劉聰張墨Hong-Long Ji,2

間充質(zhì)干細(xì)胞的惡性轉(zhuǎn)化研究進(jìn)展

劉聰1張墨1Hong-Long Ji1,2

間充質(zhì)干細(xì)胞（MSCs）是一種多能干細(xì)胞，在體外的特定誘導(dǎo)條件下可以分化為多種組織細(xì)胞。其獨(dú)特的生物學(xué)特性，在組織損傷修復(fù)與腫瘤靶向治療等臨床應(yīng)用方面展現(xiàn)出廣闊的應(yīng)用前景。然而有研究表明MSCs在應(yīng)用過程中有可能發(fā)生惡性轉(zhuǎn)化。本文主要對(duì)MSCs發(fā)生惡性轉(zhuǎn)化的影響因素、分子機(jī)制以及如何預(yù)防MSCs發(fā)生惡性轉(zhuǎn)化的新近研究進(jìn)行綜述。

間質(zhì)干細(xì)胞； 細(xì)胞轉(zhuǎn)化，腫瘤

作者單位：453003 新鄉(xiāng)，河南省新鄉(xiāng)醫(yī)學(xué)院肺病與分子治療研究所1；75708 Tyler Texas，Department of Cellular and Molecular Biology，University of Texas Health Science Center at Tyler1,2

間充質(zhì)干細(xì)胞（mesenchymal stromal/stem cells，MSCs）是干細(xì)胞家族的重要成員，來源于發(fā)育早期的中胚層和外胚層，屬于多能干細(xì)胞。MSCs最初在骨髓中發(fā)現(xiàn)，因其具有多向分化潛能、腫瘤靶向、定向分化、免疫抑制和自我更新等特點(diǎn)而日益受到人們的關(guān)注[1-2]。體內(nèi)MSCs獲取的主要來源是骨髓、脂肪組織、羊水和臍帶血等[3-5]。MSCs在體內(nèi)或體外特定的誘導(dǎo)條件下，可分化為脂肪、骨、軟骨和心肌等多種組織細(xì)胞[6]，連續(xù)傳代培養(yǎng)后仍具有多向分化潛能，可用于組織器官的損傷與修復(fù)，對(duì)移植物抗宿主病、肝硬化的治療都有一定的作用[7-9]。多個(gè)基礎(chǔ)和臨床實(shí)驗(yàn)已證實(shí)了MSCs療法的安全性和有效性。然而由于未分化的MSCs基因組具有可塑性和較長(zhǎng)的壽命，使其更具有發(fā)生惡性轉(zhuǎn)化的傾向。與分化的成熟細(xì)胞相比較，MSCs可以進(jìn)行連續(xù)分裂增殖，更容易將獲得的突變基因遺傳給子代細(xì)胞。隨著研究的深入，人們逐漸發(fā)現(xiàn)MSCs有發(fā)生惡性轉(zhuǎn)化的風(fēng)險(xiǎn)。

2006年Arai等[10]臨床案例表明，在骨髓移植治療中，骨髓間充質(zhì)干細(xì)胞（bone marrow mesenchymal stem cells，BMMSCs）可能發(fā)生惡性轉(zhuǎn)化。研究報(bào)道了1例58歲的日本男性白血病患者接受了來自曾經(jīng)患有癌癥已經(jīng)治愈的女性的骨髓，后來該男子被診斷患癌。2009年Ruiz-Arguelles等[11]報(bào)道了1例患者骨髓移植成功之后發(fā)生了B細(xì)胞性白血病。另外Gol fi nopouloss等[12]也報(bào)道了1例急性白血病女患者接受了她曾經(jīng)患有乳腺癌妹妹的骨髓之后發(fā)生了乳腺上皮細(xì)胞瘤，采用干細(xì)胞移植治療的手段，會(huì)發(fā)生BMMSCs惡性轉(zhuǎn)化。Mohamadnejad等[13]發(fā)現(xiàn)了1例骨髓單核細(xì)胞治療肝硬化3個(gè)月后，肝硬化轉(zhuǎn)變?yōu)榱烁伟Ａ碛醒芯繄?bào)道1例23個(gè)月大的患有β地中海貧血癥的男孩接受了曾經(jīng)患有Norrie氏病眼球的哥哥的骨髓移植，17年后在男孩的骨盆處發(fā)現(xiàn)肉瘤[15]。MSCs的惡性轉(zhuǎn)化潛能為其臨床應(yīng)用帶來了巨大的風(fēng)險(xiǎn)。

