Mechanism of regulation and suppression of melanoma invasiveness by novel retinoic acid receptor-gamma target gene carbohydrate sulfotransferase 10

High expression of RARG accelerates ovarian cancer progression by regulating cell proliferation

PURPOSE

To explore the relationship between retinoic acid receptor gamma (RARG) and ovarian cancer (OC) cell proliferation and the prognosis of patients.

METHODS

The transcriptome and clinical information of 379 OC and 88 normal ovarian samples were downloaded from the Cancer Genome Atlas (TCGA) database and the Genotype Tissue Expression (GTEx) database. We compared the mRNA level of RARG between ovrian normal and tumor tissues with the Wilcoxon rank sum test.The R package "limma" was used to analyze the differences in RARG expression between different clinical subgroups. Kaplan-Meier analysis was applied to evaluate the correlation between RARG and prognosis of patients. A nomogram was established to predict the effect of RARG on prognosis of OC patients. Immunohistochemistry and qRT-PCR experiments were conducted to determine the differential expression of RARG between ovarian normal and tumor tissues. Finally, we altered RARG expression using specific siRNA and lentiviral expression vectors to explore the function of RARG by CCK-8, cell cycle, colony formation, and xenograft assays in nude mice.

RESULTS

RARG was highly expressed in ovarian tumors and was an independent predictor of poor overall survival outcomes. Subgroup analysis showed the high expression of RARG was related to FIGO stage III-IV (P=0.027), overall survival time <5 years (P=0.013) and dead status (P=0.041). The Kaplan-Meier curve indicated that patients with high RARG expression level had poor prognosis. The area under the curve (AUC) of RAGR expression for predicting patient survival rates at 1, 5 and 9 years were 0.659, 0.616 and 0.627, respectively. The GSEA enrichment analysis revealed that RARG was involved in ovarian cancer progression through multiple pathways. In cellular experiments in vitro, downregulation of RARG expression significantly suppressed the proliferation and colony formation capacity of OC cells. In cellular experiments in vivo, knockdown of RARG significantly reduced tumor growth in nude mice, decreased expression levels of Ki-67 and proliferation cell nuclear antigen (PCNA).

CONCLUSIONS

High expression of RARG could promote OC cell proliferation and was an independent predictor of poor prognosis. RARG might work as a potential molecular target and biomarker for individualized diagnosis and treatment in OC patients.

Synthetic Retinoid Kills Drug-Resistant Cancer Stem Cells via Inducing RARγ-Translocation-Mediated Tension Reduction and Chromatin Decondensation

A recently developed synthetic retinoid abrogates proliferation and induces apoptosis of drug-resistant malignant-cancer-stem-cell-like cells. However, the underlying mechanisms of how the synthetic retinoid induces cancer-stem-cell-like cell tumor-repopulating cell (TRC) apoptosis are elusive. Here, it is shown that although the retinoid and conventional anticancer drugs cisplatin, all-trans retinoic acid, and tazarotene all inhibit cytoskeletal tension and decondense chromatin prior to inducing TRC apoptosis, half-maximal inhibitory concentration of the retinoid is 20-fold lower than those anticancer drugs. The synthetic retinoid induces retinoic acid receptor gamma (RARγ) translocation from the nucleus to the cytoplasm, leading to reduced RARγ binding to Cdc42 promoter and Cdc42 downregulation, which decreases filamentous-actin (F-actin) and inhibits cytoskeletal tension. Elevating F-actin or upregulating histone 3 lysine 9 trimethylation decreases retinoid-induced DNA damage and apoptosis of TRCs. The combinatorial treatment with a chromatin decondensation molecule and the retinoid inhibits tumor metastasis in mice more effectively than the synthetic retinoid alone. These findings suggest a strategy of lowering cell tension and decondensing chromatin to enhance DNA damage to abrogate metastasis of cancer-stem-cell-like cells with high efficacy.

