Should parafibromin staining replace HRTP2 gene analysis as an additional tool for histologic diagnosis of parathyroid carcinoma?

Objective: HRPT2 gene mutations are associated with parathyroid carcinomas, and absence of parafibromin immunoreactivity has been suggested as a diagnostic marker of malignancy. The aim of our study was to extend parafibromin studies in a series of benign and malignant parathyroid tumors and cross-validate the results of immunohistochemistry with those of HRPT2 analysis. Design and patients: We performed parafibromin and cyclin D1 immunostaining and HRPT2 gene analysis using loss of heterozygosity studies and sequencing analysis in parathyroid specimens from 11 patients with carcinoma (eleven primary tumors, one skin, and four lung metastases), 22 with sporadic adenomas, and 4 with atypical adenomas. Results: Ten out of eleven parathyroid cancers were negative for parafibromin staining and showed HRPT2 gene abnormalities. The remaining sample was negative for immunostaining and genetic analyses. All but one sporadic adenomas showed parafibromin immunoreactivity and no HRPT2 gene abnormalities. The sample with negative immunostaining carried an HRPT2 mutation. Two atypical adenomas were positive and two negative with parafibromin staining. No HRPT2 abnormalities were found in these samples. Cyclin D1 expression was heterogeneous and there was no relationship between expression/expression level of cyclin D1 and parafibromin expression. Conclusions: We have shown that negative parafibromin staining is almost invariably associated with HRPT2 mutations and confirm that loss of parafibromin staining strongly predicts parathyroid malignancy. In clinical practice, these tests could be particularly useful in the subset of parathyroid tumors with equivocal histological examination. However, their diagnostic value in this setting remains to be proven

Estrogens Attenuate Oxidative Stress and the Differentiation and Apoptosis of Osteoblasts by DNA-Binding-Independent Actions of the ERα

Estrogens diminish oxidative stress in bone and bone marrow, attenuate the generation of osteoblasts, and decrease the prevalence of mature osteoblast apoptosis. We have searched for the molecular mechanism of these effects using as tools a mouse model bearing an estrogen receptor α (ERα) knock-in mutation that prevents binding to DNA (ERαNERKI/−) and several osteoblast progenitor cell models expressing the wild-type ERα or the ERαNERKI/−. We report that the ability of estrogens to diminish the generation of reactive oxygen species, stimulate the activity of glutathione reductase, and decrease the phosphorylation of p66shc, as well as osteoblastogenesis and osteoblast number and apoptosis, were fully preserved in ERαNERKI/− mice, indicating that the DNA-binding function of the ERα is dispensable for all these effects. Consistent with the attenuation of osteoblastogenesis in this animal model, 17β-estradiol attenuated bone morphogenetic protein 2 (BMP-2)–induced gene transcription and osteoblast commitment and differentiation in murine and human osteoblastic cell lines. Moreover, 17β-estradiol attenuated BMP-2-induced differentiation of primary cultures of calvaria- or bone marrow–derived osteoblastic cells from ERαNERKI/− mice as effectively as in cells from wild-type littermates. The inhibitory effect of the hormone on BMP-2 signaling resulted from an ERα-mediated activation of ERKs and the phosphorylation of Smad1 at the linker region of the protein, which leads to proteasomal degradation. These results illustrate that the effects of estrogens on oxidative stress and the birth and death of osteoblasts do not require the binding of ERα to DNA response elements, but instead they result from the activation of cytoplasmic kinases. © 2010 American Society for Bone and Mineral Researc

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 [Ca2C]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 (IVS2C1GOC) mutation. The H595Y, P748H, and C765W mutant receptors, although expressed at normal levels on the cell surface, showed a reduced response in [Ca2C]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.L'articolo è disponibile sul sito dell'editore http://www.euro-endo.org/default.asp

A NOTCH3-CXCL12-driven myeloma-tumor niche signaling axis promotes chemoresistance in multiple myeloma

