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

Epithelial CEBPD activates fibronectin and enhances macrophage adhesion in renal ischemia-reperfusion injury

Ischemia-reperfusion injury (IRI) is a cause of acute kidney injury in patients after renal transplantation and leads to high morbidity and mortality. Damaged kidney resident cells release cytokines and chemokines, which rapidly recruit leukocytes. Fibronectin (FN-1) contributes to immune cell migration, adhesion and growth in inflamed tissues. CCAAT/enhancer-binding protein delta is responsive to inflammatory cytokines and stresses and plays functional roles in cell motility, extracellular matrix production and immune responses. We found that the expression of CCAAT/enhancer-binding protein delta was increased in renal epithelial cells in IRI mice compared with sham mice. Following IRI, the colocalization of FN-1 with the macrophage marker F4/80 was increased in renal injury model wild-type mice but was significantly attenuated in Cebpd-deficient mice. Inactivation of CEBPD can repress hypoxia-induced FN-1 expression in HK-2 cells. Moreover, the inactivation of CEBPD and FN-1 also reduces macrophage accumulation in HK-2 cells. These findings suggest that the involvement of CEBPD in macrophage accumulation through the activation of FN-1 expression and the inhibition of CEBPD can protect against renal IRI.

Dissecting tumor microenvironment from spatially resolved transcriptomics data by heterogeneous graph learning

Spatially resolved transcriptomics (SRT) has enabled precise dissection of tumor-microenvironment (TME) by analyzing its intracellular molecular networks and intercellular cell-cell communication (CCC). However, lacking computational exploration of complicated relations between cells, genes, and histological regions, severely limits the ability to interpret the complex structure of TME. Here, we introduce stKeep, a heterogeneous graph (HG) learning method that integrates multimodality and gene-gene interactions, in unraveling TME from SRT data. stKeep leverages HG to learn both cell-modules and gene-modules by incorporating features of diverse nodes including genes, cells, and histological regions, allows for identifying finer cell-states within TME and cell-state-specific gene-gene relations, respectively. Furthermore, stKeep employs HG to infer CCC for each cell, while ensuring that learned CCC patterns are comparable across different cell-states through contrastive learning. In various cancer samples, stKeep outperforms other tools in dissecting TME such as detecting bi-potent basal populations, neoplastic myoepithelial cells, and metastatic cells distributed within the tumor or leading-edge regions. Notably, stKeep identifies key transcription factors, ligands, and receptors relevant to disease progression, which are further validated by the functional and survival analysis of independent clinical data, thereby highlighting its clinical prognostic and immunotherapy applications.

Epigenetic regulation of breast cancer metastasis

Breast cancer is the most frequently diagnosed malignancy and the second leading cause of cancer-related mortality among women worldwide. Recurrent metastasis is associated with poor patient outcomes and poses a significant challenge in breast cancer therapies. Cancer cells adapting to a new tissue microenvironment is the key event in distant metastasis development, where the disseminating tumor cells are likely to acquire genetic and epigenetic alterations during the process of metastatic colonization. Despite several decades of research in this field, the exact mechanisms governing metastasis are not fully understood. However, emerging body of evidence indicates that in addition to genetic changes, epigenetic reprogramming of cancer cells and the metastatic niche are paramount toward successful metastasis. Here, we review and discuss the latest knowledge about the salient attributes of metastasis and epigenetic regulation in breast cancer and crucial research domains that need further investigation.

The Janus kinase 1 is critical for pancreatic cancer initiation and progression

Interleukin-6 (IL-6)-class inflammatory cytokines signal through the Janus tyrosine kinase (JAK)/signal transducer and activator of transcription (STAT) pathway and promote the development of pancreatic ductal adenocarcinoma (PDAC); however, the functions of specific intracellular signaling mediators in this process are less well defined. Using a ligand-controlled and pancreas-specific knockout in adult mice, we demonstrate in this study that JAK1 deficiency prevents the formation of KRASG12D-induced pancreatic tumors, and we establish that JAK1 is essential for the constitutive activation of STAT3, whose activation is a prominent characteristic of PDAC. We identify CCAAT/enhancer binding protein δ (C/EBPδ) as a biologically relevant downstream target of JAK1 signaling, which is upregulated in human PDAC. Reinstating the expression of C/EBPδ was sufficient to restore the growth of JAK1-deficient cancer cells as tumorspheres and in xenografted mice. Collectively, the findings of this study suggest that JAK1 executes important functions of inflammatory cytokines through C/EBPδ and may serve as a molecular target for PDAC prevention and treatment.

Feedback loop between hypoxia and energy metabolic reprogramming aggravates the radioresistance of cancer cells

Radiotherapy is one of the mainstream approaches for cancer treatment, although the clinical outcomes are limited due to the radioresistance of tumor cells. Hypoxia and metabolic reprogramming are the hallmarks of tumor initiation and progression and are closely linked to radioresistance. Inside a tumor, the rate of angiogenesis lags behind cell proliferation, and the underdevelopment and abnormal functions of blood vessels in some loci result in oxygen deficiency in cancer cells, i.e., hypoxia. This prevents radiation from effectively eliminating the hypoxic cancer cells. Cancer cells switch to glycolysis as the main source of energy, a phenomenon known as the Warburg effect, to sustain their rapid proliferation rates. Therefore, pathways involved in metabolic reprogramming and hypoxia-induced radioresistance are promising intervention targets for cancer treatment. In this review, we discussed the mechanisms and pathways underlying radioresistance due to hypoxia and metabolic reprogramming in detail, including DNA repair, role of cancer stem cells, oxidative stress relief, autophagy regulation, angiogenesis and immune escape. In addition, we proposed the existence of a feedback loop between energy metabolic reprogramming and hypoxia, which is associated with the development and exacerbation of radioresistance in tumors. Simultaneous blockade of this feedback loop and other tumor-specific targets can be an effective approach to overcome radioresistance of cancer cells. This comprehensive overview provides new insights into the mechanisms underlying tumor radiosensitivity and progression.

Tumor microenvironment of cancer stem cells: Perspectives on cancer stem cell targeting

There are few tumor cell subpopulations with stem cell characteristics in tumor tissue, defined as cancer stem cells (CSCs) or cancer stem-like cells (CSLCs), which can reconstruct neoplasms with malignant biological behaviors such as invasiveness via self-renewal and unlimited generation. The microenvironment that CSCs depend on consists of various cellular components and corresponding medium components. Among these factors existing at a variety of levels and forms, cytokine networks and numerous signal pathways play an important role in signaling transduction. These factors promote or maintain cancer cell stemness, and participate in cancer recurrence, metastasis, and resistance. This review aims to summarize the recent molecular data concerning the multilayered relationship between CSCs and CSC-favorable microenvironments. We also discuss the therapeutic implications of targeting this synergistic interplay, hoping to give an insight into targeting cancer cell stemness for tumor therapy and prognosis.

CCAAT enhancer binding protein delta activates vesicle associated membrane protein 3 transcription to enhance chemoresistance and extracellular PD-L1 expression in triple-negative breast cancer

BACKGROUND

Chemoresistance and immunosuppression are two major obstacles in the current anti-cancer treatments. This study investigates the involvements of a CCAAT enhancer binding protein delta (CEBPD)/vesicle associated membrane protein 3 (VAMP3) axis in paclitaxel (PTX) resistance and immune evasion in triple-negative breast cancer (TNBC).

