Biology subjects

Foy, R.

Publications and source records attributed to Foy, R..

8 recordsLinked to original sources

bioRxiv2025

The mitotic stopwatch limits the proliferation of whole genome doubled cells

AO_SCPLOWBSTRACTC_SCPLOWWhole genome doubling (WGD) is a frequent event in tumourigenesis that promotes chromosomal instability and tumour evolution. WGD is sensed indirectly due to the presence of extra centrosomes, which activate the PIDDosome to induce a p53-dependent G1-arrest. Here we uncouple WGD from centrosome amplification and show that p53 still arrests tetraploid cells, but via the mitotic stopwatch; a p53/53BP1/USP28-dependent pathway that causes G1-arrest following an extended mitotic delay. Mitotic timing is unaffected by WGD, but the threshold mitotic delay needed to invoke a G1-arrest is reduced. This sensitivity to the stopwatch mechanism is not associated with altered levels of mitotic stopwatch components, but instead, is associated with enhanced p21 concentrations prior to mitosis. Similar effects are observed in diploid cells treated with CDK4/6 inhibitors to double their size, implicating G1 delays and cell size as key determinants of stopwatch sensitivity. This ability of the mitotic stopwatch to arrest proliferation after increases to genome or cell size has important implications for the progression and treatment of cancer. It also demonstrates that the stopwatch pathway can sense more than just mitotic delays.

cell biology↗

bioRxiv2023

Effects of ocean acidification on red king crab larval survival and development

Ocean acidification, a decrease in oceanic pH resulting from the uptake of anthropogenic CO2, can be a significant stressor for marine organisms. In this study, we reared red king crab larvae from hatching to the first crab stage in four different pH treatments: current surface ambient, diel fluctuation to mimic larval migration between the surface and mixed layer under current ambient conditions, pH 7.8, and pH 7.5. Larvae were monitored throughout development and the average length of each stage was determined. At each of the zoeal stages, the glaucothoe stage, and the first crab stage, we measured survival, morphometry, dry mass, and carbon, nitrogen, calcium, and magnesium content. Red king crab larvae were highly resilient to ocean acidification. There were no differences among treatments in survival or in average stage length. Although there were clear ontogenetic trends in size, weight, and elemental composition, most of these did not vary with pH treatment. Zoeal morphology did not vary among treatments, although glaucothoe and C1 crabs were slightly smaller in pH 7.8 than in the ambient treatment. Ambient larvae also had a slightly higher mass than pH 7.8 larvae but not pH 7.5. Ambient larvae had higher magnesium contents than pH 7.8 and pH 7.5, but calcium levels were the same. Ambient larvae also had slightly lower carbon and nitrogen content than pH 7.8 and pH 7.5 larvae but only in the 4th zoeal stage. Overall this study suggests that red king crab larvae are well adapted to a wide range of pH conditions and are unlikely to be significantly affected by ocean acidification levels projected for the next two centuries.

ecology↗

bioRxiv2023

The search for CDK4/6 inhibitor biomarkers has been hampered by inappropriate proliferation assays

CDK4/6 inhibitors arrest the cell cycle in G1 and are used in combination with hormone therapy to treat advanced HR+/HER- breast cancer. To allow more effective use of these drugs in breast cancer, and to facilitate their use in other tumour types, biomarkers that can predict response are urgently needed. We demonstrate here that previous large-scale screens designed to identify the most sensitive tumour types and genotypes have misrepresented the responsive cell lines because of a reliance on ATP-based proliferation assays. When cells arrest in G1 following CDK4/6 inhibition, they continue to grow in size, producing more mitochondria and ATP. This cellular overgrowth masks an efficient arrest using metabolic ATP-based assays, but not if DNA-based assays are used instead. By comparing tumour cells using different assay types, we demonstrate that the lymphoma lines previously identified as the most responsive cell types, simply appear to respond the best because they fail to overgrow during the G1 arrest. Similarly, the CDK4/6 inhibitor abemaciclib appears to inhibit proliferation better than palbociclib, but this is because it also inhibits cell overgrowth through off-target effects. DepMap analysis of previous screening data using only the reliable assay types, demonstrates that palbociclib-sensitivity is associated with sensitivity to Cyclin D1, CDK4 and CDK6 knockout/knockdown, and resistance is associated with sensitivity to Cyclin E1, CDK2 and SKP2 knockout/knockdown. Furthermore, potential biomarkers of palbociclib-sensitivity are increased expression of Cyclin D1 (CCND1) and RB1, and reduced expression of Cyclin E1 (CCNE1) and CDKN2A. None of these associations are present when analysing DepMap using similar data from metabolic assays. This reinforces the importance of new screens to assess CDK4/6 inhibitors, and potentially other anti-cancer drugs, against a wide range of cell types using an appropriate proliferation assay. This would help to better inform clinical trials and to identify much needed biomarkers of response.

cancer biology↗

bioRxiv2022

Effects of high pCO2 on snow crab embryos: Ocean acidification does not affect embryo development or larval hatching

Ocean acidification, a decrease in ocean pH due to absorption of anthropogenic CO2, has variable effects on different species. To examine the effects of decreased pH on snow crab (Chionoecetes opilio), a commercial species in Alaska, we reared ovigerous females in one of three treatments: ambient pH (~8.1), pH 7.8, and pH 7.5, through two annual reproductive cycles. Morphometric changes during development and hatching success were measured for embryos both years and calcification was measured for the adult females at the end of the 2-year experiment. Embryos and larvae analyzed in year one were from oocytes developed, fertilized, and extruded in situ, whereas embryos and larvae in year two were from oocytes developed, fertilized, and extruded under acidified conditions in the laboratory. Embryo morphology during development was unaffected by pH during both years. The number of successfully hatched live larvae was unaffected by pH treatment in both years. Embryo mortality was very low, hatching success high, and neither differed with treatment in either year. Percent calcium in adult females carapaces did not differ among treatments at the end of the experiment. The results from this two-year study suggest that snow crabs are well adapted to projected ocean pH levels within the next 2 centuries, although other life-history stages still need to be examined for sensitivity.

