Yin Yang 1 positively regulates BRCA1 and inhibits mammary cancer formation

The Role of YY1 in the Regulation of LAG-3 Expression in CD8 T Cells and Immune Evasion in Cancer: Therapeutic Implications

The treatment of cancers with immunotherapies has yielded significant milestones in recent years. Amongst these immunotherapeutic strategies, the FDA has approved several checkpoint inhibitors (CPIs), primarily Anti-Programmed Death-1 (PD-1) and Programmed Death Ligand-1/2 (PDL-1/2) monoclonal antibodies, in the treatment of various cancers unresponsive to immune therapeutics. Such treatments resulted in significant clinical responses and the prolongation of survival in a subset of patients. However, not all patients responded to CPIs, due to various mechanisms of immune resistance. One such mechanism is that, in addition to PD-1 expression on CD8 T cells, other inhibitory receptors exist, such as Lymphocyte Activation Gene 3 (LAG-3), T cell Immunoglobulin Mucin 3 (TIM3), and T cell immunoreceptor with Ig and ITIM domains (TIGIT). These inhibitory receptors might be active in the presence of the above approved CPIs. Clearly, it is clinically challenging to block all such inhibitory receptors simultaneously using conventional antibodies. To circumvent this difficulty, we sought to target a potential transcription factor that may be involved in the molecular regulation of more than one inhibitory receptor. The transcription factor Yin Yang1 (YY1) was found to regulate the expression of PD-1, LAG-3, and TIM3. Therefore, we hypothesized that targeting YY1 in CD8 T cells should inhibit the expression of these receptors and, thus, prevent the inactivation of the anti-tumor CD8 T cells by these receptors, by corresponding ligands to tumor cells. This strategy should result in the prevention of immune evasion, leading to the inhibition of tumor growth. In addition, this strategy will be particularly effective in a subset of cancer patients who were unresponsive to approved CPIs. In this review, we discuss the regulation of LAG-3 by YY1 as proof of principle for the potential use of targeting YY1 as an alternative therapeutic approach to preventing the immune evasion of cancer. We present findings on the molecular regulations of both YY1 and LAG-3 expressions, the direct regulation of LAG-3 by YY1, the various approaches to targeting YY1 to evade immune evasion, and their clinical challenges. We also present bioinformatic analyses demonstrating the overexpression of LAG-3, YY1, and PD-L1 in various cancers, their associations with immune infiltrates, and the fact that when LAG-3 is hypermethylated in its promoter region it correlates with a better overall survival. Hence, targeting YY1 in CD8 T cells will result in restoring the anti-tumor immune response and tumor regression. Notably, in addition to the beneficial effects of targeting YY1 in CD8 T cells to inhibit the expression of inhibitory receptors, we also suggest targeting YY1 overexpressed in the tumor cells, which will also inhibit PD-L1 expression and other YY1-associated pro-tumorigenic activities.

The YY1-CPT1C signaling axis modulates the proliferation and metabolism of pancreatic tumor cells under hypoxia

Carnitine palmitoyltransferase 1C (CPT1C) is an enzyme that regulates tumor cell proliferation and metabolism by modulating mitochondrial function and lipid metabolism. Hypoxia, commonly observed in solid tumors, promotes the proliferation and progression of pancreatic cancer by regulating the metabolic reprogramming of tumor cells. So far, the metabolic regulation of hypoxic tumor cells by CPT1C and the upstream mechanisms of CPT1C remain poorly understood. Yin Yang 1 (YY1) is a crucial oncogene for pancreatic tumorigenesis and acts as a transcription factor that is involved in multiple metabolic processes. This study aimed to elucidate the relationship between YY1 and CPT1C under hypoxic conditions and explore their roles in hypoxia-induced proliferation and metabolic alterations of tumor cells. The results showed enhancements in the proliferation and metabolism of PANC-1 cells under hypoxia, as evidenced by increased cell growth, cellular ATP levels, up-regulation of mitochondrial membrane potential, and decreased lipid content. Interestingly, knockdown of YY1 or CPT1C inhibited hypoxia-induced rapid cell proliferation and vigorous cell metabolism. Importantly, for the first time, we reported that YY1 directly activated the transcription of CPT1C and clarified that CPT1C was a novel target gene of YY1. Moreover, the YY1 and CPT1C were found to synergistically regulate the proliferation and metabolism of hypoxic cells through transfection with YY1 siRNA to CRISPR/Cas9-CPT1C knockout PANC-1 cells. Taken together, these results indicated that the YY1-CPT1C axis could be a new target for the intervention of pancreatic cancer proliferation and metabolism.

Transcription Factor yin-Yang 1 augments nucleoporin 93 oncogene activity and modulates bladder Cancer malignancy

OBJECTIVE

This study aims to investigate the functional interplay between transcription factor YY1 and nucleoporin 93 (NUP93) in regulating the malignancy of bladder cancer cells.

METHODS

NUP93 expressions in bladder cancer tissues and normal counterparts were analyzed using a public dataset and clinical samples. NUP93 and Yin Yang 1 (YY1) mRNA expression and protein levels in T24 and RT4 cells were determined by Quantitative real-time polymerase chain reaction (qRT-PCR) and Western blotting. The effect of NUP93 knockdown on the proliferation, migration, and invasion capabilities of cells was evaluated. Concurrently, transcriptional regulation of NUP93 by YY1 was confirmed using a dual luciferase assay. The effect of NUP93 knockdown on tumorigenesis was evaluate in a subcutaneous xenograft mouse model.

RESULTS

Elevated levels of NUP93 in bladder cancer tissues and cell lines were observed. Silencing NUP93 significantly suppressed glycolysis, impeded the growth, migration, invasion and tumor formation of bladder cancer cells. The transcription factor YY1 acted as a positive regulator to upregulate NUP93 expression. YY1 overexpression partially rescued the effects of NUP93 silencing on bladder cancer cells.

CONCLUSION

Our results uncovered transcription factor YY1 as a positive regulator of NUP93 expression, and NUP93 serves as an oncogenic factor to sustain the malignancy of bladder cancer cells. These findings suggest that targeting the YY1-NUP93 axis could offer novel therapeutic strategies for bladder cancer treatment.

Activation of the YY1-UGT2B7 Axis Promotes Mammary Estrogen Homeostasis Dysregulation and Exacerbates Breast Tumor Metastasis

Metastasis is the most common pathway of cancer death. The lack of effective predictors of breast cancer metastasis is a pressing issue in clinical practice. Therefore, exploring the mechanism of breast cancer metastasis to uncover reliable predictors is very important for the clinical treatment of breast cancer patients. In this study, tandem mass tag quantitative proteomics technology was used to detect protein content in primary breast tumor tissue samples from patients with metastatic and nonmetastatic breast cancer at diagnosis. We found that the high expression of yin-yang 1(YY1) is strongly associated with poor prognosis in high-grade breast cancer. YY1 expression was detected in both clinical tumor tissue samples and tumor tissue samples from mammary-specific polyomavirus middle T antigen overexpression mouse model mice. We demonstrated that upregulation of YY1 expression was closely associated with breast cancer metastasis and that high YY1 expression could promote the migratory invasive ability of breast cancer cells. Mechanistically, YY1 directly binds to the UGT2B7 mRNA initiation sequence ATTCAT, thereby transcriptionally regulating the inhibition of UGT2B7 expression. UGT2B7 can regulate the development of breast cancer by regulating estrogen homeostasis in the breast, and the abnormal accumulation of estrogen, especially 4-OHE2, promotes the migration and invasion of breast cancer cells, ultimately causing the development of breast cancer metastasis. In conclusion, YY1 can regulate the UGT2B7-estrogen metabolic axis and induce disturbances in estrogen metabolism in breast tumors, ultimately leading to breast cancer metastasis. Disturbances in estrogen metabolism in the breast tissue may be an important risk factor for breast tumor progression and metastasis SIGNIFICANCE STATEMENT: In this study, we propose for the first time a regulatory relationship between YY1 and the UGT2B7/estrogen metabolism axis and explore the molecular mechanism. Our study shows that the YY1/UGT2B7/estrogen axis plays an important role in the development and metastasis of breast cancer. This study further elucidates the potential mechanisms of YY1-mediated breast cancer metastasis and the possibility and promise of YY1 as a predictor of cancer metastasis.

YY1 is regulated by ALKBH5-mediated m6A modification and promotes autophagy and cancer progression through targeting ATG4B

YY1 affects tumorigenesis and metastasis in multiple ways. However, the function of YY1 and the potential mechanisms through which it operates in gastric cancer (GC) progression by regulating autophagy remains poorly understood. This study aimed to assess the essential transcription factors (TFs) involved in autophagy regulation in GC. Western blot, RFP-GFP-LC3 double fluorescence and transmission electron microscopy (TEM) assays were used to probe autophagy activity in GC cells. Methylated RNA immunoprecipitation (MeRIP) was utilized to evaluate the ALKBH5-regulated m6A levels of YY1. Gain- and loss-of-function assays were employed in the scrutiny of the biological effects of the ALKBH5/YY1/ATG4B axis on cancer cell proliferation and invasion abilities in vitro. Per the findings, YY1 was identified as a crucial transcriptional activator of cancer autophagy-related genes and promoted the proliferation and aggressiveness of cancer cells associated with enhanced ATG4B-mediated autophagy. However, ectopic ALKBH5 expression abolished the YY1-induced effect via m6A modification. Importantly, YTHDF1 facilitated the mRNA stability of YY1 through m6A recognition. Collectively, this study found that YY1 was regulated by ALKBH5 and YTHDF1-mediated m6A modification and served as an autophagy-dependent tumor driver to accelerate cancer progression through ATG4B transactivation, providing an exploitable therapeutic target for GC.

