Transcriptional regulation and transformation by Myc proteins

Serine/arginine-rich splicing factors: the bridge linking alternative splicing and cancer

The serine/arginine-rich splicing factors (SRs) belong to the serine arginine-rich protein family, which plays an extremely important role in the splicing process of precursor RNA. The SRs recognize the splicing elements on precursor RNA, then recruit and assemble spliceosome to promote or inhibit the occurrence of splicing events. In tumors, aberrant expression of SRs causes abnormal splicing of RNA, contributing to proliferation, migration and apoptosis resistance of tumor cells. Here, we reviewed the vital role of SRs in various tumors and discussed the promise of analyzing mRNA alternative splicing events in tumor. Further, we highlight the challenges and discussed the perspectives for the identification of new potential targets for cancer therapy via SRs family members.

Therapeutic potential of targeting MYCN: A case series report of neuroblastoma with MYCN amplification

INTRODUCTION

Neuroblastoma (NB) with MYCN amplification has a poor prognosis and high mortality. The potential molecular biological relationship between clinical features and MYCN amplification should be explored.

METHODS

NB patients were examined by fluorescence in situ hybridization (FISH) for MYCN amplification in the tumor mass or bone marrow samples to determine whether MYCN was amplified. A series of eleven MYCN-amplified NB patients were included. The age, primary site, tumor size, specific biomarkers, and invaded organs were analyzed. All patients accepted standardized treatment of surgery, chemotherapy, and radiotherapy. Progression-free survival (PFS) and overall survival (OS) were evaluated.

RESULTS

The median age at diagnosis was 24 months. Nine patients (81.8%) were in stage IV, with high serum neuron-specific enolase (NSE) expression, normal urine vanillylmandelic acid (VMA) level and extensive metastases. All patients accepted a chemotherapy protocol with 8 to 10 cycles, and 9 patients (81.8%) were sensitive to the initial chemotherapy protocol. At the end of follow-up, four patients (36.3%) died with a median OS of 15 months. Five patients (45%) survived with a median PFS of 13 months. Two patients were still receiving chemotherapy.

CONCLUSION

Given the effect of MYCN amplification on poor outcome in NB, novel treatments targeting MYCN should be developed for patients with NB.

MYC protein stability is negatively regulated by BRD4

Dysregulation of MYC protein levels is associated with most human cancers. MYC is regulated by both transcription and protein stability. BRD4, a driver of oncogenesis that activates Myc transcription, is being investigated as a therapeutic target in MYC-driven cancers. We report that BRD4 directly destabilizes MYC protein by phosphorylating it at a site leading to ubiquitination and degradation, thereby maintaining homeostatic levels of MYC protein. While JQ1, an inhibitor which releases BRD4 from chromatin and reduces MYC transcription has no effect on MYC protein stability, MZ1, which degrades BRD4 has the paradoxical effect of decreasing MYC transcription but increasing MYC stability. Our findings demonstrating BRD4-mediated MYC degradation are likely to have significant translational implications.

The protooncogene MYC regulates a variety of cellular processes, including proliferation and metabolism. Maintaining MYC at homeostatic levels is critical to normal cell function; overexpression drives many cancers. MYC stability is regulated through phosphorylation: phosphorylation at Thr58 signals degradation while Ser62 phosphorylation leads to its stabilization and functional activation. The bromodomain protein 4 (BRD4) is a transcriptional and epigenetic regulator with intrinsic kinase and histone acetyltransferase (HAT) activities that activates transcription of key protooncogenes, including MYC. We report that BRD4 phosphorylates MYC at Thr58, leading to MYC ubiquitination and degradation, thereby regulating MYC target genes. Importantly, BRD4 degradation, but not inhibition, results in increased levels of MYC protein. Conversely, MYC inhibits BRD4’s HAT activity, suggesting that MYC regulates its own transcription by limiting BRD4-mediated chromatin remodeling of its locus. The MYC stabilizing kinase, ERK1, regulates MYC levels directly and indirectly by inhibiting BRD4 kinase activity. These findings demonstrate that BRD4 negatively regulates MYC levels, which is counteracted by ERK1 activation.

Transcriptional, Epigenetic and Metabolic Programming of Tumor-Associated Macrophages

Macrophages are key innate immune cells in the tumor microenvironment (TME) that regulate primary tumor growth, vascularization, metastatic spread and tumor response to various types of therapies. The present review highlights the mechanisms of macrophage programming in tumor microenvironments that act on the transcriptional, epigenetic and metabolic levels. We summarize the latest knowledge on the types of transcriptional factors and epigenetic enzymes that control the direction of macrophage functional polarization and their pro- and anti-tumor activities. We also focus on the major types of metabolic programs of macrophages (glycolysis and fatty acid oxidation), and their interaction with cancer cells and complex TME. We have discussed how the regulation of macrophage polarization on the transcriptional, epigenetic and metabolic levels can be used for the efficient therapeutic manipulation of macrophage functions in cancer.

Bee Viruses: Routes of Infection in Hymenoptera

Numerous studies have recently reported on the discovery of bee viruses in different arthropod species and their possible transmission routes, vastly increasing our understanding of these viruses and their distribution. Here, we review the current literature on the recent advances in understanding the transmission of viruses, both on the presence of bee viruses in Apis and non-Apis bee species and on the discovery of previously unknown bee viruses. The natural transmission of bee viruses will be discussed among different bee species and other insects. Finally, the research potential of in vivo (host organisms) and in vitro (cell lines) serial passages of bee viruses is discussed, from the perspective of the host-virus landscape changes and potential transmission routes for emerging bee virus infections.

FGFR1 is associated with c-MYC and proangiogenic molecules in metastatic renal cell carcinoma under anti-angiogenic therapy

AIMS

This study aimed to investigate the clinicopathological significance of FGFR1 and c-MYC expression, particularly in relation to angiogenesis in clear cell renal cell carcinoma (CCRCC).

METHODS AND RESULTS

Immunohistochemistry and fluorescence in-situ hybridisation were conducted with tissue microarrays from 91 metastatic CCRCC patients who received VEGF receptor tyrosine kinase inhibitors (VEGFR-TKIs). The expression of angiogenic molecules, FGFR1 and c-MYC, and tumoral vascular density (TVD) and mRNA expression and TVD of 533 CCRCCs in The Cancer Genome Atlas (TCGA) were analysed. FGFR1, pFGFR1 and c-MYC expression was observed in 29.1, 74.4 and 30.8% of tumours, respectively. FGFR1^high was an independent worse prognostic factor for overall (HR = 1.871, P = 0.032) and progression-free (HR = 1.976, P = 0.016) survival. FGFR1^high was significantly related to VEGFR-TKI responsiveness (P = 0.011). The presence of FGFR1^high /c-MYC^high showed a positive correlation with proangiogenic markers, including VEGF (P = 0.018) and HIF-1α (P < 0.0001). FGFR1^high /c-MYC^high tumours showed higher TVDs together with higher VEGFR2 and PDGFR-β expression (both P < 0.0001). FGFR1 and c-MYC expression was also positively correlated with the expression of hypoxia-related and proangiogenic-related genes in the TCGA data.

CONCLUSIONS

FGFR1 and c-MYC may be involved in tumour angiogenesis and FGFR1 may represent a promising therapeutic target in metastatic CCRCC.

PHF20L1 as a H3K27me2 reader coordinates with transcriptional repressors to promote breast tumorigenesis

TUDOR domain-containing proteins (TDRDs) are chiefly responsible for recognizing methyl-lysine/arginine residue. However, how TDRD dysregulation contributes to breast tumorigenesis is poorly understood. Here, we report that TUDOR domain-containing PHF20L1 as a H3K27me2 reader exerts transcriptional repression by recruiting polycomb repressive complex 2 (PRC2) and Mi-2/nucleosome remodeling and deacetylase (NuRD) complex, linking PRC2-mediated methylation and NuRD-mediated deacetylation of H3K27. Furthermore, PHF20L1 was found to serve as a potential MYC and hypoxia-driven oncogene, promoting glycolysis, proliferation, and metastasis of breast cancer cells by directly inhibiting tumor suppressors such as HIC1, KISS1, and BRCA1. PHF20L1 expression was also strongly correlated with higher histologic grades of breast cancer and markedly up-regulated in several cancers. Meanwhile, Phf20l1 deletion not only induces growth retardation and mammary ductal outgrowth delay but also inhibits tumorigenesis in vivo. Our data indicate that PHF20L1 promotes tumorigenesis, supporting the pursuit of PHF20L1 as a target for cancer therapy.

