The C/EBPδ protein is stabilized by estrogen receptor α activity, inhibits SNAI2 expression and associates with good prognosis in breast cancer

FBXW7 in breast cancer: mechanism of action and therapeutic potential

Breast cancer is one of the frequent tumors that seriously endanger the physical and mental well-being in women. F-box and WD repeat domain-containing 7 (FBXW7) is a neoplastic repressor. Serving as a substrate recognition element for ubiquitin ligase, FBXW7 participates in the ubiquitin-proteasome system and is typically in charge of the ubiquitination and destruction of crucial oncogenic proteins, further performing a paramount role in cell differentiation, apoptosis and metabolic processes. Low levels of FBXW7 cause abnormal stability of pertinent substrates, mutations and/or deletions in the FBXW7 gene have been reported to correlate with breast cancer malignant progression and chemoresistance. Given the lack of an effective solution to breast cancer's clinical drug resistance dilemma, elucidating FBXW7's mechanism of action could provide a theoretical basis for targeted drug exploration. Therefore, in this review, we focused on FBXW7's role in a range of breast cancer malignant behaviors and summarized the pertinent cellular targets, signaling pathways, as well as the mechanisms regulating FBXW7 expression. We also proposed novel perspectives for the exploitation of alternative therapies and specific tumor markers for breast cancer by therapeutic strategies aiming at FBXW7.

The Dual Role of C/EBPδ in Cancer

CCAAT/Enhancer-Binding Protein delta (C/EBPδ) is a transcription factor involved in differentiation and inflammation. While sparsely expressed in adult tissues, aberrant expression of C/EBPδ has been associated with different cancers. Initially, re-expression of C/EBPδ in cell cultures limited tumor cell proliferation, assigning it a tumor suppressor role. However, opposing observations were made in pre-clinical models and patients, suggesting that C/EBPδ not only mediates cell proliferation but dictates a broader spectrum of tumorigenesis-related effects. It is now widely accepted that C/EBPδ contributes to an inflammatory, tumor-promoting microenvironment, aids hypoxia adaption and contributes to the recruitment of blood vessels for improved nutrient supply to tumor cells and facilitated extravasation. This review summarizes the work published on this transcription factor in the field of cancer over the past decade. It points out areas in which a consensus on C/EBPδ's role appears to emerge and seek to explain seemingly contradictory results.

Stabilization of E-cadherin adhesions by COX-2/GSK3β signaling is a targetable pathway in metastatic breast cancer

Metastatic progression of epithelial cancers can be associated with epithelial-mesenchymal transition (EMT) including transcriptional inhibition of E-cadherin (CDH1) expression. Recently, EM plasticity (EMP) and E-cadherin-mediated, cluster-based metastasis and treatment resistance have become more appreciated. However, the mechanisms that maintain E-cadherin expression in this context are less understood. Through studies of inflammatory breast cancer (IBC) and a 3D tumor cell "emboli" culture paradigm, we discovered that cyclooxygenase 2 (COX-2; PTGS2), a target gene of C/EBPδ (CEBPD), or its metabolite prostaglandin E2 (PGE2) promotes protein stability of E-cadherin, β-catenin, and p120 catenin through inhibition of GSK3β. The COX-2 inhibitor celecoxib downregulated E-cadherin complex proteins and caused cell death. Coexpression of E-cadherin and COX-2 was seen in breast cancer tissues from patients with poor outcome and, along with inhibitory GSK3β phosphorylation, in patient-derived xenografts (PDX) including triple negative breast cancer (TNBC).Celecoxib alone decreased E-cadherin protein expression within xenograft tumors, though CDH1 mRNA levels increased, and reduced circulating tumor cell (CTC) clusters. In combination with paclitaxel, celecoxib attenuated or regressed lung metastases. This study has uncovered a mechanism by which metastatic breast cancer cells can maintain E-cadherin-mediated cell-to-cell adhesions and cell survival, suggesting that some patients with COX-2+/E-cadherin+ breast cancer may benefit from targeting of the PGE2 signaling pathway.

