本文關(guān)鍵詞：TLR4信號通路參與人結(jié)腸癌細胞免疫逃逸機制的研究　出處：《武漢大學(xué)》2009年博士論文　論文類型：學(xué)位論文

  更多相關(guān)文章： Toll樣受體4 結(jié)腸癌 免疫逃逸 NF-κB 凋亡耐受

【摘要】：慢性感染和炎癥可以導(dǎo)致腫瘤的發(fā)生、發(fā)展,但其機制并不太清楚。許多研究發(fā)現(xiàn)在此過程中天然免疫系統(tǒng)發(fā)揮了重要的作用,而在天然免疫過程中起決定性作用的Toll樣受體(Toll-like receptors, TLRs)家族在腫瘤中的作用也越來越受到人們的重視。 TLRs最早在果蠅中發(fā)現(xiàn),起初人們認為其對節(jié)肢動物胚胎發(fā)育時的傾向性具有重要作用。隨著研究的進一步進展,人們發(fā)現(xiàn)其具有對抗病原微生物感染的能力。1997年Medzhitov等發(fā)現(xiàn)了人類的第一個TLR(后來被命名為TLR4)。接著,人類的其他TLRs相繼被發(fā)現(xiàn)。迄今為止,在人類已經(jīng)發(fā)現(xiàn)了11個TLRs成員,對它們相應(yīng)的配體也有所了解。TLRs主要表達于免疫細胞尤其是巨噬細胞和樹突狀細胞表面,通過廣泛地特異性地識別病原體相關(guān)的分子模式(pathogen-associated molecular patterns, PAMPs),偶聯(lián)信號傳導(dǎo)途徑,激活免疫細胞分泌大量炎性細胞因子和趨化因子,發(fā)揮機體的抗病原微生物感染能力,構(gòu)成機體免疫反應(yīng)的第一道防線。TLRs不僅能激活天然免疫,而且也為激活獲得性免疫提供共刺激信號,是天然免疫與獲得性免疫兩者之間的橋梁。因此,TLRs的功能及其作用信號轉(zhuǎn)導(dǎo)機制的研究具有重要的理論意義和應(yīng)用價值。 當(dāng)人們在研究免疫細胞表面TLRs的結(jié)構(gòu)、功能及信號轉(zhuǎn)導(dǎo)途徑的時候,卻發(fā)現(xiàn)多種腫瘤細胞表面也表達多種TLRs,并且可能與腫瘤細胞的免疫逃逸相關(guān)。本課題主要目的是檢測TLR4在人結(jié)腸癌細胞的表達,檢測結(jié)腸癌細胞表達的TLR4是否參與結(jié)腸癌細胞免疫逃逸及其可能的機制。 我們選取了人結(jié)腸癌細胞HT-29及SW480,發(fā)現(xiàn)TLR4在nRNA與蛋白水平均有表達。接下來,我們用TLR4外源性配體LPS作為激活劑,觀察TLR4信號轉(zhuǎn)導(dǎo)通路是否活化以及活化后細胞生物學(xué)活性的改變。結(jié)果表明,LPS刺激HT-29與SW480細胞后,NF-κB及MAPK信號轉(zhuǎn)導(dǎo)通路被激活,而且IL-8分泌水平增加,表明HT-29與SW480表達的TLR4具有功能活性,能被LPS激活。同時HT-29與SW480可以自發(fā)分泌一定水平的TGF-β、VEGF,LPS可通過TLR4增強TGF-β、VEGF及IL-8的分泌。進一步研究發(fā)現(xiàn),LPS刺激對HT-29與SW480細胞的增殖無影響,但對TRAIL誘導(dǎo)的細胞凋亡有耐受作用。表明TLR4信號活化可以促進人結(jié)腸癌細胞逃逸機體的免疫攻擊,有利于腫瘤的發(fā)生發(fā)展。 總之,本研究發(fā)現(xiàn)人結(jié)腸癌細胞HT-29與SW480表達TLR4, TLR4配體LPS刺激可以促進人結(jié)腸癌細胞分泌免疫抑制性細胞因子TGF-β、VEGF及IL-8,并提高結(jié)腸癌細胞對TRAIL誘導(dǎo)的凋亡的耐受作用,這一作用可能與NF-κB信號通路被激活有關(guān)。本實驗結(jié)果將有助于了解TLR4信號途徑活化后在結(jié)腸癌細胞中的作用,對TLR4信號在腫瘤生物學(xué)和腫瘤免疫學(xué)的功能增添了新的認識,并為結(jié)腸癌的治療提供了新靶點。
[Abstract]:Chronic infection and inflammation can lead to tumorigenesis and progression, but its mechanism is not very clear. Many studies have found that innate immune system plays an important role in this process. Toll-like receptors, a Toll like receptor that plays a decisive role in the innate immune process. The role of TLRs family in tumor has been paid more and more attention. TLRs was first found in Drosophila, initially thought to play an important role in the developmental tendency of arthropod embryos. In 1997, Medzhitov et al discovered the first human TLRs (later named TLR4). Other human TLRs have been discovered. So far, 11 TLRs members have been discovered in humans. It is also known that the corresponding ligands. TLRs are mainly expressed on the surface of immune cells, especially macrophages and dendritic cells. Pathogen-associated molecular patterns (PAMPs) are widely and specifically identified by pathogen-associated molecular patterns. The coupling signal transduction pathway activates the immune cells to secrete a large number of inflammatory cytokines and chemokines to exert the ability of anti-pathogenic microorganism infection. TLRs can not only activate innate immunity, but also provide costimulatory signal for activation of acquired immunity, which is the bridge between innate immunity and acquired immunity. The study of the function and signal transduction mechanism of TLRs has important theoretical significance and application value. When people are studying the structure, function and signal transduction pathway of TLRs on immune cells, it is found that many kinds of TLRs are also expressed on the surface of many tumor cells. The main purpose of this study is to detect the expression of TLR4 in human colon cancer cells. To determine whether the TLR4 expressed in colon cancer cells is involved in the immune escape of colon cancer cells and its possible mechanism. We selected human colon cancer cells HT-29 and SW480 and found that TLR4 was expressed at both nRNA and protein levels. Then we used TLR4 exogenous ligand LPS as activator. The activation of TLR4 signal transduction pathway and the changes of cell biological activity after activation were observed. The results showed that LPS-stimulated HT-29 and SW480 cells. NF- 魏 B and MAPK signal transduction pathway were activated, and the level of IL-8 secretion increased, indicating that TLR4 expressed by HT-29 and SW480 had functional activity. At the same time, HT-29 and SW480 could spontaneously secrete a certain level of TGF- 尾. VEGF could enhance TGF- 尾 through TLR4. The secretion of VEGF and IL-8. Further study showed that LPS-stimulated proliferation of HT-29 and SW480 cells had no effect. The results showed that the activation of TLR4 signal could promote the immune attack of human colon cancer cells, which was beneficial to the occurrence and development of tumor. In conclusion, we found that human colon cancer cells HT-29 and SW480 express TLR4. TLR4 ligand LPS stimulation can promote the secretion of immunosuppressive cytokines TGF- 尾 -VEGF and IL-8 in human colon cancer cells. And to improve the tolerance of colon cancer cells to TRAIL induced apoptosis. This effect may be related to the activation of NF- 魏 B signaling pathway. Our results may be helpful to understand the role of TLR4 signaling pathway activation in colon cancer cells. New understanding of the function of TLR4 signal in tumor biology and tumor immunology has been added, and a new target for the treatment of colon cancer has been provided.
【學(xué)位授予單位】：武漢大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2009
【分類號】：R392;R735.35

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