Apoptosis inhibitor ARC promotes breast tumorigenesis, metastasis, and chemoresistance

Role of apoptosis repressor with caspase recruitment domain in human health and chronic diseases

Apoptosis repressor with caspase recruitment domain (ARC) is a highly potent and multifunctional suppressor of various types of programmed cell death (PCD) (e.g. apoptosis, necroptosis, and pyroptosis) and plays a key role in determining cell fate. Under physiological conditions, ARC is predominantly expressed in terminally differentiated cells, such as cardiomyocytes and skeletal muscle cells. Its expression and activity are tightly controlled by a complicated system consisting of transcription factor (TF), non-coding RNA (ncRNA), and post-translational modification (PTM). ARC dysregulation has been shown to be closely associated with many chronic diseases, including cardiovascular disease, cancer, diabetes, and neurodegenerative disease. However, the detailed mechanisms of ARC involved in the progression of these diseases remain unclear to a large extent. In this review, we mainly focus on the regulatory mechanisms of ARC expression and activity and its role in PCD. We also discuss the underlying mechanisms of ARC in health and disease and highlight the potential implications of ARC in the clinical treatment of patients with chronic diseases. This information may assist in developing ARC-based therapeutic strategies for patients with chronic diseases and expand researchers' understanding of ARC.

Combination Treatment of Resistant Acute Promyelocytic Leukemia Cells with Arsenic Trioxide and Anti-Apoptotic Gene Inhibitors

BACKGROUND

Arsenic trioxide (ATO) is an anticancer agent for treating acute promyelocytic leukemia (APL). However, 5-10% of patients fail to respond, developing relapsed/refractory disease. The aim of this study was to identify potential new therapeutic approaches for ATO-unresponsive APL by targeting the anti-apoptotic genes that contribute to drug resistance.

METHODS

RNA expression of dysregulated genes involved in the apoptotic pathway was analyzed by comparing ATO-resistant APL cell clones generated in our lab with the corresponding sensitive clones, at basal levels and after 48 h of treatment with ATO.

RESULTS

ATO-resistant APL cells showed upregulation of APAF1, BCL2, BIRC3, and NOL3 genes, while CD70 and IL10 genes were downregulated, compared to ATO-sensitive cells. Treatment with ATO strongly increased the expression of the anti-apoptotic genes BIRC3, NOL3, and BCL2A1 and significantly downregulated BCL2 in ATO-sensitive clones. Although all these genes can be relevant to ATO-resistance, we selected BCL2 and BIRC3 as druggable targets. A direct correlation between BCL2 expression and the sensitivity to the BCL2 inhibitor venetoclax was observed, indicating BCL2 as predictive biomarker of the response. Moreover, the combination of venetoclax with ATO exerted synergistic cytotoxic effects, thus reverting the resistance to ATO. APL treatment with SMAC mimetics such as LCL161 and xevinapant (inhibitors of BIRC3) was not as effective as the BCL2 inhibitor as a monotherapy but exerted synergistic effects in combination with ATO in cells with low BIRC expression.

CONCLUSIONS

This study demonstrates the therapeutic potential of venetoclax in combination with ATO in vitro and strongly encourages further investigation of relapsed/refractory APL with high BCL2 expression.

Single-nucleus RNA sequencing-based construction of a hippocampal neuron atlas in mice with epileptic cognitive impairment

The hippocampus plays a critical role in learning and memory, and mice with epileptic cognitive impairment exhibit hippocampal atrophy. However, there is still a lack of research on the hippocampal cell atlas related to these disorders. Here, we utilized snRNA-seq to characterize the transcriptomic changes in hippocampal neurons of drug-resistant epilepsy (DRE) cognitive-impaired mice. The intercellular heterogeneity of 20 subpopulations of neurons was analyzed, focusing on aspects such as cell communication, gene expressions, GO and KEGG enrichment analysis, and module gene set analysis. Based on the degree of relevance to synaptic biological functions, the subpopulations associated with cognitive impairment (ExN1, 3, 8 and InN1, 6) were preliminarily identified. We also identified some key biomarkers in DRE cognitive-impaired mice, such as Ptprz1 and Calb1. Finally, we integrate and validate our dataset using identified well-annotated marker genes in the hippocampal region, further supporting the functional annotation of neuronal subpopulations.

Single-Cell Spatial MIST for Versatile, Scalable Detection of Protein Markers

High-multiplex detection of protein biomarkers across tissue regions has been an attractive spatial biology approach due to significant advantages over traditional immunohistochemistry (IHC) methods. Different from most methods, spatial multiplex in situ tagging (MIST) transfers the spatial protein expression information to an ultrahigh-density, large-scale MIST array. This technique has been optimized to reach single-cell resolution by adoption of smaller array units and 30% 8-arm PEG polymer as transfer medium. Tissue cell nuclei stained with lamin B have been clearly visualized on the MIST arrays and are colocalized with detection of nine mouse brain markers. Pseudocells defined at 10 μm in size have been used to fully profile tissue regions including cells and the intercellular space. We showcased the versatility of our technology by successfully detecting 20 marker proteins in kidney samples with the addition of five minutes atop the duration of standard immunohistochemistry protocols. Spatial MIST is amenable to iterative staining and detection on the same tissue samples. When 25 proteins were co-detected on 1 mouse brain section for each round and 5 rounds were executed, an ultrahigh multiplexity of 125 proteins was obtained for each pseudocell. With its unique abilities, this single-cell spatial MIST technology has the potential to become an important method in advanced diagnosis of complex diseases.

Changes of Mutations and Copy-Number and Enhanced Cell Migration during Breast Tumorigenesis

Although cancer stem cells (CSCs) play a major role in tumorigenesis and metastasis, the role of genetic alterations in invasiveness of CSCs is still unclear. Tumor microenvironment signals, such as extracellular matrix (ECM) composition, significantly influence cell behaviors. Unfortunately, these signals are often lost in in vitro cell culture. This study determines putative CSC populations, examines genetic changes during tumorigenesis of human breast epithelial stem cells, and investigates single-cell migration properties on ECM-mimetic platforms. Whole exome sequencing data indicate that tumorigenic cells have a higher somatic mutation burden than non-tumorigenic cells, and that mutations exclusive to tumorigenic cells exhibit higher predictive deleterious scores. Tumorigenic cells exhibit distinct somatic copy number variations (CNVs) including gain of duplications in chromosomes 5 and 8. ECM-mimetic topography selectively enhances migration speed of tumorigenic cells, but not of non-tumorigenic cells, and results in a wide distribution of tumorigenic single-cell migration speeds, suggesting heterogeneity in cellular sensing of contact guidance cues. This study identifies mutations and CNVs acquired during breast tumorigenesis, which can be associated with enhanced migration of breast tumorigenic cells, and demonstrates that a nanotopographically-defined platform can be applied to recapitulate an ECM structure for investigating cellular migration in the simulated tumor microenvironment.

A double-edged sword: role of apoptosis repressor with caspase recruitment domain (ARC) in tumorigenesis and ischaemia/reperfusion (I/R) injury

Apoptosis repressor with caspase recruitment domain (ARC) acts as a potent and multifunctional inhibitor of apoptosis, which is mainly expressed in postmitotic cells, including cardiomyocytes. ARC is special for its N-terminal caspase recruitment domain and caspase recruitment domain. Due to the powerful inhibition of apoptosis, ARC is mainly reported to act as a cardioprotective factor during ischaemia‒reperfusion (I/R) injury, preventing cardiomyocytes from being devastated by various catastrophes, including oxidative stress, calcium overload, and mitochondrial dysfunction in the circulatory system. However, recent studies have found that ARC also plays a potential regulatory role in tumorigenesis especially in colorectal cancer and renal cell carcinomas, through multiple apoptosis-associated pathways, which remains to be explored in further studies. Therefore, ARC regulates the body and maintains the balance of physiological activities with its interesting duplex. This review summarizes the current research progress of ARC in the field of tumorigenesis and ischaemia/reperfusion injury, to provide overall research status and new possibilities for researchers.

