Retinoids, retinoic acid receptors, and cancer

Retinoic acid elicits a coordinated expression of gut homing markers on T lymphocytes of Zambian men receiving oral Vivotif, but not Rotarix, Dukoral or OPVERO vaccines

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ATRA increased vaccine specific IgA in gut secretions to Vivotif but not Dukoral or Rotarix.

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ATRA increased α4β7 and CCR9 gut marker expression in a coordinated manner only when given simultaneously with Vivotif vaccine.

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In individuals with coordinated gut marker expression Vivotif specific IgA increase was much stronger.

All-trans retinoic acid (ATRA) up-regulates, in laboratory animals, the expression of the gut homing markers α4β7 integrin and CCR9 on lymphocytes, increasing their gut tropism. Here, we show that, in healthy adult volunteers, ATRA induced an increase of these gut homing markers on T cells in vivo in a time dependent manner. The coordinated increase of α4β7 and CCR9 by ATRA was seen in 57% (12/21) of volunteers and only when given together with an oral Vivotif vaccine. When this coordinated response to ATRA and Vivotif vaccine was present, it was strongly correlated with the gut immunoglobulin A (IgA) specific response to vaccine LPS (ρ = 0.82; P = 0.02). Using RNA-Seq analysis of whole blood transcription, patients receiving ATRA and Vivotif in conjunction showed transcriptomic changes in immune-related pathways, particularly including interferon α/β signaling pathway, membrane-ECM interactions and immune hubs. These results suggest that exogenous ATRA can be used to manipulate responses to a subclass of oral vaccines, so far limited to a live attenuated Vivotif vaccine.

Histone Deacetylases as New Therapeutic Targets in Triple-negative Breast Cancer: Progress and Promises

Triple-negative breast cancer (TNBC) lacks expression of estrogen receptor (ER), progesterone receptor (PR) and HER2 gene. It comprises approximately 15-20% of breast cancers (BCs). Unfortunately, TNBC's treatment continues to be a clinical problem because of its relatively poor prognosis, its aggressiveness and the lack of targeted therapies, leaving chemotherapy as the mainstay of treatment. It is essential to find new therapies against TNBC, in order to surpass the resistance and the invasiveness of already existing therapies. Given the fact that epigenetic processes control both the initiation and progression of TNBC, there is an increasing interest in the mechanisms, molecules and signaling pathways that participate at the epigenetic modulation of genes expressed in carcinogenesis. The acetylation of histone proteins provokes the transcription of genes involved in cell growth, and the expression of histone deacetylases (HDACs) is frequently up-regulated in many malignancies. Unfortunately, in the field of BC, HDAC inhibitors have shown limited effect as single agents. Nevertheless, their use in combination with kinase inhibitors, autophagy inhibitors, ionizing radiation, or two HDAC inhibitors together is currently being evaluated. HDAC inhibitors such as suberoylanilidehydroxamic acid (SAHA), sodium butyrate, mocetinostat, panobinostat, entinostat, YCW1 and N-(2-hydroxyphenyl)-2-propylpentanamide have shown promising therapeutic outcomes against TNBC, especially when they are used in combination with other anticancer agents. More studies concerning HDAC inhibitors in breast carcinomas along with a more accurate understanding of the TNBC's pathobiology are required for the possible identification of new therapeutic strategies.

Quantitative proteomics analysis of differentially expressed proteins in ruptured and unruptured cerebral aneurysms by iTRAQ

The underlying pathophysiological mechanisms involved in cerebral aneurysms rupture remain unclear. This study was performed to investigate the differentially expressed proteins between ruptured and unruptured aneurysms using quantitative proteomics. The aneurysmal walls of six ruptured aneurysms and six unruptured aneurysms were collected during the surgical operation. The isobaric tags for relative and absolute quantification (iTRAQ) were used to identify the differentially expressed proteins and western blotting was performed to validate the expression of the proteins of interest. Bioinformatics analysis of the differentially expressed proteins was also performed using the KEGG database and GO database. Between ruptured and unruptured aneurysms, 169 proteins were found differently expressed, including 74 up-regulated proteins and 95 down-regulated proteins with a fold change ≥ 2 and p value ≤ .05. KEGG pathway analysis revealed that phagosome, focal adhesion and ECM-receptor interaction were the most common pathways involved in aneurysm rupture. In addition, the differential expressions of ITGB3, CRABP1 and S100A9 were validated by western blotting. Through the iTRAQ method, we found that inflammatory responses and cell-matrix interactions may play a significant role in the rupture of cerebral aneurysms. These findings provide a basis for better understanding of pathophysiological mechanisms associated with aneurysm rupture.

BIOLOGICAL SIGNIFICANCE

Intracranial aneurysm is the leading cause of life-threating subarachnoid hemorrhage which can cause 45% patients die within 30 days and severe morbidity in long-term survivors. With a high prevalence ranging from 1% to 5% in general population, cerebral aneurysm has become a widespread health hazard over past decades. Though great advances have been achieved in the diagnosis and treatment of this disease, the underlying pathophysiological mechanisms of aneurysm rupture remains undetermined and a lot of uncertainty still exists surrounding the treatment of unruptured cerebral aneurysms. Clarifying the mechanism associated with aneurysm rupture is important for estimating the rupture risk, as well as the development of new treatment strategy. Some previous studies have analyzed the molecular differences between ruptured and unruptured IAs at gene and mRNA levels, but further comprehensive proteomic studies are relatively rare. Here we performed a comparative proteomics study to investigate the differentially expressed proteins between ruptured IAs (RIAs) and unruptured IAs (UIAs). Results of our present study will provide more insights into the pathogenesis of aneurysm rupture at protein level. With a better understanding of pathophysiological mechanisms associated with aneurysm rupture, some noninvasive treatment strategies may be developed in the future.

Ultrasound-enhanced delivery of doxorubicin/all-trans retinoic acid-loaded nanodiamonds into tumors

Aim: To build up a combined therapy strategy to address limitations of the enhanced permeability and retention (EPR) effect and improve the efficiency of tumor therapy. Materials & methods: A pH-sensitive nanocomplex for co-delivery of doxorubicin (DOX) and all-trans retinoic acid (ATRA) was developed based on nanodiamonds (DOX/ATRA-NDs) to enhance intracellular retention of drugs. Meanwhile, ultrasound was employed to enhance tumor vascular penetration of DOX-ATRA-NDs. Results: The distribution of DOX/ATRA-NDs in the tumor tissues increased threefold when ultrasound was applied at 1 MHz and 0.6 W/cm2. Comparing with unmodified chemotherapeutics, the combined therapy induced more tumor cells apoptosis and greater tumor growth inhibition in both liver and breast tumor models. Conclusion: DOX-ATRA-NDs demonstrate great potential in clinical applications.

Bexarotene inhibits the viability of non-small cell lung cancer cells via slc10a2/PPARγ/PTEN/mTOR signaling pathway

Background

Thirty to 40 % of non-small cell lung cancer (NSCLC) patients developed higher hypertriglyceridemia in the process of treatment with bexarotene. And bioinformatics studies discovered that the expression of slc10a2 was increased in high-grade hypertriglyceridemia patients. So, we will explore the mechanism which may involve in this process.

Methods

We constructed slc10a2 overexpressed A549 cells and H1299 cells as cell models, normal A549 cells and H1299 cells as control. Then we explored the effects of slc10a2 on A549 cells and H1299 cells behaviors, including proliferation, invasion and apoptosis. The expression of apoptotic related genes and anti-cancer genes also been detected.