C/EBP-Family Redundancy Determines Patient Survival and Lymph Node Involvement in PDAC

Pancreatic ductal adenocarcinoma (PDAC) is a dismal disease with a poor clinical prognosis and unsatisfactory treatment options. We previously found that the transcription factor CCAAT/Enhancer-Binding Protein Delta (C/EBPδ) is lowly expressed in PDAC compared to healthy pancreas duct cells, and that patient survival and lymph node involvement in PDAC is correlated with the expression of C/EBPδ in primary tumor cells. C/EBPδ shares a homologous DNA-binding sequence with other C/EBP-proteins, leading to the presumption that other C/EBP-family members might act redundantly and compensate for the loss of C/EBPδ. This implies that patient stratification could be improved when expression levels of multiple C/EBP-family members are considered simultaneously. In this study, we assessed whether the quantification of C/EBPβ or C/EBPγ in addition to that of C/EBPδ might improve the prediction of patient survival and lymph node involvement using a cohort of 68 resectable PDAC patients. Using Kaplan-Meier analyses of patient groups with different C/EBP-expression levels, we found that both C/EBPβ and C/EBPγ can partially compensate for low C/EBPδ and improve patient survival. Further, we uncovered C/EBPβ as a novel predictor of a decreased likelihood of lymph node involvement in PDAC, and found that C/EBPβ and C/EBPδ can compensate for the lack of each other in order to reduce the risk of lymph node involvement. C/EBPγ, on the other hand, appears to promote lymph node involvement in the absence of C/EBPδ. Altogether, our results show that the redundancy of C/EBP-family members might have a profound influence on clinical prognoses and that the expression of both C/EPBβ and C/EBPγ should be taken into account when dichotomizing patients according to C/EBPδ expression.

Tumor suppressor DEAR1 regulates mammary epithelial cell fate and predicts early onset and metastasis in triple negative breast cancer

Triple negative breast cancer (TNBC) is a disease of poor prognosis, with the majority classified as the basal-like subtype associated with epithelial-mesenchymal transition and metastasis. Because basal breast cancers originate from proliferative luminal progenitor-like cells upon dysregulation of proper luminal differentiation, genes regulating luminal-basal transition are critical to elucidate novel therapeutic targets to improve TNBC outcomes. Herein we demonstrate that the tumor suppressor DEAR1/TRIM62 is a critical regulator of luminal cell fate. DEAR1 loss in human mammary epithelial cells results in significantly enhanced mammosphere formation that is accelerated in the presence of TGF-β/SMAD3 signaling. Mammospheres formed following DEAR1 loss are enriched for ALDH1A1 and CK5 expression, EpCAM^-/CD49f⁺ and CD44^high/24^low basal-like epithelial cells, indicating that DEAR1 regulates stem/progenitor cell properties and luminal-basal progenitor transition. We show that DEAR1 maintains luminal differentiation as a novel ubiquitin ligase for SNAI2/SLUG, a master regulator driving stemness and generation of basal-like progenitor populations. We also identify a significant inverse correlation between DEAR1 and SNAI2 expression in a 103 TNBC case cohort and show that low DEAR1 expression significantly correlates with young age of onset and shorter time to metastasis, suggesting DEAR1 could serve as a biomarker to stratify early onset TNBCs for targeted stem cell therapies.

Targeting MYO1B impairs tumorigenesis via inhibiting the SNAI2/cyclin D1 signaling in esophageal squamous cell carcinoma

Myosin‐related proteins play an important role in cancer progression. However, the clinical significance, biological functions, and mechanisms of myosin 1B (MYO1B), in esophageal squamous cell carcinoma (ESCC) remain unclear. The clinical relevance of MYO1B, SNAI2, and cyclin D1 in ESCC was determined by immunohistochemistry, Oncomine, and GEPIA databases. The oncogenic roles of MYO1B were determined by CCK8, colony formation assays, wound healing, and Transwell assay. MYO1B, SNAI2, and cyclin D1 at mRNA and protein levels in ESCC cells were detected by qPCR and Western blot analysis. In our study, we found that MYO1B expression was increased in ESCC tissue samples and correlated with tumor stage, TNM stage, and poor outcomes. Functional assays indicated that depletion of MYO1B impaired oncogenesis, and enhanced chemosensitivity in ESCC. Bioinformatic analysis and mechanistic studies illustrated that SNAI2 was a key downstream effector of MYO1B. Suppression of MYO1B downregulated expression of SNAI2, thereby inhibiting the SNAI2/cyclin D1 pathway. Furthermore, a selective inhibitor of cyclin D1 activation reversed siMYO1B cells overexpressing SNAI2‐elicited aggressive phenotypes of ESCC cells. MYO1B positively correlated with SNAI2 and cyclin D1 in ESCC samples, and higher SNAI2 expression was also associated with poor prognosis in ESCC patients. Our finding demonstrated that MYO1B activates the SNAI2/cyclin D1 pathway to drive tumorigenesis and cisplatin cytotoxicity in ESCC, indicating that MYO1B is a potential therapeutic target for patients with ESCC.