MetastaSite: Predicting metastasis to different sites using deep learning with gene expression data

Deep learning has massive potential in predicting phenotype from different omics profiles. However, deep neural networks are viewed as black boxes, providing predictions without explanation. Therefore, the requirements for these models to become interpretable are increasing, especially in the medical field. Here we propose a computational framework that takes the gene expression profile of any primary cancer sample and predicts whether patients' samples are primary (localized) or metastasized to the brain, bone, lung, or liver based on deep learning architecture. Specifically, we first constructed an AutoEncoder framework to learn the non-linear relationship between genes, and then DeepLIFT was applied to calculate genes' importance scores. Next, to mine the top essential genes that can distinguish the primary and metastasized tumors, we iteratively added ten top-ranked genes based upon their importance score to train a DNN model. Then we trained a final multi-class DNN that uses the output from the previous part as an input and predicts whether samples are primary or metastasized to the brain, bone, lung, or liver. The prediction performances ranged from AUC of 0.93-0.82. We further designed the model's workflow to provide a second functionality beyond metastasis site prediction, i.e., to identify the biological functions that the DL model uses to perform the prediction. To our knowledge, this is the first multi-class DNN model developed for the generic prediction of metastasis to various sites.

Circulating Tumor Cell Transcriptomics as Biopsy Surrogates in Metastatic Breast Cancer

BACKGROUND

Metastatic breast cancer (MBC) and the circulating tumor cells (CTCs) leading to macrometastases are inherently different than primary breast cancer. We evaluated whether whole transcriptome RNA-Seq of CTCs isolated via an epitope-independent approach may serve as a surrogate for biopsies of macrometastases.

METHODS

We performed RNA-Seq on fresh metastatic tumor biopsies, CTCs, and peripheral blood (PB) from 19 newly diagnosed MBC patients. CTCs were harvested using the ANGLE Parsortix microfluidics system to isolate cells based on size and deformability, independent of a priori knowledge of cell surface marker expression.

RESULTS

Gene expression separated CTCs, metastatic biopsies, and PB into distinct groups despite heterogeneity between patients and sample types. CTCs showed higher expression of immune oncology targets compared with corresponding metastases and PB. Predictive biomarker (n = 64) expression was highly concordant for CTCs and metastases. Repeat observation data post-treatment demonstrated changes in the activation of different biological pathways. Somatic single nucleotide variant analysis showed increasing mutational complexity over time.

CONCLUSION

We demonstrate that RNA-Seq of CTCs could serve as a surrogate biomarker for breast cancer macrometastasis and yield clinically relevant insights into disease biology and clinically actionable targets.

Mini review: The FDA-approved prescription drugs that target the MAPK signaling pathway in women with breast cancer

Breast cancer (BC) is the most common cancer and the prevalent type of malignancy among women. Multiple risk factors, including genetic changes, biological age, dense breast tissue, and obesity are associated with BC. The mitogen-activated protein kinases (MAPK) signaling pathway has a pivotal role in regulating biological functions such as cell proliferation, differentiation, apoptosis, and survival. It has become evident that the MAPK pathway is associated with tumorigenesis and may promote breast cancer development. The MAPK/RAS/RAF cascade is closely associated with breast cancer. RAS signaling can enhance BC cell growth and progression. B-Raf is an important kinase and a potent RAF isoform involved in breast tumor initiation and differentiation. Depending on the reasons for cancer, there are different strategies for treatment of women with BC. Till now, several FDA-approved treatments have been investigated that inhibit the MAPK pathway and reduce metastatic progression in breast cancer. The most common breast cancer drugs that regulate or inhibit the MAPK pathway may include Farnesyltransferase inhibitors (FTIs), Sorafenib, Vemurafenib, PLX8394, Dabrafenib, Ulixertinib, Simvastatin, Alisertib, and Teriflunomide. In this review, we will discuss the roles of the MAPK/RAS/RAF/MEK/ERK pathway in BC and summarize the FDA-approved prescription drugs that target the MAPK signaling pathway in women with BC.

Combined photodynamic therapy with chloroaluminum phthalocyanine and doxorubicin nanoemulsions in breast cancer model

Breast cancer is the most common neoplasm among women but thanks to innovative therapies, patients' prognosis has considerably improved. In this aspect, nanotechnology has been applied for cancer therapy aiming to reduce its usual side effects. In this study we aimed to evaluate the effects of nanoemulsions containing photosensitizer and chemotherapeutic agents associated with photodynamic therapy in a breast cancer in vivo model. Our results showed that synergistic treatments in which chloroaluminum phthalocyanine (NE-Pc) administered together with Doxorubicin (Dox) in the presence of laser irradiation (NE-PcDoxo + PDT) led to a reduction of 4 T1 induced breast cancer in mice, decline of tumor VEGF expression, increase in Caspase-3 expression, tissue necrosis and massive decrease in proliferative cells, as shown by Ki67 immunostaining. Furthermore, this associated treatment induced overexpression of apoptotic genes ABL1, CD70, CRADD, FASL, and NME5 and a reduction in expression of anticancer drug target genes CDK2, ERBB2, FIGF, IGF2, PARP4 and PGR. These results validate this treatment as a promising alternative to improve the currently applied anticancer strategies.

Conversion of the death inhibitor ARC to a killer activates pancreatic β cell death in diabetes

Loss of insulin-secreting pancreatic β cells through apoptosis contributes to the progression of type 2 diabetes, but underlying mechanisms remain elusive. Here, we identify a pathway in which the cell death inhibitor ARC paradoxically becomes a killer during diabetes. While cytoplasmic ARC maintains β cell viability and pancreatic architecture, a pool of ARC relocates to the nucleus to induce β cell apoptosis in humans with diabetes and several pathophysiologically distinct mouse models. β cell death results through the coordinate downregulation of serpins (serine protease inhibitors) not previously known to be synthesized and secreted by β cells. Loss of the serpin α₁-antitrypsin from the extracellular space unleashes elastase, triggering the disruption of β cell anchorage and subsequent cell death. Administration of α₁-antitrypsin to mice with diabetes prevents β cell death and metabolic abnormalities. These data uncover a pathway for β cell loss in type 2 diabetes and identify an FDA-approved drug that may impede progression of this syndrome.

Expression of apoptosis repressor with caspase recruitment domain (ARC) in familial adenomatous polyposis (FAP) adenomas and its correlation with DNA mismatch repair proteins, p53, Bcl-2, COX-2 and beta-catenin

Background

Colorectal familial adenomatous polyposis (FAP) adenomas exhibit a uniform pathogenetic basis caused by a germline mutation in the adenomatous polyposis gene (APC), but the molecular changes leading to their development are incompletely understood. However, dysregulated apoptosis is known to substantially affect the development of colonic adenomas. One of the key regulatory proteins involved in apoptosis is apoptosis repressor with caspase recruitment domain (ARC).

Methods

The expression of nuclear and cytoplasmic ARC in 212 adenomas from 80 patients was analyzed by immunohistochemistry. We also compared expression levels of ARC with the expression levels of p53, Bcl-2, COX-2, and MMR proteins. Statistical analyses were performed by Spearman’s rank correlation and linear regression test.

Results

ARC was overexpressed in the nuclei and cytoplasm of most FAP adenomas investigated. Cytoplasmic ARC staining was moderately stronger (score 2) in 49.1% (n = 104/212) and substantially stronger (score 3) in 32.5% (n = 69/212) of adenomas compared to non-tumorous colorectal mucosa. In 18.4% (n = 39/212) of adenomas, cytoplasmic ARC staining was equivalent to that in non-tumorous mucosa.

Nuclear expression of ARC in over 75% of cells was present in 30.7% (n = 65/212) of investigated adenomas, and nuclear expression in 10–75% of cells was detected in 62.7% (n = 133/212). ARC expression in under 10% of nuclei was found in 6.6% (n = 14/212) of adenomas.

The correlation between nuclear ARC expression and cytoplasmic ARC expression was highly significant (p = 0.001). Moreover, nuclear ARC expression correlated positively with overexpression of Bcl-2, COX-2 p53 and β-catenin. Cytoplasmic ARC also correlated with overexpression of Bcl-2. Sporadic MMR deficiency was detected in very few FAP adenomas and showed no correlation with nuclear or cytoplasmic ARC.

Conclusions

Our results demonstrated that both cytoplasmic and nuclear ARC are overexpressed in FAP adenomas, thus in a homogenous collective. The highly significant correlation between nuclear ARC and nuclear β-catenin suggested that ARC might be regulated by β-catenin in FAP adenomas. Because of its further correlations with p53, Bcl-2, and COX-2, nuclear ARC might play a substantial role not only in carcinomas but also in precursor lesions.

