Manganese superoxide dismutase promotes anoikis resistance and tumor metastasis. Cell Death Dis. 2013;4:e504. [PMID: 23429290 PMCID: PMC3734828 DOI: 10.1038/cddis.2013.20]

Cancer metastasis: molecular mechanisms and therapeutic interventions

The metastatic cascade is a complicated process where cancer cells travel across multiple organs distant from their primary site of onset. Despite the wide acceptance of the 'seed and soil' theory, mechanisms driving metastasis organotropism remain mystery. Using breast cancer of different subtypes as the disease model, we characterized the 'metastatic profile of cancer cells' and the 'redox status of the organ microenvironment' as the primary determinants of cancer metastasis organotropism. Mechanically, we identified a positive correlation between cancer metabolic plasticity and stemness, and proposed oxidative stress as the selection power of cancer cells succeeding the metastasis cascade. Therapeutically, we proposed the use of pro-oxidative therapeutics in ablating cancer cells taking advantages of this fragile moment during metastasis. We comprehensively reviewed current pro-oxidative strategies for treating cancers that cover the first line chemo- and radio-therapies, approaches relying on naturally existing power including magnetic field, electric field, light and sound, nanoparticle-based anti-cancer composites obtained through artificial design, as well as cold atmospheric plasma as an innovative pro-oxidative multi-modal modality. We discussed possible combinations of pro-oxidative approaches with existing therapeutics in oncology prior to the forecast of future research directions. This paper identified the fundamental mechanics driving metastasis organotropism and proposed intervention strategies accordingly. Insights provided here may offer clues for the design of innovative solutions that may open a new paradigm for cancer treatment.

Lipid dysregulation in triple negative breast cancer: Insights from mass spectrometry-based approaches

Triple negative breast cancer (TNBC) has the worst prognosis among breast cancers due to its aggressive nature and the absence of targeted treatments. Development of novel anti-cancer drugs for TNBC faces challenges stemming from its heterogeneity and high potential for metastasis. Metabolomics can be a useful technology in finding novel therapeutic targets and probing the heterogeneity of TNBC. Metabolomics has been enabled by advancements in mass spectrometry (MS)-based platforms that facilitated comprehensive profiling of TNBC metabolism. This review provides an overview of metabolomic changes in TNBC with emphasis on lipid alterations, and describes the key MS analytical techniques, providing the necessary background for examining the role of lipids in TNBC development.

Upregulated FSP1 by GPD1/1L mediated lipid droplet accumulation enhances ferroptosis resistance and peritoneal metastasis in gastric cancer

To successfully metastasize, cancer cells must evade detachment induced cell death, known as anoikis. Unraveling the mechanisms that gastric cancer (GC) circumvent anoikis and achieve peritoneal metastasis especially during unanchored growth, could significantly improve patient outcomes. Our study reveals that GC cells exhibit increased lipid peroxidation, MDA production, and cell death during suspension culture, which can be mitigated by the intervention with liproxstatin-1 and ferrostatin-1. We discovered that oleic acid (OA) or adipocytes stimulate lipid accumulation in GC cells, thereby inhibiting lipid peroxidation and cell death. Lipid mass spectrometry confirmed an upregulation of triglyceride synthesis, indicating that the accumulation of lipid droplet may confer resistance to ferroptosis during suspension growth. In vitro assays demonstrated that OA not only induces lipid droplet accumulation but also upregulates the expression of ferroptosis suppressor protein 1 (FSP1), a process that can be abrogated by the double knockout of GPD1/1L genes. Additionally, we have demonstrated that a decrease in the ubiquitination of FSP1 in GC cells upon lipid droplet accumulation, as well as silencing or pharmacological targeting FSP1, promotes ferroptosis and disrupts the peritoneal metastatic potential of GC cells. Collectively, our findings highlight the potential of FSP1 as a promising therapeutic target for metastatic gastric cancer.

6-Gingerol Induced Apoptosis and Cell Cycle Arrest in Glioma Cells via MnSOD and ERK Phosphorylation Modulation

6-gingerol, a bioactive compound from ginger, has demonstrated promising anticancer properties across various cancer models by inducing apoptosis and inhibiting cell proliferation and invasion. In this study, we explore its mechanisms against glioblastoma multiforme (GBM), a notably aggressive and treatment-resistant brain tumor. We found that 6-gingerol crosses the blood-brain barrier more effectively than curcumin, enhancing its potential as a therapeutic agent for brain tumors. Our experiments show that 6-gingerol reduces cell proliferation and triggers apoptosis in GBM cell lines by disrupting cellular energy homeostasis. This process involves an increase in mitochondrial reactive oxygen species (mtROS) and a decrease in mitochondrial membrane potential, primarily due to the downregulation of manganese superoxide dismutase (MnSOD). Additionally, 6-gingerol reduces ERK phosphorylation by inhibiting EGFR and RAF, leading to G1 phase cell cycle arrest. These findings indicate that 6-gingerol promotes cell death in GBM cells by modulating MnSOD and ROS levels and arresting the cell cycle through the ERFR-RAF-1/MEK/ERK signaling pathway, highlighting its potential as a therapeutic agent for GBM and setting the stage for future clinical research.

GRP94 promotes anoikis resistance and peritoneal metastasis through YAP/TEAD1 pathway in gastric cancer

Anoikis resistance allows cancer cells to avoid death caused by detachment from the extracellular matrix's adhesion, enabling these cells to infiltrate and migrate to regions such as the peritoneum. This study emphasizes GRP94's involvement in anoikis resistance and peritoneal metastasis in gastric cancer (GC). It's found that GRP94 overexpression, linked to poor prognosis, was potentially due to SP1 and GRP94 promoter interactions, confirmed through dual luciferase reporter (DLR), chromatin immunoprecipitation (ChIP), and quantitative real-time PCR (real-time qPCR). Increased GRP94 enhanced GC cells' anoikis resistance and metastasis. Decreasing GRP94 had opposite effects, potentially through yes-associated protein (YAP)/TEAD1 axis inhibition, with raised YAP phosphorylation and decreased TEAD1 levels detected by western blotting (WB). Inhibiting YAP counteracted GRP94's effects on anoikis resistance and metastasis, while activating YAP reversed the effects of GRP94 reduction. Animal experiments verified GRP94's contribution to GC's peritoneal metastasis. In conclusion, our work highlights the effect of GRP94 on anoikis resistance, showing potential value in treating peritoneal metastasis of GC.

Targeting anoikis resistance as a strategy for cancer therapy

Anoikis, known as matrix detachment-induced apoptosis or detachment-induced cell death, is crucial for tissue development and homeostasis. Cancer cells develop means to evade anoikis, e.g. anoikis resistance, thereby allowing for cells to survive under anchorage-independent conditions. Uncovering the mechanisms of anoikis resistance will provide details about cancer metastasis, and potential strategies against cancer cell dissemination and metastasis. Here, we summarize the principal elements and core molecular mechanisms of anoikis and anoikis resistance. We discuss the latest progress of how anoikis and anoikis resistance are regulated in cancers. Furthermore, we summarize emerging data on selective compounds and nanomedicines, explaining how inhibiting anoikis resistance can serve as a meaningful treatment modality against cancers. Finally, we discuss the key limitations of this therapeutic paradigm and possible strategies to overcome them. In this review, we suggest that pharmacological modulation of anoikis and anoikis resistance by bioactive compounds could surmount anoikis resistance, highlighting a promising therapeutic regimen that could be used to overcome anoikis resistance in cancers.

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.

Synergistic effects of photodynamic therapy and chemotherapy: Activating the intrinsic/extrinsic apoptotic pathway of anoikis for triple-negative breast cancer treatment

Triple-negative breast cancer (TNBC) is a highly invasive and metastatic subtype of breast cancer that often recurs after surgery. Herein, we developed a cyclodextrin-based tumor-targeted nano delivery system that incorporated the photosensitizer chlorin e6 (Ce6) and the chemotherapeutic agent lonidamine (LND) to form the R6RGD-CMβCD-se-se-Ce6/LND nanoparticles (RCC/LND NPS). This nanosystem could target cancer cells, avoid lysosomal degradation and further localize within the mitochondria. The RCC/LND NPS had pH and redox-responsive to control the release of Ce6 and LND. Consequently, the nanosystem had a synergistic effect by effectively alleviating hypoxia, enhancing the production of cytotoxic reactive oxygen species (ROS) and amplifying the efficacy of photodynamic therapy (PDT). Furthermore, the RCC/LND NPS + light weakened anoikis resistance, disrupted extracellular matrix (ECM), activated both the intrinsic apoptotic pathway (mitochondrial pathway) and extrinsic apoptotic pathway (receptor death pathway) of anoikis. In addition, the nanosystem showed significant anti-TNBC efficacy in vivo. These findings collectively demonstrated that RCC/LND NPS + light enhanced the anticancer effects, induced anoikis and inhibited tumor cell migration and invasion through a synergistic effect of chemotherapy and PDT. Overall, this study highlighted the promising potential of the RCC/LND NPS + light for the treatment of TNBC.