Targeting Transcription Factor YY1 for Cancer Treatment: Current Strategies and Future Directions

Cancer represents a significant and persistent global health burden, with its impact underscored by its prevalence and devastating consequences. Whereas numerous oncogenes could contribute to cancer development, a group of transcription factors (TFs) are overactive in the majority of tumors. Targeting these TFs may also combat the downstream oncogenes activated by the TFs, making them attractive potential targets for effective antitumor therapeutic strategy. One such TF is yin yang 1 (YY1), which plays crucial roles in the development and progression of various tumors. In preclinical studies, YY1 inhibition has shown efficacy in inhibiting tumor growth, promoting apoptosis, and sensitizing tumor cells to chemotherapy. Recent studies have also revealed the potential of combining YY1 inhibition with immunotherapy for enhanced antitumor effects. However, clinical translation of YY1-targeted therapy still faces challenges in drug specificity and delivery. This review provides an overview of YY1 biology, its role in tumor development and progression, as well as the strategies explored for YY1-targeted therapy, with a focus on their clinical implications, including those using small molecule inhibitors, RNA interference, and gene editing techniques. Finally, we discuss the challenges and current limitations of targeting YY1 and the need for further research in this area.

Prognostic Implication of YY1 and CP2c Expression in Patients with Primary Breast Cancer

Yin Yang 1 (YY1) is a transcription factor that regulates epigenetic pathways and protein modifications. CP2c is a transcription factor that functions as an oncogene to regulate cell proliferation. YY1 is known to interact with CP2c to suppress CP2c's transcriptional activity. This study aimed to investigate YY1 and CP2c expression in breast cancer and prognostic implications. In this study, YY1 and CP2c expression was evaluated using immunohistochemical staining, Western blot and RT-PCR assays. Of 491 patients with primary breast cancer, 138 patients showed YY1 overexpression. Luminal subtype and early stage were associated with overexpression (p < 0.001). After a median follow-up of 68 months, YY1 overexpression was found to be associated with a better prognosis (disease-free survival rates of 92.0% vs. 79.2%, p = 0.014). In Cox proportional hazards model, YY1 overexpression functioned as an independent prognostic factor after adjustment of hormone receptor/HER2 status and tumor size (hazard ratio of 0.50, 95% CI 0.26-0.98, p = 0.042). Quantitative analysis of YY1 and CP2c protein expression in tumors revealed a negative correlation between them. In conclusion, YY1 overexpression is a favorable prognostic biomarker in patients with breast cancer, and it has a negative correlation with CP2c at the protein level.

Targeting HSF1 for cancer treatment: mechanisms and inhibitor development

Heat Shock Factor 1 (HSF1) is a master regulator of heat shock responsive signaling. In addition to playing critical roles in cellular heat shock response, emerging evidence suggests that HSF1 also regulates a non-heat shock responsive transcriptional network to handle metabolic, chemical, and genetic stress. The function of HSF1 in cellular transformation and cancer development has been extensively studied in recent years. Due to important roles for HSF1 for coping with various stressful cellular states, research on HSF1 has been very active. New functions and molecular mechanisms underlying these functions have been continuously discovered, providing new targets for novel cancer treatment strategies. In this article, we review the essential roles and mechanisms of HSF1 action in cancer cells, focusing more on recently discovered functions and their underlying mechanisms to reflect the new advances in cancer biology. In addition, we emphasize new advances with regard to HSF1 inhibitors for cancer drug development.

Dissecting the roles and clinical potential of YY1 in the tumor microenvironment

Yin-Yang 1 (YY1) is a member of the GLI-Kruppel family of zinc finger proteins and plays a vital dual biological role in cancer as an oncogene or a tumor suppressor during tumorigenesis and tumor progression. The tumor microenvironment (TME) is identified as the “soil” of tumor that has a critical role in both tumor growth and metastasis. Many studies have found that YY1 is closely related to the remodeling and regulation of the TME. Herein, we reviewed the expression pattern of YY1 in tumors and summarized the function and mechanism of YY1 in regulating tumor angiogenesis, immune and metabolism. In addition, we discussed the potential value of YY1 in tumor diagnosis and treatment and provided a novel molecular strategy for the clinical diagnosis and treatment of tumors.

BAP1 loss induces mitotic defects in mesothelioma cells through BRCA1-dependent and independent mechanisms

The tumour suppressor BRCA1-associated protein 1 (BAP1) is the most frequently mutated cancer gene in mesothelioma. Here we report novel functions for BAP1 in mitotic progression highlighting the relationship between BAP1 and control of genome stability in mesothelioma cells with therapeutic implications. Depletion of BAP1 protein induced proteasome-mediated degradation of BRCA1 in mesothelioma cells while loss of BAP1 correlated with BRCA1 loss in mesothelioma patient tumour samples. BAP1 loss also led to mitotic defects that phenocopied the loss of BRCA1 including spindle assembly checkpoint failure, centrosome amplification and chromosome segregation errors. However, loss of BAP1 also led to additional mitotic changes that were not observed upon BRCA1 loss, including an increase in spindle length and enhanced growth of astral microtubules. Intriguingly, these consequences could be explained by loss of expression of the KIF18A and KIF18B kinesin motors that occurred upon depletion of BAP1 but not BRCA1, as spindle and astral microtubule defects were rescued by re-expression of KIF18A and KIF18B, respectively. We therefore propose that BAP1 inactivation causes mitotic defects through BRCA1-dependent and independent mechanisms revealing novel routes by which mesothelioma cells lacking BAP1 may acquire genome instability and exhibit altered responses to microtubule-targeted agents.

YY1 promotes pancreatic cancer cell proliferation by enhancing mitochondrial respiration

KRAS-driven metabolic reprogramming is a known peculiarity features of pancreatic ductal adenocarcinoma (PDAC) cells. However, the metabolic roles of other oncogenic genes, such as YY1, in PDAC development are still unclear. In this study, we observed significantly elevated expression of YY1 in human PDAC tissues, which positively correlated with a poor disease progression. Furthermore, in vitro studies confirmed that YY1 deletion inhibited PDAC cell proliferation and tumorigenicity. Moreover, YY1 deletion led to impaired mitochondrial RNA expression, which further inhibited mitochondrial oxidative phosphorylation (OXPHOS) complex assembly and altered cellular nucleotide homeostasis. Mechanistically, the impairment of mitochondrial OXPHOS function reduced the generation of aspartate, an output of the tricarboxylic acid cycle (TCA), and resulted in the inhibition of cell proliferation owing to unavailability of aspartate-associated nucleotides. Conversely, exogenous supplementation with aspartate fully restored PDAC cell proliferation. Our findings suggest that YY1 promotes PDAC cell proliferation by enhancing mitochondrial respiration and the TCA, which favors aspartate-associated nucleotide synthesis. Thus, targeting nucleotide biosynthesis is a promising strategy for PDAC treatment.

Yin Yang 1 regulates ITGAV and ITGB1, contributing to improved prognosis of colorectal cancer

Yin Yang 1 (YY1) is a multifunctional transcription factor with critical roles in carcinogenesis and metastasis. However, its biological role and clinical impact in colorectal cancer (CRC) remain unclear. In the present study, the function and underlying molecular mechanisms of YY1 in CRC progression were investigated. The immunohistochemistry (IHC) of 143 CRC tissues revealed a significant correlation of low YY1 expression with aggressive clinicopathological features, increased metastasis and recurrence and poor patient survival. Multivariate analysis identified low YY1 expression as an independent poor prognostic factor. Subsequently, the IHC of 66 paired CRC primary tumor and liver metastasis tissues revealed that low YY1 expression in the primary CRC was significantly associated with multiple liver metastases, major hepatectomy, extrahepatic metastasis and poor prognosis. In vitro experiments revealed that YY1 knockdown promoted the migration and invasion of CRC cells. To examine the downstream genes of YY1, a cDNA microarray assay was conducted and the differentially expressed genes between the YY1‑knockdown and control cells were compared. Integrin alpha V (ITGAV) and integrin beta 1 (ITGB1) were identified as upregulated hub genes using gene enrichment analysis and protein‑protein interaction analyses. Western blotting and IHC confirmed YY1 expression to be negatively correlated with ITGAV and ITGB1 expression. In summary, it was revealed that YY1, as a tumor‑suppressor in CRC, contributes to the survival of patients with CRC. Low YY1 expression was associated with the poor prognosis of the patients with primary CRC and liver metastases. YY1 suppressed the expression of ITGAV and ITGB1, and this transcriptional regulation may lead to the suppression of CRC cell migration and invasion.

High expression of eIF4E is associated with tumor macrophage infiltration and leads to poor prognosis in breast cancer

Background

The expression and activation of eukaryotic translation initiation factor 4E (eIF4E) is associated with cell transformation and tumor initiation, but the functional role and the mechanism whereby it drives immune cell infiltration in breast cancer (BRCA) remain uncertain.

Methods

Oncomine, Timer and UALCAN were used to analyze the expression of eIF4E in various cancers. PrognoScan, Kaplan–Meier plotter, and GEPIA were utilized to analyze the prognostic value of eIF4E in select cancers. In vitro cell experiments were used to verify the role of eIF4E in promoting the progression of BRCA. ImmuCellAI and TIMER database were used to explore the relationship between eIF4E and tumor infiltrating immune cells. The expression of a macrophage marker (CD68⁺) and an M2-type marker (CD163⁺) was evaluated using immunohistochemistry in 50 invasive BRCA samples on tissue microarrays. The Human Protein Atlas (HPA) database was used to show the expression of eIF4E and related immune markers. LinkedOmics and NetworkAnalyst were used to build the signaling network.

