Phase 1 safety, tolerability, pharmacokinetics and pharmacodynamic results of KCL-286, a novel retinoic acid receptor-ß agonist for treatment of spinal cord injury, in male healthy participants.

AIMS: KCL-286 is an orally available agonist that activates the retinoic acid receptor (RAR) ß2, a transcription factor which stimulates axonal outgrowth. The investigational medicinal product is being developed for treatment of spinal cord injury (SCI). This adaptive dose escalation study evaluated the tolerability, safety and pharmacokinetics and pharmacodynamic activity of KCL-286 in male healthy volunteers to establish dosing to be used in the SCI patient population. METHODS: The design was a double blind, randomized, placebo-controlled dose escalation study in 2 parts: a single ascending dose adaptive design with a food interaction arm, and a multiple ascending dose design. RARß2 mRNA expression was evaluated in white blood cells. RESULTS: At the highest single and multiple ascending doses (100 mg), no trends or clinically important differences were noted in the incidence or intensity of adverse events (AEs), serious AEs or other safety assessments with none leading to withdrawal from the study. The AEs were dry skin, rash, skin exfoliation, raised liver enzymes and eye disorders. There was an increase in mean maximum observed concentration and area under the plasma concentration-time curve up to 24 h showing a trend to subproportionality with dose. RARß2 was upregulated by the investigational medicinal product in white blood cells. CONCLUSION: KCL-286 was well tolerated by healthy human participants following doses that exceeded potentially clinically relevant plasma exposures based on preclinical in vivo models. Target engagement shows the drug candidate activates its receptor. These findings support further development of KCL-286 as a novel oral treatment for SCI.

Hepatocyte Nuclear Factor 4α (HNF4α) Plays a Controlling Role in Expression of the Retinoic Acid Receptor ß (RARß) Gene in Hepatocytes.

HNF4α, a member of the nuclear receptor superfamily, regulates the genes involved in lipid and glucose metabolism. The expression of the RARß gene in the liver of HNF4α knock-out mice was higher versus wildtype controls, whereas oppositely, RARß promoter activity was 50% reduced by the overexpression of HNF4α in HepG2 cells, and treatment with retinoic acid (RA), a major metabolite of vitamin A, increased RARß promoter activity 15-fold. The human RARß2 promoter contains two DR5 and one DR8 binding motifs, as RA response elements (RARE) proximal to the transcription start site. While DR5 RARE1 was previously reported to be responsive to RARs but not to other nuclear receptors, we show here that mutation in DR5 RARE2 suppresses the promoter response to HNF4α and RARα/RXRα. Mutational analysis of ligand-binding pocket amino acids shown to be critical for fatty acid (FA) binding indicated that RA may interfere with interactions of FA carboxylic acid headgroups with side chains of S190 and R235, and the aliphatic group with I355. These results could explain the partial suppression of HNF4α transcriptional activation toward gene promoters that lack RARE, including APOC3 and CYP2C9, while conversely, HNF4α may bind to RARE sequences in the promoter of the genes such as CYP26A1 and RARß, activating these genes in the presence of RA. Thus, RA could act as either an antagonist towards HNF4α in genes lacking RAREs, or as an agonist for RARE-containing genes. Overall, RA may interfere with the function of HNF4α and deregulate HNF4α targets genes, including the genes important for lipid and glucose metabolism.

[Effects of all-trans retinoic acid on the macrophage function of prostatic stromal cells].