Retinoic Acid and Its Derivatives in Skin

The retinoids are a group of compounds including vitamin A and its active metabolite all-trans-retinoic acid (ATRA). Retinoids regulate a variety of physiological functions in multiple organ systems, are essential for normal immune competence, and are involved in the regulation of cell growth and differentiation. Vitamin A derivatives have held promise in cancer treatment and ATRA is used in differentiation therapy of acute promyelocytic leukemia (APL). ATRA and other retinoids have also been successfully applied in a variety of dermatological conditions such as skin cancer, psoriasis, acne, and ichthyosis. Moreover, modulation of retinoic acid receptors and retinoid X (or rexinoid) receptors function may affect dermal cells. The studies using complex genetic models with various combinations of retinoic acid receptors (RARs) and retinoid X (or rexinoid) receptors (RXRs) indicate that retinoic acid and its derivatives have therapeutic potential for a variety of serious dermatological disorders including some malignant conditions. Here, we provide a synopsis of the main advances in understanding the role of ATRA and its receptors in dermatology.

Secreted breast tumor interstitial fluid microRNAs and their target genes are associated with triple-negative breast cancer, tumor grade, and immune infiltration

Background

Studies on tumor-secreted microRNAs point to a functional role of these in cellular communication and reprogramming of the tumor microenvironment. Uptake of tumor-secreted microRNAs by neighboring cells may result in the silencing of mRNA targets and, in turn, modulation of the transcriptome. Studying miRNAs externalized from tumors could improve cancer patient diagnosis and disease monitoring and help to pinpoint which miRNA-gene interactions are central for tumor properties such as invasiveness and metastasis.

Methods

Using a bioinformatics approach, we analyzed the profiles of secreted tumor and normal interstitial fluid (IF) microRNAs, from women with breast cancer (BC). We carried out differential abundance analysis (DAA), to obtain miRNAs, which were enriched or depleted in IFs, from patients with different clinical traits. Subsequently, miRNA family enrichment analysis was performed to assess whether any families were over-represented in the specific sets. We identified dysregulated genes in tumor tissues from the same cohort of patients and constructed weighted gene co-expression networks, to extract sets of co-expressed genes and co-abundant miRNAs. Lastly, we integrated miRNAs and mRNAs to obtain interaction networks and supported our findings using prediction tools and cancer gene databases.

Results

Network analysis showed co-expressed genes and miRNA regulators, associated with tumor lymphocyte infiltration. All of the genes were involved in immune system processes, and many had previously been associated with cancer immunity. A subset of these, BTLA, CXCL13, IL7R, LAMP3, and LTB, was linked to the presence of tertiary lymphoid structures and high endothelial venules within tumors. Co-abundant tumor interstitial fluid miRNAs within this network, including miR-146a and miR-494, were annotated as negative regulators of immune-stimulatory responses. One co-expression network encompassed differences between BC subtypes. Genes differentially co-expressed between luminal B and triple-negative breast cancer (TNBC) were connected with sphingolipid metabolism and predicted to be co-regulated by miR-23a. Co-expressed genes and TIF miRNAs associated with tumor grade were BTRC, CHST1, miR-10a/b, miR-107, miR-301a, and miR-454.

Conclusion

Integration of IF miRNAs and mRNAs unveiled networks associated with patient clinicopathological traits, and underlined molecular mechanisms, specific to BC sub-groups. Our results highlight the benefits of an integrative approach to biomarker discovery, placing secreted miRNAs within a biological context.

