ObjectiveTo observe the effects of different concentrations of trastuzumab alone or in combination with oxaliplatin on proliferation, apoptosis, and cell cycle of SW-620 human colon cancer cell, and to explore its mechanism. MethodsSW-620 human colon cancer cells were cultured in vitro. ① Cell proliferation experiment: the cells were divided into two large groups: trastuzumab group and trastuzumab combined with oxaliplatin group. There were eight concentration groups in each large group (five holes for each group). The concentration of the trastuzumab group was 0, 0.001, 0.01, 0.1, 1, 10, 100, and 1 000 μg/mL, corresponding to the trastuzumab combined with oxaliplatin group. The concentration of the antibiotic was the same as before, except that oxaliplatin (10 μmol/L) was added. The absorbance (A) value of each group was measured by CCK-8 method. ② Apoptosis experiment: the same proliferation experiment was performed in the group, except that the concentrations of trastuzumab only included 0, 0.1, 1 and 10 μg/mL. Flow cytometry was used to detect the proportion of apoptotic cells and cell cycle distribution in each group. ③ Determination of human epidermalgrowth factor receptor-2 (her-2). The SW-620 cells were divided into two large groups, the concentration of trastuzumab group concluded 0, 100, and 1 000 μg/mL, as well as the concentration of trastuzumab in the trastuzumab combined with oxaliplatin group concluded 0, 1, and 10 μg/mL. Expressions of her-2 protein in SW-620 cells were detected by Western blot method. Results① Cell proliferation assay: the A values at100 μg/mL and 1 000 μg/mL were significantly lower than that at 0 μg/mL (P<0.05). At the same concentration, the A value of the trastuzumab combined with oxaliplatin group was lower than that of the trastuzumab group (P<0.05 ), and the A value gradually decreased with the increase of the concentration of trastuzumab. ② Apoptosis experiment: the proportion of apoptotic cells in the trastuzumab combined with oxaliplatin group was higher than that in the trastuzumab group (P<0.05) at the same concentration of trastuzumab. Flow cytometry: after treatment with different concentrations of trastuzumab combined with oxaliplatin, cells in G1 phase showed a downward trend, and cells in S phase showed an upward trend in a dose-dependent manner. At 1 and 10 μg/mL concentration of trastuzumab, the trastuzumab combined with oxaliplatin group significantly reduced the proportion of cells in the G1 phase of SW-620 cell cycle compared with the trastuzumab group, but S phase ratio was higher (P<0.05). The proportion of G2 phase cells was significantly higher in the trastuzumab combined with oxaliplatin group than the trastuzumab group at 0.1, 1 and 10 μg/mL concentrations of trastuzumab (P<0.01). ③ Expressions of her-2 protein: the expression level of her-2 protein gradually decreased at 1, 100, and 1 000 μg/mL trastuzumab group (P<0.05). The expression levels of her-2 protein in 0, 1 and 10 μg/mL trastuzumab combined with oxaliplatin group also gradually decreased (P<0.01). ConclusionsHigh concentration of trastuzumab can inhibit the proliferation of SW-620 human colon cancer cells and induce apoptosis. Trastuzumab combined with oxaliplatin has synergistic effect on inhibiting cell proliferation and promoting apoptosis.