Y-box Binding Protein-1 Inhibition Research Articles

Inhibition of protein translational machinery in triple-negative breast cancer as a promising therapeutic strategy

Y-box binding protein-1 (YB-1) is a proto-oncogenic protein associated with protein translation regulation. It plays a crucial role in the development and progression of triple-negative breast cancer (TNBC). In this study, we describe a promising approach to inhibit YB-1 using SU056, a small-molecule inhibitor. SU056 physically interacts with YB-1 and reduces its expression, which helps to restrain the progression of TNBC. Proteome profiling analysis indicates that the inhibition of YB-1 by SU056 can alter the proteins that regulate protein translation, an essential process for cancer cell growth. Preclinical studies on human cells, mice, and patient-derived xenograft tumor models show the effectiveness of SU056. Moreover, toxicological studies have shown that SU056 treatment and dosing are well tolerated without any adverse effects. Overall, our study provides a strong foundation for the further development of SU056 as a potential treatment option for patients with TNBC by targeting YB-1.

Abstract 5926: YB-1 inhibition as an effective approach for the treatment of osteosarcoma

Abstract Background: Osteosarcoma (OS) is a bone cancer primarily affecting adolescents and young adults, with about 20% of patients having detectable metastatic disease at the time of diagnosis. Despite a large number of clinical trial efforts, metastatic sarcoma remains a lethal disease, and there have been no meaningful advances in therapy or improvements in patient outcomes for decades. Y-box binding protein 1 (YB-1) is a multifunctional cold-shock protein that translationally activates diverse stress response factors with pro-metastatic activities in many cancer types. Importantly, YB-1 is strongly associated with poor outcomes in sarcoma patients and is a major metastatic driver in high-risk sarcomas. Methods: We recently described a novel compound, CET056, that inhibits cancer progression via YB-1 inhibition. We hypothesized that CET056 had the potential to suppress the progression of OS and could provide a new treatment for this disease. We screened osteosarcoma human and mouse cell lines for YB-1 protein expression. OS cells were functionally characterized for responses to CET056 in vitro and in vivo. Results: YB-1 expression was seen in nearly all cell lines tested. CET056 treatment of OS cells resulted in reduced cell viability and YB-1 protein expression in a dose- and time- dependent manner, as well as reduced formation of colonies and spheroids. In vivo efficacy studies, which employed a syngeneic subcutaneous tumor model, revealed that CET056 effectively inhibited tumor progression and enhanced overall survival in contrast to vehicle treated control mice. Conclusion: These results support our hypothesis and illustrate that YB-1 inhibition by CET056 is a promising candidate for further development as a therapy for OS. Citation Format: Kirsten Stefan, Arpit Dheeraj, Dhanir Tailor, Lara E. Davis, Sanjay V. Malhotra. YB-1 inhibition as an effective approach for the treatment of osteosarcoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5926.

Abstract 668: Enhancing chemosensitivity of lung adenocarcinoma via Y-box binding protein 1 (YB-1) inhibition

Abstract Background: Y-box binding protein 1 (YB-1, YBX1) is a multifunctional nucleic acid binding protein that regulates the expression of various genes by binding to their mRNA and stabilizing them. In over 20 cancer types, including lung adenocarcinoma (LUAD), YBX1 expression is significantly elevated in tumor samples compared to normal tissue. Within cancer cells, YB-1 promotes the expression of genes involved in tumorigenesis and chemoresistance. Consequently, elevated YBX1 expression in tumor is associated with poor clinical outcomes and significantly reduced overall survival in LUAD patients. Therefore, YB-1 emerges as a promising therapeutic target for LUAD treatment. Utilizing a small molecule YB-1 inhibitor, CET056, we performed a series of in vitro and in vivo analyses to assess the therapeutic efficacy of YB-1 inhibition and unravel YB-1’s role in tumorigenesis and disease progression in LUAD. Methods: Four human and one mouse LUAD cell lines were treated with CET056 and/or chemotherapeutic drugs and analyzed for the in vitro therapeutic activity of CET056. Using xenograft and syngeneic LUAD mouse models, the preclinical therapeutic efficacy of CET056 on disease progression of LUAD was also tested. Results: CET056 was shown to effectively decrease YB-1 expression in both human and mouse LUAD cell lines and exert inhibitory effects on LUAD in vitro and in vivo. This treatment delayed tumor progression and metastasis in CMT-64 syngeneic mouse model. Proteomics analysis revealed that translational machinery-associated pathways were down-regulated in LUAD cells after CET056 treatment whereas apoptosis and cell death-associated pathways were up-regulated. In alignment with this finding, CET056 treatment in combination with cisplatin showed chemo-sensitizing effect on LUAD in vitro and in vivo. Conclusion: Our studies suggest that YB-1 could be a promising target for combating chemoresistance in LUAD. Inhibition of YB-1 with a small molecule drug as a monotherapy or combination therapy could an effective strategy to treat LUAD. Citation Format: Jee Min Lee, Dhanir Tailor, Fernando J. Garcia-Marques, Abel Bermudez, Sharon Pitteri, Sanjay V. Malhotra. Enhancing chemosensitivity of lung adenocarcinoma via Y-box binding protein 1 (YB-1) inhibition [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 668.

