Cellular Retinoic Acid–Binding Protein II Is a Direct Transcriptional Target of MycN in Neuroblastoma

Cellular Retinoic Acid Binding Protein 2 (CRABP2), Up-regulated by HPV E6/E7, Leads to Aberrant Activation of the Integrin β1/FAK/ERK Signaling Pathway and Aggravates the Malignant Phenotypes of Cervical Cancer

The ectopic expression of cellular retinoic acid binding protein 2 (CRABP2) is associated with various tumorigenesis. However, the effects of CRABP2 on the progression of cervical cancer are still unclear. The current study aimed to investigate the role of CRABP2 in the malignant phenotypes of cervical cancer cells. CRABP2 was artificially regulated in CaSki, SiHa, and C-33A cells. CCK-8 assay and flow cytometry were used to assess the cell proliferation and apoptosis abilities, respectively. Wound healing assay and transwell assay were employed to measure the cell migration and invasion abilities, respectively. The results showed that CRABP2 was highly expressed in cervical carcinoma tissues and cell lines, and its high expression was associated with poor overall survival. Knockdown of CRABP2 promoted the cell apoptosis and inhibited cell proliferation, migration, and invasion in cervical carcinoma cells, whereas CRABP2 overexpression exhibited the opposite results. Mechanically, CRABP2 silencing suppressed the Integrin β1/FAK/ERK signaling via HuR. Treatment with siITGB1 or a FAK inhibitor PF-562271 or an ERK inhibitor FR180204 reversed the promoting effects of CRABP2 on cell proliferation, migration, and invasion. Moreover, the overexpression of CRABP2 reverted the HPV16 E6/E7 knockdown-induced inhibition of cell proliferation, migration, and invasion in cervical cancer cells. These results suggested that HPV16 E6/E7 promoted the malignant phenotypes of cervical cancer by upregulating the expression of CRABP2. In conclusion, CRABP2, upregulated by HPV E6/E7, promoted the progression of cervical cancer through activating the Integrin β1/FAK/ERK signaling pathway via HuR.

Defining the Regulatory Logic of Breast Cancer Using Single-Cell Epigenetic and Transcriptome Profiling

Annotation of the cis-regulatory elements that drive transcriptional dysregulation in cancer cells is critical to improving our understanding of tumor biology. Herein, we present a compendium of matched chromatin accessibility (scATAC-seq) and transcriptome (scRNA-seq) profiles at single-cell resolution from human breast tumors and healthy mammary tissues processed immediately following surgical resection. We identify the most likely cell-of-origin for luminal breast tumors and basal breast tumors and then introduce a novel methodology that implements linear mixed-effects models to systematically quantify associations between regions of chromatin accessibility (i.e. regulatory elements) and gene expression in malignant cells versus normal mammary epithelial cells. These data unveil regulatory elements with that switch from silencers of gene expression in normal cells to enhancers of gene expression in cancer cells, leading to the upregulation of clinically relevant oncogenes. To translate the utility of this dataset into tractable models, we generated matched scATAC-seq and scRNA-seq profiles for breast cancer cell lines, revealing, for each subtype, a conserved oncogenic gene expression program between in vitro and in vivo cells. Together, this work highlights the importance of non-coding regulatory mechanisms that underlie oncogenic processes and the ability of single-cell multi-omics to define the regulatory logic of BC cells at single-cell resolution.

Opposite Effects of CRABP1 and CRABP2 Homologs on Proliferation of Breast Cancer Cells and Their Sensitivity to Retinoic Acid

Resistance of tumor cells to retinoic acid (RA), a promising therapeutic agent, is the major factor limiting the use of RA in clinical practice. The mechanisms of resistance to RA are still poorly understood. Cellular Retinoic Acid Binding Proteins, CRABP1 and CRABP2, are essential mediators of RA signaling, but role of the two CRABP homologs in regulating cellular sensitivity to RA has not been well studied. In addition, the effects of CRABP1 and CRABP2 on cell proliferation have not been compared. Here, using a broad panel of breast cancer cell lines with different levels of RA sensitivity/resistance, we show for the first time that in the RA-sensitive cells, CRABP1 expression is restricted by methylation, and protein levels are highly variable. In the moderately-RA-resistant cell lines, high level of CRABP1 is observed both at the mRNA and protein levels, unchanged by inhibition of DNA methylation. The cell lines with maximum resistance to RA are characterized by complete repression of CRABP1 expression realized at transcriptional and posttranscriptional levels, and exogenous expression of each of the CRABP homologs has no effect on the studied characteristics. CRABP1 and CRABP2 proteins have opposing effects on proliferation and sensitivity to RA. In particular, CRABP1 stimulates and CRABP2 reduces proliferation and resistance to RA in the initially RA-sensitive cells, while in the more resistant cells the role of each homolog in both of these parameters is reversed. Overall, we have shown for the first time that CRABP proteins exert different effects on the growth and sensitivity to RA of breast cancer cells (stimulation, suppression, or no effect) depending on the baseline level of RA-sensitivity, with the effects of CRABP1 and CRABP2 homologs on the studied properties always being opposite.

CRABP2 - A novel biomarker for high-risk endometrial cancer

OBJECTIVE

Investigate the clinical and functional implications of elevated CRABP2 expression in endometrial cancer (EC) patients.

METHODS

Patients were stratified into high and low CRABP2 expression groups using a decision tree classifier. Univariate and multivariate statistical analyses determined the prognostic and clinicopathological consequences of increased CRABP2 expression. A CRABP2 gene signature was generated using differential expression analysis, and analyzed using network-based approaches. The findings were validated in The Clinical Proteomic Tumor Analysis Consortium (CPTAC), a newly generated cohort of 120 endometrial tissues, and The Cancer Dependency Map (DepMap).

