第4卷，第1期

We devoted this short interview piece with Dr Shou-Ching Tang at Augusta University to feature some promising results from a clinical phase II trial on a novel brain-penetrating peptide-paclitaxel-conjugate, ANG1005, in treating brain metastatic breast cancer. These results were presented by Dr. Tang at the recent annual meeting of the European Society for Medical Oncology (ESMO 2016 Congress). This development heralds an important step forward towards the development of effective chemotherapeutic agents, which can cross the blood-brain-barrier and effectively treat and prevent the brain metastatic cancers.

1965

Although remarkable progress has been made in oncology research, cancer is still a leading cause of death worldwide. It is well recognized that cancer is a genetic disease, yet metabolic alterations or reprogramming are the major phenotypes associated with the (epi-) genetic modifications of cancer cells. Thus, understanding the metabolic changes of tumor cells will facilitate the diagnosis of cancer, alleviate drug resistance and provide novel druggable targets that can lead to cures for cancer. The first Sino-US Symposium on Cancer Metabolism was held in Chongqing on October 10th and 11th, with the theme of "cancer metabolism and precision cancer therapy". The symposium brought about a dozen keynote speakers each from the US and mainland China, as well as one hundred delegates with an interest in cancer metabolism. This short article will briefly summarize the advances reported during this meeting.

2027

A number of recent studies revealed that DNA methylation plays a central role in the regulation of lipid metabolism. DNA methylation modifications are important regulators of transcriptional networks that do not affect the DNA sequence and can translate genetic variants and environmental factors into phenotypic traits. Therefore, elucidating the factors that underlie inter-individual DNA methylation variations gives us an opportunity to predict diseases and interfere with the establishment of aberrant DNA methylation early. In this review, we summarize the findings of DNA methylation-related studies focused on unravelling the potential role of genetic and environmental factors in DNA methylation and the regulatory effect of DNA methylation on gene expression in lipid metabolism.

1802

Chromosome 17p deletions are among the most frequent genetic abnormalities in various cancers and associated with a dismal prognosis. However, compared to comprehensive studies on individual gene mutations role in cancer biology, the impact of 17p deletions have long been simply considered as the inactivation of tumor suppressor gene TP53.Previous work in our laboratory identified additional tumor suppressor genes next to TP53, indicating that large deletions on 17p may contribute to cancer biology beyond their impact on eliminating wildtype TP53 allele. To explore this further, we generated a novel genetically-engineered mouse model that incorporates conditional deletion of chromosome 11B3, which is syntenic to the common deletion region on human 17p13.We found that besides p53, heterozygous deletion of linked genes on 11B3 not only promotes Myc-driven lymphomagenesis or Nf1; Mll3-defective leukemogenesis as seen by shorter tumor latency and overall survival than controls with only p53 loss, but also contributes to the poor outcome of chemotherapy treatments as shown by additional resistance to cyclophosphamide, vincristine and methotrexate. Furthermore, most lymphomas generated from heterozygous deletion of 11B3 have spontaneously missense or frame-shift mutations on the other wildtype p53 allele during the loss of p53 heterozygosity, which represents the major p53 configurations in human cancers. In contrast, no large deletion has been detected in lymphomas generated from current p53 mouse model with either deletion or mutation. Furthermore, to comprehensively understand the impact of individual 17p13 gene on tumorigenesis, we have performed a corresponding 17p13 shRNA library screening and identified several new tumor suppressors that is capable of promoting Em-Myc lymphoma development by its own or cooperating with p53 suppression in tumorigenesis. Moreover, three of them are clustered together, and all belong to arachidonate lipoxygenase (ALOX) family members, Alox15b-Alox12b-Aloxe3. Loss of Alox15b are found to be correlated with the cellular increase of its substrate, arachidonic acid, as measured by Lipid Chromatography-Mass Spectrometry (LC-MS).Additionally, in vitro extracellular arachidonic acid treatment suppresses the apoptosis of lymphoma-origin pre-B cells. Together, these results indicate that arachidonic acid metabolism pathway may contribute to the roles of 17p deletions in driving tumor. In summary, our results provide the new aspects of chromosome 17p deletions in cancer biology and may shed light on developing new therapeutic methods.

