Abstract
Purpose :
Advanced retinoblastoma (Rb) tumors, if neglected can metastasize through the optic nerves to distant tissues and cause potent threat to vision and life. Since tumor metastasis by the epithelial to mesenchymal transition(EMT) also confers chemotherapy resistance, it is critical to understand this process in Rb tumors.
Methods :
Transcriptomic analyses were performed on Rb tumor samples (n=9) & paediatric control retina (n=2) to identify EMT specific genes and microRNAs. Q-PCR & western blot was performed on WERI-Rb1 cells, under RB1 null & RB1 over expression, to assess EMT related miRNAs, genes & protein expression. Validation was performed by immunochemistry in tumor sections. Functions of miR-181a on tumor pathways were assessed using mimics and antagomirs.
Results :
We found EMT and drug resistance genes to be differentially regulated in advanced and non-advanced Rb tumors compared to healthy pediatric controls (P<0.05, FC>2). EMT transcription factors ZEB1, SNAI2, Twist and drug resistance genes MDR1, CTSL were significantly upregulated in advanced tumors. ZEB1, SNAI2, MDR1 protein expression was higher in Rb tumor tissues. Reduced miR-181a observed in advanced Rb tumors inversely correlated with EMT and drug resistance genes. RB1 overexpression or miR-181a mimics significantly reduced cancer and EMT hallmarks. MiR-181a mimic enhanced chemosensitivity and reduced proliferative capacity of Rb null lines.
Conclusions :
EMT and chemoresistance in advanced Rb tumors is characterised by higher expression of ZEB1, SNAI2, MDR1, CTSL, etc which mediate invasion and metastasis. MiR-181a transcriptionally controls the EMT program, reducing proliferation/invasion and enhances chemosensitivity, highlighting its potential for therapeutic applications.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.