高 昆 張連峰
(中國(guó)醫(yī)學(xué)科學(xué)院實(shí)驗(yàn)動(dòng)物研究所北京協(xié)和醫(yī)學(xué)院比較醫(yī)學(xué)中心衛(wèi)生部人類(lèi)疾病比較醫(yī)學(xué)重點(diǎn)實(shí)驗(yàn)室,北京100021)
白細(xì)胞介素(Interleukin,IL)最初被發(fā)現(xiàn)是一種由白細(xì)胞產(chǎn)生的分泌型蛋白或信號(hào)分子,它能夠非特異性地調(diào)節(jié)機(jī)體免疫反應(yīng),并在炎癥反應(yīng)中發(fā)揮重要作用。近年來(lái)有許多關(guān)于白細(xì)胞介素與腫瘤發(fā)生、發(fā)展相關(guān)方面研究的報(bào)道,本文主要對(duì)與腫瘤相關(guān)的白細(xì)胞介素進(jìn)行綜述。
IL-1主要由活化的巨噬細(xì)胞產(chǎn)生,其生物學(xué)功能主要是促進(jìn)T、B細(xì)胞的增殖和分化,協(xié)同IL-2、IFN-γ誘導(dǎo)產(chǎn)生CTL,增強(qiáng)NK細(xì)胞活性。經(jīng)過(guò)學(xué)者們多年的研究發(fā)現(xiàn)炎癥介質(zhì)和細(xì)胞因子在腫瘤局部環(huán)境中發(fā)揮著重要作用[1]。IL-1作為一種重要的促炎性細(xì)胞因子[2],它能夠促進(jìn)趨化性細(xì)胞因子釋放,吸引中性粒細(xì)胞來(lái)影響腫瘤的發(fā)生、發(fā)展及轉(zhuǎn)移,腫瘤局部侵潤(rùn)的中性粒細(xì)胞是產(chǎn)生活性氧及致癌作用的關(guān)鍵細(xì)胞。另外IL-1還能夠誘導(dǎo)粘附分子及金屬蛋白酶的產(chǎn)生從而促進(jìn)腫瘤的侵襲。IL-1主要有IL-1α及 IL-1β兩種存在形式,它們作用于相同的受體IL-1RⅠ,同時(shí)募集IL-1受體輔助蛋白(IL-1RAcP)觸發(fā)信號(hào)轉(zhuǎn)導(dǎo),而后活化IL-1受體相關(guān)激酶-1(IRAK-1)及IL-1受體相關(guān)激酶-2(IRAK-2),IRAK-1活化并募集泛素連接酶TRAF6,TRAF6能夠激活 NF-κB 及 MAPK/c-Jun 兩條信號(hào)通路[3-5]。IL-1α及IL-1β均能促進(jìn)炎癥反應(yīng)及刺激產(chǎn)生前列腺素E2(PGE2)。與IL-1α相比,IL-1β在炎癥反應(yīng)中的作用更為重要,F(xiàn)antuzzi等[6]的研究結(jié)果顯示在炎癥刺激物誘導(dǎo)下IL-1β基因缺陷小鼠未產(chǎn)生炎癥反應(yīng)。IL-1α、IL-1β二者在腫瘤中發(fā)揮不同的作用,天然的膜結(jié)合型IL-1α能夠像粘附分子一樣增效腫瘤細(xì)胞與攜帶IL-1R的免疫效應(yīng)細(xì)胞之間的相互作用,通過(guò)激發(fā)機(jī)體免疫細(xì)胞對(duì)腫瘤的殺傷而抑制腫瘤發(fā)生。而IL-1β則通過(guò)促進(jìn)腫瘤血管生成及誘導(dǎo)宿主的免疫抑制而增強(qiáng)腫瘤的侵襲性,研究發(fā)現(xiàn)表達(dá)IL-1β的腫瘤細(xì)胞具有更強(qiáng)的侵襲與轉(zhuǎn)移特性,并且能夠產(chǎn)生由未成熟CD11b+/Gr-1+髓樣細(xì)胞介導(dǎo)的T細(xì)胞免疫抑制[7-9]。
