PAX5, NOTCH3, CBFB, and ACD drive an activated RAS pathway and monosomy 7 to B-ALL and AML in donor cell leukemia

The Relevance of Telomerase and Telomere-Associated Proteins in B-Acute Lymphoblastic Leukemia

Telomeres and telomerase are closely linked to uncontrolled cellular proliferation, immortalization and carcinogenesis. Telomerase has been largely studied in the context of cancer, including leukemias. Deregulation of human telomerase gene hTERT is a well-established step in leukemia development. B-acute lymphoblastic leukemia (B-ALL) recovery rates exceed 90% in children; however, the relapse rate is around 20% among treated patients, and 10% of these are still incurable. This review highlights the biological and clinical relevance of telomerase for B-ALL and the implications of its canonical and non-canonical action on signaling pathways in the context of disease and treatment. The physiological role of telomerase in lymphocytes makes the study of its biomarker potential a great challenge. Nevertheless, many works have demonstrated that high telomerase activity or hTERT expression, as well as short telomeres, correlate with poor prognosis in B-ALL. Telomerase and related proteins have been proven to be promising pharmacological targets. Likewise, combined therapy with telomerase inhibitors may turn out to be an alternative strategy for B-ALL.

Genetics of donor cell leukemia in acute myelogenous leukemia and myelodysplastic syndrome

Allogeneic hematopoietic stem cell transplantation (HSCT) is an important therapeutic modality for patients with acute myelogenous leukemia (AML) with poor risk features. Nonetheless, roughly 30% of such patients have leukemia recurrence and up to 2% of these are donor-derived leukemias, in which malignancy develops in the donor's transplanted cells, despite extremely low rates of leukemia in the donors themselves. Notably, over 20% of these malignancies carry chromosome 7 abnormalities nearly all of which are monosomies. Recent advances in whole exome and genome sequencing have allowed for detection of candidate genes that likely contribute to the development of AML in donor cells (donor leukemia, DCL). These genes include CEBPA, GATA2, JAK2, RUNX1, DDX41, EZH2, IDH1/2, DNMT3A, ASXL1, XPD, XRCC3, and CHEK1. The potential roles of variants in these genes are evaluated based on familial clustering of MDS/AML and corresponding animal studies demonstrating their leukemogenic nature. This review describes the spectrum of genetic aberrations detected in DCL cases in the literature with regard to the character of the individual cases, existing family cohorts that carry individual genes, and functional studies that support etiologic roles in AML development. DCL presents a unique opportunity to examine genetic variants in the donors and recipients with regards to progression to malignancy.