Hyaluronic acid optimises therapeutic effects of hydrogen peroxide‐induced oxidative stress on breast cancer.

Distinguishing the multiple effects of reactive oxygen species (ROS) on cancer cells is important to understand their role in tumour biology. On one side, ROS can be oncogenic by promoting hypoxic conditions, genomic instability and tumorigenesis. Conversely, elevated levels of ROS‐induced oxidative stress can induce cancer cell death. This is evidenced by the conflicting results of research using antioxidant therapy, which in some cases promoted tumour growth and metastasis. However, some antioxidative or ROS‐mediated oxidative therapies have also yielded beneficial effects. To better define the effects of oxidative stress, in vitro experiments were conducted on 4T1 and splenic mononuclear cells (MNCs) under hypoxic and normoxic conditions. Furthermore, hydrogen peroxide (H2O2; 10–1,000 μM) was used as an ROS source alone or in combination with hyaluronic acid (HA), which is frequently used as drug delivery vehicle. Our result indicated that the treatment of cancer cells with H2O2 + HA was significantly more effective than H2O2 alone. In addition, treatment with H2O2 + HA led to increased apoptosis, decreased proliferation, and multiphase cell cycle arrest in 4T1 cells in a dose‐dependent manner under normoxic or hypoxic conditions. As a result, migratory tendency and the messenger RNA levels of vascular endothelial growth factor, matrix metalloproteinase‐2 (MMP‐2), and MMP‐9 were significantly decreased in 4T1 cells. Of note, HA treatment combined with 100–1,000 μM H2O2 caused more damage to MNCs as compared to treatment with lower concentrations (10–50 μM). Based on these results, we propose to administer high‐dose H2O2 + HA (100–1000 μM) for intratumoural injection and low doses for systemic administration. Intratumoural route could have toxic and inhibitory effects not only on the tumour but also on residential myeloid cells defending it, whereas systemic treatment could stimulate peripheral immune responses against the tumour. More in vivo research is required to confirm this hypothesis. [ABSTRACT FROM AUTHOR]