Multiple myeloma (MM) remains incurable due to disease relapse and drug resistance. Notch signals from the tumor microenvironment (TME) confer chemoresistance, but the cellular and molecular mechanisms are not entirely understood. Using clinical and transcriptomic datasets, we found that NOTCH3 is upregulated in CD138+ cells from newly diagnosed MM (NDMM) patients compared to healthy individuals and increased in progression/relapsed MM (PRMM) patients. Further, NDMM patients with high NOTCH3 expression exhibited worse responses to Bortezomib (BOR)-based therapies. Cells of the TME, including osteocytes, upregulated NOTCH3 in MM cells and protected them from apoptosis induced by BOR. NOTCH3 activation (NOTCH3OE) in MM cells decreased BOR anti-MM efficacy and its ability to improve survival in in vivo myeloma models. Molecular analyses revealed that NDMM and PRMM patients with high NOTCH3 exhibit CXCL12 upregulation. TME cells upregulated CXCL12 and activated the CXCR4 pathway in MM cells in a NOTCH3-dependent manner. Moreover, genetic or pharmacologic inhibition of CXCL12 in NOTCH3OE MM cells restored sensitivity to BOR regimes in vitro and in human bones bearing NOTCH3OE MM tumors cultured ex vivo. Our clinical and preclinical data unravel a novel NOTCH3-CXCL12 pro-survival signaling axis in the TME and suggest that osteocytes transmit chemoresistance signals to MM cells

The role of FoxO transcription factors in skeletal homeostasis in mice

Aging is associated with decrease bone mass and increase in reactive oxygen species (ROS) that shorten the lifespan of mature osteoblasts and osteocytes by apoptosis. ROS divert the limited pool of β-catenin available in the cells from Wnt–T-Cell factor (Tcf) to FoxO-mediated transcription. Forkhead box O (FoxO) transcription factors defend against oxidative stress by activating genes involved in free radical scavenging and apoptosis. Based on this and evidence that decreased defense against oxidative stress is responsible, at least in part, for the adverse effects of aging on the murine skeleton, we have genetically manipulated FoxOs in mice and investigated the impact of such manipulation on skeletal homeostasis. Conditional deletion of FoxO1, 3 and 4 in three month-old mice resulted in an increase in oxidative stress in bone and osteoblast apoptosis and a decrease in the number of osteoblasts, the rate of bone formation, and bone mass at cancellous and cortical sites. The effect of the deletion on osteoblast apoptosis was cell autonomous and resulted from oxidative stress. Conversely, over-expression of a FoxO3 transgene in mature osteoblasts decreased oxidative stress and osteoblast apoptosis, and increased osteoblast number, bone formation rate and vertebral bone mass. FoxO-dependent oxidative defense provides a mechanism to handle the oxygen free radicals constantly generated by the aerobic metabolism of osteoblasts and is thereby indispensable for bone mass homeostasis. However, deletion of FoxOs selectively in committed osteoblast precursors expressing Osterix since development increases Wnt signaling and leads to bone anabolism. Indeed, while defending against oxidative stress FoxOs attenuate Wnt signaling and its potent influence on bone mass. Thus, the β-catenin diversion from Wnts to FoxOs is very important to skeletal aging and leads to the fundamental concept that defense against oxidative stress comes with a price, that in the case of the skeleton is decreased bone mass. Selective inactivation of FoxOs in Osterix positive cells unleashes the restraining effects of FoxOs on Wnt signaling thereby increasing the number of osteoblasts to an extent that overcompensates for the adverse effects of ROS on cell survival and causes bone anabolism. Collectively, these findings suggest that the balance between ROS production and its amplification in osteoblastic cells versus defense against ROS by activated FoxOs transcription programs, are critical for bone homeostasis throughout life. An increase in ROS with advancing age decreases the number of osteoblasts by 1) exhausting adult self-renewing mesenchimal progenitors, 2) restraining the proliferation/differentiation of Osterix expressing committed osteoblast precursors, at least in part by the diversion of β-catenin from Wnt/Tcf to FoxO-mediated transcription and 3) by promoting the apoptosis of post mitotic osteoblasts and osteocytes. Aging is associated also with decrease osteoclast number. ROS, are required for osteolast generation, function and survival and overexpression of FoxO3 in cells of the osteoclast lineage decreases osteoclastogenesis, increases osteoclast apoptosis and increases bone mass. These lines of evidence suggest that osteoblasts and osteoclasts handle (or compartimentalize) ROS in fundametally different ways and that FoxOs defense mechanism play very different roles in the two cell types

