Human Aldehyde Dehydrogenase 3A1 (ALDH3A1) Exhibits Chaperone-Like Function

Aldehyde dehydrogenase 3A1 (ALDH3A1) is a metabolic enzyme that catalyzes the oxidation of various aldehydes. Certain types of epithelial tissues in mammals, especially those continually exposed to environmental stress (e.g., corneal epithelium), express ALDH3A1 at high levels and its abundance in such tissues is perceived to help to maintain cellular homeostasis under conditions of oxidative stress. Metabolic as well as non-metabolic roles for ALDH3A1 have been associated with its mediated resistance to cellular oxidative stress. In this study, we provide evidence that ALDH3A1 exhibits molecular chaperone-like activity further supporting its multifunctional role. Specifically, we expressed and purified the human ALDH3A1 in E. coli and used the recombinant protein to investigate its in vitro ability to protect SmaI and citrate synthase (from precipitation and/or deactivation) under thermal stress conditions. Our results indicate that recombinant ALDH3A1 exhibits significant chaperone function in vitro. Furthermore, over-expression of the fused histidine-tagged ALDH3A1 confers host E. coli cells with enhanced resistance to thermal shock, while ALDH3A1 over-expression in the human corneal cell line HCE-2 was sufficient for protecting them from the cytotoxic effects of both hydrogen peroxide and tert-butyl hydroperoxide. These results further support the chaperone-like function of human ALDH3A1. Taken together, ALDH3A1, in addition to its primary metabolic role in fundamental cellular detoxification processes, appears to play an essential role in protecting cellular proteins against aggregation under stress conditions

Identification of a peptide ligand for human ALDH3A1 through peptide phage display: Prediction and characterization of protein interaction sites and inhibition of ALDH3A1 enzymatic activity

Aldehyde dehydrogenase 3A1 (ALDH3A1) by oxidizing medium chain aldehydes to their corresponding carboxylic acids, is involved in the detoxification of toxic byproducts and is considered to play an important role in antioxidant cellular defense. ALDH3A1 has been implicated in various other functions such as cell proliferation, cell cycle regulation, and DNA damage response. Recently, it has been identified as a putative biomarker of prostate, gastric, and lung cancer stem cell phenotype. Although ALDH3A1 has multifaceted functions in both normal and cancer homeostasis, its modes of action are currently unknown. To this end, we utilized a random 12-mer peptide phage display library to identify efficiently human ALDH3A1-interacting peptides. One prevailing peptide (P1) was systematically demonstrated to interact with the protein of interest, which was further validated in vitro by peptide ELISA. Bioinformatic analysis indicated two putative P1 binding sites on the protein surface implying biomedical potential and potent inhibitory activity of the P1 peptide on hALDH3A1 activity was demonstrated by enzymatic studies. Furthermore, in search of potential hALDH3A1 interacting players, a BLASTp search demonstrated that no protein in the database includes the full-length amino acid sequence of P1, but identified a list of proteins containing parts of the P1 sequence, which may prove potential hALDH3A1 interacting partners. Among them, Protein Kinase C Binding Protein 1 and General Transcription Factor II-I are candidates of high interest due to their cellular localization and function. To conclude, this study identifies a novel peptide with potential biomedical applications and further suggests a list of protein candidates be explored as possible hALDH3A1-interacting partners in future studies

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 and and the consequent downregulation of 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

Propolis Extracts Inhibit UV-Induced Photodamage in Human Experimental In Vitro Skin Models

