Rosas Gutierrez, Itzel et al. (2021) International Worm Meeting "Regulation of the duration of breast cancer dormancy by UNK"

Kohtz, Donald Stave, Karp, Xantha, Rosas Gutierrez, Itzel

[International Worm Meeting, 2021]

Breast cancer is the most frequent malignancy diagnosed in women worldwide. After an initially successful treatment, the main cause of breast cancer related mortality remains cancer recurrence. During the time between remission and relapse to active disease (Disease-Free Survival, DFS), quiescent cancer cells persist in a state referred to as cellular dormancy. The molecular mechanisms involved in the transitions between dormancy and active disease remain obscure. Kaplan-Meier analyses of all intrinsic molecular subtypes of breast cancer revealed that increased expression of Unkempt (UNK) is associated with longer DFS periods in treated patients. UNK is a conserved zinc-finger protein that functions by binding target mRNAs in a sequence-specific manner and reducing protein production. Expression analyses of breast cancers using the cBioportal for Cancer Genomics revealed a group of genes that showed inverse expression from UNK, and further Kaplan-Meier analyses showed that increased expression of a subset of these genes was associated with reduced DFS. We hypothesized that this subset of genes may contain targets of UNK inhibition in breast cancer cells. UNK has one ortholog in C. elegans, unk-1. As many underlying molecular pathways are conserved between mammalian and nematode development, we hypothesized that a functional model for cancer cellular dormancy could be the transition of C. elegans into dauer diapause, and that C. elegans could provide a robust readout for genetic analysis of UNK targets involved in breast cancer. While in dauer, progenitor cells remain multipotent and quiescent, similar to dormant cancer stem cells. Previous work from the Karp laboratory has shown that unk-1 is involved in determination of cell fate, and that unk-1(0) dauer larvae aberrantly express the adult cell-fate marker col-19p::gfp. We are using RNAi of C. elegans orthologs of the inversely expressed putative UNK targets to screen unk-1(0) dauer larvae for suppression of the col-19p::gfp expression phenotype. By identifying potential targets of UNK inhibition, surrogate pharmacological inhibitors could be developed that would improve DFS when used as combination therapeutics in breast cancer.

Kinchen JM et al. (2005) Curr Top Dev Biol "Tales of cannibalism, suicide, and murder: Programmed cell death in C. elegans."

Hengartner MO, Kinchen JM

[Curr Top Dev Biol, 2005]

"Life is pleasant. Death is peaceful. It''s the transition that''s troublesome," said Isaac Asimov. Indeed, much scientific work over the last hundred years centered around attempts either to stave off or to induce the onset of death, at both the organismal and the cellular levels. In this quest, the nematode C. elegans has proven an invaluable tool, first, in the articulation of the genetic pathway by which programmed cell death proceeds, and also as a continuing source of inspiration. It is our purpose in this Chapter to familiarize the reader with the topic of programmed cell death in C. elegans and its relevance to current research in the fields of apoptosis and cell corpse clearance.

Xiao H et al. (2009) Mol Biol Cell "Lysosome biogenesis mediated by vps-18 affects apoptotic cell degradation in Caenorhabditis elegans."

Yang C, Liu J, Sun X, Xiao H, Chen D, Song S, Xu J, Fang Z

[Mol Biol Cell, 2009]

Monitoring Editor: Donald D. Newmeyer Appropriate clearance of apoptotic cells (cell corpses) is an important step of programmed cell death. Although genetic and biochemical studies have identified several genes that regulate the engulfment of cell corpses, how these are degraded after being internalized in engulfing cell remains elusive. Here we show that VPS-18, the C. elegans homolog of yeast Vps18p, is critical to cell corpse degradation. VPS-18 is expressed and functions in engulfing cells. Deletion of vps-18 leads to significant accumulation of cell corpses that are not degraded properly. Furthermore, vps-18 mutation causes strong defects in the biogenesis of endosomes and lysosomes, thus affecting endosomal/lysosomal protein degradation. Importantly, we demonstrate that phagosomes containing internalized cell corpses are unable to fuse with lysosomes in vps-18 mutants. Our findings thus provide direct evidence for the important role of endosomal/lysosomal degradation in proper clearance of apoptotic cells during programmed cell death.

Victor L. Jensen et al. (2006) European Worm Meeting "A Potential DAF-16 Target Involved in Longevity"

David L. Baillie, Victor L. Jensen, Donald L. Riddle

[European Worm Meeting, 2006]

Victor L. Jensen1, David L. Baillie2, and Donald L. Riddle3. Genes differing in steady-state RNA levels between N2 and daf-2 adults and N2 dauer larvae were identified using Serial Analysis of Gene Expression (SAGE) databases. One gene, a putative transcription factor, was isolated from a screen for genes involved in longevity. The outcrossed knockout allele was shown to have extended longevity, ~3% Him and ~2% Vab phenotypes. The 1 kb of genomic sequence 5? of the confirmed transcription start site contains several possible DAF-16 binding sites. By using a series of truncated promoter sequences to drive GFP expression, possible in vivo activity for these DAF-16 binding sites was observed. One consensus site DBE (DAF-16 Binding Element) may act to repress transcription. This is in agreement with the SAGE data which shows down regulation of this transcription factor in the daf-2 background. In daf-2 mutants DAF-16 is activated and is required for extended longevity. Transcriptional targets and the DNA binding motif for the transcription factor will be elucidated, and its role in longevity will be characterized.

Venegas V et al. (2007) Mol Biol Cell "Two alternative mechanisms that regulate the presentation of apoptotic cell engulfment signal in Caenorhabditis elegans."

Venegas V, Zhou Z

[Mol Biol Cell, 2007]

Monitoring Editor: Donald Newmeyer Phosphatidylserine exposed on the surface of apoptotic mammalian cells is considered an "eat me" signal that attracts phagocytes. The generality of using phosphatidylserine as a clearance signal for apoptotic cells in animals and the regulation of this event remain uncertain. Using ectopically expressed mouse MFG-E8, a secreted phosphatidylserine-binding protein, we detected specific exposure of phosphatidylserine on the surface of apoptotic cells in C. elegans. Masking the surface phosphatidylserine inhibits apoptotic cell-engulfment. CED-7, an ABC transporter, is necessary for the efficient exposure of phosphatidylserine on apoptotic somatic cells, and for the recognition of these cells by phagocytic receptor CED-1. On the other hand, phosphatidylserine exposure on apoptotic germ cells is not CED-7-dependent, but instead requires PLSC-1, a homolog of mammalian phospholipid scramblases. Moreover, deleting plsc-1 results in the accumulation of apoptotic germ cells but not apoptotic somatic cells. These observations suggest that phosphatidylserine might be recognized by CED-1 and act as a conserved "eat me" signal from nematodes to mammals. Furthermore, the two different biochemical activities used in somatic cells (ABC transporter) and germ cells (phospholipid scramblase) suggest an increased complexity in the regulation of phosphatidylserine presentation in response to apoptotic signals in different tissues and during different developmental stages.