METHODS

PTX resistance-related genes were screened by bioinformatics. CEBPD and VAMP3 expression in clinical TNBC samples was examined by immunohistochemistry. Three PTX-resistant TNBC cell lines (MDA-MB-231/PTX, MDA-MB-468/PTX and MDA-MB-453/PTX) were generated, and their drug resistance was analyzed. Autophagy of cells was analyzed by immunofluorescence staining. Interaction between CEBPD and VAMP3 promoter was identified by immunoprecipitation and luciferase assays. The extracellular expression of programmed cell death-ligand 1 (PD-L1) in TNBC cells was detected. Extracellular vesicles (EVs) from TNBC cells were isolated to examine their effects on CD8+ T cell exhaustion.

RESULTS

CEBPD and VAMP3 were upregulated in chemo-resistant tissue samples and in PTX-resistant TNBC cells. The CEBPD downregulation enhanced PTX sensitivity of cells. However, further upregulation of VAMP3 in cells restored PTX resistance, which was likely due to the activation of autophagy, as the autophagy antagonist chloroquine enhanced PTX sensitivity of cells. CEBPD was found to bind to the VAMP3 promoter to activate its transcription. The CEBPD/VAMP3 axis also increased the PD-L1 expression in the conditioned medium of TNBC cells. The TNBC cell-derived EVs increased the exhaustion of co-cultured CD8+ T cells.

CONCLUSION

This study provides novel evidence that CEBPD plays a key role in enhancing PTX resistance in TNBC cells across various subtypes through VAMP3-mediated autophagy activation. Additionally, the CEBPD/VAMP3 axis also increases extracellular PD-L1 level, delivered by cancer cell-derived EVs, to suppress CD8+ T cell-mediated anti-tumor immune response. These significant observations may provide new insights into the treatment of TNBC, suggesting CEBPD and VAMP3 as promising targets to overcome treatment resistance.

Dexpanthenol ameliorates lipopolysaccharide-induced cardiovascular toxicity by regulating the IL-6/HIF1α/VEGF pathway

Introduction

Lipopolysaccharide (Lps) is an essential component responsible for the virulence of gram-negative bacteria. Lps can cause damage to many organs, including the heart, kidneys, and lungs. Dexpanthenol (Dex) is an agent that exhibits anti-oxidative and anti-inflammatory effects and stimulates epithelialization. In this study, we aimed to investigate the effects of Dex on Lps-induced cardiovascular toxicity.

Methods

Rats were divided into four groups: control, Lps (5 mg/kg, intraperitoneal), Dex (500 mg/kg, intraperitoneal), and Lps + Dex. The control group received saline intraperitoneally (i.p.) once daily for three days. The Lps group received saline i.p. once daily for three days and a single dose of Lps i.p. was administered on the third day. The Dex group received Dex i.p. once daily for three days and saline on the third day. The Lps + Dex group received Dex i.p. once daily for three days and a single dose of Lps i.p. on the third day. Heart and aortic tissues were taken for biochemical, histopathological, immunohistochemical, and genetic analysis.

Results

Lps injection caused histopathological changes in both heart and aortic tissues and significantly increased total oxidant status and oxidative stress index levels. Interleukin-6, and Tumor necrosis factor-α mRNA expressions were significantly altered in heart and aorta, likely do to the anti-inflammatory and antioxidative effects of Dex. Furthermore, Dex affected Caspase-3 and Hypoxia-inducible factor 1-α staining patterns.

Conclusions

Our results show that Dex treatment has a protective effect on Lps-induced cardiac and endothelial damage in rats by reducing inflammation, oxidative stress, and apoptosis.

The Dual Roles of Activating Transcription Factor 3 (ATF3) in Inflammation, Apoptosis, Ferroptosis, and Pathogen Infection Responses

Transcription factors are pivotal regulators in the cellular life process. Activating transcription factor 3 (ATF3), a member of the ATF/CREB (cAMP response element-binding protein) family, plays a crucial role as cells respond to various stresses and damage. As a transcription factor, ATF3 significantly influences signal transduction regulation, orchestrating a variety of signaling pathways, including apoptosis, ferroptosis, and cellular differentiation. In addition, ATF3 serves as an essential link between inflammation, oxidative stress, and immune responses. This review summarizes the recent advances in research on ATF3 activation and its role in regulating inflammatory responses, cell apoptosis, and ferroptosis while exploring the dual functions of ATF3 in these processes. Additionally, this article discusses the role of ATF3 in diseases related to pathogenic microbial infections. Our review may be helpful to better understand the role of ATF3 in cellular responses and disease progression, thus promoting advancements in clinical treatments for inflammation and oxidative stress-related diseases.

Cancer stem cell-immune cell crosstalk in breast tumor microenvironment: a determinant of therapeutic facet

Breast cancer (BC) is globally one of the leading killers among women. Within a breast tumor, a minor population of transformed cells accountable for drug resistance, survival, and metastasis is known as breast cancer stem cells (BCSCs). Several experimental lines of evidence have indicated that BCSCs influence the functionality of immune cells. They evade immune surveillance by altering the characteristics of immune cells and modulate the tumor landscape to an immune-suppressive type. They are proficient in switching from a quiescent phase (slowly cycling) to an actively proliferating phenotype with a high degree of plasticity. This review confers the relevance and impact of crosstalk between immune cells and BCSCs as a fate determinant for BC prognosis. It also focuses on current strategies for targeting these aberrant BCSCs that could open avenues for the treatment of breast carcinoma.

Tumor microenvironment-induced tumor cell plasticity: relationship with hypoxic stress and impact on tumor resistance

The role of tumor interaction with stromal components during carcinogenesis is crucial for the design of efficient cancer treatment approaches. It is widely admitted that tumor hypoxic stress is associated with tumor aggressiveness and thus impacts susceptibility and resistance to different types of treatments. Notable biological processes that hypoxia functions in include its regulation of tumor heterogeneity and plasticity. While hypoxia has been reported as a major player in tumor survival and dissemination regulation, the significance of hypoxia inducible factors in cancer stem cell development remains poorly understood. Several reports indicate that the emergence of cancer stem cells in addition to their phenotype and function within a hypoxic tumor microenvironment impacts cancer progression. In this respect, evidence showed that cancer stem cells are key elements of intratumoral heterogeneity and more importantly are responsible for tumor relapse and escape to treatments. This paper briefly reviews our current knowledge of the interaction between tumor hypoxic stress and its role in stemness acquisition and maintenance. Our review extensively covers the influence of hypoxia on the formation and maintenance of cancer stem cells and discusses the potential of targeting hypoxia-induced alterations in the expression and function of the so far known stem cell markers in cancer therapy approaches. We believe that a better and integrated understanding of the effect of hypoxia on stemness during carcinogenesis might lead to new strategies for exploiting hypoxia-associated pathways and their targeting in the clinical setting in order to overcome resistance mechanisms. More importantly, at the present time, efforts are oriented towards the design of innovative therapeutical approaches that specifically target cancer stem cells.

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.

MiR-662 is associated with metastatic relapse in early-stage breast cancer and promotes metastasis by stimulating cancer cell stemness

BACKGROUND

Breast cancer (BC) metastasis, which often occurs in bone, contributes substantially to mortality. MicroRNAs play a fundamental role in BC metastasis, although microRNA-regulated mechanisms driving metastasis progression remain poorly understood.

