GULP1 regulates the NRF2-KEAP1 signaling axis in urothelial carcinoma

Heme oxygenase 1 (HO-1) is a drug target for reversing cisplatin resistance in non-small cell lung cancer

INTRODUCTION

Platinum-based drugs, the most widely used chemotherapeutic drugs in clinical oncology, have long faced the problem of drug resistance, which is urgently in need of resolution. Identifying biomarkers of drug resistance may help reduce platinum resistance and improve therapeutic efficacy.

OBJECTIVES

This study aims to identify potential biomarkers associated with the development of cisplatin resistance in non-small cell lung cancer (NSCLC) and explore mechanisms to overcome chemoresistance.

METHODS

NSCLC cisplatin resistance cell lines were constructed, and transcriptome sequencing was performed. Results were validated using Gene Expression Omnibus (GEO) and The Cancer Genome Atlas (TCGA) databases. Molecular docking, proteomics sequencing, and in vitro and in vivo experiments were conducted to evaluate the role of Heme Oxygenase 1 (HO-1) in cisplatin resistance.

RESULTS

NSCLC cisplatin resistance cell lines, GEO and TCGA data identified HMOX1, downstream of Nrf2, as a key drug resistance gene induced by cisplatin. Activation of the Nrf2/HO-1 pathway was found to induce ferroptosis resistance, a critical mechanism of cisplatin resistance. Candidate compounds SB 202190 and Nordihydroguaiaretic acid (NDGA) effectively reactivated ferroptosis by inhibiting HO-1, thereby increasing cisplatin sensitivity.

CONCLUSION

The Nrf2/HO-1 pathway is a significant contributor to cisplatin resistance in NSCLC. Targeting HO-1 with SB 202190 and NDGA presents a promising strategy to overcome resistance and improve chemotherapy outcomes.

Transcriptional Heterogeneity and Differential Response of Rod Photoreceptor Pathway Uncovered by Single-Cell RNA Sequencing of the Aging Mouse Retina

Visual function deteriorates throughout the natural course of aging. Age-related structural and functional adaptations are observed in the retina, the light-sensitive neuronal tissue of the eye where visual perception begins. Molecular mechanisms underlying retinal aging are still poorly understood, highlighting the need to identify biomarkers for better prognosis and alleviation of aging-associated vision impairment. Here, we investigate dynamics of transcriptional dysregulation in the retina and identify affected pathways within distinct retinal cell types. Using an optimized protocol for single-cell RNA sequencing of mouse retinas at 3, 12, 18, and 24 months, we detect a progressive increase in the number of differentially expressed genes across all retinal cell types. The extent and direction of expression changes varies, with photoreceptor, bipolar, and Müller cells showing the maximum number of differentially expressed genes at all age groups. Furthermore, our analyses uncover transcriptionally distinct, heterogeneous subpopulations of rod photoreceptors and bipolar cells, distributed across distinct areas of the retina. Our findings provide a plausible molecular explanation for enhanced susceptibility of rod cells to aging and correlate with the observed loss of scotopic sensitivity in elderly individuals.

Epigenetic modifications in bladder cancer: crosstalk between DNA methylation and miRNAs

Bladder cancer (BC) is a malignant tumor characterized by a high incidence of urinary system diseases. The complex pathogenesis of BC has long been a focal point in medical research. With the robust development of epigenetics, the crucial role of epigenetic modifications in the occurrence and progression of BC has been elucidated. These modifications not only affect gene expression but also impact critical biological behaviors of tumor cells, including proliferation, differentiation, apoptosis, invasion, and metastasis. Notably, DNA methylation, an important epigenetic regulatory mechanism, often manifests as global hypomethylation or hypermethylation of specific gene promoter regions in BC. Alterations in this methylation pattern can lead to increased genomic instability, which profoundly influences the expression of proto-oncogenes and tumor suppressor genes. MiRNAs, as noncoding small RNAs, participate in various biological processes of BC by regulating target genes. Consequently, this work aims to explore the interaction mechanisms between DNA methylation and miRNAs in the occurrence and development of BC. Research has demonstrated that DNA methylation not only directly influences the expression of miRNA genes but also indirectly affects the maturation and functionality of miRNAs by modulating the methylation status of miRNA promoter regions. Simultaneously, miRNAs can regulate DNA methylation levels by targeting key enzymes such as DNA methyltransferases (DNMTs), thereby establishing a complex feedback regulatory network. A deeper understanding of the crosstalk mechanisms between DNA methylation and miRNAs in BC will contribute to elucidating the complexity and dynamics of epigenetic modifications in this disease, and may provide new molecular targets and strategies for the early diagnosis, treatment, and prognostic evaluation of BC.

