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Tanupriya Contractor, Richard Clausen, Grant R Harris, Jeffrey A Rosenfeld, Darren R Carpizo, Laura Tang, and Chris R Harris

By the strictest of definitions, a genetic driver of tumorigenesis should fulfill two criteria: it should be altered in a high percentage of patient tumors, and it should also be able to cause the same type of tumor to form in mice. No gene that fits either of these criteria has ever been found for ileal neuroendocrine tumors (I-NETs), which in humans are known for an unusual lack of recurrently mutated genes, and which have never been detected in mice. In the following report, we show that I-NETs can be generated by transgenic RT2 mice, which is a classic model for a genetically unrelated disease, pancreatic neuroendocrine tumors (PNETs). The ability of RT2 mice to generate I-NETs depended upon genetic background. I-NETs appeared in a B6AF1 genetic background, but not in a B6 background nor even in an AB6F1 background. AB6F1 and B6AF1 have identical nuclear DNA but can potentially express different allelic forms of imprinted genes. This led us to test human I-NETs for loss of imprinting, and we discovered that the IGF2 gene showed loss of imprinting and increased expression in the I-NETs of 57% of patients. By increasing IGF2 activity genetically, I-NETs could be produced by RT2 mice in a B6 genetic background, which otherwise never developed I-NETs. The facts that IGF2 is altered in a high percentage of patients with I-NETs and that I-NETs can form in mice that have elevated IGF2 activity, define IGF2 as the first genetic driver of ileal neuroendocrine tumorigenesis.

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Tara Williamson, Thais Biude Mendes, Natalie Joe, Janete M Cerutti, and Gregory J Riggins

The most common thyroid malignancy is papillary thyroid cancer. While a majority respond to therapy and have a favorable prognosis, some papillary thyroid cancers persist. This subset may dedifferentiate to anaplastic thyroid cancer, an aggressive, highly invasive and rapidly fatal cancer. Thyroid cancer patients at risk for disease progression and metastasis need earlier, safer and more effective therapies. The purpose of this translational study was to determine if mebendazole could be repurposed to effectively treat thyroid cancer, in particular before metastasis. In vitro, mebendazole potently inhibited the growth of a panel of human papillary and anaplastic thyroid cancer cells. In papillary (B-CPAP) and anaplastic (8505c) cell lines, mebendazole increased the percentage of cells in G2/M cell cycle arrest and induced late stage apoptosis by activation of the caspase-3 pathway. In aggressive 8505c cells, mebendazole significantly repressed migratory and invasive potential in a wound healing and transwell invasion assay and inhibited expression of phosphorylated Akt and Stat3 and reduced Gli1. In vivo, mebendazole treatment resulted in significant orthotopic thyroid tumor regression (B-CPAP) and growth arrest (8505c), with treated tumors displaying reduced expression of the proliferation maker KI67 and less vascular epithelium as indicated by CD31+ immunohistochemistry. Most importantly, daily oral mebendazole prevented established thyroid tumors from metastasizing to the lung. Given the low toxicity and published anticancer mechanisms of mebendazole, this novel preclinical study of mebendazole in thyroid cancer has promising therapeutic implications for patients with treatment refractory papillary or anaplastic thyroid cancer.

Open access

Martina Gruber, Lavinia Ferrone, Martin Puhr, Frédéric R Santer, Tobias Furlan, Iris E Eder, Natalie Sampson, Georg Schäfer, Florian Handle, and Zoran Culig

Administration of the microtubule inhibitor docetaxel is a common treatment for metastatic castration-resistant prostate cancer (mCRPC) and results in prolonged patient overall survival. Usually, after a short period of time chemotherapy resistance emerges and there is urgent need to find new therapeutic targets to overcome therapy resistance. The lysine-acetyltransferase p300 has been correlated to prostate cancer (PCa) progression. Here, we aimed to clarify a possible function of p300 in chemotherapy resistance and verify p300 as a target in chemoresistant PCa. Immunohistochemistry staining of tissue samples revealed significantly higher p300 protein expression in patients who received docetaxel as a neoadjuvant therapy compared to control patients. Elevated p300 expression was confirmed by analysis of publicly available patient data, where significantly higher p300 mRNA expression was found in tissue of mCRPC tumors of docetaxel-treated patients. Consistently, docetaxel-resistant PCa cells showed increased p300 protein expression compared to docetaxel-sensitive counterparts. Docetaxel treatment of PCa cells for 72 h resulted in elevated p300 expression. shRNA-mediated p300 knockdown did not alter colony formation efficiency in docetaxel-sensitive cells, but significantly reduced clonogenic potential of docetaxel-resistant cells. Downregulation of p300 in docetaxel-resistant cells also impaired cell migration and invasion. Taken together, we showed that p300 is upregulated by docetaxel, and our findings suggest that p300 is a possible co-target in treatment of chemoresistant PCa.

