ALDH1A1 in Cancers: Bidirectional Function, Drug Resistance, and Regulatory Mechanism

Identification of approved drugs with ALDH1A1 inhibitory potential aimed at enhancing chemotherapy sensitivity in cancer cells: an in-silico drug repurposing approach

The aldehyde dehydrogenase 1A1 (ALDH1A1) also known as retinal dehydrogenase, is an enzyme normally involved in the cellular metabolism, development and detoxification processes in healthy cells. However, it's also considered a cancer stem cell marker and its high levels of expression in several cancers, including breast, lung, ovarian, and colon cancer have been associated with poor prognosis and resistance to chemotherapy. Given its crucial role in chemotherapy resistance by detoxification of chemotherapeutic drugs, ALDH1A1 has attracted significant research interest as a potential therapeutic target for cancer. Though a few synthetic inhibitors of ALDH1A1 have been synthesized and their efficacy has been proved in-vitro and in-vivo studies, none of them have passed clinical trials so far. In this scenario, we have performed an in-silico study to verify whether any of the already approved drugs used for various purposes has the ability to inhibit catalytic activity of ALDH1A1, so that they can be repurposed for cancer therapy. Keeping in mind the feasibility of repurposing in a larger population we have selected the approved drugs from five widely used drug categories such as antibiotic, antiviral, antifungal, anti diabetic and antihypertensive for screening. Computational techniques like molecular docking, molecular dynamics simulations and MM-PBSA binding energy calculation have been used in this study to screen the approved drugs. Based on the logical analysis of results, we propose that three drugs - telmisartan, irbesartan and maraviroc can inhibit the catalytic activity of ALDH1A1 and thus can be repurposed to increase chemotherapy sensitivity in cancer cells.

RETRACTED: Development of gene panel for predicting recurrence in early-stage cervical cancer patients

Cervical cancer (CC) is a common malignancy affecting women worldwide. Our objective was to develop a consensus-based gene panel using multi-omics data that could effectively predict recurrence in early-stage cervical cancer patients. We utilized the "Multi-Omics Consensus Integration Analysis (MOVICS)" package for consensus clustering design to integrate multiple omics datasets and improve the molecular classification landscape of early-stage CC. We identified the "resting and naive" tumor microenvironment (TME) as cancer subtype (CS) 2. Leveraging the feature genes from the CS classifier, we employed machine learning algorithms to identify a gene panel, including ALDH1A1, CLDN10, MUC13, and C10orf99, which could generate a consensus machine learning-driven score (CMLS) for each patient. Stratifying patients into high and low CMLS groups resulted in Kaplan-Meier curves demonstrating a significant difference in recurrence rates between the two groups. This difference remained significant even after adjusting for clinical features in multivariate Cox regression analysis, with the risk ratio of CMLS surpassing that of clinical characteristics. Furthermore, the TME exhibited notable differences between the different CMLS groups, suggesting that patients with low CMLS may exhibit a better response to immunotherapy. This study highlights the potential of the CMLS approach in predicting recurrence in early-stage cervical cancer patients and provides a screening model for selecting patients suitable for immunotherapy.

ALDH1A1 in breast cancer: A prospective target to overcome therapy resistance (Review)

The expression of cytosolic aldehyde dehydrogenases (ALDHs), which mediate the last step in the pathway of the synthesis of all-trans retinoic acid, is dysregulated in various types of human cancer, and has been associated with the development of cancer stem cells (CSCs) in solid tumors and hematological malignancies. CSCs are considered a minor fraction of cancer cells with the capacity to initiate neoplastic tumors. ALDH1A1 serves a crucial role in the emergence of the CSC phenotype, induces the malignant behavior of cancer cells and promotes treatment resistance. Notably, ALDH1A1-induced therapy resistance is not exclusive to just one group of drugs, but affects diverse types of drugs that use different mechanisms to kill cells. This diversity of drug resistance-inducing effects is associated with the stemness-supporting functions of ALDH1A1. The inhibition of ALDH1A1 activity using chemicals or the depletion of ALDH1A1 via genetic approaches, such as the use of small interfering RNA, can overcome diverse pathways of therapy resistance. In the context of breast cancer, it is critical that only a fraction of malignant cells are expected to manifest stem-like features, which include increased expression of ALDH1A1. From the angle of disease prognosis, the extent of the association of ALDH1A1 with increased malignant behavior and drug resistance remains to be determined through the application of cutting-edge methods that detect the expression of tracked biomarkers within tumors.

A scaffold repositioning approach: dihydroBenzoImidazoTriazineDione (BITD) derivatives as selective ALDH1A1 inhibitors

The overexpression of the Aldehyde Dehydrogenases 1A subfamily (ALDH1As) in various diseases, particularly in cancer, has made it an important target for therapeutic applications. Interestingly, the 1A1 isoenzyme plays a role in tumor initiation and progression, being identified as a biomarker for cancer stem cells. However, although promising, current ALDH1A1 inhibitors suffer from a lack of isoform selectivity and off-target toxicity. This study aims to address these limitations by developing a new class of ALDH1A1-selective inhibitors. By leveraging structural analogies with Isatin-based ALDH1A1 inhibitors, we designed compounds containing a dihydrobenzo[4,5]imidazo[2,1-c][1,2,4]triazine-3,4-dione (BITD) core, that emerged from a repositioning approach. Using a microwave-assisted protocol, a small library of derivatives was synthesized, and enzymatic assays highlighted a promising isoform specificity for ALDH1A1 among ALDH1As, with the best-in-class compound 5, showing an inhibition of the enzyme activity of 86% for ALDH1A1 and no inhibition for 1A2 and 1A3 isoenzymes. In silico studies further elucidated the binding mode of 5, providing a rational basis for the observed selectivity. These findings represent a promising strategy for the development of more selective ALDH1A1 inhibitors, laying the foundation for further optimization processes.

Serum exosome-derived ALDH1A1 can greatly predict the prognosis of patients with hepatitis E virus-related acute liver failure

BACKGROUND

Despite the insights into the role of aldehyde dehydrogenase 1 family member A1 (ALDH1A1) in various liver diseases, the expression and its prognostic significance in patients with hepatitis E virus-related acute liver failure (HEV-ALF) remain unclear. This study delved into the assessment of serum exosome-derived ALDH1A1 expression and its prognostic implications for HEV-ALF patients.

METHODS

Between January 2018 and December 2023, a total of 226 individuals with acute hepatitis E (AHE) and 210 patients with HEV-ALF were recruited from member units of Chinese Consortium for the Study of Hepatitis E. According to the number of organ failure, we categorized 210 HEV-ALF patients into three groups: two organs failure (n = 131), three organs failure (n = 46), and more than three organs failure (n = 33). In addition, 200 health controls from Suzhou Municipal Hospital were included.