Exploration of YBX1 role in the prognostic value and immune characteristics by single-cell and bulk sequencing analysis for liver hepatocellular carcinoma.

Y-box binding protein 1 (YBX1) plays a variety of roles in progression of multiple tumors. However, the role of YBX1 in prognostic value and immune regulation for liver hepatocellular carcinoma (LIHC) remains unclear. The present study aimed to examine the effect of YBX1 on the regulation of tumor immunity and survival prediction in LIHC patients. YBX1-related expression profiles and single-cell and bulk sequencing analysis were performed using online databases. YBX1 expression was validated by a quantitative real-time PCR (qRT-PCR), western blotting and immunohistochemistry. Univariate/multivariate Cox regression analysis was performed to determine independent predictors of overall survival (OS). The ESTIMATE (i.e., Estimation of STromal and Immune cells in MAlignant Tumor tissues using Expression data) algorithm and Tumor Immune Dysfunction and Exclusion (TIDE) analysis were used to assess the relationships between YBX1 and LIHC immunity. YBX1 was over-expressed in LIHC tissues and cell lines. High YBX1 expression was significantly associated with poor OS. Univariate/multivariate Cox regression analysis revealed that YBX1 was an independent prognostic factor for LIHC. Gene set enrichment analysis revealed that YBX1 was associated with multiple signaling pathways correlated to LIHC. Additionally, YBX1 was expressed in multiple immune cells and was significantly correlated with immune cells, immune checkpoint markers and tumor immune microenvironment. The TIDE analysis demonstrated that LIHC patients with high YBX1 expression showed a higher T-cell dysfunction score and a higher exclusion score, as well as poorer immunotherapy response. YBX1 plays crucial oncogenic roles in LIHC and is closely associated with the immune defense system. YBX1 inhibition may serve as a potential treatment for LIHC.

EXTH-32. SYNERGISTIC EFFICACY OF Y BOX BINDING PROTEIN 1 (YBX1) INHIBITION COMBINED WITH CHEMOTHERAPY FOR THE TREATMENT OF MYC-AMPLIFIED MEDULLOBLASTOMA

Abstract Medulloblastoma is the most common pediatric brain tumor in children. Patients diagnosed with MYC-amplified group 3 (G3) have a dismal prognosis with a 5 year survival rate of < 50%. Standard of care consists of maximal resection surgery followed by craniospinal irradiation and chemotherapy, but patients experience diminished quality of life from these extensive treatment regimens. Recent observations have shown that Y-box binding protein 1 (YBX1) is upregulated across human medulloblastoma subgroups compared to normal cerebellum. G3 patient tumors have the highest expression of YBX1, possibly due to an oncogenic feedback loop. We utilized an orthogonal pharmacogenetic approach to target YBX1. Knockdown/out of YBX1 significantly inhibits proliferation of G3 MB cells in vitro and in vivo. We next investigated the therapeutic potential of a novel YBX1 inhibitor, which displays single agent efficacy at decreasing the proliferation of medulloblastoma cell line derived xenografts (CDX). Since YBX1 targeting downregulated ABC transporter expression, we hypothesize that inhibition of YBX1 may sensitize medulloblastoma cells to chemotherapeutic agents. We performed drug synergy experiments combining YBX1 inhibition and commonly used standard of care chemotherapy. We identify that combining YBX1 inhibition sensitizes to both gemcitabine and vincristine in vitro and in vivo. We are currently evaluating this YBX1 inhibitor in an “anchor-probe” screen combining with all currently FDA approved drugs. Our findings impart an alluring prospect of targeting YBX1 in combination with chemotherapy, and possibly other compounds could improve patients’ outcomes.

