Retinoid metabolism and ALDH1A2 (RALDH2) expression are altered in the transgenic adenocarcinoma mouse prostate model

Retinoid metabolism: new insights

Vitamin A (retinol) is a critical micronutrient required for the control of stem cell functions, cell differentiation, and cell metabolism in many different cell types, both during embryogenesis and in the adult organism. However, we must obtain vitamin A from food sources. Thus, the uptake and metabolism of vitamin A by intestinal epithelial cells, the storage of vitamin A in the liver, and the metabolism of vitamin A in target cells to more biologically active metabolites, such as retinoic acid (RA) and 4-oxo-RA, must be precisely regulated. Here, I will discuss the enzymes that metabolize vitamin A to RA and the cytochrome P450 Cyp26 family of enzymes that further oxidize RA. Because much progress has been made in understanding the regulation of ALDH1a2 (RALDH2) actions in the intestine, one focus of this review is on the metabolism of vitamin A in intestinal epithelial cells and dendritic cells. Another focus is on recent data that 4-oxo-RA is a ligand required for the maintenance of hematopoietic stem cell dormancy and the important role of RARβ (RARB) in these stem cells. Despite this progress, many questions remain in this research area, which links vitamin A metabolism to nutrition, immune functions, developmental biology, and nuclear receptor pharmacology.

Inhibitor of Growth 4 (ING4) Plays a Tumor-Repressing Role in Oral Squamous Cell Carcinoma via Nuclear Factor kappa-B (NF-kB)/DNA Methyltransferase 1 (DNMT1) Axis-Mediated Regulation of Aldehyde Dehydrogenase 1A2 (ALDH1A2)

BACKGROUND

Inhibitor of growth 4 (ING4) level was reported to be decreased in head and neck squamous cell carcinoma (HNSC) tissue, however, it is unknown whether and how ING4 participates in regulating the development of oral squamous cell carcinoma (OSCC).

OBJECTIVE

To investigate the role and mechanism of ING4 in OSCC.

METHODS

ING4 was forced up-or down-regulated in two OSCC cell lines, and its effects on the malignant behavior of OSCC cells were investigated in vitro. The ubiquitination level of NF-kB p65 in ING4 upregulated cells was measured by co-immunoprecipitation. Moreover, the effects of ING4 on the methylation level of ALDH1A2 were evaluated by methylation-specific polymerase chain reaction (MSP) assay. The role of ING4 in OSCC growth in vivo was observed in nude mice.

RESULTS

Our results showed that the expression of ING4 in OSCC cell lines was lower than that in normal oral keratinocyte cells. In vitro, ING4 overexpression inhibited the proliferation, migration, and invasion of OSCC cell lines and ING4 silencing exhibited opposite results. We also demonstrated that ING4 overexpression promoted the ubiquitination and degradation of P65 and reduced DNA methyltransferase 1 (DNMT1) expression, and Aldehyde dehydrogenase 1A2 (ALDH1A2) methylation. Moreover, overexpression of p65 rescued the suppression of malignant behavior, induced by ING4 overexpression. In addition, ING4 negatively regulated the growth of OSCC xenograft tumors in vivo.

CONCLUSION

Our data evidenced that ING4 played a tumor-repressing role in OSCC in vivo and in vitro via NF-κB/DNMT1/ALDH1A2 axis.

Epigenetic study of early breast cancer (EBC) based on DNA methylation and gene integration analysis

Breast cancer (BC) is one of the leading causes of cancer-related deaths in women. The purpose of this study is to identify key molecular markers related to the diagnosis and prognosis of early breast cancer (EBC). The data of mRNA, lncRNA and DNA methylation were downloaded from The Cancer Genome Atlas (TCGA) dataset for identification of differentially expressed mRNAs (DEmRNAs), differentially expressed lncRNAs (DElncRNAs) and DNA methylation analysis. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyzes were used to identify the biological functions of DEmRNAs. The correlation analysis between DNA methylation and DEmRNAs was carried out. Then, diagnostic analysis and prognostic analysis of identified DEmRNAs and DElncRNAs were also performed in the TCGA database. Subsequently, methylation state verification for identified DEmRNAs was performed in the GSE32393 dataset. In addition, real-time polymerase chain reaction (RT-PCR) in vitro verification of genes was performed. Finally, AC093110.1 was overexpressed in human BC cell line MCF-7 to verify cell proliferation and migration. In this study, a total of 1633 DEmRNAs, 750 DElncRNAs and 8042 differentially methylated sites were obtained, respectively. In the Venn analysis, 11 keys DEmRNAs (ALDH1L1, SPTBN1, MRGPRF, CAV2, HSPB6, PITX1, WDR86, PENK, CACNA1H, ALDH1A2 and MME) were we found. ALDH1A2, ALDH1L1, HSPB6, MME, MRGPRF, PENK, PITX1, SPTBN1, WDR86 and CAV2 may be considered as potential diagnostic gene biomarkers in EBC. Strikingly, CAV2, MME, AC093110.1 and AC120498.6 were significantly actively correlated with survival. Methylation state of identified DEmRNAs in GSE32393 dataset was consistent with the result in TCGA. AC093110.1 can affect the proliferation and migration of MCF-7. ALDH1A2, ALDH1L1, HSPB6, MME, MRGPRF, PENK, PITX1, SPTBN1, WDR86 and CAV2 may be potential diagnostic gene biomarkers of EBC. Strikingly, CAV2, MME, AC093110.1 and AC120498.6 were significantly actively correlated with survival. The identification of these genes can help in the early diagnosis and treatment of EBC. In addition, AC093110.1 can regulate SPTBN1 expression and play an important role in cell proliferation and migration, which provides clues to clarify the regulatory mechanism of EBC.

