Characterization of β2-microglobulin expression in different types of breast cancer

Βeta-2-microglobulin (β2-M) has been demonstrated as a growth factor and signaling molecule in breast cancer and leukemia. The purpose of the study is to characterize β2-M expression in molecular subtypes of breast cancer, thereby investigating the mechanism of β2-M action in breast cancer.

The expression of β2-M transcripts demonstrated no significant differences between the four breast cancer molecular subtypes and no significant correlations with age, clinical stage or lymph node metastasis. β2-M transcript expression demonstrated a positive correlation when compared to Bcl-2 transcript expression (P < 0.05). The β2-M protein expression was significantly higher in breast cancer when compared with benign breast tumors (P < 0.01), and have no significant correlation with age, clinical stage or lymph node metastasis. There was a significant difference demonstrated in β2-M protein expression in the four breast cancer molecular subtypes (P < 0.05), and between the ER⁺ and ER⁻ groups (P < 0.01); however, no significant difference was demonstrated between the HER-2⁺ and HER-2⁻ groups. β2-M protein expression had a negative correlation with ER protein expression (P < 0.01), a positive correlation with p53 protein expression (P < 0.01), and no correlation with Ki67 protein expression. β2-M silencing significantly inhibited Bcl-2 mRNA expression, but did not inhibit ER, PR and HER-2 mRNA expression in MCF-7 cells (ER⁺, PR⁺ and HER-2⁻). In addition, Bcl-2 and HER-2 mRNA expression were significantly up-regulated in MDA-MB-231 cells (ER⁻, PR⁻ and HER-2⁻), which is consistent with the silencing effect seen at the protein level.

β2-M expression demonstrated a significant difference in the four breast cancer molecular subtypes, and may be related to apoptosis regulation in breast cancer.