends upon methylation of guanine at the O-6 position in DNA. O-6 methylguanine DNA methyltransferase (MGMT) is a DNA repair enzyme, which removes the alkyl group adducts from the O-6 position and induces resistance to temozolomide [6, 9, 11]. Previous immunohistochemical studies showed that gliomas with low MGMT levels respond, whereas those with high levels resist temozolomide eVect [6, 9, 11]. This suggests that MGMT immunostaining may serve as an indicator of treatment responsiveness. Based on the results of previous studies, we investigated MGMT immunopositivity in the above noted cases and in an additional three pituitary adenomas. The immunohistochemical method was described in previous publication [3, 8]. Similar to the results obtained in gliomas, our study showed lack of MGMT staining in the responsive tumor (Fig. 1) and high expression in the resistant tumor (Fig. 2) as well as in the three other adenomas studied. We suggest that MGMT expression should be immunohistochemically assessed before embarking upon temozolomide treatment of aggressive pituitary tumors. If MGMT expression is K. Kovacs Department of Pathology, St. Michael’s Hospital, University of Toronto, Toronto, ON, Canada

Antitumour effects of temozolomide in a man with a large, invasive prolactin‐producing pituitary neoplasm

1 Libe, R., Morpurgo, P.S., Cappiello, V., Maffini, A., Bondioni, S., Locatelli, M., Zavarone, M., Beck-Peccoz, P. & Spada, A. (2005) Ghrelin and adiponectin in patients with Cushing’s disease before and after transsphenoidal surgery. Clinical Endocrinology , 62 , 30–36. 2 Degawa-Yamauchi, M., Moss, K.A., Bovenkerk, J.E., Shankar, S.S., Morrison, C.L., Lelliott, C.J., Vidal-Puig, A., Jones, R. & Considine, R.V. (2005) Regulation of adiponectin expression in human adipocytes: effects of adiposity, glucocorticoids, and tumor necrosis factor alpha. Obesity Research , 13 , 662–669. 3 Shojima, N., Sakoda, H., Ogihara, T., Fujishiro, M., Katagiri, H., Anai, M., Onishi, Y., Ono, H., Inukai, K., Abe, M., Fukushima, Y., Kikuchi, M., Oka, Y. & Asano, T. (2002) Humoral regulation of resistin expression in 3T3-L1 and mouse adipose cells. Diabetes , 51 , 1737–1744. 4 Arnaldi, G., Angeli, A., Atkinson, A.B., Bertagna, X., Cavagnini, F., Chrousos, G.P., Fava, G.A., Findling, J.W., Gaillard, R.C., Grossman, A.B., Kola, B., Lacroix, A., Mancini, T., Mantero, F., Newell-Price, J., Nieman, L.K., Sonino, N., Vance, M.L., Giustina, A. & Boscaro, M. (2003) Diagnosis and complications of Cushing’s syndrome: a consensus statement. Journal of Clinical Endocrinology and Metabolism , 88 , 5593–5602 5 Fallo, F., Scarda. A., Sonino, N., Paoletta, A., Boscaro, M., Pagano, C., Federspil, G. & Vettor, R. (2004) Effect of glucocorticoids on adiponectin: a study in healthy subjects and in Cushing syndrome. European Journal of Endocrinology , 150 , 339–344.

Treatment of pituitary neoplasms with temozolomide: a review.