The Multifaceted Role of Aldehyde Dehydrogenases in Prostate Cancer Stem Cells

Cancer stem cells (CSCs) are the only tumor cells possessing self-renewal and differentiation properties, making them an engine of tumor progression and a source of tumor regrowth after treatment. Conventional therapies eliminate most non-CSCs, while CSCs often remain radiation and drug resistant, leading to tumor relapse and metastases. Thus, targeting CSCs might be a powerful tool to overcome tumor resistance and increase the efficiency of current cancer treatment strategies. The identification and isolation of the CSC population based on its high aldehyde dehydrogenase activity (ALDH) is widely accepted for prostate cancer (PCa) and many other solid tumors. In PCa, several ALDH genes contribute to the ALDH activity, which can be measured in the enzymatic assay by converting 4, 4-difluoro-4-bora-3a, 4a-diaza-s-indacene (BODIPY) aminoacetaldehyde (BAAA) into the fluorescent product BODIPY-aminoacetate (BAA). Although each ALDH isoform plays an individual role in PCa biology, their mutual functional interplay also contributes to PCa progression. Thus, ALDH proteins are markers and functional regulators of CSC properties, representing an attractive target for cancer treatment. In this review, we discuss the current state of research regarding the role of individual ALDH isoforms in PCa development and progression, their possible therapeutic targeting, and provide an outlook for the future advances in this field.

Identification of genes associated with endometrial cell ageing

Ageing of the uterine endometrium is a critical factor that affects reproductive success, but the mechanisms associated with uterine ageing are unclear. In this study, we conducted a qualitative examination of age-related changes in endometrial tissues and identified candidate genes as markers for uterine ageing. Gene expression patterns were assessed by two RNA-sequencing experiments using uterine tissues from wild type (WT) C57BL/6 mice. Gene expression data obtained by RNA-sequencing were validated by real-time PCR. Genes expressing the pro-inflammatory cytokines Il17rb and chemokines Cxcl12 and Cxcl14 showed differential expression between aged WT mice and a group of mice composed of 5- and 8-week-old WT (young) animals. Protein expression levels of the above-mentioned genes and of IL8, which functions downstream of IL17RB, were analysed by quantitative immunohistochemistry of unaffected human endometrium tissue samples from patients in their 20s and 40s (10 cases each). In the secretory phase samples, 3,3'- diaminobenzidine staining intensities of IL17RB, CXCL12 and CXCL14 for patients in their 40s were significantly higher than that for patients in their 20s, as detected by a Mann-hitney U test. These results suggest that these genes are candidate markers for endometrial ageing and for prediction of age-related infertility, although confirmation of these findings is needed in larger studies involving fertile and infertile women.

Nuclear receptors in podocyte biology and glomerular disease

Nuclear receptors have a broad spectrum of biological functions in normal physiology and in the pathology of various diseases, including glomerular disease. The primary therapies for many glomerular diseases are glucocorticoids, which exert their immunosuppressive and direct podocyte protective effects via the glucocorticoid receptor (GR). As glucocorticoids are associated with important adverse effects and a substantial proportion of patients show resistance to these therapies, the beneficial effects of selective GR modulators are now being explored. Peroxisome proliferator-activated receptor-γ (PPARγ) agonism using thiazolidinediones has potent podocyte cytoprotective and nephroprotective effects. Repurposing of thiazolidinediones or identification of novel PPARγ modulators are potential strategies to treat non-diabetic glomerular disease. Retinoic acid receptor-α is the key mediator of the renal protective effects of retinoic acid, and repair of the endogenous retinoic acid pathway offers another potential therapeutic strategy for glomerular disease. Vitamin D receptor, oestrogen receptor and mineralocorticoid receptor modulators regulate podocyte injury in experimental models. Further studies are needed to better understand the mechanisms of these nuclear receptors, evaluate their synergistic pathways and identify their novel modulators. Here, we focus on the role of nuclear receptors in podocyte biology and non-diabetic glomerular disease.

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.

Combinatorial Ranking of Gene Sets to Predict Disease Relapse: The Retinoic Acid Pathway in Early Prostate Cancer

Background

Quantitative high-throughput data deposited in consortia such as International Cancer Genome Consortium (ICGC) and The Cancer Genome Atlas (TCGA) present opportunities and challenges for computational analyses.

Methods

We present a computational strategy to systematically rank and investigate a large number (2¹⁰–2²⁰) of clinically testable gene sets, using combinatorial gene subset generation and disease-free survival (DFS) analyses. This approach integrates protein–protein interaction networks, gene expression, DNA methylation, and copy number data, in association with DFS profiles from patient clinical records.