Towards abstraction of computational modelling of mammalian cell cycle: Model reduction pipeline incorporating multi-level hybrid petri nets

Cell cycle is a large biochemical network and it is crucial to simplify it to gain a clearer understanding and insights into the cell cycle. This is also true for other biochemical networks. In this study, we present a model abstraction scheme/pipeline to create a minimal abstract model of the whole mammalian cell cycle system from a large Ordinary Differential Equation model of cell cycle we published previously (Abroudi et al., 2017). The abstract model is developed in a way that it captures the main characteristics (dynamics of key controllers), responses (G1-S and G2-M transitions and DNA damage) and the signalling subsystems (Growth Factor, G1-S and G2-M checkpoints, and DNA damage) of the original model (benchmark). Further, our model exploits: (i) separation of time scales (slow and fast reactions), (ii) separation of levels of complexity (high-level and low-level interactions), (iii) cell-cycle stages (temporality), (iv) functional subsystems (as mentioned above), and (v) represents the whole cell cycle - within a Multi-Level Hybrid Petri Net (MLHPN) framework. Although hybrid Petri Nets is not new, the abstraction of interactions and timing we introduced here is new to cell cycle and Petri Nets. Importantly, our models builds on the significant elements, representing the core cell cycle system, found through a novel Global Sensitivity Analysis on the benchmark model, using Self Organising Maps and Correlation Analysis that we introduced in (Abroudi et al., 2017). Taken the two aspects together, our study proposes a 2-stage model reduction pipeline for large systems and the main focus of this paper is on stage 2, Petri Net model, put in the context of the pipeline. With the MLHPN model, the benchmark model with 61 continuous variables (ODEs) and 148 parameters were reduced to 14 variables (4 continuous (Cyc_Cdks - the main controllers of cell cycle) and 10 discrete (regulators of Cyc_Cdks)) and 31 parameters. Additional 9 discrete elements represented the temporal progression of cell cycle. Systems dynamics simulation results of the MLHPN model were in close agreement with the benchmark model with respect to the crucial metrics selected for comparison: order and pattern of Cyc_Cdk activation, timing of G1-S and G2-M transitions with or without DNA damage, efficiency of the two cell cycle checkpoints in arresting damaged cells and passing healthy cells, and response to two types of global parameter perturbations. The results show that the MLHPN provides a close approximation to the comprehensive benchmark model in robustly representing systems dynamics and emergent properties while presenting the core cell cycle controller in an intuitive, transparent and subsystems format.

MicroRNA dysregulation interplay with childhood abdominal tumors

Abdominal tumors (AT) in children account for approximately 17% of all pediatric solid tumor cases, and frequently exhibit embryonal histological features that differentiate them from adult cancers. Current molecular approaches have greatly improved the understanding of the distinctive pathology of each tumor type and enabled the characterization of novel tumor biomarkers. As seen in abdominal adult tumors, microRNAs (miRNAs) have been increasingly implicated in either the initiation or progression of childhood cancer. Moreover, besides predicting patient prognosis, they represent valuable diagnostic tools that may also assist the surveillance of tumor behavior and treatment response, as well as the identification of the primary metastatic sites. Thus, the present study was undertaken to compile up-to-date information regarding the role of dysregulated miRNAs in the most common histological variants of AT, including neuroblastoma, nephroblastoma, hepatoblastoma, hepatocarcinoma, and adrenal tumors. Additionally, the clinical implications of dysregulated miRNAs as potential diagnostic tools or indicators of prognosis were evaluated.

Antiproliferative and proapoptotic effects of Inula viscosa extract on Burkitt lymphoma cell line

Burkitt lymphoma is a very aggressive B-cell non-Hodgkin lymphoma. Although remarkable progress has been made in the therapeutic scenario for patients with Burkitt lymphoma, search and development of new effective anticancer agents to improve patient outcome and minimize toxicity has become an urgent issue. In this study, the antitumoral activity of Inula viscosa, a traditional herb obtained from plants collected on the Asinara Island, Italy, was evaluated in order to explore potential antineoplastic effects of its metabolites on Burkitt lymphoma. Raji human cell line was treated with increasing Inula viscosa extract concentration for cytotoxicity screening and subsequent establishment of cell cycle arrest and apoptosis. Moreover, gene expression profiles were performed to identify molecular mechanisms involved in the anticancer activities of this medical plant. The Inula viscosa extract exhibited powerful antiproliferative and cytotoxic activities on Raji cell line, showing a dose- and time-dependent decrease in cell viability, obtained by cell cycle arrest in the G2/M phase and an increase in cell apoptosis. The treatment with Inula viscosa caused downregulation of genes involved in cell cycle and proliferation (c-MYC, CCND1) and inhibition of cell apoptosis (BCL2, BCL2L1, BCL11A). The Inula viscosa extract causes strong anticancer effects on Burkitt lymphoma cell line. The molecular mechanisms underlying such antineoplastic activity are based on targeting and downregulation of genes involved in cell cycle and apoptosis. Our data suggest that Inula viscosa natural metabolites should be further exploited as potential antineoplastic agents against Burkitt lymphoma.

MAL2-Induced Actin-Based Protrusion Formation is Anti-Oncogenic in Hepatocellular Carcinoma

Recent studies report that the polarity gene myelin and lymphocyte protein 2 (MAL2), is overexpressed in multiple human carcinomas largely at the transcript level. Because chromosome 8q24 amplification (where MAL2 resides) is associated with hepatocellular- and cholangio-carcinomas, we examined MAL2 protein expression in these human carcinoma lesions and adjacent benign tissue using immunohistochemistry. For comparison, we analyzed renal cell carcinomas that are not associated with chromosome 8q24 amplification. Surprisingly, we found that MAL2 protein levels were decreased in the malignant tissues compared to benign in all three carcinomas, suggesting MAL2 expression may be anti-oncogenic. Consistent with this conclusion, we determined that endogenously overexpressed MAL2 in HCC-derived Hep3B cells or exogenously expressed MAL2 in hepatoma-derived Clone 9 cells (that lack endogenous MAL2) promoted actin-based protrusion formation with a reciprocal decrease in invadopodia. MAL2 overexpression also led to decreased cell migration, invasion and proliferation (to a more modest extent) while loss of MAL2 expression reversed the phenotypes. Mutational analysis revealed that a putative Ena/VASP homology 1 recognition site confers the MAL2-phenotype suggesting its role in tumor suppression involves actin remodeling. To reconcile decreased MAL2 protein expression in human carcinomas and its anti-oncogenic phenotypes with increased transcript levels, we propose a transcriptional regulatory model for MAL2 transient overexpression.

The expression of MYC is strongly dependent on the circular PVT1 expression in pure Gleason pattern 4 of prostatic cancer

PVT1 is a long-noncoding RNA and is highly expressed in various cancers including prostate cancers with stabilizing MYC protein. To characterize the objective biological features of the different morphological components such as Gleason patterns (GP) in prostate cancer, biopsy specimens containing only single pure GP (GP3, GP4, GP5) are used to analyze the relationship between PVT1 expression and MYC protein expression. The expressions of PVT1 and MYC were analyzed by quantitative PCR and the labeling index (LI) of MYC protein by immunohistochemical staining. PVT1, MYC, and MYC protein were highly expressed in GP 4, and interestingly the expression between PVT1 and MYC LI significantly correlated only in GP 4. In vitro experiments, the expression of MYC protein was slightly reduced by small interfering RNA against PVT1, while strongly reduced against specifically circular PVT1, splicing variants derived from the PVT1. Taken together, the expression characteristics of PVT1, MYC, and MYC protein differed depending on the GP. In particular, circular PVT1 might be strongly involved in the stabilization of MYC protein in GP4 and suggest different biological features.

