Abstract 1225: the existence, characteristics and underlying regulators of spontaneous epithelial-mesenchymal transition from a monophasic metaplastic squamous carcinoma patient-derived cancer cell model

Abstract

Abstract Epithelial-mesenchymal transition (EMT) has been considered the mechanism underlying distant metastasis in epithelial cancers. The hallmarks of the EMT phenomenon are mainly the loss of cell-cell adhesion, acquisition of a mesenchymal phenotype, gain of mobility and invasiveness, and attainment of enhanced tumorigenicity and anchorage-independent growth. After EMT, cancer cells can enter and survive in fluid-filled spaces and subsequently colonize distant sites. Despite a huge body of in vitro and in vivo evidence recognizing EMT as an important event in tumor progression, whether EMT exists in naturally-occurring experimental settings remains a contentious debate in the field of pathology. Lack of convincing histopathological evidence of EMT in tumor subtypes without spindle sarcomatous tumor components and lack of dynamic change demonstration of EMT are to blame. In this report, we devised a naturally-occurring experimental setting to prove the existence of EMT in tumors completely lacking histological evidence of EMT. Further, we demonstrated dynamic change of EMT in in vitro and in vivo settings. We performed primary culture 37H from a monophasic metaplastic squamous cell carcinoma tissue (MMSCC), which exhibited no histologic features reminiscent of EMT, to examine whether EMT exists in tumors without sarcomatous histology. Two dominant subtypes demonstrating different morphology were derived from parental 37H: polygonal epithelial-type (HE) and epithelioid mesenchymal-type (HM) cells. The HE cells were E-cadherin+vimentin- predominant; while the HM cells were E-cadherin-vimentin+ predominant, and functionally concomitant with increased migration and invasion and anchorage-independent tumorigenicity. Taking advantage of the inherited differences between the HE and HM cells, we performed head-to-head comparison by RNA-seq and subsequently identified key EMT transcription factors (EMT-TFs) ZEB1 and ZEB2 in this naturally-occurring experimental setting. In the primary MMSCC tissue where 37H was derived, the upregulation of ZEB1 and ZEB2 was also observed in vimentin+ carcinoma cells. Further, the dynamic change of EMT was demonstrated in the HE and HM cells in in vitro and in vivo settings. Spontaneous EMT was observed specifically in the ZEB1-or ZEB2-overexpressed polygonal epithelial-type cells; the knockdown of ZEB1 and ZEB2 reverted EMT in the HM cells; and reverse EMT was found a requirement for HM cells to grow in a xenograft mouse model. In conclusion, this report backed up the existence of EMT in naturally-occurring tumor without histologic evidence of EMT. The identification of underlying regulators contributing to spontaneous EMT, and the demonstration of EMT dynamic change were also included. Citation Format: Huang-Chun Lien, Hui-Chieh Yu, Tom Wei-Wu Chen, I-Chun Chen, Chiao Lo, Ling-Chun Yeh, Li-Ping Hsiao, Yen-Shen Lu. the existence, characteristics and underlying regulators of spontaneous epithelial-mesenchymal transition from a monophasic metaplastic squamous carcinoma patient-derived cancer cell model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1225.