一、MSCs惡性轉(zhuǎn)化的影響因素

影響MSCs發(fā)生惡性轉(zhuǎn)化的因素主要包括體外因素與體內(nèi)因素。體外因素包括MSCs的來源、培養(yǎng)代數(shù)、培養(yǎng)環(huán)境。體內(nèi)因素包括供體的自身因素與微環(huán)境。

（一）體外影響因素

1. MSCs的來源：MSCs發(fā)生惡性轉(zhuǎn)化與其來源有關(guān)。來源的差別主要在不同種屬之間和不同組織之間。從種屬來源方面來看，源自小鼠，兔子和獼猴的MSCs在體外長(zhǎng)期培養(yǎng)過程中可以自發(fā)發(fā)生惡性轉(zhuǎn)化[16-22]，然而人源的MSCs發(fā)生惡性轉(zhuǎn)化的概率要小。Liu等[23]研究表明了大鼠MSCs和人間充質(zhì)干細(xì)胞（human mesenchymal stem cells，hMSCs）在相同條件下培養(yǎng)，只有大鼠MSCs發(fā)生惡性轉(zhuǎn)化。從組織來源方面來看，脂肪組織來源的MSCs（adipose derived mesenchymal stem cells，AdMSCs）和 BMMSCs 更易發(fā)生惡性轉(zhuǎn)化[24-26]，Pan等[27]的研究表明在46個(gè)獨(dú)立體外培養(yǎng)的人BMMSCs和肝來源的MSCs有4個(gè)發(fā)生了惡性轉(zhuǎn)化，惡性轉(zhuǎn)化的總概率為8.6﹪，BMMSCs發(fā)生惡性轉(zhuǎn)化的概率為40﹪（2/5）。Roland等[28]也研究表明人BMMSCs在體外培養(yǎng)5～106周發(fā)生惡性轉(zhuǎn)化的概率為45.8﹪（11/24）。然而胎兒來源的人胎盤間充質(zhì)干細(xì)胞（fetal placental mesenchymal stem cells，fPMSCs）發(fā)生惡性轉(zhuǎn)化的風(fēng)險(xiǎn)比較小[29]。

2.培養(yǎng)代數(shù)（時(shí)間）：MSCs發(fā)生惡性轉(zhuǎn)化與其培養(yǎng)代數(shù)有關(guān)。隨著培養(yǎng)代數(shù)的增加，染色體異常細(xì)胞的比例也在增加，Notch1，MLH1，GNAS和TP53基因的突變概率也在增加[30-31]。Sawada等[32]研究表明，人MSCs在體外培養(yǎng)1～2月很少發(fā)生自發(fā)轉(zhuǎn)化，在體外培養(yǎng)大于3個(gè)月時(shí)容易出現(xiàn)異常。Aguilar等[33]研究表明通過靜脈途徑移植鼠MSCs第4代以后MSCs肺泡微環(huán)境呈現(xiàn)生長(zhǎng)失調(diào)及異常分化，而第1、2、3代無類似情況。有研究表明BMMSCs隨著培養(yǎng)代數(shù)的增加，移植到小鼠體內(nèi)出現(xiàn)腫瘤的概率也會(huì)大大增加[19]。Rubio等[25]和Zheng等[26]研究表明人AdMSCs在4～8周是安全的，然而培養(yǎng)到4～5個(gè)月時(shí)就會(huì)發(fā)生惡性轉(zhuǎn)化。

3.培養(yǎng)環(huán)境：MSCs發(fā)生惡性轉(zhuǎn)化也與培養(yǎng)環(huán)境有關(guān)。培養(yǎng)環(huán)境主要包括血清的濃度、培養(yǎng)液的種類、含氧濃度和培養(yǎng)液的污染。在20﹪FBS培養(yǎng)液中，大鼠BMSCs培養(yǎng)到第8代，染色體突變率為43.2﹪，然而用10﹪FBS培養(yǎng)液培養(yǎng)突變率達(dá)到69.4﹪。用DMEM培養(yǎng)時(shí)，大鼠BMSCs培養(yǎng)到第8代后，染色體突變率為67.6﹪，比用α-MEM培養(yǎng)時(shí)的突變率減少了1.8﹪[34]。在含氧濃度低的早期培養(yǎng)中，雖然加快了MSCs的增殖，但是也增加了染色體的變異風(fēng)險(xiǎn)，主要包括染色體結(jié)構(gòu)的改變與非整倍體的增加[35]。雖然如此，Guarnerio等[36]研究表明低的含氧濃度（1﹪）能夠保持基因組的穩(wěn)定性從而阻止惡性轉(zhuǎn)化的發(fā)生。另外在培養(yǎng)早期如果為了加快MSCs的增殖速度，加入一些生長(zhǎng)因子等物質(zhì)，這個(gè)過程會(huì)導(dǎo)致一些細(xì)菌的污染，異種基因的引入。

