ABSTRACT
Cancer has become more prevalent and diverse as human lifespans have increased. There is almost no natural recourse, making cancer the primary cause of death worldwide (WHO). Yet, we struggle to understand the most life-threatening aspects-metastasis, cancer recurrence and associated tumour dormancy. The vast majority of human cancers are carcinomas, which by defi nition derive from epithelial tissues. In tumour formation, normal epithelial cells acquire genetic and/or epigenetic changes that bypass normal check-points for cell division resulting in excessive cell proliferation. There may be further changes that mimic a developmental process called epithelial to mesenchymal transition (EMT) that allow tumour cells to migrate away from the primary tumour (Lafl eur et al. 2006; Soon 2009). Metastasis is a late stage disease where secondary tumours grow at distant sites away from the primary tumour such as the lung and bones. This spread of cancer requires several steps including invasion into the stroma, intravasation, extravasation and growth at secondary sites (Soon et al. 2003; Liotta and Kohn 2001). There is also evidence to suggest that cell invasion occurs at an early stage in cancer well before metastasis sets in (Pantel et al. 2003).
