CTSL and chronic obstructive pulmonary disease: For example, a large study performing transcriptomic analysis on single‐cell RNA‐sequencing data showed comparable expression profiles of SARS‐CoV‐2 entry factors (including ACE2, TMPRSS2, CTSL, and Furin) in the epithelial cell population of lung samples from healthy and chronic lung disease patients, including COPD patients [34].