Dose-Dependent Effect of Mitochondrial Superoxide Dismutase Gene Overexpression on Radioresistance of HEK293T Cells

Over the last two decades, a multitude of gain-of-function studies have been conducted on genes that encode antioxidative enzymes, including one of the key enzymes, manganese superoxide dismutase (SOD2). The results of such studies are often contradictory, as they strongly depend on many factors, such as the gene overexpression level. In this study, the effect of altering the ectopic expression level of major transcript variants of the SOD2 gene on the radioresistance of HEK293T cells was investigated using CRISPRa technology. A significant increase in cell viability in comparison with the transfection control was detected in cells with moderate SOD2 overexpression after irradiation at 2 Gy, but not at 3 or 5 Gy. A further increase in the level of SOD2 ectopic expression up to 22.5-fold resulted in increased cell viability detectable only after irradiation at 5 Gy. Furthermore, a 15-20-fold increase in SOD2 expression raised the clonogenic survival of cells after irradiation at 5 Gy. Simultaneous overexpression of genes encoding SOD2 and Catalase (CAT) enhanced clonogenic cell survival after irradiation more effectively than separate overexpression of both. In conjunction with the literature data on the suppression of the procarcinogenic effects of superoxide dismutase overexpression by ectopic expression of CAT, the data presented here suggest the potential efficacy of simultaneous overexpression of SOD2 and CAT to reduce oxidative stress occurring in various pathological processes. Moreover, these results illustrate the importance of selecting the degree of SOD2 overexpression to obtain a protective effect.

Anoikis resistance and immune escape mediated by Epstein-Barr virus-encoded latent membrane protein 1-induced stabilization of PGC-1α promotes invasion and metastasis of nasopharyngeal carcinoma

BACKGROUND

Epstein-Barr virus (EBV) is the first discovered human tumor virus that is associated with a variety of malignancies of both lymphoid and epithelial origin including nasopharyngeal carcinoma (NPC). The EBV-encoded latent membrane protein 1 (LMP1) has been well-defined as a potent oncogenic protein, which is intimately correlated with NPC pathogenesis. Anoikis is considered to be a physiological barrier to metastasis, and avoiding anoikis is a major hallmark of metastasis. However, the role of LMP1 in anoikis-resistance and metastasis of NPC has not been fully identified.

METHODS

Trypan blue staining, colony formation assay, flow cytometry, and TUNEL staining, as well as the detection of apoptosis and anoikis resistance-related markers was applied to evaluate the anoikis-resistant capability of NPC cells cultured in ultra-low adhesion condition. Co-immunoprecipitation (Co-IP) experiment was performed to determine the interaction among LMP1, PRMT1 and PGC-1α. Ex vivo ubiquitination assay was used to detect the ubiquitination level of PGC-1α. Anoikis- resistant LMP1-positive NPC cell lines were established and applied for the xenograft and metastatic animal experiments.

RESULTS

Our current findings reveal the role of LMP1-stabilized peroxisome proliferator activated receptor coactivator-1a (PGC-1α) in anoikis resistance and immune escape to support the invasion and metastasis of NPC. Mechanistically, LMP1 enhances PGC-1α protein stability by promoting the interaction between arginine methyltransferase 1 (PRMT1) and PGC-1α to elevate the methylation modification of PGC-1α, thus endowing NPC cells with anoikis-resistance. Meanwhile, PGC-1α mediates the immune escape induced by LMP1 by coactivating with STAT3 to transcriptionally up-regulate PD-L1 expression.

CONCLUSION

Our work provides insights into how virus-encoded proteins recruit and interact with host regulatory elements to facilitate the malignant progression of NPC. Therefore, targeting PGC-1α or PRMT1-PGC-1α interaction might be exploited for therapeutic gain for EBV-associated malignancies.

Anoikis resistance--protagonists of breast cancer cells survive and metastasize after ECM detachment

Breast cancer exhibits the highest global incidence among all tumor types. Regardless of the type of breast cancer, metastasis is a crucial cause of poor prognosis. Anoikis, a form of apoptosis initiated by cell detachment from the native environment, is an outside-in process commencing with the disruption of cytosolic connectors such as integrin-ECM and cadherin-cell. This disruption subsequently leads to intracellular cytoskeletal and signaling pathway alterations, ultimately activating caspases and initiating programmed cell death. Development of an anoikis-resistant phenotype is a critical initial step in tumor metastasis. Breast cancer employs a series of stromal alterations to suppress anoikis in cancer cells. Comprehensive investigation of anoikis resistance mechanisms can inform strategies for preventing and regressing metastatic breast cancer. The present review first outlines the physiological mechanisms of anoikis, elucidating the alterations in signaling pathways, cytoskeleton, and protein targets that transpire from the outside in upon adhesion loss in normal breast cells. The specific anoikis resistance mechanisms induced by pathological changes in various spatial structures during breast cancer development are also discussed. Additionally, the genetic loci of targets altered in the development of anoikis resistance in breast cancer, are summarized. Finally, the micro-RNAs and targeted drugs reported in the literature concerning anoikis are compiled, with keratocin being the most functionally comprehensive. Video Abstract.

Expression Changes of SIRT1 and FOXO3a Significantly Correlate with Oxidative Stress Resistance Genes in AML Patients

The increased metabolism in acute myeloid leukemia (AML) malignant cells resulted in the production of high levels of free radicals, called oxidative stress conditions. To avoid this situation, malignant cells produce a considerable amount of antioxidant agents, which will lead to the release of a continuous low level of reactive oxygen species (ROS), causing genomic damage and subsequent clonal evolution. SIRT1 has a key role in driving the adaptation to this condition, mainly through the deacetylation of FOXO3a that affects the expression of oxidative stress resistance target genes such as Catalase and Manganese superoxide dismutase (MnSOD). The aim of this study is to simultaneously investigate the expression of SIRT1, FOXO3a, and free radical-neutralizing enzymes such as Catalase and MnSOD in AML patients and measure their simultaneous change in relation to each other. The gene expression was analyzed using Real Time-PCR in 65 AML patients and 10 healthy controls. Our finding revealed that expression of SIRT1, FOXO3a, MnSOD and Catalase was significantly higher in AML patients in comparison to healthy controls. Also, there was a significant correlation between the expression of SIRT1 and FOXO3a, as well as among the expression of FOXO3a, MnSOD and Catalase genes in patients. According to the results, the expression of genes involved in oxidative stress resistance was higher in AML patients, which possibly contributed to the development of malignant clones. Also, the correlation between the expression of SIRT1 and FOXO3a gene reflects the importance of these two genes in increased oxidative stress resistance of cancer cells.

IGFBP1 Sustains Cell Survival during Spatially-Confined Migration and Promotes Tumor Metastasis

Cell migration is a pivotal step in metastatic process, which requires cancer cells to navigate a complex spatially-confined environment, including tracks within blood vessels and in the vasculature of target organs. Here it is shown that during spatially-confined migration, the expression of insulin-like growth factor-binding protein 1 (IGFBP1) is upregulated in tumor cells. Secreted IGFBP1 inhibits AKT1-mediated phosphorylation of mitochondrial superoxide dismutase (SOD2) serine (S) 27 and enhances SOD2 activity. Enhanced SOD2 attenuates mitochondrial reactive oxygen species (ROS) accumulation in confined cells, which supports tumor cell survival in blood vessels of lung tissues, thereby accelerating tumor metastasis in mice. The levels of blood IGFBP1 correlate with metastatic recurrence of lung cancer patients. This finding reveals a unique mechanism by which IGFBP1 sustains cell survival during confined migration by enhancing mitochondrial ROS detoxification, thereby promoting tumor metastasis.

