TMPRSS2 and infection: Since ACE2 and TMPRSS2 expression is more abundant at basal condition (unstimulated condition) in Calu-3 than in MeT5A cells, we speculated that treatment with MS-275 acting on ACE2/TMPRSS2 expression may favor virus infection and replication in cells expressing at basal conditions low levels of receptors, thus favoring viral spreading to secondary sites of infection.