梁夏宜，孫娟 綜述 劉軍杰 審校

（1. 廣西醫(yī)科大學(xué)腫瘤醫(yī)學(xué)院，廣西 南寧 530021；2. 廣西醫(yī)科大學(xué)附屬腫瘤醫(yī)院 物理診斷中心，廣西 南寧 530021）

胰腺癌是世界上最常見的消化道惡性腫瘤之一[1]，大約有85%的胰腺癌屬于胰腺導(dǎo)管腺癌（pancreatic ductal adenocarcinoma cancer，PDAC）[2]，近年P(guān)DAC患者的5年生存率從4%～5%略改善到7%[3]。手術(shù)切除是唯一可能治愈PDAC的方法。在早期完全切除術(shù)中，淋巴結(jié)陰性患者的5年生存率為25%～30%，而淋巴結(jié)陽性患者的5年生存率僅為10%[4]。大部分患者在確診時已處于胰腺癌晚期，僅有15%～20%的患者能夠得到及時有效的治療[2]。

胰腺癌的早期診斷對選擇最佳治療方案并提高PDAC患者的預(yù)后具有重要意義。許多腫瘤標(biāo)志物與胰腺癌有關(guān)聯(lián)，但CA19-9（carbohydrate antigen 19-9，CA19-9）是目前唯一被食品藥品監(jiān)督管理局（Food and Drug Administration，F(xiàn)DA）認可的對PDAC有監(jiān)測效能的生物標(biāo)志物。盡管它普遍用于早期診斷、預(yù)后評估以及術(shù)后監(jiān)測復(fù)發(fā)和轉(zhuǎn)移，但仍具有局限性[5]，因此，急需尋求新的腫瘤標(biāo)志物對胰腺癌進行早期診斷及預(yù)后評估。本文就腫瘤標(biāo)志物在評估PDAC患者術(shù)后復(fù)發(fā)、轉(zhuǎn)移、治療效能以及早期診斷PDAC的應(yīng)用等方面進行綜述。

1 診斷標(biāo)志物

1.1 CA19-9、癌胚抗原（carcinoembryonic antigen，CEA）及其他碳水化合物

CA19-9是目前被最廣泛應(yīng)用于PDAC定位的一種單克隆抗體，也是FDA唯一認可的能對胰腺癌預(yù)后有預(yù)測作用的標(biāo)志物[6]。CA19-9診斷PDAC的平均靈敏性與特異性分別為77.5%與77.6%[7]，對有明顯病癥的PDAC患者來說陽性預(yù)測值和陰性預(yù)測值分別為72%和81%～96%[8]。但有研究顯示在急性膽管炎、胰腺炎、肝癌、膽管癌等患者的血清中可出現(xiàn)假陽性[9]，容易受到血清膽紅素的影響而升高，且路易斯（Lewis）血型患者的血清中不表達CA19-9[10]，因此將CA19-9單獨作為診斷胰腺癌的指標(biāo)是不完全準確的。

CEA是從人結(jié)腸癌組織中分離出來的一種可溶性蛋白。在胚胎時期生存于肝臟和胰腺，在出生后逐漸下降。當(dāng)正常細胞發(fā)生惡變時，血清CEA水平異常升高。在確定CA19-9的預(yù)測能力之前，CEA是唯一用于診斷PDAC的血清抗原[11]，但與CA19-9相比，CEA在診斷胰腺癌時更易出現(xiàn)誤診[12]。因此在臨床上，其常應(yīng)用于臨床療效觀察和術(shù)后隨訪的重要指標(biāo)，與其他腫瘤標(biāo)志物聯(lián)合診斷，提高診斷疾病的敏感性和特異性。

