ObjectiveTo investigate the potential mechanism of Huatan Sanjie Formula （化痰散结方， HSF） in the treatment of triple negative breast cancer （TNBC） based on the integrinβ1/focal adhesion kinase/yes-associated protein （integrinβ1/FAK/YAP） mechanotransduction signaling pathway. MethodsFifty BALB/c mice were randomly assigned to a model group， doxorubicin group， low-， medium-， and high-dose HSF groups， with 10 mice per group. An orthotopic TNBC transplantation model was established in all mice using syngeneic implantation of 4T1 cells. After successful modeling， mice in the model group received intragastric administration of normal saline 0.2 ml each day. Mice in the low-， medium-， and high-dose HSF groups received HSF by gavage at doses of 5.99， 11.97， and 23.94 g/（kg·d）， respectively. The doxorubicin group received intraperitoneal injections of doxorubicin （1.5 mg/kg） once every two days. All treatments lasted for 30 days. After the final administration， mice were sacrificed， and tumor weight and volume were measured. Hematoxylin-eosin （HE）， Masson's trichrome， and Sirius Red staining were performed to evaluate histopathological changes and collagen fiber deposition in tumor tissues. TUNEL staining was used to assess apoptosis. The Young's modulus of tumor tissues was measured using atomic force microscopy （AFM）. The nuclear-cytoplasmic localization of YAP was determined by immunofluorescence staining. Protein expression levels of integrinβ1， focal adhesion kinase （FAK）， YAP， and phosphorylated focal adhesion kinase （p-FAK） were detected by Western Blotting. The mRNA expression levels of integrinβ1， FAK， and YAP were assessed by quantitative real-time polymerase chain reaction （qRT-PCR）. Pearson correlation analysis was performed to evaluate the relationships among tumor tissue Young's modulus， apoptosis rate， and the expression levels of proteins related to the integrinβ1/FAK/YAP signaling pathway. ResultsCompared to the model group， tumor weight was significantly reduced in the doxorubicin group and the medium- and high-dose HSF groups， while tumor volume significantly decreased in the doxorubicin group and the high-dose HSF group （P＜0.01）. Tumor weight in the high-dose HSF group was significantly lower than that in the low-dose group， and tumor volume was significantly smaller than that in both the low- and medium-dose groups （P＜0.05）. Marked improvements in histopathological morphology were observed in the medium- and high-dose HSF groups and the doxorubicin group， while the proportion of collagen fiber deposition and the nuclear-to-cytoplasmic ratio of YAP were significantly reduced （P＜0.01）. Compared to the model group， all three HSF groups and the doxorubicin group exhibited significantly increased apoptosis rates， decreased Young's modulus， and reduced mRNA expression levels of integrinβ1， and YAP （P＜0.05 or P＜0.01）. Furthermore， protein expression levels of integrinβ1， p-FAK， and YAP in the high-dose HSF group were significantly lower than those in the model group （P＜0.05 or P＜0.01）. Pearson correlation analysis demonstrated a significant negative correlation between tumor tissue Young's modulus and apoptosis rate （r =-0.93， P＜0.01）. In contrast， the protein expression levels of integrinβ1， p-FAK， and YAP were positively correlated with Young's modulus （r=0.88， 0.97， and 0.98， respectively； P＜0.05） and negatively correlated with apoptosis rate （r=-0.93，-0.97， and -0.93， respectively； P＜0.05）. ConclusionHSF can significantly inhibit tumor growth in TNBC model mice. Its antitumor effect may be associated with reducing tumor tissue stiffness through suppression of the integrinβ1/FAK/YAP mechanotransduction signaling pathway.