李曉潔 姜俊 朱蓓
[摘要] 目的 探討人質(zhì)膜型唾液酸酶(Neu3)表達(dá)降低對前列腺癌PC-3細(xì)胞增殖、遷移、侵襲能力的影響。 方法 構(gòu)建pGCsi-Neu3質(zhì)粒,從GeneBank中尋找符合Neu3 mRNA特異的靶序列,合成siRNA模板鏈后與載體相連接,轉(zhuǎn)入感受態(tài)細(xì)胞,測序鑒定。應(yīng)用真核細(xì)胞轉(zhuǎn)染技術(shù)轉(zhuǎn)染前列腺癌PC-3細(xì)胞,利用熒光顯微鏡檢測轉(zhuǎn)染效率;細(xì)胞增殖實(shí)驗(yàn)檢測pGCsi-Neu3質(zhì)粒對細(xì)胞增殖的影響;流式細(xì)胞術(shù)檢測細(xì)胞凋亡的改變;Transwell遷移、侵襲實(shí)驗(yàn)檢測細(xì)胞遷移、侵襲能力的變化。 結(jié)果 針對Neu3基因設(shè)計(jì)了siRNA序列并成功構(gòu)建pGCsi-Neu3質(zhì)粒,pGCsi-Neu3-3質(zhì)粒對基因Neu3的抑制最為有效。與對照組比較,pGCsi-Neu3-3質(zhì)粒可有效抑制腫瘤細(xì)胞增殖(P < 0.01);pGCsi-Neu3-3質(zhì)粒可引起前列腺癌PC-3細(xì)胞凋亡,凋亡率明顯高于空白對照組(MOCK組),差異有統(tǒng)計(jì)學(xué)意義(P < 0.05);pGCsi-Neu3-3質(zhì)粒可使前列腺癌PC-3細(xì)胞增殖細(xì)胞核抗原表達(dá)明顯下降;pGCsi-Neu3-3質(zhì)??梢种魄傲邢侔㏄C-3細(xì)胞遷移、侵襲能力,且與對照組比較,差異有高度統(tǒng)計(jì)學(xué)意義(P < 0.01)。結(jié)論 針對Neu3基因siRNA表達(dá)質(zhì)粒的構(gòu)建、鑒定和初始研究,為Neu3對前列腺癌細(xì)胞生長、轉(zhuǎn)移發(fā)揮作用機(jī)制的研究奠定實(shí)驗(yàn)基礎(chǔ)。
[關(guān)鍵詞] 人質(zhì)膜型唾液酸酶;前列腺癌;質(zhì)粒構(gòu)建;增殖;侵襲
[中圖分類號] R737.25 [文獻(xiàn)標(biāo)識碼] A [文章編號] 1673-7210(2018)10(a)-0008-05
Influence of down regulation of Neu3′s to PC-3 cell′s proliferation, invasiveness, and its mechanism
LI Xiaojie JIANG Jun ZHU Bei
Department of Basic and Pharmacy, School of Medicine and Technology, Taizhou Polytechnic College, Jiangsu Province, Taizhou 225300, China
[Abstract] Objective To investigate the influence of Neu3 gene silencing in growth inhibition of PC-3 cell and to elucidate the underlying mechanisms. Methods Three pieces of siRNA sequences on the Neu3 gene were designed and then a recombinant plasmid carrying siRNA was constructed, which was used to transfer PC-3 cells in order to screen the most effective sequence among the three siRNA sequences against Neu3; PC-3 cell transfection pGCsi-Neu3 plasmid, inverted microscope was used to observe the transfection efficiency, determined by MTT test their effects on cell proliferation and flow cytometry was used to detect the change of cell apoptosis; Transwell migration and invasion assay were performed to detect the migration and invasion cells of groups. Results The siRNA sequences targeted to Neu3 gene were designed and their expression vectors were cloned and verified successfully. Compared with control group, pGCsi-Neu3-3 plasmid significantly inhibited cell proliferation (P < 0.01); pGCsi-Neu3-3 plasmid significantly promoted the apoptosis of PC-3 cells of prostate cancer compared with the blank control group (Mock group), the difference was statistically significant (P < 0.05). pGCsi-Neu3-3 plasmid could inhibit the migration and invasion assay of PC-3 cells of prostate cancer, compared with the control group, with statistically significant difference (P < 0.01). Conclusion Construction, identification and initial study of Neu3, might lay the foundation of experiment for the study of growth and metastasis mechanism of prostate cancer cell.
