Peroxisome proliferator-activated receptor γ (PPARγ) plays a critical role in the development of TGFβ resistance of H460 cell

The primary goal of the study was to investigate how peroxisome proliferator-activated receptor γ (PPARγ) played a critical role in the protection of H460 cell, one of the non-small cell lung cancer (NSCLC) cells with multidrug resistance, from transforming growth factor β (TGFβ)-mediated mitoinhibition. In the study, TGFβ resistance of H460 cell was first confirmed by analyses of PPARγ expression, its interaction with TGFβ-induced Smad3 and phospho-Smad3 (p-Smad3) and survival of H460. Results showed that enable to escape from G2/M phase arrest, H460 cell had higher resistance to TGFβ-mediated mitoinhibition than CH27 (a drug sensitive control). TGFβ significantly increased PPARγ expression of H460 but not of CH27 cell whereas nuclear accumulation of p-Smad3 was only limited to CH27, the latter was believed to contribute to the induction of P21 waf1/cip1 and cyclin B1, cell cycle arrest at G2/M phase and TGFβ-mediated mitoinhibition of CH27 cell. TGFβ-induced PPARγ of H460 cell was further demonstrated to bind to Smad3 and p-Smad3, and GW9662 (PPARγ inhibitor) or PPARγ-specific shRNA could disrupt the binding. GW9662 also increased the nuclear accumulation of p-Smad3 that eventually led to the reduction of TGFβ resistance of H460. A transient knockdown of PPARγ with shRNA revealed a similar effect as GW9662. In addition, activation of P38 instead of ERK played a critical role in TGFβ-induced expression of PPARγ, which subsequently activated RhoA in H460 cell.

Research Highlights
► PPARγ plays a critical role in the development of TGFβ resistance of H460.
► PPARγ binds to Smad3/p-Smad3 and interrupts Smad3-mediated mitoinhibition of H460.
► GW9662 (PPARγ inhibitor) can reinstate TGFβ-mediated growth inhibition in H460.
► TGFβ activates P38/PPARγ and PPARγ/RhoA signaling in H460 cells.
► PPARγ is also important for the maintenance of normal growth of H460.