FOXM1-Induced PRX3 Regulates Stemness and Survival of Colon Cancer Cells via Maintenance of Mitochondrial Function

Activin and Hepatocyte Growth Factor Promotes Colorectal Cancer Stemness and Metastasis through FOXM1/SOX2/CXCR4 Signaling

Background/Aims

Cancer stem cells (CSCs) are believed to drive tumor development and metastasis. Activin and hepatocyte growth factor (HGF) are important cytokines with the ability to induce cancer stemness. However, the effect of activin and HGF combination treatment on CSCs is still unclear.

Methods

In this study, we sequentially treated colorectal cancer cells with activin and HGF and examined CSC marker expression, self-renewal, tumorigenesis, and metastasis. The roles of forkhead box M1 (FOXM1) and sex-determining region Y-box 2 (SOX2), two stemness-related transcription factors, in activin/HGF-induced aggressive phenotype were explored.

Results

Activin and HGF treatment increased the expression of CSC markers and enhanced sphere formation in colorectal cancer cells. The tumorigenic and metastatic capacities of colorectal cancer cells were enhanced upon activin and HGF treatment. Activin and HGF treatment preferentially promoted stemness and metastasis of CD133+ subpopulations sorted from colorectal cancer cells. FOXM1 was upregulated by activin and HGF treatment, and the knockdown of FOXM1 blocked activin/HGF-induced stemness, tumorigenesis, and metastasis of colorectal cancer cells. Similarly, SOX2 was silencing impaired sphere formation of activin/HGF-treated colorectal cancers. Overexpression of SOX2 rescued the stem cell-like phenotype in FOXM1-depleted colorectal cancer cells with activin and HGF treatment. Additionally, the inhibition of FOXM1 via thiostrepton suppressed activin/HGF-induced stemness, tumorigenesis and metastasis.

Conclusions

Sequential treatment with activin and HGF promotes colorectal cancer stemness and metastasis through activation of the FOXM1/SOX2 signaling. FOXM1 could be a potential target for the treatment of colorectal cancer metastasis.

Mitochondrial function and gastrointestinal diseases

Mitochondria are dynamic organelles that function in cellular energy metabolism, intracellular and extracellular signalling, cellular fate and stress responses. Mitochondria of the intestinal epithelium, the cellular interface between self and enteric microbiota, have emerged as crucial in intestinal health. Mitochondrial dysfunction occurs in gastrointestinal diseases, including inflammatory bowel diseases and colorectal cancer. In this Review, we provide an overview of the current understanding of intestinal epithelial cell mitochondrial metabolism, function and signalling to affect tissue homeostasis, including gut microbiota composition. We also discuss mitochondrial-targeted therapeutics for inflammatory bowel diseases and colorectal cancer and the evolving concept of mitochondrial impairment as a consequence versus initiator of the disease.

Activation of the FOXM1/ASF1B/PRDX3 axis confers hyperproliferative and antioxidative stress reactivity to gastric cancer

Nucleosome assembly during DNA replication is dependent on histone chaperones. Recent studies suggest that dysregulated histone chaperones contribute to cancer progression, including gastric cancer (GC). Further studies are required to explore the prognostic and therapeutic implications of histone chaperones and their mechanisms of action in GC progression. Here we identified histone chaperone ASF1B as a potential biomarker for GC proliferation and prognosis. ASF1B was significantly upregulated in GC, which was associated with poor prognosis. In vitro and in vivo experiments demonstrated that the inhibition of ASF1B suppressed the malignant characteristics of GC, while overexpression of ASF1B had the opposite effect. Mechanistically, transcription factor FOXM1 directly bound to the ASF1B-promoter region, thereby regulating its transcription. Treatment with thiostrepton, a FOXM1 inhibitor, not only suppressed ASF1B expression, but also inhibited GC progression. Furthermore, ASF1B regulated the mitochondrial protein peroxiredoxin 3 (PRDX3) transcription in a FOXM1-dependent manner. The crucial role of ASF1B-regulated PRDX3 in GC cell proliferation and oxidative stress balance was also elucidated. In summary, our study suggests that the FOXM1-ASF1B-PRDX3 axis is a potential therapeutic target for treating GC.

Transcription factor FOXM1 specifies chromatin DNA to extracellular vesicles

Extracellular vesicle DNAs (evDNAs) hold significant diagnostic value for various diseases and facilitate transcellular transfer of genetic material. Our study identifies transcription factor FOXM1 as a mediator for directing chromatin genes or DNA fragments (termed FOXM1-chDNAs) to extracellular vesicles (EVs). FOXM1 binds to MAP1LC3/LC3 in the nucleus, and FOXM1-chDNAs, such as the DUX4 gene and telomere DNA, are designated by FOXM1 binding and translocated to the cytoplasm before being released to EVs through the secretory autophagy during lysosome inhibition (SALI) process involving LC3. Disrupting FOXM1 expression or the SALI process impairs FOXM1-chDNAs incorporation into EVs. FOXM1-chDNAs can be transmitted to recipient cells via EVs and expressed in recipient cells when they carry functional genes. This finding provides an example of how chromatin DNA fragments are specified to EVs by transcription factor FOXM1, revealing its contribution to the formation of evDNAs from nuclear chromatin. It provides a basis for further exploration of the roles of evDNAs in biological processes, such as horizontal gene transfer.Abbreviation: ATG5: autophagy related 5; CCFs: cytoplasmic chromatin fragments; ChIP: chromatin immunoprecipitation; cytoDNA: cytoplasmic DNA; CQ: chloroquine; FOXM1-DBD: FOXM1 DNA binding domain; DUX4:double homeobox 4; EVs: extracellular vesicles; evDNAs: extracellular vesicle DNAs; FOXM1: forkhead box M1; FOXM1-chDNAs: chromatin DNA fragments directed by FOXM1 to EVs; HGT: horizontal gene transfer; LC3-II: lipid modified LC3; LMNB1: lamin B1; LIR: LC3-interacting region; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MVBs: multivesicular bodies; M1-binding DNA: a linear DNA containing 72× FOXM1 binding sites; SALI: secretory autophagy during lysosome inhibition; siRNA: small interfering RNA; TetO-DUX4: TetO array-containing DUX4 DNA; TetO: tet operator; TetR: tet repressor.

A novel SLC25A1 inhibitor, parthenolide, suppresses the growth and stemness of liver cancer stem cells with metabolic vulnerability

Liver cancer stem cells (LCSCs) are recognized as key contributors to hepatocarcinogenesis, progression, and recurrence. Consequently, eradicating LCSCs has a great chance of increasing long-term survival in patients with liver cancer. Parthenolide (PTL), a natural sesquiterpene lactone product, possesses robust antitumor activity. However, the effects of PTL on LCSCs and underlying mechanisms remain unknown. Here we show that administration of PTL stimulated cell cycle arrest at the G1 phase, induced apoptosis, and decreased the stemness of LCSCs. Further research indicates that PTL caused the production of ROS and the reduction of oxidative phosphorylation (OXPHOS) and mitochondrial membrane potential (MMP) levels of LCSCs. RNA sequencing (RNA-Seq) further shows that PTL decreased SLC25A1 expression at the mRNA level and that inhibition of SLC25A1 synergistically decreased the expression of IDH2 and several pivotal genes involved in mitochondrial respiratory chain complex, resulting in the production of ROS and mitochondrial dysfunction. In addition, the inhibitory effect of PTL on mitochondrial function and self-renewal capacity of LCSCs was abolished by the knockdown of SLC25A1 or treatment with SLC25A1 inhibitor CTPI-2. Importantly, PTL prevented liver cancer growth in vivo without clearly causing toxicity. Our research shows that PTL inhibits the growth and stemness of LCSCs through SLC25A1-mediated mitochondrial function. PTL may be a potential candidate natural agent for liver cancer treatment.

Mitochondria in cancer stem cells: Achilles heel or hard armor

Previous studies have shown that mitochondria play core roles in not only cancer stem cell (CSC) metabolism but also the regulation of CSC stemness maintenance and differentiation, which are key regulators of cancer progression and therapeutic resistance. Therefore, an in-depth study of the regulatory mechanism of mitochondria in CSCs is expected to provide a new target for cancer therapy. This article mainly introduces the roles played by mitochondria and related mechanisms in CSC stemness maintenance, metabolic transformation, and chemoresistance. The discussion mainly focuses on the following aspects: mitochondrial morphological structure, subcellular localization, mitochondrial DNA, mitochondrial metabolism, and mitophagy. The manuscript also describes the recent clinical research progress on mitochondria-targeted drugs and discusses the basic principles of their targeted strategies. Indeed, an understanding of the application of mitochondria in the regulation of CSCs will promote the development of novel CSC-targeted strategies, thereby significantly improving the long-term survival rate of patients with cancer.

