The oncoprotein HBXIP upregulates Lin28Bviaactivating TF II D to promote proliferation of breast cancer cells

Single-cell transcriptome analysis revealing the intratumoral heterogeneity of ccRCC and validation of MT2A in pathogenesis

Clear-cell renal cell carcinoma (ccRCC) appears as the most common type of kidney cancer, the carcinogenesis of which has not been fully elucidated. Tumor heterogeneity plays a crucial role in cancer progression, which could be largely deciphered by the implement of scRNA-seq. The bulk and single-cell RNA expression profile is obtained from TCGA and study conducted by Young et al. We utilized UMAP, TSNE, and clustering algorithm Louvain for dimensionality reduction and FindAllMarkers function for determining the DEGs. Monocle2 was utilized to perform pseudo-time series analysis. SCENIC was implemented for transcription factor analysis of each cell subgroup. A series of WB, CFA, CCK-8, and EDU analysis was utilized for the validation of the role of MT2A in ccRCC carcinogenesis. We observed higher infiltration of T/NK and B cells in tumorous tissues, indicating the role of immune cells in ccRCC carcinogenesis. Transcription factor analysis revealed the activation of EOMES and ETS1 in CD8 + T cells, while CAFs were divided into myo-CAFs and i-CAFs, with i-CAFs showing distinct enrichment of ATF3, JUND, JUNB, EGR1, and XBP1. Through cell trajectory analysis, we discerned three distinct stages of cellular evolution, where State2 symbolizes normal renal tubular cells that underwent transitions into State1 and State3 as the CNV score ascended. Functional enrichment examination revealed an amplification of interferon gamma and inflammatory response pathways within tumor cells. The consensus clustering algorithm yielded two molecular subtypes, with cluster 2 being associated with advanced tumor stages and an abundance of infiltrated immune cells. We identified 17 prognostic genes through Cox and LASSO regression models and used them to construct a prognostic model, the efficacy of which was verified in multiple cohorts. Furthermore, we investigated the role of MT2A, one of our hub genes, in ccRCC carcinogenesis, and found it to regulate proliferation and migration of malignant cells. We depicted a detailed single-cell landscape of ccRCC, with special focus on CAFs, endothelial cells, and renal tubular cells. A prognostic model of high stability and accuracy was constructed based on the DEGs. MT2A was found to be actively implicated in ccRCC carcinogenesis, regulating proliferation and migration of the malignant cells.

Hbxip is essential for murine embryogenesis and regulates embryonic stem cell differentiation through activating mTORC1

HBXIP, also named LAMTOR5, has been well characterized as a transcriptional co-activator in various cancers. However, the role of Hbxip in normal development remains unexplored. Here, we demonstrated that homozygous knockout of Hbxip leads to embryonic lethality, with retarded growth around E7.5, and that depletion of Hbxip compromises the self-renewal of embryonic stem cells (ESCs), with reduced expression of pluripotency genes, reduced cell proliferation and decreased colony-forming capacity. In addition, both Hbxip−/− ESCs and E7.5 embryos displayed defects in ectodermal and mesodermal differentiation. Mechanistically, Hbxip interacts with other components of the Ragulator complex, which is required for mTORC1 activation by amino acids. Importantly, ESCs depleted of Ragulator subunits, Lamtor3 or Lamtor4, displayed differentiation defects similar to those of Hbxip−/− ESCs. Moreover, Hbxip−/−, p14−/− and p18−/− mice, lacking subunits of the Ragulator complex, also shared similar phenotypes, embryonic lethality and retarded growth around E7-E8. Thus, we conclude that Hbxip plays a pivotal role in the development and differentiation of the epiblast, as well as the self-renewal and differentiation of ESCs, through activating mTORC1 signaling.

DPEP1 promotes drug resistance in colon cancer cells by forming a positive feedback loop with ASCL2

BACKGROUND

Drug resistance is an important factor affecting the efficacy of chemotherapy in patients with colon cancer. However, clinical markers for diagnosing drug resistance of tumor cells are not only a few in number, but also low in specificity, and the mechanism of action of tumor cell drug resistance remains unclear.