Results

We found that the proliferation and migration were inhibited and the apoptosis of NSCLC cells was accelerated by bexarotene. In addition, overexpressed slc10a2 in NSCLC cells can further suppress the proliferation and migration, and promote apoptosis under the treatment of bexarotene. On the contrary, the opposite results were obtained after slc10a2 gene was silenced in NSCLC cells treated with bexarotene. Moreover, the expression of caspase 3, caspase 7, PTEN, P21, P53, LKB1, TSC2 were increased and the expression of Bcl-2, cyclin D1, c-FLIP were declined in NSCLC cells and slc10a2 overexpressed NSCLC cells with the treatment of bexarotene, and the opposite situations were seen after slc10a2 gene was silenced in NSCLC cells. The further studies revealed the increased expression of slc10a2 activated the expression of peroxisome proliferator-activated receptor γ (PPARγ), then up-regulated PTEN expression and down-regulated mTOR expression.

Conclusion

These results suggest that bexarotene inhibits the viability of lung cancer cells via slc10a2/PPARγ/PTEN/mTOR signaling pathway.

Electronic supplementary material

The online version of this article (10.1186/s12885-018-4224-x) contains supplementary material, which is available to authorized users.

Inhibition of cancer stem cell like cells by a synthetic retinoid

Developing novel drugs that can abrogate the growth and metastasis of malignant tumors is a major challenge for cancer researchers. Here we describe a novel synthetic retinoid, namely WYC-209, which inhibits proliferation of malignant murine melanoma tumor-repopulating cells (TRCs), known to resist conventional drug treatment, with an IC₅₀ of 0.19 μM in a dose-dependent manner. WYC-209 also inhibits proliferation of TRCs of human melanoma, lung cancer, ovarian cancer, and breast cancer in culture. Interestingly, the treated TRCs fail to resume growth even after the drug washout. Importantly, the molecule abrogates 87.5% of lung metastases of melanoma TRCs in immune-competent wild-type C57BL/6 mice at 0.22 mg kg^-1 without showing apparent toxicity. Pretreating the melanoma TRCs with retinoic acid receptor (RAR) antagonists or with RAR siRNAs blocks or reduces the inhibitory effect of the molecule, suggesting that the target of the molecule is RAR. WYC-209 induces TRC apoptosis and pretreating the TRCs with caspase 3 inhibitor or depleting caspase 3 with siRNAs substantially rescues growth of TRCs from WYC-209 inhibition, suggesting that WYC-209 induces TRCs apoptosis primarily via the caspase 3 pathway. Our findings demonstrate the promise of the new retinoid WYC-209 in treating malignant melanoma tumors with high efficacy and little toxicity.

Pro-apoptotic signaling induced by Retinoic acid and dsRNA is under the control of Interferon Regulatory Factor-3 in breast cancer cells

Breast cancer is one of the most lethal malignancies for women. Retinoic acid (RA) and double-stranded RNA (dsRNA) are considered signaling molecules with potential anticancer activity. RA, co-administered with the dsRNA mimic polyinosinic-polycytidylic acid (poly(I:C)), synergizes to induce a TRAIL (Tumor-Necrosis-Factor Related Apoptosis-Inducing Ligand)- dependent apoptotic program in breast cancer cells. Here, we report that RA/poly(I:C) co-treatment, synergically, induce the activation of Interferon Regulatory Factor-3 (IRF3) in breast cancer cells. IRF3 activation is mediated by a member of the pathogen recognition receptors, Toll-like receptor-3 (TLR3), since its depletion abrogates IRF3 activation by RA/poly(I:C) co-treatment. Besides induction of TRAIL, apoptosis induced by RA/poly(I:C) correlates with the increased expression of pro-apoptotic TRAIL receptors, TRAIL-R1/2, and the inhibition of the antagonistic receptors TRAIL-R3/4. IRF3 plays an important role in RA/poly(I:C)-induced apoptosis since IRF3 depletion suppresses caspase-8 and caspase-3 activation, TRAIL expression upregulation and apoptosis. Interestingly, RA/poly(I:C) combination synergizes to induce a bioactive autocrine/paracrine loop of type-I Interferons (IFNs) which is ultimately responsible for TRAIL and TRAIL-R1/2 expression upregulation, while inhibition of TRAIL-R3/4 expression is type-I IFN-independent. Our results highlight the importance of IRF3 and type-I IFNs signaling for the pro-apoptotic effects induced by RA and synthetic dsRNA in breast cancer cells.

Lunasin is a novel therapeutic agent for targeting melanoma cancer stem cells

Recent studies provide compelling evidence that melanoma is initiated and maintained by a small population of malignant cells called cancer-initiating cells (CICs) that exhibit stem-cell-like properties. Observations that CICs have a distinct biology when compared to that of the bulk tumor cells and, importantly, are resistant to chemotherapies and radiation, suggest that CICs are involved in invasion, metastasis, and ultimately relapse. Lunasin, a bioactive peptide present in soybean, has both chemopreventive activity and chemotherapeutic activity against multiple cancer types. In this study, we tested the potential of Lunasin to specifically target CICs in melanoma tumor cell populations. In vitro studies using human melanoma cell lines showed that Lunasin treatment decreased the size of a subpopulation of melanoma cells expressing the surrogate CIC marker, Aldehyde Dehydrogenase, concomitant with a reduction in the ability to form colonies in soft agar assays, and reduced tumor growth in mouse xenografts. Similarly, Lunasin inhibited colony formation by isolated melanoma CICs in soft agar and reduced oncosphere formation in vitro and substantially inhibited tumor growth in mouse xenografts. Mechanistic studies revealed that Lunasin treatment of isolated melanoma CICs induced expression of the melanocyte-associated differentiation markers Tyrosinase and Microphthalmia-associated Transcription Factor concomitant with reduced expression of the stemness factor NANOG. These findings document for the first time that Lunasin has significant therapeutic activity against melanoma by specifically targeting melanoma CICs, and inducing a more differentiated, non-CIC phenotype. Thus, Lunasin may represent a novel therapeutic option for both chemoresistant and advanced metastatic melanoma management.

Regulation of Active DNA Demethylation through RAR-Mediated Recruitment of a TET/TDG Complex

Retinoic acid (RA) plays important roles in development, growth, and homeostasis through regulation of the nuclear receptors for RA (RARs). Herein, we identify Hypermethylated in Cancer 1 (Hic1) as an RA-inducible gene. HIC1 encodes a tumor suppressor, which is often silenced by promoter hypermethylation in cancer. Treatment of cells with an RAR agonist causes a rapid recruitment of an RAR/RXR complex consisting of TDG, the lysine acetyltransferase CBP, and TET 1/2 to the Hic1 promoter. Complex binding coincides with a transient accumulation of 5fC/5caC and concomitant upregulation of Hic1 expression, both of which are TDG dependent. Furthermore, conditional deletion of Tdg in vivo is associated with Hic1 silencing and DNA hypermethylation of the Hic1 promoter. These findings suggest that the catalytic and scaffolding activities of TDG are essential for RA-dependent gene expression and provide important insights into the mechanisms underlying targeting of TET-TDG complexes.

CYP26C1 Is a Hydroxylase of Multiple Active Retinoids and Interacts with Cellular Retinoic Acid Binding Proteins

The clearance of retinoic acid (RA) and its metabolites is believed to be regulated by the CYP26 enzymes, but the specific roles of CYP26A1, CYP26B1, and CYP26C1 in clearing active vitamin A metabolites have not been defined. The goal of this study was to establish the substrate specificity of CYP26C1, and determine whether CYP26C1 interacts with cellular retinoic acid binding proteins (CRABPs). CYP26C1 was found to effectively metabolize all-trans retinoic acid (atRA), 9-cis-retinoic acid (9-cis-RA), 13-cis-retinoic acid, and 4-oxo-atRA with the highest intrinsic clearance toward 9-cis-RA. In comparison with CYP26A1 and CYP26B1, CYP26C1 resulted in a different metabolite profile for retinoids, suggesting differences in the active-site structure of CYP26C1 compared with other CYP26s. Homology modeling of CYP26C1 suggested that this is attributable to the distinct binding orientation of retinoids within the CYP26C1 active site. In comparison with other CYP26 family members, CYP26C1 was up to 10-fold more efficient in clearing 4-oxo-atRA (intrinsic clearance 153 μl/min/pmol) than CYP26A1 and CYP26B1, suggesting that CYP26C1 may be important in clearing this active retinoid. In support of this, CRABPs delivered 4-oxo-atRA and atRA for metabolism by CYP26C1. Despite the tight binding of 4-oxo-atRA and atRA with CRABPs, the apparent Michaelis-Menten constant in biological matrix (K_m) value of these substrates with CYP26C1 was not increased when the substrates were bound with CRABPs, in contrast to what is predicted by free drug hypothesis. Together these findings suggest that CYP26C1 is a 4-oxo-atRA hydroxylase and may be important in regulating the concentrations of this active retinoid in human tissues.

