Protease-activated receptor (PAR)-1 and PAR-2 participate in the cell growth of alveolar capillary endothelium in primary lung adenocarcinomas.
BACKGROUND
Cell growth can be induced via elicitation of protease-activated receptors (PAR) with serine proteases such as thrombin and trypsin.


METHODS
To understand whether PAR are involved in tumor vessel formation in the neoplastic cell-bearing alveolar walls, immunohistochemical and reverse transcriptase-polymerase chain reaction analyses were performed using the lung tissues from 16 patients with primary lung adenocarcinomas.


RESULTS
In microdissected tumor alveolar walls, the expressions of PAR-1 and PAR-2 mRNA were increased by 10-fold (P < 0.05) and 16-fold (P < 0.01), respectively, as compared with normal alveolar walls. Confocal microscopy revealed that tumor capillary endothelial cells in alveolar walls lost thrombomodulin expression. Instead, the expression of PAR-2 often became obvious at the normal border. Both PAR-1 and PAR-2 were expressed in the microvessel endothelial cells in tumors. Trypsin mRNA was expressed in 7 of the 16 cancer cell-bearing tissue specimens in contrast to 1 of the 14 normal alveolar walls. Immunohistochemically, trypsin was positive in the neoplastic cells from 10 patients and in lung adenocarcinoma cell lines (A549, HLC-1, LC-2, and PC-14). An in vitro assay showed a significant increase in idoxuridine (IdU) or bromodeoxyuridine uptake in human pulmonary artery endothelial cells and human umbilical cord vein endothelial cells after treatments with alpha-thrombin or activating peptides; SFLLRN for PAR-1 and SLIGKV for PAR-2, respectively.


CONCLUSIONS
Thus, proliferation of alveolar capillary endothelial cells is initialized in part by PAR activation with serum thrombin and neoplastic cell-released trypsin. These results suggest a synergistic effect of PAR with vascular endothelial growth factor in alveolar angiogenesis.
Jin
Enjing
E
Department of Molecular Pathology, Institute of Gerontology, Nippon Medical School, Graduate School of Medicine, Kawasaki, Japan.
Fujiwara
Masakazu
M
Pan
Xin
X
Ghazizadeh
Mohammad
M
Arai
Satoru
S
Ohaki
Yoshiharu
Y
Kajiwara
Keiko
K
Takemura
Tamiko
T
Kawanami
Oichi
O
D000230:Adenocarcinoma / Q000098:blood supply* / Q000378:metabolism / Q000473:pathology; D002196:Capillaries / Q000378:metabolism / Q000473:pathology; D002455:Cell Division / Q000187:drug effects / Q000235:genetics; D004730:Endothelium, Vascular / Q000378:metabolism / Q000473:pathology; D005455:Fluorescent Antibody Technique; D006801:Humans; D007150:Immunohistochemistry; D008175:Lung Neoplasms / Q000098:blood supply* / Q000378:metabolism / Q000473:pathology; D018613:Microscopy, Confocal; D009389:Neovascularization, Pathologic / Q000235:genetics* / Q000378:metabolism; D009842:Oligopeptides / Q000494:pharmacology; D010446:Peptide Fragments / Q000494:pharmacology; D011650:Pulmonary Alveoli / Q000098:blood supply*; D012333:RNA, Messenger / Q000032:analysis; D044463:Receptor, PAR-1; D044464:Receptor, PAR-2; D018179:Receptors, Thrombin / Q000235:genetics* / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013917:Thrombin / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D009842:Oligopeptides; D010446:Peptide Fragments; D012333:RNA, Messenger; D044463:Receptor, PAR-1; D044464:Receptor, PAR-2; D018179:Receptors, Thrombin; C109968:seryl-leucyl-isoleucyl--glycyl-lysyl-valine; C082835:thrombin receptor peptide (42-47); D013917:Thrombin