By contrast, in H1299 lung cancer epithelial cells, Hela-ACE2 (overexpressing ACE2), and 293T cells overexpressing ACE2 and deleted for TMPRSS2 (293T-A2ΔT2), we did not observe large differences in entry efficiency for Delta and Omicron (Figure 2b). The gene discussed is TMPRSS2; the disease is lung cancer.