Autophagy supports generation of cells with high CD44 expression via modulation of oxidative stress and Parkin-mediated mitochondrial clearance

Mitophagy at the crossroads of cancer development: Exploring the role of mitophagy in tumor progression and therapy resistance

Preserving a functional mitochondrial network is crucial for cellular well-being, considering the pivotal role of mitochondria in ensuring cellular survival, especially under stressful conditions. Mitophagy, the selective removal of damaged mitochondria through autophagy, plays a pivotal role in preserving cellular homeostasis by preventing the production of harmful reactive oxygen species from dysfunctional mitochondria. While the involvement of mitophagy in neurodegenerative diseases has been thoroughly investigated, it is becoming increasingly evident that mitophagy plays a significant role in cancer biology. Perturbations in mitophagy pathways lead to suboptimal mitochondrial quality control, catalyzing various aspects of carcinogenesis, including establishing metabolic plasticity, stemness, metabolic reconfiguration of cancer-associated fibroblasts, and immunomodulation. While mitophagy performs a delicate balancing act at the intersection of cell survival and cell death, mounting evidence indicates that, particularly in the context of stress responses induced by cancer therapy, it predominantly promotes cell survival. Here, we showcase an overview of the current understanding of the role of mitophagy in cancer biology and its potential as a target for cancer therapy. Gaining a more comprehensive insight into the interaction between cancer therapy and mitophagy has the potential to reveal novel targets and pathways, paving the way for enhanced treatment strategies for therapy-resistant tumors in the near future.

Mitophagy and cancer: role of BNIP3/BNIP3L as energetic drivers of stemness features, ATP production, proliferation, and cell migration

Mitophagy is a selective form of autophagy which permits the removal of dysfunctional or excess mitochondria. This occurs as an adaptative response to physiological stressors, such as hypoxia, nutrient deprivation, or DNA damage. Mitophagy is promoted by specific mitochondrial outer membrane receptors, among which are BNIP3 and BNIP3L. The role of mitophagy in cancer is being widely studied, and more specifically in the maintenance of cancer stem cell (CSC) properties, such as self-renewal. Given that CSCs are responsible for treatment failure and metastatic capacity, targeting mitophagy could be an interesting approach for CSC elimination. Herein, we describe a new model system to enrich sub-populations of cancer cells with high basal levels of mitophagy, based on the functional transcriptional activity of BNIP3 and BNIP3L. Briefly, we employed a BNIP3(L)-promoter-eGFP-reporter system to isolate cancer cells with high BNIP3/BNIP3L transcriptional activity by flow cytometry (FACS). The model was validated by using complementary lysosomal and mitophagy-specific probes, as well as the mitochondrially-targeted red fluorescent protein (RFP), namely mt-Keima. High BNIP3/BNIP3L transcriptional activity was accompanied by increases in i) BNIP3/BNIP3L protein levels, ii) lysosomal mass, and iii) basal mitophagy activity. Furthermore, cancer cells with increased BNIP3/BNIP3L transcriptional activity exhibited CSC features, such as greater mammosphere-forming ability and high CD44 levels. To further explore the model, we also analysed other stemness characteristics in MCF7 and MDA-MB-231 breast cancer cell lines, directly demonstrating that BNIP3(L)-high cells were more metabolically active, proliferative, migratory, and drug-resistant, with elevated anti-oxidant capacity. Therefore, high levels of basal mitophagy appear to enhance CSC features.

Mitochondrial quality control in human health and disease

Mitochondria, the most crucial energy-generating organelles in eukaryotic cells, play a pivotal role in regulating energy metabolism. However, their significance extends beyond this, as they are also indispensable in vital life processes such as cell proliferation, differentiation, immune responses, and redox balance. In response to various physiological signals or external stimuli, a sophisticated mitochondrial quality control (MQC) mechanism has evolved, encompassing key processes like mitochondrial biogenesis, mitochondrial dynamics, and mitophagy, which have garnered increasing attention from researchers to unveil their specific molecular mechanisms. In this review, we present a comprehensive summary of the primary mechanisms and functions of key regulators involved in major components of MQC. Furthermore, the critical physiological functions regulated by MQC and its diverse roles in the progression of various systemic diseases have been described in detail. We also discuss agonists or antagonists targeting MQC, aiming to explore potential therapeutic and research prospects by enhancing MQC to stabilize mitochondrial function.

Immune checkpoints between epithelial-mesenchymal transition and autophagy: A conflicting triangle

Inhibitory immune checkpoint (ICP) molecules are pivotal in inhibiting innate and acquired antitumor immune responses, a mechanism frequently exploited by cancer cells to evade host immunity. These evasion strategies contribute to the complexity of cancer progression and therapeutic resistance. For this reason, ICP molecules have become targets for antitumor drugs, particularly monoclonal antibodies, collectively referred to as immune checkpoint inhibitors (ICI), that counteract such cancer-associated immune suppression and restore antitumor immune responses. Over the last decade, however, it has become clear that tumor cell-associated ICPs can also induce tumor cell-intrinsic effects, in particular epithelial-mesenchymal transition (EMT) and macroautophagy (hereafter autophagy). Both of these processes have profound implications for cancer metastasis and drug responsiveness. This article reviews the positive or negative cross-talk that tumor cell-associated ICPs undergo with autophagy and EMT. We discuss that tumor cell-associated ICPs are upregulated in response to the same stimuli that induce EMT. Moreover, ICPs themselves, when overexpressed, become an EMT-inducing stimulus. As regards the cross-talk with autophagy, ICPs have been shown to either stimulate or inhibit autophagy, while autophagy itself can either up- or downregulate the expression of ICPs. This dynamic equilibrium also extends to the autophagy-apoptosis axis, further emphasizing the complexities of cellular responses. Eventually, we delve into the intricate balance between autophagy and apoptosis, elucidating its role in the broader interplay of cellular dynamics influenced by ICPs. In the final part of this article, we speculate about the driving forces underlying the contradictory outcomes of the reciprocal, inhibitory, or stimulatory effects between ICPs, EMT, and autophagy. A conclusive identification of these driving forces may allow to achieve improved antitumor effects when using combinations of ICIs and compounds acting on EMT and/or autophagy. Prospectively, this may translate into increased and/or broadened therapeutic efficacy compared to what is currently achieved with ICI-based clinical protocols.

Autophagy Contributes to Homeostasis in Esophageal Epithelium Where High Autophagic Vesicle Level Marks Basal Cells With Limited Proliferation and Enhanced Self-Renewal Potential

BACKGROUND & AIMS

Autophagy plays roles in esophageal pathologies both benign and malignant. Here, we aim to define the role of autophagy in esophageal epithelial homeostasis.

METHODS

We generated tamoxifen-inducible, squamous epithelial-specific Atg7 (autophagy related 7) conditional knockout mice to evaluate effects on esophageal homeostasis and response to the carcinogen 4-nitroquinoline 1-oxide (4NQO) using histologic and biochemical analyses. We fluorescence-activated cell sorted esophageal basal cells based on fluorescence of the autophagic vesicle (AV)-identifying dye Cyto-ID and then subjected these cells to transmission electron microscopy, image flow cytometry, three-dimensional organoid assays, RNA sequencing, and cell cycle analysis. Three-dimensional organoids were subjected to passaging, single-cell RNA sequencing, cell cycle analysis, and immunostaining.

RESULTS

Genetic autophagy inhibition in squamous epithelium resulted in increased proliferation of esophageal basal cells under homeostatic conditions and also was associated with significant weight loss in mice treated with 4NQO that further displayed perturbed epithelial tissue architecture. Esophageal basal cells with high AV level (Cyto-IDHigh) displayed limited organoid formation capability on initial plating but passaged more efficiently than their counterparts with low AV level (Cyto-IDLow). RNA sequencing suggested increased autophagy in Cyto-IDHigh esophageal basal cells along with decreased cell cycle progression, the latter of which was confirmed by cell cycle analysis. Single-cell RNA sequencing of three-dimensional organoids generated by Cyto-IDLow and Cyto-IDHigh cells identified expansion of 3 cell populations and enrichment of G2/M-associated genes in the Cyto-IDHigh group. Ki67 expression was also increased in organoids generated by Cyto-IDHigh cells, including in basal cells localized beyond the outermost cell layer.

CONCLUSIONS

Autophagy contributes to maintenance of the esophageal proliferation-differentiation gradient. Esophageal basal cells with high AV level exhibit limited proliferation and generate three-dimensional organoids with enhanced self-renewal capacity.