Abstract 1281: Oncoprotein YB-1 modulation of Lyn-MAPK-NF-kB pathway, a potential therapeutic strategy combined with sorafenib for advanced stage HCC

Abstract The Y-Box Binding protein 1 (YB-1) is a 324 amino acid-long member of the Cold Shock Domain (CSD) protein superfamily. YB-1 interacts with micro RNAs and non-coding RNAs in the cytoplasm, acting as a regulator of mRNA translation. YB-1 translocation into the nucleus is circadian clock-dependent and leads to the upregulation of cyclin gene expression, among others. Another mechanism of nuclear translocation of YB-1 is mediated by phosphorylation of the Ser 102 residue in the CSD. The YB-1 oncoprotein acts as a transcription factor when bound to DNA, modulating the transcription of genes that regulate biological processes such as Multidrug Resistance Mutation 1 (MDR1). YB-1 is linked to poor prognosis in breast, prostate, and liver cancer. Despite advances in biomedicine, the incidence and mortality of hepatocellular carcinoma (HCC) remain high. Sorafenib, a tyrosine kinase Inhibitor (TKI), is the first-line treatment for advanced HCC. Sorafenib also inhibits downstream activation of NF-kB by inhibition of Lyn phosphorylation (Y397). However, it was observed in many patients that its sorafenib’s effectiveness is hampered by drug resistance, but the mechanism is still unclear. We have found that SK-HEP-1 HCC cells transfected with a YB-X-1 overexpression plasmid subsequently developed into a stable YB-1 overexpression cell line (SK-HEP-1+YB-1) displayed increased invasion, migration, proliferation, and colony formation property as compared to the vector control (SKHEP1+Vec). The SK-HEP-1+YB-1 cell line also showed increased IC50 for sorafenib and elevated phosphorylation of Lyn (Y397) and further activated NF-kB (S165/S176) phosphorylation. This indicates YB-1 may cause increased Sorafenib resistance in HCC by activating tyrosine kinases (TK), such as lyn, and simultaneous activation of NF-kB. The combination of YB-1 inhibition and sorafenib might provide a novel therapeutic strategy and improve the survival of patients with advanced-stage HCC. Citation Format: Ana G. Ayala Pazzi, Omar Karkoutly, Kristopher Ezell, Samantha Lopez, Kyle D. Doxtater, Elias George, Vijian Dhevan, Manish K. Tripathi. Oncoprotein YB-1 modulation of Lyn-MAPK-NF-kB pathway, a potential therapeutic strategy combined with sorafenib for advanced stage HCC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1281.

Abstract 2645: Targeting mRNA processing pathways in ovarian cancer with a small molecule inhibitor

Abstract mRNA processing related pathways, including spliceosome and ribosome are over-expressed and unregulated in cancer cells. To investigate the mRNA processing pathways in patient samples, we performed a comprehensive, tandem mass tag (TMT) labeling-based proteome and phosphoproteome profiling of the normal and ovarian cancerous tissues from patients treated with different chemotherapy revealed that malignant cells have overexpression of mRNA processing pathways compared to normal cells. For this analysis, equal amount of tissues were homogenized, and tissue lysates were collected and processed for the quantitative proteomics and phosphoproteomics analysis. KEGG pathway enrichment analysis revealed that spliceosome, basal transcription factors, mRNA surveillance, ribosome and ribosome biogenesis in eukaryotes pathways are upregulated in cancer cells compared to control. On other hand, pathways associated with metabolism and fatty acid biosynthesis were downregulated in malignant cells. Moreover, kinase Enrichment Analysis shows that CDK2, ATM, ATR, and MAPK associated kinases are upregulated in cancer cells compared to normal. Based on proteome analysis of patient samples, we investigated the pharmacological inhibition of Y-box binding protein 1 (YB-1). This is an RNA binding protein and key regulator of pre-mRNA alternative splicing and processing. We recently showed that a natural product-derived small molecule (SU056) inhibits YB-1 activity. We found that SU056 binds to the YB-1 and blocks the RNA binding pocket. Proteomics results suggest that treatment with this drug strongly inhibits the spliceosome pathway. SU056 treatment arrests the ovarian cancer cells in G1 phase and inhibits the CDK2 and Cyclin E. SU056 inhibits the tumor progression and metastasis in the ID8 mice model and sensitizes the OVCAR8 NSG mice model for paclitaxel treatment. Our study provides a compelling case for YB-1 inhibition using SU056 as a potential therapy for ovarian cancer. Citation Format: Dhanir Tailor, Chia-Feng Tsai, Alexander Honkala, Wenqi Li, Tao Liu, Tanja Pejovic, Sanjay V. Malhotra. Targeting mRNA processing pathways in ovarian cancer with a small molecule inhibitor [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2645.

