Hematopoietic stem/progenitor cell transplantation recovers immune defects and prevents lymphomas in Atm-deficient mice.

BACKGROUND: Ataxia-telangiectasia (A-T) is a rare autosomal recessive multi-system and life-shortening disease, characterized by progressive cerebellar neurodegeneration, immunodeficiency, radiation sensitivity and cancer predisposition, with high incidence of leukemia and lymphoma. A-T is caused by mutations in the gene encoding for ATM protein that has a major role in maintaining the integrity of the genome. Because there are no cures for A-T, we aimed to tackle immunodeficiency and prevent cancer onset/progression by transplantation therapy. METHODS: Enriched hematopoietic stem/progenitor cells (HSPCs), collected from bone marrow of wild-type mice, were transplanted in the caudal vein of 1 month old conditioned Atm-/- mice. RESULTS: Genomic analyses showed that transplanted Atm positive cells were found in lymphoid organs. B cells isolated from spleen of transplanted mice were able to undergo class switching recombination. Thymocytes were capable to correctly differentiate and consequently an increase of helper T cells and TCRßhi expressing cells was observed. Protein analysis of isolated T and B cells from transplanted mice, revealed that they expressed Atm and responded to DNA damage by initiating an Atm-dependent phosphorylation cascade. Indeed, aberrant metaphases were reduced in transplanted Atm-deficient mice. Six months after transplantation, Atm-/- mice showed signs of aging, but they maintained the rescue of T cells maturation, showed DNA damage response, and prevented thymoma. CONCLUSION: We can conclude that wild-type enriched HSPCs transplantation into young Atm-deficient mice can ameliorate A-T hematopoietic phenotypes and prevent tumor of hematopoietic origin.

Absence of ATM leads to altered NK cell function in mice.

Ataxia-telangiectasia (A-T) is a rare disorder caused by genetic defects of A-T mutated (ATM) kinase, a key regulator of stress response, and characterized by neurodegeneration, immunodeficiency, and high incidence of cancer. Here we investigated NK cells in a mouse model of A-T (Atm-/-) showing that they are strongly impaired at killing tumor cells due to a block of early signaling events. On the other hand, in Atm-/- littermates with thymic lymphoma NK cell cytotoxicity is enhanced as compared with ATM-proficient mice, possibly via tumor-produced TNF-α. Results also suggest that expansion of exhausted NKG2D+ NK cells in Atm-/- mice is driven by low-level expression of stress-inducible NKG2D ligands, whereas development of thymoma expressing the high-affinity MULT1 ligand is associated with NKG2D down-regulation on NK cells. These results expand our understanding of immunodeficiency in A-T and encourage exploring NK cell biology in A-T patients in the attempt to identify cancer predictive biomarkers and novel therapeutic targets.