RESULTS

60 (11%) patients in TCGA had high CRABP2 expression, whilst 468 (89%) had low expression. High expression was associated with serous EC, reduced overall survival, advanced stage and grade. Downstream retinoic acid receptors (RARG and RARA) were correlated with CRABP2 expression and were associated with worse prognosis in serous EC. The CRABP2 gene signature was enriched for Polycomb target gene sets, and was regulated by ELP3 and BMP7. BMP7 expression was increased in the CRABP2-high group, was associated with worse prognosis, and CRISPR-Cas9 screens revealed correlations in its cell-fitness score with CRABP2 following gene knockout. The opposite was true for ELP3, suggesting opposing effects from both master regulators.

CONCLUSIONS

CRABP2 expression is associated with poor prognosis and advanced EC. The expression of RARA and RARG correlates with CRABP2 and are associated with worse prognosis in advanced histological subtypes. Polycomb target gene sets and two master regulators, ELP3 and BMP7, were identified as functionally relevant mechanisms driving aberrant CRABP2 expression.

Coronary artery disease and cancer: a significant resemblance

Cancer and coronary artery disease (CAD) are two of the most common causes of death, and they frequently coexist, especially as the world's population ages. CAD can develop prior to or following cancer diagnosis, as well as a side effect of cancer treatment. CAD develops as complex interactions of lifestyle and hereditary variables, just like the development of the most complex and non-communicable diseases. Cancer is caused by both external/acquired factors (tobacco, food, physical activity, alcohol consumption, epigenetic alterations) and internal/inherited factors (genetic mutations, hormones, and immunological diseases). The Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)-associated protein 9 (Cas9) system has recently emerged as a strong tool for gene therapy for both cancer as well as CAD treatment due to its great accuracy and efficiency. A deeper understanding of the complex link between CAD and cancer should lead to better prevention, faster detection, and safer treatment strategies.

E-cadherin on epithelial-mesenchymal transition in thyroid cancer

Thyroid carcinoma is a common malignant tumor of endocrine system and head and neck. Recurrence, metastasis and high malignant expression after routine treatment are serious clinical problems, so it is of great significance to explore its mechanism and find action targets. Epithelial-mesenchymal transition (EMT) is associated with tumor malignancy and invasion. One key change in tumour EMT is low expression of E-cadherin. Therefore, this article reviews the expression of E-cadherin in thyroid cancers (TC), discuss the potential mechanisms involved, and outline opportunities to exploit E-cadherin on regulating the occurrence of EMT as a critical factor in cancer therapeutics.

CRABP1 and CRABP2 Protein Levels Correlate with Each Other but Do Not Correlate with Sensitivity of Breast Cancer Cells to Retinoic Acid

Retinoic acid (RA) binding proteins, CRABP1 and CRABP2, are molecular chaperones that mediate intracellular activity of RA, the key promoter of cell differentiation with tumor suppressor activity. One of the main functions of CRABP2 is delivery and transfer of RA to the nuclear receptors RAR/RXR, which leads to activation of the transcription of a wide range of retinoid-responsive genes. The functions of CRABP1 are less studied but are apparently associated with sequestration of RA in cytoplasm and limitation of its transcriptional activity, suggesting involvement of this protein in the development of RA resistance. The mechanisms regulating activity of CRABP1 are also poorly understood. Comparison of the CRABP1 level in tumor cell lines of various origins, performed for the first time here, showed absence of the CRABP1 protein in the cell lines of tumors considered to be RA-resistant, and pronounced production of this protein in the RA-sensitive cells. However, analysis carried out with a panel of breast cancer cell lines with different levels of RA-sensitivity showed that there was no correlation between the production of CRABP1 protein and the sensitivity of the cells to RA. At the same time, we found strong correlation between the expression of CRABP1 and CRABP2 proteins in all studied cell types, regardless of their origin and RA-sensitivity/resistance. Moreover, suppression of the CRABP1 level in both RA-sensitive and RA-resistant cells was shown in the cells with cells with knockdown of CRABP2 gene. The revealed CRABP2-dependent regulation of CRABP1 production is a new mechanism of the intracellular retinoic signaling system.

LINC01816 promotes the migration, invasion and epithelial‑mesenchymal transition of thyroid carcinoma cells by sponging miR‑34c‑5p and regulating CRABP2 expression levels

Thyroid carcinoma (THCA) is a common type of endocrine system cancer and its current clinical treatment method is surgical resection. Long non-coding RNAs (lncRNAs) have been revealed to serve important roles in a variety of complex human diseases. Therefore, determining the association between lncRNAs and diseases may provide novel insight into disease-related lncRNAs, with the aim of improving disease treatments and diagnoses. Long intergenic non-protein coding RNA 1816 (LINC01816) was identified to be associated with the survival of patients with colorectal cancer using the IDHI-MIRW method. The present study aimed to investigate the role and molecular mechanism of LINC01816 in THCA. Analysis of datasets from The Cancer Genome Atlas database revealed that the upregulation of LINC01816 expression levels was associated with a variety of cancer types. Reverse transcription-quantitative PCR analysis demonstrated that compared with the normal thyroid tissues, the expression levels of LINC01816 were upregulated in THCA tissues. The results of wound healing and Transwell assays, and western blotting demonstrated that the overexpression of LINC01816 could strengthen the invasive and migratory abilities of THCA cells and enhance epithelial-mesenchymal transition progression. Analysis using the starBase website and dual-luciferase reporter assays identified that microRNA (miR)-34c-5p was a target of LINC01816. The overexpression of miR-34c-5p could inhibit the invasive and migratory abilities of THCA cells, in addition to inhibiting the cellular retinoic acid binding protein 2 (CRABP2) overexpression-induced effects on invasion, migration and EMT processes. In conclusion, the findings of the present study indicated that LINC01816 may be capable of sponging miR-34c-5p to upregulate CRABP2 expression levels, which subsequently promoted the invasion, migration and EMT of THCA cells. Therefore, targeting the LINC01816/miR-34c-5p/CRABP2 pathway may be an effective therapeutic approach for patients with THCA.