Association between Retinoic acid receptor-β hypermethylation and NSCLC risk: a meta-analysis and literature review

Emerging evidence indicates that Retinoic acid receptor-β (RARβ) is a tumor suppressor in many types of tumor. However, whether or not RARβ is a risk factor and is correlated to clinicopathological characteristics of non-small cell lung cancer (NSCLC) remains unclear. In this report, we performed a meta-analysis to determine the effects of RARβ hypermethylation on the incidence of NSCLC and clinicopathological characteristics in human NSCLC patients. Final valuation and analysis of 1780 cancer patients from 16 eligible studies was performed. RARβ hypermethylation was found to be significantly higher in NSCLC than in normal lung tissue, the pooled OR from 7 studies including 646 NSCLC and 580 normal lung tissues, OR = 6.05, 95% CI = 3.56-10.25, p<0.00001. RARβ hypermethylation was significantly higher in adenocarcinoma (AC) compared to squamous cell carcinoma (SCC), pooled OR is 0.68 (95% CI = 0.52-0.89, p = 0.005). RARβ hypermethylation was also found to occur significantly higher in smoker (n = 232) than non-smoker (n = 213) (OR = 2.46, 95% CI = 1.54-3.93, p = 0.0002). Our results indicate that RARβ hypermethylation correlates well with an increased risk in NSCLC patients. RARβ geneinactivation caused by RARβ methylation contributes the NSCLC tumorigenesis and may serve as a potential risk factor, diagnostic marker and drug target of NSCLC.

Interactive effects of 9-cis-retinoic acid and androgen on proliferation, differentiation, and apoptosis of LNCaP prostate cancer cells

9-cis-Retinoic acid (9cRA), which binds to both retinoic acid receptors and retinoic X receptors, inhibits prostate cancer induction in rats and reduces growth of prostate cancer cells. However, the nature of this growth inhibition and the interactive influence of androgens are not well defined and are the subject of this report. LNCaP and PC-3 cells were cultured and treated with a range of 9cRA concentrations for 3-6 days in the absence or presence of 5α-dehydrotestosterone. 9cRA inhibited cell proliferation in a dose-dependent manner, plateauing at 10 mol/l. Treatment of cells with 10 mol/l 9cRA inhibited 5α-dihydroxytestosterone (DHT)-stimulated proliferation, the effect of which was maximal at 10 mol/l DHT. Treatment of DHT (10 mol/l)-exposed cells with 9cRA caused a dose-dependent increase in prostate-specific antigen in the medium after 6 days, but not 3 days. 9cRA caused a dose-dependent increase in apoptotic cells stained with H33258 after 3 days, but not 6 days; however, on using flow cytometry, apoptosis was apparent at both 3 and 6 days. Flow cytometry also revealed interference of G0/G1 to S phase transition by 9cRA. Inhibition by 9cRA of anchorage-independent growth of PC-3 cells was also found; LNCaP cells did not grow colonies in soft agar. 9cRA inhibited growth and induced differentiation of human LNCaP prostate cancer cells in vitro and inhibited anchorage-independent growth of PC-3 cells. Because 9cRA and 13-cis-retinoic acid, which is retinoic acid receptor-selective, prevent prostate carcinogenesis in rats, and 13-cis-retinoic acid also inhibits growth of human prostate cancer cells, the RAR is a potential molecular target for prostate cancer prevention and therapy.

Molecular characterization and gene expression patterns of retinoid receptors, in normal and regenerating tissues of the sea cucumber, Holothuria glaberrima

Retinoic acid receptors (RAR) and retinoid X receptors (RXR) are ligand-mediated transcription factors that synchronize intricate signaling networks in metazoans. Dimer formation between these two nuclear receptors mediates the recruitment of co-regulatory complexes coordinating the progression of signaling cascades during developmental and regenerative events. In the present study we identified and characterized the receptors for retinoic acid in the sea cucumber Holothuria glaberrima; a model system capable of regenerative organogenesis during adulthood. Molecular characterizations revealed the presence of three isoforms of RAR and two of RXR as a consequence of alternative splicing events. Various analyses including: primary structure sequencing, phylogenetic analysis, protein domain prediction, and multiple sequence alignment further confirmed their identity. Semiquantitative reverse transcription PCR analysis of each receptor isoform herein identified showed that the retinoid receptors are expressed in all tissues sampled: the mesenteries, respiratory trees, muscles, gonads, and the digestive tract. During regenerative organogenesis two of the receptors (RAR-L and RXR-T) showed differential expression in the posterior segment while RAR-S is differentially expressed in the anterior segment of the intestine. This work presents the first description of the components relaying the signaling for retinoic acid within this model system.

Blocking the PAH2 domain of Sin3A inhibits tumorigenesis and confers retinoid sensitivity in triple negative breast cancer

Triple negative breast cancer (TNBC) frequently relapses locally, regionally or as systemic metastases. Development of targeted therapy that offers significant survival benefit in TNBC is an unmet clinical need. We have previously reported that blocking interactions between PAH2 domain of chromatin regulator Sin3A and the Sin3 interaction domain (SID) containing proteins by SID decoys result in EMT reversal, and re-expression of genes associated with differentiation. Here we report a novel and therapeutically relevant combinatorial use of SID decoys. SID decoys activate RARα/β pathways that are enhanced in combination with RARα-selective agonist AM80 to induce morphogenesis and inhibit tumorsphere formation. These findings correlate with inhibition of mammary hyperplasia and a significant increase in tumor-free survival in MMTV-Myc oncomice treated with a small molecule mimetic of SID (C16). Further, in two well-established mouse TNBC models we show that treatment with C16-AM80 combination has marked anti-tumor effects, prevents lung metastases and seeding of tumor cells to bone marrow. This correlated to a remarkable 100% increase in disease-free survival with a possibility of "cure" in mice bearing a TNBC-like tumor. Targeting Sin3A by C16 alone or in combination with AM80 may thus be a promising adjuvant therapy for treating or preventing metastatic TNBC.

Long-Chain Metabolites of Vitamin E: Metabolic Activation as a General Concept for Lipid-Soluble Vitamins?

Vitamins E, A, D and K comprise the class of lipid-soluble vitamins. For vitamins A and D, a metabolic conversion of precursors to active metabolites has already been described. During the metabolism of vitamin E, the long-chain metabolites (LCMs) 13'-hydroxychromanol (13'-OH) and 13'-carboxychromanol (13'-COOH) are formed by oxidative modification of the side-chain. The occurrence of these metabolites in human serum indicates a physiological relevance. Indeed, effects of the LCMs on lipid metabolism, apoptosis, proliferation and inflammatory actions as well as tocopherol and xenobiotic metabolism have been shown. Interestingly, there are several parallels between the actions of the LCMs of vitamin E and the active metabolites of vitamin A and D. The recent findings that the LCMs exert effects different from that of their precursors support their putative role as regulatory metabolites. Hence, it could be proposed that the mode of action of the LCMs might be mediated by a mechanism similar to vitamin A and D metabolites. If the physiological relevance and this concept of action of the LCMs can be confirmed, a general concept of activation of lipid-soluble vitamins via their metabolites might be deduced.

