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Lisa K Philp, Anja Rockstroh, Melanie Lehman, Martin C Sadowski, Nenad Bartonicek, John D Wade, Laszlo Otvos Jr, and Colleen C Nelson

Adiponectin is an adipokine originally identified as dysregulated in obesity, with a key role in insulin sensitisation and in maintaining systemic energy balance. However, adiponectin is progressively emerging as having aberrant signalling in multiple disease states, including prostate cancer (PCa). Circulating adiponectin is lower in patients with PCa than in non-malignant disease, and inversely correlates with cancer severity. More severe hypoadiponectinemia is observed in advanced PCa than in organ-confined disease. Given the crossover between adiponectin signalling and several cancer hallmark pathways that influence PCa growth and progression, we hypothesised that targeting dysregulated adiponectin signalling may inhibit tumour growth and progression. We, therefore, aimed to test the efficacy of correcting the hypoadiponectinemia and dysregulated adiponectin signalling observed in PCa, a world-first PCa therapeutic approach, using peptide adiponectin receptor (ADIPOR) agonist ADP355 in mice bearing subcutaneous LNCaP xenografts. We demonstrate significant evidence for PCa growth inhibition by ADP355, which slowed tumour growth and delayed progression of serum PCa biomarker, prostate-specific antigen (PSA), compared to vehicle. ADP355 conferred a significant advantage by increasing time on treatment with a delayed ethical endpoint. mRNA sequencing and protein expression analyses of tumours revealed ADP355 PCa growth inhibition may be through altered cellular energetics, cellular stress and protein synthesis, which may culminate in apoptosis, as evidenced by the increased apoptotic marker in ADP355-treated tumours. Our findings highlight the efficacy of ADP355 in targeting classical adiponectin-associated signalling pathways in vivo and provide insights into the promising future for modulating adiponectin signalling through ADIPOR agonism as a novel anti-tumour treatment modality.

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Jean-Pierre Bayley and Peter Devilee

This review describes human and rodent-derived cell lines and xenografts developed over the last five decades that are suitable or potentially suitable models for paraganglioma–pheochromocytoma research. We outline the strengths and weaknesses of various models and emphasize the recurring theme that, despite the major challenges involved, more effort is required in the search for valid human and animal cell models of paraganglioma–pheochromocytoma, particularly those relevant to cancers carrying a mutation in one of the succinate dehydrogenase genes. Despite many setbacks, the recent development of a potentially important new model, the RS0 cell line, gives reason for optimism regarding the future of models in the paraganglioma–pheochromocytoma field. We also note that classic approaches to cell line derivation such as SV40-mediated immortalization and newer approaches such as organoid culture or iPSCs have been insufficiently explored. As many existing cell lines have been poorly characterized, we provide recommendations for reporting of paraganglioma and pheochromocytoma cell lines, including the strong recommendation that cell lines are made widely available via the ATCC or a similar cell repository. Basic research in paraganglioma–pheochromocytoma is currently transitioning from the analysis of genetics to the analysis of disease mechanisms and the clinically exploitable vulnerabilities of tumors. A successful transition will require many more disease-relevant human and animal models to ensure continuing progress.

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Jonathan Wesley Nyce

Androgens play a fundamental role in the morbidity and mortality of COVID-19, inducing both the ACE-2 receptor to which SARS-CoV-2 binds to gain entry into the cell, and TMPRS22, the transmembrane protease that primes the viral spike protein for efficient infection. The United States stands alone among developed nations in permitting one androgen, oral dehydroepiandrosterone (DHEA), to be freely available OTC and online as a “dietary supplement.” DHEA is widely used by males in the US to offset the age-related decline in circulating androgens. This fact may contribute to the disparate statistics of COVID-19 morbidity and mortality in this country. In regulatory antithesis, every other developed nation regulates DHEA as a controlled substance. DHEA is an extremely potent inhibitor of Glucose-6-phosphate Dehydrogenase (G6PD), with uniquely unstable uncompetitive inhibition kinetics. This has particular relevance to COVID-19, because G6PD-deficient human cells have been demonstrated to be exceptionally sensitive to infection by human coronavirus. Because DHEA is lipophilic and freely passes into cells, oral DHEA bypasses the normal controls regulating androgen biology and uncompetitive G6PD inhibition. DHEA’s status as a “dietary supplement” means that no clinical trials demonstrating safety have been performed, and, in the absence of physician supervision, no data on adverse events has been collected. During the current pandemic, the unrestricted availability of oral DHEA as a “dietary supplement” cannot be considered safe without proof from placebo-controlled clinical trials that it is not contributing to the severity of COVID-19. US physicians may therefore wish to query their patients’ use of DHEA.

