Adhesion-Controlled Proliferation Revealing Anti-Cancer Drug Resistance of Breast Cancer Cells

Abstract

Mechanical interactions of cancer cells with surrounding environments play an important role in cancer progression. More evidence suggests that the mechanical interplays between cancer cells and the extracellular matrix trigger adhesion-mediated signaling pathways that affect not only the cells’ mechanical properties such as motility and rigidity but also the cell's viability such as proliferation and apoptosis. In this study, we interrogated whether the anti-cancer drug resistance of breast cancer cells can be discerned by monitoring the proliferation of breast cancer cells seeded on nanoscaffolds. The nanoscaffolds help systematically control the maturation of focal adhesions on well-defined nano-sized areas and distances. They were fabricated as two-dimensional arrays of gold nanoislands on glass substrates using our bottom-up procedures combining nanosphere lithography and orthogonal chemistry. By varying the size of nanospheres (300 - 1,000 nm) used for nanolithography, the size and spacing of nanoislands were controlled. The MCF-7 and MCF-7/ADR cells were investigated as the drug-sensitive and the drug-resistant breast cancer cell lines, respectively. The difference in the doxorubicin-sensitivity of the two cell lines was confirmed by the MTT assay. The cell proliferation was determined from the phase contrast images taken every 24 hours after the initial cell seeding on the nanoscaffolds. We found that the proliferation of the drug-sensitive breast cancer cells was highly affected by the geometrical characteristics of the underlying nanoscaffolds. Unlike the MCF-7 cells, the proliferation of the drug-resistant breast cancer cells was not noticeably affected by the nanoscaffolds for the first two days of observation. We postulate that MCF-7/ADR cells showed the abnormal maturation of focal adhesions beyond the restricted area and thus continuously proliferated. We also observed a faster wound closure for MCR-7/ADR cells than MCF-7 cells. The increase in 2D motility of MCF-7/ADR could be resulted from higher levels of the traction force generated by the enhanced focal adhesions. In conclusion, we found that the abnormal maturation of focal adhesions via vinculin overexpression caused the uncontrolled proliferation and resulted in the acquisition of the drug resistance in breast cancer cells. We suggest that the restoration of the normal maturation of focal adhesions might be a promising way to sensitize the anti-cancer drug response from breast cancer cells.