Indirubin suppresses 4T1 murine breast cancer in vitro and in vivo by induction of ferroptosis and up-regulation of Ptgs2

Background Indirubin, isolated from Indigo Naturals, is reported to have the inhibitory activity of MCF-7 human breast cancer cells in vitro. However, studies on its anti-breast cancer activity in vivo and underlying mechanism are insufficient. We explored whether indirubin could trigger ferroptosis of breast cancer cells to exert anti-tumor activity. Methods Bioinformatical analysis was performed to detected the expression of prostaglandin-endoperoxide synthase 2 (Ptgs2) in breast cancer tissues Ptgs2-related prognosis for patients with breast cancer. Growth of 4T1 cells was assessed using wound healing assay and MTT assay. The levels of 4-HNE, GPX4, PTGS2 and GSK-3β proteins were detected by Western blot, and the mRNA of Ptgs2 was tested by qPCR. The GSH and MDA were determined by commercial kits. Molecular docking was employed to study interaction between indirubin and GSK-3β. An 4T1 murine breast cancer was adopted to evaluate the in vivo antitumor activity of indirubin. Results Indirubin promoted ferroptosis of 4T1 breast cancer cells with deplete of GSH, increased MDA and 4-HNE level, as well as decreased GPX4 expression. Indirubin suppressed the growth of 4T1 breast tumor in vivo. Mechanism study showed indirubin up regulated Ptgs2 expression by promoting phosphorylation (Ser 9) of GSK-3β. Conclusions Indirubin suppresses 4T1 murine breast cancer in vitro and in vivo by induction of ferroptosis and up-regulation of Ptgs2.