The caspase-6 variants, full length wild type (FL WT), FL C163S and constitutively two-chain (CT) were derived from the synthetic, E. coli codon-optimized (His)6 C-terminally tagged caspase-6 gene (Celtek Bioscience) that were ligated into the NdeI/BamHI sites of pET11a vector.31 (link) Selected caspase-6 tumor-associated variants were generated using FL WT as template through Phusion® site-directed mutagenesis (Thermo Scientific™). The caspase-6 R259H CT and W227A CT variants were particularly generated using caspase-6 D179CT as the template for the site-directed mutagenesis.