Inhibition of Tumor Lymphangiogenesis is an Important Part that EGFR-TKIs Play in the Treatment of NSCLC

Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) have been widely used to treat non-small cell lung cancer (NSCLC) because they inhibit tumour growth and metastasis. However, the underlying mechanisms are not fully understood. Here, we investigate whether anti-lymphangiogenesis mechanisms contribute to the anti-tumour effects of EGFR-TKIs. Three different EGFR-TKIs (Gefitinib, Afatinib, and AZD9291) were used to determine the possible biological effects of EGFR-TKIs on lymphangiogenesis in vitro and in vivo. EGFR-TKIs inhibited human lymphatic endothelial cells (HLEC) proliferation, migration and tube formation at the indicated concentrations. Conditioned medium from human lung adenocarcinoma HCC827 cells treated with EGFR-TKIs also inhibited HLEC migration and tube formation. EGFR-TKIs inhibited VEGFC secretion, which further influenced HLEC behaviour in vitro. Afatinib inhibited tumour growth and lymphangiogenesis in the HCC827 xenograft mouse model. The densities and tube diameters of the lymphatic vessels were decreased in a dose-dependent manner, as shown by lymphatic vessel endothelial hyaluronan receptor 1 (LYVE-1) staining. EGFR-TKIs also inhibited the expression of important lymphangiogenesis regulatory factors vascular endothelial growth factor 2/3 (VEGF2/3), VEGFC, and chemokine receptor 7 (CCR7) as shown by immunocytochemistry (IHC) staining. Additional assays confirmed that the JAK/STAT3 signalling pathways play important roles in the anti-lymphangiogenesis process induced by EGFR-TKIs. Inhibition of lymphangiogenesis is another important role that the three EGFR-TKIs play in the treatment of lung cancer and the Janus kinase/signal transducers and activators of transcription 3 (JAK/STAT3) maybe an important signalling pathway regulating lymphangiogenesis, which provides a new idea for clinical therapy of lung cancer.

High MYC mRNA Expression Is More Clinically Relevant than MYC DNA Amplification in Triple-Negative Breast Cancer

DNA abnormalities are used in inclusion criteria of clinical trials for treatments with specific targeted molecules. MYC is one of the most powerful oncogenes and is known to be associated with triple-negative breast cancer (TNBC). Its DNA amplification is often part of the targeted DNA-sequencing panels under the assumption of reflecting upregulated signaling. However, it remains unclear if MYC DNA amplification is a surrogate of its upregulated signaling. Thus, we investigated the difference between MYC DNA amplification and mRNA high expression in TNBCs utilizing publicly available cohorts. MYC DNA amplified tumors were found to have various mRNA expression levels, suggesting that MYC DNA amplification does not always result in elevated MYC mRNA expression. Compared to other subtypes, both MYC DNA amplification and mRNA high expression were more frequent in the TNBCs. MYC mRNA high expression, but not DNA amplification, was significantly associated with worse overall survival in the TNBCs. The TNBCs with MYC mRNA high expression enriched MYC target genes, cell cycle related genes, and WNT/β-catenin gene sets, whereas none of them were enriched in MYC DNA amplified TNBCs. In conclusion, MYC mRNA high expression, but not DNA amplification, reflects not only its upregulated signaling pathway, but also clinical significance in TNBCs.

Osmoregulation by the myo-inositol biosynthesis pathway in turbot Scophthalmus maximus and its regulation by anabolite and c-Myc

The induction of the myo-inositol biosynthesis (MIB) pathway in euryhaline fishes is an important component of the cellular response to osmotic challenge. The MIPS and IMPA1 genes were sequenced in turbot and found to be highly conserved in phylogenetic evolution, especially within the fish species tested. Under salinity stress in turbot, both MIPS and IMPA1 showed adaptive expression, a turning point in the level of expression occurred at 12 h in all tissues tested. We performed an RNAi assay mediated by long fragment dsRNA prepared by transcription in vitro. The findings demonstrated that knockdown of the MIB pathway weakened the function of gill osmotic regulation, and may induce a genetic compensation response in the kidney and gill to maintain physiological function. Even though the gill and kidney conducted stress reactions or compensatory responses to salinity stress, this inadequately addressed the consequences of MIB knockdown. Therefore, the survival time of turbot under salinity stress after knockdown was obviously less than that under seawater, especially under low salt stress. Pearson's correlation analysis between gene expression and dietary myo-inositol concentration indicated that the MIB pathway had a remarkable negative feedback control, and the dynamic equilibrium mediated by negative feedback on the MIB pathway played a crucial role in osmoregulation in turbot. An RNAi assay with c-Myc in vivo and the use of a c-Myc inhibitor (10058-F4) in vitro demonstrated that c-Myc was likely to positively regulate the MIB pathway in turbot.

Protein phosphatase 2A activation as a therapeutic strategy for managing MYC-driven cancers

The tumor suppressor protein phosphatase 2A (PP2A) is a serine/threonine phosphatase whose activity is inhibited in most human cancers. One of the best-characterized PP2A substrates is MYC proto-oncogene basic helix-loop-helix transcription factor (MYC), whose overexpression is commonly associated with aggressive forms of this disease. PP2A directly dephosphorylates MYC, resulting in its degradation. To explore the therapeutic potential of direct PP2A activation in a diverse set of MYC-driven cancers, here we used biochemical assays, recombinant cell lines, gene expression analyses, and immunohistochemistry to evaluate a series of first-in-class small-molecule activators of PP2A (SMAPs) in Burkitt lymphoma, KRAS-driven non-small cell lung cancer, and triple-negative breast cancer. In all tested models of MYC-driven cancer, the SMAP treatment rapidly and persistently inhibited MYC expression through proteasome-mediated degradation, inhibition of MYC transcriptional activity, decreased cancer cell proliferation, and tumor growth inhibition. Importantly, we generated a series of cell lines expressing PP2A-dependent phosphodegron variants of MYC and demonstrated that the antitumorigenic activity of SMAPs depends on MYC degradation. Collectively, the findings presented here indicate a pharmacologically tractable approach to drive MYC degradation by using SMAPs for the management of a broad range of MYC-driven cancers.

4-Hydroxychalcone Induces Cell Death via Oxidative Stress in MYCN-Amplified Human Neuroblastoma Cells

Neuroblastoma is an embryonal malignancy that arises from cells of sympathoadrenal lineage during the development of the nervous system. It is the most common pediatric extracranial solid tumor and is responsible for 15% of childhood deaths from cancer. Fifty percent of cases are diagnosed as high-risk metastatic disease with a low overall 5-year survival rate. More than half of patients experience disease recurrence that can be refractory to treatment. Amplification of the MYCN gene is an important prognostic indicator that is associated with rapid disease progression and a poor prognosis, highlighting the need for new therapeutic approaches. In recent years, there has been an increasing focus on identifying anticancer properties of naturally occurring chalcones, which are secondary metabolites with variable phenolic structures. Here, we report that 4-hydroxychalcone is a potent cytotoxin for MYCN-amplified IMR-32 and SK-N-BE (2) neuroblastoma cells, when compared to non-MYCN-amplified SH-SY5Y neuroblastoma cells and to the non-neuroblastoma human embryonic kidney cell line, HEK293t. Moreover, 4-hydroxychalcone treatment significantly decreased cellular levels of the antioxidant glutathione and increased cellular reactive oxygen species. In addition, 4-hydroxychalcone treatment led to impairments in mitochondrial respiratory function, compared to controls. In support of this, the cytotoxic effect of 4-hydroxychalcone was prevented by co-treatment with either the antioxidant N-acetyl-L-cysteine, a pharmacological inhibitor of oxidative stress-induced cell death (IM-54) or the mitochondrial reactive oxygen species scavenger, Mito-TEMPO. When combined with the anticancer drugs cisplatin or doxorubicin, 4-hydroxychalcone led to greater reductions in cell viability than was induced by either anti-cancer agent alone. In summary, this study identifies a cytotoxic effect of 4-hydroxychalcone in MYCN-amplified human neuroblastoma cells, which rationalizes its further study in the development of new therapies for pediatric neuroblastoma.