Targeting MYO1B impairs tumorigenesis via inhibiting the SNAI2/cyclin D1 signaling in esophageal squamous cell carcinoma

Myosin-related proteins play an important role in cancer progression. However, the clinical significance, biological functions, and mechanisms of myosin 1B (MYO1B), in esophageal squamous cell carcinoma (ESCC) remain unclear. The clinical relevance of MYO1B, SNAI2, and cyclin D1 in ESCC was determined by immunohistochemistry, Oncomine, and GEPIA databases. The oncogenic roles of MYO1B were determined by CCK8, colony formation assays, wound healing, and Transwell assay. MYO1B, SNAI2, and cyclin D1 at mRNA and protein levels in ESCC cells were detected by qPCR and Western blot analysis. In our study, we found that MYO1B expression was increased in ESCC tissue samples and correlated with tumor stage, TNM stage, and poor outcomes. Functional assays indicated that depletion of MYO1B impaired oncogenesis, and enhanced chemosensitivity in ESCC. Bioinformatic analysis and mechanistic studies illustrated that SNAI2 was a key downstream effector of MYO1B. Suppression of MYO1B downregulated expression of SNAI2, thereby inhibiting the SNAI2/cyclin D1 pathway. Furthermore, a selective inhibitor of cyclin D1 activation reversed siMYO1B cells overexpressing SNAI2-elicited aggressive phenotypes of ESCC cells. MYO1B positively correlated with SNAI2 and cyclin D1 in ESCC samples, and higher SNAI2 expression was also associated with poor prognosis in ESCC patients. Our finding demonstrated that MYO1B activates the SNAI2/cyclin D1 pathway to drive tumorigenesis and cisplatin cytotoxicity in ESCC, indicating that MYO1B is a potential therapeutic target for patients with ESCC.

Recent Insight on Regulations of FBXW7 and Its Role in Immunotherapy

SCF^FBXW7 E3 ubiquitin ligase complex is a crucial enzyme of the ubiquitin proteasome system that participates in variant activities of cell process, and its component FBXW7 (F-box and WD repeat domain–containing 7) is responsible for recognizing and binding to substrates. The expression of FBXW7 is controlled by multiple pathways at different levels. FBXW7 facilitates the maturity and function maintenance of immune cells via functioning as a mediator of ubiquitination-dependent degradation of substrate proteins. FBXW7 deficiency or mutation results in the growth disturbance and dysfunction of immune cell, leads to the resistance against immunotherapy, and participates in multiple illnesses. It is likely that FBXW7 coordinating with its regulators and substrates could offer potential targets to improve the sensitivity and effects of immunotherapy. Here, we review the mechanisms of the regulation on FBXW7 and its tumor suppression role in immune filed among various diseases (mostly cancers) to explore novel immune targets and treatments.

Non-Tumor CCAAT/Enhancer-Binding Protein Delta Potentiates Tumor Cell Extravasation and Pancreatic Cancer Metastasis Formation

