Therapeutic targeting of SETD2-deficient cancer cells with the small-molecule compound RITA

The histone methyltransferase SETD2 and its associated histone mark H3 lysine 36 trimethylation (H3K36me3) are frequently lost in certain cancer types, identifying SETD2 as an important therapeutic target. Here we show that SETD2-deficient cancer cells are profoundly sensitive to the compound RITA, resulting in significant p53 induction and apoptosis. This is further associated with defects in DNA replication, leading to delays in S-phase progression, increased recruitment of replication stress markers, and reduced replication fork progression. RITA sensitivity is linked to the phenol sulphotransferase SULT1A1, which we find to be highly upregulated in cells that lack SETD2. Depletion of SULT1A1 or addition of the phenol sulphotransferase inhibitor DCNP abolishes these phenotypes and suppresses the sensitivity of SETD2-deficient cancer cells, identifying SULT1A1 activity to be critical in mediating the potent cytotoxicity of RITA against SETD2-deficient cells. These findings define a novel therapeutic strategy for targeting the loss of SETD2 in cancer. Significance Statement The histone-modifying enzyme SETD2 has emerged as an important tumour suppressor in a number of different cancer types, identifying it as a promising therapeutic target. The concept of synthetic lethality, a genetic interaction in which the simultaneous loss of two genes or pathways that regulate a common essential process renders the cell nonviable, is a valuable tool for killing cancer cells that have known mutations. In this study, we conducted a synthetic lethality screen for compounds that specifically target SETD2-deficient cancer cells. The top hit, a compound called RITA, reduces cell viability and induces cell death only in the context of SETD2 loss, thereby highlighting a potential novel therapeutic strategy for treating SETD2-deficient cancers. ### Competing Interest Statement The authors have declared no competing interest.