1823

Although a causal role of genetic alterations in human disease such as cancer is well established, it is still unclear whether dietary fat can modulate cancer risk in a predisposed population. Omega-3 and omega-6 polyunsaturated fatty acids (PUFA) are essential fatty acids: mammals can neither synthesize them de novo nor interconvert them; therefore, they have to be taken in from diet. Homo sapiens historical diet is estimated to have an omega-6: 3 PUFA ratio of 1: 1.Current Western diets, however, have omega-6: 3 ratios of 20 and sometimes as high as 50.Diet has also been changing rapidly in Chinese population during the last three decades in terms of fat quantity and quality. Interestingly, prostate cancer occurs at a much higher frequency in the Western than Asian countries, whereas asymptomatic occult prostate cancer with genetic mutations has similar prevalence worldwide. We used transgenic/knockout animals and cell culture models to determine the influence of dietary fat on prostate cancer risk. We found that omega-3 PUFA suppresses and omega-6 accelerates prostate cancer progression and the ratio of omega-6 to 3 is important for effective tumor suppression. Modulation of prostate cancer development by PUFA is mediated in part through Bad-dependent apoptosis. Our study highlights the importance of gene-diet interactions in prostate cancer.

1825

The interconversion of metabolites provides the bases of the exchange of materials between organisms and their surroundings, and the connections among different physiologies. We found that metabolites are sensed through different mechanisms and deregulated metabolites-sensing contribute to pathology of various diseases. Acetyl-CoA, an indicator of both energy and nutrients, is sensed by protein lysine acetylation that regulates homeostasis of metabolites including glucose. α-Ketoglutarate is sensed by α-Ketoglutarate-dependent dioxygenases family proteins. IDH1 mutations produced 2-hydroxyglutarate or FH and SDH mutations accumulated fumarate and succinate promotes tumorigenesis through either disrupting α-Ketoglutarate sensing that alters epigenetics or promoting hypersuccinylation that induces cancerous metabolism and apoptosis resistance. Amino acids are sensed by tRNA synthetases and their signals are transmitted via lysine aminoacylation. The revealing of metabolites sensing and signal transmitting mechanisms is providing us opportunities to identify novel drugable targets.

1806

Due to Warburg effect, cancer cells prefer to metabolize glucose through aerobic glycolysis, which results in low efficiency of ATP production. It is reasonable to believe that tumor cells will rely more heavily on glucose uptake to make up insufficient energy produced from glycolysis. It is expected that, under glucose starvation, cancer cells will subject to more cell death than normal cells. Yet, even those solid tumors that are intermittently or constantly exposed to glucose deprivation were shown to grow vigorously. How tumors successfully cope with the glucose stress remains unclear. Metabolic reprogramming can be one of the key strategies by which cancer cells stay healthy under stresses. Tumor suppressor p53 was found to be mutated in about 50% of the human cancers and whether WT p53 in the remaining 50% tumors is tumor-preventing or tumor provoking is as yet an unanswered question. Recently, some reports have shown that p53 promotes cell survival under glucose stress. In this regard, p53 no longer acts as a tumor suppressor, rather it become an "accessory" to help cancer cells to survive harsh environment. Moreover, besides protein factors, whether and how p53 regulated lncRNA (s) is (are) involved in cancer cell death regulation has (have) been less studied. Here, we report a new p53-regulated lncRNA, which we named TRINGS (Tp53-regulated inhibitor of necrosis under glucose starvation), and it protects cancer cells from necrosis. A detailed mechanism of how TRINGS protects cancer cell against necrosis had also been delineated in this study. Here, we show that under glucose starvation condition, p53 directly upregulates lncRNA-TRINGS that in turn binds to STRAP and inhibits STRAPGSK3b-NFkB necrotic signaling axis, thus to protect tumor cells from necrotic cell death. Interestingly, TRINGS responses to glucose starvation, but not FBS-, serine-or glutamine-deprivation. Furthermore, its protective role is limited to tumor but not normal cells. Our finding reveals a p53-dependent, a long non-coding RNA TRINGS-mediated new necrotic pathway that contributes to survival of cancer cells harboring wild-type p53 under glucose stress.