IL-6是由巨噬細(xì)胞、成纖維細(xì)胞、內(nèi)皮細(xì)胞等產(chǎn)生的一種多功能細(xì)胞因子。IL-6能夠促進(jìn)T、B細(xì)胞的增殖與分化,誘導(dǎo)巨噬細(xì)胞及巨核細(xì)胞分化,活化破骨細(xì)胞,且與炎癥反應(yīng)及自身免疫性疾病等相關(guān)[10]。IL-6通過(guò)與IL-6受體結(jié)合發(fā)揮其生物學(xué)作用,IL-6與 IL-6Rα亞基結(jié)合后,使得 IL-6Rβ亞基(gp130)形成二聚體,從而活化其下游的 JAK1/STAT3 信號(hào)通路,發(fā)揮其生物學(xué)功能[11,12]。IL-6 能夠在多種人類(lèi)腫瘤中激活STAT3,在原發(fā)性人肺腺癌中突變的表皮生長(zhǎng)因子受體(EGFR)能夠以上調(diào)IL-6的方式激活 gp130/JAK/STAT3通路[13]。研究發(fā)現(xiàn)IL-6水平的升高與肝細(xì)胞癌有關(guān),IL-6能夠通過(guò)激活STAT3信號(hào)提高阿霉素處理的人肝癌細(xì)胞的存活率[14]。腫瘤局部IL-6的水平對(duì)臨床預(yù)后也有影響,在宮頸癌中腫瘤局部IL-6基因的高表達(dá)與預(yù)后不良相關(guān)[15],唾液中IL-6的水平在舌鱗狀上皮細(xì)胞癌(TSCC)從高危到產(chǎn)生贅生物進(jìn)展過(guò)程存在差異,IL-6可能成為腫瘤篩查及早期檢測(cè)的生物學(xué)指標(biāo)。另有研究發(fā)現(xiàn)肥大細(xì)胞產(chǎn)生的IL-6在TLR2介導(dǎo)的腫瘤生長(zhǎng)抑制中起重要作用,體內(nèi)肥大細(xì)胞重建實(shí)驗(yàn)也證明了這一點(diǎn)[16-18]。
IL-12是一種重要的免疫調(diào)節(jié)細(xì)胞因子,由p35和p40兩個(gè)亞基組成,其作用的受體分別為 IL-12Rβ1及IL-12Rβ2,主要表達(dá)于抗原遞呈細(xì)胞表面。它能夠促進(jìn)T細(xì)胞、NK細(xì)胞增殖,刺激CD4+T細(xì)胞分化為Ⅰ型輔助型T細(xì)胞,并通過(guò)活化STAT4通路增強(qiáng) CTL的活性[19,20]。由于 IL-12能夠促進(jìn)Th1細(xì)胞的分化,因此它在Ⅰ型細(xì)胞介導(dǎo)的抗腫瘤免疫中具有重要作用。IL-12誘導(dǎo)產(chǎn)生IFN-γ,IFN-γ能夠上調(diào)MHCⅠ及Ⅱ類(lèi)分子、ICAM-1等粘附分子、T-bet等轉(zhuǎn)錄因子的表達(dá),這些有利于激發(fā)免疫細(xì)胞對(duì)腫瘤的作用。另外,IL-12還能夠誘導(dǎo)產(chǎn)生抗血管生成趨化因子,例如IFN-γ誘導(dǎo)蛋白(IP-10,CXCL10)以及 IFN-γ誘導(dǎo)產(chǎn)生的單核因子(MIG,CXCL9)[21]。IL-12不僅能夠增強(qiáng)機(jī)體的抗腫瘤免疫應(yīng)答而且能夠降低具有免疫抑制功能細(xì)胞的活性。Steding等在研究中發(fā)現(xiàn)IL-12具有調(diào)節(jié)髓樣抑制性細(xì)胞(MDSC)活性的能力,MDSC在腫瘤微環(huán)境中發(fā)揮著重要作用,它能夠抑制腫瘤微環(huán)境中T細(xì)胞的活性,促進(jìn)腫瘤的生長(zhǎng)與轉(zhuǎn)移。研究結(jié)果顯示IL-12能夠降低乳腺癌腫瘤微環(huán)境中MDSC的百分比,升高CD8+T細(xì)胞的百分比,在提高生存率的同時(shí)也減少了轉(zhuǎn)移灶[22]。最近有學(xué)者研究發(fā)現(xiàn)IL-12對(duì)腫瘤的抑制作用并非由T細(xì)胞或NK細(xì)胞介導(dǎo)的,而是依賴(lài)于一種表達(dá)轉(zhuǎn)錄活化因子 RORγt的NKp46+淋巴組織誘導(dǎo)(LTi)細(xì)胞。這種 NKp46+LTi細(xì)胞能夠上調(diào)腫瘤脈管系統(tǒng)粘附分子的表達(dá),從而使得更多白細(xì)胞浸潤(rùn)至腫瘤局部[23]。
