BIRC5 Promoter-Driven Nanodrugs Suppress BIRC5-Positive Cancers Independent of ABCB1 Status and IDO1 Expression

BIRC5 (survivin), an inhibitor of apoptosis protein, is overexpressed in most tumors and is associated with drug resistance, proliferation, and metastasis, while being largely undetectable in normal differentiated tissues. This unique expression pattern makes BIRC5 an exceptionally selective therapeutic target, offering the potential to maximize anticancer efficacy while minimizing systemic toxicity to healthy tissues. However, few BIRC5-targeted agents have advanced to late-stage clinical trials.

We developed two nanodrug formulations using poly-L-lysine-modified NH₂-Fe₃O₄ magnetite nanoparticles (PL-MNPs) for selective targeting of BIRC5-positive cancer cells. We further evaluated their anti-cancer efficacy in vitro and in vivo (zebrafish xenograft model), using cancer cell models that expressed BIRC5 and exhibited ABCB1-mediated drug resistance and IDO1-induced immune therapy insensitivity.

The PL-MNPs delivered plasmids driven by the BIRC5 promoter (pBIRC5) encoding either antisense BIRC5 mRNA (As-BIRC5) or a dominant-negative BIRC5 protein (dN-BIRC5), for tumor-specific BIRC5 inhibition. These nanodrugs demonstrated robust in vitro and in vivo anti-cancer activity in multiple BIRC5-positive cell lines (MIA PaCa-2, NTUB1, NTU0.017, SK-OV-3, KB, and KB-TAX50). The activity was preserved across cancer types and independent of ABCB1-mediated drug resistance, while maintaining cancer cell specificity, and was not affected by IDO1 expression, a factor associated with poor responses to immune therapy. PL-MNP uptake was partially mediated by clathrin-dependent endocytosis, with acidic intracellular environments facilitating efficient plasmid release. Conjugation of nanoparticles with Herceptin^® (trastuzumab) significantly increased cellular uptake and anticancer activity, especially in clathrin-deficient SK-BR-3 cells that overexpress ERBB2.

These findings establish that the easily synthesized PL-MNP-pBIRC5/As-BIRC5 and PL-MNP-pBIRC5/dN-BIRC5 nanodrugs have strong potential to overcome BIRC5- and ABCB1-related drug resistance, representing a broadly applicable strategy against various malignancies. While the size of our nanodrug (~400 nm in hydrodynamic diameter) is compatible with reported effective nanoparticle sizes in some models, the extent to which the enhanced permeability and retention (EPR) effect contributes to tumor accumulation in human cancers remains uncertain and will require validation in more clinically relevant models and imaging modalities.