Collagen triple helix repeat containing 1 protein in primary and metastatic breast cancer

Introduction and aim: We and others have previously identified collagen triple helix repeat containing 1 (CTHRC1) by expression profiling as breast cancer related protein. It has been reported to affect Wnt signaling, collagen deposition and bone formation and generally it belongs to extracellular matrix proteins which are abnormally expressed in tumor microenvironment. As CTHRC1 has not been studied by immunohistochemistry in breast cancer yet we decided to verify its expression in our patients set together with other relevant proteins.

Material and methods: Formalin-fixed paraffin-embedded tissues of 173 invasive carcinomas (21 with metastases in bone, 29 with other distant metastases), 27 lymph node metastases, 36 benign and 31 normal cases were stained for proteins CTHRC1, periostin, versican, E-cadherin and beta-catenin using immunohistochemistry. Invasive carcinomas were classified according to hormone receptors and Her2 expression into luminal, triple negative and Her2 molecular subtypes. Specimens were assessed semiquantitatively by histoscore. Statistical analysis was performed with SPSS software using Spearman correlation, Wilcoxon and Mann-Whitney U test and Cox proportional hazard function.

Results: Unless otherwise specified below, CTHRC1 was predominantly localized in cancer cell cytoplasm and extracellular matrix, while versican and periostin were expressed mostly by peripherial areas of infiltrating carcinoma and stromal cells. Expressions of CTHRC1, versican and periostin were significantly higher in breast cancer tissue in comparison to normal (p<0.001) and benign (p<0.001) ones. Furthermore, CTHRC1 and versican were upregulated (both p<0.001) in invasive lobular carcinoma compared to invasive ductal ones, while periostin was downregulated (p=0.12). Versican was also upregulated in luminal subtype, compared to both Her2 and triple negative cases (both p<0.01). Periostin was downregulated in Her2 subtype compared to triple negative cases (p=0.018) and, importantly, its expression was higher in patients with positive lymph nodes compared to negative ones (p=0.04). There was no difference for epithelial expression of CTHRC1 between subtypes but its stromal expression was significantly higher in triple negative cases compared to luminal ones (both p=0.013). Importantly, stromal expression of CTHRC1 was higher in patients metastasizing to bone compared to non-metastisizing ones (p=0.04). The Cox regression analysis revealed that the risk of bone metastases increased with increase in CTHRC1 stromal expression in patients with high periostin stromal expression (HR=1.007, p=0.024).

Conclusions: For the first time ever, we analyzed expression of CTHRC1 by immunohistochemistry in breast cancer patients. We confirmed that CTHRC1, versican and periostin are cancer related proteins as previously found by expression profiling experiments. Stromal expression of CTHRC1 may be associated with bone metastases. Combined evaluation of CTHRC1 and periostin could serve as an important marker for breast cancer bone metastasis prediction.

Acknowledgements: This work was supported by grants NS 9956-4 from the Czech Ministry of Health, MSM 6198959216 from the Czech Ministry of Education and EU infrastructure support CZ.1.05/2.1.00/01.0030. Gvantsa Kharaishvili was also supported by LF_2010_006.