Inhibition of YBX1 by miR-216a Suppresses Proliferation and Invasion of Diffuse Large B-Cell Lymphoma

Background: MicroRNAs (miRNAs) could be implicated in tumorigenesis of diffuse large B-cell lymphoma (DLBCL).Aims: To determine the role of MiR-216a in DLBCL.Study Design: Cell culture study.Methods: Expression of miR-216a in DLBCL cells was examined by qRT-PCR. Cell counting kit-8, bromodeoxyuridine staining and transwell assays were performed to evaluate role of miR-216a on DLBCL cell growth. Target gene of miR-216a was verified by luciferase reporter assay.Results: MiR-216a was dramatically reduced in DLBCL cells compared to the normal B-cell line (P < .01). MiR-216a reduced the viability and retarded DLBCL cell proliferation. The invasion of DLBCL was suppressed by miR-216a. Y box binding protein 1 (YBX1) was validated as a target of miR-216a. Its expression was reduced by miR-216a mimic and enhanced by miR-216a inhibitor in DB and SU-DHL-10 cells. Knockdown of YBX1 reduced cell viability, proliferation, and invasion of DB and SU-DHL-10 cells.Conclusion: MiR-216a exerted tumor-suppressive effects on DLBCL cells through inhibition of YBX1, providing a new strategy for DLBCL.

Inhibition of YBX1 by miR-216a Suppresses Proliferation and Invasion of Diffuse Large B-Cell Lymphoma.

MicroRNAs (miRNAs) could be implicated in tumorigenesis of diffuse large B-cell lymphoma (DLBCL). To determine the role of MiR-216a in DLBCL. Cell culture study. Expression of miR-216a in DLBCL cells was examined by qRT-PCR. Cell counting kit-8, bromodeoxyuridine staining and transwell assays were performed to evaluate role of miR-216a on DLBCL cell growth. Target gene of miR-216a was verified by luciferase reporter assay. MiR-216a was dramatically reduced in DLBCL cells compared to the normal B-cell line (P < .01). MiR-216a reduced the viability and retarded DLBCL cell proliferation. The invasion of DLBCL was suppressed by miR-216a. Y box binding protein 1 (YBX1) was validated as a target of miR-216a. Its expression was reduced by miR-216a mimic and enhanced by miR-216a inhibitor in DB and SU-DHL-10 cells. Knockdown of YBX1 reduced cell viability, proliferation, and invasion of DB and SU-DHL-10 cells. MiR-216a exerted tumor-suppressive effects on DLBCL cells through inhibition of YBX1, providing a new strategy for DLBCL.

Y-Box Binding Protein-1 Promotes Epithelial-Mesenchymal Transition in Sorafenib-Resistant Hepatocellular Carcinoma Cells.