聯(lián)合CA19-9、CEA和其他標(biāo)志物能提高對胰腺癌患者的診斷。有研究顯示CA242（carbohydrate antigen 242，CA242）診斷胰腺癌的敏感性、特異性分別為67.8%、83.3%，CEA診斷的敏感度、特異性為39.5%、81.3%。但CA19-9與CA242聯(lián)合時，其診斷的靈敏度可高達89%（對特異性無影響）；CA19-9與CEA聯(lián)合診斷PDAC的靈敏度、特異性為89%、75%[7]。當(dāng)CA19-9、CEA、CA242三者聯(lián)合時，PDAC診斷的特異性高達95%，然而診斷的靈敏度出現(xiàn)降低。CA19-9、CEA、CA242與CA125聯(lián)合時，診斷的靈敏度達90.4%，特異性為93.8%[8]。因此，CA19-9、CEA和其他碳水化合物在臨床上對早期診斷PDAC具有重要的意義。

1.2 微小核糖核苷酸（microRNA，miRNA）和其他非編碼核糖核苷酸

miRNA影響胰腺發(fā)育、胰腺腫瘤的發(fā)生和進展。識別胰腺癌中特異的miRNA，不僅可以區(qū)別胰腺的良惡性病變，還可以提高胰腺癌的早期診斷率[13]。研究[14-22]發(fā)現(xiàn)miR-21、miR-155、miR-196a和miR-210在PDAC患者的胰腺組織、血樣、糞便和胰液中表達水平上升，miR-216與miR-217在胰腺組織、糞便、胰液中呈持續(xù)下降的趨勢。尿中的miRNA濃度可對早期PDAC進行診斷，有研究[6]證實miR-143、miR-22與miR-30e在胰腺癌患者的尿液中水平顯著升高。在聯(lián)合使用miR-143與miR-30e對胰腺癌患者進行診斷時靈敏度為83.3%、特異性為96.2%。將miR-21、miR-155和miR-216聯(lián)合作為檢測PDAC患者時亦得類似的結(jié)果（靈敏度與特異性達到83.3%）[23]。Caponi等[24]對miR-21、miR-155和miR-196a進行了特殊標(biāo)記后，發(fā)現(xiàn)它們在導(dǎo)管內(nèi)乳頭狀粘液性惡性腫瘤（intraductal papillary mucinous neoplasm，IPMN）與胰腺上皮內(nèi)腫瘤（pancreatic intraepithelial neoplasia，PanIN）的組織標(biāo)本中高水平表達，這表明它們也是潛在的生物標(biāo)記物，特別是用于早期診斷惡性潛能的疾病。

1.3 巨噬細胞抑制細胞因子1（macrophage inhibitory cytokine 1，MIC-1）與四階脈沖幅度調(diào)制（4 level pulse amplitude modulation，PAM4）

MIC-1是轉(zhuǎn)化生長因子家族的成員，在不同的腫瘤分期中高度表達[25]。有研究[26]顯示，與CA19-9相比，MIC-1能更好地從健康對照組中區(qū)分出胰腺癌患者，且其對胰腺癌的綜合診斷能力明顯優(yōu)于CA19-9，但對胰腺癌和慢性胰腺炎很難區(qū)分。Chen等[27]發(fā)現(xiàn)PDAC患者血清中檢測到MIC-1的靈敏度和特異性分別為79%、86%，且在聯(lián)合使用MIC-1與CA19-9診斷PDAC的研究中發(fā)現(xiàn)了類似的結(jié)果。在CA19-9陰性的患者中，MIC-1的檢測靈敏度為63.1%[28]，在很大程度上能夠避免對CA19-9陰性的PDAC患者出現(xiàn)漏診。

PAM4是一種能在胰腺癌早期中表達并在疾病的進展中保存下來的單克隆抗體[29]。Gold等[30]證實與胰腺良性病變相比，PAM4對PDAC的檢測總靈敏度為76%，特異性為85%，陽性似然比（positive likelihood ratio，+LR）為4.93；與PAM4相比，CA19-9對PDAC的靈敏度為77%，特異性僅為68%，+LR為2.85（P=0.026）；聯(lián)合CA19-9與PAM4時，PDAC的檢測靈敏度為84%，特異性為82%，對胰腺癌的檢出率顯著提高。