The aim of this study was to assess the antioxidant, photoprotective, and antiaging effects of Greek propolis. Propolis was subjected to n-heptane or methanol extraction. Total phenolic/flavonoid content and antioxidant potential were determined in the extracts. Promising extracts were evaluated for their cytoprotective properties using human immortalized keratinocyte (HaCaT) or reconstituted human skin tissue following exposure to UVB. Assessment of cytotoxicity, DNA damage, oxidative status, and gene/protein expression levels of various matrix metalloproteinases (MMPs) were performed. The propolis methanolic fractions exhibited higher total phenolic and flavonoid contents and significant in vitro antioxidant activity. Incubation of HaCaT cells with certain methanolic extracts significantly decreased the formation of DNA strand breaks following exposure to UVB and attenuated UVB-induced decrease in cell viability. The extracts had no remarkable effect on the total antioxidant status, but significantly lowered total protein carbonyl content used as a marker for protein oxidation in HaCaT cells. MMP-1, -3, -7, and -9, monitored as endpoints of antiaging efficacy, were significantly reduced by propolis following UVB exposure in a model of reconstituted skin tissue. In conclusion, propolis protects against the oxidative and photodamaging effects of UVB and could be further explored as a promising agent for developing natural antiaging strategies

Μελέτη του ρόλου των αλδεϋδικών αφυδρογονασών στα καρκινικά βλαστικά κύτταρα

Aldehyde dehydrogenases (ALDHs) are NAD(P)+-dependent enzymes that catalyze the oxidation of endogenous (lipids, amino acids and vitamins) and exogenous (ethanol and drugs) aldehydes to their corresponding carboxylic acids. ALDHs have been used as normal and cancer stem cell (CSC) markers in a wide spectrum of solid tumors and hematological malignancies, are related to increased tumorgenicity, chemo/radio-resistance, cancer initiation and progression and participate in a variety of cellular mechanisms, such as metabolism, proliferation, differentiation, embryogenesis, apoptosis, stemness, invasion, hypoxia, as well as in RA biosynthesis.ALDH1B1, a member of ALDHs superfamily, is a mitochondrial enzyme that detoxifies 4-HNE and malondialdehyde and may be associated with RA metabolism. It is suggested that ALDH1B1 is associated with ethanol metabolism and maintenance of stallion sperm motility. It is also correlated with colon tumorigenesis, pancreatic stem cells and beta cell development and involved in various cellular signaling pathways such as PI3K/Akt, Wnt/β-catenin and Notch, demonstrating thus its potential relation to CSC phenotype. Moreover, studies have reported that ALDH1B1 could be a novel biomarker for detecting colorectal cancer and may be a modulator of pancreatic cancer.CSCs, also known as tumor initiating cells, are characterized by a set of stem-like properties, such as self-renewal, differentiation, cell survival and asymmetric cell division. CSCs are considered important for tumor heterogeneity due to their ability to differentiate into multiple cell