Integrated analysis reveals that miR-548ab promotes the development of obesity and T2DM

Dysregulation of microRNA (miRNA) expression following the development of obesity is closely linked to the onset of type 2 diabetes mellitus (T2DM). Identifying differentially expressed miRNAs and their roles in regulating glucose metabolism will provide a theoretical foundation for the molecular mechanisms underlying obesity-induced T2DM. Here, we perform a genome-wide association study involving 5 glycolipid metabolism traits in 1783 Kazakh and 1198 Uyghur individuals to identify miRNAs associated with fasting plasma glucose (FPG) levels. A miR-548ab mimic and inhibitor are administered to hepatocytes and adipocytes, as well as obese and diabetic mice, to determine miR-548ab-related downstream signalling pathways. The effects of miR-548ab on glucose metabolism are validated using the glucose tolerance test and insulin tolerance test. Collectively, these results indicate that miR-548ab is significantly associated with FPG levels and obesity-related T2DM in both Kazakh and Uyghur populations. The miR-548ab-GULP1/SLC25A21-GLUT4 network exerts regulatory effects on glucose metabolism, obesity, and T2DM, positioning it as a candidate risk factor, potential diagnostic marker, and therapeutic target for obesity-induced T2DM. Additionally, through evolutionary analysis, the authentic variants or haplotypes of GULP1 and SLC25A21 are categorized according to their genetic susceptibility to T2DM. The miR-548ab inhibitor shows beneficial effects in obese and diabetic mice.

YAP1 induces bladder cancer progression and promotes immune evasion through IL-6/STAT3 pathway and CXCL deregulation

The Hippo signaling pathway plays a key role in tumorigenesis in different cancer types. We investigated the role of the Hippo effector YAP1 in the tumor immune microenvironment (TIME) of urothelial carcinoma of the bladder (UCB) and evaluated the efficacy of immunotherapy in the context of YAP1 signaling. We performed numerous in vitro and in vivo experiments to determine the role of YAP1 using genetic and pharmacological attenuation of YAP1 activity. Briefly, RNA sequencing was carried out with mouse and human cell lines to identify novel YAP1-regulated downstream targets unbiasedly. We then experimentally confirmed that YAP1 regulates the TIME through the IL-6/STAT3 signaling pathway and varied C-X-C motif chemokine regulation. We analyzed several human sample sets to explore the TIME status in the context of YAP1 expression. Our data indicate that YAP1 attenuation decreases M2 macrophages and myeloid-derived suppressor cells in the TIME compared with YAP1-expressing cells. In summary, this study provides insights into YAP1 signaling as a driver for cancer stemness and an inducer of immunosuppressive TIME. Moreover, the therapeutic efficacy of YAP1 attenuation indicates that combined blockade of YAP1 and immune checkpoints may yield clinical value for treating patients with UCB.

The cellular adaptor GULP1 interacts with ATG14 to potentiate autophagy and APP processing

Autophagy is a highly conserved catabolic mechanism by which unnecessary or dysfunctional cellular components are removed. The dysregulation of autophagy has been implicated in various neurodegenerative diseases, including Alzheimer's disease (AD). Understanding the molecular mechanism(s)/molecules that influence autophagy may provide important insights into developing therapeutic strategies against AD and other neurodegenerative disorders. Engulfment adaptor phosphotyrosine-binding domain-containing protein 1 (GULP1) is an adaptor that interacts with amyloid precursor protein (APP) to promote amyloid-β peptide production via an unidentified mechanism. Emerging evidence suggests that GULP1 has a role in autophagy. Here, we show that GULP1 is involved in autophagy through an interaction with autophagy-related 14 (ATG14), which is a regulator of autophagosome formation. GULP1 potentiated the stimulatory effect of ATG14 on autophagy by modulating class III phosphatidylinositol 3-kinase complex 1 (PI3KC3-C1) activity. The effect of GULP1 is attenuated by a GULP1 mutation (GULP1m) that disrupts the GULP1-ATG14 interaction. Conversely, PI3KC3-C1 activity is enhanced in cells expressing APP but not in those expressing an APP mutant that does not bind GULP1, which suggests a role of GULP1-APP in regulating PI3KC3-C1 activity. Notably, GULP1 facilitates the targeting of ATG14 to the endoplasmic reticulum (ER). Moreover, the levels of both ATG14 and APP are elevated in the autophagic vacuoles (AVs) of cells expressing GULP1, but not in those expressing GULP1m. APP processing is markedly enhanced in cells co-expressing GULP1 and ATG14. Hence, GULP1 alters APP processing by promoting the entry of APP into AVs. In summary, we unveil a novel role of GULP1 in enhancing the targeting of ATG14 to the ER to stimulate autophagy and, consequently, APP processing.

