SLC38A5 suppresses ferroptosis through glutamine-mediated activation of the PI3K/AKT/mTOR signaling in osteosarcoma

Huang et al. Journal of Translational Medicine https://doi.org/10.1186/s12967-024-05803-6 (2024) 22:1004 Journal of Translational Medicine Open Access RESEARCH SLC38A5 suppresses ferroptosis through glutamine-mediated activation of the PI3K/ AKT/mTOR signaling in osteosarcoma Xinghan Huang1†, Kezhou Xia1†, Zhun Wei1†, Wenda Liu1, Zicheng Wei1 and Weichun Guo1* Abstract Background Solute carrier family 38 member 5 (SLC38A5) is an amino acid transporter that plays a significant role in various cellular biological processes and may be involved in regulating the progression of tumors However, its function and underlying mechanism in osteosarcoma remain unexplored. Methods Utilizing various database analyses and experiments, we have explored the dysregulation of SLC38A5 in osteosarcoma and its prognostic value. A series of in vitro functional experiments, including CCK-8, colony formation, wound healing, and transwell invasion assays, were conducted to evaluate the effects of SLC38A5 on the proliferation, migration, and invasion of osteosarcoma cells. Downstream pathways of SLC38A5 were explored through methods such as western blot and metabolic assays, followed by a series of validations. Finally, we constructed a subcutaneous xenograft tumor model in nude mice to explore SLC38A5 function in vivo. Results SLC38A5 is upregulated in osteosarcoma and is associated with poor prognosis in patients. Upregulation of SLC38A5 promotes proliferation, migration, and invasion of osteosarcoma cells, while the PI3K inhibitor BKM120 can counteract these effects. Additionally, silencing of SLC38A5 inhibits tumor growth in vivo. Mechanistically, SLC38A5 mediates the activation of the PI3K/AKT/mTOR signaling pathway by transporting glutamine, which subsequently enhances the SREBP1/SCD-1 signaling pathway, thereby suppressing ferroptosis in osteosarcoma cells. Conclusion SLC38A5 promotes osteosarcoma cell proliferation, migration, and invasion via the glutamine-mediated PI3K/AKT/mTOR signaling pathway and inhibits ferroptosis. Targeting SLC38A5 and the PI3K/AKT signaling axis may provide a meaningful therapeutic strategy for the future treatment of osteosarcoma. † Xinghan Huang, Kezhou Xia and Zhun Wei authors have contributed equally to this work and share the first authorship. *Correspondence: Weichun Guo Full list of author information is available at the end of the article © The Author(s) 2024. Open Access This article is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License, which permits any non-commercial use, sharing, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if you modified the licensed material. You do not have permission under this licence to share adapted material derived from this article or parts of it. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creati vecommons.org/licenses/by-nc-nd/4.0/. Huang et al. Journal of Translational Medicine (2024) 22:1004 Page 2 of 18 Graphical abstracts Keywords Osteosarcoma, SLC38A5, PI3K/AKT/mTOR pathway, glutamine, ferroptosis Introduction Osteosarcoma is a bone tumor that originates from the malignant proliferation of mesenchymal cells that produce bone-like stroma [1]. It is the most common primary bone malignant tumor, which occurs in adolescents or children with rapid bone growth and development. According to epidemiological statistics, the combined incidence of osteosarcoma is 1 ~ 3 cases annually per million [2]. Although rare, osteosarcoma is one of the leading causes of cancer-related deaths in adolescents [3]. Surgery combined with neoadjuvant chemotherapy (preoperative and postoperative chemotherapy; doxorubicin and cisplatin with or without methotrexate) is for now the standard of care for patients with osteosarcoma, which has greatly improved the prognosis for patients with primary osteosarcoma, with 5-year survival rates increasing to 70% [4]. Nevertheless, the prognosis remains poor for patients who relapse or suffer metastases, with 5-year survival rates still below 20% [5]. Therefore, exploring the specific mechanisms of osteosarcoma development and screening for new therapeutic targets are of great significance to the diagnosis and treatment of osteosarcoma. Glutamine is the most abundant non-essential amino acid in the body and the most abundant circulating amino acid, which is a key carbon and nitrogen donor and energy source for the body [6]. It was shown that tumor cells take up large amounts of glutamine for their own biosynthesis, growth and proliferation, regulation of signaling pathways and maintenance of redox homeostasis; consequently, upregulation of glutamine transporter proteins on the cell membrane is required [7, 8]. Solute carrier (SLC) transporters are a family of more than 300 membrane-bound proteins that facilitate the transport of a wide range of substrates across biological membranes and play an essential role in cellular uptake of nutrients [9]. Solute carrier family 38 member 5 (SLC38A5), also known as sodium-coupled neutral amino acid transporter 5 (SNAT5), was functionally identified as the amino acid transport system N, which selectively transports amino acids such as glutamine, aspartic acid and histidine across cell membranes [10]. Moreover, since the function of system N transporters is associated with H flux with a significant impact on intracellular pH, the role of SLC38A5 for glutamine transport is more applicable to tumor cells [11]. Conjecturally, it may be advantageous for tumor cells to up-regulate SLC38A5. In recent years, more attention was paid to the functions of SLC38A5 in malignant tumors. For example, SLC38A5 was reported be a tumor promoter in pancreatic cancer, and its Huang et al. Journal of Translational Medicine (2024) 22:1004 overexpression leads to poor overall survival in patients with pancreatic cancer [12]. Furthermore, in breast cancer, upregulation of SLC38A5 induces cell proliferation by inducing micropinocytosis [13]. In another report, SLC38A5 promotes tumor growth by inhibiting cisplatin chemosensitivity in breast cancer cells [14]. These studies suggest that SLC38A5 may play an essential role in various tumors; however, the specific functional role of SLC38A5 in osteosarcoma and its underlying mechanism remain unclear. In this study, we aimed to determine the role of SLC38A5 in osteosarcoma based on its importance as an amino acid transporter in tum (...truncated)