胰腺癌分子靶向治療的研究進展

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(1復旦大學附屬中山醫院介入科 上海 200032;2上海市影像醫學研究所 上海 200032)

作為致死率位居美國第四、世界第七的惡性腫瘤,胰腺癌因85%～95%的轉移率導致其5年生存率僅為1.2%～6%,全球每年因此病死亡約33萬人[1-2]。外科手術切除是胰腺癌最有效的治療手段,但因術后遠處轉移和局部復發,其5年生存率仍低于20%[3]。

吉西他濱化療是胰腺癌非手術治療的首選方法,但效果差強人意。臨床研究[4]表明:Folforinox和吉西他濱聯合應用比吉西他濱單藥效果顯著。2013年批準上市的白蛋白紫杉醇也與吉西他濱聯合應用于胰腺癌化療[5]。但是,上述方法對于延長晚期胰腺癌患者的生存期極其有限,且化療的毒性作用和不良反應也明顯提高[6]。因此,人們迫切需要更加行之有效的治療方法。

隨著腫瘤分子機制逐漸被了解,一批針對實體腫瘤的分子靶向藥物得以開發并取得一定效果,包括靶向血管生成通路、表皮生長因子受體(epidermal growth factor receptor,EGFR)、MEK通路、成纖維細胞生長因子受體(fibroblast growth factor receptor,FGFR)、PI3K/mTOR通路和腫瘤干細胞等,都使得胰腺癌治療取得進展。本文將回顧這些分子靶向藥物在胰腺癌臨床及實驗研究方面的現狀,并討論其潛在的治療前景。

胰腺癌的基因突變和分子病理學研究表明[7],胰腺癌平均存在63個基因突變,因此想找到有效的治療手段需明確胰腺癌復雜的基因突變和病理學特征。胰腺癌的分子病理學分析顯示一些常見的腫瘤基因和信號通路參與其中。KRAS基因編碼小分子GTP酶,起調節生長因子受體下游信號的腫瘤突變基因的作用,多數晚期胰腺癌中都可發現[8]。KRAS基因簇的特定點位存在錯義突變(多為密碼子12)[9],而KRAS基因突變是胰腺上皮內瘤變(PanIN)過程最早的基因事件之一[10]。除了KRAS基因的突變,胰腺癌也常發生抑癌基因如INK4A、BRCA2和LKB1的突變。超過90%的胰腺癌編碼細胞周期調節蛋白的抑癌基因P16/CDKN2A處于失活狀態[11]。P53突變與導致細胞周期停滯和凋亡的毒性壓力應答密切相關[12],75%的胰腺癌存在P53突變,其中又有很高比例伴隨雜合性丟失的小的基因內突變[7]。55%的胰腺癌存在編碼轉化生長因子β (transforming growth factor β,TGFβ)信號通路的抑癌基因——SMAD4的錯義突變[13],因其與預后不良和廣泛轉移關系密切,SMAD4突變被認為是潛在的臨床觀察指標[14]。錯配修復基因MLH1和陽離子胰蛋白酶原基因PRSS1的突變也可見于胰腺癌[15]。

一些胰腺癌存在BRAF突變而不是KRAS突變[16]。BRAF編碼RAF,后者屬于MEK家族的絲氨酸/蘇氨酸激酶,MEK再激活ERK形成MAPK信號通路。MAPK信號的激活不僅見于良性病變,也見于胰腺癌[17]。KRAS和BRAF突變的激活最終導致MAPK信號通路的觸發,而后者是胰腺癌發展的關鍵。過表達的MAPK信號通過一系列RAF的活化形式促使胰腺上皮內瘤變(PanIN)/胰腺導管腺癌形成;與此相反,沉默MAPK信號能抑制腫瘤的發生[18-19]。PI3K信號通路是另一個與胰腺癌變關系密切的重要信號通路[20]。PI3K信號通過下游底物例如Akt、p70-S6k和mTOR調節細胞生長和存活。而生長因子受體如血管內皮生長因子(vascular endothelial growth factor,VEGF)和胰島素樣生長因子1受體(insulin-like growth factor-1 receptor,IGF1R)在胰腺癌中也異常表達[21]。這些通路調節一系列重要細胞功能的基因,包括生長、凋亡、分化、轉移等。

治療胰腺癌的分子靶向藥物近年來,已有多種分子靶向藥物單藥或與細胞毒藥物多藥聯合用于治療胰腺癌,除了靶向上述信號通路外,還包括可能促進腫瘤干細胞信號和腫瘤發生諸多旁分泌信號通路,如Hedgehog、Wnt、Notch和TGFβ等[22]。圖1、2總結了當前已知的有關胰腺癌的信號通路和靶向藥物的使用情況[23]。表1概括了多種分子靶向藥物的臨床試驗[23]。

血管生成通路 血管新生對于惡性腫瘤的生長至關重要。抗血管生成類的分子靶向藥物在治療腎癌、結腸癌、肺癌、惡性膠質瘤和卵巢癌等方面取得了良好的效果[24]。VEGF是血管發生、生成過程中重要的調控因子,特異性作用于血管內皮細胞,增強血管的滲透性,誘導血管發生、生成和內皮細胞生長,促進細胞遷移、抑制細胞凋亡等,從而促進惡性腫瘤的生長和轉移[25]。超過90%的胰腺癌VEGF呈高表達[26],因此以VEGF為靶點進行治療具有充足的依據。但與此前的Ⅱ期臨床試驗[27]結果相反,一項Ⅲ期臨床試驗(CALGB 80303)[23]發現聯合應用貝伐珠單抗(一種VEGF單抗)并沒有較吉西他濱單藥更好。同樣,其他類似分子靶向藥物如索拉菲尼和阿西替尼效果也一般[28-30]。另一項Ⅱ期臨床試驗應用TL-118(一種新型VEGF靶向藥物)聯合吉西他濱治療合并遠處轉移的胰腺癌(NCT01509911)仍在進行[23]。阿柏西普(Aflibercept)是一種能抑制VEGF配體依賴型信號進程的重組功能蛋白[31],雖然在細胞株和移植瘤上表現出良好的抗瘤活性,但Ⅲ期臨床試驗聯合吉西他濱對遠處轉移的胰腺癌總生存期并無獲益[32]。Foretinib是一種新型VEGF抑制劑,它競爭性抑制ATP端受體酪氨酸激酶,發揮抗VEGFRs、RON、c-Met、c-KIT、FLT-3和血小板源生長因子受體(platelet-derived growth factor receptors,PDGFRs)作用[33]。由于肝細胞生長因子(hepatocyte growth factor,HGF)和c-MET在胰腺癌中也常常呈高表達[34],所以針對這些通路的治療方法同樣引起了關注。Foretinib不僅能抑制胰腺癌荷瘤動物的VEGFR-2、VEGFR-3和TIE-2信號通路,還能抑制c-MET信號通路,發揮抑制腫瘤生長、血管生成和淋巴管生成的作用,說明多重激酶抑制劑能發揮同步抑制效果抑制胰腺腫瘤生長[35]。

