Nuclear factor kappaB transcription factors are coexpressed and convey a poor outcome in ovarian cancer

Abstract

Background: Recent work has suggested a role for nuclear factor kappaB (NF-kappaB) in the propagation of ovarian cancer cell lines, but the significance and mechanism of NF-kappaB in ovarian cancer is unknown. The authors hypothesized that the NF-kappaB pathway is over activated in aggressive ovarian cancers.

Methods: The levels of 3 NF-kappaB transcription factors, the activating inhibitors of NF-kappaB (IkappaB) kinases, and the NF-kappaB target matrix metalloproteinase 9 (MMP9) were assessed by immunohistochemistry in specimens of ovarian cancer that were obtained at diagnosis from a cohort of 33 patients who subsequently received combined paclitaxel, cisplatin, and cyclophosphamide. Associations were made between NF-kappaB pathway proteins and outcome. The validation of coexpression was performed at the gene level in 2 independently collected cohorts of 185 and 153 ovarian cancers.

Results: The presence of NF-kappaB proteins in newly diagnosed advanced ovarian cancers was established, and a potential association with overall survival was identified. Transcription factors p65 and v-rel reticuloendotheliosis viral oncogene homolog B (RelB) were coexpressed with IkappaB kinase alpha, 1 component of a key trimolecular regulatory complex. Coexpression of the NF-kappaB machinery suggested activity of NF-kappaB signaling in these ovarian tumors. A significant association of p50 with poor overall survival was observed (P = .02). MMP9 expression had the opposite association, in which patients who had tumors without MMP9 staining had the poorest prognosis (P = .01), and this association held true at the gene expression level in an independently collected cohort of 185 ovarian cancers.

Conclusions: The deregulation of NF-kappaB activity may influence outcome in women who receive standard therapy for advanced ovarian cancer. Modification of the NF-kappaB pathway may present an opportunity to improve outcome in the subset of women who have pathway activity.

Figure 1

NF-kB pathway proteins in ovarian cancer. A: Schematic diagram of NF-kB signaling components. B: Expression of NF-kB proteins in ovarian carcinoma using immunohistochemistry. Representative images of cytoplasmic localization of NF-kB p50; combined nuclear and cytoplasmic expression of NF-kB p65; cytoplasmic RelB expression; cytoplasmic expression of IKKa, IKKb and MMP-9, with no expression of IKKe in the same tumor.

Figure 2

Co-expression of NF-kB proteins in primary ovarian tumors. (A) Jonckheere-Terpstra p-values of immunohistochemistry results reported in Table 3 shows close association of NF-kB proteins. (B) Gene expression from an independent ovarian cancer dataset demonstrates a similar relationship between the transcription factors. The samples are ordered by the average expression of the transcription factors. Correlation (R) of each gene with the transcription factor average is listed, along with the p-value describing the strength of the relationship. (C) Similar analysis as (B) was calculated in a second unrelated dataset of gene expression in primary ovarian cancer samples.

Figure 3

NF-kB is associated with decreased overall and progression-free survival. (A–C) Kaplan-Meier plots of survival in ovarian cancer patients treated with triple therapy. (A) Median overall survival for patients with 3–4+ p50 staining was 29.1 months; median survival for patients with 0–2+ expression of p50 was not reached (p=0.02 unadjusted; p=0.065 after adjustment). (B) Median overall survival for patients with no MMP9 staining was 28.6 months; median survival for patients with 1–4+ expression of MMP9 was 67.0 months (p=0.01 unadjusted; p=0.02 after adjustment). (C) Combined analysis of p50 and MMP9 in ovarian cancer patients. Median survival for patients with unfavorable staining of both markers was 24.5 months; median survival for patients with favorable expression of both was not reached; median survival of the intermediate group was 30.4 months (p=0.003 for global comparison of all 3 arms); (D) Cox proportional hazards model for the immunoreactivity of MMP9 and p50 in ovarian cancer patients.