Sören Lehmann

Distinct patterns of hematopoietic stem cell involvement in acute lymphoblastic leukemia

The cellular targets of primary mutations and malignant transformation remain elusive in most cancers. Here, we show that clinically and genetically different subtypes of acute lymphoblastic leukemia (ALL) originate and transform at distinct stages of hematopoietic development. Primary ETV6-RUNX1 (also known as TEL-AML1) fusions and subsequent leukemic transformations were targeted to committed B-cell progenitors. Major breakpoint BCR-ABL1 fusions (encoding P210 BCR-ABL1) originated in hematopoietic stem cells (HSCs), whereas minor BCR-ABL1 fusions (encoding P190 BCR-ABL1) had a B-cell progenitor origin, suggesting that P190 and P210 BCR-ABL1 ALLs represent largely distinct tumor biological and clinical entities. The transformed leukemia-initiating stem cells in both P190 and P210 BCR-ABL1 ALLs had, as in ETV6-RUNX1 ALLs, a committed B progenitor phenotype. In all patients, normal and leukemic repopulating stem cells could successfully be separated prospectively, and notably, the size of the normal HSC compartment in ETV6-RUNX1 and P190 BCR-ABL1 ALLs was found to be unaffected by the expansive leukemic stem cell population.

Capsaicin, a component of red peppers, inhibits the growth of androgen-independent, p53 mutant prostate cancer cells.

Capsaicin is the major pungent ingredient in red peppers. Here, we report that it has a profound antiproliferative effect on prostate cancer cells, inducing the apoptosis of both androgen receptor (AR)-positive (LNCaP) and -negative (PC-3, DU-145) prostate cancer cell lines associated with an increase of p53, p21, and Bax. Capsaicin down-regulated the expression of not only prostate-specific antigen (PSA) but also AR. Promoter assays showed that capsaicin inhibited the ability of dihydrotestosterone to activate the PSA promoter/enhancer even in the presence of exogenous AR in LNCaP cells, suggesting that capsaicin inhibited the transcription of PSA not only via down-regulation of expression of AR, but also by a direct inhibitory effect on PSA transcription. Capsaicin inhibited NF-kappa activation by preventing its nuclear migration. In further studies, capsaicin inhibited tumor necrosis factor-alpha-stimulated degradation of IkappaBalpha in PC-3 cells, which was associated with the inhibition of proteasome activity. Taken together, capsaicin inhibits proteasome activity which suppressed the degradation of IkappaBalpha, preventing the activation of NF-kappaB. Capsaicin, when given orally, significantly slowed the growth of PC-3 prostate cancer xenografts as measured by size [75 +/- 35 versus 336 +/- 123 mm(3) (+/-SD); P = 0.017] and weight [203 +/- 41 versus 373 +/- 52 mg (+/-SD); P = 0.0006; capsaicin-treated versus vehicle-treated mice, respectively]. In summary, our data suggests that capsaicin, or a related analogue, may have a role in the management of prostate cancer.

Targeting p53 in Vivo: A First-in-Human Study With p53-Targeting Compound APR-246 in Refractory Hematologic Malignancies and Prostate Cancer

PURPOSE APR-246 (PRIMA-1MET) is a novel drug that restores transcriptional activity of unfolded wild-type or mutant p53. The main aims of this first-in-human trial were to determine maximum-tolerated dose (MTD), safety, dose-limiting toxicities (DLTs), and pharmacokinetics (PK) of APR-246. PATIENTS AND METHODS APR-246 was administered as a 2-hour intravenous infusion once per day for 4 consecutive days in 22 patients with hematologic malignancies and prostate cancer. Acute myeloid leukemia (AML; n = 7) and prostate cancer (n = 7) were the most frequent diagnoses. Starting dose was 2 mg/kg with dose escalations up to 90 mg/kg. RESULTS MTD was defined as 60 mg/kg. The drug was well tolerated, and the most common adverse effects were fatigue, dizziness, headache, and confusion. DLTs were increased ALT/AST (n = 1), dizziness, confusion, and sensory disturbances (n = 2). PK showed little interindividual variation and were neither dose nor time dependent; terminal half-life was 4 to 5 hours. Tumor cells showed cell cycle arrest, increased apoptosis, and upregulation of p53 target genes in several patients. Global gene expression analysis revealed changes in genes regulating proliferation and cell death. One patient with AML who had a p53 core domain mutation showed a reduction of blast percentage from 46% to 26% in the bone marrow, and one patient with non-Hodgkins lymphoma with a p53 splice site mutation showed a minor response. CONCLUSION We conclude that APR-246 is safe at predicted therapeutic plasma levels, shows a favorable pharmacokinetic profile, and can induce p53-dependent biologic effects in tumor cells in vivo.