EGFR通路 EGFR是ErbB家族的一種跨膜酪氨酸激酶受體,在腫瘤細胞生物學行為方面發揮著重要作用。異常活化的EGFR導致受體二聚化并隨之激活其下游通路,包括RAS和PI3K/Akt/mTOR信號通路成員[36]。90%的胰腺癌高表達EGFR[37],在胰腺癌細胞株中EGFR持續激活,加入EGFR抑制劑能抑制其增殖[38]。但臨床試驗中應用EGFR和ErbB2抗體效果都不佳[39-40]。另一種EGFR單抗——尼妥珠單抗聯合吉西他濱治療局限性胰腺癌取得生存期獲益,毒性作用與不良反應也在可忍受范圍內[23]。另一組EGFR抑制劑——厄洛替尼的大樣本Ⅲ期臨床試驗顯示[41],聯合應用吉西他濱較吉西他濱單藥在中位總生存期(P=0.038)和無進展生存期(P=0.004)均有明顯改善。推測可能存在KRAS基因突變或EGFR激活是厄洛替尼治療胰腺癌療效的預測指標[42]。雖然中位總生存期僅延長2周,但此項試驗還是意義非凡,因為這是僅有的吉西他濱/厄洛替尼能改善已發生遠處轉移的胰腺癌生存期的臨床試驗。當然,另一方面還需要平衡厄洛替尼帶來的潛在致死性并發癥的風險[43]。一項Ⅱ期臨床試驗[44]結果顯示,吉非替尼(易瑞沙)聯合吉西他濱治療已發生遠處轉移的胰腺癌的中位總生存期為7.3個月,無進展生存期為4.1個月,其聯合吉西他濱治療胰腺癌缺乏證據支持。

Reproduced by permission from Baishideng Publishing Group Inc:WordJGastroenterol[23],copyright 2016.

圖1胰腺癌的分子信號通路及靶向藥物作用位點
Fig1Molecularsignalingpathwaysofpancreaticcancerandtargetsiteoftargeted-drugs

Reproduced by permission from Baishideng Publishing Group Inc:WordJGastroenterol[23],copyright 2016.

圖2 胰腺癌的治療性抑制劑Fig 2 Therapeutic inhibitors for pancreatic cancer

Reproduced by permission from Baishideng Publishing Group Inc:WordJGastroenterol[23],copyright 2016.

IGF1R信號通路 IGF1R屬于胰島素受體家族,在胰腺癌中呈高表達,激活IGF1R能引起信號級聯放大進而觸發ERK和PI3K/Akt/mTOR信號通路[45]。抑制IGF1R信號能提高吉西他濱對胰腺癌移植瘤的細胞毒作用[46]。但臨床試驗[23]顯示IGF1R抑制劑AMG-479與其單抗(西妥木單抗)并不能讓胰腺癌患者獲益。但同時阻滯IGF1R和EGFR/Her-2能協同抑制胰腺癌的生長并使IRS-1、Akt完全滅活,阻止MAPK磷酸化[23],證明這兩種抑制劑的聯合應用能有效避免單藥耐藥的出現[47],同時將IGF1R、ErbB作為靶點進行雙重靶向治療似乎是一個克服胰腺癌耐藥的策略。

RAS信號通路 RAS/RAF/MEK/ERK(MAPK)生長信號能激活相應信號通路的受體(例如EGFR),這些通路對調節腫瘤細胞的增殖和生存至關重要[48]。曲美替尼(MEK抑制劑)聯合吉西他濱治療晚期胰腺癌并無生存期獲益[23]。AZD6244(MEK抑制劑)聯合厄洛替尼作為二線化療方案治療晚期胰腺癌的臨床試驗仍在進行(NCT01222689)中[23]。

PI3K/Akt/mTOR信號通路 被RAS或者EGFR激活后,PI3K進一步激活Akt,隨后觸發多個下游目標如mTOR,導致其對細胞進程進行必要的調節,包括腫瘤細胞的生長、代謝、生存、轉移和耐藥[49]。59%的胰腺癌存在PI3K-Akt信號通路激活[50],該信號通路常表現異常,即PTEN(同源性磷酸酶-張力蛋白,PI3K的天然拮抗劑)的缺失或低表達[51]。一項Ⅱ期臨床試驗正評估RX-0201(Akt的一種反義寡核苷酸)聯合吉西他濱治療已發生遠處轉移的胰腺癌(NCT01028495)[23]。依維莫斯(mTOR抑制劑)在聯合其他抗腫瘤藥物時,表現出抗腫瘤協同效應[52]。一項Ⅱ期臨床試驗[53]顯示,依維莫斯聯合卡培他濱治療晚期胰腺癌,緩解率達6.5%、整體生存期為8.9個月,聯合用藥能增強卡培他濱的療效。索拉非尼是一種靶向Raf-1、BRaf、VEGFR1、VEGFR2、VEGFR3和PDGFRβ的多重酶抑制劑,對晚期肝細胞肝癌有效[54]。一項Ⅰ/Ⅱ期索拉非尼聯合依維莫斯治療晚期胰腺癌的臨床試驗已近尾聲,但結果尚未發表(NCT00981162)[23]。二甲雙胍用于治療糖尿病,能通過直接影響代謝激活抑癌基因TSC2來抑制mTOR信號通路。一項Ⅱ期臨床試驗(NCT01210911)正在探索二甲雙胍和厄洛替尼聯合吉西他濱治療已發生遠處轉移的胰腺癌的安全性和有效性[23]。