All-Trans Retinoic Acid Inhibits Migration and Invasiveness of Rheumatoid Fibroblast-Like Synoviocytes

Fibroblast-like synoviocytes (FLSs) are pivotal in inflammation and joint damage of rheumatoid arthritis (RA). They acquire an active and aggressive phenotype, displaying increased migration and invasiveness and contributing to perpetuate synovial inflammation and destruction of cartilage and bone. The main current therapies of RA are focused against inflammatory factors and immune cells; however, a significant percentage of patients do not successfully respond. Combined treatments with drugs that control inflammation and that reverse the pathogenic phenotype of FLS could improve the prognosis of these patients. An unexplored area includes the retinoic acid, the main biologic retinoid, which is a candidate drug for many diseases but has reached clinical use only for a few. Here, we explored the effect of all-trans retinoic acid (ATRA) on the aggressive phenotype of FLS from patients with RA. RA FLSs were treated with ATRA, tumor necrosis factor (TNF), or TNF+ATRA, and cell migration and invasion were analyzed. In addition, a microarray analysis of expression, followed by gene-set analysis and quantitative polymerase chain reaction validation, was performed. We showed that ATRA induced a notable decrease in FLS migration and invasion that was accompanied by complex changes in gene expression. At supraphysiological doses, many of these effects were overridden or reverted by the concomitant presence of TNF. In conclusion, these results have demonstrated the therapeutic potential of retinoic acid on RA FLS provided TNF could be counterbalanced, either with high ATRA doses or with TNF inhibitors. SIGNIFICANCE STATEMENT: All-trans retinoic acid (ATRA) reduced the rheumatoid arthritis (RA) fibroblast-like synoviocyte migration and invasiveness and down-regulated gene expression of cell motility and migration genes. At supraphysiological doses, some of these effects were reverted by tumor necrosis factor. Therefore, ATRA could be an RA drug candidate that would require high doses or combined treatment with anti-inflammatory drugs.

All-trans retinoic acid-encapsulated, CD20 antibody-conjugated poly(lactic-co-glycolic acid) nanoparticles effectively target and eliminate melanoma-initiating cells in vitro

Purpose

Melanoma, which is initiated from melanocytes, is the most fatal type of skin cancer. Melanoma-initiating cells significantly contribute to the initiation, metastasis, and recurrence of melanoma, and CD20 is a marker of melanoma-initiating cells. All-trans retinoic acid (ATRA) has been demonstrated to induce differentiation, inhibit proliferation, and promote the apoptosis of cancer cells and cancer-initiating cells (CICs). However, there has been no report on ATRA activity against melanoma-initiating cells. In this study, we examined the activity of ATRA against melanoma-initiating cells and developed ATRA-encapsulated poly(lactic-co-glycolic acid) (PLGA) nanoparticles, which were conjugated with a CD20 antibody (ATRA-PNP-CD20) for targeted delivery of ATRA to CD20⁺ melanoma-initiating cells.

Materials and methods

The effects of ATRA and ATRA-PNP-CD20 against melanoma-initiating cells were investigated using a cytotoxicity assay, tumorsphere formation assay, and flow cytometry.

Results

ATRA-PNP-CD20 had a size of 126.9 nm and a negative zeta potential. The drug-loading capacity of ATRA-PNP-CD20 was 8.7%, and ATRA-PNP-CD20 displayed a sustained release of ATRA for 144 hours. The results showed that ATRA-PNP-CD20 could effectively and specifically deliver ATRA to CD20⁺ melanoma-initiating cells, achieving superior inhibitory effects against CD20⁺ melanoma-initiating cells compared with those of free ATRA and nontargeted nanoparticles. To the best of our knowledge, we report for the first time a potent activity of ATRA against CD20⁺ melanoma-initiating cells, targeted drug delivery of ATRA via nanoparticles to melanoma-initiating cells, and the achievement of a superior inhibitory effect against melanoma-initiating cells by using a CD20 antibody.

Conclusion

ATRA-PNP-CD20 represents a promising tool for eliminating melanoma-initiating cells and shows a potential for the therapy of melanoma.