Identification of HSPD1 as a novel invasive biomarker associated with mitophagy in pituitary adenomas

BACKGROUND

The crucial role of mitophagy in tumor progression has been recognized. Therefore, our study aimed to investigate the potential correlation between pituitary adenoma invasiveness and the mitophagy processes.

METHODS

In this study, we used transcriptomics of postoperative tissue from 32 patients and quantitative proteomics of 19 patients to screen for mitophagy-related invasion genes in pituitary adenomas. The invasive predictive value of target genes was analyzed by Lasso regression model, CytoHubba plugin and expression validation. Co-expression correlation analysis was used to identify paired proteins for target genes, and a predictive model for pituitary adenoma invasiveness was constructed by target genes and paired proteins and assessed using ROC analysis, calibration curves and DCA. GO function, pathway (GSEA or GSVA) and immune cell analysis (ssGSEA or CIBERSORT) were further utilized to explore the action mechanism of target gene. Finally, immunohistochemistry and cell function experiments were used to detect the differential expression and key roles of the target genes in pituitary adenomas.

RESULTS

Finally, Heat shock protein family D member 1 (HSPD1) was identified as a target gene. The quality of a predictive model for pituitary adenoma invasiveness consisting of HSPD1 and its paired protein expression profiles was satisfactory. Moreover, the expression of HSPD1 was significantly lower in invasive pituitary adenomas than in non-invasive pituitary adenomas. Downregulation of HSPD1 may be significantly related to invasion process, mitochondria-related pathway and immune cell regulation in pituitary adenomas.

CONCLUSION

The downregulation of HSPD1 may serve as a predictive indicator for identifying invasive pituitary adenomas.

ALDH2 dysfunction and alcohol cooperate in cancer stem cell enrichment

The alcohol metabolite acetaldehyde is a potent human carcinogen linked to esophageal squamous cell carcinoma (ESCC) initiation and development. Aldehyde dehydrogenase 2 (ALDH2) is the primary enzyme that detoxifies acetaldehyde in the mitochondria. Acetaldehyde accumulation causes genotoxic stress in cells expressing the dysfunctional ALDH2E487K dominant negative mutant protein linked to ALDH2*2, the single nucleotide polymorphism highly prevalent among East Asians. Heterozygous ALDH2*2 increases the risk for the development of ESCC and other alcohol-related cancers. Despite its prevalence and link to malignant transformation, how ALDH2 dysfunction influences ESCC pathobiology is incompletely understood. Herein, we characterize how ESCC and preneoplastic cells respond to alcohol exposure using cell lines, three-dimensional organoids and xenograft models. We find that alcohol exposure and ALDH2*2 cooperate to increase putative ESCC cancer stem cells with high CD44 expression (CD44H cells) linked to tumor initiation, repopulation and therapy resistance. Concurrently, ALHD2*2 augmented alcohol-induced reactive oxygen species and DNA damage to promote apoptosis in the non-CD44H cell population. Pharmacological activation of ALDH2 by Alda-1 inhibits this phenotype, suggesting that acetaldehyde is the primary driver of these changes. Additionally, we find that Aldh2 dysfunction affects the response to cisplatin, a chemotherapeutic commonly used for the treatment of ESCC. Aldh2 dysfunction facilitated enrichment of CD44H cells following cisplatin-induced oxidative stress and cell death in murine organoids, highlighting a potential mechanism driving cisplatin resistance. Together, these data provide evidence that ALDH2 dysfunction accelerates ESCC pathogenesis through enrichment of CD44H cells in response to genotoxic stressors such as environmental carcinogens and chemotherapeutic agents.

Autophagy contributes to homeostasis in esophageal epithelium where high autophagic vesicle content marks basal cells with limited proliferation and enhanced self-renewal potential

Background & Aims

Autophagy has been demonstrated to play roles in esophageal pathologies both benign and malignant. Here, we aim to define the role of autophagy in esophageal epithelium under homeostatic conditions.

Methods

We generated tamoxifen-inducible, squamous epithelial-specific Atg7 (autophagy related 7) conditional knockout mice to evaluate effects on esophageal homeostasis and response to the carcinogen 4-nitroquinoline 1-oxide (4NQO) using histological and biochemical analyses. We FACS sorted esophageal basal cells based upon fluorescence of the autophagic vesicle (AV)-identifying dye Cyto-ID, then subjected these cells to transmission electron microscopy, image flow cytometry, 3D organoid assays, RNA-Sequencing (RNA-Seq), and cell cycle analysis. 3D organoids were subjected to passaging, single cell (sc) RNA-Seq, cell cycle analysis, and immunostaining.

Results

Genetic autophagy inhibition in squamous epithelium resulted in increased proliferation of esophageal basal cells. Esophageal basal cells with high AV level (Cyto-ID High ) displayed limited organoid formation capability upon initial plating but passaged more efficiently than their counterparts with low AV level (Cyto-ID Low ). RNA-Seq suggested increased autophagy in Cyto- ID High esophageal basal cells along with decreased cell cycle progression, the latter of which was confirmed by cell cycle analysis. scRNA-Seq of 3D organoids generated by Cyto-ID Low and Cyto- ID High cells identified expansion of 3 cell populations, enrichment of G2/M-associated genes, and aberrant localization of cell cycle-associated genes beyond basal cell populations in the Cyto- ID High group. Ki67 expression was also increased in organoids generated by Cyto-ID High cells, including in cells beyond the basal cell layer. Squamous epithelial-specific autophagy inhibition induced significant weight loss in mice treated with 4NQO that further displayed perturbed epithelial tissue architecture.

Conclusions

High AV level identifies esophageal epithelium with limited proliferation and enhanced self-renewal capacity that contributes to maintenance of the esophageal proliferation- differentiation gradient in vivo .

Cancer stem cell fate determination: mito-nuclear communication

Cancer stem cells (CSCs) are considered to be responsible for tumor recurrence and metastasis. Therefore, clarification of the mechanisms involved in CSC stemness maintenance and cell fate determination would provide a new strategy for cancer therapy. Unregulated cellular energetics has been accepted as one of the hallmarks of cancer cells, but recent studies have revealed that mitochondrial metabolism can also actively determine CSC fate by affecting nuclear stemness gene expression. Herein, from the perspective of mito-nuclear communication, we review recent progress on the influence of mitochondria on CSC potential from four aspects: metabolism, dynamics, mitochondrial homeostasis, and reactive oxygen species (ROS). Video Abstract.

A p-Tyr42 RhoA Inhibitor Promotes the Regeneration of Human Corneal Endothelial Cells by Ameliorating Cellular Senescence

The development of treatment strategies for human corneal endothelial cells (hCECs) disease is necessary because hCECs do not regenerate in vivo due to the properties that are similar to senescence. This study is performed to investigate the role of a p-Tyr42 RhoA inhibitor (MH4, ELMED Inc., Chuncheon) in transforming growth factor-beta (TGF-β)- or H₂O₂-induced cellular senescence of hCECs. Cultured hCECs were treated with MH4. The cell shape, proliferation rate, and cell cycle phases were analyzed. Moreover, cell adhesion assays and immunofluorescence staining for F-actin, Ki-67, and E-cadherin were performed. Additionally, the cells were treated with TGF-β or H₂O₂ to induce senescence, and mitochondrial oxidative reactive oxygen species (ROS) levels, mitochondrial membrane potential, and NF-κB translocation were evaluated. LC3II/LC3I levels were determined using Western blotting to analyze autophagy. MH4 promotes hCEC proliferation, shifts the cell cycle, attenuates actin distribution, and increases E-cadherin expression. TGF-β and H₂O₂ induce senescence by increasing mitochondrial ROS levels and NF-κB translocation into the nucleus; however, this effect is attenuated by MH4. Moreover, TGF-β and H₂O₂ decrease the mitochondrial membrane potential and induce autophagy, while MH4 reverses these effects. In conclusion, MH4, a p-Tyr42 RhoA inhibitor, promotes the regeneration of hCECs and protects hCECs against TGF-β- and H₂O₂-induced senescence via the ROS/NF-κB/mitochondrial pathway.

