Correlation of immunoglobulin G expression and histological subtype and stage in breast cancer

Abstract

Introduction: Recently, growing evidence indicates that immunoglobulins (Igs) are not only produced by mature B lymphocytes or plasma cells, but also by various normal cells types at immune privileged sites and neoplasm, including breast cancer. However, the association of breast cancer derived IgG with genesis and development of the disease has not yet been established.

Methods: In this study we examined the expression of IgG in 186 breast cancers, 20 benign breast lesions and 30 normal breast tissues. Both immunohistochemistry with antibodies to Igκ (immunoglobulin G κ light chain) and Igγ (immunoglobulin G heavy chain) and in situ hybridization with an antisense probe to IgG1 heavy chain constant region gene were performed. Various clinicopathological features were also analyzed.

Results: We found that IgG is specifically expressed in human breast cancer cells. Both infiltrating ductal carcinoma and infiltrating lobular carcinoma had significantly greater numbers of Igκ and Igγ positive cancer cells as compared with medullary carcinoma, carcinoma in situ, and benign lesions (all p<0.05). In addition, IgG expression was correlated with breast cancer histological subtypes (p<0.01) and AJCC stages (p<0.05), with more abundance of IgG expression in more malignant histological subtypes or in more advanced stage of the disease.

Conclusions: IgG expression in breast cancer cells is correlated with malignancy and AJCC stages of the cancers. This suggests that breast cancer derived IgG may be associated with genesis, development and prognosis of the cancer.

Figure 1. Human breast cancer expresses Igγ protein and IGHG1 mRNA as detected by IHC and ISH.

a1–6, b1–3 and c1–3 are serial sections of breast cancer tissue (IDC) respectively. a1–4 showing IHC with antibodies to to Igγ (IgG heavy chain, a1), CK (an epithelial cell marker, a2), CD20 (a B cell marker, a3) and CD68 (a macrophage marker, a4). a5–6 showing ISH with an IGHG1 mRNA antisense probe (a5), and with a sense probe (a6). b1–3 showing IHC with antibody to Igγ alone, antibody to Igγ preincubated with standard human IgG of 3-fold and 20-fold concentration of the working primary antibody respectively. c1–3 showing IHC staining after incubation with antibody to Igγ, normal rabbit IgG and normal mouse IgG respectively, without positive signals in the Igγ expressing cells in the latter two sections. Original magnifications: ×400. Scale bars: 20 µm.

Figure 2. Igκ and Igγ expression in cancers, benign lesions and normal tissues of breast by immunohistochemistry.

A: Igγ (a1, a3) and Igκ (a2, a4) are diffusely positive in cell cords and single cell chains in IDC (a1 and a2) and ILC (a3 and a4) (arrowheads) with stronger staining in B lymphocytes/plasma cells (letterheads) in stroma. B: Igγ (b1) and Igκ (b2) are expressed in some cells inside large cell groups of IDC (arrowheads) and infiltrating lymphocytes (letterheads). In DCIS Igγ (b3) and Igκ (b4) expression can be seen in a few cells (arrowheads). C: Igκ positive cells can also be seen in glandular epithelial cells (arrowheads) of fibroadenoma (c1) along lumens and in a limited number of fibroblasts (letterhead) in the interstitium. Igκ expression can seldom been detected in normal breast duct adjacent to benign breast lesion (cystic hyperplasia of breast) (c2). Destain & restain with antibodies to Igκ and CD20 on IDC shows more Igκ expression in infiltrating cancer cells (c3, letterheads) than in adjacent histologically normal breast duct (c3, arrowhead), with infiltrating B lymphocytes as internal positive control (costaining with both Igκ and CD20) (c4, black arrow). D: By conducting immonostaining and destain & restaining with antibodies against Igγ, Igκ, CD20 and CK on two consecutive sections of axillary lymph node metastatic breast cancer tissue, we observed costaining of Igγ and Igκ in both breast cancer cells (d1 and d2) in cancer nest (CK positive) and stronger staining in B lymphoid/plasma cells (d1 and d2, letterheads) in tumor stroma. The lymphoid/plasma cells with or without CD20 staining (d3, letterhead) in tumor stroma showed no positive CK staining with breast cancer cells as internal positive control (d4, arrowheads). Original magnifications: a1–a4, b1 and b2 ×200, scale bars: 40 µm; others ×400, scale bars: 20 µm.