脂肪酸从头合成代谢重编程与肿瘤的发生发展

肿瘤细胞代谢重编程是肿瘤发生发展过程中最显著的特征之一,是对肿瘤有氧糖酵解（即Warburg效应）内涵的进一步扩展。细胞癌变过程的代谢模式发生显著变化,涉及到糖酵解、氧化磷酸化、氨基酸代谢、脂肪酸代谢和核酸代谢等诸多方面,其中脂肪酸代谢在肿瘤细胞的能量存储、细胞增殖及重要信号分子合成等方面起到重要作用。研究脂肪酸从头合成代谢的机制与肿瘤发生发展的关系,利用、干预和修正代谢通路上关键酶的异常,正成为肿瘤诊断、预防和治疗的新思路。本文就脂肪酸从头合成代谢重编程与肿瘤发生发展的关系做一综述。      

溶血磷脂信号在上皮性卵巢癌微环境中作用的研究进展

卵巢癌是妇科恶性肿瘤死亡的主要原因,发生在肿瘤微环境(TME)中的包括脂质代谢改变在内的代谢重编程是其主要特征。脂质中的几种溶血磷脂（也称癌脂）如溶血磷脂酸（LPA)是TME的重要组成部分,参与了肿瘤发生、发展的各个方面。本文综述了上皮性卵巢癌（EOC）TME中脂质代谢的改变,包括脂肪酸氧化增强、其它几种脂肪酸含量的改变,其次是溶血磷脂信号在EOC中的研究进展,重点介绍了LPA在EOC的TME中的作用:促进卵巢癌细胞的增殖、削弱免疫监测、侵袭转移、对化疗药物的抵抗等。     

酯酰辅酶A:胆固醇酰基转移酶1在肿瘤中的研究进展

肿瘤发生发展的共同因素是癌症自身代谢重编程，影响癌细胞三大代谢途径，促进改变细胞的增殖生长状态，并促进癌症的增殖，转移和侵袭。酯酰辅酶A:胆固醇酰基转移酶1(A:Cholesterol acyl transferases 1,ACAT1)在多数肿瘤细胞中都有表达，并通过影响脂质代谢，或者通过不同的调控通路，扰乱胆固醇的稳态，或促使糖酵解的发生，或通过影响免疫细胞的活化状态，改变肿瘤的免疫环境，影响肿瘤的发生、发展。目前研究出的多种酯酰辅酶A:胆固醇酰基转移酶1抑制剂可以用于治疗多种肿瘤。本文将对ACAT1在多种肿瘤中的作用特点及其目前的研究状况进行综述。     

Colorectal Cancer and Metabolism

Purpose of Review

Metabolic reprogramming is essential for the rapid proliferation of cancer cells and is thus recognized as a hallmark of cancer. In this review, we will discuss the etiologies and effects of metabolic reprogramming in colorectal cancer.

Recent Findings

Changes in cellular metabolism may precede the acquisition of driver mutations ultimately leading to colonocyte transformation. Oncogenic mutations and loss of tumor suppressor genes further reprogram CRC cells to upregulate glycolysis, glutaminolysis, one-carbon metabolism, and fatty acid synthesis. These metabolic changes are not uniform throughout tumors, as subpopulations of tumor cells may rely on different pathways to adapt to nutrient availability in the local tumor microenvironment. Finally, metabolic cross-communication between stromal cells, immune cells, and the gut microbiota enable CRC growth, invasion, and metastasis.

Summary

Altered cellular metabolism occurs in CRC at multiple levels, including in the cells that make up the bulk of CRC tumors, cancer stem cells, the tumor microenvironment, and host-microbiome interactions. This knowledge may inform the development of improved screening and therapeutics for CRC.

