Identification of MMP proteins secreted by HepG2 cells. To prepare a conditioned medium including the MMP proteins released from HepG2 cells, fresh HepG2 culture medium was added to HepG2 cells at 80% confluency and incubated for 4 days (Conditioned medium). For the control, fresh HepG2 culture medium was incubated for 4 days in a HepG2 cell-free culture dish (Control medium). The different MMPs present in the conditioned medium were identified using a chemiluminescence immunoassay and quantified using ImageJ software. Five MMP proteins (MMP1, MMP3, MMP9, MMP10, and MMP13) were observed in the conditioned medium; two (MMP2 and MMP8) were not expressed. No MMP proteins were observed in the control condition. The protein level of MMP3 was the highest among the MMPs detected. The expression of the remaining MMPs decreased in the following order: MMP13 > MMP10 > MMP9 > MMP1. Data are shown as the mean ± SD of three independent experiments. *p < 0.05. ND, not detected; Pos, positive control; Neg, negative control.