Results

As a case study, we applied this pipeline to systematically analyze the role of ALDH1A2 in prostate cancer (PCa). We have previously found this gene to have multiple roles in disease and homeostasis, and here we investigate the role of the associated ALDH1A2 gene/protein networks in PCa, using our methodology in combination with PCa patient clinical profiles from ICGC and TCGA databases. Relationships between gene signatures and relapse were analyzed using Kaplan–Meier (KM) log-rank analysis and multivariable Cox regression. Relative expression versus pooled mean from diploid population was used for z-statistics calculation. Gene/protein interaction network analyses generated 11 core genes associated with ALDH1A2; combinatorial ranking of the power set of these core genes identified two gene sets (out of 2¹¹ − 1 = 2,047 combinations) with significant correlation with disease relapse (KM log rank p < 0.05). For the more significant of these two sets, referred to as the optimal gene set (OGS), patients have median survival 62.7 months with OGS alterations compared to >150 months without OGS alterations (p = 0.0248, hazard ratio = 2.213, 95% confidence interval = 1.1–4.098). Two genes comprising OGS (CYP26A1 and RDH10) are strongly associated with ALDH1A2 in the retinoic acid (RA) pathways, suggesting a major role of RA signaling in early PCa progression. Our pipeline complements human expertise in the search for prognostic biomarkers in large-scale datasets.

Mining distinct aldehyde dehydrogenase 1 (ALDH1) isoenzymes in gastric cancer

Aldehyde dehydrogenase 1 (ALDH1) consists of a family of intracellular enzymes, highly expressed in stem cells populations of leukemia and some solid tumors. Up to now, 6 isoforms of ALDH1 have been reported. However, the expression patterns and the identity of ALDH1 isoenzymes contributing to ALDH1 activity, as well as the prognostic values of ALDH1 isoenzymes in cancers all remain to be elucidated. Here, we studied the expressions of ALDH1 transcripts in gastric cancer (GC) compared with the normal controls using the ONCOMINE database. Through the Kaplan-Meier plotter database, which contains updated gene expression data and survival information of 876 GC patients, we also investigated the prognostic values of ALDH1 isoenzymes in GC patients. It was found that when compared with normal tissues, ALDH1A1 mRNA expression was downregulated, whereas ALDH1A3 and ALDH1B1 were upregulated in GC patients. In survival analyses, high ALDH1A1 and ALDH1B1 expressions were associated with better overall survival (OS) in all GC patients. In addition, high transcription activity of ALDH1A1 predicted better OS in gastric intestinal type adenocarcinoma, but not in diffuse gastric adenocarcinoma. GC patients with high mRNA level of ALDH1B1 showed better OS in gastric intestinal type, and worse OS in diffuse type. Oppositely, high transcription activities of ALDH1A2, ALDH1A3 and ALDH1L1 predicted worsen overall survival in GC patients, suggesting that these isoenzymes might be responsible mainly for the ALDH1 activities in GC. These data provides ALDH1A2, ALDH1A3 and ALDH1L1 as excellent potential targets for individualized treatment of GC patients.

Impaired aldehyde dehydrogenase 1 subfamily member 2A-dependent retinoic acid signaling is related with a mesenchymal-like phenotype and an unfavorable prognosis of head and neck squamous cell carcinoma

Background

An inverse correlation between expression of the aldehyde dehydrogenase 1 subfamily A2 (ALDH1A2) and gene promoter methylation has been identified as a common feature of oropharyngeal squamous cell carcinoma (OPSCC). Moreover, low ALDH1A2 expression was associated with an unfavorable prognosis of OPSCC patients, however the causal link between reduced ALDH1A2 function and treatment failure has not been addressed so far.

Methods

Serial sections from tissue microarrays of patients with primary OPSCC (n = 101) were stained by immunohistochemistry for key regulators of retinoic acid (RA) signaling, including ALDH1A2. Survival with respect to these regulators was investigated by univariate Kaplan-Meier analysis and multivariate Cox regression proportional hazard models. The impact of ALDH1A2-RAR signaling on tumor-relevant processes was addressed in established tumor cell lines and in an orthotopic mouse xenograft model.

Results

Immunohistochemical analysis showed an improved prognosis of ALDH1A2^high OPSCC only in the presence of CRABP2, an intracellular RA transporter. Moreover, an ALDH1A2^highCRABP2^high staining pattern served as an independent predictor for progression-free (HR: 0.395, p = 0.007) and overall survival (HR: 0.303, p = 0.002), suggesting a critical impact of RA metabolism and signaling on clinical outcome. Functionally, ALDH1A2 expression and activity in tumor cell lines were related to RA levels. While administration of retinoids inhibited clonogenic growth and proliferation, the pharmacological inhibition of ALDH1A2-RAR signaling resulted in loss of cell-cell adhesion and a mesenchymal-like phenotype. Xenograft tumors derived from FaDu cells with stable silencing of ALDH1A2 and primary tumors from OPSCC patients with low ALDH1A2 expression exhibited a mesenchymal-like phenotype characterized by vimentin expression.

Conclusions

This study has unraveled a critical role of ALDH1A2-RAR signaling in the pathogenesis of head and neck cancer and our data implicate that patients with ALDH1A2^low tumors might benefit from adjuvant treatment with retinoids.

Electronic supplementary material

The online version of this article (doi:10.1186/s12943-015-0476-0) contains supplementary material, which is available to authorized users.

