CDC73 mutational status and loss of parafibromin in the outcome of parathyroid cancer

Inactivating mutations of the CDC73 tumor suppressor gene have been reported in parathyroid carcinomas (PC), in association with the loss of nuclear expression of the encoded protein, parafibromin. The aim of this study was to further investigate the role of the CDC73 gene in PC and evaluate whether gene carrier status and/or the loss of parafibromin staining might have an effect on the outcome of the disease. We performed genetic and immunohistochemical studies in parathyroid tumor samples from 35 patients with sporadic PC. Nonsense or frameshift CDC73 mutations were detected in 13 samples suitable for DNA sequencing. Six of these mutations were germline. Loss of parafibromin expression was found in 17 samples. The presence of the CDC73 mutation as well as the loss of parafibromin predicted a high likelihood of subsequent recurrence and/or metastasis (92.3%, P=0.049 and 94.1%, P=0.0017 respectively), but only the latter was associated with a decreased overall 5- and 10-year survival rates (59%, P=0.107, and 23%, P=0.0026 respectively). The presence of both the CDC73 mutation and loss of parafibromin staining compared with their absence predicted a lower overall survival at 10- (18 vs 84%, P=0.016) but not at 5-year follow-up. In conclusion, loss of parafibromin staining, better than CDC73 mutation, predicts the clinical outcome and mortality rate. The added value of CDC73 mutational analysis is the possibility of identifying germline mutations, which will prompt the screening of other family members.

Cinacalcet in the management of primary hyperparathyroidism: post marketing experience of an Italian multicentre group

OBJECTIVE

To report the Italian experience on cinacalcet use following its approval by the European Medical Agency (EMA) to control hypercalcaemia in patients with primary hyperparathyroidism (PHPT).

DESIGN

Retrospective data collection from 100 patients with sporadic (sPHPT) and 35 with familial PHPT (fPHPT) followed in eight Italian centres between October 2008 and March 2011.

MEASUREMENTS

Albumin-adjusted serum calcium, PTH, 25OHD, daily cinacalcet dose and adverse events were recorded during the follow-up (1-46 months).

RESULTS

Baseline serum calcium was 2·90 ± 0·27 nmol/l in sPHPT and 2·75 ± 0·17 nmol/l in fPHPT patients (P = 0·007). The cinacalcet EMA labelling was met in 53% sPHPT and 26% fPHPT patients. High surgical risk (34%), negative preoperative imaging (19%), control of hypercalcaemia before parathyroidectomy (PTx) (24%), and refusal of PTx (19%) accounted for cinacalcet prescription in 96% of sPHPT patients. Conversely, initial treatment (34%), persistent/relapsing PHPT after surgery (31%), and refusal of PTx (14%) were the indications in 79% fPHPT patients. Cinacalcet was started at 30 mg/daily in 64% of sPHPT and 91% of fPHPT and increased until normocalcaemia was reached or side effects occurred. The final daily dose ranged between 15 and 120 mg. The majority of patients (65% of sPHPT and 80% of fPHPT) become normocalcaemic. Treatment was withdrawn in six patients because of side effects.

CONCLUSIONS

There is a wide heterogeneity in the prescription of cinacalcet in PHPT patients in Italy and the EMA labelling is not always followed, particularly in fPHPT patients. Cinacalcet effectively reduces serum calcium in patients with either sPHPT or fPHPT.

Cinacalcet efficacy in patients with moderately severe primary hyperparathyroidism according to the European Medicine Agency prescription labeling

BACKGROUND

Patients with primary hyperparathyroidism (PHPT) with contraindications to parathyroidectomy (PTx) or persistent PHPT have few non surgical options.

AIM

The aim of the study was to investigate the efficacy of cinacalcet in reducing serum calcium in patients with PHPT, for whom PTx would be indicated according to serum calcium levels, but in whom PTx is not clinically appropriate or is contraindicated [European Medicines Agency (EMA) prescription labeling].

SUBJECTS AND METHODS

The study (open-label prospective, conducted in a single tertiary center) included 12 sporadic and 2 multiple endocrine neoplasia type 1 PHPT patients with serum calcium greater than 11.2 mg/dl. Cinacalcet was administered in increasing doses until normal serum calcium was reached or side effects preventing a further increase occurred. Serum calcium, PTH, phosphate, 25OHD, markers of bone turnover, 24h-urinary calcium and areal bone mineral density (BMD) were measured. Safety biochemical indices and adverse events were monitored.

