Search

Therapy-related myeloid neoplasms are a life-threatening and often fatal complication, associated with poor prognosis outcomes and with high-risk unfavorable cytogenetic abnormalities including complex karyotype. They occur after the treatment of primary malignancies using chemotherapy and/or radiation therapy. Such therapy is not specific to cancer cells, and also damages the deoxyribonucleic acid (DNA) of normal cells, resulting in unbalanced and balanced translocations. There are eight genetic pathways, whose details are summarized in this review, depending on the cytogenetic abnormalities induced. This abnormality is the major contributor to the development of therapy-related myeloid neoplasms. The etiology of these neoplasms depends on the complex interaction between the nature and dose of the cytotoxic agent, the environment, and the presence of subsequent inherited mutations. This review aims to elaborate upon recent knowledge regarding the etiology, pathogenesis, and genetic pathways of therapy-related myeloid neoplasms. A deeper understanding of their etiology would aid physicians in more careful monitoring of patients during or after cytotoxic therapy for hematological malignancy. Ultimately, this knowledge could influence initial treatment strategies, with the aim of reducing both the incidence and serious complications of neoplasms. Therefore, early detection of DNA lesions is vital. The authors recommend that primary malignancy be treated with targeted therapy.

A 61-year-old woman with chronic-type adult T-cell leukemia-lymphoma (ATL) had been taking low-dose oral etoposide for progressive lymphocytosis. After taking this for 3.5 years, she was diagnosed with therapy-related acute myeloid leukemia (t-AML), with a chromosomal translocation of t (6:11) (q27; q23). She thus received remission induction therapy, consolidation therapy, and allogeneic hematopoietic stem cell transplantation. Although both t-AML and ATL were in remissive states, she died of a therapy-related infection within 1 year. We reviewed 12 reported cases of AML complicating ATL to better characterize this unusual disease. We should therefore include t-AML in the differential diagnosis when administering low-dose etoposide for ATL over a long period of time.

Summary Clonal hematopoiesis (CH), in which stem cell clones dominate blood production, becomes increasingly common with age and can presage malignancy development. The conditions that promote ascendancy of particular clones are unclear. We found that mutations in PPM1D (protein phosphatase Mn2+/Mg2+-dependent 1D), a DNA damage response regulator that is frequently mutated in CH, were present in one-fifth of patients with therapy-related acute myeloid leukemia or myelodysplastic syndrome and strongly correlated with cisplatin exposure. Cell lines with hyperactive PPM1D mutations expand to outcompete normal cells after exposure to cytotoxic DNA damaging agents including cisplatin, and this effect was predominantly mediated by increased resistance to apoptosis. Moreover, heterozygous mutant Ppm1d hematopoietic cells outcompeted their wild-type counterparts in vivo after exposure to cisplatin and doxorubicin, but not during recovery from bone marrow transplantation. These findings establish the clinical relevance of PPM1D mutations in CH and the importance of studying mutation-treatment interactions. Video Abstract, Graphical Abstract, Highlights • PPM1D is mutated in ∼20% of patients with therapy-related AML or MDS • PPM1D mutations are associated with prior exposure to specific DNA-damaging agents • Mutant PPM1D confers a survival advantage after cisplatin-induced stress • PPM1D mutants lack an advantage under bone marrow transplantation stress, Cytotoxic chemotherapies put patients at risk for future hematopoietic malignancies. Goodell and colleagues show that PPM1D mutations confer a survival advantage onto hematopoietic clones by rendering them resistant to DNA-damaging agents such as cisplatin. Selective pressures will be specific to different mutations and should be considered in choice of chemotherapy.

BRCA1 plays a pivotal role in the repair of DNA damage, especially following chemotherapy and ionising radiation. We were interested in the regulation of BRCA1 expression in acute myeloid leukaemia (AML), in particular in therapy-related forms (t-AML). Using real-time PCR and Western blot, we found that BRCA1 mRNA was expressed at barely detectable levels by normal peripheral blood granulocytes, monocytes and lymphocytes, whereas control BM-mononuclear cells and selected CD34+ progenitor cells displayed significantly higher BRCA1 expression (P=0.0003). Acute myeloid leukaemia samples showed heterogeneous BRCA1 mRNA levels, which were lower than those of normal bone marrows (P=0.0001). We found a high frequency of hypermethylation of the BRCA1 promoter region in AML (51/133 samples, 38%), in particular in patients with karyotypic aberrations (P=0.026), and in t-AML, as compared to de novo AML (76 vs 31%, P=0.0002). Examining eight primary tumour samples from hypermethylated t-AML patients, BRCA1 was hypermethylated in three of four breast cancer samples, whereas it was unmethylated in the other four tumours. BRCA1 hypermethylation correlated to reduced BRCA1 mRNA (P=0.0004), and to increased DNA methyltransferase DNMT3A (P=0.003) expression. Our data show that reduced BRCA1 expression owing to promoter hypermethylation is frequent in t-AML and that this could contribute to secondary leukaemogenesis.