ALDH isozymes downregulation affects cell growth, cell motility and gene expression in lung cancer cells

Cancer stem cells: advances in knowledge and implications for cancer therapy

Cancer stem cells (CSCs), a small subset of cells in tumors that are characterized by self-renewal and continuous proliferation, lead to tumorigenesis, metastasis, and maintain tumor heterogeneity. Cancer continues to be a significant global disease burden. In the past, surgery, radiotherapy, and chemotherapy were the main cancer treatments. The technology of cancer treatments continues to develop and advance, and the emergence of targeted therapy, and immunotherapy provides more options for patients to a certain extent. However, the limitations of efficacy and treatment resistance are still inevitable. Our review begins with a brief introduction of the historical discoveries, original hypotheses, and pathways that regulate CSCs, such as WNT/β-Catenin, hedgehog, Notch, NF-κB, JAK/STAT, TGF-β, PI3K/AKT, PPAR pathway, and their crosstalk. We focus on the role of CSCs in various therapeutic outcomes and resistance, including how the treatments affect the content of CSCs and the alteration of related molecules, CSCs-mediated therapeutic resistance, and the clinical value of targeting CSCs in patients with refractory, progressed or advanced tumors. In summary, CSCs affect therapeutic efficacy, and the treatment method of targeting CSCs is still difficult to determine. Clarifying regulatory mechanisms and targeting biomarkers of CSCs is currently the mainstream idea.

Biological evaluation of levofloxacin and its thionated derivatives: antioxidant activity, aldehyde dehydrogenase enzyme inhibition, and cytotoxicity on A549 cell line

Levofloxacin (LVX) is among the fluoroquinolones antibiotics that has also been studied in vitro and in vivo for its anticancer effects. In this study, we used LVX and novel LVX thionated derivatives; compounds 2 and 3, to evaluate their antioxidant activity, aldehyde dehydrogenase (ALDH) enzymes activity inhibition, and anticancer activity. Combination treatments with doxorubicin (DOX) were investigated as well. The 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay was used to determine the antioxidant activity. The NADH fluorescence spectrophotometric activity assay was used to determine the ALDH inhibitory effects. Resazurin dye method was applied for cell viability assays. Molecular Operating Environment software was used for the molecular docking experiments. Compared to ascorbic acid, DPPH assay showed that compound 3 had the highest antioxidant activity among the tested compounds with approximately 35% scavenging activity. On ALDH enzymes, compound 3 showed a significant ALDH activity inhibition compared to compound 2 at 200 µM. The IC50 values for the tested compounds were approximately 100 µM on A549 cell line, a non-small cell lung cancer (NSCLC) cell line. However, significant enhancement of cytotoxicity and reduction of IC50 values were observed by combining DOX and synergism was achieved with LVX with a combination index value of 0.4. The molecular docking test showed a minimum binding energy with a good affinity for compound 3 towards ALDH enzymes. Thionated LVX derivatives, may be repurposed for NSCLC therapy in combination with DOX, taking into account the antioxidant activity, ALDH activity inhibition, and the molecular docking results of compound 3.

CDC45 promotes the stemness and metastasis in lung adenocarcinoma by affecting the cell cycle

OBJECTIVE

This study aimed to assess the functions of cell division cycle protein 45 (CDC45) in Non-small cell lung cancer (NSCLC) cancer and its effects on stemness and metastasis.

METHODS

Firstly, differentially expressed genes related to lung cancer metastasis and stemness were screened by differential analysis and lasso regression. Then, in vitro, experiments such as colony formation assay, scratch assay, and transwell assay were conducted to evaluate the impact of CDC45 knockdown on the proliferation and migration abilities of lung cancer cells. Western blotting was used to measure the expression levels of related proteins and investigate the regulation of CDC45 on the cell cycle. Finally, in vivo model with subcutaneous injection of lung cancer cells was performed to verify the effect of CDC45 on tumor growth.

RESULTS

This study identified CDC45 as a key gene potentially influencing tumor stemness and lymph node metastasis. Knockdown of CDC45 not only suppressed the proliferation and migration abilities of lung cancer cells but also caused cell cycle arrest at the G2/M phase. Further analysis revealed a negative correlation between CDC45 and cell cycle-related proteins, stemness-related markers, and tumor mutations. Mouse experiments confirmed that CDC45 knockdown inhibited tumor growth.

CONCLUSION

As a novel regulator of stemness, CDC45 plays a role in regulating lung cancer cell proliferation, migration, and cell cycle. Therefore, CDC45 may serve as a potential target for lung cancer treatment and provide a reference for further mechanistic research and therapeutic development.

Potential clinical significance of ALDH3B1 in auxiliary diagnosis of gastric cancer

Objective: This research aimed to explore a diagnostic method based on serum ALDH3B1 and to evaluate the clinical diagnostic efficacy in gastric cancer (GC) by comparing it with the traditional GC diagnostic method, the carcinoembryonic protein (CEA) assay. Methods: Serum samples were collected from 70 healthy volunteers and various patients (GC: 76, benign gastric lesions: 20, postoperative: 37, recurrence: 56). The diagnostic efficacy of serum ALDH3B1, CEA and the co-diagnosis were evaluated by receiver operating characteristic curve. ALDH3B1 protein levels were evaluated by western blot. Results: The co-diagnosis of ALDH3B1 and CEA had the highest diagnostic efficacy (area under the curve = 0.841). Conclusion: Serum ALDH3B1 may be used as an auxiliary diagnostic biomarker for GC, and its co-diagnosis with CEA can improve diagnostic efficacy.

Transcriptomics and molecular docking reveal the potential mechanism of lycorine against pancreatic cancer

BACKGROUND

Pancreatic cancer is an extremely malignant digestive tumor, however, owing to its high drug resistance of pancreatic cancer, the search for more effective anti-pancreatic cancer drugs is urgently needed. Lycorine, an alkaloid of natural plant origin, exerts antitumor effects on a variety of tumors.

PURPOSE

This study aimed to investigate the therapeutic effect of lycorine on pancreatic cancer and elucidate its potential molecular mechanism.

METHODS

Two pancreatic cancer cell lines, PANC-1 and BxPC-3, were used to investigate the therapeutic effects of lycorine on pancreatic cancer in vitro using the CCK8 assay, colony formation assay, 5-Ethynyl-2'- deoxyuridine (EdU) incorporation assay, flow cytometry, and western blotting. Transcriptome sequencing and gene set enrichment analysis (GSEA) were used to analyze the differentially expressed genes and pathways after lycorine treatment. Molecular docking, quantitative real-time PCR (qRT-PCR), oil red O staining, small interfering RNA (siRNA) transfection, and other experiments were performed to further validate the differentially expressed genes and pathways. In vivo experiments were conducted to investigate lycorine's inhibitory effects and toxicity on pancreatic cancer using a tumor-bearing mouse model.

RESULTS

Lycorine inhibited the proliferation of pancreatic cancer cells, caused G2/M phase cycle arrest and induced apoptosis. Transcriptome sequencing and GSEA showed that lycorine inhibition of pancreatic cancer was associated with fatty acid metabolism, and aldehyde dehydrogenase 3A1 (ALDH3A1) was a significantly enriched target in the fatty acid metabolism process. ALDH3A1 expression was significantly upregulated in pancreatic cancer and was closely associated with prognosis. Molecular docking showed that lycorine binds strongly to ALDH3A1. Further studies revealed that lycorine inhibited the fatty acid oxidation (FAO) process in pancreatic cancer cells and induced cell growth inhibition and apoptosis through ALDH3A1. Lycorine also showed significant suppressive effects in tumor-bearing mice. Importantly, it did not result in significant toxicity to liver and kidney of mice, demonstrating its therapeutic potential as a safe antitumor agent.

CONCLUSION

Lycorine inhibited pancreatic cancer cell proliferation, blocked the cell cycle, and induced apoptosis by targeting ALDH3A1. FAO inhibition was identified for the first time as a possible mechanism for the anticancer effects of lycorine. These findings enrich the theory of targeted therapy for pancreatic cancer, expand our understanding of the pharmacological targets of lycorine, and provide a reference for exploring its natural components.

ALDEFLUOR activity, ALDH isoforms, and their clinical significance in cancers

High aldehyde dehydrogenase (ALDH) activity is a metabolic feature of adult stem cells and various cancer stem cells (CSCs). The ALDEFLUOR system is currently the most commonly used method for evaluating ALDH enzyme activity in viable cells. This system is applied extensively in the isolation of normal stem cells and CSCs from heterogeneous cell populations. For many years, ALDH1A1 has been considered the most important subtype among the 19 ALDH family members in determining ALDEFLUOR activity. However, in recent years, studies of many types of normal and tumour tissues have demonstrated that other ALDH subtypes can also significantly influence ALDEFLUOR activity. In this article, we briefly review the relationships between various members of the ALDH family and ALDEFLUOR activity. The clinical significance of these ALDH isoforms in different cancers and possible directions for future studies are also summarised.