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Halfdan Sorbye, Grace Kong, and Simona Grozinsky-Glasberg

Peptide receptor radionuclide therapy (PRRT) is an established treatment for grade 1 and 2 gastroenteropancreatic neuroendocrine tumors with an increased uptake on somatostatin receptor imaging (SRI). Patients with metastatic high-grade (WHO G3) gastroenteropancreatic neuroendocrine neoplasms (NET G3 and NEC) represent a heterogeneous subgroup with poor prognosis and standard platinum-etoposide chemotherapy have limited therapeutic benefit. However, there is promising emerging evidence supporting the effectiveness of PRRT in SRI-positive G3 disease. A review search for studies reporting on PRRT in gastroenteropancreatic neuroendocrine neoplasms G3 was performed: four studies with more than ten cases were found. PRRT was mainly given as second- or third-line treatment in patients with progressive disease. Most patients had a pancreatic primary, 50% had well-differentiated tumors, and most had a Ki-67 <55%. Three studies showed similar results with promising response rates (31–41%) and disease control rates (69–78%). Progression-free survival (11–16 months) and survival (22–46 months) were best concerning patients with a Ki-67 <55%. Progression-free survival was 19 months in NET G3, 11 months for lowNEC (Ki-67 ≤55%) and 4 months for highNEC (Ki-67 >55%). PRRT should be considered for patients with increased uptake on SRI, both in gastroenteropancreatic NET G3 cases and as well as in NEC cases with a Ki-67 21–55%. PRRT for NEC with a Ki-67 >55% is less defined, but could be considered in highly selected cases after response to initial chemotherapy where all residual disease have high uptake on SRI. Dual tracer using 18F-FDG PET/CT and SRI provides important information for patient selection for PRRT in this heterogeneous complex high-grade disease.

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Suzan Stelloo, Simon Linder, Ekaterina Nevedomskaya, Eider Valle-Encinas, Iris de Rink, Lodewyk F A Wessels, Henk van der Poel, Andries M Bergman, and Wilbert Zwart

Prostate cancer development and progression is largely dependent on androgen receptor (AR) signaling. AR is a hormone-dependent transcription factor, which binds to thousands of sites throughout the human genome to regulate expression of directly responsive genes, including pro-survival genes that enable tumor cells to cope with increased cellular stress. ERN1 and XBP1 – two key players of the unfolded protein response (UPR) – are among such stress-associated genes. Here, we show that XBP1 levels in primary prostate cancer are associated with biochemical recurrence in five independent cohorts. Patients who received AR-targeted therapies had significantly lower XBP1 expression, whereas expression of the active form of XBP1 (XBP1s) was elevated. In vitro results show that AR-induced ERN1 expression led to increased XBP1s mRNA and protein levels. Furthermore, ChIP-seq analysis revealed that XBP1s binds enhancers upon stress stimuli regulating genes involved in UPR processes, eIF2 signaling and protein ubiquitination. We further demonstrate genomic overlap of AR- and XBP1s-binding sites, suggesting genomic conversion of the two signaling cascades. Transcriptomic effects of XBP1 were further studied by knockdown experiments, which lead to decreased expression of androgen-responsive genes and UPR genes. These results suggest a two-step mechanism of gene regulation, which involves androgen-induced expression of ERN1, thereby enhancing XBP1 splicing and transcriptional activity. This signaling cascade may prepare the cells for the increased protein folding, mRNA decay and translation that accompanies AR-regulated tumor cell proliferation.

Free access

Alastair Davies, Amina Zoubeidi, and Luke A Selth

Tumours adapt to increasingly potent targeted therapies by transitioning to alternative lineage states. In prostate cancer, the widespread clinical application of androgen receptor (AR) pathway inhibitors has led to the insurgence of tumours relapsing with a neuroendocrine phenotype, termed neuroendocrine prostate cancer (NEPC). Recent evidence suggests that this lineage reprogramming is driven largely by dysregulation of the epigenome and transcriptional networks. Indeed, aberrant DNA methylation patterning and altered expression of epigenetic modifiers, such as EZH2, transcription factors, and RNA-modifying factors, are hallmarks of NEPC tumours. In this review, we explore the nature of the epigenetic and transcriptional landscape as prostate cancer cells lose their AR-imposed identity and transition to the neuroendocrine lineage. Beyond addressing the mechanisms underlying epithelial-to-neuroendocrine lineage reprogramming, we discuss how oncogenic signaling and metabolic shifts fuel epigenetic/transcriptional changes as well as the current state of epigenetic therapies for NEPC.

