ACE2 and cancer: ACE2 and TMPRSS2 proteins mediate SARS-CoV-2 virus invasion into host cells, and among all cancers, only patients with COAD and rectal adenocarcinoma showed upregulated expression of ACE2 and TMPRSS2 proteins in vivo, so patients with COAD and rectal adenocarcinoma may be more susceptible to contracting SARS-CoV-2 (Hoang et al., 2021; Wang and Yang, 2021).