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Free access

Annamaria Biroccio and Carlo Leonetti

Prostate cancer is the leading cause of cancer-related deaths in men. Androgen ablation is the mainstay of treatment for advanced prostate cancer. This therapy is very effective in androgen-dependent cancer; however, these cancers eventually become androgen independent, rendering anti-androgen therapy ineffective. The exploration of novel modalities of treatment is therefore essential to improve the prognosis of this neoplasia.

Telomeres are specialized heterochromatin structures that act as protective caps at the ends of chromosomes. Telomere maintenance in the majority of tumor cells is achieved by telomerase, a reverse transcriptase enzyme that catalyzes the synthesis of further telomeric DNA. Telomerase is detected in the majority of prostate cancers, but not in normal or benign prostatic hyperplasia tissue. Moreover, the human telomerase reverse transcriptase (hTERT) gene, the catalytic subunit of telomerase, is regulated by androgens as well as by different oncogenes including Her-2, Ras, c-Myc and Bcl-2, which seem to play an important role in prostate cancer progression. Thus, telomerase may represent a very good candidate for targeted therapy in prostate tumors. To inhibit telomere maintenance by telomerase, approaches that directly target either telomerase and telomeres or the telomerase regulatory mechanisms have been used. Moreover, strategies targeting telomerase-positive cells as a means to directly kill the tumor cells have been tested. This review summarizes the most promising results achieved by anti-telomerase strategy in different solid tumors. Most of the telomeraseassociated therapies described here have proved very promising for the treatment of prostate cancer. On the basis of the good results obtained and considering the multigenic defects of human tumors, including prostate cancer, the combination of anti-telomerase strategies with conventional drugs and/or molecules capable of interfering with oncogenic pathways could efficiently improve the response of this neoplasia.

Free access

Matti L Gild, Iñigo Landa, Mabel Ryder, Ronald A Ghossein, Jeffrey A Knauf, and James A Fagin

Inhibitors of RET, a tyrosine kinase receptor encoded by a gene that is frequently mutated in medullary thyroid cancer, have emerged as promising novel therapies for the disease. Rapalogs and other mammalian target of rapamycin (mTOR) inhibitors are effective agents in patients with gastroenteropancreatic neuroendocrine tumors, which share lineage properties with medullary thyroid carcinomas. The objective of this study was to investigate the contribution of mTOR activity to RET-induced signaling and cell growth and to establish whether growth suppression is enhanced by co-targeting RET and mTOR kinase activities. Treatment of the RET mutant cell lines TT, TPC-1, and MZ-CRC-1 with AST487, a RET kinase inhibitor, suppressed growth and showed profound and sustained inhibition of mTOR signaling, which was recapitulated by siRNA-mediated RET knockdown. Inhibition of mTOR with INK128, a dual mTORC1 and mTORC2 kinase inhibitor, also resulted in marked growth suppression to levels similar to those seen with RET blockade. Moreover, combined treatment with AST487 and INK128 at low concentrations suppressed growth and induced apoptosis. These data establish mTOR as a key mediator of RET-mediated cell growth in thyroid cancer cells and provide a rationale for combinatorial treatments in thyroid cancers with oncogenic RET mutations.

Free access

Mírian Romitti, Simone Magagnin Wajner, Lucieli Ceolin, Carla Vaz Ferreira, Rafaela Vanin Pinto Ribeiro, Helena Cecin Rohenkohl, Shana de Souto Weber, Patrícia Luciana da Costa Lopez, Cesar Seigi Fuziwara, Edna Teruko Kimura, and Ana Luiza Maia

Type 3 deiodinase (DIO3, D3) is reactivated in human neoplasias. Increased D3 levels in papillary thyroid carcinoma (PTC) have been associated with tumor size and metastatic disease. The objective of this study is to investigate the signaling pathways involved in DIO3 upregulation in PTC. Experiments were performed in human PTC cell lines (K1 and TPC-1 cells) or tumor samples. DIO3 mRNA and activity were evaluated by real-time PCR and ion-exchange column chromatography respectively. Western blot analysis was used to determine the levels of D3 protein. DIO3 gene silencing was performed via siRNA transfection. DIO3 mRNA levels and activity were readily detected in K1 (BRAFV6 0 0E) and, at lower levels, in TPC-1 (RET/PTC1) cells (P<0.007 and P=0.02 respectively). Similarly, DIO3 mRNA levels were higher in PTC samples harboring the BRAF V600E mutation as compared with those with RET/PTC1 rearrangement or negative for these mutations (P<0.001). Specific inhibition of BRAF oncogene (PLX4032, 3 μM), MEK (U0126, 10–20 μM) or p38 (SB203580, 10–20 μM) signaling was associated with decreases in DIO3 expression in K1 and TPC-1 cells. Additionally, the blockage of the sonic hedgehog (SHH) pathway by cyclopamine (10 μM) resulted in markedly decreases in DIO3 mRNA levels. Interestingly, siRNA-mediated DIO3 silencing induced decreases on cyclin D1 expression and partial G1 phase cell cycle arrest, thereby downregulating cell proliferation. In conclusion, sustained activation of the MAPK and SHH pathways modulate the levels of DIO3 expression in PTC. Importantly, DIO3 silencing was associated with decreases in cell proliferation, thus suggesting a D3 role in tumor growth and aggressiveness.