     

The excitatory amino acid transporter-2 induces apoptosis and decreases glioma growth in vitro and in vivo

Accumulating evidence suggests that glutamate plays a key role in the proliferation and invasion of glioblastoma tumors. Astrocytic tumors have been shown to release glutamate at high levels, which may stimulate tumor cell proliferation and motility via activation of glutamate receptors. Excess glutamate has also been found to facilitate tumor invasion by causing excitotoxic damage to normal brain thereby paving a pathway for tumor migration. Results from tissue microarray analyses showed decreased excitatory amino acid transporter-2 (EAAT-2) expression in high-grade glial tumors compared with low-grade astrocytomas and normal brain. EAAT-2 expression was inversely correlated with tumor grade, implicating its potential role in glial tumor progression, which was reflected by an undetectable level of EAAT-2 protein in glioma cell lines. In this study, we sought to investigate the effect of reconstituted EAAT-2 on glioma cell growth in vitro and in vivo by adenoviral-mediated gene transfer. Infection of glioma cells with Ad-EAAT-2 resulted in a physiologic level of functional EAAT-2, and a subsequent dose-dependent reduction in cell proliferation in all glioma cell lines tested compared with controls. Interestingly, results from analyses of Annexin V staining, detection of poly(ADP-ribose)polymerase cleavage and caspase-3 activation all indicated that Ad-EAAT-2 infection elicited apoptosis in glioma cells. Ex vivo experiments in nude mice showed a total suppression of tumor growth at sites that received Ad-EAAT-2-infected cells. Collectively, our results uncovered a new function of EAAT-2 in controlling glioma proliferation. Further studies will improve our knowledge of the role of glutamate in glioma growth and may provide useful prognostic information and alternative therapeutic targets for the treatment of glioma.     

Autophagy activation and SREBP‐1 induction contribute to fatty acid metabolic reprogramming by leptin in breast cancer cells

Leptin, a hormone predominantly derived from adipose tissue, is well known to induce growth of breast cancer cells. However, its underlying mechanisms remain unclear. In this study, we examined the role of reprogramming of lipid metabolism and autophagy in leptin‐induced growth of breast cancer cells. Herein, leptin induced significant increase in fatty acid oxidation‐dependent ATP production in estrogen receptor‐positive breast cancer cells. Furthermore, leptin induced both free fatty acid release and intracellular lipid accumulation, indicating a multifaceted effect of leptin in fatty acid metabolism. These findings were further validated in an MCF‐7 tumor xenograft mouse model. Importantly, all the aforementioned metabolic effects of leptin were mediated via autophagy activation. In addition, SREBP‐1 induction driven by autophagy and fatty acid synthase induction, which is mediated by SREBP‐1, plays crucial roles in leptin‐stimulated metabolic reprogramming and are required for growth of breast cancer cell, suggesting a pivotal contribution of fatty acid metabolic reprogramming to tumor growth by leptin. Taken together, these results highlighted a crucial role of autophagy in leptin‐induced cancer cell‐specific metabolism, which is mediated, at least in part, via SREBP‐1 induction.

Abbreviations

2‐DG

2‐deoxyglucose

3‐MA

3‐methyladenine

ACC‐1

acetyl‐CoA carboxylase 1

ACLY

ATP citrate lyase

ER

estrogen receptor

FADS1

fatty acid desaturase 1

FADS2

fatty acid desaturase 2

FAO

fatty acid oxidation

FAS

fatty acid synthesis

FASN

fatty acid synthase

FFA

free fatty acid

IHC

immunohistochemistry

SCD‐1

stearoyl‐CoA desaturase‐1

SREBP‐1

sterol regulatory element‐binding protein 1

     

Tumor cell metabolism: an integral view

Cancer is a genetic disease that is caused by mutations in oncogenes, tumor suppressor genes and stability genes. The fact that the metabolism of tumor cells is altered has been known for many years. However, the mechanisms and consequences of metabolic reprogramming have just begun to be understood. In this review, an integral view of tumor cell metabolism is presented, showing how metabolic pathways are reprogrammed to satisfy tumor cell proliferation and survival requirements. In tumor cells, glycolysis is strongly enhanced to fulfill the high ATP demands of these cells; glucose carbons are the main building blocks in fatty acid and nucleotide biosynthesis. Glutaminolysis is also increased to satisfy NADPH regeneration, whereas glutamine carbons replenish the Krebs cycle, which produces metabolites that are constantly used for macromolecular biosynthesis. A characteristic feature of the tumor microenvironment is acidosis, which results from the local increase in lactic acid production by tumor cells. This phenomenon is attributed to the carbons from glutamine and glucose, which are also used for lactic acid production. Lactic acidosis also directs the metabolic reprogramming of tumor cells and serves as an additional selective pressure. Finally, we also discuss the role of mitochondria in supporting tumor cell metabolism.     