Targeting Nrf2 signaling pathways in the role of bladder cancer: From signal network to targeted therapy

Bladder cancer (BC) is the most common malignancy of the urinary system and often recurs after tumor removal and/or is resistant to chemotherapy. In cancer cells, the activity of the signaling pathway changes significantly, affecting a wide range of cell activities from growth and proliferation to apoptosis, invasion and metastasis. Nrf2 is a transcription factor that plays an important role in cellular defense responses to a variety of cellular stresses. There is increasing evidence that Nrf2 acts as a tumor driver and that it is involved in the maintenance of malignant cell phenotypes. Abnormal expression of Nrf2 has been found to be common in a variety of tumors, including bladder cancer. Over-activation of Nrf2 can lead to DNA damage and the development of bladder cancer, and is also associated with various pathological phenomena of bladder cancer, such as metastasis, angiogenesis, and reduced toxicity and efficacy of therapeutic anticancer drugs to provide cell protection for cancer cells. However, the above process can be effectively inhibited or reversed by inhibiting Nrf2. Therefore, Nrf2 signaling may be a potential targeting pathway for bladder cancer. In this review, we will characterize this signaling pathway and summarize the effects of Nrf2 and crosstalk with other signaling pathways on bladder cancer progression. The focus will be on the impact of Nrf2 activation on bladder cancer progression and current therapeutic strategies aimed at blocking the effects of Nrf2. To better determine how to promote new chemotherapy agents, develop new therapeutic agents, and potential therapeutic targets.

Identification of a novel ferroptosis-inducing micropeptide in bladder cancer

Bladder cancer (BC) is a common malignancy in males, and currently lacks ideal therapeutic approaches. Exploring emerging therapeutic targets from the perspective of endogenous peptides to improve the prognosis of bladder cancer patients holds promise. In this study, we have identified CTSGDP-13, a novel endogenous peptide, which demonstrates potential anti-cancer effects in BC. Our findings reveal that CTSGDP-13 can promote ferroptosis in BC cells, both in vitro and in vivo, leading to the inhibition of BC progression. Furthermore, we have identified TRIM25 as a downstream regulatory target of CTSGDP-13. The expression of TRIM25 is significantly upregulated in BC, and its inhibition of ferroptosis promotes BC progression. Mechanistic studies have shown that CTSGDP-13 promotes the ubiquitination and subsequent degradation of TRIM25 by disrupting its interaction with the deubiquitinase USP7. Further investigations indicate that CTSGDP-13 promotes ferroptosis in BC by regulating the USP7/TRIM25/KEAP1 axis. The elucidation of the functional mechanisms of natural CTSGDP-13 and TRIM25 holds promise in providing valuable therapeutic targets for BC diagnosis and treatment.

The urothelial gene regulatory network: understanding biology to improve bladder cancer management

The urothelium is a stratified epithelium composed of basal cells, one or more layers of intermediate cells, and an upper layer of differentiated umbrella cells. Most bladder cancers (BLCA) are urothelial carcinomas. Loss of urothelial lineage fidelity results in altered differentiation, highlighted by the taxonomic classification into basal and luminal tumors. There is a need to better understand the urothelial transcriptional networks. To systematically identify transcription factors (TFs) relevant for urothelial identity, we defined highly expressed TFs in normal human bladder using RNA-Seq data and inferred their genomic binding using ATAC-Seq data. To focus on epithelial TFs, we analyzed RNA-Seq data from patient-derived organoids recapitulating features of basal/luminal tumors. We classified TFs as "luminal-enriched", "basal-enriched" or "common" according to expression in organoids. We validated our classification by differential gene expression analysis in Luminal Papillary vs. Basal/Squamous tumors. Genomic analyses revealed well-known TFs associated with luminal (e.g., PPARG, GATA3, FOXA1) and basal (e.g., TP63, TFAP2) phenotypes and novel candidates to play a role in urothelial differentiation or BLCA (e.g., MECOM, TBX3). We also identified TF families (e.g., KLFs, AP1, circadian clock, sex hormone receptors) for which there is suggestive evidence of their involvement in urothelial differentiation and/or BLCA. Genomic alterations in these TFs are associated with BLCA. We uncover a TF network involved in urothelial cell identity and BLCA. We identify novel candidate TFs involved in differentiation and cancer that provide opportunities for a better understanding of the underlying biology and therapeutic intervention.