Diclofenac exhibits cytotoxic activity associated with metabolic alterations and p53 induction in ESCC cell lines and decreases ESCC tumor burden in vivo

Esophageal squamous cell carcinoma (ESCC) is one of the most aggressive forms of human malignancy, often displaying limited therapeutic response. Here, we examine the non-steroidal anti-inflammatory drug diclofenac (DCF) as a novel therapeutic agent in ESCC using complementary in vitro and in vivo models. DCF selectively reduced viability of human ESCC cell lines TE11, KYSE150, and KYSE410 as compared with normal primary or immortalized esophageal keratinocytes. Apoptosis and altered cell cycle profiles were documented in DCF-treated TE11 and KYSE 150. In DCF-treated TE11, RNA-Sequencing identified differentially expressed genes and Ingenuity Pathway Analysis predicted alterations in pathways associated with cellular metabolism and p53 signaling. Downregulation of proteins associated with glycolysis was documented in DCF-treated TE11 and KYSE150. In response to DCF, TE11 cells further displayed reduced levels of ATP, pyruvate, and lactate. Evidence of mitochondrial depolarization and superoxide production was induced by DCF in TE11 and KYSE150. In DCF-treated TE11, the superoxide scavenger MitoTempo improved viability, supporting a role for mitochondrial reactive oxygen species in DCF-mediated toxicity. DCF treatment resulted in increased expression of p53 in TE11 and KYSE150. p53 was further identified as a mediator of DCF-mediated toxicity in TE11 as genetic depletion of p53 partially limited apoptosis in response to DCF. Consistent with the anticancer activity of DCF in vitro, the drug significantly decreased tumor burdene in syngeneic ESCC xenograft tumors and 4-nitroquinoline 1-oxide-mediated ESCC lesions in vivo. These preclinical findings identify DCF as an experimental therapeutic that should be explored further in ESCC.

UVRAG Promotes Tumor Progression through Regulating SP1 in Colorectal Cancer

Colorectal cancer (CRC) is the third most common type of cancer. The ultraviolet radiation resistance-associated gene (UVRAG) plays a role in autophagy and has been implicated in tumor progression and prognosis. However, the role of UVRAG expression in CRC has remained elusive. In this study, the prognosis was analyzed via immunohistochemistry, and the genetic changes were compared between the high UVRAG expression group and the low UVRAG expression group using RNA sequencing (RNA-seq) and single-cell RNA-seq (scRNA-seq) data, and genetic changes were then identified by in vitro experiments. It was found that UVRAG could enhance tumor migration, drug resistance, and CC motif chemokine ligand 2 (CCL2) expression to recruit macrophages by upregulating SP1 expression, resulting in poor prognosis of CRC patients. In addition, UVRAG could upregulate the expression of programmed death-ligand 1 (PD-L1). In summary, the relationship between UVRAG expression and the prognosis of CRC patients as well as the potential mechanisms in CRC were explored, providing evidence for the treatment of CRC.

Crosstalk between cGAS-STING pathway and autophagy in cancer immunity

The cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING) pathway is critical in cancer immunity. Autophagy is a highly conserved process that is responsible for the degradation of cytoplasmic material and is involved in both innate and adaptive immunity. Recently, cGAS-STING and autophagy have been shown to be interconnected, which may influence the progression of cancer. Although cGAS-STING and autophagy have been shown to be interrelated in innate immunity, little has been reported about cancer immunity. As cancer immunity is key to treating tumors, it is essential to summarize the relationship and interactions between the two. Based on this, we systematically sorted out the recent findings of cGAS-STING and autophagy in cancer immunity and explored the interactions between cGAS-STING and autophagy, although these interactions have not been extensively studied. Lastly, we provide an outlook on how cGAS-STING and autophagy can be combined, with the hope that our research can help people better understand their potential roles in cancer immunity and bring light to the treatment of cancer.

Modeling Oral-Esophageal Squamous Cell Carcinoma in 3D Organoids

Esophageal squamous cell carcinoma (ESCC) is prevalent worldwide, accounting for 90% of all esophageal cancer cases each year, and is the deadliest of all human squamous cell carcinomas. Despite recent progress in defining the molecular changes accompanying ESCC initiation and development, patient prognosis remains poor. The functional annotation of these molecular changes is the necessary next step and requires models that both capture the molecular features of ESCC and can be readily and inexpensively manipulated for functional annotation. Mice treated with the tobacco smoke mimetic 4-nitroquinoline 1-oxide (4NQO) predictably form ESCC and esophageal preneoplasia. Of note, 4NQO lesions also arise in the oral cavity, most commonly in the tongue, as well as the forestomach, which all share the stratified squamous epithelium. However, these mice cannot be simply manipulated for functional hypothesis testing, as generating isogenic mouse models is time- and resource-intensive. Herein, we overcome this limitation by generating single cell-derived three-dimensional (3D) organoids from mice treated with 4NQO to characterize murine ESCC or preneoplastic cells ex vivo. These organoids capture the salient features of ESCC and esophageal preneoplasia, can be cheaply and quickly leveraged to form isogenic models, and can be utilized for syngeneic transplantation experiments. We demonstrate how to generate 3D organoids from normal, preneoplastic, and SCC murine esophageal tissue and maintain and cryopreserve these organoids. The applications of these versatile organoids are broad and include the utilization of genetically engineered mice and further characterization by flow cytometry or immunohistochemistry, the generation of isogeneic organoid lines using CRISPR technologies, and drug screening or syngeneic transplantation. We believe that the widespread adoption of the techniques demonstrated in this protocol will accelerate progress in this field to combat the severe burden of ESCC.

Redox balance and autophagy regulation in cancer progression and their therapeutic perspective

Cellular ROS production participates in various cellular functions but its accumulation decides the cell fate. Malignant cells have higher levels of ROS and active antioxidant machinery, a characteristic hallmark of cancer with an outcome of activation of stress-induced pathways like autophagy. Autophagy is an intracellular catabolic process that produces alternative raw materials to meet the energy demand of cells and is influenced by the cellular redox state thus playing a definite role in cancer cell fate. Since damaged mitochondria are the main source of ROS in the cell, however, cancer cells remove them by upregulating the process of mitophagy which is known to play a decisive role in tumorigenesis and tumor progression. Chemotherapy exploits cell machinery which results in the accumulation of toxic levels of ROS in cells resulting in cell death by activating either of the pathways like apoptosis, necrosis, ferroptosis or autophagy in them. So understanding these redox and autophagy regulations offers a promising method to design and develop new cancer therapies that can be very effective and durable for years. This review will give a summary of the current therapeutic molecules targeting redox regulation and autophagy for the treatment of cancer. Further, it will highlight various challenges in developing anticancer agents due to autophagy and ROS regulation in the cell and insights into the development of future therapies.

HA-ADT suppresses esophageal squamous cell carcinoma progression via apoptosis promotion and autophagy inhibition

Esophageal squamous cell carcinoma (ESCC) is a major cause of cancer-related deaths. We have previously connected a non-sulfated glycosaminoglycan, hyaluronic acid (HA), with a common hydrogen sulfide (H₂S) donor, 5-(4-hydroxyphenyl)-3H-1,2-dithiol-3-thione (ADT-OH), to reconstruct a novel conjugate, HA-ADT. In this study, we determined the effect of HA-ADT on the growth of ESCC. Our data suggested that HA-ADT exerted more potent effects than sodium hydrosulfide (NaHS, a fast H₂S-releasing donor) and morpholin-4-ium (4-methoxyphenyl)-morpholin-4-ylsulfanylidenesulfido-λ5-phosphane (GYY4137, a slow H₂S-releasing donor) on inhibiting the viability, proliferation, migration, and invasion of human ESCC cells. HA-ADT increased apoptosis by suppressing the protein expressions of phospho (p)-Ser473-protein kinase B (PKB/AKT), p-Tyr199/Tyr458-phosphatidylinositol 3-kinase (PI3K), and p-Ser2448-mammalian target of rapamycin (mTOR), but suppressed autophagy through the inhibition of the protein levels of p-Ser552-β-catenin, p-Ser9-glycogen synthase kinase-3β (GSK-3β), and Wnt3a in human ESCC cells. In addition, HA-ADT was more effective in terms of the growth inhibition of human ESCC xenograft tumor than NaHS and GYY4137. In conclusion, HA-ADT can suppress ESCC progression via apoptosis promotion and autophagy inhibition. HA-ADT might be efficacious for the treatment of cancer.

Epithelial-Mesenchymal Transition Gene Signature Is Associated with Neoadjuvant Chemoradiotherapy Resistance and Prognosis of Esophageal Squamous Cell Carcinoma

Background

Neoadjuvant chemoradiotherapy (neo-CRT) in combination with surgery increases survival compared to surgery alone, as indicated by the esophageal squamous cell carcinoma (ESCC) treatment recommendations. However, the benefits of neo-CRT are diverse among patients. Consequently, the development of new biomarkers that correlate with neo-CRT might be important for the treatment of ESCC.