Hepatitis C virus upregulates B-cell receptor signaling: a novel mechanism for HCV-associated B-cell lymphoproliferative disorders

B-cell receptor (BCR) signaling is essential for the development of B cells and has a critical role in B-cell neoplasia. Increasing evidence indicates an association between chronic hepatitis C virus (HCV) infection and B-cell lymphoma, however, the mechanisms by which HCV causes B-cell lymphoproliferative disorder are still unclear. Herein, we demonstrate the expression of HCV viral proteins in B cells of HCV-infected patients and show that HCV upregulates BCR signaling in human primary B cells. HCV nonstructural protein NS3/4A interacts with CHK2 and downregulates its activity, modulating HuR posttranscriptional regulation of a network of target mRNAs associated with B-cell lymphoproliferative disorders. Interestingly, the BCR signaling pathway was found to have the largest number of transcripts with increased association with HuR and was upregulated by NS3/4A. Our study reveals a previously unidentified role of NS3/4A in regulation of host BCR signaling during HCV infection, contributing to a better understanding of the molecular mechanisms underlying HCV-associated B-cell lymphoproliferative disorders.

Alcohol exposure in utero perturbs retinoid homeostasis in adult rats

BACKGROUND

Maternal alcohol exposure and adult alcohol intake have been shown to perturb the metabolism of various micro- and macro-nutrients, including vitamin A and its derivatives (retinoids). Therefore, it has been hypothesized that the well-known detrimental consequences of alcohol consumption may be due to deregulations of the metabolism of such nutrients rather than to a direct effect of alcohol. Alcohol exposure in utero also has long-term harmful consequences on the health of the offspring with mechanisms that have not been fully clarified. Disruption of tissue retinoid homeostasis has been linked not only to abnormal embryonic development, but also to various adult pathological conditions, including cancer, metabolic disorders and abnormal lung function. We hypothesized that prenatal alcohol exposure may permanently perturb tissue retinoid metabolism, predisposing the offspring to adult chronic diseases.

METHODS

Serum and tissues (liver, lung and prostate from males; liver and lung from females) were collected from 60-75 day-old sprague dawley rats born from dams that were: (I) fed a liquid diet containing 6.7% alcohol between gestational day 7 and 21; or (II) pair-fed with isocaloric liquid diet during the same gestational window; or (III) fed ad libitum with regular rat chow diet throughout pregnancy. Serum and tissue retinoid levels were analyzed by reverse-phase high-performance liquid chromatography (HPLC). Serum retinol-binding protein (RBP) levels were measured by western blot analysis, and liver, lung and prostate mRNA levels of lecithin-retinol acyltransferase (LRAT) were measured by qPCR.

RESULTS

Retinyl ester levels were significantly reduced in the lung of both males and females, as well as in the liver and ventral prostate of males born from alcohol-fed dams. Tissue LRAT mRNA levels remained unchanged upon maternal alcohol treatment.

CONCLUSIONS

Prenatal alcohol exposure in rats affects retinoid metabolism in adult life, in a tissue- and sex-dependent manner. We propose that the alcohol-induced perturbations of vitamin A metabolism may predispose to detrimental consequnces on adult health.

Acetaldehyde and retinaldehyde-metabolizing enzymes in colon and pancreatic cancers

Colorectal cancer (CRC) and pancreatic cancer are two very significant contributors to cancer-related deaths. Chronic alcohol consumption is an important risk factor for these cancers. Ethanol is oxidized primarily by alcohol dehydrogenases to acetaldehyde, an agent capable of initiating tumors by forming adducts with proteins and DNA. Acetaldehyde is metabolized by ALDH2, ALDH1B1, and ALDH1A1 to acetate. Retinoic acid (RA) is required for cellular differentiation and is known to arrest tumor development. RA is synthesized from retinaldehyde by the retinaldehyde dehydrogenases, specifically ALDH1A1, ALDH1A2, ALDH1A3, and ALDH8A1. By eliminating acetaldehyde and generating RA, ALDHs can play a crucial regulatory role in the initiation and progression of cancers. ALDH1 catalytic activity has been used as a biomarker to identify and isolate normal and cancer stem cells; its presence in a tumor is associated with poor prognosis in colon and pancreatic cancer. In summary, these ALDHs are not only biomarkers for CRC and pancreatic cancer but also play important mechanistic role in cancer initiation, progression, and eventual prognosis.

Involvement of aldehyde dehydrogenase 1A2 in the regulation of cancer stem cell properties in neuroblastoma

Despite the introduction of 13-cis-retinoic acid (13-cis-RA) into the current chemotherapy, more than half of high-risk neuroblastoma patients have experienced tumor relapses driven by chemoresistant cancer stem cells (CSCs) that can be isolated by their ability to grow as spheres. Although aldehyde dehydrogenase (ALDH) has been used to characterize CSCs in certain cancers, ALDH remains elusive in neuroblastoma. In the present study, we determined ALDH activity and expression of its 19 isoforms in spheres and parental cells of neuroblastoma. ALDH activity and several ALDH isoforms were consistently induced in spheres of different neuroblastoma cells. While ALDH1A2, ALDH1L1 and ALDH3B2 expression was consistently induced in spheres and associated with the sphere and colony formation, only ALDH1A2 expression was significantly correlated with the poor prognosis of neuroblastoma patients. ALDH1A2 expression was further associated with the growth and undifferentiation of neuroblastoma xenografts and the resistance of neuroblastoma cells to 13-cis-RA. These results suggest that ALDH1A2 is involved in the regulation of CSC properties in neuroblastoma.

