Ethnopharmacological relevance: Zhuidu Formula (ZDF) is composed of triptolide, cinobufagin and paclitaxel, which are the active ingredients of Tripterygium wilfordii Hook. F, dried toad skin and Taxus wallichiana var. chinensis (Pilg) Florin, respectively. Modern pharmacological studies show that triptolide, cinobufagin, and paclitaxel are well-known natural compounds that exert anti-tumor effects by interfering with DNA synthesis, inducing tumor cell apoptosis, and inhibiting the dynamic balance of the tubulin. However, the mechanism by which the three compounds inhibit triple-negative breast cancer (TNBC) metastasis is unknown.
Objective: The objective of this investigation was to examine the inhibitory essences of ZDF on the metastasis of TNBC and elucidate its potential mechanism.
Materials and methods: Cell viability of triptolide (TPL), cinobufagin (CBF), and paclitaxel (PTX) on MDA-MB-231 cells was assessed employing a CCK-8 assay. The drug interactions of the three drugs on MDA-MB-231 cells were determined in vitro utilizing the Chou-Talalay method. MDA-MB-231 cells were identified for migration, invasion and adhesion in vitro through the implementation of the scratch assay, transwell assay and adhesion assay, respectively. The formation of cytoskeleton protein F-actin was detected by immunofluorescence assay. The expressions of MMP-2 and MMP-9 in the supernatant of the cells were determined by ELISA analysis. The Western blot and RT-qPCR were employed to explore the protein expressions associated with the dual signaling pathways of RhoA/ROCK and CDC42/MRCK. The anti-tumor efficacy of ZDF in vivo and its preliminary mechanism were investigated in the mouse 4T1 TNBC model.
Results: The results demonstrated that ZDF could significantly reduce the viability of the MDA-MB-231 cell, and the combination index (CI) values of actual compatibility experimental points were all less than 1, demonstrating a favorable synergistic compatibility relationship. It was found that ZDF reduces RhoA/ROCK and CDC42/MRCK dual signaling pathways, which are responsible for MDA-MB-231cell migration, invasion, and adhesion. Additionally, there has been a significant reduction in the manifestation of cytoskeleton-related proteins. Furthermore, the expression levels of RhoA, CDC42, ROCK2, and MRCKβ mRNA and protein were down-regulated. ZDF significantly decreased the protein expressions of vimentin, cytokeratin-8, Arp2 and N-WASP, and inhibited actin polymerization and actomyosin contraction. Furthermore, MMP-2 and MMP-9 levels in the high-dose ZDF group were decreased by 30% and 26%, respectively. ZDF significantly reduced the tumor volume and protein expressions of ROCK2 and MRCKβ in tumor tissues without eliciting any perceptible alterations in the physical mass of the mice, and the reduction was more pronounced than that of the BDP5290 treated group.
Conclusion: The current investigation demonstrates that ZDF exhibits a proficient inhibitory impact on TNBC metastasis by regulating cytoskeletal proteins through the dual signaling pathways of RhoA/ROCK and CDC42/MRCK. Furthermore, the findings indicate that ZDF has significant anti-tumorigenic and anti-metastatic characteristics in breast cancer animal models.
Keywords: CDC42/MRCK; Metastasis; RhoA/ROCK; TNBC; Zhuidu Formula.
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