NRP1 and breast cancer: Encouraged by the apparent retention of caspase activity even in a sub-optimal pH environment when using both recombinant caspases and media collected from apoptotic immune Jurkat E6.1 cells (Figure 3), we then investigated whether the change in pH impacts the detection of extracellular caspase-mediated cleavages of membrane-bound proteins from breast cancer cells even beyond the most prominently observed cleavage of NRP-1.