Open access

S Felder, H Jann, R Arsenic, T Denecke, V Prasad, B Knappe-Drzikova, S Maasberg, B Wiedenmann, M Pavel, A Pascher, and U F Pape

Although gastric neuroendocrine neoplasias (gNEN) are an orphan disease, their incidence is rising. The heterogeneous clinical course powers the ongoing discussion of the most appropriate classification system and management. Prognostic relevance of proposed classifications was retrospectively analysed in 142 patients from a single tertiary referral centre. Baseline, management and survival data were acquired for statistical analyses. The distribution according to the clinicopathological typification was gNEN-1 (n = 86/60.6%), gNEN-2 (n = 7/4.9%), gNEN-3 (n = 24/16.9%) and gNEN-4 (n = 25/17.6%), while hypergastrinemia-associated gNEN-1 and -2 were all low-grade tumours (NET-G1/2), formerly termed sporadic gNEN-3 could be subdivided into gNEN-3 with grade 1 or 2 and gNEN-4 with grade 3 (NEC-G3). During follow-up 36 patients died (25%). The mean overall survival (OS) of all gNEN was 14.2 years. The OS differed statistically significant across all subgroups with either classification system. According to UICC 2017 TNM classification, OS differed for early and advanced stages, while WHO grading indicated poorer prognosis for NEC-G3. Cox regression analysis confirmed the independent prognostic validity of either classification system for survival. Particularly careful analysis of the clinical course of gNEN-1 (ECLomas, gastric carcinoids) confirmed their mostly benign, but recurrent and extremely slowly progressive behaviour with low risk of metastasis (7%) and an efficient long-term control by repetitive endoscopic procedures. Our study provides evidence for the validity of current classifications focusing on typing, grading and staging. These are crucial tools for risk stratification, especially to differentiate gNEN-1 as well as sporadic gNET and gNEC (gNEN-3 vs -4).

Free access

D M Peehl

This review focuses on primary cultures of human prostatic epithelial cells and their applications as models of normal and malignant biological behavior. Current abilities to culture cells from normal tissues, from premalignant dysplastic lesions (prostatic intraepithelial neoplasia), from primary adenocarcinomas, and from metastases are described. Evidence for representation of the interrelated cells of the normal prostatic epithelium — stem cells, basal epithelial cells, secretory epithelial cells, transit amplifying cells and neuroendocrine cells — in primary cultures is presented. Comparisons between normal and cancer-derived primary cultures are made regarding biological activities relevant to carcinogenesis, such as proliferation, apoptosis, differentiation, senescence, adhesion, migration, invasion, steroid hormone metabolism, other metabolic pathways and angiogenesis. Analyses of tumor suppressor activity, differential gene expression and cytogenetics in primary cultures have revealed changes relevant to prostate cancer progression. Preclinical studies with primary cultures have provided information useful for designing new strategies for chemoprevention, chemotherapy, cytotoxin therapy, radiation therapy, gene therapy and imaging. While the behavior of normal primary cultures is often used as a basis for comparison with established, immortal prostate cancer cell lines, the most informative studies are performed with donor-matched pairs of normal and malignant primary cultures, grown under identical conditions. Challenges that remain to be addressed if the full potential of primary cultures as a model system is to be realized include isolation, culture and characterization of stem cells, improved methodology to induce or maintain a fully differentiated, androgen-responsive phenotype, and identification of cell surface antigens or other markers with which to purify pure populations of live cancer or premalignant cells apart from non-malignant epithelial cells prior to culture.

