The expression level and prognostic value of Y-box binding protein-1 in rectal cancer

YB-1 activating cascades as potential targets in KRAS-mutated tumors

Y‑box binding protein‑1 (YB-1) is a multifunctional protein that is highly expressed in human solid tumors of various entities. Several cellular processes, e.g. cell cycle progression, cancer stemness and DNA damage signaling that are involved in the response to chemoradiotherapy (CRT) are tightly governed by YB‑1. KRAS gene with about 30% mutations in all cancers, is considered the most commonly mutated oncogene in human cancers. Accumulating evidence indicates that oncogenic KRAS mediates CRT resistance. AKT and p90 ribosomal S6 kinase are downstream of KRAS and are the major kinases that stimulate YB‑1 phosphorylation. Thus, there is a close link between the KRAS mutation status and YB‑1 activity. In this review paper, we highlight the importance of the KRAS/YB‑1 cascade in the response of KRAS-mutated solid tumors to CRT. Likewise, the opportunities to interfere with this pathway to improve CRT outcome are discussed in light of the current literature.

Dual Targeting of Y-Box Binding Protein-1 and Akt Inhibits Proliferation and Enhances the Chemosensitivity of Colorectal Cancer Cells

KRAS-mutated colorectal cancers (CRCs) are resistant to cetuximab treatment. The multifunctional Y-box binding protein 1 (YB-1) is overexpressed in CRC and is associated with chemoresistance. In this study, the effects of oncogenic mutated KRAS(G12V) and KRAS(G13D) on YB-1 phosphorylation were investigated in CRC cells. The effects of the inhibition of p90 ribosomal S6 kinase (RSK) on YB-1 phosphorylation, cell proliferation and survival were tested with and without treatment with 5-fluorouracil using pharmacological inhibitors and siRNA. YB-1 phosphorylation status and subcellular distribution in CRC patient tissues were determined by immunofluorescence staining and confocal microscopy. Endogenous expression of mutated KRAS(G13D) and conditional expression of KRAS(G12V) significantly stimulated YB-1 phosphorylation via RSK and were associated with cetuximab resistance. Inhibition of YB-1 by targeting RSK stimulated the Akt signaling pathway, and this stimulation occurred independently of KRAS mutational status. Akt activation interfered with the antiproliferative effect of the RSK inhibitor. Consequently, dual targeting of RSK and Akt efficiently inhibited cell proliferation in KRAS(G13D)-mutated HCT116 and KRAS wild-type SW48 cells. Treatment with 5-fluorouracil (5-FU) significantly enhanced YB-1 phosphorylation in KRAS(G13D)-mutated HCT116 cells but not in KRAS wild-type SW48 cells. Dual targeting of Akt and RSK sensitized HCT116 cells to 5-FU by stimulating 5-FU-induced apoptosis and inhibiting repair of 5-FU-induced DNA damage. YB-1 was highly phosphorylated in CRC patient tumor tissues and was mainly localized in the nucleus. Together, dual targeting of RSK and Akt may be an alternative molecular targeting approach to cetuximab for treating CRC in which YB-1 is highly phosphorylated.

Translational Dysregulation in Cancer: Molecular Insights and Potential Clinical Applications in Biomarker Development

Although transcript levels have been traditionally used as a surrogate measure of gene expression, it is increasingly recognized that the latter is extensively and dynamically modulated at the level of translation (messenger RNA to protein). Over the recent years, significant progress has been made in dissecting the complex posttranscriptional mechanisms that regulate gene expression. This advancement in knowledge came hand in hand with the progress made in the methodologies to study translation both at gene-specific as well as global genomic level. The majority of translational control is exerted at the level of initiation; nonetheless, protein synthesis can be modulated at the level of translation elongation, termination, and recycling. Sequence and structural elements and epitranscriptomic modifications of individual transcripts allow for dynamic gene-specific modulation of translation. Cancer cells usurp the regulatory mechanisms that govern translation to carry out translational programs that lead to the phenotypic hallmarks of cancer. Translation is a critical nexus in neoplastic transformation. Multiple oncogenes and signaling pathways that are activated, upregulated, or mutated in cancer converge on translation and their transformative impact "bottlenecks" at the level of translation. Moreover, this translational dysregulation allows cancer cells to adapt to a diverse array of stresses associated with a hostile microenviroment and antitumor therapies. All elements involved in the process of translation, from the transcriptional template, the components of the translational machinery, to the proteins that interact with the transcriptome, have been found to be qualitatively and/or quantitatively perturbed in cancer. This review discusses the regulatory mechanisms that govern translation in normal cells and how translation becomes dysregulated in cancer leading to the phenotypic hallmarks of malignancy. We also discuss how dysregulated mediators or components of translation can be utilized as biomarkers with potential diagnostic, prognostic, or predictive significance. Such biomarkers have the potential advantage of uniform applicability in the face of inherent tumor heterogeneity and deoxyribonucleic acid instability. As translation becomes increasingly recognized as a process gone awry in cancer and agents are developed to target it, the utility and significance of these potential biomarkers is expected to increase.