Objective: To investigate the effects of all-trans retinoic acid (ATRA) on prostatic stromal cells during wound repair after prostatectomy in vitro. METHODS: Each of the M1 and M2 types of monocytic macrophage (THP-1) cells were divided into an experimental, a control and a non-activated group, the M1 macrophages of the former two groups activated by PMA and IFNγ, and the M2 macrophages by PMA and IL-4, respectively. The cells in the two experimental groups were treated with all-trans retinoic acid (ATRA) at 100 nmol/L, followed by detection of the expressions of IL-10, IL-12, IL-6, TNF-α and TGF-ß in the supernatant by ELISA. The supernatant was co-cultured with primarily cultured prostatic stromal cells or vascular endothelial cells in different groups. The expressions of RARα, RARß, RARγ, Arg1, Mmp9 and Soat1 in the macrophages were determined by PCR. The influence of the macrophages on the function of the stromal cells was analyzed by gel shrinkage test, scratch test and vascular endothelial cell tubular vascular formation test. The expression levels of Arg1 mRNA were reexamined under the action of RAR receptor subtype inhibitors. RESULTS: Compared with the control, the M2 macrophages treated with ATRA showed dramatically up-regulated expressions of IL-10 (ï¼»213.38 ± 2.02ï¼½ vs ï¼»298.22 ± 1.70ï¼½ pg/ml, P < 0.01) and TGF-ß (ï¼»185.37 ± 1.33ï¼½ vs ï¼»246.00 ± 2.14ï¼½ pg/ml, P < 0.01). The ATRA-treated macrophage supernatant enhanced the contraction and migration of the prostatic stromal cells and tubular formation of the vascular endothelial cells. The mRNA levels of Arg1 and RARß were significantly increased in the experimental group, and RARß was further confirmed to be the key receptor subtype in this process. CONCLUSIONS: ATRA activates prostatic stromal cells and enhances their migration and angiogenesis by acting on macrophages via RARß.

Regulation of Myelination by Exosome Associated Retinoic Acid Release from NG2-Positive Cells.

In the CNS, oligodendrocytes are responsible for myelin formation and maintenance. Following spinal cord injury, oligodendrocyte loss and an inhibitory milieu compromise remyelination and recovery. Here, we explored the role of retinoic acid receptor-beta (RARß) signaling in remyelination. Using a male Sprague Dawley rat model of PNS-CNS injury, we show that oral treatment with a novel drug like RARß agonist, C286, induces neuronal expression of the proteoglycan decorin and promotes myelination and differentiation of oligodendrocyte precursor cells (NG2+ cells) in a decorin-mediated neuron-glia cross talk. Decorin promoted the activation of RARα in NG2+ cells by increasing the availability of the endogenous ligand RA. NG2+ cells synthesize RA, which is released in association with exosomes. We found that decorin prevents this secretion through regulation of the EGFR-calcium pathway. Using functional and pharmacological studies, we further show that RARα signaling is both required and sufficient for oligodendrocyte differentiation. These findings illustrate that RARß and RARα are important regulators of oligodendrocyte differentiation, providing new targets for myelination.SIGNIFICANCE STATEMENT This study identifies novel therapeutic targets for remyelination after PNS-CNS injury. Pharmacological and knock-down experiments show that the retinoic acid (RA) signaling promotes differentiation of oligodendrocyte precursor cells (OPCs) and remyelination in a cross talk between neuronal RA receptor-beta (RARß) and RARα in NG2+ cells. We show that stimulation of RARα is required for the differentiation of OPCs and we describe for the first time how oral treatment with a RARß agonist (C286, currently being tested in a Phase 1 trial, ISRCTN12424734) leads to the endogenous synthesis of RA through retinaldehyde dehydrogenase 2 (Raldh2) in NG2 cells and controls exosome-associated-RA intracellular levels through a decorin-Ca2+ pathway. Although RARß has been implicated in distinct aspects of CNS regeneration, this study identifies a novel function for both RARß and RARα in remyelination.

Procaine is a specific DNA methylation inhibitor with anti-tumor effect for human gastric cancer.

