Mechanism of IL-10 Protective Effect in Development of Childhood B Cell Acute Lymphoblastic Leukemia

B-cell acute lymphoblastic leukemia (B-ALL) is the most common malignancy of childhood. While significant progress has been made in the treatment of B-ALL, the factors that influence the development of B-ALL remain poorly understood. Epidemiological studies have established a role of early childhood infections in altering leukemia risk. The focus of these studies has been on documenting the number and timing of infectious exposures; however, the role of host immune response to infections in B-ALL development is largely unknown. Low birth levels of the immunomodulatory cytokine interleukin 10 (IL-10) are associated with a 25 fold increased risk of developing childhood B-ALL. Mechanistically, IL-10 plays a critical role in controlling the neonatal immune response to infections. Together, these findings suggest that IL-10, an important regulator of host immune responsiveness, protects against childhood B-ALL.

To establish whether loss of IL-10 has an impact on leukemogenesis, we crossed Il10 knockout mice to the TEL-AML1 (ETVX6-RUNX1I) Ckdn2a^null mouse model of childhood B-ALL. ETV6-RUNX1 t(12;21) is the most frequent chromosomal translocation in childhood B-ALLand one-fourth of these leukemias are observed in combination with loss of the Cdkn2a locus. The leukemia incidence in TEL-AML1 Ckdn2a^null mice is 60%, therefore this is a robust and clinically relevant mouse model of childhood B-ALL. We used this model to assess the role of IL-10 in leukemogenesis by following Il10 knockout TEL-AML1 Ckdn2a^null mice for the development of disease in comparison with control IL-10 expressing TEL-AML1 Ckdn2a^null mice.

We found that Il10 knockout accelerated leukemogenesis in the presence of TEL-AML1. The cancer free survival of the IL-10 expressing TEL-AML1 Ckdn2a^null mice (n=74) was 227 days, whereas the survival of IL-10 knockout mice (n=40) was reduced to 180 days (p<0.0005). These data support a causal role of low levels of IL-10 in the development of B-ALL and raise the possibility of using an IL-10 receptor agonist for leukemia prevention in children with high risk of B-ALL.

Thus, IL-10 loss is a defect in the host immune system that accelerates childhood B-ALL development, potentially through modifying immune responses to infections. Studies to understand the mechanism of how low IL-10 levels interact with infections to influence leukemogenesis are underway.