RESULTS

The levels of serum exosome-derived ALDH1A1 in HEV-ALF patients were significantly higher than those in AHE patients and health controls (both P < 0.05). Furthermore, the levels of serum exosome-derived ALDH1A1 were the highest in more than three organs failure group, followed by three organs failure group and two organs failure group (all P < 0.001). Moreover, serum exosome-derived ALDH1A1 was positively correlated with total bilirubin in HEV-ALF patients (r = 0.315, P < 0.001). The comparisons of serum exosome-derived ALDH1A1 levels in treatment response showed that serum exosome-derived ALDH1A1 levels were decreased in the improvement group, while increased in the fluctuation and deterioration groups (all P < 0.001). Moreover, serum exosome-derived ALDH1A1 was an independent risk factor for predicting the 30-day mortality (P < 0.001). Furthermore, the area under the receiver operating characteristic curve was 0.943, with the sensitivity of 94.87% and specificity of 87.72%, indicating the robust decision-making ability. However, no significant differences were found in serum exosome-derived ALDH1A1 levels between patients aged < 60 and ≥ 60 years old (P = 0.131).

CONCLUSIONS

Serum exosome-derived ALDH1A1 can greatly predict the prognosis of HEV-ALF patients.

Comparison and Analysis of the Drug-Resistance Mechanism of Osimertinib- and Almonertinib-Resistant Cell Lines

Background: Non-small-cell lung cancer remains the leading cause of cancer-related deaths globally, and epidermal growth factor receptor mutations have been identified as crucial drivers of the disease. Encouragingly, epidermal growth factor receptor tyrosine kinase inhibitors have demonstrated promising clinical outcomes. Nonetheless, the emergence of resistance to third-generation EGFR-TKIs like osimertinib and almonertinib is an inevitable challenge. Methods: In this study, we generated almonertinib-resistant cell lines from H-1975 and HCC827 lung cancer cell lines. We utilized various assays, including cell proliferation assays, hematoxylin and eosin staining, and cell cycle assays, to investigate the characteristics of drug-resistant cells. Additionally, we performed RNA transcriptome sequencing to identify differentially expressed genes (DEGs) in almonertinib-resistant cells. To further expand our analysis, we obtained sequencing data of osimertinib-resistant cells from the Gene Expression Omnibus (GEO) dataset and identified DEGs in these cells. We performed Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses to assess the biological functions and signaling mechanisms associated with DEGs. Furthermore, the survival prognosis and immune cell infiltration of common differentially expressed genes (co-DEGs) in osimertinib-and almonertinib-resistant cells were analyzed, and the expression of a co-DEG (IGFBP7) was verified through quantitative reverse transcriptase polymerase chain reaction (qPCR) and western blotting (WB) assays. Gene knockdown plasmids were constructed for cell transfection, and the invasive ability of resistant cells was assessed using a Transwell assay following the knockdown of IGFBP7. Results: Experimental cell counting kit-8 cytotoxicity studies revealed intriguing findings regarding drug resistance in lung cancer cells. Specifically, the IC50 values and resistance factors of H-1975 and HCC827 cells were found to be 1.9 nM and 833.58 and 2.2 nM and 631.95, respectively. In addition to these quantitative results, comparative observations of the cell morphology and cell cycle revealed significant alterations in drug-resistant cells. Transcriptome sequencing analysis identified 220 DEGs between H-1975 and H-1975/AR and 736 DEGs between HCC827 and HCC827/AR. Interestingly, screening of overlapping DEGs with osimertinib-resistant cells in the GEO database identified some common genes, such as IGFBP7 and RFTN1, which were found to be associated with the improved prognosis of non-small-cell lung cancer by survival analysis. Furthermore, GO analysis and KEGG pathway enrichment analysis revealed different pathway changes in different drug-resistant cells. Survival analysis indicated that a higher expression of co-DEGs (IGFBP7, RFTN1) was associated with a more favorable prognosis. Furthermore, IGFBP7 expression is strongly associated with infiltration levels of CD8+ T cells, Tregs, and macrophage cells in lung adenocarcinoma. Molecular biology experiments confirmed that the mRNA and protein expression level of IGFBP7 were over-expressed in almonertinib-resistance cells. H-1975/AR cells were transfected with si-IGFBP7, and the results of transfection were verified at the mRNA and protein levels. After knocking down gene expression, the IC50 of the cells was 0.3 ± 0.02 µM, which was significantly lower than that of untransfected cells. Additionally, the invasion of cells in the knockdown group was repressed. Conclusions: These findings indicated that almonertinib and osimertinib exhibited distinct resistance mechanisms in vitro, underscoring the need for tailored treatment approaches.

CRISPR/Cas9 Targeting of Aldehyde Dehydrogenase 1A1 Reveals Heterogeneous Roles in Radiation Response and Redox Stress Across Clonal Lines in Triple-Negative Breast Cancer

The metabolic enzyme aldehyde dehydrogenase 1A1 (ALDH1A1), a cancer stem cell marker associated with poor outcomes in breast cancer, has emerged as a promising therapeutic target in TNBC. The aim of this study was to investigate the role of ALDH1A1 in radiation resistance and redox stress in triple negative breast cancer (TNBC). Functional knockouts of ALDH1A1 were generated by the CRISPR/Cas9-mediated deletion of ALDH1A1 in the SUM159 cell line, and three distinct clonal populations were isolated. Genetic targeting was confirmed by Sanger sequencing, and the loss of ALDH1A1 protein expression was validated by Western blotting. Functional assays assessed ALDEFLUOR activity, cell viability, self-renewal capacity, and reactive oxygen species (ROS) levels with or without radiation in both the bulk population and clonal lines. Interestingly, ALDEFLUOR activity was uniformly lost across all clonal lines; however, functional effects of ALDH1A1 loss on redox stress, survival, and radiation sensitivity were observed in only one clonal population. These findings highlight significant variability in the role of ALDH1A1 among clonal populations, reflecting the complexity of tumor heterogeneity. This underscores the importance of accounting for tumor heterogeneity when targeting ALDH1A1, as certain TNBC subpopulations may rely more heavily on ALDH1A1 function. These insights are critical for developing effective ALDH1A1-targeted therapies.

Vitamin A Metabolism and Resistance of Hepatic Metastases to Immunotherapy

The liver is an immune-tolerant organ, allowing for organ transplantation with less immune suppression compared with other organs. It also provides fertile soil for tumor metastases, which tend to be more resistant to checkpoint blockade immunotherapy than metastases in other organs. This resistance may result from the sum of incremental evolutionary adaptions in various cell types to prevent overaction to antigens absorbed from the gut into the portal circulation or it might involve a central mechanism. Here, we propose that metabolism of vitamin A, which is highly concentrated in the liver, is a root source of tolerance and resistance of hepatic metastases to checkpoint blockade. Suppression of retinoic acid synthesis from vitamin A with disulfiram may mitigate tolerance and produce enhanced immunotherapy treatment results for patients with liver metastases.

Integration of scRNA-seq and bulk RNA-seq to reveal the association and potential molecular mechanisms of metabolic reprogramming regulated by lactylation and chemotherapy resistance in ovarian cancer

Objective

Ovarian cancer (OC) ranks among the foremost causes of mortality in gynecological malignancies, with chemoresistance being the primary factor contributing to unfavorable prognosis. This work seeks to clarify the mechanisms of resistance-related lactylation in OC, intending to offer novel theoretical foundations and therapy strategies for addressing chemoresistance.