METHODS

Dipeptidase 1 (DPEP1) expression was analyzed using the cancer genome atlas (TCGA) and genotype-Tissue Expression pan-cancer data. Survival analysis was performed using the survival package in R software to assess the prognostic value of DPEP1 expression in colon cancer. Correlation and Venn analyses were adopted to identify key genes. Immunohistochemistry, western blot, qRT-PCR, Co-immunoprecipitation, and dual-luciferase reporter experiments were carried out to explore the underlying associations between DPEP1 and Achaete scute-like 2 (ASCL2). MTT assays were used to evaluate the role of DPEP1 and ASCL2 in colon cancer drug resistance.

RESULTS

DPEP1 was highly expressed in colon cancer tissues. DPEP1 expression correlated negatively with disease-specific survival but not with overall survival. Bioinformatics analysis and experiments showed that the expressions of DPEP1 and ASCL2 in colon cancer tissues were markedly positively correlated. Mechanistic research indicated that DPEP1 enhanced the stability of protein ASCL2 by inhibiting its ubiquitination-mediated degradation. In turn, ASCL2 functioned as a transcription factor to activate the transcriptional activity of the DPEP1 gene and boost its expression. Furthermore, DPEP1 also could enhance the expression of colon cancer stem cell markers (LGR5, CD133, and CD44), which strengthened the tolerance of colon cancer cells to chemotherapy drugs.

CONCLUSIONS

Our findings reveal that the DPEP1 enhances the stemness of tumor cells by forming a positive feedback loop with ASCL2 to improve resistance to chemotherapy drugs.

Identification of colon tumor marker NKD1 via integrated bioinformatics analysis and experimental validation

Background

Colorectal cancer is an important death‐related disease in the worldwide. However, specific colon cancer tumor markers currently used for diagnosis and treatment are few. The purpose of this study is to screen the potential colon cancer markers by bioinformatics and verify the results with experiments.

Methods

Gene expression data were downloaded from two different databases: TCGA database and GEO datasets, which were then analyzed by two different methods (difference analysis and WGCNA method). Venn and PPI analysis obtained the potential core genes, which were then performed the GO enrichment and KEGG pathway analysis. Expressions levels of NKD1 in colon carcinoma tissues were further confirmed by immunohistochemical staining and western blot assays. Moreover, the function was measured by MTT, clone formation, and tumor transplantation experiments. Importantly, co‐immunoprecipitation, immunofluorescence, and protein stability assays were further performed to explore the underlying mechanism of NKD1 promoting cell proliferation.

Results

Nine potential core genes highly expressed in colon cancer samples were screened out by bioinformatics analysis. NKD1, one of the hub genes, highly expressed in the colon carcinoma tissues could enhance the proliferation of colon cancer cells. Mechanism research demonstrated that NKD1 was essential for the combination between Wnt signalosome (DVL) and β‐catenin, and that NKD1 knockout remarkably decreased the β‐catenin expression. Immunofluorescence assays further implied that NKD1 knockout significantly inhibited β‐catenin nuclear accumulation. Importantly, the stability of β‐catenin proteins was maintained by NKD1 in the colon cancer cells.

Conclusion

We believe that NKD1 well expressed in the colorectal carcinoma tissues can enhance the proliferation of colon cancer cells. Furthermore, the functions that NKD1 may have in colon cancer cells should be different from that NKD1 has played in the zebrafish. Thus, NKD1 could be a specific colorectal cancer marker.

Long Non-Coding RNA LINC00467 Correlates to Poor Prognosis and Aggressiveness of Breast Cancer

Breast cancer remains the leading cause of female cancer-related mortalities worldwide. Long non-coding RNAs (LncRNAs) have been increasingly reported to play pivotal roles in tumorigenesis and cancer progression. Herein, we focused on LINC00467, which has never been studied in breast cancer. Silence of LINC00467 suppressed proliferation, migration, invasion and epithelial-to-mesenchymal transition (EMT) of breast cancer cells in vitro, whereas forced expression of LINC00467 exhibited the opposite effects. Furthermore, we demonstrated overexpression of LINC00467 promoted tumor growth, while knockdown of LINC00467 inhibited pulmonary metastasis in vivo. Mechanistically, LINC00467 down-regulated miR-138-5p by acting as a miRNA “sponge”. Besides, LINC00467 also up-regulated the protein level of lin-28 homolog B (LIN28B) via a direct interaction. A higher expression level of LINC00467 was observed in breast cancer tissues as compared to the adjacent normal counterparts and elevated LINC00467 predicted poor overall survival. Our findings suggest LINC00467 promotes progression of breast cancer through interacting with miR-138-5p and LIN28B directly. LINC00467 may serve as a potential candidate for the diagnosis and treatment of breast cancer.

