Expression of membrane type 1 matrix metalloproteinase (MMP-14) in epithelial ovarian cancer: high level expression in clear cell carcinoma.

OBJECTIVE: Clear cell carcinomas of the ovary constitute approximately 5% of all ovarian neoplasms and have a distinct gene expression profile relative to other ovarian carcinoma histotypes. Tumors often present as an early stage large pelvic mass with a high degree of recurrence and frequent early metastasis. Matrix metalloproteinases (MMPs) play a role in intraperitoneal metastasis through breakdown of cell-cell and cell-matrix barriers, enabling anchoring of secondary lesions and promoting proliferation in a geometrically constrained matrix environment. The objective of this study was to evaluate MMP expression in ovarian clear cell carcinoma. METHODS: Immunohistochemistry was used to evaluate expression of membrane type 1 MMP (MMP-14), MMP-2 and MMP-9 in a panel of ovarian tumors. Western blotting and gelatin zymography were used to examine MMP-14 expression and activity in the clear cell carcinoma cell line ES2. The ability of ES2 cells to invade and proliferate within three-dimensional collagen gels was evaluated. RESULTS: High level expression of MMP-14 and MMP-2 were observed in ovarian clear cell carcinoma relative to other histotypes (94-95% strong positive). MMP-14 was expressed and active in cultured ES2 cells. ES2 cells also exhibited MMP-dependent invasion of and proliferation within three-dimensional collagen gels. CONCLUSIONS: The high level expression of MMP-14 together with in vitro functional analyses suggest that MMP-14 may contribute to both the proliferative capacity and the enhanced parenchymal metastasis of ovarian clear cell carcinoma.

Engagement of collagen-binding integrins promotes matrix metalloproteinase-9-dependent E-cadherin ectodomain shedding in ovarian carcinoma cells.

Reversible modulation of cell-cell adhesion, cell-matrix adhesion, and proteolytic activity plays a critical role in remodeling of the neoplastic ovarian epithelium during metastasis, implicating cadherins, integrins, and proteinases in i.p. metastatic dissemination of epithelial ovarian carcinoma (EOC). Aberrant epithelial differentiation is an early event in ovarian carcinogenesis; thus, in contrast to most carcinomas that lose E-cadherin expression with progression, E-cadherin is abundant in primary EOC. Metastasizing EOCs engage in integrin-mediated adhesion to submesothelial interstitial collagens and express matrix metalloproteinases (MMP) that facilitate collagen invasion, thereby anchoring secondary lesions in the submesothelial matrix. As metalloproteinases have also been implicated in E-cadherin ectodomain shedding, the current study was undertaken to model the effects of matrix-induced integrin clustering on proteinase-catalyzed E-cadherin ectodomain shedding. Aggregation of collagen-binding integrins induced shedding of an 80-kDa E-cadherin ectodomain [soluble E-cadherin (sE-cad)] in a MMP- and Src kinase-dependent manner, and sE-cad was prevalent in ascites from ovarian cancer patients. Expression of MMP-9 was elevated by integrin aggregation, integrin-mediated ectodomain shedding was inhibited by a MMP-9 function blocking antibody, and incubation of cells with exogenous MMP-9 catalyzed E-cadherin ectodomain shedding. In contrast to other tumors wherein sE-cad is released into the circulation, EOC tumors maintain direct contact with sE-cad-rich ascites at high concentration, and incubation of EOC cells with physiologically relevant concentrations of recombinant sE-cad disrupted adherens junctions. These data support a novel mechanism for posttranslational modification of E-cadherin function via MMP-9 induction initiated by cell-matrix contact and suggest a mechanism for promotion of EOC metastatic dissemination.

Venous thromboembolism and mortality associated with recombinant erythropoietin and darbepoetin administration for the treatment of cancer-associated anemia.

