Background & objective: Several researches have reported that epidermal growth factor receptor (EGFR) is expressed frequently in hepatocellular carcinoma (HCC) and paratumor tissues, most likely to contribute to the biological characteristics of HCC, including invasion, metastasis, and resistance to chemotherapy and radiotherapy. The single agent of cetuximab and erlotinib can inhibit the proliferation of HCC cells in vivo and in vitro. This study was to investigate the effects of cetuximab combined erlotinib on the proliferation of HCC cells, and explore the molecular mechanism.
Methods: Increasing concentrations of cetuximab (5-500 mg/mL) and erlotinib (2.5-250 micromol/L) alone or in combination were administrated to HCC cell lines HepG2 and Bel-7402. The inhibitory effects of the drugs on cell proliferation at different time points were observed; the combination index (CI) of these two agents was calculated. The expression of key enzymes in EGFR signaling transduction pathway in HepG2 and Bel-7402 cells after different treatments was detected by Western blot.
Results: The single agent of cetuximab and erlotinib inhibited the proliferation of HCC cells in a time-and dose-dependent manner; after 72-hour treatment, the proliferation inhibition rates of HepG2 cells were (43.1+/-1.9)% and (83.4+/-1.3)%, and those of Bel-7402 cells were (35.1+/-2.6)% and (73.9+/-1.2)%. With maximal inhibitory effects of cetuximab combined erlotinib, the proliferation inhibition rates of HepG2 and Bel-7402 cells were (91.1+/-1.0)% and (84.6+/-1.1)%, respectively. The CIs of different concentrations of these two agents at different time points were all less than 1, suggested that they have obvious synergistic activity. The expression of activated key enzymes (p-EGFR, p-ERK1/2, p-AKT) in EGFR signaling transduction pathway in HepG2 and Bel-7402 cells were down-regulated more obviously when these two agents were administrated in combination.
Conclusions: The single agent of cetuximab and erlotinib can inhibit the proliferation of HepG2 and Bel-7402 cells through down-regulating activated key enzymes in EGFR signaling transduction pathway, and they have obvious synergistic activity. The combined EGFR-targeting therapy on HCC xenografts in vivo and on HCC patients is worth of further exploration.