Chromatin looping-based CRISPR screen identifies TLK2 as chromatin loop formation regulator in cancer stemness plasticity.

Targeting cancer cell plasticity through chromatin organization is an emerging research area, yet the molecular mechanisms that govern chromatin loop formation remain unclear. Here, we develop a CRISPR screen based on our engineered live-cell CTCF-cohesin contact reporters to identify regulators of chromatin loops. Our findings reveal that tousled-like kinase 2 (TLK2) functions as a key regulator of chromatin loop formation during the cancer stemness transition. Mechanistically, TLK2 phosphorylates DYNLL1, enhancing its interaction with CTCF to promote CTCF-cohesin hub formation at the KLF4 locus. Suppressing TLK2 impairs cancer stemness plasticity, sensitizes cancer cells to cytotoxic stress in vitro, and reduces lung metastases and enhances immunotherapy response in breast cancer mouse models. Clinically, elevated TLK2 expression correlates with poor prognosis in breast cancer patients. Collectively, these findings identify TLK2 as a potential therapeutic target for mitigating cancer stemness plasticity, highlighting chromatin loop-targeting therapy as a promising strategy to eradicate cancer stem cells.