Sorafenib Maintenance After Allogeneic Hematopoietic Stem Cell Transplantation for Acute Myeloid Leukemia With FLT3-Internal Tandem Duplication Mutation (SORMAIN).

PURPOSE: Despite undergoing allogeneic hematopoietic stem cell transplantation (HCT), patients with acute myeloid leukemia (AML) with internal tandem duplication mutation in the FMS-like tyrosine kinase 3 gene (FLT3-ITD) have a poor prognosis, frequently relapse, and die as a result of AML. It is currently unknown whether a maintenance therapy using FLT3 inhibitors, such as the multitargeted tyrosine kinase inhibitor sorafenib, improves outcome after HCT. PATIENTS AND METHODS: In a randomized, placebo-controlled, double-blind phase II trial (SORMAIN; German Clinical Trials Register: DRKS00000591), 83 adult patients with FLT3-ITD-positive AML in complete hematologic remission after HCT were randomly assigned to receive for 24 months either the multitargeted and FLT3-kinase inhibitor sorafenib (n = 43) or placebo (n = 40 placebo). Relapse-free survival (RFS) was the primary endpoint of this trial. Relapse was defined as relapse or death, whatever occurred first. RESULTS: With a median follow-up of 41.8 months, the hazard ratio (HR) for relapse or death in the sorafenib group versus placebo group was 0.39 (95% CI, 0.18 to 0.85; log-rank P = .013). The 24-month RFS probability was 53.3% (95% CI, 0.36 to 0.68) with placebo versus 85.0% (95% CI, 0.70 to 0.93) with sorafenib (HR, 0.256; 95% CI, 0.10 to 0.65; log-rank P = .002). Exploratory data show that patients with undetectable minimal residual disease (MRD) before HCT and those with detectable MRD after HCT derive the strongest benefit from sorafenib. CONCLUSION: Sorafenib maintenance therapy reduces the risk of relapse and death after HCT for FLT3-ITD-positive AML.

Outcome of non-mold effective anti-fungal prophylaxis in patients at high-risk for invasive fungal infections after allogenic stem cell transplantation.

Patients who develop severe graft-versus-host disease (GvHD) after allogeneic stem cell transplantation (alloSCT) have a higher risk for invasive fungal infection (IFI). At our center, fluconazole prophylaxis is standard and upfront mold-effective prophylaxis performed only in patients with specific risk constellations. A total of 290 patients undergoing alloSCT between May 2002 and August 2011 were analyzed. Patients were regarded as high-risk if they suffered from acute GvHD II-IV° or extensive chronic GvHD. The 2-year incidence of an IFI after alloSCT was 8.97% (26/290) in the entire cohort and 7.78% (7/90) in the high-risk group. Mortality due to IFI was 3.85% (1/26) without including a high-risk patient. In the multivariate analysis a pre-transplant fungal infection was the only significant risk factor for developing an IFI after alloSCT (HR = 5.298; p = .001). A fluconazole prophylaxis in patients with GvHD after alloSCT is feasible in facilities with HEPA filtration and high awareness of clinical signs for IFI.

Maintenance of cellular respiration indicates drug resistance in acute myeloid leukemia.

Primary resistance to induction therapy is an unsolved clinical problem in acute myeloid leukemia (AML). Here we investigated drug resistance in AML at the level of cellular metabolism in order to identify early predictors of therapeutic response. Using extracellular flux analysis, we compared metabolic drug responses in AML cell lines sensitive or resistant to cytarabine or sorafenib after 24h of drug treatment to a small cell lung cancer (SCLC) cell line exposed to etoposide. Only drug-resistant AML cells maintained oxidative metabolism upon drug exposure while SCLC cells displayed an overall metabolic shift towards glycolysis, i.e. a Warburg effect to escape drug toxicity. Moreover, primary AML blasts displayed very low glycolytic activity, while oxygen consumption was readily detectable, indicating an essential role of oxidative pathways in the bioenergetics of AML blasts. In line with these observations, analysis of the mitochondrial membrane potential using tetramethylrhodamine ethyl ester staining and flow cytometry allowed for clear discrimination between drug sensitive and resistant AML cell line clones and primary blasts after 24h of treatment with cytarabine or sorafenib. Our data reveal a distinct metabolic phenotype of resistant AML cells and suggest that disrupting oxidative metabolism rather than glycolysis may enhance the cytotoxic effects of chemotherapy in AML.

Sorafenib induces paradoxical phosphorylation of the extracellular signal-regulated kinase pathway in acute myeloid leukemia cells lacking FLT3-ITD mutation.

Gain-of-function mutations in the RAS and FLT3 genes are frequently found in cells of acute myeloid leukemia (AML), leading to constitutive activation of signaling pathways that regulate fundamental cellular processes, and are therefore attractive targets for AML therapy. The multi-targeted kinase inhibitor sorafenib is efficacious in AML with FLT3-internal tandem duplication (ITD), but resistance to therapy is an important clinical problem. It is unclear whether AML lacking FLT3-ITD responds to sorafenib. Using AML cell lines, we have shown that a low concentration of sorafenib induces opposing effects depending on the oncogenic background. In FLT3-ITD positive cells sorafenib blocks Erk activity and cell proliferation, and triggers apoptosis. However, in cells lacking FLT3-ITD, sorafenib paradoxically activates Erk2, and stimulates cellular proliferation and metabolic activity. Thus, depending on the genetic context, sorafenib is a beneficial inhibitor or paradoxical activator of mitogenic signaling pathways in AML. These results harbor important consequences in planning clinical trials in AML.

Identification of interaction partners and substrates of the cyclin A1-CDK2 complex.

The CDK2-associated cyclin A1 is essential for spermatogenesis and contributes to leukemogenesis. The detailed molecular functions of cyclin A1 remain unclear, since the molecular networks involving cyclin A1-CDK2 have not been elucidated. Here, we identified novel cyclin A1/CDK2 interaction partners in a yeast triple-hybrid approach. Several novel proteins (INCA1, KARCA1, and PROCA1) as well as the known proteins GPS2 (G-protein pathway suppressor 2), Ku70, receptor for activated protein kinase C1/guanine nucleotide-binding protein beta-2-like-1, and mRNA-binding motif protein 4 were identified as interaction partners. These proteins link the cyclin A1-CDK2 complex to diverse cellular processes such as DNA repair, signaling, and splicing. Interactions were confirmed by GST pull-down assays and co-immunoprecipitation. We cloned and characterized the most frequently isolated unknown gene, which we named INCA1 (inhibitor of CDK interacting with cyclin A1). The nuclear INCA1 protein is evolutionarily conserved and lacks homology to any known gene. This novel protein and two other interacting partners served as substrates for the cyclin A1-CDK2 kinase complex. Cyclin A1 and all interaction partners were highly expressed in testis with varying degrees of tissue specificity. The highest expression levels were observed at different time points during testis maturation, whereas expression levels in germ cell cancers and infertile testes decreased. Taken together, we identified testicular interaction partners of the cyclin A1-CDK2 complex and studied their expression pattern in normal organs, testis development, and testicular malignancies. Thereby, we establish a new basis for future functional analyses of cyclin A1. We provide evidence that the cyclin A1-CDK2 complex plays a role in several signaling pathways important for cell cycle control and meiosis.