METHODS

MiRome analysis in serum from BC patients was performed by TaqMan™ low-density array. MiR-662 was overexpressed following MIMIC-transfection or lentivirus transduction. Animal models were used to investigate the role of miR-662 in BC (bone) metastasis. The effect of miR-662-overexpressing BC cell conditioned medium on osteoclastogenesis was investigated. ALDEFLUOR assays were performed to study BC stemness. RNA-sequencing transcriptomic analysis of miR-662-overexpressing BC cells was performed to evaluate gene expression changes.

RESULTS

High levels of hsa-miR-662 (miR-662) in serum from BC patients, at baseline (time of surgery), were associated with future recurrence in bone. At an early-stage of the metastatic disease, miR-662 could mask the presence of BC metastases in bone by inhibiting the differentiation of bone-resorbing osteoclasts. Nonetheless, metastatic miR-662-overexpressing BC cells then progressed as overt osteolytic metastases thanks to increased stem cell-like traits.

CONCLUSIONS

MiR-662 is involved in BC metastasis progression, suggesting it may be used as a prognostic marker to identify BC patients at high risk of metastasis.

Hypoxia inducible factor-1α (HIF-1α) in breast cancer: The crosstalk with oncogenic and onco-suppressor factors in regulation of cancer hallmarks

Low oxygen level at tumor microenvironment leads to a condition, known as hypoxia that is implicated in cancer progression. Upon hypoxia, HIF-1α undergoes activation and due to its oncogenic function and interaction with other molecular pathways, promotes tumor progression. The HIF-1α role in regulating breast cancer progression is described, Overall, HIF-1α has upregulation in breast tumor and due to its tumor-promoting function, its upregulation is in favor of breast tumor progression. HIF-1α overexpression prevents apoptosis in breast tumor and it promotes cell cycle progression. Silencing HIF-1α triggers cycle arrest and decreases growth. Migration of breast tumor enhances by HIF-1α signaling and it mainly induces EMT in providing metastasis. HIF-1α upregulation stimulates drug resistance and radio-resistance in breast tumor. Furthermore, HIF-1α signaling induces immune evasion of breast cancer. Berberine and pharmacological intervention suppress HIF-1α signaling in breast tumor and regulation of HIF-1α by non-coding RNAs occurs. Furthermore, HIF-1α is a biomarker in clinic.

Inflammatory auxo-action in the stem cell division theory of cancer

Acute inflammation is a beneficial response to the changes caused by pathogens or injuries that can eliminate the source of damage and restore homeostasis in damaged tissues. However, chronic inflammation causes malignant transformation and carcinogenic effects of cells through continuous exposure to pro-inflammatory cytokines and activation of inflammatory signaling pathways. According to the theory of stem cell division, the essential properties of stem cells, including long life span and self-renewal, make them vulnerable to accumulating genetic changes that can lead to cancer. Inflammation drives quiescent stem cells to enter the cell cycle and perform tissue repair functions. However, as cancer likely originates from DNA mutations that accumulate over time via normal stem cell division, inflammation may promote cancer development, even before the stem cells become cancerous. Numerous studies have reported that the mechanisms of inflammation in cancer formation and metastasis are diverse and complex; however, few studies have reviewed how inflammation affects cancer formation from the stem cell source. Based on the stem cell division theory of cancer, this review summarizes how inflammation affects normal stem cells, cancer stem cells, and cancer cells. We conclude that chronic inflammation leads to persistent stem cells activation, which can accumulate DNA damage and ultimately promote cancer. Additionally, inflammation not only facilitates the progression of stem cells into cancer cells, but also plays a positive role in cancer metastasis.

CEBPD is a master transcriptional factor for hypoxia regulated proteins in glioblastoma and augments hypoxia induced invasion through extracellular matrix-integrin mediated EGFR/PI3K pathway

Hypoxia contributes to the initiation and progression of glioblastoma by regulating a cohort of genes called hypoxia-regulated genes (HRGs) which form a complex molecular interacting network (HRG-MINW). Transcription factors (TFs) often play central roles for MINW. The key TFs for hypoxia induced reactions were explored using proteomic analysis to identify a set of hypoxia-regulated proteins (HRPs) in GBM cells. Next, systematic TF analysis identified CEBPD as a top TF that regulates the greatest number of HRPs and HRGs. Clinical sample and public database analysis revealed that CEBPD is significantly up-regulated in GBM, high levels of CEBPD predict poor prognosis. In addition, CEBPD is highly expressed in hypoxic condition both in GBM tissue and cell lines. For molecular mechanisms, HIF1α and HIF2α can activate the CEBPD promotor. In vitro and in vivo experiments demonstrated that CEBPD knockdown impaired the invasion and growth capacity of GBM cells, especially in hypoxia condition. Next, proteomic analysis identified that CEBPD target proteins are mainly involved in the EGFR/PI3K pathway and extracellular matrix (ECM) functions. WB assays revealed that CEBPD significantly positively regulated EGFR/PI3K pathway. Chromatin immunoprecipitation (ChIP) qPCR/Seq analysis and Luciferase reporter assay demonstrated that CEBPD binds and activates the promotor of a key ECM protein FN1 (fibronectin). In addition, the interactions of FN1 and its integrin receptors are necessary for CEBPD-induced EGFR/PI3K activation by promoting EGFR phosphorylation. Furthermore, GBM sample analysis in the database corroborated that CEBPD is positively correlated with the pathway activities of EGFR/PI3K and HIF1α, especially in highly hypoxic samples. At last, HRPs are also enriched in ECM proteins, indicating that ECM activities are important components of hypoxia induced responses in GBM. In conclusion, CEPBD plays important regulatory roles in the GBM HRG-MINW as a key TF, which activates the EGFR/PI3K pathway through ECM, especially FN1, mediated EGFR phosphorylation.

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.

Effects of extremely low-frequency magnetic fields on human MDA-MB-231 breast cancer cells: proteomic characterization

Extremely low-frequency electromagnetic fields (ELF-MF) can modify the cell viability and regulatory processes of some cell types, including breast cancer cells. Breast cancer is a multifactorial disease where a role for ELF-MF cannot be excluded. ELF-MF may influence the biological properties of breast cells through molecular mechanisms and signaling pathways that are still unclear. This study analyzed the changes in the cell viability, cellular morphology, oxidative stress response and alteration of proteomic profile in breast cancer cells (MDA-MB-231) exposed to ELF-MF (50 Hz, 1 mT for 4 h). Non-tumorigenic human breast cells (MCF-10A) were used as control cells. Exposed MDA-MB-231 breast cancer cells increased their viability and live cell number and showed a higher density and length of filopodia compared with the unexposed cells. In addition, ELF-MF induced an increase of the mitochondrial ROS levels and an alteration of mitochondrial morphology. Proteomic data analysis showed that ELF-MF altered the expression of 328 proteins in MDA-MB-231 cells and of 242 proteins in MCF-10A cells. Gene Ontology term enrichment analysis demonstrated that in both cell lines ELF-MF exposure up-regulated the genes enriched in "focal adhesion" and "mitochondrion". The ELF-MF exposure decreased the adhesive properties of MDA-MB-231 cells and increased the migration and invasion cell abilities. At the same time, proteomic analysis, confirmed by Real Time PCR, revealed that transcription factors associated with cellular reprogramming were upregulated in MDA-MB-231 cells and downregulated in MCF-10A cells after ELF-MF exposure. MDA-MB-231 breast cancer cells exposed to 1 mT 50 Hz ELF-MF showed modifications in proteomic profile together with changes in cell viability, cellular morphology, oxidative stress response, adhesion, migration and invasion cell abilities. The main signaling pathways involved were relative to focal adhesion, mitochondrion and cellular reprogramming.

