1039 Novel mouse model of recessive dystrophic epidermolysis bullosa-squamous cell carcinoma

Abstract

The high frequency and extremely aggressive behavior of squamous cell carcinoma from recessive dystrophic epidermolysis bullosa patients (RDEB-cSCC), as well as the lack of an appropriate preclinical mouse model recapitulating the RDEB-cSCC phenotype for testing effective therapies/drugs, creates an urgent need for generating such a model. Here, we established a novel mouse model for RDEB-cSCC, in which we generated 3D cSCC skin constructs (SCs) using RDEB-cSCC and RDEB fibroblasts (FB), which were then grafted onto immunocompromised mice. 16 out of 18 animals that were grafted with RDEB patient-derived cSCC and FB developed tumors within 4 weeks post-grafting, with characteristic morphological features of human RDEB-cSCC. H&E staining of RDEB-cSCC grafts revealed invading epithelial cell columns and differentiated tumor cell islands in the upper dermis. Immunofluorescence (IF) staining showed a complete lack of C7 and increased pSTAT3 expression in the RDEB-cSCC grafted skin construct. Keratin 14, keratin 10 and E-cadherin IF staining were increased within the RDEB-cSCC grafted tumor tissue, indicating the epithelial origin of RDEB-cSCC cells in the dermis and their differentiation. Further, the RDEB-cSCC grafted tumor displayed high proliferation as demonstrated by increased Ki-67+ and p63+ expression seen in IF staining and reduced expression in vimentin staining compared with normal grafts. Moreover, serial transplantation revealed that 88% of RDEB-cSCC tumors had similar biology to the primary tumor (developed on the initial immunocompetent mouse) within 2 weeks post-transplantation onto a second immunocompetent mouse. Our data established a new preclinical model RDEB-cSCC, and an important new method for drug testing in translational cancer research.