Methods

Through the combined analysis of bulk RNA-seq and single-cell RNA-seq data, we initially found lactylation genes linked to chemoresistance. Subsequently, we employed differential expression analysis, survival analysis, enrichment analysis, and other methodologies to further investigate the roles and molecular mechanisms of these genes in tumor resistance. Ultimately, we investigated the differential expression of these genes in resistant and non-resistant tissues and cells via experimentation.

Results

We found two candidate genes associated with lactylation chemoresistance, ALDH1A1 and S100A4. Analysis of single-cell data indicated that tumor cells represent the primary cell subpopulation relevant to resistance studies. Subpopulation analysis indicated that several tumor cell subtypes were markedly linked to resistance, with elevated expression levels of ALDH1A1 and S100A4 in the resistant subpopulation, notably correlating with various immunological and metabolic pathways. Analysis of metabolic pathways indicated that oxidative phosphorylation and glycolysis activity was elevated in the resistant subpopulation, and lactic acid buildup was associated with chemoresistance. The investigation of the marker gene protein-protein interaction network in the resistant subgroup elucidated the intricate interactions among these genes. The expression levels of ALDH1A1 and S100A4 in the OC tissues of the platinum-resistant cohort were markedly elevated compared to the sensitive cohort, with a considerable rise in S100A4 expression observed in resistant OC cells, demonstrating co-localization with lactylation.

Conclusion

This work elucidates the significant function of lactylation in OC chemoresistance and identifies ALDH1A1 and S100A4 as possible genes associated with drug resistance. These findings enhance our comprehension of the mechanisms behind chemoresistance in OC and offer critical insights for the formulation of novel therapeutic options.

Long non-coding RNA H19 promotes cervical cancer development via targeting the microRNA-140/ALDH1A1 axis

BACKGROUND

Dysregulation of long non-coding RNA H19 (lncRNA H19) is involved in cervical cancer (CC) progression. This study aims to unveil the specific role and relevant mechanism of lncRNA H19 in CC.

METHODS

The expression of lncRNA H19 in CC cells was detected by quantitative reverse transcriptase polymerase chain reaction (qRT-PCR). CC cells were transfected with sh-H19, followed by cell proliferation, apoptosis, migration and invasion were examined. After location of H19 in cells using fluorescence in Situ Hybridization (FISH), target microRNAs (miRNAs) and genes associated with lncRNA H19 were predicted using bioinformatics analysis and validated by dual-luciferase reporter assay. Finally, the specific role of lncRNA H19 in CC was explored in vivo.

RESULTS

The upregulation of lncRNA H19 was observed in CC cells. LncRNA H19 knockdown inhibited the proliferation, migration, and invasion of CC cells, and remarkably promoted CC cell apoptosis. LncRNA H19 was localized in the nucleus and interacted with miR-140 that was downregulated in CC cells. MiR-140 inhibition reversed the effects of lncRNA H19 knockdown on CC cell development. MiR-140 targets ALDH1A1, and lncRNA H19 knockdown decreased the ALDH1A1 expression, which was rescued by miR-140 inhibition. In vivo experiments also shown that reduction of lncRNA H19 diminishes tumor growth via targeting the miR-140/ALDH1A1 axis.

CONCLUSION

LncRNA H19 promotes the malignant progression of CC through targeting miR-140/ALDH1A1 axis.

Doxorubicin and topotecan resistance in ovarian cancer: Gene expression and microenvironment analysis in 2D and 3D models

This study explores the mechanisms underlying chemotherapy resistance in ovarian cancer (OC) using doxorubicin (DOX) and topotecan (TOP)-resistant cell lines derived from the drug-sensitive A2780 ovarian cancer cell line. Both two-dimensional (2D) monolayer cell cultures and three-dimensional (3D) spheroid models were employed to examine the differential drug responses in these environments. The results revealed that 3D spheroids demonstrated significantly higher resistance to DOX and TOP than 2D cultures, suggesting a closer mimicry of in vivo tumour conditions. Molecular analyses identified overexpression of essential drug resistance-related genes, including MDR1 and BCRP, and extracellular matrix (ECM) components, such as MYOT and SPP1, which were more pronounced in resistant cell lines. MDR1 and BCRP overexpression contribute to chemotherapy resistance in OC by expelling drugs like DOX and TOP. Targeting these transporters with inhibitors or gene silencing could improve drug efficacy, making them key therapeutic targets to enhance treatment outcomes for drug-resistant OC. The study further showed that EMT-associated markers, including VIM, SNAIL1, and SNAIL2, were upregulated in the 3D spheroids, reflecting a more mesenchymal phenotype. These findings suggest that factors beyond gene expression, such as spheroid architecture, cell-cell interactions, and drug penetration, contribute to the enhanced resistance observed in 3D cultures. These results highlight the importance of 3D cell culture models for a more accurate representation of tumour drug resistance mechanisms in ovarian cancer, providing valuable insights for therapeutic development.

Activity-Based Bioluminescent Logic-Gate Probe Reveals Crosstalk Between the Inflammatory Tumor Microenvironment and ALDH1A1 in Cancer Cells

Cancer cells with high expression of aldehyde dehydrogenase 1A1 (ALDH1A1) are more resistant to chemotherapy, contribute to tumor progression, and are associated with poor clinical outcomes. ALDH1A1 plays a critical role in protecting cells from reactive aldehydes and, in the case of stem cells, regulates their differentiation through the retinoic acid signaling pathway. Despite the importance of this enzyme, methods to study ALDH1A1 high-expressing cancer cells in vivo remain limited. In this work, we developed AlDeLuc, the first logic-gated bioluminescence probe designed to selectively evaluate ALDH1A1 activity in tumor cells. The probe is sequentially activated by acidic intracellular compartments (i.e., endosomes) and ALDH1A1, ensuring precise detection of ALDH1A1 high-expressing cells and minimizing off-target detection of non-ALDH1A1 cells. Beyond demonstrating efficacy in multiple cancer cell lines and a murine model of breast cancer, we employed AlDeLuc to investigate how the population of ALDH1A1 high-expressing cells is influenced by the inflammatory status of a tumor in the context of a high-fat diet. These findings establish a molecular link between obesity, inflammation, and tumor progression.

The Significance of Aldehyde Dehydrogenase 1 in Cancers

The goal of this paper is to discuss the role of ALDH isozymes in different cancers, review advances in ALDH1-targeting cancer therapies, and explore a mechanism that explains how ALDH expression becomes elevated during cancer development. ALDH is often overexpressed in cancer, and each isoform has a unique expression pattern and a distinct role in different cancers. The abnormal expression of ALDHs in different cancer types (breast, colorectal, lung, gastric, cervical, melanoma, prostate, and renal) is presented and correlated with patient prognosis. ALDH plays a significant role in various cellular functions, such as metabolism, oxidative stress response, detoxification, and cellular differentiation. Among the ALDH families, ALDH1 has gained considerable attention as a cancer stem cell (CSC) marker due to its significant role in the maintenance of stemness and the differentiation of stem cells (SCs), along with its involvement in tumorigenesis. A description of the cellular mechanisms and physiology of ALDH1 that underlies cancer development is provided. Moreover, current advances in ALDH1-targeting cancer therapies are discussed.