Importance of ALDH1A enzymes in determining human testicular retinoic acid concentrations

Retinoic acid (RA), the active metabolite of vitamin A, is required for spermatogenesis and many other biological processes. RA formation requires irreversible oxidation of retinal to RA by aldehyde dehydrogenase enzymes of the 1A family (ALDH1A). While ALDH1A1, ALDH1A2, and ALDH1A3 all form RA, the expression pattern and relative contribution of these enzymes to RA formation in the testis is unknown. In this study, novel methods to measure ALDH1A protein levels and intrinsic RA formation were used to accurately predict RA formation velocities in individual human testis samples and an association between RA formation and intratesticular RA concentrations was observed. The distinct localization of ALDH1A in the testis suggests a specific role for each enzyme in controlling RA formation. ALDH1A1 was found in Sertoli cells, while only ALDH1A2 was found in spermatogonia, spermatids, and spermatocytes. In the absence of cellular retinol binding protein (CRBP)1, ALDH1A1 was predicted to be the main contributor to intratesticular RA formation, but when CRBP1 was present, ALDH1A2 was predicted to be equally important in RA formation as ALDH1A1. This study provides a comprehensive novel methodology to evaluate RA homeostasis in human tissues and provides insight to how the individual ALDH1A enzymes mediate RA concentrations in specific cell types.

Sex specific retinoic acid signaling is required for the initiation of urogenital sinus bud development

The mammalian urogenital sinus (UGS) develops in a sex specific manner, giving rise to the prostate in the male and the sinus vagina in the embryonic female. Androgens, produced by the embryonic testis, have been shown to be crucial to this process. In this study we show that retinoic acid signaling is required for the initial stages of bud development from the male UGS. Enzymes involved in retinoic acid synthesis are expressed in the UGS mesenchyme in a sex specific manner and addition of ligand to female tissue is able to induce prostate-like bud formation in the absence of androgens, albeit at reduced potency. Functional studies in mouse organ cultures that faithfully reproduce the initiation of prostate development indicate that one of the roles of retinoic acid signaling in the male is to inhibit the expression of Inhba, which encodes the βA subunit of Activin, in the UGS mesenchyme. Through in vivo genetic analysis and culture studies we show that inhibition of Activin signaling in the female UGS leads to a similar phenotype to that of retinoic acid treatment, namely bud formation in the absence of androgens. Our data also reveals that both androgens and retinoic acid have extra independent roles to that of repressing Activin signaling in the development of the prostate during fetal stages. This study identifies a novel role for retinoic acid as a mesenchymal factor that acts together with androgens to determine the position and initiation of bud development in the male UGS epithelia.

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We show that sex specific retinoic acid is required for male UGS bud initiation.

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An increase in retinoic acid can lead to prostate-like formation in females.

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We find that activin repression is a downstream target of RA signalling.

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RA is a novel mesenchymal signal regulating bud initiation along the UGS.

Aldehyde dehydrogenases in cancer: an opportunity for biomarker and drug development?

Aldehyde dehydrogenases (ALDHs) belong to a superfamily of 19 isozymes that are known to participate in many physiologically important biosynthetic processes including detoxification of specific endogenous and exogenous aldehyde substrates. The high expression levels of an emerging number of ALDHs in various cancer tissues suggest that these enzymes have pivotal roles in cancer cell survival and progression. Mapping out the heterogeneity of tumours and their cancer stem cell (CSC) component will be key to successful design of strategies involving therapeutics that are targeted against specific ALDH isozymes. This review summarises recent progress in ALDH-focused cancer research and discovery of small-molecule-based inhibitors.

Aldehyde dehydrogenase 3A1 associates with prostate tumorigenesis

Background:

Accumulating evidence demonstrates high levels of aldehyde dehydrogense (ALDH) activity in human cancer types, in part, because of its association with cancer stem cells. Whereas ALDH1A1 and ALDH7A1 isoforms were reported to associate with prostate tumorigenesis, whether other ALDH isoforms are associated with prostate cancer (PC) remains unclear.

Methods:

ALDH3A1 expression was analysed in various PC cell lines. Xenograft tumours and 54 primary and metastatic PC tumours were stained using immunohistochemistry for ALDH3A1 expression.

Results:

In comparison with the non-stem counterparts, a robust upregulation of ALDH3A1 was observed in DU145-derived PC stem cells (PCSCs). As DU145 PCSCs produced xenograft tumours with more advanced features compared with those derived from DU145 cells, higher levels of ALDH3A1 were detected in the former; a dramatic elevation of ALDH3A1 occurred in DU145 cell-derived lung metastasis compared with local xenograft tumours. Furthermore, while ALDH3A1 was not observed in prostate glands, ALDH3A1 was clearly present in PIN, and further increased in carcinomas. In comparison with the paired local carcinomas, ALDH3A1 was upregulated in lymph node metastatic tumours; the presence of ALDH3A1 in bone metastatic PC was also demonstrated.

Conclusions:

We report here the association of ALDH3A1 with PC progression.