Highly immunosuppressive HLADRhi regulatory T cells are associated with unfavorable outcomes in cervical squamous cell carcinoma

Regulatory T cells (Tregs) are crucial for the maintenance of peripheral tolerance, but they also limit beneficial responses through cancer-induced immunoediting. The roles of Treg subsets in cervical squamous cell carcinoma (CSCC) are currently unknown. Here, we aimed to perform an extensive study with an increased resolution of the Treg compartment in the peripheral blood and tumor tissues of CSCC patients. We first identified that an HLADR^hi Treg population in the peripheral blood was significantly increased in CSCC patients compared to precancer patients and healthy donors. We found that HLADR^hi Tregs express high levels of a panel of inhibition and activation markers and the TCR-responsive transcription factors BATF and IRF4. However, this Treg subset showed reduced calcium influx after TCR crosslinking. In addition, HLADR^hi Tregs are highly proliferative and vulnerable to apoptosis. Further studies demonstrated that the HLADR^hi Tregs display high levels of suppressive activity. Quantitative multiplexed immunohistochemistry revealed that an increase in the number of tumor-infiltrating HLADR^hi Tregs is associated with unfavorable classical risk parameters of advanced disease stage and stromal invasion. Context-based quantification revealed that a high frequency of stromal HLADR^hi Tregs in patients is significantly associated with worse progression-free survival. In the current study, we characterized a population of highly activated and immunosuppressive HLADR^hi Tregs in CSCC patients. An increased HLADR^hi Treg frequency may be a potential biomarker to stratify CSCC patients and evaluate therapeutic efficacies in personalized immuno-oncology studies.

Identification of Regulatory Modules That Stratify Lupus Disease Mechanism through Integrating Multi-Omics Data

Although recent advances in genetic studies have shed light on systemic lupus erythematosus (SLE), its detailed mechanisms remain elusive. In this study, using datasets on SLE transcriptomic profiles, we identified 750 differentially expressed genes (DEGs) in T and B lymphocytes and peripheral blood cells. Using transcription factor (TF) binding data derived from chromatin immunoprecipitation sequencing (ChIP-seq) experiments from the Encyclopedia of DNA Elements (ENCODE) project, we inferred networks of co-regulated genes (NcRGs) based on binding profiles of the upregulated DEGs by significantly enriched TFs. Modularization analysis of NcRGs identified co-regulatory modules among the DEGs and master TFs vital for each module. Remarkably, the co-regulatory modules stratified the common SLE interferon (IFN) signature and revealed SLE pathogenesis pathways, including the complement cascade, cell cycle regulation, NETosis, and epigenetic regulation. By integrative analyses of disease-associated genes (DAGs), DEGs, and enriched TFs, as well as proteins interacting with them, we identified a hierarchical regulatory cascade with TFs regulated by DAGs, which in turn regulates gene expression. Integrative analysis of multi-omics data provided valuable molecular insights into the molecular mechanisms of SLE.

The Metabolic Landscape of Lung Cancer: New Insights in a Disturbed Glucose Metabolism

Metabolism encompasses the biochemical processes that allow healthy cells to keep energy, redox balance and building blocks required for cell development, survival, and proliferation steady. Malignant cells are well-documented to reprogram their metabolism and energy production networks to support rapid proliferation and survival in harsh conditions via mutations in oncogenes and inactivation of tumor suppressor genes. Despite the histologic and genetic heterogeneity of tumors, a common set of metabolic pathways sustain the high proliferation rates observed in cancer cells. This review with a focus on lung cancer covers several fundamental principles of the disturbed glucose metabolism, such as the “Warburg” effect, the importance of the glycolysis and its branching pathways, the unanticipated gluconeogenesis and mitochondrial metabolism. Furthermore, we highlight our current understanding of the disturbed glucose metabolism and how this might result in the development of new treatments.

Targeting bromodomain-containing protein 4 (BRD4) inhibits MYC expression in colorectal cancer cells

The transcriptional regulator BRD4 has been shown to be important for the expression of several oncogenes including MYC. Inhibiting of BRD4 has broad antiproliferative activity in different cancer cell types. The small molecule JQ1 blocks the interaction of BRD4 with acetylated histones leading to transcriptional modulation. Depleting BRD4 via engineered bifunctional small molecules named PROTACs (proteolysis targeting chimeras) represents the next-generation approach to JQ1-mediated BRD4 inhibition. PROTACs trigger BRD4 for proteasomale degradation by recruiting E3 ligases. The aim of this study was therefore to validate the importance of BRD4 as a relevant target in colorectal cancer (CRC) cells and to compare the efficacy of BRD4 inhibition with BRD4 degradation on downregulating MYC expression. JQ1 induced a downregulation of both MYC mRNA and MYC protein associated with an antiproliferative phenotype in CRC cells. dBET1 and MZ1 induced degradation of BRD4 followed by a reduction in MYC expression and CRC cell proliferation. In SW480 cells, where dBET1 failed, we found significantly lower levels of the E3 ligase cereblon, which is essential for dBET1-induced BRD4 degradation. To gain mechanistic insight into the unresponsiveness to dBET1, we generated dBET1-resistant LS174t cells and found a strong downregulation of cereblon protein. These findings suggest that inhibition of BRD4 by JQ1 and degradation of BRD4 by dBET1 and MZ1 are powerful tools for reducing MYC expression and CRC cell proliferation. In addition, downregulation of cereblon may be an important mechanism for developing dBET1 resistance, which can be evaded by incubating dBET1-resistant cells with JQ1 or MZ1.

Myc-dependent endothelial proliferation is controlled by phosphotyrosine 1212 in VEGF receptor-2

Exaggerated signaling by vascular endothelial growth factor (VEGF)-A and its receptor, VEGFR2, in pathologies results in poor vessel function. Still, pharmacological suppression of VEGFA/VEGFR2 may aggravate disease. Delineating VEGFR2 signaling in vivo provides strategies for suppression of specific VEGFR2-induced pathways. Three VEGFR2 tyrosine residues (Y949, Y1212, and Y1173) induce downstream signaling. Here, we show that knock-in of phenylalanine to create VEGFR2 Y1212F in C57Bl/6 and FVB mouse strains leads to loss of growth factor receptor-bound protein 2- and phosphoinositide 3'-kinase (PI3K)p85 signaling. C57Bl/6 Vegfr2Y1212F/Y1212F show reduced embryonic endothelial cell (EC) proliferation and partial lethality. FVB Vegfr2Y1212F/Y1212F show reduced postnatal EC proliferation. Reduced EC proliferation in Vegfr2Y1212F/Y1212F explants is rescued by c-Myc overexpression. We conclude that VEGFR2 Y1212 signaling induces activation of extracellular-signal-regulated kinase (ERK)1/2 and Akt pathways required for c-Myc-dependent gene regulation, endothelial proliferation, and vessel stability.

