IKZF3 mutation

Furthermore, AIOLOS G191R demonstrated a dominant-negative effect over the wild-type protein. This case represents the first reported instance of a mutation in the third DNA-binding zinc finger region of AIOLOS highlighting its pivotal role in immune cell functionality.

H195Y IKZF3 binding sites overlapped with a subset of STAT5 binding sites, including in the promoter of the Cish gene. These findings suggest that H195Y mutation of IKZF3 results in altered DNA binding specificity and altered binding of STAT5 to target genes.

Finally, no difference in TP53 mutation burden was observed between BTKmut versus BTKwt relapsing cases, and ibrutinib treatment did not appear to favor selection of TP53-aberrant clones. In conclusion, we show that BTK/PLCG2 mutations were absent in a substantial fraction (35%) of a real-world cohort failing ibrutinib, and propose additional mechanisms contributing to resistance.

Altogether, IKZF3-L162R mutation occurs in CLL but also in other B-cell neoplasms with similar frequencies, suggesting a common mechanism of lymphomagenesis related to the dysregulation of BCR-signaling genes. We are currently sequencing more samples, including marginal zone lymphoma, to better appreciate the distribution of this mutation among B-cell lymphomas.

The human immunophenotype was recapitulated in a murine model carrying the corresponding human mutation. As demonstrated here, AIOLOS plays a key role in T and B cell development in humans, and the particular gene variant described is strongly associated with immunodeficiency and likely malignancy.

Mechanistically, the mutant was fully penetrant and had a dominant negative effect over AIOLOS wildtype function. Our findings demonstrate that AIOLOS plays a key role in T and B cell development in humans and also associates abnormal AIOLOS function with CID, PJP and potential development of CLL.

Human CLL carrying either IKZF3 mutation or high IKZF3 expression was associated with overexpression of BCR/NF-κB pathway members and reduced sensitivity to BCR signaling inhibition by ibrutinib. Our results thus highlight IKZF3 oncogenic function in CLL via transcriptional dysregulation and demonstrate that this pro-survival function can be achieved by either somatic mutation or overexpression of this CLL driver. This emphasizes the need for combinatorial approaches to overcome IKZF3-mediated BCR inhibitor resistance.