Stable Isotope-Assisted Untargeted Metabolomics Identifies ALDH1A1-Driven Erythronate Accumulation in Lung Cancer Cells

Using an untargeted stable isotope-assisted metabolomics approach, we identify erythronate as a metabolite that accumulates in several human cancer cell lines. Erythronate has been reported to be a detoxification product derived from off-target glycolytic metabolism. We use chemical inhibitors and genetic silencing to define the pentose phosphate pathway intermediate erythrose 4-phosphate (E4P) as the starting substrate for erythronate production. However, following enzyme assay-coupled protein fractionation and subsequent proteomics analysis, we identify aldehyde dehydrogenase 1A1 (ALDH1A1) as the predominant contributor to erythrose oxidation to erythronate in cell extracts. Through modulating ALDH1A1 expression in cancer cell lines, we provide additional support. We hence describe a possible alternative route to erythronate production involving the dephosphorylation of E4P to form erythrose, followed by its oxidation by ALDH1A1. Finally, we measure increased erythronate concentrations in tumors relative to adjacent normal tissues from lung cancer patients. These findings suggest the accumulation of erythronate to be an example of metabolic reprogramming in cancer cells, raising the possibility that elevated levels of erythronate may serve as a biomarker of certain types of cancer.

Investigating Carvedilol's Repurposing for the Treatment of Non-Small Cell Lung Cancer via Aldehyde Dehydrogenase Activity Modulation in the Presence of β-Adrenergic Agonists

Repurposing existing drugs appears to be a potential solution for addressing the challenges in the treatment of non-small cell lung cancer (NSCLC). β-adrenoceptor antagonist drugs (β-blockers) have tumor-inhibiting effects, making them promising candidates for potential NSCLC treatment. This study investigates the anticancer potential of a subset of β-blockers in NSCLC cell lines; A549 and H1299. Additionally, it investigates the underlying mechanism behind β-blockers' anticancer effect by influencing a potential novel target named aldehyde dehydrogenase (ALDH). The MTT assay assessed β-blockers' cytotoxicity on both cell lines, while Western blot and NADH fluorescence assays evaluated their influence on ALDH protein expression and activity. Carvedilol (CAR) was the most effective blocker in reducing cell survival of A549 and H1299 with IC50 of 18 µM and 13.7 µM, respectively. Significantly, CAR led to a 50% reduction in ALDH expression and 80% decrease in ALDH activity in A549 cells, especially when combined with β-agonists, in comparison to the control. This effect might be attributed to β-agonist blockade or an alternative pathway. This novel finding adds to our understanding of CAR's multifaceted anticancer properties, implying that combining CAR with β-agonists could be a useful strategy for lung cancer treatment.

Hypoxia-induced ALDH3A1 promotes the proliferation of non-small-cell lung cancer by regulating energy metabolism reprogramming

Aldehyde dehydrogenase 3A1 (ALDH3A1) is an NAD+-dependent enzyme that is closely related to tumor development. However, its role in non-small-cell lung cancer (NSCLC) has not been elucidated. This study aimed to clarify the mechanism of ALDH3A1 and identify potential therapeutic targets for NSCLC. Here, for the first time, we found that ALDH3A1 expression could be induced by a hypoxic environment in NSCLC. ALDH3A1 was highly expressed in NSCLC tissue, especially in some late-stage patients, and was associated with a poor prognosis. In mechanistic terms, ALDH3A1 enhances glycolysis and suppresses oxidative phosphorylation (OXPHOS) to promote cell proliferation by activating the HIF-1α/LDHA pathway in NSCLC. In addition, the results showed that ALDH3A1 was a target of β-elemene. ALDH3A1 can be downregulated by β-elemene to inhibit glycolysis and enhance OXPHOS, thus suppressing NSCLC proliferation in vitro and in vivo. In conclusion, hypoxia-induced ALDH3A1 is related to the energy metabolic status of tumors and the efficacy of β-elemene, providing a new theoretical basis for better clinical applications in NSCLC.

Human Aldehyde Dehydrogenases: A Superfamily of Similar Yet Different Proteins Highly Related to Cancer

The superfamily of human aldehyde dehydrogenases (hALDHs) consists of 19 isoenzymes which are critical for several physiological and biosynthetic processes and play a major role in the organism's detoxification via the NAD(P) dependent oxidation of numerous endogenous and exogenous aldehyde substrates to their corresponding carboxylic acids. Over the last decades, ALDHs have been the subject of several studies as it was revealed that their differential expression patterns in various cancer types are associated either with carcinogenesis or promotion of cell survival. Here, we attempt to provide a thorough review of hALDHs' diverse functions and 3D structures with particular emphasis on their role in cancer pathology and resistance to chemotherapy. We are especially interested in findings regarding the association of structural features and their changes with effects on enzymes' functionalities. Moreover, we provide an updated outline of the hALDHs inhibitors utilized in experimental or clinical settings for cancer therapy. Overall, this review aims to provide a better understanding of the impact of ALDHs in cancer pathology and therapy from a structural perspective.

Inhibit ALDH3A2 reduce ovarian cancer cells survival via elevating ferroptosis sensitivity

Ovarian cancer (OC) is a malignant gynecologic tumor with high morbidity and mortality. As a newly discovered mode of programmed cell death, ferroptosis has been involved in various pathological processes of kinds of tumors in recent years. Aldehyde dehydrogenase 3 family member A2 (ALDH3A2) catalyzes the oxidation of long-chain aliphatic aldehydes to fatty acid. ALDH3A2 has been shown to be associated with ferroptosis in acute myeloid leukemia (AML), but the mechanism remains unclear. In this study, we analyzed the TCGA and GTEx databases and showed that high ALDH3A2 expression predicted poor prognosis in ovarian cancer. Further studies found that knockout or overexpression of ALDH3A2 correspondingly increased or attenuated the ferroptosis sensitivity of ovarian cancer cells. And sequencing revealed that ALDH3A2 knockout led to the activation of lipid metabolic, GSH metabolic, phospholipid metabolic, and aldehyde metabolic pathways, suggesting that ALDH3A2 induced changes in the sensitivity of ovarian cancer cells to ferroptosis by affecting these metabolic processes. Our results provide a new promising therapeutic strategy for the treatment of OC.

Comprehensive analysis reveals signal and molecular mechanism of mitochondrial energy metabolism pathway in pancreatic cancer

Pancreatic cancer (PAAD) is one of the most malignant tumors with the worst prognosis. The abnormalities in the mitochondrial energy metabolism pathway are intimately correlated with the occurrence and progression of cancer. For the diagnosis and treatment of pancreatic cancer, abnormal genes in the mitochondrial energy metabolism system may offer new targets and biomarkers. In this study, we compared the dysregulated mitochondrial energy metabolism-associated pathways in PAAD based on pancreatic cancer samples in the Cancer Genome Atlas (TCGA) database and normal pancreas samples from the Genotype Tissue Expression project (GTEx) database. Then identified 32 core genes of mitochondrial energy metabolism pathway-related genes (MMRG) were based on the gene set enrichment analysis (GSEA). We found most of these genes were altered among different clinical characteristic groups, and showed significant prognostic value and association with immune infiltration, suggesting critical roles of MMRG involve tumor genesis of PAAD. Therefore, we constructed a four-gene (LDHA, ALDH3B1, ALDH3A1, and ADH6) prognostic biomarker after eliminating redundant factors, and confirming its efficiency and independence. Further analysis indicated the potential therapeutic compounds based on the mitochondrial energy metabolism-associated prognostic biomarker. All of the above analyses dissected the critical role of mitochondrial energy metabolism signaling in pancreatic cancer and gave a better understanding of the clinical intervention of PAAD.

The Concept of Cancer Stem Cells: Elaborating on ALDH1B1 as an Emerging Marker of Cancer Progression

Cancer is a multifactorial, complex disease exhibiting extraordinary phenotypic plasticity and diversity. One of the greatest challenges in cancer treatment is intratumoral heterogeneity, which obstructs the efficient eradication of the tumor. Tumor heterogeneity is often associated with the presence of cancer stem cells (CSCs), a cancer cell sub-population possessing a panel of stem-like properties, such as a self-renewal ability and multipotency potential. CSCs are associated with enhanced chemoresistance due to the enhanced efflux of chemotherapeutic agents and the existence of powerful antioxidant and DNA damage repair mechanisms. The distinctive characteristics of CSCs make them ideal targets for clinical therapeutic approaches, and the identification of efficient and specific CSCs biomarkers is of utmost importance. Aldehyde dehydrogenases (ALDHs) comprise a wide superfamily of metabolic enzymes that, over the last years, have gained increasing attention due to their association with stem-related features in a wide panel of hematopoietic malignancies and solid cancers. Aldehyde dehydrogenase 1B1 (ALDH1B1) is an isoform that has been characterized as a marker of colon cancer progression, while various studies suggest its importance in additional malignancies. Here, we review the basic concepts related to CSCs and discuss the potential role of ALDH1B1 in cancer development and its contribution to the CSC phenotype.

An anti-alcoholism drug, disulfiram and copper complex improves radio-resistance of tumor-initiating cells in esophageal squamous cell carcinoma

BACKGROUND

Esophageal squamous cell carcinoma (ESCC) is a malignant cancer with a poor prognosis. Chemoradiotherapy is one of the most important strategies for patients with locally advanced unresectable ESCC; however, its therapeutic effect is unsatisfactory. Tumor-initiating cells (TICs) have been reported to be resistant to conventional chemotherapy and radiotherapy so far. Therefore, we aimed to develop a treatment strategy targeting TICs in ESCC to improve radiosensitivity.

