ABCB1 and neoplasm: In this study, we performed a detailed analysis of acute and chronic toxicity of this liposomal formulation in healthy mice, examined the correlation between the abundance of FR on the cell surface and intratumoral accumulation of NA mediated by liposome F, and analyzed the antitumor effect of PCHT supported by anti-MDR1 siRNA delivered by liposome F on a multidrug-resistant KB-8-5 tumor xenograft in SCID mice.