Small-molecule PROTACs: novel agents for cancer therapy

Proteolysis-targeting chimera (PROTAC) is a new technology to selectively degrade target proteins via ubiquitin-proteasome system. PROTAC molecules (PROTACs) are a class of heterobifunctional molecules, which contain a ligand targeting the protein of interest, a ligand recruiting an E3 ligase and a linker connecting these two ligands. They provide several advantages over traditional inhibitors in potency, selectivity and drug resistance. Thus, many promising PROTACs have been developed in the recent two decades, especially small-molecule PROTACs. In this review, we briefly introduce the mechanism of PROTACs and focus on the progress of small-molecule PROTACs based on different E3 ligases. In addition, we also introduce the opportunities and challenges of small-molecule PROTACs for cancer therapy.

Recognition Sites for Cancer-targeting Drug Delivery Systems

BACKGROUND

Target-homing drug delivery systems are now gaining significant attention for use as novel therapeutic approaches in antitumor targeting for cancer therapy. Numerous targeted drug delivery systems have been designed to improve the targeting effects because these systems can display a range of favorable properties, thus, providing suitable characteristics for clinical applicability of anticancer drugs, such as increasing the solubility, and improving the drug distribution at target sites. The majority of these targeting systems are designed with respect to differences between cancerous and normal tissues, for instance, the low pH of tumor tissues or overexpressed receptors on tumor cell membranes. Due to the growing number of targeting possibilities, it is important to know the tumor-specific recognition strategies for designing novel, targeted, drug delivery systems. Herein, we identify and summarize literature pertaining to various recognition sites for optimizing the design of targeted drug delivery systems to augment current chemotherapeutic approaches.

OBJECTIVE

This review focuses on the identification of the recognition sites for developing targeted drug delivery systems for use in cancer therapeutics.

METHODS

We have reviewed and compiled cancer-specific recognition sites and their abnormal characteristics within tumor tissues (low pH, high glutathione, targetable receptors, etc.), tumor cells (receptor overexpression or tumor cell membrane changes) and tumor cell organelles (nuclear and endoplasmic reticular dysregulation) utilizing existing scientific literature. Moreover, we have highlighted the design of some targeted drug delivery systems that can be used as homing tools for these recognition sites.

RESULTS AND CONCLUSION

Targeted drug delivery systems are a promising therapeutic approach for tumor chemotherapy. Additional research focused on finding novel recognition sites, and subsequent development of targeting moieties for use with drug delivery systems will aid in the evaluation and clinical application of new and improved chemotherapeutics.

Selective Degradation of Target Proteins by Chimeric Small-Molecular Drugs, PROTACs and SNIPERs

New therapeutic modalities are needed to address the problem of pathological but undruggable proteins. One possible approach is the induction of protein degradation by chimeric drugs composed of a ubiquitin ligase (E3) ligand coupled to a ligand for the target protein. This article reviews chimeric drugs that decrease the level of specific proteins such as proteolysis targeting chimeric molecules (PROTACs) and specific and nongenetic inhibitor of apoptosis protein (IAP)-dependent protein erasers (SNIPERs), which target proteins for proteasome-mediated degradation. We cover strategies for increasing the degradation activity induced by small molecules, and their scope for application to undruggable proteins.

CRABP2 regulates invasion and metastasis of breast cancer through hippo pathway dependent on ER status

Background

Triple Negative Breast cancer (TNBC) is incurable cancer with higher rates of relapse and shorter overall survival compared with other subtypes of breast cancer. Cellular retinoic acid binding protein 2 (CRABP2) belongs to fatty acid binding protein (FABP) family which binds with all-trans retinoic acid (RA). Previous studies from the database have reported the patients with high expression of CRABP2 showed different prognosis in ER⁺ and ER⁻ breast cancer. However, its biological role and exact mechanism in breast cancer remain unknown. This aim of this study was to explore how CRABP2 regulated invasion and metastasis based on the estrogen receptor-α (herein called ER) status in breast cancer.

Methods

Immunohistochemical staining method was used to analyze the expression of CRABP2 in human breast cancer tissues. Lentivirus vector-based shRNA technique was used to test the functional relevance of CRABP2 knockdown in breast tumors. Tail vein injection model was used to examine the lung metastasis. Co-immunoprecipitation, Western blotting, immunofluorescence, and quantitative reverse transcription polymerase chain reaction (RT-qPCR) were conducted to investigate the underlying mechanism that influenced the ER to the regulation of CRABP2 to Lats1.