Sulforaphane and bladder cancer: a potential novel antitumor compound

Bladder cancer (BC) is a common form of urinary tract tumor, and its incidence is increasing annually. Unfortunately, an increasing number of newly diagnosed BC patients are found to have advanced or metastatic BC. Although current treatment options for BC are diverse and standardized, it is still challenging to achieve ideal curative results. However, Sulforaphane, an isothiocyanate present in cruciferous plants, has emerged as a promising anticancer agent that has shown significant efficacy against various cancers, including bladder cancer. Recent studies have demonstrated that Sulforaphane not only induces apoptosis and cell cycle arrest in BC cells, but also inhibits the growth, invasion, and metastasis of BC cells. Additionally, it can inhibit BC gluconeogenesis and demonstrate definite effects when combined with chemotherapeutic drugs/carcinogens. Sulforaphane has also been found to exert anticancer activity and inhibit bladder cancer stem cells by mediating multiple pathways in BC, including phosphatidylinositol-3-kinase (PI3K)/protein kinase B (Akt)/mammalian target of rapamycin (mTOR), mitogen-activated protein kinase (MAPK), nuclear factor kappa-B (NF-κB), nuclear factor (erythroid-derived 2)-like 2 (Nrf2), zonula occludens-1 (ZO-1)/beta-catenin (β-Catenin), miR-124/cytokines interleukin-6 receptor (IL-6R)/transcription 3 (STAT3). This article provides a comprehensive review of the current evidence and molecular mechanisms of Sulforaphane against BC. Furthermore, we explore the effects of Sulforaphane on potential risk factors for BC, such as bladder outlet obstruction, and investigate the possible targets of Sulforaphane against BC using network pharmacological analysis. This review is expected to provide a new theoretical basis for future research and the development of new drugs to treat BC.

Algorithmically Reconstructed Molecular Pathways as the New Generation of Prognostic Molecular Biomarkers in Human Solid Cancers

Individual gene expression and molecular pathway activation profiles were shown to be effective biomarkers in many cancers. Here, we used the human interactome model to algorithmically build 7470 molecular pathways centered around individual gene products. We assessed their associations with tumor type and survival in comparison with the previous generation of molecular pathway biomarkers (3022 "classical" pathways) and with the RNA transcripts or proteomic profiles of individual genes, for 8141 and 1117 samples, respectively. For all analytes in RNA and proteomic data, respectively, we found a total of 7441 and 7343 potential biomarker associations for gene-centric pathways, 3020 and 2950 for classical pathways, and 24,349 and 6742 for individual genes. Overall, the percentage of RNA biomarkers was statistically significantly higher for both types of pathways than for individual genes (p < 0.05). In turn, both types of pathways showed comparable performance. The percentage of cancer-type-specific biomarkers was comparable between proteomic and transcriptomic levels, but the proportion of survival biomarkers was dramatically lower for proteomic data. Thus, we conclude that pathway activation level is the advanced type of biomarker for RNA and proteomic data, and momentary algorithmic computer building of pathways is a new credible alternative to time-consuming hypothesis-driven manual pathway curation and reconstruction.

The APC/C E3 ligase subunit ANAPC11 mediates FOXO3 protein degradation to promote cell proliferation and lymph node metastasis in urothelial bladder cancer

Urothelial bladder cancer (UBC) is one of the most prevalent malignancies worldwide, with striking tumor heterogeneity. Elucidating the molecular mechanisms that can be exploited for the treatment of aggressive UBC is a particularly relevant goal. Protein ubiquitination is a critical post-translational modification (PTM) that mediates the degradation of target protein via the proteasome. However, the roles of aberrant protein ubiquitination in UBC development and the underlying mechanisms by which it drives tumor progression remain unclear. In this study, taking advantage of clustered regularly interspaced short palindromic repeats (CRISPR)-CRISPR-associated protein (Cas) 9 technology, we identified the ubiquitin E3 ligase ANAPC11, a critical subunit of the anaphase-promoting complex/cyclosome (APC/C), as a potential oncogenic molecule in UBC cells. Our clinical analysis showed that elevated expression of ANAPC11 was significantly correlated with high T stage, positive lymph node (LN) metastasis, and poor outcomes in UBC patients. By employing a series of in vitro experiments, we demonstrated that ANAPC11 enhanced the proliferation and invasiveness of UBC cells, while knockout of ANAPC11 inhibited the growth and LN metastasis of UBC cells in vivo. By conducting immunoprecipitation coupled with mass spectrometry, we confirmed that ANAPC11 increased the ubiquitination level of the Forkhead transcription factor FOXO3. The resulting decrease in FOXO3 protein stability led to the downregulation of the cell cycle regulator p21 and decreased expression of GULP1, a downstream effector of androgen receptor signaling. Taken together, these findings indicated that ANAPC11 plays an oncogenic role in UBC by modulating FOXO3 protein degradation. The ANAPC11-FOXO3 regulatory axis might serve as a novel therapeutic target for UBC.

