Early candidate biomarkers in urine of Walker-256 lung metastasis rat model

Abstract Cancer metastasis accounts for the majority of deaths by cancer. Detection of cancer metastasis at its early stage is important for the management and prediction of cancer progression. Urine, which is not regulated by homeostatic mechanisms, reflects systemic changes in the whole body and can potentially be used for the early detection of cancer metastasis. In this study, a lung metastasis of a Walker-256 rat model was established by tail-vein injection of Walker-256 cells. Urine samples were collected at days 2, 4, 6 and 9 after injection, and the urinary proteomes were profiled using liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). The urinary protein patterns changed significantly with the development of Walker-256 lung metastasis. On the fourth day, lung metastasis nodules appeared. On the sixth day, clinical symptoms started. On days 2, 4, 6 and 9, 11, 25, 34 and 44 differential proteins were identified in 7 lung metastatic rats by LC-MS/MS. Seventeen of these 62 differential proteins were identified on the second day, and 18 of them were identified on the fourth day. The differential urinary proteins changed significantly two days before lung metastasis nodules appeared. Differential urinary proteins differed in Walker-256 lung metastasis rat models and Walker-256 subcutaneous rat models. A total of 9 differential proteins (NHRF1, CLIC1, EZRI, AMPN, ACY1A, HSP7C, BTD, NID2, and CFAD) were identified in 7 lung metastatic rats at one or more common time points, and these 9 differential proteins were not identified in the subcutaneous rat model. Seven of these 9 differential proteins were associated with both breast cancer and lung cancer, eight of the nine were identified on the second day, and 8 of the nine can be identified on the fourth day; these early changes in urine were also identified with differential abundances at late stages of lung metastasis. Our results indicate that (1) the urine proteome changed significantly, even on the second day after tail-vein injection of Walker-256 cells and that (2) the urinary differential proteins were different in Walker-256 lung metastatic tumors and Walker-256 subcutaneous tumors. Our results provide the potential to detect early breast cancer lung metastasis, monitor its progression and differentiate it from the same cancer cells grown at other locations.