Identification of Metastasis-Related Proteins and Their Clinical Relevance to Triple-Negative Human Breast Cancer

Purpose: Currently, there are no definite biomarkers of triple-negative breast cancer. The study aims to identify the metastasis-associated proteins of triple-negative breast tumors. Experimental Design: A murine metastatic breast cancer model has been established by using TA2 mice. Parallel proteomic analyses were done on a murine metastatic breast cancer model and its primary breast cancer using two-dimensional gel electrophoresis. The differentially expressed proteins were detected in TA2 mice developing spontaneous breast cancer and lung metastasis. Furthermore, their expression were detected in human breast cancer with or without metastasis, and their prediction values were assessed in a second set of samples. Results: Nineteen of 36 differentially expressed proteins were identified by peptide mass fingerprinting using matrix-assisted laser-desorption ionization-time of flight-mass spectrometry. These proteins were also validated in mouse tumor tissues by immunohistochemical staining. Actin, 14-3-3, vimentin, HSP70, CK18, and moesin were up-regulated in the metastatic tumors, whereas HSP90 and tubulin were absent or down-regulated. Furthermore, 61 patients with triple-negative breast cancer and 39 patients with estrogen receptor-positive/progesterone receptor-positive breast cancer were selected for exploring the clinical relevance of these identified proteins to human breast cancer metastasis. Expression of 14-3-3 and HSP70 was significantly correlated with metastasis of human triple-negative breast cancer. Moreover, the validation study in the second set confirmed that 14-3-3, HSP70, and their combination had high sensitivities and specificities in predicting metastatic potential of triple-negative breast cancer. Conclusions: These tumor metastasis-associated proteins validated may be useful as biomarkers and targets for diagnosis and treatment of human triple-negative breast cancer.