Original Article
Overexpression of steroid receptor coactivator-3 in bone cancers: An in vivo immunohistochemical study with tissue microarray

https://doi.org/10.1016/j.prp.2013.09.008Get rights and content

Abstract

Bone tissue is steroid-responsive and profoundly regulated by steroids and/or their receptors. Bone cancers (either primary or metastatic) belong to the most dangerous tumors. Previous studies have demonstrated overexpression of steroid receptor coactivator-3 (SRC-3) in many cancers, such as breast cancer, prostate cancer, thyroid cancer, functioning in the regulation of cancer cell proliferation, invasion, and metastasis. However, so far, the expression and function of SRC-3 in bone cancers have not yet been clarified. In this study, nickel-intensified immunohistochemistry was conducted using a commercial tissue microarray (with 94 cases of bone cancer tissue and 10 normal bone tissues), and the 4-scoring system was employed to evaluate the expression levels of SRC-3 immunoreactivity. The results showed that in normal bone tissue, levels of SRC-3 are almost negative (score = 0), the total positivity (score = 1–3) of SRC-3 immunoreactivities in bone cancers was 74.47%. There were no significant differences in gender, status (malignant or benign) or (mean) age (p > 0.05). The percentage of positivity was 77.78% in osteogenic tumors, 58.82% in cartilage tumors, 70% in giant cell tumors, 100% in hematopoietic tumors, 77.78% in miscellaneous lesions, and 75% in miscellaneous tumors. Age related differences of SRC-3 immunoreactivities were detected in cartilage tumors and giant cell tumors (p < 0.05). The above results clearly demonstrated a high frequency of overexpression of SRC-3 immunoreactivities in different bone cancers, indicating its potential roles in the prognosis and treatment of these cancers.

Introduction

It is known that bone tissue is steroid-responsive and profoundly affected by steroids such as estrogens [5], [32], androgens [32], [42], [43] and glucocorticoids [30]. For example, in human osteoblast-like cell lines (MG 63 and HOS), mRNAs for aromatase, steroid sulphatase, 5 alpha-reductase, 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD) and 3 beta-HSD, ERs, androgen receptor and progesterone receptor were found in both cell lines even without any induction [32]. Estrogens regulate the longitudinal growth of long bones [5] and enhance growth hormone receptor expression and growth hormone action in rat osteosarcoma cells and human osteoblast-like cells [35]; androgen prevents hypogonadal bone loss [43]. Many previous studies have shown the expression of steroid receptors in normal or bone cancer tissues [27], [28], [36], [42], [43]. However, the mechanisms that underlie the action of steroids on normal and/or pathological bone tissue, especially bone cancers, are still unclear.

Several studies have revealed that steroid receptor coactivators (SRCs) play important roles in the development, invasiveness and metastasis of many cancers [17], [31], [37], [40] by facilitating the transcriptional activities of nuclear steroid receptors. Among them, the p160 coactivator family was profoundly studied in the last decade. This family has three members: SRC-1, SRC-2 and SRC-3, and studies have demonstrated their ability to co-activate many kinds of nuclear receptors, such as androgen receptor (AR), estrogen receptor α and β (ERα and ERβ) and other transcriptional factors involved in the regulation of target gene transcription [44] and [45]. Among these, SRC-3 (also named AIB1, p/CIP, RAC3, ACTR or TRAM-1) was originally identified owing to its frequent amplification in breast and ovarian cancers [1]. Then it has been widely studied in many tumors because of its overexpression, including pancreatic carcinomas [9], meningiomas [4], gastric cancers [34], colorectal carcinogenesis [12], lung cancers [41] and astrocytic brain tumors [19]. Strong protein expression of SRC-3 has been suggested as a poor prognostic factor in many cancers, such as breast cancer [22], colorectal carcinogenesis [12] and some brain tumors [19].

Bone cancers damage normal bone tissue, and they are considered to be the most dangerous tumors. According to the National Cancer Institute, the estimated new cases and deaths from cancer of the bones and joints in the United States in 2012 amount to 2890 and 1410, respectively (for detail see http://www.cancer.gov/cancertopics/types/bone). Although overexpression of SRC-3 has been demonstrated in some tumors, the expression of SRC-3 in bone cancer tissues still needs to be clarified. To deepen our understanding of the roles that steroid receptor coactivators play in the regulation of bone cancers, we examined in this study SRC-3 expression in various bone cancers using tissue microarray immunohistochemistry.

Section snippets

Tissue microarray (TMA) and bone cancer pathology

Paraffin embedded bone cancer TMAs (Cat. BO2081) were purchased from Alenabio Biotech Ltd. (Xi’an, China), which is the local distributor of US Biomax Inc. (Rockville, MD, USA). The tissues on the TMA were obtained from 104 patients, and detailed information can be viewed at http://www.biomax.us/tissue-arrays/Bone_and_Cartilage/BO2081. Tumors on the TMA were categorized based on the WHO Classification of Tumors [7], as shown in Table 1 and verified by adjacent H.E. staining sections. On each

General description of SRC-3 immunoreactivities in bone cancers

Using nickel-intensified immunostaining, the final reaction product appears blue/black. The immunopositive materials of SRC-3 were predominantly detected in the cell nucleus. Meanwhile, the normal bone tissue was almost immunonegative for SRC-3 as shown in Fig. 1B, and only 2 cases showed sparse SRC-3-immunopositive nuclei. Of all the 94 tumor cases on the TMA, regardless of cancer type, 74.47% (70 cases) were positive and 25.53% (24 cases) were negative for SRC-3. Among the 42 female cases,

Discussion

Studies have shown that SRC-3 is required for normal animal growth, and it has been found to be overexpressed in many cancers. In this study, by using tissue microarray immunohistochemistry, we are the first to report the expression of SRC-3 in different bone cancers. The results showed that in normal bone tissues, only very weak/sparse SRC-3 immunopositive materials were detected, and most of the cases were immunonegative for SRC-3. However, in bone cancers, regardless of cancer type, 74.47%

Acknowledgements

The authors want to thank Dr. Kaifa Wang (Third Military Medical University, China) for assistance with statistical analysis. This work was supported predominantly by the National Science Foundation of China No. 30973065 and in part by No. 81171035.

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