The Role of miR-486-5p on CSCs Phenotypes in Colorectal Cancer

BACKGROUND

Colorectal cancer (CRC) is the third diagnosed cancer worldwide. Forty-four percent of metastatic colorectal cancer patients were diagnosed at an early stage. Despite curative resection, approximately 40% of patients will develop metastases within a few years. Previous studies indicate the presence of cancer stem cells (CSCs) and their contribution to CRC progression and metastasis. miRNAs deregulation plays a role in CSCs formation and in tumor development. In light of previous studies, we investigated the role of miR-486-5p to understand its role in CSC better.

METHODS

The expression of miR-486-5p was assessed in adherent cells and spheres generated from two CRC cell lines to observe the difference in expression in CSC-enriched spheroids. Afterward, we overexpressed and underexpressed this miRNA in adherent and sphere cultures through the transfection of a miR-486-5p mimic and a mimic inhibitor.

RESULTS

The results demonstrated that miR-486-5p exhibited a notable downregulation in CSC models, and its overexpression led to a significant decrease in colony size.

CONCLUSIONS

In this study, we confirmed that miR-486-5p plays an oncosuppressive role in CRC, thereby advancing our understanding of the role of this microRNA in the CSC phenotype.

Investigating the biology of microRNA links to ALDH1A1 reveals candidates for preclinical testing in acute myeloid leukemia

Aldehyde dehydrogenase 1 family member A1 (ALDH1A1) is a member of the aldehyde dehydrogenase gene subfamily that encode enzymes with the ability to oxidize retinaldehyde. It was recently shown that high ALDH1A1 RNA abundance correlates with a poor prognosis in acute myeloid leukemia (AML). AML is a hematopoietic malignancy associated with high morbidity and mortality rates. Although there are a number of agents that inhibit ALDH activity, it would be crucial to develop methodologies for adjustable genetic interference, which would permit interventions on several oncogenic pathways in parallel. Intervention in multiple oncogenic pathways is theoretically possible with microRNAs (miRNAs or miRs), a class of small non‑coding RNAs that have emerged as key regulators of gene expression in AML. A number of miRNAs have shown the ability to interfere with ALDH1A1 gene expression directly in solid tumor cells, and these miRNAs can be evaluated in AML model systems. There are indications that a few of these miRNAs actually do have an association with AML disease course, rendering them a promising target for genetic intervention in AML cells.

Targeted Proteomics Profiling for Biomarker Discovery in Glaucoma Using the Olink Proteomics Platform

Metabolic dysfunction plays a crucial role in the pathogenesis of glaucoma. In this study, we used Olink proteomics profiling to identify potential biomarkers for glaucoma. Aqueous humor samples were obtained from 44 cataract patients and 44 glaucoma patients. We identified 84 differentially expressed metabolic proteins between the glaucoma and the cataract group. Gene Ontology enrichment analysis highlighted the involvement of these proteins in ER-associated degradation pathway, regulation of interleukin-13 production, and DNA damage response pathway. The Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis further revealed links to pathways, such as tyrosine and pyrimidine metabolism. Among these, ALDH1A1 emerged as a candidate with a significant diagnostic potential for glaucoma. ALDH1A1 also exhibited a prominent role in the protein-protein interaction network. Elevated levels of ALDH1A1 in the aqueous humor of glaucoma patients were confirmed both in clinical samples and in an ischemia/reperfusion model. Functional assays confirmed that elevated ALDH1A1 induced retinal ganglion cell (RGC) apoptosis in vitro and demonstrated its pro-apoptotic role in RGCs in vivo. Collectively, these findings not only underscore the significance of ALDH1A1 in glaucoma but also provide valuable insights into clinical decision-making and therapeutic strategies.

The role of ALDH1A1 in glioblastoma proliferation and invasion

High-grade gliomas, including glioblastoma multiforme (GBM), continue to be a leading aggressive brain tumor in adults, marked by its rapid growth and invasive nature. Aldehyde dehydrogenase 1 family, member A1 (ALDH1A1), an enzyme, plays a significant role in tumor progression, yet its function in high-grade gliomas is still poorly investigated. In this study, we evaluated ALDH1A1 levels in clinical samples of GBM. We also assessed the prognostic significance of ALDH1A1 expression in GBM and LGG (low grade glioma) patients using TCGA (The Cancer Genome Atlas) database analysis. The MTT and transwell assays were utilized to examine cell growth and the invasive capability of U87 cells, respectively. We quantitatively examined markers for cell proliferation (Ki-67 and cyclin D1) and invasion (MMP2 and 9). A Western blot test was conducted to determine the downstream signaling of ALDH1A1. We found a notable increase in ALDH1A1 expression in high-grade gliomas compared to their low-grade counterparts. U87 cells that overexpressed ALDH1A1 showed increased cell growth and invasion. We found that ALDH1A1 promotes the phosphorylation of AKT, and inhibiting AKT phosphorylation mitigates the ALDH1A1's effects on tumor growth and migration. In summary, our findings suggest ALDH1A1 as a potential therapeutic target for GBM treatment.

Mitochondrial VDAC1 Silencing in Urethane-Induced Lung Cancer Inhibits Tumor Growth and Alters Cancer Oncogenic Properties

Alterations in cellular metabolism are vital for cancer cell growth and motility. Here, we focused on metabolic reprogramming and changes in tumor hallmarks in lung cancer by silencing the expression of the mitochondrial gatekeeper VDAC1. To better mimic the clinical situation of lung cancer, we induced lung cancer in A/J mice using the carcinogen urethane and examined the effectiveness of si-m/hVDAC1-B encapsulated in PLGA-PEI nanoparticles. si-m/hVDAC1-B, given intravenously, induced metabolism reprogramming and inhibited tumor growth as monitored using MRI. Mice treated with non-targeted (NT) PLGA-PEI-si-NT showed many large size tumors in the lungs, while in PLGA-PEI-si-m/hVDAC-B-treated mice, lung tumor number and area were markedly decreased. Immunofluorescence staining showed decreased expression of VDAC1 and metabolism-related proteins and altered expression of cancer stem cell markers. Morphological analysis showed two types of tumors differing in their morphology; cell size and organization within the tumor. Based on specific markers, the two tumor types were identified as small cell (SCLC) and non-small cell (NSCLC) lung cancer. These two types of tumors were found only in control tumors, suggesting that PLGA-PEI-si-m/hVDAC1-B also targeted SCLC. Indeed, using a xenograft mouse model of human-derived SCLC H69 cells, si-m/hVDAC1-B inhibited tumor growth and reduced the expression of VDAC1 and energy- and metabolism-related enzymes, and of cancer stem cells in the established xenograft. Additionally, intravenous treatment of urethane-induced lung cancer mice with the VDAC1-based peptide, Retro-Tf-D-LP4, showed inhibition of tumor growth, and decreased expression levels of metabolism- and cancer stem cells-related proteins. Thus, silencing VDAC1 targeting both NSCLC and SCLC points to si-VDAC1 as a possible therapeutic tool to treat these lung cancer types. This is important as target NSCLC tumors undergo transformation to SCLC.

