Correction to: Elevated expression of CST1 promotes breast cancer progression and predicts a poor prognosis.

In Figure 7f the panel for c-myc of MDA-MB-468 was erroneously duplicated. The corrected version of the figure is shown in this paper. This correction does not influence the conclusion of the study and we sincerely apologize for this oversight.

Identification of a sodium pump Na+/K+ ATPase α1-targeted peptide for PET imaging of breast cancer.

The sodium pump Na+/K+ ATPase a1 subunit(NKA a1), an attractive cancer-related biomarker and therapeutic target, is closely related to the development and progression of several cancers including breast cancer. Currently, a NKA a1 inhibitor, UNBS1450, has already evidenced its great therapeutic potential in personalized cancer treatment. The ability of non-invasive imaging of NKA a1 expression would be useful for selecting cancer patients who may benefit from this drug. Here, we identified an S3 peptide that is specifically homed to breast cancer by phage display. All data of in vitro and in vivo experiments suggested the excellent targeting character of the S3 peptide. As the binding activity of the S3 phage was positively correlated to the level of NKA α1 expression in various breast cancer cells, NKA α1 was validated as the primary target of the S3 peptide. Based on immunohistochemistry staining result of 107 breast cancer patients, NKA α1 was verified to be a novel tracking marker and a prognostic predictor for breast cancer. Importantly, we proposed and validated an S3 peptide-based radiotracer 18F-ALF-NOTA-S3 for PET (Positron Emission Tomography) imaging of breast cancer and other NKA α1-overexpressing cancers, including hepatocellular carcinoma and non-small cell lung cancer, in mouse models. Our findings demonstrated the potential application of 18F-ALF-NOTA-S3 for visualization of NKA α1-positive lesions, which provide a new approach to character tumor phenotypic imaging.

Elevated expression of CST1 promotes breast cancer progression and predicts a poor prognosis.

Cystatin SN (CST1) belongs to the type 2 cystatin (CST) superfamily, which restricts the proteolytic activities of cysteine proteases. CST1 has been recently considered to be involved in the development of several human cancers. However, the prognostic significance and function of CST1 in breast cancer remains unknown. In the current study, we found that CST1 was generally upregulated in breast cancer at both mRNA and protein level. Furthermore, overall survival (OS) and disease-free survival (DFS) in the low CST1 expression subgroup were significantly superior to the high CST1 expression subgroup (OS, p < 0.001; DFS, p < 0.001), which indicated that CST1 expression level was closely correlated to the survival risk of these patients. Univariate and multivariate analyses demonstrated that CST1 expression was an independent prognostic factor, the same as ER status and nodal status. Next, CST1 overexpression promoted breast cancer cell proliferation, clonogenicity, migration, and invasion abilities. By contrast, knockdown of CST1 attenuated these malignant characteristics in breast cancer cells. Collectively, our study indicates that CST1 cannot only serve as a significant prognostic indicator but also as a potential therapeutic target for breast cancer. KEY MESSAGES: High CST1 expression is negatively correlated with survival of breast cancer patients. CST1 promotes cell proliferation, clone formation, and metastasis in breast cancer cells. CST1 is a novel potential prognostic biomarker and therapeutic target for breast cancer.