AstraZeneca.

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Ovarian cancer remains the most lethal gynecologic malignancy, and is primarily diagnosed at late stage when considerable metastasis has occurred in the peritoneal cavity. At late stage abdominal cavity ascites accumulation provides a tumor-supporting medium in which cancer cells gain access to growth factors and cytokines that promote survival and metastasis. However, little is known about the redox status of ascites, or whether antioxidant enzymes are required to support ovarian cancer survival during transcoelomic metastasis in this medium. Gene expression cluster analysis of antioxidant enzymes identified two distinct populations of high-grade serous adenocarcinomas (HGSA), the most common ovarian cancer subtype, which specifically separated into clusters based on glutathione peroxidase 3 (GPx3) expression. High GPx3 expression was associated with poorer overall patient survival and increased tumor stage. GPx3 is an extracellular glutathione peroxidase with reported dichotomous roles in cancer. To further examine a potential pro-tumorigenic role of GPx3 in HGSA, stable OVCAR3 GPx3 knock-down cell lines were generated using lentiviral shRNA constructs. Decreased GPx3 expression inhibited clonogenicity and anchorage-independent cell survival. Moreover, GPx3 was necessary for protecting cells from exogenous oxidant insult, as demonstrated by treatment with high dose ascorbate. This cytoprotective effect was shown to be due to GPx3-dependent removal of extracellular H2O2. Importantly, GPx3 was necessary for clonogenic survival when cells were cultured in patient-derived ascites fluid. While oxidation reduction potential (ORP) of malignant ascites was heterogeneous in our patient cohort, and correlated positively with ascites iron content, GPx3 was required for optimal survival regardless of ORP or iron content. Collectively, our data suggest that HGSA ovarian cancers cluster into distinct groups of high and low GPx3 expression. GPx3 is necessary for HGSA ovarian cancer cellular survival in the ascites tumor environment and protects against extracellular sources of oxidative stress, implicating GPx3 as an important adaptation for transcoelomic metastasis.

BACKGROUNDThe authors previously identified sperm protein 17 (Sp17) as being expressed in patients with multiple myeloma. The restricted expression of Sp17 in normal tissue makes it an ideal target for tumor vaccine. In the current study, the authors extended their research to include ovarian carcinoma.METHODSA pair of sequence specific primers was used in reverse transcriptase‐polymerase chain reaction to determine the gene expression of Sp17. A recombinant Sp17 protein was used with monocyte‐derived dendritic cells and autologous peripheral blood mononuclear cells to generate Sp17 specific cytotoxic T‐lymphocytes (CTLs). The successful generation of Sp17 specific CTLs was confirmed using standard 51chromium‐release assays.RESULTSSp17 was found to be expressed in the primary tumor cells from 70% of the patients with ovarian carcinoma. Human leukocyte antigen (HLA) class I‐ restricted Sp17 specific CTLs were generated successfully from the peripheral blood of three patients with ovarian carcinoma at the time of disease presentation. These CTLs were able to lyse autologous Epstein‐Barr virus‐transformed lymphoblastoid cells in a Sp17‐dependent manner. Target lysis was HLA class I‐dependent and could be blocked by antibodies against monomorphic HLA class I but not HLA class II molecules. The CTLs also lysed Sp17‐positive autologous tumor cells, suggesting that Sp17 is processed and presented in association with the HLA class I molecules in Sp17‐ positive tumor cells in a concentration and configuration that could be recognized by recombinant protein‐primed CTLs. Tumor cell killing by the CTLs appeared to be mediated through the perforin pathway. Flow cytometric analysis of the CTLs indicated that they predominantly were CD8 in phenotype and produced interferon‐γ and scant amounts of interleukin‐4.CONCLUSIONSThe results of the current study suggest the potential of Sp17 as a target for immunotherapy in patients with ovarian carcinoma. Cancer 2002;94:2447–53. © 2002 American Cancer Society.DOI 10.1002/cncr.10506