Induction of anti-proliferative and apoptotic effects by anti-IL-25 receptor single chain antibodies in breast cancer cells.

Overexpression of IL-25 receptor (IL-25R) on the surface of malignant, but not normal, breast epithelial cells contributes to tumorigenic potential of breast cancer cells. IL-25/IL-25R binding results in specific apoptosis in breast cancer cells. In this study, the inhibitory effects of anti-IL-25R scFv antibodies on three breast cancer cells were evaluated. Panning process was performed on a phage library to isolate scFvs against two specific epitopes of IL25R. The reactivities of scFvs were assessed using phage ELISA. Cell binding capacity of the selected scFvs on breast cancer cells was analyzed using flow cytometry. Anti-proliferative and apoptotic effects of scFvs were evaluated by MTT, Annexin V/PI and quantitative caspase 3 activity assays. Two scFvs with frequencies of 47% and 68% were selected against peptides I and II, respectively. Phage ELISA demonstrated the specific reactions of the scFvs against the corresponding peptides. The scFvs against peptides I and II bound to 14% and 21% of MDA-231, 28% and 32% of MCF7, and 21% and 30% of SKBR3 cells, respectively. Treatment of the breast cancer cells with IL-25 and two anti-IL-25R scFvs resulted in significant inhibition of the cell growth in these cell compared to that in IL-25R negative Raji cells. The results also demonstrated 66% and 70% apoptosis cell death and 15.5 and 17 fold increases in caspase- 3 activity in SKBR3 cells induced by scFvs I and II, respectively. Our findings suggest the targeting of IL-25R by scFvs as a new effective strategy in breast cancer immunotherapy.