Transforming growth factor-1 promotes the transcriptional activation of plasminogen activator inhibitor type 1 in carcinoma-associated fibroblasts

Carcinoma-associated fibroblasts (CAFs) play a pivotal role in promoting the growth, invasion and metastasis of tumor cells. However, to date little is known about the oncogenic mechanisms of CAFs. This study aimed to identify the microenvironmental factors involved in tumor development and progression directed by CAFs in liver metastases. Tissue samples collected from 20 patients with colorectal liver metastases were used in this study. Histological and morphological characterization of the samples was performed using hybridization and immunohistological assays. The mRNA expression of α-smooth muscle actin (α-SMA) was measured by northern blotting. The expression of plasminogen activator inhibitor type 1 (PAI-1) was measured by enzyme-linked immunosorbent assay (ELISA). As a result, co-expression of Thy-1 (CD90) and α-SMA was identified in CAFs, while normal liver samples were negative for α-SMA and Thy-1. Compared with epidermal growth factor (EGF) and tumor necrosis factor (TNF) incubation, the expression of α-SMA increased significantly following transforming growth factor-1 (TGF-1) incubation (P