METHODS

First, we validated aldehyde dehydrogenase 1 (ALDH1) as a TIC marker and investigated its ability to mediate resistance in human ESCC cell lines using flow cytometry, Western blotting, and functional analyses. Then, we focused on disulfiram (DSF), an aldehyde dehydrogenase inhibitor, used to treat alcohol use disorder. We investigated the effect of DSF and copper (II) D-gluconate (Cu) on the radiosensitivity of ESCC in xenograft mouse models.

RESULTS

ALDH1-positive cells showed an upregulation of SOX2 and Nanog, exhibiting much stronger tumor-initiating properties than ALDH1-negative cells. Furthermore, inhibition of ALDH1 attenuated the tumor-initiating properties of ESCC cell lines. Our results also showed that ALDH1-positive cells were resistant to chemotherapy and radiotherapy, and the inhibition of ALDH1 led to the mitigation of therapeutic resistance. Our in vitro and in vivo studies revealed that the DSF/Cu complex could radiosensitize ALDH1-positive ESCC cells and downregulate the phosphoinositide 3-kinase/Akt pathway.

CONCLUSION

ALDH1 inhibition by the DSF/Cu complex enhances the radiosensitivity of TICs in ESCC. The drug repositioning approach using disulfiram is a potential treatment option to overcome radioresistance in patients with locally advanced ESCC.

ALDH1A1 overexpression in melanoma cells promotes tumor angiogenesis by activating the IL‑8/Notch signaling cascade

ALDH1A1 is a cytosolic enzyme upregulated in tumor cells, involved in detoxifying cells from reactive aldehydes and in acquiring resistance to chemotherapeutic drugs. Its expression correlates with poor clinical outcomes in a number of cancers, including melanoma. The present study hypothesized that the increased ALDH1A1 expression and activity upregulated the release of proangiogenic factors from melanoma cells, which regulate angiogenic features in endothelial cells (ECs) through a rearrangement of the Notch pathway. In vivo, when subcutaneously implanted in immunodeficient mice, ALDH1A1 overexpressing melanoma cells displayed a higher microvessel density. In a 3D multicellular system, obtained co‑culturing melanoma cancer cells with stromal cells, including ECs, melanoma ALDH1A1 overexpression induced the recruitment of ECs into the core of the tumorspheres. By using a genes array, overexpression of ALDH1A1 in tumor cells also promoted modulation of Notch cascade gene expression in ECs, suggesting an interaction between tumor cells and ECs mediated by enrichment of angiogenic factors in the tumor microenvironment. To confirm this hypothesis, inactivation of ALDH1A1 by the pharmacological inhibitor CM037 significantly affected the release of angiogenic factors, including IL‑8, from melanoma cells. High levels of ALDH1A1, through the retinoic acid pathway, regulated the activation of NF‑kB‑p65 and IL‑8. Further, in a 2D co‑culture system, the addition of an IL‑8 neutralizing antibody to ECs co‑cultured with melanoma cells forced to express ALDH1A1 dampened endothelial angiogenic features, both at the molecular (in terms of gene and protein expression of mediators of the Notch pathway) and at the functional level (proliferation, scratch assay, tube formation and permeability). In conclusion, these findings demonstrated the existence of a link between melanoma ALDH1A1 expression and EC Notch signaling modification that results in a pro‑angiogenic phenotype. Based on the crucial role of ALDH1A1 in melanoma control of the tumor microenvironment, the enzyme seems a promising target for the development of novel drugs able to interrupt the cross‑talk between cancer (stem) cells and endothelial cells.

Mesothelin Expression Is Not Associated with the Presence of Cancer Stem Cell Markers SOX2 and ALDH1 in Ovarian Cancer

Mesothelin (MSLN) overexpression (OE) is a frequent finding in ovarian carcinomas and increases cell survival and tumor aggressiveness. Since cancer stem cells (CSCs) contribute to pathogenesis, chemoresistance and malignant behavior in ovarian cancer (OC), we hypothesized that MSLN expression could be creating a favorable environment that nurtures CSCs. In this study, we analyzed the expression of MSLN and CSC markers SOX2 and ALDH1 by immunohistochemistry (IHC) in different model systems: primary high-grade serous carcinomas (HGSCs) and OC cell lines, including cell lines that were genetically engineered for MSLN expression by either CRISPR-Cas9-mediated knockout (Δ) or lentivirus-mediated OE. Cell lines, wild type and genetically engineered, were evaluated in 2D and 3D culture conditions and xenografted in nude mice. We observed that MSLN was widely expressed in HGSC, and restricted expression was observed in OC cell lines. In contrast, SOX2 and ALDH1 expression was limited in all tissue and cell models. Most importantly, the expression of CSC markers was independent of MSLN expression, and manipulation of MSLN expression did not affect CSC markers. In conclusion, MSLN expression is not involved in driving the CSC phenotype.

Biliary Epithelial Senescence in Liver Disease: There Will Be SASP

Cellular senescence is a pathophysiological phenomenon in which proliferative cells enter cell cycle arrest following DNA damage and other stress signals. Natural, permanent DNA damage can occur after repetitive cell division; however, acute stress or other injuries can push cells into premature senescence and eventually a senescence-associated secretory phenotype (SASP). In recent years, there has been increased evidence for the role of premature senescence in disease progression including diabetes, cardiac diseases, and end-stage liver diseases including cholestasis. Liver size and function change with aging, and presumably with increasing cellular senescence, so it is important to understand the mechanisms by which cellular senescence affects the functional nature of the liver in health and disease. As well, cells in a SASP state secrete a multitude of inflammatory and pro-fibrogenic factors that modulate the microenvironment. Cellular SASP and the associated, secreted factors have been implicated in the progression of liver diseases, such as cholestatic injury that target the biliary epithelial cells (i.e., cholangiocytes) lining the bile ducts. Indeed, cholangiocyte senescence/SASP is proposed to be a driver of disease phenotypes in a variety of liver injuries. Within this review, we will discuss the impact of cholangiocyte senescence and SASP in the pathogenesis of cholestatic disorders.

Non-cytochrome P450 enzymes involved in the oxidative metabolism of xenobiotics: Focus on the regulation of gene expression and enzyme activity

Oxidative metabolism is one of the major biotransformation reactions that regulates the exposure of xenobiotics and their metabolites in the circulatory system and local tissues and organs, and influences their efficacy and toxicity. Although cytochrome (CY)P450s play critical roles in the oxidative reaction, extensive CYP450-independent oxidative metabolism also occurs in some xenobiotics, such as aldehyde oxidase, xanthine oxidoreductase, flavin-containing monooxygenase, monoamine oxidase, alcohol dehydrogenase, or aldehyde dehydrogenase-dependent oxidative metabolism. Drugs form a large portion of xenobiotics and are the primary target of this review. The common reaction mechanisms and roles of non-CYP450 enzymes in metabolism, factors affecting the expression and activity of non-CYP450 enzymes in terms of inhibition, induction, regulation, and species differences in pharmaceutical research and development have been summarized. These non-CYP450 enzymes are detoxifying enzymes, although sometimes they mediate severe toxicity. Synthetic or natural chemicals serve as inhibitors for these non-CYP450 enzymes. However, pharmacokinetic-based drug interactions through these inhibitors have rarely been reported in vivo. Although multiple mechanisms participate in the basal expression and regulation of non-CYP450 enzymes, only a limited number of inducers upregulate their expression. Therefore, these enzymes are considered non-inducible or less inducible. Overall, this review focuses on the potential xenobiotic factors that contribute to variations in gene expression levels and the activities of non-CYP450 enzymes.

Ruxolitinib Combined with Gemcitabine against Cholangiocarcinoma Growth via the JAK2/STAT1/3/ALDH1A3 Pathway

Cholangiocarcinoma is the most common primary malignant tumor of the bile duct. The current standard first-line treatment for advanced or metastatic cholangiocarcinoma is gemcitabine and cisplatin. However, few effective treatment choices exist for refractory cholangiocarcinoma, and additional therapeutic drugs are urgently required. Our previous work demonstrated that the ALDH isoform 1A3 plays a vital role in the malignant behavior of cholangiocarcinoma and may serve as a new therapeutic target. In this study, we found a positive correlation between ALDH1A3 protein expression levels and the cell migration abilities of three cholangiocarcinoma cell lines, which was verified using ALDH1A3-overexpressing and ALDH1A3-knockdown clones. We also used ALDH1A3-high and ALDH1A3-low populations of cholangiocarcinoma cell lines from the library of integrated network-based cellular signatures (LINCS) program and assessed the effects of ruxolitinib, a commercially available JAK2 inhibitor. Ruxolitinib had a higher cytotoxic effect when combined with gemcitabine. Furthermore, the nuclear translocation STAT1 and STAT3 heterodimers were markedly diminished by ruxolitinib treatment, possibly resulting in decreased ALDH1A3 activation. Notably, ruxolitinib alone or combined with gemcitabine led to significantly reduced tumor size and weight. Collectively, our studies suggest that ruxolitinib might suppress the ALDH1A3 activation through the JAK2/STAT1/3 pathway in cholangiocarcinoma, and trials should be undertaken to evaluate its efficacy in clinical therapy.

