A. The human prostate cancer cells, DU145 (DU), PC3 (PC3), and LNCaP (LN) were exposed to pH 6.0 (or control) buffer to induce matriptase activation. Cell lysates from pH 6-exposed cells (A, lanes 2, 4, and 6) and the non-activation control cells (N, lanes 1, 3, and 5) were analyzed for total matriptase species (left) using the mAb M24 and activated matriptase using the mAb M69 (right). B, C, and D. The human prostate cancer cells, DU145 (B), PC3 (C), and LNCaP (D) were treated with pH 6.0 buffer to induce matriptase activation. After neutralization, the combination of the cell and the shed fractions (combine), the cells fractions alone (cell), and the shed fraction alone (shed) were analyzed for tryptic activity. RFU stands for relative fluorescent units.