Expression of periostin in breast cancer cells.

Periostin (POSTN) is a protein involved in multiple processes important for cancer development, both at the stage of cancer initiation and progression, as well as metastasis. The aim of this study was to determine the expression of POSTN in the cells of non-invasive ductal breast carcinoma in situ (DCIS) and invasive ductal carcinoma (IDC) and to correlate it with clinicopathological data. Immunohistochemical studies (IHC) were conducted on 21 cases of fibrocystic breast change (FC), 44 cases of DCIS and 92 cases of IDC. POSTN expression at mRNA (real-time PCR) and protein level (western blot analysis) was also confirmed in selected breast cancer cell lines (MCF-7, SK-BR-3, MDA-MB-231 and BO2). Statistically significant higher level of POSTN expression in IDC and DCIS cancer cells compared to FC was noted. Also, the level of POSTN expression in the cytoplasm of IDC cells was shown to increase with the increasing degree of tumour malignancy (G) and significantly higher expression of POSTN was observed in each degree of tumour malignancy (G) relative to FC. Statistically significant higher POSTN expression was observed in tumours with estrogen receptor-negative (ER-) and progesterone receptor-negative (PR-) phenotypes in comparison to estrogen receptor-positive (ER+) and progesterone receptor-positive (PR+) cases, as well as significant negative correlation between POSTN expression in cancer cells and expression of ER and PR (p<0.05). Additionally, statistically significant differences in POSTN expression were shown between particular breast cancer cell lines, both at mRNA and protein level. Observed POSTN expression was the lowest in the case of MCF-7, and the highest in MDA-MB-231 and BO2 of the most aggressive potential clinically corresponding to G3 tumours. POSTN expression in the cytoplasm of IDC cancer cells may play an important role in cancer transformation mechanism.