TMPRSS2-ERG fusion protein regulates insulin-like growth factor-1 receptor (IGF1R) gene expression in prostate cancer: involvement of transcription factor Sp1

Etiology of prostate cancer with the TMPRSS2:ERG fusion: A systematic review of risk factors

The most common somatic alteration in primary prostate cancer is the TMPRSS2:ERG gene fusion, which may be caused or promoted by distinct etiologic factors. The objective of this systematic review was to assess epidemiologic evidence on etiologic factors for prostate cancer by tumor TMPRSS2:ERG fusion status in human populations. Of 3071 publications identified, 19 cohort or case-control studies from six distinct study populations were included in this systematic review. Etiologic factors included germline genetic variants, circulating hormones, and dietary and lifestyle factors. Taller height, higher total and free testosterone levels, and fewer trinucleotide repeats in AR were possibly associated with higher risk of TMPRSS2:ERG-positive prostate cancer. Excess body weight, greater vigorous physical activity, higher lycopene intake, and the use of calcium channel blockers were associated with lower risk of TMPRSS2:ERG-positive prostate cancer. Diabetes and family history of prostate cancer were associated with both TMPRSS2:ERG-positive and TMPRSS2:ERG-negative prostate cancer. Prostate cancer germline variants had suggestive differential associations with TMPRSS2:ERG-positive or TMPRSS2:ERG-negative prostate cancer. However, results were based on few distinct study populations and generally had low precision, underscoring the need for replication. In conclusion, prostate cancer with TMPRSS2:ERG fusion is an etiologically distinct subtype that may be, in part, preventable by addressing modifiable and hormonally acting etiologic factors that align with the established mechanistic role of TMPRSS2:ERG in androgen, insulin, antioxidant, and growth factor pathways.

Extracellular Interactors of the IGF System: Impact on Cancer Hallmarks and Therapeutic Approaches

Dysregulation of the insulin-like growth factor (IGF) system determines the onset of various pathological conditions, including cancer. Accordingly, therapeutic strategies have been developed to block this system in tumor cells, but the results of clinical trials have been disappointing. After decades of research in the field, it is safe to say that one of the major reasons underlying the poor efficacy of anti-IGF-targeting agents is derived from an underestimation of the molecular complexity of this axis. Genetic, transcriptional, post-transcriptional and functional interactors interfere with the activity of canonical components of this axis, supporting the need for combinatorial approaches to effectively block this system. In addition, cancer cells interface with a multiplicity of factors from the extracellular compartment, which strongly affect cell destiny. In this review, we will cover novel extracellular mechanisms contributing to IGF system dysregulation and the implications of such dangerous liaisons for cancer hallmarks and responses to known and new anti-IGF drugs. A deeper understanding of both the intracellular and extracellular microenvironments might provide new impetus to better decipher the complexity of the IGF axis in cancer and provide new clues for designing novel therapeutic approaches.

Decoding Oncofusions: Unveiling Mechanisms, Clinical Impact, and Prospects for Personalized Cancer Therapies

Cancer-associated gene fusions, also known as oncofusions, have emerged as influential drivers of oncogenesis across a diverse range of cancer types. These genetic events occur via chromosomal translocations, deletions, and inversions, leading to the fusion of previously separate genes. Due to the drastic nature of these mutations, they often result in profound alterations of cellular behavior. The identification of oncofusions has revolutionized cancer research, with advancements in sequencing technologies facilitating the discovery of novel fusion events at an accelerated pace. Oncofusions exert their effects through the manipulation of critical cellular signaling pathways that regulate processes such as proliferation, differentiation, and survival. Extensive investigations have been conducted to understand the roles of oncofusions in solid tumors, leukemias, and lymphomas. Large-scale initiatives, including the Cancer Genome Atlas, have played a pivotal role in unraveling the landscape of oncofusions by characterizing a vast number of cancer samples across different tumor types. While validating the functional relevance of oncofusions remains a challenge, even non-driver mutations can hold significance in cancer treatment. Oncofusions have demonstrated potential value in the context of immunotherapy through the production of neoantigens. Their clinical importance has been observed in both treatment and diagnostic settings, with specific fusion events serving as therapeutic targets or diagnostic markers. However, despite the progress made, there is still considerable untapped potential within the field of oncofusions. Further research and validation efforts are necessary to understand their effects on a functional basis and to exploit the new targeted treatment avenues offered by oncofusions. Through further functional and clinical studies, oncofusions will enable the advancement of precision medicine and the drive towards more effective and specific treatments for cancer patients.

