In this context, other essential factors to be considered are the relationships between the levels of expression, polymorphisms, and epigenetic alterations, specifically for the viral entry factors ACE2, ADAM17, and TMPRSS2, since they are implicated in both susceptibility to viral infection in target cells and COVID-19 progressive symptoms (Hoffmann et al., 2020; Ortiz-Fernández and Sawalha, 2020). Here, TMPRSS2 is linked to COVID-19.