Modulatory effect of phytoglycoprotein (38 kDa) on cyclin D1/CDK4 in BNL CL.2 cells induced by N-methyl-N'-nitro-N-nitrosoguanidine.

In the developmental stages of cancer, cell transformation occurs after the promotion stage and is a marker of cancer progression. This cell transformation is related to abnormal proliferation during the cancer initiation stage. The purpose of this study was to evaluate the effect of Styrax japonica Siebold et al. Zuccarin (SJSZ) glycoprotein on cell transformation in murine embryonic liver cells (BNL CL.2) following N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) treatment. To determine abnormal proliferation during the initiation stage, intracellular reactive oxygen species (ROS), phosphorylation of extracellular signal-regulated kinase (ERK), p38 mitogen-activated protein kinase (MAPK), activities of cell cycle-related factors [cyclin D1/cyclin dependent kinase (CDK) 4], cell cycle inhibitors (p53, p21, and p27), nuclear factor (NF)-κB, and proliferating cell nuclear antigen (PCNA) were evaluated using Western blot analysis and real-time PCR. Our study demonstrated that SJSZ glycoprotein (50 μg/ml) reduces foci formation with combined treatment [MNNG and 12-O-tetradecanoyl phorbol-13-acetate] of BNL CL.2 cells. With regard to proliferation-related signals, our finding indicated that SJSZ glycoprotein (50 μg/ml) diminished the production of intracellular ROS, activity of phosphorylated ERK, p38 MAPK, NF-κB (p50 and p65), PCNA, and cyclin D1/CDK4 in MNNG-induced BNL CL.2 cells. Taken together, these results lead us to speculate that SJSZ glycoprotein can inhibit abnormal cell proliferation at the initiation stage of hepatocarcinogenesis.