Abstract LB022: A hybrid epithelial to mesenchymal transition in ex-vivo cutaneous squamous cell carcinoma tissues

Abstract

Abstract While most cases of cutaneous squamous cell carcinoma (cSCC) are benign, invasive cSCC is associated with higher mortality and is often more difficult to treat. As such, understanding the factors that influence the progression of cSCC are important. Aggressive cancers metastasize through a series of evolutionary changes, collectively called the epithelial-to-mesenchymal transition (EMT). During EMT, epithelial cells transition to a highly mobile mesenchymal cell type with metastatic capacities. While changes in expression of TGF-β, vimentin, and E-cadherin are hallmarks, EMT is not an “all or none” process. Using patient-derived cSCC and adjacent normal tissues (ANT), we observed a significant increase in mRNA expression of TGF-β (p<0.05), TGF-βR2 (p<0.001), and E-cadherin (p<0.005) in cSCC tissues by qPCR. Immunoblots performed on homogenized tissues yielded significant and parallel increases in protein expression of TGF-β (p<0.05) and E-cadherin (p<0.05). We also observed increased expression of the EMT-associated transcription factors Zeb1 and Snai1 in cSCC tissue sections using immunohistochemistry. Interestingly, we observed a significant increase in expression of vimentin (p<0.01) by immunoblot and differential expression of four oncogenic and EMT-associated miRNAs; miR-31 expression was significantly higher in cSCC tissues (p<0.001), while we observed a significant decrease in expression of miR-34a (p<0.05), miR-200b, and miR-200c in cSCC tissues. Examination of ANT and cSCC tissue sections using immunofluorescence and immunohistochemistry showed differential, and reverse, expression of E-cadherin and vimentin among cells within an individual tumor. Collectively, our data support a hypothesis that cSCC tumors are undergoing a hybrid EMT program, where there is variation in expression of EMT markers by cells within a tumor mass that may be facilitating invasion. This hybrid EMT program may be promoting both survival and invasiveness of the tumors. A better understanding of this hybrid EMT process may influence therapeutic strategies in more invasive disease. Citation Format: Christopher S. Pulford, Chandana K. Uppalapati, McKale R. Montgomery, Elizabeth E. Hull, Kathryn J. Leyva. A hybrid epithelial to mesenchymal transition in ex-vivo cutaneous squamous cell carcinoma tissues [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr LB022.