Growth inhibitory retinoid effects after recruitment of retinoid X receptor beta to the retinoic acid receptor beta promoter

Synergistic effect of co-treatment with all-trans retinoic acid and 9-cis retinoic acid on human lung cancer cell line at molecular level

The major challenge in treating cancers with ATRA is the limited availability inside the cell and resistance developed in prolonged treatment. We made an attempt for co-treatment of human NSCLC cell lines (A549) with ATRA and its isomeric precursor (9cisRA). In this study, the growth inhibitory effect of ATRA, 9cisRA and combination of both were tested in A549 cells by MTT and Trypan blue assays. As the effects of retinoid are mediated through their receptors, their gene expression levels were analyzed by RT-PCR. The target gene receptor, RAR-β protein expression, was analyzed by immunocytochemistry. The cancer cell (A549) growth inhibitory effect was significantly (p ≤ 0.001) enhanced in combination treatment when compared with the result of individual treatments. The mRNA expression levels of both RAR-β and RXR-β were found to be increased in co-treatment (band density of 0.75 and 0.806, respectively) when compared with 9cisRA treatment (0.25 and 0.112) and ATRA treatment (0.01 and 0.081). A concomitant enhancement in the target RAR-β protein expression was observed in co-treated cells when compared with individual treatments. We thus conclude that the co-treatment had increased the availability of ATRA, by isomerization of the 9cisRA which then resulted in an increased expression of both RAR-β and RXR-β receptors and the target protein RAR-β which in turn inhibited lung cancer cell growth. Our study results have explored the mechanism of synergistic effect of co-treatment with ATRA and 9cisRA and further preclinical studies are necessary to validate the application of co-treatment of retinoid in clinical use.

Synthesis, Characterization and Anti-Cancer Activity of Hydrazide Derivatives Incorporating a Quinoline Moiety

Identification of the novel (E)-N′-((2-chloro-7-methoxyquinolin-3-yl)methylene)-3-(phenylthio)propanehydrazide scaffold 18 has led to the development of a new series of biologically active hydrazide compounds. The parent compound 18 and new quinoline derivatives 19–26 were prepared from the corresponding quinoline hydrazones and substituted carboxylic acids using EDC-mediated peptide coupling reactions. Further modification of the parent compound 18 was achieved by replacement of the quinoline moiety with other aromatic systems. All the newly synthesized compounds were evaluated for their anti-cancer activity against the SH-SY5Y and Kelly neuroblastoma cell lines, as well as the MDA-MB-231 and MCF-7 breast adenocarcinoma cell lines. Analogues 19 and 22 significantly reduced the cell viability of neuroblastoma cancer cells with micromolar potency and significant selectivity over normal cells. The quinoline hydrazide 22 also induced G₁ cell cycle arrest, as well as upregulation of the p27^kip1 cell cycle regulating protein.

Progression risk assessments of individual non-invasive gastric neoplasms by genomic copy-number profile and mucin phenotype

Background

Early detection and treatment of non-invasive neoplasms can effectively reduce the incidence of advanced gastric carcinoma (GC), but only when the lineage is continuous between non-invasive and advanced tumours. Although a fraction of non-invasive neoplasms progress to invasive GC, it is difficult to identify individual progression-prone non-invasive neoplasms. To classify non-invasive gland-forming gastric neoplasms into clusters of different levels of progression risk, we applied mucin phenotyping and genomic DNA microarray analyses to intramucosal gland-forming gastric neoplasms.

Methods

Formalin-fixed, paraffin-embedded tissues from 19 non-invasive and 24 invasive gland-forming neoplasms were obtained via endoscopic submucosal dissection or surgical excision. According to the Vienna classification, intramucosal neoplasms were classified as low-grade or high-grade non-invasive neoplasms (LGNs [category 3] and HGNs [category 4], respectively) or invasive carcinomas (intramucosal GCs and mucosal parts of submucosal or deeper GCs [category 5]). Neoplastic lesions were characterized by mucin phenotypes determined using monoclonal antibodies against MUC2, MUC5AC, MUC6, and CD10. Genomic DNA samples from mucosal neoplasms were subjected to array-based comparative genomic hybridization and subsequent unsupervised, hierarchical clustering with selected large-sized genes.

