EGF and ovarian cancer: Contrary to the expectation for a COX/PGE2-mediated mechanism, human ovarian cancer (OvCa433) cells incubated with 300 μM of S-naproxen or R-naproxen +/-EGF exhibited levels of phosphorylated EGFR (pEGFR) and (pERK) that were statistically above unstimulated controls (BSA, p values on graphs) and similar to controls treated with EGF alone (without naproxen) (Fig 6A–6D).