The Fibroblast TIAM2 Promotes Lung Cancer Cell Invasion and Metastasis.

TIAM2 (T-cell lymphoma invasion and metastasis 2), a RAC1 guanine nucleotide exchange factor, plays crucial roles in human cancer cells. Its homolog, TIAM1, has been reported to promote the migration and invasion of cancer cells through regulating the functions of cancer associated fibroblasts (CAFs). However, the functions of TIAM2 in CAFs have not been investigated. In this study, we explored how fibroblast TIAM2 influences the migration and invasion of lung cancer cells. We cultured primary lung CAFs and adjacent normal lung fibroblasts (NFs) from 12 non-small cell lung cancer (NSCLC) patients. RT-PCR and western blot were used to compare TIAM2 levels between CAFs and NFs. Two co-culture systems were designed, in which cancer cells were directly co-cultured with fibroblasts and indirectly co-cultured with conditional medium (CM) from fibroblasts. Subsequently, the wound healing and transwell tests were conducted to assess the migration and invasion ability of fibroblasts and co-cultured cancer cells. Finally, cytokine antibody arrays were used to screen differentially secreted cytokines in the CM. The expression levels of TIAM2 were significantly higher in CAFs than NFs, and TIAM2-silenced fibroblasts showed decreased migration and invasion ability. In the direct co-culture system, the migration and invasion of cancer cells were retarded when co-culturing with TIAM2-silenced fibroblasts, and the expression levels of EMT-related genes also changed in cancer cells. Decreased migration and invasion of cancer cells were also observed when culturing with the CM from TIAM2-silenced fibroblasts. In addition, the cytokine antibody arrays revealed that Osteoprotegerin (OPG) was significantly decreased in the CM of TIAM2-silenced fibroblasts. This result suggested that OPG might be one of the main cytokines contributing to the migration and invasion of cancer cells in co-culture systems. Our results suggest that fibroblast TIAM2 promotes the invasion and migration of lung cancer cell, and OPG might be one of the main cytokines contributing to this pro-cancer process.