Yichao Zhang

Recurrent gain-of-function USP8 mutations in Cushing's disease

Cushings disease, also known as adrenocorticotropic hormone (ACTH)-secreting pituitary adenomas (PAs) that cause excess cortisol production, accounts for up to 85% of corticotrophin-dependent Cushings syndrome cases. However, the genetic alterations in this disease are unclear. Here, we performed whole-exome sequencing of DNA derived from 12 ACTH-secreting PAs and matched blood samples, which revealed three types of somatic mutations in a candidate gene, USP8 (encoding ubiquitin-specific protease 8), exclusively in exon 14 in 8 of 12 ACTH-secreting PAs. We further evaluated somatic USP8 mutations in additional 258 PAs by Sanger sequencing. Targeted sequencing further identified a total of 17 types of USP8 variants in 67 of 108 ACTH-secreting PAs (62.04%). However, none of these mutations was detected in other types of PAs (n = 150). These mutations aggregate within the 14-3-3 binding motif of USP8 and disrupt the interaction between USP8 and 14-3-3 protein, resulting in an elevated capacity to protect EGFR from lysosomal degradation. Accordingly, PAs with mutated USP8 display a higher incidence of EGFR expression, elevated EGFR protein abundance and mRNA expression levels of POMC, which encodes the precursor of ACTH. PAs with mutated USP8 are significantly smaller in size and have higher ACTH production than wild-type PAs. In surgically resected primary USP8-mutated tumor cells, USP8 knockdown or blocking EGFR effectively attenuates ACTH secretion. Taken together, somatic gain-of-function USP8 mutations are common and contribute to ACTH overproduction in Cushings disease. Inhibition of USP8 or EGFR is promising for treating USP8-mutated corticotrophin adenoma. Our study highlights the potentially functional mutated gene in Cushings disease and provides insights into the therapeutics of this disease.

Endoscopic endonasal pituitary adenomas surgery: the surgical experience of 178 consecutive patients and learning curve of two neurosurgeons

BackgroundWe aim to study surgical technique and analyze the related factors affecting tumor total removal and postoperative endocrinological remission for endoscopic endonasal pituitary adenomas surgery.MethodsWe retrospectively analyzed 178 endoscopic endonasal pituitary adenomas surgery from March 2011 to May 2014. Endonasal approach included the routine transnasal-sphenoidal approach, transnasal- maxillary sinus approach in four cases and transnasal-clivus approach in one case.ResultsAccording to postoperative imaging data and endocrine examination results, total removal was achieved in 129 patients (72.5%), and endocrinological remission was achieved in 38 patients with functional adenomas (44.1%). Statistical analysis of the clinical data showed that total removal rate was much closely related to tumor volume (P = 0.006), and tumor invasiveness (P < 0.001).ConclusionsIn this study, we found tumor sizes and invasion of cavernous sinus were related to total removal rate and endocrinological remission rate; the direction and degree of tumor invasion, and the surgeon’s experience were the key influence factors of the endocrinological remission rate for invasive functional pituitary adenomas.

Knockdown of immature colon carcinoma transcript-1 inhibits proliferation of glioblastoma multiforme cells through Gap 2/mitotic phase arrest.

“Glioblastoma multiforme” (GBM) is the frequent form of malignant glioma. Immature colon carcinoma transcript-1 (ICT1) is essential for cell vitality and mitochondrial function and has been recognized in several human cancers. In the study reported here, we attempted to evaluate the functional role of ICT1 in GBM cells. Lentivirus-mediated RNA interference (RNAi) was applied to silence ICT1 expression in human GBM cell lines U251 and U87. Cell proliferation was measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and colony-formation assays. Cell-cycle progression was determined by flow cytometry with propidium iodide staining. The results revealed that lentivirus-mediated short hairpin RNA (shRNA) can specifically suppress the expression of ICT1 in U251 and U87 cells. Functional investigations proved for the first time, as far as we are aware, that ICT1 knockdown significantly inhibited the proliferation of both cell lines. Moreover, the cell cycle of U251 cells was arrested at Gap 2 (G2)/mitotic (M) phase after ICT1 knockdown, with a concomitant accumulation of cells in the Sub-Gap 1 (G1) phase. This study highlights the crucial role of ICT1 in promoting GBM cell proliferation, and provides a foundation for further study into the clinical potential of lentivirus-mediated silencing of ICT1 for GBM therapy.

Identification of recurrent USP48 and BRAF mutations in Cushing’s disease

Cushing’s disease results from corticotroph adenomas of the pituitary that hypersecrete adrenocorticotropin (ACTH), leading to excess glucocorticoid and hypercortisolism. Mutations of the deubiquitinase gene USP8 occur in 35–62% of corticotroph adenomas. However, the major driver mutations in USP8 wild-type tumors remain elusive. Here, we report recurrent mutations in the deubiquitinase gene USP48 (predominantly encoding p.M415I or p.M415V; 21/91 subjects) and BRAF (encoding p.V600E; 15/91 subjects) in corticotroph adenomas with wild-type USP8. Similar to USP8 mutants, both USP48 and BRAF mutants enhance the promoter activity and transcription of the gene encoding proopiomelanocortin (POMC), which is the precursor of ACTH, providing a potential mechanism for ACTH overproduction in corticotroph adenomas. Moreover, primary corticotroph tumor cells harboring BRAF V600E are sensitive to the BRAF inhibitor vemurafenib. Our study thus contributes to the understanding of the molecular mechanism of the pathogenesis of corticotroph adenoma and informs therapeutic targets for this disease.In this study the authors report USP48 and BRAF are frequently mutated in USP8 wild-type corticotroph adenomas, and cause Cushing’s disease mainly through promoting the promoter activity of POMC. Inhibition of BRAF may be a promising therapeutic strategy for the treatment of patients with BRAF-mutated corticotroph adenomas.