Succinyl-CoA ligase ADP-forming subunit beta promotes stress granule assembly to regulate redox and drive cancer metastasis

Although recent studies demonstrate active mitochondrial metabolism in cancers, the precise mechanisms through which mitochondrial factors contribute to cancer metastasis remain elusive. Through a customized mitochondrion RNAi screen, we identified succinyl-CoA ligase ADP-forming subunit beta (SUCLA2) as a critical anoikis resistance and metastasis driver in human cancers. Mechanistically, SUCLA2, but not the alpha subunit of its enzyme complex, relocates from mitochondria to the cytosol upon cell detachment where SUCLA2 then binds to and promotes the formation of stress granules. SUCLA2-mediated stress granules facilitate the protein translation of antioxidant enzymes including catalase, which mitigates oxidative stress and renders cancer cells resistant to anoikis. We provide clinical evidence that SUCLA2 expression correlates with catalase levels as well as metastatic potential in lung and breast cancer patients. These findings not only implicate SUCLA2 as an anticancer target, but also provide insight into a unique, noncanonical function of SUCLA2 that cancer cells co-opt to metastasize.

The Metabolic Landscape of Breast Cancer and Its Therapeutic Implications

Breast cancer is the most common malignant tumor globally as of 2020 and remains the second leading cause of cancer-related death among female individuals worldwide. Metabolic reprogramming is well recognized as a hallmark of malignancy owing to the rewiring of multiple biological processes, notably, glycolysis, oxidative phosphorylation, pentose phosphate pathway, as well as lipid metabolism, which support the demands for the relentless growth of tumor cells and allows distant metastasis of cancer cells. Breast cancer cells are well documented to reprogram their metabolism via mutations or inactivation of intrinsic factors such as c-Myc, TP53, hypoxia-inducible factor, and the PI3K/AKT/mTOR pathway or crosstalk with the surrounding tumor microenvironments, including hypoxia, extracellular acidification and interaction with immune cells, cancer-associated fibroblasts, and adipocytes. Furthermore, altered metabolism contributes to acquired or inherent therapeutic resistance. Therefore, there is an urgent need to understand the metabolic plasticity underlying breast cancer progression as well as to dictate metabolic reprogramming that accounts for the resistance to standard of care. This review aims to illustrate the altered metabolism in breast cancer and its underlying mechanisms, as well as metabolic interventions in breast cancer treatment, with the intention to provide strategies for developing novel therapeutic treatments for breast cancer.

Involvement of redox signalling in tumour cell dormancy and metastasis

Decades of research on oncogene-driven carcinogenesis and gene-expression regulatory networks only started to unveil the complexity of tumour cellular and molecular biology. This knowledge has been successfully implemented in the clinical practice to treat primary tumours. In contrast, much less progress has been made in the development of new therapies against metastasis, which are the main cause of cancer-related deaths. More recently, the role of epigenetic and microenviromental factors has been shown to play a key role in tumour progression. Free radicals are known to communicate the intracellular and extracellular compartments, acting as second messengers and exerting a decisive modulatory effect on tumour cell signalling. Depending on the cellular and molecular context, as well as the intracellular concentration of free radicals and the activation status of the antioxidant system of the cell, the signalling equilibrium can be tilted either towards tumour cell survival and progression or cell death. In this regard, recent advances in tumour cell biology and metastasis indicate that redox signalling is at the base of many cell-intrinsic and microenvironmental mechanisms that control disseminated tumour cell fate and metastasis. In this manuscript, we will review the current knowledge about redox signalling along the different phases of the metastatic cascade, including tumour cell dormancy, making emphasis on metabolism and the establishment of supportive microenvironmental connections, from a redox perspective.

GPX3 expression was down-regulated but positively correlated with poor outcome in human cancers

Introduction

Cancer is a crucial public health problem and one of the leading causes of death worldwide. Previous studies have suggested that GPX3 may be involved in cancer metastasis and chemotherapy resistance. However, how GPX3 affects cancer patients' outcomes and the underlying mechanism remains unclear.

Methods

Sequencing data and clinical data from TCGA, GTEx, HPA, and CPTAC were used to explore the relationship between GPX3 expression and clinical features. Immunoinfiltration scores were used to assess the relationship between GPX3 and the tumor immune microenvironment. Functional enrichment analysis was used to predict the role of GPX3 in tumors. Gene mutation frequency, methylation level, and histone modification were used to predict the GPX3 expression regulation method. Breast, ovarian, colon, and gastric cancer cells were used to investigate the relationship between GPX3 expression and cancer cell metastasis, proliferation, and chemotherapy sensitivity.

Results

GPX3 is down-regulated in various tumor tissues, and GPX3 expression level can be used as a marker for cancer diagnosis. However, GPX3 expression is associated with higher stage and lymph node metastasis, as well as poorer prognosis. GPX3 is closely related to thyroid function and antioxidant function, and its expression may be regulated by epigenetic inheritance such as methylation modification or histone modification. In vitro experiments, GPX3 expression is associated with cancer cell sensitivity to oxidant and platinum-based chemotherapy and is involved in tumor metastasis in oxidative environments.

Discussion

We explored the relationship between GPX3 and clinical features, immune infiltration characteristics, migration and metastasis, and chemotherapy sensitivities of human cancers. We further investigated the potential genetic and epigenetic regulation of GPX3 in cancer. Our results suggested that GPX3 plays a complicated role in the tumor microenvironment, simultaneously promoting metastasis and chemotherapy resistance in human cancers.

Effects of Antioxidant Gene Overexpression on Stress Resistance and Malignization In Vitro and In Vivo: A Review

Reactive oxygen species (ROS) are normal products of a number of biochemical reactions and are important signaling molecules. However, at the same time, they are toxic to cells and have to be strictly regulated by their antioxidant systems. The etiology and pathogenesis of many diseases are associated with increased ROS levels, and many external stress factors directly or indirectly cause oxidative stress in cells. Within this context, the overexpression of genes encoding the proteins in antioxidant systems seems to have become a viable approach to decrease the oxidative stress caused by pathological conditions and to increase cellular stress resistance. However, such manipulations unavoidably lead to side effects, the most dangerous of which is an increased probability of healthy tissue malignization or increased tumor aggression. The aims of the present review were to collect and systematize the results of studies devoted to the effects resulting from the overexpression of antioxidant system genes on stress resistance and carcinogenesis in vitro and in vivo. In most cases, the overexpression of these genes was shown to increase cell and organism resistances to factors that induce oxidative and genotoxic stress but to also have different effects on cancer initiation and promotion. The last fact greatly limits perspectives of such manipulations in practice. The overexpression of GPX3 and SOD3 encoding secreted proteins seems to be the "safest" among the genes that can increase cell resistance to oxidative stress. High efficiency and safety potential can also be found for SOD2 overexpression in combinations with GPX1 or CAT and for similar combinations that lead to no significant changes in H₂O₂ levels. Accumulation, systematization, and the integral analysis of data on antioxidant gene overexpression effects can help to develop approaches for practical uses in biomedical and agricultural areas. Additionally, a number of factors such as genetic and functional context, cell and tissue type, differences in the function of transcripts of one and the same gene, regulatory interactions, and additional functions should be taken into account.

Molecular profiles of single circulating tumor cells from early breast cancer patients with different lymph node statuses

BACKGROUND

Characterization of early breast cancer circulating tumor cells (CTCs) may provide valuable information on tumor metastasis.

METHODS

We used immunomagnetic nanospheres to capture CTCs from the peripheral blood of eight early breast cancer patients and then performed single-cell RNA sequencing using our proposed bead-dd-seq method.

RESULTS

CTCs displayed obvious tumor cell characteristics, such as the activation of oxidative stress, proliferation, and promotion of metastasis. CTCs were clustered into two subtypes significantly correlated with the lymph node metastasis status of patients. CTCs in subtype 1 showed a strong metastatic ability because these CTCs have the phenotype of partial epithelial-mesenchymal transition and enriched transcripts, indicating breast cancer responsiveness and proliferation. Furthermore, DNA damage repair pathways were significantly upregulated in subtype 1. We performed in vitro and in vivo investigations, and found that cellular oxidative stress and further DNA damage existed in CTCs. The activated DNA damage repair pathway in CTCs favors resistance to cisplatin. A checkpoint kinase 1 inhibitor sensitized CTCs to cisplatin in mouse models of breast cancer metastasis.

