IL-6/STAT3 signaling pathway is activated in plasma cell mastitis

Abstract

Plasma cell mastitis (PCM), a particular type of mastitis, mainly occurs in females at nonpregnant and nonlactating stages. The infiltration of abundant plasma cells and lymphocytes is the hallmark of the disease. The incidence rate of PCM increased gradually and its pathogenesis remained unclear. In this study, we investigated the expression of IL-6/STAT3 signaling pathway, which is vital not only for the differentiation of plasma cells but also for survival of plasma cells and T lymphocytes, in 30 PCM cases, 10 acute mastitis cases and 10 normal breast tissues by immunohistochemical analysis. IL-6 level was significantly higher in PCM patients than in acute mastitis patients or normal group. The positive rate of IL-6 and p-STAT3 staining in PCM samples was 93.3% (28/30) and 70% (21/30), respectively, and there was a significant positive association between IL-6 and p-STAT3 staining (r=0.408, P=0.025). In PCM group, the rate of nipple retraction was 40% (12/30). Significantly higher IL-6 expression was found in PCM patients with nipple retraction than in other PCM patients. However, no significant difference in IL-6 or p-STAT3 staining was detected between PCM patients experiencing recurrence and other PCM patients. In addition, Bcl-2 level was higher in PCM patients than in acute mastitis patients or normal group, but there was no difference in Bcl-2 immunostaining between PCM patients experiencing recurrence and other PCM patients. These indicate that IL-6/STAT3 signaling is activated in PCM and may play an important role in the pathogenesis of PCM.

Keywords: IL-6; Plasma cell mastitis; STAT3; immunohistochemistry.

Figure 1

Representative HE staining of PCM tissues. Original magnifiation: 200×.

Figure 2

Immunohistochemical analysis of IL-6. A. Staining of IL-6 in PCM, acute mastitis (AM) and normal breast tissues. Original magnifiation: 400×. B. IL-6 staining was stronger in PCM than in acute mastitis patients (AM) (P=0.003) or normal group (P<0.001). C. IL-6 staining was stronger in PCM patients with nipple retraction (NR) than in other PCM patients (non-NR) (P=0.043). D. No significant difference in IL-6 staining was detected between PCM patients experiencing recurrence (Re) and other PCM patients (non-Re) (P=0.743). Data were presented as mean ± standard error of mean (SEM).

Figure 3

No significant difference was found in tumor size between PCM patients with nipple retraction (NR) and other PCM patients (non-NR) (P=0.461).

Figure 4

immunostaining of p-STAT3 in PCM. Original magnifiation: 400×.

Figure 5

Immunohistochemical analysis of Bcl-2. A. Staining of Bcl-2 in PCM, acute mastitis (AM) and normal breast tissue. Original magnifiation: 400×. B. Bcl-2 staining was stronger in PCM than in acute mastitis patients (AM) (P=0.039) or normal group (P<0.001). C. No significant difference in Bcl-2 staining was detected between PCM patients experiencing recurrence (Re) and other PCM patients (non-Re) (P=0.273). Data were presented as mean ± SEM.