80 ± 28.2 −16.8 109.9 0.166 43.0 ANPs 147.6 ± 22.7 250.6 ± 27.2 103.0 39.6 0.245 15.81 Control 149.4 ± 18.2 319.9 ± 30.3 170.5 0.0 0.291 0.0 n = 30. aInhibition rate of tumor volume = (Differences in mean tumor volume between the beginning and end of treatment group) / (differences in mean tumor volume between the begin and end of control group) × 100%. bThe tumor weight was measured at 35 days after administration. cInhibition rate of tumor weight = (Differences in mean tumor weight between treatment group and

control group) / (Mean tumor weight of control group) × 100%. *Significant difference compared with gemcitabine group, p < 0.05. Figure 3 Neoplastic mass comparison among different treatment groups. After being excised from the PANC-1-induced nude mice tumor model following their scarification at the end of the experiments. Vorinostat molecular weight A 110-nm GEM-ANPs, B 406-nm- GEM-ANPs, C gemcitabine, D ANPs, and E control. Histological analysis of tumor masses after various treatments for 5 weeks was performed by H & E staining; the proliferation and apoptosis of tumor cells were also determined by immunohistochemical assay on Ki-67 protein and TUNEL assay, as shown in Figure 4. H & E staining confirms that the tumor cell proliferation and division

are more active in the control group than in other groups. In addition, Ki-67 protein immunohistochemical assay indicates that the proliferation index of tumor cells in 110-nm GEM-ANP (36.4 ± 8.1%), 406-nm GEM-ANP (25.6 ± 5.7%), and gemcitabine (38.4 ± 9.4%) groups are lower than that in the blank ANP and control group, with significant difference (p < 0.05). At the same time, TUNEL assay reveals that the apoptotic index see more of tumor cells in the 406-nm GEM-ANP (38.5 ± 17.2%) group is significantly higher than that in the 110-nm GEM-ANP (33.6 ± 11.2) and gemcitabine

(32.2 ± 9.7%) groups (Figure 4). Figure 4 Histological analysis of neoplastic masses by H & E staining, Ki-67 protein, and TUNEL assay after being excised from the PANC-1-induced nude mice tumor model following their scarification at the end of the experiments. A 110nm-GEM-ANPs, B 406-nm-GEM-ANPs, C gemcitabine, D ANPs and E control. Discussion As one of the most lethal cancers, pancreatic cancer is still a frequently occurring disease and remains Phosphatidylethanolamine N-methyltransferase a therapeutic challenge to humans [18, 19]. Although gemcitabine is a currently and widely used drug in the therapy of pancreatic cancer, various approaches, such as drug delivery system, have to be tried to prolong the plasma half-life of gemcitabine and enhance its bioavailability [20, 21]. As the typical examples, liposome and carbon nanotube have been a success in delivering cancer drugs for pancreatic cancer treatment in recent animal and preclinical trials [19, 22]. Nowadays, a novel carrier system allowing for lower toxic side effects and higher tumor-targeting efficiencies is emphasized, while the high biosafety of the carrier system is also prerequisite [8, 10, 23].