Hepatocellular carcinoma is one of the most common cancer types worldwide. In cases of advanced-stage disease, sorafenib is considered the treatment of choice. However, resistance to sorafenib remains a major obstacle for effective clinical application. Based on integrated phosphoproteomic and The Cancer Genome Atlas (TCGA) data, we identified a transcription factor, Y-box binding protein-1 (YB-1), with elevated phosphorylation of Ser102 in sorafenib-resistant HuH-7R cells. Phosphoinositide-3-kinase (PI3K) and protein kinase B (AKT) were activated by sorafenib, which, in turn, increased the phosphorylation level of YB-1. In functional analyses, knockdown of YB-1 led to decreased cell migration and invasion in vitro. At the molecular level, inhibition of YB-1 induced suppression of zinc-finger protein SNAI1 (Snail), twist-related protein 1 (Twist1), zinc-finger E-box-binding homeobox 1 (Zeb1), matrix metalloproteinase-2 (MMP-2) and vimentin levels, implying a role of YB-1 in the epithelial-mesenchymal transition (EMT) process in HuH-7R cells. Additionally, YB-1 contributes to morphological alterations resulting from F-actin rearrangement through Cdc42 activation. Mutation analyses revealed that phosphorylation at S102 affects the migratory and invasive potential of HuH-7R cells. Our collective findings suggest that sorafenib promotes YB-1 phosphorylation through effect from the EGFR/PI3K/AKT pathway, leading to significant enhancement of hepatocellular carcinoma (HCC) cell metastasis. Elucidation of the specific mechanisms of action of YB-1 may aid in the development of effective strategies to suppress metastasis and overcome resistance.

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.

Y-box binding protein-1 and STAT3 independently regulate ATP-binding cassette transporters in the chemoresistance of gastric cancer cells.

Y-box binding protein-1 (YB-1) facilitates cancer chemoresistance through the upregulation of ATP-binding cassette(ABC) transporters associated with multidrug resistance, which is one of the primary obstacles in cancer treatment. Since aberrant Janus kinase (JAK)/signal transducer and activator of transcription(STAT) signaling is also implicated in chemoresistance in numerous human malignancies, the interaction between YB-1 and JAK/STAT signaling was explored underlying the chemoresistance of NUGC3 gastric cancer cells. It was demonstrated that YB-1 translocated into the nuclei of NUGC3 cells exposed to doxorubicin hydrochloride, suggesting its important role in chemoresistance. Consistently, knockdown of YB-1 significantly decreased the chemoresistance of cells to doxorubicin hydrochloride and epirubicin hydrochloride, as evidenced by a decrease in cell viability. Notably, JAK inhibitor AG490 treatment further decreased the cell viability caused by YB-1 inhibition and doxorubicin hydrochloride. It was also observed that YB-1 transcriptionally regulated the ABCC3 transporter, whereas STAT3 modulated ABCC2 transporter levels. These findings suggest that YB-1 and STAT3 act together to facilitate chemoresistance via modulating the expression of different ABC transporters in NUGC3 cells. Notably, siYB-1 did not exhibit any significant effect on STAT3 expression. Similarly, siSTAT3 failed to alter YB-1 expression, suggesting that the two may not regulate each other in a mutual manner. However, double knockdown of YB-1 and STAT3 led to a synergistic inhibition of cell invasion in NUGC3 cells. Nonetheless, the combined treatment of YB-1 antagonists with STAT3 inhibitors may serve as an effective therapy in gastric cancer.

Abstract 3080: Y-box binding protein 1 is crucial in acquiring drug resistance in advanced renal cell carcinoma

Abstract Objective: Investigating the role of Y-box binding protein 1 (YB1) in drug resistant advanced kidney cancer. Background: Renal cell carcinoma (RCC) is the 6th most common malignancy with approximately 1,800 deaths in 2015 and 2.3% annual increase in Canada. Despite the partial or total surgical removal of kidney in patients with localized RCC, metastatic patients are treated with tyrosine kinase inhibitors (TKIs) in a purely palliative approach. However, TKI-resistance (Sunitinib) is developed after a median time of 10-14 months. Therefore, identifying the factor(s) responsible for TKI-resistance development and disease advancement in RCC is imperative. It is now widely recognized that evolutionarily conserved Y-box binding protein 1 (YB1) is essential for cell growth and survival. Upregulation of YB1 in numerous cancer types was found to be positively correlated with tumor growth, metastasis and drug-resistance development. YB1 is also involved in intercellular communication through its secretion in the tumor microenvironment by cell-surface transporters, ABC-transporters. Summary of the data: Endothelial cells (HUVEC) were co-cultured with Caki-1DC (Sunitinib-resistant, developed in our lab) and Caki-1WT (Sunitinib-sensitive) RCC cell-lines, and increased migration of HUVEC was observed with Caki-1DC compared to Caki-1WT. A drastic increase in YB1 and its downstream target ABCB1 in Caki-1DC compared to Caki-1WT cells was also detected. Consistent with previous reports, we observed granular structures in the Caki-1DC cells that support potential secretion of YB1 into the tumor microenvironment. Moreover, blocking ABCB1 reverted the Caki-1DC cells to being drug-sensitive. Experimental procedures: Caki-1WT and Caki-1DC were co-cultured with HUVEC cells followed by scratch assay to test for HUVEC cell migration and associated secretory factors. Western blot and qPCR were used to determine the protein and mRNA levels respectively between the two cell-lines. Immuno-histochemical staining was carried out on the RCC tumors from Sunitinib-sensitive and resistant mouse models (developed in our animal facility). Granular structures were observed using immunofluorescence staining against YB1. Presto-blue was used for cell biomass assay following different drug treatments. Summary: The molecular function of YB1 in RCC and its potential in targeted therapy is not well understood. Therefore, understanding the function of YB1 in metastatic RCC and in drug-resistance development is of vital importance. Our data suggests that inhibition of YB1 may slow disease progression and, possibly, revert the drug resistance mechanism. The results from this study have the potential to introduce YB1 inhibitors in conventional RCC chemotherapy, alone or in combination, to improve survival in advanced kidney cancer patients. Citation Format: Ninadh M. D'Costa, Peter Raven, Zheng Tan, Werner Struss, Sebastian Frees, Claudia Chavez-Munoz, Alan I. So. Y-box binding protein 1 is crucial in acquiring drug resistance in advanced renal cell carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3080. doi:10.1158/1538-7445.AM2017-3080