types, while they are considered important therapeutic target as a result of their enhanced chemo- and radio-resistance as well as their association with cancer initiation, progression and metastasis.Silibinin is the major bioactive and most abundant component of the silymarin complex derived from the seeds of the plant Silybum marianum. Silibinin consists of a diastereoisomeric mixture of silybin A and silybin B and is reported as a compound with a safe profile, due to its low cytotoxicity against healthy cells. Plenty of studies have supported the strong chemopreventive and antineoplastic ability of silibinin through pleiotropic mechanisms of action against different type of malignancies. The present study examines the role of ALDHs in CSCs. It focuses on the pathophysiological role of ALDH1B1 in colorectal and lung carcinoma demonstrating the molecular mechanisms, in which ALDH1B1 is involved. In addition, we investigated which ALDH isoforms are associated with sphere phenotype and the potential effect of silibinin in inhibiting the sphere formation efficiency. For examining the pathophysiological role of ALDH1B1, we established two isogenic cell line pairs for human colorectal adenocarcinoma (HT-29 and Caco-2) and one isogenic cell line pair for lung carcinoma (A549), differing only in the expression of ALDH1B1. ALDH1B1 appears to be implicated in cell cycle regulation as the ALDH1B1-overexpressing cells exhibited significantly slower growth rates and a G2/M phase cell cycle arrest compared to the HT-29/mock cells. Furthermore, ALDH1B1 expression was related to enhanced chemoresistance as it protects HT-29 and A549 cells from cytotoxic effects of different chemotherapeutic agents (etoposide, DOX, 5-FU). Moreover, ALDH1B1 was correlated with EMT induction through ZEB1 or SNAIL signaling pathways and morphological alterations (HT-29, Caco-2 and A549) and exhibited increased migratory potential in HT-29 cells. ALDH1B1 expression was accompanied by increased constitutive phosphorylation of p53 and H2AX at basal levels, in HT-29/ALDH1B1 compared to HT-29/mock cells, protecting cells from the genotoxic effect of etoposide. Interestingly, real-time PCR revealed that the expression of ALDH1B1 significantly altered the expression profile of a variety of DNA damage response-related genes between the isogenic ΗΤ-29 cell lines. In particular, four important genes of DNA damage repair (MRE11A, PMS1, RAD18, and UNG) were found to be up-regulated in the ALDH1B1-overexpressing HT-29 cells at basal levels.Additionally, we utilized lung (A549) and hepatocellular (HepG2) cancer cells and generated tumor spheres to isolate the CSC sub-population. The CSC enrichment was confirmed by the up-regulation of CSC-related genes, such as EpCAM, OCT4, SOX2, SOX4, CXCR4, CD49f and NOTCH1. Real-time PCR analysis indicated the up-regulation of several ALDH isoforms such as ALDH1A1, ALDH2, ALDH3A1, ALDH3B1 in A549 and ALDH1A3, ALDH3A1, ALDH9A1 and ALDH18A1 in HepG2 spheres. Interestingly, cyclin D1 and Akt, down-stream targets of the RA signaling pathway, were also shown to be significantly up-regulated in both sphere