Inhibition of aldehyde dehydrogenase by furazolidone nanoemulsion to decrease cisplatin resistance in lung cancer cells

Aim: The overexpression of aldehyde dehydrogenase (ALDH) in cancer cells contributes to therapeutic resistance. Furazolidone (FUR) is a strong ALDH inhibitor. Methods: FUR nanoemulsion (NE) was formulated and tested for ALDH inhibitory activity in comparison with free FUR. The cytotoxic potential of cisplatin was evaluated in combination with free FUR and FUR NE. Results: The optimized FUR NE showed droplet size of 167.9 ± 3.1 nm and drug content of 84.2 ± 2.3%. FUR NE inhibited 99.75 ± 2.1% of ALDH activity while 25.0 ± 4.6% was inhibited by free FUR. FUR NE increased the sensitivity to cisplatin in A549 cells by more than tenfold by its ALDH inhibitory effects. Conclusion: This finding can be a promising approach to improve cancer survival in ALDH-positive drug-resistant cancers.

Normalization of Enzyme Expression and Activity Regulating Vitamin A Metabolism Increases RAR-Beta Expression and Reduces Cellular Migration and Proliferation in Diseases Caused by Tuberous Sclerosis Gene Mutations

Background

Mutation in a tuberous sclerosis gene (TSC1 or 2) leads to continuous activation of the mammalian target of rapamycin (mTOR). mTOR activation alters cellular including vitamin A metabolism and retinoic acid receptor beta (RARβ) expression. The goal of the present study was to investigate the molecular connection between vitamin A metabolism and TSC mutation. We also aimed to investigate the effect of the FDA approved drug rapamycin and the vitamin A metabolite retinoic acid (RA) in cell lines with TSC mutation.

Methods

Expression and activity of vitamin A associated metabolic enzymes and RARβ were assessed in human kidney angiomyolipoma derived cell lines, primary lymphangioleiomyomatosis (LAM) tissue derived LAM cell lines. RARβ protein levels were also tested in primary LAM lung tissue sections. TaqMan arrays, enzyme activities, qRT-PCRs, immunohistochemistry, immunofluorescent staining, and western blotting were performed and analysed. The functional effects of retinoic acid (RA) and rapamycin were tested in a scratch and a BrDU assay to assess cell migration and proliferation.

Results

Metabolic enzyme arrays revealed a general deregulation of many enzymes involved in vitamin A metabolism including aldehyde dehydrogenases (ALDHs), alcohol dehydrogenases (ADHs) and Cytochrome P450 2E1 (CYP2E1). Furthermore, RARβ downregulation was a characteristic feature of all TSC-deficient cell lines and primary tissues. Combination of the two FDA approved drugs -RA for acute myeloid leukaemia and rapamycin for TSC mutation- normalised ALDH and ADH expression and activity, restored RARβ expression and reduced cellular proliferation and migration.

Conclusion

Deregulation of vitamin A metabolizing enzymes is a feature of TSC mutation. RA can normalize RARβ levels and limit cell migration but does not have a significant effect on proliferation. Based on our data, translational studies could confirm whether combination of RA with reduced dosage of rapamycin would have more beneficial effects to higher dosage of rapamycin monotherapy meanwhile reducing adverse effects of rapamycin for patients with TSC mutation.

ALDH3A1 driving tumor metastasis is mediated by p53/BAG1 in lung adenocarcinoma

Lung adenocarcinoma (LUAD) is a lethal malignancy with metastasis, a major tumor feature that predominantly correlated with progression, but the molecules that mediated tumor metastasis remain elusive. To declare the critical regulatory genes, RNA sequencing data in LUAD patients was acquired from The Cancer Genome Atlas (TCGA) and found that ALDH3A1 was distinctly highly expressed in LUAD patients with metastasis (M1) compared with those without metastasis (M0), linked to the property of cancer stem cell and epithelial-mesenchymal transition (EMT). Besides, high ALDH3A1 expression predicted a poor prognosis. Knockdown of ALDH3A1 showed decreased proliferation, migration, and invasion in A549 cell line. Furthermore, BAG1 was regulated by ALDH3A1 through p53, enhanced cell proliferation, and predicted clinical prognosis. Our findings collectively uncovered a novel mechanism that orchestrates tumor cells' metastasis, and decreasing ALDH3A1 represented a potential therapeutic target for reprogramming metastasis.

Exploitation of the vitamin A/retinoic acid axis depletes ALDH1-positive cancer stem cells and re-sensitises resistant non-small cell lung cancer cells to cisplatin

Despite advances in personalised medicine and the emerging role of immune checkpoints in directing treatment decisions in subsets of lung cancer patients, non-small cell lung cancer (NSCLC) remains the most common cause of cancer-related deaths worldwide. The development of drug resistance plays a key role in the relapse of lung cancer patients in the clinical setting, mainly due to the unlimited renewal capacity of residual cancer stem cells (CSCs) within the tumour cell population during chemotherapy. In this study, we investigated the function of the CSC marker, aldehyde dehydrogenase (ALDH1) in retinoic acid cell signalling using an in vitro model of cisplatin resistant NSCLC. The addition of key components in retinoic acid cell signalling, all-trans retinoic acid (ATRA) and retinol to cisplatin chemotherapy, significantly reduced ALDH1-positive cell subsets in cisplatin resistant NSCLC cells relative to their sensitive counterparts resulting in the re-sensitisation of chemo-resistant cells to the cytotoxic effects of cisplatin. Furthermore, combination of ATRA or retinol with cisplatin significantly inhibited cell proliferation, colony formation and increased cisplatin-induced apoptosis. This increase in apoptosis may, at least in part, be due to differential gene expression of the retinoic acid (RARα/β) and retinoid X (RXRα) nuclear receptors in cisplatin-resistant lung cancer cells. These data support the concept of exploiting the retinoic acid signalling cascade as a novel strategy in targeting subsets of CSCs in cisplatin resistant lung tumours.

Aldehyde dehydrogenase inhibitors promote DNA damage in ovarian cancer and synergize with ATM/ATR inhibitors

Rationale: Aldehyde dehydrogenase (ALDH) enzymes are often upregulated in cancer cells and associated with therapeutic resistance. ALDH enzymes protect cells by metabolizing toxic aldehydes which can induce DNA double stand breaks (DSB). We recently identified a novel ALDH1A family inhibitor (ALDHi), 673A. We hypothesized that 673A, via inhibition of ALDH1A family members, could induce intracellular accumulation of genotoxic aldehydes to cause DSB and that ALDHi could synergize with inhibitors of the ATM and ATR, proteins which direct DSB repair.

Methods: We used immunofluorescence to directly assess levels of the aldehyde 4-hydroxynonenal and comet assays to evaluate DSB. Western blot was used to evaluate activation of the DNA damage response pathways. Cell counts were performed in the presence of 673A and additional aldehydes or aldehyde scavengers. ALDH inhibition results were confirmed using ALDH1A3 CRISPR knockout. Synergy between 673A and ATM or ATR inhibitors was evaluated using the Chou-Talalay method and confirmed in vivo using cell line xenograft tumor studies.

Results: The ALDHi 673A cellular accumulation of toxic aldehydes which induce DNA double strand breaks. This is exacerbated by addition of exogenous aldehydes such as vitamin-A (retinaldehyde) and ameliorated by aldehyde scavengers such as metformin and hydralazine. Importantly, ALDH1A3 knockout cells demonstrated increased sensitivity to ATM/ATR inhibitors. And, ALDHi synergized with inhibitors of ATM and ATR, master regulators of the DSB DNA damage response, both in vitro and in vivo. This synergy was evident in homologous recombination (HR) proficient cell lines.

Conclusions: ALDHi can be used to induce DNA DSB in cancer cells and synergize with inhibitors the ATM/ATR pathway. Our data suggest a novel therapeutic approach to target HR proficient ovarian cancer cells.

Aldehyde Dehydrogenase 1B1 Is Associated with Altered Cell Morphology, Proliferation, Migration and Chemosensitivity in Human Colorectal Adenocarcinoma Cells

Aldehyde dehydrogenases (ALDHs) are NAD(P)⁺-dependent enzymes that catalyze the oxidation of endogenous and exogenous aldehydes to their corresponding carboxylic acids. ALDHs participate in a variety of cellular mechanisms, such as metabolism, cell proliferation and apoptosis, as well as differentiation and stemness. Over the last few years, ALDHs have emerged as cancer stem cell markers in a wide spectrum of solid tumors and hematological malignancies. In this study, the pathophysiological role of ALDH1B1 in human colorectal adenocarcinoma was investigated. Human colon cancer HT29 cells were stably transfected either with human green fluorescent protein (GFP)-tagged ALDH1B1 or with an empty lentiviral expression vector. The overexpression of ALDH1B1 was correlated with altered cell morphology, decreased proliferation rate and reduced clonogenic efficiency. Additionally, ALDH1B1 triggered a G2/M arrest at 24 h post-cell synchronization, probably through p53 and p21 upregulation. Furthermore, ALDH1B1-overexpressing HT29 cells exhibited enhanced resistance against doxorubicin, fluorouracil (5-FU) and etoposide. Finally, ALDH1B1 induced increased migratory potential and displayed epithelial–mesenchymal transition (EMT) through the upregulation of ZEB1 and vimentin and the consequent downregulation of E-cadherin. Taken together, ALDH1B1 confers alterations in the cell morphology, cell cycle progression and gene expression, accompanied by significant changes in the chemosensitivity and migratory potential of HT29 cells, underlying its potential significance in cancer progression.