Why Differentiation Therapy Sometimes Fails: Molecular Mechanisms of Resistance to Retinoids

Retinoids represent a popular group of differentiation inducers that are successfully used in oncology for treatment of acute promyelocytic leukemia in adults and of neuroblastoma in children. The therapeutic potential of retinoids is based on their key role in the regulation of cell differentiation, growth, and apoptosis, which provides a basis for their use both in cancer therapy and chemoprevention. Nevertheless, patients treated with retinoids often exhibit or develop resistance to this therapy. Although resistance to retinoids is commonly categorized as either acquired or intrinsic, resistance as a single phenotypic feature is usually based on the same mechanisms that are closely related or combined in both of these types. In this review, we summarize the most common changes in retinoid metabolism and action that may affect the sensitivity of a tumor cell to treatment with retinoids. The availability of retinoids can be regulated by alterations in retinol metabolism or in retinoid intracellular transport, by degradation of retinoids or by their efflux from the cell. Retinoid effects on gene expression can be regulated via retinoid receptors or via other molecules in the transcriptional complex. Finally, the role of small-molecular-weight inhibitors of altered cell signaling pathways in overcoming the resistance to retinoids is also suggested.

Structural insights into a novel anticancer sulfonamide chalcone

Natural products have stood out due to their wide range of biological activities.

Polyamines and Cancer

This chapter provides an overview of how the polyamine pathway has been exploited as a target for the treatment and prevention of multiple forms of cancer, since this pathway is disrupted in all cancers. It is divided into three main sections. The first explores how the polyamine pathway has been targeted for chemotherapy, starting from the first drug to target it, difluoromethylornithine (DFMO) to the large variety of polyamine analogues that have been synthesised and tested throughout the years with all their potentials and pitfalls. The second section focuses on the use of polyamines as vectors for drug delivery. Knowing that the polyamine transport system is upregulated in cancers and that polyamines naturally bind to DNA, a range of polyamine analogues and polyamine-like structures have been synthesised to target epigenetic regulators, with encouraging results. Furthermore, the use of polyamines as transport vectors to introduce toxic/bioactive/fluorescent agents more selectively to the intended target in cancer cells is discussed. The last section concentrates on chemoprevention, where the different strategies that have been undertaken to interfere with polyamine metabolism and function for antiproliferative intervention are outlined and discussed.

Expression and Regulation of Retinoic Acid Receptor Responders in the Human Placenta

INTRODUCTION

Retinoic acid (RA) signaling through its receptors (RARA, RARB, RARG, and the retinoic X receptor RXRA) is essential for healthy placental and fetal development. An important group of genes regulated by RA are the RA receptor responders (RARRES1, 2, and 3). We set out to analyze their expression and regulation in healthy and pathologically altered placentas of preeclampsia (PE) and intrauterine growth restriction (IUGR) as well as in trophoblast cell lines.

METHODS

We performed immunohistochemical staining on placental sections and analyzed gene expression by real-time polymerase chain reaction. Additionally, we performed cell culture experiments and stimulated Swan71 and Jeg-3 cells with different RA derivates and 2'-deoxy-5-azacytidine (AZA) to induce DNA demethylation.

RESULTS

RARRES1, 2, and 3 and RARA, RARB, RARG, and RXRA are expressed in the extravillous part of the placenta. RARRES1, RARA, RARG, and RXRA were additionally detected in villous cytotrophoblasts. RARRES gene expression was induced via activation of RARA, RARB, and RARG in trophoblast cells. RARRES1 was overexpressed in villous trophoblasts and the syncytiotrophoblast from PE placentas, but not in IUGR without PE. Promoter methylation was detectable for RARRES1 and RARB based on their sensitivity toward AZA treatment of trophoblast cell lines.

DISCUSSION

RARRES1, 2 and 3 are expressed in the functional compartments of the human placenta and can be regulated by RA. We hypothesize that the epigenetic suppression of trophoblast RARRES1 and RARB expression and the upregulation of RARRES1 in PE trophoblast cells suggest an involvement of environmental factors (eg, maternal vitamin A intake) in the pathogenesis of this pregnancy complication.

Therapeutic effects of histone deacetylase inhibitors on kidney disease

Increasing evidence has shown the involvement of histone deacetylases (HDACs) in the development and progression of various renal diseases, highlighting its inhibition as a promising therapeutic strategy to prevent kidney diseases. Accordingly, numerous studies have shown that HDAC inhibitors protect the kidneys from various diseases through their effects on multiple pathways, such as suppression of transforming growth factor-β signaling pathway and nuclear factor-κB signaling pathways, augmentation of apoptosis, and inhibition of angiogenesis. To develop more effective and less toxic isoform-selective HDAC inhibitors and further improve clinical outcomes, it is necessary to identify and understand the mechanisms involved in the pathogenesis and progression of renal diseases. This review focuses on the roles of HDAC inhibitors and the mechanisms involved in their therapeutic effects in experimental models of kidney diseases including glomerulosclerosis, tubulointerstitial fibrosis, glomerular and tubulointerstitial inflammation, lupus nephritis, polycystic kidney disease, and renal cell carcinoma (RCC).

Deguelin induced differentiation of mutated NPM1 acute myeloid leukemia in vivo and in vitro

Nucleophosmin (NPM1), a restricted nucleolar localization protein, shuttles between the nucleus and the cytoplasm. Mutated (Mt)-NPM1 protein, which has aberrant cytoplasmic dislocation of nucleophosmin, occurs in approximately one-third of acute myeloid leukemia cases. Deguelin, a rotenoid isolated from several plant species, is a strong antitumor agent. NOD/SCID mice xenografted with human Mt-NPM1 OCI/AML3 cell lines served as in-vivo models. Wright-Giemsa staining and flow cytometry analysis were used for differentiation assays. Associated molecular events were assessed by western blot and histological analyses. Kaplan-Meier estimates were used to calculate survival. Deguelin toxicity in mice was assessed by immunohistochemistry staining and serum markers. Clinical samples were differentiated by flow cytometry analysis. Deguelin induced differentiation by downregulating the Mt-NPM1 protein levels, which was accompanied by a decrease in SIRT1, p21, and HDAC1 and an increase in CEBPβ and granulocyte colony-stimulating factor receptor protein expression levels. A low-deguelin dose prolonged survival compared with the control group, and there were no apparent lesions to the brain, liver, heart, and kidney in vivo. In clinical samples, deguelin induced the differentiation of fresh blasts with Mt-NPM1 protein, but not with the wild-type NPM1 protein. Taken together, these findings further provide new evidence that the Mt-NPM1 protein plays an important role in inducing differentiation in vivo and in vitro. Mutated NPM1 protein may be a therapeutic target of deguelin in acute myeloid leukemia with the NPM1 mutation.

Retinoic acid regulates avian lung branching through a molecular network

Retinoic acid (RA) is of major importance during vertebrate embryonic development and its levels need to be strictly regulated otherwise congenital malformations will develop. Through the action of specific nuclear receptors, named RAR/RXR, RA regulates the expression of genes that eventually influence proliferation and tissue patterning. RA has been described as crucial for different stages of mammalian lung morphogenesis, and as part of a complex molecular network that contributes to precise organogenesis; nonetheless, nothing is known about its role in avian lung development. The current report characterizes, for the first time, the expression pattern of RA signaling members (stra6, raldh2, raldh3, cyp26a1, rarα, and rarβ) and potential RA downstream targets (sox2, sox9, meis1, meis2, tgfβ2, and id2) by in situ hybridization. In the attempt of unveiling the role of RA in chick lung branching, in vitro lung explants were performed. Supplementation studies revealed that RA stimulates lung branching in a dose-dependent manner. Moreover, the expression levels of cyp26a1, sox2, sox9, rarβ, meis2, hoxb5, tgfβ2, id2, fgf10, fgfr2, and shh were evaluated after RA treatment to disclose a putative molecular network underlying RA effect. In situ hybridization analysis showed that RA is able to alter cyp26a1, sox9, tgfβ2, and id2 spatial distribution; to increase rarβ, meis2, and hoxb5 expression levels; and has a very modest effect on sox2, fgf10, fgfr2, and shh expression levels. Overall, these findings support a role for RA in the proximal-distal patterning and branching morphogenesis of the avian lung and reveal intricate molecular interactions that ultimately orchestrate branching morphogenesis.