populations. Specific ALDH isoforms appear to be important mediators for the acquisition of CSC phenotype and maybe promising targets for CSC-based therapeutic approaches in lung and hepatocellular carcinomas.Finally, we assessed the silibinin potential effect on sphere cultures of A549 and HepG2. We determined its cytotoxicity profile in A549 cells and then we evaluated its anti-proliferative effect in both A549 and HepG2 cells. Then, we found that silibinin induced the mRNA down-regulation of specific sphere-related ALDH isoforms and CSC markers as well as it triggered substantial decrease in the ALDH enzymatic activity. Silibinin inhibited the sphere formation efficacy of A549 and HepG2 cells, indicating that it could be considered a potential agent for the CSC-based therapeutic approach.In conclusion, the results of the present study underline the potential significance of ALDH1B1 in cancer progression as it was found that ALDH1B1 confers alterations in the cell morphology, cell cycle progression and gene expression, accompanied by significant changes in the chemosensitivity and migratory potential of colon and lung cancer cells, features related to the acquisition of a CSC phenotype. The results of this study, also, demonstrate that other ALDH isoforms may be associated with the CSC phenotype using preclinical lung and hepatocellular cancer models. Further studies are required to clarify the exact role of ALDHs in cancer stem cell biology and to enable future studies for CSC-based therapies.Οι αλδεϋδικές αφυδρογονάσες (ALDHs) είναι μια υπεροικογένεια NAD(P)+-εξαρτώμεναων ενζύμων που καταλύουν την οξείδωση των ενδογενών (λιπίδια, αμινοξέα και βιταμίνες) και εξωγενών (αιθανόλη και φάρμακα) αλδεϋδών στα αντίστοιχα καρβοξυλικά οξέα τους. Οι ALDHs έχουν χρησιμοποιηθεί ως δείκτες τόσο των φυσιολογικών όσο και των καρκινικών βλαστικών κυττάρων (CSC) σε ένα ευρύ φάσμα όγκων και αιματολογικών κακοηθειών. Τα ένζυμα αυτά, σχετίζονται με αυξημένη ογκογένεση, χήμειο- και άκτινο-ανθεκτικότητα, με την έναρξη και την εξέλιξη του καρκίνου και συμμετέχουν σε διάφορους κυτταρικούς μηχανισμούς, όπως στον μεταβολισμό, στον πολλαπλασιασμό, στη διαφοροποίηση, στην εμβρυογένεση, στην απόπτωση, στη μετάσταση, στην υποξία, καθώς επίσης και στη βιοσύνθεση του ρετινοϊκού οξέος (RA).Η ALDH1B1, είναι ένα μιτοχονδριακό ένζυμο, το οποίο ανήκει στην υπερ-οικογένεια των ALDHs και μεταβολίζει την 4-υδροξυνονενάλη (4-HNE) και τη μαλονδιαλδεΰδη (MDA) και πιθανόν σχετίζεται με τον μεταβολισμό του ρετινοϊκού οξέος. Πρόσφατες έρευνες αναφέρουν πως η ALDH1B1 σχετίζεται με τον μεταβολισμό της αιθανόλης και τη διατήρηση της κινητικότητας του σπέρματος του αλόγου. Επίσης, η έκφραση της ALDH1B1 συσχετίζεται με την ογκογένεση του παχέος εντέρου, τα παγκρεατικά βλαστοκύτταρα και την ανάπτυξη των β-κυττάρων του παγκρέατος. Το ισοένζυμο αυτό, εμπλέκεται σε διάφορα μονοπάτια κυτταρικής σηματοδότησης (PI3K/Akt, Wnt/β-catenin και Notch), αποδεικνύοντας έτσι τη δυνητική του σχέση με τον φαινότυπο των καρκινικών βλαστικών κυττάρων (CSCs). Επιπρόσθετα, μελέτες έχουν αναφέρει ότι η ALDH1B1 θα μπορούσε να είναι ένας νέος βιοδείκτης