Male dominance linked to size and age, but not to 'good genes' in brown trout (Salmo trutta)

BACKGROUND: Males that are successful in intra-sexual competition are often assumed to be of superior quality. In the mating system of most salmonid species, intensive dominance fights are common and the winners monopolise most mates and sire most offspring. We drew a random sample of mature male brown trout (Salmo trutta) from two wild populations and determined their dominance hierarchy or traits linked to dominance. The fish were then stripped and their sperm was used for in vitro fertilisations in two full-factorial breeding designs. We recorded embryo viability until hatching in both experiments, and juvenile survival during 20 months after release into a natural streamlet in the second experiment. Since offspring of brown trout get only genes from their fathers, we used offspring survival as a quality measure to test (i) whether males differ in their genetic quality, and if so, (ii) whether dominance or traits linked to dominance reveal 'good genes'. RESULTS: We found significant additive genetic variance on embryo survival, i.e. males differed in their genetic quality. Older, heavier and larger males were more successful in intra-sexual selection. However, neither dominance nor dominance indicators like body length, weight or age were significantly linked to genetic quality measured as embryo or juvenile survival. CONCLUSION: We found no evidence that females can improve their offspring's genetic viability by mating with large and dominant males. If there still were advantages of mating with dominant males, they may be linked to non-genetic benefits or to genetic advantages that are context dependent and therefore possibly not revealed under our experimental conditions - even if we found significant additive genetic variation for embryo viability under such conditions

Induction of autophagy is a key component of all-trans-retinoic acid-induced differentiation in leukemia cells and a potential target for pharmacological modulation

Acute myeloid leukemia (AML) is characterized by the accumulation of immature blood cell precursors in the bone marrow. Pharmacologically overcoming the differentiation block in this condition is an attractive therapeutic avenue, which has achieved success only in a subtype of AML, acute promyelocytic leukemia (APL). Attempts to emulate this success in other AML subtypes have thus far been unsuccessful. Autophagy is a conserved protein degradation pathway with important roles in mammalian cell differentiation, particularly within the hematopoietic system. In the study described here, we investigated the functional importance of autophagy in APL cell differentiation. We found that autophagy is increased during all-trans-retinoic acid (ATRA)-induced granulocytic differentiation of the APL cell line NB4 and that this is associated with increased expression of LC3II and GATE-16 proteins involved in autophagosome formation. Autophagy inhibition, using either drugs (chloroquine/3-methyladenine) or short-hairpin RNA targeting the essential autophagy gene ATG7, attenuates myeloid differentiation. Importantly, we found that enhancing autophagy promotes ATRA-induced granulocytic differentiation of an ATRA-resistant derivative of the non-APL AML HL60 cell line (HL60-Diff-R). These data support the development of strategies to stimulate autophagy as a novel approach to promote differentiation in AML

Low Autophagy (ATG) Gene Expression Is Associated with an Immature AML Blast Cell Phenotype and Can Be Restored during AML Differentiation Therapy

Autophagy is an intracellular degradation system that ensures a dynamic recycling of a variety of building blocks required for self-renewal, homeostasis, and cell survival under stress. We used primary acute myeloid leukemia (AML) samples and human AML cell lines to investigate the regulatory mechanisms of autophagy and its role in AML differentiation. We found a significantly lower expression of key autophagy- (ATG-) related genes in primary AML as compared to healthy granulocytes, an increased autophagic activity during all-trans retinoic acid- (ATRA-) induced neutrophil differentiation, and an impaired AML differentiation upon inhibition of ATG3, ATG4D, and ATG5. Supporting the notion of noncanonical autophagy, we found that ATRA-induced autophagy was Beclin1-independent compared to starvation- or arsenic trioxide- (ATO-) induced autophagy. Furthermore, we identified PU.1 as positive transcriptional regulator of ATG3, ATG4D, and ATG5. Low PU.1 expression in AML may account for low ATG gene expression in this disease. Low expression of the autophagy initiator ULK1 in AML can partially be attributed to high expression of the ULK1-targeting microRNA-106a. Our data clearly suggest that granulocytic AML differentiation relies on noncanonical autophagy pathways and that restoring autophagic activity might be beneficial in differentiation therapies

Targeting PI3K, IL-8/JAK2 axis and HER2 in metastatic breast cancer: which combination makes the whole greater than the sum of its parts

The phosphatidylinositol 3-kinase (PI3K) signaling pathway plays a pivotal role in cellular growth, proliferation, metabolism and survival. Not surprisingly, inappropriate activation of this pathway is very frequent in human cancers and transgenic expression of mutant PI3K in mice causes tumors. Extensive efforts have been made in the development of PI3K-pathway inhibitors but single agent therapy mostly yields limited antitumor activity in the clinical setting due to the rapid emergence of adaptive resistanc

Epigallocatechin-3-gallate induces cell death in acute myeloid leukaemia cells and supports all-trans retinoic acid-induced neutrophil differentiation via death-associated protein kinase 2

Acute promyelocytic leukaemia (APL) patients are successfully treated with all-trans retinoic acid (ATRA). However, concurrent chemotherapy is still necessary and less toxic therapeutic approaches are needed. Earlier studies suggested that in haematopoietic neoplasms, the green tea polyphenol epigallocatechin-3-gallate (EGCG) induces cell death without adversely affecting healthy cells. We aimed at deciphering the molecular mechanism of EGCG-induced cell death in acute myeloid leukaemia (AML). A significant increase of death-associated protein kinase 2 (DAPK2) levels was found in AML cells upon EGCG treatment paralleled by increased cell death that was significantly reduced upon silencing of DAPK2. Moreover, combined ATRA and EGCG treatment resulted in cooperative DAPK2 induction and potentiated differentiation. EGCG toxicity of primary AML blasts correlated with 67 kDa laminin receptor (67LR) expression. Pretreatment of AML cells with ATRA, causing downregulation of 67LR, rendered these cells resistant to EGCG-mediated cell death. In summary, it was found that (i) DAPK2 is essential for EGCG-induced cell death in AML cells, (ii) ATRA and EGCG cotreatment significantly boosted neutrophil differentiation, and 67LR expression correlates with susceptibility of AML cells to EGCG. We thus suggest that EGCG, by selectively targeting leukaemic cells, may improve differentiation therapies for APL and chemotherapy for other AML subtypes