Profiling of the transcriptional response to all-trans retinoic acid in breast cancer cells reveals RARE-independent mechanisms of gene expression

Retinoids, derivatives of vitamin A, are key physiological molecules with regulatory effects on cell differentiation, proliferation and apoptosis. As a result, they are of interest for cancer therapy. Specifically, models of breast cancer have varied responses to manipulations of retinoid signaling. This study characterizes the transcriptional response of MDA-MB-231 and MDA-MB-468 breast cancer cells to retinaldehyde dehydrogenase 1A3 (ALDH1A3) and all-trans retinoic acid (atRA). We demonstrate limited overlap between ALDH1A3-induced gene expression and atRA-induced gene expression in both cell lines, suggesting that the function of ALDH1A3 in breast cancer progression extends beyond its role as a retinaldehyde dehydrogenase. Our data reveals divergent transcriptional responses to atRA, which are largely independent of genomic retinoic acid response elements (RAREs) and consistent with the opposing responses of MDA-MB-231 and MDA-MB-468 to in vivo atRA treatment. We identify transcription factors associated with each gene set. Manipulation of the IRF1 transcription factor demonstrates that it is the level of atRA-inducible and epigenetically regulated transcription factors that determine expression of target genes (e.g. CTSS, cathepsin S). This study provides a paradigm for complex responses of breast cancer models to atRA treatment, and illustrates the need to characterize RARE-independent responses to atRA in a variety of models.

miR-542-3p Appended Sorafenib/All-trans Retinoic Acid (ATRA)-Loaded Lipid Nanoparticles to Enhance the Anticancer Efficacy in Gastric Cancers

PURPOSE

In this study, miR-542-3p appended SRF/ATRA-loaded solid lipid nanoparticle was successfully prepared and demonstrated for its therapeutic efficacy against gastric cancers.

METHODS

The particles were nanosized and typically spherical in shape. In vitro release study showed that release of ATRA was significantly slower compared to that of SRF from the NPs.

RESULTS

MTT assay showed that miR-542-3p have a strong inhibitory effect on the proliferation of MGC-803 cancer cells in a typical dose dependent manner. Nanocarrier encapsulation of SRF + ATRA induced a significantly higher cytotoxic effect compared to either individual drug or cocktail combinations indicating that the cellular uptake of different formulations was rate limiting factor in the therapeutic efficacy. Importantly, miR-542-3p-based miSRNP exhibited an extremely significant toxic effect compared to any other treated group. Importantly, miSRNP induced a significantly higher early (~55%) and late (~15%) apoptotic effect in gastric cancer cells. In vivo anticancer analysis results clearly suggest that nanoparticle encapsulation of combination of SRF and miRNA (with miRNA) will have greater antitumor efficacy in tumor mice.

CONCLUSION

Overall, unique combination of miRNA coupled with SRF + ATRA in a lipid nanocarrier could be a promising therapeutic approach in gastric cancer treatment.

All-trans retinoic acid induces mitochondria-mediated apoptosis of human adipose-derived stem cells and affects the balance of the adipogenic differentiation

The all-trans-retinoic acid (ATRA) is the most active form of vitamin A that helps to regulate the proliferation, differentiation and apoptosis of several types of cells, mainly the adipocytes, and causes weight loss through the reduction of adipogenesis and lipogenesis. In this present study we demonstrated that ATRA concentrations of 20.75, 50 and 100 μM decreased the cell viability in vitro of human adipose-derived stem cells (ADSCs), and in ADSCs during adipogenic differentiation. The cells cycle assessment showed that ATRA increased the cell frequency in Sub-G1 at 4.02x and decreased it in G1 in 2.54x. Moreover, the membrane integrity loss increased by 4.66x and apoptosis increased by 33.56x in ATRA-treated cultures. The gene expression assay suggested that the treatment using ATRA leads to mitochondrial membrane permeabilization and to consequent release of proapoptotic BAK and BAX molecules (increased expression 5.5 and 5.4x respectively); in addition, it increased CASP3 expression (by 8.8x). These events may activate the Bcl-2 (4.1x increase), GADD45 (increase 3.14x) and PPAR-γ (16x increase) expressions, as well as, to reduce the p53 (by -1.38x) expression; therefore, these events should be further mediated by increased RARα expression (by 3.8x). The results evidenced that ATRA may be a good proposal for mesotherapy strategies in order to control the development of subcutaneous adipose tissue; as this tissue have a higher development in some specific areas and ATRA interferes not only in the ADSCs differentiation but also in the apoptosis of ADSCs, preadipocytes and adipocytes.

MEK inhibitors enhance therapeutic response towards ATRA in NF1 associated malignant peripheral nerve sheath tumors (MPNST) in-vitro

OBJECTIVE

Neurofibromatosis type 1 (NF1) is a hereditary tumor syndrome characterized by an increased risk of malignant peripheral nerve sheath tumors (MPNST). Chemotherapy of MPNST is still insufficient. In this study, we investigated whether human tumor Schwann cells derived from NF1 associated MPNST respond to all-trans retinoic acid (ATRA). We analyzed effects of ATRA and MEK inhibitor (MEKi) combination therapy.

METHODS

MPNST cell lines S462, T265, NSF1 were treated with ATRA and MEKi U0126 and PD0325901. We assessed cell viability, proliferation, migration, apoptosis and differentiation as well as mRNA expression of RAR and RXR subtypes and ATRA target genes such as CRABP2, CYP26A1, RARB and PDK1. We also analyzed CRABP2 methylation in cell lines and performed immunohistochemistry of human MPNST specimens.

RESULTS

ATRA therapy reduced viability and proliferation in S462 and T265 cells, accompanied by differentiation, apoptosis and reduced migration. NSF1 cells which lacked RXRG expression did not respond to ATRA. We furthermore demonstrated that ATRA signaling was functional for common targets, and that mRNA expression of CRABP2 and its targets was raised by ATRA therapy, whereas alternative pathways via FABP5 were not induced. Finally, combination of ATRA and MEKi demonstrated additively reduced viability of T265 and S462 cells.

CONCLUSIONS

We observed therapeutic effects in two of three MPNST cell lines pronounced by combination therapy. These data point to a potentially successful treatment of MPNST by combined application of ATRA and MEK inhibitors such as U0126 or PD0325901.

Cross talk between progesterone receptors and retinoic acid receptors in regulation of cytokeratin 5-positive breast cancer cells

Half of estrogen receptor-positive breast cancers contain a subpopulation of cytokeratin 5 (CK5)-expressing cells that are therapy resistant and exhibit increased cancer stem cell (CSC) properties. We and others have demonstrated that progesterone (P4) increases CK5+ breast cancer cells. We previously discovered that retinoids block P4 induction of CK5+ cells. Here we investigated the mechanisms by which progesterone receptors (PR) and retinoic acid receptors (RAR) regulate CK5 expression and breast CSC activity. After P4 treatment, sorted CK5+ compared to CK5- cells were more tumorigenic in vivo. In vitro, P4-treated breast cancer cells formed larger mammospheres and silencing of CK5 using small hairpin RNA abolished this P4-dependent increase in mammosphere size. Retinoic acid (RA) treatment blocked the P4 increase in CK5+ cells and prevented the P4 increase in mammosphere size. Dual small interfering RNA (siRNA) silencing of RARα and RARγ reversed RA blockade of P4-induced CK5. Using promoter deletion analysis, we identified a region 1.1 kb upstream of the CK5 transcriptional start site that is necessary for P4 activation and contains a putative progesterone response element (PRE). We confirmed by chromatin immunoprecipitation that P4 recruits PR to the CK5 promoter near the -1.1 kb essential PRE, and also to a proximal region near -130 bp that contains PRE half-sites and a RA response element (RARE). RA induced loss of PR binding only at the proximal site. Interestingly, RARα was recruited to the -1.1 kb PRE and the -130 bp PRE/RARE regions with P4, but not RA alone or RA plus P4. Treatment of breast cancer xenografts in vivo with the retinoid fenretinide reduced the accumulation of CK5+ cells during estrogen depletion. This reduction, together with the inhibition of CK5+ cell expansion through RAR/PR cross talk, may explain the efficacy of retinoids in prevention of some breast cancer recurrences.

