TNF-α 在肿瘤中的作用

肿瘤坏死因子是一个特别的,并具有多重功能的细胞因子,它在免疫调节,炎症反应,机体防御当中起着关键的作用。根据不同的细胞微环境,肿瘤坏死因子可以诱导多种反应,例如凋亡,坏死,血管生成,免疫细胞激活,细胞分化,细胞迁移。TNF在肿瘤当中是一把双刃剑。一方面,TNF是一个内源性的肿瘤促进因素,因为TNF可以刺激肿瘤细胞生长,增殖,侵袭,转移,血管生成。另一方面,TNF具有杀肿瘤细胞的作用。因此,如果可以调控肿瘤坏死因子的功能,将为癌症的治疗提供可能。     

肿瘤坏死因子α在中枢神经系统中的作用

概述了肿瘤坏死因子α（TNFα）及其受体在中枢神经系统（CNS）中的作用。TNFα在神经元和胶质细胞中的表达量与神经系统疾病的发病密切相关;TNFα与神经胶质增生、Alzheimer’s病、Parkinson病和多发性硬化症都有关系。然而;当CNS受损伤以后,TNFα能够促进神经营养因子的分泌,增强神经元的粘附和促进轴突的生长;这是它有利的一面。这种双重模式的效应与其受体亚型和激活不同的信号转导途径有关。所以,在CNS的发育中,TNFα可能是一个重要的调节因子。     

巨噬细胞游走抑制因子在肿瘤中的作用研究进展

巨噬细胞游走抑制因子是一种具有多种生物学效应的糖蛋白,可以调节不同的下游信号如ERK/AKT、NF-κB等通路参与肿瘤细胞增殖、侵袭、转移、血管形成和自噬等生物学过程。临床相关研究表明巨噬细胞游走抑制因子与肿瘤发生发展关系密切,且在乳腺癌、肺癌、前列腺癌、甲状腺癌、结肠癌等多种肿瘤中高表达,因此以巨噬细胞游走抑制因子为靶点的相关肿瘤治疗逐渐受到重视。有关巨噬细胞游走抑制因子拓扑异构酶活性抑制剂及巨噬细胞游走抑制因子中和抗体在肿瘤治疗中的研究越来越多。本文对巨噬细胞游走抑制因子在肿瘤发生发展中的作用以及针对巨噬细胞游走抑制因子进行的肿瘤治疗研究作一综述。     

LZTS2 抑癌基因在肿瘤中的作用机制

亮氨酸拉链肿瘤抑制因子2(leucine zipper tumor suppressor 2,Lzts2)是一种新发现的抑癌基因,位于人类染色体10q24.3,在多种肿瘤中异常表达,且对肿瘤的发生、增殖和迁移中均发挥重要作用。LZTS2拥有亮氨酸拉链结构域(LZ),可以通过该结构域结合DNA调节基因转录。LZTS2还可以参与Wnt/β-catenin信号通路调控β-catenin的表达及细胞内分布,与NF-κB亦拥有广泛的相互作用,从而调控细胞增殖和凋亡。在微管系统中,LZTS2也有重要的调节作用,可抑制细胞的有丝分裂和迁移,增加肿瘤细胞的药物敏感性。LZTS2作为新的抑癌基因,与肿瘤的大小和淋巴结转移等生物学特性密切相关,可能成为新的诊断标志物,判断肿瘤的预后,亦可能为肿瘤的基因治疗潜在方向。然而关于LZTS2及其作用机制的研究尚为不足,本文将对LZTS2在肿瘤中的作用机制作简要综述。     

百草枯中毒大鼠TNF-a、IL-10的表达及大黄保护作用的研究

目的：观察大黄对急性百草枯中毒大鼠TNF-α、IL-10的干预作用,探讨其可能的作用机制。方法：90只SD大鼠随机分为生理盐水对照组（A组）、PQ（60 mg/kg）灌胃染毒组（B组）、生大黄（300mg/kg.d）干预组（C组）,每组30只。中毒后6h、24h、72h分批处死存活的大鼠,并且检测大鼠血浆TNF-α、IL-10水平。结果：B组、C组TNF-α、IL-10水平在染毒后6h开始升高,72h达到高峰,与A组相比,差异有统计学意义（P〈0.05、P〈0.01）,在相同时间点C组TNF-α和IL-10的表达低于B组,差异均有统计学意义（P〈0.01）。B组、C组血浆TNF-α、IL-10水平与中毒时间呈显著正性相关关系（r=0.849,P〈0.01;r=0.790,P〈0.01;r=0.0.943,P〈0.01;r=0.892,P〈0.01）。结论：大黄能够通过降低百草枯中毒大鼠体内的TNF-α、IL-10水平,减轻百草枯对大鼠的损伤作用     