CCAAT/enhancer-binding protein delta (C/EBPδ) is a transcription factor involved in apoptosis and proliferation, which is downregulated in pancreatic ductal adenocarcinoma (PDAC) cells. Loss of nuclear C/EBPδ in PDAC cells is associated with decreased patient survival and pro-tumorigenic properties in vitro. Interestingly however, next to C/EBPδ expression in tumor cells, C/EBPδ is also expressed by cells constituting the tumor microenvironment and by cells comprising the organs and parenchyma. However, the functional relevance of systemic C/EBPδ in carcinogenesis remains elusive. Here, we consequently assessed the potential importance of C/EBPδ in somatic tissues by utilizing an orthotopic pancreatic cancer model. In doing so, we show that genetic ablation of C/EBPδ does not significantly affect primary tumor growth but has a strong impact on metastases; wildtype mice developed metastases at multiple sites, whilst this was not the case in C/EBPδ^-/- mice. In line with reduced metastasis formation in C/EBPδ^-/- mice, C/EBPδ-deficiency also limited tumor cell dissemination in a specific extravasation model. Tumor cell extravasation was dependent on the platelet-activating factor receptor (PAFR) as a PAFR antagonist inhibited tumor cell extravasation in wildtype mice but not in C/EBPδ^-/- mice. Overall, we show that systemic C/EBPδ facilitates pancreatic cancer metastasis, and we suggest this is due to C/EBPδ-PAFR-dependent tumor cell extravasation.

An Integrative Single-cell Transcriptomic Atlas of the Post-natal Mouse Mammary Gland Allows Discovery of New Developmental Trajectories in the Luminal Compartment

The mammary gland is a highly dynamic organ which undergoes periods of expansion, differentiation and cell death in each reproductive cycle. Partly because of the dynamic nature of the gland, mammary epithelial cells (MECs) are extraordinarily heterogeneous. Single cell RNA-seq (scRNA-seq) analyses have contributed to understand the cellular and transcriptional heterogeneity of this complex tissue. Here, we integrate scRNA-seq data from three foundational reports that have explored the mammary gland cell populations throughout development at single-cell level using 10× Chromium Drop-Seq. We center our analysis on post-natal development of the mammary gland, from puberty to post-involution. The new integrated study corresponds to RNA sequences from 53,686 individual cells, which greatly outnumbers the three initial data sets. The large volume of information provides new insights, as a better resolution of the previously detected Procr⁺ stem-like cell subpopulation or the identification of a novel group of MECs expressing immune-like markers. Moreover, here we present new pseudo-temporal trajectories of MEC populations at two resolution levels, that is either considering all mammary cell subtypes or focusing specifically on the luminal lineages. Interestingly, the luminal-restricted analysis reveals distinct expression patterns of various genes that encode milk proteins, suggesting specific and non-redundant roles for each of them. In summary, our data show that the application of bioinformatic tools to integrate multiple scRNA-seq data-sets helps to describe and interpret the high level of plasticity involved in gene expression regulation throughout mammary gland post-natal development.

CCAAT/Enhancer-Binding Protein Delta (C/EBPδ): A Previously Unrecognized Tumor Suppressor that Limits the Oncogenic Potential of Pancreatic Ductal Adenocarcinoma Cells

Simple Summary

Here we show that a protein called C/EBPδ is present in healthy pancreas tissue but almost absent in pancreas tumors. Patients with less C/EBPδ in their tumors had the most metastases and the worst survival chances, showing that C/EBPδ has tumor-suppressive properties in pancreatic cancer. In this study, we reactivated C/EBPδ in pancreatic cancer cells in vitro and observed a reduction in cell proliferation in a 2-dimentional and 3-dimensional space. This implies that tumor cells grow slower when C/EBPδ is activated and they are likely also less capable to escape the primary tumor in order to form metastases. Conversely, when we deleted C/EBPδ in pancreatic cancer cells, we observed accelerated growth. We suggest that reactivating C/EBPδ can suppress tumor growth and formation of metastases, thereby improving patient survival.