FBXW7 attenuates tumor drug resistance and enhances the efficacy of immunotherapy

FBXW7 (F-box and WD repeat domain containing 7) is a critical subunit of the Skp1-Cullin1-F-box protein (SCF), acting as an E3 ubiquitin ligase by ubiquitinating targeted protein. Through degradation of its substrates, FBXW7 plays a pivotal role in drug resistance in tumor cells and shows the potential to rescue the sensitivity of cancer cells to drug treatment. This explains why patients with higher FBXW7 levels exhibit higher survival times and more favorable prognosis. Furthermore, FBXW7 has been demonstrated to enhance the efficacy of immunotherapy by targeting the degradation of specific proteins, as compared to the inactivated form of FBXW7. Additionally, other F-box proteins have also shown the ability to conquer drug resistance in certain cancers. Overall, this review aims to explore the function of FBXW7 and its specific effects on drug resistance in cancer cells.

Hypoxia-circular RNA crosstalk to promote breast cancer

The expression of hypoxia-inducible factors (HIFs), particularly HIF-1, plays a major role in the adaptation of solid tumors to hypoxic conditions. The activation of the HIF pathway results in an expression of genes involved in the promotion of cell growth, proliferation, vascularization, metastasis, and therapeutic resistance. Circular RNA (CircRNA) is considered as a major regulator of gene expression. CircRNAs could regulate the HIF-1 pathway in cancer cells. In addition, they might be regulated by the HIF-1 pathway to promote cancer progression. Therefore, the crosstalk between hypoxia and circRNA might be involved in the pathogenesis of cancers, including breast cancer. In this review, we discussed the function of HIF-related circRNAs in the progression, angiogenesis, metabolic reprogramming, and stemness maintenance of breast cancer. In addition, the correlation between HIF-related circRNAs and clinical features of breast cancer is reviewed.

The role of hypoxia-inducible factors in breast cancer stem cell specification

Breast tumor is heterogeneous cancer with high morbidity and mortality rates, particularly in developing countries. Despite new efforts to reduce the breast cancer implications, the number of newly diagnosed cases is increasing worldwide. It is believed that cancer stem cells (CSCs) are responsible for the implication of cancers including breast cancer. Although CSCs compose a small population in tumor bulks, they play a crucial role in tumor initiation, progression, metastasis, and chemotherapeutic resistance. These events are mediated by the hypoxia-inducible factor (HIF) pathway which regulates the transcription of genes involved in CSC maintenance and tumorigenesis. In this review, we discussed the mechanisms by which hypoxia- or chemotherapy-induced HIFs promote breast CSC specification.

Targeting Transcription Factors ATF5, CEBPB and CEBPD with Cell-Penetrating Peptides to Treat Brain and Other Cancers

Developing novel therapeutics often follows three steps: target identification, design of strategies to suppress target activity and drug development to implement the strategies. In this review, we recount the evidence identifying the basic leucine zipper transcription factors ATF5, CEBPB, and CEBPD as targets for brain and other malignancies. We describe strategies that exploit the structures of the three factors to create inhibitory dominant-negative (DN) mutant forms that selectively suppress growth and survival of cancer cells. We then discuss and compare four peptides (CP-DN-ATF5, Dpep, Bpep and ST101) in which DN sequences are joined with cell-penetrating domains to create drugs that pass through tissue barriers and into cells. The peptide drugs show both efficacy and safety in suppressing growth and in the survival of brain and other cancers in vivo, and ST101 is currently in clinical trials for solid tumors, including GBM. We further consider known mechanisms by which the peptides act and how these have been exploited in rationally designed combination therapies. We additionally discuss lacunae in our knowledge about the peptides that merit further research. Finally, we suggest both short- and long-term directions for creating new generations of drugs targeting ATF5, CEBPB, CEBPD, and other transcription factors for treating brain and other malignancies.

MAPKAPK2-centric transcriptome profiling reveals its major role in governing molecular crosstalk of IGFBP2, MUC4, and PRKAR2B during HNSCC pathogenesis

Transcriptome analysis of head and neck squamous cell carcinoma (HNSCC) has been pivotal to comprehending the convoluted biology of HNSCC tumors. MAPKAPK2 or MK2 is a critical modulator of the mRNA turnover of crucial genes involved in HNSCC progression. However, MK2-centric transcriptome profiles of tumors are not well known. This study delves into HNSCC progression with MK2 at the nexus to delineate the biological relevance and intricate crosstalk of MK2 in the tumor milieu. We performed next-generation sequencing-based transcriptome profiling of HNSCC cells and xenograft tumors to ascertain mRNA expression profiles in MK2-wild type and MK2-knockdown conditions. The findings were validated using gene expression assays, immunohistochemistry, and transcript turnover studies. Here, we identified a pool of crucial MK2-regulated candidate genes by annotation and differential gene expression analyses. Regulatory network and pathway enrichment revealed their significance and involvement in the HNSCC pathogenesis. Additionally, 3'-UTR-based filtering recognized important MK2-regulated downstream target genes and validated them by nCounter gene expression assays. Finally, immunohistochemistry and transcript stability studies revealed the putative role of MK2 in regulating the transcript turnover of IGFBP2, MUC4, and PRKAR2B in HNSCC. Conclusively, MK2-regulated candidate genes were identified in this study, and their plausible involvement in HNSCC pathogenesis was elucidated. These genes possess investigative values as targets for diagnosis and therapeutic interventions for HNSCC.

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.

Dysregulation of FBW7 in malignant lymphoproliferative disorders

The ubiquitin-proteasome system (UPS) is involved in various aspects of cell processes, including cell proliferation, differentiation, and cell cycle progression. F-box and WD repeat domain-containing protein 7 (FBW7), as a key component of UPS proteins and a critical tumor suppressor in human cancers, controls proteasome-mediated degradation by ubiquitinating oncoproteins such as c-Myc, Mcl-1, cyclin E, and Notch. It also plays a role in the development of various cancers, including solid and hematological malignancies, such as T-cell acute lymphoblastic leukemia, diffuse large B-cell lymphoma, and multiple myeloma. This comprehensive review emphasizes the functions, substrates, and expression of FBW7 in malignant lymphoproliferative disorders.

IL-6: The Link Between Inflammation, Immunity and Breast Cancer

Breast cancer is one of the leading causes of mortality in females. Over the past decades, intensive efforts have been made to uncover the pathogenesis of breast cancer. Interleukin-6 (IL-6) is a pleiotropic factor which has a vital role in host defense immunity and acute stress. Moreover, a wide range of studies have identified the physiological and pathological roles of IL-6 in inflammation, immune and cancer. Recently, several IL-6 signaling pathway-targeted monoclonal antibodies have been developed for cancer and immune therapy. Combination of IL-6 inhibitory antibody with other pathways blockage drugs have demonstrated promising outcome in both preclinical and clinical trials. This review focuses on emerging studies on the strong linkages of IL-6/IL-6R mediated regulation of inflammation and immunity in cancer, especially in breast cancer.