Results

There was no significant difference in mucin phenotype between HGNs/LGNs and invasive carcinomas. The clustering classified samples into stable, unstable, and intermediate. The histological tumour grade or mucin phenotype of non-invasive neoplasms did not correlate with the clustering results. Each cluster may represent an independent lineage of different outcome because the size distribution of non-invasive tumours among the 3 clusters almost overlapped. In contrast, the unstable cluster alone included invasive carcinomas.

Conclusions

These findings suggest that the outcome of individual tumours is not stochastically determined but can be predicted from the genomic copy-number profile even at the non-invasive stage. Non-invasive neoplasms of the unstable clusters, which accounted for 21% of non-invasive neoplasms, may progress to invasive carcinomas, whereas those of stable cluster may not.

Electronic supplementary material

The online version of this article (doi:10.1186/s12920-015-0080-6) contains supplementary material, which is available to authorized users.

Spatial learning and memory deficit of low level polybrominated diphenyl ethers-47 in male adult rat is modulated by intracellular glutamate receptors

Polybrominated diphenyl ethers (PBDEs), a class of widely used flame retardants, are extensively diffused in the environment. Of particular concern are the reported highly sensitivity of PBDEs in children or developmental animals, however, almost no information is available on their potential effects on adults and the mechanisms are still unknown. In the present study, we investigated the neurotoxic effects of sub-chronic PBDE-47 exposure on adult male Sprague-Dawley rats. Thus, PBDE-47, 0.1, 0.5 and 1 mg/kg per day was administered to rats by gavage for 30 days. The learning and memory function was tested by Morris water maze. Further, in order to explore the potential mechanism, the expression of NMDA-receptors was evaluated by using both immunohistochemistry (IHC) and RT-PCR. Our results showed that sub-chronic exposure to PBDE-47 produced learning and memory deficits in male adult rats. Also, significant decrease in the CA1, CA3 and dentate gyrus areas of hippocampus affected by all three doses of PBDE-47 on the expression of NR(1), NR(2)B and Glu were found by IHC. In addition, the evaluation of expression of the NR(1), NR(2)B and NR(2)C showed statistically significant decrease in mRNA expression in rats exposed to PBDE-47. These findings showed that sub-chronic exposure to PBDE-47 could also induce behavioral alterations and the neurotoxic effects might due to the down-regulation expression of NMDA receptors. Our data indicated that the possibility of exposure of adults to PBDE-47 warranted further studies to characterize their potential neurotoxicity.

Reversible upregulation of tropomyosin-related kinase receptor B by geranylgeranoic acid in human neuroblastoma SH-SY5Y cells

All-trans retinoic acid (ATRA) plays crucial roles in cell survival and differentiation of neuroblastoma cells. In the present study, we investigated the effects of geranylgeranoic acid (GGA), an acyclic retinoid, on differentiation and tropomyosin-related kinase receptor B (TrkB) gene expression in SH-SY5Y human neuroblastoma cells in comparison with ATRA. GGA induced growth suppression and neural differentiation to the same extent as ATRA. Two variants (145 and 95 kD) of the TrkB protein were dramatically increased by GGA treatment, comparable to the effect of ATRA. Following 6- to 8-day GGA treatment, the effect of GGA on TrkB was reversed after 2-4 days of its removal, whereas the effect of ATRA was irreversible under the same conditions. Both GGA and ATRA upregulated the cellular levels of three major TrkB messenger RNA splice variants in a time-dependent manner. Time-dependent induction of cell cycle-related genes, such as cyclin D1 and retinoblastoma protein, and amplification of the neural progenitor cell marker, brain lipid binding protein, were suppressed by GGA treatment and were completely abolished by ATRA. ATRA and GGA induced retinoic acid receptor β (RARβ) expression, whereas the time-dependent expression of both RARα and RARγ was abolished by ATRA, but not by GGA. Our results suggest that GGA may be able to restore neuronal properties of SH-SY5Y human neuroblastoma cells in a similar but not identical way to ATRA.