Abstract

CCAAT/enhancer-binding protein δ (C/EBPδ) is a transcription factor involved in growth arrest and differentiation, which has consequently been suggested to harbor tumor suppressive activities. However, C/EBPδ over-expression correlates with poor prognosis in glioblastoma and promotes genomic instability in cervical cancer, hinting at an oncogenic role of C/EBPδ in these contexts. Here, we explore the role of C/EBPδ in pancreatic cancer. We determined C/EBPδ expression in biopsies from pancreatic cancer patients using public gene-expression datasets and in-house tissue microarrays. We found that C/EBPδ is highly expressed in healthy pancreatic ductal cells but lost in pancreatic ductal adenocarcinoma. Furthermore, loss of C/EBPδ correlated with increased lymph node involvement and shorter overall survival in pancreatic ductal adenocarcinoma patients. In accordance with this, in vitro experiments showed reduced clonogenic capacity and proliferation of pancreatic ductal adenocarcinoma cells following C/EBPδ re-expression, concurrent with decreased sphere formation capacity in soft agar assays. We thus report a previously unrecognized but important tumor suppressor role of C/EBPδ in pancreatic ductal adenocarcinoma. This is of particular interest since only few tumor suppressors have been identified in the context of pancreatic cancer. Moreover, our findings suggest that restoration of C/EBPδ activity could hold therapeutic value in pancreatic ductal adenocarcinoma, although the latter claim needs to be substantiated in future studies.

SUMOylation of PUM2 promotes the vasculogenic mimicry of glioma cells via regulating CEBPD

Glioma is the most common form of primary central nervous malignant tumors. Vasculogenic mimicry (VM) is a blood supply channel that is different from endothelial blood vessels in glioma. VM is related to tumor invasion and metastasis. Therefore, it plays an important role to target therapy for glioma VM. Our experimental results showed abnormal expression of UBE2I, PUM2, CEBPD, and DSG2 in glioma cells. The Co-IP and Immunofluorescence staining were used to detect that PUM2 can be modified by SUMO2/3. The interaction between PUM2 and CEBPD mRNA was detected by the RIP assays. The interaction between transcription factor CEBPD and promoter region of DSG2 was detected by the ChIP assays and luciferase assays. The capacity for migration in glioma cells was observed by the laser holographic microscope. The capacity for invasion in glioma cells was detected by Transwell method. The VM in glioma cells was detected by three-dimensional cell culture method. The experimental results found that the upregulation of UBE2I in glioma tissues and cells promotes the SUMOylation of PUM2, which decreases not only the stability of PUM2 protein but also decreases the inhibitory effect of PUM2 on CEBPD mRNA. The upregulation of CEBPD promotes the binding to the upstream promoter region of DSG2 gene, further upregulates the expression of DSG2, and finally promotes the development of glioma VM. In conclusion, this study found that the UBE2I/PUM2/CEBPD/DSG2 played crucial roles in regulating glioma VM. It also provides potential targets and alternative strategies for combined treatment of glioma.

Prognostic values of SNAI family members in breast cancer patients

Background

Breast cancer (BC) is one of the most lethal malignant tumors and the leading cause of cancer-related death worldwide. Although early diagnostic techniques for BC have been well developed, 40% of cases are still diagnosed at the advanced stage, while for BC patients with distant metastases, the 5-year survival rate is usually lower than 30%. The Snail family, generally regarded as transcriptional repressors, has been indicated to be an essential prognostic factor in malignant tumors. However, limited data exist on public databases concerning the prognostic value of individual Snail family members in BC, especially SNAI3.

Methods

Data from public databases including cBioPortal for Cancer Genomics, Gene Expression Omnibus, UCSC Xena Browser, and Human Protein Atlas (HPA) were downloaded. Based on the Kaplan¬–Meier plotter platform, correlation of the three members of the Snail family and prognosis in BC were analyzed. Individual Snail family members and their co-expressed genes were respectively enriched on different pathways and biological processes via the functional enrichment analysis (FunRich) tool.

Results

High SNAI1 mRNA expression was associated with shorter distant metastasis-free survival (DMFS) in all BC patients regardless of PAM50 subtype. Conversely, high SNAI3 mRNA expression was associated with longer DMFS. Although the presence of SNAI2 expression was significantly associated with DMFS in the whole cohort, no significant correlation was found in patients with luminal A or HER2 subtype. For patients with the most diverse clinicopathological features, high SNAI1 expression was associated with poor survival, with the converse being true for SNAI3. However, the impact on prognosis of patients with different clinicopathological features produced by SNAI2 expression was inconclusive. Furthermore, we discovered that SNAI1 or SNAI2 and their co-expressed genes frequently enriched receptor tyrosine kinase (RTK) signaling and integrin-related pathways which mainly functioned on epithelial-mesenchymal transition and were further involved in several processes of signal transduction and cell communication. Furthermore, as SNAI3, along with its co-expressed genes, enriched immune-related pathways, it may thus play a role in mediating the immune system.