RESULTS

The maintenance cinacalcet dose [median 30 mg twice daily (range 30 daily-60 mg twice daily)] was maintained constant during follow-up (median 12 months). Mean±SE baseline serum calcium was 12.2±0.3 mg/dl. Serum calcium decreased by at least 1 mg/dl in all patients and normalized in 10. Serum calcium at the last observation was 9.9±0.2 mg/dl (p<0.0001 vs baseline). PTH decreased by 17.1% compared to baseline (p=0.13), and never reached a normal value. BMD was unchanged. Adverse events occurred in 6 patients (43%) and required treatment withdrawal in 2.

CONCLUSIONS

Cinacalcet reduced and often normalized serum calcium in PHPT patients who met the EMA labeling.

A proteomic approach to study parathyroid glands

Parathyroid tumours are heterogeneous and in some cases the diagnosis may be difficult using histological features. In this study we used a two-dimensional electrophoresis (2D)/mass spectrometry (MS)-based approach to examine the global changes of parathyroid adenoma tissues protein profile compared to the parathyroid normal tissues. Validation of protein expression was performed by immunoblotting using specific antibodies. Ingenuity software was used to identify the biological processes to which these proteins belong and to construct a potential network. A total of 30 proteins were found to be differentially expressed, of which 22 resulted in being over-expressed. Proteins identified by 2D/MS/MS proteomics were classified into functional categories and a major change (≥ 2-fold) in terms of expression was found in proteins involved in response to biotic stimuli, cell organization and signal transduction. After Ingenuity analysis, 14-3-3 ζ/δ appears to be a key protein in the network of parathyroid adenoma, where it is linked to other proteins such as annexin A2, B box and SPRY domain-containing protein (BSPRY), p53 and epidermal growth factor receptor (EGFR). Our results suggest that the proteomic approach was able to differentiate the protein profiles of normal parathyroid and parathyroid adenoma and identify a panel of proteins which are differentially expressed. The functional role of these proteins in the network of intracellular pathways is discussed.

Beta-catenin activation is not involved in sporadic parathyroid carcinomas and adenomas

Aberrant accumulation of beta-catenin has been found in various types of human tumors. The aim of this study was to evaluate whether Wnt/beta-catenin signaling is activated in parathyroid carcinomas and adenomas. We studied 154 parathyroid tumors (18 carcinomas (13 with distant metastases), six atypical adenomas, and 130 adenomas). Three normal parathyroid tissues were used as control. Direct sequencing of exon 3 of the CTNNB1 gene showed absence of stabilizing mutations in all the tumors. Immunostaining of beta-catenin was performed in all carcinomas and in 66 adenomas (including three atypical). Normal parathyroid showed a homogeneous distinct outer cell membrane staining in the majority of cells and no nuclear staining. A weak cytoplasmic staining was observed in one case. All tumors showed negative nuclear staining. With the exception of one carcinoma, which had a negative membrane staining, all other samples showed a membrane staining which was similar to that of the normal parathyroid. beta-Catenin expression was heterogeneous with a range of positive cells between 5 and 80%, independently of tumor type. Our results suggest that the Wnt/beta-catenin signaling pathway is not involved in the development of parathyroid carcinomas and adenomas.

The sulfaphenazole-sensitive pathway acts as a compensatory mechanism for impaired nitric oxide availability in patients with primary hyperparathyroidism. Effect of surgical treatment

OBJECTIVE

The aim of this study was to assess whether patients with primary hyperparathyroidism (PHPT) show reduced endothelial function and to determine the mechanisms involved. The impact of parathyroidectomy (PTx) on endothelial function was also assessed.

BACKGROUND

Endothelial dysfunction is reported in patients with PHPT, but the mechanisms involved are unknown.

METHODS

We evaluated forearm blood flow changes (strain gauge plethysmography) induced by intraarterial acetylcholine or sodium nitroprusside in 17 PHPT women and 17 age-matched controls. Nitric oxide (NO) availability and oxidative stress were studied by repeating acetylcholine during intraarterial infusion of L-N(G)-monomethyl arginine (L-NMMA, a NO synthase inhibitor) and ascorbic acid (an oxidative stress scavenger). The role of cytochrome P450 epoxygenase (CYP 2C9)-derived endothelium-derived hyperpolarizing factor (EDHF) was assessed by repeating acetylcholine under intraarterial sulfaphenazole. In six PHPT patients, the study was repeated 12 months after successful PTx.

RESULTS

Responses to sodium nitroprusside and acetylcholine were similar in PHPT patients and controls. L-NMMA inhibited the response to acetylcholine in controls (P < 0.001), whereas it had no effect in PHPT patients. In both groups, ascorbic acid failed to affect acetylcholine. Sulfaphenazole administration, although not affecting vasodilation to acetylcholine in controls, blunted the response to acetylcholine in PHPT patients (P < 0.005). After PTx, the inhibitory effect of L-NMMA on acetylcholine was restored (P < 0.001), and the inhibitory effect of sulfaphenazole on acetylcholine was abrogated.