DNA hypermethylation and the silencing of tumor suppressor genes caused by DNA hypermethylation is considered as a molecular hallmark of many kinds of cancers. Procaine, a local anesthetic, has been shown as a potential DNA methylation inhibitor in some types of cancers. However, the influence of procaine on DNA methylation regulation as well as the biological function in gastric cancer is still unknown. We report here that procaine represses the DNA-methylation level and promotes the proliferation arrest and apoptosis of gastric cancer cells. Global DNA methylation measurement demonstrates that procaine significantly reduces the global DNA methylation level. Analyses of the DNMTs expression and activity show procaine represses the activity, but not the expression, of DNMT1/DNMT3A. Further evidence on specific genes shows that procaine reduces the DNA methylation level in the promoter regions of CDKN2A and RARß genes through abrogating the binding of DNMT1/DNMT3A toward these regions. This repression would not be reversed by the overexpression of DNMT1/DNMT3A. Moreover, RT-qPCR and luciferase report assays demonstrate that procaine leads to the upregulation of CDKN2A and RARß due to the activation of the promoter of these genes. In the end, we test the function of procaine toward gastric cancer cells and find that procaine has the growth inhibitory and apoptosis inducement effect toward gastric cancer cells. Collectively, our data not only uncovers the regulation mechanisms of procaine to DNA methylation but also suggests an anti-tumor potential of procaine specific to the gastric carcinoma and provides a new therapeutic strategy for gastric carcinoma.

The association between RARß and FHIT promoter methylation and the carcinogenesis of patients with cervical carcinoma: A meta-analysis.

The RARß and FHIT promoter methylation are observed in some cervical carcinoma. However, the association between RARß and FHIT promoter methylation and cervical carcinogenesis remains unclear. This study was carried out to evaluate the correlation between RARß or FHIT promoter methylation and cervical carcinogenesis. Eligible publications were searched via online databases. The combined odds ratios and corresponding 95% confidence intervals were calculated and summarized. In all, 17 eligible articles on RARß and FHIT promoter methylation were identified in the study. RARß promoter methylation was significantly higher in cervical cancer than in cervical intraepithelial neoplasia lesions and normal cervical tissues (odds ratio = 3.90, p = 0.018; odds ratio = 12.98, p < 0.001, respectively). There was more FHIT promoter methylation in cervical cancer than in cervical intraepithelial neoplasia lesions and normal controls (odds ratio = 8.0, p = 0.055; odds ratio = 10.75, p < 0.001, respectively). In addition, FHIT promoter methylation was correlated with clinical stage (advanced stage vs early stage: odds ratio = 2.69, p = 0.056) and tumor grade (high grade vs low grade: odds ratio = 4.11, p < 0.001). RARß and FHIT promoter methylation may be associated with the carcinogenesis of cervical cancer. FHIT promoter methylation may play a crucial role in cervical cancer progression. Additional studies with large sample sizes are essential to confirm our findings.

Retinoids Regulate Adipogenesis Involving the TGFß/SMAD and Wnt/ß-Catenin Pathways in Human Bone Marrow Mesenchymal Stem Cells.

Retinoids may regulate cell differentiation as ligands of retinoic acid receptors (RARs) and/or retinoid X receptors (RXRs). We showed that RAR agonists promoted adipogenesis by upregulating the expression of CCAAT/enhancer-binding protein ß (C/EBPß) in the early stages, but blocked adipogenesis at a later stage in human bone marrow mesenchymal stem cells (hBMSCs). RXR agonists promoted adipogenesis at all time points in hBMSCs. The effect of RAR agonists was mediated mainly by the RARß subtype. RAR agonists, in contrast to RXR agonists, significantly promoted the expression of RARß. Knockdown of the RARß gene via small hairpin RNA (shRNA) attenuated the inhibition of RAR agonists toward adipogenesis. Furthermore, we found that RAR agonists upregulated the transforming growth factor ß (TGFß)/SMAD pathway and Wnt/ß-catenin pathway on adipogenesis in hBMSCs, and the stimulating effects were noticeably decreased with the RARß gene knockdown. Both RAR agonists and RXR agonists inhibited adipogenesis and blocked the promoter activity of C/EBPß and peroxisome proliferator-activated receptor γ (PPARγ) in SW872 cell. These results indicated the RAR agonists perform dual roles in adipogenesis in hBMSCs, and the TGFß/SMAD pathway and Wnt/ß-catenin pathway may involve the inhibitory effect of RAR agonists. RARß is the main receptor subtype mediating the effect. The roles of RXR agonists in adipogenesis exhibited cell type-specific differences, and may be based on the integration of signals from different RXR dimers.

