Mutations of the TP53 gene occur in a subset of patients with acute myeloid leukemia (AML) and confer an exceedingly adverse prognosis. However, whether different types of TP53 mutations exert a uniformly poor outcome has not been investigated yet. Here, we addressed this issue by analyzing data of 1537 patients intensively treated within protocols of the German-Austrian AML study group. We classified TP53 mutations depending on their impact on protein structure and according to the evolutionary action (EAp53) score and the relative fitness score (RFS). In 98/1537 (6.4%) patients, 108 TP53 mutations were detected. While the discrimination depending on the protein structure and the EAp53 score did not show a survival difference, patients with low-risk and high-risk AML-specific RFS showed a different overall survival (OS; median, 12.9 versus 5.5 months, p = 0.017) and event-free survival (EFS; median, 7.3 versus 5.2 months, p = 0.054). In multivariable analyses adjusting for age, gender, white blood cell count, cytogenetic risk, type of AML, and TP53 variant allele frequency, these differences were statistically significant for both OS (HR, 2.14; 95% CI, 1.15–4.0; p = 0.017) and EFS (HR, 1.97; 95% CI, 1.06–3.69; p = 0.033). We conclude that the AML-specific RFS is of prognostic value in patients with TP53-mutated AML and a useful tool for therapeutic decision-making.

GATA2 zinc-finger (ZF) mutations are associated with distinct entities of myeloid malignancies. The specific distribution of these mutations points toward different mechanisms of leukemogenesis depending on the ZF domain affected. In this study, we compared recurring somatic mutations in ZF1 and ZF2. All tested ZF mutants disrupted DNA binding in vitro. In transcription assays, co-expression of FOG1 counteracted GATA2-dependent transcriptional activation, while a variable response to FOG1-mediated repression was observed for individual GATA2 mutants. In primary murine bone marrow cells, GATA2 wild-type (WT) expression inhibited colony formation, while this effect was reduced for both mutants A318T (ZF1) and L359V (ZF2) with a shift toward granulopoiesis. In primary human CD34⁺ bone marrow cells and in the myeloid cell line K562, ectopic expression of GATA2 L359V, but not A318T or G320D, caused a block of erythroid differentiation accompanied by downregulation of GATA1, STAT5B, and PLCG1. Our findings may explain the role of GATA2 L359V during the progression of chronic myeloid leukemia and the collaboration of GATA2 ZF1 alterations with CEBPA double mutations in erythroleukemia.

Acute myeloid leukemia (AML) is characterized by frequent relapse, which is driven by resistant leukemic stem or progenitor cells (LSCs). Here, we reported on a tumor-suppressive mechanism that can be harnessed to simultaneously clear LSCs and promote healthy hematopoiesis. Genetic deletion of the tumor necrosis factor (TNF) superfamily member lymphotoxin alpha ( Lta ) blocked cell death and accelerated leukemogenesis in murine AML models. Accordingly, exposure of leukemic cells to exogenous recombinant lymphotoxin alpha (LTα ₃ ) induced myeloid differentiation and, in part, cell death in AML progenitors. In syngeneic and patient-derived xenograft mouse models, exposure to recombinant LTα ₃ resulted in deep and durable remissions. LTα ₃ repressed leukemia by depleting tumor necrosis factor receptor (TNFR)–associated factor 2 (TRAF2) through activation of TNF receptors TNFR1 and TNFR2. In contrast with conventional therapies, LTα ₃ exerted only minimal toxicity on the healthy hematopoiesis but instead promoted hematopoietic progenitors. Leveraging this endogenous tumor-suppressive mechanism may decouple treatment efficacy on malignant cells from undesired bone marrow suppression.

In more than 50% of human cancers, somatically acquired aberrations of the tumor suppressor gene TP53 are encountered. Approx. 10% of patients with acute myeloid leukemia (AML) reveal TP53 mutations with higher incidences in therapy-related subtypes and erythroleukemias. These mutations are regarded early events of leukemogenesis. In contrast to mere deletions at the TP53 locus, TP53 mutations confer an exceedingly adverse prognosis in AML even when occurring at a subclonal level. However whether different TP53 mutations in AML exhibit a different functional impact on disease progression or outcome remains unknown. In the present study, we have investigated this issue using four TP53 specific, functional scoring systems in a large cohort of patients of the German-Austrian AML study group (AMLSG). The AMLSG cohort consisted of a total of 1537 patients with newly diagnosed AML who were intensively treated within three multicenter, clinical trials. A total of 108 TP53 mutations were detected in 98 patients using targeted amplicon sequencing - 88 (81.4%) missense, 8 (7.4%) nonsense and 6 (5.6%) splice site mutations as well as 6 small insertions and deletions. For each of the four functional TP53 scores, we have assessed their impact on overall survival (OS) and event-free survival (EFS). First, we compared the impact of TP53 missense mutations in 84 patients with all other types of mutations (n= 14). In a next approach, TP53 mutations were grouped into disruptive (n=42) and non-disruptive (n=56) ones, based on the impact of the particular mutations on the protein structure predicted from the crystal structure of p53-DNA complexes (Poeta et al. New Engl J Med 2007). We then classified missense TP53 mutations (n=84) based on their "Evolutionary Action Scores (EAp53)" (Neskey et al. Cancer Res 2015). This algorithm takes evolutionary sensitivity and amino acid conservation into account and scores missense TP53 mutations from 0 to 100. Mutations with the high EAp53 score are considered high risk whereas wild type TP53 has an EAp53 score of zero. We extracted the EAp53 score of those AMLSG patients showing missense mutations from the respective server (http://mammoth.bcm.tmc.edu/EAp53) and used the threshold of 75 from the initial publication to divide the patients into low-risk ( -0.135, n= 58) we demonstrated a significantly better OS (P=0.009) and EFS (P=0.037) for patients with a low-risk RFS in multivariable analyses adjusting for age, white blood cell count, cytogenetics and type of AML. Using the AML-specific TP53 RFS score, we could show that more than 30% of patients with TP53 mutations (25/83) reveal a significantly better survival indicating that this score is of prognostic value. Based on these findings, we propose that - along with clinical parameters - RFS values of TP53 mutations should also be considered for a comprehensive risk assessment of TP53 mutated AML patients. Disclosures: Zebisch: Celgene: Honoraria; Novartis: Honoraria, Other: Advisory board; AbbVie: Other: Advisory board; Roche: Honoraria. Bullinger:Bristol-Myers Squibb: Honoraria; Celgene: Honoraria; Daiichi Sankyo: Honoraria; Gilead: Honoraria; Hexal: Honoraria; Menarini: Honoraria; Novartis: Honoraria; Astellas: Honoraria; Pfizer: Honoraria; Sanofi: Honoraria; Seattle Genetics: Honoraria; Bayer: Other: Financing of scientific research; Abbvie: Honoraria; Amgen: Honoraria; Janssen: Honoraria; Jazz Pharmaceuticals: Honoraria. Döhner:Daiichi: Honoraria; Jazz: Honoraria; Novartis: Honoraria; Celgene: Honoraria; Janssen: Honoraria; CTI Biopharma: Consultancy, Honoraria. Sill:Novartis: Other: Advisory board; AbbVie: Other: Advisory board; Astellas: Other: Advisory board; Astex: Other: Advisory board.