Role of Fork-Head Box Genes in Breast Cancer: From Drug Resistance to Therapeutic Targets

Breast cancer has been acknowledged as one of the most notorious cancers, responsible for millions of deaths around the globe. Understanding the various factors, genetic mutations, comprehensive pathways, etc., that are involved in the development of breast cancer and how these affect the development of the disease is very important for improving and revitalizing the treatment of this global health issue. The forkhead-box gene family, comprising 19 subfamilies, is known to have a significant impact on the growth and progression of this cancer. The article looks into the various forkhead genes and how they play a role in different types of cancer. It also covers their impact on cancer drug resistance, interaction with microRNAs, explores their potential as targets for drug therapies, and their association with stem cells.

New insights into the roles of peroxiredoxins in cancer

Oxidative stress is one of the hallmarks of cancer. Tumorigenesis and progression are accompanied by elevated reactive oxygen species (ROS) levels and adaptive elevation of antioxidant expression levels. Peroxiredoxins (PRDXs) are among the most important antioxidants and are widely distributed in a variety of cancers. PRDXs are involved in the regulation of a variety of tumor cell phenotypes, such as invasion, migration, epithelial-mesenchymal transition (EMT) and stemness. PRDXs are also associated with tumor cell resistance to cell death, such as apoptosis and ferroptosis. In addition, PRDXs are involved in the transduction of hypoxic signals in the TME and in the regulation of the function of other cellular components of the TME, such as cancer-associated fibroblasts (CAFs), natural killer (NK) cells and macrophages. This implies that PRDXs are promising targets for cancer treatment. Of course, further studies are needed to realize the clinical application of targeting PRDXs. In this review, we highlight the role of PRDXs in cancer, summarizing the basic features of PRDXs, their association with tumorigenesis, their expression and function in cancer, and their relationship with cancer therapeutic resistance.

Mitochondria in colorectal cancer stem cells - a target in drug resistance

Colorectal cancer (CRC) is the third most diagnosed cancer and the second most deadly type of cancer worldwide. In late diagnosis, CRC can resist therapy regimens in which cancer stem cells (CSCs) are intimately related. CSCs are a subpopulation of tumor cells responsible for tumor initiation and maintenance, metastasis, and resistance to conventional treatments. In this scenario, colorectal cancer stem cells (CCSCs) are considered an important key for therapeutic failure and resistance. In its turn, mitochondria is an organelle involved in many mechanisms in cancer, including chemoresistance of cytotoxic drugs due to alterations in mitochondrial metabolism, apoptosis, dynamics, and mitophagy. Therefore, it is crucial to understand the mitochondrial role in CCSCs regarding CRC drug resistance. It has been shown that enhanced anti-apoptotic protein expression, mitophagy rate, and addiction to oxidative phosphorylation are the major strategies developed by CCSCs to avoid drug insults. Thus, new mitochondria-targeted drug approaches must be explored to mitigate CRC chemoresistance via the ablation of CCSCs.

The Role of Peroxiredoxins in Cancer Development

Peroxiredoxins (Prxs) are antioxidant enzymes with ubiquitous expression in human tissues. Prxs are expressed in archaea, bacteria, and eukaryota, often in multiple isoforms. Because of their abundant expression in different cellular organelles and extraordinary sensitivity to H2O2, Prxs are among the first defenses against oxidative stress. Prxs undergo reversible oxidation to disulfides, and some family members perform chaperone or phospholipase functions upon further oxidation. Prxs are upregulated in cancer cells. Research has suggested that Prxs can function as tumor promoters in various cancers. The major objective of this review is to summarize novel findings regarding the roles of Prxs in common cancer types. Prxs have been shown to influence differentiation of inflammatory cells and fibroblasts, remodeling of extracellular matrix, and regulation of stemness. Since aggressive cancer cells have higher intracellular levels of ROS that they can utilize to proliferate and metastasize compared to normal cells, it is critical that we understand the regulation and functions of primary antioxidants such as Prxs. These small but mighty proteins could prove to be key for improving cancer therapeutics and patient survival.

RNA methylation and cellular response to oxidative stress-promoting anticancer agents

Disruption of the complex network that regulates redox homeostasis often underlies resistant phenotypes, which hinder effective and long-lasting cancer eradication. In addition, the RNA methylome-dependent control of gene expression also critically affects traits of cellular resistance to anti-cancer agents. However, few investigations aimed at establishing whether the epitranscriptome-directed adaptations underlying acquired and/or innate resistance traits in cancer could be implemented through the involvement of redox-dependent or -responsive signaling pathways. This is unexpected mainly because: i) the effectiveness of many anti-cancer approaches relies on their capacity to promote oxidative stress (OS); ii) altered redox milieu and reprogramming of mitochondrial function have been acknowledged as critical mediators of the RNA methylome-mediated response to OS. Here we summarize the current state of understanding on this topic, as well as we offer new perspectives that might lead to original approaches and strategies to delay or prevent the problem of refractory cancer and tumor recurrence.

The complex network of transcription factors, immune checkpoint inhibitors and stemness features in colorectal cancer: A recent update

Cancer immunity is regulated by several mechanisms that include co-stimulatory and/or co-inhibitory molecules known as immune checkpoints expressed by the immune cells. In colorectal cancer (CRC), CTLA-4, LAG3, TIM-3 and PD-1 are the major co-inhibitory checkpoints involved in tumor development and progression. On the other hand, the deregulation of transcription factors and cancer stem cells activity plays a major role in the development of drug resistance and in the spread of metastatic disease in CRC. In this review, we describe how the modulation of such transcription factors affects the response of CRC to therapies. We also focus on the role of cancer stem cells in tumor metastasis and chemoresistance and discuss both preclinical and clinical approaches for targeting stem cells to prevent their tumorigenic effect. Finally, we provide an update on the clinical applications of immune checkpoint inhibitors in CRC and discuss the regulatory effects of transcription factors on the expression of the immune inhibitory checkpoints with specific focus on the PD-1 and PD-L1 molecules.

MiR-4521 perturbs FOXM1-mediated DNA damage response in breast cancer

Introduction: Forkhead (FOX) transcription factors are involved in cell cycle control, cellular differentiation, maintenance of tissues, and aging. Mutation or aberrant expression of FOX proteins is associated with developmental disorders and cancers. FOXM1, an oncogenic transcription factor, is a promoter of cell proliferation and accelerated development of breast adenocarcinomas, squamous carcinoma of the head, neck, and cervix, and nasopharyngeal carcinoma. High FOXM1 expression is correlated with chemoresistance in patients treated with doxorubicin and Epirubicin by enhancing the DNA repair in breast cancer cells. Method: miRNA-seq identified downregulation of miR-4521 in breast cancer cell lines. Stable miR-4521 overexpressing breast cancer cell lines (MCF-7, MDA-MB-468) were developed to identify miR-4521 target gene and function in breast cancer. Results: Here, we showed that FOXM1 is a direct target of miR-4521 in breast cancer. Overexpression of miR-4521 significantly downregulated FOXM1 expression in breast cancer cells. FOXM1 regulates cell cycle progression and DNA damage response in breast cancer. We showed that miR-4521 expression leads to increased ROS levels and DNA damage in breast cancer cells. FOXM1 plays a critical role in ROS scavenging and promotes stemness which contributes to drug resistance in breast cancer. We observed that breast cancer cells stably expressing miR-4521 lead to cell cycle arrest, impaired FOXM1 mediated DNA damage response leading to increased cell death in breast cancer cells. Additionally, miR-4521-mediated FOXM1 downregulation perturbs cell proliferation, invasion, cell cycle progression, and epithelial-to-mesenchymal progression (EMT) in breast cancer. Discussion: High FOXM1 expression has been associated with radio and chemoresistance contributing to poor patient survival in multiple cancers, including breast cancer. Our study showed that FOXM1 mediated DNA damage response could be targeted using miR-4521 mimics as a novel therapeutic for breast cancer.