A new spontaneously transformed syngeneic model of high-grade serous ovarian cancer with a tumor-initiating cell population

Improving screening and treatment options for patients with epithelial ovarian cancer has been a major challenge in cancer research. Development of novel diagnostic and therapeutic approaches, particularly for the most common subtype, high-grade serous ovarian cancer (HGSC), has been hampered by controversies over the origin of the disease and a lack of spontaneous HGSC models to resolve this controversy. Over long-term culture in our laboratory, an ovarian surface epithelial (OSE) cell line spontaneously transformed OSE (STOSE). The objective of this study was to determine if the STOSE cell line is a good model of HGSC. STOSE cells grow faster than early passage parental M0505 cells with a doubling time of 13 and 48 h, respectively. STOSE cells form colonies in soft agar, an activity for which M0505 cells have negligible capacity. Microarray analysis identified 1755 down-regulated genes and 1203 up-regulated genes in STOSE compared to M0505 cells, many associated with aberrant Wnt/β-catenin and Nf-κB signaling. Upregulation of Ccnd1 and loss of Cdkn2a in STOSE tumors is consistent with changes identified in human ovarian cancers by The Cancer Genome Atlas. Intraperitoneal injection of STOSE cells into severe combined immunodeficient and syngeneic FVB/N mice produced cytokeratin+, WT1+, inhibin-, and PAX8+ tumors, a histotype resembling human HGSC. Based on evidence that a SCA1+ stem cell-like population exists in M0505 cells, we examined a subpopulation of SCA1+ cells that is present in STOSE cells. Compared to SCA1- cells, SCA1+ STOSE cells have increased colony-forming capacity and form palpable tumors 8 days faster after intrabursal injection into FVB/N mice. This study has identified the STOSE cells as the first spontaneous murine model of HGSC and provides evidence for the OSE as a possible origin of HGSC. Furthermore, this model provides a novel opportunity to study how normal stem-like OSE cells may transform into tumor-initiating cells.

Contributions of epithelial-mesenchymal transition and cancer stem cells to the development of castration resistance of prostate cancer

An important clinical challenge in prostate cancer therapy is the inevitable transition from androgen-sensitive to castration-resistant and metastatic prostate cancer. Albeit the androgen receptor (AR) signaling axis has been targeted, the biological mechanism underlying the lethal event of androgen independence remains unclear. New emerging evidences indicate that epithelial-to-mesenchymal transition (EMT) and cancer stem cells (CSCs) play crucial roles during the development of castration-resistance and metastasis of prostate cancer. Notably, EMT may be a dynamic process. Castration can induce EMT that may enhance the stemness of CSCs, which in turn results in castration-resistance and metastasis. Reverse of EMT may attenuate the stemness of CSCs and inhibit castration-resistance and metastasis. These prospective approaches suggest that therapies target EMT and CSCs may cast a new light on the treatment of castration-resistant prostate cancer (CRPC) in the future. Here we review recent progress of EMT and CSCs in CRPC.

Striking growth-inhibitory effects of minocycline on human prostate cancer cell lines

OBJECTIVE

To elucidate a hypothetical link between retinoic acid (RA) signaling and minocycline for targeting prostate carcinoma (PCA). RA signaling has been implicated in growth-inhibition of malignant PCA, and intracellular RA homeostasis has been investigated as a potential therapeutic target. Minocycline is a tetracycline antibiotic with pleiotropic actions in many tissues and reaches comparably high levels in human prostate tissue. Interestingly, minocycline exhibits the rare side effect of a pseudotumor cerebri, which is otherwise known to occur from vitamin A intoxication or in retinoid therapy. Therefore, we hypothesized minocycline to putatively interact with intracellular RA homeostasis in PCA.

METHODS

Using LN-CAP, DU-145, and PC-3 cell lines, effects of minocycline on microsomal RA metabolism and on cell growth were assessed in vitro.

RESULTS

Minocycline was identified to potently inhibit cell growth, at concentrations within the range of tissue levels readily reached under standard therapeutic conditions. In vitro inhibition experiments revealed inhibition of RA breakdown, yet only at comparably high concentrations of minocycline. Using all trans-RA, RA metabolism inhibitor liarozole, and different retinoid receptor antagonists, the putative RA-dependent effects of minocycline were further evaluated and confirmed to be independent of RA signaling.

CONCLUSION

Our findings add to the growing body of evidence for the many pleiotropic actions of minocycline. In view of the striking effects of minocycline on cell growth in PCA cell lines in vitro and its relatively safe side effect profile, the use of minocycline for targeting PCA should be timely clinically evaluated.

Epigenomic alterations in localized and advanced prostate cancer

Although prostate cancer (PCa) is the second leading cause of cancer death among men worldwide, not all men diagnosed with PCa will die from the disease. A critical challenge, therefore, is to distinguish indolent PCa from more advanced forms to guide appropriate treatment decisions. We used Enhanced Reduced Representation Bisulfite Sequencing, a genome-wide high-coverage single-base resolution DNA methylation method to profile seven localized PCa samples, seven matched benign prostate tissues, and six aggressive castration-resistant prostate cancer (CRPC) samples. We integrated these data with RNA-seq and whole-genome DNA-seq data to comprehensively characterize the PCa methylome, detect changes associated with disease progression, and identify novel candidate prognostic biomarkers. Our analyses revealed the correlation of cytosine guanine dinucleotide island (CGI)-specific hypermethylation with disease severity and association of certain breakpoints (deletion, tandem duplications, and interchromosomal translocations) with DNA methylation. Furthermore, integrative analysis of methylation and single-nucleotide polymorphisms (SNPs) uncovered widespread allele-specific methylation (ASM) for the first time in PCa. We found that most DNA methylation changes occurred in the context of ASM, suggesting that variations in tumor epigenetic landscape of individuals are partly mediated by genetic differences, which may affect PCa disease progression. We further selected a panel of 13 CGIs demonstrating increased DNA methylation with disease progression and validated this panel in an independent cohort of 20 benign prostate tissues, 16 PCa, and 8 aggressive CRPCs. These results warrant clinical evaluation in larger cohorts to help distinguish indolent PCa from advanced disease.

