MUC1 is responsible for the pro-metastatic potential of calycosin in pancreatic ductal adenocarcinoma(PDAC)

Introduction: Pancreatic ductal adenocarcinoma (PDAC) is the prominent type of pancreatic cancer. We have recently unveiled that the growth-inhibitory anti-tumor adjuvant calycosin concurrently possesses pro-metastatic potential in PDAC development by regulating TGF-β, which plays dual roles as both tumor suppressor and tumor promoter. Hence, we are interested to explore if we could attenuate the pro-tumorigenic property of the drug in treating PDAC. Through network pharmacology, MUC1 had been identified as a common drug target of herbal Astragalus constituents (including calycosin) in PDAC. In this study, we attempted to determine if modulation of MUC1 could switch off the pro-metastatic potential of calycosin while maintaining its anti-cancer activity.

Material and Methods: Following MUC1 siRNA gene silencing or using its pharmacological inhibitor GO201, the drug actions of calycosin on the growth, migratory activity, metabolic regulation in PDAC cells were re-evaluated in both 2D and 3D cell culture systems by qRT-PCR, Western immunoblotting, wound healing assay and flow cytometry.

Results and Discussions: Based on network pharmacology findings, 20 common gene targets had been collected, among these MUC1 was confirmed as the most relevant and potential gene target between Astragalus constituents and PDAC. Calycosin upregulated the expression of MUC1 together with TGF-β in MIA-PaCa2 PDAC cells. Genetic knockdown but not pharmacological inhibition of MUC1 provoked calycosin to inhibit MIA-PaCa2 cell migration via downregulation of the epithelial-mesenchymal transition biomarker Snail. In addition, the apoptosis was promoted by calycosin in MIA-PaCa2 cells with the regulation of the autophagy-related proteins Atg5 and Beclin1. MUC1 gene suppression also facilitated calycosin to induce a G1-phase cell cycle arrest. Nonetheless, calycosin also promoted the metabolic regulation in PDAC under MUC1 gene silencing through the AMPK-Sirt1-FGF21 signaling pathway.

Conclusion: MUC1 gene suppression could switch off the migratory and pro-metastatic properties of calycosin, while retaining its growth-inhibitory potential by inducing apoptosis and cell cycle arrest, as well as facilitating autophagy and metabolic regulation. The mode of action mainly involves downregulation of TGF-β and acts via a AMPK-Sirt1-FGF21 pathway.