Expression of Y-Box-binding protein 1 in Chinese patients with breast cancer

Y-Box binding protein 1 expression in breast cancer and its correlation with hormone receptors and other prognostic markers

INTRODUCTION:

The present histologic and immunohistochemical prognostic markers of breast carcinoma do not effectively identify the subset of patients with poor prognosis. Y-Box binding protein 1 (YB1) is a novel biomarker which may identify and aid in targeted personalized therapy for such patients.

MATERIALS AND METHODS:

The study was conducted on histopathology specimens of 74 patients of breast carcinoma who had undergone modified radical mastectomy. YB1 immunohistochemistry (IHC) was performed on manual tissue microarray blocks (each having 15 cores). The YB1 expression was quantified in terms of “immunoreactive score” which was correlated with clinical parameters, hormone receptor status, and Her2neu overexpression by IHC. The Her2neu status of the equivocal cases was further evaluated by fluorescent in situ hybridization (FISH).

RESULTS:

YB1 was positive in 36/74 (48.6%) cases. On IHC and analysis by FISH, 25/74 (34%) cases had Her2neu overexpression. Estrogen receptor (ER) and progesterone receptor (PR) positivity was found in 42% and 36.5% cases, respectively. YB1 immunopositivity was negatively correlated with ER and PR expression, but showed a significant positive correlation with Her2neu expression. No correlation was found with other clinical parameters, tumor stage, and grade, except lymph node involvement, which showed a positive association with YB1 expression. Triple-negative breast carcinoma constituted 25.6% of the total cases, out of which 73.6% were YB1 positive.

CONCLUSION:

This study found that YB1 has an association with Her2neu expression. It may in future provide a therapeutic target in Her2neu overexpressing tumors.

The value of cytoplasmic Y-box-binding protein 1 as a prognostic marker for breast cancer in Korean

BACKGROUND

The human Y-box-binding protein 1 (YB-1) is a member of the DNA/RNA-binding family of proteins that regulates transcription and translation of genes. Previous studies suggest that YB-1 may have an oncogenic role in various cancers. In this study, we evaluate the prognostic value of cytoplasmic YB-1 with respect to breast cancer.

METHODS

Immunohistochemical staining study was performed with YB-1 using tissue block from 233 patients with invasive ductal carcinoma. Patients were divided into two groups according to expression of cytoplasmic YB-1 in tumor cell (high versus low). The relationship between the expression of YB-1, clinicopathological characteristics and breast cancer prognosis was analyzed.

RESULTS

Hormone receptor negativity, worse histologic and nuclear grade, high tumor stage, lymphovascular invasion and high Ki67 (≥14 %) were related with the increased expression of cytoplasmic YB-1 in tumor cell (p < 0.05). Although there was no significant difference in relapse-free survival (RFS) between the two groups (p = 0.412), difference in overall survival (OS) was statistically significant (p = 0.035). In multivariate analysis for OS, YB-1 was an independent prognostic factor (p = 0.043).

CONCLUSION

This suggests that the increased expression of cytoplasmic YB-1 in tumor cells can be regarded as an independent prognostic factor for breast cancer, related to poor prognostics. Expression of cytoplasmic YB-1 in cancer cell could be used as an independent prognostic marker for predicting OS in breast cancer.

YB-1 disrupts mismatch repair complex formation, interferes with MutSα recruitment on mismatch and inhibits mismatch repair through interacting with PCNA

Y-box binding protein-1 (YB-1) is highly expressed in tumors and it participates in various cellular processes. Previous studies indicated that YB-1 binds to mispaired DNA and interacts with several mismatch repair (MMR)-related factors. However, its role in the MMR system remains undefined. Here, we found that YB-1 represses mutS homolog 6 (MSH6)-containing MMR complex formation and reduces MutSα mismatch binding activity by disrupting interactions among MMR-related factors. In an effort to elucidate how YB-1 exerts this inhibitory effect, we have identified two functional proliferating cell nuclear antigen (PCNA)-interacting protein (PIP)-boxes that mediate YB-1/PCNA interaction and locate within the C-terminal region of YB-1. This interaction is critical for the regulatory role of YB-1 in repressing MutSα mismatch binding activity, disrupting MutSα/PCNA/G/T heteroduplex ternary complex formation and inhibiting in vitro MMR activity. The differential regulation of 3' and 5' nick-directed MMR activity by YB-1 was also observed. Moreover, YB-1 overexpression is associated with the alteration of microsatellite pattern and the enhancement of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced and spontaneous mutations. Furthermore, upregulation of other PIP-box-containing proteins, such as myeloid cell leukemia-1 (Mcl-1) and inhibitor of growth protein 1b (ING1b), has no impact on MMR complex formation and mutation accumulation, thus revealing the significant effect of YB-1 on regulating the MMR system. In conclusion, our study suggests that YB-1 functions as a PCNA-interacting factor to exert its regulatory role on the MMR process and involves in the induction of genome instability, which may partially account for the oncogenic potential of YB-1.