Results

We observed that knockdown of CRABP2 promotes EMT, invasion and metastasis of ER⁺ breast cancer cells in vitro and in vivo, whereas overexpression of CRABP2 yields the reverse results. In ER⁺ mammary cancer cells, the interaction of CRABP2 and Lats1 suppress the ubiquitination of Lats1 to activate Hippo pathway to inhibit the invasion and metastasis of ER⁺ mammary cancer. However, in ER⁻ mammary cancer cells, the interaction of CRABP2 and Lats1 promote the ubiquitination of Lats1 to inactivate Hippo pathway to promote the invasion and metastasis of ER⁻ mammary cancer.

Conclusions

Our findings indicate that CRABP2 can suppress invasion and metastasis of ER⁺ breast cancer and promote invasion and metastasis of ER⁻ breast cancer by regulating the stability of Lats1 in vitro and in vivo, and it provides new ideas for breast cancer therapy.

Electronic supplementary material

The online version of this article (10.1186/s13046-019-1345-2) contains supplementary material, which is available to authorized users.

Crabp2 Promotes Metastasis of Lung Cancer Cells via HuR and Integrin β1/FAK/ERK Signaling

Increased Crabp2 levels have been found in various types of cancer, and are associated with poor patients’ survival. Although Crabp2 is found to be overexpressed in lung cancer, its role in metastasis of lung cancer is unclear. In this study, Crabp2 was overexpressed in high-metastatic C10F4 than low-metastatic lung cancer cells. Analysis of clinical samples revealed that high CRABP2 levels were correlated with lymph node metastases, poor overall survival, and increased recurrence. Knockdown of Crabp2 decreased migration, invasion, anoikis resistance, and in vivo metastasis. Crabp2 was co-immunoprecipitated with HuR, and overexpression of Crabp2 increased HuR levels, which promoted integrin β1/FAK/ERK signaling. Inhibition of HuR or integrin β1/FAK/ERK signaling reversed the promoting effect of Crabp2 in migration, invasion, and anoikis resistance. Knockdown of Crabp2 further inhibited the growth of cancer cells as compared with that by gemcitabine or irinotecan alone. The expression of Crabp2 in human lung tumors was correlated with stress marker CHOP. In conclusion, our findings have identified the promoting role of Crabp2 in anoikis resistance and metastasis. CRABP2 may serve as a prognostic marker and targeting CRABP2 may be exploited as a modality to reduce metastasis.

Plasma CRABP2 as a Novel Biomarker in Patients with Non-Small Cell Lung Cancer

BACKGROUND

Lung cancer is the most common cause of cancer-related mortality worldwide. We previously reported the identification of a new genetic marker, cellular retinoic acid binding protein 2 (CRABP2), in lung cancer tissues. The aim of this study was to assess plasma levels of CRABP2 from patients with non-small cell lung cancer (NSCLC).

METHODS

Blood samples that were collected from 122 patients with NSCLC between September 2009 and September 2013 were selected for the analysis, along with samples from age- (± 5 years), sex-, and cigarette smoking history (± 10 pack-years [PY])-matched controls from the Korea Biobank Network. The control specimens were from patients who were without malignancies or pulmonary diseases. We measured plasma levels of CRABP2 using commercially available enzyme-linked immunosorbent assay kits.

RESULTS

The mean age of the NSCLC patients was 71.8 ± 8.9 years, and the median cigarette smoking history was 32 PY (range, 0-150 PY). Plasma CRABP2 levels were significantly higher in patients with NSCLC than in the matched controls (37.63 ± 28.71 ng/mL vs. 24.09 ± 21.09 ng/mL, P < 0.001). Higher plasma CRABP2 levels were also correlated with lower survival rates in NSCLC patients (P = 0.014).

CONCLUSION

Plasma CRABP2 levels might be a novel diagnostic and prognostic marker in NSCLC.

Chemical Protein Degradation Approach and its Application to Epigenetic Targets

In addition to traditional drugs, such as enzyme inhibitors, receptor agonists/antagonists, and protein-protein interaction inhibitors as well as genetic technology, such as RNA interference and the CRISPR/Cas9 system, protein knockdown approaches using proteolysis-targeting chimeras (PROTACs) have attracted much attention. PROTACs, which induce selective degradation of their target protein via the ubiquitin-proteasome system, are useful for the down-regulation of various proteins, including disease-related proteins and epigenetic proteins. Recent reports have shown that chemical protein knockdown is possible not only in cells, but also in vivo and this approach is expected to be used as the therapeutic strategy for several diseases. Thus, this approach may be a significant technique to complement traditional drugs and genetic ablation and will be more widely used for drug discovery and chemical biology studies in the future. In this personal account, a history of chemical protein knockdown is introduced, and its features, recent progress in the epigenetics field, and future outlooks are discussed.

Unveiling MYCN regulatory networks in neuroblastoma via integrative analysis of heterogeneous genomics data

MYCN, an oncogenic transcription factor of the Myc family, is a major driver of neuroblastoma tumorigenesis. Due to the difficulty in drugging MYCN directly, revealing the molecules in MYCN regulatory networks will help to identify effective therapeutic targets for neuroblastoma therapy. Here we perform ChIP-sequencing and small RNA-sequencing of neuroblastoma cells to determine the MYCN-binding sites and MYCN-associated microRNAs, and integrate various types of genomic data to construct MYCN regulatory networks. The overall analysis indicated that MYCN-regulated genes were involved in a wide range of biological processes and could be used as signatures to identify poor-prognosis MYCN-non-amplified patients. Analysis of the MYCN binding sites showed that MYCN principally served as an activator. Using a computational approach, we identified 32 MYCN co-regulators, and some of these findings are supported by previous studies. Moreover, we investigated the interplay between MYCN transcriptional and microRNA post-transcriptional regulations and identified several microRNAs, such as miR-124-3p and miR-93-5p, which may significantly contribute to neuroblastoma pathogenesis. We also found MYCN and its regulated microRNAs acted together to repress the tumor suppressor genes. This work provides a comprehensive view of MYCN regulations for exploring therapeutic targets in neuroblastoma, as well as insights into the mechanism of neuroblastoma tumorigenesis.

