Specific targeting of HER2-positive human breast carcinoma SK-BR-3 cells by amygdaline-ZHER2 affibody conjugate.

Amygdalin induces apoptotic death in several carcinoma cells. Affibody is an engineered protein with a high affinity for human epidermal receptor 2 (HER2). We assessed the cytotoxic effects of the amygdalin-ZHER2 affibody conjugate on two breast carcinoma cell lines. The ZHER2 affibody gene was synthesized and transferred into E. coli BL21 as an expression host. After purification, the ZHER2 affibody was conjugated to amygdalin. The cytotoxic effects of amygdalin and its ZHER2 affibody conjugate on the SK-BR-3, with overexpression of HER2, and MCF-7 cells were evaluated by MTT assay. The effects of amygdalin and its conjugate on apoptotic death and expression of pro-apoptotic Bax and anti-apoptotic Bcl-2 proteins were measured. Amygdalin individually showed a potent cytotoxic effect against both MCF-7 (IC50 = 14.2 mg ml-1) and SK-BR-3 cells (IC50 = 13.7 mg ml-1). However, the amygdalin-ZHER2 affibody conjugate had a more cytotoxic effect on SK-BR-3 (IC50 = 8.27 mg ml-1) than MCF-7 cells (IC50 = 19.8 mg ml-1). Amygdalin had a significant apoptotic effect on both cell lines and the effect of its conjugate on SK-BR-3 cells was significantly more potent than MCF-7 cells. Amygdalin increased Bax and decreased Bcl-2 expression in both cell lines. However, the effect of its conjugate on the Bax and Bcl-2 expression in SK-BR-3 was more potent than MCF-7 cells. In conclusion, the amygdalin-ZHER2 affibody conjugate may be considered as a valuable candidate for specific treatment of breast cancer patients with overexpression of HER2. However, further in vivo studies are required to explain the antitumoral effects of constructed amygdalin-ZHER2 affibody conjugate.