Evaluation of cellular and transcriptional targeting of breast cancer stem cells via anti-HER2 nanobody conjugated PAMAM dendrimers

Abstract

According to the cancer stem cell (CSC) theory, a small subset of cells with stem cell-like characteristics is responsible for tumor initiation, progression, and recurrence. CD44+/CD24– phenotype is assumed to be one of the main characteristics of the breast CSCs. We developed an MDA-MB-231 cell line overexpressing cell surface HER2 antigen for the evaluation of targeting efficiency of anti-HER2 nanobody (Nb)-conjugated polyamidoamine (PAMAM) polyplexes. Apoptosis-inducing tBid gene under control of CXCR1 promoter was delivered by this nanoparticle. Cellular uptake study showed higher uptake of Nb-targeted PAMAM carriers compared to non-targeted nanoparticles after 6 h of incubation. Gene expression analysis showed a significant rise in the expression of tBid in both MDA-MB-231/HER2+ and MDA-MB-231 compared to the two other cell lines. The same effect was observed after transfection with Nb-conjugated polyplexes within MDA-MB-231/HER2+ cell line compared to non-conjugated PAMAM polyplexes. We confirmed the killing efficiency of the gene construct in both MDA-MB-231/HER2+ and MDA-MB-231 cell lines by caspase 3 activity assay. These findings suggest that imposing pre-entry and post-entry restrictions on tBid killer gene might be a promising approach to specifically target the breast CSCs.