Phosphatidylinositol 3-Kinase (PI3K) delta blockade increases genomic instability in B cells

ABSTRACT: Activation-induced cytidine deaminase (AID) is a B-cell specific enzyme that targets immunoglobulin (Ig) genes to initiate class switch recombination (CSR) and somatic hypermutation (SHM). Through off-target activity, however, AID has a much broader impact on genomic instability by initiating oncogenic chromosomal translocations and mutations involved in lymphoma development and progression. AID expression is tightly regulated in B cells and its overexpression leads to enhanced genomic instability and lymphoma formation. The phosphatidylinositol 3-kinase (PI3K) δ pathway plays a key role in AID regulation by suppressing its expression in B cells. Novel drugs for leukemia or lymphoma therapy such as idelalisib, duvelisib or ibrutinib inhibit PI3Kδ activity directly or indirectly through inhibition of the Bruton tyrosine kinase (BTK), thus possibly affecting AID expression and, consequently, genomic stability in B cells. Here we show that treatment of primary mouse B cells with idelalisib or duvelisib, and to a lesser extent ibrutinib, enhanced the expression of AID and increased somatic hypermutation (SHM) and chromosomal translocation frequency to the Igh locus and to several AID off-target sites. These effects were both completely abrogated in AID deficient B cells. PI3Kδ inhibitors or ibrutinib increased the formation of AID-dependent tumors in pristane-treated mice. Consistently, PI3Kδ inhibitors enhanced AID expression and translocation frequency to IgH and AID off-target sites in human chronic lymphocytic leukemia (CLL) and mantle cell lymphoma (MCL) cell lines, and patients treated with idelalisib showed increased SHM in AID off-targets. In summary, we show that PI3Kδ or BTK inhibitors increase genomic instability in normal and neoplastic B cells by an AID-dependent mechanism. Since such inhibitors are administered for years to patients, their genotoxic potential should be carefully considered while planning therapeutic protocols.

ORGANISM(S): Mus musculus Homo sapiens

PROVIDER: GSE77788 | GEO | 2017/01/31

SECONDARY ACCESSION(S): PRJNA311552

REPOSITORIES: GEO