B-cell precursor acute lymphoblastic leukemia (BCP-ALL) is the most common form of childhood cancer. Chemotherapy is associated with life-long health sequelae and fails in approximately 20% of cases. Thus, prevention of leukemia would be preferable to treatment. Childhood leukemia frequently starts before birth, during fetal hematopoiesis. A first genetic hit (e.g. the ETV6-RUNX1 gene fusion) leads to the expansion of pre-leukemic B-cell clones, which are detectable in healthy newborn cord blood (up to 5%). These pre-leukemic clones give rise to clinically overt leukemia in only about 0.2% of carriers. Experimental evidence suggests that a major driver of conversion from the pre-leukemic to the leukemic state is exposure to immune challenges. Novel insights have shed light on immune host responses and how they shape the complex interplay between (A) inherited or acquired genetic predispositions, (B) exposure to infection, and (C) abnormal cytokine release from immunologically untrained cells. Here, we integrate the recently emerging concept of "trained immunity" into existing models of childhood BCP-ALL and suggest future avenues towards leukemia prevention.
Julia Hauer, Ute Fischer, Arndt Borkhardt