sentence: Terminal differentiation of epithelial cells is also delicately regulated by extracellular serine proteases ST14 / matriptase ( r = 0.89 ) and PRSS8 / prostasin / CAP1 ( r = 0.83 ) , and their inhibitors SPINT1 / Hai1 ( r = 0.88 ) and SPINT2 / Hai2 ( r = 0.66 ) .