In vivo CRISPR knockout screen identifies Polr1a as a key driver and a potential therapeutic target for melanoma metastasis.

Identification and characterization of novel mechanisms driving melanoma metastases and ways to target them are paramount for the development of effective treatment modalities. Here, we employed in vivo CRISPR knockout screening targeting the genes associated with poor prognosis to identify Polr1a as a potent driver of melanoma metastasis. High Polr1a levels correlate with increased metastasis and reduced survival in patients. Polr1a inhibition suppressed migration, invasion, and the ability of melanoma cells to colonize lungs. Ribo-seq analysis revealed that Polr1a is involved in regulating the non-canonical NF-κB pathway. Indeed, targeting Polr1a decreased levels of RelB and p52 and suppressed non-canonical NF-κB transcriptional activity; this suppression was responsible for the effects of Polr1a on melanoma cell migration. Accordingly, pharmacological inhibition of Polr1/Polr1a suppressed cell migration, tumor growth, and metastases. We discuss the potential utilization of Polr1 inhibitors for neoadjuvant treatment of melanoma.