Inhibition of Epithelial-to-Mesenchymal Transition Augments Antitumor Efficacy of Nanotherapeutics in Pancreatic Ductal Adenocarcinoma.

Intrinsic drug resistance mechanisms of tumor cells often reduce intracellular drug concentration to sub-optimal levels. Epithelial-to-mesenchymal transition (EMT) is a pivotal process in tumor progression and metastasis that confers an aggressive phenotype as well as resistance to chemotherapeutics. Therefore, it is imperative to develop novel strategies and identify new targets to improve the overall efficacy of cancer treatment. We developed SN38 (active metabolite of irinotecan) -assembled glycol chitosan nanoparticles (cSN38) for the treatment of pancreatic ductal adenocarcinoma (PDAC). Furthermore, cSN38 and the TGF-β1 inhibitor LY364947 formed composite nanoparticles upon self-assembly (cSN38+LY), which obviated the poor aqueous solubility of LY364947 and enhanced drug sensitivity. The therapeutic efficacy of cSN38+LY nanotherapeutics was studied in vitro and in vivo using suitable models. The cSN38 nanoparticles exhibited an anti-tumor effect that was significantly attenuated by TGF-β-induced EMT. The cellular uptake of SN38 was impeded during EMT, which affected the therapeutic efficacy. The combination of LY364947 and cSN38 markedly enhanced the cellular uptake of SN38, increased cytotoxic effects, and inhibited EMT in PDAC cells in vitro. Furthermore, cSN38+LY significantly inhibited PDAC xenografts growth in vivo. The cSN38+LY nanoparticles increased the therapeutic efficacy of cSN38 via repressing the EMT of PDAC cells. Our findings provide a rationale for designing nanoscale therapeutics to combat PDAC.