Methods

The differentially expressed genes (DEG) between responsive and resistant samples from the GSE45670 dataset were obtained. On the TCGA dataset, survival analysis was performed to identify prognosis-related-EMT-genes. For EMT score model construction, lasso regression analysis in the TCGA cohort was used to identify the genes. In the TCGA-ESCC cohort, age, stage, and EMT score were used to construct a nomogram.

Results

In total, 10 prognosis-related-EMT-genes were obtained. These 10 genes consisted of 6 risky genes and 4 protective genes. Based on the lasso analysis and univariate Cox regression, an EMT score model consisting of 7 genes (CLEC18A, PIR, KCNN4, MST1R, CAPG, ALDH5A1, and COX7B) was identified. ESCC patients with a high EMT score have a worse prognosis. These genes were differentially expressed between responsive and resistant patients and had a high accuracy for distinguishing resistant and responsive patients.

Conclusions

The identified genes have the potential to function as molecular biomarkers for predicting ESCC patients' resistance to neo-CRT. This research may aid in the elucidation of the molecular processes driving resistance and the identification of targets for improving the prognosis for ESCC.

MCM7 supports the stemness of bladder cancer stem-like cells by enhancing autophagic flux

Autophagy plays critical roles in the pluripotent stemness of cancer stem cells (CSCs). However, how CSCs maintain the elevated autophagy to support stemness remains elusive. Here, we demonstrate that bladder cancer stem-like cells (BCSLCs) are at slow-cycling state with enhanced autophagy and mitophagy. In these slow-cycling BCSLCs, the DNA replication initiator MCM7 is required for autophagy and stemness. MCM7 knockdown inhibits autophagic flux and reduces the stemness of BCSLCs. MCM7 can facilitate autolysosome formation through binding with dynein to promote autophagic flux. The enhanced autophagy/mitophagy helps BCSLCs to maintain mitochondrial respiration, thus inhibiting AMPK activation. AMPK activation can trigger switch from autophagy to apoptosis, through increasing BCL2/BECLIN1 interaction and inducing P53 accumulation. In summary, we find that MCM7 can promote autophagic flux to support.

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Enhancement of autophagy and mitophagy in bladder cancer stem-like cells (BCSLCs)

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The autophagy/mitophagy sustains BCSLCs stemness

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MCM7 facilitates autophagic flux to support BCSLCs stemness

Dormancy in Breast Cancer, the Role of Autophagy, lncRNAs, miRNAs and Exosomes

Breast cancer (BC) is the most frequently diagnosed cancer in women for which numerous diagnostic and therapeutic options have been developed. Namely, the targeted treatment of BC, for the most part, relies on the expression of growth factors and hormone receptors by these cancer cells. Despite this, close to 30% of BC patients may experience relapse due to the presence of minimal residual disease (MRD) consisting of surviving disseminated tumour cells (DTCs) from the primary tumour which can colonise a secondary site. This can lead to either detectable metastasis or DTCs entering a dormant state for a prolonged period where they are undetectable. In the latter, cells can re-emerge from their dormant state due to intrinsic and microenvironmental cues leading to relapse and metastatic outgrowth. Pre- and clinical studies propose that targeting dormant DTCs may inhibit metastasis, but the choice between keeping them dormant or forcing their “awakening” is still controversial. This review will focus on cancer cells’ microenvironmental cues and metabolic and molecular properties, which lead to dormancy, relapse, and metastatic latency in BC. Furthermore, we will focus on the role of autophagy, long non-coding RNAs (lncRNAs), miRNAs, and exosomes in influencing the induction of dormancy and awakening of dormant BC cells. In addition, we have analysed BC treatment from a viewpoint of autophagy, lncRNAs, miRNAs, and exosomes. We propose the targeted modulation of these processes and molecules as modern aspects of precision medicine for BC treatment, improving both novel and traditional BC treatment options. Understanding these pathways and processes may ultimately improve BC patient prognosis, patient survival, and treatment response.

Tumour Stem Cells in Breast Cancer

Tumour stem cells (CSCs) are a self-renewing population that plays important roles in tumour initiation, recurrence, and metastasis. Although the medical literature is extensive, problems with CSC identification and cancer therapy remain. This review provides the main mechanisms of CSC action in breast cancer (BC): CSC markers and signalling pathways, heterogeneity, plasticity, and ecological behaviour. The dynamic heterogeneity of CSCs and the dynamic transitions of CSC⁻ non-CSCs and their significance for metastasis are considered.

Autophagy in Cancer Cell Transformation; A Potential Novel Therapeutic Strategy

Abstract:

Basal autophagy plays a crucial role in maintaining intracellular homeostasis and prevents the cell from escaping the cell cycle regulation mechanisms and being cancerous. Mitophagy and nucleophagy are essential for cell health. Autophagy plays a pivotal role in cancer cell transformation, where upregulated precancerous autophagy induces apoptosis. Impaired autophagy has been shown to upregulate cancer cell transformation. However, tumor cells upregulate autophagy to escape elimination and survive the unfavorable conditions and resistance to chemotherapy. Cancer cells promote autophagy through modulation of autophagy regulation mechanisms and increase expression of the autophagy-related genes. Whereas, autophagy regulation mechanisms involved microRNAs, transcription factors, and the internalized signaling pathways such as AMPK, mTOR, III PI3K and ULK-1. Disrupted regulatory mechanisms are various as the cancer cell polymorphism. Targeting a higher level of autophagy regulation is more effective, such as gene expression, transcription factors, or epigenetic modification that are responsible for up-regulation of autophagy in cancer cells. Currently, the CRISPR-CAS9 technique is available and can be applied to demonstrate the potential effects of autophagy in cancerous cells.

Single cell transcriptomic analysis reveals cellular diversity of murine esophageal epithelium

Although morphologic progression coupled with expression of specific molecular markers has been characterized along the esophageal squamous differentiation gradient, the molecular heterogeneity within cell types along this trajectory has yet to be classified at the single cell level. To address this knowledge gap, we perform single cell RNA-sequencing of 44,679 murine esophageal epithelial, to identify 11 distinct cell populations as well as pathways alterations along the basal-superficial axis and in each individual population. We evaluate the impact of aging upon esophageal epithelial cell populations and demonstrate age-associated mitochondrial dysfunction. We compare single cell transcriptomic profiles in 3D murine organoids and human esophageal biopsies with that of murine esophageal epithelium. Finally, we employ pseudotemporal trajectory analysis to develop a working model of cell fate determination in murine esophageal epithelium. These studies provide comprehensive molecular perspective on the cellular heterogeneity of murine esophageal epithelium in the context of homeostasis and aging.

The level of cellular diversity in the esophageal epithelium has yet to be classified at the single cell level. Here the authors analyze the transcriptome of 44,679 murine esophageal keratinocytes to identify an unexpected level of cellular heterogeneity.

Development of a model to predict the prognosis of esophageal carcinoma based on autophagy-related genes

Aim: To identify a potential prognostic signature of esophageal carcinoma based on autophagy-related genes (ARGs). Methods: RNA sequencing and clinical data were downloaded from the Cancer Genome Atlas. Significantly different ARGs were identified by Wilcoxon signed-rank test. A prognostic model was established employing Cox regression analysis. The model was evaluated by receiver operating characteristic and Kaplan-Meier curve. Results: A total of 28 significantly different ARGs were identified. Seven ARGs were screened to construct the prognostic model. The efficacy of the model was verified. A nomogram also validated the role of risk score in predicting prognosis. Enrichment analyses showed the possible underlying mechanisms. Conclusion: The seven-ARGs prognostic model was validated to be promising for predicting the prognosis of patients with esophageal carcinoma.

Alcohol Metabolism Enriches Squamous Cell Carcinoma Cancer Stem Cells That Survive Oxidative Stress via Autophagy

BACKGROUND

Alcohol (ethanol) consumption is a major risk factor for head and neck and esophageal squamous cell carcinomas (SCCs). However, how ethanol (EtOH) affects SCC homeostasis is incompletely understood.

METHODS

We utilized three-dimensional (3D) organoids and xenograft tumor transplantation models to investigate how EtOH exposure influences intratumoral SCC cell populations including putative cancer stem cells defined by high CD44 expression (CD44H cells).

RESULTS

Using 3D organoids generated from SCC cell lines, patient-derived xenograft tumors, and patient biopsies, we found that EtOH is metabolized via alcohol dehydrogenases to induce oxidative stress associated with mitochondrial superoxide generation and mitochondrial depolarization, resulting in apoptosis of the majority of SCC cells within organoids. However, CD44H cells underwent autophagy to negate EtOH-induced mitochondrial dysfunction and apoptosis and were subsequently enriched in organoids and xenograft tumors when exposed to EtOH. Importantly, inhibition of autophagy increased EtOH-mediated apoptosis and reduced CD44H cell enrichment, xenograft tumor growth, and organoid formation rate.