Promoter methylation of APC and RAR-ß genes as prognostic markers in non-small cell lung cancer (NSCLC).

Aberrant promoter hypermethylations of tumor suppressor genes are promising markers for lung cancer diagnosis and prognosis. The purpose of this study was to determine methylation status at APC and RAR-ß promoters in primary NSCLC, and whether they have any relationship with survival. APC and RAR-ß promoter methylation status were determined in 41 NSCLC patients using methylation specific PCR. APC promoter methylation was detectable in 9 (22.0%) tumor samples and 6 (14.6%) corresponding non-tumor samples (P=0.391). RAR-ß promoter methylation was detectable in 13 (31.7%) tumor samples and 4 (9.8%) corresponding non-tumor samples (P=0.049) in the NSCLC patients. APC promoter methylation was found to be associated with T stage (P=0.046) and nodal status (P=0.019) in non-tumor samples, and with smoking (P=0.004) in tumor samples. RAR-ß promoter methylation was found associated with age (P=0.031) in non-tumor samples and with primary tumor site in tumor samples. Patients with APC promoter methylation in tumor samples showed significantly longer survival than patients without it (Log-rank P=0.014). In a multivariate analysis of prognostic factors, APC methylation in tumor samples was an independent prognostic factor (P=0.012), as were N1 positive lymph node number (P=0.025) and N2 positive lymph node number (P=0.06). Our study shows that RAR-ß methylation detected in lung tissue may be used as a predictive marker for NSCLC diagnosis and that APC methylation in tumor sample may be a useful marker for superior survival in NSCLC patients.

Aberrant methylation of APC and RARß2 genes in breast cancer patients.

Changes in the status of DNA methylation are one of the most common molecular alterations in human neoplasia. We aimed to identify epigenetic molecular markers in serum for early detection of breast cancer. Authors analyzed retrospectively the methylation status of RARß2 and APC genes in serum samples from 121 breast cancer patients, 79 patients with benign breast diseases, and 66 healthy volunteers using methylation-specific PCR. The methylated APC and RARß2 were significantly higher in breast cancer patients (93.4%, 95.6%) than benign (7.8%, 14.5%) but not detected in healthy volunteers (0%) at (P < 0.0001). Both methylated genes showed no significant difference among clinicopathological factors apart from triple negative breast cancer patients as all of them (χ(2) = 7.4, P = 0.007) reported to be methylated RARß2 genes. Both methylated genes were detected in all grades and stages. Both sensitivities and specificities of the methylated genes for breast cancer detection were superior to traditional tumor markers in detection of breast cancer, early stage, low grade tumors, and triple negative breast cancer patients. Thus methylated APC and RARß2 genes might be valuable serum-based molecular markers for early detection of breast cancer.

Curcumin Reactivates Silenced Tumor Suppressor Gene RARß by Reducing DNA Methylation.