[Key words] Human plasma membrane-associated sialidase; Prostate cancer; Plasmid construction; Proliferation; Migration
DNA損傷后在修復(fù)過程中有時(shí)會出現(xiàn)錯(cuò)誤,致使基因突變,如癌基因的激活或過表達(dá)[1-2],抑癌基因的失活或抑癌產(chǎn)物的缺失[3-4],從而細(xì)胞生長失控、分化能力減弱形成單克隆、不斷增生的細(xì)胞團(tuán)——腫瘤。發(fā)病率與年齡密切相關(guān)的前列腺癌,在美國位居男性惡性腫瘤的首位。最新統(tǒng)計(jì)報(bào)告顯示,2016年發(fā)病人數(shù)為180 890人[5],在中國社會人口老齡化的大背景下其發(fā)病率呈現(xiàn)急劇上升的趨勢[6]。唾液酸酶可降解糖脂和糖蛋白非還原末端的唾液酸[7-8],目前根據(jù)細(xì)胞定位共分為4種亞型——Neu1、Neu2、Neu3、Neu4[9-10]。Neu3主要定位在細(xì)胞膜,參與細(xì)胞黏附、遷移等生理功能[11-12]。研究發(fā)現(xiàn)Neu3在前列腺癌中表達(dá)增高[13]。此外在肺癌[14]、結(jié)腸癌[15]、黑色素瘤[16]、膠質(zhì)母細(xì)胞瘤[17]等多種腫瘤組織中Neu3表達(dá)水平也增高[18]。但目前Neu3表達(dá)改變是腫瘤發(fā)生的原因還是結(jié)果尚不清楚,本研究選取前列腺癌激素非依賴型PC-3細(xì)胞作為研究細(xì)胞,構(gòu)建針對Neu3基因的siRNA表達(dá)質(zhì)粒,觀察其對PC-3細(xì)胞增殖、遷移過程的影響,為前列腺癌靶向治療探尋新的、潛在的靶點(diǎn)。
1 材料與方法
1.1 主要儀器
JILSON加樣器、SONY低溫高速離心機(jī)、恒溫水浴箱、SANYO CO2恒溫培養(yǎng)箱、分光光度計(jì)、SONY自動(dòng)高壓蒸氣消毒器、YZ-875超凈工作臺、SONY -80℃低溫冰箱。
1.2 主要試劑
IMDM培養(yǎng)液、胎牛血清、Transwell小室(Hyclone公司);LipofectamineTM2000(Invitrogen公司)。胰蛋白酶(GBICO美國);噻唑藍(lán)(MTT)細(xì)胞增殖及細(xì)胞毒性檢測試劑盒(Sigma美國);DL2000 DNA Marker、DL1500 DNA Marker、Taq DNA聚合酶、BamH Ⅰ酶、Hind Ⅲ酶(TAKARA日本)、膠回收試劑盒(TAKARA日本)、Annexin V-FITC/PI試劑盒(Abcom公司)。
1.3 質(zhì)粒、菌種及細(xì)胞系
PC-3細(xì)胞購于ATCC,質(zhì)粒pGCsilencer-U6/Neo/GFP(上海吉?jiǎng)P基因化學(xué)有限公司)。菌株JM-109和減毒沙門菌為吉林大學(xué)病理生理學(xué)實(shí)驗(yàn)室所保存。
1.4 細(xì)胞培養(yǎng)
PC-3細(xì)胞按ATCC培養(yǎng)條件:用含有100 μg/mL青鏈霉素、10%胎牛血清的IMDM(Hycolone,USA)培養(yǎng)液在37℃含5%CO2孵育箱中,常規(guī)培養(yǎng)、傳代。
1.5 pGCsi-Neu3重組質(zhì)粒的構(gòu)建