Regulation of USP25 by SP1 Associates with Amyloidogenesis

BACKGROUND

Trisomy 21, an extra copy of human chromosome 21 (HSA21), causes most Down's syndrome (DS) cases. Individuals with DS inevitably develop Alzheimer's disease (AD) neuropathological phenotypes after middle age including amyloid plaques and tau neurofibrillary tangles. Ubiquitin Specific Peptidase 25 (USP25), encoding by USP25 gene located on HSA21, is a deubiquitinating enzyme, which plays an important role in both DS and AD pathogenesis. However, the regulation of USP25 remains unclear.

OBJECTIVE

We aimed to determine the regulation of USP25 by specificity protein 1 (SP1) in neuronal cells and its potential role in amyloidogenesis.

METHODS

The transcription start site and promoter activity was identified by SMART-RACE and Dual-luciferase assay. Functional SP1-responsive elements were examined by EMSA. USP25 expression was examined by RT-PCR and immunoblotting. Student's t-test or one-way ANOVA were applied or statistical analysis.

RESULTS

The transcription start site of human USP25 gene was identified. Three functional SP1 responsive elements in human USP25 gene were revealed. SP1 promotes USP25 transcription and subsequent USP25 protein expression, while SP1 inhibition significantly reduces USP25 expression in both non-neuronal and neuronal cells. Moreover, SP1 inhibition dramatically reduces amyloidogenesis.

CONCLUSION

We demonstrates that transcription factor SP1 regulates USP25 gene expression, which associates with amyloidogenesis. It suggests that SP1 signaling may play an important role in USP25 regulation and contribute to USP25-mediated DS and AD pathogenesis.

Role of adaptin protein complexes in intracellular trafficking and their impact on diseases

Adaptin proteins (APs) play a crucial role in intracellular cell trafficking. The 'classical' role of APs is carried out by AP1‒3, which bind to clathrin, cargo, and accessory proteins. Accordingly, AP1-3 are crucial for both vesicle formation and sorting. All APs consist of four subunits that are indispensable for their functions. In fact, based on studies using cells, model organism knockdown/knock-out, and human variants, each subunit plays crucial roles and contributes to the specificity of each AP. These studies also revealed that the sorting and intracellular trafficking function of AP can exert varying effects on pathology by controlling features such as cell development, signal transduction related to the apoptosis and proliferation pathways in cancer cells, organelle integrity, receptor presentation, and viral infection. Although the roles and functions of AP1‒3 are relatively well studied, the functions of the less abundant and more recently identified APs, AP4 and AP5, are still to be investigated. Further studies on these APs may enable a better understanding and targeting of specific diseases.APs known or suggested locations and functions.

FusionAI: Predicting fusion breakpoint from DNA sequence with deep learning

Identifying the molecular mechanisms related to genomic breakage is an important goal of cancer mechanism studies. Among diverse locations of structural variants, fusion genes, which have the breakpoints in the gene bodies and are typically identified from the split reads of RNA-seq data, can provide a highlighted structural variant resource for studying the genomic breakages with expression and potential pathogenic impacts. In this study, we developed FusionAI, which utilizes deep learning to predict gene fusion breakpoints based on DNA sequence and let us identify fusion breakage code and genomic context. FusionAI leverages the known fusion breakpoints to provide a prediction model of the fusion genes from the primary genomic sequences via deep learning, thereby helping researchers a more accurate selection of fusion genes and better understand genomic breakage.