CONCLUSIONS

This study provides mechanistic insights into how EtOH may influence SCC cells and establishes autophagy as a potential therapeutic target for the treatment of EtOH-associated SCC.

The Nucleus/Mitochondria-Shuttling LncRNAs Function as New Epigenetic Regulators of Mitophagy in Cancer

Mitophagy is a specialized autophagic pathway responsible for the selective removal of damaged or dysfunctional mitochondria by targeting them to the autophagosome in order to maintain mitochondria quality. The role of mitophagy in tumorigenesis has been conflicting, with the process both supporting tumor cell survival and promoting cell death. Cancer cells may utilize the mitophagy pathway to augment their metabolic requirements and resistance to cell death, thereby leading to increased cell proliferation and invasiveness. This review highlights major regulatory pathways of mitophagy involved in cancer. In particular, we summarize recent progress regarding how nuclear-encoded long non-coding RNAs (lncRNAs) function as novel epigenetic players in the mitochondria of cancer cells, affecting the malignant behavior of tumors by regulating mitophagy. Finally, we discuss the potential application of regulating mitophagy as a new target for cancer therapy.

Mitochondrial dysfunction in inflammatory bowel disease alters intestinal epithelial metabolism of hepatic acylcarnitines

As the interface between the gut microbiota and the mucosal immune system, there has been great interest in the maintenance of colonic epithelial integrity through mitochondrial oxidation of butyrate, a short-chain fatty acid produced by the gut microbiota. Herein, we showed that the intestinal epithelium could also oxidize long-chain fatty acids, and that luminally delivered acylcarnitines in bile could be consumed via apical absorption by the intestinal epithelium, resulting in mitochondrial oxidation. Finally, intestinal inflammation led to mitochondrial dysfunction in the apical domain of the surface epithelium that may reduce the consumption of fatty acids, contributing to higher concentrations of fecal acylcarnitines in murine Citrobacter rodentium-induced colitis and human inflammatory bowel disease. These results emphasized the importance of both the gut microbiota and the liver in the delivery of energy substrates for mitochondrial metabolism by the intestinal epithelium.

Identification of Autophagy- and Ferroptosis-Related lncRNAs Functioned through Immune-Related Pathways in Head and Neck Squamous Carcinoma

The interplay between autophagy and ferroptosis has been highlighted as an important event to decide cancer cell fate. However, the underlying mechanisms remain largely unclear. In this study, we systematically explored the expression, prognostic value and functional roles of lncRNA in autophagy and ferroptosis. By a set of bioinformatics analyses, we identified 363 autophagy- and ferroptosis-related lncRNAs (AF-lncRNAs) and found 17 of them are dramatically related to the prognosis of head and neck squamous cell carcinoma (HNSC) patients, named as prognosis-related AF-lncRNAs (PAF-lncRNAs). Based on six key PAF-lncRNAs, a risk score model was developed and used to categorize the TCGA-retrieved HNSC patients into two groups (high-risk vs. low-risk). Functional analysis showed the differentially expressed genes (DEGs) between the two groups were mainly enriched in immune-related pathways and regulated by a PAF-lncRNA-directed ceRNA (competitive endogenous RNA) network. Combined with a variety of immune infiltration analyses, we also found a decreased landscape of immune cell infiltration in high-risk groups. Together, by revealing PAF-lncRNAs with tumor prognostic features functioned through immune-related pathways, our work would contribute to show the pathogenesis of a lncRNA-directed interplay among autophagy, ferroptosis and tumor immunity in HNSC and to develop potential prognostic biomarkers and targets for tumor immunotherapy.

Bioinformatics Analysis of Autophagy-related lncRNAs in Esophageal Carcinoma

BACKGROUND

Esophageal carcinoma (ESCA) is a malignant tumor with high invasiveness and mortality. Autophagy has multiple roles in the development of cancer; however, there are limited data on autophagy genes associated with long non-coding RNAs (lncRNAs) in ESCA. The purpose of this study was to screen potential diagnostic and prognostic molecules and to identify gene co-expression networks associated with autophagy in ESCA.

METHODS

We downloaded transcriptome expression profiles from The Cancer Genome Atlas and autophagy-related gene data from the Human Autophagy Database and analyzed the co-expression of mRNAs and lncRNAs. In addition, the diagnostic and prognostic value of autophagy-related lncRNAs was analyzed by multivariate Cox regression. Furthermore, Kyoto Encyclopedia of Genes and Genomes analysis was carried out for high-risk patients, and enriched pathways were analyzed by gene set enrichment analysis.

RESULTS

The results showed that genes of high-risk patients were enriched in protein export and spliceosome. Based on Cox stepwise regression and survival analysis, we identified seven autophagy-related lncRNAs with prognostic and diagnostic value, with the potential to be used as a combination to predict the prognosis of patients with ESCA. Finally, a co-expression network related to autophagy was constructed.

CONCLUSION

These results suggest that autophagy-related lncRNAs and the spliceosome play important parts in the pathogenesis of ESCA. Our findings provide new insight into the molecular mechanism of ESCA and suggest a new method for improving its treatment.

The role of non-apoptotic cell death in the treatment and drug-resistance of digestive tumors

Tumor cell apoptosis evasion is one of the main reasons for easy metastasis occurrence, chemotherapy resistance, and the low five-year survival rate of digestive system tumors. Current research has shown that non-apoptotic cell death plays an important role in tumors of the digestive system. Therefore, increasing the proportion of non-apoptotic tumor cells is one of the effective methods of improving therapeutic efficacies for digestive system tumors. Non-apoptotic cell death modes mainly include autophagic cell death, pyroptosis, ferroptosis, in addition to other cell death modes. This review covers a systematic review relating to the research progress made into autophagic cell death, pyroptosis, ferroptosis, and other cell death modes in the treatment of digestive system tumors. It also highlights how treatment is a reasonable prospect based on clinical experience and provides reliable guidance for the further development of digestive system tumor treatments.

NOTCH3 limits the epithelial-mesenchymal transition and predicts a favorable clinical outcome in esophageal cancer

BACKGROUND

Esophageal squamous cell carcinoma (ESCC) is the deadliest of all human squamous cell carcinomas and is characterized by chemotherapy resistance and poor prognosis associated with the epithelial-mesenchymal transition (EMT). A subset of ESCC displays loss-of-function mutations in genes encoding Notch receptor family members, including NOTCH3. Although Notch signaling regulates EMT in ESCC cells, the role of NOTCH3 in EMT and chemotherapy resistance remains elusive. This study aimed to examine the role of NOTCH3 in EMT and chemotherapy resistance, and determine whether NOTCH3 expression can be used to predict the response to chemotherapy.

METHODS

In vitro and in vivo assays were conducted to clarify the contribution of NOTCH3 to chemotherapy resistance. Using specimens from 120 ESCC patients treated with neoadjuvant chemotherapy, we compared the expression levels of NOTCH3 and genes involved in EMT according to the degree of chemotherapy sensitivity.

RESULTS

In ESCC cells, chemotherapy resistance was associated with NOTCH3 downregulation and concurrent activation of EMT. RNA interference to silence NOTCH3 resulted in induction of the EMT marker Vimentin (VIM), leading to chemotherapy resistance in ESCC cells. Conversely, ectopic expression of the activated form of NOTCH3 suppressed EMT and sensitized cells to chemotherapy. Results of chromatin immunoprecipitation assays suggested that NOTCH3 may repress transcription of the VIM.

CONCLUSIONS

Our findings suggest that NOTCH3 may control chemotherapy sensitivity by regulating EMT. NOTCH3 may serve as a novel biomarker to predict better clinical outcomes in ESCC patients.