（二）體內(nèi)影響因素

1.供體自身因素：年齡在50～70歲范圍的供體與40歲的相比較增加了染色體自我突變的風(fēng)險(xiǎn)[35]。Li等[20]研究發(fā)現(xiàn)隨著年齡的增長(zhǎng)MSCs會(huì)自發(fā)的發(fā)生p53的點(diǎn)突變，可以在小鼠體內(nèi)形成腫瘤。Tarte等[37]實(shí)驗(yàn)發(fā)現(xiàn)人BMMSCs體外培養(yǎng)過程中染色體非整倍體的發(fā)生是由供體決定的，與培養(yǎng)過程無關(guān)。

2.微環(huán)境：微環(huán)境是指鄰近的組織細(xì)胞及其分泌的各種因子，這里介紹炎癥微環(huán)境與腫瘤微環(huán)境。體內(nèi)的炎癥微環(huán)境可能是引發(fā)基因突變導(dǎo)致惡性轉(zhuǎn)化的一個(gè)應(yīng)激因子，經(jīng)常發(fā)生炎癥或者大面積損傷的區(qū)域經(jīng)過MSCs治療之后更易發(fā)生惡性轉(zhuǎn)化[28]。腫瘤微環(huán)境是一個(gè)復(fù)雜的系統(tǒng)，由許多基質(zhì)細(xì)胞構(gòu)成，腫瘤細(xì)胞通過產(chǎn)生生長(zhǎng)因子和蛋白水解酶來調(diào)節(jié)腫瘤基質(zhì)微環(huán)境，也可以激活腫瘤基質(zhì)中的細(xì)胞而活化腫瘤基質(zhì)，活化的基質(zhì)細(xì)胞會(huì)分泌胰島素依賴性生長(zhǎng)因子 -1（insulin-like growth factor-1，IGF-I）、肝細(xì)胞生長(zhǎng)因子（HGF）等多種細(xì)胞因子，可能會(huì)使MSCs分化受阻導(dǎo)致惡性增殖[38]。Liu等[39]研究表明在腫瘤微環(huán)境中癌細(xì)胞會(huì)釋放一些影響因子使MSCs發(fā)生惡性轉(zhuǎn)化。He等[40]研究也表明在C6膠質(zhì)瘤微環(huán)境中培養(yǎng)的大鼠骨髓干細(xì)胞（bone marrow stem cells，BMSCs）可以轉(zhuǎn)化為神經(jīng)膠質(zhì)癌癥干細(xì)胞。

表1 MSCs惡性轉(zhuǎn)化機(jī)制

二、惡性轉(zhuǎn)化的機(jī)制

在體外的長(zhǎng)期培養(yǎng)過程中，由于基因組的不穩(wěn)定性，細(xì)胞周期調(diào)節(jié)的喪失，以及表觀遺傳信號(hào)的解除所導(dǎo)致的DNA損傷的累積最終都會(huì)導(dǎo)致未分化的MSCs惡性轉(zhuǎn)化的發(fā)生[28]。在體外培養(yǎng)過程中發(fā)生惡性轉(zhuǎn)化最關(guān)鍵的一步就是要逃脫衰老這一階段。Rubio等[25]認(rèn)為hMSCs惡性轉(zhuǎn)化的發(fā)生首先需要上調(diào)c-myc和抑制p16的表達(dá)，繞過衰老（M1）階段，然后通過端粒酶的激活，INK4a/Arf位點(diǎn)的缺失，Rb的高磷酸化以及線粒體新陳代謝的調(diào)節(jié)，DNA損傷修復(fù)蛋白和其他細(xì)胞周期調(diào)節(jié)因子的改變，繞過危機(jī)（M2）階段進(jìn)而發(fā)生細(xì)胞的惡性轉(zhuǎn)化。Honoki等[41]也認(rèn)為通過逃脫細(xì)胞衰老階段是MSCs惡性轉(zhuǎn)化的潛在機(jī)制。有研究證明hMSCs與轉(zhuǎn)化的間充質(zhì)干細(xì)胞（transformed mesenchymal stem cells，TMSCs）相比較，TMSCs的表型發(fā)生了突變，CD44與CD166基因的表達(dá)增加，然而CD105基因的表達(dá)卻輕微地下調(diào)。CD73，CD90，ASMA和Stro-1這些標(biāo)記物在hMSCs細(xì)胞上可以檢測(cè)得到，但是在TMSCs細(xì)胞上檢測(cè)不到。另外，未分化的BMMSCs本身就有不穩(wěn)定的特性[28]。