Molecular characterization and expression profile of the ALDH1A1 gene and its functions in yak luteal cells

The ALDH1A1 gene encodes a cytoplasmic member of the aldehyde dehydrogenase 1 family, which plays an important role in regulating animal reproductive performance, including estrus cycle and embryonic development. The aim of this study was to characterize ALDH1A1 activity in ovaries of 3-5 year-old yaks and to determine its effects on cell proliferation, apoptosis, and progesterone secretion in luteal cells (LCs). The coding sequence (CDS) of the ALDH1A1 gene was cloned by reverse transcription-PCR and immunohistochemical analysis was used to confirm localization of the ALDH1A1 protein in the ovary. To assess the activity of ALDH1A1 in regulating progesterone secretion, si-ALDH1A1 was transfected into LCs in vitro and progesterone levels in LC supernatants were measured by ELISA. The interference efficiency was assessed by real-time quantitative PCR (RT-qPCR) and immunofluorescence staining, and cell proliferation and apoptosis were evaluated by EdU and TUNEL staining, respectively. The cloned ALDH1A1 sequence contained 1462 bp, encoding 487 amino acids. Immunohistochemical analysis showed that ALDH1A1 protein expression, which was significantly higher in LCs, was mainly found in antral follicles and the corpus luteum (CL). The expression of ALDH1A1 mRNA in LCs was effectively inhibited by si-ALDH1A1transfection, and progesterone secretion was markedly decreased along with the significant down-regulation of progesterone pathway-related genes, STAR, CYP11A1, CYP19A1, CYP17A1, 3β-HSD, and HSD17B1. Knockdown of ALDH1A1 mRNA expression decreased cell proliferation and increased apoptosis in LCs. The mRNA expression of the proliferation-related genes, PCNA, CCND1, CCNB1 and CDC25A, was significantly down-regulated, while expression of the apoptosis-promoting CASP3 gene was significantly increased. In summary, we characterized the yak ALDH1A1 gene and revealed that ALDH1A1 knockdown promoted apoptosis, repressed cell proliferation, and decreased progesterone secretion by yak LCs, potentially by regulating the mRNA expression of genes related to proliferation, apoptosis, and progesterone synthesis and secretion.

Tubular insulin-induced gene 1 deficiency promotes NAD+ consumption and exacerbates kidney fibrosis

Profibrotic proximal tubules (PT) were identified as a unique phenotype of proximal tubule cells (PTCs) in renal fibrosis by single-cell RNA sequencing (scRNA-seq). Controlling the process of renal fibrosis requires understanding how to manage the S1 subset's branch to the S3 subset rather than to the profibrotic PT subset. Insulin-induced gene 1 (Insig1) is one of the branch-dependent genes involved in controlling this process, although its role in renal fibrosis is unknown. Here, we discovered that tubular Insig1 deficiency, rather than fibroblast Insig1 deficiency, plays a detrimental role in the pathogenesis of renal fibrosis in vivo and in vitro. Overexpression of Insig1 profoundly inhibited renal fibrosis. Mechanistically, Insig1 deletion in PTCs boosted SREBP1 nuclear localization, increasing Aldh1a1 transcriptional activity, causing excessive NAD+ consumption and ER enlargement, as well as accelerating renal fibrosis. We also identified nicardipine as a selective inhibitor of Aldh1a1, which could restore NAD+ and maintain ER homeostasis, as well as improve renal fibrosis. Together, our findings support tubular Insig1 as a new therapeutic target for chronic kidney disease (CKD).

Flavonostilbenes natural hybrids from Rhamnoneuron balansae as potential antitumors targeting ALDH1A1: molecular docking, ADMET, MM-GBSA calculations and molecular dynamics studies

Several studies have linked Cancer stem cells (CSCs) to cancer resistance development to chemotherapy and radiotherapy. ALDH1A1 is a key enzyme that regulates the gene expression of CSCs and creates an immunosuppressive tumor microenvironment. It was reported that quercetin and resveratrol were among the inhibitors of ALDH1A1. In early 2022, it was reported that new 11 flavonostilbenes (rhamnoneuronal D-N) were isolated from Rhamnoneuron balansae as potential antiaging natural products. Rhamnoneuronal H (5) could be envisioned as a natural hybrid of quercetin and resveratrol. It was therefore hypothesized that 5 and its analogous isolates rhamnoneuronal D-G (1-4) and rhamnoneuronal I-N (6-11) would have potential ALDH1A1 inhibitory activity. To this end, all isolates were subjected to molecular docking, MM-GBSA, ADMET, and molecular dynamics simulations studies to assess their potential as new leads for cancer treatment targeting ALDH1A1. In silico findings revealed that natural hybrid 5 has a similar binding affinity, judged by MM-GBSA, to the ALDH1A1 active site when compared to the co-crystalized ligand (-64.71 kcal/mole and -64.12 kcal/mole, respectively). Despite having lesser affinity than that of the co-crystalized ligand, the rest of the flavonostilbenes, except 2-4, displayed better binding affinities (-37.55 kcal/mole to -58.6 kcal/mole) in comparison to either resveratrol (-34.44 kcal/mole) or quercetin (-36.48 kcal/mole). Molecular dynamic simulations showed that the natural hybrids 1, 5-11 are of satisfactory stability up to 100 ns. ADMET outcomes indicate that these hybrids displayed acceptable properties and hence could represent an ideal starting point for the development of potent ALDH1A1 inhibitors for cancer treatment.Communicated by Ramaswamy H. Sarma.

Loss of EIF4G2 mediates aggressiveness in distinct human endometrial cancer subpopulations with poor survival outcome in patients

The non-canonical translation initiation factor EIF4G2 plays essential roles in cellular stress responses via translation of selective mRNA cohorts. Currently there is limited and conflicting information regarding its involvement in cancer development and progression. Here we assessed its role in endometrial cancer (EC), in a cohort of 280 EC patients across different types, grades, and stages, and found that low EIF4G2 expression highly correlated with poor overall- and recurrence-free survival in Grade 2 EC patients, monitored over a period of up to 12 years. To establish a causative connection between low EIF4G2 expression and cancer progression, we stably knocked-down EIF4G2 in two human EC cell lines in parallel. EIF4G2 depletion resulted in increased resistance to conventional therapies and increased the prevalence of molecular markers for aggressive cell subsets, altering their transcriptional and proteomic landscapes. Prominent among the proteins with decreased abundance were Kinesin-1 motor proteins, KIF5B and KLC1, 2, 3. Multiplexed imaging of the EC patient tumor cohort showed a correlation between decreased expression of the kinesin proteins, and poor survival in patients with tumors of certain grades and stages. These findings reveal potential novel biomarkers for Grade 2 EC with ramifications for patient stratification and therapeutic interventions.