Results

Through multiple dataset mining, we found that the expression of eIF4E in BRCA was higher than that in normal tissues, and patients with increased eIF4E expression had poorer survival and a higher cumulative recurrence rate in BRCA. At the cellular level, BRCA cell migration and invasion were significantly inhibited after eIF4E expression was inhibited by siRNA. Immune infiltration analysis showed that the eIF4E expression level was significantly associated with the tumor purity and immune infiltration levels of different immune cells in BRCA. The results from immunohistochemical (IHC) staining further proved that the expression of CD68⁺ and CD163⁺ were significantly increased and correlated with poor prognosis in BRCA patients (P < 0.05). Finally, interaction network and functional enrichment analysis revealed that eIF4E was mainly involved in tumor-related pathways, including the cell adhesion molecule pathway and the JAK-STAT signaling pathway.

Conclusions

Our study has demonstrated that eIF4E expression has prognostic value for BRCA patients. eIF4E may act as an essential regulator of tumor macrophage infiltration and may participate in macrophage M2 polarization.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-09010-0.

CRTAC1 (Cartilage acidic protein 1) inhibits cell proliferation, migration, invasion and epithelial-mesenchymal transition (EMT) process in bladder cancer by downregulating Yin Yang 1 (YY1) to inactivate the TGF-β pathway

Cartilage acidic protein 1 (CRTAC1) is predicted to be aberrantly expressed in bladder cancer based on bioinformatics analysis. However, its functions and molecular mechanism in bladder cancer remain elusive. This study aimed to explore the role of CRTAC1 in bladder cancer. The mRNA and protein levels of CRTAC1 and Yin Yang 1 (YY1) were detected by reverse transcription quantitative polymerase chain reaction and western blotting. We found that CRTAC1 was downregulated in bladder cancer tissues and cells. Cell Counting Kit-8 assays, colony formation assays, wound healing assays and Transwell assays and western blotting revealed that CRTAC1 overexpression inhibited cell viability, proliferation, migration, invasion and epithelial-mesenchymal transition (EMT) process in bladder cancer, while CRTAC1 knockdown exerted opposite effects on these malignant behaviors. Mechanistically, CRTAC1 targeted YY1 in bladder cancer cells. YY1 was upregulated in bladder cancer tissues and cells. CRTAC1 negatively modulated the mRNA and protein expression of YY1 in bladder cancer cells. Co-localization of CRTAC1 and YY1 expression was assessed using immunofluorescence staining and Co-Immunoprecipitation assays. The interaction between CRTAC1 and YY1 was explored by Chromatin immunoprecipitation and luciferase reporter assays. Moreover, CRTAC1 inactivated the TGF-β pathway by downregulating YY1 expression. Protein levels of factors associated with the TGF-β pathway were examined by western blotting. Rescue assays indicated that CRTAC1 inhibited malignant behaviors of bladder cancer cells by targeting YY1. Overall, CRTAC1 inhibited malignant phenotypes of bladder cancer cells by targeting YY1 to inactivate the TGF-β pathway.

Activation of FGFR2 Signaling Suppresses BRCA1 and Drives Triple-Negative Mammary Tumorigenesis That is Sensitive to Immunotherapy

Fibroblast growth factor receptor 2 (FGFR2) is a membrane-spanning tyrosine kinase that mediates FGF signaling. Various FGFR2 alterations are detected in breast cancer, yet it remains unclear if activation of FGFR2 signaling initiates tumor formation. In an attempt to answer this question, a mouse model berrying an activation mutation of FGFR2 (FGFR2-S252W) in the mammary gland is generated. It is found that FGF/FGFR2 signaling drives the development of triple-negative breast cancer accompanied by epithelial-mesenchymal transition that is regulated by FGFR2-STAT3 signaling. It is demonstrated that FGFR2 suppresses BRCA1 via the ERK-YY1 axis and promotes tumor progression. BRCA1 knockout in the mammary gland of the FGFR2-S252W mice significantly accelerated tumorigenesis. It is also shown that FGFR2 positively regulates PD-L1 and that a combination of FGFR2 inhibition and immune checkpoint blockade kills cancer cells. These data suggest that the mouse models mimic human breast cancers and can be used to identify actionable therapeutic targets.

Roles of the Immune/Methylation/Autophagy Landscape on Single-Cell Genotypes and Stroke Risk in Breast Cancer Microenvironment

This study sought to perform integrative analysis of the immune/methylation/autophagy landscape on breast cancer prognosis and single-cell genotypes. Breast Cancer Recurrence Risk Score (BCRRS) and Breast Cancer Prognostic Risk Score (BCPRS) were determined based on 6 prognostic IMAAGs obtained from the TCGA-BRCA cohort. BCRRS and BCPRS, respectively, were used to construct a risk prediction model of overall survival and progression-free survival. Predictive capacity of the model was evaluated using clinical data. Analysis showed that BCRRS is associated with a high risk of stroke. In addition, PPI and drug-ceRNA networks based on differences in BCPRS were constructed. Single cells were genotyped through integrated scRNA-seq of the TNBC samples based on clustering results of BCPRS-related genes. The findings of this study show the potential regulatory effects of IMAAGs on breast cancer tumor microenvironment. High AUCs of 0.856 and 0.842 were obtained for the OS and PFS prognostic models, respectively. scRNA-seq analysis showed high expression levels of adipocytes and adipose tissue macrophages (ATMs) in high BCPRS clusters. Moreover, analysis of ligand-receptor interactions and potential regulatory mechanisms were performed. The LINC00276&MALAT1/miR-206/FZD4-Wnt7b pathway was also identified which may be useful in future research on targets against breast cancer metastasis and recurrence. Neural network-based deep learning models using BCPRS-related genes showed that these genes can be used to map the tumor microenvironment. In summary, analysis of IMAAGs, BCPRS, and BCRRS provides information on the breast cancer microenvironment at both the macro- and microlevels and provides a basis for development of personalized treatment therapy.

Effect of the transcription factor YY1 on the development of pancreatic endocrine and exocrine tumors: a narrative review

Pancreatic tumors are classified into endocrine and exocrine types, and the clinical manifestations in patients are nonspecific. Most patients, especially those with pancreatic ductal adenocarcinoma (PDAC), have lost the opportunity to receive for the best treatment at the time of diagnosis. Although chemotherapy and radiotherapy have shown good therapeutic results in other tumors, their therapeutic effects on pancreatic tumors are minimal. A multifunctional transcription factor, Yin-Yang 1 (YY1) regulates the transcription of a variety of important genes and plays a significant role in diverse tumors. Studies have shown that targeting YY1 can improve the survival time of patients with tumors. In this review, we focused on the mechanism by which YY1 affects the occurrence and development of pancreatic tumors. We found that a YY1 mutation is specific for insulinomas and has a role in driving the degree of malignancy. In addition, changes in the circadian network are a key causative factor of PDAC. YY1 promotes pancreatic clock progression and induces malignant changes, but YY1 seems to act as a tumor suppressor in PDAC and affects many biological behaviors, such as proliferation, migration, apoptosis and metastasis. Our review summarizes the progress in understanding the role of YY1 in pancreatic endocrine and exocrine tumors and provides a reasonable assessment of the potential for therapeutic targeting of YY1 in pancreatic tumors.

CircRNA circYY1 (hsa_circ_0101187) Modulates Cell Glycolysis and Malignancy Through Regulating YY1 Expression by Sponging miR-769-3p in Breast Cancer

Background

Breast cancer (BC) is a highly heterogeneous malignant tumor that affects women’s health. Circular RNAs (circRNAs) are involved in tumor growth in many cancers. However, the role of hsa_circ_0101187 (circYY1) in BC is still unclear.

Methods

Expression of circYY1, microRNA (miR)-769-3p, and YY1 (Yin Yang 1) mRNA was tested by quantitative real-time polymerase chain reaction (qRT-PCR). Cell viability, colony formation, migration, and invasion were analyzed with MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide), colony formation, and transwell assays. Glucose uptake, lactate product, and ATP (adenosine triphosphate) content were detected with corresponding kits. Several protein levels were measured with Western blotting. The regulatory mechanisms of the circYY1, miR-769-3p, and YY1 were validated by RNA immunoprecipitation (RIP) assay, dual-luciferase reporter assay, and/or RNA pull-down assay. The role of circYY1 in BC was confirmed by xenograft assay.

Results

CircYY1 and YY1 were upregulated in BC, while miR-769-3p had an opposing result. Also, BC patients with high circYY1 expression had a poor prognosis. Downregulation of circYY1 decreased xenograft tumor growth in vivo. Both circYY1 inhibition and miR-769-3p elevation constrained BC cell viability, colony formation, migration, invasion, and glycolysis in vitro. CircYY1 acted as a sponge for miR-769-3p, which targeted YY1. CircYY1 sponged miR-769-3p to modulate YY1 expression. Both miR-769-3p inhibition and YY1 upregulation antagonized circYY1 silencing-mediated influence on malignancy and glycolysis of BC cells.

Conclusion

CircYY1 promoted glycolysis and tumor growth via increasing YY1 expression through sponging miR-769-3p in BC, offering a promising therapeutic target and prognostic biomarker for BC.

Loss of YY1 expression predicts unfavorable prognosis in stage III colorectal cancer

Background

Yin Yang 1 (YY1), the multifunctional transcription factor, has recently been assigned biological properties related to human malignancies. YY1 can facilitate both tumor suppression and tumor growth. The conflicting role of YY1 in human malignancies is not yet fully explained.

Objective

In this study, we determined the clinicopathologic significance and prognostic role of YY1 in stage III colorectal cancer (CRC).

Materials and Methods

YY1 expression was evaluated immunohistochemically in tissue microarray from 345 CRCs. YY1 expression was scored by the proportion of tumor cells with nuclear staining into 4 scores (0, none; 1+, ≤10%; 2+, 10 to ≤25%; 3+, >25%). A score of 0 and 1 were considered as loss of expression.