RARβ2-dependent signaling represses neuronal differentiation in mouse ES cells

Embryonic Stem (ES) cells are pluripotent cells that can be induced to differentiate into cells of all three lineages: mesoderm, endoderm, and ectoderm. In culture, ES cells can be differentiated into mature neurons by treatment with Retinoic Acid (RA) and this effect is mediated mainly through the activation of the RA nuclear receptors (RAR α, β, and γ), and their isoforms. However, little is known about the role played by specific RAR types on ES cell differentiation. Here, we found that treatment of ES cells with AC55649, an RARβ2 agonist, increased endodermal marker gene expression. On the other hand, we found that the inhibition of RARβ with 5μM LE135, together with RA treatment, increased the efficiency of mouse ES cell differentiation into neurons by more than 4-fold as compared to cells treated with RA only. Finally, we performed proteomic analyses on ES cells treated with RA vs RA plus AC55649 in order to identify the signaling pathways activated by the RARβ agonist. Our proteomic analyses using antibody microarrays indicated that proteins such as p38 and AKT were upregulated in cells treated with RA plus the agonist, as compared to cells treated with RA alone. Our results indicate that RARβ may function as a repressor of neuronal differentiation through the activation of major cell signaling pathways, and that the pharmacological inhibition of this nuclear receptor may constitute a novel method to increase the efficiency of ES to neuronal differentiation in culture.

An Effective Model of the Retinoic Acid Induced HL-60 Differentiation Program

In this study, we present an effective model All-Trans Retinoic Acid (ATRA)-induced differentiation of HL-60 cells. The model describes reinforcing feedback between an ATRA-inducible signalsome complex involving many proteins including Vav1, a guanine nucleotide exchange factor, and the activation of the mitogen activated protein kinase (MAPK) cascade. We decomposed the effective model into three modules; a signal initiation module that sensed and transformed an ATRA signal into program activation signals; a signal integration module that controlled the expression of upstream transcription factors; and a phenotype module which encoded the expression of functional differentiation markers from the ATRA-inducible transcription factors. We identified an ensemble of effective model parameters using measurements taken from ATRA-induced HL-60 cells. Using these parameters, model analysis predicted that MAPK activation was bistable as a function of ATRA exposure. Conformational experiments supported ATRA-induced bistability. Additionally, the model captured intermediate and phenotypic gene expression data. Knockout analysis suggested Gfi-1 and PPARg were critical to the ATRAinduced differentiation program. These findings, combined with other literature evidence, suggested that reinforcing feedback is central to hyperactive signaling in a diversity of cell fate programs.

Clinical significance and prognostic value of TRIM24 expression in esophageal squamous cell carcinoma

Tripartite motif-containing 24 (TRIM24), a member of the transcription intermediary factor 1 family, is defined as a co-regulator with several nuclear receptors, such as RARα. TRIM24 has been reported to be involved in many cancers. In this study, we aimed to investigate the expression pattern and prognostic significance of TRIM24 and its relationship with RARα in esophageal squamous cell cancer (ESCC). Both mRNA and protein expression levels of TRIM24 were found to be significantly decreased in ESCC, as judged by qRT-PCR and western blot. Immunohistochemistry staining shows that the reduced TRIM24 protein is associated with lymph node metastasis (P=0.024), advance pathological TNM (pTNM) stage (P=0.046) and recurrence/metastasis (P=0.001). Upregulated TRIM24 protein predicts longer overall survival and disease-free survival (both P<0.001) and is an independent predictor for good prognosis (HR, 0.519; 95%CI, 0.341-0.788; P=0.002). TRIM24 expression has been proven remarkably to improve prediction of survival of pTNM stage in ESCC patients, especially in stage I and II. However, no significant relationship was found between TRIM24 and RARα expression levels. In conclusion, reduced TRIM24 protein is associated with poor survival in ESCC patients, suggesting TRIM24 protein is a potential prognostic biomarker for ESCC.

Precision Oncology: The Road Ahead

Current efforts in precision oncology largely focus on the benefit of genomics-guided therapy. Yet, advances in sequencing techniques provide an unprecedented view of the complex genetic and nongenetic heterogeneity within individual tumors. Herein, we outline the benefits of integrating genomic and transcriptomic analyses for advanced precision oncology. We summarize relevant computational approaches to detect novel drivers and genetic vulnerabilities, suitable for therapeutic exploration. Clinically relevant platforms to functionally test predicted drugs/drug combinations for individual patients are reviewed. Finally, we highlight the technological advances in single cell analysis of tumor specimens. These may ultimately lead to the development of next-generation cancer drugs, capable of tackling the hurdles imposed by genetic and phenotypic heterogeneity on current anticancer therapies.

Retinoic acid, CYP26, and drug resistance in the stem cell niche

The bone marrow niche is essential for hematopoietic stem cells to maintain lifelong blood production by balancing their self-renewal and differentiation. Hematologic malignancies have a similar hierarchical organization to their normal counterparts, with rare populations of cancer stem cells that rely on the microenvironment to survive and propagate their differentiated malignant progenitor cells. Cancer cells alter their microenvironment to create a supportive niche, where they endure chemotherapy, survive as minimal residual disease (MRD), and eventually prevail at relapse. Powerful morphogens, such as retinoids, Wnt/βcatenin, Notch, and Hedgehog, control stem cell fates across tissues, including normal and malignant hematopoiesis. The molecular conversations between these pathways and the mechanisms that control their activity and create gradients at cellular scale remain a mystery. Here, we discuss accumulating evidence suggesting that cytochrome P450 (CYP26), the primary retinoid-inactivating enzyme, plays a critical role in the integration of two of these molecular programs: the retinoid and Hedgehog pathways. Induction of stromal CYP26 by either one of these pathways limits retinoic acid concentration in the stem cell niche, with profound effects on tissue homeostasis and drug resistance. Bypassing this gatekeeping mechanism holds promise for overcoming drug resistance and improving clinical outcomes in hematological malignancies and cancer in general.

Vitamin A, endocrine tissues and hormones: interplay and interactions

Vitamin A (retinol) is a micronutrient critical for cell proliferation and differentiation. In adults, vitamin A and metabolites such as retinoic acid (RA) play major roles in vision, immune and brain functions, and tissue remodelling and metabolism. This review presents the physiological interactions of retinoids and endocrine tissues and hormonal systems. Two endocrine systems have been particularly studied. In the pituitary, retinoids targets the corticotrophs with a possible therapeutic use in corticotropinomas. In the thyroid, retinoids interfere with iodine metabolism and vitamin A deficiency aggravates thyroid dysfunction caused by iodine-deficient diets. Retinoids use in thyroid cancer appears less promising than expected. Recent and still controversial studies investigated the relations between retinoids and metabolic syndrome. Indeed, retinoids contribute to pancreatic development and modify fat and glucose metabolism. However, more detailed studies are needed before planning any therapeutic use. Finally, retinoids probably play more minor roles in adrenal and gonads development and function apart from their major effects on spermatogenesis.