CRABP-II enhances pancreatic cancer cell migration and invasion by stabilizing interleukin 8 expression

Our previous study shows that cellular retinoic acid binding protein II (CRABP-II) is overexpressed in pancreatic ductal adenocarcinoma (PDAC) and pre-cancerous lesions, but not detected in normal pancreatic tissues. In this study, we show that deletion of CRABP-II in PDAC cells by CRISPR/Cas9 does not affect cancer cell proliferation, but decreases cell migration and invasion. Gene expression microarray analysis reveals that IL-8 is one of the top genes whose expression is down-regulated upon CRABP-II deletion, while expression of MMP-2 and MMP-14, two targets of IL-8 are also significantly down-regulated. Moreover, we found that CRABP-II is able to form a complex with HuR, which binds to the 3'UTR of IL-8 messenger RNA (mRNA) and enhances IL-8 mRNA stability. Ectopic expression of flag-CRABP-II in CRABP-II knockout cells is able to rescue the expression of IL-8, MMP-2/MMP-14 and recovers cell migration. Using the orthotopic xenograft model, we further demonstrate that CRABP-II deletion impairs tumor metastasis to nearby lymph nodes. Taken together, our results reveal a novel pathway linking CRABP-II expression to enhanced PDAC metastasis, and hence we propose CRABP-II may serve as a new PDAC therapeutic target.

Honokiol induces autophagy of neuroblastoma cells through activating the PI3K/Akt/mTOR and endoplasmic reticular stress/ERK1/2 signaling pathways and suppressing cell migration

In children, neuroblastomas are the most common and deadly solid tumor. Our previous study showed that honokiol, a small-molecule polyphenol, can traverse the blood-brain barrier and kill neuroblastoma cells. In this study, we further investigated the mechanisms of honokiol-induced insults to neuroblastoma cells. Treatment of neuroblastoma neuro-2a cells with honokiol elevated the levels of microtubule-associated protein light chain 3 (LC3)-II and induced cell autophagy in time- and concentration-dependent manners. Interestingly, pretreatment with 3-methyladenine (3-MA), an inhibitor of autophagy, led to the simultaneous attenuation of honokiol-induced cell autophagy and apoptosis but did not influence cell necrosis. As to the mechanisms, exposure of neuro-2a cells to honokiol time-dependently decreased the amount of phosphatidylinositol 3-kinase (PI3K). Sequentially, honokiol downregulated phosphorylation of protein kinase B (Akt) and mammalian target of rapamycin (mTOR) in neuro-2a cells. Furthermore, honokiol elevated the levels of glucose-regulated protein (GpR)78, an endoplasmic reticular stress (ERS)-associated protein, and amounts of intracellular reactive oxygen species (ROS). In contrast, reducing production of intracellular ROS using N-acetylcysteine, a scavenger of ROS, concurrently suppressed honokiol-induced cellular autophagy. Consequently, honokiol stimulated phosphorylation of extracellular signal-regulated kinase (ERK)1/2. However, pretreatment of neuro-2a cells with PD98059, an inhibitor of ERK1/2, lowered honokiol-induced autophagy. The effects of honokiol on inducing autophagy and apoptosis of neuroblastoma cells were further confirmed using mouse neuroblastoma NB41A3 cells as our experimental model. Fascinatingly, treatment of neuroblastoma neuro-2a and NB41A3 cells with honokiol for 12 h did not affect cell autophagy or apoptosis but caused significant suppression of cell migration. Taken together, this study showed that honokiol can induce autophagy of neuroblastoma cells and consequent apoptosis through activating the PI3K/Akt/mTOR and ERS/ROS/ERK1/2 signaling pathways and suppressing cell migration. Thus, honokiol has potential for treating neuroblastomas.

TWIST1 is a direct transcriptional target of MYCN and MYC in neuroblastoma

In neuroblastoma, MYCN amplification is associated with a worse prognosis and is a criterion used in the clinic to provide intensive treatments to children even with localized disease. In correlation with MYCN amplification, upregulation of TWIST1, a transcription factor playing a crucial role in inhibition of apoptosis and differentiation, was previously reported. Clinical data set analysis of MYCN, MYC and TWIST1 expression permits us to confirm that TWIST1 expression is upregulated in MYCN amplified neuroblastoma but also in a subset of neuroblastoma harboring high expression of MYCN or MYC without gene amplification. In silico analyses reveal the presence of several MYC regulatory motifs (E-Boxes and INR) within the TWIST1 promoter. Using gel shift assay and reporter activity assays, we demonstrate that both N-Myc and c-Myc proteins can bind and activate the TWIST1 promoter. Therefore, we propose TWIST1 as a direct MYC transcriptional target.