Cytochrome p450 cyp26a1 alters spinal motor neuron subtype identity in differentiating embryonic stem cells

The ability to differentiate embryonic stem cells (ESCs) into specific cell types is critical for improved regenerative medicine strategies, cancer chemotherapeutic approaches, and regimens to combat chronic diseases associated with aging. Subclasses of motor neurons (MNs) are generated at different positions along the rostrocaudal axis of the spinal cord, and the signals that specify MN subtype fates remain poorly defined. We show here that the cytochrome P450 enzyme Cyp26a1, which metabolizes all-trans-retinoic acid (RA) and thereby reduces RA levels, plays a crucial role in specifying MN columnar subtypes. Lack of Cyp26a1 in ESCs during differentiation to spinal MNs increases Aldh1a2 (RALDH2) and Hoxc6, markers of the Hox-dependent, lateral motor column (LMC) subtype identity. In contrast, Lhx3, a marker for median motor column identity, showed lower expression in Cyp26a1(-/-)-derived MNs compared with WT. Without Cyp26a1, an increase in intracellular RA concentration plus sonic hedgehog agonist treatment confer an LMC fate on differentiating MNs. Our data suggest a strategy for increasing LMC-type MNs from ESCs by blocking Cyp26a1 in cell replacement/ESC differentiation therapy to treat neurodegenerative diseases, such as amyotrophic lateral sclerosis.

HPV-related methylation signature predicts survival in oropharyngeal squamous cell carcinomas

High-risk types of human papilloma virus (HPV) are increasingly associated with oropharyngeal squamous cell carcinoma (OPSCC). Strikingly, patients with HPV-positive OPSCC are highly curable with ionizing radiation and have better survival compared with HPV-negative patients, but the underlying molecular mechanisms remain poorly understood. We applied an array-based approach to monitor global changes in CpG island hypermethylation between HPV-negative and HPV-positive OPSCCs and identified a specific pattern of differentially methylated regions that critically depends on the presence of viral transcripts. HPV-related alterations were confirmed for the majority of candidate gene promoters by mass spectrometric, quantitative methylation analysis. There was a significant inverse correlation between promoter hypermethylation of ALDH1A2, OSR2, GATA4, GRIA4, and IRX4 and transcript levels. Interestingly, Kaplan-Meier analysis revealed that a combined promoter methylation pattern of low methylation levels in ALDH1A2 and OSR2 promoters and high methylation levels in GATA4, GRIA4, and IRX4 promoters was significantly correlated with improved survival in 3 independent patient cohorts. ALDH1A2 protein levels, determined by immunohistochemistry on tissue microarrays, confirmed the association with clinical outcome. In summary, our study highlights specific alterations in global gene promoter methylation in HPV-driven OPSCCs and identifies a signature that predicts the clinical outcome in OPSCCs.

Quantitative proteomics reveals that enzymes of the ketogenic pathway are associated with prostate cancer progression

Prostate cancer is the most common malignancy and the second leading cause of cancer-related deaths in men. One common treatment is androgen-deprivation therapy, which reduces symptoms in most patients. However, over time, patients develop tumors that are androgen-independent and ultimately fatal. The mechanisms that cause this transition remain largely unknown, and as a result, there are no effective treatments against androgen-independent prostate cancer. As a model platform, we used the LNCaP cell line and its androgen-independent derivative, LNCaP-SF. Utilizing stable isotope labeling with amino acids in cell culture coupled to mass spectrometry, we assessed the differential global protein expression of the two cell lines. Our proteomic analysis resulted in the quantification of 3355 proteins. Bioinformatic prioritization resulted in 42 up-regulated and 46 down-regulated proteins in LNCaP-SF cells relative to LNCaP cells. Our top candidate, HMGCS2, an enzyme involved in ketogenesis, was found to be 9-fold elevated in LNCaP-SF cells, based on peptide ratios. After analyzing the remaining enzymes of this pathway (ACAT1, BDH1, HMGCL, and OXCT1), we observed increased expression of these proteins in the LNCaP-SF cells, which was further verified using Western blotting. To determine whether these enzymes were up-regulated in clinical samples, we performed quantitative PCR and immunohistochemistry on human prostate cancer tissues, from which we observed significantly increased transcript and protein levels in high-grade cancer (Gleason grade ≥ 8). In addition, we observed significant elevation of these enzymes in the LuCaP 96AI castration-resistant xenograft. Further assessment of ACAT1 on human castration-resistant metastatic prostate cancer tissues revealed substantially elevated expression of ACAT1 in these specimens. Taken together, our results indicate that enzymes of the ketogenic pathway are up-regulated in high-grade prostate cancer and could serve as potential tissue biomarkers for the diagnosis or prognosis of high-grade disease.