Free access

Emmanouil Saloustros, Paraskevi Salpea, Matthew Starost, Sissi Liu, Fabio R Faucz, Edra London, Eva Szarek, Woo-Jin Song, Mehboob Hussain, and Constantine A Stratakis

Carney complex (CNC) is a rare disease associated with multiple neoplasias, including a predisposition to pancreatic tumors; it is caused most frequently by the inactivation of the PRKAR1A gene, a regulator of the cyclic AMP (cAMP)-dependent kinase (PKA). The method used was to create null alleles of prkar1a in mouse cells expressing pdx1 (Δ-Prkar1a). We found that these mice developed endocrine or mixed endocrine/acinar cell carcinomas with 100% penetrance by the age of 4–5 months. Malignant behavior of the tumors was seen as evidenced by stromal invasion and metastasis to locoregional lymph nodes. Histologically, most tumors exhibited an organoid pattern as seen in the islet-cell tumors. Biochemically, the lesions exhibited high PKA activity, as one would expect from deleting prkar1a. The primary neuroendocrine nature of these tumor cells was confirmed by immunohistochemical staining and electron microscopy, the latter revealing the characteristic granules. Although the Δ-Prkar1a mice developed hypoglycemia after overnight fasting, insulin and glucagon levels in the plasma were normal. Negative immunohistochemical staining for the most commonly produced peptides (insulin, c-peptide, glucagon, gastrin and somatostatin) suggested that these tumors were non-functioning. We hypothesize that the recently identified multipotent pdx1+/insulin− cell in adult pancreas, gives rise to endocrine or mixed endocrine/acinar pancreatic malignancies with complete prkar1a deficiency. In conclusion, this mouse model supports the role of prkar1a as a tumor suppressor gene in the pancreas and points to the PKA pathway as a possible therapeutic target for these lesions.

Free access

Gregory Kaltsas, Ioannis I Androulakis, Wouter W de Herder, and Ashley B Grossman

Neuroendocrine tumours may be either benign or malignant tumours, and have the ability to synthesise and secrete biologically active substances characteristic of the cell of origin that can cause distinct clinical syndromes. The term ‘paraneoplastic syndromes’ (PNSs) is used to denote syndromes secondary to substances secreted from tumours not related to their specific organ or tissue of origin and/or production of autoantibodies against tumour cells; such syndromes are mainly associated with hormonal and neurological symptoms. Appreciation of the presence of such syndromes is important as clinical presentation, if not identified, may delay the diagnosis of the underlying neoplasia. Conversely, early recognition can allow for more rapid diagnosis, particularly as the coexistence of a neoplasm with a clinical or biochemical marker offers an additional determinant of tumour status/progression. PNSs can complicate the patient's clinical course, response to treatment, impact prognosis and even be confused as metastatic spread. Their diagnosis involves a multidisciplinary approach, and detailed endocrinological, neurological, radiological and histological studies are required. Correct diagnosis is essential as the treatment of choice will be different for each disorder, particularly in the case of malignant tumours; it is therefore important to develop appropriate means to correctly identify and localise these tumours. Clinical awareness and the incorporation into clinical practise of 111In-octreotide scintigraphy, chromogranin A and other evolving biochemical marker measurement techniques have substantially contributed to the identification of patients harbouring such syndromes. Disease-specific medical therapies are mandatory in order to prevent recurrence and/or further tumour growth. Owing to their rarity, central registration of these syndromes is very helpful in order to be able to provide evidence-based diagnostic and therapeutic approaches.

Free access

Viktor Johanson, Håkan Ahlman, Peter Bernhardt, Svante Jansson, Lars Kölby, Fredrik Persson, Göran Stenman, Christina Swärd, Bo Wängberg, Mats Stridsberg, and Ola Nilsson

Hereditary medullary thyroid carcinoma (MTC) is caused by germline mutations in the RET proto-oncogene, resulting in constitutive activation of the RET tyrosine kinase. A substantial proportion of sporadic MTCs also have RET mutations, making the RET tyrosine kinase a potential therapeutic target in MTC. We have established a transplantable MTC in nude mice from a sporadic human MTC carrying a RET C634R mutation. Transplanted tumors had an exponential growth rate with an approximate doubling time of about 3 weeks, and expressed a neuroendocrine phenotype characteristic of MTC, e.g., expression of calcitonin, chromogranin A (CgA), synaptophysin, synaptic vesicle protein 2 (SV2), vesicular monoamine transporter-1 and -2, carcinoembryonic antigen, cytokeratin 8/18, epithelial cadherin, and neural cell adhesion molecule. Plasma calcitonin and CgA levels were elevated in tumor-bearing mice and correlated with tumor size. Cytogenetic analysis, including spectral karyotyping, confirmed the human origin of the xenografted tumors and demonstrated an abnormal, near triploid karyotype. Treatment of tumor-bearing nude mice with the tyrosine kinase inhibitor ZD6474, which specifically inhibits RET, epidermal growth factor receptor (EGFR), and vascular endothelium growth factor receptor (VEGFR) tyrosine kinases, resulted in a dose-dependent inhibition of tumor growth. Oral ZD6474 given once daily (250 mg/kg, 5 days/week) reduced tumor volume to 11% when compared with controls after 4 weeks. Our results show that this transplantable MTC, designated GOT2, represents a novel and useful model for studies of MTC and RET tyrosine kinase-dependent tumor growth.