Temozolomide, an orally administered alkylating agent, is used to treat malignant gliomas. Recent reports also have documented its efficacy in the treatment of pituitary adenomas and carcinomas. Temozolomide methylates DNA and thereby exhibits an antitumor effect. O6‐methylguanine‐DNA methyltransferase (MGMT), a DNA repair enzyme, removes alkylating adducts induced by temozolomide, counteracting its effects. The authors of this review conducted a Medline database search regarding temozolomide in the treatment of pituitary tumors. Demographic characteristics, tumor types, and therapeutic responses were noted in all patients. Data regarding MGMT immunoexpression, which was documented in some studies, were correlated with information regarding clinical and radiologic responses. To date, there have been 19 reported cases of adenohypophyseal tumors treated with temozolomide, including 13 adenomas and 6 carcinomas. Ten of those 13 adenomas responded favorably, and 2 nonresponsive tumors had high‐level MGMT immunoexpression. All 6 carcinomas responded to therapy, but data regarding MGMT expression were available for only 3 patients, and each had low MGMT expression. In 2 adenomas, morphologic studies were performed both before and after the patients received temozolomide. The responsive tumor had necrosis, hemorrhage, fibrosis, and neuronal differentiation. The nonresponsive tumor had no changes. There have been no reported complications attributable to temozolomide. The current results indicated that temozolomide is efficacious in the treatment of aggressive pituitary adenomas and pituitary carcinomas. Evidence indicated that low‐level MGMT immunoexpression is correlated with a favorable response. A significant proportion of pituitary adenomas and carcinomas had low MGMT immunoexpression. Cancer 2011.

Temozolomide in aggressive pituitary adenomas and carcinomas.

Temozolomide is an alkylating agent used in the treatment of gliomas and, more recently, aggressive pituitary adenomas and carcinomas. Temozolomide methylates DNA and, thereby, has antitumor effects. O6-methylguanine-DNA methyltransferase, a DNA repair enzyme, removes the alkylating adducts that are induced by temozolomide, thereby counteracting its effects. A Medline search for all of the available publications regarding the use of temozolomide for the treatment of pituitary tumors was performed. To date, 46 cases of adenohypophysial tumors that were treated with temozolomide, including 30 adenomas and 16 carcinomas, have been reported. Eighteen of the 30 (60%) adenomas and 11 of the 16 (69%) carcinomas responded favorably to treatment. One patient with multiple endocrine neoplasia type 1 and an aggressive prolactin-producing adenoma was also treated and demonstrated a good response. No significant complications have been attributed to temozolomide therapy. Thus, temozolomide is an effective treatment for the majority of aggressive adenomas and carcinomas. Evidence indicates that there is an inverse correlation between levels of O6-methylguanine-DNA methyltransferase immunoexpression and therapeutic response. Alternatively, high-level O6-methylguanine-DNA methyltransferase immunoexpression correlates with an unfavorable response. Here, we review the use of temozolomide for treating pituitary neoplasms.

Pituitary tumors in patients with MEN1 syndrome

We briefly review the characteristics of pituitary tumors associated with multiple endocrine neoplasia type 1. Multiple endocrine neoplasia type 1 is an autosomal-dominant disorder most commonly characterized by tumors of the pituitary, parathyroid, endocrine-gastrointestinal tract, and pancreas. A MEDLINE search for all available publications regarding multiple endocrine neoplasia type 1 and pituitary adenomas was undertaken. The prevalence of pituitary tumors in multiple endocrine neoplasia type 1 may vary from 10% to 60% depending on the studied series, and such tumors may occur as the first clinical manifestation of multiple endocrine neoplasia type 1 in 25% of sporadic and 10% of familial cases. Patients were younger and the time between initial and subsequent multiple endocrine neoplasia type 1 endocrine lesions was significantly longer when pituitary disease was the initial manifestation of multiple endocrine neoplasia type 1. Tumors were larger and more invasive and clinical manifestations related to the size of the pituitary adenoma were significantly more frequent in patients with multiple endocrine neoplasia type 1 than in subjects with non-multiple endocrine neoplasia type 1. Normalization of pituitary hypersecretion was much less frequent in patients with multiple endocrine neoplasia type 1 than in subjects with non-multiple endocrine neoplasia type 1. Pituitary tumors in patients with multiple endocrine neoplasia type 1 syndrome tend to be larger, invasive and more symptomatic, and they tend to occur in younger patients when they are the initial presentation of multiple endocrine neoplasia type 1.