Development of 2,5-dihydro-4H-pyrazolo[3,4-d]pyrimidin-4-one inhibitors of aldehyde dehydrogenase 1A (ALDH1A) as potential adjuncts to ovarian cancer chemotherapy

There is strong evidence that inhibition of one or more Aldehyde Dehydrogenase 1A (ALDH1A) isoforms may be beneficial in chemotherapy-resistant ovarian cancer and other tumor types. While many previous efforts have focused on development of ALDH1A1 selective inhibitors, the most deadly ovarian cancer subtype, high-grade serous (HGSOC), exhibits elevated expression of ALDH1A3. Herein, we report continued development of pan-ALDH1A inhibitors to assess whether broad spectrum ALDH1A inhibition is an effective adjunct to chemotherapy in this critical tumor subtype. Optimization of the CM39 scaffold, aided by metabolite ID and several new ALDH1A1 crystal structures, led to improved biochemical potencies, improved cellular ALDH inhibition in HGSOC cell lines, and substantial improvements in microsomal stability culminating in orally bioavailable compounds. We demonstrate that two compounds 68 and 69 are able to synergize with chemotherapy in a resistant cell line and patient-derived HGSOC tumor spheroids, indicating their suitability for future in vivo proof of concept experiments.

Loss of ARID1A induces a stemness gene ALDH1A1 expression with histone acetylation in the malignant subtype of cholangiocarcinoma

Genomic analyses have recently discovered the malignant subtype of human intrahepatic cholangiocarcinoma (ICC) characterized by frequent mutations of chromatin remodeling gene ARID1A; however, the biological and molecular functions still remain obscure. We here examined the clinical and biological significances of ARID1A deficiency in human ICC. Immunohistochemical analysis demonstrated that the loss of ARID1A was an independent prognostic factor for overall survival of ICC patients (P = 0.023). We established ARID1A-knockout (KO) cells by using the CRISPR/Cas9 system from two human cholangiocarcinoma cell lines. ARID1A-KO cells exhibited significantly enhanced migration, invasion, and sphere formation activity. Microarray analysis revealed that ALDH1A1, a stemness gene, was the most significantly elevated genes in ARID1A-KO cells. In addition, ALDH enzymatic activity as a hallmark of cancer stem cells was markedly high in the KO cells. ARID1A and histone deacetylase 1 were directly recruited to the ALDH1A1 promoter region in cholangiocarcinoma cells with undetectable ALDH1A1 expression by chromatin immunoprecipitation assay. The histone H3K27 acetylation level at the ALDH1A1 promoter region was increased in cells when ARID1A was disrupted (P < 0.01). Clinically, inverse correlation between ARID1A and ALDH1A1 expression was also identified in primary ICC (P = 0.018), and ARID1A-negative and ALDH1A1-positve ICCs showed worse prognosis than only ARID1A-negative cases (P = 0.002). In conclusion, ARID1A may function as a tumor suppressor in ICC through transcriptional downregulation of ALDH1A1 expression with decreasing histone H3K27 acetylation. Our studies provide the basis for the development of new epigenetic approaches to ARID1A-negative ICC. Immunohistochemical loss of ARID1A is an independent prognostic factor in intrahepatic cholangiocarcinoma patients. ARID1A recruits HDAC1 to the promoter region of ALDH1A1, a stemness gene, and epigenetically suppresses ALDH1A1 expression with decreasing histone H3K27 acetylation in cholangiocarcinoma cells.

Targeting cancer stem cells in cholangiocarcinoma (Review)

The incidence of cholangiocarcinoma has been increasing steadily over the past 50 years, but the survival rates remained low due to the disease being highly resistant to non-surgical treatment interventions. Cancer stem cell markers are expressed in cholangiocarcinoma, suggesting that they serve a significant role in the physiology of the disease. Cancer stem cells are frequently implicated in tumor relapse and acquired resistance to a number of therapeutic strategies, including chemotherapy, radiation and immune checkpoint inhibitors. Novel targeted therapies to eradicate cancer stem cells may assist in overcoming treatment resistance in cholangiocarcinoma and reduce the rates of relapse and recurrence. Several signaling pathways have been previously documented to regulate the development and survival of cancer stem cells, including Notch, janus kinase/STAT, Hippo/yes-associated protein 1 (YAP1), Wnt and Hedgehog signaling. Although pharmacological agents have been developed to target these pathways, only modest effects were reported in clinical trials. The Hippo/YAP1 signaling pathway has come to the forefront in the field of cancer stem cell research due to its reported involvement in epithelium-mesenchymal transition, cell adhesion, organogenesis and tumorigenesis. In the present article, recent findings in terms of cancer stem cell research in cholangiocarcinoma were reviewed, where the potential therapeutic targeting of cancer stem cells in this disease was discussed.

ALDH3A1 acts as a prognostic biomarker and inhibits the epithelial mesenchymal transition of oral squamous cell carcinoma through IL-6/STAT3 signaling pathway

Objectives: Aldehyde dehydrogenase 3A1 (ALDH3A1) is a member of the ALDH superfamily and its relationship with oral squamous cell carcinoma (OSCC) still unknown. In our subject, we aimed to reveal the expression pattern and clinical value of ALDH3A1 in OSCC and its biological function in OSCC cell lines.

Materials and methods: The expression level of ALDH3A1 in paired OSCC tissues and adjacent noncancerous tissues were detected by quantitative real-time PCR, Western blot and immunohistochemistry. The relationship between ALDH3A1 expression and clinical characteristics was analyzed. Besides, cell-counting kit 8, colony formation, wound healing, transwell invasion, apoptosis and cell cycle assays were employed to assess the role of ALDH3A1 in OSCC cells. To explore the influence of ALDH3A1 on OSCC epithelial-to-mesenchymal transition (EMT), the expression of EMT markers (E-cadherin, vimentin, snail, MMP3) on OSCC cells were detected, and possible mechanisms were analyzed.

Results: In OSCC tissues, ALDH3A1 was significantly decreased compared to the adjacent normal tissues. Lower ALDH3A1 expression in OSCC tissues was associated with a higher incidence of lymph node metastasis (LNM). Moreover, the overall survival of OSCC with low ALDH3A1 expression was significantly worse compared to that of OSCC with high ALDH3A1 expression. Restored expression of ALDH3A1 suppressed cell proliferation, migration and invasion in OSCC cells. Further experiments showed that ALDH3A1 might inhibit EMT in OSCC via a regulation of the IL-6/STAT3 signal pathway.

Conclusion: These data indicate that ALDH3A1 may serve as a biomarker and may be developed into a novel treatment for OSCC.

Potentiation of cancerous progression by LISCH7 via direct stimulation of TGFB1 transcription in triple-negative breast cancer

As an aggressive breast cancer (BCa) subtype, triple-negative breast cancer (TNBC) responses poorly to chemotherapy and endocrine therapy, and usually has a worse prognosis. This is largely due to the lack of specific therapeutic targets, laying claim to an imperious demand to clarify the key signaling pathways potentiating TNBC progression. Herein, we report that expression levels of the liver-specific bHLH-Zip transcription factor (LISCH7), a recently identified key player in cancerous progression, preferentially enriched in TNBC in comparison with other BCa subtypes, and this upregulation was observed to be correlated to a poor survival outcome in patients with TNBC. Ablation of LISCH7 in TNBC cells impaired cell proliferation, reduced cell invasiveness, and enhanced sensitivity to the first-line chemotherapeutic drug docetaxel at both in vitro and in vivo levels. Importantly, concurrent induction of TGFB1, the gene encoding transforming growth factor-β1 (TGF-β1), an essential multipluripotent regulator of TNBC, was accompanied with these alterations in cancerous properties. We further showed that LISCH7 could directly bind to the TGFB1 promoter and stimulate TGFB1 transcription in TNBC cells. The recruitment of LISCH7 onto the TGFB1 chromatin and transactivation of TGFB1 were substantially augmented by treatment with the exogenous TGF-β1 in a time- and dose-dependent manner. Collectively, these findings suggest that LISCH7 and TGF-β1 form a reciprocal positive regulatory loop and cooperatively regulate cancerous progression in TNBC cells. Thus, simultaneous inhibition of both LISCH7 and TGF-β1 signaling may represent a more effective approach to counteract advanced TNBC.

