Epidermal growth factor-stimulated human cervical cancer cell growth is associated with EGFR and cyclin D1 activation, independent of COX-2 expression levels

Cervical cancer constitutes the second most common cancer in women. It isevident from earlier studies that epidermal growth factor (EGF) is a mitogen,in that it mimics the function of estrogen by mediating cross-talk with otheroncoproteins. Although epidermal growth factor receptor (EGFR) is highly expressedin breast and ovarian tumor tissues, its regulation by the exogenous source ofits ligand EGF in human papillomavirus (HPV)-associated cervical cancer remainsunclear. In this study, we addressed the question of whether EGF is required forthe proliferation of HPV-positive cervical cancer cells and what mechanisms areinvolved. To determine this, we conducted a series of studies using HPV-positivehuman cervical cancer cells, CaSki and HeLa, and stimulated the cells with EGF.Our findings suggest that 6 h of stimulation with 10 ng/ml of EGF is sufficientto induce cell cycle progression associated with a significant increase in DNAsynthesis, EGFR, COX-2 and cyclin D1 levels. Consistently, cellular localizationand Western blot analysis for p-EGFR (Try-1045) protein showed an increase afterEGF stimulation. Using siRNA gene knockdown assays we have shown that cyclin D1siRNA has a significant negative effect on EGFR and inhibit cell growth independentof COX-2 levels. In summary, our findings reveal that an exogenous EGF stimulationmay enhance HPV-related cervical cancer cell proliferation by activating EGFRand cyclin D1 that is independent of COX-2 levels, suggesting that the inhibitorsof EGFR and cyclin D1 may be effective against cervical cancer cell proliferation.