Richardson - Cell polarity, cell signalling and cancer
Our group uses the vinegar fly, Drosophila, to model cancer with the vision of understanding how regulators of cell shape (polarity) impact on cell signaling and cancer development. Additionally, we seek to understanding the signaling pathways in the tumour microenvironment that dictate whether polarity-impaired mutant cells live or die.
To achieve this, we collaborate with Professor Patrick Humbert (Cancer Theme), Dr Marc Kvansakul (Infection and Immunity Theme) and Professor Andrew Hill (Infection and Immunity Theme).
Understanding how cell polarity regulators control endocytosis, vesicle acidification and cell signalling
We have discovered that the cell polarity regulator, Lgl, regulates the Notch signalling pathway by effecting vesicle acidification and g-secretase activity (Parsons et al., 2014; Portela et al., 2015). We found that in lgl mutant tissue, early and MVB endosomes accumulate and vesicle acidification occurs leading to increased γ−secretase activity, which depends upon low pH. Activated γ−secretase then leads to increased cleavage of Notch-ext (Next) to form the transcriptionally active Nicd form. Over-expression of Next in Drosophila tissues induces overgrowth of the thorax and perturbs eye development, which is dependent on g-secretase activity. Over-expression of Lgl suppresses the Next-induced overgrowth and eye phenotypes, but does not prevent Nicd-induced overgrowth, which bypasses the γ−secretase step.
This data shows that Lgl acts at the level of g-secretase activity to regulate Notch signalling. Using mass spec analysis (in collaboration with Dr Alexey Veraksa, University or Massachusetts, Boston, USA) we have identified proteins that might be involved in linking Lgl to these processes, and are currently investigating these using genetic, cell biological and biochemical approaches.
Modelling cooperative tumourigenesis in Drosophila: understanding the link between cell polarity, cell signalling, tissue growth and tumourigenesis
We have identified novel tumour suppressors that cooperate with oncogenic Ras (RasV12) in cancer progression in a genetic screen in collaboration with Professor Josef Penninger (IMBA, Vienna, Austria). These novel tumour suppressors include Tetraspanins, Autophagy, vesicular trafficking, cytoskeletal and metabolic regulators. We seek to determine how knockdown of these tumour suppressors results in tumourigenesis with RasV12.
We are currently focusing on genes involved in Autophagy, which is a catabolic process involved in the break down of proteins and organelles in order to generate energy, and is important in cell survival under stress conditions. We have found that knockdown of autophagy genes cooperates with RasV12 to promote hyperplasia of the Drosophila eye. We have dissected the mechanism by which this occurs and have found that autophagic gene knockdown together with RasV12leads to an upregulation of the JNK signalling pathway, and that this is crucial for the cooperation.
This is in agreement with our previous data showing that JNK signalling cooperates with RasV12 to enhance tissue overgrowth (Brumby et al., 2011). We are also investigating a Tetraspanin, which is a four-pass membrane protein involved in signalling pathway regulation, which acts via a novel mechanism to cooperate with RasV12 in tumourigenesis.
Discovery of novel anti-cancer drugs using Drosophila tumour models
We have set up a drug screening platform of whole Drosophila larvae carrying Ras-activated polarity-impaired tumours (Willoughby et al., 2013, Richardson et al., 2015). These tumours are generated genetically in Drosophila larvae and marked by green fluorescent protein (GFP). The larvae are fed a different drug per well, which is dissolved in the food. The effect of the drug on tumour development can be observed by quantifying the amount of GFP per larvae per well.
We have already identified that a MEK inhibitor (that blocks the Ras signalling pathway) and inhibitors of glutamine utilization are highly potent in reducing tumourigenesis in this model (Willoughby et al., 2013). Using this system we are currently screening new drug libraries for compounds that can inhibit tumour growth and invasion.
Meet the team
Natalia (Natasha) Fahey Lozano (co-supervised with Professor Patrick Humbert)
Charlene Magtoto (co-supervised with Professor Patrick Humbert)
Rebecca Stephens (co-supervised with Professor Patrick Humbert)