Association of Epstein Barr virus infection (EBV) with breast cancer in rural Indian women

Abstract

Introduction: Breast cancer is the most common malignancy affecting females worldwide but conventional risk factors are able to explain only a small proportion of these cases. A possible viral etiology for breast cancer has been proposed and Epstein-Barr Virus (EBV) is a widely researched candidate virus. The aim of the present study, first one of its kind from India, was to determine if there is a greater association of EBV infection with breast cancer patients as compared to patients with benign breast diseases.

Methods: We looked for expression of Epstein-Barr Virus Nuclear Antigen-1 (EBNA-1) in breast cancer tissue specimens by employing immunohistochemistry (IHC). We also measured levels of anti-EBNA-1 Immunoglobulin (IgG) antibodies in stored sera of these patients using commercial Enzyme linked Immunosorbent Assay (ELISA) kit. Patients with benign breast diseases were used as a comparison group for both immunohistochemical and serological analysis.

Results: 58 cases of malignant breast disease and 63 of benign breast disease (controls) were included in the study. Using manufacturer determined cut-off of 3 IU/ml, 50/55 tested (90.9%) cases and 27/33 tested (81.8%) controls were seropositive for anti-EBNA-1 IgG. Mean antibody levels were significantly higher for cases (54.22 IU/ml) as compared to controls (18.68 IU/ml). IHC for EBNA-1 was positive in 28/51 cases (54.9%). No IHC positivity was noted in the tested 30 controls. Our results show that EBNA-1 expression is seen in a significant proportion of breast cancer tissue specimens from rural India and as compared to patients with benign breast diseases these patients also have a higher immunological response against EBNA-1.

Figure 1. Study flow.

Figure 2. Box plot showing anti-EBNA-1 IgG antibody levels in women with benign and malignant breast disease, stratified by age.

The central horizontal line in the box indicates the median value, edges of the box indicate inter-quartile range, and the whiskers indicate values at 5^th and 95^th percentiles. The values at the bottom of the box indicate the number of women in whom serology was done, out of the total number of eligible women in particular category. The mean IgG levels in 25 to 45 year age group were significantly higher in women with malignant breast disease (48.15; SD 47.38 IU/ml) as compared to those with benign breast disease (17.37; SD 16.89 IU/mL) (p = 0.01).

Figure 3. Immunohistochemical detection of EBNA-1 in breast tissue specimens.

A. Tumor cells (infiltrating ductal carcinoma) showing intense granular nuclear positivity for EBNA-1 antibody. B. Benign breast tissue negative for EBNA-1; C. Positive control (nasopharyngeal carcinoma tumor cells showing nuclear positivity for EBNA-1) slide; D. Negative control (no signal is seen in infiltrating ductal carcinoma cells without application of primary antibody). All photographs and in 400x original magnification.