Molecular Characterization and Clinical Relevance of RNA Binding Proteins in Colorectal Cancer

Abnormal expression of RNA binding proteins (RBPs) has been reported across various cancers. However, the potential role of RBPs in colorectal cancer (CRC) remains unclear. In this study, we performed a systematic bioinformatics analysis of RBPs in CRC. We downloaded CRC data from The Cancer Genome Atlas (TCGA) database. Our analysis identified 242 differentially expressed RBPs between tumor and normal tissues, including 200 upregulated and 42 downregulated RBPs. Next, we found eight RBPs (RRS1, PABPC1L, TERT, SMAD6, UPF3B, RP9, NOL3, and PTRH1) related to the prognoses of CRC patients. Among these eight prognosis-related RBPs, four RBPs (NOL3, PTRH1, UPF3B, and SMAD6) were selected to construct a prognostic risk score model. Furthermore, our results indicated that the prognostic risk score model accurately predicted the prognosis of CRC patients [area under the receiver operating characteristic curve (AUC)for 3- and 5-year overall survival (OS) and was 0.645 and 0.672, respectively]. Furthermore, we developed a nomogram based on a prognostic risk score model. The nomogram was able to demonstrate the wonderful performance in predicting 3- and 5-year OS. Additionally, we validated the clinical value of four risk genes in the prognostic risk score model and identified that these risk genes were associated with tumorigenesis, lymph node metastasis, distant metastasis, clinical stage, and prognosis. Finally, we used the TIMER and Human Protein Atlas (HPA)database to validate the expression of four risk genes at the transcriptional and translational levels, respectively, and used a clinical cohort to validate the roles of NOL3 and UPF3B in predicting the prognosis of CRC patients. In summary, our study demonstrated that RBPs have an effect on CRC tumor progression and might be potential prognostic biomarkers for CRC patients.

ARC Is a Critical Protector against Inflammatory Bowel Disease (IBD) and IBD-Associated Colorectal Tumorigenesis

The key functional molecules involved in inflammatory bowel disease (IBD) and IBD-induced colorectal tumorigenesis remain unclear. In this study, we found that the apoptosis repressor with caspase recruitment domain (ARC) protein plays critical roles in IBD. ARC-deficient mice exhibited substantially higher susceptibility to dextran sulfate sodium (DSS)-induced IBD compared with wild-type mice. The inflammatory burden induced in ARC-deficient conditions was inversely correlated with CCL5 and CXCL5 levels in immune cells, especially CD4-positive T cells. Pathologically, ARC expression in immune cells was significantly decreased in clinical biopsy specimens from patients with IBD compared with normal subjects. In addition, ARC levels inversely correlated with CCL5 and CXCL5 levels in human biopsy specimens. ARC interacted with TNF receptor associated factor (TRAF) 6, regulating ubiquitination of TRAF6, which was associated with NF-κB signaling. Importantly, we identified a novel ubiquitination site at lysine 461, which was critical in the function of ARC in IBD. ARC played a critical role in IBD and IBD-associated colon cancer in a bone marrow transplantation model and azoxymethane/DSS-induced colitis cancer mouse models. Overall, these findings reveal that ARC is critically involved in the maintenance of intestinal homeostasis and protection against IBD through its ubiquitination of TRAF6 and subsequent modulation of NF-κB activation in T cells. SIGNIFICANCE: This study uncovers a crucial role of ARC in the immune system and IBD, giving rise to a novel strategy for IBD and IBD-associated colon cancer therapy.

Apoptosis repressor with caspase recruitment domain promotes cell proliferation and phenotypic modulation through 14-3-3ε/YAP signaling in vascular smooth muscle cells

AIMS

In response to vascular injury, vascular smooth muscle cells (VSMC) may change from a contractile phenotype to a proliferative phenotype and consequently become conducive to neointima formation. Apoptosis repressor with caspase recruitment domain (ARC) was initially discovered as an endogenous apoptosis inhibitor, but whether ARC plays a role in VSMCs and whether it can participate in the regulation of atherosclerosis are unknown.

METHODS AND RESULTS

Protein and mRNA levels of ARC in tissues and cells were detected by western blot and quantitative real-time PCR. Immunofluorescence staining was used to detect the protein location, and immunohistochemistry was used to detect protein expression in tissues. VSMC proliferation was analysed using Cell Counting Kit-8 (CCK-8) and EdU assays, while migration was assessed by Transwell assay. Mechanistically, the direct binding between two proteins was verified by immunoprecipitation. We found that ARC expression was stimulated in VSMCs during cell proliferation. Our results also showed that ARC promoted cell proliferation and induced phenotypic modulation of VSMCs in vitro and vivo. Mechanistic studies demonstrated that ARC increased the nuclear localization of Yes associated protein (YAP) by binding to 14-3-3ε and that ARC played a role in promoting cell proliferation and phenotypic modulation. Additionally, the transcription factor p53 negatively regulated ARC expression at the transcriptional level during cell proliferation and phenotypic modulation.

CONCLUSIONS

Our findings define a novel role for ARC in the phenotypic transition of proliferating VSMCs, which may provide a new strategy for regulating neointimal formation.

Inhibition of microRNA-327 ameliorates ischemia/reperfusion injury-induced cardiomyocytes apoptosis through targeting apoptosis repressor with caspase recruitment domain

Apoptosis is the major cause of cardiomyocyte death in myocardial ischemia/reperfusion injury (MI/RI). Increasing evidence suggests that microRNAs (miRNAs) can contribute to the regulation of cardiomyocytes apoptosis by posttranscriptional modulation of gene expression networks. However, the effects of miR-327 in regulating MI/RI-induced cardiomyocytes apoptosis have not been extensively investigated. This study was performed to test whether miR-327 participate in cardiomyocytes apoptosis both in vitro and in vivo, and reveal the potential molecular mechanism of miR-327 regulated MI/RI through targeting apoptosis repressor with caspase recruitment domain (ARC). Sprague-Dawley (SD) rats were subjected to MI/RI by left anterior descending coronary artery occlusion for 30 min and reperfusion for 3 hr. H9c2 cells were exposed to hypoxia for 4 hr and reoxygenation for 12 hr to mimic I/R injury. miRNA-327 recombinant adenovirus vectors were transfected into H9c2 cells for 48 hr and rats for 72 hr before H/R and MI/RI treatment, respectively. The apoptosis rate, downstream molecules of apoptotic pathway, and the target reaction between miRNA-327 and ARC were evaluated. Our results showed that miR-327 was upregulated and ARC was downregulated in the myocardial tissues of MI/RI rats and in H9c2 cells with H/R treatment. Inhibition of miR-327 decreased the expression levels of proapoptotic proteins Fas, FasL, caspase-8, Bax, cleaved caspase-9, cleaved caspase-3, and the release of cytochrome-C, as well as increasing the expression levels of antiapoptotic protein Bcl-2 via negative regulation of ARC both in vivo or vitro. In contrast, overexpression miR-327 showed the reverse effect. Moreover, the results of luciferase reporter assay indicated miR-327 targets ARC directly at the posttranscriptional level. Taken together, inhibition of miR-327 could attenuate cardiomyocyte apoptosis and alleviate I/R-induced myocardial injury via targeting ARC, which offers a new therapeutic strategy for MI/RI.

A small-molecule allosteric inhibitor of BAX protects against doxorubicin-induced cardiomyopathy

Doxorubicin remains an essential component of many cancer regimens, but its use is limited by lethal cardiomyopathy, which has been difficult to target, owing to pleiotropic mechanisms leading to apoptotic and necrotic cardiac cell death. Here we show that BAX is rate-limiting in doxorubicin-induced cardiomyopathy and identify a small-molecule BAX inhibitor that blocks both apoptosis and necrosis to prevent this syndrome. By allosterically inhibiting BAX conformational activation, this compound blocks BAX translocation to mitochondria, thereby abrogating both forms of cell death. When co-administered with doxorubicin, this BAX inhibitor prevents cardiomyopathy in zebrafish and mice. Notably, cardioprotection does not compromise the efficacy of doxorubicin in reducing leukemia or breast cancer burden in vivo, primarily due to increased priming of mitochondrial death mechanisms and higher BAX levels in cancer cells. This study identifies BAX as an actionable target for doxorubicin-induced cardiomyopathy and provides a prototype small-molecule therapeutic.

The Function of RAS Mutation in Cancer and Advances in its Drug Research

RAS (H-ras, K-ras, and N-ras), as the second largest mutated gene driver in various human cancers, has long been a vital research target for cancer. Its function is to transform the extracellular environment into a cascade of intracellular signal transduction. RAS mutant protein regulates tumor cell proliferation, apoptosis, metabolism and angiogenesis through downstream MAPK, PI3K and other signaling pathways. In KRAS or other RAS-driven cancers, current treatments include direct inhibitors and upstream/downstream signaling pathway inhibitors. However, the research on these inhibitors has been largely restricted due to their escape inhibition and off-target toxicity. In this paper, we started with the role of normal and mutant RAS genes in cancer, elucidated the relevant RAS regulating pathways, and highlighted the important research advancements in RAS inhibitor research. We concluded that for the crosstalk between RAS pathways, the effect of single regulation may be limited, and the multi-target drug combined compensation mechanism is becoming a research hotspot.

