Abstract 1540: Cutaneous squamous cell carcinoma: Evidence of epithelial to mesenchymal transition

Abstract Cutaneous Squamous Cell Carcinoma (cSCC) is the second most common form of skin cancer, frequently arising from sun-induced mutations. Most clinical cases of cSCC are non-invasive and achieve complete cure through tumor excision. However, advanced cSCC is associated with high mortality, thus research aimed at understanding factors influencing metastasis of invasive cSCC is needed. Cancer metastasis is a multistep process, including epithelial-to-mesenchymal transition (EMT). During EMT, epithelial cells undergo a dedifferentiation process whereby they transition to a highly mobile and invasive mesenchymal cell type with metastatic capacities. Changes in expression of several proteins, including TGF-β, vimentin, and E-cadherin have been identified as a hallmark of EMT, which may be promoting cancer progression. We hypothesize that during development of cSCC, cells within the lesions are undergoing EMT that facilitates invasion into the tissues. In situ and invasive cSCC tissues were obtained from excised tumors being prepped for histological sections from Mohs surgery; once clean margins were identified, adjacent normal tissues (ANT) were obtained during suturing. For all tissues, total protein was isolated; western blots were performed to determine expression of TGF-β1,2,3, Bcl-2, E-cadherin, phosphorylated E-cadherin, and vimentin. Analysis of MMP activity for each tissue type was performed using a FRET assay. For all proteins analyzed, cSCC tissues had higher levels of expression compared to ANT, with invasive cSCC tissues demonstrating increased protein expression over in situ samples (p<0.05 for all proteins). Compared to ANT, cSCC tissues also demonstrate significantly higher MMP activity both after 2 hours (p<0.01) and 4.5 hours (p<0.001). An oncology array performed using protein isolated from these cutaneous samples showed differences in the proteome profile between normal and cancer tissue, including some EMT-related markers. Immunohistochemistry (IHC) and immunofluorescent (IF) staining was performed using fixed cSCC tissue sections for the expression pattern of E-cadherin, cytokeratin, and vimentin. IHC staining reveals an inverse relationship between cytokeratin and vimentin expression, with poorly differentiated areas within lesions showing increased vimentin staining versus areas that are well-differentiated. Furthermore, IF staining reveals that poorly differentiated cells also have reduced E-cadherin staining at the junctions between cells. Our results show that cSCC is undergoing EMT at the projections of the lesions, indicating that this cancer has the potential to acquire a more aggressive phenotype. Tissues exhibiting higher rates of EMT may lead to a poorer prognosis if left untreated. Citation Format: Christopher S. Pulford, Chandana K. Uppalapati, Elizabeth E. Hull, Kathryn J. Leyva. Cutaneous squamous cell carcinoma: Evidence of epithelial to mesenchymal transition [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1540.