Targeting SUV4-20H Epigenetic Enzymes Enhances Topoisomerase II Poisoning in Prostate Cancer.

Commonly used in cancer therapy, topoisomerase II (TOP2) poisons are designed to stabilize the normally transient DNA TOP2 cleavage complexes in chromatin, leading to deleterious DNA double-strand breaks. TOP2 poisons are often associated with significant side effects, highlighting the need to identify strategies aimed at improving the efficacy of TOP2 poisons in order to lower the required dosage. In this study, we demonstrated that inhibiting histone H4-lysine 20 (H4K20) methyltransferases SUV4-20H1 and SUV4-20H2 induced synthetic lethality in combination with the TOP2 poison etoposide in prostate cancer. Remarkably, the loss of the SUV4-20H enzymes, which prevents the conversion of H4K20 monomethylation to higher methylation states, increased replication fork velocity without affecting prostate cancer cell behavior. However, these apparently innocuous epigenetic changes significantly enhanced the trapping of TOP2 complexes in chromatin and increased DNA damage in response to etoposide. Furthermore, SUV4-20H depletion and the subsequent changes in H4K20 methylation impaired the repair of TOP2-induced DNA breaks by disrupting BRCA1-mediated homologous recombination processes, ultimately leading to extensive cancer cell death and significant inhibition of prostate tumor growth in vivo. Overall, these findings demonstrate that targeting the epigenetic activity of SUV4-20H is a powerful strategy to enhance the efficacy of TOP2 poisons and may represent a therapeutic alternative in prostate cancer, in which SUV4-20H2 expression emerges as a potential marker of aggressive disease and high metastatic risk. SIGNIFICANCE: Targeting the chromatin-modifying activities of the SUV4-20H enzyme family offers a promising epigenetic strategy to enhance the potency of the topoisomerase-2 poison etoposide in prostate cancer therapy.