Role of apoptosis repressor with caspase recruitment domain (ARC) in cancer

Apoptosis repressor with caspase recruitment domain (ARC) is a potent inhibitor of apoptosis. Under physiological conditions, ARC is abundantly expressed in terminally differentiated cells, including cardiomyocytes, skeletal muscles and neurons. ARC serves a key role in determining cell fate, and abnormal ARC expression has been demonstrated to be associated with abnormal cell growth. Previous studies have revealed that ARC was upregulated in several different types of solid tumor, where it suppressed tumor cell apoptosis. Furthermore, the increased expression levels of ARC in cancer cells contributed to the development of therapeutic resistance and adverse clinical outcomes in patients with leukemia. However, the exact role of ARC, as well as the underlying molecular mechanisms involved, remain poorly understood. The present review summarizes the characteristics of ARC and its cytoprotective role under different conditions and describes the potential ARC as a new target for cancer therapy.

Role of apoptosis repressor with caspase recruitment domain (ARC) in cancer

Apoptosis repressor with caspase recruitment domain (ARC) is a potent inhibitor of apoptosis. Under physiological conditions, ARC is abundantly expressed in terminally differentiated cells, including cardiomyocytes, skeletal muscles and neurons. ARC serves a key role in determining cell fate, and abnormal ARC expression has been demonstrated to be associated with abnormal cell growth. Previous studies have revealed that ARC was upregulated in several different types of solid tumor, where it suppressed tumor cell apoptosis. Furthermore, the increased expression levels of ARC in cancer cells contributed to the development of therapeutic resistance and adverse clinical outcomes in patients with leukemia. However, the exact role of ARC, as well as the underlying molecular mechanisms involved, remain poorly understood. The present review summarizes the characteristics of ARC and its cytoprotective role under different conditions and describes the potential ARC as a new target for cancer therapy.

Identification and clinical validation of a multigene assay that interrogates the biology of cancer stem cells and predicts metastasis in breast cancer: A retrospective consecutive study

Background

Breast cancers show variations in the number and biological aggressiveness of cancer stem cells that correlate with their clinico-prognostic and molecular heterogeneity. Thus, prognostic stratification of breast cancers based on cancer stem cells might help guide patient management.

Methods

We derived a 20-gene stem cell signature from the transcriptional profile of normal mammary stem cells, capable of identifying breast cancers with a homogeneous profile and poor prognosis in in silico analyses. The clinical value of this signature was assessed in a prospective-retrospective cohort of 2, 453 breast cancer patients. Models for predicting individual risk of metastasis were developed from expression data of the 20 genes in patients randomly assigned to a training set, using the ridge-penalized Cox regression, and tested in an independent validation set.

Findings

Analyses revealed that the 20-gene stem cell signature provided prognostic information in Triple-Negative and Luminal breast cancer patients, independently of standard clinicopathological parameters. Through functional studies in individual tumours, we correlated the risk score assigned by the signature with the proliferative and self-renewal potential of the cancer stem cell population. By retraining the 20-gene signature in Luminal patients, we derived the risk model, StemPrintER, which predicted early and late recurrence independently of standard prognostic factors.

Interpretation

Our findings indicate that the 20-gene stem cell signature, by its unique ability to interrogate the biology of cancer stem cells of the primary tumour, provides a reliable estimate of metastatic risk in Triple-Negative and Luminal breast cancer patients independently of standard clinicopathological parameters.

Long noncoding RNA PCAT6 inhibits colon cancer cell apoptosis by regulating anti-apoptotic protein ARC expression via EZH2

Prostate cancer-associated ncRNA transcript 6 (PCAT6) is a long intergenic noncoding RNA that is involved in the progression of prostate and lung cancer, acting as a potential diagnostic and prognostic biomarker in nonsmall cell lung cancer. However, little is known about PCAT6 expression and its clinical significance in colon cancer. Here, we aimed to investigate the clinical significance of PCAT6 in colon cancer and its underlying mechanism. The expression of PCAT6 was analyzed in colon cancer tissues using public databases, and a series of in vitro and in vivo experiments was performed to investigate the biological functions of PCAT6 in colon cancer cells and the underlying mechanisms. Our results demonstrated that PCAT6 was upregulated in colon cancer tissues compared with that in noncancerous tissues, correlating with poorer clinical stages and a worse survival status. In vitro and in vivo experiments illustrated PCAT6 promoted cell growth and inhibited cell apoptosis in colon cancer. Mechanistically, PCAT6 enhanced the coenrichment of EZH2 and H3K4me3 at the apoptosis repressor with caspase recruitment domain (ARC) genomic region, promoting the transcriptional activity of ARC. Our data highlighted that PCAT6 acts as a key activator of ARC expression by forming a complex with EZH2, inhibiting cell apoptosis and contributing to colon cancer progression. These findings elucidated that PCAT6 may be a novel prognostic predictor and therapeutic target of colon cancer.

Understanding the Connection between Nanoparticle Uptake and Cancer Treatment Efficacy using Mathematical Modeling

Nanoparticles have shown great promise in improving cancer treatment efficacy while reducing toxicity and treatment side effects. Predicting the treatment outcome for nanoparticle systems by measuring nanoparticle biodistribution has been challenging due to the commonly unmatched, heterogeneous distribution of nanoparticles relative to free drug distribution. We here present a proof-of-concept study that uses mathematical modeling together with experimentation to address this challenge. Individual mice with 4T1 breast cancer were treated with either nanoparticle-delivered or free doxorubicin, with results demonstrating improved cancer kill efficacy of doxorubicin loaded nanoparticles in comparison to free doxorubicin. We then developed a mathematical theory to render model predictions from measured nanoparticle biodistribution, as determined using graphite furnace atomic absorption. Model analysis finds that treatment efficacy increased exponentially with increased nanoparticle accumulation within the tumor, emphasizing the significance of developing new ways to optimize the delivery efficiency of nanoparticles to the tumor microenvironment.

REC8 inhibits EMT by downregulating EGR1 in gastric cancer cells

REC8 is a component of the meiotic cohesion complex that plays a critical role in chromosome dynamics during meiosis. However, the functional role of REC8 in gastric cancer has not been elucidated. In the present study, REC8 suppressed the growth and metastasis of gastric cancer cells in vitro. Whole Human Genome Oligo Microarray results revealed that a wide range of genes with broad function were targeted by REC8. Among them early growth response-1 (EGR1), a transcription factor and an epithelial-mesenchymal transition (EMT)-associated protein in the AGR-RAGE pathway was significantly downregulated when REC8 was overexpressed in gastric cancer cells. We hypothesized that REC8 inhibits EMT by downregulating EGR1 in gastric cancer cells. Consistent with our prediction, REC8 overexpression decreased EMT in gastric cancer cells, whereas the REC8 ablation reversed these effects. In addition, the phenotypes of EGR1 overexpressed cells were similar to the phenotypes of REC8 ablated cells. Furthermore, we determined that REC8 interacted with EGR1, and inhibited EMT in gastric cancer cells. We thus propose further studies of the pathways associated with REC8 and EGR1 to potentially find novel targets in the treatment for gastric cancer.

Anti-apoptotic ARC protein confers chemoresistance by controlling leukemia-microenvironment interactions through a NFκB/IL1β signaling network

To better understand how the apoptosis repressor with caspase recruitment domain (ARC) protein confers drug resistance in acute myeloid leukemia (AML), we investigated the role of ARC in regulating leukemia-mesenchymal stromal cell (MSC) interactions. In addition to the previously reported effect on AML apoptosis, we have demonstrated that ARC enhances migration and adhesion of leukemia cells to MSCs both in vitro and in a novel human extramedullary bone/bone marrow mouse model. Mechanistic studies revealed that ARC induces IL1β expression in AML cells and increases CCL2, CCL4, and CXCL12 expression in MSCs, both through ARC-mediated activation of NFκB. Expression of these chemokines in MSCs increased by AML cells in an ARC/IL1β-dependent manner; likewise, IL1β expression was elevated when leukemia cells were co-cultured with MSCs. Further, cells from AML patients expressed the receptors for and migrated toward CCL2, CCL4, and CXCL12. Inhibition of IL1β suppressed AML cell migration and sensitized the cells co-cultured with MSCs to chemotherapy. Our results suggest the existence of a complex ARC-regulated circuit that maintains intimate connection of AML with the tumor microenvironment through NFκB/IL1β-regulated chemokine receptor/ligand axes and reciprocal crosstalk resulting in cytoprotection. The data implicate ARC as a promising drug target to potentially sensitize AML cells to chemotherapy.

