Zohra Tumur, Carlos Guerra, Peter Yanni, Ahmad Eltejaye, Christi Waer, Tursun Alkam and Bradley S Henson
Objective: Active components of natural foods are increasingly receiving attention for their chemopreventive and chemotherapeutic potential in a wide variety of cancers. Rosmarinic acid (RA), a phenolic compound in various herbal plants, is well-recognized for its anti-oxidant, anti-inflammatory, anti-proliferative properties in a variety of cell types. In this report, we describe a novel role for RA as an inhibitor of epidermal growth factor (EGF) stimulated signaling in HNSCC and propose a cellular reactive oxygen species (ROS)-mediated mechanism for the observed effects.
Methods: Cellular growth, migration and reactive oxygen species (ROS) profiles were examined in RA-treated and untreated HNSCC cell lines (UM- SCC-6 and UM-SCC-10B) using the WST-1 viability assay, established in vitro migration assays, and the CM-H2DCFDA ROS assay, respectively. The influence of RA on EGF-stimulated phosphorylation and its downstream pathways was evaluated using Western-blotting techniques.
Results: RA inhibited cell viability, migration and cellular production of ROS in HNSCC cell lines. Furthermore, RA inhibited EGF-induced phosphorylation of the EGFR at tyrosine residues 992 and 845, which led to downregulation of the phosphatidylinositol 3-kinase Akt (PI3K/Akt) and mitogen-activated protein kinase ERK (MAPK/ ERK) pathways.
Conclusions: This is the first report describing both growth- and motility-inhibitory roles for RA in HNSCC cells. Additionally, our study is the first to demonstrate that treatment with RA can reduce EGF-induced activation of PI3K/ Akt in tumor cells. The present data suggests that RA holds promise as a chemotherapeutic agent against HNSCC.
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