Genetic polymorphisms in the 9p21 region associated with risk of multiple cancers

The chromosome 9p21 region has been implicated in the pathogenesis of multiple cancers. We analyzed 9p21 single nucleotide polymorphisms (SNPs) from eight genome-wide association studies (GWAS) with data deposited in dbGaP, including studies of esophageal squamous cell carcinoma (ESCC), gastric cancer (GC), pancreatic cancer, renal cell carcinoma (RCC), lung cancer (LC), breast cancer (BrC), bladder cancer (BC) and prostate cancer (PrC). The number of subjects ranged from 2252 (PrC) to 7619 (LC). SNP-level analyses for each cancer were conducted by logistic regression or random-effects meta-analysis. A subset-based statistical approach (ASSET) was performed to combine SNP-level P values across multiple cancers. We calculated gene-level P values using the adaptive rank truncated product method. We identified that rs1063192 and rs2157719 in the CDKN2A/2B region were significantly associated with ESCC and rs2764736 (3' of TUSC1) was associated with BC (P ≤ 2.59 × 10(-6)). ASSET analyses identified four SNPs significantly associated with multiple cancers: rs3731239 (CDKN2A intronic) with ESCC, GC and BC (P = 3.96 × 10(-) (4)); rs10811474 (3' of IFNW1) with RCC and BrC (P = 0.001); rs12683422 (LINGO2 intronic) with RCC and BC (P = 5.93 × 10(-) (4)) and rs10511729 (3' of ELAVL2) with LC and BrC (P = 8.63 × 10(-) (4)). At gene level, CDKN2B, CDKN2A and CDKN2B-AS1 were significantly associated with ESCC (P ≤ 4.70 × 10(-) (5)). Rs10511729 and rs10811474 were associated with cis-expression of 9p21 genes in corresponding cancer tissues in the expression quantitative trait loci analysis. In conclusion, we identified several genetic variants in the 9p21 region associated with the risk of multiple cancers, suggesting that this region may contribute to a shared susceptibility across different cancer types.

In-frame cDNA library combined with protein complementation assay identifies ARL11-binding partners

The cDNA expression libraries that produce correct proteins are essential in facilitating the identification of protein-protein interactions. The 5′-untranslated regions (UTRs) that are present in the majority of mammalian and non-mammalian genes are predicted to alter the expression of correct proteins from cDNA libraries. We developed a novel cDNA expression library from which 5′-UTRs were removed using a mixture of polymerase chain reaction primers that complement the Kozak sequences we refer to as an “in-frame cDNA library.” We used this library with the protein complementation assay to identify two novel binding partners for ras-related ADP-ribosylation factor-like 11 (ARL11), cellular retinoic acid binding protein 2 (CRABP2), and phosphoglycerate mutase 1 (PGAM1). Thus, the in-frame cDNA library without 5′-UTRs we describe here increases the chance of correctly identifying protein interactions and will have wide applications in both mammalian and non-mammalian detection systems.

Double protein knockdown of cIAP1 and CRABP-II using a hybrid molecule consisting of ATRA and IAPs antagonist

Protein knockdown can be achieved by the use of a small molecule that possesses affinity for both the target protein and ubiquitin ligase. We have designed such a degradation-inducing molecule targeting cIAP1 and CRABP-II, which are involved in proliferation of several cancer cell lines and in neuroblastoma growth, respectively. As a CRABP-II-recognizing moiety, all-trans retinoic acid (ATRA, 3), a physiological ligand of CRABP, was chosen. As a cIAP1-recognizing moiety, MV1 (5), which is a cIAP1/cIAP2/XIAP pan-ligand, was chosen. Although cIAP1 itself possesses ubiquitin ligase activity, we expected that its decomposition would be efficiently mediated by related molecules, including cIAP2 and XIAP, which also possess ubiquitin ligase activity. The designed degradation inducer 6, in which ATRA (3) and MV1 (5) moieties are connected via a linker, was synthesized and confirmed to induce efficient degradation of both cIAP1 and CRABP-II. It showed potently inhibited the proliferation of IMR32 cells.

Retinoid receptors trigger neuritogenesis in retinal degenerations

Anomalous neuritogenesis is a hallmark of neurodegenerative disorders, including retinal degenerations, epilepsy, and Alzheimer's disease. The neuritogenesis processes result in a partial reinnervation, new circuitry, and functional changes within the deafferented retina and brain regions. Using the light-induced retinal degeneration (LIRD) mouse model, which provides a unique platform for exploring the mechanisms underlying neuritogenesis, we found that retinoid X receptors (RXRs) control neuritogenesis. LIRD rapidly triggered retinal neuron neuritogenesis and up-regulated several key elements of retinoic acid (RA) signaling, including retinoid X receptors (RXRs). Exogenous RA initiated neuritogenesis in normal adult retinas and primary retinal cultures and exacerbated it in LIRD retinas. However, LIRD-induced neuritogenesis was partly attenuated in retinol dehydrogenase knockout (Rdh12(-/-)) mice and by aldehyde dehydrogenase inhibitors. We further found that LIRD rapidly increased the expression of glutamate receptor 2 and β Ca(2+)/calmodulin-dependent protein kinase II (βCaMKII). Pulldown assays demonstrated interaction between βCaMKII and RXRs, suggesting that CaMKII pathway regulates the activities of RXRs. RXR antagonists completely prevented and RXR agonists were more effective than RA in inducing neuritogenesis. Thus, RXRs are in the final common path and may be therapeutic targets to attenuate retinal remodeling and facilitate global intervention methods in blinding diseases and other neurodegenerative disorders.

Co-localization of the oncogenic transcription factor MYCN and the DNA methyl binding protein MeCP2 at genomic sites in neuroblastoma

Background

MYCN is a transcription factor that is expressed during the development of the neural crest and its dysregulation plays a major role in the pathogenesis of pediatric cancers such as neuroblastoma, medulloblastoma and rhabdomyosarcoma. MeCP2 is a CpG methyl binding protein which has been associated with a number of cancers and developmental disorders, particularly Rett syndrome.

