Autophagy stimulation influenced the angiogenesis and metastasis behavior of human triple-negative breast cancer cells.

INTRODUCTION: Breast cancer (BC) is a devastating condition with high morbidity and mortality rates in females. Autophagy is an early-stage cell response against stressful conditions. Emerging data have revealed the autophagy-angiogenesis interaction in terms of tumor development and metastasis. METHODS: Here, the angiogenesis behavior of human MDA-MB-231 cells was monitored after modulation of autophagy response in the presence of free 3-methyladenine (3-MA), metformin (Met), or drug-loaded exosomes (3-MA@Exos and Met@Exos). Orthotopic transplantation was done using human BC cell-laden alginate/gelatin (Alg/Gel) microspheres in mice after treatment with Met and/or 3-MA. RESULTS: Met, and/or Met@Exos increased the cell migration rate and promoted human endothelial cell migration compared to the control cells (P<0.05). However, these features were blunted in 3-MA and 3-MA@Exos groups (P<0.05). Flow cytometry analysis revealed that the drug loading into Exos did not influence internalization capacity or cell survival (P>0.05). ELISA revealed that vascular endothelial growth factor (VEGF) levels were reduced in Met and 3-MA-treated cells, with more pronounced reductions in the free 3-MA groups. Real-time PCR analysis showed diminished expression of several angiogenesis-related genes, except for platelet endothelial cell adhesion molecule-1 (PECAM-1) in the Met@Exos, 3-MA, and 3-MA@Exos groups. Met treatment increased the metastasis and tumor formation in mice mammary glands after orthotopic transplantation of BC tumoroids. CONCLUSION: These data indicate that autophagy modulation can alter the angiogenesis and metastatic behavior of human BC cells in vitro and in vivo. Exos are valid bio-shuttles for the delivery of autophagy modulators in CSC-targeted therapies.