Reactivation of tumor suppressor genes by nontoxic bioactive food component represents a promising strategy for cancer chemoprevention. Retinoic acid receptor ß (RARß), one member of the RAR receptor family, is considered as a tumor suppressor. Reduced expression of RARß has been reported in lung cancer and other solid tumors. DNA hypermethylation of the promoter region of RARß is a major mechanism for its silencing in tumors. Recently, curcumin has been considered as a potential DNA methyltransferase inhibitor. Herein, we demonstrated that curcumin significantly elevate RARß expression at the mRNA and protein levels in tested cancer cells. Additionally, curcumin decreased RARß promoter methylation in lung cancer A549 and H460 cells. Mechanistic study demonstrated that curcumin was able to downregulate the mRNA levels of DNMT3b. In a lung cancer xenograft node mice model, curcumin exhibited protective effect against weight loss because of tumor burden. Tumor growth was strongly repressed by curcumin treatment. As the results from in vitro, RARß mRNA were increased and DNMT3b mRNA were decreased by curcumin treatment compared with the mice in control group. Altogether, this study reveals a novel molecular mechanism of curcumin as a chemo-preventive agent for lung cancer through reactivation of RARß.

Retinoic acid reduces migration of human breast cancer cells: role of retinoic acid receptor beta.

Breast cancer is the most common malignancy in women and the appearance of distant metastases produces the death in 98% of cases. The retinoic acid receptor ß (RARß) is not expressed in 50% of invasive breast carcinoma compared with normal tissue and it has been associated with lymph node metastasis. Our hypothesis is that RARß protein participates in the metastatic process. T47D and MCF7 breast cancer cell lines were used to perform viability assay, immunobloting, migration assays, RNA interference and immunofluorescence. Administration of retinoic acid (RA) in breast cancer cells induced RARß gene expression that was greatest after 72 hrs with a concentration 1 µM. High concentrations of RA increased the expression of RARß causing an inhibition of the 60% in cell migration and significantly decreased the expression of migration-related proteins [moesin, c-Src and focal adhesion kinase (FAK)]. The treatment with RARα and RARγ agonists did not affect the cell migration. On the contrary, the addition of the selective retinoid RARß-agonist (BMS453) significantly reduced cell migration comparable to RA inhibition. When RARß gene silencing was performed, the RA failed to significantly inhibit migration and resulted ineffective to reduce moesin, c-Src and FAK expressions. RARß is necessary to inhibit migration induced by RA in breast cancer cells modulating the expression of proteins involved in cell migration.

Methylation status of retinoic acid receptor beta2 promoter and global DNA in esophageal squamous cell carcinoma.

BACKGROUND: Focal hypermethylation in promoter regions of tumor suppressor genes against the background of global hypomethylation is a landmark of carcinogenesis. This study aimed to investigate the methylation status of retinoic acid receptor beta2 (RARß2) and long interspersed nuclear elements (LINE-1) in different stages of esophageal squamous cell carcinoma (ESCC). METHOD: The tumor and adjacent normal esophageal tissues from 125 male ESCC patients who underwent primary surgery were analyzed for the methylation status of RARß2 promoter and LINE-1 through methylation-specific polymerase chain reaction and pyrosequencing. RESULTS: RARß2 hypermethylation was detected in 20% of the tumor samples, but not in the normal counterparts. The methylation frequency of LINE-1 was significantly lower in the tumor than in the normal parts (median: 67.7% vs. 80%, P < 0.0005). Ninety-eight patients (78.4%) had both RARß2 hypermethylation and LINE-1 hypomethylation or either one. There was a trend toward higher risk of advanced T stage (P for trend = 0.05) or lymph node metastasis (P for trend = 0.02) when more adverse gene methylation profiles were present. CONCLUSION: Methylation status of RARß2 and LINE-1 was related to the development and possibly the severity of ESCC.

Deletion of retinoic acid receptor ß (RARß) impairs pancreatic endocrine differentiation.

All-trans retinoic acid (RA) signals via binding to retinoic acid receptors (RARs α, ß, and γ). RA directly influences expression of Pdx1, a transcription factor essential for pancreatic development and beta-cell (ß-cell) maturation. In this study we follow the differentiation of cultured wild-type (WT) vs. RARß knockout (KO) embryonic stem (ES) cells into pancreatic islet cells. We found that RARß KO ES cells show greatly reduced expression of some important endocrine markers of differentiated islet cells, such as glucagon, islet amyloid polypeptide (Iapp), and insulin 1 (Ins1) relative to WT. We conclude that RARß activity is essential for proper differentiation of ES cells to pancreatic endocrine cells.