MicroRNA-421 regulated by HIF-1α promotes metastasis, inhibits apoptosis, and induces cisplatin resistance by targeting E-cadherin and caspase-3 in gastric cancer

Hypoxia and dysregulation of microRNAs (miRNAs) have been identified as crucial factors in carcinogenesis. However, the potential mechanisms of HIF-1α and miR-421 in gastric cancer have not been well elucidated. In this study, we found that miR-421 was up-regulated by HIF-1α. Overexpression of miR-421 promoted metastasis, inhibited apoptosis, and induced cisplatin resistance in gastric cancer in vivo and in vitro. E-cadherin and caspase-3 were identified as targets of miR-421. Besides, relative mRNA expression of miR-421 was significantly increased in gastric cancer tumor tissues compared with non-tumor tissues in a cohort of gastric cancer specimens (n=107). The expression of miR-421 was higher in advanced gastric cancers compared with localized ones. Moreover, Kaplan–Meier analysis illustrated that those patients with low levels of miR-421 had a significant longer overall survival (p = 0.006) and time to relapse (p = 0.007). Therefore, miR-421 could serve as an important prognostic marker and a potential molecular target for therapy in gastric cancer.

ARC is essential for maintaining pancreatic islet structure and β-cell viability during type 2 diabetes

Pancreatic β-cell loss through apoptosis is an important disease mechanism in type 2 diabetes. Apoptosis Repressor with CARD (ARC) is a cell death inhibitor that antagonizes multiple death programs. We previously reported that ARC is abundant in pancreatic β-cells and modulates survival of these cells in vitro. Herein we assessed the importance of endogenous ARC in maintaining islet structure and function in vivo. While generalized loss of ARC did not result in detectable abnormalities, its absence in ob/ob mice, a model of type 2 diabetes, induced a striking pancreatic phenotype: marked β-cell death, loss of β-cell mass, derangements of islet architecture, and impaired glucose-stimulated insulin secretion in vivo. These abnormalities contributed to worsening of hyperglycemia and glucose-intolerance in these mice. Mechanistically, the absence of ARC increased levels of C/EBP homologous protein (CHOP) in wild type isolated islets stimulated with ER stress and in ob/ob isolated islets at baseline. Deletion of CHOP in ob/ob; ARC −/− mice led to reversal of β-cell death and abnormalities in islet architecture. These data indicate that suppression of CHOP by endogenous levels of ARC is critical for β-cell viability and maintenance of normal islet structure in this model of type 2 diabetes.

Overexpression of NAC1 confers drug resistance via HOXA9 in colorectal carcinoma cells

Colorectal carcinoma (CRC) is one of the most common types of malignancy worldwide. Recently, neoadjuvant chemotherapy has become an important treatment strategy for CRC. However, treatment frequently fails due to the development of chemoresistance, which is a major obstacle for positive prognosis. However, the underlying mechanisms of chemoresistance remain unclear. The present study assessed the functions of nucleus accumbens-associated protein 1 (NAC1), an important transcriptional regulator, in CRC progression. Reverse transcription-quantitative polymerase chain reaction, western blot analysis and immunohistochemistry were performed to detect the expression levels of NAC1. It was identified that NAC1 was significantly overexpressed in CRC compared with non-tumorous tissues, indicating an oncogenic role. Following this, gain and loss of function analyses were performed in vitro to further investigate the function of NAC1. Cell viability and caspase-3/7 activity assays were used to assess chemotherapy-induced apoptosis. These results indicated that overexpression of NAC1 in CRC cells increased resistance to chemotherapy and inhibited apoptosis. Additionally, RNA interference-mediated knockdown of NAC1 restored the chemosensitivity of CRC cells. Furthermore, mechanistic investigation revealed that NAC1 increased drug resistance via inducing homeobox A9 (HOXA9) expression, and that knockdown of HOXA9 abrogated NAC1-induced drug resistance. In conclusion, the results of the present study demonstrated that NAC1 may be a critical factor in the development of chemoresistance, offering a potential novel target for the treatment of CRC.

The role of apoptosis repressor with a CARD domain (ARC) in the therapeutic resistance of renal cell carcinoma (RCC): the crucial role of ARC in the inhibition of extrinsic and intrinsic apoptotic signalling

Background

Renal cell carcinomas (RCCs) display broad resistance against conventional radio- and chemotherapies, which is due at least in part to impairments in both extrinsic and intrinsic apoptotic pathways. One important anti-apoptotic factor that is strongly overexpressed in RCCs and known to inhibit both apoptotic pathways is ARC (apoptosis repressor with a CARD domain).

Methods

Expression and subcellular distribution of ARC in RCC tissue samples and RCC cell lines were determined by immunohistochemistry and fluorescent immunohistochemistry, respectively. Extrinsic and intrinsic apoptosis signalling were induced by TRAIL (TNF-related apoptosis-inducing ligand), ABT-263 or topotecan. ARC knock-down was performed in clearCa-12 cells using lentiviral transduction of pGIPZ. shRNAmir constructs. Extrinsic respectively intrinsic apoptosis were induced by TRAIL (TNF-related apoptosis-inducing ligand), ABT263 or topotecan. Potential synergistic effects were tested by pre-treatment with topotecan and subsequent treatment with ABT263. Activation of different caspases and mitochondrial depolarisation (JC-1 staining) were analysed by flow cytometry. Protein expression of Bcl-2 family members and ARC in RCC cell lines was measured by Western blotting. Statistical analysis was performed by Student’s t-test.

Results

Regarding the extrinsic pathway, ARC knockdown strongly enhanced TRAIL-induced apoptosis by increasing the activation level of caspase-8. Regarding the intrinsic pathway, ARC, which was only weakly expressed in the nuclei of RCCs in vivo, exerted its anti-apoptotic effect by impairing mitochondrial activation rather than inhibiting p53. Topotecan- and ABT-263-induced apoptosis was strongly enhanced following ARC knockdown in RCC cell lines. In addition, topotecan pre-treatment enhanced ABT-263-induced apoptosis and this effect was amplified in ARC-knockdown cells.

Conclusion

Taken together, our results are the first to demonstrate the importance of ARC protein in the inhibition of both the extrinsic and intrinsic pathways of apoptosis in RCCs. In this context, ARC cooperates with anti-apoptotic Bcl-2 family members to exert its strong anti-apoptotic effects and is therefore an important factor not only in the therapeutic resistance but also in future therapy strategies (i.e., Bcl-2 inhibitors) in RCC. In sum, targeting of ARC may enhance the therapeutic response in combination therapy protocols.

A myeloid tumor suppressor role for NOL3

Despite the identification of several oncogenic driver mutations leading to constitutive JAK-STAT activation, the cellular and molecular biology of myeloproliferative neoplasms (MPN) remains incompletely understood. Recent discoveries have identified underlying disease-modifying molecular aberrations contributing to disease initiation and progression. Here, we report that deletion of Nol3 (Nucleolar protein 3) in mice leads to an MPN resembling primary myelofibrosis (PMF). Nol3^-/- MPN mice harbor an expanded Thy1⁺LSK stem cell population exhibiting increased cell cycling and a myelomonocytic differentiation bias. Molecularly, this phenotype is mediated by Nol3^-/--induced JAK-STAT activation and downstream activation of cyclin-dependent kinase 6 (Cdk6) and MycNol3^-/- MPN Thy1⁺LSK cells share significant molecular similarities with primary CD34⁺ cells from PMF patients. NOL3 levels are decreased in CD34⁺ cells from PMF patients, and the NOL3 locus is deleted in a subset of patients with myeloid malignancies. Our results reveal a novel genetic PMF-like mouse model and identify a tumor suppressor role for NOL3 in the pathogenesis of myeloid malignancies.

