Targeting MYCN Degradation by HLB-0532259 Induces Senescence in Retinoblastoma
Purpose Amplification of MYCN is a primary driver of aggressive retinoblastoma (RB), yet it remains a challenging therapeutic target. This study aimed to evaluate the therapeutic potential of the PROTAC molecule HLB-0532259 in degrading MYCN and suppressing RB growth. Methods Y79 and WERI-Rb1 RB cell lines were treated with HLB-0532259, and MYCN protein degradation, cell viability, and time-dependent transcriptional changes were assessed by Western blotting, cell viability assays, RNA-seq, and proteomics. The therapeutic potential was further validated in an orthotopic Y79 xenograft mouse model through intravitreal administration, with tumor burden evaluated by histology and immunohistochemistry. Results HLB-0532259 induced dose-dependent degradation of MYCN in both cell lines, with Y79 cells showing higher sensitivity. Transcriptomic and proteomic analyses revealed rapid activation of the p53–p21 pathway, downregulation of DNA repair and epigenetic regulators, and accumulation of DNA damage. Proteomic profiling confirmed upregulation of senescence-associated secretory phenotype factors and downregulation of MYCN-dependent effectors, including HMGA1 and TRAF6. In orthotopic xenografts, intravitreal administration of HLB-0532259 reduced intraocular tumor burden, decreased Ki-67 and MYCN-positive cells, and activated p53, p21, and NF-κB signaling. Conclusions Targeted MYCN degradation by HLB-0532259 effectively inhibits RB growth and induces a DNA damage–associated senescence program, highlighting targeted MYCN degradation as a promising therapeutic strategy for MYCN-driven RB.