Abstract 1819: Esculetin modulates SLC31A1 and ATP7B to influence copper homeostasis and trigger cell death in colorectal cancer
Authors: Guo Fangyue , Liu Mengying , Zhu Kaihe , Ru Jiapeng , Li Pei , Zhang Shanfeng 
Published: March 2024

Abstract
Background: Esculetin is a naturally occurring dihydroxycoumarin with anti-inflammatory, antioxidant, and anti-tumor activities. Copper ion transport proteins, notably SLC31A1 and ATP7B, are essential in maintaining intracellular copper homeostasis, averting disruptions that might lead to copper-induced cell death under normal physiological conditions. However, prior research has not explored Esculetin's role in inducing copper-induced cell death. Hence, this study aims to investigate the biological process of Esculetin-induced cell death and the molecular mechanism underlying dysregulation of intracellular copper ion homeostasis.
Methods: Initially, the CCK-8 assay was used to determine the IC50 values of Esculetin on colorectal cancer cell lines (HCT116, HT29, SW480) and normal colonic epithelial cell lines (NCM460). In terms of biological behaviors, the effects of Esculetin on the proliferation of colorectal cancer cell lines were assessed using CCK-8, colony formation assay, and EdU staining. Flow cytometry was used to examine the impact of Esculetin on apoptosis and cell cycle distribution in colorectal cancer cells. A subcutaneous xenograft tumor model in nude mice was employed to evaluate the in vivo anti-tumor effects of Esculetin, while IHC staining was conducted to detect Ki-67 levels, and Western blotting was performed to assess EMT-related protein expression. To investigate copper ion homeostasis, qPCR was used to measure the expression levels of copper ion transporters SLC31A1 and ATP7B before and after Esculetin treatment.
Results: The CCK-8 results revealed that the IC50 of Esculetin for normal colonic epithelial cell lines was significantly higher than that for colorectal cancer cell lines. Meanwhile, a notable inhibitory effect of Esculetin on the proliferation of colorectal cancer cells was observed. Additionally, Esculetin treatment suppressed colony formation and reduced the proportion of EdU-positive cells in colorectal cancer cells. Flow cytometry demonstrated an increase in apoptosis and S-phase arrest following Esculetin treatment. The subcutaneous xenograft tumor model showed significant inhibition of tumor growth by Esculetin, as evidenced by reduced Ki-67-positive cells in the Esculetin-treated group. Western blot analysis revealed a significant decrease in the expression levels of Vimentin and N-Cadherin and an increase in E-Cadherin expression. Furthermore, qPCR analysis post-Esculetin treatment showed an elevation in the inward copper transporter SLC31A1 levels, while the outward transporter ATP7B expression decreased.
Conclusion: Esculetin induces dysregulation of intracellular copper ion homeostasis by upregulating SLC31A1 expression and downregulating ATP7B expression, leading to intracellular copper accumulation and subsequent disruption of copper homeostasis, thereby inducing copper-induced cell death.
Citation Format: Fangyue Guo, Mengying Liu, Kaihe Zhu, Jiapeng Ru, Pei Li, Shanfeng Zhang. Esculetin modulates SLC31A1 and ATP7B to influence copper homeostasis and trigger cell death in colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1819.