ATP7A is a novel target of retinoic acid receptor beta2 in neuroblastoma cells

Increased retinoic acid receptor β (RARβ₂) gene expression is a hallmark of cancer cell responsiveness to retinoid anticancer effects. Moreover, low basal or induced RARβ₂ expression is a common feature of many human cancers, suggesting that RARβ₂ may act as a tumour suppressor gene in the absence of supplemented retinoid. We have previously shown that low RARβ₂ expression is a feature of advanced neuroblastoma. Here, we demonstrate that the ABC domain of the RARβ₂ protein alone was sufficient for the growth inhibitory effects of RARβ₂ on neuroblastoma cells. ATP7A, the copper efflux pump, is a retinoid-responsive gene, was upregulated by ectopic overexpression of RARβ₂. The ectopic overexpression of the RARβ₂ ABC domain was sufficient to induce ATP7A expression, whereas, RARβ₂ siRNA blocked the induction of ATP7A expression in retinoid-treated neuroblastoma cells. Forced downregulation of ATP7A reduced copper efflux and increased viability of retinoid-treated neuroblastoma cells. Copper supplementation enhanced cell growth and reduced retinoid-responsiveness, whereas copper chelation reduced the viability and proliferative capacity. Taken together, our data demonstrates ATP7A expression is regulated by retinoic acid receptor β and it has effects on intracellular copper levels, revealing a link between the anticancer action of retinoids and copper metabolism.

The estrogen-responsive B box protein (EBBP) restores retinoid sensitivity in retinoid-resistant cancer cells via effects on histone acetylation

Retinoids have significant clinical activity in several human cancers, yet the factors determining retinoid sensitivity in cancer cells are still unclear. Retinoid-induced expression of retinoic acid receptor (RAR) beta(2) is a necessary component of the retinoid anticancer signal in cancer cells. We have previously identified the Estrogen-responsive B Box Protein (EBBP), a member of the Tripartite Motif (TRIM) protein family, as a novel RARbeta2 transcriptional regulator in the retinoid signal. Here we examined the mechanism of the EBBP effect on the retinoid anticancer signal. We assessed retinoid-responsive RARbeta2 transcription in retinoid-resistant breast and lung cancer cells in the presence of chromatin modifying agents. A histone deacetylase (HDAC) inhibitor alone, or in combination with retinoid, was more effective than a demethylating agent in restoring RARbeta2 transcription in resistant cells. Overexpression of EBBP alone markedly increased histone acetylation. The effect of EBBP on retinoid-responsive transcription appeared to be limited to genes with the retinoic acid response element (betaRARE) regulatory sequence, such as CYP26A1. EBBP inhibited cell growth by effects on cyclin D1 and Phospho-Rb, and, reduced cell viability in retinoid-resistant cancer cells. The viability of non-cancer cells was unaffected by EBBP overexpression. Taken together our data suggests that EBBP acts to de-repress transcription of RARbeta2 and CYP26A1, by modifying histone acetylation in retinoid-resistant cancer cells, and, is an important target for drug discovery in retinoid-resistant cancers.

Histone deacetylase inhibitors regulate retinoic acid receptor beta expression in neuroblastoma cells by both transcriptional and posttranscriptional mechanisms

The retinoic acid receptor beta (RARbeta) is a retinoic acid (RA)-inducible tumor suppressor, which plays an important role in the arrest of neuroblastoma cell growth. Using human neuroblastoma SH-SY5Y cells, we have examined the regulation of RARbeta expression by histone deacetylase inhibitors (HDACi), considered to be promising agents in anticancer therapy. Our results show that HDACi cooperated with RA to increase RARbeta mRNA levels and to activate the RARbeta2 promoter in transient transfection assays. Chromatin immunoprecipitation assays showed that the basal RARbeta2 promoter that contains the RA response element was refractory to acetylation by both HDACi and RA. In addition, HDACi caused a transient increase in acetylation of a downstream RARbeta2 region, even though global histones remain hyperacetylated after a prolonged treatment with the inhibitors. RA potentiated this response and maintained acetylation for a longer period. Despite the cooperation of RA with HDACi to increase transcription of the RARbeta gene, these inhibitors caused a paradoxical reduction of the cellular levels of the RARbeta protein in cells treated with the retinoid. This reduction is secondary to a change in the protein half-life that is decreased by the HDACi due to increased ubiquitin-independent proteasomal degradation. These results show that HDACi regulate expression of the tumor suppressor gene RARbeta by both transcriptional and posttranscriptional mechanisms and might then modulate sensitivity to the retinoid in neuroblastoma cells.

