ObjectiveTo explore the mechanism by which Ruyan Neixiao cream （RUC） induces ferroptosis in breast precancerous lesion （BPL） cells， and to enrich the theoretical foundation for its use in the treatment of BPL. MethodsThe inhibition of cell proliferation by 1%， 2%， and 4% concentrations of Ruyanneixiao Cream transdermal solution （RUT） was assessed using cell counting kit-8 （CCK-8） and a colony formation assay. Reactive oxygen species （ROS） were measured using the DCFH-DA probe， and the levels of ferrous ions （Fe²⁺）， glutathione （GSH）， and malondialdehyde （MDA） were determined using appropriate kits. Lipid peroxidation was detected with the C11-BODIPY^581/591 fluorescent probe. The expression of nuclear factor E₂-related factor 2 （Nrf2）， solute carrier family 7 member 11 （SLC7A11）， and glutathione peroxidase 4 （GPX4） proteins was analyzed by Western blot. The BPL rat model was constructed using 2，2′-bis（hydroxymethyl）butyric acid （DMBA） combined with estrogen and progesterone， and the rats were treated with RUC for external application. After the 12^th cycle， the rats were euthanized， and histopathological changes in breast tissue were observed by hematoxylin-eosin （HE） staining. Fe²⁺ and MDA levels in breast tissue were measured using corresponding kits. The expression of Nrf2， SLC7A11， and GPX4 proteins in BPL rat breast tissue was detected by immunohistochemistry （IHC） and Western blot. ResultsCompared with the matrix group， the cell viability of MCF-10AT cells in the 1%， 2%， and 4% RUT groups was significantly reduced （P<0.05） in a concentration-dependent manner， with the 24-hour half inhibitory concentration （IC₅₀） being 2.23%. Compared with the 4% RUT group， cell viability in the RUT + Fer-1 group was significantly increased （P<0.05）. Compared with the matrix group， the colony formation rates of MCF-10AT cells in the 1%， 2%， and 4% RUT groups were significantly decreased （P<0.05）. Compared with the 4% RUT group， the cell colony formation rate of the RUT + Fer-1 group was significantly increased （P<0.05）. Compared with the matrix group， the levels of ROS and Fe²⁺ in the 1%， 2%， and 4% RUT groups were significantly increased （P<0.05）， while GSH levels were significantly decreased （P<0.05）， and MDA and lipid peroxidation levels were significantly increased （P<0.05）. Compared with the 4% RUT group， ROS and Fe²⁺ levels in the RUT + Fer-1 group were significantly reduced （P<0.05）， while GSH levels were significantly increased （P<0.05）， and MDA and lipid peroxidation levels were significantly reduced （P<0.05）. Compared with the matrix group， the protein expression levels of Nrf2， SLC7A11， and GPX4 in the 1%， 2%， and 4% RUT groups were significantly decreased （P<0.05）. Compared with the 4% RUT group， the protein expression levels of Nrf2， SLC7A11， and GPX4 in the RUT + Fer-1 group were significantly increased （P<0.05）. In the in vivo experiment， compared with the matrix group， the breast tissue histopathological status of the BPL rats in the RUC group was effectively improved， with less dilatation of the mammary ducts and more orderly duct arrangement. No pathological morphology indicative of invasive cancer was observed. Compared with the matrix group， Fe²⁺ and MDA levels in the mammary tissue of the RUC group were significantly increased （P<0.05）. Compared with the matrix group， the protein expression levels of Nrf2， SLC7A11， and GPX4 in the mammary tissue of the RUC group were significantly reduced （P<0.05）. ConclusionRUC may induce ferroptosis in BPL cells by inhibiting the Nrf2/SLC7A11/GPX4 signaling pathway， increasing Fe²⁺ accumulation， and promoting lipid peroxidation.

ObjectiveTo explore the mechanism by which Ruyan Neixiao cream （RUC） induces ferroptosis in breast precancerous lesion （BPL） cells， and to enrich the theoretical foundation for its use in the treatment of BPL. MethodsThe inhibition of cell proliferation by 1%， 2%， and 4% concentrations of Ruyanneixiao Cream transdermal solution （RUT） was assessed using cell counting kit-8 （CCK-8） and a colony formation assay. Reactive oxygen species （ROS） were measured using the DCFH-DA probe， and the levels of ferrous ions （Fe²⁺）， glutathione （GSH）， and malondialdehyde （MDA） were determined using appropriate kits. Lipid peroxidation was detected with the C11-BODIPY^581/591 fluorescent probe. The expression of nuclear factor E₂-related factor 2 （Nrf2）， solute carrier family 7 member 11 （SLC7A11）， and glutathione peroxidase 4 （GPX4） proteins was analyzed by Western blot. The BPL rat model was constructed using 2，2′-bis（hydroxymethyl）butyric acid （DMBA） combined with estrogen and progesterone， and the rats were treated with RUC for external application. After the 12^th cycle， the rats were euthanized， and histopathological changes in breast tissue were observed by hematoxylin-eosin （HE） staining. Fe²⁺ and MDA levels in breast tissue were measured using corresponding kits. The expression of Nrf2， SLC7A11， and GPX4 proteins in BPL rat breast tissue was detected by immunohistochemistry （IHC） and Western blot. ResultsCompared with the matrix group， the cell viability of MCF-10AT cells in the 1%， 2%， and 4% RUT groups was significantly reduced （P<0.05） in a concentration-dependent manner， with the 24-hour half inhibitory concentration （IC₅₀） being 2.23%. Compared with the 4% RUT group， cell viability in the RUT + Fer-1 group was significantly increased （P<0.05）. Compared with the matrix group， the colony formation rates of MCF-10AT cells in the 1%， 2%， and 4% RUT groups were significantly decreased （P<0.05）. Compared with the 4% RUT group， the cell colony formation rate of the RUT + Fer-1 group was significantly increased （P<0.05）. Compared with the matrix group， the levels of ROS and Fe²⁺ in the 1%， 2%， and 4% RUT groups were significantly increased （P<0.05）， while GSH levels were significantly decreased （P<0.05）， and MDA and lipid peroxidation levels were significantly increased （P<0.05）. Compared with the 4% RUT group， ROS and Fe²⁺ levels in the RUT + Fer-1 group were significantly reduced （P<0.05）， while GSH levels were significantly increased （P<0.05）， and MDA and lipid peroxidation levels were significantly reduced （P<0.05）. Compared with the matrix group， the protein expression levels of Nrf2， SLC7A11， and GPX4 in the 1%， 2%， and 4% RUT groups were significantly decreased （P<0.05）. Compared with the 4% RUT group， the protein expression levels of Nrf2， SLC7A11， and GPX4 in the RUT + Fer-1 group were significantly increased （P<0.05）. In the in vivo experiment， compared with the matrix group， the breast tissue histopathological status of the BPL rats in the RUC group was effectively improved， with less dilatation of the mammary ducts and more orderly duct arrangement. No pathological morphology indicative of invasive cancer was observed. Compared with the matrix group， Fe²⁺ and MDA levels in the mammary tissue of the RUC group were significantly increased （P<0.05）. Compared with the matrix group， the protein expression levels of Nrf2， SLC7A11， and GPX4 in the mammary tissue of the RUC group were significantly reduced （P<0.05）. ConclusionRUC may induce ferroptosis in BPL cells by inhibiting the Nrf2/SLC7A11/GPX4 signaling pathway， increasing Fe²⁺ accumulation， and promoting lipid peroxidation.