Gulp1 deficiency augments bone mass in male mice by affecting osteoclasts due to elevated 17β-estradiol levels

The engulfment adaptor phosphotyrosine-binding domain containing 1 (GULP1) is an adaptor protein involved in the engulfment of apoptotic cells via phagocytosis. Gulp1 was first found to promote the phagocytosis of apoptotic cells by macrophages, and its role in various tissues, including neurons and ovaries, has been well studied. However, the expression and function of GULP1 in bone tissue are poorly understood. Consequently, to determine whether GULP1 plays a role in the regulation of bone remodeling in vitro and in vivo, we generated Gulp1 knockout (KO) mice. Gulp1 was expressed in bone tissue, mainly in osteoblasts, while its expression is very low in osteoclasts. Microcomputed tomography and histomorphometry analysis in 8-week-old male Gulp1 KO mice revealed a high bone mass in comparison with male wild-type (WT) mice. This was a result of decreased osteoclast differentiation and function in vivo and in vitro as confirmed by a reduced actin ring and microtubule formation in osteoclasts. Gas chromatography-mass spectrometry analysis further showed that both 17β-estradiol (E2) and 2-hydroxyestradiol levels, and the E2/testosterone metabolic ratio, reflecting aromatase activity, were also higher in the bone marrow of male Gulp1 KO mice than in male WT mice. Consistent with mass spectrometry analysis, aromatase enzymatic activity was significantly higher in the bone marrow of male Gulp1 KO mice. Altogether, our results suggest that GULP1 deficiency decreases the differentiation and function of osteoclasts themselves and increases sex steroid hormone-mediated inhibition of osteoclast differentiation and function, rather than affecting osteoblasts, resulting in a high bone mass in male mice. To the best of our knowledge, this is the first study to explore the direct and indirect roles of GULP1 in bone remodeling, providing new insights into its regulation.

Regulation of cisplatin resistance in bladder cancer by epigenetic mechanisms

Bladder cancer is one of the most common malignancies in the world. Cisplatin is one of the most potent and widely used anticancer drugs and has been employed in several malignancies. Cisplatin-based combination chemotherapies have become important adjuvant therapies for bladder cancer patients. Cisplatin-based treatment often results in the development of chemoresistance, leading to therapeutic failure and limiting its application and effectiveness in bladder cancer. To develop improved and more effective cancer therapy, research has been conducted to elucidate the underlying mechanism of cisplatin resistance. Epigenetic modifications have been demonstrated involved in drug resistance to chemotherapy, and epigenetic biomarkers, such as urine tumor DNA methylation assay, have been applied in patients screening or monitoring. Here, we provide a systematic description of epigenetic mechanisms, including DNA methylation, noncoding RNA regulation, m6A modification and posttranslational modifications, related to cisplatin resistance in bladder cancer.

High-risk HPV infection-associated hypermethylated genes in oropharyngeal squamous cell carcinomas

Background

HPV-positive oropharyngeal squamous cell carcinomas (OPSCCs) are sensitive to chemo-radiation therapy and have favorable survival outcomes compared with HPV-negative cancers. These tumors are usually not related to tobacco and alcohol exposure. Therefore, diagnosing HPV-positive OPSCCs for the appropriate disease management is crucial, and no suitable markers are available for detecting early malignancies in HPV-infected tissues. In this study, we attempt to find HPV-specific epigenetic biomarkers for OPSCCs.

Methods

A total of 127 surgical samples were analyzed for HPV positivity and promoter methylation of a panel of genes. HPV detection was performed by PCR detection of HPV E6 and E7 viral oncoproteins. In addition, promoter methylation of a total of 8 genes (DAPK, FHIT, RASSF1A, TIMP3, AGTR1, CSGALNACT2, GULP1 and VGF) was analyzed by quantitative-methylation specific PCR (QMSP), and their associations with HPV positivity or RB/p16 expressions were evaluated.

Results

AGTR1 and FHIT were frequently methylated in HPV-positive OPSCC samples with a good area under the curve (AUC over 0.70). In addition, these genes' promoter methylation was significantly associated with p16 positive and RB negative cases, which were the characteristics of OPSCC cases with favorable survival outcomes. Either AGTR1 or FHIT methylated cases were significantly associated with HPV-positive cancers with 92.0% sensitivity (P < 0.001). Also, they had significantly better overall survival (P = 0.047) than both unmethylated cases.

Conclusions

A combination of AGTR1 and FHIT methylation demonstrated a suitable detection marker of OPSCCs derived from the HPV-infected field, familiar with p16-positive and RB-negative phenotypes.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-022-10227-w.

DNA Methylation Biomarkers for Prediction of Response to Platinum-Based Chemotherapy: Where Do We Stand?

