The tumor suppressor HRPT2/CDC73 is mutated in constitutive DNA from patients with the familial disorder hyperparathyroidism–jaw tumor syndrome and in ∼70% of all parathyroid carcinomas. In a number of HRPT2 mutant tumors however, expression of the encoded protein parafibromin is lost in the absence of a clear second event such as HRPT2 allelic loss or the presence of a second mutation in this tumor suppressor gene. We sought to determine whether hypermethylation of a 713 bp CpG island extending 648 nucleotides upstream of the HRPT2 translational start site and 65 nucleotides into exon 1 might be a mechanism contributing to the loss of expression of parafibromin in parathyroid tumors. Furthermore, we asked whether mutations might be present in the 5′-untranslated region (5′-UTR) of HRPT2. We investigated a pool of tissue from 3 normal parathyroid glands, as well as 15 individual parathyroid tumor samples including 6 tumors with known HRPT2 mutations, for hypermethylation of the HRPT2 CpG island. Methylation was not identified in any specimens despite complete loss of parafibromin expression in two parathyroid carcinomas with a single detectable HRPT2 mutation and retention of the wild-type HRPT2 allele. Furthermore, no mutations of a likely pathogenic nature were identified in the 5′-UTR of HRPT2. These data strongly suggest that alternative mechanisms such as mutation in HRPT2 intronic regions, additional epigenetic regulation such as histone modifications, or other regulatory inactivation mechanisms such as targeting by microRNAs may play a role in the loss of parafibromin expression.
Michael A Hahn, Viive M Howell, Anthony J Gill, Adele Clarkson, Graham Weaire-Buchanan, Bruce G Robinson, Leigh Delbridge, Oliver Gimm, Wolfgang D Schmitt, Bin T Teh, and Deborah J Marsh
Tanya K Day and Tina Bianco-Miotto
Epigenetic modifications, such as DNA methylation, are widely studied in cancer as they are stable and easy to measure genome wide. DNA methylation changes have been used to differentiate benign from malignant tissue and to predict tumor recurrence or patient outcome. Multiple genome wide DNA methylation studies in breast and prostate cancers have identified genes that are differentially methylated in malignant tissue compared with non-malignant tissue or in association with hormone receptor status or tumor recurrence. Although this has identified potential biomarkers for diagnosis and prognosis, what is highlighted by reviewing these studies is the similarities between breast and prostate cancers. In particular, the gene families/pathways targeted by DNA methylation in breast and prostate cancers have significant overlap and include homeobox genes, zinc finger transcription factors, S100 calcium binding proteins, and potassium voltage-gated family members. Many of the gene pathways targeted by aberrant methylation in breast and prostate cancers are not targeted in other cancers, suggesting that some of these targets may be specific to hormonal cancers. Genome wide DNA methylation profiles in breast and prostate cancers will not only define more specific and sensitive biomarkers for cancer diagnosis and prognosis but also identify novel therapeutic targets, which may be direct targets of agents that reverse DNA methylation or which may target novel gene families that are themselves DNA methylation targets.
Thais Biude Mendes, Bruno Heidi Nozima, Alexandre Budu, Rodrigo Barbosa de Souza, Marcia Helena Braga Catroxo, Rosana Delcelo, Marcos Leoni Gazarini, and Janete Maria Cerutti
We have identified previously a panel of markers (C1orf24, ITM1 and PVALB) that can help to discriminate benign from malignant thyroid lesions. C1orf24 and ITM1 are specifically helpful for detecting a wide range of thyroid carcinomas, and PVALB is particularly valuable for detecting the benign Hürthle cell adenoma. Although these markers may ultimately help patient care, the current understanding of their biological functions remains largely unknown. In this article, we investigated whether PVALB is critical for the acquisition of Hürthle cell features and explored the molecular mechanism underlying the phenotypic changes. Through ectopic expression of PVALB in thyroid carcinoma cell lines (FTC-133 and WRO), we demonstrated that PVALB sequesters free cytoplasmic Ca2+, which ultimately lowers calcium levels and precludes endoplasmic reticulum (ER) Ca2+ refilling. These results were accompanied by induced expression of PERK, an ER stress marker. Additionally, forced expression of PVALB reduces Ca2+ inflow in the mitochondria, which can in turn cause changes in mitochondria morphology, increase mitochondria number and alter subcellular localization. These findings share striking similarity to those observed in Hürthle cell tumors. Moreover, PVALB inhibits cell growth and induces cell death, most likely through the AKT/GSK-3β. Finally, PVALB expression coincides with Ca2+ deposits in HCA tissues. Our data support the hypothesis that the loss of PVALB plays a role in the pathogenesis of thyroid tumors.