1920

Cancer metabolism and epigenetic alteration, especially in chromatin remodeling, are two critical mechanisms for carcinogenesis, however, the dynamic interplay between them in tumors remains poorly understood. Lymphocyte-specific helicase (LSH), a member of the ATP-dependent helicase in sucrose nonfermenting 2 (SNF2), is not only involved in DNA methylation, but it also promotes RNA polymerase II stalling. Epithelial-mesenchymal transition (EMT) is thought to be activated in cancer cells, linked to their dissociation from the primary tumor and their intravasation into blood vessels. However, the effect of EMT in cancer progression, especially in chromatin remodeling, remains poorly understood. Oncoprotein latent membrane protein 1 (LMP1) encoded by Epstein-Barr virus (EBV) infects more than 90% of the global adult population and contributes to several malignancies, including nasopharyngeal carcinoma (NPC).We here provide robust evidence that LSH is highly expressed in NPC, where it is controlled by LMP1.Furthermore, we found that LSH does not only promote growth, migration, and invasion of NPC cancer cells in vitro, but also links with EMT, including cell migration, invasion, and tumor growth and colonization in vivo, indicating that LSH plays a critical role in tumor growth and metastasis through promoting transition from the epithelial stage to the mesenchymal stage. Then we found a repressive regulatory role of LSH in the expression of fumarate hydratase (FH) expression. a key component of the TCA cycle, catalyzes the hydration of fumarate to malate and is essential for cellular energy production and macromolecular biosynthesis. We confirmed that LSH is an important regulator of FH expression and down-regulates FH protein level in NPC derived from xenograft and clinical samples. We found that LSH was associated with the fh promoter; therefore, FH may serve as a direct target of LSH function. However, LSH may repress the fh promoter independent of DNA methylation, indicating that another mechanism is involved. G9a, also known as euchromatic histone-lysine N-methyltransferase 2, is an important epigenetic regulator, which monomethylates and dimethylates lysine-9.We provided the evidence of an interaction between LSH and G9a; the evidence of recruitment of G9a to the fh promoter in a LSH-dependent manner; and the evidence of subsequent chromatin modification leading to FH promoter repression, thus linking epigenetic regulation by LSH with suppression of the emerging tumor suppressor gene FH. Then, we found further that TCA cycle intermediates and the ratio of a-KG/succinate and a-KG/fumarate are regulated by LSH, However, we found no association between the EBV status and the intermediates of TCA cycles in NPC patients. Moreover, TCA intermediates promote cancer progression through the decrease of epithelial markers and the increase of mesenchymal marker expression. Finally, we demonstrate that the chromatin regulator and transcriptional activator inhibitor of nuclear factor kappa-B kinase alpha (IKKa) may be involved in the regulation of EMT markers, mediating the effect of LSH and TCA intermediates. LSH overexpression, as well as de-regulation of TCA intermediates, leads to IKKa recruitment to the promoters of EMT-related genes. In this way, LSH induces a cascade of epigenetic and metabolic changes that result in further epigenetic regulations via IKKa and EMT.

1899

Increased de novo nucleotide biosynthesis is required for cancer cell proliferation. However, it remains unclear how cancer cells obtain ribose-5-phosphate, glycine, glutamine, aspartate, and NADPH from glucose and glutamine metabolism to achieve increased de novo nucleotide biosynthesis. Mondo family transcription factors including MondoA and ChREBP play important roles in regulating glucose, lipid and amino acid metabolism. We recently identified a novel role of MondoA and ChREBP in promoting de novo nucleotide biosynthesis. In order to investigate the mechanism by which ChREBP and MondoA increased de novo nucleotide biosynthesis, we searched for target genes for ChREBP and MondoA which played critical roles in nucleotide biosynthesis. We found that transketolase (TKT), a target gene for Mondo family, could be important for nucleotide biosynthesis. TKT is a regulatory enzyme in the non-oxidative branch of pentose phosphate pathway and plays an important role in providing cancer cells with building blocks for de novo nucleotide biosynthesis.We generated a liver specific TKT knockout mice strain by crossing TKTfl/fl mice with albumin (Alb)-Cre mice.2-week old male mice were injected 25mg/kg diethylnitrosamine (DEN), followed by high fat diet (HFD) feeding from one-month postbirth. We found that about 100% TKT+/+Alb-Cre and TKTfl/+Alb-Cre mice developed liver cancer whereas the tumor incidence decreased to 40% in TKTfl/fl Alb-Cre mice at 9 month postbirth. Tumor number and size were significantly reduced in TKTfl/fl Alb-Cre mice when compared to control littermates. Intriguingly, TKT deficiency reduced NADPH levels while promoting R5P production. Notably, loss of TKT in liver not only attenuated DEN/HFD-induced hepatic steatosis and fibrosis, but also led to increased apoptosis, reduced cell proliferation and decreased expression of TNF-a, IL-6 and Stat3. Our study may provide new strategies for liver cancer prevention and therapy through transcriptional and metabolic regulation.

