Abstract
Background:
The high mortality rate associated with epithelial ovarian cancer (EOC) is primarily due to recurrence and chemoresistance, underscoring the urgent need for innovative therapeutic approaches that leverage newly identified vulnerabilities in cancer cells. While conventional chemotherapies induce apoptosis by targeting DNA or mitotic machinery, ferroptosis represents a new distinct form of programmed cell death characterised by the accumulation of lipid peroxides.
Methods:
The sensitivity of different EOC cell lines to ferroptosis inducers was evaluated using cell viability assays and lipid peroxidation measurements. Live-cell imaging with the pH-sensitive CD63-pHuji reporter was performed to track the extracellular export of acyl-CoA synthetase long-chain family member 4 (ACSL4) via exosomes. The upstream regulator of ACSL4 were identified through immunoprecipitation-mass spectrometry (IP-MS) and validated using protein binding assays. Finally, cell-derived xenograft (CDX) and patient-derived xenograft (PDX) models were utilised to evaluate the therapeutic potential overcoming ferroptosis resistance.
Findings:
In this study, we found that interferon (IFN)-γ combined with arachidonic acid (AA), which are endogenous ferroptosis inducers, could initiate ferroptosis in most EOC cells. However, some EOC cells displayed significant resistance. Contrary to the typical increase in ACSL4 protein observed in ferroptosis-sensitive cells, resistant EOC cells exhibited surprisingly low levels of this pro-ferroptotic lipid metabolic protein. Intriguingly, this reduction is attributed to the exosomal expulsion of ACSL4 protein, revealing a distinct cellular mechanism to evade ferroptosis. We further identified VIPAS39 as a pivotal regulator in sorting ACSL4 into late endosomes, thereby facilitating their subsequent release as exosomes. Notably, targeting VIPAS39 not only overcomes the resistance to ferroptotic cell death but also markedly suppresses tumour growth.
Interpretation:
Our findings uncover the crucial role of VIPAS39 in ferroptosis evasion by facilitating the exporting of ACSL4 protein via exosomes, highlighting VIPAS39 as a promising target for ferroptosis-based anti-cancer therapy.
Funding:
Funded by Beijing Municipal Natural Science Foundation (Key program Z220011), National Natural Science Foundation of China (NSFC) (T2225006, T2488301, 82272948), Peking University Medicine Youth Science and Technology Innovation 'Sail Plan' Project Type B Medical Interdisciplinary Seed Fund (71006Y3171), GuangDong Basic and Applied Basic Research Foundation (2021A1515110820), and the special fund of the National Clinical Key Speciality Construction Program, P. R. China (2023).
Keywords:
ACSL4; Epithelial ovarian cancer; Exosome; Ferroptosis; VIPAS39.