Glycyrrhizin ameliorates melanoma cell extravasation into mouse lungs by regulating signal transduction through HMGB1 and its receptors

Metastasis, which accounts for the majority of all cancer-related deaths, occurs through several steps, namely, local invasion, intravasation, transport, extravasation, and colonization. Glycyrrhizin has been reported to inhibit pulmonary metastasis in mice inoculated with B16 melanoma. This study aimed to identify the mechanism through which glycyrrhizin ameliorates the extravasation of melanoma cells into mouse lungs. Following B16 melanoma cell injection, mice were orally administered glycyrrhizin once every two days over 2 weeks; lung samples were then obtained and analyzed. Blood samples were collected on the final day, and cytokine plasma levels were determined. We found that glycyrrhizin ameliorated the extravasation of melanoma cells into the lungs and suppressed the plasma levels of interleukin-6, tumor necrosis factor-α, and transforming growth factor-β. Furthermore, glycyrrhizin ameliorated the lung tissue expression of high mobility group box-1 protein (HMGB1), receptor for advanced glycation end products (RAGE), Toll-like receptor (TLR)-4, RAS, extracellular signal-related kinase, NF-κB, myeloid differentiation primary response 88, IκB kinase complex, epithelial-mesenchymal transition markers, and vascular endothelial growth factor-A. Our study demonstrates that glycyrrhizin ameliorates melanoma metastasis by regulating the HMGB1/RAGE and HMGB1/TLR-4 signal transduction pathways.