Severe lymphocytic adenohypophysitis with selective disappearance of prolactin cells: a histologic, ultrastructural and immunoelectron microscopic study

Abstract. We report the first documented example (case 1) of lymphocytic adenohypophysitis (LAH) associated with selective destruction of prolactin cells. The morphologic data are compared to those obtained in another, more typical case (case 2). Case 1 was a 35-year-old woman with remote history of pregnancy who presented with headache, oligomenorrhea and visual disturbances. The blood prolactin level was nearly undetectable, but no deficiency of other pituitary hormones was evident. A sellar and parasellar mass compressing the optic chiasm was removed transsphenoidally. Histology demonstrated massive infiltration with lymphocytes, plasma cells and macrophages causing marked destruction of pituitary acini. Part of the gland was fibrotic. Immunocytochemistry documented all pituitary hormones, but only few cells, probably mammosomatotrophs, were immunoreactive for prolactin. Electron microscopy and immunoelectron microscopy using double gold labeling for growth hormone and prolactin detected no prolactin cells. A striking ultrastructural finding was the prominence of folliculostellate cells in areas of active cell destruction supporting the presumed immune role of these cells. LAH in case 2 (24-year-old woman) became manifest during late pregnancy, causing pituitary enlargement and visual field defects. Pituitary tests showed no major hormonal deficits. Moderate hyperprolactinemia was appropriate for her pregnancy status. A sellar mass, thought to be adenoma, was removed. Histology demonstrated multifocal LAH without major destruction of acinar structures. Immunocytochemistry and electron microscopy documented all pituitary cell types including the marked abundance of prolactin-producing cells, resultant of gestational prolactin cell hyperplasia. In addition to prolactin cells and growth hormone cells, immunoelectron microscopy showed several bihormonal mammosomatotrophs, also appropriate for pregnancy.

Ultrastructural and immunoelectron microscopic study of three unusual plurihormonal pituitary adenomas.

Monomorphous pituitary adenomas expressing several hormones by immunocytochemistry are common, whereas adenomas displaying multiple immunoreactivities and consisting of more than one morphologic cell types are rare. Three such unusual pituitary adenomas, surgically removed from two patients with acromegaly and one patient with hyperprolactinemia, were investigated by histology, immunocytochemistry, transmission electron microscopy, as well as immunoelectron microscopy using double immunogold labeling. Immunocytochemistry revealed variable degrees of immunoreactivities for growth hormone (GH), prolactin (PRL), thyroid-stimulating hormone (beta-TSH), and alpha-subunit of glycoprotein hormones in all three tumors. The three adenomas consisted of phenotypically diverse cell populations as documented by transmission electron microscopy. In addition to monohormonal GH cells, immunoelectron microscopy demonstrated numerous cells colocalizing GH and PRL or GH and beta-TSH, and rarely PRL and beta-TSH in tumors of acromegalics. The adenoma causing hyperprolactinemia consisted chiefly of mammosomatotrophs colocalizing PRL and GH, whereas beta-TSH labeling was scant. The three tumors in the study were selected from a cluster of five plurimorphous plurihormonal adenomas received from the same locale where they accounted for an unprecedented 21% of adenomas producing GH and/or PRL. The enhanced susceptibility to develop plurimorphous adenomas of the acidophil cell line may have a genetic basis in the stable population the patients came from.

Plurihormonality in pituitary adenomas associated with acromegaly.