Hinokitiol induces DNA demethylation via DNMT1 and UHRF1 inhibition in colon cancer cells

BACKGROUND

DNA hypermethylation is a key epigenetic mechanism for the silencing of many genes in cancer. Hinokitiol, a tropolone-related natural compound, is known to induce apoptosis and cell cycle arrest and has anti-inflammatory and anti-tumor activities. However, the relationship between hinokitiol and DNA methylation is not clear. The aim of our study was to explore whether hinokitiol has an inhibitory ability on the DNA methylation in colon cancer cells.

RESULTS

MTT data showed that hinokitiol had higher sensitivity in colon cancer cells, HCT-116 and SW480, than in normal colon cells, CCD18Co. Hinokitiol reduced DNA methyltransferase 1 (DNMT1) and ubiquitin-like plant homeodomain and RING finger domain 1 (UHRF1) expression in HCT-116 cells. In addition, the expression of ten-eleven translocation protein 1 (TET1), a known DNA demethylation initiator, was increased by hinokitiol treatment. ELISA and FACS data showed that hinokitiol increased the 5-hydroxymethylcytosine (5hmC) level in the both colon cancer cells, but 5-methylcytosine (5mC) level was not changed. Furthermore, hinokitiol significantly restored mRNA expression of O⁶-methylguanine DNA methyltransferase (MGMT), carbohydrate sulfotransferase 10 (CHST10), and B-cell translocation gene 4 (BTG4) concomitant with reduction of methylation status in HCT-116 cells.

CONCLUSIONS

These results indicate that hinokitiol may exert DNA demethylation by inhibiting the expression of DNMT1 and UHRF1 in colon cancer cells.

RARγ-induced E-cadherin downregulation promotes hepatocellular carcinoma invasion and metastasis

BACKGROUND

Aberrant expression of Retinoic acid receptor γ (RARγ) is implicated in cancer development. Our previous study identified that RARγ functions as a tumor promoter to drive hepatocellular carcinoma (HCC) growth. However, its contribution to HCC invasion and metastasis remains unclear.

METHODS

RARγ expression in clinical HCC samples was detected by western blot and immunohistochemistry. The relationship between RARγ expression levels and the clinical characteristics were evaluated. HCC cell line MHCC-97H were stably knocked down RARγ using a lentivirus vector-based shRNA technique. The cells were analyzed by migration and invasion assays, and injected into nude mice to assess tumor metastasis. E-cadherin expression regulated by RARγ was examined by qPCR, western blot and immunofluorescence staining.

RESULTS

The expression of RARγ is significantly upregulated in human HCC tissues. Moreover, its expression positively correlates with tumor size, distant metastasis and TNM stage, and negatively correlates with length of survival of HCC patients. Knockdown of RARγ markedly inhibits HCC cell invasion and metastasis both in vitro and in vivo. Mechanistic investigations reveal that RARγ functions through regulation of NF-κB-mediated E-cadherin downregulation to promote HCC invasion and metastasis. Notably, RARγ expression status negatively correlates with E-cadherin expression in HCC cell lines and clinical HCC samples.

CONCLUSIONS

These findings demonstrate that RARγ could promote HCC invasion and metastasis by regulating E-cadherin reduction, and implicate new strategies to aggressively treat HCC through targeting RARγ/E-cadherin signaling axis.

ATRA mechanically reprograms pancreatic stellate cells to suppress matrix remodelling and inhibit cancer cell invasion

Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive malignancy with a dismal survival rate. Persistent activation of pancreatic stellate cells (PSCs) can perturb the biomechanical homoeostasis of the tumour microenvironment to favour cancer cell invasion. Here we report that ATRA, an active metabolite of vitamin A, restores mechanical quiescence in PSCs via a mechanism involving a retinoic acid receptor beta (RAR-β)-dependent downregulation of actomyosin (MLC-2) contractility. We show that ATRA reduces the ability of PSCs to generate high traction forces and adapt to extracellular mechanical cues (mechanosensing), as well as suppresses force-mediated extracellular matrix remodelling to inhibit local cancer cell invasion in 3D organotypic models. Our findings implicate a RAR-β/MLC-2 pathway in peritumoural stromal remodelling and mechanosensory-driven activation of PSCs, and further suggest that mechanical reprogramming of PSCs with retinoic acid derivatives might be a viable alternative to stromal ablation strategies for the treatment of PDAC.