Simple Summary

Platinum-based agents are one of the most widely used chemotherapy drugs for various types of cancer. However, one of the main challenges in the application of platinum drugs is resistance, which is currently being widely investigated. Epigenetic DNA methylation-based biomarkers are promising to aid in the selection of patients, helping to foresee their platinum therapy response in advance. These biomarkers enable minimally invasive patient sample collection, short analysis, and good sensitivity. Hence, improved methodologies for the detection and quantification of DNA methylation biomarkers will facilitate their use in the choice of an optimal treatment strategy.

Abstract

Platinum-based chemotherapy is routinely used for the treatment of several cancers. Despite all the advances made in cancer research regarding this therapy and its mechanisms of action, tumor resistance remains a major concern, limiting its effectiveness. DNA methylation-based biomarkers may assist in the selection of patients that may benefit (or not) from this type of treatment and provide new targets to circumvent platinum chemoresistance, namely, through demethylating agents. We performed a systematic search of studies on biomarkers that might be predictive of platinum-based chemotherapy resistance, including in vitro and in vivo pre-clinical models and clinical studies using patient samples. DNA methylation biomarkers predictive of response to platinum remain mostly unexplored but seem promising in assisting clinicians in the generation of more personalized follow-up and treatment strategies. Improved methodologies for their detection and quantification, including non-invasively in liquid biopsies, are additional attractive features that can bring these biomarkers into clinical practice, fostering precision medicine.

Therapeutic Targeting of Cancer Stem Cells in Lung, Head and Neck, and Bladder Cancers

Simple Summary

Effective cancer treatment hinges upon overcoming therapeutic resistance mechanisms that allow for the continued proliferation of cancer cell subpopulations. Exposure to pharmacotherapy invariably leads to resistance as tumor cells with selected advantageous features evade destruction and alter the tumor composition. Cancer stem cells (CSCs) with features of plasticity that allow for regeneration and differentiation are particularly responsible for this phenomenon. Advances in tumor biology and molecular signaling have highlighted their role in neoplastic initiation, invasion, and maintenance. Novel strategies to direct therapy against these tumor cell subpopulations have the potential to dramatically alter tumor response and change the course of cancer care.

Abstract

Resistance to cancer therapy remains a significant obstacle in treating patients with various solid malignancies. Exposure to current chemotherapeutics and targeted agents invariably leads to therapy resistance, heralding the need for novel agents. Cancer stem cells (CSCs)—a subpopulation of tumor cells with capacities for self-renewal and multi-lineage differentiation—represent a pool of therapeutically resistant cells. CSCs often share physical and molecular characteristics with the stem cell population of the human body. It remains challenging to selectively target CSCs in therapeutically resistant tumors. The generation of CSCs and induction of therapeutic resistance can be attributed to several deregulated critical growth regulatory signaling pathways such as WNT/β-catenin, Notch, Hippo, and Hedgehog. Beyond growth regulatory pathways, CSCs also change the tumor microenvironment and resist endogenous immune attack. Thus, CSCs can interfere with each stage of carcinogenesis from malignant transformation to the onset of metastasis to tumor recurrence. A thorough review of novel targeted agents to act against CSCs is fundamental for advancing cancer treatment in the setting of both intrinsic and acquired resistance.

Androgen Receptor Signaling Induces Cisplatin Resistance via Down-Regulating GULP1 Expression in Bladder Cancer

The underlying molecular mechanisms of resistance to cisplatin-based systemic chemotherapy in bladder cancer patients remain to be elucidated, while the link between androgen receptor (AR) activity and chemosensitivity in urothelial cancer has been implicated. Our DNA microarray analysis in control vs. AR knockdown bladder cancer lines identified GULP1 as a potential target of AR signaling. We herein determined the relationship between AR activity and GULP1 expression in bladder cancer cells and then assessed the functional role of GULP1 in cisplatin sensitivity. Androgen treatment in AR-positive cells or AR overexpression in AR-negative cells considerably reduced the levels of GULP1 expression. Chromatin immunoprecipitation further showed direct interaction of AR with the promoter region of GULP1. Meanwhile, GULP1 knockdown sublines were significantly more resistant to cisplatin treatment compared with respective controls. GULP1 knockdown also resulted in a significant decrease in apoptosis, as well as a significant increase in G2/M phases, when treated with cisplatin. In addition, GULP1 was immunoreactive in 74% of muscle-invasive bladder cancers from patients who had subsequently undergone neoadjuvant chemotherapy, including 53% of responders showing moderate (2+)/strong (3+) expression vs. 23% of non-responders showing 2+/3+ expression (P = 0.044). These findings indicate that GULP1 represents a key downstream effector of AR signaling in enhancing sensitivity to cisplatin treatment.