ALDH3A1 Overexpression in Melanoma and Lung Tumors Drives Cancer Stem Cell Expansion, Impairing Immune Surveillance through Enhanced PD-L1 Output

Melanoma and non-small-cell lung carcinoma (NSCLC) cell lines are characterized by an intrinsic population of cancer stem-like cells (CSC), and high expression of detoxifying isozymes, the aldehyde dehydrogenases (ALDHs), regulating the redox state. In this study, using melanoma and NSCLC cells, we demonstrate that ALDH3A1 isozyme overexpression and activity is closely associated with a highly aggressive mesenchymal and immunosuppressive profile. The contribution of ALDH3A1 to the stemness and immunogenic status of melanoma and NSCLC cells was evaluated by their ability to grow in 3D forming tumorspheres, and by the expression of markers for stemness, epithelial to mesenchymal transition (EMT), and inflammation. Furthermore, in specimens from melanoma and NSCLC patients, we investigated the expression of ALDH3A1, PD-L1, and cyclooxygenase-2 (COX-2) by immunohistochemistry. We show that cells engineered to overexpress the ALDH3A1 enzyme enriched the CSCs population in melanoma and NSCLC cultures, changing their transcriptome. In fact, we found increased expression of EMT markers, such as vimentin, fibronectin, and Zeb1, and of pro-inflammatory and immunosuppressive mediators, such as NFkB, prostaglandin E2, and interleukin-6 and -13. ALDH3A1 overexpression enhanced PD-L1 output in tumor cells and resulted in reduced proliferation of peripheral blood mononuclear cells when co-cultured with tumor cells. Furthermore, in tumor specimens from melanoma and NSCLC patients, ALDH3A1 expression was invariably correlated with PD-L1 and the pro-inflammatory marker COX-2. These findings link ALDH3A1 expression to tumor stemness, EMT and PD-L1 expression, and suggest that aldehyde detoxification is a redox metabolic pathway that tunes the immunological output of tumors.

ALDH1A1 effect on Yan Yellow Cattle preadipocyte differentiation

Aldehyde dehydrogenase 1A1 (ALDH1A1) is a cytosolic enzyme that mainly catalyzes the oxidation of acetaldehyde into acetic acid and participates in the regulation of differentiation and gene expression in fat cell growth and development. However, the physiological role of ALDH1A1 in the formation of fat cell precursors in the Yan Yellow Cattle is still not clear. Herein, we investigated the specific regulation of the gene encoding for ALDH1A1 during the differentiation process of the adipocyte cells of the Yan Yellow Cattle by interfering or overexpressing the ALDH1A1 gene. As a result, we found that the mRNA expression levels of ALDH1A1 were significantly increased during the formation of progenitor cells. In addition, the expression levels of the Lipoprotein lipase (LPL) and transcription factors (PPARγ, C/EBPα) were also significantly increased. ALDH1A1 gene overexpression and RNA interfering promoted and inhibited respectively the lipid accumulation and triglyceride production in mature adipocytes, and the expression of the LPL and transcription factors (PPARγ, C/EBPα). The changes in the protein expression levels of ALDH1A1 and adipogenic factors were in accord with the changes observed in the mRNA levels. In conclusion, our results indicate that ALDH1A1 plays an important regulatory role in the differentiation of preadipocyte cells.

ALDH7A1 inhibits the intracellular transport pathways during hypoxia and starvation to promote cellular energy homeostasis

The aldehyde dehydrogenase (ALDH) family of metabolic enzymes converts aldehydes to carboxylates. Here, we find that the reductive consequence of ALDH7A1 activity, which generates NADH (nicotinamide adenine dinucleotide, reduced form) from NAD, underlies how ALDH7A1 coordinates a broad inhibition of the intracellular transport pathways. Studying vesicle formation by the Coat Protein I (COPI) complex, we elucidate that NADH generated by ALDH7A1 targets Brefeldin-A ADP-Ribosylated Substrate (BARS) to inhibit COPI vesicle fission. Moreover, defining a physiologic role for the broad transport inhibition exerted by ALDH7A1, we find that it acts to reduce energy consumption during hypoxia and starvation to promote cellular energy homeostasis. These findings advance the understanding of intracellular transport by revealing how the coordination of multiple pathways can be achieved, and also defining circumstances when such coordination is needed, as well as uncovering an unexpected way that NADH acts in cellular energetics.

Intracellular vesicle transport can be regulated by Brefeldin‐A ADP‐Ribosylated Substrate (BARS) during vesicle fission. Here, the authors show that NADH generated by aldehyde dehydrogenase 7A1 (ALDH7A1) inhibits intracellular transport by targeting BARS and inhibiting COPI vesicle fission during situations of energy deprivation

ALDH7A1 inhibits the intracellular transport pathways during hypoxia and starvation to promote cellular energy homeostasis

The aldehyde dehydrogenase (ALDH) family of metabolic enzymes converts aldehydes to carboxylates. Here, we find that the reductive consequence of ALDH7A1 activity, which generates NADH (nicotinamide adenine dinucleotide, reduced form) from NAD, underlies how ALDH7A1 coordinates a broad inhibition of the intracellular transport pathways. Studying vesicle formation by the Coat Protein I (COPI) complex, we elucidate that NADH generated by ALDH7A1 targets Brefeldin-A ADP-Ribosylated Substrate (BARS) to inhibit COPI vesicle fission. Moreover, defining a physiologic role for the broad transport inhibition exerted by ALDH7A1, we find that it acts to reduce energy consumption during hypoxia and starvation to promote cellular energy homeostasis. These findings advance the understanding of intracellular transport by revealing how the coordination of multiple pathways can be achieved, and also defining circumstances when such coordination is needed, as well as uncovering an unexpected way that NADH acts in cellular energetics.

High Aldehyde Dehydrogenase Levels Are Detectable in the Serum of Patients with Lung Cancer and May Be Exploited as Screening Biomarkers

Objectives

Since early detection improves overall survival in lung cancer, identification of screening biomarkers for patients at risk represents an area of intense investigation. Tumor liberated protein (TLP) has been previously described as a tumor-associated antigen (complex) present in the sera from lung cancer patients. Here, we set out to identify the nature of TLP to develop this as a potential biomarker for lung cancer screening.

Materials and Methods

Beginning from the peptide epitope RTNKEASI previously identified from the TLP complex, we produced a rabbit anti-RTNKEASI serum and evaluated it in the lung cancer cell line A549 by means of immunoblot and peptide completion assay (PCA). The TLP sequence identification was conducted by mass spectrometry. The detected protein was, then, analyzed in patients with non-small cell lung cancer (NSCLC) and benign lung pathologies and healthy donors, by ELISA.

Results

The anti-RTNKEASI antiserum detected and immunoprecipitated a 55 kDa protein band in the lysate of A549 cells identified as aldehyde dehydrogenase isoform 1A1, revealing the molecular nature of at least one component of the previously described TLP complex. Next, we screened blood samples from a non-tumor cohort of 26 patients and 45 NSCLC patients with different disease stages for the presence of ALDH1A1 and global ALDH. This analysis indicated that serum positivity was highly restricted to patients with NSCLC (ALDH p < 0.001; ALDH1A1 p=0.028). Interestingly, the global ALDH test resulted positive in more NSCLC samples compared to the ALDH1A1 test, suggesting that other ALDH isoforms might add to the sensitivity of the assay.

Conclusion

Our data indicate that ALDH levels are elevated in the sera of NSCLC patients, even with early stage disease, and may thus be evaluated as part of a marker panel for non-invasive detection of NSCLC.

Targeting Cancer Stem Cells: A Strategy for Effective Eradication of Cancer

Cancer stem cells (CSCs) are subpopulations of tumor cells with the ability to self-renew, differentiate, and initiate and maintain tumor growth, and they are considered to be the main drivers of intra- and inter-tumoral heterogeneity. While conventional chemotherapy can eradicate the majority of non-CSC tumor cells, CSCs are often drug-resistant, leading to tumor recurrence and metastasis. The heterogeneity of CSCs is the main challenge in developing CSC-targeting therapy; therefore, we and other investigators have focused on developing novel therapeutic strategies that combine conventional chemotherapy with inhibitors of CSC-regulating pathways. Encouraging preclinical findings have suggested that CSC pathway blockade can indeed enhance cellular sensitivity to non-targeted conventional therapy, and this work has led to several ongoing clinical trials of CSC pathway inhibitors. Our studies in bladder cancer and lung adenocarcinoma have demonstrated a crucial role of YAP1, a transcriptional regulator of genes that promote cell survival and proliferation, in regulating CSC phenotypes. Moreover, using cell lines and patient-derived xenograft models, we showed that inhibition of YAP1 enhances the efficacy of conventional therapies by attenuating CSC stemness features. In this review, we summarize the therapeutic strategies for targeting CSCs in several cancers and discuss the potential and challenges of the approach.

