Cyano Enone-Bearing Triterpenoid Soloxolone Methyl Inhibits Epithelial-Mesenchymal Transition of Human Lung Adenocarcinoma Cells In Vitro and Metastasis of Murine Melanoma In Vivo

Abstract

Introduction of α-cyano α,β-unsaturated carbonyl moiety into natural cyclic compounds markedly improves their bioactivities, including inhibitory potential against tumor growth and metastasis. Previously, we showed that cyano enone-bearing derivatives of 18βH-glycyrrhetinic (GA) and deoxycholic acids displayed marked cytotoxicity in different tumor cell lines. Moreover, GA derivative soloxolone methyl (SM) was found to induce ER stress and apoptosis in tumor cells in vitro and inhibit growth of carcinoma Krebs-2 in vivo. In this work, we studied the effects of these compounds used in non-toxic dosage on the processes associated with metastatic potential of tumor cells. Performed screening revealed SM as a hit compound, which inhibits motility of murine melanoma B16 and human lung adenocarcinoma A549 cells and significantly suppresses colony formation of A549 cells. Further study showed that SM effectively blocked transforming growth factor β (TGF-β)-induced epithelial-mesenchymal transition (EMT) of A549 cells: namely, inhibited TGF-β-stimulated motility and invasion of tumor cells as well as loss of their epithelial characteristics, such as, an acquisition of spindle-like phenotype, up- and down-regulation of mesenchymal (vimentin, fibronectin) and epithelial (E-cadherin, zona occludens-1 (ZO-1)) markers, respectively. Network pharmacology analysis with subsequent verification by molecular modeling revealed that matrix metalloproteinases MMP-2/-9 and c-Jun N-terminal protein kinase 1 (JNK1) can be considered as hypothetical primary targets of SM, mediating its marked anti-EMT activity. The inhibitory effect of SM on EMT revealed in vitro was further confirmed in a metastatic model of murine B16 melanoma: SM was found to effectively block metastatic dissemination of melanoma B16 cells in vivo, increase expression of E-cadherin and suppress expression of MMP-9 in lung metastatic foci. Altogether, our data provided valuable information for a better understanding of the antitumor activity of cyano enone-bearing semisynthetic compounds and revealed SM as a promising anti-metastatic drug candidate.

Novel A-Ring Chalcone Derivatives of Oleanolic and Ursolic Amides with Anti-Proliferative Effect Mediated through ROS-Triggered Apoptosis

“…Similar chemical modifications have been conducted to other triterpene cores to improve their potency and overcome the drawbacks. For example, glycyrrhetinic acid has been used for the synthesis of CDDO analogs (soloxolones), which significantly improved cytotoxicity [ 11 , 12 , 13 ], and recently the effective inhibition by methyl soloxolone TGF-β-driven EMT of tumor cells was shown [ 14 ]. The same ursane-type analogs were obtained by an oxidative ozonolysis-mediated C-ring enone formation with a potency of approximately five-fold less than the corresponding oleanolic acid derivatives [ 15 ].…”

Novel Epoxides of Soloxolone Methyl: An Effect of the Formation of Oxirane Ring and Stereoisomerism on Cytotoxic Profile, Anti-Metastatic and Anti-Inflammatory Activities In Vitro and In Vivo

“…It is known that pentacyclic triterpenoids, including SM and its analogs, not only induce the death of tumor cells but also significantly suppress their pro-metastatic phenotype [ 17 , 51 ]. To explore this possibility, the effect of novel epoxides of SM on the clonogenicity, motility and adhesiveness of B16 melanoma cells was evaluated.…”

“…Previously, our research group reported that a semisynthetic derivative of 18βH-glycyrrhetinic acid (18βH-GA), soloxolone methyl (methyl-2-cyano-3,12-dioxo-18βH-olean-9(11),1(2)-dien-30-oate; SM ), obtained by direct modification of the A- and C-rings of 18βH-GA, effectively inhibits tumor cell growth in vitro [ 15 ] and in vivo [ 16 ], impedes their epithelial-mesenchymal transition [ 17 ], and significantly suppresses B16 melanoma cell metastasis in a murine model [ 17 ]. Along with pronounced antitumor potential, SM displays anti-inflammatory activity, inhibiting macrophage functionality in vitro [ 18 ] and inflammatory processes in a range of murine models, including phlogogen-induced paw edema [ 16 ] and peritonitis [ 18 ], influenza A-induced pneumonia [ 19 ] and lipopolysaccharide-driven acute lung injury [ 20 ].…”

Novel Soloxolone Amides as Potent Anti-Glioblastoma Candidates: Design, Synthesis, In Silico Analysis and Biological Activities In Vitro and In Vivo

“…Previously, our group synthesized and characterized soloxolone methyl (SM), a first-generation cyano enone-bearing derivative of 18βH-glycyrrhetinic acid [ 29 ]—a structural isomer of bardoxolone methyl at the ester location ( Figure 1 ). We found that SM induced tumor cell death via mitochondrial apoptosis [ 30 ] and endoplasmic reticulum stress [ 31 , 32 ], markedly suppressed the epithelial–mesenchymal transition of tumor cells [ 33 ] and effectively inhibited the growth of murine Krebs-2 carcinoma [ 30 ] and metastasis of murine B16 melanoma [ 33 ] in vivo.…”