Immunophenotypic dysplasia and aberrant T-cell antigen expression in acute myeloid leukaemia with complex karyotype and TP53 mutations

The International Consensus Classification of acute myeloid leukemia

Acute myeloid leukemias (AMLs) are overlapping hematological neoplasms associated with rapid onset, progressive, and frequently chemo-resistant disease. At diagnosis, classification and risk stratification are critical for treatment decisions. A group with expertise in the clinical, pathologic, and genetic aspects of these disorders developed the International Consensus Classification (ICC) of acute leukemias. One of the major changes includes elimination of AML with myelodysplasia-related changes group, while creating new categories of AML with myelodysplasia-related cytogenetic abnormalities, AML with myelodysplasia-related gene mutations, and AML with mutated TP53. Most of recurrent genetic abnormalities, including mutations in NPM1, that define specific subtypes of AML have a lower requirement of ≥ 10% blasts in the bone marrow or blood, and a new category of MDS/AML is created for other case types with 10-19% blasts. Prior therapy, antecedent myeloid neoplasms or underlying germline genetic disorders predisposing to the development of AML are now recommended as qualifiers to the initial diagnosis of AML. With these changes, classification of AML is updated to include evolving genetic, clinical, and morphologic findings.

CD44v6 chimeric antigen receptor T cell specificity towards AML with FLT3 or DNMT3A mutations

Background

Chimeric antigen receptor T‐cell (CAR‐T) therapy for acute myeloid leukaemia (AML) has thus far been elusive, in part due to target restriction and phenotypic heterogeneity of AML cells. Mutations of the FMS‐like tyrosine kinase 3 (FLT3) and DNA methyltransferase 3A (DNMT3A) genes are common driver mutations that present with a poor prognosis in AML patients. We found that AML patients with FLT3 or DNMT3A mutations had higher expression of CD44 isoform 6 (CD44v6) compared to normal specimens. Therefore, we intended to demonstrate CD44v6 could be a specific option for AML with FLT3 or DNMT3A mutations.

Methods

Internal tandem duplication (ITD) mutations of FLT3 (FLT3/ITD) knock‐in clone and DNMT3A‐R882H mutant clones of SKM‐1 cells were generated using CRISPR/Cas9 and lentiviral transfection, respectively. CD44v6 CAR‐T cells were constructed by transfecting T cells with lentivirus containing CD44v6 CAR. CD44v6 expression in AML cell lines, AML patients and healthy donors was evaluated by flow cytometry. DNA methylation assays were used to analyse the mechanisms of FLT3 and DNMT3A mutations affecting CD44v6 expression.

Results

Aberrant overexpression of CD44v6 was observed in AML cell lines with FLT3 or DNMT3A mutations compared to the wild‐type SKM‐1 or K562 cells. AML patients with FLT3 or DNMT3A mutations had higher expression of CD44v6 compared to normal specimens. Then we constructed CD44v6 CAR‐T cells and found that CD44v6 CAR‐T specifically lysed CD44v6⁺ cells, accompanied by cytokines release. No significant killing effect was observed from CD44v6^‐ AML cells and normal cells after co‐culture with CD44v6 CAR‐T. These results were also observed in vivo. Furthermore, we found that FLT3 or DNMT3A mutations induced CD44v6 overexpression by downregulating the CpG methylation of CD44 promoter.

Conclusions

Collectively, CD44v6 is a promising target of CAR‐T for AML patients with FLT3 or DNMT3A mutations.

[Clinical and prognostic values of TP53 mutation in patients with acute myeloid leukemia]

Objective: To explore the clinical and prognostic values of TP53 gene mutation in patients with acute myeloid leukemia (AML) . Methods: A retrospective analysis of 265 newly diagnosed AML patients with next-generation sequencing (NGS) data in the Hematology Department of Changhai Hospital from January 2010 to January 2019 was performed. Mutation analysis was carried out by targeted sequencing technology including 200 hematological malignancy related genes. The association of TP53 mutation with clinical features was analyzed. Results: Alterations in TP53 were found in 20 (7.5%) patients, including 17 case (6.4%) of missense mutations, 2 cases (0.7%) of frame-shift deletion mutations and 1 case (0.4%) of splicing sites mutation. A total of 23 kinds of TP53 mutations were detected, most of them (16, 69.6%) were located in the DNA binding domain of exon 5-8, 4 in the DNA binding domain of exon 3-4, 2 in exon 10 and 1 in splice site, respectively. The median age of patients with TP53 alterations was higher than those without [52 (26-72) years old vs 45 (14-75) years old, P= 0.008]. The frequency of complex karyotypes was higher in patients with TP53 alterations than those without [45.0% (9/20) vs 6.1% (15/245) , P<0.001]. Median overall survival (OS) of patients with TP53 alterations was shorter than those without[14.1 (95%CI 6.78-21.42) months vs 31.4 (95%CI 13.20-49.59) months, P=0.029]. The OS of patients treated with "Decitabine + CAG" was superior than that of patients treated with "3 + 7" regimen [30.0 (95%CI 27.35-38.84) months vs 12.5 (95%CI 5.80-19.19) months, P=0.018]. Multivariate analysis indicated that TP53, DNMT3A and USH2A alterations, WBC ≥ 12.45×10(9)/L had negative impacts on OS. Conclusion: The frequency of TP53 mutation was 7.5% in our cohort. Most mutations were located in the DNA binding domain. TP53 alterations were strongly associated with older age, complex karyotype and shorter OS. Decitabine-based induction chemotherapy and hematopoietic stem cell transplantation may improve OS, more cases and/or multicenter randomized studies are needed for further confirmation.