The angiotensin II type I receptor (AGTR1) has a strong influence on tumor growth, angiogenesis, inflammation and immunity. However, the role of AGTR1 on lymph node metastasis (LNM) in breast cancer, which correlates with tumor progression and patient survival, has not been examined. AGTR1 was highly expressed in lymph node-positive tumor tissues, which was confirmed by the Oncomine database. Next, inhibition of AGTR1 reduced tumor growth and LNM in orthotopic xenografts by bioluminescence imaging (BLI). Losartan, an AGTR1-specific inhibitor, decreased the chemokine pair CXCR4/SDF-1α levels in vivo and inhibited AGTR1-induced cell migration and invasion in vitro . Finally, the molecular mechanism of AGTR1-induced cell migration and LNM was assessed by knocking down AGTR1 in normal cells or CXCR4 in AGTR1 high cells. AGTR1-silenced cells treated with losartan showed lower CXCR4 expression. AGTR1 overexpression caused the upregulation of FAK/RhoA signaling molecules, while knocking down CXCR4 in AGTR1 high cells downregulated these molecules. Collectively, AGTR1 promotes LNM by increasing the chemokine pair CXCR4/SDF-1α and tumor cell migration and invasion. The potential mechanism of AGTR1-mediated cell movement relies on activating the FAK/RhoA pathway. Our study indicated that inhibiting AGTR1 may be a potential therapeutic target for LNM in early-stage breast cancer.

RAS protein activator-like 1 (RASAL1) is a member of the RAS GTPase-activating protein family, and previous studies indicate that RASAL1 is involved in the progression of hypoxia resistance in breast cancer cells. In the present study, increased levels of hypoxia inducible factor-1α (HIF-1α) were observed to be accompanied with increased expression of RASAL1 in the breast cancer cell lines MCF-7 and MDA-MB-231 cells under hypoxia. Based on this, it was postulated that RASAL1 may serve a functional role in the development of hypoxia resistant in breast cancer cells. In the present study it was demonstrated that: i) Exogenous expression of RASAL1 in MCF-7 and MDA-MB-231 sensitized its reaction to the treatment of hypoxia, which is associated with its ability to directly reduce HIF-1α expression, inhibit migration activity and decrease the accumulation of reactive oxygen species (ROS); ii) knockdown of RASAL1 reversed its reaction to treatment with hypoxia; iii) RASAL1 directly regulated the expression of HIF-1α through the ROS-mediated, extracellular signal-regulated kinase and Akt pathway. These findings provide direct evidence that the RASAL1/HIF-1α axis may serve an essential role in the hypoxia resistance of breast cancer cells, suggesting that this signaling cohort may serve as a novel therapeutic target for the treatment of breast cancer.