In Vivo Modeling of Leukemia by Murine Stem Cell Transplantation.

Murine stem cell transplantation is a well-established method for the in vivo study of leukemic pathophysiology. Adoptive transfer of murine leukemic cells into lethally irradiated recipient mice leads to reconstitution of the hematopoietic system with malignant cells and eventually to leukemic progression in the recipient mice. Here, we describe the detailed protocol of the production of retroviral particles carrying the leukemic oncogene of interest as well as the isolation, retroviral transduction, and adoptive transfer of murine bone marrow cells.

Urinary Incontinence, Quality of Life, and Risk Factors in a Geriatric Cohort.

INTRODUCTION: The aim of the study was to evaluate the prevalence of urinary incontinence (UI) and its subtypes, associated clinical factors, and impact on quality of life (QoL) in a geriatric population aged 80 years or older. METHODS: Male and female residents (inclusion criterion: 80 years or older) of three Viennese senior citizen homes were personally interviewed with the aid of a structured questionnaire based on the Bristol Female Lower Urinary Tract Symptom Questionnaire within a 12-month period. UI was defined as any involuntary loss of urine during the past 4 weeks. Several demographic parameters were obtained additionally. RESULTS: 434 participants with a mean age of 86.8 years (women: 87.6 years; men: 86.1 years) were included. UI was present in 52.5% (57% female vs. 23% male, p < 0.001), stress UI affected 36% (41% female vs. 5% male, p < 0.001), urge UI 38% (40.5% female vs. 23% male, p < 0.01), and mixed UI 28% (24% female vs. 5.0% male, p < 0.01). While the overall prevalence of UI remained rather stable in the four age cohorts (80-84 years, 85-89 years, 90-94 years, >94 years), there was a constant decline of SUI paralleled by an increase of UI and - to a lesser extent - of MUI with age. 36.5% (33% female vs. 57% male) participants did not report any negative impact on QoL, while a severe reduction of QoL was present in 31% of cases (35% female vs. 10.0% male). Risk factors for UI and its subtypes included female sex, reduced/no mobility, hysterectomy, and number of births. CONCLUSION: This study provides data on the high prevalence of UI in a low-morbid geriatric cohort and evaluates gender-specific differences in UI prevalence, associated risk factors, and QoL.

A kinase-independent role for CDK8 in BCR-ABL1+ leukemia.

Cyclin-dependent kinases (CDKs) are frequently deregulated in cancer and represent promising drug targets. We provide evidence that CDK8 has a key role in B-ALL. Loss of CDK8 in leukemia mouse models significantly enhances disease latency and prevents disease maintenance. Loss of CDK8 is associated with pronounced transcriptional changes, whereas inhibiting CDK8 kinase activity has minimal effects. Gene set enrichment analysis suggests that the mTOR signaling pathway is deregulated in CDK8-deficient cells and, accordingly, these cells are highly sensitive to mTOR inhibitors. Analysis of large cohorts of human ALL and AML patients reveals a significant correlation between the level of CDK8 and of mTOR pathway members. We have synthesized a small molecule YKL-06-101 that combines mTOR inhibition and degradation of CDK8, and induces cell death in human leukemic cells. We propose that simultaneous CDK8 degradation and mTOR inhibition might represent a potential therapeutic strategy for the treatment of ALL patients.

Twins with different personalities: STAT5B-but not STAT5A-has a key role in BCR/ABL-induced leukemia.

Deregulation of the Janus kinase/signal transducers and activators of transcription (JAK/STAT) signaling pathway is found in cancer with STAT5A/B controlling leukemic cell survival and disease progression. As mutations in STAT5B, but not STAT5A, have been frequently described in hematopoietic tumors, we used BCR/ABL as model systems to investigate the contribution of STAT5A or STAT5B for leukemogenesis. The absence of STAT5A decreased cell survival and colony formation. Even more drastic effects were observed in the absence of STAT5B. STAT5B-deficient cells formed BCR/ABL+ colonies or stable cell lines at low frequency. The rarely evolving Stat5b-/- cell lines expressed enhanced levels of BCR/ABL oncoprotein compared to wild-type cells. In line, Stat5b-/- leukemic cells induced leukemia with a significantly prolonged disease onset, whereas Stat5a-/- cells rapidly caused a fatal disease superimposable to wild-type cells. RNA-sequencing (RNA-seq) profiling revealed a marked enhancement of interferon (IFN)-α and IFN-γ signatures in Stat5b-/- cells. Inhibition of IFN responses rescued BCR/ABL+ colony formation of Stat5b-/--deficient cells. A downregulated IFN response was also observed in patients suffering from leukemia carrying STAT5B mutations. Our data define STAT5B as major STAT5 isoform driving BCR/ABL+ leukemia. STAT5B enables transformation by suppressing IFN-α/γ, thereby facilitating leukemogenesis. Our findings might help explain the high frequency of STAT5B mutations in hematopoietic tumors.

NK Cell-Specific CDK8 Deletion Enhances Antitumor Responses.

Cyclin-dependent kinase 8 (CDK8) is a member of the transcription-regulating CDK family. CDK8 activates or represses transcription by associating with the mediator complex or by regulating transcription factors. Oncogenic activity of CDK8 has been demonstrated in several cancer types. Targeting CDK8 represents a potential therapeutic strategy. Because knockdown of CDK8 in a natural killer (NK) cell line enhances cytotoxicity and NK cells provide the first line of immune defense against transformed cells, we asked whether inhibiting CDK8 would improve NK-cell antitumor responses. In this study, we investigated the role of CDK8 in NK-cell function in vivo using mice with conditional ablation of CDK8 in NKp46+ cells (Cdk8fl/flNcr1Cre). Regardless of CDK8 expression, NK cells develop and mature normally in bone marrow and spleen. However, CDK8 deletion increased expression of the lytic molecule perforin, which correlated with enhanced NK-cell cytotoxicity in vitro This translates into improved NK cell-mediated tumor surveillance in vivo in three independent models: B16F10 melanoma, v-abl+ lymphoma, and a slowly developing oncogene-driven leukemia. Our results thereby define a suppressive effect of CDK8 on NK-cell activity. Therapies that target CDK8 in cancer patients may enhance NK-cell responses against tumor cells. Cancer Immunol Res; 6(4); 458-66. ©2018 AACR.

Expansion of BCR/ABL1+ cells requires PAK2 but not PAK1.

The p21-activated kinases (PAKs) are key nodes in oncogenic signalling pathways controlling growth, survival, and motility of cancer cells. Their activity is increased in many human cancers and is associated with poor prognosis. To date, PAK deregulation has mainly been studied in solid tumours, where PAK1 and PAK4 are the main isoforms deregulated. We show that PAK1 and PAK2 are the critical isoforms in a BCR/ABL1+ haematopoietic malignancy. In suspension, leukaemic cells deficient for PAK1 and PAK2 undergo apoptosis, while the loss of either protein is well tolerated. Transfer of medium conditioned by shPAK2- but not shPAK1-expressing leukaemic cells interferes with endothelial cell growth. We found that leukaemic cells produce exosomes containing PAK2. Transfer of isolated exosomes supports endothelial cell proliferation. In parallel, we found that leukaemic cells explicitly require PAK2 to grow towards an extracellular matrix. PAK2-deficient cells fail to form colonies in methylcellulose and to induce lymphomas in vivo. PAK2 might therefore be the critical isoform in leukaemic cells by controlling tumour growth in a dual manner: vascularization via exosome-mediated transfer to endothelial cells and remodelling of the extracellular matrix. This finding suggests that the PAK2 isoform represents a promising target for the treatment of haematological diseases.