Expression of autophagy related proteins in invasive lobular carcinoma: Comparison to invasive ductal carcinoma

The aim of this study is to compare the expression of autophagy related proteins in invasive lobular carcinoma (ILC) with that of autophagy related proteins in invasive ductal carcinoma (IDC), and to determinate its implication. Tissue microarray containing 114 ILC and 692 IDC was constructed, and immunohistochemistry was performed for autophagy related protein (beclin-1, LC3A, LC3B, p62) and Ki-67. No significant difference in expression of autophagy-related proteins between pleomorphic type (n = 12) and classic type (n = 102) of ILC was observed, whereas ILC and IDC showed distinguished features that tumoral beclin-1, stromal LC3A, tumoral LC3B, tumoral p62 were highly expressed in IDC and tumoral BNIP3 was highly expressed in ILC (P < 0.001). Beclin-1 expression was correlated with ER negativity (P = 0.016) and TNBC type (P = 0.024). BNIP3 expression was correlated with ER positivity (p = 0.040). Using multivariate Cox analysis, shorter overall survival was associated with tumoral beclin-1 positivity (hazard ratio: 21.19, 95% CI: 1.098-409.1, P = 0.043). In conclusion, ILC and IDC showed different expression pattern of autophagy-related proteins in tumor and stroma that demonstrated by higher expression of tumoral beclin-1, stromal LC3A, tumoral LC3B, tumoral p62 in IDC, and higher expression of tumoral BNIP3 in ILC.