Increased bcl-2 expression is associated with primary resistance to chemotherapy in human epithelial ovarian cancer

doi:10.1016/S0009-9120(99)00026-0

Clinical Biochemistry

Volume 32, Issue 5, July 1999, Pages 333-338

https://doi.org/10.1016/S0009-9120(99)00026-0 Get rights and content

Abstract

Objective: bcl-2, an anti-apoptotic factor, has a role in the pathogenesis of ovarian cancer as well as in resistance to chemotherapy.

Design and Methods: 20 benign, and 26 malignant epithelial ovarian tissues were analyzed for bcl-2 protein and mutant p53 by enzyme-immunoassay (EIA). Flowcytometric analysis was also performed. Patients of malignant group were followed up to monitor overall survival and primary resistance to chemotherapy.

Results: bcl-2 was significantly higher in malignant group than benign group (p < 0.001). A cutoff value was determined for bcl-2 (63.8 kU/g protein). At this cutoff, sensitivity is 80.7%, and specificity is 85%. Using chi square analysis, a significant correlation was found between bcl-2 and FIGO stage (p = 0.01), overall survival (p = 0.01), as well as primary resistance to chemotherapy (p = 0.03). By correlation coefficient analysis the relation between bcl-2 and synthetic phase fraction was highly significant (p = 0.002). Bcl-2, p53, and FIGO stage were significantly correlated to poor survival (p = 0.01) in univariate analysis. However, in multivariate analysis, only FIGO stage, and p53 were independent risk factors.

Conclusion: EIA could be a useful tool for investigating the prognostic value of bcl-2, and its possible prediction of platinum resistance in epithelial ovarian cancer. This might help in selecting patients for future anti-bcl-2 therapy.

Introduction

P rogrammed cell death (apoptosis) is now known to play a major role in embryogenesis, tissue homeostasis, and neoplasia (1). It can be initiated when DNA damage occurs causing the cell to pause in its reproductive cycle. If the DNA damage is beyond repair, the cell proceeds to apoptotic cell death. Apoptosis has been implicated in several events that occur during the ovarian life cycle: the reduction in oocyte number that occurs during fetal life, the process of follicular atresia, and the regression of corpus luteum (2). When the genetic mechanism(s) involved in the pathway of apoptosis is altered, the cell does not die. Additional mutational events can lead to a malignant phenotype and oncogenesis (1).

Apoptosis is known to play an important role in the cellular response to genotoxic stress. Therefore, loss of apoptotic response in tumor cells is thought to be one of the mechanisms involved in malignant progression and resistance to chemotherapy (3). Specific genes have been implicated in controlling cell fate (e.g., p53, which promotes apoptosis), and the bcl-2 family. The bcl-2 family consists of many genes (e.g., bcl-2, bax, and bcl-x) encoding apoptosis antagonists as bcl-2, and bcl-x long, and also apoptosis agonists as Bax, and bcl-x short (2). Bcl-2, as an anti-apoptotic factor, is implicated in the pathogenesis of ovarian cancer (4). The tumor supressor gene p53 mediates activation of programmed cell death, in part by up-regulation of Bax expression (5).

In contrast, bcl-2 can block p53-mediated apoptosis (6). P53 causes a DNA-damaged cell to rest and attempt repair. If damage is irreparable, p53 levels will continue to increase, initiating apoptosis. Loss of functional p53 leads to more rapid cell proliferation (7). Mutation of p53 results in a protein product with abnormal conformation, inability to form tetramer, loss of DNA binding function, prolonged protein half-life and significantly increased levels of protein within the nuclei (8). Accumulation of p53 is established to be an indicator of poor prognosis in ovarian cancer (9). Studies of bcl-2, have been conducted primarily by immunohistochemistry and/or molecular techniques (1). These methods, although important in investigating the biological characteristics of tumors, are subjective and cumbersome for clinical application. In contrast, enzyme immunoassay (EIA) allows for rapid quantitation and objective assessment of the variable for clinical purposes. In this study, we estimate bcl-2 quantitatively using EIA, for the first time, in epithelial ovarian cancer tissues. Selected cases with different bcl-2 values, and from different groups have been confirmed by Western blotting, and immunohistochemistry. We correlate the results with flowcytometric DNA findings, and to mutant p53 as established genetic markers. The relation of bcl-2 to overall survival and primary resistance to platinum-based combination chemotherapy is highlighted to test if we can select particular cases for future anti-bcl-2 antisense genetherapy in ovarian cancer.

Section snippets

Methods

This study was conducted in the period from March 1995–April 1998. The clinical specimens were obtained from the Obstetrics and Gynecology Department, Ain Shams University Hospitals. The laboratory work was carried out at the Oncology Diagnostic Unit (ODU), Biochemistry Department, Ain Shams Faculty of Medicine.

Results

The study included 20 patients with benign ovarian conditions (17–55 years, mean 41), and 26 patients with different ovarian epithelial neoplasms (25–66 years, mean 43.7). Of the malignant group, 6 patients were FIGO stage I, 4 were stage II, 10 were stage III, 6 were stage IV. By histopathology, 12 tumors were serous, 7 were mucinous cystadenocarcinoma, and 7 belonged to other different pathological types. The clinical follow-up period was 9–37 months (mean 21.6). Over this period, 10 patients

Discussion

The majority of normal ovarian follicles undergo atresia, a hormonally controlled apoptotic process. During follicle development, gonadotropins, together with local ovarian growth factors (IGF-I, EGF/TGF-α, basic FGF), and cytokine (interleukin-1β), as well as estrogens, activate different intracellular pathways to rescue follicles from apoptotic demise. In contrast, TNF-α, Fas ligand presumably acting through receptors with a death domain, and androgens are atretogenic factors. These diverse

Acknowledgements

The authors thank Dr. Sanaa Eissa, Assistant Professor of Biochemistry, Oncology Diagnostic Unit, Ain Shams Faculty of Medicine, for her guidance and support.

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Original ArticlesIncreased bcl-2 expression is associated with primary resistance to chemotherapy in human epithelial ovarian cancer

Abstract

Introduction

Section snippets

Methods

Results

Discussion

Acknowledgements

Cell

Cell

The role of apoptosis in gynecological malignancies

Ann Med

Apoptosismechanisms and roles in pathology

Int Rev Exp Pathol

The prognostic significance of bcl-2 and p53 expression in ovarian carcinoma

Cancer Res

Bcl-2 blocks p53-dependent apoptosis

Mol Cell Biol

Bcl-2 expression, p53 accumulation, and apoptosis in ovarian carcinomas

Am J Clin Pathol

Quantitation of bcl-2 protein in bladder cancer tissue by enzyme immunoassaycomparison with Western blot and immunohistochemistry

Clin Chem

A rapid and sensitive method for quantification of microgram quantities of protein utilizing the principle of protein dye binding

Anal Bioch

Original Articles
Increased bcl-2 expression is associated with primary resistance to chemotherapy in human epithelial ovarian cancer