1.5.1 Neu3-siRNA模板寡核苷酸的設(shè)計(jì) 根據(jù)Neu3 mRNA特異的靶序列,合成針對其編碼區(qū)130-149、220-239及839-858位堿基序列的3條DNA寡核苷酸鏈,分別命名為shRNA-Neu3-1、shRNA-Neu3-2和shRNA-Neu3-3,每條正義鏈包括5′末端BamH Ⅰ酶切位點(diǎn)和反向的兩個(gè)一致的靶序列(19 bp)。設(shè)計(jì)時(shí),shRNA模板中的loop結(jié)構(gòu)選用了TTCAAGAGA以避免形成終止信號,shRNA的轉(zhuǎn)錄終止序列采用T6結(jié)構(gòu)[19]。shRNA-Scramble對照:堿基順序隨機(jī)排列,與人類基因的外顯子沒有同源性(實(shí)驗(yàn)室提供)。
1.5.2 pGCsilencer-U6/Neo/GFP載體線性化及回收 使用BamH Ⅰ和Hind Ⅲ兩種內(nèi)切酶將pGCsilencer-U6/Neo/GFP質(zhì)粒切開,瓊脂糖凝膠電泳分離酶切產(chǎn)物,切取含有線性化質(zhì)粒的凝膠,按照TAKARA膠回收試劑盒的操作流程說明書進(jìn)行回收,采用λDNA Marker做標(biāo)準(zhǔn)品對線性化質(zhì)粒定量。
1.5.3 載體與siRNA模板鏈連接 T4連接酶連接模板與載體,模板與載體按照摩爾數(shù)比約為4︰1的比例加入,16℃反應(yīng)過夜。
1.5.4 重組質(zhì)粒的鑒定 BamH Ⅰ和Hind Ⅲ酶切pGCsilencer-U6-siRNA-Neu3質(zhì)粒(以下簡稱“pGCsi-Neu3”)。酶切后產(chǎn)物電泳結(jié)果顯示有小片段者初步預(yù)測可能為陽性重組質(zhì)粒。懷疑為陽性克隆的重組質(zhì)粒委托上海生物工程技術(shù)服務(wù)有限公司進(jìn)行cDNA序列測定鑒定。
1.5.5 熒光顯微鏡檢測PC-3細(xì)胞轉(zhuǎn)染pGCsi-Neu3質(zhì)粒的轉(zhuǎn)染效率 pGCsi-Neu3質(zhì)粒攜帶GFP基因,當(dāng)質(zhì)粒轉(zhuǎn)染PC-3細(xì)胞后可表達(dá)綠色熒光蛋白,為保證后續(xù)實(shí)驗(yàn)的可靠性,首選需要確定細(xì)胞的轉(zhuǎn)染效率不低于50%。轉(zhuǎn)染效率=發(fā)綠色熒光的細(xì)胞數(shù)/可見光下細(xì)胞數(shù)×100%。該實(shí)驗(yàn)重復(fù)3次。
1.6 細(xì)胞增殖實(shí)驗(yàn)
細(xì)胞生長融合度達(dá)90%時(shí),進(jìn)行瞬時(shí)轉(zhuǎn)染,只加入轉(zhuǎn)染試劑的命名為空白對照組(Mock組),轉(zhuǎn)染pGCsi-Scramble質(zhì)粒的命名為pGCsi-Scramble組,轉(zhuǎn)染3個(gè)不同位點(diǎn)的pGCsi-Neu3質(zhì)粒的分別命名為pGCsi-Neu3-1組、pGCsi-Neu3-2組、pGCsi-Neu3-3組,后續(xù)實(shí)驗(yàn)參照此分組命名。用PBS將MTT配置為終濃度為5 mg/mL的工作液,細(xì)胞瞬時(shí)轉(zhuǎn)染后分別在24、48、72 h檢測細(xì)胞數(shù)目,檢測時(shí)每孔加入含有10 μL MTT工作液的培養(yǎng)液繼續(xù)培養(yǎng)4 h后,去除上清,每孔加入100 μL的DMSO,震蕩混勻后檢測A490吸光度值。該實(shí)驗(yàn)重復(fù)3次。
1.7流式細(xì)胞術(shù)
收集轉(zhuǎn)染后48 h的PC-3細(xì)胞,預(yù)冷PBS洗滌細(xì)胞3次后,參照Abcom公司Annexin V-FIFC試劑盒說明書進(jìn)行實(shí)驗(yàn)操作,流式細(xì)胞術(shù)分析細(xì)胞凋亡。該實(shí)驗(yàn)重復(fù)3次。
1.8 Transwell檢測pGCsi-Neu3質(zhì)粒對細(xì)胞遷移、侵襲的影響