CONCLUSION

The present study dissects the molecular characteristics of CTCs from early-stage breast cancer, providing novel insight into the understanding of CTC behavior in breast cancer metastasis.

Necroptosis-related lncRNAs: Combination of bulk and single-cell sequencing reveals immune landscape alteration and a novel prognosis stratification approach in lung adenocarcinoma

Necroptosis, which is recently recognized as a form of programmed cell death, plays a critical role in cancer biology, including tumorigenesis and cancer immunology. It was recognized not only to defend against tumor progression by suppressing adaptive immune responses but also to promote tumorigenesis and cancer metastasis after recruiting inflammatory responses. Thus the crucial role of necrosis in tumorigenesis has attracted increasing attention. Due to the heterogeneity of the tumor immune microenvironment (TIME) in lung adenocarcinoma (LUAD), the prognosis and the response to immunotherapy vary distinctly across patients, underscoring the need for a stratification algorithm for clinical practice. Although previous studies have formulated the crucial role of lncRNAs in tumorigenicity, the relationship between necroptosis-related lncRNAs, TIME, and the prognosis of patients with LUAD was still elusive. In the current study, a robust and novel prognostic stratification model based on Necroptosis-related LncRNA Risk Scoring (NecroLRS) and clinicopathological parameters was constructed and systemically validated in both internal and external validation cohorts. The expression profile of four key lncRNAs was further validated by qRT-PCR in 4 human LUAD cell lines. And a novel immune landscape alteration was observed between NecroLRS-High and -Low patients. To further elucidate the mechanism of necroptosis in the prognosis of LUAD from a single-cell perspective, a novel stratification algorithm based on K-means clustering was introduced to extract both malignant and NecroLRS-High subsets from epithelial cells. And the necroptosis-related immune infiltration landscape and developmental trajectory were investigated respectively. Critically, NecroLRS was found to be positively correlated with neutrophil enrichment, inflammatory immune response, and malignant phenotypes of LUAD. In addition, novel ligand-receptor pairs between NecroLRS-High cells and other immunocytes were investigated and optimal therapeutic compounds were screened to provide potential targets for future studies. Taken together, our findings reveal emerging mechanisms of necroptosis-induced immune microenvironment alteration on the deteriorative prognosis and may contribute to improved prognosis and individualized precision therapy for patients with LUAD.

A Bioinformatics-Based Analysis of an Anoikis-Related Gene Signature Predicts the Prognosis of Patients with Low-Grade Gliomas

Low-grade glioma (LGG) is a highly aggressive disease in the skull. On the other hand, anoikis, a specific form of cell death induced by the loss of cell contact with the extracellular matrix, plays a key role in cancer metastasis. In this study, anoikis-related genes (ANRGs) were used to identify LGG subtypes and to construct a prognostic model for LGG patients. In addition, we explored the immune microenvironment and enrichment pathways between different subtypes. We constructed an anoikis-related gene signature using the TCGA (The Cancer Genome Atlas) cohort and investigated the differences between different risk groups in clinical features, mutational landscape, immune cell infiltration (ICI), etc. Kaplan-Meier analysis showed that the characteristics of ANRGs in the high-risk group were associated with poor prognosis in LGG patients. The risk score was identified as an independent prognostic factor. The high-risk group had higher ICI, tumor mutation load (TMB), immune checkpoint gene expression, and therapeutic response to immune checkpoint blockers (ICB). Functional analysis showed that these high-risk and low-risk groups had different immune statuses and drug sensitivity. Risk scores were used together with LGG clinicopathological features to construct a nomogram, and Decision Curve Analysis (DCA) showed that the model could enable patients to benefit from clinical treatment strategies.

Anoikis resistance in diffuse glioma: The potential therapeutic targets in the future

Glioma is the most common malignant intracranial tumor and exhibits diffuse metastasis and a high recurrence rate. The invasive property of glioma results from cell detachment. Anoikis is a special form of apoptosis that is activated upon cell detachment. Resistance to anoikis has proven to be a protumor factor. Therefore, it is suggested that anoikis resistance commonly occurs in glioma and promotes diffuse invasion. Several factors, such as integrin, E-cadherin, EGFR, IGFR, Trk, TGF-β, the Hippo pathway, NF-κB, eEF-2 kinase, MOB2, hypoxia, acidosis, ROS, Hsp and protective autophagy, have been shown to induce anoikis resistance in glioma. In our present review, we aim to summarize the underlying mechanism of resistance and the therapeutic potential of these molecules.

TGFBR3 supports anoikis through suppressing ATF4 signaling

Epithelial morphogenesis and oncogenic transformation can cause loss of cell adhesion, and detached cells are eliminated by anoikis. Here, we reveal that transforming growth factor beta receptor 3 (TGFBR3) acts as an anoikis mediator through the coordination of activating transcription factor 4 (ATF4). In breast cancer, TGFBR3 is progressively lost, but elevated TGFBR3 is associated with a histologic subtype characterized by cellular adhesion defects. Dissecting the impact of extracellular matrix (ECM) deprivation, we demonstrate that ECM loss promotes TGFBR3 expression, which in turn differentiates cell aggregates to a prosurvival phenotype and drives the intrinsic apoptotic pathway. We demonstrate that inhibition of TGFBR3 impairs epithelial anoikis by activating ATF4 signaling. These preclinical findings provide a rationale for therapeutic inhibition of ATF4 in the subgroup of breast cancer patients with low TGFBR3 expression.

Recent trends in the application of nanoparticles in cancer therapy: The involvement of oxidative stress

In the biomedical area, the interdisciplinary field of nanotechnology has the potential to bring numerous unique applications, including better tactics for cancer detection, diagnosis, and therapy. Nanoparticles (NPs) have been the topic of many research and material applications throughout the last decade. Unlike small-molecule medications, NPs are defined by distinct physicochemical characteristics, such as a large surface-to-volume ratio, which allows them to permeate live cells with relative ease. The versatility of NPs as both therapeutics and diagnostics makes them ideal for a broad spectrum of illnesses, from infectious diseases to cancer. A significant amount of data has been participated in the current scientific publications, emphasizing the concept that NPs often produce reactive oxygen species (ROS) to a larger degree than micro-sized particles. It is important to note that oxidative stress governs a wide range of cell signaling cascades, many of which are responsible for cancer cell cytotoxicity. Here, we aimed to provide insight into the signaling pathways triggered by oxidative stress in cancer cells in response to several types of nanomaterials, such as metallic and polymeric NPs and quantum dots. We discuss recent advances in developing integrated anticancer medicines based on NPs targeted to destroy malignant cells by increasing their ROS setpoint.

HuR-dependent SOD2 protein synthesis is an early adaptation to anchorage-independence

During metastasis cancer cells must adapt to survive loss of anchorage and evade anoikis. An important pro-survival adaptation is the ability of metastatic tumor cells to increase their antioxidant capacity and restore cellular redox balance. Although much is known about the transcriptional regulation of antioxidant enzymes in response to stress, how cells acutely adapt to alter antioxidant enzyme levels is less well understood. Using ovarian cancer cells as a model, we demonstrate that an increase in mitochondrial superoxide dismutase SOD2 protein expression is a very early event initiated in response to detachment, an important step during metastasis that has been associated with increased oxidative stress. SOD2 protein synthesis is rapidly induced within 0.5-2 h of matrix detachment, and polyribosome profiling demonstrates an increase in the number of ribosomes bound to SOD2 mRNA, indicating an increase in SOD2 mRNA translation in response to anchorage-independence. Mechanistically, we find that anchorage-independence induces cytosolic accumulation of the RNA binding protein HuR/ELAVL1 and promotes HuR binding to SOD2 mRNA. Using HuR siRNA-mediated knockdown, we show that the presence of HuR is necessary for the increase in SOD2 mRNA association with the heavy polyribosome fraction and consequent nascent SOD2 protein synthesis in anchorage-independence. Cellular detachment also activates the stress-response mitogen-activated kinase p38, which is necessary for HuR-SOD2 mRNA interactions and induction of SOD2 protein output. These findings illustrate a novel translational regulatory mechanism of SOD2 by which ovarian cancer cells rapidly increase their mitochondrial antioxidant capacity as an acute stress response to anchorage-independence.