CONTEXT: The erythropoiesis-stimulating agents (ESAs) erythropoietin and darbepoetin are licensed to treat chemotherapy-associated anemia in patients with nonmyeloid malignancies. Although systematic overviews of trials have identified venous thromboembolism (VTE) risks, none have identified mortality risks with ESAs. OBJECTIVE: To evaluate VTE and mortality rates associated with ESA administration for the treatment of anemia among patients with cancer. DATA SOURCES: A published overview from the Cochrane Collaboration (search dates: January 1, 1985-April 1, 2005) and MEDLINE and EMBASE databases (key words: clinical trial, erythropoietin, darbepoetin, and oncology), the public Web site of the US Food and Drug Administration and ESA manufacturers, and safety advisories (search dates: April 1, 2005-January 17, 2008). STUDY SELECTION: Phase 3 trials comparing ESAs with placebo or standard of care for the treatment of anemia among patients with cancer. DATA EXTRACTION: Mortality rates, VTE rates, and 95% confidence intervals (CIs) were extracted by 3 reviewers from 51 clinical trials with 13 611 patients that included survival information and 38 clinical trials with 8172 patients that included information on VTE. DATA SYNTHESIS: Patients with cancer who received ESAs had increased VTE risks (334 VTE events among 4610 patients treated with ESA vs 173 VTE events among 3562 control patients; 7.5% vs 4.9%; relative risk, 1.57; 95% CI, 1.31-1.87) and increased mortality risks (hazard ratio, 1.10; 95% CI, 1.01-1.20). CONCLUSIONS: Erythropoiesis-stimulating agent administration to patients with cancer is associated with increased risks of VTE and mortality. Our findings, in conjunction with basic science studies on erythropoietin and erythropoietin receptors in solid cancers, raise concern about the safety of ESA administration to patients with cancer.

Probing the mechanism of hamster arylamine N-acetyltransferase 2 acetylation by active site modification, site-directed mutagenesis, and pre-steady state and steady state kinetic studies.

Arylamine N-acetyltransferases (NATs) catalyze an acetyl group transfer from acetyl coenzyme A (AcCoA) to arylamines, hydrazines, and their N-hydroxylated arylamine metabolites. The recently determined three-dimensional structures of prokaryotic NATs have revealed a cysteine protease-like Cys-His-Asp catalytic triad, which resides in a deep and hydrophobic pocket. This catalytic triad is strictly conserved across all known NATs, including hamster NAT2 (Cys-68, His-107, and Asp-122). Treatment of NAT2 with either iodoacetamide (IAM) or bromoacetamide (BAM) at neutral pH rapidly inactivated the enzyme with second-order rate constants of 802.7 +/- 4.0 and 426.9 +/- 21.0 M(-1) s(-1), respectively. MALDI-TOF and ESI mass spectral analysis established that Cys-68 is the only site of alkylation by IAM. Unlike the case for cysteine proteases, no significant inactivation was observed with either iodoacetic acid (IAA) or bromoacetic acid (BAA). Pre-steady state and steady state kinetic analysis with p-nitrophenyl acetate (PNPA) and NAT2 revealed a single-exponential curve for the acetylation step with a second-order rate constant of (1.4 +/- 0.05) x 10(5) M(-1) s(-1), followed by a slow linear rate of (7.85 +/- 0.65) x 10(-3) s(-1) for the deacetylation step. Studies of the pH dependence of the rate of inactivation with IAM and the rate of acetylation with PNPA revealed similar pK(a)(1) values of 5.23 +/- 0.09 and 5.16 +/- 0.04, respectively, and pK(a)(2) values of 6.95 +/- 0.27 and 6.79 +/- 0.25, respectively. Both rates reached their maximum values at pH 6.4 and decreased by only 30% at pH 9.0. Kinetic studies in the presence of D(2)O revealed a large inverse solvent isotope effect on both inactivation and acetylation of NAT2 [k(H)(inact)/k(D)(inact) = 0.65 +/- 0.02 and (k(2)/K(m)(acetyl))(H)/(k(2)/K(m)(acetyl))(D) = 0.60 +/- 0.03], which were found to be identical to the fractionation factors (Phi) derived from proton inventory studies of the rate of acetylation at pL 6.4 and 8.0. Substitution of the catalytic triad Asp-122 with either alanine or asparagine resulted in the complete loss of protein structural integrity and catalytic activity. From these results, it can be concluded that the catalytic mechanism of NAT2 depends on the formation of a thiolate-imidazolium ion pair (Cys-S(-)-His-ImH(+)). However, in contrast to the case with cysteine proteases, a pH-dependent protein conformational change is likely responsible for the second pK(a), and not deprotonation of the thiolate-imidazolium ion. In addition, substitutions of the triad aspartate are not tolerated. The enzyme appears, therefore, to be engineered to rapidly form a stable acetylated species poised to react with an arylamine substrate.