Src信號通路 Src屬于原癌非受體蛋白酪氨酸激酶家族,通過一系列蛋白間的相互作用調控多個信號轉導通路,包括受體酪氨酸激酶和G-蛋白連接受體。約70%的胰腺癌可見C-Src高表達[55]。達沙替尼[Dasatinib,Bcr-Abl及SRC激酶家族(SRC、LCK、YES、FYN)、c-KIT、EPHA2和PDGFR-B等多種激酶抑制劑]是一種與塞卡替尼有關的化合物,一項Ⅱ期臨床試驗正評估其與5-FU、亞葉酸、奧沙利鉑聯合治療已發生遠處轉移的胰腺癌的效果(FOLFOX-D、NCT01652976)[23]。

JAK/STAT信號通路 很多腫瘤都能發現Janus激酶/信號傳感和轉錄(JAK/STAT)信號通路激活[56]。JAK/STAT信號通路的異常直接促使細胞內轉化,增強腫瘤細胞的增殖、抑制凋亡和促進血管生成。胰腺癌存在JAK突變和STAT活化[57-58]。一項Ⅱ期臨床試驗(NCT01423604)發現卡培他濱聯合魯索利替尼(Ruxolitinib,JAK1和JAK2酪氨酸激酶抑制劑)能改善已發生遠處轉移的胰腺癌生存期。另一項吉西他濱、魯索利替尼聯合或不聯合白蛋白紫杉醇的臨床試驗(NCT01822756)仍在進行[23]。

腫瘤干細胞胰腺癌干細胞是一小群對化療和放療都能耐受的細胞,是癌變、進展和轉移的主因[59]。Notch、Hedgehog、Wnt在胰腺癌干細胞發展過程中起關鍵作用[60]。隨著對于胰腺癌干細胞了解的深入,這些都成為胰腺癌靶向治療的新熱點。

Notch信號通路 Notch參與許多器官的發育和功能,調控胰腺祖細胞發育成胰腺和調節胰腺導管細胞分化[61],也參與了腫瘤的增殖和生存[62],在胰腺癌組織中Notch配體和受體均呈高表達[63]。研究表明耐藥的胰腺癌干細胞與Notch信號通路激活有關[64]。一項Ⅰb期的臨床試驗發現,OMP-59R5(一種抗Notch2/3抑制劑)聯合白蛋白紫杉醇和吉西他濱治療已發生遠處轉移的胰腺癌,顯示了良好的耐受性和緩解率(部分緩解46%,持續完全緩解77%)[23]。另一種類似抑制劑(MK0752)聯合吉西他濱治療晚期胰腺癌的臨床試驗也在進行中(NCT01098344)[23]。

Hedgehog信號通路 Hedgehog發揮調控胚胎發育的作用,在正常胰腺組織中沒有表達。Hedgehog與胞外受體和轉錄的目標基因——Patched(Ptch)結合,后者進一步釋放SMO,導致SMO異位到細胞表面,引起GLI轉錄因子活化和包括GLI和Ptch1在內的Hedgehog靶基因順向感應。Hedgehog在胰腺癌組織內呈明顯高表達[65]。早期的胰腺癌瘤組織內可發現Hedgehog磷酸化,晚期其間質內也可高表達[66]。Hedgehog與KRAS突變關系密切,兩者共同促進胰腺瘤變發展為早期胰腺癌[67]。Hedgehog局限于胰腺癌組織基質池內并維持微環境,如使音猬因子(sonic Hedgehog)高表達會誘導轉基因小鼠正常胰腺發生癌前病變[68];相反,如減少音猬因子的表達,則能促使吉西他濱遞送到荷瘤鼠胰腺癌模型病灶部位,引起基質消散和腫瘤血管化[69],這表明Hedgehog信號通路是藥物靶向遞送發展的一個方向。GDC-0449(類似維莫德吉的小分子化合物,SMO小分子拮抗劑)能抑制Hedgehog信號通路,但聯合吉西他濱治療已發生遠處轉移的胰腺癌并沒有優于吉西他濱單藥[70],但可單藥用于外科手術后的輔助化療(NCT01064622、NCT01096732)。而維莫德吉(Vismodegib)聯合吉西他濱治療復發或已轉移的胰腺癌結果令人失望(NCT01064622)。SMO的另一種小分子拮抗劑IPI-926聯合吉西他濱的臨床試驗(NCT01130142)[23]剛剛結束,結果令人期待。

Wnt信號通路 Wnt信號通路發揮調控干細胞的重要作用[71-72],也在胰腺癌腫瘤生物學和發病機制方面發揮重要作用,并且很可能與胰腺癌耐藥密切相關[73]。Wnt信號抑制劑如LGK974(NCT01302405)和PRI-724(NCT01351103)還在Ⅰ期臨床試驗評估中[23]。

TGFβ TGFβ密切參與了胰腺癌細胞的一系列生理過程,包括細胞的分化、內穩態和上皮細胞間質轉化(epithelial-mesenchymal transition,EMT)[74]。一項Ⅱ期臨床試驗(NCT01373164)正在評估LY2157299(TGFβ-1受體特異性抑制劑)聯合吉西他濱的治療效果[23]。