1796

Eukaryotic cells can sense glucose and evoke signaling pathways to regulate growth and development. An immediate response to glucose is the expression of a set of genes mediated by cis carbohydrate response elements (ChoRE) and their associated transcription factors MondoA and Max-like protein X (MLX). Thioredoxin interacting protein (TXNIP), the product of an immediate glucose response gene TXNIP, functions as a negative regulator for glucose uptake, and its expression is dysregulated in diabetes and cancer. We have observed that the ChoRE cis regulatory element is duplicated during vertebrate evolution, with one ChoRE in fish and two in mammals. In mammalian cells, both ChoREs are required for an optimal glucose response. With assistance by nuclear factor Y (NF-Y), MondoA/MLX complex is recruited to TXNIP promoter upon glucose stimulation, which in turn recruits general transcription factors and RNA polymerases to initiate gene transcription. In addition to glucose or its derived metabolites, MondoA/MLX activity and TXNIP expression is tightly correlated with status of mitochondrial oxidative phosphorylation (OXPHOS), and inhibition of OXPHOS by drugs such as metformin can dramatically repress TXNIP transcription by inducing glycolytic flux. Moreover, we have discovered that the expression of TXNIP is induced by an array of adenosine-containing molecules, and these molecules function as amplifiers of glucose signaling. Thus, MondoA/MLX complex serves as a hub integrating diverse upstream signals and a master regulator of glucose homeostasis.

1746

Transcriptionfactorcarbohydrateresponsiveelementbindingprotein (ChREBP) is abundant in liver and adipose tissues. ChREBP promotes glycolysis and lipogenesis in metabolic tissues and cancer cells. ChREBP-a and ChREBP-b are two isoforms of ChREBP transcribed from different promoters. Both ChREBP-a and ChREBP-b are transcriptionally induced by glucose. However, the mechanism by which glucose promotes ChREBP transcription remains unclear. Here we report that hepatocyte nuclear factor 4 alpha (HNF-4a) mediates transcription of ChREBP-a and ChREBP-b induced by glucose. Ectopic HNF-4a expression promoted ChREBP transcription while knockdown of HNF-4a reduced ChREBP mRNA levels in liver cancer cells and mouse primary hepatocytes. We found that the expression of HNF-4a and ChREBP was positively correlated by analyzing levels of ChREBP and HNF-4a in the liver of mice under fasting and feeding conditions. HNF-4a directly bound to an E-box-containing region in intron 12 of the ChREBP gene, in addition to directly binding to DR1 sites of the ChREBP-b promoter. Moreover, HNF-4a interacted with ChREBP-a and synergistically promoted ChREBP-b transcription. Interestingly, HNF-4a knockdown decreased glucose-dependent ChREBP induction in liver cancer cells. Glucose increased expression and nuclear abundance of HNF-4a and its binding to cis-elements of ChREBP gene, which contributed to glucose-induced ChREBP transcription in liver cancer cells.Taken together, our results revealed the novel mechanism by which HNF-4a increased ChREBP transcription in response to glucose in liver cancer cells.