Impact of Long-Acting Somatostatin Analogues on Glucose Metabolism in Acromegaly: A Hospital-Based Study

Purpose To evaluate the change in glucose tolerance in treatment-naïve patients with acromegaly after administration of SSA and to identify predictive factors of glucose impairment during SSA therapy. Methods Oral glucose tolerance testing (OGTT) was performed on 64 newly diagnosed and treatment-naïve patients with acromegaly both at pretreatment and 3 months after initiation of treatment with long-acting SSA. Insulin resistance (IR) was assessed by homeostatic model assessment- (HOMA-) IR and ISOGTT. Insulin secretion was assessed by HOMA-β, INS0/BG0, IGI (insulinogenic index), IGI/IR, ISSI2, and AUCINS/AUCBG. Receiver-operating characteristic (ROC) curves were generated to determine the optimal cutoffs to predict the impact of SSA on glucose metabolism. Results Pretreatment, 19, 24, and 21 patients were categorized as having normal glucose tolerance (NGT), impaired glucose tolerance (IGT), and diabetes mellitus (DM), respectively. Posttreatment, IR, represented by ISOGTT, was significantly improved in all 3 groups. Insulin secretion, represented by HOMA-β, declined in the NGT and IGT groups, but was unaltered in the DM group. The glucose tolerance status deteriorated in 18 (28.1%) patients, including 13 patients in the NGT group and 5 patients in the IGT group. Deterioration was associated with lower baseline BG120 (plasma glucose 120 min post-OGTT), less reduction of growth hormone (GH), and greater reduction of insulin secretion after SSA therapy. BG120 greater than 8.1 mmol/l provided the greatest sensitivity and specificity in predicting the stabilization and/or improvement of glucose tolerance status after SSA treatment (PPV 90.7%, NPV 66.7%, p < 0.001). Conclusions The deterioration of glucose metabolism induced by SSA treatment is caused by the less reduction of GH and the more inhibition of insulin secretion, which can be predicted by the baseline BG120 during OGTT.

The comprehensive impact on human body induced by resolution of growth hormone excess

CONTEXT Chronic excess of growth hormone (GH) often leads to systemic complications. The reversibility of these complications after GH resolution is not fully understood. OBJECTIVE To investigate when and to what extent will the comorbidities be ameliorated. DESIGN We conducted a prospective study comprising 24 patients with acromegaly, who achieved remission after transsphenoidal surgery. The dynamic changes of endocrine, cardiovascular, respiratory, sleep, bone and morphology parameters were evaluated at enrollment and 1 week, 1 month, 3 months, 6 months and 12 months after surgery. RESULTS Random GH dropped by 98.4% at the first day postoperatively. IGF-I index dropped by 50% and 64% at 1 week and 1 month respectively and remained unchanged onwards. Glucose metabolism improved significantly at 1 week and stabilized at 1 month. Testosterone in male patients recovered to normal range since 1 month. Systolic blood pressures dropped markedly at 3 months while diastolic blood pressures fell mildly at later visits. Abnormal lung function showed no improvement. The decrease of bone formation and resorption markers occurred at 1 week and 3 months, respectively. At 1 month, the tongue area declined while the airway volume increased significantly, accompanied with improved obstructive sleep apnea syndrome. Extremities, lips and nasal ala became smaller since 1 week. Liver, kidney and spleen volumes declined by 6.4, 15.9, 9.2%, respectively at 1 month. The volumes of pancreas and adrenal showed no change. CONCLUSIONS The rapid resolution of excessive GH led to the reversible changes of systemic comorbidities in a time-dependent and organ-specific manner.

Surgical outcomes and predictors of glucose metabolism alterations for growth hormone-secreting pituitary adenomas: a hospital-based study of 151 cases

PurposeThe surgical outcome on glucose metabolism in acromegaly patients is not fully understood. We aimed to investigate the impact of surgery on glucose metabolism and identify key factors that influence alterations of glucose metabolic status in acromegaly patients.MethodsOral glucose tolerance test was performed in 151 newly diagnosed acromegaly patients before and 3–12 months after surgery. Insulin resistance and insulin secretion was assessed. Patients were grouped as cured, discordant, and having active disease according to postoperative growth hormone (GH) and insulin-like growth factor-1 (IGF-1) levels. Receiver-operating characteristic curves were generated to determine the optimal cut-off points to predict the impact of surgery on glucose metabolism.ResultsAt baseline, 32.5%, 41.7%, and 25.8% patients were categorized as having normal glucose tolerance (NGT), impaired glucose tolerance (IGT), and diabetes mellitus (DM), respectively. After surgery, improved glucose tolerance was observed in 87.3% patients with IGT and 66.7% patients with DM. Deterioration was observed in 14.3% patients with NGT. Glucose tolerance improved in patients with lower preoperative FBG, 2 h-BG, and HbA1c and higher HOMA-β and IGI/IR. The proportion of NGT was significantly increased in surgically cured patients (28.3% vs. 79.2%, P < 0.001) and those with normal GH but elevated IGF-1 levels (25.6% vs. 79.5%, P < 0.001), but not in patients with active disease (42.9% vs. 57.1%, P = 0.131). Baseline FBG < 6.35 mmol/l predicted improved glucose metabolism after surgery.ConclusionsGlucose metabolic status improved in patients with preserved β-cell function. Preoperative FBG was an independent predictor for improved glucose tolerance status after surgery.

Ganglion cell complex loss precedes retinal nerve fiber layer thinning in patients with pituitary adenoma

• A new pattern of retinal ganglion thickness changes over time in patients with pituitary adenoma is proposed.