Specific and non-specific adhesion in cancer cells with various metastatic potentials

The majority of cancer deaths are caused by metastasis, not by the parent tumor. During metastasis, cancer cells detach from their neighbors in the tumor, enter the circulation system, and invade other organs. Thus metastasis initiates with the decrease of adhesion between cancer cells and regaining of adhesion to invade new organs during circulation. In this chapter, we first introduce the altered tumor cells' behavior during malignant transition with the focus on alterations of cell adhesion. Second, we discuss the cell-cell vs. cell-matrix interaction during cancer metastasis in the context of hierarchical changes in cell-properties during metastasis. Finally, we review the current state-of-the-art devices of single-cell adhesion measurement and present our results on non-specific adhesion measurement between cancer cells and a glass micro probe, using a novel micro force sensor. Adhesion measurements are compared for malignant, metastatic cells (HCT-8), malignant, non-metastatic adenocarcinoma cells (Caco-2), and normal monkey kidney MA104 cells. The non-specific adhesion force for HCT-8 is about twice that compared to Caco-2, and insignificant for MA104. We then measured the specific homotypic cell-cell adhesion rates using a Coulter Counter for PC3M (highly metastatic human prostate cancer), PC3 (less metastatic than PC3M), HCT8 and MA104 cell lines. We found, specific cell adhesion rates decrease with increasing metastatic potential. These results suggest, while specific adhesion of malignant cancer cells are often reduced to facilitate their detachment from the parent tumor, the high non-specific adhesion force on them can strategically maximize their adherence and invasion to diverse tissues during metastasis.