1751

Cysteine as well as glutamine and alanine are critical substrates for synthesis of glutathione (GSH).Glutamine and alanine, but not cysteine, are most upregulated intermediate metabolites in cancer cells, suggesting cysteine uptake is increased. However, it's not clear how the uptake of cysteine is regulated. Here, we report that the cysteine carrier SLC3A1 is upregulated in breast cancer cells, and its expression levels are correlated with clinical stages and patients'survival. In breast cancer cells, overexpression of SLC3A1 accelerates the uptake of cysteine, which in turn increases the concentration of reductive GSH and the GSH/GSSH ratio and concomitantly decreases the cellular level of ROS (reactive oxygen species).Consequently, overexpression of SLC3A1 promotes the tumorigenesis of breast cancer cells, whereas knocking-down or inhibition of SLC3A1 decreases tumorigenesis of breast cancer cells in mice. Moreover, SLC3A1 inhibitor Sulfasazine suppressed tumor growth and abolished dietary NAC-promoted tumor growth. Mechanistically, our data manifest that ROS catalyzes thiol into sulfenic acid at the HC (X) 4EXV motif of serine/threonine phosphatase PP2Ac which is similar as the ROS-induced sulfenylation at the HC (X) 5RS/T motif of protein tyrosine phosphatases (PTPs); however, unlike PTPs, sulfenylation increases the stability and activity of PP2Ac rather than deactivating PTPs. SLC3A1 activates the Akt pathway through decreasing the sulfenylation and stability of protein phosphatase PP2Ac. Collectively, our data demonstrate that SLC3A1-mediated increase of cysteine uptake promotes the tumorigenesis of breast cancer cells, and SLC3A1 determines breast cancer cell response to antioxidant N-acetylcysteine, suggesting SLC3A1 is a potential therapeutic target for breast cancer.

1858

Melanoma is a highly aggressive cancer with an alarmingly increasing incidence. A major question in melanoma biology is why are red-haired individuals at a high risk of developing melanoma. Polymorphisms in the melanocortin-1-receptor (MC1R) gene, encoding a trimeric G proteincoupled receptor activated by a-melanocyte-stimulating hormone (a-MSH), are frequently associated with red or blonde hair, fair skin, freckling and skin sensitivity to ultraviolet (UV) light, and several (RHC-polymorphisms) also associate with increased melanoma risk. However, some polymorphisms appear to affect melanoma risk independent of phenotype; using an in vivo model system we recently reported that some MC1R mutations synergize with UV to induce melanoma independently of their effects on melanogenesis. Understanding precisely how MC1R polymorphisms differentially affect melanoma biology is therefore a key issue. Importantly, we also found that UV irradiation triggered MC1R-interaction with and degradation of PTEN, leading to increased PI3K-signallingedriven senescence in melanocytes, but senescence bypass in BRaf mutant melanoma. Importantly, WT MC1R but not red-hair associated MC1R mutants could interact with PTEN. Furthermore, we used newly generated MC1R conditional RHC-polymorphism mouse models to dissect the tumor suppressive functions of MC1R in melanoma initiation in vivo and specifically its role in controlling PI3K signaling via PTEN degradation. Our studies identify intracellular molecular targets of MC1R in suppressing melanoma initiation that are directed towards identifying novel strategies for melanoma prevention and therapeutic intervention.

1794

Triple-negative Breast Cancer (TNBC) is associated with an aggressive clinical history, development of recurrence, distant metastasis and shorter patient survival. Intriguingly, TNBC has activated the epithelial-mesenchymal transition (EMT) program, which is a cellular de-differentiation process that provides cells with the increased plasticity and stem cell-like properties required during embryonic development, tissue remodeling, wound healing and metastasis. Using unbiased protein purification coupled with mass spectrometry analysis, we identified that Snail and Twist, two key EMT-inducing transcriptional factors, act as transcriptional repressor and activator, respectively. Snail is a labile protein and is subjected to protein ubiquitination and degradation, and we have identified the protein kinase, phosphatase, ubiquitin E3 ligase and de-ubiquitinase in the regulation of Snail. Interestingly, the protein stability of Snail and its interaction with these effectors are controlled by signals from the tumor microenvironment, resulting in the EMT induction and invasive phenotypes that commonly observed at the tumor-stromal boundary. Our study provides new insights and opportunities for the development of effective therapeutic approaches against metastatic breast cancer.