Results

Loss of YY1 expression was observed in 49 (14.2%) out of 345 CRCs and was associated with larger tumor size (P = 0.004), tumor deposit (P = 0.008), and higher pathologic tumor (pT) stage (P = 0.004). In stage III group, loss of YY1 expression was associated with larger tumor size (P = 0.027) and tumor deposit (P = 0.011). Kaplan-Meier survival curves revealed no significant difference between patients with YY1 loss and patients with intact YY1 in both cancer-specific survival and recurrence-free survival (P = 0.330 and P = 0.470, respectively). In American Joint Committee on Cancer (AJCC) stage subgroup, loss of YY1 expression was associated with poor recurrence-free survival in AJCC stage III CRC (P = 0.038).

Conclusion

Loss of YY1 expression was significantly associated with aggressive phenotypes and poor patient outcome in AJCC stage III CRC.

Human Papillomavirus Infection in Head and Neck Squamous Cell Carcinomas: Transcriptional Triggers and Changed Disease Patterns

Head and neck squamous cell carcinoma (HNSCC) is a heterogeneous group of cancers. Collectively, HNSCC ranks sixth in incidence rate worldwide. Apart from classical risk factors like tobacco and alcohol, infection of human papillomavirus (HPV) is emerging as a discrete risk factor for HNSCC. HPV-positive HNSCC represent a distinct group of diseases that differ in their clinical presentation. These lesions are well-differentiated, occur at an early age, and have better prognosis. Epidemiological studies have demonstrated a specific increase in the proportions of the HPV-positive HNSCC. HPV-positive and HPV-negative HNSCC lesions display different disease progression and clinical response. For tumorigenic-transformation, HPV essentially requires a permissive cellular environment and host cell factors for induction of viral transcription. As the spectrum of host factors is independent of HPV infection at the time of viral entry, presumably entry of HPV only selects host cells that are permissive to establishment of HPV infection. Growing evidence suggest that HPV plays a more active role in a subset of HNSCC, where they are transcriptionally-active. A variety of factors provide a favorable environment for HPV to become transcriptionally-active. The most notable are the set of transcription factors that have direct binding sites on the viral genome. As HPV does not have its own transcription machinery, it is fully dependent on host transcription factors to complete the life cycle. Here, we review and evaluate the current evidence on level of a subset of host transcription factors that influence viral genome, directly or indirectly, in HNSCC. Since many of these transcription factors can independently promote carcinogenesis, the composition of HPV permissive transcription factors in a tumor can serve as a surrogate marker of a separate molecularly-distinct class of HNSCC lesions including those cases, where HPV could not get a chance to infect but may manifest better prognosis.

YY1-mediated long non-coding RNA Kcnq1ot1 promotes the tumor progression by regulating PTEN via DNMT1 in triple negative breast cancer

Triple-negative breast cancer (TNBC) is an aggressive cancer, and rapidly progresses following relapse in advanced stage. This cancer is usually associated with worse overall survival, so the carcinogenesis of TNBC needs to be further explored to find more effective therapies. In this study, we intended to identify the roles of YY1-mediated long non-coding RNA Kcnq1ot1 in TNBC. First, the paired samples of tumor tissues and adjacent tissues were collected to determine YY1, lncRNA Kcnq1ot1, and PTEN expression using RT-qPCR and Western blot analysis followed by analysis of the relationship between them and patient survival. The results revealed that YY1 and lncRNA Kcnq1ot1 were upregulated in TNBC tissues, and high expression of YY1 and lncRNA Kcnq1ot1 was associated with poor patient survival. Then, ChIP and MSP assays were employed to explore interactions between YY1, lncRNA Kcnq1ot1, and PTEN gene. We obtained that YY1 upregulated lncRNA Kcnq1ot1, which mediated PTEN methylation via DNMT1, thus decreasing PTEN expression. Afterward, TNBC cells were examined for their viability using functional assays with the results displaying that overexpression of YY1 facilitated TNBC cell proliferation, invasion, and migration. Mechanistically, upregulated YY1 repressed tumor growth by inhibiting PTEN via upregulation of lncRNA Kcnq1ot1. Mouse models were also constructed, and the above effects of YY1, lncRNA Kcnq1ot1, and PTEN on TNBC were also established in vivo. Taken together, this study demonstrates that the silencing of YY1 exerted tumor-suppressive effects on TNBC by modulating lncRNA Kcnq1ot1/DNMT1/PTEN pathway, in support of further investigation into anti-tumor therapy for TNBC.

Dysregulated YY1/PRMT5 axis promotes the progression and metastasis of laryngeal cancer by targeting Hippo pathway

Metastases lead to high mortality in laryngeal cancer, but the regulation of its underlying mechanisms remains elusive. We identified Protein arginine methyltransferase 5 (PRMT5) was significantly up‐regulated in laryngeal cancer tissues, which predicts poor patient prognosis. Functional assays demonstrated that PRMT5 overexpression promoted the invasive capacity and lymph node metastasis in vitro and in vivo. Mechanistic experiments suggested that LATS2 was a downstream target of PRMT5. PRMT5 inhibition increased the expression of LATS2 and YAP phosphorylation in laryngeal cancer cells, thereby promoting laryngeal cancer metastasis. Furthermore, informatics and experimental data confirmed that PRMT5 gene was transcriptionally activated by YY1. Collectively, our results unravelled the important role of PRMT5 in laryngeal cancer tumorigenesis and metastasis. The dysregulation YY1/PRMT5/LATS2/YAP axis may contribute to laryngeal cancer progression; thus, PRMT5 may be a potential therapeutic strategy for patients with laryngeal cancer.

Identification of DHX36 as a tumour suppressor through modulating the activities of the stress-associated proteins and cyclin-dependent kinases in breast cancer

The nucleic acid guanine-quadruplex structures (G4s) are involved in many aspects of cancer progression. The DEAH-box polypeptide 36 (DHX36) has been identified as a dominant nucleic acid helicase which targets and disrupts DNA and RNA G4s in an ATP-dependent manner. However, the actual role of DHX36 in breast cancer remains unknown. In this study, we observed that the gene expression of DHX36 was positively associated with patient survival in breast cancer. The abundance of DHX36 is also linked with pathologic conditions and the stage of breast cancer. By using the xenograft mouse model, we demonstrated that the stable knockdown of DHX36 via lentivirus in breast cancer cells significantly promoted tumour growth. We also found that, after the DHX36 knockdown (KD), the invasion of triple-negative breast cancer cells was enhanced. In addition, we found a significant increase in the number of cells in the S-phase and a reduction of apoptosis with the response to cisplatin. DHX36 KD also desensitized the cytotoxic cellular response to paclitaxel and cisplatin. Transcriptomic profiling analysis by RNA sequencing indicated that DHX36 altered gene expression profile through the upstream activation of TNF, IFNγ, NFκb and TGFβ1. High throughput signalling analysis showed that one cluster of stress-associated kinase proteins including p53, ROCK1 and JNK were suppressed, while the mitotic checkpoint protein-serine kinases CDK1 and CDK2 were activated, as a consequence of the DHX36 knockdown. Our study reveals that DHX36 functions as a tumour suppressor and may be considered as a potential therapeutic target in breast cancer.

Transcription factor YY1 mediates epithelial-mesenchymal transition through the TGFβ signaling pathway in bladder cancer

Bladder cancer is one of the most aggressive urothelial tumors. Previous studies have suggested that epithelial-mesenchymal transition (EMT) contributes to bladder cancer progression. However, the regulatory network of EMT in bladder cancer remains elusive. In this study, we found Yin Yang 1 (YY1) is a critical regulator of EMT in bladder cancer. First, we showed that YY1 was upregulated in bladder cancer tissues than that in adjacent normal tissues. Then, we proved that YY1 promoted EMT of bladder cancer cells. Further experiments indicated that YY1 affected the EMT of bladder cancer through transforming growth factor-β (TGFβ) signaling pathway. Taken together, our study identifies YY1 as a key EMT driver in bladder cancer, suggesting it as a potential therapeutic target.

Transcriptional Factor Yin Yang 1 Promotes the Stemness of Breast Cancer Cells by Suppressing miR-873-5p Transcriptional Activity

Transcription factor Yin Yang 1 (YY1) is upregulated in multiple tumors and plays essential roles in tumor proliferation and metastasis. However, the function of YY1 in breast cancer stemness remains unclear. Herein, we found that YY1 expression was negatively correlated with the overall survival and relapse-free survival of breast cancer patients and positively correlated with the expression of stemness markers in breast cancer. Overexpression of YY1 increased the expression of stemness markers, elevated CD44⁺CD24⁻ cell sub-population, and enhanced the capacity of cell spheroid formation and tumor-initiation. In contrast, YY1 knockdown exhibited the opposite effects. Mechanistically, YY1 decreased microRNA-873-5p (miR-873-5p) level by recruiting histone deacetylase 4 (HDAC4) and HDAC9 to miR-873-5p promoter and thus increasing the deacetylation level of miR-873-5p promoter. Sequentially, YY1 activated the downstream PI3K/AKT and ERK1/2 pathways, which have been confirmed to be suppressed by miR-873-5p in our recent work. Moreover, the suppressed effect of YY1/miR-873-5p axis on the stemness of breast cancer cells was partially dependent on PI3K/AKT and ERK1/2 pathways. Finally, it was found that the YY1/miR-873-5p axis is involved in the chemoresistance of breast cancer cells. Our study defines a novel YY1/miR-873-5p axis responsible for the stemness of breast cancer cells.