基質環境胰腺癌化療效果不佳的一個重要原因就是細胞外基質(extracellular matrix,ECM)和基質細胞[75]。胰腺癌擁有豐富的腫瘤基質微環境[76],被認為是唯一的富基質腫瘤,其豐富的基質阻礙了化療藥物到達腫瘤部位。因此,消除基質例如降解透明質酸等可能成為一個潛在的有效遞送化療藥物的策略[69]。一項Ⅱ期臨床試驗(NCT01839487)正在評估PEGPH20(聚乙二醇化重組人透明質酸酶)聯合白蛋白紫杉醇和吉西他濱的效果[23]。另一項Ⅰ/Ⅱ期臨床試驗(NCT01959139)也在評估改良FOLFIRINOX方案聯合PEGPH20治療新診斷的已發生轉移的胰腺癌[23]。硫酸乙酰肝素蛋白多糖(heparan sulfate proteoglycans,HSPGs)是一種多糖,也是細胞間質的重要組成部分,與膠原蛋白一起維持間質結構的穩定,參與調節腫瘤生物學行為的多個方面(如腫瘤的發生、發展和轉移)[77]。M402(一種硫酸乙酰肝素的類似物)能阻斷硫酸乙酰肝素與腫瘤間的相互作用[77]。一項Ⅱ期臨床試驗(NCT01621243)正在評估M402聯合標準化療方案[23]?；|金屬蛋白酶(matrix metalloproteinases,MMPs)是一類蛋白水解酶家族,可降解結締組織蛋白,在胰腺癌中經常異常表達。馬馬司他(Marimastat)作為其抑制劑在Ⅲ期臨床試驗中聯合吉西他濱并沒有表現出令人滿意的結果[78]。

選擇性多聚ADP核糖聚合酶通路通過BRCA1和BRCA2蛋白介導的同源重組可以修復DNA雙鏈的斷裂以維持基因穩定性或細胞死亡。當BRCA發生障礙,多聚ADP核糖聚合酶通路則在DNA修復中發揮作用[79]。多聚ADP核糖聚合酶蛋白(poly ADP-ribose polymerase,PRAP)在包括DNA轉錄、DNA損傷應答、基因組穩定性維護和細胞周期調控等方面發揮重要作用。多聚ADP核糖聚合酶抑制劑能導致致死性的腫瘤DNA修復失敗或同源性修復缺陷。有5%～7%的胰腺癌伴腫瘤細胞DNA修復不良導致BRCA1和BRCA2的胚系突變,而多聚ADP核糖聚合酶抑制劑能對此產生積極的臨床效果。Ⅱ期臨床試驗(NCT01585805)應用Veliparib(多聚ADP核糖聚合酶的選擇性抑制劑)聯合順鉑和吉西他濱治療晚期或伴轉移的胰腺癌正在進行。另一項Ⅰ/Ⅱ期臨床試驗(NCT01296763)應用奧拉帕尼(Olaparib,多聚ADP核糖聚合酶抑制劑,也作用于BRCA1或BRCA2突變)聯合伊立替康、順鉑和絲裂霉素C治療晚期胰腺癌也在進行中[23]。

近期的有關胰腺癌治療的實驗研究盡管很多臨床試驗在驗證已開發的靶向藥物,但相較于其他腫瘤,在胰腺癌治療方面進展并不大。因此,此處匯報最新的實驗室研究,希望能為找新的治療胰腺癌策略提供方向。

一些新穎的酪氨酸激酶抑制劑可以靶向多個不同的信號通路來發揮抗癌效果。多重激酶抑制劑Foretinib能針對胰腺癌發揮多重抑制效果[35]。通過先導化合物優化而獲得的SKLB261發揮抗EGFR、Src和 VEGFR2活性。對于胰腺癌移植瘤鼠[80],SKLB261不僅比吉西他濱單藥治療組,同時也比達沙替尼、吉西他濱或厄洛替尼聯合治療組擁有更強大的抗腫瘤效果,明顯延長了荷瘤鼠生存期。尼達尼布(Nintedanib)是一種靶向VEGFR1/2/3、FGFR1/2/3和 PDGFRα/β信號通路的三重靶向血管激酶抑制劑[81-82],對胰腺癌細胞株擁有強大的抗腫瘤活性,也增強了吉西他濱的抑癌作用[81,83]。尼達尼布能誘導胰腺癌細胞和間質細胞凋亡,這為臨床上聯合傳統細胞毒藥物治療胰腺癌提供了強大的理論支持[83]。馬賽替尼(Masitinib)也是一種多重靶向的酪氨酸激酶抑制劑,能選擇性綁定并抑制干細胞因子受體突變體(c-Kit、SCFR)和PDGFR、FGFR3。一項Ⅲ期臨床試驗發現,馬賽替尼聯合吉西他濱能延長ACOX1高表達組生存期,其中位整體生存期達11.7個月(95%CI:8.3～19.9),而吉西他濱+安慰劑中位整體生存期僅5.6個月(95%CI:3.7～12.9)[84]。

缺氧誘導因子-1 (hypoxia inducible factor-1,HIF-1)是細胞適應乏氧環境的主要介質,88%的胰腺癌都有表達[85]。PX-478是HIF-1抑制劑,通過促進胰腺癌細胞免疫源性死亡來增強吉西他濱的抗腫瘤效果[86]。

糖原合成酶激酶-3β (glycogen synthase kinase-3β,GSK3β)與胰腺癌細胞增殖密切相關,這為以GSK3β為靶點治療胰腺癌提供了論據支持[87]。GSK3β抑制劑能通過包括JNK-cJUN活化的機制誘導腫瘤細胞凋亡[88]。CXCR4 (CXC趨化因子受體-4)通過調控GSK3β表達和Akt信號來增強胰腺癌細胞的侵襲力,因此CXCR4抑制劑能應用于胰腺癌的靶向治療[89]。

FOXM1(forkhead box M1)是FOX蛋白家族的轉錄因子[90],是調控一系列腫瘤進程(包括腫瘤細胞的存活、增殖和上皮細胞間質轉化)的關鍵基因,在胰腺癌發展過程中起著重要的作用[91]。研究報道[92]FOXM1通過增強uPAR基因轉錄和隨后的腫瘤上皮細胞間質轉化來促進胰腺癌發展。這都表明抑制FOXM1信號通路可能成為胰腺癌靶向治療的一個新方向。