1888

Tumor relapse after radiotherapy is a big challenge to oncologists. Here, we discovered that cancer-associated fibroblasts (CAFs), a major component of cancer stromal cells, promote cancer cell recovery and tumor relapse postradiation. We provided evidences that CAFs-produced cytokines/chemokines and intermediate metabolites are capable of inducing autophagy in cancer cells post-radiation and promoting cancer cells recovery from radiationinduced damage in vitro and in mice, which was consistent with our clinical observation that the newly developed image-guided stereotactic body radiation therapy (SBRT) was less effective than the conventional external beam radiotherapy (EBRT) in term of recurrence and survival of cancer patients. Mechanistically, CAF-derived cytokines maintained the redox homeostasis post-radiation and increased ROS level compared to control irradiated cancer cells, ROS enhanced the activity of PP2Ac through a reversible sulfenylation on the cysteine residue in the motif of HC (X) 4EXV, similar as the motif of HC (X) 5RS/T in PTPs (protein tyrosine phosphatases), distinct from the sulfenylation of HC (X) 5RS/T motif, which inactivates the activity of PTPs. Moreover, the inhibition of autophagy abolished the CAF-promoted tumor relapse post-radiotherapy. Taken together, our findings demonstrate that CAFs promote cancer cell recovery and tumor regrowth post-radiation, suggesting CAFs are critical for tumor recurrence after radiation and autophagy pathway is a therapeutic target for radiotherapy sensitization.

1833

Autophagy is an evolutionarily conserved protein degradation pathway in eukaryotes that plays key role in a number of pathological conditions including cancer. Understanding the mechanism of autophagy will offer hope for the development of new therapeutic approaches for cancer treatment. To elucidate the role of autophagy in tumorigenesis or tumor progression, we explored the expression of autophagy-associated proteins in tumor tissues. Our results showed that low expression of Beclin 1 was significantly associated with poor prognosis in ovarian tumors, colon cancers with stage IIIB, lymphoma. We also found that the patients with lower level of ULK1 had a significant shorter cancer-related survival time and distant metastasis-free survival time. To understand whether anticancer drugs induces autophagy in cancer cells, topotecan and ceramide were employed. The results showed that activation of JNK pathway can phosphorylate c-Jun and promote c-Jun binding to the promoters of Beclin 1, LC3 and Sestrin 2 to upregulate Beclin 1, LC3 and Sestrin 2 expression, which plays a key role in anticancer agentsinduced autophagy in cancer cells. We also found that Beclinacetylated by p300 at lysine residues 430 and 437. The phosphorylation of Beclin 1 at S409 by CK1 is required for the subsequent p300 binding and Beclin. Beclin 1 acetylation inhibits autophagosome maturation and endocytic trafficking by promoting the recruitment of Rubicon. In tumor xenografts, the expression of 2KR mutant Beclin 1 leads to enhanced autophagosome maturation and tumor growth suppression. In order to explore the role of autophagy in cancer treatment, our investigation showed that Rhabdastrellic acid-A, an isomalabaricane triterpenoid isolated from the sponge Rhabdastrella globostellata, induced autophagy of cancer cells. SYUIQ-5, previously identified by us as a novel G-quadruplex stabilizer and potent telomerase inhibitor, inhibited proliferation of cancer cells, triggered a rapid and potent telomere DNA damage response and obviously induced autophagy. These phenomena may primarily depend on the delocalization of TRF2 from telomere. We found that wild-type p53 can activate AMPK, inhibit mTORC1 and promote colon cancer cells survival by enabling cytoprotective autophagy in response to topotecan treatment. In contrast, the inhibition of autophagy alleviated the anti-tumour effect of topotecan treatment in p53 mutant or knockout colon cancer cells both in vitro and in vivo. We also found that topotecan, a topoisomerase I inhibitor, and cisplatin induced DNA damage and activated ATM, which phosphorylates PTEN at serine 113 and further regulates PTEN nuclear translocation in A549 and HeLa cells. After nuclear translocation, PTEN induces autophagy, in association with the activation of the p-JUNSESN2/AMPK pathway, in response to topotecan. Our researches show that decreased autophagy-related protein expression is associated with tumor progression and poor prognosis in ovarian cancer, breast cancer, colon cancer. We also found that some anticancer agents-mediated autophagyassociated cell death or survival dependent of cancer cell context. Therefore, understanding the mechanisms of autophagy and the role of autophagy in cancers will facilitate novel therapeutics for cancer.