Methods and Findings

Using an integrative global genomics approach involving chromatin immunoprecipitation applied to microarrays, we have determined that MYCN and MeCP2 co-localize to gene promoter regions, as well as inter/intragenic sites, within the neuroblastoma genome (MYCN amplified Kelly cells) at high frequency (70.2% of MYCN sites were also positive for MeCP2). Intriguingly, the frequency of co-localization was significantly less at promoter regions exhibiting substantial hypermethylation (8.7%), as determined by methylated DNA immunoprecipitation (MeDIP) applied to the same microarrays. Co-immunoprecipitation of MYCN using an anti-MeCP2 antibody indicated that a MYCN/MeCP2 interaction occurs at protein level. mRNA expression profiling revealed that the median expression of genes with promoters bound by MYCN was significantly higher than for genes bound by MeCP2, and that genes bound by both proteins had intermediate expression. Pathway analysis was carried out for genes bound by MYCN, MeCP2 or MYCN/MeCP2, revealing higher order functions.

Conclusions

Our results indicate that MYCN and MeCP2 protein interact and co-localize to similar genomic sites at very high frequency, and that the patterns of binding of these proteins can be associated with significant differences in transcriptional activity. Although it is not yet known if this interaction contributes to neuroblastoma disease pathogenesis, it is intriguing that the interaction occurs at the promoter regions of several genes important for the development of neuroblastoma, including ALK, AURKA and BDNF.

Development of target protein-selective degradation inducer for protein knockdown

Our previous technique for inducing selective degradation of target proteins with ester-type SNIPER (Specific and Nongenetic Inhibitor-of-apoptosis-proteins (IAPs)-dependent Protein ERaser) degrades both the target proteins and IAPs. Here, we designed a small-molecular amide-type SNIPER to overcome this issue. As proof of concept, we synthesized and biologically evaluated an amide-type SNIPER which induces selective degradation of cellular retinoic acid binding protein II (CRABP-II), but not IAPs. Such small-molecular, amide-type SNIPERs that induce target protein-selective degradation without affecting IAPs should be effective tools to study the biological roles of target proteins in living cells.

Dissection of the oncogenic MYCN transcriptional network reveals a large set of clinically relevant cell cycle genes as drivers of neuroblastoma tumorigenesis

Amplification of the oncogenic transcription factor MYCN plays a major role in the pathogenesis of several pediatric cancers, including neuroblastoma, medulloblastoma, and rhabodomyosarcoma. For neuroblastoma, MYCN amplification is the most powerful genetic predictor of poor patient survival, yet the mechanism by which MYCN drives tumorigenesis is only partially understood. To gain an insight into the distribution of MYCN binding and to identify clinically relevant MYCN target genes, we performed an integrated analysis of MYCN ChIP-chip and mRNA expression using the MYCN repressible SHEP-21N neuroblastoma cell line. We hypothesized that genes exclusively MYCN bound in SHEP-21N cells over-expressing MYCN would be enriched for direct targets which contribute to the process of disease progression. Integrated analysis revealed that MYCN drives tumorigenesis predominantly as a positive regulator of target gene transcription. A high proportion of genes (24%) that are MYCN bound and up-regulated in the SHEP-21N model are significantly associated with poor overall patient survival (OS) in a set of 88 tumors. In contrast, the proportion of genes down-regulated when bound by MYCN in the SHEP-21N model and which are significantly associated with poor overall patient survival when under-expressed in primary tumors was significantly lower (5%). Gene ontology analysis determined a highly statistically significant enrichment for cell cycle related genes within the over-expressed MYCN target group which were also associated with poor OS. We conclude that the over-expression of MYCN leads to aberrant binding and over-expression of genes associated with cell cycle regulation which are significantly correlated with poor OS and MYCN amplification.

Effect of cytotoxic agents and retinoic acid on Myc-N protein expression in neuroblastoma

AIM

Neuroblastoma is an important pediatric tumor in which Myc-N amplification is a well-known poor prognostic indicator. It has a great diversity in clinical behavior. The effect of pharmacologic agents used in neuroblastoma treatment on Myc-N expression is still unclear.

METHOD

We analyzed Myc-N expression changes by immunocytochemistry in Myc-N-positive Kelly human neuroblastoma cell line using retinoic acid and cytotoxic drugs (cisplatin, vincristine, cyclophosphamide, etoposide, and doxorubicin) and their combinations compared with control conditions. First, concentration of drugs were determined as LD50 doses. Kelly cells and drugs were incubated for 24 hours in 5% CO2, 37 degrees C in 96-well plates. Myc-N expression was scored semiquantitatively as negative, mild, moderate, or high positive.

RESULTS

Myc-N amplification did not change with any agent or combination. It was higher than 20 copies in all conditions. Myc-N protein expression was high in control and doxorubicin group. It was moderate in retinoic acid, cyclophosphamide, retinoic acid combined with cyclophosphamide and retinoic acid combined with doxorubicin groups. The expression was mild in cisplatin, vincristine, etoposide, retinoic acid combined with etoposide, and retinoic acid combined with cisplatin groups. Myc-N expression was negative in retinoic acid combined with vincristine group.

CONCLUSIONS

Myc-N expression is reduced with cytotoxic agents and retinoic acid in neuroblastoma although Myc-N amplification remains the same. Retinoic acid combined with vincristine is the most effective combination to reduce Myc-N expression. Our results suggest that therapeutic applications of these agents as low dose maintenance therapy might be useful.

