Overexpression of PGC1α and accumulation of p62 in apocrine carcinoma of the breast.

Apocrine carcinoma is categorized as a special type of breast carcinoma because of its specific morphological features. To clarify the characteristics of apocrine carcinoma from the point of view of the mitochondrial profile, we conducted a comparative study between apocrine and non-apocrine carcinomas. The expressions of mitochondrial related factors (PGC1α, Nrf1, Nrf2, mtTFA and COX4) were examined in a testing set of breast cancer tissue. Apocrine carcinomas showed a clear tendency towards higher mRNA expression levels of PGC1α than non-apocrine carcinomas. The expression of the selected factor, PGC1α, as well as that of p62 was further examined. The results revealed that apocrine carcinomas showed a higher immunohistochemical positivity rate for PGC1α (21.3% vs. 3.2%; P = 0.008), and that the mRNA expression level of PGC1α was significantly higher in apocrine carcinoma than in non-apocrine carcinoma (P = 0.007). The immunohistochemical positivity rate for p62 protein was also higher in apocrine carcinomas (44.7% vs. 21.0%; P = 0.015), although no significant difference in the p62 mRNA expression level was detected between the two types of carcinoma (P = 0.633). In conclusion, this study revealed that apocrine carcinoma overexpressed PGC1α contributing to mitochondrial biogenesis, and also p62 protein accumulation.