για την ανίχνευση του καρκίνου του παχέος εντέρου και ένας ρυθμιστής του καρκίνου του παγκρέατος. Τα CSCs, γνωστά και ως κύτταρα εκκίνησης του όγκου, ονομάζονται έτσι λόγω των παρόμοιων χαρακτηριστικών/ιδιοτήτων τους με τα φυσιολογικά βλαστοκύτταρα, όπως είναι η αυτο-ανανέωση, η διαφοροποίηση, η κυτταρική επιβίωση και η ασύμμετρη κυτταρική διαίρεση. Τα CSCs θεωρούνται σημαντικά για την ετερογένεια των όγκων, λόγω της ικανότητάς τους να διαφοροποιούνται σε πολλαπλούς τύπους κυττάρων. Τα κύτταρα αυτά, θεωρούνται επίσης σημαντικός θεραπευτικός στόχος, λόγω της ενισχυμένης χήμειο- και άκτινο-ανθεκτικότητάς τους, καθώς και της συσχέτισής τους με την έναρξη, την εξέλιξη και τη μετάσταση του καρκίνου. Η σιλιμπινίνη είναι ένα φυσικό προϊόν, το οποίο αποτελεί το κύριο βιοδραστικό και το πιο άφθονο συστατικό του συμπλέγματος της σιλυμαρίνης, που προέρχεται από τους σπόρους του φυτού Silybum marianum. Η σιλιμπινίνη αποτελείται από ένα διαστερεοϊσομερές μίγμα της σιλυμπίνης Α και της σιλυμπίνης Β και θεωρείται μια ένωση με ασφαλές προφίλ, λόγω της χαμηλής κυτταροτοξικότητάς της έναντι των υγιών κυττάρων. Πολλές μελέτες έχουν υποστηρίξει την ισχυρή χημειο-προφυλακτική και αντι-νεοπλασματική ικανότητα της σιλιμπινίνης, μέσω των πλειοτροπικών μηχανισμών δράσης της ενάντια σε διαφορετικούς τύπους κακοήθειας.Η παρούσα μελέτη εξετάζει τον ρόλο των ALDHs στα CSCs. Επικεντρώνεται, κυρίως στον παθοφυσιολογικό ρόλο της ALDH1B1 στο καρκίνο του παχέος εντέρου και του πνεύμονα, επιδεικνύοντας τους μοριακούς μηχανισμούς, στους οποίους εμπλέκεται. Επιπλέον, έχει ως στόχο τόσο τη διερεύνηση των ισομορφών των ALDHs, που σχετίζονται με τον καρκινικό βλαστικό φαινότυπο, όσο και την πιθανή επίδραση της σιλιμπινίνης στην αναστολή της ικανότητας δημιουργίας σφαιρών, σε προκλινικά μοντέλα καρκίνου του πνεύμονα και του ήπατος.Για τη διερεύνηση του παθοφυσιολογικού ρόλου της ALDH1B1, δημιουργήσαμε δύο ζεύγη ισογονιδιακών κυτταρικών σειρών για τον καρκίνο του παχέος εντέρου (HT-29 και Caco-2) και ένα ζεύγος ισογονιδιακών κυτταρικών σειρών για τον καρκίνο του πνεύμονα (A549), τα οποία διαφέρουν μόνο ως προς την έκφραση της ALDH1B1. Το ισοένζυμο φαίνεται να εμπλέκεται στην κυτταρική μορφολογία και στον κυτταρικό πολλαπλασιασμό, καθώς τα κύτταρα που τεχνητά το υπερεκφράζουν εμφανίζουν αλλαγές στη μορφολογία τους (γίνονται πιο επιμήκη) και χαμηλότερο ρυθμό πολλαπλασιασμού. Επίσης, η ALDH1B1 ενέχεται στη ρύθμιση του κυτταρικού κύκλου, καθώς τα κύτταρα που την υπερεκφράζουν παρουσίασαν σημαντικά βραδύτερους ρυθμούς ανάπτυξης και καθυστέρηση του κυτταρικού κύκλου στη φάση G2/M, σε σύγκριση με τα HT-29 κύτταρα ελέγχου (mock). Επιπλέον, η έκφραση της ALDH1B1 σχετίζεται με αυξημένη χημειο-ανθεκτικότητα, καθώς προστατεύει τα κύτταρα ΗΤ-29 και Α549 από την κυτταροτοξική επίδραση διαφόρων χημειοθεραπευτικών παραγόντων (ετοποσίδη, DOX, 5-FU). Επιπλέον, η ALDH1B1 συσχετίστηκε με την επαγωγή της διαδικασίας της επιθηλιακής-μεσεγχυματικής μετάπτωσης (EMT), μέσω των μονοπατιών σηματοδότησης ZEB1 ή SNAIL, και παρουσίασε αυξημένο μεταναστευτικό δυναμικό στα κύτταρα HT-29. Η έκφραση της ALDH1B1 συνοδεύτηκε από αυξημένη ιδιοστατική φωσφορυλίωση