A MYC-GCN2-eIF2α negative feedback loop limits protein synthesis to prevent MYC-dependent apoptosis in colorectal cancer

Tumours depend on altered rates of protein synthesis for growth and survival, which suggests that mechanisms controlling mRNA translation may be exploitable for therapy. Here, we show that loss of APC, which occurs almost universally in colorectal tumours, strongly enhances the dependence on the translation initiation factor eIF2B5. Depletion of eIF2B5 induces an integrated stress response and enhances translation of MYC via an internal ribosomal entry site. This perturbs cellular amino acid and nucleotide pools, strains energy resources and causes MYC-dependent apoptosis. eIF2B5 limits MYC expression and prevents apoptosis in APC-deficient murine and patient-derived organoids and in APC-deficient murine intestinal epithelia in vivo. Conversely, the high MYC levels present in APC-deficient cells induce phosphorylation of eIF2α via the kinases GCN2 and PKR. Pharmacological inhibition of GCN2 phenocopies eIF2B5 depletion and has therapeutic efficacy in tumour organoids, which demonstrates that a negative MYC-eIF2α feedback loop constitutes a targetable vulnerability of colorectal tumours.

MicroRNA in Pancreatic Cancer: From Biology to Therapeutic Potential

Pancreatic cancer is one of the most aggressive malignancies, accounting for more than 45,750 deaths annually in the U.S. alone. The aggressive nature and late diagnosis of pancreatic cancer, coupled with the limitations of existing chemotherapy, present the pressing need for the development of novel therapeutic strategies. Recent reports have demonstrated a critical role of microRNAs (miRNAs) in the initiation, progression, and metastasis of cancer. Furthermore, aberrant expressions of miRNAs have often been associated with the cause and consequence of pancreatic cancer, emphasizing the possible use of miRNAs in the effective management of pancreatic cancer patients. In this review, we provide a brief overview of miRNA biogenesis and its role in fundamental cellular process and miRNA studies in pancreatic cancer patients and animal models. Subsequent sections narrate the role of miRNA in, (i) cell cycle and proliferation; (ii) apoptosis; (iii) invasions and metastasis; and (iv) various cellular signaling pathways. We also describe the role of miRNA's in pancreatic cancer; (i) diagnosis; (ii) prognosis and (iii) therapeutic intervention. Conclusion section describes the gist of review with future directions.

PLK1 contributes to autophagy by regulating MYC stabilization in osteosarcoma cells

Background

PLK1, a typical PLK protein, is the main driver of cancer cell growth and proliferation. It is an inhibitor of the protein kinases that is currently being investigated in clinical studies. It is often used as a tumor marker, as high PLK1 expression correlates with poor prognosis in cancer. Overexpression of MYC is a hallmark of many human cancers. MYC modulates the transcription of thousands of genes that required to coordinate a series of cellular processes, including those essential for growth, proliferation, differentiation, self-renewal and apoptosis. To date, functions of PLK1 and MYC on tumor are mostly studied in separate researches, and studies on their mutual crosstalk are lacking.

Purpose

To investigate the mechanism of PLK1 and MYC in regulating progress of osteosarcoma.

Methods

Protein level was examined using Western blot. Animal experiments were performed with female FOX CHASE severe combined immunodeficient mice. Mice were randomly divided into experimental or control groups.

Results

PLK1 or MYC promoted the proliferation of osteosarcoma cells through the autophagy pathway. PLK1 contributed to MYC protein stabilization. PLK1 inhibition enhanced MYC degradation in osteosarcoma cells. PLK1 inhibition led to a marked decline in MYC protein abundance. The representative MYC target genes were deregulated by PLK1 inhibitors. BI2536 treatment caused a significant delay in xenograft tumor growth in mice injected with U-2 OS cells subcutaneously, with lower mean tumor weight compared to the control group.

Conclusion

PLK1 is crucial for MYC stabilization. It promotes cell proliferation by autophagy pathway in osteosarcoma cells. Data validate PLK1 as a potential therapeutic target in osteosarcoma caused by MYC-amplified.

MYC gene associated polymorphisms and Wilms tumor risk in Chinese children: a four-center case-control study

BACKGROUND

Wilms tumor (WT) is a common embryonal malignancy in the kidney, ranking fourth in childhood cancer worldwide. MYC, a critical proto-oncogene, plays an important role in tumorigenesis. Single nucleotide polymorphisms in the MYC gene may lead to the deregulation of MYC proto-oncogene protein and thereby promote the initiation and development of tumors.

METHODS

Here, we assessed the association between MYC gene associated polymorphisms and WT susceptibility by performing a case-control study with 355 cases and 1070 controls. Two MYC gene associated polymorphisms (rs4645943 C > T, rs2070583 A > G) were genotyped by TaqMan technique. Odds ratios (ORs) and 95% confidence intervals (CIs) were used for evaluating the association between these two polymorphisms and WT susceptibility.

RESULTS

No significant association was detected between the selected polymorphisms and WT risk in the overall analysis as well as stratification analysis.

CONCLUSIONS

These results indicate that neither of two selected MYC gene associated polymorphisms might affect WT susceptibility in the Chinese population. Large well-designed studies with diverse ethnicities are warranted to verify these results.

Risk stratification for lung adenocarcinoma on EGFR and TP53 mutation status, chemotherapy, and PD-L1 immunotherapy

The overall survival rates for lung cancer remain unsatisfactorily low, even for patients with biomarkers for which target therapies or immunotherapies are recommended. Better identification of at‐risk patients is needed to achieve more effective personalized treatment. Here, we derived a risk‐stratifying gene signature consisting of five genes that had the greatest differential expression by stage from lung adenocarcinoma (LUAD) transcriptomes. The new gene signature enabled survival prognosis for multiple LUAD datasets from different platforms of transcriptomics and risk stratification for patients with and without a mutation in TP53 or EGFR, with high and low levels of PD‐L1, and with and without adjuvant chemotherapy treatment. Using these evaluations, it was also shown to be more robust compared to several other gene signatures. Functional analysis of the five genes and their protein‐protein interaction partners indicated that they are functionally enriched in cell cycle, endocytosis, and EGFR regulation, which are biological processes associated with lung cancer and drug resistance. Extensive discussions on related experimental studies suggest that the five genes are novel and sensible targets for developing new drugs and/or tackling drug resistance problems for LUAD.

FDA-approved drug screen identifies proteasome as a synthetic lethal target in MYC-driven neuroblastoma

MYCN amplification in neuroblastoma predicts poor prognosis and resistance to therapy. Yet pharmacological strategies of direct MYC inhibition remain unsuccessful due to its "undruggable" protein structure. We herein developed a synthetic lethal screen against MYCN-amplified neuroblastomas using clinically approved therapeutic reagents. We performed a high-throughput screen, from a library of 938 FDA-approved drugs, for candidates that elicit synthetic lethal effects in MYC-driven neuroblastoma cells. The proteasome inhibitors, which are FDA approved for the first-line treatment of multiple myeloma, emerge as top hits to elicit MYC-mediated synthetic lethality. Proteasome inhibition activates the PERK-eIF2α-ATF4 axis in MYC-transformed cells and induces BAX-mediated apoptosis through ATF4-dependent NOXA and TRIB3 induction. A combination screen reveals the proteasome inhibitor bortezomib (BTZ) and the histone deacetylase (HDAC) inhibitor vorinostat (SAHA) concertedly induce dramatic cell death in part through synergistic activation of BAX. This combination causes marked tumor suppression in vivo, supporting dual proteasome/HDAC inhibition as a potential therapeutic approach for MYC-driven cancers. This FDA-approved drug screen with in vivo validation thus provides a rationale for clinical evaluation of bortezomib, alone or in combination with vorinostat, in MYC-driven neuroblastoma patients.

Writing and erasing MYC ubiquitination and SUMOylation

The transcription factor c-MYC (MYC thereafter) controls diverse transcription programs and plays a key role in the development of many human cancers. Cells develop multiple mechanisms to ensure that MYC levels and activity are precisely controlled in normal physiological context. As a short half-lived protein, MYC protein levels are tightly regulated by the ubiquitin proteasome system. Over a dozen of ubiquitin ligases have been found to ubiquitinate MYC whereas a number of deubiquitinating enzymes counteract this process. Recent studies show that SUMOylation and deSUMOylation can also regulate MYC protein stability and activity. Interestingly, evidence suggests an intriguing crosstalk between MYC ubiquitination and SUMOylation. Deregulation of the MYC ubiquitination-SUMOylation regulatory network may contribute to tumorigenesis. This review is intended to provide the current understanding of the complex regulation of the MYC biology by dynamic ubiquitination and SUMOylation and their crosstalk.

