It is possible that endogenous GPP130 shedding may be readily observed in cells derived from such cancers that overexpress Furin and/or PC7 endogenously, as observed in our previous report in breast cancer tumors, e.g., MDA-MB-231 [4], which is what this study is trying to mimic using PC7 or Furin overexpression in model cell lines. Here, FURIN is linked to cancer.