Estrogenic terpenes and terpenoids: Pathways, functions and applications

Terpenes are made of the isoprene unit (C₅), and along with their derivatives, terpenoids, they are widely distributed in plants as active ingredients involved in anti-inflammation, anti-carcinogenesis and neuroprotection. Estrogenic terpenes and terpenoids are an important category of phytoestrogens and have been used as traditional medicines. The comprehensive list of estrogenic terpenes and terpenoids includes hemi-, mono-, sesqui-, di-, tri-, tetra- and polyterpenes, their derivatives, and meroterpenes, along with the signaling pathways and cellular functions on which their estrogenicity is exerted. Signaling pathways are further classified as bidirectional or unidirectional, the latter being further divided into two types depending upon the presence of both ligands, or the absence of one or both ligands. Although estrogenic activity of terpenes and terpenoids was evaluated by ligand-binding assays, yeast two-hybrid assays, reporter-gene assays, transcription assays, protein assays, cell assays and animal testing, the mechanism of estrogenic activity is still not fully understood. Applications of estrogenic terpenes and terpenoids are categorized into cancer treatment and prevention, cardioprotection, endocrine toxicity/reproductive dysfunction, food/supplement/traditional medicine, immunology/inflammation, menopausal syndromes and neuroprotection, where their benefits are discussed based on their availability, stability and variations.

The WHHERE coactivator complex is required for retinoic acid-dependent regulation of embryonic symmetry

Bilateral symmetry is a striking feature of the vertebrate body plan organization. Vertebral precursors, called somites, provide one of the best illustrations of embryonic symmetry. Maintenance of somitogenesis symmetry requires retinoic acid (RA) and its coactivator Rere/Atrophin2. Here, using a proteomic approach we identify a protein complex, containing Wdr5, Hdac1, Hdac2 and Rere (named WHHERE), which regulates RA signaling and controls embryonic symmetry. We demonstrate that Wdr5, Hdac1, and Hdac2 are required for RA signaling in vitro and in vivo. Mouse mutants for Wdr5 and Hdac1 exhibit asymmetrical somite formation characteristic of RA-deficiency. We also identify the Rere-binding histone methyltransferase Ehmt2/G9a, as a RA coactivator controlling somite symmetry. Upon RA treatment, WHHERE and Ehmt2 become enriched at RA target genes to promote RNA polymerase II recruitment. Our work identifies a protein complex linking key epigenetic regulators acting in the molecular control of embryonic bilateral symmetry.Retinoic acid (RA) regulates the maintenance of somitogenesis symmetry. Here, the authors use a proteomic approach to identify a protein complex of Wdr5, Hdac1, Hdac2 that act together with RA and coactivator Rere/Atrophin2 and a histone methyltransferase Ehmt2 to regulate embryonic symmetry.

RaRF confers RA resistance by sequestering RAR to the nucleolus and regulating MCL1 in leukemia cells

Retinoic acid (RA) has broad clinical applications for the treatment of various cancers, particularly acute promyelocytic leukemia. However, RA-based therapy is limited by relapse in patients associated with RA resistance, the mechanism of which is poorly understood. Here, we suggest a new molecular mechanism of RA resistance by a repressor, named RA resistance factor (RaRF). RaRF suppressed transcriptional activity of the RA receptor (RAR) by directly interacting with and sequestering RAR to the nucleolus in response to RA. RaRF was highly expressed in RA-resistant leukemia cells and its expression was strongly correlated with RA sensitivity. MCL1 was upregulated by RA treatment upon RaRF depletion, accompanying leukemic myeloblast differentiation, which is negatively regulated by ectopic RaRF expression. Collectively, we propose that RaRF may be a factor in the resistance mechanism and thus a potential target for leukemia therapy using RA.

Alcohol consumption and breast tumor gene expression

Background

Alcohol consumption is an established risk factor for breast cancer and the association generally appears stronger among estrogen receptor (ER)-positive tumors. However, the biological mechanisms underlying this association are not completely understood.

Methods

We analyzed messenger RNA (mRNA) microarray data from both invasive breast tumors (N = 602) and tumor-adjacent normal tissues (N = 508) from participants diagnosed with breast cancer in the Nurses’ Health Study (NHS) and NHSII. Multivariable linear regression, controlling for other known breast cancer risk factors, was used to identify differentially expressed genes by pre-diagnostic alcohol intake. For pathway analysis, we performed gene set enrichment analysis (GSEA). Differentially expressed genes or enriched pathway-defined gene sets with false discovery rate (FDR) <0.1 identified in tumors were validated in RNA sequencing data of invasive breast tumors (N = 166) from The Cancer Genome Atlas.

Results

No individual genes were significantly differentially expressed by alcohol consumption in the NHS/NHSII. However, GSEA identified 33 and 68 pathway-defined gene sets at FDR <0.1 among 471 ER+ and 127 ER- tumors, respectively, all of which were validated. Among ER+ tumors, consuming 10+ grams of alcohol per day (vs. 0) was associated with upregulation in RNA metabolism and transport, cell cycle regulation, and DNA repair, and downregulation in lipid metabolism. Among ER- tumors, in addition to upregulation in RNA processing and cell cycle, alcohol intake was linked to overexpression of genes involved in cytokine signaling, including interferon and transforming growth factor (TGF)-β signaling pathways, and translation and post-translational modifications. Lower lipid metabolism was observed in both ER+ tumors and ER+ tumor-adjacent normal samples. Most of the significantly enriched gene sets identified in ER- tumors showed a similar enrichment pattern among ER- tumor-adjacent normal tissues.

Conclusions

Our data suggest that moderate alcohol consumption (i.e. 10+ grams/day, equivalent to one or more drinks/day) is associated with several specific and reproducible biological processes and pathways, which adds potential new insight into alcohol-related breast carcinogenesis.

Electronic supplementary material

The online version of this article (doi:10.1186/s13058-017-0901-y) contains supplementary material, which is available to authorized users.

Melatonin and Hippo Pathway: Is There Existing Cross-Talk?

Melatonin is an indolic hormone that regulates a plethora of functions ranging from the regulation of circadian rhythms and antioxidant properties to the induction and maintenance of tumor suppressor pathways. It binds to specific receptors as well as to some cytosolic proteins, leading to several cellular signaling cascades. Recently, the involvement of melatonin in cancer insurgence and progression has clearly been demonstrated. In this review, we will first describe the structure and functions of melatonin and its receptors, and then discuss both molecular and epidemiological evidence on melatonin anticancer effects. Finally, we will shed light on potential cross-talk between melatonin signaling and the Hippo signaling pathway, along with the possible implications for cancer therapy.

Alcohol and Cancer: Mechanisms and Therapies

Several scientific and clinical studies have shown an association between chronic alcohol consumption and the occurrence of cancer in humans. The mechanism for alcohol-induced carcinogenesis has not been fully understood, although plausible events include genotoxic effects of acetaldehyde, cytochrome P450 2E1 (CYP2E1)-mediated generation of reactive oxygen species, aberrant metabolism of folate and retinoids, increased estrogen, and genetic polymorphisms. Here, we summarize the impact of alcohol drinking on the risk of cancer development and potential underlying molecular mechanisms. The interactions between alcohol abuse, anti-tumor immune response, tumor growth, and metastasis are complex. However, multiple studies have linked the immunosuppressive effects of alcohol with tumor progression and metastasis. The influence of alcohol on the host immune system and the development of possible effective immunotherapy for cancer in alcoholics are also discussed here. The conclusive biological effects of alcohol on tumor progression and malignancy have not been investigated extensively using an animal model that mimics the human disease. This review provides insights into cancer pathogenesis in alcoholics, alcohol and immune interactions in different cancers, and scope and future of targeted immunotherapeutic modalities in patients with alcohol abuse.

Retinoic acid-induced upregulation of miR-219 promotes the differentiation of embryonic stem cells into neural cells

MicroRNAs (miRNAs) regulate critical cell processes, such as apoptosis, proliferation, and development. However, the role of miRNAs in embryonic stem cell (ESC) neural differentiation induced by retinoic acid (RA) and factors that govern neural directional differentiation remain poorly understood. In this study, we demonstrated that miR-219 is sufficient in promoting mouse ESCs to undergo neural differentiation. We discovered that Foxj3 and Zbtb18, two target genes of miR-219, are not able to determine the process of RA-induced differentiation, however they prevent ESCs from differentiating into neural cells. We identified four downstream genes, namely, Olig1, Zic5, Erbb2, and Olig2, which are essential to the gene interaction networks for neural differentiation. These data explain the mechanism of RA-induced neural differentiation of mESCs on the basis of miRNAs and support the crucial role of miR-219 in neurodevelopment.