G Bidaux, M Roudbaraki, C Merle, A Crépin, P Delcourt, C Slomianny, S Thebault, J-L Bonnal, M Benahmed, F Cabon, B Mauroy, and N Prevarskaya
TRPM8 (melastatine-related transient receptor potential member 8), a member of the transient receptor potential (TRP) superfamily of cation channels, has been shown to be a calcium-channel protein. TRPM8 mRNA has also been shown to be overexpressed in prostate cancer and is considered to play an important role in prostate physiology. This study was designed to determine the androgen-regulation mechanisms for TRPM8 mRNA expression and to identify the phenotype of TRPM8-expressing cells in the human prostate. Our findings show that trpm8 gene expression requires a functional androgen receptor. Furthermore, this article argues strongly in favour of the fact that the trpm8 gene is a primary androgen-responsive gene. Single-cell reverse transcriptase PCR and immunohistochemical experiments also showed that the trpm8 gene was mainly expressed in the apical secretory epithelial cells of the human prostate and trpm8 down-regulation occurred during the loss of the apical differentiated phenotype of the primary cultured human prostate epithelial cells. The androgen-regulated trpm8 expression mechanisms are important in understanding the progression of prostate cancer to androgen-independence. These findings may contribute to design a strategy to predict prostate cancer status from the TRPM8 mRNA level. Furthermore, as the TRPM8 channel is localized in human prostate cells, it will be interesting to understand its physiological function in the normal prostate and its potential role in prostate cancer development.
Haojun Luo, Guanglun Yang, Tenghua Yu, Shujuan Luo, Chengyi Wu, Yan Sun, Manran Liu, and Gang Tu
Cancer-associated fibroblasts (CAFs) are crucial co-mediators of breast cancer progression. Estrogen is the predominant driving force in the cyclic regulation of the mammary extracellular matrix, thus potentially affecting the tumor-associated stroma. Recently, a third estrogen receptor, estrogen (G-protein-coupled) receptor (GPER), has been reported to be expressed in breast CAFs. In this study, GPER was detected by immunohistochemical analysis in stromal fibroblasts of 41.8% (59/141) of the primary breast cancer samples. GPER expression in CAFs isolated from primary breast cancer tissues was confirmed by immunostaining and RT-PCR analyses. Tamoxifen (TAM) in addition to 17β-estradiol (E2) and the GPER agonist G1 activated GPER, resulting in transient increases in cell index, intracellular calcium, and ERK1/2 phosphorylation. Furthermore, TAM, E2, and G1 promoted CAF proliferation and cell-cycle progression, both of which were blocked by GPER interference, the selective GPER antagonist G15, the epidermal growth factor receptor (EGFR) inhibitor AG1478, and the ERK1/2 inhibitor U0126. Importantly, TAM as well as G1 increased E2 production in breast CAFs via GPER/EGFR/ERK signaling when the substrate of E2, testosterone, was added to the medium. GPER-induced aromatase upregulation was probably responsible for this phenomenon, as TAM- and G1-induced CYP19A1 gene expression was reduced by GPER knockdown and G15, AG1478, and U0126 administration. Accordingly, GPER-mediated CAF-dependent estrogenic effects on the tumor-associated stroma are conceivable, and CAF is likely to contribute to breast cancer progression, especially TAM resistance, via a positive feedback loop involving GPER/EGFR/ERK signaling and E2 production.
