CKLF instigates a "cold" microenvironment to promote MYCN-mediated tumor aggressiveness.

Solid tumors, especially those with aberrant MYCN activation, often harbor an immunosuppressive microenvironment to fuel malignant growth and trigger treatment resistance. Despite this knowledge, there are no effective strategies to tackle this problem. We found that chemokine-like factor ( CKLF ) is highly expressed by various solid tumor cells and transcriptionally up-regulated by MYCN. Using the MYCN-driven high-risk neuroblastoma as a model system, we demonstrated that as early as the premalignant stage, tumor cells secrete CKLF to attract CCR4-expressing CD4 + cells, inducing immunosuppression and tumor aggression. Genetic depletion of CD4 + T regulatory cells abolishes the immunorestrictive and protumorigenic effects of CKLF. Our work supports that disrupting CKLF-mediated cross-talk between tumor and CD4 + suppressor cells represents a promising immunotherapeutic approach to battling MYCN-driven tumors.