IL-23屬于IL-12家族的成員,主要由活化的DC細(xì)胞釋放產(chǎn)生,能夠影響T細(xì)胞的成熟與分化,在細(xì)胞介導(dǎo)的免疫中發(fā)揮重要作用。IL-23由其自身特異性的p19亞基及IL-12p40亞基組成,這兩個(gè)亞基作用的受體分別為IL-23R及IL-12Rβ1。IL-23能夠激活STAT3,優(yōu)先作用于記憶性CD4+T細(xì)胞,能夠誘導(dǎo)產(chǎn)生IL-17、IL-22等細(xì)胞因子,并在維持Th17細(xì)胞的生物學(xué)功能及其擴(kuò)增中具有重要作用[24,25]。研究發(fā)現(xiàn)外源性IL-23過(guò)表達(dá)具有抗腫瘤效應(yīng),轉(zhuǎn)染IL-23的小鼠結(jié)腸癌CT26細(xì)胞及黑色素瘤B16F10細(xì)胞均表現(xiàn)出很強(qiáng)的抗腫瘤及抗轉(zhuǎn)移效應(yīng),而這種外源性IL-23介導(dǎo)的抗腫瘤效應(yīng)主要依賴(lài)于記憶性T細(xì)胞[26]。與外源性IL-23不同,許多研究顯示內(nèi)源性的IL-23能夠促進(jìn)腫瘤的發(fā)生,其作用機(jī)制主要為IL-23能夠誘發(fā)炎性反應(yīng)包括IL-17的釋放,通過(guò)活化 STAT3促進(jìn)腫瘤的發(fā)生發(fā)展[27]。在多種人類(lèi)腫瘤中都存在IL-23表達(dá)增加,IL-23表達(dá)對(duì)于腫瘤微環(huán)境中的局部炎癥反應(yīng)和上皮內(nèi)淋巴細(xì)胞浸潤(rùn)起負(fù)調(diào)控作用[28]。IL-23能夠通過(guò)上調(diào)基質(zhì)金屬蛋白酶9(MMP9)增強(qiáng)炎癥反應(yīng),促進(jìn)血管生成,減少CD8+T細(xì)胞的浸潤(rùn)。研究發(fā)現(xiàn)移植腫瘤在IL-23衰竭或IL-23受體缺陷的小鼠中生長(zhǎng)受限,該研究證明了IL-23是聯(lián)系腫瘤促發(fā)的炎癥反應(yīng)和機(jī)體對(duì)腫瘤適應(yīng)性免疫監(jiān)視失效之間的重要分子[29]。
IL-27也是IL-12家族的成員之一,由活化的樹(shù)突狀細(xì)胞(DC)產(chǎn)生,它通過(guò)上調(diào)ICAM-1及T-bet的方式參與誘導(dǎo)早期Th1細(xì)胞的分化,并能夠促進(jìn)初始T細(xì)胞(naive T cell)增殖,誘導(dǎo)產(chǎn)生Tr1及CTL細(xì)胞,抑制Th2細(xì)胞、Th17細(xì)胞以及促炎性細(xì)胞因子的產(chǎn)生。它還能夠與IL-12協(xié)同刺激T細(xì)胞產(chǎn)生IFN-γ,在調(diào)控細(xì)胞介導(dǎo)的免疫方面具有重要作用[30,31]。IL-27 由 p28 和 EBV 誘導(dǎo)基因 3(EBI3)兩個(gè)亞基組成,其作用的受體分別為 WSX-1及gp130,能夠活化STAT1及STAT3信號(hào),發(fā)揮抗腫瘤免疫應(yīng)答效應(yīng)[32]。