SOD2, a Potential Transcriptional Target Underpinning CD44-Promoted Breast Cancer Progression

CD44, a cell-adhesion molecule has a dual role in tumor growth and progression; it acts as a tumor suppressor as well as a tumor promoter. In our previous work, we developed a tetracycline-off regulated expression of CD44's gene in the breast cancer (BC) cell line MCF-7 (B5 clone). Using cDNA oligo gene expression microarray, we identified SOD2 (superoxide dismutase 2) as a potential CD44-downstream transcriptional target involved in BC metastasis. SOD2 gene belongs to the family of iron/manganese superoxide dismutase family and encodes a mitochondrial protein. SOD2 plays a role in cell proliferation and cell invasion via activation of different signaling pathways regulating angiogenic abilities of breast tumor cells. This review will focus on the findings supporting the underlying mechanisms associated with the oncogenic potential of SOD2 in the onset and progression of cancer, especially in BC and the potential clinical relevance of its various inhibitors.

Targeting Oxidative Phosphorylation-Proteasome Activity in Extracellular Detached Cells Promotes Anoikis and Inhibits Metastasis

Metastasis arises owing to tumor cells’ capacity to evade pro-apoptotic signals. Anoikis—the apoptosis of detached cells (from the extracellular matrix (ECM)) is often circumvented by metastatic cells as a result of biochemical and molecular transformations. These facilitate cells’ ability to survive, invade and reattach to secondary sites. Here, we identified deregulated glucose metabolism, oxidative phosphorylation, and proteasome in anchorage-independent cells compared to adherent cells. Metformin an anti-diabetic drug that reduces blood glucose (also known to inhibit mitochondrial Complex I), and proteasome inhibitors were employed to target these changes. Metformin or proteasome inhibitors alone increased misfolded protein accumulation, sensitized tumor cells to anoikis, and impaired pulmonary metastasis in the B16F10 melanoma model. Mechanistically, metformin reduced cellular ATP production, activated AMPK to foster pro-apoptotic unfolded protein response (UPR) through enhanced expression of CHOP in ECM detached cells. Furthermore, AMPK inhibition reduced misfolded protein accumulation, thus highlight relevance of AMPK activation in facilitating metformin-induced stress and UPR cell death. Our findings provide insights into the molecular biology of anoikis resistance and identified metformin and proteasome inhibitors as potential therapeutic options for tumor metastasis.

Mitochondrial Redox Metabolism: The Epicenter of Metabolism during Cancer Progression

Mitochondrial redox metabolism is the central component in the cellular metabolic landscape, where anabolic and catabolic pathways are reprogrammed to maintain optimum redox homeostasis. During different stages of cancer, the mitochondrial redox status plays an active role in navigating cancer cells’ progression and regulating metabolic adaptation according to the constraints of each stage. Mitochondrial reactive oxygen species (ROS) accumulation induces malignant transformation. Once vigorous cell proliferation renders the core of the solid tumor hypoxic, the mitochondrial electron transport chain mediates ROS signaling for bringing about cellular adaptation to hypoxia. Highly aggressive cells are selected in this process, which are capable of progressing through the enhanced oxidative stress encountered during different stages of metastasis for distant colonization. Mitochondrial oxidative metabolism is suppressed to lower ROS generation, and the overall cellular metabolism is reprogrammed to maintain the optimum NADPH level in the mitochondria required for redox homeostasis. After reaching the distant organ, the intrinsic metabolic limitations of that organ dictate the success of colonization and flexibility of the mitochondrial metabolism of cancer cells plays a pivotal role in their adaptation to the new environment.

Redox Regulation in Cancer Cells during Metastasis

Metastasis is an inefficient process in which the vast majority of cancer cells are fated to die, partly because they experience oxidative stress. Metastasizing cancer cells migrate through diverse environments that differ dramatically from their tumor of origin, leading to redox imbalances. The rare metastasizing cells that survive undergo reversible metabolic changes that confer oxidative stress resistance. We review the changes in redox regulation that cancer cells undergo during metastasis. By better understanding these mechanisms, it may be possible to develop pro-oxidant therapies that block disease progression by exacerbating oxidative stress in cancer cells. SIGNIFICANCE: Oxidative stress often limits cancer cell survival during metastasis, raising the possibility of inhibiting cancer progression with pro-oxidant therapies. This is the opposite strategy of treating patients with antioxidants, an approach that worsened outcomes in large clinical trials.

Metabolite Biomarkers of Response (BoRs): Towards a fingerprint for the evolution of metastatic breast cancer

Breast cancer is the most common cancer in women worldwide and despite improved treatment strategies, it persists as the second leading cause of death of women globally. Overall prognosis drops drastically once the cancer has metastasized, which is also associated with resistance to therapy. The evolution from a localized breast cancer to metastatic disease is complex and multifactorial. Metabolic reprogramming is a pre-requisite for this transition. In this graphical review, we provide an overview of altered metabolic pathways observed in metastatic breast cancer (mBC) and detail how metabolite biomarkers could serve as a novel class of precision medicine tools to improve the diagnosis, monitoring, and treatment of mBC.

Emerging role of ferroptosis in breast cancer: New dawn for overcoming tumor progression

Breast cancer has become a serious threat to women's health. Cancer progression is mainly derived from resistance to apoptosis induced by procedures or therapies. Therefore, new drugs or models that can overcome apoptosis resistance should be identified. Ferroptosis is a recently identified mode of cell death characterized by excess reactive oxygen species-induced lipid peroxidation. Since ferroptosis is distinct from apoptosis, necrosis and autophagy, its induction successfully eliminates cancer cells that are resistant to other modes of cell death. Therefore, ferroptosis may become a new direction around which to design breast cancer treatment. Unfortunately, the complete appearance of ferroptosis in breast cancer has not yet been fully elucidated. Furthermore, whether ferroptosis inducers can be used in combination with traditional anti- breast cancer drugs is still unknown. Moreover, a summary of ferroptosis in breast cancer progression and therapy is currently not available. In this review, we discuss the roles of ferroptosis-associated modulators glutathione, glutathione peroxidase 4, iron, nuclear factor erythroid-2 related factor-2, superoxide dismutases, lipoxygenase and coenzyme Q in breast cancer. Furthermore, we provide evidence that traditional drugs against breast cancer induce ferroptosis, and that ferroptosis inducers eliminate breast cancer cells. Finally, we put forward prospect of using ferroptosis inducers in breast cancer therapy, and predict possible obstacles and corresponding solutions. This review will deepen our understanding of the relationship between ferroptosis and breast cancer, and provide new insights into breast cancer-related therapeutic strategies.

Expression of Autophagy and Mitophagy Markers in Breast Cancer Tissues

Mitochondria play important roles in regulating cell bioenergetics status and reactive oxygen species (ROS) generation. ROS-induced mitochondrial damage is among the main intracellular signal inducers of autophagy. Autophagy is a cellular catabolic process that regulates protein and organelle turnover, while a selective form of autophagy, mitophagy, specifically targets dysfunctional mitochondrial degradation. This study aims to measure the levels of autophagy, mitophagy, oxidative stress, and apoptosis in invasive breast carcinoma tissues using immunohistochemistry (IHC). Tissue microarrays of 76 patients with breast cancer were stained with six IHC markers (MnSOD, Beclin-1, LC3, BNIP3, Parkin, and cleaved caspase 3). The expression intensity was determined for each tumor tissue and the adjacent tumor-matched control tissues. Intermediate and strong staining scores of MnSOD, Beclin-1, LC-3, BNIP-3, and Parkin were significantly higher in tumor tissues compared to the adjacent matched control. The scoring intensity was further classified into tissues with negative staining and positive staining, which showed that positive scores of Beclin-1 and Parkin were significantly high in tumor tissues compared to other markers. Positive association was also noted between BNIP-3 and Beclin-1 as well as LC-3 and cleaved caspase-3 immunostaining. To our knowledge, this is one of the first studies that measure both mitophagy and autophagy in the same breast cancer tissues and the adjacent matched control. The findings from this study will be of great potential in identifying new cancer biomarkers and inspire significant interest in applying anti-autophagy therapies as a possible treatment for breast cancer.

