High expression of ACE2 has also been detected in cells of the digestive system, such as upper esophageal cells; accordingly, this system is a potential route of infection.102 In addition to the lungs and intestines, other organs, such as the heart, esophagus, kidney, bladder, testis, ileum, and adipose tissue, also express ACE2, and the expression level is higher than that in the lungs.103,104 Certain tumor tissues have higher expression of ACE2, making cancer patients more vulnerable than other people.104. This evidence concerns the gene ACE2 and cancer.