1812

SIRT1, the most conserved NAD+-dependent protein deacetylase, is an important cellular metabolic and stress sensor. However, the role of this critical factor in cancer development remains unclear and inconclusive. SIRT1 has been shown to directly maintain genome stability and repress inflammation, thereby decreasing tumor growth. On the other hand, SIRT1 also has been reported to inhibit activities of tumor suppressors, promoting growth and survival of cancer cells. As a result, whether SIRT1 is an oncogene or tumor suppressor remains controversial.We recently explored the possibility that SIRT1 regulates cancer development in a quantitative dose-dependent manner. We hypothesized that different SIRT1-regulated cellular pathways have distinct sensitivities to changes of SIRT1 dosages. These distinct sensitivities may differentiate the outcomes in cancer cell proliferation and growth, contributing to observed dual functions of SIRT1 in tumor development.To test this hypothesis, we generated immortalized mouse embryonic fibroblasts (MEFs) and human colorectal cancer cell lines carrying two copies (WT), one copy (Het), or no copy (KO) of SIRT1 gene. Consistent with our hypothesis, SIRT1 Het cells displayed elevated proliferation in culture, increased colony formation on soft agar, and enhanced tumor formation in nude mice in a xenograft model, whereas SIRT1 KO cells exhibited reduced proliferation, colony formation, and cancer formation. Further mechanistic studies revealed that deletion of one copy of SIRT1 gene is sufficient to activate NF-κB and induce c-Myc expression, promoting cell proliferation, autophagy, and stress resistance in a glutamine-dependent manner. Deletion of both copies of SIRT1 gene, on the other hand, triggers cellular apoptotic pathways, leading to increased cell death, diminished autophagy, and reduced cancer formation. Consistently, intestine-specific SIRT1 heterozygous mice have enhanced intestinal tumor formation, whereas intestine-specific SIRT1 homozygous knockout mice have reduced development of colon cancer. Finally, expression levels of SIRT1 are reduced in human colorectal tumors, and reduced tumor SIRT1 expression correlates with poor prognosis in colorectal cancer patients.In summary, our findings indicate that the dose-dependent regulation of tumor metabolism and possibly apoptosis by SIRT1 mechanistically contributes to the observed dual roles of SIRT1 in tumorigenesis. Our study highlights the importance of maintenance of a suitable SIRT1 dosage for metabolic and tissue homeostasis, which will have important implications in SIRT1 small molecule activators/inhibitors based therapeutic strategies for cancers.

1837

Circular RNAs (circRNAs) with a covalently closed loop structure which was different with linear RNAs, recently re-merged as novel regulator and exerted function in multiple biological processes. Through deep RNA sequencing (RNA-seq) technology coupled with bioinformatic analyses, a number of circRNAs has been identified. Moreover, circRNAs exhibit tissue-and development-specific expression indicating their potential biological significance. Actually, function of circRNAs as miRNA sponge has been well demonstrated in some diseases, besides, circRNAs also could function as RNA binding protein sponge and regulate alternative splicing and gene transcription. Notably, Emerging evidences showed that circRNAs played a pivotal role on the development of diseases including atherosclerotic vascular disease, neurological disorders and liver diseases, and served as diagnostic or predictive biomarkers of some diseases. This review mainly discusses the current advance of circRNAs as regulator involved in many diseases, and highlights circRNAs which have been well elucidated biological and pathogenic mechanism.

1890

Metabolic abnormalities is a hallmark of cancer. About 100 years ago, Nobel laureate Otto Heinrich Warburg first described high rate of glycolysis in cancer cells. Recently more and more novel opinions about cancer metabolism supplement to this hypothesis, consist of glucose uptake, lactic acid generation and secretion, acidification of the microenvironment and cancer immune evasion. Here we briefly review metabolic pathways generating lactate, and discuss the function of higher lactic acid in cancer microenvironments.