Resistance to platinum-based cancer drugs: a special focus on epigenetic mechanisms

Chemoresistance is a significant clinical challenge, limiting the drug response in cancer. Several mechanisms associated with drug resistance have been characterized, and the role of epigenetics in generating resistance to platinum-based drugs has been clarified. Epigenetic mechanisms such as DNA methylation, histone modification, long noncoding RNA, and microRNA affect the expression of genes implicated in absorption, distribution, metabolism and excretion (ADME) of drugs, and other non-ADME genes that encode enzymes involved in the processes of cell proliferation, DNA repair, apoptosis and signal transduction key in the development of chemoresistance in cancer, specifically in platinum-based drugs. This review summarizes current discoveries in epigenetic regulation implicated in platinum drug resistance in cancer and the main clinical trials based on epigenetic therapy, evaluating their potential synergy with platinum-based drugs.

Nrf2 signaling pathway in cisplatin chemotherapy: Potential involvement in organ protection and chemoresistance

Nuclear factor erythroid 2-related factor 2 (Nrf2) is a vital transcription factor and its induction is of significant importance for protecting against oxidative damage. Increased levels of Reactive Oxygen Species (ROS) stimulate Nrf2 signaling, enhancing the activity of antioxidant enzymes such as catalase, superoxide dismutase and glutathione peroxidase. These enzymes are associated with retarding oxidative stress. On the other hand, Nrf2 activation in cancer cells is responsible for the development of chemoresistance due to disrupting oxidative mediated-cell death by reducing ROS levels. Cisplatin (CP), cis-diamminedichloroplatinum(II), is a potent anti-tumor agent extensively used in cancer therapy, but its frequent application leads to the development of chemoresistance as well. In the present study, association of Nrf2 signaling with chemoresistance to CP and protection against its deleterious effects is discussed. Anti-tumor compounds, mainly phytochemicals, retard chemoresistance by suppressing Nrf2 signaling. Upstream mediators such as microRNAs can regulate Nrf2 expression during CP chemotherapy regimens. Protection against side effects of CP is mediated via activating Nrf2 signaling and its downstream targets activating antioxidant defense system. Protective agents that activate Nrf2 signaling, can ameliorate CP-mediated ototoxicity, nephrotoxicity and neurotoxicity. Reducing ROS levels and preventing cell death are the most important factors involved in alleviating CP toxicity upon Nrf2 activation. As pre-clinical experiments advocate the role of Nrf2 in chemoprotection and CP resistance, translating these findings to the clinic can provide a significant progress in treatment of cancer patients.

The ABCA1-efferocytosis axis: A new strategy to protect against atherosclerosis

Atherosclerosis, a disease process characterized by lipid accumulation and inflammation, is the main cause of coronary heart disease (CHD) and myocardial infarction (MI). Efferocytosis involves the clearance of apoptotic cells by phagocytes. Successful engulfment triggers the release of anti-inflammatory cytokines to suppress atherosclerosis. ABCA1 is a key mediator of cholesterol efflux to apoA-I for the generation of HDL-C in reverse cholesterol transport (RCT). Intriguingly, ABCA1 promotes not only cholesterol efflux but also efferocytosis. ABCA1 promotes efferocytosis by regulating the release of "find-me" ligands, including LPC, and the exposure, release, and expression of "eat-me" ligands, including PtdSer, ANXA1, ANXA5, MEGF10, and GULP1. ABCA1 has a pathway similar to TG2, which is an "eat-me" ligand. ABCA1 has the highest known homology to ABCA7, which controls efferocytosis as the engulfment and processing ligand. In addition, ABCA1 can form several regulatory feedback axes with ANXA1, MEGF10, GULP1, TNFα, and IL-6. Therefore, ABCA1 is the central factor that links cholesterol efflux and apoptotic cell clearance. Several drugs have been studied or approved for apoptotic cell clearance, such as CD47 antibody and PD1-/PD-L1 antibody. In this article, we review the role and mechanism of action of ABCA1 in efferocytosis and focus on new insights into the ABCA1-efferocytosis axis and its potential as a novel therapeutic target in atherosclerosis.

Comprehensive analysis of the lncRNA-miRNA-mRNA regulatory network for bladder cancer

Background

Long non-coding RNAs (lncRNAs) are essential regulators for various human cancers. However, these lncRNAs need to be further classified for cancer. In the present study, we identified novel competing endogenous RNA (ceRNA) network for bladder cancer (BC) and explored the gene functions of the ceRNA regulatory network.

