Preparation of a novel antiserum to aromatase with high affinity and specificity: Its clinicopathological significance on breast cancer tissue.

Naoki Kanomata,Jo Kitawaki,Takuya Moriya,Junichi Kurebayashi,Taisuke Mori,Shiro Matsuura,Tsunehisa Nomura

doi:10.1371/journal.pone.0177439

Abstract

Aromatase inhibitors have been widely used for the endocrine treatment of estrogen-dependent breast cancer in postmenopausal patients. However, clinicopathological studies of aromatase have been limited due to unsatisfactory specificity and/or restricted availability of anti-aromatase antibodies. Here, we have generated a polyclonal antiserum with high affinity and specificity for human aromatase using a monoclonal antibody tagged immunoaffinity chromatography on an industrial production scale. Our preliminary immunohistochemical analysis of 221 invasive breast cancer cases indicated that 87.3% (193/221) had at least 5% aromatase positive cells. The histoscore for aromatase was inversely correlated with pT (p = 0.019), pN (p = 0.001), stage (p < 0.001), histologic grade (p = 0.003), lymphatic infiltration (p < 0.001), venous infiltration (p < 0.001), and Ki-67 index (p < 0.001). However, cancer aromatase expression was independent of estrogen receptor (ER), progesterone receptor (PgR), and human epidermal growth factor receptor 2 statuses. This antiserum will be applicable to clinicopathological examination of aromatase in addition to ER and PgR for an appropriate use of aromatase inhibitor on the treatment of breast cancer. Further studies on the relationship between Aromatase inhibitors have been widely used for the endocrine treatment of estrogen-dependent breast cancer in postmenopausal patients. However, clinicopathological studies of aromatase have been limited due to unsatisfactory specificity and/or restricted availability of anti-aromatase antibodies. Here, we have generated a polyclonal antiserum with high affinity and specificity for human aromatase using a monoclonal antibody tagged immunoaffinity chromatography on an industrial production scale. Our preliminary immunohistochemical analysis of 221 invasive breast cancer cases indicated that 87.3% (193/221) had at least 5% aromatase positive cells. The histoscore for aromatase was inversely correlated with pT (p = 0.019), pN (p = 0.001), stage (p < 0.001), histologic grade (p = 0.003), lymphatic infiltration (p < 0.001), venous infiltration (p < 0.001), and Ki-67 index (p < 0.001). However, cancer aromatase expression was independent of estrogen receptor (ER), progesterone receptor (PgR), and human epidermal growth factor receptor 2 statuses. This antiserum will be applicable to clinicopathological examination of aromatase in addition to ER and PgR for an appropriate use of aromatase inhibitor on the treatment of breast cancer. Further studies on the relationship between aromatase expression and aromatase inhibitors are warranted.

Highlights

Breast cancer is one of the most common cancers in the world, affecting women with a prevalence of more than 10% in the general population [1]
Cancer aromatase expression was independent of estrogen receptor (ER), progesterone receptor (PgR), and human epidermal growth factor receptor 2 statuses
These sequences were identical to amino acids 2–6 and 5–9 from the N-terminal of aromatase, respectively, indicating that the main band was a mixture of the n-1 and n-4 forms of the aromatase monomer [19] (S1 Fig)

Summary

Introduction

Breast cancer is one of the most common cancers in the world, affecting women with a prevalence of more than 10% in the general population [1]. The estrogen-activated estrogen receptor is a key driver of the breast cancer phenotype in around 70% of patients [2, 3]. One of the antagonists of estrogen receptor (ER) in mammary tissues, is a well-established and effective treatment for both premenopausal and postmenopausal patients with ER-positive breast cancers. Tamoxifen significantly reduces the risk of estrogen-dependent breast cancer [3]. Inhibition of aromatase activity is a key approach in treating estrogen-dependent breast cancers, because aromatization of androgens is the last and rate-limiting step in estrogen synthesis. Third-generation aromatase inhibitors, anastrozole, letrozole, and exemestane, have been widely used for the endocrine treatment of estrogen-dependent breast cancer in postmenopausal patients [7, 8]

Methods

Results

Conclusion