CONCLUSIONS

PHPT patients show compromised NO availability, whereas oxidative stress generation is not involved. A compensatory CYP 2C9-derived EDHF pathway is activated to sustain endothelium-dependent vasodilation. This PHPT-related endothelial dysfunction is reversed after PTx.

Morphometric vertebral fractures in postmenopausal women with primary hyperparathyroidism

CONTEXT

An increased risk of fracture in patients with primary hyperparathyroidism (PHPT) compared to the general population has been reported, but available data are controversial.

OBJECTIVE

The aim of the study was to evaluate the rate of vertebral fractures (VFs) by dual-energy x-ray absorptiometry in postmenopausal women with sporadic PHPT and compare the results with a control group.

DESIGN AND SETTING

A case-control study was performed at a referral center.

PARTICIPANTS

A total of 150 consecutive patients and 300 healthy women matched for age and menopausal age participated in the study.

RESULTS

VFs were detected in 37 of 150 (24.6%) patients and 12 of 300 (4.0%) controls (P < 0.0001). The majority of VFs were mild. Stepwise multiple logistic regression analysis showed that in PHPT patients lumbar spine bone mineral density was the only variable independently associated with the prevalence of VFs (P = 0.003). The rate of fracture was higher in symptomatic (34.1%) than asymptomatic (21.1%) patients, but this difference was not statistically significant (P = 0.15). Among asymptomatic patients, fracture rate was significantly higher in those who met the criteria for parathyroidectomy (28.1%) than in those who did not (11.1%) (P = 0.03). Compared to controls, the fracture rate was significantly higher in patients with symptomatic and asymptomatic PHPT who met the criteria for surgery (P < 0.0001), but not in those who did not meet the criteria (P = 0.06).

CONCLUSIONS

VF rate is increased in postmenopausal women with PHPT compared to controls, independently of whether they are classified as symptomatic or asymptomatic. The question of whether the finding of mild morphometric VFs in the latter represents an indication for parathyroid surgery remains to be established.

Identification and functional characterization of loss-of-function mutations of the calcium-sensing receptor in four Italian kindreds with familial hypocalciuric hypercalcemia

OBJECTIVE

Identification and characterization of calcium-sensing receptor (CASR) mutations in four unrelated Italian kindreds with familial hypocalciuric hypercalcemia.

DESIGN

Clinical evaluation and genetic analysis of CASR gene. Functional characterization of mutated CASRs.

METHODS

Direct sequencing of CASR gene in genomic DNA. Studies of CASR-mediated increases in cytosolic calcium concentration [Ca(2)(+)](i) in CASR-transfected COS-7 cells in vitro.

RESULTS

Four unreported heterozygous CASR mutations were identified, including three missense (H595Y, P748H, and C765W) and one splice site (IVS2+1G>C) mutation. The H595Y, P748H, and C765W mutant receptors, although expressed at normal levels on the cell surface, showed a reduced response in [Ca(2)(+)](i) relative to the wildtype (WT) CASR to increasing extracellular calcium concentrations. Cotransfection experiments showed that the H595Y and P748H mutants did not affect the apparent affinity of the WT CASR for calcium, suggesting that they do not exert a dominant-negative effect. On the other hand, the co-transfected C765W mutant decreased the maximum response of the WT CASR to calcium, suggesting that it may reduce the effective concentration of the normal CASR on the cell surface or impair its maximal signaling capacity.

CONCLUSIONS

Four CASR mutations were identified. The reduced functional responses to extracellular calcium and normal expression of the mutant receptors suggest that conformational changes account for altered CASR activity. Moreover, a reduced complement of normal CASRs in these heterozygous patients, perhaps combined with a mutant receptor-induced decrease in maximal activity of the WT receptor, may contribute to defective calcium-sensing in vivo.