της p53 και της H2AX στα HT-29/ALDH1B1 κύτταρα, σε σύγκριση με HT-29/κύτταρα ελέγχου, προστατεύοντας έτσι τα κύτταρα από τη γονοτοξική επίδραση της ετοποσίδης. Είναι ενδιαφέρον ότι η PCR πραγματικού χρόνου κατέδειξε ότι η έκφραση της ALDH1B1 άλλαξε σημαντικά το προφίλ γονιδιακής έκφρασης διαφόρων μορίων που σχετίζονται με την απόκριση στη βλάβη του DNA μεταξύ του ισογονιδιακού ζεύγους HT-29 κυττάρων. Συγκεκριμένα, τα επίπεδα έκφρασης τεσσέρων σημαντικών πρωτεϊνών για την αποκατάσταση της βλάβης του DNA (MRE11A, PMS1, RAD18 και UNG) βρέθηκαν αυξημένα στα κύτταρα HT-29 που υπερεκφράζουν την ALDH1B1 σε φυσιολογικές συνθήκες.Επιπλέον, χρησιμοποιήσαμε καρκινικά κύτταρα πνεύμονα (A549) και ήπατος (HepG2) και προχωρήσαμε στη δημιουργία σφαιρών, οι οποίες προσομοιάζουν σε μεγάλο βαθμό τον υπο-πληθυσμό των CSCs in vitro. Η απομόνωση του πληθυσμού των CSCs επιβεβαιώθηκε με την αύξηση της μεταγραφικής έκφρασης γονιδίων που σχετίζονται με τον καρκινικό βλαστικό φαινότυπο. Η ανάλυση PCR πραγματικού χρόνου έδειξε την αύξηση της έκφρασης αρκετών ισομορφών των ALDHs όπως τις ALDH1A1, ALDH2, ALDH3A1, ALDH3B1, στις σφαίρες των A549 και τις ALDH1A3, ALDH3A1, ALDH9A1 και ALDH18A1, στις σφαίρες των HepG2 κυττάρων. Είναι, επίσης, ενδιαφέρον ότι η κυκλίνη D1 και η Akt, σημαντικά μόρια της σηματοδότησης του ρετινοϊκού οξέος (RA), παρουσιάζουν αυξημένα επίπεδα μεταγραφικής έκφρασης και στους δύο πληθυσμούς σφαιρών που απομονώθηκαν (A549 και HepG2). Ειδικές ισομορφές των ALDHs αποτελούν σημαντικούς ρυθμιστές για την εμφάνιση του καρκινικού βλαστικού φαινοτύπου και θεωρούνται πολλά υποσχόμενοι στόχοι για νέες θεραπευτικές προσεγγίσεις που βασίζονται στα CSCs του πνεύμονα και του ήπατος.Τέλος, αξιολογήσαμε τη δυνητική δράση της σιλιμπινίνης στις καλλιέργειες των σφαιρών των κυττάρων A549 και HepG2. Εκτιμήσαμε το προφίλ κυτταροτοξικότητας της σιλιμπινίνης στα κύτταρα Α549 και στη συνέχεια αξιολογήσαμε την αντιπολλαπλασιαστική της δράση τόσο στα κύτταρα Α549, όσο και στα κύτταρα HepG2. Στη συνέχεια, διαπιστώσαμε ότι η σιλιμπινίνη επάγει τη μείωση τόσο των μεταγραφικών και ενζυμικών επιπέδων έκφρασης συγκεκριμένων ισομορφών των ALDHs που σχετίζονται με τον καρκινικό βλαστικό φαινότυπο, όσο και γνωστών μορίων που θεωρούνται δείκτες των CSCs. Η σιλιμπινίνη, επίσης, μειώνει την αποτελεσματικότητα σχηματισμού των σφαιρών στα κύτταρα A549 και HepG2, υποδεικνύοντας ότι θα μπορούσε να θεωρηθεί ένας δυνητικός παράγοντας για μια νέα θεραπευτική προσέγγιση έναντι των καρκινικών βλαστοκυττάρων.Συμπερασματικά, τα αποτελέσματα της μελέτης αυτής υποστηρίζουν ότι η ALDH1B1 μπορεί να έχει σημαντικό ρόλο στην εξέλιξη του καρκίνου και εμπλέκεται σε αρκετές κυτταρικές διεργασίες που σχετίζονται με τον καρκινικό βλαστικό φαινότυπο. Ενδεχομένως και άλλες ισομορφές των ALDHs μπορεί να σχετίζονται με τον καρκινικό βλαστικό φαινότυπο ανάλογα με τον τύπο του καρκίνου. Περαιτέρω μελέτες είναι απαραίτητες για την αποσαφήνιση του ακριβούς ρόλου των ALDHs και των επιμέρους ισομορφών τους στη βιολογία των καρκινικών βλαστικών κυττάρων, που μπορεί να αποτελέσουν στο μέλλον τη βάση για το σχεδιασμό νέων θεραπευτικών προσεγγίσεων έναντι των CSCs