Up regulation and nuclear translocation of Y-box binding protein 1 (YB-1) is linked to poor prognosis in ERG-negative prostate cancer

Y-box binding protein 1 (YB-1) is an RNA and DNA binding factor with potential prognostic cancer. To evaluate the clinical impact of YB-1, a tissue microarray with 11,152 prostate cancers was analysed by immunohistochemistry. Cytoplasmic and nuclear staining was separately analysed. Cytoplasmic YB-1 was absent or weak in normal epithelium but seen in 86,3% of carcinomas. Cytoplasmic staining was weak, moderate, and strong in 29.6%, 43.7% and 13.0% of tumours and was accompanied by nuclear YB-1 staining in 32.1% of cases. Particularly nuclear staining was strongly linked to poor patient prognosis (p < 0.0001). YB-1 protein was more abundant in ERG positive (95.1%) than in ERG negative cancers (80.4%; p < 0.0001), but any prognostic impact of YB-1 staining was limited to the ERG-negative subset. Similarly, significant associations with pT stage and Gleason grade (p < 0.0001 each) were driven by the ERG negative subset. The significant association of YB-1 protein detection with deletions of PTEN, 5q21 and 6q15 fits well in the protein’s role as an inhibitor of DNA damage dependent cell cycle arrest, a role that is likely to induce genomic instability. In summary, the data show, that the prognostic impact of YB-1 expression is limited to ERG negative prostate cancers.

Positive expression of Y-box binding protein 1 and prognosis in non-small cell lung cancer: a meta-analysis

Background

Y-box binding protein 1 (YB-1) belongs to the cold shock domain protein family involved in transcription and translation. We conducted a meta-analysis of the association between YB-1 expression and the survival and clinicopathological features in NSCLC.

Methods

PubMed and Embase were searched to identify studies that evaluated the YB-1 expression (by immunohistochemistry) and overall survival (OS) in NSCLC. Hazard ratios (HRs) and 95% confidence intervals (CI) of OS were pooled. Odds ratios (ORs) of clinicopathological features were computed. Meta-analysis was performed using STATA 12.0 software.

Results

Data on 692 NSCLC patients were collected from six eligible studies. Meta-analysis revealed that YB-1 was associated with worse OS (HR = 1.59, 95% CI [1.27, 2.00], P < 0.001, fixed effect), tumor stage (OR = 0.43, 95% CI [0.22-0.82], P = 0.01, random effect), and depth of invasion (OR = 0.37, 95%CI [0.22-0.63], P < 0.001, fixed effect). A subgroup was analyzed by IHC staining to determine the location of YB-1 positive expression. Poor OS was observed in nucleus staining (pooled HR = 1.86, 95% CI [1.41, 2.45], P < 0.001). However, no statistical significance was observed in combined cytoplasmic and nuclear staining (pooled HR = 1.14, 95% CI [0.76, 1.72], P = 0.536).

Conclusions

Meta-analysis indicated that YB-1 overexpression is correlated with worse OS and clinicopathological features in NSCLC. Subgroup analysis revealed that the nucleus expression of YB-1 may be more closely associated with NSCLC prognosis than cytoplasmic expression.

Uncoupling of EGFR-RAS signaling and nuclear localization of YBX1 in colorectal cancer

The transcription factor YBX1 can act as a mediator of signals transmitted via the EGFR-RAS-MAPK axis. YBX1 expression has been associated with tumor progression and prognosis in multiple types of cancer. Immunohistochemical studies have revealed dependency between YBX1 expression and individual EGFR family members. We analyzed YBX1 and EGFR family proteins in a colorectal cancer (CRC) cohort and provide functional analyses of YBX1 in the context of EGFR-RAS-MAPK signaling. Immunohistochemistry for YBX1 and EGFR family receptors with two antibodies for YBX1 and EGFR were performed and related to clinicopathological data. We employed Caco2 cells expressing an inducible KRASV12 gene to determine effects on localization and levels of YBX1. Mouse xenografts of Caco2-KRASV12 cells were used to determine YBX1 dynamics in a tissue context. The two different antibodies against YBX1 showed discordant immunohistochemical stainings in cell culture and clinical specimens. Expression of YBX1 and EGFR family members were not correlated in CRC. Analysis of Caco2 xenografts displayed again heterogeneity of YBX1 staining with both antibodies. Our results suggest that YBX1 is controlled via complex regulatory mechanisms involving tumor stroma interaction and signal transduction processes. Our study highlights that YBX1 antibodies have different specificities, advocating their use in a combined manner.