Indenoisoquinoline Topoisomerase Inhibitors Strongly Bind and Stabilize the MYC Promoter G-Quadruplex and Downregulate MYC

MYC is one of the most important oncogenes and is overexpressed in the majority of cancers. G-Quadruplexes are noncanonical four-stranded DNA secondary structures that have emerged as attractive cancer-specific molecular targets for drug development. The G-quadruplex formed in the proximal promoter region of the MYC oncogene (MycG4) has been shown to be a transcriptional silencer that is amenable to small-molecule targeting for MYC suppression. Indenoisoquinolines are human topoisomerase I inhibitors in clinical testing with improved physicochemical and biological properties as compared to the clinically used camptothecin anticancer drugs topotecan and irinotecan. However, some indenoisoquinolines with potent anticancer activity do not exhibit strong topoisomerase I inhibition, suggesting a separate mechanism of action. Here, we report that anticancer indenoisoquinolines strongly bind and stabilize MycG4 and lower MYC expression levels in cancer cells, using various biochemical, biophysical, computer modeling, and cell-based methods. Significantly, a large number of active indenoisoquinolines cause strong MYC downregulation in cancer cells. Structure-activity relationships of MycG4 recognition by indenoisoquinolines are investigated. In addition, the analysis of indenoisoquinoline analogues for their MYC-inhibitory activity, topoisomerase I-inhibitory activity, and anticancer activity reveals a synergistic effect of MYC inhibition and topoisomerase I inhibition on anticancer activity. Therefore, this study uncovers a novel mechanism of action of indenoisoquinolines as a new family of drugs targeting the MYC promoter G-quadruplex for MYC suppression. Furthermore, the study suggests that dual targeting of MYC and topoisomerase I may serve as a novel strategy for anticancer drug development.

Differential regulation of myc homologs by Wnt/β-Catenin signaling in the early metazoan Hydra

The c-Myc protein is a transcription factor with oncogenic potential controlling fundamental cellular processes. Homologs of the human c-myc protooncogene have been identified in the early diploblastic cnidarian Hydra (myc1, myc2). The ancestral Myc1 and Myc2 proteins display the principal design and biochemical properties of their vertebrate derivatives, suggesting that important Myc functions arose very early in metazoan evolution. c-Myc is part of a transcription factor network regulated by several upstream pathways implicated in oncogenesis and development. One of these signaling cascades is the Wnt/β-Catenin pathway driving cell differentiation and developmental patterning, but also tumorigenic processes including aberrant transcriptional activation of c-myc in several human cancers. Here, we show that genetic or pharmacological stimulation of Wnt/β-Catenin signaling in Hydra is accompanied by specific downregulation of myc1 at mRNA and protein levels. The myc1 and myc2 promoter regions contain consensus binding sites for the transcription factor Tcf, and Hydra Tcf binds to the regulatory regions of both promoters. The myc1 promoter is also specifically repressed in the presence of ectopic Hydra β-Catenin/Tcf in avian cell culture. We propose that Hydra myc1 is a negative Wnt signaling target, in contrast to vertebrate c-myc, which is one of the best studied genes activated by this pathway. On the contrary, myc2 is not suppressed by ectopic β-Catenin in Hydra and presumably represents the structural and functional c-myc ortholog. Our data implicate that the connection between β-Catenin-mediated signaling and myc1 and myc2 gene regulation is an ancestral metazoan feature. Its impact on decision making in Hydra interstitial stem cells is discussed.

Cancer Cells Tune the Signaling Pathways to Empower de Novo Synthesis of Nucleotides

Cancer cells exhibit a dynamic metabolic landscape and require a sufficient supply of nucleotides and other macromolecules to grow and proliferate. To meet the metabolic requirements for cell growth, cancer cells must stimulate de novo nucleotide synthesis to obtain adequate nucleotide pools to support nucleic acid and protein synthesis along with energy preservation, signaling activity, glycosylation mechanisms, and cytoskeletal function. Both oncogenes and tumor suppressors have recently been identified as key molecular determinants for de novo nucleotide synthesis that contribute to the maintenance of homeostasis and the proliferation of cancer cells. Inactivation of tumor suppressors such as TP53 and LKB1 and hyperactivation of the mTOR pathway and of oncogenes such as MYC, RAS, and AKT have been shown to fuel nucleotide synthesis in tumor cells. The molecular mechanisms by which these signaling hubs influence metabolism, especially the metabolic pathways for nucleotide synthesis, continue to emerge. Here, we focus on the current understanding of the molecular mechanisms by which oncogenes and tumor suppressors modulate nucleotide synthesis in cancer cells and, based on these insights, discuss potential strategies to target cancer cell proliferation.

Establishment of an erythroid progenitor cell line capable of enucleation achieved with an inducible c-Myc vector

BACKGROUND

A robust scalable method for producing enucleated red blood cells (RBCs) is not only a process to produce packed RBC units for transfusion but a potential platform to produce modified RBCs with applications in advanced cellular therapy. Current strategies for producing RBCs have shortcomings in the limited self-renewal capacity of progenitor cells, or difficulties in effectively enucleating erythroid cell lines. We explored a new method to produce RBCs by inducibly expressing c-Myc in primary erythroid progenitor cells and evaluated the proliferative and maturation potential of these modified cells.

RESULTS

Primary erythroid progenitor cells were genetically modified with an inducible gene transfer vector expressing a single transcription factor, c-Myc, and all the gene elements required to achieve dox-inducible expression. Genetically modified cells had enhanced proliferative potential compared to control cells, resulting in exponential growth for at least 6 weeks. Inducibly proliferating erythroid (IPE) cells were isolated with surface receptors similar to colony forming unit-erythroid (CFU-Es), and after removal of ectopic c-Myc expression cells hemoglobinized, decreased in cell size to that of native RBCs, and enucleated achieving cultures with 17% enucleated cells. Experiments with IPE cells at various levels of ectopic c-Myc expression provided insight into differentiation dynamics of the modified cells, and an optimized two-stage differentiation strategy was shown to promote greater expansion and maturation.

CONCLUSIONS

Genetic engineering of adult erythroid progenitor cells with an inducible c-Myc vector established an erythroid progenitor cell line that could produce RBCs, demonstrating the potential of this approach to produce large quantities of RBCs and modified RBC products.

Lack of effective translational regulation of PLD expression and exosome biogenesis in triple-negative breast cancer cells

Triple-negative breast cancer (TNBC) is an aggressive subtype of breast cancer that is difficult to treat since cells lack the three receptors (ES, PR, or HER) that the most effective treatments target. We have used a well-established TNBC cell line (MDA-MB-231) from which we found evidence in support for a phospholipase D (PLD)-mediated tumor growth and metastasis: high levels of expression of PLD, as well as the absence of inhibitory miRs (such as miR-203) and 3'-mRNA PARN deadenylase activity in these cells. Such findings are not present in a luminal B cell line, MCF-7, and we propose a new miR•PARN•PLD node that is not uniform across breast cancer molecular subtypes and as such TNBC could be pharmacologically targeted differentially. We review the participation of PLD and phosphatidic acid (PA), its enzymatic product, as new "players" in breast cancer biology, with the aspects of regulation of the tumor microenvironment, macrophage polarization, regulation of PLD transcripts by specific miRs and deadenylases, and PLD-regulated exosome biogenesis. A new signaling miR•PARN•PLD node could serve as new biomarkers for TNBC abnormal signaling and metastatic disease staging, potentially before metastases are able to be visualized using conventional imaging.