Sequential Treatment with Activin and Hepatocyte Growth Factor Induces FOXM1 to Promote Colorectal Cancer Liver Metastasis

BACKGROUND

Cancer stem cells (CSCs) are involved in liver metastasis in colorectal cancer (CRC). Activin and hepatocyte growth factor (HGF) are important regulators of stem cell properties. This study was performed to explore the effect of activin and HGF on CRC invasion and metastasis. The key genes involved in the action of activin and HGF in CRC were identified.

METHODS

HCT116 CRC cells were sequentially treated with activin and HGF and examined for migration and invasion in vitro and liver metastasis in vivo. RNA sequencing was performed to identify differentially expressed genes in response to activin and HGF.

RESULTS

Sequential treatment with activin and HGF-enhanced CRC cell migration, invasion, and metastasis. CXCR4 and AFP expressions were increased by activin and HGF treatment. Knockdown of FOXM1 blocked liver metastasis from HCT116 cells pretreated with activin and HGF and suppressed CXCR4 and AFP expression. Activin alone increased the mRNA and protein expression of FOXM1. In contrast, HGF alone enhanced the phosphorylation of FOXM1, without altering the total protein level of FOXM1. SMAD2 was required for activin-mediated FOXM1 induction. FOXM1 transactivated CXCR4 by directly binding to the promoter of CXCR4. Additionally, CXCR4 regulated AFP expression through the NF-κB pathway.

CONCLUSIONS

Sequential treatment with activin and HGF accelerates CRC invasion and liver metastasis, which involves the upregulation and activation of FOXM1 and induction of CXCR4 and AFP.

The Effect of Oxidative Phosphorylation on Cancer Drug Resistance

Recent studies have shown that oxidative phosphorylation (OXPHOS) is a target for the effective attenuation of cancer drug resistance. OXPHOS inhibitors can improve treatment responses to anticancer therapy in certain cancers, such as melanomas, lymphomas, colon cancers, leukemias and pancreatic ductal adenocarcinoma (PDAC). However, the effect of OXPHOS on cancer drug resistance is complex and associated with cell types in the tumor microenvironment (TME). Cancer cells universally promote OXPHOS activity through the activation of various signaling pathways, and this activity is required for resistance to cancer therapy. Resistant cancer cells are prevalent among cancer stem cells (CSCs), for which the main metabolic phenotype is increased OXPHOS. CSCs depend on OXPHOS to survive targeting by anticancer drugs and can be selectively eradicated by OXPHOS inhibitors. In contrast to that in cancer cells, mitochondrial OXPHOS is significantly downregulated in tumor-infiltrating T cells, impairing antitumor immunity. In this review, we summarize novel research showing the effect of OXPHOS on cancer drug resistance, thereby explaining how this metabolic process plays a dual role in cancer progression. We highlight the underlying mechanisms of metabolic reprogramming in cancer cells, as it is vital for discovering new drug targets.

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.

Dysregulated FOXM1 signaling in the regulation of cancer stem cells

Since the introduction of the cancer stem cell (CSC) paradigm, significant advances have been made in understanding the functional and biological plasticity of these elusive components in malignancies. Endowed with self-renewing abilities and multilineage differentiation potential, CSCs have emerged as cellular drivers of virtually all facets of tumor biology, including metastasis, tumor recurrence/relapse, and drug resistance. The functional and biological characteristics of CSCs, such as self-renewal, cell fate decisions, survival, proliferation, and differentiation are regulated by an array of extracellular factors, signaling pathways, and pluripotent transcriptional factors. Besides the well-characterized regulatory role of transcription factors OCT4, SOX2, NANOG, KLF4, and MYC in CSCs, evidence for the central role of Forkhead box transcription factor FOXM1 in the establishment, maintenance, and functions of CSCs is accumulating. Conventionally identified as a master regulator of the cell cycle, a comprehensive understanding of this molecule has revealed its multifarious oncogenic potential and uncovered its role in angiogenesis, invasion, migration, self-renewal, and drug resistance. This review compiles the large body of literature that has accumulated in recent years that provides evidence for the mechanisms by which FOXM1 expression promotes stemness in glioblastoma, breast, colon, ovarian, lung, hepatic, and pancreatic carcinomas. We have also compiled the data showing the association of stem cell mediators with FOXM1 using TCGA mRNA expression data. Further, the prognostic importance of FOXM1 and other stem cell markers is presented. The delineation of FOXM1-mediated regulation of CSCs can aid in the development of molecularly targeted pharmacological approaches directed at the selective eradication of CSCs in several human malignancies.

Essential Roles of Peroxiredoxin IV in Inflammation and Cancer

Peroxiredoxin IV (Prx4) is a 2-Cysteine peroxidase with ubiquitous expression in human tissues. Prx4 scavenges hydrogen peroxide and participates in oxidative protein folding in the endoplasmic reticulum. In addition, Prx4 is secreted outside the cell. Prx4 is upregulated in several cancers and is a potential therapeutic target. We have summarized historical and recent advances in the structure, function and biological roles of Prx4, focusing on inflammatory diseases and cancer. Oxidative stress is known to activate pro-inflammatory pathways. Chronic inflammation is a risk factor for cancer development. Hence, redox enzymes such as Prx4 are important players in the crosstalk between inflammation and cancer. Understanding molecular mechanisms of regulation of Prx4 expression and associated signaling pathways in normal physiological and disease conditions should reveal new therapeutic strategies. Thus, although Prx4 is a promising therapeutic target for inflammatory diseases and cancer, further research needs to be conducted to bridge the gap to clinical application.

Mitochondrial DNA mutations in aging and cancer

Advancing age is a major risk factor for malignant transformation and the development of cancer. As such, over 50% of neoplasms occur in individuals over the age of 70. The pathologies of both ageing and cancer have been characterized by respective groups of molecular hallmarks, and while some features are divergent between the two pathologies, several are shared. Perturbed mitochondrial function is one such common hallmark, and this observation therefore suggests that mitochondrial alterations may be of significance in age‐related cancer development. There is now considerable evidence documenting the accumulation of somatic mitochondrial DNA (mtDNA) mutations in ageing human postmitotic and replicative tissues. Similarly, mutations of the mitochondrial genome have been reported in human cancers for decades. The plethora of functions in which mitochondria partake, such as oxidative phosphorylation, redox balance, apoptosis and numerous biosynthetic pathways, manifests a variety of ways in which alterations in mtDNA may contribute to tumour growth. However, the specific mechanisms by which mtDNA mutations contribute to tumour progression remain elusive and often contradictory. This review aims to consolidate current knowledge and describe future direction within the field.

Oncofetal proteins and cancer stem cells

Cancer stem cells (CSCs) are considered as a small population of cells with stem-like properties within the tumor bulk, and are largely responsible for tumor recurrence, metastasis, and therapy resistance. CSCs share critical features with embryonic stem cells (ESCs). The pluripotent transcription factors (TFs) and developmental signaling pathways of ESCs are invariably hijacked by CSCs termed ‘oncofetal drivers’ in many cancers, which are rarely detectable in adult tissues. The unique expression pattern makes oncofetal proteins ideal therapeutic targets in cancer treatment. Therefore, elucidation of oncofetal drivers in cancers is critical for the development of effective CSCs-directed therapy. In this review, we summarize the common pluripotent TFs such as OCT4, SOX2, NANOG, KLF4, MYC, SALL4, and FOXM1, as well as the development signaling including Wnt/β-catenin, Hedgehog (Hh), Hippo, Notch, and TGF-β pathways of ESCs and CSCs. We also describe the newly identified oncofetal proteins that drive the self-renewal, plasticity, and therapy-resistance of CSCs. Finally, we explore how the clinical implementation of targeting oncofetal drivers, including small-molecule inhibitors, vaccines, antibodies, and CAR-T (chimeric antigen receptor T cell) can facilitate the development of CSCs-directed therapy.

Targeting cellular energy metabolism- mediated ferroptosis by small molecule compounds for colorectal cancer therapy

Alterations in cellular energy metabolism, including glycolysis, glutamine and lipid metabolism that affects ferroptosis in the tumour microenvironment (TME), play a critical role in the development and progression of colorectal cancer (CRC) and offer evolutionary advantages to tumour cells and even enhance their aggressive phenotype. This review summarises the findings on the dysregulated energy metabolism pathways, including lipid and fatty acid metabolism especially for regulating the ferroptosis in TME. Moreover, the cellular energy metabolism and tumour ferroptosis to be regulated by small molecule compounds, which targeting the different aspects of metabolic pathways of energy production as well as metabolic enzymes that connect with the tumour cell growth and ferroptosis in CRC are also discussed. In this review, we will provide a comprehensive summary on small molecule compounds regulatory function of different energy metabolic routes on ferroptosis in tumour cells and discuss those metabolic vulnerabilities for the development of potential ferroptosis-based tumour therapies for colorectal cancer.