（一）MSCs發(fā)生惡性轉(zhuǎn)化與癌相關(guān)基因表達(dá)異常有關(guān)

Wang等[42]研究發(fā)現(xiàn)c-myc過度表達(dá)和Rb沉默的共同作用可以使hMSCs在免疫缺陷的小鼠體內(nèi)形成骨肉瘤。Shimizu等[43]也研究表明在小鼠MSCs中過表達(dá)c-myc和缺失p16INK4a/p19ARF可以使MSCs轉(zhuǎn)化為骨肉瘤。體外培養(yǎng)12個(gè)月后的小鼠MSCs可自發(fā)發(fā)生基因表達(dá)改變及p53突變[20]。有研究表明只有p21與p53都缺失才可以導(dǎo)致小鼠MSCs繞過衰老發(fā)生惡性轉(zhuǎn)化[44]。Guarnerio等[36]也表明在無效p53的MSCs中過度的表達(dá)c-myc和K-RasG12V，缺失Pten基因或者缺失LRF/Pokemon都可以使MSCs惡性轉(zhuǎn)化。LRF通過控制DIK1和SOX9的活性可以抑制惡性轉(zhuǎn)化。Liu等[39]在實(shí)驗(yàn)中用大鼠C6膠質(zhì)瘤細(xì)胞與大鼠MSCs間接共培養(yǎng)之后發(fā)現(xiàn)野生型p53表達(dá)降低，突變型p53表達(dá)增加，mdm2蛋白表達(dá)增加，并且出現(xiàn)非整倍體型細(xì)胞。MSCs注入免疫缺陷小鼠體內(nèi)后，小鼠體內(nèi)形成腫瘤。鼠MSCs體外培養(yǎng)14代后c-myc表達(dá)增加[19]，而hMSCs隨著培養(yǎng)時(shí)間的增加，Smad3 mRNA表達(dá)增加[32]。Rubio等[45]研究表明人AdMSCs在體外培養(yǎng)4～5個(gè)月后通過c-myc的上調(diào)與p16的下調(diào)發(fā)生了惡性轉(zhuǎn)化，但是在體外培養(yǎng)6～8周的細(xì)胞中沒有此現(xiàn)象的發(fā)生。以上幾項(xiàng)研究表明2個(gè)或2個(gè)以上癌相關(guān)基因發(fā)生突變才能使MSCs發(fā)生惡性轉(zhuǎn)化。

Takeuchi等[46]研究表明滅活的hMSCs在早期的體外培養(yǎng)過程中，染色體13的復(fù)制出現(xiàn)丟失，腫瘤抑制基因，DNA修復(fù)基因和凋亡活化基因過度表達(dá)，在后期的培養(yǎng)過程中染色體出現(xiàn)易位，細(xì)胞出現(xiàn)錨定不依賴性生長(zhǎng)和致瘤性。Teng等[47]研究表明異常的HIC1和RassF1A超甲基化可以把干細(xì)胞轉(zhuǎn)化為癌干細(xì)胞（cancer stem cells，CSCs），HIC1和RassF1A的超甲基化不僅可以抑制腫瘤抑制因子的作用，還可以破壞多能分子網(wǎng)絡(luò)導(dǎo)致致瘤性。通過DNA甲基化使HIC1和RassF1A沉默，可以導(dǎo)致p53調(diào)節(jié)凋亡的信號(hào)通路受阻進(jìn)而導(dǎo)致MSCs的惡性轉(zhuǎn)化。研究表明H3K9me增強(qiáng)p16基因的DNA超甲基化是MSCs自我轉(zhuǎn)化的表觀遺傳信號(hào)[26]。

