Mesenchymal–epithelial transition in lymph node metastases of oral squamous cell carcinoma is accompanied by ZEB1 expression

Abstract

Background Oral squamous cell carcinoma (OSCC), an HPV-negative head and neck cancer, frequently metastasizes to the regional lymph nodes but only occasionally beyond. Initial phases of metastasis are associated with an epithelial–mesenchymal transition (EMT), while the consolidation phase is associated with mesenchymal–epithelial transition (MET). This dynamic is referred to as epithelial–mesenchymal plasticity (EMP). While it is known that EMP is essential for cancer cell invasion and metastatic spread, less is known about the heterogeneity of EMP states and even less about the heterogeneity between primary and metastatic lesions. Methods To assess both the heterogeneity of EMP states in OSCC cells and their effects on stromal cells, we performed single-cell RNA sequencing (scRNAseq) of 5 primary tumors, 9 matching metastatic and 5 tumor-free lymph nodes and re-analyzed publicly available scRNAseq data of 9 additional primary tumors. For examining the cell type composition, we performed bulk transcriptome sequencing. Protein expression of selected genes were confirmed by immunohistochemistry. Results From the 23 OSCC lesions, the single cell transcriptomes of a total of 7263 carcinoma cells were available for in-depth analyses. We initially focused on one lesion to avoid confounding inter-patient heterogeneity and identified OSCC cells expressing genes characteristic of different epithelial and partial EMT stages. RNA velocity and the increase in inferred copy number variations indicated a progressive trajectory towards epithelial differentiation in this metastatic lesion, i.e., cells likely underwent MET. Extension to all samples revealed a less stringent but essentially similar pattern. Interestingly, MET cells show increased activity of the EMT-activator ZEB1. Immunohistochemistry confirmed that ZEB1 was co-expressed with the epithelial marker cornifin B in individual tumor cells. The lack of E-cadherin mRNA expression suggests this is a partial MET. Within the tumor microenvironment we found immunomodulating fibroblasts that were maintained in primary and metastatic OSCC. Conclusions This study reveals that EMP enables different partial EMT and epithelial phenotypes of OSCC cells, which are endowed with capabilities essential for the different stages of the metastatic process, including maintenance of cellular integrity. During MET, ZEB1 appears to be functionally active, indicating a more complex role of ZEB1 than mere induction of EMT.

The Chemokine CXCL14 as a Potential Immunotherapeutic Agent for Cancer Therapy

“…Conversely, metastasis enhanced by CXCL14 has been shown in pancreatic and breast cancers [ 30 , 47 , 48 ]. Overall, these findings suggest CXCL14 has diverse and likely context-specific functions in antitumor immunity and metastasis [ 30 , 35 , 49 , 50 ].…”

New perspectives on biology, disease progression, and therapy response of head and neck cancer gained from single cell RNA sequencing and spatial transcriptomics

“…Specifically, an expression program related to extracellular matrix and epithelial-mesenchymal transition (EMT) was found in 7/10 patients included in this part of the analysis [82]. This signature was referred to as partial EMT, or p-EMT, signature, because expression of most of the key EMT transcription factors was undetectable (yet inferred based on the expression of their target genes in a re-analysis of these data [83]). The p-EMT signature was also expressed in a subset of cells from the OSCC cell line SCC-9 and associated with decreased proliferation and increased invasiveness.…”

Correction: Mesenchymal–epithelial transition in lymph node metastases of oral squamous cell carcinoma is accompanied by ZEB1 expression

“…Following publication of the original article [ 1 ], we have been notified by the authors that the legends of supplementary material was not provided. Now legends are as follows:…”