Persistent activation of pancreatic stellate cells (PSCs) can perturb the biomechanical homeostasis of the tumour microenvironment. Here the authors show that all-trans retinoic acid reduces retinoic acid receptor beta dependent-actomyosin contractility and restores mechanical quiescence in PSCs.

The Retinoid Agonist Tazarotene Promotes Angiogenesis and Wound Healing

Therapeutic angiogenesis is a major goal of regenerative medicine, but no clinically approved small molecule exists that enhances new blood vessel formation. Here we show, using a phenotype-driven high-content imaging screen of an annotated chemical library of 1,280 bioactive small molecules, that the retinoid agonist Tazarotene, enhances in vitro angiogenesis, promoting branching morphogenesis, and tubule remodeling. The proangiogenic phenotype is mediated by retinoic acid receptor but not retinoic X receptor activation, and is characterized by secretion of the proangiogenic factors hepatocyte growth factor, vascular endothelial growth factor, plasminogen activator, urokinase and placental growth factor, and reduced secretion of the antiangiogenic factor pentraxin-3 from adjacent fibroblasts. In vivo, Tazarotene enhanced the growth of mature and functional microvessels in Matrigel implants and wound healing models, and increased blood flow. Notably, in ear punch wound healing model, Tazarotene promoted tissue repair characterized by rapid ear punch closure with normal-appearing skin containing new hair follicles, and maturing collagen fibers. Our study suggests that Tazarotene, an FDA-approved small molecule, could be potentially exploited for therapeutic applications in neovascularization and wound healing.

RARγ Downregulation Contributes to Colorectal Tumorigenesis and Metastasis by Derepressing the Hippo-Yap Pathway

The Hippo-Yap pathway conveys oncogenic signals, but its regulation during cancer development is not well understood. Here, we identify the nuclear receptor RARγ as a regulator of the Hippo-Yap pathway in colorectal tumorigenesis and metastasis. RARγ is downregulated in human colorectal cancer tissues, where its expression correlates inversely with tumor size, TNM stage, and distant metastasis. Functional studies established that silencing of RARγ drove colorectal cancer cell growth, invasion, and metastatic properties both in vitro and in vivo Mechanistically, RARγ controlled Hippo-Yap signaling to inhibit colorectal cancer development, acting to promote phosphorylation and binding of Lats1 to its transcriptional coactivator Yap and thereby inactivating Yap target gene expression. In clinical specimens, RARγ expression correlated with overall survival outcomes and expression of critical Hippo-Yap pathway effector molecules in colorectal cancer patients. Collectively, our results defined RARγ as tumor suppressor in colorectal cancer that acts by restricting oncogenic signaling by the Hippo-Yap pathway, with potential implications for new approaches to colorectal cancer therapy. Cancer Res; 76(13); 3813-25. ©2016 AACR.

