Enhanced blebbing as a marker for metastatic prostate cancer

Experiments with cells flowing through a microfluidic channel show that highly metastatic prostate cancer cells form more plasma membrane blebs than lowly metastatic or normal prostate cells. Increased blebbing of metastatic breast cancer cells flowing through a micropipette was previously attributed to decreased phosphorylated ERM (p-ERM) protein expression – p-ERMs bind the plasma membrane to the actin cortex and increase cell stiffness. Myosin II also influences blebbing as cortical actomyosin contraction, due to myosin II, can increase cellular hydrostatic pressure – leading to cortex rupture and bleb formation. Surprisingly, we find that highly metastatic prostate cells express higher levels of p-ERM and lower levels of myosin II than lowly metastatic or normal prostate cells – suggesting that their level changes do not alter metastatic prostate cell blebbing. Rather, increased blebbing is correlated with reduced cortical actin expression and reduced cell stiffness – already widely accepted as markers of metastatic cancer. These findings indicate that, regardless of p-ERM and myosin II levels, extracted cell blebbing can be used as a simple diagnostic marker for metastatic cancer.