Narciclasine (Lycoricidinol), an isocarbostyril alkaloid narciclasine, targets STAT3 via distinct mechanisms in tamoxifen-resistant breast cancer cells. Narciclasine suppresses phosphorylation, activation, dimerization, and nuclear translocation of STAT3 by directly binding with the STAT3 SH2 domain and leads STAT3 degradation. Narciclasine is a plant growth modulator. Narciclasine modulates the Rho/Rho kinase/LIM kinase/cofilin signaling pathway, greatly increasing GTPase RhoA activity as well as inducing actin stress fiber formation in a RhoA-dependent manner.