結語胰腺癌具有基因異質性和分子信號通路串擾的復雜性,這直接導致現有治療的失敗。迄今,只有很少的分子靶向藥物,例如厄洛替尼,取得了生存期延長。

針對單個信號通路的靶向藥物的聯合應用對抗腫瘤療效至關重要,例如抑制PI3K/Akt /mTOR信號通路,腫瘤通過MAPK信號通路能加強不同信號通路間的串擾,產生逃逸效果,最終減弱抑瘤效果。研究發現[93],以PI3K抑制劑ZSTK474和Raf/MEK抑制劑RO5126766為原型的雙效藥物在體外細胞實驗中能高效的抑制PI3K和MEK1,起到降低胰腺癌細胞株生存能力的效果。另一項研究表明[94],Dinaciclib(周期蛋白依賴性激酶抑制劑)聯合MK-2206(Akt抑制劑)能明顯抑制8種胰腺癌模型的腫瘤生長和轉移,取得完全緩解的效果,表明同時阻滯RAF和KRAS下游通路能顯著提高治療效果。臨床前研究也表明EGFR和其他通路抑制劑聯合應用具有抗胰腺癌移植瘤前景:雙抗EGFR和HER2的曲美替尼能顯著增強MEK1/2抑制劑對胰腺癌移植瘤的抑瘤效果[95],這表明針對胰腺癌的治療既需要靶向EGFR-HER2,也需要靶向KRAS以達到療效最大化[96]。

新的靶向藥物既能針對腫瘤細胞,又能兼顧腫瘤基質或許更有意義。越來越多的證據顯示基質細胞分泌的蛋白質(Cox-2、基質衍生因子、整合素、分泌蛋白的酸性蛋白、豐富的半胱氨酸)與放、化療耐受導致的預后不良密切相關[97]。

迄今,絕大多數靶向藥物的胰腺癌臨床試驗并未取得滿意效果;動物和細胞實驗雖有進展,結果還需觀察、驗證。分子靶向藥物在不斷取得進展的同時,在胰腺癌面前卻無能為力,這也證明胰腺癌的生物學行為還有待更多揭示。

[1] SIEGEL R,NAISHADHAM D,JEMAL A.Cancer statistics,2012[J].CACancerJClin,2012,62(1):10-29.

[2] SIEGEL RL,MILLER KD,JEMAL A.Cancer statistics,2015[J].CACancerJClin,2015,65(1):5-29.

[3] OETTLE H,POST S,NEUHAUS P,etal.Adjuvant chemotherapy with gemcitabine vs observation in patients undergoing curative-intent resection of pancreatic cancer:a randomized controlled trial[J].JAMA,2007,297(3):267-277.

[4] CONROY T,DESSEIGNE F,YCHOU M,etal.FOLFIRINOX versus gemcitabine for metastatic pancreatic cancer[J].NEnglJMed,2011,364(19):1817-1825.

[5] BORAZANCI E,VON HOFF DD.Nab-paclitaxel and gemcitabine for the treatment of patients with metastatic pancreatic cancer[J].ExpertRevGastroenterolHepatol,2014,8(7):739-747.

[6] THOTA R,PAUFF JM,BERLIN JD.Treatment of metastatic pancreatic adenocarcinoma:a review[J].Oncology,2014,28(1):70-74.

[7] JONES S,ZHANG X,PARSONS DW,etal.Core signaling pathways in human pancreatic cancers revealed by global genomic analyses[J].Science,2008,321(5897):1801-1806.

[8] ROZENBLUM E,SCHUTTE M,GOGGINS M,etal.Tumor-suppressive pathways in pancreatic carcinoma[J].CancerRes,1997,57(9):1731-1734.

[9] YASHIRO M,CARETHERS JM,LAGHI L,etal.Genetic pathways in the evolution of morphologically distinct colorectal neoplasms[J].CancerRes,2001,61(6):2676-2683.

[10] MOSKALUK CAHRUBAN RH,KERN SE.p16 and K-ras gene mutations in the intraductal precursors of human pancreatic adenocarcinoma[J].CancerRes,1997,57(11):2140-2143.

[11] SCHUTTE M,HRUBAN RH,GERADTS J,etal.Abrogation of the Rb/p16 tumor-suppressive pathway in virtually all pancreatic carcinomas[J].CancerRes,1997,57(15):3126-3130.

[12] MULLER PA,VOUSDEN KH.p53 mutations in cancer[J].NatCellBiol,2013,15(1):2-8.

[13] IACOBUZIO-DONAHUE CA,SONG J,PARMIAGIANI G,etal.Missense mutations of MADH4:characterization of the mutational hot spot and functional consequences in human tumors[J].ClinCancerRes,2004,10(5):1597-1604.

[14] BLACKFORD A,SERRANO OK,WOLFGANG CL,etal.SMAD4 gene mutations are associated with poor prognosis in pancreatic cancer[J].ClinCancerRes,2009,15(14):4674-4679.

[15] HEZEL AF,KIMMELMAN AC,STANGER BZ,etal.Genetics and biology of pancreatic ductal adenocarcinoma[J].GenesDev,2006,20(10):1218-1249.

[16] CALHOUN ES,JONES JB,ASHFAQ R,etal.BRAF and FBXW7 (CDC4,FBW7,AGO,SEL10) mutations in distinct subsets of pancreatic cancer:potential therapeutic targets[J].AmJPathol,2003,163(4):1255-1260.

[17] HINGORANI SR,PETRICOIN EF,MAITRA A,etal.Preinvasive and invasive ductal pancreatic cancer and its early detection in the mouse[J].CancerCell,2003,4(6):437-450.

[18] ARDITO CM,GRUNER BM,TAKEUCHI KK,etal.EGF receptor is required for KRAS-induced pancreatic tumorigenesis[J].CancerCell,2012,22(3):304-317.

[19] COLLINS MA,BEDNAR F,ZHANG Y,etal.Oncogenic Kras is required for both the initiation and maintenance of pancreatic cancer in mice[J].JClinInvest,2012,122(2):639-653.

[20] CANTLEY LC.The phosphoinositide 3-kinase pathway [J].Science,2002,296(5573):1655-1657.

