Abstract A076 Inhibiting iron-sulfur cluster export activates ferroptosis and potentiates cisplatin response in pediatric group 3 medulloblastomas
Authors: Mahapatra Sidharth , Kanchan Ranjana K. , Doss David , Alsafwani Zahraa W. , Khan Parvez , Nasser Mohd W. , Batra Surinder K. 
Published: September 2024

Abstract
Background: Medulloblastoma (MB) is the most common malignant pediatric brain tumor, with group 3 tumors (G3MB) being the most aggressive. Uniquely, their aggressiveness is inversely related to the activation of ferroptosis, a form of programmed cell death mediated by iron overload that attenuates tumor growth. The low ferroptosis activation in G3MBs is associated with significantly higher mortality. Intracellularly, G3MBs activate iron-sulfur (Fe-S) cluster export and upregulate the expression of glutathione peroxidase 4 (GPX4), the central regulator of ferroptosis. Our main objective was to investigate whether ferroptosis evasion was a targetable driver of aggressiveness in G3MBs that can be inhibited to potentiate classical chemotherapy. We hypothesized that inhibiting Fe-S cluster export by targeting ABCB7, the principal mitochondrial Fe-S exporter, would induce iron overload, trigger ferroptosis, and ultimately potentiate cisplatin cytotoxicity in G3MBs. Methods: We repressed ABCB7 expression (si-/sh-/KO) in classic G3MB cell lines (HDMB03 and D425) and studied its impact on cancer cell stemness, ferroptosis activation, mitochondrial function, and cisplatin cytotoxicity. We further investigated the impact of artesunate, an FDA-approved anti-malarial agent capable of inducing iron overload and inhibiting ABCB7, on cisplatin action and tumor burden. To rescue cells from iron overload and ferroptosis, we used deferoxamine and ferrostatin-1, respectively. Results: Silencing ABCB7 resulted in cytoplasmic and mitochondrial iron overload, oxidative stress, and lipid ROS, culminating in ferroptosis and growth retardation. Seahorse studies revealed a switch from oxidative phosphorylation to glycolysis, and TMRM staining revealed loss of mitochondrial membrane potential in ABCB7-silenced cells. Notably, silencing ABCB7 abrogated GPX4 expression and reduced GSH levels. Moreover, ABCB7 silencing reduced the IC50 of cisplatin 2-fold, and ABCB7-silenced cells treated with cisplatin experienced a heightened index of ferroptosis. In vivo, silencing ABCB7 resulted in smaller tumors, dramatically prolonged survival, and potentiated cisplatin action. Artesunate recapitulated ABCB7 silencing by potentiating cisplatin action, reducing tumor burden, and prolonging survival in vivo. Conclusion: The current study illustrates how targeting mitochondrial Fe-S cluster export can trigger ferroptosis and potentiate cisplatin in G3MBs. Our study also provides evidence for using an FDA-approved drug with the same mechanism of action to treat G3MB tumors.
Citation Format: Sidharth Mahapatra, Ranjana K. Kanchan, David Doss, Zahraa W. Alsafwani, Parvez Khan, Mohd W. Nasser, Surinder K. Batra. Inhibiting iron-sulfur cluster export activates ferroptosis and potentiates cisplatin response in pediatric group 3 medulloblastomas [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Pediatric Cancer Research; 2024 Sep 5-8; Toronto, Ontario, Canada. Philadelphia (PA): AACR; Cancer Res 2024;84(17 Suppl):Abstract nr A076.