Retinoic acid receptors: from molecular mechanisms to cancer therapy

Retinoic acid (RA), the major bioactive metabolite of retinol or vitamin A, induces a spectrum of pleiotropic effects in cell growth and differentiation that are relevant for embryonic development and adult physiology. The RA activity is mediated primarily by members of the retinoic acid receptor (RAR) subfamily, namely RARα, RARβ and RARγ, which belong to the nuclear receptor (NR) superfamily of transcription factors. RARs form heterodimers with members of the retinoid X receptor (RXR) subfamily and act as ligand-regulated transcription factors through binding specific RA response elements (RAREs) located in target genes promoters. RARs also have non-genomic effects and activate kinase signaling pathways, which fine-tune the transcription of the RA target genes. The disruption of RA signaling pathways is thought to underlie the etiology of a number of hematological and non-hematological malignancies, including leukemias, skin cancer, head/neck cancer, lung cancer, breast cancer, ovarian cancer, prostate cancer, renal cell carcinoma, pancreatic cancer, liver cancer, glioblastoma and neuroblastoma. Of note, RA and its derivatives (retinoids) are employed as potential chemotherapeutic or chemopreventive agents because of their differentiation, anti-proliferative, pro-apoptotic, and anti-oxidant effects. In humans, retinoids reverse premalignant epithelial lesions, induce the differentiation of myeloid normal and leukemic cells, and prevent lung, liver, and breast cancer. Here, we provide an overview of the biochemical and molecular mechanisms that regulate the RA and retinoid signaling pathways. Moreover, mechanisms through which deregulation of RA signaling pathways ultimately impact on cancer are examined. Finally, the therapeutic effects of retinoids are reported.

3'LIFE: a functional assay to detect miRNA targets in high-throughput

MicroRNAs (miRNAs) are short non-coding RNAs that regulate gene output at the post-transcriptional level by targeting degenerate elements primarily in 3'untranslated regions (3'UTRs) of mRNAs. Individual miRNAs can regulate networks of hundreds of genes, yet for the majority of miRNAs few, if any, targets are known. Misexpression of miRNAs is also a major contributor to cancer progression, thus there is a critical need to validate miRNA targets in high-throughput to understand miRNAs' contribution to tumorigenesis. Here we introduce a novel high-throughput assay to detect miRNA targets in 3'UTRs, called Luminescent Identification of Functional Elements in 3'UTRs (3'LIFE). We demonstrate the feasibility of 3'LIFE using a data set of 275 human 3'UTRs and two cancer-relevant miRNAs, let-7c and miR-10b, and compare our results to alternative methods to detect miRNA targets throughout the genome. We identify a large number of novel gene targets for these miRNAs, with only 32% of hits being bioinformatically predicted and 27% directed by non-canonical interactions. Functional analysis of target genes reveals consistent roles for each miRNA as either a tumor suppressor (let-7c) or oncogenic miRNA (miR-10b), and preferentially target multiple genes within regulatory networks, suggesting 3'LIFE is a rapid and sensitive method to detect miRNA targets in high-throughput.

Identification of novel hypermethylated genes and demethylating effect of vincristine in colorectal cancer

BACKGROUND

Colorectal cancer (CRC) arises as a consequence of genetic events such as gene mutation and epigenetic alteration. The aim of this study was to identify new hypermethylated candidate genes and methylation-based therapeutic targets using vincristine in CRC.

METHODS

We analyzed the methylation status of 27,578 CpG sites spanning more than 14,000 genes in CRC tissues compared with adjacent normal tissues and normal colon tissues using Illumina bead chip array. Twenty-one hypermethylated genes and 18 CpG island methylator phenotype markers were selected as candidate genes. The methylation status of 39 genes was validated by quantitative methylation-specific polymerase chain reaction in CRC tissues, adjacent normal tissues, normal colon cells, and three CRC cell lines. Of these, 29 hypermethylated candidate genes were investigated using the demethylating effects of 5-aza-2'-deoxycytidine (5-aza-dC) and vincristine in CRC cells.

RESULTS

Thirty-two out of 39 genes were hypermethylated in CRC tissues compared with adjacent normal tissues. Vincristine induced demethylation of methylated genes in CRC cells to the same extent as 5-aza-dC. The mRNA expression of AKR1B1, CHST10, ELOVL4, FLI1, SOX5, STK33, and ZNF304 was restored by treatment with 5-aza-dC and vincristine.

CONCLUSION

These results suggest that these novel hypermethylated genes AKR1B1, CHST10, ELOVL4, SOX5, STK33, and ZNF304 may be potential methylation biomarkers and therapeutic targets of vincristine in CRC.

