Expression profile of SARS-CoV-2 cellular entry proteins in normal oral mucosa and oral squamous cell carcinoma

Objective: Besides angiotensin converting enzyme 2 (ACE2), an active involvement of proteases (FURIN and/or TMPRSS2) is important for cellular entry of SARS-CoV-2. Therefore, a simultaneous expression profiling of entry proteins in a tissue might provide a better risk assessment of SARS-CoV-2 infection as compared to individual proteins. In an attempt to understand the relative susceptibility of oral squamous cell carcinoma (OSCC) lesions as compared to the normal oral mucosa (NOM) for SARS-CoV-2 attachment/entry, this study examined the mRNA and protein expression profiles of ACE2, FURIN, and TMPRSS2 in the corresponding tissues using public transcriptomic and proteomics datasets. Methods and methods: Public transcriptomic and proteomics datasets (the Cancer Genome Atlas (TCGA)/the Genotype-Tissue Expression (GTEx), the Human Protein Atlas (HPA), and two independent microarray datasets) were used to examine the expression profiles of ACE2, TMPRSS2 and FURIN in NOM and OSCC. Results: ACE2, TMPRSS2, and FURIN mRNAs were detected in NOM, however, at lower levels as compared to other body tissues. Except for moderate up-regulation of FURIN, expression levels of ACE2 and TMPRSS2 mRNA were unchanged/downregulated in OSCC as compared to the NOM. Conclusions: These results indicate that NOM may serve as a possible site for SARS-CoV-2 attachment, however, to a lesser extent as compared to organs with higher expression levels of the SARS-CoV-2 entry proteins. However, the evidence is lacking to suggest that expression status of entry proteins predisposes OSCC lesions to additional risk for SARS-CoV-2 attachment/entry as compared to NOM.