Aloxistatin (E64d) is an inhibitor of cysteine protease with blood platelet aggregation inhibiting activity. Aloxistatin is an irreversible, membrane-permeable inhibitor of lysosomal and cytosolic cysteine proteases with the ability to inhibit calpain activity in intact platelets.

The CTLs and NK cells (0.8×106/mL) are treated with the inhibitors L1 (10-20 μM) or Aloxistatin (20-30 μM) for 24 hr at 37°C in 24-well plates. Cells are then used in 51Cr-release assays or are lysed to examine perforin in Western blots. The inhibitor is also added at the same concentration during the 4 hr reactions in some 51Cr-release assays, as indicated. Cell lysates are prepared using NP-40 lysis buffer (25 mM HEPES, 250 mM NaCl, 2.5 mM ethylenediaminetetraacetic acid, 0.1% volume/volume Nonidet P-40) and total protein concentration is determined using the Bradford assay. Equal amounts of protein are loaded and resolved on 8% SDS-PAGE gels. Human or mouse perforin is detected using the appropriate antibodies as indicated. Anti-actin antibody is used as a loading control[2].

Aloxistatin (E64d) is dissolved in DMSO and stored, and then diluted with appropriate medium (final DMSO 0.1 %) before use[3]. Cell proliferation and apoptosis are assessed by staining for a proliferation marker, Ki67, or an apoptotic marker, cleaved caspase 3, following the protocol described above for the polarity markers. MCF10 variants are grown in 3D rBM overlay cultures for 4 days and are treated with 0.1 % DMSO, 5 μM CA074Me or 5 μM Aloxistatin. The percentage of structures that are positive for Ki67 or cleaved caspase 3 is determined by counting a total of 100 structures on two separate coverslips with a Zeiss Axiophot epifluorescent microscope. Structures are considered Ki67 positive if they contained at least one cell staining for Ki67. Structures are considered to be caspase 3 positive if they contained at least one cell that is positive for cleaved caspase 3 and the positive cell(s) is not localized in the center of a developing lumen[3].