Proteinase-activated receptor 4 stimulation-induced epithelial-mesenchymal transition in alveolar epithelial cells

BACKGROUND: Proteinase-activated receptors (PARs; PAR(1–4)) that can be activated by serine proteinases such as thrombin and neutrophil catepsin G are known to contribute to the pathogenesis of various pulmonary diseases including fibrosis. Among these PARs, especially PAR(4), a newly identified subtype, is highly expressed in the lung. Here, we examined whether PAR(4 )stimulation plays a role in the formation of fibrotic response in the lung, through alveolar epithelial-mesenchymal transition (EMT) which contributes to the increase in myofibroblast population. METHODS: EMT was assessed by measuring the changes in each specific cell markers, E-cadherin for epithelial cell, α-smooth muscle actin (α-SMA) for myofibroblast, using primary cultured mouse alveolar epithelial cells and human lung carcinoma-derived alveolar epithelial cell line (A549 cells). RESULTS: Stimulation of PAR with thrombin (1 U/ml) or a synthetic PAR(4 )agonist peptide (AYPGKF-NH(2), 100 μM) for 72 h induced morphological changes from cobblestone-like structure to elongated shape in primary cultured alveolar epithelial cells and A549 cells. In immunocytochemical analyses of these cells, such PAR(4 )stimulation decreased E-cadherin-like immunoreactivity and increased α-SMA-like immunoreactivity, as observed with a typical EMT-inducer, tumor growth factor-β (TGF-β). Western blot analyses of PAR(4)-stimulated A549 cells also showed similar changes in expression of these EMT-related marker proteins. Such PAR(4)-mediated changes were attenuated by inhibitors of epidermal growth factor receptor (EGFR) kinase and Src. PAR(4)-mediated morphological changes in primary cultured alveolar epithelial cells were reduced in the presence of these inhibitors. PAR(4 )stimulation increased tyrosine phosphorylated EGFR or tyrosine phosphorylated Src level in A549 cells, and the former response being inhibited by Src inhibitor. CONCLUSION: PAR(4 )stimulation of alveolar epithelial cells induced epithelial-mesenchymal transition (EMT) as monitored by cell shapes, and epithelial or myofibroblast marker at least partly through EGFR transactivation via receptor-linked Src activation

Tumor-To-Tumor Metastasis of Poorly Differentiated Gastric Carcinoma to Uterine Lipoleiomyoma

The rare phenomenon of tumor-to-tumor metastasis was first described in 1930. The donor neoplasm is most frequently lung or breast carcinoma, whereas intracranial meningiomas are reportedly the commonest recipient neoplasm. Here we report a case of metastasis from a primary gastric cancer to a uterine lipoleiomyoma. A 65-year-old woman presented with locally advanced gastric cancer with computed tomography (CT) evidence of peritoneal dissemination and a 9 cm pelvic mass. She underwent 16 courses of TS-1/cisplatin chemotherapy, which achieved significant tumor reduction. However, repeat CT and magnetic resonance imaging revealed a 9 cm diameter pelvic mass adjacent to the uterus. The mass was heterogeneously hyperintense on T1- and T2-weighted images with some low signal spots on fat-suppressed T1-weighted images, suggesting a benign ovarian tumor such as a mature cystic teratoma. After 3 months, pelvic CT revealed a 10 cm multilocular cystic mass that exhibited heterogeneous enhancement after intravenous contrast administration. A diagnostic laparotomy revealed a subserosal uterine tumor extending into the right broad ligament; total abdominal hysterectomy and bilateral salpingo-oophorectomy was performed. The uterine tumor showed histological features of lipoleiomyoma infiltrated by well- to moderately differentiated carcinoma cells that were similar to those of the gastric biopsy, supporting a diagnosis of metastatic gastric adenocarcinoma