A critical role of Gbetagamma in tumorigenesis and metastasis of breast cancer

A growing body of evidence indicates that G protein-coupled receptors (GPCRs) are involved in breast tumor progression and that targeting GPCRs may be a novel adjuvant strategy in cancer treatment. However, due to the redundant role of multiple GPCRs in tumor development, it may be necessary to target a common signaling component downstream of these receptors to achieve maximum efficacy. GPCRs transmit signals through heterotrimeric G proteins composed of Gα and Gβγ subunits. Here we evaluated the role of Gβγ in breast tumor growth and metastasis both in vitro and in vivo. Our data show that blocking Gβγ signaling with Gα(t) or small molecule inhibitors blocked serum-induced breast tumor cell proliferation as well as tumor cell migration induced by various GPCRs in vitro. Moreover, induced expression of Gα(t) in MDA-MB-231 cells inhibited primary tumor formation and retarded growth of existing breast tumors in nude mice. Blocking Gβγ signaling also dramatically reduced the incidence of spontaneous lung metastasis from primary tumors and decreased tumor formation in the experimental lung metastasis model. Additional studies indicate that Gβγ signaling may also play a role in the generation of a tumor microenvironment permissive for tumor progression, because the inhibition of Gβγ signaling attenuated leukocyte infiltration and angiogenesis in primary breast tumors. Taken together, our data demonstrate a critical role of Gβγ signaling in promoting breast tumor growth and metastasis and suggest that targeting Gβγ may represent a novel therapeutic approach for breast cancer.     

Protein engineering to target complement evasion in cancer

The complement system is composed of soluble factors in plasma that enhance or “complement” immune-mediated killing through innate and adaptive mechanisms. Activation of complement causes recruitment of immune cells; opsonization of coated cells; and direct killing of affected cells through a membrane attack complex (MAC). Tumor cells up-regulate complement inhibitory factors – one of several strategies to evade the immune system. In many cases as the tumor progresses, dramatic increases in complement inhibitory factors are found on these cells. This review focuses on the classic complement pathway and the role of major complement inhibitory factors in cancer immune evasion as well as on how current protein engineering efforts are being employed to increase complement fixing or to reverse complement resistance leading to better therapeutic outcomes in oncology. Strategies discussed include engineering of antibodies to enhance complement fixation, antibodies that neutralize complement inhibitory proteins as well as engineered constructs that specifically target inhibition of the complement system.     

The role of PML ubiquitination in human malignancies

Tumor suppressors are frequently downregulated in human cancers and understanding of the mechanisms through which tumor cells restrict the expression of tumor suppressors is important for the prognosis and intervention of diseases. The promyelocytic leukemia (PML) protein plays a critical role in multiple tumor suppressive functions, such as growth inhibition, apoptosis, replicative senescence, suppression of oncogenic transformation, and inhibition of migration and angiogenesis. These tumor suppression functions are recapitulated in several mouse models. The expression of PML protein is frequently downregulated in diverse types of human tumors and this downregulation often correlates with tumor progression. Recent evidence has emerged that PML is aberrantly degraded in various types of tumors through ubiquitination-dependent mechanisms. Here, we summarize our current understanding of the PML ubiquitination/degradation pathways in human cancers. We point out that multiple pathways lead to PML ubiquitination and degradation. Furthermore, the PML ubiquitination processes are often dependent on other types of posttranslational modifications, such as phosphorylation, prolylisomerization, and sumoylation. Such feature indicates a highly regulated nature of PML ubiquitination in different cellular conditions and cell contexts, thus providing many avenues of opportunity to intervene PML ubiquitination pathways. We discuss the potential of targeting PML ubiquitination pathways for anti-cancer therapeutic strategies.     

