Prognostic Association of YB-1 Expression in Breast Cancers: A Matter of Antibody

Abstract

The literature concerning the subcellular location of Y-box binding protein 1 (YB-1), its abundance in normal and cancer tissues, and its prognostic significance is replete with inconsistencies. An explanation for this could be due in part to the use of different antibodies in immunohistochemical and immunofluorescent labeling of cells and tissues. The inconsistencies could also be due to poor resolution of immunohistochemical data. We analyzed two cohorts of breast tumours for both abundance and subcellular location of YB-1 using three different antibodies; two targeting N-terminal epitopes (AB- a and AB- b) and another (AB- c) targeting a C-terminal epitope. We also investigated stress-induced nuclear translocation of YB-1 in cell culture. We report that both AB- a and AB- c detected increased YB-1 in the cytoplasm of high-grade breast cancers, and in those lacking estrogen and progesterone receptors; however the amount of YB-1 detected by AB- a in these cancers is significantly greater than that detected by AB- c. We confirm our previously published findings that AB- b is also detecting hnRNP A1, and cannot therefore be used to reliably detect YB-1 by immunohistochemistry. We also report that AB- a detected nuclear YB-1 in some tumour tissues and stress treated cells, whereas AB- c did not. To understand this, cancer cell lines were analyzed using native gel electrophoresis, which revealed that the antibodies detect different complexes in which YB-1 is a component. Our data suggest that different YB-1 antibodies show different staining patterns that are determined by the accessibility of epitopes, and this depends on the nature of the YB-1 complexes. It is important therefore to standardize the protocols if YB-1 is to be used reproducibly as a prognostic guide for different cancers.

Cyr61 and YB-1 are novel interacting partners of uPAR and elevate the malignancy of triple-negative breast cancer

“…Depending on the specificity of the used antibody, YB-1 could be detected in the nucleus or in the cytoplasm. For this study, we have applied an antibody, which is directed against the carboxy terminus of YB-1 detecting its cytoplasmic expression [38]. With regard to its relevance for cellular invasion, YB-1 was also analyzed in connection to the uPA system.…”

Cold shock Y-box protein-1 proteolysis autoregulates its transcriptional activities

“…Additionally, YB-1 associates via its N-terminus with FBX33, a component of an SCF E3–ubiquitin ligase; an interaction that targets YB-1 for proteasomal degradation [43]. However, the issue of whether proteolytic processing of YB-1 occurs is still disputed [44,45]. …”

“…It is interesting to speculate to what extent these processes may contribute to pathology, particularly as enhanced levels of nuclear YB-1 are often associated with a poor prognosis in cancer [45,48,49]. Proteasome inhibitors have been introduced into therapeutical regimens of hematological disorders like multipe myeloma.…”

Low expression of the X-linked ribosomal protein S4 in human serous epithelial ovarian cancer is associated with a poor prognosis

“…Another confounding parameter in the interpretation of the results is the anti-YB-1 antibodies used in the different studies. Antibodies recognizing epitopes on the C-terminus [7,24] or the N-terminus portion of the YB-1 protein (our study) as well as the immunohistochemistry protocol can impact staining [25]. Finally, as our study focused exclusively on high-grade serous epithelial ovarian cancers, it is possible that within this subset of serous cancer YB-1 has little prognostic value.…”