The black Vitis vinifera seed oil saponifiable fraction ameliorates hepatocellular carcinoma in vitro and in vivo via modulating apoptosis and ROS/NF-κB signaling

To date, no total curative therapy for hepatocellular carcinoma (HCC) is available. This study aimed to evaluate the anticancer effect of black Vitis vinifera (VV) seed oil saponifiable (Sap) fraction (BSap) using five different cancer cell lines. The apoptotic and anti-inflammatory impacts of BSap on the cell line with the highest cytotoxic effect were studied. Furthermore, its therapeutic effect on p-dimethylaminoazobenzene (p-DAB)-induced HCC in mice was investigated. The phenolic and vitamin content, as well as the antiradical activities of BSap, were assessed. BSap demonstrated a greater cytotoxic effect on HepG-2 cells (lowest IC50 and highest SI values) than did the other tested cell lines. BSap showed superior anticancer efficacy to 5-FU on all examined cancer cells, particularly HepG-2 cells, by inducing apoptosis and downregulating NF-κB. In HCC-bearing mice, BSap reduced hepatic lipid peroxidation and boosted GSH levels due to its potent antiradical activities and high reducing power. In addition, it had an apoptotic effect by upregulating p53 and BAX and downregulating Bcl-2 fold expression. Moreover, BSap lowered the fold expression of various crucial HCC-related genes: CD133, ALAD1α1, COX-2, ABCG1, AKT1, Gli, Notch1, and HIF1α. Liver function markers and histopathology showed significant improvements in HCC-bearing mice after BSap administration compared to 5-FU. In silico analysis revealed that the most abundant phenolic and fatty acid ingredients of BSap exhibited competitive inhibitory effects on valuable HCC-associated enzymes (NADPH oxidase, histone deacetylase 1, and sepiapterin reductase). Thus, BSap fraction may be a promising treatment of HCC.

Combining microfluidic chip and low-attachment culture devices to isolate oral cancer stem cells

Background/purpose

Cancer stem cells (CSCs) are widely recognized as key drivers of cancer initiation, progression, and therapeutic resistance. Microfluidic chip technology offers a promising approach for CSC isolation and study. This study investigated the efficacy of a microfluidic chip-based method for isolating single cells from oral cancer cell lines characterized by high stem-like phenotypes. Specifically, the study focused on examining the sphere-forming capability and the expression of CSC markers, including aldehyde dehydrogenase 1A1 (ALDH1A1), CD44, and CD133, in isolated cell clones from OECM-1 and SAS cell lines.

Materials and methods

Oral cancer cell lines were subjected to isolation using a microfluidic chip. The captured single cells were cultured to assess their sphere-forming capacity in ultra-low binding culture. Furthermore, the protein expression levels of ALDH1A1, CD44, and CD133 in the isolated cell clones were analyzed using western blotting.

Results

The microfluidic chip-assisted isolation method significantly enhanced the sphere-forming capability of both OECM-1 and SAS cell clones compared to their parent cell lines. Moreover, the expression levels of CSC markers ALDH1A1, CD44, and CD133 were upregulated in the microfluidic chip-assisted isolated cell clones, indicating a higher stem-like phenotype.

Conclusion

This study demonstrates the effectiveness of the microfluidic chip-based approach in isolating oral cancer cell clones with elevated stem-like characteristics. This method offers a valuable tool for further investigation of CSCs and their role in cancer progression, as well as future therapy development for oral cancers.

N-Substituted 2-(Benzenosulfonyl)-1-Carbotioamide Derivatives Exert Antimicrobial and Cytotoxic Effects via Aldehyde Dehydrogenase Pathway: Synthesis, In Silico and In Vitro Studies

A series of N-Substituted 2-(benzenosulfonyl)-1-carbotioamide derivatives (WZ1-WZ4) were synthesized and characterized using spectral methods. A comprehensive activity study was performed for each compound. All compounds were tested for antibacterial activity. Moreover, in silico studies were carried out to determine the anticancer potential of the designed WZ1-WZ4 ligands. Based on molecular docking, aldehyde dehydrogenase was selected as a molecular target. The obtained data were compared with experimental data in vitro tests. Novel hybrids of the thiosemicarbazide scaffold and sulfonyl groups may have promising anticancer activity via the aldehyde dehydrogenase pathway. The best candidate for further studies appears to be WZ2, due to its superior selectivity in comparison to the other tested compounds.

Valproic acid reprograms the metabolic aberration of cisplatin treatment via ALDH modulation in triple-negative breast cancer cells

We recently demonstrated that the histone deacetylase inhibitor valproic acid (VPA) reprograms the cisplatin-induced metabolome of triple-negative breast cancer (TNBC) cells, including a shift in hexose levels. Accordingly, here, we tested the hypothesis that VPA alters glucose metabolism in correlation with cisplatin sensitivity. Two TNBC cell lines, MDA-MB-231 (a cisplatin-resistant line) and MDA-MB-436 (a cisplatin-sensitive line), were analyzed. The glycolysis and oxidative metabolism were measured using the Glycolysis Stress Test kit. The expression of aldehyde dehydrogenases (ALDHs), enzymes linked to drug resistance, was investigated by Western blot and real-time PCR analyses. We additionally studied the influence of ALDH inhibition by disulfiram on the viability of MDA-MB-231 cells and on a TNBC patient-derived organoid system. Cisplatin treatment reduced the extracellular acidification rate in MDA-MB-436 cells but not MDA-MB-231 cells, whereas VPA addition increased the extracellular acidification rate in both cell lines. VPA further reduced the oxygen consumption rate of cisplatin-treated MDA-MB-436 cells, which correlated with cell cycle alterations. However, in MDA-MB-231 cells, the cell cycle distribution did not change between cisplatin/VPA-cisplatin treatments. In both cell lines, VPA increased the expression of ALDH isoform and ALDH1A1 expression. However, only in MDA-MB-231 cells, VPA synergized with cisplatin to augment this effect. Disulfiram sensitized the cells to the cytotoxic effects of the VPA-cisplatin combination. Furthermore, the disulfiram-VPA-chemotherapy combination was most effective in TNBC organoids. Our results show that ALDH overexpression may act as one mechanism of cellular resistance to VPA in TNBC and that its inhibition may enhance the therapeutic efficacy of VPA-chemotherapeutic drug combinations.

Tumor microenvironment-induced tumor cell plasticity: relationship with hypoxic stress and impact on tumor resistance

The role of tumor interaction with stromal components during carcinogenesis is crucial for the design of efficient cancer treatment approaches. It is widely admitted that tumor hypoxic stress is associated with tumor aggressiveness and thus impacts susceptibility and resistance to different types of treatments. Notable biological processes that hypoxia functions in include its regulation of tumor heterogeneity and plasticity. While hypoxia has been reported as a major player in tumor survival and dissemination regulation, the significance of hypoxia inducible factors in cancer stem cell development remains poorly understood. Several reports indicate that the emergence of cancer stem cells in addition to their phenotype and function within a hypoxic tumor microenvironment impacts cancer progression. In this respect, evidence showed that cancer stem cells are key elements of intratumoral heterogeneity and more importantly are responsible for tumor relapse and escape to treatments. This paper briefly reviews our current knowledge of the interaction between tumor hypoxic stress and its role in stemness acquisition and maintenance. Our review extensively covers the influence of hypoxia on the formation and maintenance of cancer stem cells and discusses the potential of targeting hypoxia-induced alterations in the expression and function of the so far known stem cell markers in cancer therapy approaches. We believe that a better and integrated understanding of the effect of hypoxia on stemness during carcinogenesis might lead to new strategies for exploiting hypoxia-associated pathways and their targeting in the clinical setting in order to overcome resistance mechanisms. More importantly, at the present time, efforts are oriented towards the design of innovative therapeutical approaches that specifically target cancer stem cells.