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

Aldehyde Dehydrogenase 1B1 Is Implicated in DNA Damage Response in Human Colorectal Adenocarcinoma

Aldehyde dehydrogenase 1B1 (ALDH1B1) has been correlated with colorectal tumorigenesis and is considered a potential biomarker for colon cancer. Its expression has been associated with attenuation of the cell cycle in the G2/M phase and resistance to DNA damaging agents. The present study examines the role of ALDH1B1 in DNA damage response (DDR) in human colorectal adenocarcinoma. To this end, we utilized an isogenic HT29 cell line pair differing in the expression of ALDH1B1. The overexpression of ALDH1B1 was related to the translational upregulation of the total and phosphorylated (at ser15) p53. Comet and apoptosis assays revealed that the expression of ALDH1B1 protected HT29 cells from etoposide-induced DNA damage as well as apoptosis, and its overexpression led to increased constitutive phosphorylation of H2AX (at ser139). Furthermore, the expression profile of a variety of DNA damage signaling (DDS)-related genes was investigated by utilizing the RT2 profiler™ PCR array. Our results demonstrated that ALDH1B1 triggered a transcriptional activation of several DNA repair-related genes (MRE11A, PMS1, RAD18 and UNG). Finally, Spearman’s rank correlation coefficient analysis in 531 publicly available colorectal adenocarcinoma clinical samples indicated the statistically significant positive correlation between ALDH1B1 and DDR and repair genes or proteins, such as APEX1, FEN1, MPG, UNG, XRCC1, DDB1, XPC, CIB1, MRE11, PRKDC, RAD50, RAD21, TP53BP1, XRCC6 and H2AX. Collectively, our results suggest that ALDH1B1 may play an essential role in the DDR and DNA repair processes. Further studies on ALDH1B1 will elucidate its precise role in DDR

DataSheet1_Identification of a peptide ligand for human ALDH3A1 through peptide phage display: Prediction and characterization of protein interaction sites and inhibition of ALDH3A1 enzymatic activity.ZIP

Aldehyde dehydrogenase 3A1 (ALDH3A1) by oxidizing medium chain aldehydes to their corresponding carboxylic acids, is involved in the detoxification of toxic byproducts and is considered to play an important role in antioxidant cellular defense. ALDH3A1 has been implicated in various other functions such as cell proliferation, cell cycle regulation, and DNA damage response. Recently, it has been identified as a putative biomarker of prostate, gastric, and lung cancer stem cell phenotype. Although ALDH3A1 has multifaceted functions in both normal and cancer homeostasis, its modes of action are currently unknown. To this end, we utilized a random 12-mer peptide phage display library to identify efficiently human ALDH3A1-interacting peptides. One prevailing peptide (P1) was systematically demonstrated to interact with the protein of interest, which was further validated in vitro by peptide ELISA. Bioinformatic analysis indicated two putative P1 binding sites on the protein surface implying biomedical potential and potent inhibitory activity of the P1 peptide on hALDH3A1 activity was demonstrated by enzymatic studies. Furthermore, in search of potential hALDH3A1 interacting players, a BLASTp search demonstrated that no protein in the database includes the full-length amino acid sequence of P1, but identified a list of proteins containing parts of the P1 sequence, which may prove potential hALDH3A1 interacting partners. Among them, Protein Kinase C Binding Protein 1 and General Transcription Factor II-I are candidates of high interest due to their cellular localization and function. To conclude, this study identifies a novel peptide with potential biomedical applications and further suggests a list of protein candidates be explored as possible hALDH3A1-interacting partners in future studies.</p

A New Controlled Release System for Propolis Polyphenols and Its Biochemical Activity for Skin Applications

Propolis is a resinous substance produced by bees that exhibits antimicrobial, immunostimulatory and antioxidant activity. Its use is common in functional foods, cosmetics and traditional medicine despite the fact that it demonstrates low extraction yields and inconsistency in non-toxic solvents. In this work, a new encapsulation and delivery system consisting of liposomes and cyclodextrins incorporating propolis polyphenols has been developed and characterized. The antioxidant, antimutagenic and antiaging properties of the system under normal and UVB-induced oxidative stress conditions were investigated in cultured skin cells and/or reconstituted skin model. Furthermore, the transcript accumulation for an array of genes involved in many skin-related processes was studied. The system exhibits significant polyphenol encapsulation efficiency, physicochemical stability as well as controlled release rate in appropriate conditions. The delivery system can retain the anti-mutagenic, anti-oxidative and anti-ageing effects of propolis polyphenols to levels similar and comparable to those of propolis methanolic extracts, making the system ideal for applications where non-toxic solvents are required and controlled release of the polyphenol content is desired