Enhanced epithelial to mesenchymal transition and chemoresistance in advanced Retinoblastoma tumors is driven by miR-181a

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Abstract Advanced retinoblastoma (Rb) tumors can infiltrate distant tissues and cause a potent threat to vision and life. Through transcriptomic profiling, we discovered key epithelial to mesenchymal transition (EMT) and chemotherapy resistance genes at higher expression levels in advanced Rb tumors. Rb-/- tumor cells acquire metastasis-like phenotype through the EMT program that critically contributes to chemoresistance. We demonstrate that prolonged chemo-drug exposure in Rb cells elicits an EMT program through ZEB1 and SNAI2 that further acquires therapeutic resistance through cathepsin L and MDR1 mediated drug efflux mechanisms. Further, 16 significantly differentially expressed miRNAs were identified in patient tumors, of which miR-181a-5p was significantly reduced in advanced Rb tumors and associated with altered EMT and drug resistance genes. Enhancing miR-181a-5p levels in Rb-/- cells and Rb-/- chemo-resistant sublines controls EMT transcription factors ZEB1 and SNAI2 and halts the transition switch, thereby reversing drug resistance. We thus identify miR-181a-5p as a potential therapeutic target for EMT triggered drug-resistant cancers that can halt their invasion and sensitize them to low dose chemotherapy drugs. Graphical Abstract

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