Drug-resistant human lung cancer cells are more sensitive to selenium cytotoxicity. Effects on thioredoxin reductase and glutathione reductase.

The human U-1285 and GLC(4) cell lines, both derived from small cell carcinoma of the lung, are present in doxorubicin-sensitive (U-1285 and GLC(4)) and doxorubicin-resistant MRP-expressing (U-1285dox and GLC(4)/ADR) variants. These sublines were examined here with respect to their susceptibilities to the toxic effects of selenite and compared to the toxic effects of selenite on the promyelocytic leukemia cell line HL-60 and its doxorubicin-resistant P-glycoprotein expressing variant. The drug-resistant U-1285dox and GLC(4)/ADR sublines proved to be 3- and 4-fold, respectively, more sensitive to the cytotoxicity of selenite than the drug-sensitive U-1285 and GLC(4) sublines, whereas no difference was observed between the HL-60 sublines. The presence of doxorubicin at a concentration equal to the IC(10) did not significantly potentiate the toxic effects of selenite. The presence of selenite did not significantly affect the expression of the multi-drug resistant proteins (MRP1, LRP and topoisomerase IIalpha) in the drug-resistant cells. The activities of thioredoxin reductase (TrxR) were higher (50 and 25%, respectively) in the drug resistant cell sublines U-1285dox and GLC(4)/ADR compared to the drug-sensitive parental lines. The activity of glutathione reductase (GR) was essentially the same in the drug-sensitive and -resistant cell lines. Exposure to selenite resulted in a 4-fold increase in both TrxR and GR activities in U-1285 cells, an effect, which was less pronounced in the presence of doxorubicin. Under similar conditions the increase in the TrxR activity in the resistant U-1285dox cell line, was only 30% and the activity of GR was unaltered. Different responses in the activity of the key enzymes in selenium metabolism are one possible mechanism explaining the differential cytotoxicity of selenium in these cells.

Targeting SAMHD1 with the Vpx protein to improve cytarabine therapy for hematological malignancies

The cytostatic deoxycytidine analog cytarabine (ara-C) is the most active agent available against acute myelogenous leukemia (AML). Together with anthracyclines, ara-C forms the backbone of AML treatment for children and adults. In AML, both the cytotoxicity of ara-C in vitro and the clinical response to ara-C therapy are correlated with the ability of AML blasts to accumulate the active metabolite ara-C triphosphate (ara-CTP), which causes DNA damage through perturbation of DNA synthesis. Differences in expression levels of known transporters or metabolic enzymes relevant to ara-C only partially account for patient-specific differential ara-CTP accumulation in AML blasts and response to ara-C treatment. Here we demonstrate that the deoxynucleoside triphosphate (dNTP) triphosphohydrolase SAM domain and HD domain 1 (SAMHD1) promotes the detoxification of intracellular ara-CTP pools. Recombinant SAMHD1 exhibited ara-CTPase activity in vitro, and cells in which SAMHD1 expression was transiently reduced by treatment with the simian immunodeficiency virus (SIV) protein Vpx were dramatically more sensitive to ara-C-induced cytotoxicity. CRISPR–Cas9-mediated disruption of the gene encoding SAMHD1 sensitized cells to ara-C, and this sensitivity could be abrogated by ectopic expression of wild-type (WT), but not dNTPase-deficient, SAMHD1. Mouse models of AML lacking SAMHD1 were hypersensitive to ara-C, and treatment ex vivo with Vpx sensitized primary patient-derived AML blasts to ara-C. Finally, we identified SAMHD1 as a risk factor in cohorts of both pediatric and adult patients with de novo AML who received ara-C treatment. Thus, SAMHD1 expression levels dictate patient sensitivity to ara-C, providing proof-of-concept that the targeting of SAMHD1 by Vpx could be an attractive therapeutic strategy for potentiating ara-C efficacy in hematological malignancies.