Mark A White, Efrosini Tsouko, Chenchu Lin, Kimal Rajapakshe, Jeffrey M Spencer, Sandi R Wilkenfeld, Sheiva S Vakili, Thomas L Pulliam, Dominik Awad, Fotis Nikolos, Rajasekhara Reddy Katreddy, Benny Abraham Kaipparettu, Arun Sreekumar, Xiaoliu Zhang, Edwin Cheung, Cristian Coarfa, and Daniel E Frigo
Despite altered metabolism being an accepted hallmark of cancer, it is still not completely understood which signaling pathways regulate these processes. Given the central role of androgen receptor (AR) signaling in prostate cancer, we hypothesized that AR could promote prostate cancer cell growth in part through increasing glucose uptake via the expression of distinct glucose transporters. Here, we determined that AR directly increased the expression of SLC2A12, the gene that encodes the glucose transporter GLUT12. In support of these findings, gene signatures of AR activity correlated with SLC2A12 expression in multiple clinical cohorts. Functionally, GLUT12 was required for maximal androgen-mediated glucose uptake and cell growth in LNCaP and VCaP cells. Knockdown of GLUT12 also decreased the growth of C4-2, 22Rv1 and AR-negative PC-3 cells. This latter observation corresponded with a significant reduction in glucose uptake, indicating that additional signaling mechanisms could augment GLUT12 function in an AR-independent manner. Interestingly, GLUT12 trafficking to the plasma membrane was modulated by calcium/calmodulin-dependent protein kinase kinase 2 (CaMKK2)-5′-AMP-activated protein kinase (AMPK) signaling, a pathway we previously demonstrated to be a downstream effector of AR. Inhibition of CaMKK2-AMPK signaling decreased GLUT12 translocation to the plasma membrane by inhibiting the phosphorylation of TBC1D4, a known regulator of glucose transport. Further, AR increased TBC1D4 expression. Correspondingly, expression of TBC1D4 correlated with AR activity in prostate cancer patient samples. Taken together, these data demonstrate that prostate cancer cells can increase the functional levels of GLUT12 through multiple mechanisms to promote glucose uptake and subsequent cell growth.
Faith Nutter, Ingunn Holen, Hannah K Brown, Simon S Cross, C Alyson Evans, Matthew Walker, Robert E Coleman, Jules A Westbrook, Peter J Selby, Janet E Brown, and Penelope D Ottewell
Advanced breast cancer is associated with the development of incurable bone metastasis. The two key processes involved, tumour cell homing to and subsequent colonisation of bone, remain to be clearly defined. Genetic studies have indicated that different genes facilitate homing and colonisation of secondary sites. To identify specific changes in gene and protein expression associated with bone-homing or colonisation, we have developed a novel bone-seeking clone of MDA-MB-231 breast cancer cells that exclusively forms tumours in long bones following i.v. injection in nude mice. Bone-homing cells were indistinguishable from parental cells in terms of growth rate in vitro and when grown subcutaneously in vivo. Only bone-homing ability differed between the lines; once established in bone, tumours from both lines displayed similar rates of progression and caused the same extent of lytic bone disease. By comparing the molecular profile of a panel of metastasis-associated genes, we have identified differential expression profiles associated with bone-homing or colonisation. Bone-homing cells had decreased expression of the cell adhesion molecule fibronectin and the migration and calcium signal binding protein S100A4, in addition to increased expression of interleukin 1B. Bone colonisation was associated with increased fibronectin and upregulation of molecules influencing signal transduction pathways and breakdown of extracellular matrix, including hRAS and matrix metalloproteinase 9. Our data support the hypothesis that during early stages of breast cancer bone metastasis, a specific set of genes are altered to facilitate bone-homing, and that disruption of these may be required for effective therapeutic targeting of this process.