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Yuanzhong Wang, Yen-Dun Tony Tzeng, Gregory Chang, Xiaoqiang Wang, and Shiuan Chen

Acquired resistance to aromatase inhibitors (AIs) is a significant clinical issue in endocrine therapy for estrogen receptor (ER) positive breast cancer which accounts for the majority of breast cancer. Despite estrogen production being suppressed, ERα signaling remains active and plays a key role in most AI-resistant breast tumors. Here, we found that amphiregulin (AREG), an ERα transcriptional target and EGF receptor (EGFR) ligand, is crucial for maintaining ERα expression and signaling in acquired AI-resistant breast cancer cells. AREG was deregulated and critical for cell viability in ER+ AI-resistant breast cancer cells, and ectopic expression of AREG in hormone responsive breast cancer cells promoted endocrine resistance. RNA-sequencing and reverse phase protein array analyses revealed that AREG maintains ERα expression and signaling by activation of PI3K/Akt/mTOR signaling and upregulation of forkhead box M1 (FOXM1) and serum- and glucocorticoid-inducible kinase 3 (SGK3) expression. Our study uncovers a previously unappreciated role of AREG in maintaining ERα expression and signaling, and establishes the AREG-ERα crosstalk as a driver of acquired AI resistance in breast cancer.

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Sophie Moog, Charlotte Lussey-Lepoutre, and Judith Favier

Pheochromocytomas and paragangliomas (PPGL) are rare neuroendocrine tumors arising from the adrenal medulla or extra-adrenal paraganglia. Around 40% of all cases are caused by a germline mutation in a susceptibility gene, half of which being found in an SDHx gene (SDHA, SDHB, SDHC, SDHD or SDHAF2). They encode the four subunits and assembly factor of succinate dehydrogenase (SDH), a mitochondrial enzyme involved both in the tricarboxylic acid cycle and electron transport chain. SDHx mutations lead to the accumulation of succinate, which acts as an oncometabolite by inhibiting iron(II) and alpha-ketoglutarate-dependent dioxygenases thereby regulating the cell’s hypoxic response and epigenetic processes. Moreover, SDHx mutations induce cell metabolic reprogramming and redox imbalance. Major discoveries in PPGL pathophysiology have been made since the initial discovery of SDHD gene mutations in 2000, improving the understanding of their biology and patient management. It indeed provides new opportunities for diagnostic tools and innovative therapeutic targets in order to improve the prognosis of patients affected by these rare tumors, in particular in the context of metastatic diseases associated with SDHB mutations. This review first describes an overview of the pathophysiology and then focuses on clinical implications of the epigenetic and metabolic reprogramming of SDH-deficient PPGL.

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Kathrin A Schmohl, Yang Han, Mariella Tutter, Nathalie Schwenk, Rim S J Sarker, Katja Steiger, Sibylle I Ziegler, Peter Bartenstein, Peter J Nelson, and Christine Spitzweg

Thyroid hormones are emerging as critical regulators of tumour growth and progression. To assess the contribution of thyroid hormone signalling via integrin αvβ3, expressed on many tumour cells, endothelial cells, and stromal cells, to tumour growth, we compared the effects of thyroid hormones vs tetrac, a specific inhibitor of thyroid hormone action at integrin αvβ3, in two murine xenograft tumour models with and without integrin αvβ3 expression. Integrin αvβ3-positive human anaplastic thyroid cancer cells SW1736 and integrin αvβ3-negative human hepatocellular carcinoma cells HuH7 were injected into the flanks of nude mice. Tumour growth was monitored in euthyroid, hyperthyroid, hypothyroid, and euthyroid tetrac-treated mice. In SW1736 xenografts, hyperthyroidism led to a significantly increased tumour growth resulting in a decreased survival compared to euthyroid mice, while tumour growth was significantly reduced and, hence, survival prolonged in hypothyroid and tetrac-treated mice. Both proliferation and vascularisation, as determined by Ki67 and CD31 immunofluorescence staining, respectively, were significantly increased in tumours from hyperthyroid mice as compared to hypothyroid and tetrac-treated mice. No differences in tumour growth, survival, or Ki67 staining were observed between the different groups in integrin αvβ3-negative HuH7 xenografts. Vascularisation, however, was significantly decreased in hypothyroid and tetrac-treated mice compared to euthyroid and hyperthyroid mice. Apoptosis was not affected in either tumour model, nor were cell proliferation or apoptosis in vitro. Tumour growth regulation by thyroid hormones in αvβ3-positive tumours has important implications for cancer patients, especially those with thyroid dysfunctions and thyroid cancer patients treated with thyrotropin-suppressive L-thyroxine doses.