[21] HIRAKAWA T,YASHIRO M,MURATA A,etal.IGF-1 receptor and IGF binding protein-3 might predict prognosis of patients with resectable pancreatic cancer[J].BMCCancer,2013,13(21):392.

[22] NEESSE A,MICHL P,FRESE KK,etal.Stromal biology and therapy in pancreatic cancer[J].Gut,2011,60(6):861-868.

[23] MATSUOKA T,YASHIRO M.Molecular targets for the treatment of pancreatic cancer:Clinical and experimental studies[J].WorldJGastroenterol,2016,22(2):776-789.

[24] WHIPPLE C,KORC M.Targeting angiogenesis in pancreatic cancer:rationale and pitfalls[J].LangenbecksArchSurg,2008,393(6):901-910.

[25] KOCH S,CLAESSON-WELSH L.Signal transduction by vascular endothelial growth factor receptors[J].ColdSpringHarbPerspectMed,2012,2(7):a006502.

[26] SEO Y,BABA H,FUKUDA T,etal.High expression of vascular endothelial growth factor is associated with liver metastasis and a poor prognosis for patients with ductal pancreatic adenocarcinoma[J].Cancer,2000,88(10):2239-2245.

[27] KINDLER HL,NIEDZWIECKI D,HOLLIS D,etal.Gemcitabine plus bevacizumab compared with gemcitabine plus placebo in patients with advanced pancreatic cancer:phase III trial of the Cancer and Leukemia Group B (CALGB 80303)[J].JClinOncol,2010,28(22):3617-3622.

[28] CARDIN DB,GOFF L,LI CI,etal.Phase II trial of sorafenib and erlotinib in advanced pancreatic cancer[J].CancerMed,2014,3(3):572-579.

[29] SAIF MW.Pancreatic cancer:Sorafenib:no effect on efficacy of chemotherapy in pancreatic cancer[J].NatRevGastroenterolHepatol,2014,11(1):8-9.

[30] IOKA T,OKUSAKA T,OHKAWA S,etal.Efficacy and safety of axitinib in combination with gemcitabine in advanced pancreatic cancer:subgroup analyses by region,including Japan,from the global randomized Phase III trial[J].JpnJClinOncol,2015,45(5):439-448.

[31] KINDLER HL,IOKA T,RICHEL DJ,etal.Axitinib plus gemcitabine versus placebo plus gemcitabine in patients with advanced pancreatic adenocarcinoma:a double-blind randomised phase 3 study[J].LancetOncol,2011,12(3):256-262.

[32] ROUGIER P,RIESS H,MANGES R,etal.Randomised,placebo-controlled,double-blind,parallel-group phase III study evaluating aflibercept in patients receiving first-line treatment with gemcitabine for metastatic pancreatic cancer[J].EurJCancer,2013,49(12):2633-2642.

[33] KATAOKA Y,MUKOHARA T,TOMIOKA H,etal.Foretinib (GSK1363089),a multi-kinase inhibitor of MET and VEGFRs,inhibits growth of gastric cancer cell lines by blocking inter-receptor tyrosine kinase networks[J].InvestNewDrugs,2012,30(4):1352-1360.

[34] KIEHNE K,HERZIG KH,FOLSCH UR.c-met expression in pancreatic cancer and effects of hepatocyte growth factor on pancreatic cancer cell growth[J].Pancreas,1997,15(1):35-40.

[35] CHEN HM,TSAI CH,HUNG WC.Foretinib inhibits angiogenesis,lymphangiogenesis and tumor growth of pancreatic cancerinvivoby decreasing VEGFR-2/3 and TIE-2 signaling[J].Oncotarget,2015,6(17):14940-14952.

[36] VOLDBORG BR,DAMSTRUP L,SPANG-THOMSEN M,etal.Epidermal growth factor receptor (EGFR) and EGFR mutations,function and possible role in clinical trials[J].AnnOncol,1997,8(12):1197-1206.

[37] TOBITA K,KIJIMA H,DOWAKI S,etal.Epidermal growth factor receptor expression in human pancreatic cancer:Significance for liver metastasis[J].IntJMolMed,2003,11(3):305-309.

[38] YAMANAKA Y,FRIESS H,KOBRIN MS,etal.Coexpression of epidermal growth factor receptor and ligands in human pancreatic cancer is associated with enhanced tumor aggressiveness[J].AnticancerRes,1993,13(3):565-569.

[39] SAFRAN H,IANNITTI D,RAMANATHAN R,etal.Herceptin and gemcitabine for metastatic pancreatic cancers that overexpress HER-2/neu[J].CancerInvest,2004,22(5):706-712.

[40] PHILIP PA,BENEDETTI J,CORLESS CL,etal.Phase III study comparing gemcitabine plus cetuximab versus gemcitabine in patients with advanced pancreatic adenocarcinoma:Southwest Oncology Group-directed intergroup trial S0205[J].JClinOncol,2010,28(22):3605-3610.

[41] MOORE MJ,GOLDSTEIN D,HAMM J,etal.Erlotinib plus gemcitabine compared with gemcitabine alone in patients with advanced pancreatic cancer:a phase III trial of the National Cancer Institute of Canada Clinical Trials Group[J].JClinOncol,2007,25(15):1960-1966.

[42] DA CUNHA SANTOS G,DHANI N,TU D,etal.Molecular predictors of outcome in a phase 3 study of gemcitabine and erlotinib therapy in patients with advanced pancreatic cancer:National Cancer Institute of Canada Clinical Trials Group Study PA.3[J].Cancer,2010,116(24):5599-5607.

[43] TOGASHI Y,HAYASHI H,NAKAGAWA K,etal.Clinical utility of erlotinib for the treatment of non-small-cell lung cancer in Japanese patients:current evidence[J].DrugDesDevelTher,2014,8(31):1037-1046.

[44] FOUNTZILAS G,BOBOS M,KALOGERA-FOUNTZILA A,etal.Gemcitabine combined with gefitinib in patients with inoperable or metastatic pancreatic cancer:a phase II Study of the Hellenic Cooperative Oncology Group with biomarker evaluation[J].CancerInvest,2008,26(8):784-793.