Antônio Ribeiro-Oliveira Jr, Giulia Franchi, Blerina Kola, Paolo Dalino, Sérgio Veloso Brant Pinheiro, Nabila Salahuddin, Madalina Musat, Miklós I Góth, Sándor Czirják, Zoltán Hanzély, Deivid Augusto da Silva, Eduardo Paulino Jr, Ashley B Grossman, and Márta Korbonits
The molecular analysis of pituitary tumours has received a great deal of attention, although the majority of studies have concentrated on the genome and the transcriptome. We aimed to study the proteome of human pituitary adenomas. A protein array using 1005 monoclonal antibodies was used to study GH-, corticotrophin- and prolactin-secreting as well as non-functioning pituitary adenomas (NFPAs). Individual protein expression levels in the tumours were compared with the expression profile of normal pituitary tissue. Out of 316 proteins that were detected in the pituitary tissue samples, 116 proteins had not previously been described in human pituitary tissue. Four prominent differentially expressed proteins with potential importance to tumorigenesis were chosen for validation by immunohistochemistry and western blotting. In the protein array analysis heat shock protein 110 (HSP110), a chaperone associated with protein folding, and B2 bradykinin receptor, a potential regulator of prolactin secretion, were significantly overexpressed in all adenoma subtypes, while C-terminal Src kinase (CSK), an inhibitor of proto-oncogenic enzymes, and annexin II, a calcium-dependent binding protein, were significantly underexpressed in all adenoma subtypes. The immunohistochemical analysis confirmed the overexpression of HSP110 and B2 bradykinin receptor and underexpression of CSK and annexin II in pituitary adenoma cells when compared with their corresponding normal pituitary cells. Western blotting only partially confirmed the proteomics data: HSP110 was significantly overexpressed in prolactinomas and NFPAs, the B2 bradykinin receptor was significantly overexpressed in prolactinomas, annexin II was significantly underexpressed in somatotrophinomas, while CSK did not show significant underexpression in any tumour. Protein expression analysis of pituitary samples disclosed both novel proteins and putative protein candidates for pituitary tumorigenesis, though validation using conventional techniques are necessary to confirm the protein array data.
Xiong Wang, Li Ma, Qiao-yan Ding, Wen-yu Zhang, Yong-gang Chen, Jin-hu Wu, Hong-feng Zhang, and Xiu-li Guo
Prolactinomas have harmful effects on human health, and the pathogenesis is still unknown. Furthermore, 25% of prolactinoma patients do not respond to the therapy of dopamine receptor agonist in the clinic. Thus, it is important to reveal the pathogenesis and develop new therapeutic methods for prolactinomas. Herein, two animal models of prolactinomas, namely oestrogen-treated rats and transgenic D2 dopamine receptor-deficient mice, were used. PET/CT imaging detection showed that translocator protein-mediated microglia activation and inflammation significantly increased in the pituitary glands of prolactinomas rats. Messenger RNA microarrays were used to analyze and compare the differential gene and signal pathways of the pituitary glands between control and prolactinomas rats. Statistical results pertaining to gene enrichment showed that the innate immune response genes were upregulated in the pituitary glands of prolactinoma rats. This suggested that the innate immune response was activated. We analyzed the NLRP3 (NOD-, LRR- and pyrin domain-containing protein 3) inflammasome that is one of the most important members of the innate immune system in mammals and found that the expressions of NLRP3, Caspase-1, apoptosis-associated speck-like, interleukin 1B (IL1B) and IL18 proteins of pituitary glands in prolactinomas rats were increased considerably compared with those in control rats. This suggested the activation of the NLRP3 inflammasome during the emergence and evolution of prolactinomas. Immunohistochemistry results also confirmed that the NLRP3 expression was elevated in human prolactinoma tissues, and the microglia marker-ionised calcium binding adaptor molecule-1 was co-located with the NLRP3 protein in prolactinomas by immunofluorescence assay. Finally, compared with the WT mice, NLRP3−/− mice had smaller pituitary glands (weight/body weight) and diminished prolactin (PRL) expressions and secretions. These findings were associated with a reduction in the caspase-1 activation and maturation of IL1B. Furthermore, MCC950 decreased the PRL expression and secretion following the inhibition of NLRP3 inflammasome activation in GH3 cells stimulated with lipopolysaccharide and nigericin. And MCC950 inhibited the pituitary tumor overgrowth and PRL expression and secretion in prolactinoma rats. These data confirm that the microglial NLRP3 inflammasome activation upregulates the inflammatory cytokines IL1/IL18 in the pituitary glands and induces prolactinomas. Our findings showed that microglial NLRP3 inflammasome activation-mediated IL1B-related inflammation promoted the development of prolactinomas and identified the inflammasome as a new therapeutic target for prolactinomas.