Astrocytes as a regulated source of retinoic acid for the brain

Retinaldehyde dehydrogenases (RALDH) catalyze the synthesis of the regulatory factor retinoic acid (RA). Cultured astrocytes express several of the RALDH enzyme family, and it has been assumed that this can be extrapolated to astrocytes in vivo. However, this study finds that few astrocytes in the rodent brain express detectable RALDH enzymes, and only when these cells are grown in culture are these enzymes upregulated. Factors controlling the expression of the RALDHs in cultured astrocytes were explored to determine possible reasons for differences between in vitro versus in vivo expression. Retinoids were found to feedback to suppress several of the RALDHs, and physiological levels of retinoids may be one route by which astrocytic RALDHs are maintained at low levels. In the case of RALDH2, in vivo reduction of vitamin A levels in rats resulted in an increase in astrocyte RALDH2 expression in the hippocampus. Other factors though are likely to control RALDH expression. A shift in astrocytic RALDH subcellular localization is a potential mechanism for regulating RA signaling. Under conditions of vitamin A deficiency, RALDH2 protein moved from the cytoplasm to the nucleus where it may synthesize RA at the site of the nuclear RA receptors. Similarly, in conditions of oxidative stress RALDH1 and RALDH2 moved from the cytoplasm to a predominantly nuclear position. Thus, the RALDHs have been revealed to be dynamic in their expression in astrocytes where they may maintain retinoid homeostasis in the brain.

DNA methylation in promoter region as biomarkers in prostate cancer

The prostate gland is the most common site of cancer and the second leading cause of cancer death in American men. Recent emerging molecular biological technologies help us to know that epigenetic alterations such as DNA methylation within the regulatory (promoter) regions of genes are associated with transcriptional silencing in cancer. Promoter hypermethylation of critical pathway genes could be potential biomarkers and therapeutic targets for prostate cancer. In this chapter, we updated current information on methylated genes associated with the development and progression of prostate cancer. Over 40 genes have been investigated for methylation in promoter region in prostate cancer. These methylated genes are involved in critical pathways, such as DNA repair, metabolism, and invasion/metastasis. The role of hypermethylated genes in regulation of critical pathways in prostate cancer is discussed. These findings may provide new information of the pathogenesis, the exciting potential to be predictive and to provide personalized treatment of prostate cancer. Indeed, some epigenetic alterations in prostate tumors are being translated into clinical practice for therapeutic use.

Retinoids, retinoic acid receptors, and cancer

Retinoids (i.e., vitamin A, all-trans retinoic acid, and related signaling molecules) induce the differentiation of various types of stem cells. Nuclear retinoic acid receptors mediate most but not all of the effects of retinoids. Retinoid signaling is often compromised early in carcinogenesis, which suggests that a reduction in retinoid signaling may be required for tumor development. Retinoids interact with other signaling pathways, including estrogen signaling in breast cancer. Retinoids are used to treat cancer, in part because of their ability to induce differentiation and arrest proliferation. Delivery of retinoids to patients is challenging because of the rapid metabolism of some retinoids and because epigenetic changes can render cells retinoid resistant. Successful cancer therapy with retinoids is likely to require combination therapy with drugs that regulate the epigenome, such as DNA methyltransferase and histone deacetylase inhibitors, as well as classical chemotherapeutic agents. Thus, retinoid research benefits both cancer prevention and cancer treatment.

p27(Kip1) deficiency promotes prostate carcinogenesis but does not affect the efficacy of retinoids in suppressing the neoplastic process

BACKGROUND

p27 is a cell cycle suppressor gene, whose protein is a negative regulator of cyclin/cdk complexes. p27 is also a potential target of retinoids in cancer prevention studies. In benign prostate hyperplasia (BPH), and in most carcinomas, p27(Kip1) is down-regulated, suggesting its potential resistance to retinoids. To test this hypothesis, we examined the efficacy of 9-cis retinoic acid (9cRA) to suppress prostate cell proliferation (PECP) and carcinogenesis in p27(Kip1) deficient mice.

METHODS

p27(Kip1) deficient (-/-), heterozygous (+/-) and homozygous (+/+) mice were treated for 7 days with testosterone, 9cRA, or with both, and cell proliferation in dorsolateral prostate (DLP) was determined by BrdU labeling. Prostate carcinogenesis was induced by N-Methyl-N-Nitrosourea (MNU) and hormone stimulation.

RESULTS

PECP in DLP of two-month-old mice of all genotypes was similar but significantly increased in old p27-/- mice only. Testosterone treatment increased PECP in all three p27 genotypes with the highest values in p27-/- mice. p27(Kip1) deficiency did not affect the response of PEC to 9cRA and to 9cRA+testosterone. The decrease of p27(Kip1) in p27+/- and p27-/- mice progressively increased the incidence and frequency of PIN and tumors. 9cRA suppressed PIN in all three p27 genotypes and this was associated with decreased PECP and increased cellular senescence.

CONCLUSIONS

This data indicates that p27(Kip1) deficiency promotes prostate cell proliferation and carcinogenesis but does not affect 9cRA's potential to suppress prostate carcinogenesis, suggesting that patients with PIN and carcinomas lacking or having a low level of p27(Kip1) expression may also benefit from clinical trials with retinoids.