Vitamin A influences the incretin hormone profiles by activating the retinoic acid receptor ß.

BACKGROUND: This study aimed to investigate the impact of Vitamin A (VA) on intestinal glucose metabolic phenotypes. METHODS: Male C57BL/6 mice were randomized assigned to a VA-normal diet (VAN) or a VA-deficient diet (VAD) for 12 weeks. After12 weeks, the VAD mice were given 30 IU/g/d retinol for 10 days and VAN diet (VADN) for 10 weeks. By using glucose tolerance tests, immunofluorescence staining, quantitative polymerase chain reaction, siRNA transduction, and enzyme-linked immunosorbent assay, the glucose metabolic phenotypes as well as secretory function and intracellular hormone changes of STC-1 were assessed. RESULTS: VAD mice showed a decrease of glucose-stimulated insulin secretion and a loss of intestinal glucagon-like peptide-1 (GLP-1) expression. Through reintroducing dietary VA to VAD mice, the intestinal VA levels, GLP-1 expression and normal glucose can be restored. The incubation with retinol increased VA signaling factors expression within STC-1 cells, especially retinoic acid receptor ß (RARß). The activation of RARß restored intracellular incretin hormone synthesis and secretory function. CONCLUSIONS: VA deficiency leads to an imbalance of intestinal glucose metabolic phenotypes through a mechanism involving RARß signaling pathway, suggesting a new method to achieve the treatment for VAD induced glucose metabolism impairment.

Retinoic acid protects against lipopolysaccharide-induced ferroptotic liver injury and iron disorders by regulating Nrf2/HO-1 and RARß signaling.

Acute liver injury (ALI) can progress to severe liver diseases, making its prevention and treatment a focus of research. Retinoic acid (RA) has been shown to have anti-oxidative and iron-regulatory effects on organs. In this study, we investigated the effect of RA on lipopolysaccharide (LPS)-induced ALI in both in vivo and in vitro experiments. We found that RA significantly reduced LPS-induced serum iron and red blood cell-associated disorders, as well as decreased serum ALT and AST levels. RA also reversed the accumulation of non-heme iron and labile iron in LPS-induced mice and hepatocytes by increasing the expression of FTL/H and Fpn. Furthermore, RA inhibited tissue reactive oxygen species (ROS) and malondialdehyde (MDA) production and improved the expression of Nrf2/HO-1/GPX4 in mice and Nrf2 signaling in hepatocytes. In vitro experiments employing RAR agonists and antagonists have revealed that retinoic acid (RA) can effectively inhibit cell ferroptosis induced by lipopolysaccharide (LPS), erastin, and RSL3. The mechanism underlying this inhibition may involve the activation of retinoic acid receptors beta (RARß) and gamma (RARγ). Knocking down the RARß gene in Hepatocytes cells significantly diminished the RA's protective effect, indicating that the anti-ferroptotic role of RA was partially mediated by RARß signaling. Overall, our study demonstrated that RA inhibited ferroptosis-induced liver damage by regulating Nrf2/HO-1/GPX4 and RARß signaling.

Aberrant epigenetic regulation of RARß by TET2 is involved in cutaneous squamous cell carcinoma resistance to retinoic acid.