Understanding metabolic alterations and heterogeneity in cancer progression through validated immunodetection of key molecular components: a case of carbonic anhydrase IX

Cancer metabolic heterogeneity develops in response to both intrinsic factors (mutations leading to activation of oncogenic pathways) and extrinsic factors (physiological and molecular signals from the extracellular milieu). Here we review causes and consequences of metabolic alterations in cancer cells with focus on hypoxia and acidosis, and with particular attention to carbonic anhydrase IX (CA IX). CA IX is a cancer-associated enzyme induced and activated by hypoxia in a broad range of tumor types, where it participates in pH regulation as well as in molecular mechanisms supporting cancer cells’ invasion and metastasis. CA IX catalyzes reversible conversion of carbon dioxide to bicarbonate ion plus proton and cooperates with a spectrum of molecules transporting ions or metabolites across the plasma membrane. Thereby CA IX contributes to extracellular acidosis as well as to buffering intracellular pH, which is essential for cell survival, metabolic performance, and proliferation of cancer cells. Since CA IX expression pattern reflects gradients of oxygen, pH, and other intratumoral factors, we use it as a paradigm to discuss an impact of antibody quality and research material on investigating metabolic reprogramming of tumor tissue. Based on the validation, we propose the most reliable CA IX-specific antibodies and suggest conditions for faithful immunohistochemical analysis of molecules contributing to heterogeneity in cancer progression.

     

转化生长因子βⅢ型受体在人类肿瘤发生发展中作用的研究进展

转化生长因子βⅢ型受体(TGFBR3,也称为betaglycan),作为肿瘤抑制和肿瘤促进基因,在肿瘤发生发展中起着调节细胞迁移、侵袭、增殖和血管生成的作用。近年来的研究结果证实TGFBR3与人类肿瘤的发生发展密切相关。TGFBR3在肿瘤中的作用多样,在乳腺癌和胰腺癌等恶性肿瘤中可作为抑癌基因,抑制细胞的增殖和分化,但在结肠癌中则可促进肿瘤的侵袭和转移。本文中,我们回顾了目前已知的文献,作为TGF-β超家族中的一员,TGFBR3扮演着上皮表型守护者的角色,其表达能抑制人类肿瘤的发生发展。     

Mesenchymal stem cell‐derived CCN2 promotes the proliferation,migration and invasion of human tongue squamous cell carcinoma cells

Recent studies have demonstrated that mesenchymal stem cells (MSC) exhibit a tropism to tumors and form the tumor stroma. In addition, we found that MSC can secrete different types of factors. However, the involvement of MSC‐derived factors in human tongue squamous cell carcinoma (TSCC) growth has not been clearly addressed. The CCN family includes multifunctional signaling molecules that affect the initiation and development events of various tumors. In our study, we report that CCN2/connective tissue growth factor (CTGF) was the most highly induced among the CCN family members in MSC that were co‐cultured with TSCC cells. To evaluate the relationship between CCN2 and TSCC growth, we downregulated MSC‐derived CCN2 expression with shRNA targeting CCN2 and found that MSC‐secreted CCN2 promotes TSCC cell proliferation, migration and invasion. We also confirmed that MSC‐derived CCN2 partially accelerated tumor growth in vitro. Taken together, these results suggest that MSC‐derived CCN2 contributes to the promotion of proliferation, migration and invasion of TSCC cells and may be a possible therapy target in the future.     

Effects of tumor metabolic microenvironment on regulatory T cells

Recent studies have shown that on one hand, tumors need to obtain a sufficient energy supply, and on the other hand they must evade the body’s immune surveillance. Because of their metabolic reprogramming characteristics, tumors can modify the physicochemical properties of the microenvironment, which in turn affects the biological characteristics of the cells infiltrating them. Regulatory T cells (Tregs) are a subset of T cells that regulate immune responses in the body. They exist in large quantities in the tumor microenvironment and exert immunosuppressive effects. The main effect of tumor microenvironment on Tregs is to promote their differentiation, proliferation, secretion of immunosuppressive factors, and chemotactic recruitment to play a role in immunosuppression in tumor tissues. This review focuses on cell metabolism reprogramming and the most significant features of the tumor microenvironment relative to the functional effects on Tregs, highlighting our understanding of the mechanisms of tumor immune evasion and providing new directions for tumor immunotherapy.     