Upregulation of V-ATPase by STAT3 Activation Promotes Anoikis Resistance and Tumor Metastasis

Most cancer mortality results from metastatic tumor cells and not the localized tumor. Overcoming anoikis is one of the most important steps for detached tumor cells to migrate and metastasize. However, the molecular mechanisms remain to be fully deciphered. Herein, our study revealed upregulation of vacuolar ATPase (V-ATPase) in cancer cells during ECM detachment plays a key role in anoikis evasion. V-ATPase is an enzyme complex that utilizes energy from ATP hydrolysis to maintain cellular homeostasis and had been reported to enhance cancer progression. In this study, V-ATPase inhibition sensitized human cervical cancer, breast cancer, and murine melanoma cells to anoikis via increased ROS production, accumulation of misfolded protein, and impaired pulmonary metastasis in vivo. Scavenging ROS restored anoikis resistance and clearance of misfolded protein accumulation in the tumor cells. Mechanistically, STAT3 upregulates V-ATPase expression while blockade of STAT3 activity repressed V-ATPase expression in these tumor cells as well as sensitized cells to anoikis, increased ROS production, and misfolded protein accumulation. Altogether, our data demonstrate an unreported role of STAT3 in mediating the upregulation of V-ATPase to promote anoikis resistance, thus provides an alternative option to target cancer metastasis.

High Expression of SOD2 Protein Is a Strong Prognostic Factor for Stage IIIB Squamous Cell Cervical Carcinoma

High superoxide dismutase 2 (SOD2) expression is associated with a poor prognosis at many cancer sites, the presence of metastases, and more advanced cervical cancer. This study aims to determine whether SOD2 protein expression is associated with the prognosis of stage IIIB cervical carcinoma. Methods: sixty-three patients with stage IIIB squamous cell cervical carcinoma were included. The evaluation of SOD2 expression by immunohistochemistry was based on a positive cell ratio score and the staining intensity score. Taking disease recurrence and death as endpoints, receiver operating characteristic curves were used to discriminate between high and low SOD2 expression. Results: high SOD2 expression was associated with recurrence (p = 0.001), distant recurrence (p = 0.002), and death (p = 0.005). A multivariate analysis showed that patients with high SOD2 expression had a threefold increased risk for recurrence (HR = 3.16; 1.33–7.51) and death (HR = 2.98; 1.20–7.40) compared with patients who had low SOD2 expression. Patients with high SOD2 expression had shorter disease-free survival (p = 0.001) and overall survival (p = 0.003) than patients with low SOD2 expression. Conclusion: high SOD2 expression is a strong prognostic factor for stage IIIB squamous cell carcinoma of the cervix and could be used as a prognostic marker in women with cervical carcinoma.

microRNAs and Corresponding Targets Involved in Metastasis of Colorectal Cancer in Preclinical In Vivo Models

The high death toll of colorectal cancer patients is due to metastatic disease which is difficult to treat. The liver is the preferred site of metastasis, followed by the lungs and peritoneum. In order to identify new targets and new modalities of intervention we surveyed the literature for microRNAs (miRs) which modulate metastasis of colorectal cancer in preclinical in vivo models. We identified 12 up-regulated and 19 down-regulated miRs corresponding to the latter criterium. The vast majority (n=16) of identified miRs are involved in modulation of epithelial-mesenchymal transition (EMT). Other categories of metastasis-related miRs exhibit tumor- and metastasis-suppressing functions, modulation of signaling pathways, transmembrane receptors and a class of miRs, which interfere with targets which do not fit into these categories. Finally, we discuss the principles of miR inhibition and reconstitution of function, prospective clinical evaluation of with miR-related agents in the context of clinical evaluation in metastasis relevant settings.

lncRNA APOC1P1-3 promoting anoikis-resistance of breast cancer cells

BACKGROUND

Anoikis resistance plays a critical role in the tumor metastasis by allowing survival of cancer cells in the systemic circulation. We previously showed that long non-coding RNAs APOC1P1-3 (lncRNA APOC1P1-3) inhibit apoptosis of breast cancer cells. In this study, we explored its role in anoikis resistance.

METHODS

We induced anoikis resistance in two breast cancer cell lines (MCF-7 and MDA-MB-231) under anchorage-independent culture conditions and studied lncRNA APOC1P1-3 effects on apoptosis. Using Dual-Luciferase activity assay, we determined whether it specifically binds to miRNA-188-3P. We further explored its role in lung metastasis by injecting MDA-MB-231 and MDA-MB-231-APOC1P1-3-knock-down cells in female BALB/c nude mice.

RESULTS

We found that lncRNA APOC1P1-3 suppressed early apoptosis of these cells (demonstrated by gain or loss of their function, respectively) and promoted anoikis resistance via reducing activated- Caspase 3, 8, 9 and PARP. Moreover, it specifically binds to the target miRNA-188-3p acting as a "sponge" to block the inhibition of Bcl-2 (an anti-apoptosis protein).

CONCLUSIONS

Our study supports a theory that lncRNA APOC1P1-3 can promote development of breast cancer metastasis via anoikis resistance by specifically binding to miRNA-188-3p to block the inhibition of Bcl-2.

Oxidative Stress in Cancer Cell Metabolism

Reactive oxygen species (ROS) are important in regulating normal cellular processes whereas deregulated ROS leads to the development of a diseased state in humans including cancers. Several studies have been found to be marked with increased ROS production which activates pro-tumorigenic signaling, enhances cell survival and proliferation and drives DNA damage and genetic instability. However, higher ROS levels have been found to promote anti-tumorigenic signaling by initiating oxidative stress-induced tumor cell death. Tumor cells develop a mechanism where they adjust to the high ROS by expressing elevated levels of antioxidant proteins to detoxify them while maintaining pro-tumorigenic signaling and resistance to apoptosis. Therefore, ROS manipulation can be a potential target for cancer therapies as cancer cells present an altered redox balance in comparison to their normal counterparts. In this review, we aim to provide an overview of the generation and sources of ROS within tumor cells, ROS-associated signaling pathways, their regulation by antioxidant defense systems, as well as the effect of elevated ROS production in tumor progression. It will provide an insight into how pro- and anti-tumorigenic ROS signaling pathways could be manipulated during the treatment of cancer.

SOD3 Is a Non-Mutagenic Growth Regulator Affecting Cell Migration and Proliferation Signal Transduction

Superoxide dismutase (SOD) family isoenzymes, SOD1, SOD2, and SOD3, synthesize hydrogen peroxide (H₂O₂), which regulates the signal transduction. H₂O₂ is a second messenger able to enter into the cells through aquaporin 3 cell membrane channels and to modify protein tyrosine phosphatase activity. SOD3 has been shown to activate signaling pathways in tissue injuries, inflammation, and cancer models. Similar to the H₂O₂ response in the cells, the cellular response of SOD3 is dose-dependent; even a short supraphysiological concentration reduces the cell survival and activates the growth arrest and apoptotic signaling, whereas the physiological SOD3 levels support its growth and survival. In the current work, we studied the signaling networks stimulated by SOD3 overexpression demonstrating a high diversity in the activation of signaling cascades. The results obtained suggest that SOD3, although inducing cell growth and affecting various biological processes, does not cause detectable long-term DNA aberrations. Therefore, according to the present data, SOD3 is not a mutagen. Additionally, we compared SOD3-driven immortalized mouse embryonic fibroblasts to SV40 immortalized NIH3T3 cells, demonstrating a marked difference in the activation of cellular kinases. The data presented may contain important druggable targets to abrogate unwanted cell growth.

Mechanisms for Modulating Anoikis Resistance in Cancer and the Relevance of Metabolic Reprogramming

The attachment of cells to the extracellular matrix (ECM) is the hallmark of structure–function stability and well-being. ECM detachment in localized tumors precedes abnormal dissemination of tumor cells culminating in metastasis. Programmed cell death (PCD) is activated during tumorigenesis to clear off ECM-detached cells through “anoikis.” However, cancer cells develop several mechanisms for abrogating anoikis, thus promoting their invasiveness and metastasis. Specific factors, such as growth proteins, pH, transcriptional signaling pathways, and oxidative stress, have been reported as drivers of anoikis resistance, thus enhancing cancer proliferation and metastasis. Recent studies highlighted the key contributions of metabolic pathways, enabling the cells to bypass anoikis. Therefore, understanding the mechanisms driving anoikis resistance could help to counteract tumor progression and prevent metastasis. This review elucidates the dynamics employed by cancer cells to impede anoikis, thus promoting proliferation, invasion, and metastasis. In addition, the authors have discussed other metabolic intermediates (especially amino acids and nucleotides) that are less explored, which could be crucial for anoikis resistance and metastasis.

