Thus, further study is needed before one can generalize the results whether PEA-15 induced autophagy is not dependent on Ras. Whether PEA-15 has similar functions in other types of cancer is unknown. the antitumor activity of PEA-15 is mediated in part by the induction of autophagy involving activation of the ERK1/2 pathway. Multivariable analyses indicated that the women with high-PEA-15-expressing tumors survived longer than those with low-PEA-15-expressing tumors (hazard ratio = 1.973,P= 0.0167). Our findings indicate that PEA-15 expression is an important prognostic marker in ovarian cancer. Keywords:survival, autophagy, ovarian neoplasms, PEA-15, ERK == Introduction == Ovarian cancer is a major cause of cancer death among women in the United States. In 2007, 22,430 new cases are expected to be diagnosed and 15,280 women are expected Deferasirox Fe3+ chelate to die of the disease; ovarian cancer will account for approximately 6% of all cancer deaths in women. Because very few ovarian cancers are detected at an early stage, understanding the molecular mechanisms of tumor development is crucial if more effective treatments are Deferasirox Fe3+ chelate to be developed. Epithelial ovarian cancer is the most common type, accounting for 85% to 90% of all ovarian Deferasirox Fe3+ chelate cancers. Currently, no definitive biomarkers have been identified for early detection of ovarian cancer; the only known biomarker in current use is CA125, a protein produced in increased amounts in 80% of ovarian cancer cases but also in benign conditions such as endometriosis, pregnancy, and liver disease (1). In our previous study of gene therapy for ovarian cancer with the adenovirus type 5 geneE1A, we discovered that the antitumor effects ofE1Aresulted from the suppression of extracellular signal-regulated kinase (ERK) activity by phospho-enriched protein in astrocytes (PEA-15; also called PED), which sequestered phosphorylated ERK (pERK) in the cytoplasm (2). PEA-15 is an acidic, serine-phosphorylated, 15-kDa phosphoprotein that contains a death effector domain and is associated with microtubules. It blocks ERK-dependent proliferation by binding to ERK in the cytoplasm and preventing ERK entry into the nucleus. In NIH3T3 cells, this sequestration renders ERK unable to phosphorylate the transcription factor Elk-1, which is involved in ERK-dependent transcription (3). Genetic deletion of PEA-15 results in increased localization of ERK in the nucleus followed by increased cFos transcription and cell proliferation (3). Normal astrocytes containing high levels of PEA-15 can proliferate, but they do so more slowly than do PEA-15-depleted astrocytes (3). Thus, the expression level of PEA-15 seems to control the biological outcome of ERK/mitogen-activated protein kinase (MAPK) signaling by regulating the localization of ERK (3). However, we do not know how PEA-15 inhibits ovarian cancer cell growth or the clinical significance of PEA-15 expression levels in ovarian cancer. In this study, we evaluated the role of PEA-15 in ovarian cancer cellsin vitro. We found that PEA-15 resulted in inhibition of cell proliferation and induction of autophagy. Autophagy is a type of programmed cell death important in preventing cell aging and in providing the energy required for cell survival and repair during environmental stresses such as hypoxia, infection, and nutrient starvation (5,9). Two main pathways that regulate autophagy in response to starvation are the class I PI3K/Akt/mTor signaling pathway and the MAPK/ERK signaling pathway. The Akt/mTor pathway negatively regulates autophagy (4). Nutrient starvation, a known activator of autophagy, enhances ERK activity (5,6), and the ERK1/2 pathway is also stimulated in curcumin-induced autophagy (7). Conversely, MAPK/ERK activation is essential in lindane-induced carcinogenesis (8). Further, we assessed the clinical significance of Rabbit Polyclonal to XRCC4 PEA-15 expression by comparing PEA-15 expression in a microarray of human ovarian cancer Deferasirox Fe3+ chelate tissue specimens with clinical and pathological data on the specimen donors. Collectively, our findings indicate that PEA-15 expression may be an important prognostic marker in ovarian cancer. == Materials and Methods == == Cell lines and culture conditions == OVCA-420, OVCA-432, and HEY ovarian cancer cells were kindly provided by Dr. Robert Bast of The University of Texas M. D. Anderson Cancer Center. OVCAR-3 ovarian cancer cells were obtained from the American Type Culture Collection (Manassas, VA) Deferasirox Fe3+ chelate and PEA-15 expression was assessed in all four cell.