Z.L. Jiang

Modulation of redox signaling promotes apoptosis in epithelial ovarian cancer cells.

OBJECTIVE Epithelial ovarian cancer (EOC) cells are known to be resistant to apoptosis through a mechanism that may involve alteration in their redox balance. NADPH oxidase is a major source of intracellular superoxide, which is converted to the less toxic product by superoxide dismutase (SOD). Superoxide contributes to hypoxia inducible factor (HIF)-1α stabilization. We sought to determine the effects of inhibiting the generation of intracellular reactive oxygen species (ROS) on apoptosis of EOC cells. METHODS Diphenyleneiodonium (DPI), an irreversible ROS inhibitor, was used to inhibit the generation of ROS in EOC cell lines, SKOV-3 and MDAH-2774, followed by assessment of apoptosis, NADPH oxidase, SOD3 and HIF-1α expression. A combination of immunohistochemistry, immunoprecipitation/western blot, and real-time RT-PCR were utilized to evaluate the expression of these enzymes in EOC cells as well as normal ovarian tissue and ovarian cancer tissue specimens. RESULTS DPI treatment significantly induced apoptosis in both EOC cell lines as evident by increased caspase-3 activity and TUNEL assay. Additionally, both EOC cell lines were found to express NADPH oxidase, HIF-1α, and SOD3, which were highly sensitive to DPI treatment. DPI treatment resulted in reduced NADPH oxidase, SOD3 and HIF-1α levels. Furthermore, ovarian cancer tissues were found to manifest higher NADPH oxidase levels as compared to normal ovarian tissues. CONCLUSIONS These data suggest that lowering oxidative stress, possibly through the inhibition of NADPH oxidase, induces apoptosis in ovarian cancer cells and may serve as a potential target for cancer therapy.

Myeloperoxidase and free iron levels: Potential biomarkers for early detection and prognosis of ovarian cancer

OBJECTIVE The study sought to identify whether a relationship exists between serum myeloperoxidase (MPO) and free iron with stages of ovarian cancer. METHODS Serum and tissue samples were collected from women with stages I through IV ovarian cancer, benign gynecologic conditions, inflammation, and healthy controls. Myeloperoxidase ELISA and VITROS Fe Slide assays were used to measure serum and tissue MPO and free iron levels, respectively. Data were analyzed with a one-way ANOVA with post-hoc comparisons (p < 0.05 considered significant). RESULTS There was a significant increase in the level of free iron in serum and tissues obtained from stages II-IV as compared to early-stage (stage I) ovarian cancer. There was an overlap between early-stage and inflammation serum MPO levels, however serum free iron levels were significantly higher in early-stage. There was no significant change in serum free iron levels between non-cancer groups. In contrast, there was a significant increase in serum free iron levels in early-stage as compared to non-cancer groups. CONCLUSIONS Collectively, these findings clearly indicate a role for the combination of serum MPO and free iron as biomarkers for early detection and prognosis of ovarian cancer.

The role of myeloperoxidase in the pathogenesis of postoperative adhesions

Hypoxia induces the adhesion phenotype, characterized by enhanced extracellular matrix molecule and cytokine expression. Additionally, hypoxia reduces myeloperoxidase (MPO) activity in normal peritoneal fibroblasts to basal levels of adhesion fibroblasts indicating the importance of this enzyme in the development of the adhesion phenotype and also in tissue fibrosis. Immunohistochemistry was used to detect and localize MPO and inducible nitric oxide synthase (iNOS) in fibroblasts. Silencing of these genes was performed using siRNA technology. Levels of iNOS, MPO, type I collagen, and transforming growth factor were detected using real‐time reverse transcription‐polymerase chain reaction (RT‐PCR), while HPLC was used to measure nitrate/nitrite levels. Our results show a unique interaction between MPO and iNOS, which are colocalized in both cell lines. Silencing iNOS reduced MPO and nitric oxide levels while silencing MPO had similar results, but to a lesser extent in both cell types. Additionally, silencing iNOS reduced type I collagen and transforming growth factor‐β in adhesion fibroblasts, but to a lesser extent in peritoneal fibroblasts. These studies identify MPO and iNOS as key enzymes in the cellular response to hypoxia and consequent development of tissue fibrosis.