Shoshani等[48]研究表明多倍體的小鼠MSCs的致瘤性遠(yuǎn)遠(yuǎn)小于二倍體的小鼠MSCs，二倍體的MSCs可以通過抑制非編碼RNA19的表達(dá)轉(zhuǎn)化為多倍體，從而減少腫瘤的發(fā)生。Mohseny等[17]也發(fā)現(xiàn)小鼠MSCs發(fā)生惡性轉(zhuǎn)化是出現(xiàn)非整倍體與Cdkn2/p16INK4a基因缺失的結(jié)果。

另外，Lu等[49]研究表明新陳代謝基因異檸檬酸脫氫酶2（IDH2）中的突變能使小鼠MSCs分化受阻導(dǎo)致肉瘤的產(chǎn)生。

（二）MSCs發(fā)生惡性轉(zhuǎn)化與細(xì)胞因子的誘導(dǎo)有關(guān)

Zhou等[50]實(shí)驗(yàn)中用粒-巨噬細(xì)胞集落刺激因子（GMCSF）和白細(xì)胞介素4（IL-4）同時(shí)刺激人BMMSCs 1個(gè)月后經(jīng)過尾靜脈注射到裸鼠體內(nèi)，3周后在裸鼠肺部檢測(cè)到腫瘤，然而對(duì)照組卻沒有類似現(xiàn)象。Cui等[51]用白細(xì)胞介素6（IL-6）誘導(dǎo)大鼠MSCs惡性轉(zhuǎn)化的實(shí)驗(yàn)中證明惡性轉(zhuǎn)化與信號(hào)轉(zhuǎn)導(dǎo)和轉(zhuǎn)錄因子3的激活（STAT3）增強(qiáng)有關(guān)。Hou等[52]實(shí)驗(yàn)研究表明在腫瘤微環(huán)境中MSCs的惡性轉(zhuǎn)化與SIL-6R和GP130的過度表達(dá)有關(guān)。Liu等[53]研究也表明腫瘤微環(huán)境中過表達(dá)的白介素6（IL-6）對(duì)MSCs的惡性轉(zhuǎn)化具有促進(jìn)作用。Wang等[54]研究證明了一些炎癥因子IFN-γ和TNF-α利用協(xié)同作用通過NFκB/SMAD7信號(hào)通道導(dǎo)致MSCs損傷，并且通過NFκB使致癌基因激活導(dǎo)致MSCs的致瘤性。

（三）MSCs發(fā)生惡性轉(zhuǎn)化與病毒的感染有關(guān)

Jones等[55]用卡波西氏肉瘤皰疹病毒（KSHV）感染大鼠的MSCs經(jīng)過皮下注射到裸鼠體內(nèi)，12周后致瘤率大約為84.6﹪，然而對(duì)照組卻沒有檢測(cè)到腫瘤的形成。因此在MSCs的培養(yǎng)過程中要防止病毒以及外源基因的污染。

（四）MSCs發(fā)生惡性轉(zhuǎn)化與細(xì)胞信號(hào)通路異常有關(guān)

有研究表明惡性轉(zhuǎn)化的MSCs失去了典型的標(biāo)記物CD90，CD105后，反而獲得了CD34的表達(dá)。Notch通路被激活，而Hedgehog通路和Wnt通路失活[56]。Notch可以調(diào)節(jié)CSCs的形成和自我更新能力[57]，Notch通路突變會(huì)引起急性白血病和多種血液腫瘤[58-60]。而Hedgehog和Wnt可以調(diào)控腫瘤細(xì)胞生長(zhǎng)，有研究表明通過抑制Hedgehog通路可以減少腫瘤細(xì)胞的生長(zhǎng)。Matushansky等[61]研究證明抑制Wnt通路可以使hMSCs轉(zhuǎn)化為纖維組織細(xì)胞瘤。

（五）MSCs發(fā)生惡性轉(zhuǎn)化與基因組的不穩(wěn)定性有關(guān)

研究表明DNA修復(fù)機(jī)制異常，端粒危機(jī)，有絲分裂紡錘體異常和減數(shù)分裂通路不合理的誘導(dǎo)都可能會(huì)引起基因組的不穩(wěn)定性[62]。Shirah等[63]研究證明了在人的膠質(zhì)瘤模型中，基因組的不穩(wěn)定性導(dǎo)致無致瘤性的干細(xì)胞自發(fā)的轉(zhuǎn)變成了CSCs。