Unraveling the IGF System Interactome in Sarcomas Exploits Novel Therapeutic Options

Aberrant bioactivity of the insulin-like growth factor (IGF) system results in the development and progression of several pathologic conditions including cancer. Preclinical studies have shown promising anti-cancer therapeutic potentials for anti-IGF targeted therapies. However, a clear but limited clinical benefit was observed only in a minority of patients with sarcomas. The molecular complexity of the IGF system, which comprises multiple regulators and interactions with other cancer-related pathways, poses a major limitation in the use of anti-IGF agents and supports the need of combinatorial therapeutic strategies to better tackle this axis. In this review, we will initially highlight multiple mechanisms underlying IGF dysregulation in cancer and then focus on the impact of the IGF system and its complexity in sarcoma development and progression as well as response to anti-IGF therapies. We will also discuss the role of Ephrin receptors, Hippo pathway, BET proteins and CXCR4 signaling, as mediators of sarcoma malignancy and relevant interactors with the IGF system in tumor cells. A deeper understanding of these molecular interactions might provide the rationale for novel and more effective therapeutic combinations to treat sarcomas.

Insight into mithramycin disruption of ETS transcription leads to improved understanding of more selective analogs

Fusion products with the ETS family of transcription factors play critical roles in the etiology of several cancers. In this issue of Structure, Hou et al. (2020) provide insight into allosteric mechanisms by which mithramycin and its analogs perturb protein-DNA interactions in higher-order complexes at a DNA enhancer site.

Alantolactone inhibits cell autophagy and promotes apoptosis via AP2M1 in acute lymphoblastic leukemia

Background

Acute lymphoblastic leukemia (ALL) is an aggressive hematopoietic malignancy that is most commonly observed in children. Alantolactone (ALT) has been reported to exhibit anti-tumor activity in different types of cancer. The aim of the present study was to investigate the anti-tumor activity and molecular mechanism of ALT in ALL.

Methods

ALL cell lines were treated with 1, 5 and 10 μM ALT, and cell viability was assessed using an MTT assay and RNA sequencing. Flow cytometry, JC-1 staining and immunofluorescence staining assays were used to measure cell apoptosis and autophagy. Additionally, western blot analysis was used to detect expression of apoptosis and autophagy related proteins. Finally, the effects of ALT on tumor growth were assessed in a BV173 xenograft nude mouse model.

Results

ALT inhibited the proliferation of ALL cells in a dose-dependent manner. Additionally, it was demonstrated that ALT inhibited cell proliferation, colony formation, autophagy, induced apoptosis and reduced tumor growth in vivo through upregulating the expression of adaptor related protein complex 2 subunit mu 1 (AP2M1). Moreover, the autophagy activator rapamycin, attenuated the pro-apoptotic effects of ALT on BV173 and NALM6 cell lines. Overexpression of AP2M1 decreased the expression of Beclin1 and the LC3-II/LC3-1 ratio, and increased p62 expression. Knockdown of Beclin1 increased the levels of bax, cleaved caspase 3 and cytochrome C, and decreased bcl-2 expression.

Conclusions

The present study demonstrated that ALT exerts anti-tumor activity through inducing apoptosis and inhibiting autophagy by upregulating AP2M1 in ALL, highlighting a potential therapeutic strategy for treatment of ALL.

The role of insulin-like growth factors in the development of prostate cancer

INTRODUCTION

Preclinical, clinical, and population studies have provided robust evidence for an important role for the insulin-like growth factor (IGF) system in the development of prostate cancer.

AREAS COVERED

An overview of the IGF system is provided. The evidence implicating the IGF system in the development of prostate cancer is summarized. The compelling evidence culminated in a number of clinical trials of agents targeting the system; the reasons for the failure of these trials are discussed.

EXPERT OPINION

Clinical trials of agents targeting the IGF system in prostate cancer were terminated due to limited objective clinical responses and are unlikely to be resumed unless a convincing predictive biomarker is identified that would enable the selection of likely responders. The aging population and increased screening will lead to greater diagnosis of prostate cancer. Although the vast majority will be indolent disease, the epidemics of obesity and diabetes will increase the proportion that progress to clinical disease. The increased population of worried men will result in more trials aimed to reduce the risk of disease progression; actual clinical endpoints will be challenging and the IGFs remain the best intermediate biomarkers to indicate a response that could alter the course of disease.

