Effect of CDK7 inhibitor on MYCN-amplified retinoblastoma

Retinoblastoma (RB) is a common malignancy that primarily affects pediatric populations. Although a well-known cause of RB is RB1 mutation, MYCN amplification can also lead to the disease, which is a poor prognosis factor. Studies conducted in various tumor types have shown that MYCN inhibition is an effective approach to impede tumor growth. Various indirect approaches have been developed to overcome the difficulty of directly targeting MYCN, such as modulating the super enhancer (SE) upstream of MYCN. The drug used in this study to treat MYCN-amplified RB was THZ1, a CDK7 inhibitor that can effectively suppress transcription by interfering with the activity of SEs. The study findings confirmed the anticancer activity of THZ1 against RB in both in vitro and in vivo experiments. Therapy with THZ1 was found to affect numerous genes in RB according to the RNA-seq analysis. Moreover, the gene expression changes induced by THZ1 treatment were enriched in ribosome, endocytosis, cell cycle, apoptosis, etc. Furthermore, the combined analysis of ChIP-Seq and RNA-seq data suggested a potential role of SEs in regulating the expression of critical transcription factors, such as MYCN, OTX2, and SOX4. Moreover, ChIP-qPCR experiments were conducted to confirm the interaction between MYCN and SEs. In conclusion, THZ1 caused substantial changes in gene transcription in RB, resulting in inhibited cell proliferation, interference with the cell cycle, and increased apoptosis. The efficacy of THZ1 is positively correlated with the degree of MYCN amplification and is likely exerted by interfering with MYCN upstream SEs.