Expression and Function of Mammary Epithelial Cell-Derived Immunoglobulins

Area of Science:

• Immunology
• Oncology
• Cell Biology

Background:

• Increasing evidence shows non-B cells, including mammary epithelial cells, can generate immunoglobulins (Igs).
• Normal breast epithelial cells produce IgG and IgA during lactation, potentially aiding neonatal immunity.
• Non-B cell-derived IgG is highly expressed in breast cancer, correlating with poor patient prognosis.

Purpose of the Study:

• To investigate the dual role of immunoglobulins produced by breast epithelial cells under physiological and pathological conditions.
• To characterize a specific form of IgG, sialylated IgG (SIA-IgG), found in breast cancer stem cells and assess its function.

Main Methods:

• Analysis of immunoglobulin expression in normal and malignant breast tissues.
• Identification and characterization of specific glycan modifications on IgG (sialylation at Asn162).
• In vitro and in vivo assays to evaluate the functional impact of SIA-IgG on cancer cell migration, invasion, self-renewal, and tumorigenicity.

Main Results:

• Breast epithelial cells express both IgG and IgA, which are secreted into milk during lactation, contributing to neonatal immunity.
• A distinct sialylated IgG (SIA-IgG) variant is found in breast cancer stem/progenitor-like cells.
• SIA-IgG significantly enhances breast cancer cell migration, invasiveness, metastasis, self-renewal, and tumorigenicity.

Conclusions:

• Breast epithelial cells produce immunoglobulins with distinct biological activities depending on the physiological or pathological context.
• While beneficial for neonatal immunity during lactation, these epithelial-derived Igs, particularly SIA-IgG, exhibit oncogenic properties in breast cancer, promoting tumor progression.