IL-27具有較強(qiáng)的抗腫瘤活性,其作用機(jī)制主要包括CD8+T細(xì)胞、NK細(xì)胞介導(dǎo)的抗腫瘤效應(yīng),抗體依賴(lài)的細(xì)胞介導(dǎo)的細(xì)胞毒作用(ADCC)、抗腫瘤血管生成作用、直接抑制腫瘤細(xì)胞生長(zhǎng)以及抑制COX-2的表達(dá)等,但具體依賴(lài)何種機(jī)制還取決于腫瘤自身的特性。研究發(fā)現(xiàn)IL-27在人食管癌細(xì)胞(Eca109)中的抗腫瘤效應(yīng)是通過(guò)活化NK細(xì)胞及產(chǎn)生炎性反應(yīng)來(lái)實(shí)現(xiàn)的[33]。在使用小鼠結(jié)腸癌C26腫瘤模型評(píng)價(jià)IL-27抗腫瘤作用的研究中發(fā)現(xiàn),這種抗腫瘤作用主要是由CD8+T細(xì)胞、IFN-γ 及 T-bet介導(dǎo)[34]。而在 Chiyo 等[35]的研究中發(fā)現(xiàn)小鼠結(jié)腸癌C26局部表達(dá)的IL-27的抗腫瘤作用主要依賴(lài)于T細(xì)胞和NK細(xì)胞。在對(duì)IL-27的抗腫瘤和抗血管生成活性的研究中發(fā)現(xiàn),IL-27不僅能夠抑制小鼠黑色素瘤細(xì)胞(B16F10)皮下的生長(zhǎng),而且對(duì)實(shí)驗(yàn)性肺轉(zhuǎn)移模型也具有抗腫瘤作用,并能夠明顯抑制肺轉(zhuǎn)移灶中腫瘤誘導(dǎo)的新生血管形成[36]。
IL-32主要由T細(xì)胞、NK細(xì)胞和上皮細(xì)胞產(chǎn)生,它具有促炎性細(xì)胞因子的特性,能夠通過(guò)激活P38MAPK和NF-κB信號(hào)通路誘導(dǎo)產(chǎn)生IL-1β、IL-6、TNF-α等促炎性細(xì)胞因子,在固有免疫應(yīng)答和特異性免疫應(yīng)答中發(fā)揮重要作用[37,38]。IL-32在健康人上皮細(xì)胞中的表達(dá)水平很低,但在某些疾病中表達(dá)水平顯著升高。例如慢阻肺、克羅恩病、銀屑病等。在人類(lèi)胃癌、肺癌、乳腺癌及胰腺癌組織中也發(fā)現(xiàn)其表達(dá)升高[39-41]。Sorrentino 等[42]發(fā)現(xiàn)在 73%的腺癌及癌前病變、64%的肺大細(xì)胞癌和77%的肺小細(xì)胞癌中IL-32的表達(dá)也是明顯上調(diào)的,并且其在腫瘤浸潤(rùn)性淋巴細(xì)胞(TIL)及腫瘤細(xì)胞(TC)中的表達(dá)與侵襲和遷移表型有關(guān),故其有可能成為評(píng)價(jià)臨床預(yù)后的指標(biāo)。研究發(fā)現(xiàn)IL-32γ能夠通過(guò)抑制NF-κB及STAT3信號(hào)從而抑制腫瘤細(xì)胞的生長(zhǎng),在T細(xì)胞凋亡過(guò)程中IL-32能夠特異性表達(dá),并且IL-32表達(dá)下調(diào)能夠抑制Hela細(xì)胞的凋亡,然而也有研究發(fā)現(xiàn)IL-32能夠促進(jìn)胰腺癌細(xì)胞的生長(zhǎng)[43-45]。
隨著對(duì)白細(xì)胞介素在腫瘤中作用研究的不斷發(fā)展,學(xué)者們通過(guò)體內(nèi)外實(shí)驗(yàn)或臨床標(biāo)本分析發(fā)現(xiàn)了多種與腫瘤相關(guān)的白細(xì)胞介素,及其相關(guān)的作用機(jī)制及信號(hào)通路,針對(duì)白細(xì)胞介素調(diào)節(jié)的效應(yīng)細(xì)胞或信號(hào)通路中的某一環(huán)節(jié)都有可能為今后臨床抗腫瘤治療提供新的靶點(diǎn)。
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