The estrogen-responsive B box protein is a novel regulator of the retinoid signal

Retinoic acid (RA) induces growth arrest, cell death, and differentiation in many human cancer cells in vitro and has entered routine clinical use for the treatment of several human cancer types. One mechanism by which cancer cells evade retinoid-induced effects is through repression of retinoic acid receptor beta (RARbeta) gene transcription. The RA response element beta (betaRARE) is the essential DNA sequence required for retinoid-induced RARbeta transcription. Here we show that the estrogen-responsive B box protein (EBBP), a member of the RING-B box-coiled-coil protein family, is a betaRARE-binding protein. EBBP undergoes serine threonine phosphorylation and enhanced protein stability after RA treatment. Following RA treatment, we also observed increased nuclear EBBP levels in aggregates with the promyelocytic leukemia protein at promyelocytic leukemia nuclear bodies. EBBP enhanced RA-responsive RARbeta transcription in RA-sensitive and -resistant cancer cells, which were resistant to both a histone deacetylase inhibitor and a demethylating agent. EBBP-specific small interfering RNA reduced basal and RA-induced RARbeta expression. EBBP increased betaRARE-transactivating function through its coiled-coil domain. Taken together, our work suggests that EBBP may have a pivotal role in the retinoid anti-cancer signal.

The retinoid anticancer signal: mechanisms of target gene regulation

Retinoids induce growth arrest, differentiation, and cell death in many cancer cell types. One factor determining the sensitivity or resistance to the retinoid anticancer signal is the transcriptional response of retinoid-regulated target genes in cancer cells. We used cDNA microarray to identify 31 retinoid-regulated target genes shared by two retinoid-sensitive neuroblastoma cell lines, and then sought to determine the relevance of the target gene responses to the retinoid anticancer signal. The pattern of retinoid responsiveness for six of 13 target genes (RARβ2, CYP26A1, CRBP1, RGS16, DUSP6, EGR1) correlated with phenotypic retinoid sensitivity, across a panel of retinoid-sensitive or -resistant lung and breast cancer cell lines. Retinoid treatment of MYCN transgenic mice bearing neuroblastoma altered the expression of five of nine target genes examined (RARβ2, CYP26A1, CRBP1, DUSP6, PLAT) in neuroblastoma tumour tissue in vivo. In retinoid-sensitive neuroblastoma, lung and breast cancer cell lines, direct inhibition of retinoid-induced RARβ2 expression blocked induction of only one of eight retinoid target genes (CYP26A1). DNA demethylation, histone acetylation, and exogenous overexpression of RARβ2 partially restored retinoid-responsive CYP26A1 expression in RA-resistant MDA-MB-231 breast, but not SK-MES-1 lung, cancer cells. Combined, rather than individual, inhibition of DUSP6 and RGS16 was required to block retinoid-induced growth inhibition in neuroblastoma cells, through phosphorylation of extracellular-signal-regulated kinase. In conclusion, sensitivity to the retinoid anticancer signal is determined in part by the transcriptional response of key retinoid-regulated target genes, such as RARβ2, DUSP6, and RGS16.

Identification of a molecular signature of sarcopenia

Investigating the molecular mechanisms underlying sarcopenia in humans with the use of microarrays has been complicated by low sample size and the variability inherent in human gene expression profiles. We have conducted a study using Affymetrix GeneChips to identify a molecular signature of aged skeletal muscle. The molecular signature was defined as the set of expressed genes that best distinguished the vastus lateralis muscle of young (n = 10) and older (n = 12) male subjects, when a k-nearest neighbor supervised classification method was used in conjunction with a signal-to-noise ratio gene selection method and a holdout cross-validation procedure. The age-specific expression signature was comprised of 45 genes; 27 were upregulated and 18 were downregulated. This signature also correctly classified 75% of the muscle samples from young and older subjects published by an independent laboratory, based on their expression profiles. The signature revealed increased expression of several genes involved in mediating cellular responses to inflammation and apoptosis, including complement component C1QA, Galectin-1, C/EBP-beta, and FOXO3A, among others. The increased expressions of genes that regulate pre-mRNA splicing, localization, and modification of RNA comprise markers of the aging signature. Downregulated genes in the signature were the glutamine transporter SLC38A1, a TRAF-6 inhibitory zinc finger protein, and membrane-bound transcription factor protease S2P, among others. The sarcopenia signature developed here will be useful as a molecular model to judge the effectiveness of exercise and other therapeutic treatments aimed at ameliorating the effects of muscle loss associated with aging.