Effects of arsenic trioxide (As2O3) on leukemic cells from patients with non-M3 acute myelogenous leukemia: studies of cytotoxicity, apoptosis and the pattern of resistance

Abstract: Arsenic oxide (As2O3) has recently been reported to induce remission in a high percentage of patients with acute promyelocytic leukemia (APL). The aim of this study was to investigate the effects of As2O3 at therapeutic concentrations on cell viability and apoptosis on leukemic cells from patients with non‐M3 acute myelogenous leukemia (AML) and to study the resistance profile compared to conventional AML drugs. Cells from 20 patients were exposed to therapeutic concentrations of As2O3 continuously for 96h. As2O3 reduced the viability in blast cells from all the 20 tested patients compared to unexposed controls (p‐value: 0.02 at 0.05 µM; <0.005 at 1.0 µM and higher concentrations). An increase in the apoptotic rate was also seen after incubation with As2O3. Parallel to the incubation with arsenic the in vitro sensitivity to a number of chemotherapeutic agents commonly used in AML was studied. Correlation coefficients for the in vitro sensitivity were highly significant between the conventional AML drugs except for Ara‐C. For As2O3, all the correlation coefficients were negative and ranged between −0.05 and −0.51. Furthermore, increased P‐gp expression in a multidrug resistant HL‐60 cell line did not decrease the sensitivity to As2O3 as compared to the parental cell line. Neither did a P‐gp‐transfected variant of the K562 cell line show decreased sensitivity to As2O3. We conclude that As2O3 at therapeutic concentrations induces apoptosis and cytotoxic effects in blast cells from patients with non‐M3 AML, and that As2O3 differs from conventional AML drugs with respect to the mechanisms that confer resistance to the drugs.

Chromosomal aberrations in 17p predict in vitro drug resistance and short overall survival in acute myeloid leukemia.

Chromosomal aberrations are important prognostic parameters in acute myeloid leukemia (AML). Indicators of poor prognosis include del(5q)/−5, del(7q)/−7, abnormal 3q or complex karyotype. In recent years, it has become clear that aberrations in 17p represent one of the indicators of poor prognosis in haematological malignancies. In AML, deletions in 17p have been shown to indicate a dismal prognosis; genetic aberrations in 9p have also been discussed as influencing long-term survival in AML. In this study, we correlated genetic abnormalities in chromosomes 9 and 17 in patients with de novo AML to in vitro cytotoxicity of conventional anti-leukemic drugs, and long-term overall survival. Blast cells were isolated from 387 patients diagnosed with AML. Chromosomal analysis was successful in 336 cases. All samples were tested for in vitro cytotoxicity against fludarabine, amsacrine, mitoxantrone, etoposide, daunorubicin and Ara-C after being cultured for 4 days, using an ATP assay. Among the 336 patients, five main groups were identified. Abnormal chromosome 17 (n = 22), abnormal 9p (n = 13), monosomy 7 or deletion 7q (n = 35), complex karyotype (n = 52) and normal karyotype (n = 132). Patients with abnormalities of chromosome 17 showed significantly greater resistance to all drugs tested and significantly shorter overall survival compared with patients with normal and complex karyotypes (p = 0.0001 and 0.041, respectively). All patients with abnormalities of chromosome 17 died within 11 months of diagnosis. A tendency towards shorter overall survival and greater drug resistance was also noted when comparing chromosome 17 abnormalities with del(7q)/−7, but the differences did not reach statistical significance. Patients with abnormal 9p showed significantly shorter overall survival but did not differ significantly as regards in vitro drug resistance compared with patients presenting with a normal karyotype. Chromosomal abnormalities affecting the p53 pathway have a significant impact on cytostatic drug resistance and survival in AML. Developing new drugs targeting the p53 pathway could be a way to improve treatment of AML.

