Abstract Solid tumors, especially those with aberrant MYCN activation, harbor an immunosuppressive microenvironment to fuel malignant growth and trigger treatment resistance 1,2 , yet the underlying mechanisms are elusive and effective strategies to tackle this challenge are lacking. Here we demonstrated the crucial role of T regulatory (T reg ) cells in MYCN-mediated immune repression and tumor aggression using high-risk neuroblastoma (NB) as a model system. Human MYCN-activated NB attracts CD4 + T reg cells, which are also found enriched in MYCN-high primary patient samples. Zebrafish MYCN -overexpressing neural crests recruit Cd4 + cells before tumor formation and induce an immunosuppressive microenvironment, thereby promoting tumor onset and progression. Strikingly, disruption of T reg cells through depletion of forkhead box protein 3a restores anti-tumor immunity and impairs NB development. Together, our studies establish T reg cells as the key driver of MYCN-mediated immunosuppression and tumor aggressiveness, providing mechanistic insights and therapeutic implications.

Tregcells drive MYCN-mediated immunosuppression and tumor aggressiveness in high-risk neuroblastoma