Generation and Characterization of Patient-Derived Head and Neck, Oral, and Esophageal Cancer Organoids

Esophageal cancers comprise adenocarcinoma and squamous cell carcinoma, two distinct histologic subtypes. Both are difficult to treat and among the deadliest human malignancies. We describe protocols to initiate, grow, passage, and characterize patient-derived organoids (PDO) of esophageal cancers, as well as squamous cell carcinomas of oral/head-and-neck and anal origin. Formed rapidly (<14 days) from a single-cell suspension embedded in basement membrane matrix, esophageal cancer PDO recapitulate the histology of the original tumors. Additionally, we provide guidelines for morphological analyses and drug testing coupled with functional assessment of cell response to conventional chemotherapeutics and other pharmacological agents in concert with emerging automated imaging platforms. Predicting drug sensitivity and potential therapy resistance mechanisms in a moderate-to-high throughput manner, esophageal cancer PDO are highly translatable in personalized medicine for customized esophageal cancer treatments. © 2020 by John Wiley & Sons, Inc. Basic Protocol 1: Generation of esophageal cancer PDO Basic Protocol 2: Propagation and cryopreservation of esophageal cancer PDO Basic Protocol 3: Imaged-based monitoring of organoid size and growth kinetics Basic Protocol 4: Harvesting esophageal cancer PDO for histological analyses Basic Protocol 5: PDO content analysis by flow cytometry Basic Protocol 6: Evaluation of drug response with determination of the half-inhibitory concentration (IC₅₀ ) Support Protocol: Production of RN in HEK293T cell conditioned medium.

Tenacissoside H Induces Autophagy and Radiosensitivity of Hepatocellular Carcinoma Cells by PI3K/Akt/mTOR Signaling Pathway

Tenacissoside H (TEH), which has anti-inflammatory and anti-tumor effects, is a major active ingredient extracted from the stem of Marsdenia tenacissima. However, the effect of TEH on hepatocellular carcinoma (HCC) as well as the underlying mechanisms are still indistinct. Presently, HCC cells (including Huh-7 and HepG2) were dealt with different concentrations of TEH. The proliferation and apoptosis of HCC cells were determined via Cell Counting Kit-8 (CCK8) assay and flow cytometry. In addition, Western blot was conducted to evaluate the expressions of autophagy—and apoptosis-related proteins. Tissue immunofluorescence was carried out to evaluate LC3B expression in the tumor tissues. The data showed that TEH suppressed the growth of HCC cells in a concentration-dependent manner. Besides, TEH enhanced radiosensitivity and promoted the apoptosis of HCC cells. Moreover, the mRNA and protein levels of autophagy-related genes (LC3-II/LC2-I, ATG5, Beclin-1) were significantly promoted by TEH. Mechanistically, TEH attenuated the activation of PI3K/Akt/mTOR signaling pathway. However, inhibition of PI3 K pathway abolished the anti-tumor effects of TEH in HCC cells. Collectively, this study suggested that TEH increases the radiosensitivity of HCC cells via inducing autophagy and apoptosis through downregulating PI3K/Akt/mTOR signaling pathway.

Mitochondrial dynamics in cancer stem cells

Many tumors are now understood to be heterogenous cell populations arising from a minority of epithelial-like cancer stem cells (CSCs). CSCs demonstrate distinctive metabolic signatures from the more differentiated surrounding tumor bulk that confer resistance to traditional chemotherapeutic regimens and potential for tumor relapse. Many CSC phenotypes including metabolism, epithelial-to-mesenchymal transition, cellular signaling pathway activity, and others, arise from altered mitochondrial function and turnover, which are regulated by constant cycles of mitochondrial fusion and fission. Further, recycling of mitochondria through mitophagy in CSCs is associated with maintenance of reactive oxygen species levels that dictate gene expression. The protein machinery that drives mitochondrial dynamics is surprisingly simple and may represent attractive new therapeutic avenues to target CSC metabolism and selectively eradicate tumor-generating cells to reduce the risks of metastasis and relapse for a variety of tumor types.

Parkin: A targetable linchpin in human malignancies

Parkin, an E3 ubiquitin ligase has been found to be deregulated in a variety of human cancers. Our current understanding is endowed with strong evidences that Parkin plays crucial role in the pathogenesis of cancer by controlling/interfering with major hallmarks of cancer delineated till today. Consistent with the idea of mitophagy, the existing studies imitates the tumor suppressive potential of Parkin, resolved by its capacity to regulate cell proliferation, cell migration, angiogenesis, apoptosis and overall cellular survival. Dysfunction of Parkin has resulted in the loss of ubiquitination of cell cycle components followed by their accumulation leading to genomic instability, perturbed cell cycle and eventually tumor progression. In this review, we provide an overview of current knowledge about the critical role of Parkin in cancer development and progression and have focussed on its therapeutic implications highlighting the diagnostic and prognostic value of Parkin as a biomarker. We earnestly hope that an in-depth knowledge of Parkin will provide a linchpin to target in various cancers that will open a new door of clinical applications and therapeutics.

IL-17B/IL-17RB signaling cascade contributes to self-renewal and tumorigenesis of cancer stem cells by regulating Beclin-1 ubiquitination

Cancer stem cells (CSCs) are characterized by robust self-renewal and tumorigenesis and are responsible for metastasis, drug resistance, and angiogenesis. However, the molecular mechanisms for the regulation of CSC homeostasis are incompletely understood. This study demonstrated that the interleukin-17 (IL-17)B/IL-17RB signaling cascade promotes the self-renewal and tumorigenesis of CSCs by inducing Beclin-1 ubiquitination. We found that IL-17RB expression was significantly upregulated in spheroid cells and Lgr5-positive cells from the same tumor tissues of patients with gastric cancer (GC), which was closely correlated with the degree of cancer cell differentiation. Recombinant IL-17B (rIL-17B) promoted the sphere-formation ability of CSCs in vitro and enhanced tumor growth and metastasis in vivo. Interestingly, IL-17B induced autophagosome formation and cleavage-mediated transformation of LC3 in CSCs and 293T cells. Furthermore, inhibition of autophagy activation by ATG7 knockdown reversed rIL-17B-induced self-renewal of GC cells. In addition, we showed that IL-17B also promoted K63-mediated ubiquitination of Beclin-1 by mediating the binding of tumor necrosis factor receptor-associated factor 6 to Beclin-1. Silencing IL-17RB expression abrogated the effects of IL-17B on Beclin-1 ubiquitination and autophagy activation in GC cells. Finally, we showed that IL-17B level in the serum of GC patients was positively correlated with IL-17RB expression in GC tissues, and IL-17B could induce IL-17RB expression in GC cells. Overall, the results elucidate the novel functions of IL-17B for CSCs and suggest that the intervention of the IL-17B/IL-17RB signaling pathway may provide new therapeutic targets for the treatment of cancer.

PRKAA/AMPKα phosphorylation switches the role of RASAL2 from a suppressor to an activator of autophagy

RASAL2 (RAS protein activator like 2), a RASGTPase activating protein, can catalyze the hydrolysis of RAS-GTP into RAS-GDP to inactivate the RAS pathway in various types of cancer cells. However, the cellular function of RASAL2 remains elusive. Here we showed that RASAL2 can attenuate PRKAA/AMPKα phosphorylation by recruiting phosphatase PPM1B/pp2cβ, thus inhibiting the initiation of basal autophagy under normal conditions. In addition, we found that glucose starvation could induce dissociation of PPM1B from RASAL2 and then RASAL2 at S351 be phosphorylated by PRKAA, followed by the binding of phosphorylated-RASAL2 with to PIK3C3/VPS34-ATG14-BECN1/Beclin1 complex to increase PIK3C3 activity and autophagy. Furthermore, RASAL2 S351 phosphorylation facilitated breast tumor growth and correlated to poor clinical outcomes in breast cancer patients. Our study demonstrated that the phosphorylation status of RASAL2 S351 can function as a molecular switch to either suppress or promote AMPK-mediated autophagy. Inhibition of RASAL2 S351 phosphorylation might be a potential therapeutic strategy to overcome the resistance of AMPK-activation agents.

Dysregulation of mitophagy and mitochondrial homeostasis in cancer stem cells: Novel mechanism for anti-cancer stem cell-targeted cancer therapy

Despite the potential of cancer medicine, cancer stem cells (CSCs) associated with chemoresistance and disease recurrence are the significant challenges currently opposing the efficacy of available cancer treatment options. Mitochondrial dynamics involving the fission-fusion cycle and mitophagy are the major contributing factors to better adaptation, enabling CSCs to survive and grow better under tumour micro-environment-associated stress. Moreover, mitophagy is balanced with mitochondrial biogenesis to maintain mitochondrial homeostasis in CSCs, which are necessary for the growth and maintenance of CSCs and regulate metabolic switching from glycolysis to oxidative phosphorylation. In this review, we discuss different aspects of mitochondrial dynamics, mitophagy, and mitochondrial homeostasis and their effects on modulating CSCs behaviour during cancer development. Moreover, the efficacy of pharmacological targeting of these cellular processes using anti-CSC drugs in combination with currently available chemotherapeutic drugs improves the patient's survival of aggressive cancer types.