The key role of extracellular vesicles in the metastatic process

Extracellular vesicles (EVs), including exosomes, have a key role in the paracrine communication between organs and compartments. EVs shuttle virtually all types of biomolecules such as proteins, lipids, nucleic acids, metabolites and even pharmacological compounds. Their ability to transfer their biomolecular cargo into target cells enables EVs to play a key role in intercellular communication that can regulate cellular functions such as proliferation, apoptosis and migration. This has led to the emergence of EVs as a key player in tumor growth and metastasis through the formation of “tumor niches” in target organs. Recent data have also been shown that EVs may transform the microenvironment of primary tumors thus favoring the selection of cancer cells with a metastatic behavior. The release of EVs from resident non-malignant cells may contribute to the metastatic processes as well. However, cancer EVs may induce malignant transformation in resident mesenchymal stem cells, suggesting that the metastatic process is not exclusively due to circulating tumor cells. In this review, we outline and discuss evidence-based roles of EVs in actively regulating multiple steps of the metastatic process and how we can leverage EVs to impair metastasis.     

Evaluation of possible mechanisms of protective role of Tamarix gallica against DEN initiated and 2-AAF promoted hepatocarcinogenesis in male Wistar rats

We have previously reported that Tamarix gallica caused a marked inhibition of thioacetamide-induced hepatotoxicity, oxidative damage and early tumor promotion related events in the liver. These results strongly indicates that T. gallica may have chemopreventive potential. Therefore, in the present study, we examined the inhibitory effects of T. gallica methanolic extract on diethylnitrosamine (DEN) initiated and 2-acetyl aminofluorene (2-AAF) promoted liver carcinogenesis in male Wistar rats. Interestingly, it was found that T. gallica (25 and 50 mg/kg body wt.) resulted in a marked reduction of the incidence of liver tumors. The study was further histologically confirmed. Furthermore to understand the underlying mechanisms of chemopreventive action by T. gallica we evaluated the levels activities of hepatic antioxidant defense enzymes, ornithine decarboxylase activity and hepatic DNA synthesis as a marker for tumor promotion since direct correlation between these marker parameters and carcinogenicity have been well documented. Treatment of male Wistar rats for five consecutive days with 2-AAF i.p. induced significant hepatic toxicity, oxidative stress and hyperproliferation. Pretreatment of T. gallica extract (25 and 50 mg/kg body wt.) prevented oxidative stress by restoring the levels of antioxidant enzymes and also prevented toxicity at both the doses. The promotion parameters induced (ornithine decarboxylase activity and DNA synthesis) by 2-AAF administration in diet with partial hepatectomy (PH) were also significantly suppressed dose-dependently by T. gallica. Therefore, we can conclude that ultimately the protection against liver carcinogenesis by T. gallica methanolic extract might be mediated by multiple actions, which include restoration of cellular antioxidant enzymes, detoxifying enzymes, ODC activity and DNA synthesis.     

Macrophage infiltration in human non-small-cell lung cancer: the role of CC chemokines

 Bronchogenic carcinoma is the leading cause of malignancy-related mortality in the United States, with an overall 5-year survival rate of less than 15%. This aggressive behavior reflects, among other traits, the capacity of the tumor to evade normal host immune defenses, and to induce a pro-angiogenic environment. A central feature of any immune response toward tumors is the recruitment of specific immune cell populations. In the present study we investigated the infiltration of monocytes in human specimens of non-small-cell lung cancer (NSCLC). The presence of macrophages in NSCLC tumors was documented by immunohistochemistry. In vitro chemotaxis assays demonstrated higher monocyte chemotactic activity in NSCLC tumor homogenates than in normal lung tissue. We next investigated the expression of CC chemokines within specimens of NSCLC tumors. Levels of the CC chemokines were higher in NSCLC tumor tissue than in normal lung tissue. Immunolocalization showed that the cells associated with antigenic CC chemokines were the malignant tumor cells, as well as occasional stromal cells. Maximal inhibition of monocyte chemotaxis induced by NSCLC in vitro occurred in the presence of neutralizing antibodies to MCP-1 and MIP-1β. On follow-up of 15 patients in whom we quantified macrophage infiltration, we found that those with recurrence of disease had higher levels of macrophage infiltration in their initial tumors. However, the functional significance of CC-chemokine-mediated macrophage infiltration into NSCLC remains to be determined. Received: 12 November 1999 / Accepted: 10 December 1999     

The role of microenvironment in tumor angiogenesis

Tumor microenvironment is essential for tumor cell proliferation, angiogenesis, invasion and metastasis through its provision of survival signals, secretion of growth and pro-angiogenic factors, and direct adhesion molecule interactions. This review examines its importance in the induction of an angiogenic response in tumors and in multiple myeloma. The encouraging results of pre-clinical and clinical trials in which tumors have been treated by targeting the tumor microenvironment are also discussed.