Vassiliki E. Mpakou

Dasatinib inhibits proliferation and induces apoptosis in the KASUMI-1 cell line bearing the t(8;21)(q22;q22) and the N822K c-kit mutation

Activating mutations of the c-kit gene are frequently found in CBF (core binding factor) leukemias. We evaluated the effect of tyrosine kinase inhibitor dasatinib in leukemic cell lines bearing or not c-kit mutations. Our data demonstrate that in the AML Kasumi-1 cell line, bearing the N822K c-kit mutation, dasatinib is a potent suppressor of c-kit and Src kinase activity and inhibits the phosphorylation of their downstream target AKT, possibly through the Src-mediated VEGF/VEGFR receptor type 2 pathway. Dasatinib also effectively blocks proliferation and induces apoptosis through caspase-3 activation in Kasumi-1 cells. These data further encourage the integration of dasatinib in the treatment of CBF AML with c-kit mutations in the context of clinical trials, which are eagerly anticipated.

Detrimental effects of proteasome inhibition activity in Drosophila melanogaster: implication of ER stress, autophagy, and apoptosis.

In eukaryotes, the ubiquitin–proteasome machinery regulates a number of fundamental cellular processes through accurate and tightly controlled protein degradation pathways. We have, herein, examined the effects of proteasome functional disruption in Dmp53+/+ (wild-type) and Dmp53−/−Drosophila melanogaster fly strains through utilization of Bortezomib, a proteasome-specific inhibitor. We report that proteasome inhibition drastically shortens fly life-span and impairs climbing performance, while it also causes larval lethality and activates developmentally irregular cell death programs during oogenesis. Interestingly, Dmp53 gene seems to play a role in fly longevity and climbing ability. Moreover, Bortezomib proved to induce endoplasmic reticulum (ER) stress that was able to result in the engagement of unfolded protein response (UPR) signaling pathway, as respectively indicated by fly Xbp1 activation and Ref(2)P-containing protein aggregate formation. Larva salivary gland and adult brain both underwent strong ER stress in response to Bortezomib, thus underscoring the detrimental role of proteasome inhibition in larval development and brain function. We also propose that the observed upregulation of autophagy operates as a protective mechanism to “counterbalance” Bortezomib-induced systemic toxicity, which is tightly associated, besides ER stress, with activation of apoptosis, mainly mediated by functional Drice caspase and deregulated dAkt kinase. The reduced life-span of exposed to Bortezomib flies overexpressing Atg1_RNAi or Atg18_RNAi supports the protective nature of autophagy against proteasome inhibition-induced stress. Our data reveal the in vivo significance of proteasome functional integrity as a major defensive system against cellular toxicity likely occurring during critical biological processes and morphogenetic courses.

Programmed cell death of the ovarian nurse cells during oogenesis of the ladybird beetle Adalia bipunctata (Coleoptera: Coccinellidae).

Programmed cell death (PCD) is an evolutionary conserved and genetically regulated form of cell death, in which the cell plays an active role in its own demise. It is widely recognized that PCD can be morphologically classified into three major types: type I, known as apoptosis, type II, called autophagy, and type III, specified as cytoplasmic cell death. So far, PCD has been morphologically analyzed in certain model insect species of the meroistic polytrophic ovary‐type, but has never been examined before in insects carrying meroistic telotrophic ovaries. In the present study, we attempted to thoroughly describe the three different types (I, II and III) of PCD occurring during oogenesis in the meroistic telotrophic ovary of the Coleoptera species Adalia bipunctata, at different developmental ages of the adult female insects. We reveal that in the ladybird beetle A. bipunctata, the ovarian tropharia undergo age‐dependent forms of apoptotic, autophagic and cytoplasmic (paraptotic‐like) cell death, which seem to operate in a rather synergistic fashion, in accordance with previous observations in Diptera and Lepidoptera species. Furthermore, we herein demonstrate the occurrence of morphogenetically abnormal ovarioles in A. bipunctata female insects. These atretic ovarioles collapse and die through a PCD‐mediated process that is characterized by the combined activation of all three types of PCD. Conclusively, the distinct cell death programs (I, II and III) specifically engaged during oogenesis of A. bipunctata provide strong evidence for the structural and functional conserved nature of PCD during insect evolution among meroistic telotrophic and meroistic polytrophic ovary‐type insects.

