Metastasis is the main cause of mortatility (90%) in patients diagnosed with Breast Cancer. Two trains of thoughts currently dominate this field. Epithelial Mesenchymal Transition (EMT) could allow generation of these metastatic subpopulations and the reverse (MET) could allow subsequent colonisation of secondary sites. The second theory points to the existence of Cancer Stem Cells which potentially could regenerate the primary tumour as well as possess metastatic properties. Ultimately, these cells traverse through the transporting channels (such as arteries and veins) as Circulating tumour cells (CTC) or remain dormant in a secondary site as Disseminated tumour cells (DTC)
Epithelial cell adhesion molecule (EpCAM) is widely used clinically to isolate CTCs and DTCs from patient material. Studies have demonstrated the loss of EpCAM expression in cells following an EMT. Loss of EpCAM expression by CTC in blood and DTC in bone marrow could challenge current CTC isolation techniques and have implications in diagnosis and prognosis for patients. Contrastingly, high EpCAM expression correlates poor patient prognosis and increased tumorigenicity. We employed a functional genomics approach where the basal like EpCAM+ve PMC42LA cells have been transduced with a shRNA library targeting the genes responsible for maintenance of cell polarity, breast cancer stem cell markers and markers of EMP and metastasis. FACS sorted EpCAMlow cells from this transduced population display a very aggressive mesenchymal morphology, low proliferative index and increased invasiveness in vitro while EpCAMhigh cells increased tumour growth, greater colony formation capabilities and increased proliferative capacity. These samples will be subjected to next generation sequencing for identification of hairpins responsible for these phenotypes. Further studies would incorporate the utilisation of individual hairpins and subsequent functional studies in vitro and in vivo to identify to role of these genes in cancer biology.