ecology↗

bioRxiv2022

Effects of high pCO2 on snow crab larvae: Carryover effects from embryogenesis and oogenesis reduce direct effects on larval survival

Ocean acidification, a decrease in ocean pH with increasing anthropogenic CO2 concentrations, is expected to affect many marine animals. We determined the effects of ocean acidification on the economically important snow crab, Chionoecetes opilio. By holding females in treatment pH for two brooding cycles and using the resulting larvae, we assessed carryover effects from oogenesis and embryogenesis. Ovigerous females were held at three pHs: ~8.1 (Ambient), 7.8, and 7.5. Larvae were exposed to the same pH treatments in a fully crossed experimental design. Starvation-survival, morphology, condition, and calcium/magnesium content were assessed for larvae. In the first year, starvation-survival of larvae reared at ambient pH but hatched from embryos reared at reduced pH was lowered; however, the negative effect was eliminated when the larvae were reared at reduced pH. In the second year, there was no direct effect of either embryo or larval pH treatment, but larvae reared as embryos at reduced pH survived longer if reared at reduced pH. Larvae hatched from embryos held at pH 7.5 had lower calcium content right after hatching, but the effect was transitory in the second year. There was no effect of larval treatment on calcium content or effect of embryo or larval treatment on magnesium content. Larval morphometrics were slightly altered, though effect sizes were small smaller in the second year. These results suggest both that larvae are highly tolerant of reduced pH, and that embryos are able to acclimate to low pH and this effect carries over to the larval stage.

ecology↗

bioRxiv2022

Cell overgrowth during G1 arrest triggers an osmotic stress response and chronic p38 activation to promote cell cycle exit

Cell size and the cell cycle are intrinsically coupled and abnormal increases in cell size are associated with senescence. The mechanism by which overgrowth primes cells to exit the cell cycle remains unclear. We investigate this using CDK4/6 inhibitors that arrest cell cycle progression in G0/G1 and are used to treat ER+/HER2-metastatic breast cancer. We demonstrate that long-term CDK4/6 inhibition promotes cellular overgrowth during the G0/G1 arrest, causing widespread proteome remodeling and p38-p53-p21-dependent cell cycle exit. Cell cycle exit is triggered by two waves of p21 induction. First, overgrowth during a G0/G1 arrest induces an osmotic stress response, producing the first wave of p21 induction. Second, when CDK4/6 inhibitors are removed, a fraction of cells escape G0/G1 arrest and enter S-phase where overgrowth-driven replication stress results in a second wave of p21 induction that causes cell cycle withdrawal from G2, or the subsequent G1. This could explain why cellular hypertrophy is associated with senescence and why CDK4/6 inhibitors have long-lasting anti-proliferative effects in patients.

cell biology↗

bioRxiv2022

Oncogenic signals prime cancer cells for toxic cell growth during a G1 cell cycle arrest

A long-term goal in cancer research has been to inhibit the cell cycle in tumour cells without causing toxicity in proliferative healthy tissues. The best evidence that this is achievable is provided by CDK4/6 inhibitors, which arrest the cell cycle in G1, are well-tolerated in patients, and are effective in treating ER+/HER2-breast cancer. CDK4/6 inhibitors are effective because they arrest tumour cells more efficiently than some healthy cell types and, in addition, they affect the tumour microenvironment to enhance anti-tumour immunity. We demonstrate here another reason to explain their efficacy. Tumour cells are specifically vulnerable to CDK4/6 inhibition because during the G1 arrest, oncogenic signals drive toxic cell overgrowth. This overgrowth causes permanent cell cycle withdrawal by either preventing exit from G1 or by inducing replication stress and genotoxic damage during the subsequent S-phase and mitosis. Inhibiting or reverting oncogenic signals that converge onto mTOR can rescue this excessive growth, DNA damage and cell cycle exit in cancer cells. Conversely, inducing oncogenic signals in non-transformed cells can drive these toxic phenotypes and sensitize cells to CDK4/6 inhibition. Together, this demonstrates how oncogenic signals that have evolved to stimulate constitutive tumour growth and proliferation can be driven to cause toxic cell growth and irreversible cell cycle exit when proliferation is halted in G1.

cancer biology↗

bioRxiv2021

CDK4/6 inhibitors induce replication stress to cause long-term cell cycle withdrawal

AO_SCPLOWBSTRACTC_SCPLOWCDK4/6 inhibitors arrest the cell cycle in G1-phase. They are approved to treat breast cancer and are also undergoing clinical trials against a range of other tumour types. To facilitate these efforts, it is important to understand why a cytostatic arrest in G1 causes long-lasting effects on tumour growth. Here we demonstrate that a prolonged G1-arrest following CDK4/6 inhibition downregulates replisome components and impairs origin licencing. This causes a failure in DNA replication after release from that arrest, resulting in a p53-dependent withdrawal from the cell cycle. If p53 is absent, then cells bypass the G2-checkpoint and undergo a catastrophic mitosis resulting in excessive DNA damage. These data therefore link CDK4/6 inhibition to genotoxic stress; a phenotype that is shared by most other broad-spectrum anti-cancer drugs. This provides a rationale to predict responsive tumour types and effective combination therapies, as demonstrated by the fact that CDK4/6 inhibition induces sensitivity to chemotherapeutics that also cause replication stress.

cancer biology↗