Methods

Differential gene expression analysis were performed on The Cancer Genome Atlas Urothelial Bladder Carcinoma (TCGA-BLCA) datasets to identify differentially expressed messenger RNAs (mRNAs), lncRNAs, and microRNAs (miRNAs). Based on the competing endogenous RNA (ceRNA) hypothesis, a lncRNA-miRNA-mRNA network was constructed using the StarBase database and visualization by Cytoscape software. Functional enrichment analyses of Gene Ontology and the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway were performed via R package ClusterProfiler. The protein-protein interaction network was constructed by STRING database and visualization by Cytoscape. Finally, we used CIBERSORT and the TIMER database to analyze the immune infiltrations for BC.

Results

The regulatory network was constructed via TCGA BLCA cohort. The differential expressions of lncRNA, miRNA, and mRNA were 186, 200, and 2,661, respectively. There were 106 lncRNA, miRNA, and mRNA included in the ceRNA network. In this network, Calcium Voltage-gated Channel Auxiliary Subunit Alpha2delta1 (CACNA2D1, P<0.001), domain containing engulfment adaptor1 (GULP1, P=0.001), latent transforming growth factor beta binding protein 1 (LTBP1, P=0.006), myosin light chain kinase (MYLK, P=0.001), serpin family E member 2 (SERPINE2, P=0.002), spectrin beta non-erythrocytic 2 (SPTBN2, P=0.047), and hsa-miR-590-3p (P<0.001) significantly affected the prognosis of BC patients. Functional enrichment analyses showed that the biological functions included negative regulation of protein phosphorylation, cell morphogenesis, and sensory organ morphogenesis. Important cancer pathways of KEGG included parathyroid hormone synthesis secretion action, the notch signaling pathway, MAPK signaling pathway, the Rap1 signaling pathway, signaling pathways regulating the pluripotency of stem cells, and the transforming growth factor-β signaling pathway. Our findings demonstrated that the ceRNA network has important biological functions and a significant influence on the prognosis of BC.

Conclusions

The lncRNA-miRNA-mRNA network constructed in the present study could provide useful insight into the underlying tumorigenesis of BC, and can determine new molecular biomarkers for the diagnosis and therapeutical treatment of BC.

Expression of lipid transport-associated genes in lipid-deprived cancer cells

Cancer cells are known to significantly alter their lipid profiles in response to changes in extracellular lipid availability. Recent studies have shown that in response to lipid deprivation, cancer cells display significant changes in their cellular lipid homeostasis. These changes have been linked to the modulation of de novo lipid synthesis pathways that are markedly altered under lipid-deprived growth conditions. However, the effects of such environment on intracellular lipid trafficking-that could also affect cellular lipid homeostasis-have not been widely investigated. The presented work studies the effect of lipid deprivation on expression of genes for lipid transport proteins (LTPs) in cancer cell lines.

NRF2 and the Ambiguous Consequences of Its Activation during Initiation and the Subsequent Stages of Tumourigenesis

NF-E2 p45-related factor 2 (NRF2, encoded in the human by NFE2L2) mediates short-term adaptation to thiol-reactive stressors. In normal cells, activation of NRF2 by a thiol-reactive stressor helps prevent, for a limited period of time, the initiation of cancer by chemical carcinogens through induction of genes encoding drug-metabolising enzymes. However, in many tumour types, NRF2 is permanently upregulated. In such cases, its overexpressed target genes support the promotion and progression of cancer by suppressing oxidative stress, because they constitutively increase the capacity to scavenge reactive oxygen species (ROS), and they support cell proliferation by increasing ribonucleotide synthesis, serine biosynthesis and autophagy. Herein, we describe cancer chemoprevention and the discovery of the essential role played by NRF2 in orchestrating protection against chemical carcinogenesis. We similarly describe the discoveries of somatic mutations in NFE2L2 and the gene encoding the principal NRF2 repressor, Kelch-like ECH-associated protein 1 (KEAP1) along with that encoding a component of the E3 ubiquitin-ligase complex Cullin 3 (CUL3), which result in permanent activation of NRF2, and the recognition that such mutations occur frequently in many types of cancer. Notably, mutations in NFE2L2, KEAP1 and CUL3 that cause persistent upregulation of NRF2 often co-exist with mutations that activate KRAS and the PI3K-PKB/Akt pathway, suggesting NRF2 supports growth of tumours in which KRAS or PKB/Akt are hyperactive. Besides somatic mutations, NRF2 activation in human tumours can occur by other means, such as alternative splicing that results in a NRF2 protein which lacks the KEAP1-binding domain or overexpression of other KEAP1-binding partners that compete with NRF2. Lastly, as NRF2 upregulation is associated with resistance to cancer chemotherapy and radiotherapy, we describe strategies that might be employed to suppress growth and overcome drug resistance in tumours with overactive NRF2.