Carnosol alleviates nonalcoholic fatty liver disease by inhibiting mitochondrial dysfunction and apoptosis through targeting of PRDX3

Mitochondrial dysfunction is a major factor in nonalcoholic fatty liver disease (NAFLD), preceding insulin resistance and hepatic steatosis. Carnosol (CAR) is a kind of diterpenoid with antioxidant, anti-inflammatory and antitumor activities. Peroxiredoxin 3 (PRDX3), a mitochondrial H2O2-eliminating enzyme, undergoes overoxidation and subsequent inactivation under oxidative stress. The purpose of this study was to investigate the protective effect of the natural phenolic compound CAR on NAFLD via PRDX3. Mice fed a high-fat diet (HFD) and AML-12 cells treated with palmitic acid (PA) were used to detect the molecular mechanism of CAR in NAFLD. We found that pharmacological treatment with CAR notably moderated HFD- and PA- induced steatosis and liver injury, as shown by biochemical assays, Oil Red O and Nile Red staining. Further mechanistic investigations revealed that CAR exerted anti-NAFLD effects by inhibiting mitochondrial oxidative stress, perturbation of mitochondrial dynamics, and apoptosis in vivo and in vitro. The decreased protein and mRNA levels of PRDX3 were accompanied by intense oxidative stress after PA intervention. Interestingly, CAR specifically bound PRDX3, as shown by molecular docking assays, and increased the expression of PRDX3. However, the hepatoprotection of CAR in NAFLD was largely abolished by specific PRDX3 siRNA, which increased mitochondrial dysfunction and exacerbated apoptosis in vitro. In conclusion, CAR suppressed lipid accumulation, mitochondrial dysfunction and hepatocyte apoptosis by activating PRDX3, mitigating the progression of NAFLD, and thus, CAR may represent a promising candidate for clinical treatment of steatosis.

LRPPRC regulates redox homeostasis via the circANKHD1/FOXM1 axis to enhance bladder urothelial carcinoma tumorigenesis

Reactive oxygen species (ROS) which are continuously generated mainly by mitochondria, have been proved to play an important role in the stress signaling of cancer cells. Moreover, pentatricopeptide repeat (PPR) proteins have been suggested to take part in mitochondrial metabolism. However, the mechanisms integrating the actions of these distinct networks in urothelial carcinoma of the bladder (UCB) pathogenesis are elusive. In this study, we found that leucine rich pentatricopeptide repeat containing (LRPPRC) was frequently upregulated in UCB and that it was an independent prognostic factor in UCB. We further revealed that LRPPRC promoted UCB tumorigenesis by regulating the intracellular ROS homeostasis. Mechanistically, LRPPRC modulates ROS balance and protects UCB cells from oxidative stress via mt-mRNA metabolism and the circANKHD1/FOXM1 axis. In addition, the SRA stem-loop interacting RNA binding protein (SLIRP) directly interacted with LRPPRC to protect it from ubiquitination and proteasomal degradation. Notably, we showed that LRPPRC modulated the tumorigenesis of UCB cells in a circANKHD1-FOXM1-dependent manner. In conclusion, LRPPRC exerts critical roles in regulating UCB redox homeostasis and tumorigenesis, and is a prognostic factor for UCB; suggesting that LRPPRC may serve as an exploitable therapeutic target in UCB.

The distinct responsiveness of cytokeratin 19-positive hepatocellular carcinoma to regorafenib

Cytokeratin 19-positive (CK19+) hepatocellular carcinoma (HCC) is an aggressive subtype characterized by early recurrence and chemotherapy tolerance. However, there is no specific therapeutic option for CK19+ HCC. The correlation between tumor recurrence and expression status of CK19 were studied in 206 patients undergoing liver transplantation for HCC. CK19-/+ HCC cells were isolated to screen effective antitumor drugs. The therapeutic effects of regorafenib were evaluated in patient-derived xenograft (PDX) models from 10 HCC patients. The mechanism of regorafenib on CK19+ HCC was investigated. CK19 positiveness indicated aggressiveness of tumor and higher recurrence risk of HCC after liver transplantation. The isolated CK19+ HCC cells had more aggressive behaviors than CK19- cells. Regorafenib preferentially increased the growth inhibition and apoptosis of CK19+ cells in vitro, whereas sorafenib, apatinib, and 5-fluorouracil did not. In PDX models from CK19-/+ HCC patients, the tumor control rate of regorafenib achieved 80% for CK19+ HCCs, whereas 0% for CK19- HCCs. RNA-sequencing revealed that CK19+ cells had elevated expression of mitochondrial ribosomal proteins, which are essential for mitochondrial function. Further experiments confirmed that regorafenib attenuated the mitochondrial respiratory capacity in CK19+ cells. However, the mitochondrial respiration in CK19- cells were faint and hardly repressed by regorafenib. The mitochondrial respiration was regulated by the phosphorylation of signal transducer and activator of transcription 3 (STAT3), which was inhibited by regorafenib in CK19+ cells. Hence, CK19 could be a potential marker of the therapeutic benefit of regorafenib, which facilitates the individualized therapy for HCC. STAT3/mitochondria axis determines the distinct response of CK19+ cells to regorafenib treatment.

The sulfiredoxin-peroxiredoxin redox system regulates the stemness and survival of colon cancer stem cells

Cancer stem cells (CSCs) initiate tumor formation and are known to be resistant to chemotherapy. A metabolic alteration in CSCs plays a critical role in stemness and survival. However, the association between mitochondrial energy metabolism and the redox system remains undefined in colon CSCs. In this study, we assessed the role of the Sulfiredoxin-Peroxiredoxin (Srx-Prx) redox system and mitochondrial oxidative phosphorylation (OXPHOS) in maintaining the stemness and survival of colon CSCs. Notably, Srx contributed to the stability of PrxI, PrxII, and PrxIII proteins in colon CSCs. Increased Srx expression promoted the stemness and survival of CSCs and was important for the maintenance of the mitochondrial OXPHOS system. Furthermore, Nrf2 and FoxM1 led to OXPHOS activation and upregulated expression of Srx-Prx redox system-related genes. Therefore, the Nrf2/FoxM1-induced Srx-Prx redox system is a potential therapeutic target for eliminating CSCs in colon cancer.

FOXM1: A Multifunctional Oncoprotein and Emerging Therapeutic Target in Ovarian Cancer

Forkhead box M1 (FOXM1) is a member of the conserved forkhead box (FOX) transcription factor family. Over the last two decades, FOXM1 has emerged as a multifunctional oncoprotein and a robust biomarker of poor prognosis in many human malignancies. In this review article, we address the current knowledge regarding the mechanisms of regulation and oncogenic functions of FOXM1, particularly in the context of ovarian cancer. FOXM1 and its associated oncogenic transcriptional signature are enriched in >85% of ovarian cancer cases and FOXM1 expression and activity can be enhanced by a plethora of genomic, transcriptional, post-transcriptional, and post-translational mechanisms. As a master transcriptional regulator, FOXM1 promotes critical oncogenic phenotypes in ovarian cancer, including: (1) cell proliferation, (2) invasion and metastasis, (3) chemotherapy resistance, (4) cancer stem cell (CSC) properties, (5) genomic instability, and (6) altered cellular metabolism. We additionally discuss the evidence for FOXM1 as a cancer biomarker, describe the rationale for FOXM1 as a cancer therapeutic target, and provide an overview of therapeutic strategies used to target FOXM1 for cancer treatment.

Peroxiredoxin 3 Inhibits Acetaminophen-Induced Liver Pyroptosis Through the Regulation of Mitochondrial ROS

Pyroptosis is a newly discovered form of cell death. Peroxiredoxin 3 (PRX3) plays a crucial role in scavenging reactive oxygen species (ROS), but its hepatoprotective capacity in acetaminophen (APAP)-induced liver disease remains unclear. The aim of this study was to assess the role of PRX3 in the regulation of pyroptosis during APAP-mediated hepatotoxicity. We demonstrated that pyroptosis occurs in APAP-induced liver injury accompanied by intense oxidative stress and inflammation, and liver specific PRX3 silencing aggravated the initiation of pyroptosis and liver injury after APAP intervention. Notably, excessive mitochondrial ROS (mtROS) was observed to trigger pyroptosis by activating the NLRP3 inflammasome, which was ameliorated by Mito-TEMPO treatment, indicating that the anti-pyroptotic role of PRX3 relies on its powerful ability to regulate mtROS. Overall, PRX3 regulates NLRP3-dependent pyroptosis in APAP-induced liver injury by targeting mitochondrial oxidative stress.

