Icariside I reduces breast cancer proliferation, apoptosis, invasion, and metastasis probably through inhibiting IL-6/STAT3 signaling pathway

Objectives: Breast Cancer is a common malignancy in women. More than 90% of breast Cancer deaths are caused by metastasis. Epimedii Folium (EF) is a commonly used herb with anti-tumor benefits, but its underlying mechanisms and active components for breast Cancer prevention are little understood. This study assessed the therapeutic role of Icariside I (ICS I) in Epimedium Flavonoids (EF) on lung metastasis of breast Cancer, including the underlying mechanism.

Methods: Western blot, RT-qPCR, wound healing assay, colony formation assay, and flow cytometry were used to investigate the inhibition of breast Cancer cells growth and migration by EF and ICS I through disrupting the IL-6/STAT3 pathway. Combined with 4T1 breast Cancer model in mice, Western blot, RT-qPCR, Hematoxylin and Eosin staining, immunohistochemistry were used to evaluate the therapeutic role of ICS I in proliferation, Apoptosis, invasion, and metastasis of breast Cancer.

Key findings: EF can inhibit STAT3 phosphorylation and reduce the colony formation and migration of breast Cancer cells. Detecting the active ingredients in EF, we found ICS I can reduce the activation of STAT3 in 4T1 breast Cancer cells, impair colony formation and migration. Moreover, ICS I induced cells G1 phase arrest and modulated Cyclin D1, CDK4, Bcl-2, and Bax to inhibit proliferation and survival of breast Cancer cells. Similarly, the in vivo studies demonstrated that ICS I significantly suppressed tumor development and lung metastasis in the 4T1 mouse model. Tumor cells in vehicle group were arranged in a spoke-like pattern with obvious heterogeneity, and multinucleated tumor giant cells were seen. But, the tumor cells in the ICS I group were disorganized and necrotic lysis was seen in some areas. In ICS I-treated group, tumors' STAT3 phosphorylation level, IL-6, Cyclin D1, CDK4, Bcl-2, and vimentin expression were downregulated, Bax and cleaved Caspase 3 expression were upregulated. In the lung tissue, we could find less metastasis of breast Cancer cells and less lung injury in the ICS I group. Besides, the expression of metastasis-related genes MMP9 and vimentin was decreased in the lung tissue of ICS I group.

Conclusions: These findings suggest that ICS I can inhibit breast Cancer proliferation, Apoptosis, invasion and metastasis probably via targeting IL-6/STAT3 pathway. Therefore, ICS I has the potential to become an innovative therapeutic candidate to breast Cancer prevention and treatment.