Conclusions

Our analysis revealed that SNAI1 mRNA expression may potentially be a negative prognostic factor, whereas SNAI3 mRNA was associated with positive prognosis in BC. Therefore, the assessment of SNAI1 and SNAI3 expression may be valuable for predicting prognosis in BC patients.

Slug and E-Cadherin: Stealth Accomplices?

During physiological epithelial-mesenchymal transition (EMT), which is important for embryogenesis and wound healing, epithelial cells activate a program to remodel their structure and achieve a mesenchymal fate. In cancer cells, EMT confers increased invasiveness and tumor-initiating capacity, which contribute to metastasis and resistance to therapeutics. However, cellular plasticity that navigates between epithelial and mesenchymal states and maintenance of a hybrid or partial E/M phenotype appears to be even more important for cancer progression. Besides other core EMT transcription factors, the well-characterized Snail-family proteins Snail (SNAI1) and Slug (SNAI2) play important roles in both physiological and pathological EMT. Often mentioned in unison, they do, however, differ in their functions in many scenarios. Indeed, Slug expression does not always correlate with complete EMT or loss of E-cadherin (CDH1). For example, Slug plays important roles in mammary epithelial cell progenitor cell lineage commitment and differentiation, DNA damage responses, hematopoietic stem cell self-renewal, and in pathologies such as pulmonary fibrosis and atherosclerosis. In this Perspective, we highlight Slug functions in mammary epithelial cells and breast cancer as a “non-EMT factor” in basal epithelial cells and stem cells with focus reports that demonstrate co-expression of Slug and E-cadherin. We speculate that Slug and E-cadherin may cooperate in normal mammary gland and breast cancer/stem cells and advocate for functional assessment of such Slug⁺/E-cadherin^low/+ (SNAI2⁺/CDH1^low/+) “basal-like epithelial” cells. Thus, Slug may be regarded as less of an EMT factor than driver of the basal epithelial cell phenotype.

Adipose Tissue Hypertrophy, An Aberrant Biochemical Profile and Distinct Gene Expression in Lipedema

BACKGROUND

Lipedema is a common adipose tissue disorder affecting women, characterized by a symmetric subcutaneous adipose tissue deposition, particularly of the lower extremities. Lipedema is usually underdiagnosed, thus remaining an undertreated disease. Importantly, no histopathologic or molecular hallmarks exist to clearly diagnose the disease, which is often misinterpreted as obesity or lymphedema.

MATERIALS AND METHODS

The aim of the present study is to characterize in detail morphologic and molecular alterations in the adipose tissue composition of lipedema patients compared with healthy controls. Detailed histopathologic and molecular characterization was performed using lipid and cytokine quantification as well as gene expression arrays. The analysis was conducted on anatomically matched skin and fat tissue biopsies as well as fasting serum probes obtained from 10 lipedema and 11 gender and body mass index-matched control patients.

RESULTS

Histologic evaluation of the adipose tissue showed increased intercellular fibrosis and adipocyte hypertrophy. Serum analysis showed an aberrant lipid metabolism without changes in the circulating adipokines. In an adipogenesis gene array, a distinct gene expression profile associated with macrophages was observed. Histologic assessment of the immune cell infiltrate confirmed the increased presence of macrophages, without changes in the T-cell compartment.

CONCLUSIONS

Lipedema presents a distinguishable disease with typical tissue architecture and aberrant lipid metabolism, different to obesity or lymphedema. The differentially expressed genes and immune cell infiltration profile in lipedema patients further support these findings.

Molecular regulation of Snai2 in development and disease

The transcription factor Snai2, encoded by the SNAI2 gene, is an evolutionarily conserved C2H2 zinc finger protein that orchestrates biological processes critical to tissue development and tumorigenesis. Initially characterized as a prototypical epithelial-to-mesenchymal transition (EMT) transcription factor, Snai2 has been shown more recently to participate in a wider variety of biological processes, including tumor metastasis, stem and/or progenitor cell biology, cellular differentiation, vascular remodeling and DNA damage repair. The main role of Snai2 in controlling such processes involves facilitating the epigenetic regulation of transcriptional programs, and, as such, its dysregulation manifests in developmental defects, disruption of tissue homeostasis, and other disease conditions. Here, we discuss our current understanding of the molecular mechanisms regulating Snai2 expression, abundance and activity. In addition, we outline how these mechanisms contribute to disease phenotypes or how they may impact rational therapeutic targeting of Snai2 dysregulation in human disease.

