Scientists attached a tumor‑targeting tag (iRGD) to the immune‑boosting peptide thymosin‑alpha‑1, creating a new version that gets into breast cancer cells more easily and kills them better in lab dishes and mice, while still keeping its immune‑stimulating effects.

Thymosin alpha 1 (Tα1) is commonly used for treating several diseases; however its usage has been limited because of poor penetration of the target tissue, such as tumor cells. In the present study, Tα1-iRGD, a peptide by conjugating Tα1 with the iRGD fragment, was evaluated its performance in MCF-7 and MDA-MB-231 human breast cancer cells. Compared with the wild-type peptide, Tα1-iRGD was more selective in binding tumor cells in the cell attachment assay. Furthermore, the MTT assay confirmed that Tα1-iRGD proved more effective in significantly inhibiting the growth of MCF-7 cells in contrast to the general inhibition displayed by Tα1. Further, conjugation of Tα1 with iRGD preserved the immunomodulatory activity of the drug by increasing the proliferation of mouse spleen lymphocytes. Further, compared with Tα1 treatment, Tα1-iRGD treatment of MCF-7 cells considerably increased the number of cells undergoing apoptosis, resulting in a dose-dependent inhibition of cancer cell growth, which was associated with a much better effect on up-regulation of the expression of BCL2-associated X protein (Bax), caspase 9, etc. More importantly, treatment with Ta1-iRGD was more efficacious than treatment with Ta1 in vivo. This study highlights the importance of iRGD on enhancement of cell penetration and tumor accumulation. In summary, our findings demonstrate that the novel modified Tα1 developed in this study has the potential to be used for treating breast cancer.