PP471 Exploring trastuzumab deruxtecan (DS-8201) resistance mechanisms through clinically relevant PDX models and implications for combination strategies with pembrolizumab

were employed to detect and quantify specific protein markers present in cell lysates.Flow Cytometry: Fixed cells were stained with binding dye and passed through a laser, emitted by fluorescence, and recorded by detectors.The portion of each phase is quantified by appropriate gates.Zebrafish Embryo Exposure: Zebrafish embryos were exposed to 4-Methylimidazole (4-MEI).Dorsal images of the treated zebrafish embryos were acquired, and quantitative analysis was performed to evaluate the concentration and distribution patterns of melanin pigmentation.Results: 4-MEI induces expression level of tyrosinase and MITF, a transcription factor of tyrosinase, in a dose-dependent manner by western blot analysis.Furthermore, we assess the melanin production with tyrosinase activity and melanin content assay to check the melanin synthesis.Furthermore, 4-MEI-exposed zebrafish are showing rising melanin production.These results indicate that 4-MEI induces melanin production in B16F10 mouse melanoma cells.Conclusions: 4-MEI induced accumulation of melanin and suppresses melanoma proliferation in B16F10 mouse cells and zebrafish.Thus, this study suggests that 4-MEI possesses therapeutic action on hypopigmentation.