High copy number variations, particular transcription factors, and low immunity contribute to the stemness of prostate cancer cells

Background

Tumor metastasis is the main cause of death of cancer patients, and cancer stem cells (CSCs) is the basis of tumor metastasis. However, systematic analysis of the stemness of prostate cancer cells is still not abundant. In this study, we explore the effective factors related to the stemness of prostate cancer cells by comprehensively mining the multi-omics data from TCGA database.

Methods

Based on the prostate cancer transcriptome data in TCGA, gene expression modules that strongly relate to the stemness of prostate cancer cells are obtained with WGCNA and stemness scores. Copy number variation of stemness genes of prostate cancer is calculated and the difference of transcription factors between prostate cancer and normal tissues is evaluated by using CNV (copy number variation) data and ATAC-seq data. The protein interaction network of stemness genes in prostate cancer is constructed using the STRING database. Meanwhile, the correlation between stemness genes of prostate cancer and immune cells is analyzed.

Results

Prostate cancer with higher Gleason grade possesses higher cell stemness. The gene set highly related to prostate cancer stemness has higher CNV in prostate cancer samples than that in normal samples. Although the transcription factors of stemness genes have similar expressions, they have different contributions between normal and prostate cancer tissues; and particular transcription factors enhance the stemness of prostate cancer, such as PUM1, CLOCK, SP1, TCF12, and so on. In addition, the lower tumor immune microenvironment is conducive to the stemness of prostate cancer. CD8 + T cells and M1 macrophages may play more important role in the stemness of prostate cancer than other immune cells in the tumor microenvironment. Finally, EZH2 is found to play a central role in stemness genes and is negatively correlated with resting mast cells and positively correlated with activated memory CD4 + T cells.

Conclusions

Based on the systematic and combined analysis of multi-omics data, we find that high copy number variation, specific transcription factors, and low immune microenvironment jointly contribute to the stemness of prostate cancer cells. These findings may provide us new clues and directions for the future research on stemness of prostate cancer.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-021-02870-x.

Cellular senescence in hepatocellular carcinoma induced by a long non-coding RNA-encoded peptide PINT87aa by blocking FOXM1-mediated PHB2

Rationale: Recently, long non-coding RNAs (lncRNAs), known to be involved in human cancer progression, have been shown to encode peptides with biological functions, but the role of lncRNA-encoded peptides in cellular senescence is largely unexplored. We previously reported the tumor-suppressive role of PINT87aa, a peptide encoded by the long intergenic non-protein coding RNA, p53 induced transcript (LINC-PINT). Here, we investigated PINT87aa's role in hepatocellular carcinoma (HCC) cellular senescence. Methods: We examined PINT87aa and truncated PINT87aa functions in vitro by monitoring cell proliferation and performed flow cytometry, senescence-associated β-galactosidase staining, JC-1 staining indicative of mitochondrial membrane potential, the ratio of the overlapping area of light chain 3 beta (LC3B) and mitochondrial probes and the ratio of lysosomal associated membrane protein 1 (LAMP1) overlapping with cytochrome c oxidase subunit 4I1 (COXIV) denoting mitophagy. PINT87aa and truncated PINT87aa functions in vivo were verified by subcutaneously transplanted tumors in nude mice. The possible binding between PINT87aa and forkhead box M1 (FOXM1) was predicted through structural analysis and verified by co-immunoprecipitation and immunofluorescence co-localization. Rescue experiments were performed in vivo and in vitro following FOXM1 overexpression. Further, chromatin immunoprecipitation, polymerase chain reaction, and dual-luciferase reporter gene assay were conducted to validate FOXM1 binding to the prohibitin 2 (PHB2) promoter. Results: PINT87aa was significantly increased in the hydrogen peroxide-induced HCC cell senescence model. Overexpression of PINT87aa induced growth inhibition, cellular senescence, and decreased mitophagy in vitro and in vivo. In contrast, FOXM1 gain-of-function could partially reduce the proportion of senescent HCC cells and enhance mitophagy. PINT87aa overexpression did not affect the expression of FOXM1 itself but reduced that of its target genes involved in cell cycle and proliferation, especially PHB2, which was involved in mitophagy and transcribed by FOXM1. Structural analysis indicated that PINT87aa could bind to the DNA-binding domain of FOXM1, which was confirmed by co-immunoprecipitation and immunofluorescence co-localization. Furthermore, we demonstrated that the 2 to 39 amino acid truncated form of the peptide exerted effects similarly to the full form. Conclusion: Our study established the role of PINT87aa as a novel biomarker and a key regulator of cellular senescence in HCC and identified PINT87aa as a potential therapeutic target for HCC.

Drug resistance and Cancer stem cells

Therapy resistance is a major problem when treating cancer patients as cancer cells develop mechanisms that counteract the effect of therapeutic compounds, leading to fit and more aggressive clones that contribute to poor prognosis. Therapy resistance can be both intrinsic and/or acquired. These are multifactorial events, and some are related to factors including adaptations in cancer stem cells (CSCs), epithelial-mesenchymal transition (EMT), deregulation of key signaling pathways, drug efflux through ABC transporters, acquired mutations, evading apoptosis, and activation of DNA damage response among others. Among these factors, CSCs represent the major source of therapy resistance. CSCs are a subset of tumor cells that are capable of self-renewal and multilineage progenitor expansion that are known to be intrinsically resistant to anticancer treatments. Multiple clones of CSCs pre-exist, and some can adopt and expand easily to changes in the tumor microenvironment (TME) and/or in response to radio- and chemotherapy. A combination of both intrinsic and extrinsic factors contributes to CSC-mediated therapy resistance. In this review, we will focus on CSCs and therapy resistance as well as suggest strategies to eliminate CSCs and, therefore, overcome resistance. Video abstract.

Transcription factors in colorectal cancer: molecular mechanism and therapeutic implications

Colorectal cancer (CRC) is a major cause of cancer mortality worldwide, however, the molecular mechanisms underlying the pathogenesis of CRC remain largely unclear. Recent studies have revealed crucial roles of transcription factors in CRC development. Transcription factors essential for the regulation of gene expression by interacting with transcription corepressor/enhancer complexes and they orchestrate downstream signal transduction. Deregulation of transcription factors is a frequent occurrence in CRC, and the accompanying drastic changes in gene expression profiles play fundamental roles in multistep process of tumorigenesis, from cellular transformation, disease progression to metastatic disease. Herein, we summarized current and emerging key transcription factors that participate in CRC tumorigenesis, and highlighted their oncogenic or tumor suppressive functions. Moreover, we presented critical transcription factors of CRC, emphasized the major molecular mechanisms underlying their effect on signal cascades associated with tumorigenesis, and summarized of their potential as molecular biomarkers for CRC prognosis therapeutic response, as well as drug targets for CRC treatment. A better understanding of transcription factors involved in the development of CRC will provide new insights into the pathological mechanisms and reveal novel prognostic biomarkers and therapeutic strategies for CRC.