The Contributions of Prostate Cancer Stem Cells in Prostate Cancer Initiation and Metastasis

Research in the last decade has clearly revealed a critical role of prostate cancer stem cells (PCSCs) in prostate cancer (PC). Prostate stem cells (PSCs) reside in both basal and luminal layers, and are the target cells of oncogenic transformation, suggesting a role of PCSCs in PC initiation. Mutations in PTEN, TP53, and RB1 commonly occur in PC, particularly in metastasis and castration-resistant PC. The loss of PTEN together with Ras activation induces partial epithelial–mesenchymal transition (EMT), which is a major mechanism that confers plasticity to cancer stem cells (CSCs) and PCSCs, which contributes to metastasis. While PTEN inactivation leads to PC, it is not sufficient for metastasis, the loss of PTEN concurrently with the inactivation of both TP53 and RB1 empower lineage plasticity in PC cells, which substantially promotes PC metastasis and the conversion to PC adenocarcinoma to neuroendocrine PC (NEPC), demonstrating the essential function of TP53 and RB1 in the suppression of PCSCs. TP53 and RB1 suppress lineage plasticity through the inhibition of SOX2 expression. In this review, we will discuss the current evidence supporting a major role of PCSCs in PC initiation and metastasis, as well as the underlying mechanisms regulating PCSCs. These discussions will be developed along with the cancer stem cell (CSC) knowledge in other cancer types.

Role of Aldehyde Dehydrogenases in Physiopathological Processes

Many different diseases are associated with oxidative stress. One of the main consequences of oxidative stress at the cellular level is lipid peroxidation, from which toxic aldehydes may be generated. Below their toxicity thresholds, some aldehydes are involved in signaling processes, while others are intermediaries in the metabolism of lipids, amino acids, neurotransmitters, and carbohydrates. Some aldehydes ubiquitously distributed in the environment, such as acrolein or formaldehyde, are extremely toxic to the cell. On the other hand, aldehyde dehydrogenases (ALDHs) are able to detoxify a wide variety of aldehydes to their corresponding carboxylic acids, thus helping to protect from oxidative stress. ALDHs are located in different subcellular compartments such as cytosol, mitochondria, nucleus, and endoplasmic reticulum. The aim of this review is to analyze, and highlight, the role of different ALDH isoforms in the detoxification of aldehydes generated in processes that involve high levels of oxidative stress. The ALDH physiological relevance becomes evident by the observation that their expression and activity are enhanced in different pathologies that involve oxidative stress such as neurodegenerative disorders, cardiopathies, atherosclerosis, and cancer as well as inflammatory processes. Furthermore, ALDH mutations bring about several disorders in the cell. Thus, understanding the mechanisms by which these enzymes participate in diverse cellular processes may lead to better contend with the damage caused by toxic aldehydes in different pathologies by designing modulators and/or protocols to modify their activity or expression.

C1 CAGE detects transcription start sites and enhancer activity at single-cell resolution

Single-cell transcriptomic profiling is a powerful tool to explore cellular heterogeneity. However, most of these methods focus on the 3′-end of polyadenylated transcripts and provide only a partial view of the transcriptome. We introduce C1 CAGE, a method for the detection of transcript 5′-ends with an original sample multiplexing strategy in the C1^TM microfluidic system. We first quantifiy the performance of C1 CAGE and find it as accurate and sensitive as other methods in the C1 system. We then use it to profile promoter and enhancer activities in the cellular response to TGF-β of lung cancer cells and discover subpopulations of cells differing in their response. We also describe enhancer RNA dynamics revealing transcriptional bursts in subsets of cells with transcripts arising from either strand in a mutually exclusive manner, validated using single molecule fluorescence in situ hybridization.

Single-cell transcriptomic profiling allows the exploration of cellular heterogeneity but commonly focuses on the 3′-end of the transcript. Here the authors introduce C1 CAGE, which detects the 5′ transcript end in a multiplexed microfluidic system.

Aldehyde Dehydrogenases: Not Just Markers, but Functional Regulators of Stem Cells

Aldehyde dehydrogenase (ALDH) is a superfamily of enzymes that detoxify a variety of endogenous and exogenous aldehydes and are required for the biosynthesis of retinoic acid (RA) and other molecular regulators of cellular function. Over the past decade, high ALDH activity has been increasingly used as a selectable marker for normal cell populations enriched in stem and progenitor cells, as well as for cell populations from cancer tissues enriched in tumor-initiating stem-like cells. Mounting evidence suggests that ALDH not only may be used as a marker for stem cells but also may well regulate cellular functions related to self-renewal, expansion, differentiation, and resistance to drugs and radiation. ALDH exerts its functional actions partly through RA biosynthesis, as all-trans RA reverses the functional effects of pharmacological inhibition or genetic suppression of ALDH activity in many cell types in vitro. There is substantial evidence to suggest that the role of ALDH as a stem cell marker comes down to the specific isoform(s) expressed in a particular tissue. Much emphasis has been placed on the ALDH1A1 and ALDH1A3 members of the ALDH1 family of cytosolic enzymes required for RA biosynthesis. ALDH1A1 and ALDH1A3 regulate cellular function in both normal stem cells and tumor-initiating stem-like cells, promoting tumor growth and resistance to drugs and radiation. An improved understanding of the molecular mechanisms by which ALDH regulates cellular function will likely open new avenues in many fields, especially in tissue regeneration and oncology.

Structure-Based Optimization of a Novel Class of Aldehyde Dehydrogenase 1A (ALDH1A) Subfamily-Selective Inhibitors as Potential Adjuncts to Ovarian Cancer Chemotherapy

Aldehyde dehydrogenase (ALDH) activity is commonly used as a marker to identify cancer stem-like cells. The three ALDH1A isoforms have all been individually implicated in cancer stem-like cells and in chemoresistance; however, which isoform is preferentially expressed varies between cell lines. We sought to explore the structural determinants of ALDH1A isoform selectivity in a series of small-molecule inhibitors in support of research into the role of ALDH1A in cancer stem cells. An SAR campaign guided by a cocrystal structure of the HTS hit CM39 (7) with ALDH1A1 afforded first-in-class inhibitors of the ALDH1A subfamily with excellent selectivity over the homologous ALDH2 isoform. We also discovered the first reported modestly selective single isoform 1A2 and 1A3 inhibitors. Two compounds, 13g and 13h, depleted the CD133⁺ putative cancer stem cell pool, synergized with cisplatin, and achieved efficacious concentrations in vivo following IP administration. Compound 13h additionally synergized with cisplatin in a patient-derived ovarian cancer spheroid model.

Screening of potential biomarkers in uterine leiomyomas disease via gene expression profiling analysis

The present study aimed to screen potential biomarkers for uterine leiomyomas disease, particularly target genes associated with the mediator of RNA polymerase II transcription subunit 12 (MED12) mutation. The microarray data of GSE30673, including 10 MED12 wild-type myometrium, 8 MED12 mutation leiomyoma and 2 MED12 wild-type leiomyoma samples, were downloaded from the Gene Expression Omnibus database. Compared with myometrium samples, differently-expressed genes (DEGs) in the MED12 mutation and wild-type leiomyoma samples were identified using the Limma package. The two sets of DEGs obtained were intersected to screen common DEGs. The DEGs in the MED12 mutation and wild-type leiomyoma samples, and common DEGs were defined as group A, B and C. Gene Ontology (GO) and pathway enrichment analyses were performed using the Database for Annotation, Visualization and Integrated Discovery online tool. Based on the Kyoto Encyclopedia of Genes and Genomes database, pathway relation networks were constructed. DEGs in GO terms and pathways were intersected to screen important DEGs. Subsequently, a gene co-expression network was constructed and visualized using Cytoscape software. Reverse transcription-quantitative polymerase chain reaction was used to detect the expression levels of important DEGs. A total of 1,258 DEGs in group A were screened, and enriched for extracellular matrix (ECM) organization and ECM-receptor interaction. In addition, a total of 1,571 DEGs in group B were enriched for cell adhesion. Furthermore, 391 DEGs were involved in extracellular matrix organization. Pathway relation networks of group A, B and C were constructed with nodes of 48, 39, and 28, respectively. Finally, 135 important DEGs were obtained, including Acyl-CoA synthetase medium-chain family member 3, protein S (α) (PROS1) and F11 receptor. A gene co-expression network with 68 nodes was constructed. The expression of caspase 1 (CASP1) and aldehyde dehydrogenase 1 family member A1 (ALDH1A1) was significant higher in SK-UT-1 compared with that in PHM1-31 cells, while the expression of PROS1 was significant lower in SK-UT-1 cells. These results that CASP1, ALDH1A1 and PROS1 may be potential biomarkers for uterine leiomyomas. Furthermore, hematopoietic prostaglandin D synthase and carbonyl reductase 3 (CBR3) may be particular genes associated with the MED12 mutation in this disease.

Serum ALDH1A1 is a Tumor Marker for the Diagnosis of Non-Small Cell Lung Cancer

Background

ALDH1A1 (aldehyde dehydrogenase 1 family, member A1) is highly expressed in non-small-cell lung cancer (NSCLC). We assessed the potential clinical value of serum ALDH1A1 in the diagnosis and prognosis of non-small-cell lung cancer.

Method

Between 2010 and 2011, serum samples from 100 non-small-cell lung cancer patients before tumor resection, 60 patients with benign lung disease, and 60 healthy volunteers were collected and analyzed retrospectively for ALDH1A1, using sandwich ELISA. We further evaluated the serum and tumor ALDH1A1 levels of non-small-cell lung cancer patients before and after surgery. We compared the diagnostic and prognostic values of serum ALDH1A1 with that of carcinoembryonic antigen.