Mitochondrial metabolism-mediated redox regulation in cancer progression

Cancer cells display abnormal metabolic activity as a result of activated oncogenes and loss of tumor suppressor genes. The Warburg Effect is a common metabolic feature of cancer that involves a preference for aerobic glycolysis over oxidative phosphorylation to generate ATP and building blocks for biosynthesis. However, emerging evidence indicates that mitochondrial metabolic pathways are also reprogrammed in cancer and play vital roles in bioenergetics, biosynthesis, and managing redox homeostasis. The mitochondria act a central hub for metabolic pathways that generate ATP and building blocks for lipid, nucleic acid and protein biosynthesis. However, mitochondrial respiration is also a leading source of reactive oxygen species that can damage cellular organelles and trigger cell death if levels become too high. In general, cancer cells are reported to have higher levels of reactive oxygen species than their non-cancerous cells of origin, and therefore must employ diverse metabolic strategies to prevent oxidative stress. However, mounting evidence indicates that the metabolic profiles between proliferative and disseminated cancer cells are not the same. In this review, we will examine mitochondrial metabolic pathways, such as glutaminolysis, that proliferative and disseminated cancer cells utilize to control their redox status.

Kallistatin Inhibits Anoikis Resistance and Metastasis of Ectopic Endometrium Cells by Modulating MnSOD and Caspase 3 Signaling

Endometriosis (EM) is a disease that involves active endometrial cell invasion and migration which is an important reason for infertility. Anoikis resistance is the most important prerequisite for EM, but the molecular mechanism is not yet clear. Kallistatin (KS) is one kind of serine protease inhibitors which had extensive biological function including anti-inflammatory, antioxidant stress, anti-angiogenesis, and anti-tumor. Our preliminary data showed that the level of KS in EM patients' endometrial tissue and blood were much lower than control (non-EM) patients without endometriosis. Interestingly, the decrease of KS is correlated with the severity of endometriosis. Moreover, kallistatin recombinant protein could increase the anoikis rate of ectopic endometrium cells (EESCs), and then inhibits its metastasis and invasion. Mechanically, our data show that the EESCs have lower intracellular reactive oxygen species (ROS) production and KS can elevate the ROS levels significantly. Further, KS modulate expression of MnSOD and caspase 3 signaling in EESCs grown in suspended conditions. These findings reveal novel mechanisms of KS in inducing anoikis and metastasis in EESCs, thus inhibiting EM progression by regulation of MnSOD and caspase 3 signaling. Our findings suggest that KS is a significant protein with prospects for application in EM.

FAM188B Downregulation Sensitizes Lung Cancer Cells to Anoikis via EGFR Downregulation and Inhibits Tumor Metastasis In Vivo

Simple Summary

Cancer cells should acquire anoikis resistance for successful metastasis. Family with sequence similarity 188 member B (FAM188B) has been identified as a new deubiquitinase (DUB) member. Here, we demonstrate that FAM188B knockdown makes lung cancer cells sensitive to anoikis and inhibits lung metastasis. FAM188B knockdown reduced the levels of tumor proteins such as EGFR and FOXM1, suggesting that FAM188B may be a potential target controlling tumor malignancies.

Abstract

Anoikis is a type of apoptosis induced by cell detachment from the extracellular matrix (ECM), which removes mislocalized cells. Acquisition of anoikis resistance is critical for cancer cells to survive during circulation and, thus, metastasize at a secondary site. Although the sensitization of cancer cells to anoikis is a potential strategy to prevent metastasis, the mechanism underlying anoikis resistance is not well defined. Although family with sequence similarity 188 member B (FAM188B) is predicted as a new deubiquitinase (DUB) member, its biological function has not been fully studied. In this study, we demonstrated that FAM188B knockdown sensitized anoikis of lung cancer cell lines expressing WT-EGFR (A549 and H1299) or TKI-resistant EGFR mutant T790M/L858R (H1975). FAM188B knockdown using si-FAM188B inhibited the growth of all three human lung cancer cell lines cultured in both attachment and suspension conditions. FAM188B knockdown resulted in EGFR downregulation and thus decreased its activity. FAM188B knockdown decreased the activities of several oncogenic proteins downstream of EGFR that are involved in anoikis resistance, including pAkt, pSrc, and pSTAT3, with little changes to their protein levels. Intriguingly, si-FAM188B treatment increased EGFR mRNA levels but decreased its protein levels, which was reversed by treatment with the proteasomal inhibitor MG132, indicating that FAM188B regulates EGFR levels via the proteasomal pathway. In addition, cells transfected with si-FAM188B had decreased expression of FOXM1, an oncogenic transcription factor involved in cell growth and survival. Moreover, FAM188B downregulation reduced metastatic characteristics, such as cell adhesion, invasion, and migration, as well as growth in 3D culture conditions. Finally, tail vein injection of si-FAM188B-treated A549 cells resulted in a decrease in lung metastasis and an increase in mice survival in vivo. Taken together, these findings indicate that FAM188B plays an important role in anoikis resistance and metastatic characteristics by maintaining the levels of various oncogenic proteins and/or their activity, leading to tumor malignancy. Our study suggests FAM188B as a potential target for controlling tumor malignancy.

The Metabolic Mechanisms of Breast Cancer Metastasis

Breast cancer is one of the most common malignancy among women worldwide. Metastasis is mainly responsible for treatment failure and is the cause of most breast cancer deaths. The role of metabolism in the progression and metastasis of breast cancer is gradually being emphasized. However, the regulatory mechanisms that conduce to cancer metastasis by metabolic reprogramming in breast cancer have not been expounded. Breast cancer cells exhibit different metabolic phenotypes depending on their molecular subtypes and metastatic sites. Both intrinsic factors, such as MYC amplification, PIK3CA, and TP53 mutations, and extrinsic factors, such as hypoxia, oxidative stress, and acidosis, contribute to different metabolic reprogramming phenotypes in metastatic breast cancers. Understanding the metabolic mechanisms underlying breast cancer metastasis will provide important clues to develop novel therapeutic approaches for treatment of metastatic breast cancer.

Exosome-mediated metabolic reprogramming: the emerging role in tumor microenvironment remodeling and its influence on cancer progression

Metabolic reprogramming is reported to be one of the hallmarks of cancer, which is an adaptive mechanism by which fast-growing cancer cells adapt to their increasing energy demands. Recently, extracellular vesicles (EVs) known as exosomes have been recognized as crucial signaling mediators in regulating the tumor microenvironment (TME). Meanwhile, the TME is a highly heterogeneous ecosystem incorporating cancer cells, fibroblasts, adipocytes, endothelial cells, mesenchymal stem cells, and extracellular matrix. Accumulated evidence indicates that exosomes may transfer biologically functional molecules to the recipient cells, which facilitate cancer progression, angiogenesis, metastasis, drug resistance, and immunosuppression by reprogramming the metabolism of cancer cells and their surrounding stromal cells. In this review, we present the role of exosomes in the TME and the underlying mechanism of how exosomes exacerbate tumor development through metabolic reprogramming. In addition, we will also discuss the potential role of exosomes targeting metabolic process as biomarkers for tumor diagnosis and prognosis, and exosomes-mediated metabolic reprogramming as potential targets for cancer therapy. Furthermore, a better understanding of the link between exosomes and metabolic reprogramming, and their impact on cancer progression, would provide novel insights for cancer prevention and treatment in the future.

