Protein expression of transmembrane protease serine 4 in the gastrointestinal tract and in healthy, cancer, and SARS‑CoV‑2 infected lungs

Abstract

In addition to the angiotensin‑converting enzyme 2 (ACE2), a number of host cell entry mediators have been identified for severe acute respiratory syndrome coronavirus‑2 (SARS‑CoV‑2), including transmembrane protease serine 4 (TMPRSS4). The authors have recently demonstrated the upregulation of TMPRSS4 in 11 different cancers, as well as its specific expression within the central nervous system using in silico tools. The present study aimed to expand the initial observations and, using immunohistochemistry, TMPRSS4 protein expression in the gastrointestinal (GI) tract and lungs was further mapped. Immunohistochemistry was performed on tissue arrays and lung tissues of patients with non‑small cell lung cancer with concurrent coronavirus disease 2019 (COVID‑19) infection using TMPRSS4 antibody. The results revealed that TMPRSS4 was abundantly expressed in the oesophagus, stomach, small intestine, jejunum, ileum, colon, liver and pancreas. Moreover, the extensive TMPRSS4 protein expression in the lungs of a deceased patient with COVID‑19 with chronic obstructive pulmonary disease and bronchial carcinoma, as well in the adjacent normal tissue, was demonstrated for the first time, at least to the best of our knowledge. On the whole, the immunohistochemistry data of the present study suggest that TMPRSS4 may be implicated in the broader (pulmonary and extra‑pulmonary) COVID‑19 symptomatology; thus, it may be responsible for the tropism of this coronavirus both in the GI tract and lungs.

Keywords: coronavirus disease 2019; gastrointestinal tract; lung; severe acute respiratory syndrome coronavirus‑2; transmembrane protease serine 4; tropism.

Figure 1.

Immunohistochemical staining for transmembrane protease serine 4 in the upper and lower gastrointestinal tract, liver and pancreas at ×20 magnification. (A) Mid-oesophagus exhibiting cytoplasmic staining in the oesophageal epithelial cells (*), submucosal glands (**) and lower muscularis mucosae (***). (B) Gastric fundic mucosa exhibiting positivity in the surface epithelial cells and the mucinous parietal cells (*). The zymogenic and endocrine cells in the basal zone also exhibited diffuse cytoplasmic staining. (C) In the small intestine, there was weak staining of the cytoplasm of goblet cells and enterocytes (*). In the (D) jejunum and (E) ileum, the cytoplasmic expression was more pronounced compared to the large intestine (**). (F) Colonic mucosa exhibiting simple columnar surface epithelium and mucosal crypts with cytoplasmic and weak nuclear membrane staining of goblet cells and adjacent enterocytes (*). (G) The liver exhibited cytoplasmic staining of hepatocytes together with bile ducts and ductules (*). (H) In the pancreas, there was pronounced cytoplasmic staining of acinar cells (**). Scale bar, 500 nm.

Figure 2.

Immunohistochemical staining for TMPRSS4 in human non-small cell lung cancer at ×20 magnification. High expression of TMPRSS4 in LUSC cells (black arrowhead) with a lesser expression in (A) the adjacent peritumoral tissue, and a high expression in alveolar epithelial cells (red arrowhead) in (B) the NAT of a male patient (53 years of age, T2N0M0; grade 2, stage IB). (C) Lesser, but detectable staining of TMPRSS4 in lung squamous cell carcinoma cells (black arrowhead) with minor staining in the adjacent peritumoral tissue, and (D) a high expression on alveolar epithelial cells (red arrowhead) in the NAT of a female patient (56 years of age, T2N0M0; grade 3, stage IIIA). Protein expression in lung adenocarcinoma cells (black arrowhead) with (E) a lesser expression in the adjacent peritumoral tissue (LUAD) and (F) a high expression on alveolar epithelial cells (red arrowhead) in cancer adjacent lung tissue (AT) of a male patient (65 years of age, T2N2M0, grade 3, stage IIIA). (G) Expression in LUAD (black arrowhead) and a (H) high expression on both bronchial (blue arrowhead) and alveolar epithelial cells (red arrowhead) in cancer adjacent lung tissue of a female patient (35 years of age, T4N1M0, grade 3, stage IIIA). Scale bar, 500 nm. TMPRSS4, transmembrane protease serine 4; LUSC, lung squamous cell carcinoma; LUAD, lung adenocarcinoma; NAT, normal adjacent tissue; AT, adjacent tissue.

Figure 3.

Immunohistochemical staining for transmembrane protease serine 4 in (A and B) human normal lung tissue (A) ×20 magnification; (B) ×40 magnification, and in (C and D) human lung tumour tissue [(C) ×20 magnification; bronchial carcinoma non-small cell lung cancer following radiation treatment; (D) ×40 magnification; male, 77 years old with chronic obstructive pulmonary disease]. Of note is the prominent expression on bronchial epithelial cells (panel A, arrowhead) and alveolar epithelial cells (panel B, arrowhead) in (A and B) normal lung tissue, as well as the prominent expression on bronchial carcinoma cells (panels C and D, arrowhead) with peritumoral stroma showing less staining.