TMPRSS2 and COVID-19: Figure 3b shows that ACE2 is significantly co-expressed with TMPRSS2 (p < 2.0 × 10−16), FURIN (p < 2.0 × 10−16), and NRP1 (p = 2.3 × 10−6) in squamous cells from male patients with critical COVID-19 (Fig. 3b).