REC8 functions as a tumor suppressor and is epigenetically downregulated in gastric cancer, especially in EBV-positive subtype

REC8 meiotic recombination protein (REC8) was found to be preferentially methylated in gastric cancer (GC) using promoter methylation array. We aimed to elucidate the epigenetic alteration and biological function of REC8 in GC. REC8 was downregulated in 100% (3/3) of Epstein-Barr virus (EBV)-positive and 80% (8/10) of EBV-negative GC cell lines by promoter methylation, but the expression could be restored through demethylation treatment. Protein expression of REC8 was significantly lower in human primary gastric tumors than in adjacent non-tumor tissues. A negative correlation between methylation and mRNA expression of REC8 was observed in 223 gastric samples of The Cancer Genome Atlas study (r=-0.7018, P<0.001). The methylation level (%) of the REC8 promoter was significantly higher in EBV-positive gastric tumors than in EBV-negative gastric tumors, as shown by bisulfite genomic sequencing (77.6 (69.3-80.5) vs 51.4 (39.5-62.3), median (interquartile range); P<0.001); methylation levels in both subtypes of tumors were significantly higher than in normal stomach tissues (14.8 (4.2-24.0)) (both P<0.001). Multivariate analysis revealed that REC8 methylation was an independent factor for poor survival in GC patients (hazard ratio=1.68, P<0.05). REC8 expression significantly suppressed cell viability, clonogenicity and cell cycle progression; it induced apoptosis and inhibited migration of AGS-EBV (EBV-positive) and BGC823 (EBV-negative) GC cells, and it suppressed tumorigenicity in nude mice. In contrast, knockdown of REC8 in gastric epithelial immortalized GES-1 cells significantly increased cell viability, clonogenicity and migration ability. The tumor-suppressive effect of REC8 is mediated at least in part by the downregulation of genes involved in cell growth (G6PD, SLC2A1, NOL3, MCM2, SNAI1 and SNAI2), and the upregulation of apoptosis/migration inhibitors (GADD45G and LDHA) and tumor suppressors (PinX1, IGFBP3 and ETS2). In conclusion, REC8 is a novel tumor suppressor that is commonly downregulated by promoter methylation in GC, especially in the EBV-associated subtype. Promoter methylation of REC8 is an independent risk factor for the shortened survival of GC patients.

Growth inhibitory effect of Scrophularia oxysepala extract on mouse mammary carcinoma 4T1 cells in vitro and in vivo systems

INTRODUCTION

Medical plants have been intensively studied as a source of antitumor compounds. In the present study, we determine the effect of Scrophularia oxysepala on triggering apoptosis and diminishing growth, size and weight of the tumor in the allograft model of Balb/c mice.

MATERIAL & METHODS

The cytotoxic effects of Scrophularia oxysepala extract on 4T1 cells were studied using MTT (3-[4,5-dimethyl-2-thiazolyl]-2, 5 diphenyl tetrazolium bromide) assay and Trypan blue staining. DNA fragmentation assay was done for apoptosis detection. After the establishment of tumor in Balb/c mice, two groups of mice were received the extract at two doses of 50 and 100mg/kg respectively using intraperitoneal injection once every two days for 28 days. In order to assess the induction of apoptosis in cancer cells, the TUNEL assay was carried out in tumoral tissues. Moreover, the Ki67 test was used to evaluate tumor proliferation.

RESULTS

According to the findings, the Scrophularia oxysepala extract inhibited cell growth. In vivo results showed that tumor size in mice treated with the extract was significantly reduced. The weight of tumor mass in treated mice after resection was less than the control group. According to the TUNEL (Terminal deoxynucleotidyl transferase dUTP nick end labeling) assay results, the herbal extract induced apoptosis in tumoral cells. Ki67 test also demonstrated that administration of the extract suppressed the growth of tumor cells.

CONCLUSION

Our data well approved the anti-proliferative effect of Scrophularia oxysepala extract, and clearly showed that, the plant extract can decrease the growth of breast cancer cells in tumor mass. Thus it may represent an ideal therapeutic tool for breast cancer.

Tumor microenvironment-mediated chemoresistance in breast cancer

Therapy resistance or tumor relapse in cancer is common. Tumors develop resistance to chemotherapeutic through a variety of mechanisms, with tumor microenvironment (TM) serving pivotal roles. Using breast cancer as a paradigm, we propose that responses of cancer cells to drugs are not exclusively determined by their intrinsic characteristics but are also controlled by deriving signals from TM. Affected microenvironment by chemotherapy is an avenue to promote phenotype which tends to resist on to be ruined. Therefore, exclusively targeting cancer cells does not demolish tumor recurrence after chemotherapy. Regardless of tumor-microenvironment pathways and their profound influence on the responsiveness of treatment, diversity of molecular properties of breast cancer also behave differently in terms of response to chemotherapy. And also it is assumed that there is cross-talk between phenotypic diversity and TM. Collectively, raising complex signal from TM in chemotherapy condition often encourages cancer cells are not killed but strengthen. Here, we summarized how TM modifies responses to chemotherapy in breast cancer. We also discussed successful treatment strategies have been considered TM in breast cancer treatment.

N-Myristoyltransferase Inhibition Induces ER-Stress, Cell Cycle Arrest, and Apoptosis in Cancer Cells

N-Myristoyltransferase (NMT) covalently attaches a C14 fatty acid to the N-terminal glycine of proteins and has been proposed as a therapeutic target in cancer. We have recently shown that selective NMT inhibition leads to dose-responsive loss of N-myristoylation on more than 100 protein targets in cells, and cytotoxicity in cancer cells. N-myristoylation lies upstream of multiple pro-proliferative and oncogenic pathways, but to date the complex substrate specificity of NMT has limited determination of which diseases are most likely to respond to a selective NMT inhibitor. We describe here the phenotype of NMT inhibition in HeLa cells and show that cells die through apoptosis following or concurrent with accumulation in the G1 phase. We used quantitative proteomics to map protein expression changes for more than 2700 proteins in response to treatment with an NMT inhibitor in HeLa cells and observed down-regulation of proteins involved in cell cycle regulation and up-regulation of proteins involved in the endoplasmic reticulum stress and unfolded protein response, with similar results in breast (MCF-7, MDA-MB-231) and colon (HCT116) cancer cell lines. This study describes the cellular response to NMT inhibition at the proteome level and provides a starting point for selective targeting of specific diseases with NMT inhibitors, potentially in combination with other targeted agents.

miR-100 antagonism triggers apoptosis by inhibiting ubiquitination-mediated p53 degradation

During tumourigenesis, p53 functions as 'the guardian of the genome' because p53-dependent apoptosis strongly regulates the fate of cancer cells. Therefore, p53 regulation must be sensitive and accurate. p53 activity is regulated through its ubiquitination and deubiquitination. However, the role of microRNA in ubiquitin-mediated p53 degradation has not been previously studied. Our previous studies indicated that miR-100 is required for apoptosis. In the current study, the mechanism of p53 protein ubiquitination mediated by miR-100 was characterized. An analysis of primary tumour samples from gastric cancer patients showed a significant correlation between miR-100 upregulation and primary human gastric tumourigenesis and progression. The in vivo and in vitro data indicated that miR-100 antagonism specifically induced the apoptosis of poorly differentiated gastric cancer cells but not non-cancerous gastric cells, indicating that miR-100 has a crucial role in regulating the progression of gastric tumours. In the regulation of p53-dependent apoptosis, miR-100 antagonism inhibited ubiquitin-mediated p53 protein degradation by activating RNF144B, an E3 ubiquitination ligase. Consequently, the miR-100-RNF144B-pirh2-p53-dependent pathway was initiated. Our findings highlight a novel mechanism of ubiquitin-mediated p53 protein degradation in apoptosis.

The Cell Death Inhibitor ARC Is Induced in a Tissue-Specific Manner by Deletion of the Tumor Suppressor Gene Men1, but Not Required for Tumor Development and Growth

Multiple endocrine neoplasia type 1 (MEN1) is a genetic disorder characterized by tissue-specific tumors in the endocrine pancreas, parathyroid, and pituitary glands. Although tumor development in these tissues is dependent upon genetic inactivation of the tumor suppressor Men1, loss of both alleles of this gene is not sufficient to induce these cancers. Men1 encodes menin, a nuclear protein that influences transcription. A previous ChIP on chip analysis suggested that menin binds promoter sequences of nol3, encoding ARC, which is a cell death inhibitor that has been implicated in cancer pathogenesis. We hypothesized that ARC functions as a co-factor with Men1 loss to induce the tissue-restricted distribution of tumors seen in MEN1. Using mouse models that recapitulate this syndrome, we found that biallelic deletion of Men1 results in selective induction of ARC expression in tissues that develop tumors. Specifically, loss of Men1 in all cells of the pancreas resulted in marked increases in ARC mRNA and protein in the endocrine, but not exocrine, pancreas. Similarly, ARC expression increased in the parathyroid with inactivation of Men1 in that tissue. To test if ARC contributes to MEN1 tumor development in the endocrine pancreas, we generated mice that lacked none, one, or both copies of ARC in the context of Men1 deletion. Studies in a cohort of 126 mice demonstrated that, although mice lacking Men1 developed insulinomas as expected, elimination of ARC in this context did not significantly alter tumor load. Cellular rates of proliferation and death in these tumors were also not perturbed in the absence of ARC. These results indicate that ARC is upregulated by loss Men1 in the tissue-restricted distribution of MEN1 tumors, but that ARC is not required for tumor development in this syndrome.

