Investigating the role of RUNX3 in Epithelial-Mesenchymal Transition (EMT).

RUNX3 is a transcription factor known for its tumor suppressor activity, and more recently has been implicated in cancer metastasis. One of the factors involved in successful cancer metastasis is the acquisition of phenotypic plasticity for migration and re-colonization, a process known as Epithelial-mesenchymal transition (EMT). To elucidate the role of RUNX3 in EMT progression, RUNX3 expression in A549 cells was knocked down, and the progression of EMT stages was assessed and compared to that of control cells expressing endogenous RUNX3 after growth factor stimulation. Herein, we found that in the absence of RUNX3, mesenchymal markers were induced earlier and expressed higher than control cells. These findings indicate that RUNX3 possibly imparts an inhibitory effect in A549 cells undergoing EMT. Further biochemical studies need to be followed up to investigate the mechanistic principles involved in RUNX3 mediated inhibition of EMT in intermediate stage A549 cell lines.Bachelor of Science in Biological Science

POPX2 is a novel LATS phosphatase that regulates the Hippo pathway

The Hippo pathway regulates cell proliferation, survival, apoptosis and differentiation. During carcinogenesis, members of the Hippo pathway are mutated to avoid anoikis and promote anchorage independent growth. Although many regulators of the Hippo pathway have been reported, negative regulators of the hippo kinases are not well studied. Through an interactome screen, we found that POPX2 phosphatase interacts with several of the Hippo pathway core kinases, including LATS1 which is the direct kinase regulating the transcription co-activators, YAP and TAZ. Phosphorylated YAP/TAZ are retained in the cytoplasm and prevented from translocation into the nucleus to activate transcription of target genes. We found that POPX2 could dephosphorylate LATS1 on Threonine-1079, leading to inactivation of LATS1 kinase. As a result, YAP/TAZ are not phosphorylated and are able to translocate into the nucleus to activate target genes involved in cell proliferation. Furthermore, POPX2 knock-out using CRISPR in the highly metastatic MDA-MB-231 breast cancer cells results in decreased cell proliferation and impairment of anchorage independent growth. We propose that POPX2 act as a suppressor of the Hippo pathway through LATS1 dephosphorylation and inactivation.MOE (Min. of Education, S’pore)Published versio

Enhanced Delta-Notch lateral inhibition model incorporating intracellular notch heterogeneity and tension-dependent rate of Delta-Notch binding that reproduces sprouting angiogenesis patterns

Endothelial cells adopt unique cell fates during sprouting angiogenesis, differentiating into tip or stalk cells. The fate selection process is directed by Delta-Notch lateral inhibition pathway. Classical Delta-Notch models produce a spatial pattern of tip cells separated by a single stalk cell, or the salt-and-pepper pattern. However, classical models cannot explain alternative tip-stalk patterning, such as tip cells that are separated by two or more stalk cells. We show that lateral inhibition models involving only Delta and Notch proteins can also recapitulate experimental tip-stalk patterns by invoking two mechanisms, specifically, intracellular Notch heterogeneity and tension-dependent rate of Delta-Notch binding. We introduce our computational model and analysis where we establish that our enhanced Delta-Notch lateral inhibition model can recapitulate a greater variety of tip-stalk patterning which is previously not possible using classical lateral inhibition models. In our enhanced Delta-Notch lateral inhibition model, we observe the existence of a hybrid cell type displaying intermediate tip and stalk cells’ characteristics. We validate the existence of such hybrid cells by immuno-staining of endothelial cells with tip cell markers, Delta and CD34, which substantiates our enhanced model.MOE (Min. of Education, S’pore)Published versio