Action and clinical significance of CCAAT/enhancer-binding protein delta in hepatocellular carcinoma

CCAAT/enhancer-binding protein delta (CEBPD) is associated with the regulation of apoptosis and cell proliferation and is a candidate tumor suppressor gene. Here, we investigated its role in hepatocellular carcinoma (HCC). We observe that CEBPD mRNA expression is significantly downregulated in HCC tumors as compared with adjacent tissues. Protein levels of CEBPD are also lower in tumors relative to adjacent tissues. Reduced expression of CEBPD in the tumor correlates with worse clinical outcome. In both Huh7 and HepG2 cells, shRNA-mediated CEBPD knockdown significantly reduces cell proliferation, single cell colony formation and arrests cells in the G0/G1 phase. Subcutaneous xenografting of Huh7 in nude mice show that CEBPD knockdown results in smaller tumors. Gene expression analysis shows that CEBPD modulates interleukin-1 signaling. We conclude that CEBPD expression uncouples cancer compartment expansion and clinical outcome in HCC, potentially by modulating interleukin-1 signaling. Thus, although our results support the notion that CEBPD acts as a tumor suppressor in HCC, its action does not involve impairing compartment expansion per se but more likely acts through improving anticancer immunity.

C/EBPδ-Slug-Lox1 axis promotes metastasis of lung adenocarcinoma via oxLDL uptake

Cancer cells undergo significant lipid metabolic reprogramming to ensure sufficient energy supply for survival and progression. However, how cancer cells integrate lipid metabolic signaling with cancer progression is not well understood. In the present study, we demonstrated that C/EBPδ, a critical lipid metabolic regulator, is a TGF-β1 downstream gene and promotes lung adenocarcinoma metastasis. Importantly, C/EBPδ caused significant oscillations in both lipid metabolic and epithelial to mesenchymal transition (EMT) gene networks. Mechanistically, we demonstrated that C/EBPδ recruited oncogene NCOA3 to transcriptionally activate Slug, a canonical EMT transcription factor, which in turn induced oxLDL receptor-1 (Lox1) expression and enhanced oxLDL uptake to promote cancer metastasis, which could be blocked with LOX1 neutralizing antibody. In summary, our results unveiled a previously unappreciated interplay between lipid metabolic and metastatic program, as well as the existence of a pivotal C/EBPδ-Slug-Lox1 transcription axis to promote oxLDL levels and cancer metastasis.

C/EBPδ links IL-6 and HIF-1 signaling to promote breast cancer stem cell-associated phenotypes

To improve cancer patient outcome significantly, we must understand the mechanisms regulating stem-like cancer cells, which have been implicated as a cause of metastasis and treatment resistance. The transcription factor C/EBPδ can exhibit pro- and anti-tumorigenic activities, but the mechanisms underlying the complexity of its functions are poorly understood. Here we identify a role for breast cancer cell intrinsic C/EBPδ in promoting phenotypes that have been associated with cancer stem cells (CSCs). While C/EBPδ expression is not abundant in most metastatic breast cancers, our data support a pro-tumorigenic role of C/EBPδ when expressed in subsets of tumor cells and/or through transient activation by the tumor microenvironment or loss of substrate adhesion. Using genetic mouse models and human breast cancer cell lines, we show that deletion or depletion of C/EBPδ reduced expression of stem cell factors and stemnness markers, sphere formation and self-renewal, along with growth of tumors and established experimental metastases in vivo. C/EBPδ is also known as a mediator of the innate immune response, which is enhanced by hypoxia and interleukin-6 (IL-6) signaling, two conditions that also play important roles in cancer progression. Our mechanistic data reveal C/EBPδ as a link that engages two positive feedback loops, in part by directly targeting the IL-6 receptor (IL6RA) gene, and, thus, amplifying IL-6 and HIF-1 signaling. This study provides a molecular mechanism for the synergism of tumor microenvironmental conditions in cancer progression with potential implications for the targeting of CSCs.

