Tumor necrosis factor-alpha (TNF-α) promotes in vitro retinal pigment epithelial 
(RPE) cell migration to initiate proliferative vitreoretinopathy (PVR). Here we 
report that TNF-α promotes human RPE cell migration by inducing matrix 
metallopeptidase 9 (MMP-9) expression. Inhibition of MMP-9 by its inhibitor or 
its neutralizing antibody inhibited TNF-α-induced in vitro RPE cell migration. 
Reversely, exogenously-added active MMP-9 promoted RPE cell migration. 
Suppression Akt/mTOR complex 1(mTORC1) activation by LY 294002 and rapamycin 
inhibited TNF-α-mediated MMP-9 expression. To introduce a constitutively active 
Akt (CA-Akt) in cultured RPE cells increased MMP-9 expression, and to block 
mTORC1 activation by rapamycin inhibited its effect. RNA interference 
(RNAi)-mediated silencing of SIN1, a key component of mTOR complex 2 (mTORC2), 
had no effect on MMP-9 expression or secretion. In conclusion, this study 
suggest that TNF-α promotes RPE cell migration by inducing MMP-9 expression 
through activation of Akt/ mTORC1, but not mTORC2 signaling.