Inhibiting Notch activity in breast cancer stem cells by functionalized gold nanoparticles with gamma-secretase inhibitor DAPT and vitamin C

Cancer stem cells (CSCs) are responsible for tumor initiation, drug resistance and cancer relapses. The Notch pathway regulates CSCs, and it is essential for the self-renewal and maintenance of CSCs. Gamma-secretase inhibitor such as DAPT, reduces the CSCs by inhibiting Notch pathway. Apart from its advantages, DAPT causes side effects which making it necessary to use new strategies. Since vitamin C (Ascorbic Acid: AA) receptors are high on CSCs, they are high in AA uptake and can be used in CSCs targeted therapy. Therefore, in this study we functionalized Au nanoparticles (NPs) with DAPT and AA to target CSCs and increase particle uptake by them. Here, we functionalized Au-AA NPs with DAPT as the target agent. The morphological characteristics of Au-AA NPs and Au-AA-DAPT NPs were investigated by the transmission electron microscopy, Fourier-transform infrared spectroscopy, dynamic light scattering, and zeta potential. After NPs-modified synthesis and confirmation of inhibitor stabilization, their effects on MCF-7 cells were determined by MTT assay. Then, the colony formation and self-renewal ability of MCF-7 cells was evaluated by SP cells analysis and Soft agar colony formation assay. The results of this study indicated that conjugation of DAPT with Au-AA NPs increases the inhibitory effect of DAPT on the growth of MCF-7 cells. Also, it has been shown that Au-AA-DAPT NPs significantly inhibits colony formation and depletes CSCs compared to control cells. Our data demonstrate the involvement of the vitamin C receptors in the increased cellular uptake of DAPT by CSCs. Therefore, targeting CSCs with Au-AA-DAPT NPs could be a promising approach for the treatment. For effective delivery of GSI to CSCs we functionalized Au NPs with vitamin C to target SVCTs that are high on CSCs. The Au-AA-DAPT NP is imported to the cell where it suppresses the γ-secretase, which is responsible for Notch signaling activation.