Proteasome, but Not Autophagy, Disruption Results in Severe Eye and Wing Dysmorphia: A Subunit- and Regulator-Dependent Process in Drosophila

Proteasome-dependent and autophagy-mediated degradation of eukaryotic cellular proteins represent the two major proteostatic mechanisms that are critically implicated in a number of signaling pathways and cellular processes. Deregulation of functions engaged in protein elimination frequently leads to development of morbid states and diseases. In this context, and through the utilization of GAL4/UAS genetic tool, we herein examined the in vivo contribution of proteasome and autophagy systems in Drosophila eye and wing morphogenesis. By exploiting the ability of GAL4-ninaE. GMR and P{GawB}BxMS1096 genetic drivers to be strongly and preferentially expressed in the eye and wing discs, respectively, we proved that proteasomal integrity and ubiquitination proficiency essentially control fly’s eye and wing development. Indeed, subunit- and regulator-specific patterns of severe organ dysmorphia were obtained after the RNAi-induced downregulation of critical proteasome components (Rpn1, Rpn2, α5, β5 and β6) or distinct protein-ubiquitin conjugators (UbcD6, but not UbcD1 and UbcD4). Proteasome deficient eyes presented with either rough phenotypes or strongly dysmorphic shapes, while transgenic mutant wings were severely folded and carried blistered structures together with loss of vein differentiation. Moreover, transgenic fly eyes overexpressing the UBP2-yeast deubiquitinase enzyme were characterized by an eyeless-like phenotype. Therefore, the proteasome/ubiquitin proteolytic activities are undoubtedly required for the normal course of eye and wing development. In contrast, the RNAi-mediated downregulation of critical Atg (1, 4, 7, 9 and 18) autophagic proteins revealed their non-essential, or redundant, functional roles in Drosophila eye and wing formation under physiological growth conditions, since their reduced expression levels could only marginally disturb wing’s, but not eye’s, morphogenetic organization and architecture. However, Atg9 proved indispensable for the maintenance of structural integrity of adult wings in aged flies. In toto, our findings clearly demonstrate the gene-specific fundamental contribution of proteasome, but not autophagy, in invertebrate eye and wing organ development.

Proteasome inhibition induces developmentally deregulated programs of apoptotic and autophagic cell death during Drosophila melanogaster oogenesis.

Ubiquitin/proteasome‐mediated degradation of eukaryotic proteins is critically implicated in a number of signalling pathways and cellular processes. To specifically impair proteasome activities, in vitro developing Drosophila melanogaster egg chambers were exposed to the MG132 or epoxomicin proteasome inhibitors, while a GAL4/UAS binary genetic system was employed to generate double transgenic flies overexpressing β2 and β6 conditional mutant proteasome subunits in a cell type‐specific manner. MG132 and epoxomicin administration resulted in severe deregulation of in vitro developing egg chambers, which was tightly associated with precocious induction of nurse cell‐specific apoptotic and autophagic death programmes, featured by actin cytoskeleton disorganization, nuclear chromatin condensation, DRICE caspase activation and autophagosome accumulation. In vivo targeted overexpression of β2 and β6 conditional mutants, specifically in the nurse cell compartment, led to a notable up‐regulation of sporadic apoptosis potency during early and mid‐oogenesis ‘checkpoints’, thus reasonably justifying the observed reduction in eclosion efficiency. Furthermore, in response to the intracellular abundance of β2 and β6 conditional mutant forms, specifically in numerous tissues of third instar larval stage, the developmental course was arrested, and lethal phenotypes were obtained at this particular embryonic period, with the double transgenic heterozygote embryos being unable to further proceed to complete maturation to adult flies. Our data demonstrate that physiological proteasome function is required to ensure normal oogenesis and embryogenesis in D. melanogaster, since targeted and cell type‐dependent proteasome inactivation initiates developmentally deregulated apoptotic and autophagic mechanisms.

Quantitative Measurement of L1 Human Papillomavirus Type 16 Methylation for the Prediction of Preinvasive and Invasive Cervical Disease

Background Methylation of the human papillomavirus (HPV) DNA has been proposed as a novel biomarker. Here, we correlated the mean methylation level of 12 CpG sites within the L1 gene, to the histological grade of cervical precancer and cancer. We assessed whether HPV L1 gene methylation can predict the presence of high-grade disease at histology in women testing positive for HPV16 genotype. Methods Pyrosequencing was used for DNA methylation quantification and 145 women were recruited. Results We found that the L1 HPV16 mean methylation (±SD) significantly increased with disease severity (cervical intraepithelial neoplasia [CIN] 3, 17.9% [±7.2] vs CIN2, 11.6% [±6.5], P < .001 or vs CIN1, 9.0% [±3.5], P < .001). Mean methylation was a good predictor of CIN3+ cases; the area under the curve was higher for sites 5611 in the prediction of CIN2+ and higher for position 7145 for CIN3+. The evaluation of different methylation thresholds for the prediction of CIN3+ showed that the optimal balance of sensitivity and specificity (75.7% and 77.5%, respectively) and positive and negative predictive values (74.7% and 78.5%, respectively) was achieved for a methylation of 14.0% with overall accuracy of 76.7%. Conclusions Elevated methylation level is associated with increased disease severity and has good ability to discriminate HPV16-positive women that have high-grade disease or worse.