The YY1/miR-548t-5p/CXCL11 signaling axis regulates cell proliferation and metastasis in human pancreatic cancer

Pancreatic cancer (PC) is a malignant tumor with a poor prognosis and high mortality. However, the biological role of miR-548t-5p in PC has not been reported. In this study, we found that miR-548t-5p expression was significantly decreased in PC tissues compared with adjacent tissues, and that low miR-548t-5p expression was associated with malignant PC behavior. In addition, high miR-548t-5p expression inhibited the proliferation, migration, and invasion of PC cell lines. Regarding the molecular mechanism, the luciferase reporter gene, chromatin immunoprecipitation (ChIP), and functional recovery assays revealed that YY1 binds to the miR-548t-5p promoter and positively regulates the expression and function of miR-548t-5p. miR-548t-5p also directly regulates CXCL11 to inhibit its expression. A high level of CXCL11 was associated with worse Tumor Node Metastasis (TNM) staging in patients with PC, enhancing proliferation and metastasis in PC cells. Our study shows that the YY1/miR-548t-5p/CXCL11 axis plays an important role in PC and provides a new potential candidate for the treatment of PC.

Human Papillomavirus Infection in Head and Neck Squamous Cell Carcinomas: Transcriptional Triggers and Changed Disease Patterns

Head and neck squamous cell carcinoma (HNSCC) is a heterogeneous group of cancers. Collectively, HNSCC ranks sixth in incidence rate worldwide. Apart from classical risk factors like tobacco and alcohol, infection of human papillomavirus (HPV) is emerging as a discrete risk factor for HNSCC. HPV-positive HNSCC represent a distinct group of diseases that differ in their clinical presentation. These lesions are well-differentiated, occur at an early age, and have better prognosis. Epidemiological studies have demonstrated a specific increase in the proportions of the HPV-positive HNSCC. HPV-positive and HPV-negative HNSCC lesions display different disease progression and clinical response. For tumorigenic-transformation, HPV essentially requires a permissive cellular environment and host cell factors for induction of viral transcription. As the spectrum of host factors is independent of HPV infection at the time of viral entry, presumably entry of HPV only selects host cells that are permissive to establishment of HPV infection. Growing evidence suggest that HPV plays a more active role in a subset of HNSCC, where they are transcriptionally-active. A variety of factors provide a favorable environment for HPV to become transcriptionally-active. The most notable are the set of transcription factors that have direct binding sites on the viral genome. As HPV does not have its own transcription machinery, it is fully dependent on host transcription factors to complete the life cycle. Here, we review and evaluate the current evidence on level of a subset of host transcription factors that influence viral genome, directly or indirectly, in HNSCC. Since many of these transcription factors can independently promote carcinogenesis, the composition of HPV permissive transcription factors in a tumor can serve as a surrogate marker of a separate molecularly-distinct class of HNSCC lesions including those cases, where HPV could not get a chance to infect but may manifest better prognosis.

The Two Sides of YY1 in Cancer: A Friend and a Foe

Yin Yang 1 (YY1), a dual function transcription factor, is known to regulate transcriptional activation and repression of many genes associated with multiple cellular processes including cellular differentiation, DNA repair, autophagy, cell survival vs. apoptosis, and cell division. Owing to its role in processes that upon deregulation are linked to malignant transformation, YY1 has been implicated as a major driver of many cancers. While a large body of evidence supports the role of YY1 as a tumor promoter, recent reports indicated that YY1 also functions as a tumor suppressor. The mechanism by which YY1 brings out opposing outcome in tumor growth vs. suppression is not completely clear and some of the recent reports have provided significant insight into this. Likewise, the mechanism by which YY1 functions both as a transcriptional activator and repressor is not completely clear. It is likely that the proteins with which YY1 interacts might determine its function as an activator or repressor of transcription as well as its role as a tumor suppressor or promoter. Hence, a collection of YY1-protein interactions in the context of different cancers would help us gain an insight into how YY1 promotes or suppresses cancers. This review focuses on the YY1 interacting partners and its target genes in different cancer models. Finally, we discuss the possibility of therapeutically targeting the YY1 in cancers where it functions as a tumor promoter.

LINC00673 is activated by YY1 and promotes the proliferation of breast cancer cells via the miR-515-5p/MARK4/Hippo signaling pathway

Background

An increasing number of studies have shown that long noncoding RNAs (lncRNAs) play essential roles in tumor initiation and progression. LncRNAs act as tumor promoters or suppressors by targeting specific genes via epigenetic modifications and competing endogenous RNA (ceRNA) mechanisms. In this study, we explored the function and detailed mechanisms of long intergenic nonprotein coding RNA 673 (LINC00673) in breast cancer progression.

Methods

Quantitative real-time PCR (qRT-PCR) was used to examine the expression of LINC00673 in breast cancer tissues and in adjacent normal tissues. Gain-of-function and loss-of function experiments were conducted to investigate the biological functions of LINC00673 in vitro and in vivo. We also explored the potential role of LINC00673 as a therapeutic target using antisense oligonucleotide (ASO) in vivo. RNA sequencing (RNA-seq), dual-luciferase reporter assays, chromatin immunoprecipitation (ChIP) assay, and rescue experiments were performed to uncover the detailed mechanism of LINC00673 in promoting breast cancer progression.

Results

In the present study, LINC00673 displayed a trend of remarkably increased expression in breast cancer tissues and was associated with poor prognosis in breast cancer patients. Importantly, LINC00673 depletion inhibited breast cancer cell proliferation by inhibiting the cell cycle and increasing apoptosis. Furthermore, ASO therapy targeting LINC00673 substantially suppressed breast cancer cell proliferation in vivo. Mechanistically, LINC00673 was found to act as a ceRNA by sponging miR-515-5p to regulate MARK4 expression, thus inhibiting the Hippo signaling pathway. Finally, ChIP assay showed that the transcription factor Yin Yang 1 (YY1) could bind to the LINC00673 promoter and increase its transcription in cis.

Conclusions

YY1-activated LINC00673 may exert an oncogenic function by acting as a sponge for miR-515-5p to upregulate the MARK4 and then inhibit Hippo signaling pathway, and may serve as a potential therapeutic target.

Hybrid 18F-FDG-PET/MRI Measurement of Standardized Uptake Value Coupled with Yin Yang 1 Signature in Metastatic Breast Cancer. A Preliminary Study

Purpose: Detection of breast cancer (BC) metastasis at the early stage is important for the assessment of BC progression status. Image analysis represents a valuable tool for the management of oncological patients. Our preliminary study combined imaging parameters from hybrid ¹⁸F-FDG-PET/MRI and the expression level of the transcriptional factor Yin Yang 1 (YY1) for the detection of early metastases. Methods: The study enrolled suspected n = 217 BC patients that underwent ¹⁸F-FDG-PET/MRI scans. The analysis retrospectively included n = 55 subjects. n = 40 were BC patients and n = 15 imaging-negative female individuals were healthy subjects (HS). Standard radiomics parameters were extracted from PET/MRI image. RNA was obtained from peripheral blood mononuclear cells and YY1 expression level was evaluated by real time reverse transcription polymerase chain reactions (qRT-PCR). An enzyme-linked immuosorbent assay (ELISA) was used to determine the amount of YY1 serum protein. Statistical comparison between subgroups was evaluated by Mann-Whitney U and Spearman’s tests. Results: Radiomics showed a significant positive correlation between Greg-level co-occurrence matrix (GLCM) and standardized uptake value maximum (SUVmax) (r = 0.8 and r = 0.8 respectively) in BC patients. YY1 level was significant overexpressed in estrogen receptor (ER)-positive/progesteron receptor-positive/human epidermal growth factor receptor2-negative (ER+/PR+/HER2-) subtype of BC patients with synchronous metastasis (SM) at primary diagnosis compared to metachronous metastasis (MM) and HS (p < 0.001) and correlating significantly with ¹⁸F-FDG-uptake parameter (SUVmax) (r = 0.48). Conclusions: The combination of functional ¹⁸F-FDG-PET/MRI parameters and molecular determination of YY1 could represent a novel integrated approach to predict synchronous metastatic disease with more accuracy than ¹⁸F-FDG-PET/MRI alone.

Activating transcription factor 1 promoted migration and invasion in lung cancer cells through regulating EGFR and MMP-2

Lung cancer is among the most frequently occurring cancers and the leading cause of cancer-related deaths worldwide. Nonsmall cell lung cancer is accountable for 85% to 90% of all lung cancer cases and develops distant metastases with high mortality. In this work, we elucidated the role of activating transcription factor 1 (ATF1) in migration and invasion of lung cancer cells. We found that the migration and invasion were inhibited with ATF1 silencing in lung cancer cells. By contrast, ATF1 overexpression led to promotion in migration and invasion. The alteration in ATF1 expression induced a change in the epidermal growth factor receptor (EGFR) and matrix metalloproteinases (MMP)-2 expression level in the same tendency. Thus, we provided a potential new candidate for therapies against lung cancer, showing the possible mechanism underlying the invasion and migration of lung cancer cells.

YY1 inhibits the migration and invasion of pancreatic ductal adenocarcinoma by downregulating the FER/STAT3/MMP2 signaling pathway

Pancreatic ductal adenocarcinoma (PDAC) has a poor prognosis and a high mortality rate. The transcription factor YY1 acts as an inhibitor of many types of tumors. We found that YY1 knockdown promoted the invasion and migration of PANC-1 and BxPC-3 cells; FER knockdown partially restored the promotion of pancreatic cancer caused by YY1 knockdown. In vivo experiments yielded the same results. According to luciferase reporter gene, electrophoretic mobility shift (EMSA) and chromatin immunoprecipitation (ChIP) assays, YY1 directly binds to the FER promoter region. Moreover, higher level FER expression results in a worse TNM stage and prognosis for patients with PDAC. Furthermore, by downregulating FER, YY1 inhibits the formation of the STAT3-MMP2 complex, thereby suppressing expression of MMP2 and ultimately inhibiting the migration and invasion of pancreatic cancer. Our study demonstrates that the YY1/FER/STAT3/MMP2 axis is associated with the progression of pancreatic cancer and may provide a new therapeutic target for the treatment of pancreatic cancer.