Regulation of retinoic acid synthetic enzymes by WT1 and HDAC inhibitors in 293 cells

All-trans retinoic acid (atRA), which is mainly generated endogenously via two steps of oxidation from vitamin A (retinol), plays an indispensible role in the development of the kidney and many other organs. Enzymes that catalyze the oxidation of retinol to generate atRA, including aldehyde dehydrogenase 1 family (ALDH1)A1, ALDH1A2 and ALDH1A3, exhibit complex expression patterns at different stages of renal development. However, molecular triggers that control these differential expression levels are poorly understood. In this study, we provide in vitro evidence to demonstrate that Wilms' tumor 1 (WT1) negatively regulates the expression of the atRA synthetic enzymes, ALDH1A1, ALDH1A2 and ALDH1A3, in the 293 cell line, leading to significant blockage of atRA production. Furthermore, we demonstrate that the suppression of ALDH1A1 by WT1 can be markedly attenuated by histone deacetylase inhibitors (HDACis). Taken together, we provide evidence to indicate that WT1 and HDACs are strong regulators of endogenous retinoic acid synthetic enzymes in 293 cells, indicating that they may be involved in the regulation of atRA synthesis.

Challenging the great vascular wall: Can we envision a simple yet comprehensive therapy for stroke?

Stroke is a leading cause of death in adult life, closely behind ischemic heart disease, and causes a significant and abiding socioeconomic burden. However, current therapies are not able to ensure full neurologic and/or sequelae-free recovery to all stroke survivors. We believe treatment efficacy and patient rehabilitation could be enhanced significantly by targeting blood-brain barrier (BBB) deregulation and inflammation-induced barrier loss that occurs after stroke. In this pathological context, bone marrow-derived endothelial progenitor cells (EPC) enter the bloodstream towards the lesion site, but their insufficient numbers and impaired angiogenic ability compromise neurovascular regeneration. In this context, cell-based therapies have become increasingly appealing since treating patients with large numbers of mesenchymal or hematopoietic stem/progenitor cells alone may boost repair. However, this approach could be met with several challenges in terms of logistics and cost; hence, the development of a drug delivery system suitable for intravenous administration and functionalized for selective uptake by circulating EPC could enhance their restorative potential without perceived complications. The ability to encapsulate proangiogenic and anti-inflammatory agents, such as retinoic acid, and to safely and easily deliver them systemically may open new therapeutic perspectives for the treatment of cerebrovascular disorders. Copyright © 2017 John Wiley & Sons, Ltd.

Retinoic acid directs breast cancer cell state changes through regulation of TET2-PKCζ pathway

The key molecular mechanism governing the cancer cell state (stem cell-like state vs differentiation state) to control the cancer stem cell (CSC) pool remains elusive. This study provides the first evidence showing that all-trans retinoic acid (ATRA) induces the interaction and chromatin recruitment of a novel RARβ-TET2 complex to epigenetically activate a specific cohort of gene targets, including MiR-200c. TET2-activated miR-200c further targets and suppresses PKCζ, a cell polarity protein that has a pivotal role in directing asymmetric division of mammalian stem cells to sustain the stem cell pool. Our data reveal that pharmacological concentration of ATRA effectively downregulates PKCζ through activation of miR-200c, leading to a decrease of the stem cell-like populations from non-tumorigenic mammary epithelial cells and non-aggressive breast cancer cells. However, aggressive breast cancer cells that manifest TET2-miR-200c dysregulation sustain a CSC pool highly resistant to ATRA, where inhibition of PKCζ directs the resistant CSCs to the luminal cell-like state and sensitization to tamoxifen, resulting in abrogation of mammary tumor growth and progression. Together, these findings elucidate a novel RARβ-TET2-miR-200c-PKCζ signaling pathway that directs cancer cell state changes and also provide previously unidentified therapeutic implications for PKCζ inhibitors in diminishment of breast CSCs to eradicate breast cancer.

Vitamin A-Retinoic Acid Signaling Regulates Hematopoietic Stem Cell Dormancy

Dormant hematopoietic stem cells (dHSCs) are atop the hematopoietic hierarchy. The molecular identity of dHSCs and the mechanisms regulating their maintenance or exit from dormancy remain uncertain. Here, we use single-cell RNA sequencing (RNA-seq) analysis to show that the transition from dormancy toward cell-cycle entry is a continuous developmental path associated with upregulation of biosynthetic processes rather than a stepwise progression. In addition, low Myc levels and high expression of a retinoic acid program are characteristic for dHSCs. To follow the behavior of dHSCs in situ, a Gprc5c-controlled reporter mouse was established. Treatment with all-trans retinoic acid antagonizes stress-induced activation of dHSCs by restricting protein translation and levels of reactive oxygen species (ROS) and Myc. Mice maintained on a vitamin A-free diet lose HSCs and show a disrupted re-entry into dormancy after exposure to inflammatory stress stimuli. Our results highlight the impact of dietary vitamin A on the regulation of cell-cycle-mediated stem cell plasticity. VIDEO ABSTRACT.

Melanoma Chemoprevention: Current Status and Future Prospects

The incidence of skin cancers, both nonmelanoma and melanoma, is increasing in the United States. The ultraviolet radiation, mainly from sun, is considered the major cause for these neoplasms. While nonmelanoma skin cancers are far more numerous, melanoma remains the most challenging. This is because melanoma can become extremely aggressive and its incidence is increasing worldwide due to lack of effective early detection, as well as disease recurrence, following both surgery and chemotherapy. Therefore, in addition to better treatment options, newer means are required to prevent melanomas from developing. Chemoprevention is a reasonable cost-effective approach to prevent carcinogenesis by inhibiting the processes of tumor initiation, promotion and progression. Melanoma is a progressive disease, which makes it very suitable for chemopreventive interventions, by targeting the processes and molecular pathways involved in the progression of melanoma. This review discusses the roles of various chemopreventive agents such as NSAIDs, statins, vitamins and dietary agents in melanoma and highlights current advancements and our perspective on future of melanoma chemoprevention. Although considerable preclinical data suggest that melanoma may be prevented or delayed by a numerous chemopreventive agents, we realize there are insufficient clinical studies evaluating their efficacy and long-term safety for human use.

Assessment of histone tail modifications and transcriptional profiling during colon cancer progression reveals a global decrease in H3K4me3 activity

During colon cancer, epigenetic alterations contribute to the dysregulation of major cellular functions and signaling pathways. Modifications in chromatin signatures such as H3K4me3 and H3K9ac, which are associated with transcriptionally active genes, can lead to genomic instability and perturb the expression of gene sets associated with oncogenic processes. In order to further elucidate early pre-tumorigenic epigenetic molecular events driving CRC, we integrated diverse, genome-wide, epigenetic inputs (by high throughput sequencing of RNA, H3K4me3, and H3K9ac) and compared differentially expressed transcripts (DE) and enriched regions (DER) in an in-vivo rat colon cancer progression model. Carcinogen (AOM) effects were detected genome-wide at the RNA (116 DE genes), K9ac (49 DERs including 24 genes) and K4me3 (7678 DERs including 3792 genes) level. RNA-seq differential expression and pathway analysis indicated that interferon-associated innate immune responses were impacted by AOM exposure. Despite extensive associations between K4me3 DERs and colon tumorigenesis (1210 genes were linked to colorectal carcinoma) including FOXO3, GNAI2, H2AFX, MSH2, NR3C1, PDCD4 and VEGFA, these changes were not reflected at the RNA gene expression level during early cancer progression. Collectively, our results indicate that carcinogen-induced changes in gene K4me3 DERs are harbingers of future transcriptional events, which drive malignant transformation of the colon.