The response and resistance to drugs in ovarian cancer cell lines in 2D monolayers and 3D spheroids

Ovarian cancer is the most common type of gynecologic cancer. One of the leading causes of high mortality is chemoresistance, developed primarily or during treatment. Different mechanisms of drug resistance appear at the cellular and cancer tissue organization levels. We examined the differences in response to the cytotoxic drugs CIS, MTX, DOX, VIN, PAC, and TOP using 2D (two-dimensional) and 3D (three-dimensional) culture methods. We tested the drug-sensitive ovarian cancer cell line W1 and established resistant cell lines to appropriate cytotoxic drugs. The following qualitative and quantitative methods were used to assess: 1) morphology - inverted microscope and hematoxylin & eosin staining; 2) viability - MTT assay; 3) gene expression - a quantitative polymerase chain reaction; 4) identification of proteins - immunohistochemistry, and immunofluorescence. Our results indicate that the drug-sensitive and drug-resistant cells cultured in 3D conditions exhibit stronger resistance than the cells cultured in 2D conditions. A traditional 2D model shows that drug resistance of cancer cells is caused mainly by changes in the expression of genes encoding ATP-binding cassette transporter proteins, components of the extracellular matrix, "new" established genes related to drug resistance in ovarian cancer cell lines, and universal marker of cancer stem cells. Whereas in a 3D model, the drug resistance in spheroids can be related to other mechanisms such as the structure of the spheroid (dense or loose), the cell type (necrotic, quiescent, proliferating cells), drug concentrations or drug diffusion into the dense cellular/ECM structure.

Epigenetic control of cell signalling in cancer stem cells

The self-renewing cancer stem cells (CSCs) represent one of the distinct cell populations occurring in a tumour that can differentiate into multiple lineages. This group of sparsely abundant cells play a vital role in tumour survival and resistance to different treatments during cancer. The lack of exclusive markers associated with CSCs makes diagnosis and prognosis in cancer patients extremely difficult. This calls for the identification of unique regulators and markers for CSCs. Various signalling pathways like the Wnt/β-catenin pathway, Hedgehog pathway, Notch pathway, and TGFβ/BMP play a major role in the regulation and maintenance of CSCs. Epigenetic regulatory mechanisms add another layer of complexity to control these signalling pathways. In this chapter, we discuss about the role of epigenetic mechanisms in regulating the cellular signalling pathways in CSCs. The epigenetic regulatory mechanisms such as DNA methylation, histone modification and microRNAs can modulate the diverse effectors of signalling pathways and consequently the growth, differentiation and tumorigenicity of CSCs. In the end, we briefly discuss the therapeutic potential of targeting these epigenetic regulators and their target genes in CSCs.

ALDH1A1 promotes PARP inhibitor resistance by enhancing retinoic acid receptor-mediated DNA polymerase θ expression

Poly (ADP-ribose) Polymerase (PARP) inhibitors (PARPi) have been approved for both frontline and recurrent setting in ovarian cancer with homologous recombination (HR) repair deficiency. However, more than 40% of BRCA1/2-mutated ovarian cancer lack the initial response to PARPi treatment, and the majority of those that initially respond eventually develop resistance. Our previous study has demonstrated that increased expression of aldehyde dehydrogenase 1A1 (ALDH1A1) contributes to PARPi resistance in BRCA2-mutated ovarian cancer cells by enhancing microhomology-mediated end joining (MMEJ) but the mechanism remains unknown. Here, we find that ALDH1A1 enhances the expression of DNA polymerase θ (Polθ, encoded by the POLQ gene) in ovarian cancer cells. Furthermore, we demonstrate that the retinoic acid (RA) pathway is involved in the transcription activation of the POLQ gene. The RA receptor (RAR) can bind to the retinoic acid response element (RARE) located in the promoter of the POLQ gene, promoting transcription activation-related histone modification in the presence of RA. Given that ALDH1A1 catalyzes the biosynthesis of RA, we conclude that ALDH1A1 promotes POLQ expression via the activation of the RA signaling pathway. Finally, using a clinically-relevant patient-derived organoid (PDO) model, we find that ALDH1A1 inhibition by the pharmacological inhibitor NCT-505 in combination with the PARP inhibitor olaparib synergistically reduce the cell viability of PDOs carrying BRCA1/2 mutation and positive ALDH1A1 expression. In summary, our study elucidates a new mechanism contributing to PARPi resistance in HR-deficient ovarian cancer and shows the therapeutic potential of combining PARPi and ALDH1A1 inhibition in treating these patients.

Anticancer Potential of Natural Chalcones: In Vitro and In Vivo Evidence

There is no doubt that significant progress has been made in tumor therapy in the past decades. However, the discovery of new molecules with potential antitumor properties still remains one of the most significant challenges in the field of anticancer therapy. Nature, especially plants, is a rich source of phytochemicals with pleiotropic biological activities. Among a plethora of phytochemicals, chalcones, the bioprecursors of flavonoid and isoflavonoids synthesis in higher plants, have attracted attention due to the broad spectrum of biological activities with potential clinical applications. Regarding the antiproliferative and anticancer effects of chalcones, multiple mechanisms of action including cell cycle arrest, induction of different forms of cell death and modulation of various signaling pathways have been documented. This review summarizes current knowledge related to mechanisms of antiproliferative and anticancer effects of natural chalcones in different types of malignancies including breast cancers, cancers of the gastrointestinal tract, lung cancers, renal and bladder cancers, and melanoma.

Refining Classification of Cholangiocarcinoma Subtypes via Proteogenomic Integration Reveals New Therapeutic Prospects

BACKGROUND & AIMS

Intrahepatic cholangiocarcinomas (iCCs) are characterized by their rarity, difficult diagnosis, and overall poor prognosis. The iCC molecular classification for developing precision medicine strategies was investigated.

METHODS

Comprehensive genomic, transcriptomic, proteomic, and phosphoproteomic analyses were performed on treatment-naïve tumor samples from 102 patients with iCC who underwent surgical resection with curative intent. An organoid model was constructed for testing therapeutic potential.

RESULTS

Three clinically supported subtypes (stem-like, poorly immunogenic, and metabolism) were identified. NCT-501 (aldehyde dehydrogenase 1 family member A1 [ALDH1A1] inhibitor) exhibited synergism with nanoparticle albumin-bound-paclitaxel in the organoid model for the stem-like subtype. The oncometabolite dysregulations were associated with different clinical outcomes in the stem-like and metabolism subtypes. The poorly immunogenic subtype harbors the non-T-cell tumor infiltration. Integrated multiomics analysis not only reproduced the 3 subtypes but also showed heterogeneity in iCC.

CONCLUSIONS

This large-scale proteogenomic analysis provides information beyond that obtained with genomic analysis, allowing the functional impact of genomic alterations to be discerned. These findings may assist in the stratification of patients with iCC and in developing rational therapeutic strategies.

