The concomitant tumor suspension cells derived from SKBR-3 exhibit circulating tumor cell features

Metastatic diseases are the major causes of cancer related deaths. Circulating tumor cells are important mediators for distant metastases. However, knowledge about circulating tumor cells is still limited due to their small quantity, lack of explicit markers, interferences from blood cells and immune cells, and so on. In this study, we discovered the concomitant tumor suspension cells in a human epidermal growth factor receptor 2 enriched type breast cancer cell line, SKBR-3. In vitro cultured SKBR-3 shed suspension cells in a spontaneous and continuous manner, which can survive and proliferate infinitely under suspension state. We therefore established the "progeny" suspension cell line of its adherent counterpart, or so-called the concomitant tumor suspension cell line. The concomitant tumor suspension cells were in an intermediate partial-epithelial-mesenchymal transition state and were highly adapted to survival in the blood circulation system. The tendency to form microtumors suggests that they are closely related to the metastases of cancers. This study provides a new direction for investigating metastases. By screening more cancer cell lines and establishing more concomitant tumor suspension cell lines, we can acquire much more knowledge implying the evolution of circulating tumor cells, and achieve a better understanding of cancer metastases.