Photoproximity labeling of c-Myc reveals SLK as a cancer-specific co-regulator [ChIP-Seq]

We find that a cancer-specific c-Myc interactor, STE20 like kinase (SLK), selectively promotes c-Myc stabilization at the protein level, drives epithelial morphology, and is essential for tumorigenesis, validating it as a viable therapeutic target. Mechanistically, this stabilization is driven by SLK-mediated phosphorylation of c-Myc at serine 329, which antagonizes GSK3β-dependent phosphorylation of the c-Myc phosphodegron and effectively increases the stability of c-Myc.

This cancer-selective interaction is enabled by a change in SLK splicing that promotes nuclear localization of the long isoform, rather than changes at the protein or total RNA level. Furthermore, analysis of cancer patient data shows a strong correlation between the SLK long splice isoform and expression of c-Myc targets across multiple tumor types. Importantly, the SLK-c-Myc interaction is validated in cancer cell lines from diverse tissues, suggesting this novel regulatory axis is broadly operative across human cancer.