（六）MSCs發(fā)生惡性轉(zhuǎn)化與染色體突變有關(guān)

染色體突變是癌癥的標(biāo)志[64]，染色體的突變包括染色體數(shù)目改變和染色體結(jié)構(gòu)改變。染色體數(shù)目改變包括非整倍體和整倍體，染色體結(jié)構(gòu)的改變包括染色體的缺失，重復(fù)，易位，倒位。研究表明尤因肉瘤的產(chǎn)生是由于染色體發(fā)生了易位，骨肉瘤的產(chǎn)生是由于基因組的不穩(wěn)定性[65-66]。Wang等[67]研究表明人BMMSCs在體外培養(yǎng)過程中產(chǎn)生了一個(gè)具備高端粒酶活性，非整倍體染色體，并且染色體易位的細(xì)胞亞群，把這些細(xì)胞注射到小鼠體內(nèi)后產(chǎn)生了實(shí)體瘤。Miura等[19]也研究表明染色體變異的增加導(dǎo)致小鼠BMMSCs發(fā)生惡性轉(zhuǎn)化。Jeong等[30]研究發(fā)現(xiàn)小鼠BMMSCs在早期培養(yǎng)過程中發(fā)生染色體的突變，并且移植到糖尿病性神經(jīng)病小鼠體內(nèi)后生成腫瘤，對(duì)MSCs進(jìn)行染色體分析發(fā)現(xiàn)染色體發(fā)生了融合，裂解和環(huán)的生成。許多研究者也表明小鼠和大鼠MSCs發(fā)生惡性轉(zhuǎn)化的過程中都存在染色體的突變[33,68-69]。Kim等[31]用人AdMSCs和人臍帶血來源的間充質(zhì)干細(xì)胞（human umbilical cord blood mesenchymal stem cells，hUCB-MSCs）在培養(yǎng)過程中都出現(xiàn)了染色體的易位，三倍染色體細(xì)胞，及染色體衍生物的出現(xiàn)。

端粒變短是細(xì)胞衰老的標(biāo)志，在人AdMSCs和hUCBMSCs培養(yǎng)過程中也發(fā)現(xiàn)了端粒的長(zhǎng)度動(dòng)態(tài)變化。Kim等[70]用正常人和患有乳腺癌患者的hUCB-MSCs，正常人AdMSCs，BMSCs和神經(jīng)干細(xì)胞（neural stem cell，NSCs），培養(yǎng)過程中這些細(xì)胞上均發(fā)現(xiàn)染色體16、17、18和X染色體頻繁的出現(xiàn)三倍體型。染色體的突變對(duì)MSCs的惡性轉(zhuǎn)化產(chǎn)生了影響，因此在MSCs培養(yǎng)過程中需要監(jiān)測(cè)染色體的變化。

（七）MSCs發(fā)生惡性轉(zhuǎn)化與上皮間充質(zhì)轉(zhuǎn)化或間充質(zhì)上皮轉(zhuǎn)化（EMT/MET）有關(guān)

有研究發(fā)現(xiàn)無致瘤性的胃上皮細(xì)胞與MSCs混合之后發(fā)生EMT，混合細(xì)胞注入裸鼠體內(nèi)后，可以形成腫瘤。胃上皮細(xì)胞與MSCs混合可能是導(dǎo)致MSCs發(fā)生惡性轉(zhuǎn)化的一個(gè)潛在機(jī)制[71]。Rubio等[72]也證明了MSCs的自我惡性轉(zhuǎn)化與MET有關(guān)。

三、預(yù)防措施

1.盡量不要使用患有癌癥或有癌癥病史患者的MSCs：Borgonovo等[73]研究報(bào)道了1例患者，曾經(jīng)患有腎腫瘤已被切除，現(xiàn)在患有缺血性心肌病，其自體的MSCs在體外培養(yǎng)過程中第二代就出現(xiàn)超倍體，重復(fù)以上操作在第三代就出現(xiàn)染色體的易位，并且經(jīng)常性的突變。

2.盡量使用fPMSCs：有研究表明fPMSCs在體外培養(yǎng)過程中比其他來源的MSCs惡性轉(zhuǎn)化的風(fēng)險(xiǎn)較小，同時(shí)治療效果也更好[29]。