Identification of Two Novel Circular RNAs Deriving from BCL2L12 and Investigation of Their Potential Value as a Molecular Signature in Colorectal Cancer

The utility of circular RNAs (circRNAs) as molecular biomarkers has recently emerged. However, only a handful of them have already been studied in colorectal cancer (CRC). The purpose of this study was to identify new circRNAs deriving from BCL2L12, a member of the BCL2 apoptosis-related family, and investigate their potential as biomarkers in CRC. Total RNA extracts from CRC cell lines and tissue samples were reversely transcribed. By combining PCR with divergent primers and nested PCR followed by Sanger sequencing, we were able to discover two BCL2L12 circRNAs. Subsequently, bioinformatical tools were used to predict the interactions of these circRNAs with microRNAs (miRNAs) and RNA-binding proteins (RBPs). Following a PCR-based pre-amplification, real-time qPCR was carried out for the quantification of each circRNA in CRC samples and cell lines. Biostatistical analysis was used to assess their potential prognostic value in CRC. Both novel BCL2L12 circRNAs likely interact with particular miRNAs and RBPs. Interestingly, circ-BCL2L12-2 expression is inversely associated with TNM stage, while circ-BCL2L12-1 overexpression is associated with shorter overall survival in CRC, particularly among TNM stage II patients. Overall, we identified two novel BCL2L12 circRNAs, one of which can further stratify TNM stage II patients into two subgroups with substantially distinct prognosis.

miR-20b-5p functions as tumor suppressor microRNA by targeting cyclinD1 in colon cancer

MicroRNA functions as an oncogenic regulator or tumor suppressor in various human tumors. Although bioinformatics analysis suggested that miRNA-20b-5p may be associated with the tumorigenesis, its role in colon cancer remains elusive. To investigate the role of miRNA-20b-5p, HCT116 cell, a human colon cancer cell line used in therapeutic research and drug screenings, was chosen as a model system for our in vitro studies. We first carried out bioinformatics and microarray analysis. To gain further mechanism insight, flow cytometry was performed to determine cell apoptosis and cell cycle, and western blot or immunohistochemistry were employed to check the expression of CCND1/CDK/FOXM1 axis in HCT116 cells. In addition, wound-healing migration assay and transwell assay were conducted to uncover the effect of miR-20b-5p on tumor migration and invasion. Finally, we examined the role of miR-20b-5p by subcutaneous xenograft mouse models. Our data have shown that miRNA-20b-5p inhibited the cell cycle, migration, and invasion in HCT116 cells, but had no effect on cell apoptosis. CyclinD1 (CCND1) was identified as a direct target of miR-20b-5p. Overexpression of miRNA-20b-5p downregulated CCND1 level in HCT-116 cells. Mechanically, the inhibition of cell cycle, migration, and invasion of CC cells mediated by miRNA-20b-5p are through regulating the CCND1/CDK4/FOXM1 axis. Furthermore, miRNA-20b-5p inhibited the tumorigenesis in Balb/c nude mice CC xenograft models. Our data demonstrated that miR-20b-5p may serve as a tumor suppressor in colon cancer by negatively regulating CCND1, implying that miR-20b-5p could be a potential therapeutic target for the treatment of colon cancer.

Advances in Therapeutic Targeting of Cancer Stem Cells within the Tumor Microenvironment: An Updated Review

Despite great strides being achieved in improving cancer patients' outcomes through better therapies and combinatorial treatment, several hurdles still remain due to therapy resistance, cancer recurrence and metastasis. Drug resistance culminating in relapse continues to be associated with fatal disease. The cancer stem cell theory posits that tumors are driven by specialized cancer cells called cancer stem cells (CSCs). CSCs are a subpopulation of cancer cells known to be resistant to therapy and cause metastasis. Whilst the debate on whether CSCs are the origins of the primary tumor rages on, CSCs have been further characterized in many cancers with data illustrating that CSCs display great abilities to self-renew, resist therapies due to enhanced epithelial to mesenchymal (EMT) properties, enhanced expression of ATP-binding cassette (ABC) membrane transporters, activation of several survival signaling pathways and increased immune evasion as well as DNA repair mechanisms. CSCs also display great heterogeneity with the consequential lack of specific CSC markers presenting a great challenge to their targeting. In this updated review we revisit CSCs within the tumor microenvironment (TME) and present novel treatment strategies targeting CSCs. These promising strategies include targeting CSCs-specific properties using small molecule inhibitors, immunotherapy, microRNA mediated inhibitors, epigenetic methods as well as targeting CSC niche-microenvironmental factors and differentiation. Lastly, we present recent clinical trials undertaken to try to turn the tide against cancer by targeting CSC-associated drug resistance and metastasis.

Targeting Altered Energy Metabolism in Colorectal Cancer: Oncogenic Reprogramming, the Central Role of the TCA Cycle and Therapeutic Opportunities

Colorectal cancer (CRC) is among the most frequent cancer entities worldwide. Multiple factors are causally associated with CRC development, such as genetic and epigenetic alterations, inflammatory bowel disease, lifestyle and dietary factors. During malignant transformation, the cellular energy metabolism is reprogrammed in order to promote cancer cell growth and proliferation. In this review, we first describe the main alterations of the energy metabolism found in CRC, revealing the critical impact of oncogenic signaling and driver mutations in key metabolic enzymes. Then, the central role of mitochondria and the tricarboxylic acid (TCA) cycle in this process is highlighted, also considering the metabolic crosstalk between tumor and stromal cells in the tumor microenvironment. The identified cancer-specific metabolic transformations provided new therapeutic targets for the development of small molecule inhibitors. Promising agents are in clinical trials and are directed against enzymes of the TCA cycle, including isocitrate dehydrogenase, pyruvate dehydrogenase kinase, pyruvate dehydrogenase complex (PDC) and α-ketoglutarate dehydrogenase (KGDH). Finally, we focus on the α-lipoic acid derivative CPI-613, an inhibitor of both PDC and KGDH, and delineate its anti-tumor effects for targeted therapy.

FoxM1-dependent and fatty acid oxidation-mediated ROS modulation is a cell-intrinsic drug resistance mechanism in cancer stem-like cells

Increased oxidative phosphorylation (OXPHOS) and reactive oxygen species (ROS) levels are inherently linked. ROS are essential signaling molecules, with detrimental effects when produced in excess during chemotherapy, leading to cell death. Cancer stem-like cells (CSCs) are a subpopulation of tumor cells resistant to chemotherapy, highly invasive and metastagenic, driving malignant cancer behavior. In this study, we demonstrated that CSCs exhibit increased OXPHOS but paradoxically low ROS levels. Considering the detrimental effects of large amounts of ROS, CSCs have developed potential mechanisms for quenching excess ROS to maintain redox homeostasis. We aimed to investigate the distinct metabolic features and mechanisms of ROS regulation in gastric CSCs and explore potential therapeutic strategies targeting CSCs. Human gastric cancer cell lines, AGS and MKN1, were subjected to liquid chromatography/mass spectrometry-based metabolomic and microarray analyses. Mitochondrial properties such as mitochondrial mass, membrane potential, and ROS were assessed by flow cytometric analysis. CSCs with increased OXPHOS levels maintained low ROS levels by coupling FoxM1-dependent Prx3 expression and fatty acid oxidation-mediated NADPH regeneration. Thus, interventions targeting ROS homeostasis in CSCs may be a useful strategy for targeting this drug-resistant tumor cell subpopulation.

Three-dimensional culture models mimic colon cancer heterogeneity induced by different microenvironments

Colorectal cancer demonstrates intra-tumour heterogeneity formed by a hierarchical structure comprised of cancer stem cells (CSCs) and their differentiated progenies. The mechanism by which CSCs are maintained and differentiated needs to be further elucidated, and there is evidence that the tumour microenvironment governs cancer stemness. Using PLR123, a colon cancer cell line with CSC properties, we determined the culture conditions necessary to establish a pair of three-dimensional (3D) culture models grown in Matrigel, designated stemCO and diffCO. The conditions were determined by comparing the phenotypes in the models with PLR123 mouse xenografts colonising lung and liver. StemCO resembled LGR5-positive undifferentiated tumours in the lung, and diffCO had lumen structures composed of polarised cells that were similar to the ductal structures found in differentiated tumours in the liver. In a case using the models for biomedical research, treatment with JAG-1 peptide or a γ-secretase inhibitor modified the Notch signaling and induced changes indicating that the signal participates in lumen formation in the models. Our results demonstrate that culture conditions affect the stemness of 3D culture models generated from CSCs and show that comparing models with different phenotypes is useful for studying how the tumour environment regulates cancer.

FOXM1: a potential therapeutic target in human solid cancers

Introduction: FOXM1 is one of the most frequently overexpressed proteins in human solid cancers. Here, we discuss novel direct targets of FOXM1 as well as new pathways involving FOXM1, through which this protein exerts its oncogenic activity.Areas covered: We give a detailed review of FOXM1 transcriptional targets involved in 16 different types of human cancer as published in the literature in the last 5 years. We also discuss a novel positive feedback loop between FOXM1 and AKT - both well-established master regulators of cancer.Expert opinion: Despite the discovery of several FOXM1 inhibitors over the years (by our team and others), their therapeutic use is limited by their adverse off-target effects.Newly-discovered proteins regulated by FOXM1 present a promising alternative approach to target its pro-cancer activity. In addition, targeting regulating proteins that take part in the positive feedback loop between FOXM1/AKT has the double advantage of suppressing both, and can lead to developing novel anti-cancer drugs.

