Abstract
It is now emerging that a number of cellular targets of pathogens are involved in the establishment and/or maintenance of epithelial cell polarity. Increasing evidence also suggests that cancer-causing pathogens such as Helicobacter pylori (H. pylori) and human papilloma virus (HPV) may induce oncogenesis by disrupting cell polarity. This is mainly achieved through their ability to deregulate the function of cell polarity components and/or regulators. Hence cell polarity represents the first line of defence against infection. Interestingly, EGFR/RAS oncogenic signals also induce cancer cell invasion by inducing epithelial to mesenchymal transition (EMT). Since the loss of cell polarity is a prerequisition of EMT, cell polarity also represents the last line of defence against cancer cell invasion. As such we argue that cell polarity may be a key defence mechanism against infection and cancer cell invasion. The potential role of cell polarity as a gatekeeper against cancer through its ability to regulate asymmetric cell division and tumour suppression has been discussed in a number of recent reviews. In this review we will focus on the role of cell polarity as a potential target of infection and cancer cell invasion.