Green Tea Catechin Epigallocatechin-3-Gallate (EGCG) Induces Cell Death in Acute Myeloid Leukemic Cells Via DAPK2 and Potentiates ATRA-Induced Neutrophil Differentiation

Abstract Acute promyelocytic leukemia (APL) patients are currently treated with all-trans retinoic acid (ATRA) successfully resolving the differentiation block. However, concurrent chemotherapy is still necessary in combination with ATRA and novel less toxic therapeutic approaches are a major demand. Epigallocatechin-3-gallate (EGCG), the main polyphenolic compound present in green tea, has been reported to have chemopreventive and chemotherapeutic effects in different neoplasms. EGCG inhibits cell growth in vitro and in vivo and induces apoptosis in cancer cells without adversely affecting normal cells. Also, EGCG has been found in earlier studies to effectively kill AML blasts, but it has never been applied in combination with ATRA. We have previously shown that expression of the death-associated protein kinase 2 (DAPK2) enhanced ATRA-induced neutrophil development, and recently it was shown that EGCG specifically killed multiple myeloma cells while inducing DAPK2. Therefore, we first tested whether EGCG treatment induces DAPK2 expression in myeloid leukemic blast cells and whether this will lead to cell death. EGCG treatment of HL60 and NB4 acute myeloid leukemic cells led to a dose-dependent increase of DAPK2 mRNA with a maximum of 5.5- and 3.9-fold, respectively. In parallel, DAPK2 protein was markedly upregulated in both cell lines accompanied by a 72% increase of cell death after 24h, as measured by reduction of tetrazolium salt (XTT assay), and by hallmarks of apoptosis: activation of caspase-3 and phosphatidylserine exposure on the plasma membrane surface. EGCG-induced cytotoxicity was reduced by 48% in HL60 and by 46% in NB4 cells upon stable short hairpin RNA-mediated silencing of DAPK2. Moreover, combined ATRA and EGCG treatment of HL60 cells resulted in cooperative DAPK2 induction and potentiated myeloid differentiation as measured by CD11b and CD15 expression using flow cytometry (Figure A) as well as by C/EBPε and G-CSFR mRNA levels using quantitative RT-PCR. Enhanced differentiation was significantly reversed by knocking down DAPK2. Moreover, EGCG toxicity of NB4 and HL60 cells correlated with 67 kDa laminin receptor (67LR) protein expression which is downregulated during ATRA treatment of HL60 and NB4 cells but not in the ATRA-resistant sublines HL60-R and NB4-R. In line, HL60-R and NB4-R cells are still susceptible to EGCGinduced cell killing, whereas pretreatment of parental HL60 and NB4 cells with ATRA, causing downregulation of 67LR, rendered these cells resistant to EGCG mediated killing. Likewise, susceptibility of primary AML (n=8) samples to EGCG treatment was closely associated with 67LR expression. Moreover, neutrophils and PBMCs from healthy donors did not express 67LR and hence were resistant to EGCG treatment (Figure B). Figure Figure In summary, we found that DAPK2 is essential for EGCG-induced cell death in myeloid leukemic cells, and that a combination of ATRA and EGCG treatment significantly boosted neutrophil differentiation. This enhanced differentiation is most likely due to preferred EGCG-induced killing of ATRA-resistant leukemic cells expressing the EGCG receptor 67LR. We thus conclude that simultaneous ATRA and EGCG treatment might improve differentiation therapies for APL. In addition, other AML subtypes with high 67LR expression might also benefit from a combined chemotherapy and EGCG regimen.</jats:p

The tumor suppressor gene hypermethylated in cancer 1 is transcriptionally regulated by E2F1

The Hypermethylated in Cancer 1 (HIC1) gene encodes a zinc finger transcriptional repressor that cooperates with p53 to suppress cancer development. We and others recently showed that HIC1 is a transcriptional target of p53. To identify additional transcriptional regulators of HIC1, we screened a set of transcription factors for regulation of a human HIC1 promoter reporter. We found that E2F1 strongly activates the full-length HIC1 promoter reporter. Promoter deletions and mutations identified two E2F responsive elements in the HIC1 core promoter region. Moreover, in vivo binding of E2F1 to the HIC1 promoter was shown by chromatin immunoprecipitation assays in human TIG3 fibroblasts expressing tamoxifen-activated E2F1. In agreement, activation of E2F1 in TIG3-E2F1 cells markedly increased HIC1 expression. Interestingly, expression of E2F1 in the p53(-/-) hepatocellular carcinoma cell line Hep3B led to an increase of endogenous HIC1 mRNA, although bisulfite genomic sequencing of the HIC1 promoter revealed that the region bearing the two E2F1 binding sites is hypermethylated. In addition, endogenous E2F1 induced by etoposide treatment bound to the HIC1 promoter. Moreover, inhibition of E2F1 strongly reduced the expression of etoposide-induced HIC1. In conclusion, we identified HIC1 as novel E2F1 transcriptional target in DNA damage responses