Sirtuins' control of autophagy and mitophagy in cancer

Mammalian cells use a specialized and complex machinery for the removal of altered proteins or dysfunctional organelles. Such machinery is part of a mechanism called autophagy. Moreover, when autophagy is specifically employed for the removal of dysfunctional mitochondria, it is called mitophagy. Autophagy and mitophagy have important physiological implications and roles associated with cellular differentiation, resistance to stresses such as starvation, metabolic control and adaptation to the changing microenvironment. Unfortunately, transformed cancer cells often exploit autophagy and mitophagy for sustaining their metabolic reprogramming and growth to a point that autophagy and mitophagy are recognized as promising targets for ongoing and future antitumoral therapies. Sirtuins are NAD+ dependent deacylases with a fundamental role in sensing and modulating cellular response to external stresses such as nutrients availability and therefore involved in aging, oxidative stress control, inflammation, differentiation and cancer. It is clear, therefore, that autophagy, mitophagy and sirtuins share many common aspects to a point that, recently, sirtuins have been linked to the control of autophagy and mitophagy. In the context of cancer, such a control is obtained by modulating transcription of autophagy and mitophagy genes, by post translational modification of proteins belonging to the autophagy and mitophagy machinery, by controlling ROS production or major metabolic pathways such as Krebs cycle or glutamine metabolism. The present review details current knowledge on the role of sirtuins, autophagy and mitophagy in cancer to then proceed to discuss how sirtuins can control autophagy and mitophagy in cancer cells. Finally, we discuss sirtuins role in the context of tumor progression and metastasis indicating glutamine metabolism as an example of how a concerted activation and/or inhibition of sirtuins in cancer cells can control autophagy and mitophagy by impinging on the metabolism of this fundamental amino acid.

Mitochondrial rewiring through mitophagy and mitochondrial biogenesis in cancer stem cells: A potential target for anti-CSC cancer therapy

Cancer stem cells (CSCs) are distinct subpopulations of cancer cells with stem cell-like abilities and are more resilient to chemotherapy, causing tumor relapse. Mitophagy, a selective form of autophagy, removes damaged unwanted mitochondria from cells through a lysosome-based degradation pathway to maintain cellular homeostasis. CSCs use mitophagy as a chief survival response mechanism for their growth, propagation, and tumorigenic ability. Mitochondrial biogenesis is a crucial cellular event replacing damaged mitochondria through the coordinated regulation of several transcription factors to achieve the bioenergetic demands of the cell. Because of the high mitochondrial content in CSCs, mitochondrial biogenesis is an interesting target to address the resistance mechanisms of anti-CSC therapy. However, to what extent both mitophagy and mitochondrial biogenesis are vital in promoting stemness, metabolic reprogramming, and drug resistance in CSCs has yet to be established. Therefore, in this review, we focus on understanding the interesting aspects of mitochondrial rewiring that involve mitophagy and mitochondrial biogenesis in CSCs. We also discuss their coordinated regulation in the elimination of CSCs, with respect to stemness and differentiation of the CSC phenotype, and the different aspects of tumorigenesis such as cancer initiation, progression, resistance, and tumor relapse. Finally, we address several other unanswered questions relating to targeted anti-CSC cancer therapy, which improves patient survival.

Autophagy mitigates ethanol-induced mitochondrial dysfunction and oxidative stress in esophageal keratinocytes

During alcohol consumption, the esophageal mucosa is directly exposed to high concentrations of ethanol (EtOH). We therefore investigated the response of normal human esophageal epithelial cell lines EPC1, EPC2 and EPC3 to acute EtOH exposure. While these cells were able to tolerate 2% EtOH for 8 h in both three-dimensional organoids and monolayer culture conditions, RNA sequencing suggested that EtOH induced mitochondrial dysfunction. With EtOH treatment, EPC1 and EPC2 cells also demonstrated decreased mitochondrial ATPB protein expression by immunofluorescence and swollen mitochondria lacking intact cristae by transmission electron microscopy. Mitochondrial membrane potential (ΔΨm) was decreased in a subset of EPC1 and EPC2 cells stained with ΔΨm–sensitive dye MitoTracker Deep Red. In EPC2, EtOH decreased ATP level while impairing mitochondrial respiration and electron transportation chain functions, as determined by ATP fluorometric assay, respirometry, and liquid chromatography-mass spectrometry. Additionally, EPC2 cells demonstrated enhanced oxidative stress by flow cytometry for mitochondrial superoxide (MitoSOX), which was antagonized by the mitochondria-specific antioxidant MitoCP. Concurrently, EPC1 and EPC2 cells underwent autophagy following EtOH exposure, as evidenced by flow cytometry for Cyto-ID, which detects autophagic vesicles, and immunoblots demonstrating induction of the lipidated and cleaved form of LC3B and downregulation of SQSTM1/p62. In EPC1 and EPC2, pharmacological inhibition of autophagy flux by chloroquine increased mitochondrial oxidative stress while decreasing cell viability. In EPC2, autophagy induction was coupled with phosphorylation of AMP activated protein kinase (AMPK), a cellular energy sensor responding to low ATP levels, and dephosphorylation of downstream substrates of mechanistic Target of Rapamycin Complex (mTORC)-1 signaling. Pharmacological AMPK activation by AICAR decreased EtOH-induced reduction of ΔΨm and ATP in EPC2. Taken together, acute EtOH exposure leads to mitochondrial dysfunction and oxidative stress in esophageal keratinocytes, where the AMPK-mTORC1 axis may serve as a regulatory mechanism to activate autophagy to provide cytoprotection against EtOH-induced cell injury.

Molecular modulation of autophagy: New venture to target resistant cancer stem cells

Autophagy is a highly regulated catabolic process in which superfluous, damaged organelles and other cytoplasmic constituents are delivered to the lysosome for clearance and the generation of macromolecule substrates during basal or stressed conditions. Autophagy is a bimodal process with a context dependent role in the initiation and the development of cancers. For instance, autophagy provides an adaptive response to cancer stem cells to survive metabolic stresses, by influencing disease propagation via modulation of essential signaling pathways or by promoting resistance to chemotherapeutics. Autophagy has been implicated in a cross talk with apoptosis. Understanding the complex interactions provides an opportunity to improve cancer therapy and the clinical outcome for the cancer patients. In this review, we provide a comprehensive view on the current knowledge on autophagy and its role in cancer cells with a particular focus on cancer stem cell homeostasis.

Starvation-induced suppression of DAZAP1 by miR-10b integrates splicing control into TSC2-regulated oncogenic autophagy in esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC) accounts for about 90% of all incident esophageal cancers, with a 5-year survival rate of < 20%. Autophagy is of particular importance in cancers; however, the detailed regulatory mechanisms of oncogenic autophagy in ESCC have not been fully elucidated. In the present study, we address how splicing control of TSC2 is involved in mTOR-regulated oncogenic autophagy. Methods: Alternative splicing events controlled by DAZAP1 in ESCC cells were identified via RNAseq. Differential phosphorylation of short or long TSC2 splicing variants by AKT and their impacts on mTOR signaling were also examined. Results: We found that starvation-induced miR-10b could enhance autophagy via silencing DAZAP1, a key regulator of pre-mRNA alternative splicing. Intriguingly, we observed a large number of significantly changed alternative splicing events, especially exon skipping, upon RNAi of DAZAP1. TSC2 was verified as one of the crucial target genes of DAZAP1. Silencing of DAZAP1 led to the exclusion of TSC2 exon 26 (from Leu947 to Arg988), producing a short TSC2 isoform. The short TSC2 isoform cannot be phosphorylated at Ser981 by AKT, which resulted in continuous activation of TSC2 in ESCC. The active TSC2 inhibited mTOR via RHEB, leading to continually stimulated oncogenic autophagy of ESCC cells. Conclusions: Our data revealed an important physiological function of tumor suppressor DAZAP1 in autophagy regulation and highlighted the potential of controlling mRNA alternative splicing as an effective therapeutic application for cancers.

Mitophagy and Mitochondrial Dysfunction in Cancer

The process of mitophagy, in which mitochondria are selectively turned over at the autophagolysosome, plays a central role in both eliminating dysfunctional mitochondria and reducing mitochondrial mass as an adaptive response to key physiological stresses, such as hypoxia, nutrient deprivation, and DNA damage. Defects in mitophagy have been linked to altered mitochondrial metabolism, production of excess reactive oxygen species and ferroptosis, heightened inflammasome activation, altered cell fate decisions, and senescence, among other cellular consequences. Consequently, functional mitophagy contributes to proper tissue differentiation and repair and metabolic homeostasis, limiting inflammatory responses and modulating tumor progression and metastasis. This review examines the major pathways that control mitophagy, including PINK1-dependent mitophagy and BNIP3/NIX-dependent mitophagy. It also discusses the cellular signaling mechanisms used to sense mitochondrial dysfunction to activate mitophagy and how defective mitophagy results in deregulated tumor cell growth and cancer.