[45] SACHDEV D,YEE D.Disrupting insulin-like growth factor signaling as a potential cancer therapy[J].MolCancerTher,2007,6(1):1-12.

[46] POLLAK MN,SCHERNHAMMER ES,HANKINSON SE.Insulin-like growth factors and neoplasia[J].NatRevCancer,2004,4(7):505-518.

[47] URTASUN N,VIDAL-PLA A,PEREZ-TORRAS S,etal.Human pancreatic cancer stem cells are sensitive to dual inhibition of IGF-IR and ErbB receptors[J].BMCCancer,2015,15:223.

[48] DE LUCA A,MAIELLO MR,D′ALESSIO A,etal.The RAS/RAF/MEK/ERK and the PI3K/AKT signalling pathways:role in cancer pathogenesis and implications for therapeutic approaches[J].ExpertOpinTherTargets,2012,16(Suppl 2):S17-S27.

[49] WILLEMS L,TAMBURINI J,CHAPUIS N,etal.PI3K and mTOR signaling pathways in cancer:new data on targeted therapies [J].CurrOncolRep,2012,14(2):129-138.

[50] SCHLIEMAN MG,FAHY BN,RAMSAMOOJ R,etal.Incidence,mechanism and prognostic value of activated AKT in pancreas cancer[J].BrJCancer,2003,89(11):2110-2115.

[51] ASANO T,YAO Y,ZHU J,etal.The PI 3-kinase/Akt signaling pathway is activated due to aberrant Pten expression and targets transcription factors NF-kappaB and c-Myc in pancreatic cancer cells[J].Oncogene,2004,23(53):8571-8580.

[52] MATSUZAKI T,YASHIRO M,KAIZAKI R,etal.Synergistic antiproliferative effect of mTOR inhibitors in combination with 5-fluorouracil in scirrhous gastric cancer[J].CancerSci,2009,100(12):2402-2410.

[53] KORDES S,KLUMPEN HJ,WETERMAN MJ,etal.Phase II study of capecitabine and the oral mTOR inhibitor everolimus in patients with advanced pancreatic cancer[J].CancerChemotherPharmacol,2015,75(6):1135-1141.

[54] LLOVET JM,RICCI S,MAZZAFERRO V,etal.Sorafenib in advanced hepatocellular carcinoma[J].NEnglJMed,2008,359(4):378-390.

[55] THOMAS SM,BRUGGE JS.Cellular functions regulated by Src family kinases[J].AnnuRevCellDevBiol,1997,13:513-609.

[56] JATIANI SS,BAKER SJ,SILVERMAN LR,etal.Jak/STAT pathways in cytokine signaling and myeloproliferative disorders:approaches for targeted therapies[J].GenesCancer,2010,1(10):979-993.

[57] MULLER S,RAULEFS S,BRUNS P,etal.Next-generation sequencing reveals novel differentially regulated mRNAs,lncRNAs,miRNAs,sdRNAs and a piRNA in pancreatic cancer[J].MolCancer,2015,14:94.

[58] LILI LN,MATYUNINA LV,WALKER LD,etal.Evidence for the importance of personalized molecular profiling in pancreatic cancer[J].Pancreas,2014,43(2):198-211.

[59] RAO CV,MOHAMMED A.New insights into pancreatic cancer stem cells[J].WorldJStemCells,2015,7(3):547-555.

[60] CASTELLANOS JA,MERCHANT NB,NAGATHIHALLI NS.Emerging targets in pancreatic cancer:epithelial-mesenchymal transition and cancer stem cells[J].OncoTargetsTher,2013,6:1261-1267.

[61] AVILA JL,KISSIL JL.Notch signaling in pancreatic cancer:oncogene or tumor suppressor?[J].TrendsMolMed,2013,19(5):320-327.

[62] LEACH SD.Epithelial differentiation in pancreatic development and neoplasia:new niches for nestin and Notch[J].JClinGastroenterol,2005,39(4 Suppl 2):S78-S82.

[63] RISTORCELLI E,LOMBARDO D.Targeting Notch signaling in pancreatic cancer[J].ExpertOpinTherTargets,2010,14(5):541-552.

[64] WANG Z,AHMAD A,LI Y,etal.Targeting notch to eradicate pancreatic cancer stem cells for cancer therapy[J].AnticancerRes,2011,31(4):1105-1113.

[65] CHEN JK,TAIPALE J,YOUNG KE,etal.Small molecule modulation of Smoothened activity[J].ProcNatlAcadSciUSA,2002,99(22):14071-14076.

[66] THAYER SP,DI MAGLIANO MP,HEISER PW,etal.Hedgehog is an early and late mediator of pancreatic cancer tumorigenesis[J].Nature,2003,425(6960):851-856.

[67] PASCA DI MAGLIANO M,SEKINE S,ERMILOV A,etal.Hedgehog/Ras interactions regulate early stages of pancreatic cancer[J].GenesDev,2006,20(22):3161-3173.

[68] TANAKA S.Cancer stem cells as therapeutic targets of hepato-biliary-pancreatic cancers[J].JHepatobiliaryPancreatSci,2015,22(7):531-537.

[69] OLIVE KP,JACOBETZ MA,DAVIDSON CJ,etal.Inhibition of Hedgehog signaling enhances delivery of chemotherapy in a mouse model of pancreatic cancer[J].Science,2009,324(5933):1457-1461.

[70] KIM EJ,SAHAI V,ABEL EV,etal.Pilot clinical trial of hedgehog pathway inhibitor GDC-0449 (vismodegib) in combination with gemcitabine in patients with metastatic pancreatic adenocarcinoma[J].ClinCancerRes,2014,20(23):5937-5945.

[71] ESPADA J,CALVO MB,DIAZ-PRADO S,etal.Wnt signalling and cancer stem cells[J].ClinTranslOncol,2009,11(7):411-427.

[72] BAARSMA HA,KONIGSHOFF M,GOSENS R.The WNT signaling pathway from ligand secretion to gene transcription:molecular mechanisms and pharmacological targets[J].PharmacolTher,2013,138(1):66-83.