Transwell細(xì)胞遷移實(shí)驗(yàn)[20]按照ECM550系列遷移實(shí)驗(yàn)操作說明,將200 μL含有5×104個(gè)細(xì)胞的IMDM無血清培養(yǎng)基混懸液加入Transwell上室,下室加入600 μL含有10%FBS的培養(yǎng)基,培養(yǎng)24 h后,多聚甲醛固定,結(jié)晶紫染色,于倒置顯微鏡選取3個(gè)視野拍照記錄,選用濃度為33%醋酸進(jìn)行結(jié)晶紫脫色,洗脫液混勻后在酶標(biāo)儀上595 nm測其OD值,間接反映細(xì)胞數(shù)。該實(shí)驗(yàn)重復(fù)3次。Transwell細(xì)胞侵襲實(shí)驗(yàn)[20]:上室加入40 μL的1︰7無血清培養(yǎng)基稀釋的Matrigel膠,37℃細(xì)胞培養(yǎng)箱過夜,于次日進(jìn)行遷移實(shí)驗(yàn)。其固定、染色、拍照、洗脫等實(shí)驗(yàn)步驟參照Transwell遷移實(shí)驗(yàn)。該實(shí)驗(yàn)重復(fù)3次。
1.9統(tǒng)計(jì)學(xué)方法
采用SPSS 16.0統(tǒng)計(jì)學(xué)軟件進(jìn)行數(shù)據(jù)分析,計(jì)量資料用均數(shù)±標(biāo)準(zhǔn)差(x±s)表示,多組間比較采用F檢驗(yàn),兩組間比較采用q檢驗(yàn),以P < 0.05為差異有統(tǒng)計(jì)學(xué)意義。
2 結(jié)果
2.1 pGCsi-Neu3質(zhì)粒構(gòu)建及測序結(jié)果
原始質(zhì)粒及酶切后電泳結(jié)果見圖1A,根據(jù)不同靶點(diǎn)構(gòu)建的3個(gè)pGCsi-Neu3質(zhì)粒進(jìn)行BamH Ⅰ和Hind Ⅲ酶切鑒定,均有小片段被切下,見圖1B,酶切鑒定成功后,進(jìn)行DNA測序鑒定,測序結(jié)果與連入siRNA模板鏈序列完全一致,見圖1C。
2.2 pGCsi-Neu3質(zhì)粒轉(zhuǎn)染結(jié)果及熒光顯微鏡檢測
PC-3細(xì)胞轉(zhuǎn)染質(zhì)粒48 h后,在藍(lán)色熒光激發(fā)下發(fā)現(xiàn)轉(zhuǎn)入pGCsi-Neu3-1、pGCsi-Neu3-2、pGCsi-Neu3-3質(zhì)粒的PC-3細(xì)胞發(fā)出綠色熒光。轉(zhuǎn)染效率超過70%,可以保證后續(xù)實(shí)驗(yàn)數(shù)據(jù)的可信性。見圖2(封底)。
2.3 pGCsi-Neu3質(zhì)粒沉默效率
轉(zhuǎn)染48 h后,Mock組、pGCsi-Scramble組、pGCsi-Neu3-1組、pGCsi-Neu3-2組、pGCsi-Neu3-3組PC-3細(xì)胞中Neu3相對表達(dá)量分別為:0.752±0.029、0.741±0.019、0.493±0.033、0.427±0.024、0.219±0.023。pGCsi-Neu3-3組PC-3細(xì)胞中Neu3相對表達(dá)量明顯低于對照組(Mock組、pGCsi-Scramble組),差異有統(tǒng)計(jì)學(xué)意義(P < 0.05)。
2.4 pGCsi-Neu3質(zhì)粒對PC-3細(xì)胞增殖、凋亡的影響