Silencing of Y-box binding protein-1 by RNA interference inhibits proliferation, invasion, and metastasis, and enhances sensitivity to cisplatin through NF-κB signaling pathway in human neuroblastoma SH-SY5Y cells.

Y-box binding protein-1 (YB-1), a member of Y-box protein family binding DNA and RNA, has been proposed as a novel marker in multiple malignant tumors and found to be associated with tumor malignancy. Neuroblastoma is an embryonal tumor arising from neuroblast cells of the autonomic nervous system, which is the most common cancer diagnosed in infants. It has been reported that YB-1 is highly expressing in various human tumors including nasopharynx, thyroid, lung, breast, colon, ovary, and prostate cancers. This study aimed to investigate the functional role of YB-1 in neuroblastoma by silencing YB-1 using RNA interference (shRNA) in neuroblastoma SH-SY5Y cells. We found that silencing of YB-1 decreased the proliferation, migration, and invasion of SH-SY5Y cells. At molecular level, inhibition of YB-1 decreased the expression level of PCNA as well as MMP-2 in neuroblastoma SH-SY5Y cells. Also, we discovered that YB-1 silencing sensitized SH-SY5Y cells to cisplatin and promoted the apoptosis induced by cisplatin due to down-regulation of multidrug resistance (MDR) 1 protein via NF-κB signaling pathway. Therefore, we consider that targeting YB-1 is promising for neuroblastoma treatment and for overcoming its cisplatin resistance in the development of new neuroblastoma therapeutic strategies.

Y-box-binding protein 1 contributes to IL-7-mediated survival signaling in B-cell precursor acute lymphoblastic leukemia.

Y-box-binding protein 1 (YB-1) is a regulatory protein that is associated with drug resistance and relapse in solid tumors. As YB-1 mediates some of its activity through growth factor receptor signaling dysregulation, the present study compared the expression of YB-1 and interleukin 7 (IL-7) receptor α (IL-7Rα) in pediatric B-cell precursor (BCP) acute lymphoblastic leukemia (ALL) and normal BCP cells. The expression levels of IL-7Rα and YB-1 were higher in relapsed vs. diagnostic samples of primary BCP ALL; however, co-expression was also observed in a minor BCP cell population in samples from healthy donors. Functional crosstalk between YB-1 and IL-7R was detected: Overexpression of YB-1 increased surface levels of IL-7R in B cells, and the stimulation of BCP ALL cell lines and primary samples by IL-7 activated YB-1 by phosphorylation at S102 in a phosphatidylinositol 3-kinase-independent and MEK1/2-dependent manner. Targeted knockdown of YB-1 reduced IL-7-mediated protection against rapamycin, and an inhibitor of MEK1/2 potentiated rapamycin-mediated killing in the presence of IL-7. These data establish a novel link between two well-characterized pro-survival factors in acute leukemia, and suggest that YB-1 inhibition may represent a novel therapeutic strategy for increasing sensitivity to chemotherapy in patients with refractory acute B-cell leukemia.