OBJECTIVES: With the growing incidence of cutaneous squamous cell carcinoma (CSCC), the treatment-resistant invasive CSCC should be taken seriously. Retinoic acid receptor ß (RARß) functions as a tumor suppressor gene and is associated with the proliferation inhibition to retinoic acid. Demethylase TET2 directed epigenetic landscape contributes to cell malignant transform and is involved in therapeutic resistance in tumors. Whether aberrant TET2 participated in the deficient RARß remains largely unknown. Hereby, we identified the aberrant-TET2 directed epigenetic landscape contribute to the deficient RARß in CSCC. METHODS: The immunohistochemistry was used to detect the expression of RARß and TET2. The bisulfite sequencing PCR was used to detect the RARß promoter methylation. Plasmid transfection was used to upregulate TET2 in CSCC cells. Stable overxpressed TET2 cells were used to detect the effect of TET2 on RARß and drug sensitivity in the CCSC. RESULTS: We observed RARß decreased with promoter hypermethylation in CSCC and aberrant TET2 associated with deficient RARß. We upregulated TET2 could reverse promoter hypermethylation and showed a significantly increased expression of RARß, which enhanced the sensitivity of tumor cells to retinoic acid treatment. CONCLUSION: Aberrant TET2 leaded to the hypermethylation of RARß promoter, which contributed to the deficient RARß in CSCC. While reversing the hypermethylation of the RARß promoter by recovering the TET2 could enhance tumor cells to be sensitive to retinoic acid.

Reduced Retinoic Acid Receptor Beta (Rarß) Affects Pancreatic ß-Cell Physiology.

Various studies have suggested a link between vitamin A (VA), all-trans-retinol, and type 2 diabetes (T2D). However, the functional role/expression of vitamin A receptors (Rarα, ß, and γ) in pancreatic ß-cells is not clear yet. Accordingly, we performed a series of bioinformatics, molecular and functional experiments in human islet and INS-1 cells to evaluate the role of Rarß on insulin secretion and pancreatic ß-cell function. Microarray and RNA-sequencing (RAN-seq) expression analysis showed that RARα, ß, and γ are expressed in human pancreatic islets. RNA-seq expression of RARß in diabetic/hyperglycemic human islets (HbA1c ≥ 6.3%) revealed a significant reduction (p = 0.004) compared to nondiabetic/normoglycemic cells (HbA1c < 6%). The expression of RARß with INS and PDX1 showed inverse association, while positive correlations were observed with INSR and HbA1c levels. Exploration of the T2D knowledge portal (T2DKP) revealed that several genetic variants in RARß are associated with BMI. The most associated variant is rs6804842 (p = 1.2 × 10−25). Silencing of Rarß in INS-1 cells impaired insulin secretion without affecting cell viability or apoptosis. Interestingly, reactive oxygen species (ROS) production levels were elevated and glucose uptake was reduced in Rarß-silenced cells. mRNA expression of Ins1, Pdx1, NeuroD1, Mafa, Snap25, Vamp2, and Gck were significantly (p < 0.05) downregulated in Rarß-silenced cells. For protein levels, Pro/Insulin, PDX1, GLUT2, GCK, pAKT/AKT, and INSR expression were downregulated considerably (p < 0.05). The expression of NEUROD and VAMP2 were not affected. In conclusion, our results indicate that Rarß is an important molecule for ß-cell function. Hence, our data further support the potential role of VA receptors in the development of T2D.

Stem Cells as Target for Prostate cancer Therapy: Opportunities and Challenges.

Cancer stem cells (CSCs) and cells in a cancer stem cell-like (CSCL) state have proven to be responsible for tumor initiation, growth, and relapse in Prostate Cancer (PCa) and other cancers; therefore, new strategies are being developed to target such cellular populations. TLR3 activation-based immunotherapy using Polyinosinic:Polycytidylic acid (PIC) has been proposed to be used as a concomitant strategy to first-line treatment. This strategy is based on the induction of apoptosis and an inflammatory response in tumor cells. In combination with retinoids like 9cRA, this treatment can induce CSCs differentiation and apoptosis. A limitation in the use of this combination is the common decreased expression of TLR3 and its main positive regulator p53. observed in many patients suffering of different cancer types such as PCa. Importantly, human exposure to certain toxicants, such as iAs, not only has proven to enrich CSCs population in an in vitro model of human epithelial prostate cells, but additionally, it can also lead to a decreased p53, TLR3 and RA receptor (RARß), expression/activation and thus hinder this treatment efficacy. Therefore, here we point out the relevance of evaluating the TLR3 and P53 status in PCa patients before starting an immunotherapy based on the use of PIC +9cRA to determine whether they will be responsive to treatment. Additionally, the use of strategies to overcome the lower TLR3, RARß or p53 expression in PCa patients, like the inclusion of drugs that increase p53 expression, is encouraged, to potentiate the use of PIC+RA based immunotherapy in these patients.