Oncogenic activity of retinoic acid receptor γ is exhibited through activation of the Akt/NF-κB and Wnt/β-catenin pathways in cholangiocarcinoma

Aberrant expression and function of retinoic acid receptor γ (RARγ) are often involved in the progression of several cancers. However, the role of RARγ in cholangiocarcinoma (CCA), chemoresistant bile duct carcinoma with a poor prognosis, remains unclear. In the present study, we found that RARγ was frequently overexpressed in human CCA specimens. Its overexpression was associated with poor differentiation, lymph node metastasis, high serum carbohydrate antigen 19-9 level, and poor prognosis of CCA. Downregulation of RARγ reduced CCA cell proliferation, migration, invasion, and colony formation ability in vitro and tumorigenic potential in nude mice. RARγ knockdown resulted in upregulation of cell cycle inhibitor P21, as well as downregulation of cyclin D1, proliferating cell nuclear antigen, and matrix metallopeptidase 9, in parallel with suppression of the Akt/NF-κB pathway. Furthermore, overexpression of RARγ contributed to the multidrug chemoresistance of CCA cells, at least in part due to upregulation of P glycoprotein via activation of the Wnt/β-catenin pathway. Molecular mechanism studies revealed that RARγ interacted with β-catenin and led to β-catenin nuclear translocation. Taken together, our results suggested that RARγ plays an important role in the proliferation, metastasis, and chemoresistance of CCA through simultaneous activation of the Akt/NF-κB and Wnt/β-catenin pathways, serving as a potential molecular target for CCA treatment.

Oncogenic activity of retinoic acid receptor γ is exhibited through activation of the Akt/NF-κB and Wnt/β-catenin pathways in cholangiocarcinoma

Aberrant expression and function of retinoic acid receptor γ (RARγ) are often involved in the progression of several cancers. However, the role of RARγ in cholangiocarcinoma (CCA), chemoresistant bile duct carcinoma with a poor prognosis, remains unclear. In the present study, we found that RARγ was frequently overexpressed in human CCA specimens. Its overexpression was associated with poor differentiation, lymph node metastasis, high serum carbohydrate antigen 19-9 level, and poor prognosis of CCA. Downregulation of RARγ reduced CCA cell proliferation, migration, invasion, and colony formation ability in vitro and tumorigenic potential in nude mice. RARγ knockdown resulted in upregulation of cell cycle inhibitor P21, as well as downregulation of cyclin D1, proliferating cell nuclear antigen, and matrix metallopeptidase 9, in parallel with suppression of the Akt/NF-κB pathway. Furthermore, overexpression of RARγ contributed to the multidrug chemoresistance of CCA cells, at least in part due to upregulation of P glycoprotein via activation of the Wnt/β-catenin pathway. Molecular mechanism studies revealed that RARγ interacted with β-catenin and led to β-catenin nuclear translocation. Taken together, our results suggested that RARγ plays an important role in the proliferation, metastasis, and chemoresistance of CCA through simultaneous activation of the Akt/NF-κB and Wnt/β-catenin pathways, serving as a potential molecular target for CCA treatment.

Nuclear hormone receptor functions in keratinocyte and melanocyte homeostasis, epidermal carcinogenesis and melanomagenesis

Skin homeostasis is maintained, in part, through regulation of gene expression orchestrated by type II nuclear hormone receptors in a cell and context specific manner. This group of transcriptional regulators is implicated in various cellular processes including epidermal proliferation, differentiation, permeability barrier formation, follicular cycling and inflammatory responses. Endogenous ligands for the receptors regulate actions during skin development and maintenance of tissue homeostasis. Type II nuclear receptor signaling is also important for cellular crosstalk between multiple cell types in the skin. Overall, these nuclear receptors are critical players in keratinocyte and melanocyte biology and present targets for cutaneous disease management.