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Irasema Mendieta, Gabriel Rodríguez-Gómez, Bertha Rueda-Zarazúa, Julia Rodríguez-Castelán, Winniberg Álvarez-León, Evangelina Delgado-González, Brenda Anguiano, Olivia Vázquez-Martínez, Mauricio Díaz-Muñoz, and Carmen Aceves

Neuroblastoma (NB) is the most common solid childhood tumor, and all-trans retinoic acid (ATRA) is used as a treatment to decrease minimal residual disease. Molecular iodine (I2) induces differentiation and/or apoptosis in several neoplastic cells through activation of PPARγ nuclear receptors. Here, we analyzed whether the coadministration of I2 and ATRA increases the efficacy of NB treatment. ATRA-sensitive (SH-SY5Y), partially-sensitive (SK-N-BE(2)), and non-sensitive (SK-N-AS) NB cells were used to analyze the effect of I2 and ATRA in vitro and in xenografts (Foxn1 nu/nu mice), exploring actions on cellular viability, differentiation, and molecular responses. In the SH-SY5Y cells, 200 μM I2 caused a 100-fold (0.01 µM) reduction in the antiproliferative dose of ATRA and promoted neurite extension and neural marker expression (tyrosine hydroxylase (TH) and tyrosine kinase receptor alpha (Trk-A)). In SK-N-AS, the I2 supplement sensitized these cells to 0.1 μM ATRA, increasing the ATRA-receptor (RARα) and PPARγ expression, and decreasing the Survivin expression. The I2 supplement increased the mitochondrial membrane potential in SK-N-AS suggesting the participation of mitochondrial-mediated mechanisms involved in the sensibilization to ATRA. In vivo, oral I2 supplementation (0.025%) synergized the antitumor effect of ATRA (1.5 mg/kg BW) and prevented side effects (body weight loss and diarrhea episodes). The immunohistochemical analysis showed that I2 supplementation decreased the intratumoral vasculature (CD34). We suggest that the I2 + ATRA combination should be studied in preclinical and clinical trials to evaluate its potential adjuvant effect in addition to conventional treatments.

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Eliot B Blatt, Noa Kopplin, Shourya Kumar, Ping Mu, Suzanne D Conzen, and Ganesh V Raj

Prostate cancer (PCa) and breast cancer (BCa) are both hormone-dependent cancers that require the androgen receptor (AR) and estrogen receptor (ER) for growth and proliferation, respectively. Endocrine therapies that target these nuclear receptors (NRs) provide significant clinical benefit for metastatic patients. However, these therapeutic strategies are seldom curative and therapy resistance is prevalent. Because the vast majority of therapy-resistant PCa and BCa remain dependent on the augmented activity of their primary NR driver, common mechanisms of resistance involve enhanced NR signaling through overexpression, mutation, or alternative splicing of the receptor, coregulator alterations, and increased intracrine hormonal synthesis. In addition, a significant subset of endocrine therapy-resistant tumors become independent of their primary NR and switch to alternative NR or transcriptional drivers. While these hormone-dependent cancers generally employ similar mechanisms of endocrine therapy resistance, distinct differences between the two tumor types have been observed. In this review, we compare and contrast the most frequent mechanisms of antiandrogen and antiestrogen resistance, and provide potential therapeutic strategies for targeting both advanced PCa and BCa.

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Charis Eng

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V Craig Jordan

Following the discovery and approval of the oral contraceptive, the pharmaceutical industry sought new opportunities for the regulation of reproduction. The discovery of the first non-steroidal anti-oestrogen MER25, with antifertility properties in laboratory animals, started a search for “morning after pills.” There were multiple options in the 1960s, however one compound ICI 46,474 was investigated, but found to induce ovulation in subfertile women. A second option was to treat stage IV breast cancer. Although the patent for ICI 46,474 was awarded in the early 1960s in the United Kingdom and around the world, a patent in the United States of America (USA) was denied on the basis that the claims for breast cancer treatment were not supported by evidence. A trial at the Christie Hospital and Holt Radium Institute in Manchester, published in 1971, showed activity compared with alternatives: high dose oestrogen or androgen treatment, but the US Patent Office was unswayed until 1985! The future of tamoxifen to be, was in the balance in 1972 but the project went forward as an orphan drug looking for applications and a translational research strategy was needed. Today, tamoxifen is known as the first targeted therapy in cancer with successful applications to treat all stages of breast cancer, male breast cancer, and the first medicine for the reduction of breast cancer incidence in high risk pre and post-menopausal women. This is the unlikely story of how an orphan medicine changed medical practice around the world, with millions of women's lives extended.