Interactions of PVT1 and CASC11 on Prostate Cancer Risk in African Americans

BACKGROUND

African American (AA) men have a higher risk of developing prostate cancer than white men. SNPs are known to play an important role in developing prostate cancer. The impact of PVT1 and its neighborhood genes (CASC11 and MYC) on prostate cancer risk are getting more attention recently. The interactions among these three genes associated with prostate cancer risk are understudied, especially for AA men. The objective of this study is to investigate SNP-SNP interactions in the CASC11-MYC-PVT1 region associated with prostate cancer risk in AA men.

METHODS

We evaluated 205 SNPs using the 2,253 prostate cancer patients and 2,423 controls and applied multiphase (discovery-validation) design. In addition to SNP individual effects, SNP-SNP interactions were evaluated using the SNP Interaction Pattern Identifier, which assesses 45 patterns.

RESULTS

Three SNPs (rs9642880, rs16902359, and rs12680047) and 79 SNP-SNP pairs were significantly associated with prostate cancer risk. These two SNPs (rs16902359 and rs9642880) in CASC11 interacted frequently with other SNPs with 56 and 9 pairs, respectively. We identified the novel interaction of CASC11-PVT1, which is the most common gene interaction (70%) in the top 79 pairs. Several top SNP interactions have a moderate to large effect size (OR, 0.27-0.68) and have a higher prediction power to prostate cancer risk than SNP individual effects.

CONCLUSIONS

Novel SNP-SNP interactions in the CASC11-MYC-PVT1 region have a larger impact than SNP individual effects on prostate cancer risk in AA men.

IMPACT

This gene-gene interaction between CASC11 and PVT1 can provide valuable information to reveal potential biological mechanisms of prostate cancer development.

MYC Oncogene Contributions to Release of Cell Cycle Brakes

Promotion of the cell cycle is a major oncogenic mechanism of the oncogene c-MYC (MYC). MYC promotes the cell cycle by not only activating or inducing cyclins and CDKs but also through the downregulation or the impairment of the activity of a set of proteins that act as cell-cycle brakes. This review is focused on the role of MYC as a cell-cycle brake releaser i.e., how MYC stimulates the cell cycle mainly through the functional inactivation of cell cycle inhibitors. MYC antagonizes the activities and/or the expression levels of p15, ARF, p21, and p27. The mechanism involved differs for each protein. p15 (encoded by CDKN2B) and p21 (CDKN1A) are repressed by MYC at the transcriptional level. In contrast, MYC activates ARF, which contributes to the apoptosis induced by high MYC levels. At least in some cells types, MYC inhibits the transcription of the p27 gene (CDKN1B) but also enhances p27's degradation through the upregulation of components of ubiquitin ligases complexes. The effect of MYC on cell-cycle brakes also opens the possibility of antitumoral therapies based on synthetic lethal interactions involving MYC and CDKs, for which a series of inhibitors are being developed and tested in clinical trials.

Pulsed SILAC-based proteomic analysis unveils hypoxia- and serum starvation-induced de novo protein synthesis with PHD finger protein 14 (PHF14) as a hypoxia sensitive epigenetic regulator in cell cycle progression

Hypoxia is an environmental cue that is associated with multiple tumorigenic processes such as immunosuppression, angiogenesis, cancer invasion, metastasis, drug resistance, and poor clinical outcomes. When facing hypoxic stress, cells initiate several adaptive responses such as cell cycle arrest to reduce excessive oxygen consumption and co-activation of oncogenic factors. In order to identify the critical novel proteins for hypoxia responses, we used pulsed-SILAC method to trace the active cellular translation events in A431 cells. Proteomic discovery data and biochemical assays showed that cancer cells selectively activate key glycolytic enzymes and novel ER-stress markers, while protein synthesis is severely suppressed. Interestingly, deprivation of oxygen affected the expression of various epigenetic regulators such as histone demethylases and NuRD (nucleosome remodeling and deacetylase) complex in A431 cells. In addition, we identified PHF14 (the plant homeodomain finger-14) as a novel hypoxia-sensitive epigenetic regulator that plays a key role in cell cycle progress and protein synthesis. Hypoxia-mediated inhibition of PHF14 was associated with increase of key cell cycle inhibitors, p14^ARF, p15^INK4b, and p16^INK4a, which are responsible for G1-S phase transition and decrease of AKT-mTOR-4E-BP1/pS6K signaling pathway, a master regulator of protein synthesis, in response to environmental cues. Analysis of TCGA colon cancer (n=461) and skin cancer (n=470) datasets revealed a positive correlation between PHF14 expression and protein translation initiation factors, eIF4E, eIF4B, and RPS6. Significance of PHF14 gene was further demonstrated by in vivo mouse xenograft model using PHF14 KD cell lines.

The Selection of NFκB Inhibitors to Block Inflammation and Induce Sensitisation to FasL-Induced Apoptosis in HNSCC Cell Lines Is Critical for Their Use as a Prospective Cancer Therapy

Inflammation is a central aspect of tumour biology and can contribute significantly to both the origination and progression of tumours. The NFκB pathway is one of the most important signal transduction pathways in inflammation and is, therefore, an excellent target for cancer therapy. In this work, we examined the influence of four NFκB inhibitors—Cortisol, MLN4924, QNZ and TPCA1—on proliferation, inflammation and sensitisation to apoptosis mediated by the death ligand FasL in the HNSCC cell lines PCI1, PCI9, PCI13, PCI52 and SCC25 and in the human dermal keratinocyte cell line HaCaT. We found that the selection of the inhibitor is critical to ensure that cells do not respond by inducing counteracting activities in the context of cancer therapy, e.g., the extreme IL-8 induction mediated by MLN4924 or FasL resistance mediated by Cortisol. However, TPCA1 was qualified by this in vitro study as an excellent therapeutic mediator in HNSCC by four positive qualities: (1) proliferation was inhibited at low μM-range concentrations; (2) TNFα-induced IL-8 secretion was blocked; (3) HNSCC cells were sensitized to TNFα-induced cell death; and (4) FasL-mediated apoptosis was not disrupted.

Nuclear ERK: Mechanism of Translocation, Substrates, and Role in Cancer

The extracellular signal-regulated kinases 1/2 (ERK) are central signaling components that regulate stimulated cellular processes such as proliferation and differentiation. When dysregulated, these kinases participate in the induction and maintenance of various pathologies, primarily cancer. While ERK is localized in the cytoplasm of resting cells, many of its substrates are nuclear, and indeed, extracellular stimulation induces a rapid and robust nuclear translocation of ERK. Similarly to other signaling components that shuttle to the nucleus upon stimulation, ERK does not use the canonical importinα/β mechanism of nuclear translocation. Rather, it has its own unique nuclear translocation signal (NTS) that interacts with importin7 to allow stimulated shuttling via the nuclear pores. Prevention of the nuclear translocation inhibits proliferation of B-Raf- and N/K-Ras-transformed cancers. This effect is distinct from the one achieved by catalytic Raf and MEK inhibitors used clinically, as cells treated with the translocation inhibitors develop resistance much more slowly. In this review, we describe the mechanism of ERK translocation, present all its nuclear substrates, discuss its role in cancer and compare its translocation to the translocation of other signaling components. We also present proof of principle data for the use of nuclear ERK translocation as an anti-cancer target. It is likely that the prevention of nuclear ERK translocation will eventually serve as a way to combat Ras and Raf transformed cancers with less side-effects than the currently used drugs.

Oncogenic MYC Activates a Feedforward Regulatory Loop Promoting Essential Amino Acid Metabolism and Tumorigenesis

Most tumor cells exhibit obligatory demands for essential amino acids (EAAs), but the regulatory mechanisms whereby tumor cells take up EAAs and EAAs promote malignant transformation remain to be determined. Here, we show that oncogenic MYC, solute carrier family (SLC) 7 member 5 (SLC7A5), and SLC43A1 constitute a feedforward activation loop to promote EAA transport and tumorigenesis. MYC selectively activates Slc7a5 and Slc43a1 transcription through direct binding to specific E box elements within both genes, enabling effective EAA import. Elevated EAAs, in turn, stimulate Myc mRNA translation, in part through attenuation of the GCN2-eIF2α-ATF4 amino acid stress response pathway, leading to MYC-dependent transcriptional amplification. SLC7A5/SLC43A1 depletion inhibits MYC expression, metabolic reprogramming, and tumor cell growth in vitro and in vivo. These findings thus reveal a MYC-SLC7A5/SLC43A1 signaling circuit that underlies EAA metabolism, MYC deregulation, and tumorigenesis.

