Integrin b 6-Targeted Immunoliposomes Mediate Tumor-Speci fi c Drug Delivery and Enhance Therapeutic Ef fi cacy in Colon Carcinoma

Purpose: Adjuvant chemotherapy is one of the significant treatments for colon cancer in clinic. However, it does not achieve the desired therapeutic efficacy, largely due to chemotherapeutic resistance. Integrinb6 (ITGB6) is expressed in malignant colonic epithelia, but not in normal epithelia, and is associated with the progression, metastasis, and chemotherapeutic resistance of colon cancer. Accordingly, it is necessary to design therapeutic approaches for efficient and targeted drug delivery into ITGB6positive cancer cells to improve chemotherapeutic efficacy in colon cancer. Experimental Design: PEGylated liposomes were employed to design ITGB6-targeted immunoliposomes, which have ITGB6 monoclonal antibodies (mAbs) conjugated. We evaluated the ITGB6-targeted immunoliposomes internalization into colon cancer cells and examined 5-fluorouracil (5-FU)–induced cellular apoptosis produced by ITGB6-targeted immunoliposomesþ5FU. In addition, the biodistribution and antitumor efficiency of ITGB6-targeted immunoliposomes were observed in vivo. Results: ITGB6-targeted immunoliposomes enhanced cellular internalization in ITGB6-positive colon cancer cells compared with liposomes. Furthermore, the ITGB6-targeted immunoliposome internalization was dependent on the ITGB6 expression level on cellular surface. ITGB6-targeted immunoliposomes decreased the 5-FU IC50 more than 90% in HT-29 and SW480b6 cells relative to liposomes. Moreover, when loaded with 5-FU, ITGB6-targeted immunoliposomes produced an approximately 1.5-fold higher 5-FU–induced cellular apoptosis rate than liposomes. In vivo, the therapeutic activity of ITGB6-targeted immunoliposomesþ5-FU was significantly superior, resulting in 25% to 35% reduction of tumor weight compared with 5-FU or liposomesþ5-FU. Conclusions: ITGB6-targeted immunoliposomes provide a highly efficient approach for targeted drug delivery in colon cancer and thus offer the potential of a novel and promising anticancer strategy for clinical therapy. Clin Cancer Res; 21(5); 1183–95. 2014 AACR. Introduction Colon cancer is the third most common cancer and the fourth leading cause of cancer-related deaths worldwide (1). Although surgery remains the preferred treatment, 5-fluorouracil (5-FU)– based adjuvant chemotherapy is the conventional care for stage III (lymph node–positive) patients and can reducemortality by 25% compared with surgery alone (2). However, because the response rate of chemotherapy is only 10% to 20%, the treatment of advanced and metastatic cases remains a challenging problem (3). Therefore, it is urgent to explore novel therapeutic strategies for colon cancer treatment to overcome chemotherapeutic drug resistance and to improve chemotherapeutic efficacy. The targeted delivery of anticancer drugs to tumors has been broadly recognized as an important method for improving chemotherapeutic efficacy and attenuating chemotherapeutic side effects. Sterically stabilized liposomes with a polymeric PEG coating, which have prolonged circulation times, lower reticuloendothelial system (RES) uptake andhigher tumor accumulation, were thought to be an ideal drug delivery system (4, 5). However, these liposomes passively interact with tumor cells, in vitro or in vivo, resulting in nonspecific drug release that leads to the eventual diffusion of the drugs into somenormal tissues or cells rather than tumors (6). Immunoliposomes, which are conjugated with monoclonal antibodies (mAb), are capable of both drug delivery and molecular targeting (7, 8). By combining the specific targeting properties of mAbs and drug delivery advantages of liposomes, immunoliposomes are a promising approach for the targeted delivery of anticancer drugs to tumors (9). To date, various tumor-associated antigens have been validated as targets for antibody-based immunoliposomes in cancer therapeutics. Immunoliposomes targeting CD30, HER2/neu, EGFR, and VEGFR, which are expressed on various tumor cell types, have been developed and thoroughly characterized (10–13). On the basis of encouraging preclinical data and advances in largescale production processes, EGFR-specific immunoliposomes are already being used in clinical trials (14). Department of Hepatobiliary Surgery, Qilu Hospital, Shandong University, Jinan, Shandong, P.R. China. Key Laboratory of Cardiovascular Remodeling and Function Research, ChineseMinistry of Education and Public Health, Jinan, Shandong, P.R. China. School of Pharmaceutical Sciences, Shandong University, Jinan, Shandong, P.R. China. Corresponding Author: Jun Niu, Department of Hepatobiliary Surgery, Qilu Hospital, Shandong University, 44 Wenhua Xi Road, Jinan 250012, Shandong, China. Phone:/Fax: 86 531 82166651; E-mail: NiuJun001@hotmail.com doi: 10.1158/1078-0432.CCR-14-1194 2014 American Association for Cancer Research. Clinical Cancer Research www.aacrjournals. org 1183 on June 9, 2017. © 2015 American Association for Cancer Research. clincancerres.aacrjournals. org Downloaded from Published OnlineFirst December 30, 2014; DOI: 10.1158/1078-0432.CCR-14-1194