ANKRD22, a novel tumor microenvironment-induced mitochondrial protein promotes metabolic reprogramming of colorectal cancer cells

Background: The leading cause of poor prognosis in colorectal cancer (CRC) is the presence of colorectal cancer-initiating cells (CCICs). The interplay between the tumor microenvironment (TME) and CRC cells induces reacquisition of initiating cell characteristics, but the underlying mechanisms remain elusive.

Methods: Candidate molecules were screened by global differential cDNA expression profiles of CCICs, which were enriched from patient-derived tumor xenograft models. Luciferase reporters and chromatin immunoprecipitation assays were used to explore the mechanism of TME factors regulating the transcription of ANKRD22. The effects of Ankyrin repeat domain-containing protein 22 (ANKRD22) on energy metabolism were monitored by extracellular flux and ¹³C-based metabolic flux analysis. Mass spectrometry was used to identify the interacting partners of ANKRD22. Morphological changes of CCICs overexpressing ANKRD22 were observed by electron microscopy. The effects of ANKRD22 on mitochondrial lipid metabolism were analyzed by lipidomics.

Results: We identified a novel nucleus-encoded mitochondrial membrane protein, ANKRD22, which was upregulated in CCICs. We found that ANKRD22 was induced by the p38/MAX pathway activated by different TME stimuli. As a key transcription factor, MAX promoted the transcription of ANKRD22. Expression of ANKRD22 promoted glycolysis associated with a decrease in ATP/ADP and an increase in AMP/ATP levels, which were related to its interaction with pyruvate dehydrogenase kinase isoform 1 (PDK1) and multiple subunits of ATP synthase. Further, in CCICs, ANKRD22 cooperated with the lipid transport protein, Extended Synaptotagmin-1 (E-Syt1), to transport excess lipids into mitochondria and reduced the number of mitochondria in an autophagy-independent manner, thus meeting the metabolic requirements of CCICs.

Conclusion: ANKRD22 induced by TME promotes the metabolic reprogramming of CRC cells. Our study has identified ANKRD22/E-Syt1 as a potential target for eradicating CCICs.

PRDX3 is associated with metastasis and poor survival in uveal melanoma

AIMS

Uveal melanoma (UM) is the most common primary intraocular malignancy in adults, and 40% develop fatal metastatic disease. Overexpression of thioredoxin-dependent peroxidase reductase (PRDX3) has been implicated in several cancers, including prostate, breast, colorectal and lung cancer. The aim of this study was to compare the immunohistochemical expression of PRDX3 in formalin-fixed, paraffin-embedded (FFPE) primary UM tissues of patients who did and did not develop metastatic disease.

METHODS

Immunohistochemical staining of PRDX3 was performed on FFPE tissue microarray samples of 92 primary UM tumours from patients who did and did not develop metastatic disease. The immunohistochemical staining was assessed by two observers who were blinded to all clinicopathological and cytogenetic details including metastatic/non-metastatic information. Based on a scoring system, expression of PRDX3 was graded as high or low.

RESULTS

There were 55 tumours (59.8%) from patients who developed metastatic disease, while 37 (40.2%) were from patients who did not develop metastasis. A statistically significant difference in PRDX3 expression was observed in patients who did and did not develop metastasis (p=0.001). A significant positive correlation between high PRDX3 expression and metastasis was observed (p=0.001). A significant negative correlation between PRDX3 expression and survival was found (p=0.005). Kaplan-Meier survival analysis showed a statistically significant difference in overall survival between tumours that demonstrated low and high expression of PRDX3 (67.61 vs 130.64 months, respectively, p=0.013).

CONCLUSIONS

High immunohistochemical expression of PRDX3 in primary UM tissue is associated with metastasis and poor survival.

The Prognosis Of Peroxiredoxin Family In Breast Cancer

Purpose

PRDX (Peroxiredoxin) family has involved in breast cancer tumorigenesis from the evidence obtained from cell lines, human tissues and mouse models. Nonetheless, the diversified expression patterns, coupled with the prognostic values of PRDX family, still require explanation. This study aimed at investigating the clinical importance and biological of PRDXs in breast cancer.

Patients and methods

Specimens of paraffin sections used for immunohistochemistry were collected from the hospital and the remaining patient information was retrieved from online databases. The expression and survival data of PRDXs in patients with breast cancer were from ONCOMINE, GEPIA, Kaplan–Meier Plotter. cBioPortal, Metascape, String, Cytoscape and DAVID were used to predict functions and pathways of the changes in PRDXs and their frequently altered neighbor genes. Immunohistochemistry was used to detect the expression of PRDXs in breast cancer.

Results

We discovered the expression levels of PRDX1-5 were higher in breast cancer tissues than in normal tissues, whereas the expression level of PRDX6 was observed as lower in the former one in comparison with that of the latter one. There existed a correlation between the expression levels of PRDX4, 5 and the advanced tumor stage. Survival analysis revealed that the expression of PRDXs were all associated with relapse-free survival (RFS) in all of the patients with breast cancer. Eventually, we discovered significant regulation of the cellular oxidant detoxification and detoxification of ROS by the PRDX changes, together with obtaining the core modules of genes (TXN, TXN2, TXNRD1, TXNRD2, GPX1 and GPX2) linked to the PRDX family of genes in breast cancer.

Conclusion

The PRDX family is widely involved in the development of breast cancer and affects the prognosis of patients. The functions and pathways of the changes in PRDXs and their frequently altered neighbor genes can be further verified by wet experiments.

The nuclear transcription factor FoxG1 affects the sensitivity of mimetic aging hair cells to inflammation by regulating autophagy pathways

Inflammation is a self-defense response to protect individuals from infection and tissue damage, but excessive or persistent inflammation can have adverse effects on cell survival. Many individuals become especially susceptible to chronic-inflammation-induced sensorineural hearing loss as they age, but the intrinsic molecular mechanism behind aging individuals' increased risk of hearing loss remains unclear. FoxG1 (forkhead box transcription factor G1) is a key transcription factor that plays important roles in hair cell survival through the regulation of mitochondrial function, but how the function of FoxG1 changes during aging and under inflammatory conditions is unknown. In this study, we first found that FoxG1 expression and autophagy both increased gradually in the low concentration lipopolysaccharide (LPS)-induced inflammation model, while after high concentration of LPS treatment both FoxG1 expression and autophagy levels decreased as the concentration of LPS increased. We then used siRNA to downregulate Foxg1 expression in hair cell-like OC-1 cells and found that cell death and apoptosis were significantly increased after LPS injury. Furthermore, we used d-galactose (D-gal) to create an aging model with hair cell-like OC-1 cells and cochlear explant cultures in vitro and found that the expression of Foxg1 and the level of autophagy were both decreased after D-gal and LPS co-treatment. Lastly, we knocked down the expression of Foxg1 under aged inflammation conditions and found increased numbers of dead and apoptotic cells. Together these results suggest that FoxG1 affects the sensitivity of mimetic aging hair cells to inflammation by regulating autophagy pathways.

Sirtuin-1/Mitochondrial Ribosomal Protein S5 Axis Enhances the Metabolic Flexibility of Liver Cancer Stem Cells

Metabolic reprogramming endows cancer cells with the ability to adjust metabolic pathways to support heterogeneously biological processes. However, it is not known how the reprogrammed activities are implemented during differentiation of cancer stem cells (CSCs). In this study, we demonstrated that liver CSCs relied on the enhanced mitochondrial function to maintain stemness properties, which is different from aerobic glycolysis playing main roles in the differentiated non-CSCs. We found that liver CSCs exhibit increased mitochondrial respiratory capacity and that complex-I of mitochondria was necessary for stemness properties of liver CSCs through regulation of mitochondrial respiration. Bioinformatics analysis reveals that mitochondrial ribosomal protein S5 (MRPS5) is closely related with the function of complex-I. Further experiments confirmed that MRPS5 promoted the production of nicotinamide adenine dinucleotide (NAD⁺ ), which is necessary for enhanced mitochondrial function in liver CSCs. MRPS5 played a critical role for liver CSCs to maintain stemness properties and to participate in tumor progression. Mechanistically, the acetylation status of MRPS5 is directly regulated by NAD⁺ dependent deacetylase sirtuin-1 (SIRT1), which is abundant in liver CSCs and decreased during differentiation. Deacetylated MRPS5 locates in mitochondria to promote the function complex-I and the generation of NAD⁺ to enhance mitochondrial respiration. Conversely, the acetylated MRPS5 gathered in nuclei leads to increased expression of glycolytic proteins and promotion of the Warburg Effect. Therefore, liver CSCs transform mitochondrial-dependent energy supply to a Warburg phenotype by the dual function of MRPS5. Clinical analysis of SIRT1 and MRPS5 expression in tumor tissues showed the SIRT1^High /Cytoplasmic-MRPS5^High profile was associated with patients with hepatocellular carcinoma with poor prognosis. Conclusion: SIRT1/MRPS5 axis participates in metabolic reprogramming to facilitate tumor progression and may serve as a promising therapeutic target of liver cancer.