Breast Cancer Metastasis: Mechanisms and Therapeutic Implications

Breast cancer is the most common malignancy in women worldwide. Metastasis is the leading cause of high mortality in most cancers. Although predicting the early stage of breast cancer before metastasis can increase the survival rate, breast cancer is often discovered or diagnosed after metastasis has occurred. In general, breast cancer has a poor prognosis because it starts as a local disease and can spread to lymph nodes or distant organs, contributing to a significant impediment in breast cancer treatment. Metastatic breast cancer cells acquire aggressive characteristics from the tumor microenvironment (TME) through several mechanisms including epithelial–mesenchymal transition (EMT) and epigenetic regulation. Therefore, understanding the nature and mechanism of breast cancer metastasis can facilitate the development of targeted therapeutics focused on metastasis. This review discusses the mechanisms leading to metastasis and the current therapies to improve the early diagnosis and prognosis in patients with metastatic breast cancer.

Hypoxia as a Modulator of Inflammation and Immune Response in Cancer

A clear association between hypoxia and cancer has heretofore been established; however, it has not been completely developed. In this sense, the understanding of the tumoral microenvironment is critical to dissect the complexity of cancer, including the reduction in oxygen distribution inside the tumoral mass, defined as tumoral hypoxia. Moreover, hypoxia not only influences the tumoral cells but also the surrounding cells, including those related to the inflammatory processes. In this review, we analyze the participation of HIF, NF-κB, and STAT signaling pathways as the main components that interconnect hypoxia and immune response and how they modulate tumoral growth. In addition, we closely examine the participation of the immune cells and how they are affected by hypoxia, the effects of the progression of cancer, and some innovative applications that take advantage of this knowledge, to suggest potential therapies. Therefore, we contribute to the understanding of the complexity of cancer to propose innovative therapeutic strategies in the future.

Angiogenesis Driven by the CEBPD–hsa-miR-429–VEGFA Signaling Axis Promotes Urothelial Carcinoma Progression

Background and Purpose: This research aimed to excavate the alternative mechanism of CEBPD on tumor growth and explore the biological significance of the CEBPD/hsa-miR-429/VEGFA axis on angiogenesis in urothelial carcinoma (UC). Methods: Quantitative RT-PCR, immunoblotting assay and tube formation examined the effect of hsa-miR-429 mimic or/and inhibitor on VEGFA expression and angiogenesis in CEBPD-overexpressing UC-derived cells. The association between CEBPD, hsa-miR-429, VEGFA and microvascular density (MVD) and clinical outcome were evaluated in 296 patients with UBUC and 340 patients with UTUC, respectively. Results: The increase in the transcript and protein of VEGFA as well as HUVECs tube formation was diminished upon the treatment of hsa-miR-429 mimic in CEBPD-overexpressing BFTC909 and TCCSUP. Nevertheless, the inhibited regulation of hsa-miR-429 mimic on the expression of VEGFA and ability of HUVECs tube formation was rescued by the combined incubation with hsa-miR-429 inhibitor in these two UC-derived cell lines. Furthermore, the clinical correlations showed that the higher level of VEGFA or MVD has a positive correlation with the expression of CEBPD and a negative relation to hsa-miR-429 and leads to tumor aggressiveness with worse disease-specific, metastasis-free survival in UBUC and UTUC cohorts. Conclusions: We decipher the oncogenic mechanism of CEBPD on angiogenesis through the hsa-miR-429 inhibition to stabilize the expression of VEGFA in UC. The novel research unveiled the modulation of the CEBPD/hsa-miR-429/VEGFA axis on the progression of UC and could be accessible to theranostic biomarkers.

Biological effects and regulation of IGFBP5 in breast cancer

The insulin-like growth factor receptor (IGF1R) pathway plays an important role in cancer progression. In breast cancer, the IGF1R pathway is linked to estrogen-dependent signaling. Regulation of IGF1R activity is complex and involves the actions of its ligands IGF1 and IGF2 and those of IGF-binding proteins (IGFBPs). Six IGFBPs are known that share the ability to form complexes with the IGFs, by which they control the bioavailability of these ligands. Besides, each of the IGFBPs have specific features. In this review, the focus lies on the biological effects and regulation of IGFBP5 in breast cancer. In breast cancer, estrogen is a critical regulator of IGFBP5 transcription. It exerts its effect through an intergenic enhancer loop that is part of the chromosomal breast cancer susceptibility region 2q35. The biological effects of IGFBP5 depend upon the cellular context. By inhibiting or promoting IGF1R signaling, IGFBP5 can either act as a tumor suppressor or promoter. Additionally, IGFBP5 possesses IGF-independent activities, which contribute to the complexity by which IGFBP5 interferes with cancer cell behavior.

The Methyltransferase Smyd1 Mediates LPS-Triggered Up-Regulation of IL-6 in Endothelial Cells

The lysine methyltransferase Smyd1 with its characteristic catalytic SET-domain is highly enriched in the embryonic heart and skeletal muscles, participating in cardiomyogenesis, sarcomere assembly and chromatin remodeling. Recently, significant Smyd1 levels were discovered in endothelial cells (ECs) that responded to inflammatory cytokines. Based on these biochemical properties, we hypothesized that Smyd1 is involved in inflammation-triggered signaling in ECs and therefore, investigated its role within the LPS-induced signaling cascade. Human endothelial cells (HUVECs and EA.hy926 cells) responded to LPS stimulation with higher intrinsic Smyd1 expression. By transfection with expression vectors containing gene inserts encoding either intact Smyd1, a catalytically inactive Smyd1-mutant or Smyd1-specific siRNAs, we show that Smyd1 contributes to LPS-triggered expression and secretion of IL-6 in EA.hy926 cells. Further molecular analysis revealed this process to be based on two signaling pathways: Smyd1 increased the activity of NF-κB and promoted the trimethylation of lysine-4 of histone-3 (H3K4me3) within the IL-6 promoter, as shown by ChIP-RT-qPCR combined with IL-6-promoter-driven luciferase reporter gene assays. In summary, our experimental analysis revealed that LPS-binding to ECs leads to the up-regulation of Smyd1 expression to transduce the signal for IL-6 up-regulation via activation of the established NF-κB pathway as well as via epigenetic trimethylation of H3K4.

