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

Abstract

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 inTA2 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, 61patients 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.Breast cancer metastasis is the main cause of treatment failure, exerting a remarkably negative effect on the cure and survival of patients suffering from breast cancer. Metastasis is a multiplestep process involving numerous genes (1, 2). There are two distinct hypotheses regarding tumor metastasis: heterogeneous metastasis and synchronous metastasis. Heterogeneous metastasis is defined as malignant tumor cells spreading to other organs in the late stage (3), whereas synchronous metastasis is described as tumor cells disseminating very early and evolving into metastatic disease independent from the primary tumor (4), suggesting that protein expression in the metastatic tumor may be different from the primary tumor (5). Therefore, the identification of metastasis protein markers in the early stage may contribute to early diagnosis and treatment of breast cancer patients with high risk of metastasis.Triple-negative breast cancer is the subtype of invasive breast cancer with estrogen receptor (ER)-negative, progesterone receptor (PR)-negative, and HER-2-negative phenotype, an important subtype of breast cancer due to its re...

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