Elsevier

Regulatory Peptides

Volume 178, Issues 1–3, 10 October 2012, Pages 36-42
Regulatory Peptides

Association of expression of XIAP-associated factor 1 (XAF1) with clinicopathologic factors, overall survival, microvessel density and cisplatin-resistance in ovarian cancer

https://doi.org/10.1016/j.regpep.2012.06.005Get rights and content

Abstract

XIAP-associated factor 1 (XAF1) was identified as a novel X-linked inhibitor of apoptosis (XIAP) binding partner that can reverse the anti-apoptotic effect of XIAP. XAF1 levels are greatly decreased in many cancer tissues and cell lines. The aim of this study was to investigate the expression of XAF1 and XIAP in advanced epithelial ovarian cancer and role of XAF1 in cisplatin resistance of ovarian cancer cells. Tissues from 94 patients with advanced epithelial ovarian cancer (EOC) and 30 ovarian cystadenomas were obtained. We analyzed the association of the immunohistochemical-determined expression of these two factors and clinicopathologic variables, overall survival, and angiogenesis. We established SKOV3 cells stably overexpressing XAF1 and explored the possible functions of XAF1 in ovarian cancer cells in vitro and in vivo. The protein expression of XAF1 was significantly lower and that of XIAP higher in malignant than nonmalignant tissues. Low XAF1 expression was associated with high-grade tumors and poor overall survival for patients. XAF1 expression was associated with microvessel density. Overexpression of XAF1 suppressed cell proliferation and enhanced SKOV3 cells sensitivity to cisplatin, as well as inhibited tumor growth and decreased MVD in vivo. Overexpression of XAF1 induced XIAP inactivation, caspase‐3 activation and cytosolic expression of cytochrome c. These results suggested that XAF1 may be involved in ovarian cancer development and up-regulation of XAF1 may confer sensitivity of ovarian cancer cells to cisplatin-mediated apoptosis.

Highlights

► We analyzed XAF1 and XIAP expressions in ovarian tumors. ► Association of XAF1 and XIAP with prognostic factors and MVD was analyzed. ► XAF1 inhibited tumor growth and decreased MVD in vivo. ► XAF1 enhanced SKOV3 cells sensitivity to cisplatin and the mechanism was described.

Introduction

Ovarian cancer is a major lethal gynecological malignancy worldwide. Because of the insidious malignancy of ovarian tumors within the abdominal cavity, they are often detected at advanced stages. The standard therapy is surgical debulking and a systemic chemotherapy regimen that includes a platinum-based drug. Cisplatin-based chemotherapy has been a standard of care for women diagnosed with advanced epithelial ovarian cancer. However, cisplatin resistance is the major hurdle that limits successful treatment outcome. Over the last decade, researchers have pursued for novel therapeutic strategies in epithelial ovarian cancer (EOC) treatment. The identification of molecules that can promote tumor progression and enhance sensitivity to chemotherapeutic drugs is essential for developing adequate therapeutic modalities against ovarian cancer.

X-linked inhibitor of apoptosis protein (XIAP) is considered to be one of the most potent inhibitors of apoptosis proteins. It plays a crucial role that range from apoptotic inhibition by interacting with downstream caspases to form the mitotic spindle during cytokinesis [1]. Overexpressed XIAP is associated with tumor progression in various human cancers, including pancreatic cancer [2], melanoma [3] and large B-cell lymphoma [4]. Down regulation of XIAP expression in ovarian cancer cells resulted in apoptosis in vitro and a prolonged survival time of ovarian-cancer-bearing mice [5].

XIAP-associated factor 1 (XAF1) was identified as a novel XIAP binding partner that can reverse the anti-apoptotic effect of XIAP [6]. XAF1 is a nuclear protein of 301-amino-acids containing 7 zinc fingers. XAF1 can block the XlAP-mediated inhibition of caspase-3 and reverse its anti-apoptotic effect in response to apoptotic stimuli triggered by serum withdrawal and etoposide treatment [7]. XAF1 levels are greatly decreased in many cancer cell lines [6] including ovarian cancer cells. The molecule sensitizes cells to apoptotic triggers such as TRAIL [8], 5-fluorouracil, H2O2 and tumor necrosis factor-α [9]. Thus, XAF1 may have potential for gene therapy of ovarian cancer.

As well, ectopically expressed XAF1 was found to suppress migration and tube formation of mouse endothelial cells in vitro [10], so XAF1 may be involved in angiogenesis. The extent of angiogenesis is an important prognostic factor for ovarian cancer [11], [12]. Measurement of microvessel density (MVD) is a means of quantifying tumor angiogenesis in tissue sections.

We aimed to analyze the expression and prognostic value of immunohistochemically detected expression of XAF1, XIAP in advanced EOC (EOC) and association with clinicopathologic prognostic factors and MVD. To investigate the potential role of XAF1 in ovarian cancer cells, we selected SKOV3 human ovarian carcinoma cell line which was described as cis-platinum-resistant in ACTT and established cell lines stably overexpressing XAF. Our finding indicated that XAF1 may be involved in ovarian cancer development and enhances the sensitivity of ovarian cancer cells to cisplatin-induced apoptosis.

Section snippets

Tissue samples

Immunohistochemical examination was performed on formalin-fixed, paraffin-embedded sections of 94 primary advanced EOC tissue and 30 ovarian cystadenomas obtained in QiLu Hospital of Shandong University between 2003 and 2008. The mean age of patients with carcinoma and cystadenomas was 53 years (range 29–78 years) and 47 years (range 25–74 years), respectively. No patients received treatment before surgery. All cases were staged according to the criteria of the International Federation of

Immunohistochemical staining for XAF1 and XIAP

The clinical backgrounds of patients with carcinoma were as follows: stage II, 26; III, 59; IV, 9; histologic type mucinous, 21; serous, 60; endometrioid, 13; and histologic grade G1, 21; G2, 14; and G3, 59. Among the cystadenomas, 21 cases were of serous and 9 mucinous.

Staining of XAF1 was predominantly in the cytoplasm of epithelial cells with scarce nuclei stained positively. The proportion of tumor cells with positive staining ranged from 0 to 85%. All 30 cystadenoma sections but only 79

Discussion

In the present study, we first explored the association of XAF1 and XIAP expressions and overall survival in advanced ovarian tumors. The protein expression of XAF1 was significantly lower and that of XIAP higher in malignant than nonmalignant tissues. Low XAF1 and high XIAP levels in advanced EOC may confer a survival advantage for cancerous cells in the presence of various apoptotic triggers.

XAF1 expression was significantly reduced in poorly differentiated hepatocellular carcinoma [16] and

Acknowledgments

We thank Dr. Douglas W. Leaman of the University of Toledo for providing plasmid pcDNA3-HA-XAF1. This work was supported by Promotive Research Fund for Excellent Young and Middle-aged Scientists of Shandong Province of China (2008BS03031). The authors have no financial disclosures.

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    Contributed equally to this work.

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