Expression of IGF/insulin receptor in prostate cancer tissue and progression to lethal disease

Circulating insulin-like growth factor-1 (IGF-1) is consistently associated with prostate cancer risk. IGF-1 binds to IGF-1 receptor (IGF1R) and insulin receptor (IR), activating cancer hallmark pathways. Experimental evidence suggests that TMPRSS2:ERG may interact with IGF/insulin signaling to influence progression. We investigated IGF1R and IR expression and its association with lethal prostate cancer among 769 men. Protein expression of IGF1R, IR and ERG (i.e. a surrogate of ERG fusion genes) were assayed by immunohistochemistry. Cox models estimated hazard ratios (HR) and 95% confidence intervals (CI) adjusted for clinical characteristics. Among patients, 29% had strong tumor IGF1R expression and 10% had strong IR expression. During a mean follow-up of 13.2 years through 2012, 80 men (11%) developed lethal disease. Tumors with strong IGF1R or IR expression showed increased cell proliferation, decreased apoptosis and a higher prevalence of ERG. In multivariable models, strong IGF1R was associated with a borderline increased risk of lethal prostate cancer (HR 1.7; 95% CI 0.9-3.1). The association appeared greater in ERG-positive tumors (HR 2.8; 95% CI 0.9-8.4) than in ERG-negative tumors (HR 1.3; 95% CI 0.6-3.0, p-heterogeneity 0.08). There was no association between IR and lethal prostate cancer (HR 0.8; 95% CI 0.4-1.9). These results suggest that tumor IGF1R expression may play a role in prostate cancer progression to a lethal phenotype and that ERG-positive tumors may be more sensitive to IGF signaling. These data may improve our understanding of IGF signaling in prostate cancer and suggest therapeutic options for disease subtypes.

The Evolutionarily Conserved Cassette Exon 7b Drives ERG's Oncogenic Properties

The oncogene ERG encodes an ETS family transcription factor and is implicated in blood, vascular, and bone development and in prostate, blood, and bone cancer. The ERG gene is alternatively spliced; of particular interest is its cassette exon 7b which adds 24 amino acids, in frame, to the transcriptional activation domain. Higher exon 7b inclusion rates are associated with increased cell proliferation and advanced prostate cancer. The 24 amino acids encoded by exon 7b show evolutionary conservation from humans to echinoderms, highlighting their functional importance. Throughout evolution, these 24 amino acids are encoded by a distinct short exon. Splice-switching oligonucleotides based on morpholino chemistry were designed to induce skipping of ERG exon 7b in MG63 osteosarcoma and VCaP prostate cancer cells. Induction of exon 7b skipping reduced cell proliferation and invasion, increased apoptosis in vitro, and reduced xenograft growth in vivo. We also show that ERG's exon 7b is required for the induction of tissue nonspecific alkaline phosphatase. Together, these findings show that the evolutionarily conserved cassette exon 7b is central to ERG's oncogenic properties.

Transcriptional Reprogramming and Inhibition of Tumor-propagating Stem-like Cells by EC-8042 in ERG-positive Prostate Cancer

BACKGROUND

The TMPRSS2-ERG gene fusion is the most frequent genetic rearrangement in prostate cancers and results in broad transcriptional reprogramming and major phenotypic changes. Interaction and cooperation of ERG and SP1 may be instrumental in sustaining the tumorigenic and metastatic phenotype and could represent a potential vulnerability in ERG fusion-positive tumors.

OBJECTIVE

To test the activity of EC-8042, a compound able to block SP1, in cellular and mouse models of ERG-positive prostate cancer.