CCL9 Induced by TGFβ Signaling in Myeloid Cells Enhances Tumor Cell Survival in the Premetastatic Organ

Tumor cell survival in the hostile distant organ is a rate-limiting step in cancer metastasis. Bone marrow-derived myeloid cells can form a premetastatic niche and provide a tumor-promoting microenvironment. However, it is unclear whether these myeloid cells in the premetastatic site have any direct effect on tumor cell survival. Here, we report that chemokine CCL9 was highly induced in Gr-1(+)CD11b(+) immature myeloid cells and in premetastatic lung in tumor-bearing mice. Knockdown of CCL9 in myeloid cells decreased tumor cell survival and metastasis. Importantly, CCL9 overexpression in myeloid cells lacking TGFβ signaling rescued the tumor metastasis defect observed in mice with myeloid-specific Tgfbr2 deletion. The expression level of CCL23, the human orthologue for CCL9, in peripheral blood mononuclear cells correlated with progression and survival of cancer patients. Our study demonstrates that CCL9 could serve as a good candidate for anti-metastasis treatment by targeting the rate-limiting step of cancer cell survival. In addition, targeting CCL9 may avoid the adverse effects of TGFβ-targeted therapy.

Apoptosis repressor with caspase recruitment domain is regulated by MAPK/PI3K and confers drug resistance and survival advantage to AML

The apoptosis repressor with caspase recruitment domain (ARC) protein is known to suppress both intrinsic and extrinsic apoptosis. We previously reported that ARC expression is a strong, independent adverse prognostic factor in acute myeloid leukemia (AML). Here, we investigated the regulation and role of ARC in AML. ARC expression is upregulated in AML cells co-cultured with bone marrow-derived mesenchymal stromal cells (MSCs) and suppressed by inhibition of MAPK and PI3K signaling. AML patient samples with RAS mutations (N = 64) expressed significantly higher levels of ARC than samples without RAS mutations (N = 371) (P = 0.016). ARC overexpression protected and ARC knockdown sensitized AML cells to cytarabine and to agents that selectively induce intrinsic (ABT-737) or extrinsic (TNF-related apoptosis inducing ligand) apoptosis. NOD-SCID mice harboring ARC-overexpressing KG-1 cells had significantly shorter survival than mice injected with control cells (median 84 vs 111 days) and significantly fewer leukemia cells were present when NOD/SCID IL2Rγ null mice were injected with ARC knockdown as compared to control Molm13 cells (P = 0.005 and 0.03 at 2 and 3 weeks, respectively). Together, these findings demonstrate that MSCs regulate ARC in AML through activation of MAPK and PI3K signaling pathways. ARC confers drug resistance and survival advantage to AML in vitro and in vivo, suggesting ARC as a novel target in AML therapy.

Global profiling of co- and post-translationally N-myristoylated proteomes in human cells

Protein N-myristoylation is a ubiquitous co- and post-translational modification that has been implicated in the development and progression of a range of human diseases. Here, we report the global N-myristoylated proteome in human cells determined using quantitative chemical proteomics combined with potent and specific human N-myristoyltransferase (NMT) inhibition. Global quantification of N-myristoylation during normal growth or apoptosis allowed the identification of >100 N-myristoylated proteins, >95% of which are identified for the first time at endogenous levels. Furthermore, quantitative dose response for inhibition of N-myristoylation is determined for >70 substrates simultaneously across the proteome. Small-molecule inhibition through a conserved substrate-binding pocket is also demonstrated by solving the crystal structures of inhibitor-bound NMT1 and NMT2. The presented data substantially expand the known repertoire of co- and post-translational N-myristoylation in addition to validating tools for the pharmacological inhibition of NMT in living cells.

Protein N-myristoylation is a ubiquitous modification implicated in the regulation of multiple cellular processes. Here, Thinon et al. report the development of a general method to identify N-myristoylated proteins in human cells and identify over 100 endogenous post- and co-translational substrates of N-myristoyltransferase.

Establishment of a lung metastatic breast tumor xenograft model in nude rats

Objective

Larger animal models provide relevant tumor burden in the development of advanced clinical imaging methods for non-invasive cancer detection and diagnosis, and are especially valuable for studying metastatic disease. Most available experimental models, however, are based on immune-compromised mice. To lay the foundation for studying spontaneous metastasis using non-invasive magnetic resonance imaging (MRI), this study aims to establish a highly metastatic breast cancer xenograft model in nude rats.

Materials and Methods

A highly metastatic variant of human adenocarcinoma MDA-MB-231 known as LM2 was inoculated into nude rats. Orthotopic and subcutaneous (flank) sites were compared, with half of the orthotopic injections guided by ultrasound imaging. MRI with gadolinium contrast administration was performed weekly beginning on Day 6 and ending on Day 104. Excised tumors were assessed on histology using hematoxylin and eosin and CD34. Fisher's exact test was used to compare successful tumor induction amongst different inoculation methods.

Results

Primary LM2 tumors were established orthotopically in all cases under ultrasound-guided injection, and none otherwise (p = 0.0028). Contrast-enhanced MRI revealed rapidly progressing tumors that reached critical size (15 mm diameter) in 2 to 3 weeks after inoculation. MRI and histology findings were consistent: LM2 tumors were characterized by low vascularity confined to the tumor rim and large necrotic cores with increasing interstitial fluid pressure.

Conclusions

The metastatic LM2 breast tumor model was successfully established in the mammary fat pads of nude rats, using ultrasound needle guidance as a non-invasive alternative to surgery. This platform lays the foundation for future development and application of MRI to study spontaneous metastasis and different stages throughout the metastatic cascade.

MicroRNA-185 regulates chemotherapeutic sensitivity in gastric cancer by targeting apoptosis repressor with caspase recruitment domain

Gastric cancer remains the second leading cause of cancer deaths worldwide. Resistance to chemotherapy is a significant barrier for effective cancer treatment. Here, we identified miR-185 to be a contributor to chemosensitivity in gastric cancer. We observed low levels of miR-185 in gastric cancer cell lines and clinical tissues, compared with gastric epithelium cell line and noncancerous tissues. Furthermore, enforced expression of miR-185 increased the sensitivity of gastric cancer cells to low-dose chemotherapeutic agents, which alone cannot trigger significant apoptosis. Conversely, knockdown of endogenous miR-185 prevented high-dose chemotherapy-induced apoptosis. In elucidating the molecular mechanism by which miR-185 participated in the regulation of chemosensitivity in gastric cancer, we discovered that apoptosis repressor with caspase recruitment domain (ARC) is a direct target of miR-185. The role of miR-185 was confirmed in gastric tumor xenograft model. The growth of established tumors was suppressed by a combination therapy using enforced miR-185 expression and a low dose of anticancer drugs. Finally, we found that RUNX3 (Runt-related transcription factor) was involved in the activation of miR-185 at the transcriptional level. Taken together, our results reveal that RUNX3, miR-185 and ARC regulate the sensitivity of gastric cancer cells to chemotherapy.

A novel role for the apoptosis inhibitor ARC in suppressing TNFα-induced regulated necrosis

TNFα signaling can promote apoptosis or a regulated form of necrosis. ARC (apoptosis repressor with CARD (caspase recruitment domain)) is an endogenous inhibitor of apoptosis that antagonizes both the extrinsic (death receptor) and intrinsic (mitochondrial/ER) apoptosis pathways. We discovered that ARC blocks not only apoptosis but also necrosis. TNFα-induced necrosis was abrogated by overexpression of wild-type ARC but not by a CARD mutant that is also defective for inhibition of apoptosis. Conversely, knockdown of ARC exacerbated TNFα-induced necrosis, an effect that was rescued by reconstitution with wild-type, but not CARD-defective, ARC. Similarly, depletion of ARC in vivo exacerbated necrosis caused by infection with vaccinia virus, which elicits severe tissue damage through this pathway, and sensitized mice to TNFα-induced systemic inflammatory response syndrome. The mechanism underlying these effects is an interaction of ARC with TNF receptor 1 that interferes with recruitment of RIP1, a critical mediator of TNFα-induced regulated necrosis. These findings extend the role of ARC from an apoptosis inhibitor to a regulator of the TNFα pathway and an inhibitor of TNFα-mediated regulated necrosis.