Induction of GNMT by 1,2,3,4,6-penta-O-galloyl-beta-D-glucopyranoside through proteasome-independent MYC downregulation in hepatocellular carcinoma

Glycine-N-methyl transferase (GNMT) a tumor suppressor for hepatocellular carcinoma (HCC) plays a crucial role in liver homeostasis. Its expression is downregulated in almost all the tumor tissues of HCC while the mechanism of this downregulation is not yet fully understood. Recently, we identified 1,2,3,4,6-penta-O-galloyl-beta-D-glucopyranoside (PGG) as a GNMT promoter enhancer compound in HCC. In this study, we aimed to delineate the mechanism by which PGG enhances GNMT expression and to investigate its effect on GNMT suppression in HCC. Microarray and pathway enrichment analysis revealed that MYC was a major target of PGG. PGG suppressed MYC mRNA and protein expression in Huh7 and Hep G2 cells in a dose- and time-dependent fashion. Furthermore, MYC expression was also reduced in xenograft tumors in PGG treated mice. Moreover, shRNA-mediated knocked-down or pharmacological inhibition of MYC resulted in a significant induction of GNMT promoter activity and endogenous GNMT mRNA expression in Huh7 cells. In contrast, overexpression of MYC significantly inhibited GNMT promoter activity and endogenous GNMT protein expression. In addition, antibodies against MYC effectively precipitated the human GNMT promoter in a chromatin immunoprecipitation assay. Lastly, GNMT expression was negatively correlated with MYC expression in human HCC samples. Interestingly, PGG not only inhibited MYC gene expression but also promoted MYC protein degradation through proteasome-independent pathways. This work reveals a novel anticancer mechanism of PGG via downregulation of MYC expression and establishes a therapeutic rationale for treatment of MYC overexpressing cancers using PGG. Our data also provide a novel mechanistic understanding of GNMT regulation through MYC in the pathogenesis of HCC.

Zinc-finger protein YY1 suppresses tumor growth of human nasopharyngeal carcinoma by inactivating c-Myc-mediated microRNA-141 transcription

Yin Yang 1 (YY1) is a zinc-finger protein that plays critical roles in various biological processes by interacting with DNA and numerous protein partners. YY1 has been reported to play dual biological functions as either an oncogene or tumor suppressor in the development and progression of multiple cancers, but its role in human nasopharyngeal carcinoma (NPC) has not yet been revealed. In this study, we found that YY1 overexpression significantly inhibits cell proliferation and cell-cycle progression from G₁ to S and promotes apoptosis in NPC cells. Moreover, we identified YY1 as a component of the c-Myc complex and observed that ectopic expression of YY1 inhibits c-Myc transcriptional activity, as well as the promoter activity and expression of the c-Myc target gene microRNA-141 (miR-141). Furthermore, restoring miR-141 expression could at least partially reverse the inhibitory effect of YY1 on cell proliferation and tumor growth and on the expression of some critical c-Myc targets, such as PTEN/AKT pathway components both in vitro and in vivo We also found that YY1 expression is reduced in NPC tissues, negatively correlates with miR-141 expression and clinical stages in NPC patients, and positively correlates with survival prognosis. Our results reveal a previously unappreciated mechanism in which the YY1/c-Myc/miR-141 axis plays a critical role in NPC progression and may provide some potential and valuable targets for the diagnosis and treatment of NPC.

Recent Progress of Targeted G-Quadruplex-Preferred Ligands Toward Cancer Therapy

A G-quadruplex (G4) is a well-known nucleic acid secondary structure comprising guanine-rich sequences, and has profound implications for various pharmacological and biological events, including cancers. Therefore, ligands interacting with G4s have attracted great attention as potential anticancer therapies or in molecular probe applications. To date, a large variety of DNA/RNA G4 ligands have been developed by a number of laboratories. As protein-targeting drugs face similar situations, G-quadruplex-interacting drugs displayed low selectivity to the targeted G-quadruplex structure. This low selectivity could cause unexpected effects that are usually reasons to halt the drug development process. In this review, we address the recent research on synthetic G4 DNA-interacting ligands that allow targeting of selected G4s as an approach toward the discovery of highly effective anticancer drugs.

The expression of FOXP3 and its role in human cancers

FOXP3 is a transcription factor, which belongs to the family of FOX protein. FOXP3 was initially discovered in regulatory T cells and supposed to play a significant role in the process of regulatory T cell differentiation. Increasing evidence has shown that FOXP3 is also expressed in tumor cells. However, the results of tumor FOXP3 is inconsistent and even the opposite. In some types of human cancers, the expression of FOXP3 is upregulated, and it can promote the development of cancers, leading to a poor prognosis. While in some other types of cancers, it is a different story. The reason for the contradictory data is unknown. The discovery of FOXP3 isoforms, interaction between tumor cells and lymphocytes in the tumor microenvironment, subcellular location, and mutation of FOXP3 may provide some clues. In this review, we first summarize and analyze the recent development. The final section focuses on the regulation of FOXP3 expression.

Tumour stem cells in schwannoma: A review

Schwannoma is a peripheral nerve tumour, accounting for 5% of benign soft tissue tumours, with vestibular schwannoma comprising 6% of all intracranial tumours. The tumour stem cell concept is rapidly gaining traction underscoring the understanding of tumourigenesis. It proposes a small subpopulation of primitive cells as the origin of the tumour and these cells account for treatment resistance, local recurrence and distant metastasis in malignant tumours. This review outlines the stem cell markers used to identify and characterise stem cells and progenitor cells in tumours and examines current evidence of the presence of tumour stem cells in schwannoma.

A Functional 5'-UTR Polymorphism of MYC Contributes to Nasopharyngeal Carcinoma Susceptibility and Chemoradiotherapy Induced Toxicities

MYC is a transcription factor acting as a pivotal regulator of genes involved in cell cycle progression, apoptosis, differentiation and metabolism. In this study, we evaluated the association of MYC polymorphisms with nasopharyngeal carcinoma (NPC) risk and chemoradiotherapy induced toxicities among Chinese population. By using bioinformatic tools, five potential functional single nucleotide polymorphisms of MYC were genotyped in a case-control study with 684 NPC patients and 823 healthy controls. We found two SNPs rs4645948 (C>T) and rs2071346 (G>T) were significantly associated with increased risk of developing NPC (TT+CT vs CC, OR=1.557, P=3.34×10^-4; TT+GT vs GG, OR=1.361, P=0.007, respectively). In addition, rs4645948 (C>T) was conferred with increased risk of anemia (CT vs CC, OR=2.152, P=0.001) and severe leukopenia (CT vs CC, OR=1.893, P=0.034) for NPC patients receiving chemoradiotherapy. We also found rs2071346 (G>T) variant genotype carriers were subjected to higher risk of anemia (GT vs GG, OR=1.665, P=0.022) and thrombocytopenia (GT vs GG, OR=1.685, P=0.035). Our results demonstrated that the relative expression of MYC was dramatically higher in NPC tissues compared to rhinitis tissues. Over-expression of MYC was positively correlated with advanced T stage, N stage, and late clinical stage. Notably, the expression of MYC in rs4645948 CT and TT genotypes carriers were significantly higher than CC genotype carriers. Luciferase reporter assay indicated that the T allele of rs4645948 led to significantly higher transcription activity of MYC compared to the C allele. These findings suggested that individual carrying the rs4645948 T allele may be at greater risk for NPC due to an increase of MYC transcriptional activity and an augment of MYC expression.