Increased AID Results in Mutations at the CRLF2 Locus Implicated in Latin American ALL Health Disparities.

Activation-induced cytidine deaminase (AID) is a B cell-specific base editor required during class switch recombination and somatic hypermutation for B cell maturation and antibody diversification. However, it has also been implicated as a factor in the etiology of several B cell malignancies. Evaluating the AID-induced mutation load in patients at-risk for certain types of blood cancers is critical in assessing disease severity and treatment options. Here, we have developed a digital PCR (dPCR) assay that allows us to track the mutational landscape resulting from AID modification or DNA double-strand break (DSB) formation and repair at sites known to be prone to DSBs. Implementation of this new assay showed that increased AID levels in immature B cells increases genome instability at loci linked to translocation formation. This included the CRLF2 locus that is often involved in chromosomal translocations associated with a subtype of acute lymphoblastic leukemia (ALL) that disproportionately affects Latin Americans (LAs). To support this LA-specific identification of AID mutation signatures, we characterized DNA from immature B cells isolated from the bone marrow of ALL patients. Our ability to detect and quantify these mutation signatures will potentiate future risk identification, early detection of cancers, and reduction of associated cancer health disparities.

Diversity upon diversity: linking DNA double-strand break repair to blood cancer health disparities.

Chromosomal translocations arising from aberrant repair of multiple DNA double-strand breaks (DSBs) are a defining characteristic of many cancers. DSBs are an essential part of physiological processes in antibody-producing B cells. The B cell environment is poised to generate genome instability leading to translocations relevant to the pathology of blood cancers. These are a diverse set of cancers, but limited data from under-represented groups have pointed to health disparities associated with each. We focus on the DSBs that occur in developing B cells and propose the most likely mechanism behind the formation of translocations. We also highlight specific cancers in which these rearrangements occur and address the growing concern of health disparities associated with them.