The Molecular Context of Oxidant Stress Response in Cancer Establishes ALDH1A1 as a Critical Target: What This Means for Acute Myeloid Leukemia

The protein family of aldehyde dehydrogenases (ALDH) encompasses nineteen members. The ALDH1 subfamily consists of enzymes with similar activity, having the capacity to neutralize lipid peroxidation products and to generate retinoic acid; however, only ALDH1A1 emerges as a significant risk factor in acute myeloid leukemia. Not only is the gene ALDH1A1 on average significantly overexpressed in the poor prognosis group at the RNA level, but its protein product, ALDH1A1 protects acute myeloid leukemia cells from lipid peroxidation byproducts. This capacity to protect cells can be ascribed to the stability of the enzyme under conditions of oxidant stress. The capacity to protect cells is evident both in vitro, as well as in mouse xenografts of those cells, shielding cells effectively from a number of potent antineoplastic agents. However, the role of ALDH1A1 in acute myeloid leukemia has been unclear in the past due to evidence that normal cells often have higher aldehyde dehydrogenase activity than leukemic cells. This being true, ALDH1A1 RNA expression is significantly associated with poor prognosis. It is hence imperative that ALDH1A1 is methodically targeted, particularly for the acute myeloid leukemia patients of the poor prognosis risk group that overexpress ALDH1A1 RNA.

Differential Regulation of Retinoic Acid Metabolism in Fanconi Anemia

Fanconi anemia (FA) is a rare genetic disease characterized by heterogeneous congenital abnormalities and increased risk for bone marrow failure and cancer. FA is caused by mutation of any one of 23 genes, the protein products of which function primarily in the maintenance of genome stability. An important role for the FA proteins in the repair of DNA interstrand crosslinks (ICLs) has been established in vitro . While the endogenous sources of ICLs relevant to the pathophysiology of FA have yet to be clearly determined, a role for the FA proteins in a two-tier system for the detoxification of reactive metabolic aldehydes has been established. To discover new metabolic pathways linked to FA, we performed RNA-seq analysis on non-transformed FA-D2 ( FANCD2 ^-/- ) and FANCD2-complemented patient cells. Multiple genes associated with retinoic acid metabolism and signaling were differentially expressed in FA-D2 ( FANCD2 ^-/- ) patient cells, including ALDH1A1 and RDH10 , which encode for retinaldehyde and retinol dehydrogenases, respectively. Increased levels of the ALDH1A1 and RDH10 proteins was confirmed by immunoblotting. FA-D2 ( FANCD2 ^-/- ) patient cells displayed increased aldehyde dehydrogenase activity compared to the FANCD2-complemented cells. Upon exposure to retinaldehyde, FA-D2 ( FANCD2 ^-/- ) cells exhibited increased DNA double-strand breaks and checkpoint activation indicative of a defect in the repair of retinaldehyde-induced DNA damage. Our findings describe a novel link between retinoic acid metabolism and FA and identify retinaldehyde as an additional reactive metabolic aldehyde relevant to the pathophysiology of FA.

Zebrafish as a Model to Study Retinoic Acid Signaling in Development and Disease

Retinoic acid (RA) is a metabolite of vitamin A (retinol) that plays various roles in development to influence differentiation, patterning, and organogenesis. RA also serves as a crucial homeostatic regulator in adult tissues. The role of RA and its associated pathways are well conserved from zebrafish to humans in both development and disease. This makes the zebrafish a natural model for further interrogation into the functions of RA and RA-associated maladies for the sake of basic research, as well as human health. In this review, we explore both foundational and recent studies using zebrafish as a translational model for investigating RA from the molecular to the organismal scale.

A Sequential Targeting Strategy Interrupts AKT-Driven Subclone-Mediated Progression in Glioblastoma

PURPOSE

Therapy resistance and fatal disease progression in glioblastoma are thought to result from the dynamics of intra-tumor heterogeneity. This study aimed at identifying and molecularly targeting tumor cells that can survive, adapt, and subclonally expand under primary therapy.

EXPERIMENTAL DESIGN

To identify candidate markers and to experimentally access dynamics of subclonal progression in glioblastoma, we established a discovery cohort of paired vital cell samples obtained before and after primary therapy. We further used two independent validation cohorts of paired clinical tissues to test our findings. Follow-up preclinical treatment strategies were evaluated in patient-derived xenografts.

RESULTS

We describe, in clinical samples, an archetype of rare ALDH1A1+ tumor cells that enrich and acquire AKT-mediated drug resistance in response to standard-of-care temozolomide (TMZ). Importantly, we observe that drug resistance of ALDH1A1+ cells is not intrinsic, but rather an adaptive mechanism emerging exclusively after TMZ treatment. In patient cells and xenograft models of disease, we recapitulate the enrichment of ALDH1A1+ cells under the influence of TMZ. We demonstrate that their subclonal progression is AKT-driven and can be interfered with by well-timed sequential rather than simultaneous antitumor combination strategy.

CONCLUSIONS

Drug-resistant ALDH1A1+/pAKT+ subclones accumulate in patient tissues upon adaptation to TMZ therapy. These subclones may therefore represent a dynamic target in glioblastoma. Our study proposes the combination of TMZ and AKT inhibitors in a sequential treatment schedule as a rationale for future clinical investigation.

A Case of Early-Stage Gallbladder Cancer, Positive for ALDH1A1, Which Arose from Adenomyomatosis of the Gallbladder

Adenomyomatosis (ADM) of the gallbladder is a condition characterized by the proliferation of Rokitansky–Aschoff sinus (RAS), in which the epithelium of the gallbladder extends into the muscular layer, causing a thickening of the gallbladder wall. Although ADM is generally considered not to be a precancerous lesion of gallbladder cancer, there are some reports of cases of gallbladder cancer from ADM. Therefore, the relationship between ADM and gallbladder cancer remains controversial. We herein report a case of early-stage gallbladder cancer, BilIN3 (high grade), arising from ADM that was positive for ALDH1A1, an important marker of stem cells and cancer stem cells.

ALDH1: A potential therapeutic target for cancer stem cells in solid tumors

Solid tumors can be divided into benign solid tumors and solid malignant tumors in the academic community, among which malignant solid tumors are called cancers. Cancer is the second leading cause of death in the world, and the global incidence of cancer is increasing yearly New cancer patients in China are always the first. After the concept of stem cells was introduced in the tumor community, the CSC markers represented by ALDH1 have been widely studied due to their strong CSC cell characteristics and potential to be the driving force of tumor metastasis. In the research results in the past five years, it has been found that ALDH1 is highly expressed in various solid cancers such as breast cancer, lung cancer, colorectal cancer, liver cancer, gastric cancer, cervical cancer, esophageal cancer, ovarian cancer, head,and neck cancer. ALDH1 can activate and transform various pathways (such as the USP28/MYC signaling pathway, ALDH1A1/HIF-1α/VEGF axis, wnt/β-catenin signaling pathway), as well as change the intracellular pH value to promote formation and maintenance, resulting in drug resistance in tumors. By targeting and inhibiting ALDH1 in tumor stem cells, it can enhance the sensitivity of drugs and inhibit the proliferation, differentiation, and metastasis of solid tumor stem cells to some extent. This review discusses the relationship and pathway of ALDH1 with various solid tumors. It proposes that ALDH1 may serve as a diagnosis and therapeutic target for CSC, providing new insights and new strategies for reliable tumor treatment.