Yorkie drives Ras-induced tumor progression by microRNA-mediated inhibition of cellular senescence

Epithelial cell-fate switch triggering ectopic ligand-receptor-mediated JAK-STAT signaling promotes tumorigenesis in Drosophila

Disruption of epithelial architecture is a hallmark of human malignant cancers, yet whether and how epithelial deformation influences tumor progression has been elusive. Here, through a genetic screen in Drosophila eye disc, we explored mutations that potently promoted Ras-activated (RasV12) tumor growth and identified eyes absent (eya), an eye determination gene, whose mutation compromised tissue growth but synergized with RasV12 to cause massive overgrowth. Furthermore, induction of cell-fate switch by mis-expression of Abd-B in the eye disc also induced massive RasV12 overgrowth. Mechanistically, cell-fate switch caused epithelial invagination accompanied by partial mislocalization of the transmembrane receptor Domeless (Dome) from the apical to the basal membrane of the eye epithelium, where its ligand Unpaired3 (Upd3) is present. This led to JAK-STAT activation that cooperates with RasV12 to drive tumor progression. Our data provide a mechanistic explanation for how cell-fate switch and subsequent epithelial deformation creates a cancer-prone environment in the epithelium.

Programmed cell senescence is required for sensory organ development in Drosophila

Cellular senescence is an irreversible cell-cycle arrest often associated with cancer and aging, yet its physiological role remains elusive. Here, we show developmentally programmed cellular senescence occurs in Drosophila imaginal epithelium. In developing wing discs, two clusters of cells exhibit hallmarks of cellular senescence such as elevated senescence-associated β-galactosidase activity, cell-cycle arrest, heterochromatinization, upregulation of a cyclin-dependent kinase (CDK) inhibitor Dacapo, cellular hypertrophy, Ras signaling activation, and upregulation of an inflammatory cytokine unpaired3, a possible component of the senescence-associated secretory phenotype. Blocking programmed cell senescence by inhibiting Ras signaling or its downstream transcription factor Pointed (Pnt) results in loss of sensory organ campaniform sensilla. Ras-Pnt signaling causes programmed cell senescence through a transcription factor Zfh2, thereby contributing to campaniform sensilla formation via the achaete-scute complex. Our observations uncover the evolutionary conservation of programmed cell senescence in invertebrates, which is required for the induction of the proper number of sensory organs.

Computational Screening to Predict MicroRNA Targets in the Flavivirus 3' UTR Genome: An Approach for Antiviral Development

MicroRNAs (miRNAs) are molecules that influence messenger RNA (mRNA) expression levels by binding to the 3' untranslated region (3' UTR) of target genes. Host miRNAs can influence flavivirus replication, either by inducing changes in the host transcriptome or by directly binding to viral genomes. The 3' UTR of the flavivirus genome is a conserved region crucial for viral replication. Cells might exploit this well-preserved region by generating miRNAs that interact with it, ultimately impacting viral replication. Despite significant efforts to identify miRNAs capable of arresting viral replication, the potential of all these miRNAs to interact with the flavivirus 3' UTR is still poorly characterised. In this context, bioinformatic tools have been proposed as a fundamental part of accelerating the discovery of interactions between miRNAs and the 3' UTR of viral genomes. In this study, we performed a computational analysis to reveal potential miRNAs from human and mosquito species that bind to the 3' UTR of flaviviruses. In humans, miR-6842 and miR-661 were found, while in mosquitoes, miR-9-C, miR-2945-5p, miR-11924, miR-282-5p, and miR-79 were identified. These findings open new avenues for studying these miRNAs as antivirals against flavivirus infections.

Senescent cells and macrophages cooperate through a multi-kinase signaling network to promote intestinal transformation in Drosophila

Cellular senescence is a conserved biological process that plays a crucial and context-dependent role in cancer. The highly heterogeneous and dynamic nature of senescent cells and their small numbers in tissues make in vivo mechanistic studies of senescence challenging. As a result, how multiple senescence-inducing signals are integrated in vivo to drive senescence in only a small number of cells is unclear. Here, we identify cells that exhibit multiple features of senescence in a Drosophila model of intestinal transformation, which emerge in response to concurrent activation of AKT, JNK, and DNA damage signaling within transformed tissue. Eliminating senescent cells, genetically or by treatment with senolytic compounds, reduces overgrowth and improves survival. We find that senescent cells promote tumorigenesis by recruiting Drosophila macrophages to the transformed tissue, which results in non-autonomous activation of JNK signaling. These findings identify senescent cell-macrophage interactions as an important driver of epithelial transformation.

Cell-cell interactions that drive tumorigenesis in Drosophila

Cell-cell interactions within tumour microenvironment play crucial roles in tumorigenesis. Genetic mosaic techniques available in Drosophila have provided a powerful platform to study the basic principles of tumour growth and progression via cell-cell communications. This led to the identification of oncogenic cell-cell interactions triggered by endocytic dysregulation, mitochondrial dysfunction, cell polarity defects, or Src activation in Drosophila imaginal epithelia. Such oncogenic cooperations can be caused by interactions among epithelial cells, mesenchymal cells, and immune cells. Moreover, microenvironmental factors such as nutrients, local tissue structures, and endogenous growth signalling activities critically affect tumorigenesis. Dissecting various types of oncogenic cell-cell interactions at the single-cell level in Drosophila will greatly increase our understanding of how tumours progress in living animals.

Longevity Regulation by Proline Oxidation in Yeast

Proline is a pivotal and multifunctional amino acid that is used not only as a nitrogen source but also as a stress protectant and energy source. Therefore, proline metabolism is known to be important in maintaining cellular homeostasis. Here, we discovered that proline oxidation, catalyzed by the proline oxidase Put1, a mitochondrial flavin-dependent enzyme converting proline into ∆¹-pyrroline-5-carboxylate, controls the chronological lifespan of the yeast Saccharomyces cerevisiae. Intriguingly, the yeast strain with PUT1 deletion showed a reduced chronological lifespan compared with the wild-type strain. The addition of proline to the culture medium significantly increased the longevity of wild-type cells but not that of PUT1-deleted cells. We next found that induction of the transcriptional factor Put3-dependent PUT1 and degradation of proline occur during the aging of yeast cells. Additionally, the lifespan of the PUT3-deleted strain, which is deficient in PUT1 induction, was shorter than that of the wild-type strain. More importantly, the oxidation of proline by Put1 helped maintain the mitochondrial membrane potential and ATP production through the aging period. These results indicate that mitochondrial energy metabolism is maintained through oxidative degradation of proline and that this process is important in regulating the longevity of yeast cells.