RAS signalling through PI3-Kinase controls cell migration via modulation of Reelin expression

RAS signalling through Phosphoinositide 3-kinase (PI3-Kinase) has been shown to have an essential role in tumour initiation and maintenance. RAS also regulates cell motility and tumor invasiveness, but the role of direct RAS binding to PI3-Kinase in this remains uncertain. Here, we provide evidence that disruption of RAS interaction with PI3-Kinase p110adecreases cell motility and prevents activation of Rac GTPase. Analysis of gene expression in cells lacking RAS interaction with p110areveals increased levels of the extracellular matrix glycoprotein Reelin and activation of its downstream pathway resulting in upregulation of E-Cadherin expression. Induction of the Reelin / E-Cadherin axis is also observed in Kras mutant lung tumours that are regressing due to blockade of RAS interaction with PI3-Kinase. Furthermore, loss of Reelin correlates with decreased survival of lung and breast cancer patients. Reelin thus plays a role in restraining RAS and PI3-kinase promotion of cell motility and potentially tumour metastasis. MEFs with or without RAS binding to p110a were seeded in a 10cm dish and left to attach during 24 hours. Full serum media was then removed and media with no FBS was added to the plates. Starvation was carried out during a period of 16 hours (over night starvation). Assay was performed in triplicates: for each genotype two diferent fibroblasts clones (and a mix of both of the clones) were used on the analysis. After starvation RNA was extracted using RNAsy kit (Quiagen). RNA was quantified and sent to Oxford Gene Technology microarray facility.