Hyperparathyroidism 2 gene (HRPT2, CDC73) and parafibromin studies in two patients with primary hyperparathyroidism and uncertain pathological assessment

HRPT2 and parafibromin studies improved the diagnostic accuracy in two patients with primary hyperparathyroidism (PHPT) referred to us after surgery, in whom the clinical data were at variance with the pathological diagnosis of adenoma and carcinoma, respectively. Patients were referred to us after parathyroidectomy. Patient #1 had had a 1.5-cm tumor easily removed with a histological diagnosis of parathyroid carcinoma and normocalcemia for 2 years. Re-examination of the histology showed no cardinal signs of parathyroid cancer. Patient #2, with severe PHPT, had had the removal of a 3.5-cm tumor described histologically as adenoma. Ten years later PHPT recurred and persisted despite removal of two mildly enlarged parathyroid glands that were histologically normal. Re-review of the initial histology showed a trabecular pattern, fibrous bands, and atypical mitoses, suggesting an atypical adenoma. Because of the suspicion that case #1 could be an atypical adenoma and case #2 a carcinoma further molecular studies were performed. No HRPT2 and parafibromin abnormalities were identified in patient #1, strongly indicating a benign lesion. In patient #2, an HRPT2 germline mutation was found (E115X in exon 4) and associated with no parafibromin staining. These data, together with the clinical features, supported the suspicion of a parathyroid carcinoma that was confirmed by histological examination of further slides of the tumor, showing capsular and vascular invasion. A lung 1.5-cm nodule detected by computed tomography was excised. Histology showed a metastasis of parathyroid carcinoma. HRPT2 gene studies improved the diagnostic accuracy in 2 parathyroid tumors that are of uncertain type.

HRPT2 gene analysis and the diagnosis of parathyroid carcinoma

Parathyroid carcinoma is an uncommon cause of primary hyperparathyroidism (PHPT) and is usually associated with more severe clinical manifestations than its much more common benign counterpart, the parathyroid adenomas. The histopathological distinction between benign and malignant parathyroid tumors is difficult. Currently, pathological diagnosis of parathyroid carcinoma is restricted to lesions showing unequivocal growth, as evidenced by perineural invasion, full-thickness capsular invasion with growth into adjacent tissues, or metastasis. Major advances in the molecular pathogenesis of parathyroid carcinoma have been made by the cloning of the HRPT2 gene, which encodes parafibromin, a 531-amino acid putative tumor-suppressor protein. Germline mutations of HRPT2 confer susceptibility to the hyperparathyroidism-jaw tumor syndrome (HPT-JT), an autosomal dominant syndrome with high but incomplete penetrance. Somatic inactivating mutations of the HRPT2 gene have been reported in the majority of apparently sporadic parathyroid carcinomas but, unexpectedly, germline HRPT2 mutation have been found in up to 30% of these patients. Several studies have been performed to evaluate whether parafibromin immunostaining might have some diagnostic utility. Loss of parafibromin immunoreactivity has been found in the majority of parathyroid carcinomas, in 50% of equivocal carcinomas and, very rarely, in benign adenomas. On the other hand, with the exception of HPT-JT-related tumors, loss of parafibromin associated with HRPT2 mutations strongly predicts parathyroid malignancy. In clinical practice, parafibromin immunostaining and HRPT2 gene analysis could be particularly useful in the subset of parathyroid tumors with equivocal histology.

Surgery or surveillance for mild asymptomatic primary hyperparathyroidism: a prospective, randomized clinical trial

CONTEXT

It is unclear whether patients with asymptomatic primary hyperparathyroidism (PHPT) do better with parathyroidectomy (PTx) as compared with conservative medical management.

OBJECTIVE

The aim of the study was to evaluate the beneficial effect of PTx vs. conservative management in patients with mild asymptomatic PHPT.

DESIGN

We conducted a prospective, randomized study.

SETTING

The study took place at a referral center.

PATIENTS

We studied 50 patients who did not meet any guidelines for parathyroid surgery as recommended by the National Institutes of Health Consensus Development Conference on Asymptomatic PHPT.

INTERVENTION

Patients were randomly assigned to PTx or no PTx and were evaluated at 6 months and at 1 yr.

MAIN OUTCOME MEASURES

We compared changes (percentage of basal) of lumbar spine bone mineral density (BMD) between the two groups at 1 yr.

RESULTS

The change in BMD at lumbar spine was greater after PTx (+4.16 +/- 1.13 for PTx vs. -1.12 +/- 0.71 for no PTx; P = 0.0002). The change in BMD at the total hip was also significantly greater in the PTx group (+2.61 +/- 0.71 for PTx vs. -1.88 +/- 0.60 for no PTx; P = 0.0001). There was no difference in BMD after 1 yr between both groups at the one-third radius site. In comparison with those who did not undergo surgery, the PTx subjects, after 1 yr, showed significant differences in four quality of life measures as determined by the 36-item short form health survey scale: bodily pain (P = 0.001), general health (P = 0.008), vitality (P = 0.003), and mental health (P = 0.017).

CONCLUSIONS

In patients with mild asymptomatic PHPT, successful PTx is followed by an improvement in BMD and quality of life. Most patients followed without surgery did not show evidence of progression.