Parathyroid tumorigenesis

Primary hyperparathyroidism (PHPT) is a common endocrinopathy, mostly caused by a monoclonal parathyroid adenoma. This review primarily summarizes current knowledge concerning molecular pathogenesis of familial forms of primary hyperparathyroidism and sporadic (non familial) parathyroid tumors. The hereditary syndromes have been recognized as exhibiting Mendelian inheritance patterns and include multiple endocrine neoplasia types 1 (MEN 1) and 2A (MEN 2A), hereditary hyperparathyroidism- jaw tumor (HPT-JT) syndrome, familial isolated hyperparathyroidism (FIHP), familial hypocalciuric hypercalcemia (FHH) and severe neonatal hyperparathyroidism (NSHPT). Inactivating mutations of MEN1 tumor suppressor gene are responsible for MEN 1 in >90% of cases. MEN1 gene has also an established role in the pathogenesis of sporadic parathyroid adenomas. Allelic loss (LOH) of chromosome 11q13 occurs in about 30-40% and somatic mutation of MEN1 gene occur in about 12-20% of sporadic parathyroid adenomas. A mouse model of MEN1 deficiency causes a phenotype that includes the same range of major endocrine tumors as in MEN 1 patients, and exhibits multistage tumor progression with metastatic potential. Hormonal disturbances, such as abnormal PTH and insulin levels, were also observed in these mice. Mutations in a newly identified tumor suppressor gene, HRPT2, have been recently associated with the development of HPT-JT. HRPT2 mutations are also frequent in sporadic parathyroid carcinomas and central to their pathogenesis. MEN1 and HRPT2 genes mutations have also been found in a subset of FIHP families. FHH and NSHPT represent the mildest and severest variants of PHPT, respectively. Both cause hypercalcemia from birth and atypical PHPT that always uniquely persists after subtotal parathyroidectomy. Future identification of additional oncogenes and tumor suppressor genes will clarify the molecular basis of abnormalities of parathyroid proliferation and regulatory function and other specific features unique to the parathyroid tumorigenesis

MEN1 gene alterations do not correlated with the pèhenotype of sporadic primary hyperparathyroidism

Abstract: Loss of heterozygosity (LOH) in the MEN1 region on chromosome 11q13 and MEN1 gene mutations have been found in a subset of sporadic parathyroid tumors. The question of whether these genetic abnormalities in the parathyroid tumors might influence the clinical and biochemical characteristics of primary hyperparathyroidism (PHPT) remains to be elucidated. The aim of the present study was to correlate the presence of MEN1 gene alterations in PHPT tumors with the clinical phenotype. Using microsatellite analysis for LOH at 11q13 and DNA sequencing of the coding exons, the MEN1 gene was studied in 38 parathyroid tumors of patients with sporadic PHIPT. Fourteen tumors showed LOH at 11q13, and mutations of MEN1 gene were detected in 7 cases. The clinical and biochemical characteristics of patients were unrelated to the presence or absence of LOH and/or MEN1 gene mutations. In conclusion, MEN1 gene alterations are rather common in sporadic PHPT and their presence does not correlate with the clinical manifestations of the disease. (C) 2002, Editrice Kurtis

Oxidation-specific epitopes restrain bone formation.

Atherosclerosis and osteoporosis are epidemiologically linked and oxidation specific epitopes (OSEs), such as phosphocholine (PC) of oxidized phospholipids (PC-OxPL) and malondialdehyde (MDA), are pathogenic in both. The proatherogenic effects of OSEs are opposed by innate immune antibodies. Here we show that high-fat diet (HFD)-induced bone loss is attenuated in mice expressing a single chain variable region fragment of the IgM E06 (E06-scFv) that neutralizes PC-OxPL, by increasing osteoblast number and stimulating bone formation. Similarly, HFD-induced bone loss is attenuated in mice expressing IK17-scFv, which neutralizes MDA. Notably, E06-scFv also increases bone mass in mice fed a normal diet. Moreover, the levels of anti-PC IgM decrease in aged mice. We conclude that OSEs, whether produced chronically or increased by HFD, restrain bone formation, and that diminished defense against OSEs may contribute to age-related bone loss. Anti-OSEs, therefore, may represent a novel therapeutic approach against osteoporosis and atherosclerosis simultaneously