1357

Changes in the abundance and activity of long non-coding RNAs (lncRNAs) have an important impact on the development of cancer. The nuclear paraspeckle assembly transcript 1 (NEAT1) has been reported to be overexpressed in many types of cancer since its discovery. However, inconsistencies exist as NEAT1 can also function as a tumor suppressor in certain types of cancer, such as acute promyelocytic leukemia. Here we systematically describe our current understanding of NEAT1 in tumor initiation and progression. First, we analyzed the expression patterns of NEAT1 in various normal tissues and malignant cancers using data from public data portals, the Genotype-Tissue Expression Project (GTEx) and the Cancer Genome Atlas (TCGA), together with recent progress in the study of NEAT1 in various types of cancer. Second, we discussed the functions and mechanisms of NEAT1 in modulating tumor activity. Then, the upstream transcription factors and downstream microRNA targets of NEAT1 in the transcription cascade of cancers were also summarized. These data highlight the emerging role of NEAT1 in tumorigenesis, and present promising targetable pathways and clinical opportunities for tumor prevention and classifications.

1950

As membrane-bound structures that could be shedded by a parental cell, and fuse with others after shedding, and then release its contents, extracellular vesicles (EVs) are considered as an indispensable part of intercellular communication system. The EV contents might be all kinds of bioactive molecules including non-coding RNAs (ncRNAs), a large and complex group of RNAs with various subtypes that function to regulate biological events but classically do not code for proteins. In this review we covered the recently published works that validated the underlying molecular mechanisms regulating EV-associated ncRNAs' biogenesis, signaling, and particularly the systemic bio-effects related mostly to any stage of cancer progression, and the clinical potential of ncRNA-carrying EVs as diagnostic biomarkers and drugdelivery system that is being engineered for better loading and targeting capacity. Our views on the future direction of basic research and applications of EVs containing ncRNAs have also been shared.

2006

Blockade of immune checkpoint molecules to reverse cancer-induced immune suppression can improve anti-tumor immune responses in cancer patients. Monoclonal antibodies targeting two such molecules, Programmed cell death protein 1 (PD-1) and cytotoxic T-lymphocyte associated protein 4 (CTLA-4) have shown clinical benefit in the treatment of advanced malignancies, including metastatic melanoma. Adverse effects of these immune checkpoint inhibitors include immune-related adverse events (irAE), of which one of the most common is autoimmune thyroiditis. Though thyroiditis is increasingly recognized, there are no reports of the pathological findings that occur in immunotherapy-induced thyroiditis. We present a case of immunotherapy-induced thyroiditis demonstrating its unique cytopathologic features. A 51-year-old woman with metastatic melanoma was found to have a suppressed TSH and elevated free thyroxine concentration 14 days after starting treatment with nivolumab (PD-1 antagonist) plus ipilimumab (CTLA-4 antagonist) therapy. A thyroid biopsy was performed based on ultrasound findings and cytopathology revealed unique features including abundant clusters of necrotic cells, lymphocytes and CD163-positive histiocytes. This case reports cytopathologic features found in immune checkpoint inhibitor related thyroiditis. These appear to be unique findings and may help inform future research regarding the pathophysiology and mechanisms of this condition.

1882

SOX4 is highly expressed in gastric cancer (GC) and is associated with tumor grade, metastasis and prognosis, however the mechanism is not clear. We report herein that SOX4 was upregulated and overexpression of SOX4 was associated with increased expression of the markers of Epitheliale-mesenchymal transition (EMT) and stemness in clinic patient samples. In vitro, overexpression of SOX4 promoted the invasion as showed by Transwell assay and stemness of GC cells as assessed by sphere formation assay, which was suppressed by silencing SOX4 with shRNA. Further studies showed that SOX4 up-regulated the expression of EMT transcription factors Twist1, snail1 and zeb1 and stemness transcription factors SOX2 and OCT4, and promoted the nuclear translocation of b-catenin. Moreover, we revealed that TGF-β treatment significantly up-regulated the expression of SOX4 and silencing SOX4 reversed TGF-β induced invasion and sphere formation ability of GC cells. Finally, we showed that SOX4 promoted the lung metastasis and tumor formation ability of gastric cancer cells in nude mice. Our results suggest that SOX4 is a target TGF-β signaling and mediates TGF-β-induced EMT and stem cell characteristics of GC cells, revealing a novel role of TGF-β/SOX4 axis in the regulation of malignant behavior of GC.

1846