Abstract
BackgroundSevere acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infects host cells through interactions with its receptor, Angiotensin-converting enzyme 2 (ACE2), causing severe acute respiratory syndrome and death in a considerable proportion of people. Patients infected with SARS-CoV-2 experience digestive symptoms. However, the precise protein expression atlas of ACE2 in the gastrointestinal tract remains unclear. In this study, we aimed to explore the ACE2 protein expression pattern and the underlying function of ACE2 in the gastrointestinal tract, including the colon, stomach, liver, and pancreas.MethodsWe measured the protein expression of ACE2 in the gastrointestinal tract using immunohistochemical (IHC) staining with an ACE2-specific antibody of paraffin-embedded colon, stomach, liver, and pancreatic tissues. The correlation between the protein expression of ACE2 and the prognosis of patients with gastrointestinal cancers was analyzed by the log-rank (Mantel–Cox) test. The influence of ACE2 on colon, stomach, liver, and pancreatic tumor cell line proliferation was tested using a Cell Counting Kit 8 (CCK-8) assay.ResultsACE2 presented heterogeneous expression patterns in the gastrointestinal tract, and it showed a punctate distribution in hepatic cells. Compared to that in parallel adjacent non-tumor tissues, the protein expression of ACE2 was significantly increased in colon cancer, stomach cancer, and pancreatic cancer tissues but dramatically decreased in liver cancer tissues. However, the expression level of the ACE2 protein was not correlated with the survival of patients with gastrointestinal cancers. Consistently, ACE2 did not affect the proliferation of gastrointestinal cancer cells in vitro.ConclusionThe ACE2 protein is widely expressed in the gastrointestinal tract, and its expression is significantly altered in gastrointestinal tumor tissues. ACE2 is not an independent prognostic marker of gastrointestinal cancers.
Highlights
The recent outbreak of novel coronavirus disease 2019 (COVID19), which is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has become a pandemic and a threat to global health (Wang C. et al, 2020; Zhu N. et al, 2020)
The receptor-binding domain (RBD) of SARS-CoV2 binds to the protease domain (PD) of Angiotensin-converting enzyme 2 (ACE2), forming the RBD–PD complex, which is distinct from the ACE2 catalytic site (Lan et al, 2020; Wang Q. et al, 2020)
To fully understand the precise ACE2 location and expression patterns in the gastrointestinal tract, we collected gastrointestinal tissues from patients with cancers, which were diagnosed as adjacent non-tumor tissues by a professional pathologist via hematoxylin and eosin (H&E) staining
Summary
The recent outbreak of novel coronavirus disease 2019 (COVID19), which is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has become a pandemic and a threat to global health (Wang C. et al, 2020; Zhu N. et al, 2020). As of April 18, 2021, over 140 million people have been infected, and over 3.0 million people have died from COVID-19 due to its severe symptoms, including severe pneumonia, acute respiratory distress, and organ failure driven by hyperinflammation and cytokine storm syndrome (Huang et al, 2020; Wang D. et al, 2020; Wolfel et al, 2020), with a much larger number of infected people suffering worldwide. Angiotensin-converting enzyme 2 (ACE2) was identified as the key human host receptor for SARS-CoV-2 infection. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infects host cells through interactions with its receptor, Angiotensin-converting enzyme 2 (ACE2), causing severe acute respiratory syndrome and death in a considerable proportion of people. We aimed to explore the ACE2 protein expression pattern and the underlying function of ACE2 in the gastrointestinal tract, including the colon, stomach, liver, and pancreas
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