In T-ALL, PHF6 mutations occur in 16% of pediatric and 38% of adult patients and are predominantly enriched within the TLX1/3 subgroup. Recent in vitro data indicate that both TLX1 and PHF6 regulate expression of IL7R, an established key oncogene in T-ALL formation. We aim to further explore the PHF6 – IL7R - TLX1 axis both in vitro as in vivo.