ACE2 and lung carcinoma: Significant to COVID-19, ACE2 has been established as the functional host receptor for SARS-CoV-2, and many factors have proved to be associated with both altered ACE2 expression and disease severity and progression, including age, sex, ethnicity, medication, and several co-morbidities (such as cardiovascular disease, metabolic syndrome, and lung cancer) (53–57).