Enhanced penetration and cytotoxicity of metformin and collagenase conjugated gold nanoparticles in breast cancer spheroids

Aims: The extracellular matrix (ECM) within the tumor nest plays a key role in cancer cell proliferation and invasion. It has been proven that the increased density of ECM, especially collagen network, correlates with the poor distribution of gold-nanoparticles (GNPs) to the tumor mass. Here, for the first time, we examined the combined effect of collagenase (COL) with metformin (MET)-conjugated GNPs on mammosphere generated from JIMT-1 breast cell line in vitro. Main methods: Mammospheres (on days 7 and 14) and monolayer culture were treated with MET, MET-GNPs, and a mixture of COL-GNPs and MET-GNPs for 5 days. To assess the impacts of the engineered nanoparticles (NPs) on the survival/apoptosis of cancer cells and cancer stem cells (CSCs), the amount/activity of collagen and the expression of pyruvate kinase M2, different methods were applied, including MTT, flow cytometry, immunofluorescence, ELISA and real-time PCR analyses. Our results confirmed the enhanced cytotoxic effects of MET-GNPs combined with COL-GNPs on mammospheres compared to the cells treated with MET alone or MET-GNPs. Key findings: Upon treatment with the mixture of MET-GNPs and COL-GNPs, the population of the apoptotic cells was significantly increased. A marked reduction was found in the number of CD24−/CD44+ CSCs and the amount of collagen in the group received a mixture of MET-GNPs and COL-GNPs. Significance: Based on our findings, the use of COL can improve the cellular interaction/penetration of MET-GNPs in mammospheres and its antitumor impacts on the CSCs.