3. MSCs培養(yǎng)所用的培養(yǎng)基盡量使用同種異體血清：Paula等[74]研究通過比較分別用人的同種異體血清與胎牛血清培養(yǎng)的脂肪來源的人干細(xì)胞（human adipose stem cells，hASCs）發(fā)現(xiàn)用同種異體血清培養(yǎng)的hASCs增殖的更快，能在較短的時(shí)間內(nèi)達(dá)到所需要的數(shù)目，這樣就保證了表型，基因組的穩(wěn)定性，減少了發(fā)生惡性轉(zhuǎn)化的風(fēng)險(xiǎn)。

4. MSCs培養(yǎng)過程中要保證培養(yǎng)環(huán)境的潔凈與安全性：Garcia等[75]和Torsvik等[76]發(fā)現(xiàn)人MSCs發(fā)生惡性轉(zhuǎn)化是培養(yǎng)過程中受到腫瘤細(xì)胞的污染造成的，所以在體外培養(yǎng)中要減少外源基因的接觸。

5. MSCs用于臨床治療之前要用G顯帶分析和熒光原位雜交檢測(cè)染色體的突變性[31,77]。

6. MSCs要在低氧的環(huán)境下進(jìn)行體外培養(yǎng)，這樣可以保持基因組的穩(wěn)定性和提高生長(zhǎng)動(dòng)力[78]。

四、小結(jié)與展望

近年來，MSCs應(yīng)用于臨床的研究成為人們廣泛關(guān)注的熱點(diǎn)，因其具有較強(qiáng)的體外迅速擴(kuò)增能力，較低的免疫原性，能在宿主細(xì)胞內(nèi)長(zhǎng)期的存活，外源基因易于轉(zhuǎn)染等特點(diǎn)，MSCs成為基因治療以及藥物治療的理想載體。但是在基礎(chǔ)及臨床研究中發(fā)現(xiàn)MSCs有惡性轉(zhuǎn)化的風(fēng)險(xiǎn)，MSCs發(fā)生惡性轉(zhuǎn)化對(duì)臨床治療產(chǎn)生了巨大的危害，MSCs安全性是臨床治療的基本要求。目前關(guān)于MSCs在體外培養(yǎng)階段所用培養(yǎng)液的種類，濃度，含氧濃度等培養(yǎng)環(huán)境以及MSCs的來源沒有統(tǒng)一的規(guī)范標(biāo)準(zhǔn)，判斷MSCs發(fā)生惡性轉(zhuǎn)化也沒有統(tǒng)一的指標(biāo)，關(guān)于MSCs能否發(fā)生惡性轉(zhuǎn)化仍存在很大爭(zhēng)議，而且關(guān)于MSCs惡性轉(zhuǎn)化的機(jī)制也尚不清楚，需要進(jìn)一步研究MSCs惡性轉(zhuǎn)化的具體機(jī)制，MSCs的純化方法，培養(yǎng)條件以及如何減少M(fèi)SCs惡性轉(zhuǎn)化的風(fēng)險(xiǎn)，為以后相關(guān)疾病的治療開辟新的道路，為MSCs應(yīng)用于臨床的安全性提供更好的保障。

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Current opinions on malignant transformation of mesenchymal stem cell

Liu Cong1, Zhang Mo1,Hong-Long Ji1,2.1Institute of Lung and Molecular Therapy, Xinxiang Medical University, Xinxiang Henan 453003, China;2Department of Cellular and Molecular Biology, University of Texas Health Science Center at Tyler, Tyler Texas 75708, USA

Mesenchymal stromal（stem）cells（MSCs）are pluripotent stem cells to differentiate into various types of cells. This unique characteristic allowed MSCs to be used in cytotherapy, which holds most promising for repair of injured cells/tissues and anti-tumor intervention.However, malignant transformation of MSCs is a major challenge for clinical applications. This review focuses on the recent studies regarding culture conditions, molecular mechanisms, and preventive strategies of malignance of MSCs in practice.

Mesenchymal stem cell； Cell transformation, neoplastic

Hong-Long Ji, Email: james.ji@uthct.edu

2017-03-23）

（本文編輯：蔡曉珍）

10.3877/cma.j.issn.2095-1221.2017.04.008

Hong-Long Ji, Email：james.ji@uthct.edu

劉聰，張墨，Hong-Long Ji.間充質(zhì)干細(xì)胞的惡性轉(zhuǎn)化研究進(jìn)展[J/CD].中華細(xì)胞與干細(xì)胞雜志（電子版），2017，7（4）：231-236.