1.4 鈣結(jié)合蛋白（calcyclin，Cacy，S100A6）

S100A6是一種鈣結(jié)合蛋白，在PDAC患者的血清水平中升高。有研究[31]發(fā)現(xiàn)胰液中S100A6水平的測定對于區(qū)分慢性胰腺炎、PDAC與IPMN具有重要的作用。雖然部分PDAC患者在超聲內(nèi)鏡引導(dǎo)下細針穿刺活檢（endoscopicultrasonographyfineneedleaspiration，EUS-FNA）的標(biāo)本中發(fā)現(xiàn)S100A6處于高水平狀態(tài)[32]，但目前為止未能證實循環(huán)中血清S100A6水平對胰腺癌具有診斷作用。

1.5 骨橋蛋白（osteopontin，OPN）

OPN是一種具有多功能的分泌蛋白，能在PDAC患者中表達升高，與侵襲性胰腺癌的癌細胞轉(zhuǎn)移生長有關(guān)[33]。研究[13]顯示血清中高濃度OPN對PDAC患者的檢測靈敏度為80%，特異性為97%。OPN能區(qū)分出慢性胰腺炎和PDAC患者，同時能區(qū)分出早期PDAC患者。雖然OPN的診斷靈敏度低于CA19-9，但是在聯(lián)合使用OPN、CA19-9與金屬蛋白酶組織抑制劑1（tissue inhibitor of metalloproteases 1，TIMP-1）時，診斷靈敏度為87%，特異性為91%[34]，均優(yōu)于這三種生物標(biāo)志物單獨應(yīng)用。

1.6 鼠類肉瘤病毒癌基因（kirsten rat sarcoma viral oncogene，KRAS）

KRAS基因是胰腺癌中最常見的突發(fā)型致癌基因。近期研究[35]顯示KARS突變分析與EUS-FNA樣本的細胞邏輯分析結(jié)合可使PDAC患者診斷的靈敏度由80.6提高到88.7%。KARS突變患者的總體生存率比無突變的患者小，這表明這KARS基因的檢測是用于診斷PDAC和預(yù)測生存率的新策略[36]。在細胞學(xué)不確定時可用KARS突變進行輔助診斷PDAC患者，但Singh等[37]沒有發(fā)現(xiàn)血清中KARS突變的狀態(tài)與不同的臨床病理參數(shù)或生存率之間存在明顯的相關(guān)性。因此，仍需要研究來證實KARS突變可作為PDAC患者潛在的生物標(biāo)記物。

2 治療效果的預(yù)測指標(biāo)

2.1 吉西他濱標(biāo)記

對胰腺癌轉(zhuǎn)移以及在輔助性治療中發(fā)生轉(zhuǎn)移的PDAC患者來說，吉西他濱可作為標(biāo)準的化療藥物[38]，目前蛋白家族中平衡型核苷轉(zhuǎn)運蛋白（equilibrative nucleoside transporters，ENTs）和集中型核苷轉(zhuǎn)運蛋白（concentrative nucleoside transporters，CNTs）被認為是吉西他濱治療的生物標(biāo)記[39]。

2.1.1 人平衡型核苷轉(zhuǎn)運蛋白1（human ENT1，hENT1） 研究[40]發(fā)現(xiàn)hENT1升高能夠作為吉西他濱治療中的預(yù)測和評價預(yù)后效果的標(biāo)志物，使用免疫組織化學(xué)分析對用吉西他濱治療的晚期PDAC患者進行活檢時發(fā)現(xiàn)hENT1高度表達，且在吉西他濱治療檢測中發(fā)現(xiàn)hENT1高度表達的患者總體生存率與無復(fù)發(fā)生存率更高。Yamada等[41]進行了不同階段的PDAC患者治療前hENT1水平的測定，并將其與用吉西他濱治療后的切除標(biāo)本中的hENT1水平對比，發(fā)現(xiàn)hENT1是所有PDAC患者以及接受切除術(shù)的患者的獨立預(yù)后預(yù)測因子。

