Yuji Tani, Naoko Inoshita, Toru Sugiyama, Masako Kato, Shozo Yamada, Masayoshi Shichiri and Yukio Hirata
Cushing's disease (CD) is usually caused by ACTH-secreting pituitary microadenomas, while silent corticotroph adenomas (SCA) are macroadenomas without Cushingoid features. However, the molecular mechanism(s) underlying their different tumor growth remains unknown. The aim of the current study was to evaluate and compare the gene expression profile of cell cycle regulators and cell growth-related transcription factors in CD, SCA, and non-functioning adenomas (NFA).
Design and methods
Tumor tissue specimens resected from 43 pituitary tumors were studied: CD (n=10), SCA (n=11), and NFA (n=22). The absolute transcript numbers of the following genes were quantified with real-time quantitative PCR assays: CDKN2A (or p16
INK4a), cyclin family (A1, B1, D1, and E1), E2F1, RB1, BUB1, BUBR1, ETS1, and ETS2. Protein expressions of p16 and cyclin D1 were semi-quantitatively evaluated by immunohistochemical study.
Results and conclusion
CDKN2A gene expression was about fourfold greater in CD than in SCA and NFA. The gene expressions of cyclins D1, E1, and B1, but not of A1, in CD were significantly suppressed than those in NFA. Cyclin D1 gene expression positively correlated with cyclins B1 and E1. The gene expressions of E2F1, RB1, BUB1, BUBR1, ETS1, and ETS2 did not differ between each group. Positive immunostaining for p16 and negative immunostaining for cyclin D1 were more frequent in CD than in NFA; there were positive correlations between mRNA and protein expressions of p16 and cyclin D1. Thus, it is suggested that upregulated CDKN2A with the concomitant downregulated cyclin gene family is partly involved in the small size of ACTH-secreting adenoma.
Satoko Shimazu, Akira Shimatsu, Shozo Yamada, Naoko Inoshita, Yuko Nagamura, Takeshi Usui and Toshihiko Tsukada
Dopamine agonists normalize prolactin (PRL) levels and reduce tumour size in responsive prolactinoma. However, several cases have shown resistance to dopamine agonists upon initial treatment. Infrequently, prolactinoma initially responds, but then becomes refractory to prolonged treatment (secondary resistance). We investigated the possible mechanisms of resistance to dopamine agonists.
Subjects and methods
Twelve cases of prolactinoma were surgically resected and classified according to the responsiveness of PRL levels and tumour size to dopamine agonists: good responders (n=5), poor responders (n=5), or secondary resistance (n=2). We examined the expression of dopamine D2 receptor (D2R) isoform (short: D2S and long: D2L) mRNA and protein. We investigated DNA methylation patterns in the promoter region of the DRD2 gene.
The predominant D2R isoform expressed in prolactinoma was D2L. Levels of D2L mRNA were significantly lower in secondary resistance and poor responders than in good responders. Expression of D2R protein was variable among cases. Almost no CpG sites of the DRD2 gene promoter region were methylated.
Resistance of prolactinoma to dopamine agonists is correlated with a reduction in D2L isoform mRNA levels. Silencing of the DRD2 gene by methylation in the promoter region is unlikely to play a role in dopamine agonist resistance in prolactinoma.
Toru Tateno, Hajime Izumiyama, Masaru Doi, Takanobu Yoshimoto, Masayoshi Shichiri, Naoko Inoshita, Kenichi Oyama, Shozo Yamada and Yukio Hirata
Differential expression of several genes between ACTH-secreting pituitary tumors causing Cushing' disease (CD), silent corticotroph adenoma (SCA), and non-functioning pituitary tumors (NFT) was investigated.
Design and methods
We used tissue specimens from 35 pituitary tumors (12 CD, 8 SCA, and 15 NFT). Steady-state mRNA levels of the genes related to proopiomelanocortin (POMC) transcription, synthesis, processing, and secretion, such as neurogenic differentiation 1 (NeuroD1), T-box 19 (Tpit), corticotropin releasing hormone receptor (CRHR), vasopressin receptor 1b (V1bR), prohormone convertase (PC) 1/3 and PC2, 11β-hydroxysteroid dehydrogenase (11β-HSD) type 1 and type 2, glucocorticoid receptor α (GRα), annexin A1, histone deacetylase 2 (HDAC2), and BRM/SWI2-related gene 1, were determined by real-time RT-PCR.
Results and conclusion
POMC and Tpit mRNA levels were greater in CD and SCA than those in NFT. NeuroD1 mRNA levels were less in CD than those in NFT, but almost comparable between SCA and NFT. PC1/3 mRNA levels were greater in CD, but less in SCA than those in NFT. PC2 mRNA levels in CD and SCA were less than those in NFT. CRHR, V1bR, and 11β-HSD2 mRNA levels in CD were greater than those in SCA and NFT. HDAC2 mRNA levels in CD and SCA were lower than those in NFT. In conclusion, our study demonstrated that the genes related to transcription, synthesis, processing, and secretion of POMC are differentially regulated in ACTH-secreting pituitary tumors causing CD and SCA compared with those in NFT. This may partly explain the development of clinically active and inactive CD.
