Aim: To study the expression level and localization of insulin-like growth factor -I receptor (IGF-IR) in HepG2 cells and Chang liver cells, and to observe the effect of anti-IGF-IR monoclonal antibody (alphaIR3) on the growth of HepG2 cells.
Methods: The expression of IGF-IR in HepG2 cells and Chang liver cells was detected by immunohistochemistry. The influences of alphaIR3 on proliferation and apoptosis were examined by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and electron microscopy, respectively. Flow cytometry (FCM) was applied for the analysis of cell cycle and apoptosis was observed under electron microscope.
Results: IGF-IR was located in the membranes of both HepG2 and Chang liver cell lines, and the expression level of IGF-IR was higher in HepG2 cells than in Chang liver cells. Treated with 0.1 microg/mL alphaIR3 for 48 h in vitro, the cell growth index (GI) of HepG2 cells was significantly higher than that of control (103.41% vs 100%, P<0.01). However, the alphaIR3 for 24 h at final concentration of 4.0 microg/mL made the GI of HepG2 cells lower than that of control (93.37% vs 100%, P<0.01). Compared with control, treated with alphaIR3 for 48 h at final concentrations ranging from 1.0 microg/mL to 4.0 microg/mL markedly reduced the GIs of HepG2 cells (97.63%, 97.16%, 95.13%, 92.53% vs 100%, P<0.05 or P<0.01), treated with alphaIR3 for 72 h at final concentrations ranging from 0.2 microg/mL to 4.0 microg/mL decreased the GIs of HepG2 cells obviously (95%, 91.63%, 90.77%, 89.84%, 88.51% vs 100%, P<0.01), and treated with alphaIR3 for 96 h at final concentrations ranging from 0.5 microg/mL to 4.0 microg/mL made GIs of HepG2 cells lower significantly (88.86%, 83.97%, 79.81%, 77.24%, 70.51% vs 100%, P<0.05 or P<0.01). Moreover, treated with alphaIR3 from 24 h to 96 h at final concentrations ranging from 0.2 microg/mL to 4.0 microg/mL reduced the GI of HepG2 cells from 97.63% to 70.51% in a dose- and time-dependent manner. Also, alphaIR3 treatment for 72 h at final concentration from 0.5 microg/mL to 2.0 microg/mL increased the proportion of G0/G1 phase cells (61.73%, 67.1%, 83.7%, 76.87% vs 44.47%, P<0.01) and significantly decreased that of S phase cells (28.63%, 25.13%, 15.63%, 23.13% vs 53.17%, P<0.01), in contrast to the proportion of G2/M phase cells. The apoptotic rates of HepG2 cells were increased more than that of control (7.83%, 16.13%, 21.1%, 37.73% vs 4.13%, P<0.01).
Conclusion: The malignant cell phenotype of human hepatocarcinoma cell is related to overexpression of IGF-IR. The blockage of IGF-IR with alphaIR3 may contribute to the inhibition of proliferation and induction of apoptosis in HepG2 cells.