Expression of the chromatin remodeling factor Rsf-1 is upregulated in ovarian carcinoma effusions and predicts poor survival
Introduction
Ovarian carcinoma is the most lethal gynecologic cancer and currently ranks as the fifth in causing cancer-related deaths among women [1]. The major difficulty in achieving cure of ovarian carcinoma is the fact that the majority of patients are diagnosed with advanced-stage (FIGO III–IV) disease, thereby impeding efforts directed at surgical removal of all tumor burden. Another significant problem is that research has focused on studying the molecular characteristics of primary tumors, lesions that are amenable to surgical removal in the majority of cases, rather than metastatic cells in the peritoneal and pleural cavities, the most common site of dissemination and recurrence in ovarian carcinoma.
Identification and characterization of new cancer-associated genes will not only elucidate the pathogenesis of neoplastic diseases but also provide new diagnostic markers and therapeutic targets for cancer patients. In an effort to search for new amplified tumor-associated genes, we have previously applied a genome-wide technology, digital karyotyping [2], to identify novel amplicons that may harbor new potential oncogenes in ovarian cancer. Using digital karyotyping, we recently identified amplification at the 11q13.5 chromosome region and overexpression of the chromatin remodeling gene Rsf-1 (HBXAPα) that is localized to the amplicon in high-grade ovarian carcinoma [3]. Analysis of Rsf-1 amplification using FISH in primary tumors and of Rsf-1 mRNA levels in effusions using quantitative real-time PCR showed that its amplification and overexpression are associated with poor survival in both cohorts [3]. In that study, we also demonstrated a positive association between Rsf-1 gene amplification and immunointensity. In the present study, we analyzed the clinical role of Rsf-1 protein expression in a large cohort of ovarian carcinoma patients with malignant effusions using immunocytochemistry. The new data lend further support to the association between Rsf-1 expression and aggressive clinical behavior in this disease and provide evidence that Rsf-1 immunostaining can be a valuable tool to assess Rsf-1 expression and its relationship with the clinical outcome in the subset of ovarian carcinoma patients with disease recurrence effusions.
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Study cohort
Specimens and relevant clinical data were obtained from the Department of Gynecologic Oncology, Norwegian Radium Hospital (Table 1). Informed consent was obtained according to national Norwegian and institutional guidelines. One hundred and sixty-eight fresh non-fixed malignant peritoneal (n = 134, 80% of specimens) and pleural (n = 34, 20% of specimens) effusions were obtained from 121 patients diagnosed with epithelial (predominantly serous) ovarian carcinoma (151 effusions, 90%), 4 patients
Results
Rsf-1 immunoreactivity was detected in carcinoma cells in 157/168 (93%) effusions. Of these, 70 (45%) stained weakly and 87 (55%) stained strongly (Figs. 1A to C). The percentage of Rsf-1 positive cells in the 157 specimens was as follows: 1–5%: 14 specimens (9%); 6–25%: 15 specimens (10%); 26–75%: 51 specimens (32%); 76–100%: 77 specimens (49%). Cancer cells in a given specimen tended to have a generally homogenous staining intensity. Inflammatory cells (lymphocytes and macrophages) and
Discussion
As in other cancer types, gene amplification is one of the major mechanisms mediating oncogene activation and thereby dysregulated growth in ovarian cancer. Chromosomal regions that have been shown to be amplified in cell lines or clinical specimens of ovarian carcinoma include 17q21–23 [8], 19q13.1–q13.2 [9], 3q26, 8q24 and 20q13 [10] or 20q12–13 [11]. Specific genes that have been reported as amplified in ovarian cancer are Ki-ras [12], HER2/neu [13], [14], INT-2 [14], AKT2 [15], cyclin E [16]
Acknowledgments
We gratefully acknowledge the competent technical help of Mrs. Inger-Liv Nordli, Mrs. Mai Nguyen and Mrs. Ann Larsen at the Department of Pathology, Norwegian Radium Hospital in performing the immunohistochemical analysis.
Financial acknowledgement: this study was supported in part by National Cancer Institute grant (RO1 CA103937).
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