PERK signaling through C/EBPδ contributes to ER stress-induced expression of immunomodulatory and tumor promoting chemokines by cancer cells

Cancer cells experience endoplasmic reticulum (ER) stress due to activated oncogenes and conditions of nutrient deprivation and hypoxia. The ensuing unfolded protein response (UPR) is executed by ATF6, IRE1 and PERK pathways. Adaptation to mild ER stress promotes tumor cell survival and aggressiveness. Unmitigated ER stress, however, will result in cell death and is a potential avenue for cancer therapies. Because of this yin-yang nature of ER stress, it is imperative that we fully understand the mechanisms and dynamics of the UPR and its contribution to the complexity of tumor biology. The PERK pathway inhibits global protein synthesis while allowing translation of specific mRNAs, such as the ATF4 transcription factor. Using thapsigargin and tunicamycin to induce acute ER stress, we identified the transcription factor C/EBPδ (CEBPD) as a mediator of PERK signaling to secretion of tumor promoting chemokines. In melanoma and breast cancer cell lines, PERK mediated early induction of C/EBPδ through ATF4-independent pathways that involved at least in part Janus kinases and the STAT3 transcription factor. Transcriptional profiling revealed that C/EBPδ contributed to 20% of thapsigargin response genes including chaperones, components of ER-associated degradation, and apoptosis inhibitors. In addition, C/EBPδ supported the expression of the chemokines CXCL8 (IL-8) and CCL20, which are known for their tumor promoting and immunosuppressive properties. With a paradigm of short-term exposure to thapsigargin, which was sufficient to trigger prolonged activation of the UPR in cancer cells, we found that conditioned media from such cells induced cytokine expression in myeloid cells. In addition, activation of the CXCL8 receptor CXCR1 during thapsigargin exposure supported subsequent sphere formation by cancer cells. Taken together, these investigations elucidated a novel mechanism of ER stress-induced transmissible signals in tumor cells that may be particularly relevant in the context of pharmacological interventions.

Up-down regulation of HIF-1α in cancer progression

Hypoxia induicible factor-1 alpha (HIF-1α) is a key transcription factor in cancer progression and target therapy in cancer. HIF-1α acts differently depending on presence or absence of Oxygen. In an oxygen-immersed environment, HIF-1α completely deactivated and destroyed by the ubiquitin proteasome pathway (UPP). In contrast, in the oxygen-free environment, it escapes destruction and enters to the nucleus of cells then upregulates many genes involved in cancer progression. Overexpressed HIF-1α and downstream genes support cancer progression through various mechanisms including angiogenesis, proliferation and survival of cells, metabolism reprogramming, invasion and metastasis, cancer stem cell maintenance, induction of genetic instability, and treatment resistance. HIF-1α can be provoked by signaling pathways unrelated to hypoxia during cancer progression. Therefore, cancer development and progression can be modulated by targeting HIF-1α and its downstream signaling molecules. In this regard, HIF-1α inhibitors which are categorized into the agents that regulate HIF-1α in gene, mRNA and protein levels used as an efficient way in cancer treatment. Also, HIF-1α expression can be negatively affected by the agents suppressing the activation of mTOR, PI3k/Akt and MAPK pathways.

p97/VCP is highly expressed in the stem-like cells of breast cancer and controls cancer stemness partly through the unfolded protein response

p97/VCP, an evolutionarily concerned ATPase, partakes in multiple cellular proteostatic processes, including the endoplasmic reticulum (ER)-associated protein degradation (ERAD). Elevated expression of p97 is common in many cancers and is often associated with poor survival. Here we report that the levels of p97 positively correlated with the histological grade, tumor size, and lymph node metastasis in breast cancers. We further examined p97 expression in the stem-like cancer cells or cancer stem cells (CSCs), a cell population that purportedly underscores cancer initiation, therapeutic resistance, and recurrence. We found that p97 was consistently at a higher level in the CD44⁺/CD24^-, ALDH⁺, or PKH26⁺ CSC populations than the respective non-CSC populations in human breast cancer tissues and cancer cell lines and p97 expression also positively correlated with that of SOX2, another CSC marker. To assess the role of p97 in breast cancers, cancer proliferation, mammosphere, and orthotopic growth were analyzed. Similarly as p97 depletion, two pharmacological inhibitors, which targets the ER-associated p97 or globally inhibits p97's ATPase activity, markedly reduced cancer growth and the CSC population. Importantly, depletion or inhibition of p97 greatly suppressed the proliferation of the ALDH⁺ CSCs and the CSC-enriched mammospheres, while exhibiting much less or insignificant inhibitory effects on the non-CSC cancer cells. Comparable phenotypes produced by blocking ERAD suggest that ER proteostasis is essential for the CSC integrity. Loss of p97 gravely activated the unfolded protein response (UPR) and modulated the expression of multiple stemness and pluripotency regulators, including C/EBPδ, c-MYC, SOX2, and SKP2, which collectively contributed to the demise of CSCs. In summary, p97 controls the breast CSC integrity through multiple targets, many of which directly affect cancer stemness and are induced by UPR activation. Our findings highlight the importance of p97 and ER proteostasis in CSC biology and anticancer therapy.

Immune evasion by cancer stem cells

Tumor immunity represents a new avenue for cancer therapy. Immune checkpoint inhibitors have successfully improved outcomes in several tumor types. In addition, currently, immune cell-based therapy is also attracting significant attention. However, the clinical efficacy of these treatments requires further improvement. The mechanisms through which cancer cells escape the immune response must be identified and clarified. Cancer stem cells (CSCs) play a central role in multiple aspects of malignant tumors. CSCs can initiate tumors in partially immunocompromised mice, whereas non-CSCs fail to form tumors, suggesting that tumor initiation is a definitive function of CSCs. However, the fact that non-CSCs also initiate tumors in more highly immunocompromised mice suggests that the immune evasion property may be a more fundamental feature of CSCs rather than a tumor-initiating property. In this review, we summarize studies that have elucidated how CSCs evade tumor immunity and create an immunosuppressive milieu with a focus on CSC-specific characteristics and functions. These profound mechanisms provide important clues for the development of novel tumor immunotherapies.

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Cancer stem cells (CSCs) play a central role in multiple aspects of malignant tumors.

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Immune evasion is a fundamental feature of CSCs.

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Immune evasion mechanisms must be precisely clarified to improve tumor immunotherapy.

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CSCs are promising targets for tumor immunotherapy.

Regulation of breast cancer metastasis signaling by miRNAs

Despite the decline in death rate from breast cancer and recent advances in targeted therapies and combinations for the treatment of metastatic disease, metastatic breast cancer remains the second leading cause of cancer-associated death in U.S. women. The invasion-metastasis cascade involves a number of steps and multitudes of proteins and signaling molecules. The pathways include invasion, intravasation, circulation, extravasation, infiltration into a distant site to form a metastatic niche, and micrometastasis formation in a new environment. Each of these processes is regulated by changes in gene expression. Noncoding RNAs including microRNAs (miRNAs) are involved in breast cancer tumorigenesis, progression, and metastasis by post-transcriptional regulation of target gene expression. miRNAs can stimulate oncogenesis (oncomiRs), inhibit tumor growth (tumor suppressors or miRsupps), and regulate gene targets in metastasis (metastamiRs). The goal of this review is to summarize some of the key miRNAs that regulate genes and pathways involved in metastatic breast cancer with an emphasis on estrogen receptor α (ERα+) breast cancer. We reviewed the identity, regulation, human breast tumor expression, and reported prognostic significance of miRNAs that have been documented to directly target key genes in pathways, including epithelial-to-mesenchymal transition (EMT) contributing to the metastatic cascade. We critically evaluated the evidence for metastamiRs and their targets and miRNA regulation of metastasis suppressor genes in breast cancer progression and metastasis. It is clear that our understanding of miRNA regulation of targets in metastasis is incomplete.