Akira Takeshita, Naoko Inoshita, Manabu Taguchi, Chikao Okuda, Noriaki Fukuhara, Kenichi Oyama, Kenichi Ohashi, Toshiaki Sano, Yasuhiro Takeuchi and Shozo Yamada
Crooke's cell adenoma (CCA), characterized by massive Crooke's hyaline change in corticotroph adenoma, causes a rare subtype of Cushing's disease. In contrast to ordinary corticotroph adenomas, CCAs are generally aggressive and present as invasive macroadenomas, which are refractory to both surgery and radiotherapy and have a high-recurrence rate. Moreover, some patients with CCA present with distant or craniospinal metastases. Currently, there are no effective standard therapies for CCA.
We report a patient with Crooke's cell carcinoma who presented with local invasion and liver metastases, which was refractory to conventional therapeutic modalities including transsphenoidal surgery, radiosurgery, medications, and hepatic transcatheter arterial embolization. After all these treatments failed, the patient had monthly temozolomide administrations, resulting in gradual clinical improvement and biochemical data that were consistent with tumor shrinkage. In glioblastoma, low O6-methylguanine DNA methyltransferase (MGMT) expression is associated with epigenetic gene silencing and predicts a better response to temozolomide.
We thus investigated MGMT expression, immunohistochemically, in seven CCAs (five invasive macroadenomas and two invasive microadenomas) and 17 ordinary-type adenomas (OTAs; three noninvasive macroadenomas, 12 noninvasive microadenomas, and two invasive microadenomas) from patients with Cushing's disease.
In seven CCAs, all five invasive macroadenomas exhibited low MGMT expression, defined as <5% nuclear MGMT staining. In 17 OTAs, only one adenoma showed low MGMT expression.
In Cushing's disease, invasive macroadenomas including CCA usually have low-MGMT expression. Temozolomide thus may be a new therapeutic option for invasive macroadenomas such as CCA particularly when conventional treatments are ineffective.
Kyohei Hayashi, Naoko Inoshita, Kohei Kawaguchi, Arif Ibrahim Ardisasmita, Hisanori Suzuki, Noriaki Fukuhara, Mitsuo Okada, Hiroshi Nishioka, Yasuhiro Takeuchi, Masayuki Komada, Akira Takeshita and Shozo Yamada
Somatic mutations in the ubiquitin-specific peptidase USP8 gene were recently detected in one- to two-third(s) of corticotroph adenomas of Cushing's disease (CD). These mutations may lead to the deubiquitination of EGFR, thereby increasing EGFR signaling, which has been implicated in ACTH hypersecretion.
Our objective was to determine the impact of USP8 mutations on the clinicopathological features of CD.
Subjects and methods
USP8 mutations as well as clinicopathological characteristics were examined in 60 corticotroph adenomas including 15 Crooke's cell adenomas (CCAs), a rare histological variant presenting with generally aggressive behavior, using qRT-PCR and/or immunohistochemistry.
USP8 mutations were exclusively detected in women, except for one case, with a prevalence of 42.2% in non-CCA and 13.3% in CCA (overall 35%). Clinically well-behaved presentations including microadenoma and curative resection were more common in mutated cases. The expression of EGFR was not associated with the mutation status. In contrast, mutated tumors expressed significantly higher levels of POMC, SSTR5, and MGMT.
Microadenomas that strongly express POMC were common among mutated tumors, which may lead to the mechanisms by which very small adenomas secrete excess ACTH to present overt CD. While USP8 mutations were less likely to enhance tumorous ACTH hypersecretion via EGFR-mediated activation, the presence of USP8 mutations may predict favorable responses to the somatostatin analog pasireotide, which exhibits high affinity for SSTR5. In contrast, non-mutated aggressive tumors such as CCA may respond better to the alkylating agent temozolomide because of their significantly weak expression of MGMT.
Yorinari Ochiai, Naoko Inoshita, Toshiro Iizuka, Hiroshi Nishioka, Shozo Yamada, Masanobu Kitagawa and Shu Hoteya
Patients with acromegaly are at increased risk of colorectal polyps. However, their risk of colorectal cancer remains unclear. This study aimed to identify the histopathological features of colorectal polyps in patients with acromegaly and compare their risk of colorectal cancer with that in healthy controls.
The study participants were 178 patients who underwent Hardy’s operation and perioperative colonoscopy at our hospital between April 2008 and September 2016. For the control group, we randomly selected 356 age- and sex-matched patients who underwent colonoscopy at our hospital during the same period. The incidence, size, location, and histology of the colorectal polyps detected were compared between the groups.
Colorectal polyps were detected in 66.8% of the acromegaly group and 24.2% of the control group (P < 0.001). The average number and size of the polyps were 2.44 and 4.74 mm, respectively, in the acromegaly group and 1.77 and 3.89 mm in the control group (P = 0.001). Polyps in the acromegaly group were more likely to be in the rectosigmoid region (P = 0.006). In the acromegaly group, the frequency of polyps ≥5 mm was 34.3% and that for polyps ≥10 mm was 15.2%; the respective values were 7.6% and 2.2% in the control group (P < 0.001). We found no evidence of between-group histopathological differences in the polyp specimens resected by endoscopy.
Patients with acromegaly are at an increased risk of colorectal polyps, especially in the rectosigmoid region. However, there is no pathological evidence that they are at greater risk of colorectal cancer than the general population.