Functional interplay between YY1 and CARM1 promotes oral carcinogenesis

Coactivator associated arginine methyltransferase 1 (CARM1) has been functionally implicated in maintenance of pluripotency, cellular differentiation and tumorigenesis; where it plays regulatory roles by virtue of its ability to coactivate transcription as well as to modulate protein function as an arginine methyltransferase. Previous studies establish an oncogenic function of CARM1 in the context of colorectal and breast cancer, which correlate to its overexpressed condition. However, the mechanism behind its deregulated expression in the context of cancer has not been addressed before. In the present study we uncover an oncogenic function of CARM1 in the context of oral cancer, where it was found to be overexpressed. We also identify YY1 to be a positive regulator of CARM1 gene promoter, where silencing of YY1 in oral cancer cell line could lead to reduction in expression of CARM1. In this context, YY1 showed concomitant overexpression in oral cancer patient samples compared to adjacent normal tissue. Cell line based experiments as well as xenograft study revealed pro-neoplastic functions of YY1 in oral cancer. Transcriptomics analysis as well as qRT-PCR validation clearly indicated pro-proliferative, pro-angiogenic and pro-metastatic role of YY1 in oral cancer. We also show that YY1 is a substrate of CARM1 mediated arginine methylation, where the latter could coactivate YY1 mediated reporter gene activation in vivo. Taken together, CARM1 and YY1 were found to regulate each other in a positive feedback loop to facilitate oral cancer progression.

YY1 regulates cancer cell immune resistance by modulating PD-L1 expression

Recent advances in the treatment of various cancers have resulted in the adaptation of several novel immunotherapeutic strategies. Notably, the recent intervention through immune checkpoint inhibitors has resulted in significant clinical responses and prolongation of survival in patients with several therapy-resistant cancers (melanoma, lung, bladder, etc.). This intervention was mediated by various antibodies directed against inhibitory receptors expressed on cytotoxic T-cells or against corresponding ligands expressed on tumor cells and other cells in the tumor microenvironment (TME). However, the clinical responses were only observed in a subset of the treated patients; it was not clear why the remaining patients did not respond to checkpoint inhibitor therapies. One hypothesis stated that the levels of PD-L1 expression correlated with poor clinical responses to cell-mediated anti-tumor immunotherapy. Hence, exploring the underlying mechanisms that regulate PD-L1 expression on tumor cells is one approach to target such mechanisms to reduce PD-L1 expression and, therefore, sensitize the resistant tumor cells to respond to PD-1/PD-L1 antibody treatments. Various investigations revealed that the overexpression of the transcription factor Yin Yang 1 (YY1) in most cancers is involved in the regulation of tumor cells' resistance to cell-mediated immunotherapies. We, therefore, hypothesized that the role of YY1 in cancer immune resistance may be correlated with PD-L1 overexpression on cancer cells. This hypothesis was investigated and analysis of the reported literature revealed that several signaling crosstalk pathways exist between the regulations of both YY1 and PD-L1 expressions. Such pathways include p53, miR34a, STAT3, NF-kB, PI3K/AKT/mTOR, c-Myc, and COX-2. Noteworthy, many clinical and pre-clinical drugs have been utilized to target these above pathways in various cancers independent of their roles in the regulation of PD-L1 expression. Therefore, the direct inhibition of YY1 and/or the use of the above targeted drugs in combination with checkpoint inhibitors should result in enhancing the cell-mediated anti-tumor cell response and also reverse the resistance observed with the use of checkpoint inhibitors alone.

FAM3C-YY1 axis is essential for TGFβ-promoted proliferation and migration of human breast cancer MDA-MB-231 cells via the activation of HSF1

Family with sequence similarity three member C (FAM3C) (interleukin‐like EMT inducer [ILEI]), heat shock factor 1 (HSF1) and Ying‐Yang 1 (YY1) have been independently reported to be involved in the pathogenesis of various cancers. However, whether they are coordinated to trigger the development of cancer remains unknown. This study determined the role and mechanism of YY1 and HSF1 in FAM3C‐induced proliferation and migration of breast cancer cells. In human MDA‐MB‐231 breast cancer cell line, transforming growth factor‐β (TGFβ) up‐regulated FAM3C, HSF1 and YY1 expressions. FAM3C overexpression promoted the proliferation and migration of MDA‐MB‐231 cells with YY1 and HSF1 up‐regulation, whereas FAM3C silencing exerted the opposite effects. FAM3C inhibition repressed TGFβ‐induced HSF1 activation, and proliferation and migration of breast cancer cells. YY1 was shown to directly activate HSF1 transcription to promote the proliferation and migration of breast cancer cells. YY1 silencing blunted FAM3C‐ and TGFβ‐triggered activation of HSF1‐Akt‐Cyclin D1 pathway, and proliferation and migration of breast cancer cells. Inhibition of HSF1 blocked TGFβ‐, FAM3C‐ and YY1‐induced proliferation and migration of breast cancer cells. YY1 and HSF1 had little effect on FAM3C expression. Similarly, inhibition of HSF1 also blunted FAM3C‐ and TGFβ‐promoted proliferation and migration of human breast cancer BT‐549 cells. In human breast cancer tissues, FAM3C, YY1 and HSF1 protein expressions were increased. In conclusion, FAM3C activated YY1‐HSF1 signalling axis to promote the proliferation and migration of breast cancer cells. Furthermore, novel FAM3C‐YY1‐HSF1 pathway plays an important role in TGFβ‐triggered proliferation and migration of human breast cancer MDA‐MB‐231 cells.

Zinc-finger protein YY1 suppresses tumor growth of human nasopharyngeal carcinoma by inactivating c-Myc-mediated microRNA-141 transcription

Yin Yang 1 (YY1) is a zinc-finger protein that plays critical roles in various biological processes by interacting with DNA and numerous protein partners. YY1 has been reported to play dual biological functions as either an oncogene or tumor suppressor in the development and progression of multiple cancers, but its role in human nasopharyngeal carcinoma (NPC) has not yet been revealed. In this study, we found that YY1 overexpression significantly inhibits cell proliferation and cell-cycle progression from G₁ to S and promotes apoptosis in NPC cells. Moreover, we identified YY1 as a component of the c-Myc complex and observed that ectopic expression of YY1 inhibits c-Myc transcriptional activity, as well as the promoter activity and expression of the c-Myc target gene microRNA-141 (miR-141). Furthermore, restoring miR-141 expression could at least partially reverse the inhibitory effect of YY1 on cell proliferation and tumor growth and on the expression of some critical c-Myc targets, such as PTEN/AKT pathway components both in vitro and in vivo We also found that YY1 expression is reduced in NPC tissues, negatively correlates with miR-141 expression and clinical stages in NPC patients, and positively correlates with survival prognosis. Our results reveal a previously unappreciated mechanism in which the YY1/c-Myc/miR-141 axis plays a critical role in NPC progression and may provide some potential and valuable targets for the diagnosis and treatment of NPC.

Distinct mechanisms by which two forms of miR-140 suppress the malignant properties of lung cancer cells

In this study we attempted to determine the molecular mechanisms underlying the two mature products of pre-miR-140 (3p and 5p) in malignant properties of lung cancer cells. The differential expression of the two forms of miR-140 in both NSCLC tissues and cell lines was determined by quantitative real-time PCR (qRT-PCR). The effects of the miR-140 mimics on the malignant properties of lung cancer cells were evaluated using invasion assay, adhesion assay, tubule formation assay and metabolite profiling. Biotin-miRNA pulldown and transcriptome profiling by RNA-seq were utilized to distinguish their mRNA targets of the miR-140 strands. Their downstream signalling pathways were unveiled using a high-throughput antibody array. Although both strands of the miR-140 are downregulated in the NSCLC, miR-140-3p is more predominant compared to miR-140-5p in lung cancer cell lines. Both miR-140 mimics suppress the invasion of lung cancer cells and the inhibitory effect of the miR-140 on adhesion is cell-dependent. Tumor conditioned media from A549 cells after treatment with miR-140-3p mimic reduce the tubule formation ability of the endothelial cells. Metabolite profiling indicates the alteration of glycine in both lung cancer cells following treatment with miR-140 mimics. The data from the RNA-sequencing and antibody array indicate that two miR-140 strands present different targeting and signalling profiles despite the existence of mutual targets such as IGF1R and FOS. In conclusion, two forms of miR-140 both suppress the malignant properties of lung cancer cells but through distinct and multiple mechanisms.

YY1 suppresses proliferation and migration of pancreatic ductal adenocarcinoma by regulating the CDKN3/MdM2/P53/P21 signaling pathway

Pancreatic ductal adenocarcinoma (PDAC) is one of the malignant lethal tumors. It has been reported that the transcriptional regulator Yin Yang-1 (YY1) suppressed the invasion and metastasis of PDAC. However, the function of YY1 on proliferation and migration of pancreatic cancer remains to be clarified. In this study, we found that YY1 overexpression or knockdown can inhibit or promote the proliferation and migration of pancreatic cancer cells. Digital gene expression sequencing indicates that cyclin-dependent kinase inhibitor 3 (CDKN3) may be the candidate target gene of YY1. Then we found that YY1 can downregulate the expression of CDKN3 by directly binding to the promoter region of CDKN3. Silencing CDKN3 expression could inhibit the ability of cell proliferation and migration and overexpression of CDKN3 could restore the effects induced by YY1 overexpression in pancreatic cancer cells. The expression levels of YY1 and CDKN3 were negatively correlated in pancreatic cancer tissues and PDAC patients with higher levels of CDKN3 have poor prognosis. Vitro and vivo study show that CDKN3 can form a complex with MdM2-P53, thus leading to inhibiting the expression of P21, which is the target gene of P53, and finally facilitates the cell cycle to promote the proliferation of pancreatic cancer cells. Hence, YY1 can directly regulate the expression of CDKN3 and participate in the cycle of pancreatic cancer cells, which can inhibit the progression of pancreatic cancer. These results reveal that YY1-CDKN3-MDM2/P53-P21 axis is involved in pancreatic tumorigenesis, which may develop new methods for human pancreatic cancer therapy.