Bihormonal or plurihormonal pituitary tumors produce two or more hormones different in chemical composition, immunoreactivity, and clinical significance. Immunohistochemical and electron microscopic investigations and more recently molecular-genetic studies have provided conclusive evidence of the production of multiple hormones by pituitary adenomas. Most frequently, they produce GH, PRL, TSH, and/or alpha-subunit of the g/y-coprotein hormones. Other uncommon combinations may also be apparent. We report the case of a 40-yr-old acromegalic man with a pituitary macrodenoma. The pituitary tumor was removed by transsphenoidal surgery. Histological, immunohistochemical, electron microscopic, and immunoelectron microscopic examinations revealed that the tumor contains multiple hormones (GH, LH, and alpha subunit) and transcription factors. The application of different reagents yielded different patterns of positivity indicating that the validity of some common immunohistochemical reagents must be re-evaluated.

Non-uniform response to temozolomide therapy in a pituitary gonadotroph adenoma.

Endocrinologically active pituitary adenomas are treated either with surgery, radiotherapy or various drugs, including dopamine agonists, long-acting somatostatin analogs, growth hormone receptor antagonists, or corticosteroid secretion inhibitors. Fully 35% to 55% of pituitary adenomas invade adjacent structures. This figure is lower in gonadotroph adenomas, less than 5% compared to other adenoma types. Clinical management of invasive adenomas is challenging, and most of them tend to recur after surgery. Hormonally active pituitary adenomas may even be resistant to combined medical, surgical, and radiotherapy treatments. In comparison, pituitary carcinomas represent 0.2% of all adenohypophysial neoplasms1, and not only invade adjacent structures but give rise to cerebrospinal and/or systemic metastases with high mortality. The lack of response to aggressive pituitary adenomas, particularly carcinomas to conventional therapies, drives search for new approaches1. Temozolomide (TMZ) is a chemotherapeutic agent which can cross the blood-brain barrier and has proven utility in the treatment of glioblastoma. More recently, it has been used to treat aggressive pituitary adenomas and carcinomas2. To date, cases of such aggressive pituitary tumors have been reported in terms of clinical outcomes. The morphologic effects of therapy have been described in only three patients2. Of these, two tumors responded, both radiologically and morphologically. The first case, a prolactin cell adenoma, did not express MGMT (06methylguanine-DNA methyltransferase), a DNA repair protein that counteracts TMZ anti-neoplastic action. The second case, an aggressive silent subtype 2 corticotroph adenoma, showed no morphological change after therapy. This tumor showed highlevel immunoexpression of MGMT by immunohistochemistry. The third case, a corticotroph adenoma in a patient with Cushing’s disease, showed no MGMT immunoexpression, and 80% reduction in tumor volume was noted on magnetic resonance imaging (MRI) scan. The Ki-67 labeling index decreased after the therapy. Herein, we report a recurrent pituitary gonadotroph adenoma in which the partial response to TMZ appeared to result from non-uniform MGMT immunoexpression, portions of the tumor lacking immunoreactivity and the remainder showing high-level immunostaining.

Prolactin-producing pituitary adenoma associated with prolactin cell hyperplasia.

A 24-yr-old woman with amenorrhea, galactorrhea, hyperprolactinemia, and sellar mass underwent transsphenoidal surgery. Histologic, immunohistochemical, and electron microscopic investigation revealed a well-differentiated, sparsely granulated prolactin (PRL) cell adenoma of the pituitary showing conclusive PRL immunoreactivity. In the nontumorous adenohypophysis PRL cell hyperplasia was noted. Marked differences were evident between the neoplastic and hyperplastic areas. The tumor consisted of sparsely granulated PRL cells immunoreactive only for PRL. As demonstrated by immunoelectron microscopy, the hyperplastic are a comprised monohormonal sparsely granulated PRL cells as well as bihormonal mammosomatotrophs immunoreactive for both PRL and growth hormone. The MIB-1 index was higher whereas microvessel density was lower in the adenoma as compared with the hyperplastic area. In addition, the nontumorous area showed lymphocytic infiltration whereas inflammatory reaction was not seen in the adenoma. This case represents a rare association of a PRL cell adenoma and PRL cell hyperplasia. The fact that these two lesions were contiguous in the surgically removed material raises the possibility that hyperplasia can precede and transform into adenoma.