Anti-metastatic Properties of Bacterial Cyclodipeptides are Potentialized with Methotrexate in Xenotransplant Mice Model of the Triple-negative Breast Cancer MDA-MB-231 Line

Background: Triple-negative breast cancer (TN-BC) is the leading cause of death from neoplasms in women worldwide, related to a high rate of metastasis and low survival in patients. Bacterial cyclodipeptides (CDPs) have anticancer properties in several types of cancer in vitro as in vivo models, targeting several signaling pathways. Methods: The effect of the CDPs on advanced-stage tumors developed and their ability to prevent the appearance of metastatic foci through the implantation of the TN-BC MDA-MB-231 cells in the mammary tissue of mice model was evaluated. Results: CDPs treatment decreased the migratory and invasive capacity of the MDA-MB-231 and MCF-7 breast cancer lines in vitro more efficiently than methotrexate (MTX) (p>0.001). The anti-metastatic effect in the TN-BC was associated with the down-regulation of the Akt/mTOR/S6K pathway and the metastasis markers Gab1, MMP-9, and Vimentin. Mice xenografted with MDA-MB-231 administrated with CDPs and combined with CDPs+MXT showed a significant decrease in primary tumor development and metastatic foci (p>0.001). Likewise, the metastatic foci were observed in the lungs, liver, and femur, which were inhibited by CDPs. Metastatic behavior in the skeletal system was alleviated with the CDPs and CDPs+MTX treatments. In addition, the metastasis markers p-Akt, Gab1, and FOX01 were significantly down-expressed in the tumor tissue of mice implanted with TN-BC submitted to CDPs treatment. Conclusions: The anti-metastatic effects of bacterial CDPs involve the phosphorylation inhibition of the Akt/mTOR/S6K pathway and the metastasis markers Gab1, MMP-9, Vimentin, and FOX01. The finding indicates that the CDPs, in combination with MTX, potentialize the anti-neoplastic property in TN-BC, proposing the CDPs as a viable alternative in human breast cancer therapy.