The Yin and Yang of YY1 in tumor growth and suppression

Yin Yang-1 (YY1) is a zinc finger protein and member of the GLI-Kruppel family that can activate or inactivate gene expression depending on interacting partners, promoter context and chromatin structure, and may be involved in the transcriptional control of ∼10% of the total mammalian gene set. A growing body of literature indicates that YY1 is overexpressed in multiple cancer types and that increased YY1 levels correlate with poor clinical outcomes in many cancers. However, the role of YY1 in the promotion or suppression of tumor growth remains controversial and its regulatory effects may be tumor cell type dependent at least in experimental systems. The molecular mechanisms responsible for the apparently conflicting roles of YY1 are not yet fully elucidated. This review highlights recent advances in our understanding of regulatory insights involving YY1 function in a range of cancer types. For example, YY1's roles in tumor growth involve stabilization of hypoxia-inducible factor HIF-1α in a p53 independent manner, negative regulation of miR-9 transcription, control of MYCT1 transcription, a novel miR-193a-5p-YY1-APC axis, intracellular ROS and mitochondrial superoxide generation, p53 reduction and EGFR activation, control of genes associated with mitochondrial energy metabolism and miRNA regulatory networks involving miR-7, miR-9, miR-34a, miR-186, miR-381, miR-584-3p and miR-635. On the other hand, tumor suppressor roles of YY1 appear to involve YY1 stimulation of tumor suppressor BRCA1, increased Bax transcription and apoptosis involving cytochrome c release and caspase-3/-7 cleavage, induction of heme oxygenase-1, inhibition of pRb phosphorylation and p21 binding to cyclin D1 and cdk4, reduced expression of long noncoding RNA of SOX2 overlapping transcript, and MUC4/ErbB2/p38/MEF2C-dependent downregulation of MMP-10. YY1 expression is associated with that of cancer stem cell markers SOX2, BMI1 and OCT4 across many cancers suggesting multidynamic regulatory control and groups of cancers with distinct molecular signatures. Greater understanding of the mechanistic roles of YY1 will in turn lead to the development of more specific approaches to modulate YY1 expression and activity with therapeutic potential.

Prognostic significance of high YY1AP1 and PCNA expression in colon adenocarcinoma

To investigate the relationship between YY1AP1 and various clinicopathological features of colon adenocarcinoma (COAD), we conducted immunohistochemical (IHC) analyses of human tissue microarrays. We found that YY1AP1 protein expression was significantly higher in tumor tissue of the colon and liver, and was significantly lower in tumor tissue of the kidney. An analysis that employed the SurvExpress database indicated that increased expression of YY1AP1 mRNA was significantly associated with the overall survival of COAD patients. To clarify the validity of YY1AP1 or PCNA as determined by the IHC analysis was performed on 59 paired samples from COAD and adjacent normal tissue. Statistically significant differences of immunoreactivity for YY1AP1 or PCNA protein expression was observed between COAD tissue and adjacent normal tissue. High protein expression levels of YY1AP1 and PCNA were also found to be significantly correlated with M-class and distant metastasis. We also determined that YY1AP1 was correlated with PCNA expression in COAD samples, and Kaplan-Meier survival curves indicated that YY1AP1 protein expression was significantly associated with poor survival. Finally, a univariate analysis demonstrated that YY1AP1 protein expression was related to YY1AP1 score, and multivariate analysis revealed that the YY1AP1 protein expression level was an independent risk factor of overall COAD survival. Taken together, our findings indicate that YY1AP1 expression plays an important role in the tumorigenesis and progression of COAD and could serve as a clinical prognostic indicator for COAD.

Identification of OCTN2 variants and their association with phenotypes of Crohn's disease in a Korean population

Crohn’s disease (CD) is a chronic inflammatory bowel disease and a genetic variant in the OCTN2, g.-207G > C is significantly associated with CD susceptibility. This study was aimed to identify novel OCTN2 functional promoter variants and their roles in transcriptional regulation using various in vitro assays. In addition, we investigated the association between OCTN2 genotypes and CD through genetic analysis using DNA samples from 193 patients with CD and 281 healthy controls. Among the three major promoter haplotypes of OCTN2 identified, one haplotype, H3, showed a significant decrease in promoter activity: two polymorphisms in H3 were associated with a significant reduction in promoter activity. In particular, we found that the reduced transcriptional activity of those two polymorphisms results from a reduction in the binding affinity of the activators, NF-E2 and YY1, to the OCTN2 promoter. The functional haplotype of the OCTN2 promoter was associated with clinical course of CD such as the disease behavior and need for surgery. However, genetic variants or haplotypes of OCTN2 did not affect the susceptibility to CD. Our results suggest that a common promoter haplotype of OCTN2 regulates the transcriptional rate of OCTN2 and influences the clinical course of CD.

Yin Yang 1 promotes mTORC2-mediated AKT phosphorylation

Yin Yang 1 (YY1) regulates both gene expression and protein modifications, and has shown a proliferative role in cancers. In this study, we demonstrate that YY1 promotes AKT phosphorylation at S473, a marker of AKT activation. YY1 expression positively correlated with AKT(S473) phosphorylation in a tissue microarray and cultured cells of breast cancer, but negatively associated with the distant metastasis-free survival of 166 breast cancer patients. YY1 promotes AKT phosphorylation at S473 through direct interaction with AKT, and the AKT-binding site is mapped to the residues G201-S226 on YY1. These residues are also involved in YY1 interaction with Mdm2, Ezh2, and E1A, and thus are designated as the oncogene protein binding (OPB) domain. YY1-promoted AKT phosphorylation relies on the OPB domain but is independent of either transcriptional activity of YY1 or the activity of phosphoinositide-3-kinases. We also determine that YY1-promoted mTORC2 access to AKT leads to its phosphorylation at S473. Importantly, a peptide based on the OPB domain blocks YY1 interaction with AKT and reduces AKT phosphorylation and cell proliferation. Thus, we demonstrate for the first time that YY1 promotes mTORC2-mediated AKT activation and disrupting YY1-AKT interaction by OPB domain-based peptide may represent a potential strategy for cancer therapy.

Expression of YY1 in Differentiated Thyroid Cancer

The transcription factor Yin Yang 1 (YY1) has an important regulatory role in tumorigenesis, but its implication in thyroid cancer has not been yet investigated. In the present study, we have analyzed the expression of YY1 in differentiated thyroid cancer and assessed the association of YY1 expression with clinical features. Expression of YY1 was evaluated in human thyroid cancer cell lines, a series of matched normal/tumor thyroid tissues and in a thyroid cancer tissue microarray, using real-time PCR, Western blot, and/or immunohistochemistry. YY1 was overexpressed in thyroid cancer cells, at transcription and protein levels. A significant increase of YY1 mRNA was also observed in tumor thyroid tissues. Moreover, immunohistochemical analysis of the thyroid cancer tissue microarray revealed that both papillary thyroid cancer (PTC) and follicular thyroid cancer (FTC) present increased YY1 protein levels (48 and 19%, respectively). After stratification by the level of YY1 protein, positive YY1 expression identifies 88% of patients with PTC. The association of YY1 expression with clinicopathological features in PTC and FTC showed that YY1 expression was related with age at diagnosis. Our data indicates for the first time overexpression of YY1 in differentiated thyroid cancer, with YY1 being more frequently overexpressed in the PTC subtype.

YY1 positively regulates human UBIAD1 expression

Vitamin K is involved in bone formation and blood coagulation. Natural vitamin K compounds are composed of the plant form phylloquinone (vitamin K1) and a series of bacterial menaquionones (MK-n; vitamin K2). Menadione (vitamin K3) is an artificial vitamin K compound. MK-4 contains 4-isoprenyl as a side group in the 2-methyl-1,4-naphthoquinone common structure and has various bioactivities. UbiA prenyltransferase domain containing 1 (UBIAD1 or TERE1) is the menaquinone-4 biosynthetic enzyme. UBIAD1 transcript expression significantly decreases in patients with prostate carcinoma and overexpressing UBIAD1 inhibits proliferation of a tumour cell line. UBIAD1 mRNA expression is ubiquitous in mouse tissues, and higher UBIAD1 mRNA expression levels are detected in the brain, heart, kidneys and pancreas. Several functions of UBIAD1 have been reported; however, regulation of the human UBIAD1 gene has not been elucidated. Here we report cloning and characterisation of the human UBIAD1 promoter. A 5' rapid amplification of cDNA ends analysis revealed that the main transcriptional start site was 306 nucleotides upstream of the translation initiation codon. Deletion and mutation analyses revealed the functional importance of the YY1 consensus motif. Electrophoretic gel mobility shift and chromatin immunoprecipitation assays demonstrated that YY1 binds the UBIAD1 promoter in vitro and in vivo. In addition, YY1 small interfering RNA decreased endogenous UBIAD1 mRNA expression and UBIAD1 conversion activity. These results suggest that YY1 up-regulates UBIAD1 expression and UBIAD1 conversion activity through the UBIAD1 promoter.

