TGF-β1 and FOXM1 siRNA co-loaded nanoparticles by disulfide crosslinked PEG-PDMAEMA for the treatment of triple-negative breast cancer and its bone metastases in vitro.

Introduction: Triple-negative breast cancer (TNBC) is characterized by higher malignancy and mortality and is prone to distant metastasis, among which bone is the most common site. It's urgent to explore new strategies for the treatment of TNBC and its bone metastases.

Methods: A tumor environment responsive vector, poly-(dimethylaminoethyl methacrylate)-SS-poly(ethylene glycol)-SS-poly-(dimethylaminoethyl methacrylate) (PDMAEMA-SS-PEG-SS-PDMAEMA), was constructed to co-delivery transforming growth factor-β1 (TGF-β1) siRNA and forkhead box M1 (FOXM1) siRNA in MDA-MB-231 cells. The preparation, characterization, release, stability, and transfection efficiency of nanoparticles were measured. Cell viability, migration, and invasion of MDA-MB-231 cells were determined. Cell chemotactic migration and cell heterogeneity adhesion of MDA-MB-231 cells to the human osteoblast-like cell line MG-63 were determined.

Results: PDMAEMA-SS-PEG-SS-PDMAEMA self-assembled with siRNA at N/P of 15:1 into nanoparticles with a particle size of 122 nm. release exhibited redox and pH sensitivity, and the nanoparticles protected siRNA from degradation by RNase and serum protein, remaining stable at 4 °C with similar transfection efficiency with lipo2000. Nanoparticles co-loaded with TGF-β1 siRNA and FOXM1 siRNA inhibited the cell viability, migration and invasion of MDA-MB-231 cells, as well as chemotactic migration and heterogeneous adhesion of MDA-MB-231 cells to MG-63 cells, showing a synergetic effect. After gene silencing on TGF-β1 and FOXM1, the epithelial to mesenchymal transition (EMT) related molecules vimentin mRNA expression decreased while E-cadherin increased.

Conclusions: PDMAEMA-SS-PEG-SS-PDMAEMA was suitable for TGF-β1 siRNA and FOXM1 siRNA delivery, exhibiting a synergetic inhibition effect on TNBC and its bone metastases, which might be related to its synergetic inhibition on EMT.