Open access

Frances Collins, Nozomi Itani, Arantza Esnal-Zufiaurre, Douglas A Gibson, Carol Fitzgerald, and Philippa T K Saunders

Endometrial cancer is a common gynaeological malignancy: life time exposure to oestrogen is a key risk factor. Oestrogen action is mediated by receptors encoded by ESR1 (ERα) and ESR2 (ERβ): ERα plays a key role in regulating endometrial cell proliferation. A truncated splice variant isoform (ERβ5) encoded by ESR2 is highly expressed in cancers. This study explored whether ERβ5 alters oestrogen responsiveness of endometrial epithelial cells. Immunhistochemistry profiling of human endometrial cancer tissue biopsies identified epithelial cells co-expressing ERβ5 and ERα in stage I endometrial adenocarcinomas and post menopausal endometrium. Induced co-expression of ERβ5 in ERαpos endometrial cancer cells (Ishikawa) significantly increased ligand-dependent activation of an ERE-luciferase reporter stimulated by either E2 or the ERα-selective agonist 1,3,5-(4-hydroxyphenyl)-4-propyl-1H-pyrazole (PPT) compared to untransfected cells. Fluorescence recovery after photobleaching (FRAP) analysis of tagged yellow fluorescent protein (YFP)-ERβ5 transfected into Ishikawa cells revealed that incubation with E2 induced a transient reduction in intra-nuclear mobility characterised by punctate protein redistribution which phenocopied the behaviour of ERα following ligand activation with E2. In ERαneg MDA-MD-231 breast cancer cells, there was no E2-dependent change in mobility of YFP-ERβ5 and no activation of the ERE reporter in cells expressing ERβ5. In conclusion, we demonstrate that ERβ5 can act as heterodimeric partner to ERα in Ishikawa cells and increases their sensitivity to E2. We speculate that expression of ERβ5 in endometrial epithelial cells may increase the risk of malignant transformation and suggest that immunostaining for ERβ5 should be included in diagnostic assessment of women with early grade cancers.

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Xiaqing Xu, Meimei Si, Honggang Lou, Youyou Yan, Yunxi Liu, Hong Zhu, Xiaoe Lou, Jian Ma, Difeng Zhu, Honghai Wu, Bo Yanz, Haoshu Wu, Ling Ding, and Qiaojun He

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Wei-Chun Chang, Hsiao-Ching Wang, Wei-Chung Cheng, Juan-Cheng Yang, Wei-Min Chung, Yen-Pin Ho, Lumin Chen, Yao-Ching Hung, and Wen-Lung Ma

Platinum-based therapy remains the cornerstone for cancer therapy; however, its efficacy varies. The role of lipoprotein receptor-mediated lipid entry for cancer development has been reported. Yet, the roles and mechanism of the low-density lipoprotein receptor (LDLR) in chemo-sensitivities are unknown. In the current report, we used epithelial ovarian cancer (EOC), composed of various cellularities, to study this issue. Using public cDNA microarray database and single cohort study, LDLR expressions were positively associated with epithelial ovarian carcinomas (EOCs) platinum-based chemotherapy patients’ disease prognosis. In vitro and in vivo add-in/silencing LDLR was introduced to determine cisplatin sensitivity and cancer growth. Results revealed that knocked-down LDLR could sensitize while overexpressed LDLR could insensitize EOC cells to the cytotoxic effects of cisplatin. Moreover, the trans-omics approaches depicted an LDLR→LPC (Lyso-phosphatidylcholine)→FAM83B (phospholipase-related)→FGFRs (cisplatin sensitivity and phospholipase-related) regulatory axis. Finally, the manipulation of LDLR expression in EOC cells was found to determine the efficacy of cisplatin therapy in terms of tumor suppression. In conclusion, the LDLR→LPC→FAM83B→FGFRs axis is an example of tumor macroenvironmental regulation of therapy outcomes. Relatedly, LDLR expression could serve as a biomarker of chemotherapy sensitivity in EOCs. Significance: this study describes the role of LDLR in the development of insensitivity to platinum-based chemotherapy in epithelial ovarian cancer. The lipidome (e.g., LPC) and transcriptome (e.g., FAM38B) interactions revealed using trans-omics approaches an LDLR→LPC→FAM83B→FGFRs regulatory axis in cancer cells, in an animal model, and in patients.

Open access

Jonathan Wesley Nyce

We have recently described in this journal our detection of an anthropoid primate-specific, adrenal androgen-dependent, p53-mediated, ‘kill switch’ tumor suppression mechanism that reached its fullest expression only in humans, as a result of human-specific exposure to polycyclic aromatic hydrocarbons caused by the harnessing of fire – but which has components reaching all the way back to the origin of the primate lineage. We proposed that species-specific mechanisms of tumor suppression are a generalized requirement for vertebrate species to increase in body size or lifespan beyond those of species basal to their lineage or to exploit environmental niches which increase exposure to carcinogenic substances. Using empirical dynamic modeling, we have also reported our detection of a relationship between body size, lifespan, and species-specific mechanism of tumor suppression (and here add carcinogen exposure), such that a change in any one of these variables requires an equilibrating change in one or more of the others in order to maintain lifetime cancer risk at a value of about 4%, as observed in virtually all larger, longer-lived species under natural conditions. Here we show how this relationship, which we refer to as the lex naturalis of vertebrate speciation, elucidates the evolutionary steps underlying an adrenal androgen-dependent, human-specific ‘kill switch’ tumor suppression mechanism; and further, how it prescribes a solution to ‘normalize’ lifetime cancer risk in our species from its current aberrant 40% to the 4% that characterized primitive humans. We further argue that this prescription writ by the lex naturalis represents the only tenable strategy for meaningful suppression of the accelerating impact of cancer upon our species.