Breast cancer stem cells: A review of their characteristics and the agents that affect them

The evolving concept that cancer stem cells (CSCs) are the driving element in cancer development, evolution and heterogeneity, has overridden the previous model of a tumor consisting of cells all with similar sequentially acquired mutations and a similar potential for renewal, invasion and metastasis. This paradigm shift has focused attention on therapeutically targeting CSCs directly as a means of eradicating the disease. In breast cancers, CSCs can be identified by cell surface markers and are characterized by their ability to self-renew and differentiate, resist chemotherapy and radiation, and initiate new tumors upon serial transplantation in xenografted mice. These functional properties of CSCs are regulated by both intracellular and extracellular factors including pluripotency-related transcription factors, intracellular signaling pathways and external stimuli. Several classes of natural products and synthesized compounds have been studied to target these regulatory elements and force CSCs to lose stemness and/or terminally differentiate and thereby achieve a therapeutic effect. However, realization of an effective treatment for breast cancers, focused on the biological effects of these agents on breast CSCs, their functions and signaling, has not yet been achieved. In this review, we delineate the intrinsic and extrinsic factors identified to date that control or promote stemness in breast CSCs and provide a comprehensive compilation of potential agents that have been studied to target breast CSCs, transcription factors and stemness-related signaling. Our aim is to stimulate further study of these agents that could become the basis for their use as stand-alone treatments or components of combination therapies effective against breast cancers.

The STAT3 inhibitor Stattic acts independently of STAT3 to decrease histone acetylation and modulate gene expression

Signal transducer and activator of transcription 3 (STAT3) is an important transcription factor involved in many physiological functions including embryonic development and immune responses and is often activated under pathological conditions such as cancer. Strategies to inactivate STAT3 are being pursued as potential anticancer therapies and have led to the identification of Stattic (6-nitrobenzo[b]thiophene-1,1-dioxide) as a "specific" STAT3 inhibitor that is often used to interrogate STAT3-mediated gene expression in vitro and in vivo. Here, we show that Stattic exerts many STAT3-independent effects on cancer cells, calling for reassessment of results previously ascribed to STAT3 functions. Studies of the STAT3-deficient prostate cancer cell line PC-3 (PC3) along with STAT3-proficient breast cancer cell lines (MDA-MB-231, SUM149) revealed that Stattic attenuated histone acetylation and neutralized effects of the histone deacetylase (HDAC) inhibitor romidepsin. In PC3 cells, Stattic alone inhibited gene expression of CCL20 and CCL2, but activated expression of TNFA, CEBPD, SOX2, and MYC. In addition, we found that Stattic promoted autophagy and caused cell death. These data point to profound epigenetic effects of Stattic that are independent of its function as a STAT3 inhibitor. Our results demonstrate that Stattic directly or indirectly reduces histone acetylation and suggest reevaluation of Stattic and related compounds as polypharmacological agents through multipronged cytotoxic effects on cancer cells.

Cancer stem cells: Culprits in endocrine resistance and racial disparities in breast cancer outcomes

Breast cancer stem cells (BCSCs) promote endocrine therapy (ET) resistance, also known as endocrine resistance in hormone receptor (HR) positive breast cancer. Endocrine resistance occurs via mechanisms that are not yet fully understood. In vitro, in vivo and clinical data suggest that signaling cascades such as Notch, hypoxia inducible factor (HIF), and integrin/Akt promote BCSC-mediated endocrine resistance. Once HR positive breast cancer patients relapse on ET, targeted therapy agents such as cyclin dependent kinase inhibitors are frequently implemented, though secondary resistance remains a threat. Here, we discuss Notch, HIF, and integrin/Akt pathway regulation of BCSC activity and potential strategies to target these pathways to counteract endocrine resistance. We also discuss a plausible link between elevated BCSC-regulatory gene levels and reduced survival observed among African American women with basal-like breast cancer which lacks HR expression. Should future studies reveal a similar link for patients with luminal breast cancer, then the use of agents that impede BCSC activity could prove highly effective in improving clinical outcomes among African American breast cancer patients.

Loss of Fbxw7 triggers mammary tumorigenesis associated with E2F/c-Myc activation and Trp53 mutation

Fbw7 is a tumor suppressor that regulates the degradation of oncogenic substrates such as c-Jun, c-Myc, Notch1 intracellular domain (ICD), and cyclin E by functioning as the substrate recognition protein in the Skp1-Cullin-F-box (SCF) ubiquitin ligase complex. Consequently, low expression or loss of FBXW7 in breast cancer has been hypothesized to result in the accumulation of oncogenic transcription factors that are master regulators of proliferation, apoptosis, and ultimately transformation. Despite this, the direct effect of Fbw7 loss on mammary gland morphology and tumorigenesis has not been examined. Here, we demonstrate that conditional deletion of Fbxw7 in murine mammary tissue initiates breast tumor development and also results in lactation and involution defects. Further, while Fbxw7 loss results in the overexpression of Notch1-ICD, c-Jun, cyclin E, and c-Myc, the downstream transcription factor pathways associated with c-Myc and cyclin E are the most dysregulated, including at the single-cell level. These pathways are dysregulated early after Fbxw7 loss, and their sustained loss results in tumorigenesis and reinforced c-Myc and cyclin E-E2F pathway disruption. We also find that loss of Fbxw7 is linked to the acquisition of Trp53 mutations, similar to the mutational spectrum observed in patients. Our results demonstrate that the loss of Fbxw7 promotes the acquisition of Trp53 mutations and that the two cooperate in breast tumor development. Targeting c-Myc, E2F, or p53 may therefore be a beneficial treatment strategy for FBXW7-altered breast cancer patients.

COVID-19-Induced Modifications in the Tumor Microenvironment: Do They Affect Cancer Reawakening and Metastatic Relapse?

Severe coronavirus disease 2019 (COVID-19) causes an uncontrolled activation of the innate immune response, resulting in acute respiratory distress syndrome and systemic inflammation. The effects of COVID-19–induced inflammation on cancer cells and their microenvironment are yet to be elucidated. Here, we formulate the hypothesis that COVID-19–associated inflammation may generate a microenvironment favorable to tumor cell proliferation and particularly to the reawakening of dormant cancer cells (DCCs). DCCs often survive treatment of primary tumors and populate premetastatic niches in the lungs and other organs, retaining the potential for metastatic outgrowth. DCCs reawakening may be promoted by several events associated to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, including activation of neutrophils and monocytes/macrophages, lymphopenia and an uncontrolled production of pro-inflammatory cytokines. Among pro-inflammatory factors produced during COVID-19, neutrophil extracellular traps (NETs) released by activated neutrophils have been specifically shown to activate premetastatic cancer cells disseminated in the lungs, suggesting they may be involved in DCCs reawakening in COVID-19 patients. If confirmed by further studies, the links between COVID-19, DCCs reactivation and tumor relapse may support the use of specific anti-inflammatory and anti-metastatic therapies in patients with COVID-19 and an active or previous cancer.