Roles for Autophagy in Esophageal Carcinogenesis: Implications for Improving Patient Outcomes

Esophageal cancer is among the most aggressive forms of human malignancy with five-year survival rates of <20%. Autophagy is an evolutionarily conserved catabolic process that degrades and recycles damaged organelles and misfolded proteins to maintain cellular homeostasis. While alterations in autophagy have been associated with carcinogenesis across tissues, cell type- and context-dependent roles for autophagy have been reported. Herein, we review the current knowledge related to autophagy in esophageal squamous cell carcinoma (ESCC) and esophageal adenocarcinoma (EAC), the two most common subtypes of esophageal malignancy. We explore roles for autophagy in the development and progression of ESCC and EAC. We then continue to discuss molecular markers of autophagy as they relate to esophageal patient outcomes. Finally, we summarize current literature examining roles for autophagy in ESCC and EAC response to therapy and discuss considerations for the potential use of autophagy inhibitors as experimental therapeutics that may improve patient outcomes in esophageal cancer.

Autophagy inhibition elicits emergence from metastatic dormancy by inducing and stabilizing Pfkfb3 expression

Breast cancer stem cells (BCSCs) are unique in their ability to undergo unlimited self-renewal, an essential process in breast cancer recurrence following metastatic dormancy. Emergent metastatic lesions were subjected to microarray analysis, which identified 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 3 (Pfkfb3) as a differentially expressed gene coupled to metastatic recurrence. Here, we report that elevated Pfkfb3 expression correlates with the appearance of aggressive breast cancers and reduces relapse-free survival, as well as enhances BCSC self-renewal and metastatic outgrowth. We observe an inverse relationship between Pfkfb3 expression and autophagy, which reduces Pfkfb3 expression and elicits cellular dormancy. Targeted depletion of Atg3, Atg7, or p62/sequestosome-1 to inactivate autophagy restores aberrant Pfkfb3 expression in dormant BCSCs, leading to their reactivation of proliferative programs and outgrowth. Moreover, Pfkfb3 interacts physically with autophagy machinery, specifically the UBA domain of p62/sequestosome-1. Importantly, disrupting autophagy and this event enables Pfkfb3 to drive dormant BCSCs and metastatic lesions to recur.

Targeting cancer stem cells in drug discovery: Current state and future perspectives

In recent decades, cancer stem cells (CSCs) have been increasingly identified in many malignancies. CSC-related signaling pathways and their functions provide new strategies for treating cancer. The aberrant activation of related signaling pathways (e.g., Wnt, Notch, and Hedgehog pathways) has been linked to multiple types of malignant tumors, which makes these pathways attractive targets for cancer therapy. CSCs display many characteristic features, such as self-renewal, differentiation, high tumorigenicity, and drug resistance. Therefore, there is an urgent need to develop new therapeutic strategies to target these pathways to control stem cell replication, survival, and differentiation. Notable crosstalk occurs among different signaling pathways and potentially leads to compensatory escape. Therefore, multitarget inhibitors will be one of the main methods to overcome the drug resistance of CSCs. Many small molecule inhibitors of components of signaling pathways in CSCs have entered clinical trials, and some inhibitors, such as vismodegib, sonidegib, and glasdegib, have been approved. Tumor cells are susceptible to sonidegib and vismodegib resistance due to mutations in the Smo protein. The signal transducers and activators of transcription 3 (STAT3) inhibitor BBI608 is being evaluated in a phase III trial for a variety of cancers. Structural derivatives of BBI608 are the main focus of STAT3 inhibitor development, which is another strategy for CSC therapy. In addition to the potential pharmacological inhibitors targeting CSC-related signaling pathways, other methods of targeting CSCs are available, such as nano-drug delivery systems, mitochondrion targeting, autophagy, hyperthermia, immunotherapy, and CSC microenvironment targeting. In addition, we summarize the latest advances in the clinical development of agents targeting CSC-related signaling pathways and other methods of targeting CSCs.

The emerging, multifaceted role of mitophagy in cancer and cancer therapeutics

Mitophagy is an evolutionarily conserved cellular process which selectively eliminates dysfunctional mitochondria by targeting them to the autophagosome for degradation. Dysregulated mitophagy results in the accumulation of damaged mitochondria, which plays an important role in carcinogenesis and tumor progression. The role of mitophagy receptors and adaptors including PINK1, Parkin, BNIP3, BNIP3L/NIX, and p62/SQSTM1, and the signaling pathways that govern mitophagy are impaired in cancer. Furthermore, the contribution of mitophagy in regulating the metabolic switch may establish a balance between aerobic glycolysis and oxidative phosphorylation for cancer cell survival. Moreover, ROS-driven mitophagy achieves different goals depending on the stage of tumorigenesis. Mitophagy promotes plasticity in the cancer stem cell through the metabolic reconfiguration for better adaption to the tumor microenvironment. In addition, the present review sheds some light on the role of mitophagy in stemness and differentiation during the transition of cell's fate, which could have a crucial role in cancer progression and metastasis. In conclusion, this review deals with the detailed molecular mechanisms underlying mitophagy, along with highlighting the dual role of mitophagy in different aspects of cancer, suggesting it as a possible target in the mitophagy-modulated cancer therapy.

Fibrostenotic eosinophilic esophagitis might reflect epithelial lysyl oxidase induction by fibroblast-derived TNF-α

BACKGROUND

Fibrosis and stricture are major comorbidities in patients with eosinophilic esophagitis (EoE). Lysyl oxidase (LOX), a collagen cross-linking enzyme, has not been investigated in the context of EoE.

OBJECTIVE

We investigated regulation of epithelial LOX expression as a novel biomarker and functional effector of fibrostenotic disease conditions associated with EoE.

METHODS

LOX expression was analyzed by using RNA-sequencing, PCR assays, and immunostaining in patients with EoE; cytokine-stimulated esophageal 3-dimensional organoids; and fibroblast-epithelial cell coculture, the latter coupled with fluorescence-activated cell sorting.

RESULTS

Gene ontology and pathway analyses linked TNF-α and LOX expression in patients with EoE, which was validated in independent sets of patients with fibrostenotic conditions. TNF-α-mediated epithelial LOX upregulation was recapitulated in 3-dimensional organoids and coculture experiments. We find that fibroblast-derived TNF-α stimulates epithelial LOX expression through activation of nuclear factor κB and TGF-β-mediated signaling. In patients receiver operating characteristic analyses suggested that LOX upregulation indicates disease complications and fibrostenotic conditions in patients with EoE.

CONCLUSIONS

There is a novel positive feedback mechanism in epithelial LOX induction through fibroblast-derived TNF-α secretion. Esophageal epithelial LOX might have a role in the development of fibrosis with substantial translational implications.

The Best for the Most Important: Maintaining a Pristine Proteome in Stem and Progenitor Cells

Pluripotent stem cells give rise to reproductively enabled offsprings by generating progressively lineage-restricted multipotent stem cells that would differentiate into lineage-committed stem and progenitor cells. These lineage-committed stem and progenitor cells give rise to all adult tissues and organs. Adult stem and progenitor cells are generated as part of the developmental program and play critical roles in tissue and organ maintenance and/or regeneration. The ability of pluripotent stem cells to self-renew, maintain pluripotency, and differentiate into a multicellular organism is highly dependent on sensing and integrating extracellular and extraorganismal cues. Proteins perform and integrate almost all cellular functions including signal transduction, regulation of gene expression, metabolism, and cell division and death. Therefore, maintenance of an appropriate mix of correctly folded proteins, a pristine proteome, is essential for proper stem cell function. The stem cells' proteome must be pristine because unfolded, misfolded, or otherwise damaged proteins would interfere with unlimited self-renewal, maintenance of pluripotency, differentiation into downstream lineages, and consequently with the development of properly functioning tissue and organs. Understanding how various stem cells generate and maintain a pristine proteome is therefore essential for exploiting their potential in regenerative medicine and possibly for the discovery of novel approaches for maintaining, propagating, and differentiating pluripotent, multipotent, and adult stem cells as well as induced pluripotent stem cells. In this review, we will summarize cellular networks used by various stem cells for generation and maintenance of a pristine proteome. We will also explore the coordination of these networks with one another and their integration with the gene regulatory and signaling networks.