Inhibition of PAI-1 limits chemotherapy resistance in lung cancer through suppressing myofibroblast characteristics of cancer-associated fibroblasts.

Plasminogen activator inhibitor-1 (PAI-1) promotes pulmonary fibrosis through increasing myofibroblast (MF) characteristics, expressing alpha-smooth muscle actin (alpha-SMA) in fibroblasts. Fibroblasts in the tumour stroma are called cancer-associated fibroblasts (CAFs). Some CAFs have MF characteristics and substantially promote tumour progression and chemotherapy resistance. This study determined whether inhibition of PAI-1 suppressed MF characteristics of CAFs and limited chemotherapy resistance in lung cancer. To investigate cellular PAI-1 expression and its correlation with alpha-SMA expression of CAFs, 34 patients' paraffin-embedded lung adenocarcinoma tissue sections were immunohistochemically stained for PAI-1 and alpha-SMA. Immunohistochemical analysis of lung adenocarcinoma tissues showed that PAI-1 expression was correlated with that of alpha-SMA (r = 0.71, p < 0.001). Furthermore, in vitro, alpha-SMA expression of CAFs was limited by PAI-1 inhibition, and apoptosis of CAFs was increased. In addition, the effectiveness of cisplatin on lung cancer cells co-cultured with CAFs was increased by suppressing alpha-SMA expression using PAI-1 inhibitor. In lung adenocarcinoma tissues, PAI-1 expression was associated with T factor and TNM stage. Our data suggest that inhibition of PAI-1 increased the chemotherapeutic effect on lung cancer through suppressing the MF characteristics of CAFs. Hence, PAI-1 might be a promising therapeutic target for patients with chemotherapeutic-resistant lung cancer with CAFs.