Relatively favorable prognosis for MLL-rearranged childhood acute leukemia with reciprocal translocations

The KMT2A recombinome of acute leukemias in 2023

Chromosomal rearrangements of the human KMT2A/MLL gene are associated with de novo as well as therapy-induced infant, pediatric, and adult acute leukemias. Here, we present the data obtained from 3401 acute leukemia patients that have been analyzed between 2003 and 2022. Genomic breakpoints within the KMT2A gene and the involved translocation partner genes (TPGs) and KMT2A-partial tandem duplications (PTDs) were determined. Including the published data from the literature, a total of 107 in-frame KMT2A gene fusions have been identified so far. Further 16 rearrangements were out-of-frame fusions, 18 patients had no partner gene fused to 5'-KMT2A, two patients had a 5'-KMT2A deletion, and one ETV6::RUNX1 patient had an KMT2A insertion at the breakpoint. The seven most frequent TPGs and PTDs account for more than 90% of all recombinations of the KMT2A, 37 occur recurrently and 63 were identified so far only once. This study provides a comprehensive analysis of the KMT2A recombinome in acute leukemia patients. Besides the scientific gain of information, genomic breakpoint sequences of these patients were used to monitor minimal residual disease (MRD). Thus, this work may be directly translated from the bench to the bedside of patients and meet the clinical needs to improve patient survival.

Genomic Mechanisms Influencing Outcome in Chronic Myeloid Leukemia

Chronic myeloid leukemia (CML) represents the disease prototype of genetically based diagnosis and management. Tyrosine kinase inhibitors (TKIs), that target the causal BCR::ABL1 fusion protein, exemplify the success of molecularly based therapy. Most patients now have long-term survival; however, TKI resistance is a persistent clinical problem. TKIs are effective in the BCR::ABL1-driven chronic phase of CML but are relatively ineffective for clinically defined advanced phases. Genomic investigation of drug resistance using next-generation sequencing for CML has lagged behind other hematological malignancies. However, emerging data show that genomic abnormalities are likely associated with suboptimal response and drug resistance. This has already been supported by the presence of BCR::ABL1 kinase domain mutations in drug resistance, which led to the development of more potent TKIs. Next-generation sequencing studies are revealing additional mutations associated with resistance. In this review, we discuss the initiating chromosomal translocation that may not always be a straightforward reciprocal event between chromosomes 9 and 22 but can sometimes be accompanied by sequence deletion, inversion, and rearrangement. These events may biologically reflect a more genomically unstable disease prone to acquire mutations. We also discuss the future role of cancer-related gene mutation analysis for risk stratification in CML.

Mature B cell acute lymphoblastic leukaemia with KMT2A-MLLT3 transcripts in children: three case reports and literature reviews

BACKGROUND

Mature B cell acute lymphoblastic leukaemia (BAL) is characterised by French-American-British (FAB)-L3 morphology and the presence of surface immunoglobulin (sIgM) light chain restriction. BAL is also considered as the leukaemic phase of Burkitt lymphoma (BL), in which t (8; 14) (q24; q32) or its variants are related to the myelocytomatosis oncogene (MYC) rearrangement (MYCr) is usually present. However, BAL with lysine methyltransferase 2A (KMT2A, previously called Mixed lineage leukaemia, MLL) gene rearrangement (KMT2Ar, previously called MLLr) is rare.

RESULTS

Three BAL patients with KMT2Ar were enrolled between January 2017 and November 2019, accounting for 1.37% of the B-ALL population in our hospital. We also reviewed 24 previously reported cases of BAL and KMT2Ar and analysed the features, treatment, and prognosis. Total 13 males and 14 females were enrolled in our research, and the average age at diagnosis was 19.5 ± 4.95 months old. In these 27 patients, renal, central nervous system (CNS) and skin involvement were existent in 6, 4 and 3 patients, respectively; 26 patients (26/27) showed non-ALL-L3 morphology, while one patient is ALL-L3; overexpression of CD19 was detected in most cases, negative or suspicious expression of CD20 was found in 64% of patients. KMT2Ar was reported, but MYCr was not observed. 25 patients (25/27) achieved complete remission after chemotherapy or Stem cell transplantation. The patients were sensitive to chemotherapy, prospective event-free survival (pEFS) of BAL patients with KMT2Ar who received allogeneic haematopoietic stem cell transplantation (allo-HSCT) was higher than that in patients who received chemotherapy alone (83.33% vs 41.91%).

CONCLUSION

BAL patients with KMT2Ar had unique manifestations, including younger age at diagnosis and overexpression of CD19; expression of CD20 was rare, and MYCr was undetectable. The pEFS was higher in patients undergoing allo-HSCT than in patients undergoing chemotherapy alone.

How I treat pediatric acute myeloid leukemia

Treatment outcomes for pediatric patients with acute myeloid leukemia (AML) have continued to lag behind outcomes reported for children with acute lymphoblastic leukemia (ALL), in part because of the heterogeneity of the disease, a paucity of targeted therapies, and the relatively slow development of immunotherapy compared to ALL. In addition, we have reached the limits of treatment intensity and, even with outstanding supportive care, it is highly unlikely that further intensification of conventional chemotherapy alone will impact relapse rates. However, comprehensive genomic analyses and a more thorough characterization of the leukemic stem cell have provided insights that should lead to tailored and more effective therapies in the near future. In addition, new therapies are finally emerging, including the BCL-2 inhibitor venetoclax, CD33 and CD123-directed chimeric antigen receptor T cell therapy, CD123-directed antibody therapy, and menin inhibitors. Here we present four cases to illustrate some of the controversies regarding the optimal treatment of children with newly diagnosed or relapsed AML.

Novel Targeted Therapeutics in Acute Myeloid Leukemia: an Embarrassment of Riches

PURPOSE OF REVIEW

Acute myeloid leukemia (AML) is an aggressive malignancy of the bone marrow that has a poor prognosis with traditional cytotoxic chemotherapy, especially in elderly patients. In recent years, small molecule inhibitors targeting AML-associated IDH1, IDH2, and FLT3 mutations have been FDA approved. However, the majority of AML cases do not have a targetable mutation. A variety of novel agents targeting both previously untargetable mutations and general pathways in AML are currently being investigated. Herein, we review selected new targeted therapies currently in early-phase clinical investigation in AML.

RECENT FINDINGS

The DOT1L inhibitor pinometostat in KMT2A-rearranged AML, the menin inhibitors KO-539 and SYNDX-5613 in KMT2Ar and NPM1-mutated AML, and the mutant TP53 inhibitor APR-246 are examples of novel agents targeting specific mutations in AML. In addition, BET inhibitors, polo-like kinase inhibitors, and MDM2 inhibitors are promising new drug classes for AML which do not depend on the presence of a particular mutation. AML remains in incurable disease for many patients but advances in genomics, epigenetics, and drug discovery have led to the development of many potential novel therapeutic agents, many of which are being investigated in ongoing clinical trials. Additional studies will be necessary to determine how best to incorporate these novel agents into routine clinical treatment of AML.