Integrated molecular analysis of Tamoxifen-resistant invasive lobular breast cancer cells identifies MAPK and GRM/mGluR signaling as therapeutic vulnerabilities

Invasive lobular breast cancer (ILC) is an understudied malignancy with distinct clinical, pathological, and molecular features that distinguish it from the more common invasive ductal carcinoma (IDC). Mounting evidence suggests that estrogen receptor-alpha positive (ER+) ILC has a poor response to Tamoxifen (TAM), but the mechanistic drivers of this are undefined. In the current work, we comprehensively characterize the SUM44/LCCTam ILC cell model system through integrated analysis of gene expression, copy number, and mutation, with the goal of identifying actionable alterations relevant to clinical ILC that can be co-targeted along with ER to improve treatment outcomes. We show that TAM has several distinct effects on the transcriptome of LCCTam cells, that this resistant cell model has acquired copy number alterations and mutations that impinge on MAPK and metabotropic glutamate receptor (GRM/mGluR) signaling networks, and that pharmacological inhibition of either improves or restores the growth-inhibitory actions of endocrine therapy.

Meeting summary: 2nd Aegean Conference on Cytokine Signaling in Cancer

Cytokines and chemokines are intricately connected to cancer initiation, progression and metastasis as well as to innate and adaptive host defense mechanisms against transformed cells. The Aegean Conference on Cytokine Signaling in Cancer (ACCSC) aims to bring together researchers in this highly targeted area of cancer research in a lovely and relaxing Greek-Mediterranean backdrop to discuss latest developments. Being small in size with about one hundred participants, this conference fosters scientific and social interactions among established and emerging scientists in clinical and basic research in diverse fields of oncology, biochemistry, biophysics, genetics and immunology. The 2nd ACCSC held at Heraklion on the Greek island of Crete was organized by Serge Fuchs (University of Pennsylvania), Mathias Muller (University of Veterinary Medicine Vienna), Leonidas Platanias (Northwestern University, Chicago) and Belinda Parker (La Trobe University, Melbourne) between May 30 and June 04, 2017, was a great success in every single aspect of a high level scientific meeting. Signaling within cancer cells as well as in stromal and immune cells is the common thread of this conference series. An outline of the research topics discussed at this conference is presented here to emphasize its high quality and to stimulate interest among cytokine researchers to participate in future ACCSC meetings.

Integrative analysis of miRNA and gene expression reveals regulatory networks in tamoxifen-resistant breast cancer

Tamoxifen is an effective anti-estrogen treatment for patients with estrogen receptor-positive (ER+) breast cancer, however, tamoxifen resistance is frequently observed. To elucidate the underlying molecular mechanisms of tamoxifen resistance, we performed a systematic analysis of miRNA-mediated gene regulation in three clinically-relevant tamoxifen-resistant breast cancer cell lines (TamRs) compared to their parental tamoxifen-sensitive cell line. Alterations in the expression of 131 miRNAs in tamoxifen-resistant vs. parental cell lines were identified, 22 of which were common to all TamRs using both sequencing and LNA-based quantitative PCR technologies. Although the target genes affected by the altered miRNA in the three TamRs differed, good agreement in terms of affected molecular pathways was observed. Moreover, we found evidence of miRNA-mediated regulation of ESR1, PGR1, FOXM1 and 14-3-3 family genes. Integrating the inferred miRNA-target relationships, we investigated the functional importance of 2 central genes, SNAI2 and FYN, which showed increased expression in TamR cells, while their corresponding regulatory miRNA were downregulated. Using specific chemical inhibitors and siRNA-mediated gene knockdown, we showed that both SNAI2 and FYN significantly affect the growth of TamR cell lines. Finally, we show that a combination of 2 miRNAs (miR-190b and miR-516a-5p) exhibiting altered expression in TamR cell lines were predictive of treatment outcome in a cohort of ER+ breast cancer patients receiving adjuvant tamoxifen mono-therapy. Our results provide new insight into the molecular mechanisms of tamoxifen resistance and may form the basis for future medical intervention for the large number of women with tamoxifen-resistant ER+ breast cancer.