[Effects of interferon-gamma on Her-2/neu expression and antitumor activity of 131I-Herceptin in breast cancer cell lines].

Background & Objective: Herceptin plays an important role in treating metastatic breast cancer by targeting Her2/neu, therefore, combining Herceptin with iodine-131 (131I) might enhance its antitumor activity. This study was to up-regulate Her2/neu expression by interferon-gamma (IFN-gamma), and explore its effect on binding and antitumor activity of 131I-Herceptin in breast cancer cell lines MCF-7, SKBR-3 and BT-474.

Methods: MCF-7, SKBR-3 and BT-474 cells were cultured with or without IFN-gamma (500 U/ml) for 48 h. The positive rate and mean fluorescence intensity (MFI) of Her2/neu on the 3 cell lines were tested by flow cytometry. Herceptin was labeled with 131I by Iodogen method, and its radiochemical purity (RCP) was tested by size-exclusion high-pressure liquid chromatography (HPLC). The binding rate of 131I-Herceptin on cells was measured by non-competitive saturation analysis, and its killing effect was estimated by colony-forming assay. The positive rate and MFI of Her2/neu, binding rate of 131I-Herceptin, and colony-forming rate were compared between IFN-gamma-induced group and control group by t test.

Results: For MCF-7 cells, the positive rate and MFI of Her2/neu were significantly higher in IFN-gamma-induced cells than in control cells [(15.2+/-4.7)% vs. (8.5+/-1.9)%, t=3.515, P<0.05; 121+/-17 vs. 38+/-7, t=7.823, P<0.002]; for SKBR-3 and BT-474 cells, no obvious difference of Her2/neu positive rate was observed between IFN-gamma-induced cells and control cells [(99.7+/-0.9)% vs. (98.9+/-1.1)%, P>0.05; (99.5+/-1.2)% vs. (98.1+/-0.9)%, P>0.05], but the MFI of Her2/neu was significantly higher in IFN-gamma-induced cells than in control cells (1,608+/-201 vs. 952+/-125, t=4.802, P<0.01; 1,968+/-192 vs. 1,020+/-98, t=7.614, P<0.002). The binding rates of Her2/neu were increased from (5.2+/-1.4)% to (12.3+/-3.4)% by 2.4 folds in MCF-7 cells, from (35.8+/-4.5)% to (48.9+/-7.1)% by 1.4 folds in SKBR-3 cells, and from (37.2+/-3.6)% to (59.5+/-8.7)% by 1.6 folds in BT-474 cells after inducement with IFN-gamma. The colony-forming rates were significantly lower in IFN-gamma-induced MCF-7, SKBR-3 and BT-474 cells than in control cells [(30+/-4)% vs. (49+/-3)%, t=6.574, P<0.05; (23+/-5)% vs. (37+/-6)%, t=3.105, P<0.05; (19+/-6)% vs. (34+/-5)%, t=3.323, P<0.05].

Conclusion: IFN-gamma can up-regulate Her-2/neu expression and increase the binding of 131I-Herceptin, hence, improve the inhibitory effect of 131I-Herceptin on proliferation of breast cancer cells.