Visit our Expo - Redox and Inflammation signaling 2012

Session III : Protein kinase cascades as therapeutic targets Poster III, 43
Expression of HPV E5 protein induces expression of EP4 prostanoid receptor through
PKA- and CREB-dependent pathway in C33A cervical cancer cells.
Jung Min OH and Yong-Sung JUHNN
Department of Biochemistry and Molecular Biology, Cancer Research Institute, Seoul
National University College of Medicine, Seoul 110-799, Korea
HPV (Human Papilloma Virus) infection is the major cause of cervical cancer development.
The role of HPV E6 and E7 protein in the carcinogenesis has been extensively studied,
however, the role of E5 protein in cervical carcinogenesis is not understood clearly. The
prostaglandin signaling pathway mediated by cyclooxygenase-2(COX-2) is activated in
cervical cancer cells and many other types of cancer cells, therefore, this study aimed to
analyze the effect of E5 protein on prostaglandin signaling pathway.
Stable expression of E5 protein caused an increase in COX-2 protein and EP4 prostanoid
receptor in C33A cervical cancer cells. Stable expressing COX-2 protein also increased
mRNA expression of EP4 and prostaglandin E synthase and secretion of prostaglandin E2
(PGE2), major product of COX-2 in inflammatory process, in C33A cervical cancer cells.
Treatment of E5 expressing cells with NS-398, a COX-2 inhibitor, decreased the expression
of EP4, and furthermore, treatment of HeLa cells that expresses high level of COX-2 with
NS-398 also resulted in decrease in EP4 mRNA expression and PGE2 secretion. Treatment
with H89, a PKA inhibitor or decoy CRE reduced expression of EP4 mRNA in COX-2
expressing cells. However, expression of COX-2 in HaCaT cells, immortalized human
keratinocytes did not induce expression of EP4.
Because the EP4 protein level did not increase in parallel with EP4 mRNA following E5
overexpression, the degradation rate of EP4 protein was analyzed. The EP4 protein in COX-2
expressing cells was found to degrade faster in the presence of cycloheximide than that of
vector-transfected control cells. The degradation of EP4 protein was blocked by treatment
with MG-132, a proteasome inhibitor.
From this result, we conclude that HPV E5 protein induces EP4 mRNA through COX-2-,
PKA-, and CREB-dependent pathway in cervical cancer cells, not in HaCaT cells.
- 229 -