The Sin3A/MAD1 Complex, through Its PAH2 Domain, Acts as a Second Repressor of Retinoic Acid Receptor Beta Expression in Breast Cancer Cells.

Retinoids are essential in balancing proliferation, differentiation and apoptosis, and they exert their effects through retinoic acid receptors (RARs) and retinoid X receptors (RXRs). RARß is a tumor-suppressor gene silenced by epigenetic mechanisms such as DNA methylation in breast, cervical and non-small cell lung cancers. An increased expression of RARß has been associated with improved breast cancer-specific survival. The PAH2 domain of the scaffold protein SIN3A interacts with the specific Sin3 Interaction Domain (SID) of several transcription factors, such as MAD1, bringing chromatin-modifying proteins such as histone deacetylases, and it targets chromatin for specific modifications. Previously, we have established that blocking the PAH2-mediated Sin3A interaction with SID-containing proteins using SID peptides or small molecule inhibitors (SMI) increased RARß expression and induced retinoic acid metabolism in breast cancer cells, both in in vitro and in vivo models. Here, we report studies designed to understand the mechanistic basis of RARß induction and function. Using human breast cancer cells transfected with MAD1 SID or treated with the MAD SID peptide, we observed a dissociation of MAD1, RARα and RARß from Sin3A in a coimmunoprecipitation assay. This was associated with increased RARα and RARß expression and function by a luciferase assay, which was enhanced by the addition of AM580, a specific RARα agonist; EMSA showed that MAD1 binds to E-Box, similar to MYC, on the RARß promoter, which showed a reduced enrichment of Sin3A and HDAC1 by ChIP and was required for the AM580-enhanced RARß activation in MAD1/SID cells. These data suggest that the Sin3A/HDAC1/2 complex co-operates with the classical repressors in regulating RARß expression. These data suggest that SIN3A/MAD1 acts as a second RARß repressor and may be involved in fine-tuning retinoid sensitivity.

RARß Expression in Keratinocytes from Potentially Malignant Oral Lesions: The Functional Consequences of Re-Expression by De-Methylating Agents.

Loss of RARß2 expression by promoter methylation is an early event in oral carcinogenesis. Understanding the mechanisms and consequences of RARß loss may aid in understanding the disappointing results of retinoid chemoprevention trials. This study aimed to describe the effects of all-trans retinoic acid (ATRA) and the de-methylating agent 5-Aza-2' deoxycytidine (5-AZA-CdR) on a panel of immortal potentially malignant oral lesion (PMOL) cell cultures. RARß expression was assessed in PMOL tissues by immunohistochemistry. Cells were treated with ATRA ± 5-AZA-CdR, and the effects on the cell cycle and senescence were assessed. In PMOL tissues, RARß expression was variable, but lower in biopsies which gave rise to immortal cell cultures. Treatment of iPMOL cells with ATRA resulted in little change in RARß expression, but the addition of 5-AZA-CdR resulted in significant increases. The effects on the cell cycle and senescence were variable and may be related to 5-AZA-CdR, as this has wider effects on the cell cycle. Overall, the response of iPMOL cells to ATRA and 5-AZA-CdR treatment was variable and is dependent on several factors, including RARß-promoter methylation. These findings may help to explain the lack of consistent effect of retinoids in PMOLs seen in chemoprevention trials.