MYCN oncoprotein targets and their therapeutic potential

The MYCN oncogene encodes a transcription factor which is amplified in up to 40% of high risk neuroblastomas. MYCN amplification is a well-established poor prognostic marker in neuroblastoma, however the role of MYCN expression and the mechanisms by which it acts to promote an aggressive phenotype remain largely unknown. This review discusses the current evidence identifying the direct and indirect downstream transcriptional targets of MYCN from recent studies, with particular reference to how MYCN affects the cell cycle, DNA damage response, differentiation and apoptosis in neuroblastoma.

Gene expression profiling supports the hypothesis that human ovarian surface epithelia are multipotent and capable of serving as ovarian cancer initiating cells

BACKGROUND

Accumulating evidence suggests that somatic stem cells undergo mutagenic transformation into cancer initiating cells. The serous subtype of ovarian adenocarcinoma in humans has been hypothesized to arise from at least two possible classes of progenitor cells: the ovarian surface epithelia (OSE) and/or an as yet undefined class of progenitor cells residing in the distal end of the fallopian tube.

METHODS

Comparative gene expression profiling analyses were carried out on OSE removed from the surface of normal human ovaries and ovarian cancer epithelial cells (CEPI) isolated by laser capture micro-dissection (LCM) from human serous papillary ovarian adenocarcinomas. The results of the gene expression analyses were randomly confirmed in paraffin embedded tissues from ovarian adenocarcinoma of serous subtype and non-neoplastic ovarian tissues using immunohistochemistry. Differentially expressed genes were analyzed using gene ontology, molecular pathway, and gene set enrichment analysis algorithms.

RESULTS

Consistent with multipotent capacity, genes in pathways previously associated with adult stem cell maintenance are highly expressed in ovarian surface epithelia and are not expressed or expressed at very low levels in serous ovarian adenocarcinoma. Among the over 2000 genes that are significantly differentially expressed, a number of pathways and novel pathway interactions are identified that may contribute to ovarian adenocarcinoma development.

CONCLUSIONS

Our results are consistent with the hypothesis that human ovarian surface epithelia are multipotent and capable of serving as the origin of ovarian adenocarcinoma. While our findings do not rule out the possibility that ovarian cancers may also arise from other sources, they are inconsistent with claims that ovarian surface epithelia cannot serve as the origin of ovarian cancer initiating cells.

Global MYCN transcription factor binding analysis in neuroblastoma reveals association with distinct E-box motifs and regions of DNA hypermethylation

Background

Neuroblastoma, a cancer derived from precursor cells of the sympathetic nervous system, is a major cause of childhood cancer related deaths. The single most important prognostic indicator of poor clinical outcome in this disease is genomic amplification of MYCN, a member of a family of oncogenic transcription factors.

Methodology

We applied MYCN chromatin immunoprecipitation to microarrays (ChIP-chip) using MYCN amplified/non-amplified cell lines as well as a conditional knockdown cell line to determine the distribution of MYCN binding sites within all annotated promoter regions.

Conclusion

Assessment of E-box usage within consistently positive MYCN binding sites revealed a predominance for the CATGTG motif (p<0.0016), with significant enrichment of additional motifs CATTTG, CATCTG, CAACTG in the MYCN amplified state. For cell lines over-expressing MYCN, gene ontology analysis revealed enrichment for the binding of MYCN at promoter regions of numerous molecular functional groups including DNA helicases and mRNA transcriptional regulation. In order to evaluate MYCN binding with respect to other genomic features, we determined the methylation status of all annotated CpG islands and promoter sequences using methylated DNA immunoprecipitation (MeDIP). The integration of MYCN ChIP-chip and MeDIP data revealed a highly significant positive correlation between MYCN binding and DNA hypermethylation. This association was also detected in regions of hemizygous loss, indicating that the observed association occurs on the same homologue. In summary, these findings suggest that MYCN binding occurs more commonly at CATGTG as opposed to the classic CACGTG E-box motif, and that disease associated over expression of MYCN leads to aberrant binding to additional weaker affinity E-box motifs in neuroblastoma. The co-localization of MYCN binding and DNA hypermethylation further supports the dual role of MYCN, namely that of a classical transcription factor affecting the activity of individual genes, and that of a mediator of global chromatin structure.

Expression and functional analysis of the cellular retinoic acid binding protein from silkworm pupae (Bombyx mori)

Cellular retinoic acid binding protein (CRABP) is a member of intracellular lipid-binding protein (iLBP), and closely associated with retinoic acid (RA) activity. We have cloned the CRABP gene from silkworm pupae and studied the interaction between Bombyx mori CRABP (BmCRABP) and all-trans retinoic acid (atRA). The MTT assay data indicated that when BmCRABP is overexpressed in Bm5 cells, the cells dramatically resisted to atRA-induced growth inhibition. Conversely, the cells were sensitive to atRA treatment upon knocking down the BmCRABP expression. Subcellular localization revealed that BmCRABP is a cytoplasm protein, even when treated with atRA, the CRABP still remained in the cytoplasm. These data demonstrated that the function of BmCRABP have an effect on the physiological function of atRA.

Neuroblastoma

Neuroblastomas continue to remain a clinical challenge, despite advances in multimodal therapy. Currently, studies are aimed at novel targets for neuroblastoma directed toward poor prognostic indicators such as the MYCN oncogene and marked angiogenesis. There have also been recent discoveries in neuroblastoma pathogenesis involving epigenetic regulation and retinoic acid therapy. Understanding the intricate complexities of this tumor may lead to innovative agents for more effective combinational therapy.