KLK expression is cell- and tissue-dependent [28], and although KLK6 and KLK7 have been suggested to promote tumor cell invasion [14, 29, 30], loss of KLK5 has been observed in prostate [31], lung [32], breast [33], testicular [34], and renal cancer tissues [35] versus their normal counterparts, similar to our PDAC data presented herein. This evidence concerns the gene KLK5 and neoplasm.