Hypoxia induces an endometrial cancer stem-like cell phenotype via HIF-dependent demethylation of SOX2 mRNA

Endometrial cancer stem cells (ECSCs) are stem-like cells endowed with self-renewal and differentiation abilities, and these cells are essential for cancer progression in endometrial cancer (EC). As hallmarks of the tumour microenvironment (TME), hypoxia and hypoxia-inducing factors (HIFs) give rise to the dysregulation of tumour stemness genes, such as SOX2. Against this backdrop, we investigated the regulatory mechanisms regulated by HIFs and SOX2 in ECSCs during EC development. Here, ECSCs isolated from EC cell lines and tissues were found to express stemness genes (CD133 and aldehyde dehydrogenase, ALDH1) following the induction of their ECSC expansion. Notably, m⁶A methylation of RNA and HIF-1α/2α-dependent AlkB homologue 5 (ALKBH5) participate in the regulation of HIFs and SOX2 in EC, as confirmed by the observations that mRNA levels of m⁶A demethylases and ALKBH5 significantly increase under hypoxic conditions in ECSCs. Moreover, hypoxia and high ALKBH5 levels restore the stem-like state of differentiated ECSCs and increase the ECSC-like phenotype, whereas the knockdown of HIFs or ALKBH5 significantly reduces their tumour initiation capacity. In addition, our findings validate the role of ALKBH5 in promoting SOX2 transcription via mRNA demethylation, thereby maintaining the stem-like state and tumorigenicity potential of ECSCs. In conclusion, these observations demonstrate a critical role for m⁶A methylation-mediated regulation of the HIF-ALKBH5-SOX2 axis during ECSC expansion in hypoxic TMEs.

The Importance of Breast Adipose Tissue in Breast Cancer

Adipose tissue is a complex endocrine organ, with a role in obesity and cancer. Adipose tissue is generally linked to excessive body fat, and it is well known that the female breast is rich in adipose tissue. Hence, one can wonder: what is the role of adipose tissue in the breast and why is it required? Adipose tissue as an organ consists of adipocytes, an extracellular matrix (ECM) and immune cells, with a significant role in the dynamics of breast changes throughout the life span of a female breast from puberty, pregnancy, lactation and involution. In this review, we will discuss the importance of breast adipose tissue in breast development and its involvement in breast changes happening during pregnancy, lactation and involution. We will focus on understanding the biology of breast adipose tissue, with an overview on its involvement in the various steps of breast cancer development and progression. The interaction between the breast adipose tissue surrounding cancer cells and vice-versa modifies the tumor microenvironment in favor of cancer. Understanding this mutual interaction and the role of breast adipose tissue in the tumor microenvironment could potentially raise the possibility of overcoming breast adipose tissue mediated resistance to therapies and finding novel candidates to target breast cancer.

Dominant-Negative ATF5 Compromises Cancer Cell Survival by Targeting CEBPB and CEBPD

The basic leucine zipper transcription factor ATF5 is overexpressed in many tumor types and interference with its expression or function inhibits cancer cell survival. As a potential therapeutic approach to exploit these findings, we created dominant-negative (DN) ATF5 forms lacking DNA-binding ability that retain the ATF5 leucine zipper, and thus associate with and sequester ATF5's requisite leucine zipper-binding partners. Preclinical studies with DN-ATF5, including a cell-penetrating form, show in vitro and in vivo efficacy in compromising cancer cell survival. However, DN-ATF5's targets, and particularly those required for tumor cell survival, have been unknown. We report that cells lacking ATF5 succumb to DN-ATF5, indicating that ATF5 itself is not DN-ATF5's obligate target. Unbiased pull-down assays coupled with mass spectrometry and immunoblotting revealed that DN-ATF5 associates in cells with the basic leucine zipper proteins CEBPB and CEBPD and coiled-coil protein CCDC6. Consistent with DN-ATF5 affecting tumor cell survival by suppressing CEBPB and CEBPD function, DN-ATF5 interferes with CEBPB and CEBPD transcriptional activity, while CEBPB or CEBPD knockdown promotes apoptotic death of multiple cancer cells lines, but not of normal astrocytes. We propose a two-pronged mechanism by which DN-ATF5 kills tumor cells. One is by inhibiting heterodimer formation between ATF5 and CEBPB and CDBPD, thus suppressing ATF5-dependent transcription. The other is by blocking the formation of transcriptionally active CEBPB and CEBPD homodimers as well as heterodimers with partners in addition to ATF5. IMPLICATIONS: This study indicates that the potential cancer therapeutic DN-ATF5 acts by associating with and blocking the transcriptional activities of CEBPB and CEBPD.

Hypoxia inducible factors in the tumor microenvironment as therapeutic targets of cancer stem cells

Cancer stem cells (CSC) constitute a small area of the tumor mass and are characterized by self-renewal, differentiation and the ability to promote the development of secondary chemo-resistant tumors. Self-renewal of CSCs is regulated through various signaling pathways including Hedgehog, Notch, and Wnt/β-catenin pathways. A few surface markers have been identified, which provide a means of targeting CSCs according to tumor type. Depending on the proximity of CSCs to the tumor hypoxic niche, hypoxia-inducible factors (HIFs) can play a critical role in modulating several CSC-related characteristics. For instance, the upregulation of HIF-1 and HIF-2 at tumor sites, which correlates with the expansion of CSCs and poor cancer prognosis, has been demonstrated. In this review, we will discuss the mechanisms by which hypoxia enhances the development of CSCs in the tumor microenvironment. Targeting HIFs in combination with other common therapeutics is pre-requisite for effective eradication of CSCs.

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.

Role of the Microenvironment in Regulating Normal and Cancer Stem Cell Activity: Implications for Breast Cancer Progression and Therapy Response

The epithelial cells in an adult woman’s breast tissue are continuously replaced throughout their reproductive life during pregnancy and estrus cycles. Such extensive epithelial cell turnover is governed by the primitive mammary stem cells (MaSCs) that proliferate and differentiate into bipotential and lineage-restricted progenitors that ultimately generate the mature breast epithelial cells. These cellular processes are orchestrated by tightly-regulated paracrine signals and crosstalk between breast epithelial cells and their tissue microenvironment. However, current evidence suggests that alterations to the communication between MaSCs, epithelial progenitors and their microenvironment plays an important role in breast carcinogenesis. In this article, we review the current knowledge regarding the role of the breast tissue microenvironment in regulating the special functions of normal and cancer stem cells. Understanding the crosstalk between MaSCs and their microenvironment will provide new insights into how an altered breast tissue microenvironment could contribute to breast cancer development, progression and therapy response and the implications of this for the development of novel therapeutic strategies to target cancer stem cells.

Cancer stem cell (CSC) resistance drivers

Cancer stem cells (CSCs) are a population of self-renewal cells with high tumorigenic potency. CSCs can adopt easily with changes in the nearby milieu, and are more resistant to conventional therapies than other cells within a tumor. CSC resistance can be induced secondary to radio- and chemotherapy, or even after chemotherapy secession. A combination of both intrinsic and extrinsic factors is contributed to CSC-mediated therapy resistance. CSCs represent protective autophagy and efficient cell cycling, along with highly qualified epithelial-mesenchymal transition (EMT) regulators, reactive oxygen species (ROS) scavengers, drug transporters, and anti-apoptotic and DNA repairing systems. In addition, CSCs develop cross-talking and share some characteristics with other cells within the tumor microenvironment (TME) being more intense in higher stage tumors, and thereby sophisticating tumor-targeted therapies. TME, in fact, is a nest for aggravating resistance mechanisms in CSCs. TME is exposed constantly to the nutritional, metabolic and oxygen deprivation; these conditions promote CSC adaptation. This review is aimed to discuss main (intrinsic and extrinsic) mechanisms of CSC resistance and suggest some strategies to revoke this important promoter of therapy failure.