非小细胞肺癌组织中circ_0006692的表达及其对肺癌细胞增殖转移的调控机制

目的 探讨非小细胞肺癌（NSCLC）中circ_0006692的表达与临床病理特征的关系及机制。方法 收集50对NSCLC和癌旁组织，qRT-PCR法检测癌和癌旁组织中circ_0006692的表达，并分析其与临床病理特征之间的关系。构建过表达、敲低的circ_0006692的A549肺癌细胞株，MTS、克隆形成实验、划痕创伤愈合实验和Transwell侵袭实验检测circ_0006692表达变化对细胞增殖、迁移和侵袭能力的影响。qRT-PCR和Western blot检测circ_0006692表达变化对EMT相关基因表达的影响。结果 非小细胞肺癌组织中circ_0006692表达水平高于癌旁组织（P<0.05），其表达水平与肿瘤大小、TNM分期及肺膜侵犯密切相关（P<0.05）。circ_0006692敲低抑制细胞增殖、侵袭和转移，过表达可促进细胞增殖、侵袭和转移。qRT-PCR和Western blot结果显示circ_0006692敲低抑制A549肺癌细胞EMT相关基因CDH2和MMP7促进CDH1表达。结论 非小细胞肺癌组织中circ_0006692的表达上调与肿瘤大小、TNM分期及肺膜侵犯密切相关；circ_0006692表达可调节A549肺癌细胞增殖、侵袭、转移以及EMT进展。     

脂代谢重编程在前列腺癌中的研究进展

代谢重编程在肿瘤的发生发展过程中扮演着重要角色,为肿瘤细胞的生命活动提供了必要的物质基础,并对肿瘤的生物学行为起促进作用。代谢重编程可引起肿瘤细胞中氨基酸、葡萄糖和脂肪酸的代谢模式发生改变,是肿瘤的标志性特征之一。目前发现大多数肿瘤倾向利用糖酵解产生的Warburg效应为自身供能,而研究表明前列腺癌细胞更依赖脂肪酸氧化途径进行代谢重编程获取能量物质。因此,深度掌握脂质代谢关键酶和相关调控基因间的关系,对前列腺癌早期诊断、精准靶向治疗及获得更好的疾病预后具有重要意义。     

细胞膜磷脂与肿瘤侵袭、转移及靶向治疗的相关性研究进展

侵袭和转移是肿瘤进展的标志,是肿瘤临床治疗的难题及肿瘤患者死亡的主要原因。磷脂是生物膜的重要物质基础,参与肿瘤细胞增殖、运动、黏附、凋亡、信号转导、细胞周期调节等活动。本文对膜磷脂在肿瘤侵袭、转移、靶向治疗中的作用研究进展进行了综述。细胞膜磷脂成分及分布、磷脂代谢产物、磷脂酶及磷脂结合蛋白在肿瘤细胞膜流动性、黏附、凋亡、增殖、侵袭、转移、血管及淋巴管形成中具有重要作用,以细胞膜磷脂及其代谢产物为靶点治疗恶性肿瘤具有广阔前景。     

Decreased Expression of FADS1 Predicts a Poor Prognosis in Patients with Esophageal Squamous Cell Carcinoma

FADS1 (fatty acid desaturase 1) plays a crucial role in fatty acid metabolism, and it was recently reportedto be involved in tumorigenesis. However, the role of FADS1 expression in esophageal squamous cell carcinoma(ESCC) remains unknown. In the current study, we investigated the expression and clinical pathologic andprognostic significance of FADS1 in ESCC. Immunohistochemical analyses revealed that 58.2% (146/251) ofthe ESCC tissues had low levels of FADS1 expression, whereas 41.8% (105/251) exhibited high levels of FADS1expression. In positive cases, FADS1 expression was detected in the cytoplasm of cells. Correlation analysesdemonstrated that FADS1 expression was significantly correlated with tumor location (p=0.025) but not withage, gender, histological grade, tumor status, nodal status or TNM staging. Furthermore, patients with tumorsexpressing high levels of FADS1had a longer disease-free survival time (p<0.001) and overall survival time (p<0.001). Univariate and multivariate analyses revealed that, along with nodal status, FADS1 expression was anindependent and significant predictive factor (p<0.001). In conclusion, our study suggested that FADS1 mightbe a valuable biomarker and potential therapeutic target for ESCC.     

