PXDN and carcinoma: For example, whereas basement membranes in vivo are type IV collagen-rich and mechanically rigid as a consequence of lysyl oxidase- and peroxidasin-mediated covalent crosslinks, in vitro constructs that rely on EHS carcinoma extracts (i.e., Matrigel) are alternatively enriched with laminin, mechanically soft and largely devoid of the critical type IV collagen crosslinks that define basement membrane structure4,5,8,89,90.