2.1.2 人集中型核苷轉(zhuǎn)運蛋白（human CNT3，hCNT3） hCNTs是第二組吉西他濱的細胞膜轉(zhuǎn)運體，能利用鈉梯度轉(zhuǎn)移吉西他濱通過質(zhì)膜[42]。Maréchal等[43]對45例以吉西他濱為基礎(chǔ)治療的患者分析發(fā)現(xiàn)hCNT3高表達患者的3年生存率與hCNT3低表達的患者相比顯著延長（54.6% vs.26.1%，P=0.028）。hCNT3與 hENT1聯(lián)合應(yīng)用時，hCNT3與hENT1高表達的患者3年生存率為81.1%[43]。

2.1.3 脫氧胞苷激酶（deoxycytidine kinase，dCK） dCK是一種限速酶，它通過磷酸化將吉西他濱轉(zhuǎn)化為其活化的形式。研究[44]發(fā)現(xiàn)dCK信使RNA（mRNA）水平升高能顯著延長應(yīng)用吉西他濱治療患者的生存期。但考慮到目前有限的數(shù)據(jù)，仍需要進一步的臨床研究證實dCK與hCNT3能否作為評估吉西他濱治療的標(biāo)志物。

3 預(yù)后標(biāo)志物

3.1 CA19-9

術(shù)后CA19-9正常或術(shù)前輕度升高（＜100 U/mL）預(yù)測預(yù)后良好，而CA19-9血清水平術(shù)前＞100 U/mL或術(shù)后＞37 U/mL與不良預(yù)后有關(guān)[8,24]。此外，胰腺切除術(shù)后正常CA19-9的下降趨勢亦與生存期延長有關(guān)。術(shù)后持續(xù)升高的CA19-9水平則表明有病灶殘留并可能生存期更短。CA19-9術(shù)前改變率可以預(yù)測切除腫瘤包塊患者的生存率。術(shù)后的CA19-9水平正?；c提高患者術(shù)后生存率有很大的聯(lián)系，而術(shù)后CA19-9的非正?；c發(fā)生轉(zhuǎn)移性疾病或術(shù)后復(fù)發(fā)有很大的關(guān)聯(lián)[10]。研究路易斯陽性血伴術(shù)后高CA19-9患者的預(yù)后情況，發(fā)現(xiàn)術(shù)后有54.5%的患者發(fā)生了局部復(fù)發(fā)和遠處轉(zhuǎn)移，這些患者術(shù)后CA19-9再次上升發(fā)生在腫瘤復(fù)發(fā)2～9個月之前[45-46]，術(shù)后CA19-9持續(xù)性升高可比影像學(xué)檢測出復(fù)發(fā)早2周至5個月[11,47]。但也有研究顯示術(shù)后CA19-9水平正?；⒉坏韧诹己玫念A(yù)后效果[12,47]。

3.2 富含半胱氨酸的分泌型酸性蛋白（secreted protein acidic and rich incysteine，SPARC）

SPARC是一種鈣結(jié)合蛋白，能分泌到細胞外基質(zhì)并被多種蛋白酶迅速降解，影響細胞的遷移、增殖以及血管生成等[48-50]。SPARC已在紫杉醇治療中作為預(yù)測胰腺癌患者預(yù)后的生物標(biāo)志物。在PDAC切除術(shù)后聯(lián)合吉西他濱與替吉奧膠囊（S-1）或單獨使用吉西他濱治療時，SPARC的高表達與患者的低生存率有關(guān)[51]。SPARC對胰腺癌的治療的研究中，Vaz等[52]發(fā)現(xiàn)在PDAC和大部分其他實體性腫瘤中SPARC表達與預(yù)后不良有關(guān)[53]。SPARC表達的位置在胰腺癌中似乎起決定性的作用。Infant等[54]發(fā)現(xiàn)過度表達SPARC的腫瘤周圍成纖維細胞能預(yù)測PDAC患者預(yù)后，腫瘤間質(zhì)細胞SPARC陽性患者的平均生存期要短于陰性患者（15個月vs. 30個月，P＜0.001），因此腫瘤間質(zhì)細胞能延長患者生存期。許多研究[53,55]表明存在腫瘤間質(zhì)成纖維細胞不代表預(yù)后不良，相反，它甚至可以延長總體生存期。