P-cadherin induces anoikis-resistance of matrix-detached breast cancer cells by promoting pentose phosphate pathway and decreasing oxidative stress

Successful metastatic spreading relies on cancer cells with stem-like properties, glycolytic metabolism and increased antioxidant protection, allowing them to escape anoikis and to survive in circulation. The expression of P-cadherin, a poor prognostic factor in breast cancer, is associated with hypoxic, glycolytic and acidosis biomarkers. In agreement, P-cadherin-enriched breast cancer cell populations presents a glycolytic and an acid-resistance phenotype. Our aim was to evaluate whether P-cadherin expression controls the glycolytic and oxidative phosphorylation fluxes of matrix-detached breast cancer cells, acting as an antioxidant and enhancing their survival in anchorage-independent conditions. By using matrix-detached breast cancer cells, we concluded that P-cadherin increases glucose-6-phosphate dehydrogenase expression, up-regulating the carbon flux through the pentose phosphate pathway, while inhibiting pyruvate oxidation to acetyl-coA via pyruvate dehydrogenase kinase-4 (PDK-4) activation. Accordingly, P-cadherin expression conferred increased sensitivity to dichloroacetate (DCA), a PDK inhibitor. P-cadherin expression also regulates oxidative stress in matrix-detached breast cancer cells, through the control of antioxidant systems, such as catalase and superoxide dismutases (SOD)1 and 2, providing these cells with an increased resistance to doxorubicin-induced anoikis. Importantly, this association was validated in primary invasive breast carcinomas, where an enrichment of SOD2 was found in P-cadherin-overexpressing breast carcinomas. In conclusion, we propose that P-cadherin up-regulates carbon flux through the pentose phosphate pathway and decreases oxidative stress in matrix-detached breast cancer cells. These metabolic remodeling and antioxidant roles of P-cadherin can promote the survival of breast cancer cells in circulation and in metastatic sites, being a possible player in breast cancer therapeutic resistance to pro-oxidant-based interventions.

[Expression of superoxide dismutase 2 in breast cancer and its clinical significance]

OBJECTIVE

To evaluate the expression and prognostic value of superoxide dismutase 2 (SOD2) in breast cancer and explore its possible role in the occurrence and progression of breast cancer.

METHODS

We performed bioinformatics analysis of the TCGA data for the expression and clinical relevance of SOD2 in patients with breast cancer. Gene enrichment analysis (GSEA) was performed using the KEGG gene set, the protein interaction network was constructed using the STRING database, and the key genes were screened using Cytoscape software. We also collected 60 pairs of primary breast cancer tissue samples and adjacent samples for detecting SOD2 expressions using immunohistochemistry and RT-qPCR and analyzed the correlation of SOD2 expression with the clinicopathological parameters of the patients.

RESULTS

The expression of SOD2 was significantly lower in breast cancer tissue than in adjacent tissues with significant correlation with TNM stage and axillary lymph node metastasis (P < 0.05). Kaplan-Meier survival analysis showed that the recurrence-free survival, distant metastasis-free survival (RFS) and post-progressive survival were significantly shorted in patients with high SOD2 expression than in those with low SOD2 expression (P < 0.05). GSEA enrichment analysis indicated that SOD2 played an important role in the JAK-STAT signaling pathway. IL10 and STAT4 were identified as the key genes in the PPI network, and they were both positively correlated with SOD2. In the 60 pairs of clinical samples, SOD2 was highly expressed in breast cancer tissues with close correlation with axillary lymph node metastasis and the expressions of estrogen receptor and androgen receptor (P < 0.05).

CONCLUSIONS

The expression of SOD2 in breast cancer is significantly correlated with TNM stage and axillary lymph node metastasis. SOD2 may affect the proliferation, invasion and metastasis of breast cancer cells possibly by regulating IL10 and/or STAT4 to affect the JAK/STAT signaling pathway.

SDHA-mediated Warburg effect in malignantly transformed human bronchial epithelial cells following long-term exposure to radon

Radon and its progeny have been classified as human class I carcinogens by the IARC. However, the mechanisms by which radon induces lung and other cancers, especially the radon-induced Warburg effect, have not been fully elucidated. The aim of this study was to investigate the role of the succinate dehydrogenase subunit A (SDHA)-mediated Warburg effect in (human bronchial epithelial) BEAS-2B cells with malignant transformations induced by long-term radon exposure. Soft agar colony formation and MMP-9 were increased following radon-induced malignant transformation. Additionally, we observed the Warburg effect in BEAS-2B cells following long-term radon exposure, evidenced by increases in the levels of glucose uptake, lactate, and lactate dehydrogenase (LDH). Following radon exposure, the expression of SDHA was decreased, while the levels of HIF-1α and hexokinase-2 (HK2) were increased. Our findings suggested that the SDHA-associated pathway may be involved in mediating the Warburg effect in radon-induced malignant transformation of BEAS-2B.

BRAF Mutant Melanoma Adjusts to BRAF/MEK Inhibitors via Dependence on Increased Antioxidant SOD2 and Increased Reactive Oxygen Species Levels

B-Rapidly Accelerated Fibrosarcoma (BRAF) mutations are found in about 50% of melanoma patients. Treatment with Food and Drug Administration (FDA)-approved BRAF and MAP/ERK kinase (MEK) inhibitors has improved progression free and overall survival of patients with BRAF mutant melanoma. However, all responders develop resistance typically within 1 year of treatment with these inhibitors. Evidence indicates that reactive oxygen species (ROS) levels are elevated after BRAF pathway inhibition treatment. We aim to decipher the role of mitochondrial antioxidant proteins relative to ROS levels and BRAF pathway inhibitor resistance. We observed BRAF mutant melanoma cells treated with the combination of a MEK inhibitor (trametinib) and a BRAF inhibitor (dabrafenib), exhibited elevated ROS levels, both in in vitro and in vivo melanoma models. We next generated trametinib- and dabrafenib-resistant (TDR) cells and found increased ROS levels after acquisition of resistance. An immunofluorescence experiment showed an increase of DNA damage in TDR cell lines. Furthermore, we observed that TDR cells increased superoxide dismutase 2 (SOD2), an antioxidant, at both mRNA and protein levels, with the upregulation of the transcription factor Nuclear Factor (NF)-κB. Knockdown of SOD2 significantly reduced the growth of BRAF pathway inhibitor-resistant cells. In addition, the results indicate that TDR cells can be re-sensitized to BRAF pathway inhibitors by the ROS scavenger, N-Acetyl Cysteine (NAC). Overall, these data indicate that BRAF pathway inhibitor-resistant cells can compensate for elevated ROS via increased expression of the antioxidant SOD2.

From Orai to E-Cadherin: Subversion of Calcium Trafficking in Cancer to Drive Proliferation, Anoikis-Resistance, and Metastasis

The common currency of epithelial differentiation and homeostasis is calcium, stored primarily in the endoplasmic reticulum, rationed according to need, and replenished from the extracellular milieu via store-operated calcium entry (SOCE). This currency is disbursed by the IP3 receptor in response to diverse extracellular signals. The rate of release is governed by regulators of proliferation, autophagy, survival, and programmed cell death, the strength of the signal leading to different outcomes. Intracellular calcium acts chiefly through intermediates such as calmodulin that regulates growth factor receptors such as epidermal growth factor receptor (EGFR), actin polymerization, and adherens junction assembly and maintenance. Here we review this machinery and its role in differentiation, then consider how cancer cells subvert it to license proliferation, resist anoikis, and enable metastasis, either by modulating the level of intracellular calcium or its downstream targets or effectors such as EGFR, E-cadherin, IQGAP1, TMEM16A, CLCA2, and TRPA1. Implications are considered for the roles of E-cadherin and growth factor receptors in circulating tumor cells and metastasis. The discovery of novel, cell type-specific modulators and effectors of calcium signaling offers new possibilities for cancer chemotherapy.

The Warburg metabolism fuels tumor metastasis

The Warburg effect is prevalent in human cancer. Accordingly, most cancer cells display highly elevated glycolysis without proportionally increasing pyruvate oxidation. The metastatic process imposes strong selective pressure on cancer cells, and metastasizing cancer cells experience heightened oxidative stress. By constraining mitochondrial oxidative metabolism, the Warburg effect helps cancer cells to minimize oxidative stress, thereby facilitating metastatic dissemination. The PGC1α transcriptional coactivator is a central coordinator of oxidative metabolism. While promoting oxidative metabolism and reversing the Warburg effect, PGC1α critically activates antioxidant genes and protects cells against oxidative damage. Therefore, depending on the context, PGC1α may promote or suppress tumor metastasis. Cancer cells generally retain metabolic flexibility and can resist antiglycolysis treatment by undergoing metabolic reprogramming. Synthetic lethal combination therapies are thus essential to attack the liabilities of the Warburg metabolism for therapeutic benefit.