YY1 suppresses FEN1 over-expression and drug resistance in breast cancer

Background

Drug resistance is a major challenge in cancer therapeutics. Abundant evidence indicates that DNA repair systems are enhanced after repetitive chemotherapeutic treatments, rendering cancers cells drug-resistant. Flap endonuclease 1 (FEN1) plays critical roles in DNA replication and repair and in counteracting replication stress, which is a key mechanism for many chemotherapeutic drugs to kill cancer cells. FEN1 was previously shown to be upregulated in response to DNA damaging agents. However, it is unclear about the transcription factors that regulate FEN1 expression in human cancer. More importantly, it is unknown whether up-regulation of FEN1 has an adverse impact on the prognosis of chemotherapeutic treatments of human cancers.

Methods

To reveal regulation mechanism of FEN1 expression, we search and identify FEN1 transcription factors or repressors and investigate their function on FEN1 expression by using a combination of biochemical, molecular, and cellular approaches. Furthermore, to gain insights into the impact of FEN1 levels on the response of human cancer to therapeutic treatments, we determine FEN1 levels in human breast cancer specimens and correlate them to the response to treatments and the survivorship of corresponding breast cancer patients.

Results

We observe that FEN1 is significantly up-regulated upon treatment of chemotherapeutic drugs such as mitomycin C (MMC) and Taxol in breast cancer cells. We identify that the transcription factor/repressor YY1 binds to the FEN1 promoter and suppresses the expression of FEN1 gene. In response to the drug treatments, YY1 is dissociated from the FEN1 promoter region leading over-expression of FEN1. Overexpression of YY1 in the cells results in down-regulation of FEN1 and sensitization of the cancer cells to MMC or taxol. Furthermore, we observe that the level of FEN1 is inversely correlated with cancer drug and radiation resistance and with survivorship in breast cancer patients.

Conclusion

Altogether, our current data indicate that YY1 is a transcription repressor of FEN1 regulating FEN1 levels in response to DNA damaging agents. FEN1 is up-regulated in human breast cancer and its levels inversely correlated with cancer drug and radiation resistance and with survivorship in breast cancer patients.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1043-1) contains supplementary material, which is available to authorized users.

Prognostic significance of YY1 protein expression and mRNA levels by bioinformatics analysis in human cancers: a therapeutic target

Conventional therapeutic treatments for various cancers include chemotherapy, radiotherapy, hormonal therapy and immunotherapy. While such therapies have resulted in clinical responses, they were coupled with non-tumor specificity, toxicity and resistance in a large subset of the treated patients. During the last decade, novel approaches based on scientific knowledge on the biology of cancer were exploited and led to the development of novel targeted therapies, such as specific chemical inhibitors and immune-based therapies. Although these targeted therapies resulted in better responses and less toxicity, there still remains the problem of the inherent or acquired resistance. Hence, current studies are seeking additional novel therapeutic targets that can overcome several mechanisms of resistance. The transcription factor Yin Yang 1 (YY1) is a ubiquitous protein expressed in normal and cancer tissues, though the expression level is much higher in a large number of cancers; hence, YY1 has been considered as a potential novel prognostic biomarker and therapeutic target. YY1 has been reported to be involved in the regulation of drug/immune resistance and also in the regulation of EMT. Several excellent reviews have been published on YY1 and cancer (see below), and, thus, this review will update recently published reports as well as report on the analysis of bioinformatics datasets for YY1 in various cancers and the relationship between reported protein expression and mRNA levels. The potential clinical significance of YY1 is discussed.

A DNA repair variant in POLQ (c.-1060A > G) is associated to hereditary breast cancer patients: a case-control study

BACKGROUND

One of the hallmarks of cancer is the occurrence of high levels of chromosomal rearrangements as a result of inaccurate repair of double-strand breaks (DSB). Germline mutations in BRCA and RAD51 genes, involved in DSB repair, are strongly associated with hereditary breast cancer. Pol θ, a translesional DNA polymerase specialized in the replication of damaged DNA, has been also shown to contribute to DNA synthesis associated to DSB repair. It is noteworthy that POLQ is highly expressed in breast tumors and this expression is able to predict patient outcome. The objective of this study was to analyze genetic variants related to POLQ as new population biomarkers of risk in hereditary (HBC) and sporadic (SBC) breast cancer.

METHODS

We analyzed through case-control study nine SNPs of POLQ in hereditary (HBC) and sporadic (SBC) breast cancer patients using Taqman Real Time PCR assays. Polymorphisms were systematically identified through the NCBI database and are located within exons or promoter regions. We recruited 204 breast cancer patients (101 SBC and 103 HBC) and 212 unaffected controls residing in Southern Brazil.

RESULTS

The rs581553 SNP located in the promoter region was strongly associated with HBC (c.-1060A > G; HBC GG = 15, Control TT = 8; OR = 5.67, CI95% = 2.26-14.20; p < 0.0001). Interestingly, 11 of 15 homozygotes for this polymorphism fulfilled criteria for Hereditary Breast and Ovarian Cancer (HBOC) syndrome. Furthermore, 12 of them developed bilateral breast cancer and one had a familial history of bilateral breast cancer. This polymorphism was also associated with bilateral breast cancer in 67 patients (OR = 9.86, CI95% = 3.81-25.54). There was no statistically significant difference of age at breast cancer diagnosis between SNP carriers and non-carriers.

CONCLUSIONS

Considering that Pol θ is involved in DBS repair, our results suggest that this polymorphism may contribute to the etiology of HBC, particularly in patients with bilateral breast cancer.

Drug repurposing screen identifies lestaurtinib amplifies the ability of the poly (ADP-ribose) polymerase 1 inhibitor AG14361 to kill breast cancer associated gene-1 mutant and wild type breast cancer cells

Introduction

Breast cancer is a devastating disease that results in approximately 40,000 deaths each year in the USA. Current drug screening and chemopreventatitive methods are suboptimal, due in part to the poor specificity of compounds for cancer cells. Poly (ADP-ribose) polymerase 1 (PARP1) inhibitor (PARPi)-mediated therapy is a promising approach for familial breast cancers caused by mutations of breast cancer-associated gene-1 and -2 (BRCA1/2), yet drug resistance frequently occurs during the treatment. Moreover, PARPis exhibit very little effect on cancers that are proficient for DNA repair and clinical efficacy for PARPis as single-agent therapies has yet to be illustrated.

Methods

Using a quantitative high-throughput screening approach, we screened a library containing 2,816 drugs, most of which are approved for human or animal use by the Food and Drug Administration (FDA) or other countries, to identify compounds that sensitize breast cancer cells to PARPi. After initial screening, we performed further cellular and molecular analysis on lestaurtinib, which is an orally bioavailable multikinase inhibitor and has been used in clinical trials for myeloproliferative disorders and acute myelogenous leukemia.

Results

Our study indicated that lestaurtinib is highly potent against breast cancers as a mono-treatment agent. It also strongly enhanced the activity of the potent PARPi AG14361 on breast cancer cell growth both in vitro and in vivo conditions. The inhibition of cancer growth is measured by increased apoptosis and reduced cell proliferation. Consistent with this, the treatment results in activation of caspase 3/7, and accumulation of cells in the G2 phase of the cell cycle, irrespective of their BRCA1 status. Finally, we demonstrated that AG14361 inhibits NF-κB signaling, which is further enhanced by lestaurtinib treatment.

Conclusions

Lestaurtinib amplifies the ability of the PARP1 inhibitor AG14361 to kill BRCA1 mutant and wild-type breast cancer cells, at least in part, by inhibiting NF-κB signaling. Each of these drugs has been approved for clinical trials for several different cancers, thus, their combination treatment should be applicable for a breast cancer trial in the future.

Yin Yang-1 suppresses invasion and metastasis of pancreatic ductal adenocarcinoma by downregulating MMP10 in a MUC4/ErbB2/p38/MEF2C-dependent mechanism

BACKGROUND

Increasing evidence indicates an important role of transcription factor Yin Yang-1 (YY1) in human tumorigenesis. However, its function in cancer remains controversial and the relevance of YY1 to pancreatic ductal adenocarcinoma (PDAC) remains to be clarified.

METHODS

In this study, we detected YY1 expression in clinical PDAC tissue samples and cell lines using quantitative RT-PCR, immunohistochemistry and western blotting. We also detected MUC4 and MMP10 mRNA levels in 108 PDAC samples using qRT-PCR and analyzed the correlations between YY1 and MUC4 or MMP10 expression. The role of YY1 in the proliferation, invasion and metastatic abilities of PDAC cells in vitro was studied by CCK-8 assay, cell migration and invasion assays. In vivo pancreatic tumor growth and metastasis was studied by a xenogenous subcutaneously implant model and a tail vein metastasis model. The potential mechanisms underlying YY1 mediated tumor progression in PDAC were explored by digital gene expression (DGE) sequencing, signal transduction pathways blockage experiments and luciferase assays. Statistical analysis was performed using the SPSS 15.0 software.

RESULTS

We found that the expression of YY1 in PDACs was higher compared with their adjacent non-tumorous tissues and normal pancreas tissues. However, PDAC patients with high level overexpression of YY1 had better outcome than those with low level overexpression. YY1 expression levels were statistically negatively correlated with MMP10 expression levels, but not correlated with MUC4 expression levels. YY1 overexpression suppressed, whereas YY1 knockdown enhanced, the proliferation, invasion and metastatic properties of BXPC-3 cells, both in vitro and in vivo. YY1 suppresses invasion and metastasis of pancreatic cancer cells by downregulating MMP10 in a MUC4/ErbB2/p38/MEF2C-dependent mechanism.

CONCLUSIONS

The present study suggested that YY1 plays a negative role, i.e. is a tumor suppressor, in PDAC, and may become a valuable diagnostic and prognostic marker of PDAC.