A Novel Plant-Derived Choline Transporter-like Protein 1 Inhibitor, Amb544925, Induces Apoptotic Cell Death via the Ceramide/Survivin Pathway in Tongue Squamous Cell Carcinoma

SIMPLE SUMMARY: In many cancer cells, the choline uptake mechanism via the choline transporter-like protein 1 (CTL1) is involved in cell proliferation, and inhibiting its function is known to induce cell death by apoptosis. Therefore, CTL1 is attracting attention as a target molecule for cancer therapy. Here, we investigated the mechanism of the antitumor effect and metastasis inhibition of Amb544925, a novel CTL1 inhibitor discovered from plant-derived organic compounds in the tongue squamous cell carcinoma (TSCC) cell line, HSC-3. Amb544925 increased caspase-3/7 activity and caused apoptotic cell death. The antitumor effect of Amb544925 was brought about by suppressing the expression of survivin, an apoptosis inhibitor, through ceramide, an apoptosis-inducing factor (ceramide/survivin pathway). Furthermore, it was suggested that the inhibitory effect of Amb544925 on cell migration was also mediated by the ceramide/survivin pathway. Plant-derived Amb544925 is a lead compound in the treatment of TSCC that exerts antitumor effects via the ceramide/survivin pathway by targeting CTL1. ABSTRACT: Background: Despite recent advances in the early detection and treatment of TSCC patients, recurrence rates and survival rates have not improved. The high frequency of lymph node metastasis is one of the causes, and the drug development of new therapeutic mechanisms such as metastasis control is desired. Choline transporter-like protein 1 (CTL1) has attracted attention as a target molecule in cancer therapy. In this study, we examined the antitumor effects of Amb544925, a plant-derived CTL1 inhibitor. Methods: The TSCC cell line HSC-3 was used to measure [(3)H]choline uptake, cell survival, caspase activity, and cell migration. Xenograft model mice were prepared to verify the antitumor effect of Amb544925. Results: Amb544925 inhibited cell viability and increased caspase-3/7 activity at concentrations that inhibited choline uptake. Amb544925 and ceramide increased SMPD4 expression and suppressed surivivin expression. Furthermore, Amb544925 and ceramide inhibited the migration of HSC-3 cells. In the xenograft model mice, Amb544925 suppressed tumor growth and CTL1 mRNA expression. Conclusions: The plant-derived CTL1 inhibitor Amb544925 is a lead compound of a new anticancer agent exhibiting antitumor effects and inhibition of cell migration through the ceramide/survivin pathway.