When tumor tissue samples were analyzed in comparison to normal samples, colon adenocarcinoma (COAD) and rectal adenocarcinoma (READ) samples exhibited significantly elevated expression of ACE2, SCARB1, TMPRSS2 and TMPRSS4 genes while pancreatic adenocarcinoma (PAAD) and stomach adenocarcinoma (STAD) samples demonstrated increased expression of ACE2, CTSL, NRP1, SCARB1 and TMPRSS4 genes relative to normal samples (Fig. 1b). This evidence concerns the gene CTSL and colon adenocarcinoma.