新穎標的微脂體於肺癌治療之研究

Abstract

肺癌，是所有癌中的魁首，也是目前全世界癌症死因的第一名，且罹癌死亡人數依舊每年持續增加。其中，導致化學治療低療效的一個主要因素是抗癌藥物缺乏腫瘤專一性，因而對人體產生毒性。配體藥引之藥物傳輸系統（ligand-mediated drug delivery system）可以給予化學藥物對抗腫瘤細胞更高的療效，以及對正常組織產生較低的毒性。本研究中，利用噬菌體顯現法（phage display）已尋找出能與非小細胞肺癌細胞株結合的一新穎胜肽。表現此胜肽之噬菌體能與數種非小細胞肺癌細胞株結合但卻不與正常細胞產生作用，同時，其所表現的胜肽也具有相同功能；而此二者辨識人類非小細胞肺癌組織檢體樣本可高達75%。於免疫不全鼠上移植人類腫瘤後，施打此噬菌體，發現此噬菌體能專一地結合至腫瘤組織。再者，當同時施打此噬菌體與其相同序列的胜肽，此胜肽會和噬菌體競爭與腫瘤的結合，因而抑制了噬菌體與腫瘤的結合能力；然而，若施打的是作為對照組或突變的胜肽則無法抑制噬菌體的腫瘤結合能力。結合標的胜肽與包覆抗癌藥物之微脂體（liposomes carrying doxorubicin）後，施打於帶有人類非小細胞肺癌的老鼠，可發現其明顯抑制了腫瘤的生長、增進了化學藥物的治療療效，並改善了其存活率。更甚者，此標的微脂體增加了抗癌藥物累積於腫瘤組織中，相對於游離態的化學藥物（free drug）而言，其劑量提高了五點七倍。此外，此標的微脂體也因其提高了生物利用的藥物濃度，進而引發了癌細胞進行細胞凋亡程序。本研究顯示此腫瘤專一性胜肽能用於增進化學療法的腫瘤專一性，以期有對非小細胞肺癌較佳治療療效，且也能用於偵檢惡性腫瘤。

Lung cancer is the leading cause of cancer-related mortality worldwide. The lack of tumor specificity remains a major drawback for effective chemotherapies and results in dose-limiting toxicities. However, a ligand-mediated drug delivery system should be able to render chemotherapy more specific to tumor cells and less toxic to normal tissues. In this study, we isolated a novel peptide ligand from a phage-displayed peptide library that bound to non-small cell lung cancer (NSCLC) cell lines. The targeting phage bound to several NSCLC cell lines but not to normal cells. Both the targeting phage and the synthetic peptide recognized the surgical specimens of NSCLC with a positive rate of 75% (27 of 36 specimens). In severe combined immunodeficiency (SCID) mice bearing NSCLC xenografts, the targeting phage specifically bound to tumor masses. The tumor homing ability of the targeting phage was inhibited by the cognate synthetic peptide, but not by a control or a WTY-mutated peptide. When the targeting peptide was coupled to liposomes carrying doxorubicin or vinorelbine, the therapeutic index of the chemotherapeutic agents and the survival rates of mice with human lung cancer xenografts markedly increased. Furthermore, the targeting liposomes increased drug accumulation in tumor tissues by 5.7-fold compared with free drugs and enhanced cancer cell apoptosis resulting from a higher concentration of bioavailable doxorubicin. The current study suggests that this tumor-specific peptide may be used to create chemotherapies specifically targeting tumor cells in the treatment of NSCLC and to design targeted gene transfer vectors or it may be used one in the diagnosis of this malignancy.