3.3 miRNA

miRNA不僅作為PDAC的潛在診斷標(biāo)志物，還在預(yù)后評估上具有重要的作用。目前，研究證實腫瘤中高度表達miR-21能明顯縮短PDAC患者的總體生存期和無病生存期[56]；miR-155與miR-203表達升高，以及miR-34a表達降低使患者總體生存期縮短[57]；miR-221/222在PDAC中過度表達，這說明了miR-221/222基因的表達顯著促進生長和侵襲，抑制細胞凋亡。此外，低表達水平miR-218與miR-494以及高表達水平miR-744也與預(yù)測PDAC患者的生存率低有關(guān)[49-60]。

3.4 預(yù)后指數(shù)

各種預(yù)后標(biāo)志物的結(jié)合構(gòu)成預(yù)后指數(shù)。Park等[61]應(yīng)用5個參數(shù)（PS、血紅蛋白、白細胞計數(shù)、中性粒細胞比值、CEA）將轉(zhuǎn)移性胰腺癌患者分為3個亞組，即低風(fēng)險組，中風(fēng)險組和高風(fēng)險組，三者的平均總體生存期分別為11.7、6.2、1.3個月（P＜0.001）。對接受姑息性化療的PDAC晚期患者，Xue等[62]創(chuàng)建由3個臨床參數(shù)（美國東部腫瘤協(xié)作組體能狀態(tài)評分標(biāo)準(Eastern Cooperative Oncology Group Performance Status,ECOG PS)、血清CA19-9水平與血清中C反應(yīng)蛋白水平）組成的預(yù)后指數(shù)，將胰腺癌晚期患者分為低風(fēng)險和高風(fēng)險兩組，低風(fēng)險組與高風(fēng)險組的平均總體生存期和1年生存率分別為9.9、5.3個月（P＜0.001）和40.5%、5.9%（P＜0.05）。預(yù)后指數(shù)模型的建立是聯(lián)合不利于患者預(yù)后的因素進行統(tǒng)計學(xué)分析，這些易于從患者身上獲得的預(yù)處理參數(shù)和預(yù)后指數(shù)模型可以幫助臨床醫(yī)生識別高危患者，并在臨床實踐中為胰腺癌晚期患者選擇恰當(dāng)?shù)闹委煼椒ā５壳盀橹?，沒有一個可靠的評分系統(tǒng)可用于胰腺導(dǎo)管腺癌患者的常規(guī)預(yù)后判斷[63]。

4 總結(jié)與展望

綜上所述，早期診斷、及時治療可極大的提高胰腺癌患者的總體生存率。因此各種腫瘤標(biāo)志物、血清蛋白、miRNA以及在未來可能滿足這些需求的基因標(biāo)記等，在很大程度上能提高胰腺癌的檢出率。聯(lián)合使用腫瘤標(biāo)志物能更好地提高胰腺癌的檢出率，并在指導(dǎo)治療和評估預(yù)后上具有重要意義。

近年來，基于腫瘤標(biāo)志物在早期診斷、指導(dǎo)治療和評估預(yù)后等方面具有重要作用，使PDAC患者的治療效果有所改善。但尋找敏感性高、特異性強、結(jié)果穩(wěn)定的腫瘤標(biāo)志物，仍是胰腺癌早期診斷中待解決的問題。相信今后隨著技術(shù)的發(fā)展和胰腺癌分子生物學(xué)研究的深入，胰腺癌的早期診斷、預(yù)后以及總體生存率將會得到極大的改善。

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