Effects of retinoids on cell toxicity and apoptosis in leukemic blast cells from patients with non-M3 AML

All-trans retinoic acid (ATRA) induces complete remission in acute promyelocytic leukemia (APL or M3). In this study we measured the effect of retinoids alone and in combination with daunorubicin (DNR) on cell growth and apoptosis in blast cells from patients with non-M3 AML. Cells from 21 patients were incubated in 0.2 microM daunorubicin for 1 h or in 1 microM ATRA or 9-cis-RA continuously and in the combinations of DNR with both retinoids. Cell toxicity and apoptosis were analyzed after 96 h. Both ATRA and 9-cis-RA reduced the viability significantly to 86 and 84%, respectively (P = 0.003 for ATRA and 0.02 for 9-cis-RA). The expression of CD34 correlated to a higher sensitivity to ATRA (P = 0.003). When retinoids were added to DNR the mean decrease in viability was 11 percentage points with ATRA (P = 0.003) and nine percentage points with 9-cis-RA (P = 0.02). Apoptosis was induced by both retinoids and the percentage of apoptotic cells was increased from 16% in the controls to 24% with ATRA (P = 0.03) and to 26% with 9-cis-RA (P = 0.04). When the retinoids were added to DNR the apoptotic rate increased from 41% with DNR alone to 51% with ATRA (P = 0.01) and to 49% with 9-cis-RA (P = 0.03). We conclude that ATRA and RA exert a slight but clear cytotoxic and apoptotic effect on AML blast cells after 96 h incubation and that retinoids can have an additive or synergistic effects on cell toxicity when added to daunorubicin.

A critical appraisal of tools available for monitoring epigenetic changes in clinical samples from patients with myeloid malignancies

Research over the past decade has confirmed that epigenetic alterations act in concert with genetic lesions to deregulate gene expression in acute myeloid leukemia and myelodysplastic syndromes. Epigenetic alterations may serve as markers of disease, and may potentially be used for classification, prognostication and to monitor minimal residual disease. In addition, we now have the capability to pharmaceutically target epigenetic modifications, and there is an urgent need for early validation of the efficacy of the drugs. Also, an improved understanding of the functionality of epigenetic modifications may further pave the road towards individualized therapy. The recent advances in biotechnology and bioinformatics provide a plethora of novel tools for characterizing the epigenome in clinical samples, but at this point the practical, clinical utility of these methodologies needs further exploration. Here, we provide the pros and cons of the currently most feasible methods used for characterizing the methylome in clinical samples, and give a brief introduction to novel approaches to sequencing that may revolutionize our abilities to characterize the genomes and epigenomes in acute myeloid leukemia and myelodysplastic syndrome patients.

Single nucleotide polymorphism genomic arrays analysis of t(8;21) acute myeloid leukemia cells

Translocation of chromosomes 8 and 21, t(8;21), resulting in the AML1-ETO fusion gene, is associated with acute myeloid leukemia (AML). The findings of this study indicate that genomic alterations and KIT-D816 mutation confer a poor prognosis in t(8;21) AML patients. Translocation of chromosomes 8 and 21, t(8;21), resulting in the AML1-ETO fusion gene, is associated with acute myeloid leukemia. We searched for additional genomic abnormalities in this acute myeloid leukemia subtype by performing single nucleotide polymorphism genomic arrays (SNP-chip) analysis on 48 newly diagnosed cases. Thirty-two patients (67%) had a normal genome by SNP-chip analysis (Group A), and 16 patients (33%) had one or more genomic abnormalities including copy number changes or copy number neutral loss of heterozygosity (Group B). Two samples had copy number neutral loss of heterozygosity on chromosome 6p including the PIM1 gene; and one of these cases had E135K mutation of Pim1. Interestingly, 38% of Group B and only 13% of Group A samples had a KIT-D816 mutation, suggesting that genomic alterations are often associated with a KIT-D816 mutation. Importantly, prognostic analysis revealed that overall survival and event-free survival of individuals in Group B were significantly worse than those in Group A.