Potential Role for YB-1 in Castration-Resistant Prostate Cancer and Resistance to Enzalutamide Through the Androgen Receptor V7.

Although androgen deprivation therapy for advanced prostate cancer initially exerts excellent anticancer effects, most prostate cancer treated with androgen deprivation therapy eventually recurs as castration-resistant prostate cancer (CRPC). Although aberrant kinase activation has been proposed as a mechanism of castration resistance, comprehensive kinase profiles in CRPC remain unknown. Therefore, we aimed to elucidate the kinome in CRPC as well as the role of key molecules. We utilized a kinome array in androgen-dependent LNCaP and castration-resistant CxR cells. The effect of Y-box binding protein-1 (YB-1) on androgen receptor (AR) expression was examined by quantitative polymerase chain reaction and western blot analysis. The association between polymorphisms in the YB-1 gene determined by genotyping and YB-1 expression evaluated by immunohistochemistry in prostate cancer tissues, as well as outcome in metastatic prostate cancer, were investigated by the Cochran-Armitage test and the Cox proportional hazards model, respectively. All statistical tests were two-sided. One hundred fifty-six of 180 kinase phosphorylation sites, including ERK and RSK, were activated in CRPC cells, leading to increased phosphorylation of YB-1, which is a key molecule in the progression to CRPC. YB-1 signaling regulated AR V7 expression, and YB-1 inhibition augmented the anticancer effect of enzalutamide. Moreover, polymorphism (rs12030724) in the YB-1 gene affected YB-1 expression in 93 prostate cancer tissues (YB-1 positive rate; 14.3% in TT, 40.0% in AT, and 52.9% in AA, P = .04) and associated with probability of progression in 104 metastatic prostate cancer case patients (AT/TT vs AA, hazard ratio = 0.49, 95% confidence interval = 0.32 to 0.77, P = .001). YB-1 appears to be a promising target to inhibit the development of castration resistance, even at the AR variant-expressing stage. Polymorphism in the YB-1 gene may be a promising predictive biomarker in hormonal therapy.

Inhibition of RSK/YB-1 signaling enhances the anti-cancer effect of enzalutamide in prostate cancer

Previously, we have shown that Y-box binding protein-1 (YB-1) regulates androgen receptor (AR) expression and contributes to castration resistance. However, the mechanism of YB-1 activation remains unknown. In this study, we aimed to elucidate the mechanism and role of YB-1 activation in relation to castration resistance as well as enzalutamide resistance, with a view to developing a novel therapeutic concept for castration-resistant prostate cancer (CRPC) treatment. The expression and phosphorylation levels of ribosomal S6 kinase 1 (RSK1), YB-1 and AR were examined by quantitative PCR and Western blotting using prostate cancer cells. In addition, the effects of YB-1 inhibition using specific siRNA and small molecule inhibitor SL0101 on AR expression as well as combination treatment with enzalutamide and SL0101 were examined. We found that androgen deprivation, as well as treatment with the next-generation anti-androgen enzalutamide, induced RSK1 and YB-1 activation followed by AR induction, which could be reversed by YB-1 shutdown and RSK inhibitor SL0101. SL0101 and enzalutamide exerted a synergistic tumor-suppressive effect on cell proliferation in androgen-dependent prostate cancer LNCaP cells, as well as castration-resistant C4-2 cells. Furthermore, the phosphorylation levels of RSK1 and YB-1 were elevated in castration- and enzalutamide-resistant cells, compared with their parental cells. Taken together, these findings indicate that RSK1/YB-1 signaling contributes to castration as well as enzalutamide resistance, and that the therapeutic targeting of RSK1/YB-1 signaling would be a promising novel therapy against prostate cancer, especially CRPC when combined with enzalutamide.

YB-1 suppression induces STAT3 proteolysis and sensitizes renal cancer to interferon-α.