The apoptosis repressor with a CARD domain (ARC) gene is a direct hypoxia-inducible factor 1 target gene and promotes survival and proliferation of VHL-deficient renal cancer cells

The induction of hypoxia-inducible factors (HIFs) is essential for the adaptation of tumor cells to a low-oxygen environment. We found that the expression of the apoptosis inhibitor ARC (apoptosis repressor with a CARD domain) was induced by hypoxia in a variety of cancer cell types, and its induction is primarily HIF1 dependent. Chromatin immunoprecipitation (ChIP) and reporter assays also indicate that the ARC gene is regulated by direct binding of HIF1 to a hypoxia response element (HRE) located at bp -190 upstream of the transcription start site. HIFs play an essential role in the pathogenesis of renal cell carcinoma (RCC) under normoxic conditions, through the loss of the Von Hippel-Lindau gene (VHL). Accordingly, our results show that ARC is not expressed in normal renal tissue but is highly expressed in 65% of RCC tumors, which also express high levels of carbonic anhydrase IX (CAIX), a HIF1-dependent protein. Compared to controls, ARC-deficient RCCs exhibited decreased colony formation and increased apoptosis in vitro. In addition, loss of ARC resulted in a dramatic reduction of RCC tumor growth in SCID mice in vivo. Thus, HIF-mediated increased expression of ARC in RCC can explain how loss of VHL can promote survival early in tumor formation.

Apoptosis repressor with a CARD domain (ARC) restrains Bax-mediated pathogenesis in dystrophic skeletal muscle

Myofiber wasting in muscular dystrophy has largely been ascribed to necrotic cell death, despite reports identifying apoptotic markers in dystrophic muscle. Here we set out to identify the contribution of canonical apoptotic pathways to skeletal muscle degeneration in muscular dystrophy by genetically deleting a known inhibitor of apoptosis, apoptosis repressor with a card domain (Arc), in dystrophic mouse models. Nol3 (Arc protein) genetic deletion in the dystrophic Sgcd or Lama2 null backgrounds showed exacerbated skeletal muscle pathology with decreased muscle performance compared with single null dystrophic littermate controls. The enhanced severity of the dystrophic phenotype associated with Nol3 deletion was caspase independent but dependent on the mitochondria permeability transition pore (MPTP), as the inhibitor Debio-025 partially rescued skeletal muscle pathology in Nol3 (-/-) Sgcd (-/-) double targeted mice. Mechanistically, Nol3 (-/-) Sgcd (-/-) mice showed elevated total and mitochondrial Bax protein levels, as well as greater mitochondrial swelling, suggesting that Arc normally restrains the cell death effects of Bax in skeletal muscle. Indeed, knockdown of Arc in mouse embryonic fibroblasts caused an increased sensitivity to cell death that was fully blocked in Bax Bak1 (genes encoding Bax and Bak) double null fibroblasts. Thus Arc deficiency in dystrophic muscle exacerbates disease pathogenesis due to a Bax-mediated sensitization of mitochondria-dependent death mechanisms.

Cisplatin inhibits hippocampal cell proliferation and alters the expression of apoptotic genes

The hippocampus, which is critical for memory and spatial navigation, contains a proliferating stem cell niche that is especially vulnerable to antineoplastic drugs such as cisplatin. Although the damaging effects of cisplatin have recently been recognized, the molecular mechanisms underlying its toxic effects on this vital region are largely unknown. Using a focused apoptosis gene array, we analyzed the early cisplatin-induced changes in gene expression in the hippocampus of adult Sprague-Dawley rats and compared the results to those from the inferior colliculus, a non-mitotic auditory region resistant to cisplatin-induced cell death. Two days after a 12 mg/kg dose of cisplatin, significant increases were observed in five proapoptotic genes: Bik, Bid, Bok, Trp53p2, and Card6 and a significant decrease in one antiapoptotic gene Bcl2a1. In contrast, Nol3, an antiapoptotic gene, showed a significant increase in expression. The cisplatin-induced increase in Bid mRNA and decrease in Bcl2a1 mRNA were accompanied by a corresponding increase and decrease of their respective proteins in the hippocampus. In contrast, the cisplatin-induced changes in Bcl2a1, Bid, Bik, and Bok gene expression in the inferior colliculus were strikingly different from those in the hippocampus consistent with the greater susceptibility of the hippocampus to cisplatin toxicity. Cisplatin also significantly reduced immunolabeling of the cell proliferation marker Ki67 in the subgranular zone of the hippocampus 2 days post-treatment. These results indicate that cisplatin-induced hippocampal cell death is mediated by increased expression of proapoptotic and decreased antiapoptotic genes and proteins that likely inhibit hippocampal cell proliferation.

The apoptosis inhibitor ARC alleviates the ER stress response to promote β-cell survival

Type 2 diabetes involves insulin resistance and β-cell failure leading to inadequate insulin secretion. An important component of β-cell failure is cell loss by apoptosis. Apoptosis repressor with caspase recruitment domain (ARC) is an inhibitor of apoptosis that is expressed in cardiac and skeletal myocytes and neurons. ARC possesses the unusual property of antagonizing both the extrinsic (death receptor) and intrinsic (mitochondria/endoplasmic reticulum [ER]) cell death pathways. Here we report that ARC protein is abundant in cells of the endocrine pancreas, including >99.5% of mouse and 73% of human β-cells. Using genetic gain- and loss-of-function approaches, our data demonstrate that ARC inhibits β-cell apoptosis elicited by multiple inducers of cell death, including ER stressors tunicamycin, thapsigargin, and physiological concentrations of palmitate. Unexpectedly, ARC diminishes the ER stress response, acting distal to protein kinase RNA-like ER kinase (PERK) and inositol-requiring protein 1α, to suppress C/EBP homologous protein (CHOP) induction. Depletion of ARC in isolated islets augments palmitate-induced apoptosis, which is dramatically rescued by deletion of CHOP. These data demonstrate that ARC is a previously unrecognized inhibitor of apoptosis in β-cells and that its protective effects are mediated through suppression of the ER stress response pathway.

Schisandrin B attenuates cancer invasion and metastasis via inhibiting epithelial-mesenchymal transition

Background

Metastasis is the major cause of cancer related death and targeting the process of metastasis has been proposed as a strategy to combat cancer. Therefore, to develop candidate drugs that target the process of metastasis is very important. In the preliminary studies, we found that schisandrin B (Sch B), a naturally-occurring dibenzocyclooctadiene lignan with very low toxicity, could suppress cancer metastasis.

Methodology

BALB/c mice were inoculated subcutaneously or injected via tail vein with murine breast cancer 4T1 cells. Mice were divided into Sch B-treated and control groups. The primary tumor growth, local invasion, lung and bone metastasis, and survival time were monitored. Tumor biopsies were examined immuno- and histo-pathologically. The inhibitory activity of Sch B on TGF-β induced epithelial-mesenchymal transition (EMT) of 4T1 and primary human breast cancer cells was assayed.

Principal Findings

Sch B significantly suppressed the spontaneous lung and bone metastasis of 4T1 cells inoculated s.c. without significant effect on primary tumor growth and significantly extended the survival time of these mice. Sch B did not inhibit lung metastasis of 4T1 cells that were injected via tail vein. Delayed start of treatment with Sch B in mice with pre-existing tumors did not reduce lung metastasis. These results suggested that Sch B acted at the step of local invasion. Histopathological evidences demonstrated that the primary tumors in Sch B group were significantly less locally invasive than control tumors. In vitro assays demonstrated that Sch B could inhibit TGF-β induced EMT of 4T1 cells and of primary human breast cancer cells.

Conclusions

Sch B significantly suppresses the lung and bone metastasis of 4T1 cells via inhibiting EMT, suggesting its potential application in targeting the process of cancer metastasis.

Hypoxia-inducible factor 1 regulated ARC expression mediated hypoxia induced inactivation of the intrinsic death pathway in p53 deficient human colon cancer cells

Apoptosis repressor with caspase recruitment domain (ARC), an anti-apoptotic protein, plays an important role in the regulation of apoptosis by blocking both the extrinsic and intrinsic death pathways. However, its regulatory mechanism remains largely undefined. Here, we reported that hypoxia up-regulated the expression of ARC in p53 deficient human colon cancer cells. Moreover, ARC is a direct target of the hypoxia-inducible factor 1 (HIF-1), a key transcriptional factor for the cellular response to hypoxia. Silencing the expression of HIF-1α in SW480 colon cancer cells by RNA interference abolished hypoxia induced ARC expression. Using luciferase reporter and ChIP assay, we showed that HIF-1α directly bound to hypoxia-responsive element located at -419 to -414 of ARC gene, which is essential for HIF-1-induced expression. As a result of the increased ARC expression, TRAIL-induced apoptosis was reduced by hypoxia. These discoveries would shed novel insights on the mechanisms for ARC expression regulation and hypoxia induced inactivation of the intrinsic death pathway.