Results

Elevated serum ALDH1A1 levels were observed in 55 of the 100 (55%) non-small-cell lung cancer patients. The ALDH1A1 levels were much higher in patients with advanced stages than in those with early stage tumors. Of the 30 non-small-cell lung cancer patients who underwent surgery, 19 had elevated serum ALDH1A1 levels before surgery, but the serum ALDH1A1 level was undetectable by postoperative day 7. Analysis of receiver operating characteristic curves showed that ALDH1A1 might be better than carcinoembryonic antigen in distinguishing non-small-cell lung cancer from benign disease or the healthy control. Combined application of ALDH1A1 and carcinoembryonic antigen significantly increased the sensitivity of carcinoembryonic antigen alone, with an accuracy of 83%.

Conclusions

Our results showed that serum levels of ALDH1A1 were correlated with carcinogenesis and progression of non-small-cell lung cancer. Detection of serum ALDH1A1 can be helpful in the diagnosis and prognosis of non-small-cell lung cancer. The diagnosis rate of non-small-cell lung cancer could be significantly improved when carcinoembryonic antigen is combined with ALDH1A1.

Differential Functional Roles of ALDH1A1 and ALDH1A3 in Mediating Metastatic Behavior and Therapy Resistance of Human Breast Cancer Cells

Previous studies indicate that breast cancer cells with high aldehyde dehydrogenase (ALDH) activity and CD44 expression (ALDH^hiCD44⁺) contribute to metastasis and therapy resistance, and that ALDH1 correlates with poor outcome in breast cancer patients. The current study hypothesized that ALDH1 functionally contributes to breast cancer metastatic behavior and therapy resistance. Expression of ALDH1A1 or ALDH1A3 was knocked down in MDA-MB-468 and SUM159 human breast cancer cells using siRNA. Resulting impacts on ALDH activity (Aldefluor^® assay); metastatic behavior and therapy response in vitro (proliferation/adhesion/migration/colony formation/chemotherapy and radiation) and extravasation/metastasis in vivo (chick choroiallantoic membrane assay) was assessed. Knockdown of ALDH1A3 but not ALDH1A1 in breast cancer cells decreased ALDH activity, and knockdown of ALDH1A1 reduced breast cancer cell metastatic behavior and therapy resistance relative to control (p < 0.05). In contrast, knockdown of ALDH1A3 did not alter proliferation, extravasation, or therapy resistance, but increased adhesion/migration and decreased colony formation/metastasis relative to control (p < 0.05). This is the first study to systematically examine the function of ALDH1 isozymes in individual breast cancer cell behaviors that contribute to metastasis. Our novel results indicate that ALDH1 mediates breast cancer metastatic behavior and therapy resistance, and that different enzyme isoforms within the ALDH1 family differentially impact these cell behaviors.

ALDH1A3 is epigenetically regulated during melanocyte transformation and is a target for melanoma treatment

Despite the promising targeted and immune-based interventions in melanoma treatment, long-lasting responses are limited. Melanoma cells present an aberrant redox state that leads to the production of toxic aldehydes that must be converted into less reactive molecules. Targeting the detoxification machinery constitutes a novel therapeutic avenue for melanoma. Here, using 56 cell lines representing nine different tumor types, we demonstrate that melanoma cells exhibit a strong correlation between reactive oxygen species amounts and aldehyde dehydrogenase 1 (ALDH1) activity. We found that ALDH1A3 is upregulated by epigenetic mechanisms in melanoma cells compared with normal melanocytes. Furthermore, it is highly expressed in a large percentage of human nevi and melanomas during melanocyte transformation, which is consistent with the data from the TCGA, CCLE and protein atlas databases. Melanoma treatment with the novel irreversible isoform-specific ALDH1 inhibitor [4-dimethylamino-4-methyl-pent-2-ynthioic acid-S methylester] di-methyl-ampal-thio-ester (DIMATE) or depletion of ALDH1A1 and/or ALDH1A3, promoted the accumulation of apoptogenic aldehydes leading to apoptosis and tumor growth inhibition in immunocompetent, immunosuppressed and patient-derived xenograft mouse models. Interestingly, DIMATE also targeted the slow cycling label-retaining tumor cell population containing the tumorigenic and chemoresistant cells. Our findings suggest that aldehyde detoxification is relevant metabolic mechanism in melanoma cells, which can be used as a novel approach for melanoma treatment.

Garcinol from Garcinia indica Downregulates Cancer Stem-like Cell Biomarker ALDH1A1 in Nonsmall Cell Lung Cancer A549 Cells through DDIT3 Activation

Nonsmall cell lung cancer (NSCLC) is the predominant type of lung cancer. Patients with NSCLC show high mortality rates because of failure to clean up cancer stem cells (CSCs). The anticancer activity of phytochemical garcinol has been identified in various cancer cell models. However, the effect of garcinol on NSCLC cell lines is still lacking. Of the NSCLC cell lines we tested, A549 cells were the most sensitive to garcinol. Interestingly, Aldehyde Dehydrogenase 1 Family Member A1 (ALDH1A1) was preferentially expressed in A549 cells and downregulated by the addition of garcinol. We also found that garcinol enriched DNA damage-inducible transcript 3 (DDIT3) and then altered DDIT3-CCAAT-enhancer-binding proteins beta (C/EBPβ) interaction resulting in a decreased binding of C/EBPβ to the endogenous ALDH1A1 promoter. Furthermore, garcinol's inhibition of ALDH1A1 was identified in a xenograft mice model. Garcinol repressed ALDH1A1 transcription in A549 cells through alterations in the interaction between DDIT3 and C/EBPβ. Garcinol could be a potential dietary phytochemical candidate for NSCLCs patients whose tumors harbored high ALDH1A1 expression.

Aldehyde dehydrogenase activity plays no functional role in stem cell-like properties in anaplastic thyroid cancer cell lines

Recent studies have revealed that aldehyde dehydrogenase (ALDH) is a candidate marker for thyroid cancer stem cells, although its activity is flexible. The goal of this study is to clarify the functional significance of ALDH enzymatic activity on thyroid cancer stem cells properties in anaplastic thyroid cancer cell lines. In vitro sphere formation assay was used to judge the stemness of 4 anaplastic thyroid cancer cell lines (FRO, ACT1, 8505C, and KTC3). Two well-known ALDH inhibitors, N,N-diethylaminobenzaldehyde (DEAB) and disulfiram (DS), were first used. DEAB (50 μM) almost completely suppressed ALDH activity without affecting cell proliferation or spherogenicity. Lack of effect of ALDH suppression on spherogenicity was confirmed using shRNA for ALDH1A3, an ALDH isozyme predominantly expressed in anaplastic thyroid cancer cell lines. In contrast, an ALDH2 inhibitor DS (1 μM) inhibited spherogenicity but did not inhibit ALDH1A3 activity. Based on the recent article from another group reporting the importance of sonic hedgehog (Shh) signaling in ALDH activity and spherogenicity in thyroid cancer, the effects of the Shh inhibitor cyclopamine were also studied. Like DS, cyclopamine (1 μM) decreased spherogenicity but not ALDH activity. Finally, exogenous expression of ALDH1A3 in otherwise ALDH^- TPC1 cells (a papillary thyroid cancer cell line) revealed no effect on spherogenicity. In conclusion, we here show no functional role for ALDH activity in thyroid thyroid cancer stem cells properties. That is, ALDH activity and spherogenicity are clearly dissociable. Further understanding of thyroid cancer stem cells biology in thyroid cancers remains necessary for the future development of thyroid thyroid cancer stem cells-targeted therapies.

The role of epithelial-mesenchymal transition drivers ZEB1 and ZEB2 in mediating docetaxel-resistant prostate cancer

Docetaxel is the main treatment for advanced castration‐resistant prostate cancer; however, resistance eventually occurs. The development of intratumoral drug‐resistant subpopulations possessing a cancer stem cell (CSC) morphology is an emerging mechanism of docetaxel resistance, a process driven by epithelial–mesenchymal transition (EMT). This study characterised EMT in docetaxel‐resistant sublines through increased invasion, MMP‐1 production and ZEB1 and ZEB2 expression. We also present evidence for differential EMT across PC‐3 and DU145 in vitro resistance models as characterised by differential migration, cell colony scattering and susceptibility to the CSC inhibitor salinomycin. siRNA manipulation of ZEB1 and ZEB2 in PC‐3 and DU145 docetaxel‐resistant sublines identified ZEB1, through its transcriptional repression of E‐cadherin, to be a driver of both EMT and docetaxel resistance. The clinical relevance of ZEB1 was also determined through immunohistochemical tissue microarray assessment, revealing significantly increased ZEB1 expression in prostate tumours following docetaxel treatment. This study presents evidence for a role of ZEB1, through its transcriptional repression of E‐cadherin to be a driver of both EMT and docetaxel resistance in docetaxel‐resistant prostate cancer. In addition, this study highlights the heterogeneity of prostate cancer and in turn emphasises the complexity of the clinical management of docetaxel‐resistant prostate cancer.