Regulated expression and neural functions of human natural killer-1 (HNK-1) carbohydrate

Human natural killer-1 (HNK-1) carbohydrate, comprising a unique trisaccharide HSO(3)-3GlcAβ1-3Galβ1-4GlcNAc, shows well-regulated expression and unique functions in the nervous system. Recent studies have revealed sophisticated and complicated expression mechanisms for HNK-1 glycan. Activities of biosynthetic enzymes are controlled through the formation of enzyme-complexes and regulation of subcellular localization. Functional aspects of HNK-1 carbohydrate were examined by overexpression, knockdown, and knockout studies of these enzymes. HNK-1 is involved in several neural functions such as synaptic plasticity, learning and memory, and the underlying molecular mechanisms have been illustrated upon identification of the target carrier glycoproteins of HNK-1 such as the glutamate receptor subunit GluA2 or tenascin-R. In this review, we describe recent findings about HNK-1 carbohydrate that provide further insights into the mechanism of its expression and function in the nervous system.

Human natural killer-1 sulfotransferase (HNK-1ST)-induced sulfate transfer regulates laminin-binding glycans on α-dystroglycan

Retinoic acid (RA) is a well established anti-tumor agent inducing differentiation in various cancer cells. Recently, a robust up-regulation of human natural killer-1 sulfotransferase (HNK-1ST) was found in several subsets of melanoma cells during RA-mediated differentiation. However, the molecular mechanism underlying the tumor suppression mediated by HNK-1ST remains unclear. Here, we show that HNK-1ST changed the glycosylation state and reduced the ligand binding activity of α-dystroglycan (α-DG) in RA-treated S91 melanoma cells, which contributed to an attenuation of cell migration. Knockdown of HNK-1ST restored the glycosylation of α-DG and the migration of RA-treated S91 cells, indicating that HNK-1ST functions through glycans on α-DG. Using CHO-K1 cells, we provide direct evidence that HNK-1ST but not other homologous sulfotransferases (C4ST1 and GalNAc4ST1) suppresses the glycosylation of α-DG. The activity-abolished mutant of HNK-1ST did not show the α-DG-modulating function, indicating that the sulfotransferase activity of HNK-1ST is essential. Finally, the HNK-1ST-dependent incorporation of [(35)S]sulfate groups was detected on α-DG. These findings suggest a novel role for HNK-1ST as a tumor suppressor controlling the functional glycans on α-DG and the importance of sulfate transfer in the glycosylation of α-DG.

Sequencing and comparative genomic analysis of 1227 Felis catus cDNA sequences enriched for developmental, clinical and nutritional phenotypes

Background

The feline genome is valuable to the veterinary and model organism genomics communities because the cat is an obligate carnivore and a model for endangered felids. The initial public release of the Felis catus genome assembly provided a framework for investigating the genomic basis of feline biology. However, the entire set of protein coding genes has not been elucidated.

Results

We identified and characterized 1227 protein coding feline sequences, of which 913 map to public sequences and 314 are novel. These sequences have been deposited into NCBI's genbank database and complement public genomic resources by providing additional protein coding sequences that fill in some of the gaps in the feline genome assembly. Through functional and comparative genomic analyses, we gained an understanding of the role of these sequences in feline development, nutrition and health. Specifically, we identified 104 orthologs of human genes associated with Mendelian disorders. We detected negative selection within sequences with gene ontology annotations associated with intracellular trafficking, cytoskeleton and muscle functions. We detected relatively less negative selection on protein sequences encoding extracellular networks, apoptotic pathways and mitochondrial gene ontology annotations. Additionally, we characterized feline cDNA sequences that have mouse orthologs associated with clinical, nutritional and developmental phenotypes. Together, this analysis provides an overview of the value of our cDNA sequences and enhances our understanding of how the feline genome is similar to, and different from other mammalian genomes.

Conclusions

The cDNA sequences reported here expand existing feline genomic resources by providing high-quality sequences annotated with comparative genomic information providing functional, clinical, nutritional and orthologous gene information.