DESIGN, SETTING, AND PARTICIPANTS

We evaluated the activity of EC-8042 in cell cultures and ERG/PTEN transgenic/knockout mice that provide reliable models for testing novel therapeutics in this specific disease context. Using a new protocol to generate tumor spheroids from ERG/PTEN mice, we also examined the effects of EC-8042 on tumor-propagating stem-like cancer cells with high self-renewal and tumorigenic capabilities.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

The efficacy of EC-8042 was determined by measuring the proliferative capacity and target gene expression in cell cultures, invasive and metastatic capabilities in chick chorioallantoic membrane assays, and tumor development in mice. Significance was determined using statistical test.

RESULTS AND LIMITATIONS

EC-8042 blocked transcription of ERG-regulated genes and reverted the invasive and metastatic phenotype of VCaP cells. EC-8042 blocked the expansion of stem-like tumor cells in tumor spheroids from VCaP cells and mouse-derived tumors. In ERG/PTEN mice, systemic treatment with EC-8042 inhibited ERG-regulated gene transcription, tumor progression, and tumor-propagating stem-like tumor cells.

CONCLUSIONS

Our data support clinical testing of EC-8042 for the treatment of ERG-positive prostate cancer in precision medicine approaches.

PATIENT SUMMARY

In this study, EC-8042, a novel compound with a favorable pharmacological and toxicological profile, exhibited relevant activity in cell cultures and in vivo in a genetically engineered mouse model that closely recapitulates the features of clinically aggressive ERG-positive prostate cancer. Our data indicate that further evaluation of EC-8042 in clinical trials is warranted.

Molecular Signatures of the Insulin-like Growth Factor 1-mediated Epithelial-Mesenchymal Transition in Breast, Lung and Gastric Cancers

The insulin-like growth factor (IGF) system, which is constituted by the IGF-1 and IGF-2 peptide hormones, their corresponding receptors and several IGF binding proteins, is involved in physiological and pathophysiological processes. The IGF system promotes cancer proliferation/survival and its signaling induces the epithelial-mesenchymal transition (EMT) phenotype, which contributes to the migration, invasiveness, and metastasis of epithelial tumors. These cancers share two major IGF-1R signaling transduction pathways, PI3K/AKT and RAS/MEK/ERK. However, as far as we could review at this time, each type of cancer cell undergoes EMT through tumor-specific routes. Here, we review the tumor-specific molecular signatures of IGF-1-mediated EMT in breast, lung, and gastric cancers.

Oncogenic fusion proteins adopt the insulin-like growth factor signaling pathway

The insulin-like growth factor-1 receptor (IGF1R) has been identified as a potent anti-apoptotic, pro-survival tyrosine kinase-containing receptor. Overexpression of the IGF1R gene constitutes a typical feature of most human cancers. Consistent with these biological roles, cells expressing high levels of IGF1R are expected not to die, a quintessential feature of cancer cells. Tumor specific chromosomal translocations that disrupt the architecture of transcription factors are a common theme in carcinogenesis. Increasing evidence gathered over the past fifteen years demonstrate that this type of genomic rearrangements is common not only among pediatric and hematological malignancies, as classically thought, but may also provide a molecular and cytogenetic foundation for an ever-increasing portion of adult epithelial tumors. In this review article we provide evidence that the mechanism of action of oncogenic fusion proteins associated with both pediatric and adult malignancies involves transactivation of the IGF1R gene, with ensuing increases in IGF1R levels and ligand-mediated receptor phosphorylation. Disrupted transcription factors adopt the IGF1R signaling pathway and elicit their oncogenic activities via activation of this critical regulatory network. Combined targeting of oncogenic fusion proteins along with the IGF1R may constitute a promising therapeutic approach.

MELODI: Mining Enriched Literature Objects to Derive Intermediates

BACKGROUND

The scientific literature contains a wealth of information from different fields on potential disease mechanisms. However, identifying and prioritizing mechanisms for further analytical evaluation presents enormous challenges in terms of the quantity and diversity of published research. The application of data mining approaches to the literature offers the potential to identify and prioritize mechanisms for more focused and detailed analysis.

METHODS

Here we present MELODI, a literature mining platform that can identify mechanistic pathways between any two biomedical concepts.