Targeted Downregulation of s36 Protein Unearths its Cardinal Role in Chorion Biogenesis and Architecture during Drosophila melanogaster Oogenesis

Drosophila chorion represents a model biological system for the in vivo study of gene activity, epithelial development, extracellular-matrix assembly and morphogenetic-patterning control. It is produced during the late stages of oogenesis by epithelial follicle cells and develops into a highly organized multi-layered structure that exhibits regional specialization and radial complexity. Among the six major proteins involved in chorion’s formation, the s36 and s38 ones are synthesized first and regulated in a cell type-specific and developmental stage-dependent manner. In our study, an RNAi-mediated silencing of s36 chorionic-gene expression specifically in the follicle-cell compartment of Drosophila ovary unearths the essential, and far from redundant, role of s36 protein in patterning establishment of chorion’s regional specialization and radial complexity. Without perturbing the developmental courses of follicle- and nurse-cell clusters, the absence of s36 not only promotes chorion’s fragility but also induces severe structural irregularities on chorion’s surface and entirely impairs fly’s fertility. Moreover, we herein unveil a novel function of s36 chorionic protein in the regulation of number and morphogenetic integrity of dorsal appendages in follicles sporadically undergoing aged fly-dependent stress.

Apoptosis Induction and Gene Expression Profile Alterations of Cutaneous T-Cell Lymphoma Cells following Their Exposure to Bortezomib and Methotrexate

Mycosis fungoides (MF) and its leukemic variant Sézary syndrome (SS) comprise the majority of CTCL, a heterogenous group of non-Hodgkins lymphomas involving the skin. The CTCL’s resistance to chemotherapy and the lack of full understanding of their pathogenesis request further investigation. With the view of a more targeted therapy, we evaluated in vitro the effectiveness of bortezomib and methotrexate, as well as their combination in CTCL cell lines, regarding apoptosis induction. Our data are of clinical value and indicate that the bortezomib/methotrexate combinational therapy has an inferior impact on the apoptosis of CTCL compared to monotherapy, with bortezomib presenting as the most efficient treatment option for SS and methotrexate for MF. Using PCR arrays technology, we also investigated the alterations in the expression profile of genes related to DNA repair pathways in CTCL cell lines after treatment with bortezomib or methotrexate. We found that both agents, but mostly bortezomib, significantly deregulate a large number of genes in SS and MF cell lines, suggesting another pathway through which these agents could induce apoptosis in CTCL. Finally, we show that SS and MF respond differently to treatment, verifying their distinct nature and further emphasizing the need for discrete treatment approaches.

Quantitative and qualitative analysis of regulatory T cells in B cell chronic lymphocytic leukemia

Accumulated data indicate a significant role of T cell dysfunction in the pathogenesis of chronic lymphocytic leukemia. In CLL, regulatory T cells are significantly higher and show lower apoptotic levels compared to healthy donors. We demonstrate that CLL derived CD4+CD25-CD127- and CD4+CD25lowCD127- subpopulations share a common immunophenotypic profile with conventional Tregs and are associated with advanced stage disease. We further provide evidence that the increased number of Tregs contributes indirectly to the proliferation of the CLL clone, by suppressing the proliferation of Teffs which in turn suppress CLL cells. These data are further supported by our observations that CLL derived Tregs appear rather incapable of inducing apoptosis of both normal B cells and CLL cells, in contrast to normal Tregs, suggesting an immunoediting effect of CLL cells on Tregs which negatively affects the functionality of the latter and contributes to the failure of Tregs in CLL to efficiently eliminate the abnormal clone.

Data of sperm-entry inability in Drosophila melanogaster ovarian follicles that are depleted of s36 chorionic protein

This paper presents data associated with the research article entitled “Targeted downregulation of s36 protein unearths its cardinal role in chorion biogenesis and architecture during Drosophila melanogaster oogenesis” [1]. Drosophila chorion is produced by epithelial follicle cells and one of its functional serving role is egg fertilization through the micropyle, a specialized narrow channel at the anterior tip of the egg [2]. Sperm entry during fertilization is necessary for the egg to complete meiosis [3]. D. melanogaster flies being characterized by severe downregulation of the s36 chorionic protein, specifically in the follicle-cell compartment of their ovary, appear with impaired fly fertility (Velentzas et al., 2016) [1]. In an effort to further investigate whether the observed infertility in the s36-targeted flies derives from a fertilization failure, such as the inability of sperm to pass through egg׳s micropyle, we mated females carrying s36-depleted ovaries with males expressing the GFP protein either in their sperm tails, or in both their sperm tails and sperm heads.