PC-3細(xì)胞轉(zhuǎn)染重組質(zhì)粒后,采用MTT法監(jiān)測在24、48、72 h等時(shí)間點(diǎn)細(xì)胞的生長。在48、72 h時(shí),pGCsi-Neu3-1組、pGCsi-Neu3-2組和pGCsi-Neu3-3組與Mock組、pGCsi-Scramble組比較,可有效抑制細(xì)胞增殖,差異有統(tǒng)計(jì)學(xué)意義(P < 0.01),其中pGCsi-Neu3-3組抑制效果最為明顯。根據(jù)MTT實(shí)驗(yàn)結(jié)果,收集轉(zhuǎn)染后48 h的各組細(xì)胞,PI和Annexin V雙重染色后通過流式細(xì)胞術(shù)檢測凋亡發(fā)現(xiàn),pGCsi-Neu3-3組與Mock組比較細(xì)胞凋亡明顯,凋亡率為18.1%,見圖3B。免疫組織化學(xué)法檢測PCNA的表達(dá),結(jié)果發(fā)現(xiàn)pGCsi-Neu3-3組與對照組比較,細(xì)胞核中少見棕黃色顆粒。見圖3A。
2.5 pGCsi-Neu3質(zhì)粒抑制細(xì)胞遷移和侵襲
PC-3細(xì)胞轉(zhuǎn)染質(zhì)粒后,利用Transwell實(shí)驗(yàn)檢測PC-3細(xì)胞轉(zhuǎn)移、侵襲能力的改變。結(jié)果發(fā)現(xiàn)pGCsi-Neu3-3組,無論是遷移實(shí)驗(yàn)還是侵襲實(shí)驗(yàn),其細(xì)胞數(shù)目與Mock組比較,均有所下降,差異有統(tǒng)計(jì)學(xué)意義(P < 0.05)。見圖4(封底)。
3 討論
Neu3是唾液酸酶家族重要的一員,廣泛表達(dá)于人體各種組織中,參與多種生理活動(dòng)。Neu3表達(dá)增高對腫瘤的發(fā)生、發(fā)展發(fā)揮重要影響。本研究構(gòu)建針對Neu3基因siRNA表達(dá)質(zhì)粒,并對其進(jìn)行鑒定和篩選后,在體外檢測降低Neu3表達(dá)對前列腺癌的生長、轉(zhuǎn)移的作用及機(jī)制。
本研究根據(jù)Neu3基因信息,使用在線siRNA序列設(shè)計(jì)軟件,設(shè)計(jì)了3條針對目的基因編碼序列區(qū)的siRNA序列,測序鑒定質(zhì)粒構(gòu)建成功。為保證實(shí)驗(yàn)數(shù)據(jù)的可信性,首先進(jìn)行了轉(zhuǎn)染效率的測定,結(jié)果發(fā)現(xiàn)利用脂質(zhì)體進(jìn)行轉(zhuǎn)染,PC-3細(xì)胞轉(zhuǎn)染效率可以超過70%,可以保證后續(xù)實(shí)驗(yàn)需求。Neu3 mRNA檢測發(fā)現(xiàn)3號Neu3 siRNA抑制目的基因效率最高,MTT實(shí)驗(yàn)結(jié)果顯示3號Neu3 siRNA抑制細(xì)胞增殖效果最為明顯,根據(jù)上述兩個(gè)實(shí)驗(yàn)結(jié)果因此后續(xù)實(shí)驗(yàn)均選擇3號pGCsi-Neu3-3質(zhì)粒進(jìn)行。流式細(xì)胞術(shù)結(jié)果顯示pGCsi-Neu3-3質(zhì)粒促進(jìn)PC-3細(xì)胞凋亡,凋亡率可達(dá)18.1%。細(xì)胞增殖相關(guān)基因(PCNA)在細(xì)胞增殖的啟動(dòng)上起重要作用,是反映細(xì)胞增殖狀態(tài)的良好指標(biāo)[21]。pGCsi-Neu3-3組細(xì)胞核棕黃色顆粒明顯減少,表明細(xì)胞增殖能力明顯下降。Transwell實(shí)驗(yàn)結(jié)果顯示pGCsi-Neu3-3組細(xì)胞數(shù)目減少,說明細(xì)胞遷移、侵襲能力下降。降低Neu3表達(dá)可抑制細(xì)胞增殖、遷移、侵襲,促進(jìn)細(xì)胞凋亡,為今后前列腺癌靶向治療提供一個(gè)新的參考治療靶點(diǎn)。
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(收稿日期:2018-01-02 本文編輯:任 念)