Abstract
Cell membrane dynamics based on membrane morphology and fluidity are critical for cancer metastasis. We imaged the membrane dynamics of tumor cells in mice with a high spatial precision of < 9 nm under a confocal microscope. A metastasis-promoting factor on the cell membrane, protease-activated receptor 1 (PAR1), was labeled with quantum dots (QDs) conjugated with an anti-PAR1 antibody (PAR1 ab-QDs). Movements of cancer cells and PAR1 were clearly observed in tumors. We found that the tumor cells showed increases in membrane fluidity (over 1000-fold) and formed local pseudopodia in the process of metastasis, suggesting that membrane fluidity and morphological changes are critical for metastasis. Moreover, to estimate the PAR1-expression level in breast cancer tissues of human epidermal growth factor receptor 2 (HER2)-negative patients, user-friendly immunohistochemistry with high quantitative sensitivity was developed using autofluorescence-subtracted images and single-particle quantum dot imaging of PAR1 ab-QDs. The immunohistochemistry showed that PAR1 expression correlated strongly with relapse-free survival in HER2-negative breast cancer patients. Thus, this result suggests that our new method to diagnose PAR1 expression levels by immunohistochemistry with PAR1 ab-QDs may facilitate clinical decisions in HER2-negative patients.