RESULTS

Two case studies demonstrate the potential uses of MELODI and how it can generate hypotheses for further investigation. First, an analysis of ETS-related gene ERG and prostate cancer derives the intermediate transcription factor SP1, recently confirmed to be physically interacting with ERG. Second, examining the relationship between a new potential risk factor for pancreatic cancer identifies possible mechanistic insights which can be studied in vitro.

CONCLUSIONS

We have demonstrated the possible applications of MELODI, including two case studies. MELODI has been implemented as a Python/Django web application, and is freely available to use at [www.melodi.biocompute.org.uk].

Insulin-Like Growth Factor (IGF) Pathway Targeting in Cancer: Role of the IGF Axis and Opportunities for Future Combination Studies

Despite a strong preclinical rationale for targeting the insulin-like growth factor (IGF) axis in cancer, clinical studies of IGF-1 receptor (IGF-1R)-targeted monotherapies have been largely disappointing, and any potential success has been limited by the lack of validated predictive biomarkers for patient enrichment. A large body of preclinical evidence suggests that the key role of the IGF axis in cancer is in driving treatment resistance, via general proliferative/survival mechanisms, interactions with other mitogenic signaling networks, and class-specific mechanisms such as DNA damage repair. Consequently, combining IGF-targeted agents with standard cytotoxic agents, other targeted agents, endocrine therapies, or immunotherapies represents an attractive therapeutic approach. Anti-IGF-1R monoclonal antibodies (mAbs) do not inhibit IGF ligand 2 (IGF-2) activation of the insulin receptor isoform-A (INSR-A), which may limit their anti-proliferative activity. In addition, due to their lack of specificity, IGF-1R tyrosine kinase inhibitors are associated with hyperglycemia as a result of interference with signaling through the classical metabolic INSR-B isoform; this may preclude their use at clinically effective doses. Conversely, IGF-1/IGF-2 ligand-neutralizing mAbs inhibit proliferative/anti-apoptotic signaling via IGF-1R and INSR-A, without compromising the metabolic function of INSR-B. Therefore, combination regimens that include these agents may be more efficacious and tolerable versus IGF-1R-targeted combinations. Herein, we review the preclinical and clinical experience with IGF-targeted therapies to-date, and discuss the rationale for future combination approaches as a means to overcome treatment resistance.

Insulin-like growth factor 1 receptor affects the survival of primary prostate cancer patients depending on TMPRSS2-ERG status

BACKGROUND

Prostate cancer (PCa) is characterized by clinical and biological heterogeneity and has differential outcomes and mortality rates. Therefore, it is necessary to identify molecular alterations to define new therapeutic strategies based on the risk of progression. In this study, the prognostic relevance of the insulin-like growth factor (IGF) system was examined in molecular subtypes defined by TMPRSS2-ERG (T2E) gene fusion within a series of patients with primary localized PCa.

METHODS

A cohort of 270 formalin-fixed and paraffin-embedded (FFPE) primary PCa samples from patients with more than 5 years' follow-up was collected. IGF-1R, IGF-1, IGFBP-3 and INSR expression was analyzed using quantitative RT-PCR. The T2E status and immunohistochemical ERG findings were considered in the analyses. The association with both biochemical and clinical progression-free survival (BPFS and PFS, respectively) was evaluated for the different molecular subtypes using the Kaplan-Meier proportional risk log-rank test and the Cox proportional hazards model.

RESULTS

An association between IGF-1R overexpression and better BPFS was found in T2E-negative patients (35.3% BPFS, p-value = 0.016). Multivariate analysis demonstrated that IGF-1R expression constitutes an independent variable in T2E-negative patients [HR: 0.41. CI 95% (0.2-0.82), p = 0.013]. These data were confirmed using immunohistochemistry of ERG as subrogate of T2E. High IGF-1 expression correlated with prolonged BPFS and PFS independent of the T2E status.

CONCLUSIONS

IGF-1R, a reported target of T2E, constitutes an independent factor for good prognosis in T2E-negative PCa. Quantitative evaluation of IGF-1/IGF-1R expression combined with molecular assessment of T2E status or ERG protein expression represents a useful marker for tumor progression in localized PCa.