Interplay Between Mitochondrial Peroxiredoxins and ROS in Cancer Development and Progression

Mitochondria are multifunctional cellular organelles that are major producers of reactive oxygen species (ROS) in eukaryotes; to maintain the redox balance, they are supplemented with different ROS scavengers, including mitochondrial peroxiredoxins (Prdxs). Mitochondrial Prdxs have physiological and pathological significance and are associated with the initiation and progression of various cancer types. In this review, we have focused on signaling involving ROS and mitochondrial Prdxs that is associated with cancer development and progression. An upregulated expression of Prdx3 and Prdx5 has been reported in different cancer types, such as breast, ovarian, endometrial, and lung cancers, as well as in Hodgkin's lymphoma and hepatocellular carcinoma. The expression of Prdx3 and Prdx5 in different types of malignancies involves their association with different factors, such as transcription factors, micro RNAs, tumor suppressors, response elements, and oncogenic genes. The microenvironment of mitochondrial Prdxs plays an important role in cancer development, as cancerous cells are equipped with a high level of antioxidants to overcome excessive ROS production. However, an increased production of Prdx3 and Prdx5 is associated with the development of chemoresistance in certain types of cancers and it leads to further complications in cancer treatment. Understanding the interplay between mitochondrial Prdxs and ROS in carcinogenesis can be useful in the development of anticancer drugs with better proficiency and decreased resistance. However, more targeted studies are required for exploring the tumor microenvironment in association with mitochondrial Prdxs to improve the existing cancer therapies and drug development.

E2A attenuates tumor-initiating capacity of colorectal cancer cells via the Wnt/beta-catenin pathway

BACKGROUND

The E2A gene, which encodes two basic helix-loop-helix transcription factors, E12 and E47, regulates colorectal cancer progression and epithelial-mesenchymal transition. However, whether E2A regulates the tumor-initiating capacity of colorectal cancer is unclear. Thus, we have studied E2A expression in the initiation of colorectal cancer in vivo and in vitro.

METHODS

Immunohistochemistry and immunoblot were performed to determine protein levels of E2A in colorectal cancer specimens and cells. RNAi was employed to downregulate E2A expression, and the subsequent change in protein level was evaluated by immunoblot. Sphere-forming assay and enumeration of liver metastasis in mouse models were used to identify the tumor formation ability of colorectal cancer cells.

RESULTS

E2A expression in colorectal cancer clinical specimens was inversely associated with patients' progression-free survival. Functional studies demonstrated that E2A significantly decreased tumor formation in vitro and in vivo. Furthermore, nuclear translocation of beta-catenin and activation of the Wnt/beta-catenin pathway occurred after suppression of E2A in colorectal cancer cells. FoxM1 was identified as a down-stream target by mRNA microarray, implying that FoxM1 plays a main role in determining how E2A regulates the tumor-initiating capacity of colorectal cancer.

CONCLUSION

E2A suppresses tumor-initiating capacity by targeting the FoxM1-Wnt/β-catenin pathway.

Loss of PKM2 in Lgr5+ intestinal stem cells promotes colitis-associated colorectal cancer

The regulatory properties of pyruvate kinase M2 isoform (PKM2), the key glycolytic enzyme, influence altered energy metabolism including glycolysis in cancer. In this study, we found that PKM2 was highly expressed in patients with ulcerative colitis or colorectal cancer (CRC). We then investigated the effectiveness of conditionally ablating PKM2 in Lgr5+ intestinal stem cells (ISC) using a mouse model of colitis-associated CRC (AOM plus DSS). Tamoxifen-inducible Lgr5-driven deletion of PKM2 in ISC (PKM2ΔLgr5-Tx) significantly promoted tumor incidence and size in the colon and lower body weight compared with findings in vehicle-treated mice (PKM2ΔLgr5-Veh). Histopathologic analysis revealed considerable high-grade dysplasia and adenocarcinoma in the colon of PKM2ΔLgr5-Tx mice while PKM2ΔLgr5-Veh mice had low- and high-grade dysplasia. Loss of PKM2 was associated with dominant expression of PKM1 in Lgr5+ ISC and their progeny cells. Further, the organoid-forming efficiency of whole cancer cells or Lgr5+ cells obtained from colon polyps of PKM2ΔLgr5-Tx mice was significantly increased when compared with PKM2ΔLgr5-Veh mice. Cancer organoids from PKM2ΔLgr5-Tx mice exhibited increased mitochondrial oxygen consumption and a shift of metabolites involved in energy metabolism. These findings suggest that loss of PKM2 function in ISC promotes colitis-associated CRC.

The mitochondrial retrograde signaling regulates Wnt signaling to promote tumorigenesis in colon cancer

Cancer cells are known to upregulate aerobic glycolysis to promote growth, proliferation, and survival. However, the role of mitochondrial respiration in tumorigenesis remains elusive. Here we report that inhibition of mitochondrial function by silencing TFAM, a key transcription factor essential for mitochondrial DNA (mtDNA) replication and the transcription of mtDNA-encoded genes, markedly reduced tumor-initiating potential of colon cancer cells. Knockdown of TFAM significantly decreased mitochondrial respiration in colon cancer cells; however, the cellular levels of ATP remained largely unchanged as a result of increased glycolysis. This metabolic alteration rendered cancer cells highly susceptible to glucose deprivation. Interestingly, upregulation of glycolysis was independent of hypoxia-inducible factor-1 (HIF1) as TFAM knockdown cells fail to stabilize HIF1α under hypoxic conditions. Moreover, knockdown of TFAM results in decreased expression of genes-associated cancer stem cells downstream of Wnt/β-catenin signaling. Metabolic analysis reveals that the level of α-ketoglutarate (α-KG) was significantly upregulated in TFAM knockout cells. Silencing of prolyl hydroxylase domain-containing protein 2 (PHD2), a α-KG-dependent dioxyenase, rescued the expression of target genes of both HIF1α and Wnt/β-catenin. Furthermore, intestinal-specific knockout of TFAM prevents tumor formation in Apc-mutant mouse models of colon cancer. Taken together, our findings identify a novel role of mitochondria-mediated retrograde signaling in regulating Wnt signaling and tumor initiation in colon cancer.

The forkhead-box family of transcription factors: key molecular players in colorectal cancer pathogenesis

Colorectal cancer (CRC) is the third most commonly occurring cancer worldwide and the fourth most frequent cause of death having an oncological origin. It has been found that transcription factors (TF) dysregulation, leading to the significant expression modifications of genes, is a widely distributed phenomenon regarding human malignant neoplasias. These changes are key determinants regarding tumour’s behaviour as they contribute to cell differentiation/proliferation, migration and metastasis, as well as resistance to chemotherapeutic agents. The forkhead box (FOX) transcription factor family consists of an evolutionarily conserved group of transcriptional regulators engaged in numerous functions during development and adult life. Their dysfunction has been associated with human diseases. Several FOX gene subgroup transcriptional disturbances, affecting numerous complex molecular cascades, have been linked to a wide range of cancer types highlighting their potential usefulness as molecular biomarkers. At least 14 FOX subgroups have been related to CRC pathogenesis, thereby underlining their role for diagnosis, prognosis and treatment purposes.

This manuscript aims to provide, for the first time, a comprehensive review of FOX genes’ roles during CRC pathogenesis. The molecular and functional characteristics of most relevant FOX molecules (FOXO, FOXM1, FOXP3) have been described within the context of CRC biology, including their usefulness regarding diagnosis and prognosis. Potential CRC therapeutics (including genome-editing approaches) involving FOX regulation have also been included. Taken together, the information provided here should enable a better understanding of FOX genes’ function in CRC pathogenesis for basic science researchers and clinicians.