[73] CUI J,JIANG W,WANG S,etal.Role of Wnt/beta-catenin signaling in drug resistance of pancreatic cancer[J].CurrPharmDes,2012,18(17):2464-2471.

[74] FUXE J,KARLSSON MC.TGF-beta-induced epithelial-mesenchymal transition:a link between cancer and inflammation[J].SeminCancerBiol,2012,22(5-6):455-461.

[75] OBERSTEIN PE,OLIVE KP.Pancreatic cancer:why is it so hard to treat?[J].TherapAdvGastroenterol,2013,6(4):321-337.

[76] RUCKI AA,ZHENG L.Pancreatic cancer stroma:understanding biology leads to new therapeutic strategies[J].WorldJGastroenterol,2014,20(9):2237-2246.

[77] ZHOU H,ROY S,COCHRAN E,etal.M402,a novel heparan sulfate mimetic,targets multiple pathways implicated in tumor progression and metastasis[J].PLoSOne,2011,6(6):e21106.

[78] BRAMHALL SR,SCHULZ J,NEMUNAITIS J,etal.A double-blind placebo-controlled,randomised study comparing gemcitabine and marimastat with gemcitabine and placebo as first line therapy in patients with advanced pancreatic cancer[J].BrJCancer,2002,87(2):161-167.

[79] HELLEDAY T,BRYANT HE,SCHULTZ N.Poly(ADP-ribose) polymerase (PARP-1) in homologous recombination and as a target for cancer therapy[J].CellCycle,2005,4(9):1176-1178.

[80] PAN Y,ZHENG M,ZHONG L,etal.A preclinical evaluation of SKLB261,a multikinase inhibitor of EGFR/Src/VEGFR2,as a therapeutic agent against pancreatic cancer[J].MolCancerTher,2015,14(2):407-418.

[81] KUTLUK CENIK B,OSTAPOFF KT,GERBER DE,etal.BIBF 1120 (nintedanib),a triple angiokinase inhibitor,induces hypoxia but not EMT and blocks progression of preclinical models of lung and pancreatic cancer[J].MolCancerTher,2013,12(6):992-1001.

[82] ROLFO C,RAEZ LE,BRONTE G,etal.BIBF 1120/ nintedanib :a new triple angiokinase inhibitor-directed therapy in patients with non-small cell lung cancer[J].ExpertOpinInvestigDrugs,2013,22(8):1081-1088.

[83] AWASTHI N,HINZ S,BREKKEN RA,etal.Nintedanib,a triple angiokinase inhibitor,enhances cytotoxic therapy response in pancreatic cancer[J].CancerLett,2015,358(1):59-66.

[84] DEPLANQUE G,DEMARCHI M,HEBBAR M,etal.A randomized,placebo-controlled phase III trial of masitinib plus gemcitabine in the treatment of advanced pancreatic cancer[J].AnnOncol,2015,26(6):1194-1200.

[85] SHIBAJI T,NAGAO M,IKEDA N,etal.Prognostic significance of HIF-1 alpha overexpression in human pancreatic cancer[J].AnticancerRes,2003,23(6C):4721-4727.

[86] ZHAO T,REN H,JIA L,etal.Inhibition of HIF-1alpha by PX-478 enhances the anti-tumor effect of gemcitabine by inducing immunogenic cell death in pancreatic ductal adenocarcinoma[J].Oncotarget,2015,6(4):2250-2262.

[87] MIYASHITA K,NAKADA M,SHAKOORI A,etal.An emerging strategy for cancer treatment targeting aberrant glycogen synthase kinase 3 beta[J].AnticancerAgentsMedChem,2009,9(10):1114-1122.

[88] MARCHAND B,TREMBLAY I,CAGNOL S,etal.Inhibition of glycogen synthase kinase-3 activity triggers an apoptotic response in pancreatic cancer cells through JNK-dependent mechanisms[J].Carcinogenesis,2012,33(3):529-537.

[89] MA S,LI Q,PAN F.CXCR4 promotes GSK3beta expression in pancreatic cancer cells via the Akt pathway[J].IntJClinOncol,2015,20(3):525-530.

[90] CLARK KL,HALAY ED,LAI E,etal.Co-crystal structure of the HNF-3/fork head DNA-recognition motif resembles histone H5[J].Nature,1993,364(6436):412-420.

[91] WANG Z,BANERJEE S,KONG D,etal.Down-regulation of Forkhead Box M1 transcription factor leads to the inhibition of invasion and angiogenesis of pancreatic cancer cells[J].CancerRes,2007,67(17):8293-8300.

[92] HUANG C,XIE D,CUI J,etal.FOXM1c promotes pancreatic cancer epithelial-to-mesenchymal transition and metastasis via upregulation of expression of the urokinase plasminogen activator system[J].ClinCancerRes,2014,20(6):1477-1488.

[93] VAN DORT ME,GALBAN S,WANG H,etal.Dual inhibition of allosteric mitogen-activated protein kinase (MEK) and phosphatidylinositol 3-kinase (PI3K) oncogenic targets with a bifunctional inhibitor[J].BioorgMedChem,2015,23(7):1386-1394.

[94] HU C,DADON T,CHENNA V,etal.Combined inhibition of cyclin-dependent kinases (Dinaciclib) and AKT (MK-2206) blocks pancreatic tumor growth and metastases in patient-derived xenograft models[J].MolCancerTher,2015,14(7):1532-1539.

[95] NEWHOOK TE,LINDBERG JM,ADAIR SJ,etal.Adjuvant trametinib delays the outgrowth of occult pancreatic cancer in a mouse model of patient-derived liver metastasis[J].AnnSurgOncol,2016,23(6):1993-2000.

[96] LINDBERG JM,NEWHOOK TE,ADAIR SJ,etal.Co-treatment with panitumumab and trastuzumab augments response to the MEK inhibitor trametinib in a patient-derived xenograft model of pancreatic cancer[J].Neoplasia,2014,16(7):562-571.

[97] TANG SC,CHEN YC.Novel therapeutic targets for pancreatic cancer[J].WorldJGastroenterol,2014,20(31):10825-10844.