Renal cell carcinoma (RCC) accounts for 80-95% of kidney tumors, and approximately 30% of RCC patients have metastatic disease at diagnosis. Conventional chemotherapy is not effective in patients with metastatic RCC (MRCC); therefore, immunotherapy with interferon-α (IFN-α) has been employed to improve survival. However, the response rate of MRCC to IFN-α therapy is low. We previously reported that a signal transducer and activator 3 (STAT3) polymorphism was a useful diagnostic marker to predict the response to IFN-α therapy in patients with MRCC. Therefore, we hypothesized the inhibition of STAT3 in the addition of IFN-α therapy might be useful. Moreover, the blockage of STAT3 itself has been reported to enhance the antitumor effects. However, because IFN-α is thought to elicit its therapeutic effect via enhancement of an antitumor immune response mediated by lymphocytes that can be activated by IFN-α administrations, it is probable that the suppression of STAT3 in vivo relates to autoimmune disorders. In the present study, we found Y-box binding protein-1 (YB-1) was poorly expressed in T lymphocytes, as compared with cancer tissues. YB-1 was reported to have an important effect on the STAT3 pathway. Suppression of STAT3 by YB-1 inhibition did not seem to enhance the potential risk for autoimmune disorders. Moreover, we found sensitivity to IFN-α was increased by YB-1 suppression, and this suppression did not down-regulate IFN-α activation of T lymphocytes.

Inhibition of Y-box binding protein-1 slows the growth of glioblastoma multiforme and sensitizes to temozolomide independent O6-methylguanine-DNA methyltransferase

Glioblastoma multiforme (GBM) is an aggressive type of brain tumor where <3% of newly diagnosed cases in the patients will survive >5 years. In adults, GBM is the most common type of brain tumor. It is rarer in children, where it constitutes approximately 15% of all brain tumors diagnosed. These tumors are often invasive, making surgical resection difficult. Further, they can be refractory to current therapies such as temozolomide. The current dogma is that temozolomide resistance rests on the expression of O6-methylguanine-DNA methyltransferase (MGMT) because it cleaves methylated DNA adducts formed by the drug. Our laboratory recently reported that another drug resistance gene known as the Y-box binding protein-1 (YB-1) is highly expressed in primary GBM but not in normal brain tissues based on the evaluation of primary tumors. We therefore questioned whether GBM depend on YB-1 for growth and/or response to temozolomide. Herein, we report that YB-1 inhibition reduced tumor cell invasion and growth in monolayer as well as in soft agar. Moreover, blocking this protein ultimately delayed tumor onset in mice. Importantly, inhibiting YB-1 enhanced temozolomide sensitivity in a manner that was independent of MGMT in models of adult and pediatric GBM. In conclusion, inhibiting YB-1 may be a novel way to improve the treatment of GBM.

Targeting YB-1 in HER-2 Overexpressing Breast Cancer Cells Induces Apoptosis via the mTOR/STAT3 Pathway and Suppresses Tumor Growth in Mice

The Y-box binding protein-1 (YB-1) is a transcription/translation factor that is highly expressed in primary breast tumors where it is consistently associated with poor survival. It induces human epidermal growth factor receptor (her-2) along with its dimerization partner egfr by directly binding to their promoters. In addition to promoting growth by inducing receptor tyrosine kinases, YB-1 also protects cells against apoptosis through mechanisms that have not been fully revealed. Given this, we addressed whether YB-1 might be an eventual therapeutic target for breast cancer by inhibiting it with small interfering RNAs in vitro and in vivo. Inhibiting YB-1 suppressed the growth of six of seven breast cancer cell lines that had amplified her-2 or were triple negative. Importantly, targeting YB-1 induced apoptosis in BT474-m1 and Au565 breast cancer cells known to have her-2 amplifications. The potential role of signal transducers and activators of transcription 3 (STAT3) was pursued to address the underlying mechanism for YB-1-mediated survival. Inhibition of YB-1 decreased P-STAT3(S727) but not P-STAT3(Y705) or total STAT3. This was accompanied by decreased P-ERK1/2(T202/Y204), P-mTOR(S2448), and total mammalian target of rapamycin mTOR. Furthering the role of STAT3 in these cells, we show that knocking it down recapitulated the induction of apoptosis. Alternatively, constitutively active P-STAT3 rescued YB-1-induced apoptosis. Finally, targeting YB-1 with 2 different siRNAs remarkably suppressed tumor cell growth in soft agar by >90% and delayed tumorigenesis in nude mice. We conclude that HER-2 overexpressing as well as triple-negative breast cancer cells are YB-1 dependent, suggesting it may be a good therapeutic target for these exceptionally aggressive tumors.