SCC9 growth inhibition correlate with EPO release and cell viability. A: IL-2 induced release of Eosinophil peroxidase (EPO) in culture media is associated with inhibition of oral cancer cell proliferation. EPO was measured by a colorimetric assay using the substrate O-phenylenediamine dihydrochloride. B: Viability of eosinophils in co-culture with oral squamous cancer cells. Viability was measured using flow cytometry by assessing cell integrity using Topro3 DNA dye and absence of apoptosis with Annexin V. All data are represented by Mean ± SEM * p < 0.05 for eosinophil:SCC9 co-culture compared with the respective controls without cytokines.