VEGFR‐2 expression in carcinoid cancer cells and its role in tumor growth and metastasis

Carcinoid tumors are slow growing and highly vascular neuroendocrine neoplasms that are increasing in incidence. Previously, we showed that carcinoid tumors express vascular endothelial growth factor receptor 2 (VEGFR‐2) in the epithelial compartment of carcinoid tumor sections; yet, its role is not completely understood. The purpose of our study was to: (i) assess the expression of VEGFR‐2 in the novel human carcinoid cell line BON, (ii) to determine the role of PI3K/Akt signaling on VEGFR‐2 expression and (iii) to assess the effect of VEGFR‐2 on BON cell invasion, migration and proliferation. We found that, although VEGFR‐2 is expressed in BON cells, reduction in VEGFR‐2 expression actually enhanced proliferation, invasion, and migration of the BON cell line. Also, expression of VEGFR‐2 was inversely related to PI3K signaling. Carcinoid liver metastases in mice demonstrated decreased VEGFR‐2 expression. Furthermore, the expression of a truncated, soluble form of VEGFR‐2 (sVEGFR‐2), a protein demonstrated to inhibit cell growth, was detected in BON cells. The presence of VEGFR‐2 in the epithelial component of carcinoid tumors and in the BON cell line suggests an alternate role for VEGFR‐2, in addition to its well‐defined role in angiogenesis. The expression of sVEGFR‐2 may explain the inverse relationship between VEGFR‐2 expression and PI3K/Akt signaling and the inhibitory effect VEGFR‐2 has on BON cell proliferation, migration and invasion.     

CUL4A is overexpressed in human pituitary adenomas and regulates pituitary tumor cell proliferation

Cullin 4A (CUL4A) encodes a core subunit of an E3 ubiquitin ligase that targets proteins for ubiquitin-mediated degradation, and aberrant expression of the CUL4A is found in many tumor types. However, its roles and clinicopathologic significance in pituitary adenomas are not clear. The aim of this study was to investigate the possible role of CUL4A in pituitary tumorigenesis. Immunohistochemistry was used to examine CUL4A expression in human normal pituitaries and pituitary tumors with respect to various clinicopathologic factors in pituitary adenomas. Cell proliferation was assessed by MTT and colony formation, and migration and invasion were analyzed by Transwell and Matrigel assays after CUL4A overexpression or knockdown in pituitary tumor cells. Overexpression of CUL4A was frequently observed in pituitary adenomas compared with normal adenohypophysial tissue and significantly associated with tumor progressiveness and invasion. CUL4A overexpression in GH3 adenoma cells increased colony numbers, cell viability and cell invasion and silencing CUL4A in AtT20 adenoma cells decreased cell proliferation, migration and invasion. Mechanistically, CUL4A could modulate the expression of p53, p21, and p27 in pituitary tumor cells. In addition, high levels of CUL4A expression also significantly inversely correlated with the p53 protein level in human pituitary adenomas. Our results indicate that CUL4A enhances pituitary cell proliferation, migration and invasion and may thus contribute to pituitary tumor development and progression.     

LncRNA SBF2-AS1在恶性肿瘤中的作用及其机制

长链非编码RNA（long noncoding RNA,LncRNA）参与肿瘤的进展已被频繁报道。 LncRNA SBF2-AS1是一种新发现的LncRNA,已被证实是一种与多种肿瘤相关的癌基因。多项研究表明其在胃癌、食管癌、肺癌、结直肠癌、胰腺癌等多种肿瘤中异常表达,可调节细胞的增殖、侵袭、迁移及凋亡,影响患者的生存预后。本文对LncRNA SBF2-AS1在恶性肿瘤中的作用及其机制的最新研究进展作一综述,以期为肿瘤的精准治疗提供参考。