Fig. 8.

Schematic representation of the proposed molecular mechanism. In normal cell, TMPRSS2 mRNA translation leads to the production of the transmembrane-bound serine protease that allows the internalization of SARS-CoV-2 bound to the ACE2 receptor. On the contrary, in tumoral cell, in particular head and neck tumoral cell, TMPRSS2 mRNA levels are downregulated by the targeting activity of upregulated miRNAs, such as miR-31-3p and miR-503-5p. This might determine a reduction in the expression of the protease and a consequent inhibition of the internalization of SARS-CoV-2-ACE2 comple