Free access

Ernst von Dobschuetz, Helena Leijon, Camilla Schalin-Jäntti, Francesca Schiavi, Michael Brauckhoff, Mariola Peczkowska, Giovanna Spiazzi, Serena Demattè, Maria Enrica Cecchini, Paola Sartorato, Jolanta Krajewska, Kornelia Hasse-Lazar, Katarzyna Roszkowska-Purska, Elisa Taschin, Angelica Malinoc, Lars A Akslen, Johanna Arola, Dariusz Lange, Ambrogio Fassina, Gianmaria Pennelli, Mattia Barbareschi, Jutta Luettges, Aleksander Prejbisz, Andrzej Januszewicz, Tim Strate, Birke Bausch, Frederic Castinetti, Barbara Jarzab, Giuseppe Opocher, Charis Eng, and Hartmut P H Neumann

The precise diagnosis of thyroid neoplasias will guide surgical management. Primary thyroid paraganglioma has been rarely reported. Data on prevalence, immunohistochemistry (IHC), and molecular genetics in a systematic series of such patients are pending. We performed a multinational population-based study on thyroid paraganglioma and analyzed prevalence, IHC, and molecular genetics. Patients with thyroid paraganglioma were recruited from the European-American-Head-and-Neck-Paraganglioma-Registry. Demographic and clinical data were registered. Histopathology and IHC were re-investigated. All patients with thyroid paraganglioma underwent molecular genetic analyses of the SDHA, SDHB, SDHC, SDHD, SDHAF2, VHL, RET, TMEM127, and MAX genes. Analyses included Sanger sequencing and multiplex ligation-dependent probe amplification (MLPA) for detection of large rearrangements. Of 947 registrants, eight candidates were initially identified. After immunohistochemical analyses of these eight subjects, 5 (0.5%) were confirmed to have thyroid paraganglioma. IHC was positive for chromogranin, synaptophysin, and S-100 and negative for calcitonin in all five thyroid paragangliomas, whereas the three excluded candidate tumors stained positive for pan-cytokeratin, a marker excluding endocrine tumors. Germline variants, probably representing mutations, were found in four of the five confirmed thyroid paraganglioma cases, two each in SDHA and SDHB, whereas the excluded cases had no mutations in the tested genes. Thyroid paraganglioma is a finite entity, which must be differentiated from medullary thyroid carcinoma, because medical, surgical, and genetic management for each is different. Notably, approximately 80% of thyroid paragangliomas are associated with germline variants, with implications for additional tumors and a potential risk for the family. As opposed to sporadic tumors, surgical management and extent of resection are different for heritable tumors, each guided by the precise gene involved.

Free access

Sara Molatore, Andrea Kügler, Martin Irmler, Tobias Wiedemann, Frauke Neff, Annette Feuchtinger, Johannes Beckers, Mercedes Robledo, Federico Roncaroli, and Natalia S Pellegata

Rats affected by the MENX syndrome spontaneously develop multiple neuroendocrine tumors (NETs) including adrenal, pituitary and thyroid gland neoplasms. MENX was initially reported to be inherited as a recessive trait and affected rats were found to be homozygous for the predisposing Cdkn1b mutation encoding p27. We here report that heterozygous MENX-mutant rats (p27+/mut) develop the same spectrum of NETs seen in the homozygous (p27mut/mut) animals but with slower progression. Consequently, p27+/mut rats have a significantly shorter lifespan compared with their wild-type (p27+/+) littermates. In the tumors of p27+/mut rats, the wild-type Cdkn1b allele is neither lost nor silenced, implying that p27 is haploinsufficient for tumor suppression in this model. Transcriptome profiling of rat adrenal (pheochromocytoma) and pituitary tumors having different p27 dosages revealed a tissue-specific, dose-dependent effect of p27 on gene expression. In p27+/mut rats, thyroid neoplasms progress to invasive and metastatic medullary thyroid carcinomas (MTCs) accompanied by increased calcitonin levels, as in humans. Comparison of expression signatures of late-stage vs early-stage MTCs from p27+/mut rats identified genes potentially involved in tumor aggressiveness. The expression of a subset of these genes was evaluated in human MTCs and found to be associated with aggressive RET-M918T-positive tumors. Altogether, p27 haploinsufficiency in MENX rats uncovered a novel, representative model of invasive and metastatic MTC exploitable for translational studies of this often aggressive and incurable cancer.