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Introduction Among CNS tumors, medulloblastoma (MB) is the most common malignant pediatric brain tumor. Of the four subgroups, group 3 (G3MB) tumors fare the worst. Haploinsufficiency of 17p13.3 is a hallmark of these high-risk tumors; included within this locus is miR-1253, which has tumor suppressive properties in medulloblastoma. Therapeutic strategies capitalizing on the anti-neoplastic properties of miRNAs can provide promising adjuncts that can improve efficacy while mitigating toxicity of current chemotherapeutic drugs.

Objective In this study, we explored the potentiation of miR-1253 on cisplatin cytotoxicity in group 3 MB.

Methods We used RNA Sequencing to isolate a putative target for miR-1253 that is upregulated in G3MB, has a poor prognostic profile, and is involved in iron balance/ferroptosis. Calein AM quenching, COX IV staining and multiple stains for iron were used to study mitochondrial vs. free cytosolic iron generation. Confocal microscopy and FACs analyses were used to examine ROS generation and lipid peroxidation. Using 2 classical group 3 MB cell lines, possessing c-Myc amplification and i17q, we determined the IC50 of cisplatin in the presence of miR-1253 expression using MTT assay. We also studied colony formation, apoptosis and oxidative stress, as cisplatin is an inducer of both. Finally, ROS and ferroptosis inhibitors were used to study effects on tumor cell rescue from miR-1253 and cisplatin therapy.

Results In silico and in vitro analyses revealed upregulation of ABCB7 in G3MB cancer cells and tumors. Overexpressing miR-1253, in turn, suppressed ABCB7, revealing it as a putative target with poor survival in high-expressing MB tumors. Overexpression also led to a suppression of GPX4, a ferroptosis regulator, consequently increasing labile iron pool within the mitochondria and resulting in mtROS induction. Cisplatin is reported as an inducer of both apoptosis and ferroptosis-mediated cancer cell death. In miR-1253-overexpressing cancer cells, we observed a cumulative effect on cell death and colony formation with cisplatin; treatment with ROS and ferroptosis inhibitors abrogated these effects.

Conclusions We conclude that miR-1253 potentiates the ferroptotic effects of cisplatin via targeting miR-1253/ABCB7/GPX4 axis.

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MiR-1253 Potentiates Cisplatin Response in Pediatric Medulloblastoma by Regulating Ferroptosis

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