FGF16 regulated by miR-520b enhances the cell proliferation of lung cancer

FGF16 is implicated in the progression of some specific types of cancers, such as embryonic carcinoma, ovarian cancer, and liver cancer. Yet, the function of FGF16 in the development of lung cancer remains largely unexplored. In this study, we present the novel function of FGF16 and the regulation of miR-520b on FGF16 in lung cancer progression. In clinical lung cancer tissues, FGF16 is overexpressed and its high level is negatively associated with the low level of miR-520b. Furthermore, both the transcription and translation levels of FGF16 are restrained by miR-520b in lung cancer cells. For the regulatory mechanism investigation, miR-520b is able to directly bind to the 3′-untranslated region (3′UTR) of FGF16 mRNA, leading to its mRNA cleavage in the cells. Functionally, miR-520b reduces the growth of lung cancer and its inhibitor anti-miR520b is able to promote the growth through competing endogenous miR-520b. Moreover, FGF16 silence using RNA interference is capable of doing great damage to anti-miR-520b-accelerated growth of lung cancer. Thus, our finding indicates that FGF16 is a new target gene of miR-520b in lung cancer. For lung cancer, FGF16 may serve as a novel biomarker and miR-520b/FGF16 may be useful in clinical treatment.

Oncoprotein HBXIP promotes tumorigenesis through MAPK/ERK pathway activation in non-small cell lung cancer

Objective:

The oncoprotein, hepatitis B X-interacting protein (HBXIP), has been reported to play an important role in human malignancies. However, its functions in non-small cell lung cancer (NSCLC) are poorly understood. The goal of the present study was to identify the role of HBXIP in the regulation of NSCLC development.

Methods:

The level of HBXIP expression in NSCLC tissue was assessed by immunohistochemical and Western blot analyses, and its relationships with clinicopathological features and outcomes were statistically evaluated. The effects of HBXIP on NSCLC cell progression were assessed through cell viability, colony formation, and flow cytometry analyses in vitro. The mechanism by which HBXIP regulated the MAPK pathway was studied by Western blot, immunofluorescence, and immunoprecipitation assays. In addition, in vivo experiments were performed to evaluate the progression of NSCLC and ERK signaling pathway activation after HBXIP knockdown.

Results:

HBXIP was overexpressed in human NSCLC and was correlated with the invasiveness of NSCLC. The high expression of HBXIP in NSCLC was significantly correlated with gender (P = 0.033), N stage (P = 0.002), and tumor-node-metastasis stage (P = 0.008). In vitro experiments using an NSCLC cell line revealed that HBXIP knockdown resulted in the suppression of cell proliferation and colony formation, which was consistent with the enhanced cell cycle arrest in G1 phase. The results of a mechanistic investigation suggested that binding of HBXIP to MEK1 protein promoted MAPK/ERK signaling pathway activation in NSCLC by preventing the proteasome-mediated degradation of MEK1. In addition, the results obtained using in vivo subcutaneous tumor xenografts confirmed that HBXIP deficiency decreased MEK1 protein levels and NSCLC tumor growth.

Conclusions:

Taken together, our results showed that the HBXIP-MEK interaction promoted oncogenesis via the MAPK/ERK pathway, which may serve as a novel therapeutic target for cancers in which MAPK/ERK signaling is a dominant feature.

The oncogenic role of HBXIP

Hepatitis B X-interacting protein (HBXIP) is a conserved protein of 19 kDa that was originally identified as a binding partner of hepatitis B virus X protein. Emerging evidence indicates that HBXIP is highly expressed in a variety of cancers and is correlated with poor clinical outcomes in cancer patients. HBXIP plays a critical role in cancer progression, but the underlying mechanisms are still unclear. In this review, we primarily focus on publications investigating HBXIP in cancer research, including its expression and clinical significance in cancer patients, its role as a coactivator of transcription factors in cancer cells, its inhibitory effects on the mitochondrial cytochrome c-caspase apoptotic pathway, as well as its roles in promoting mitosis and drug resistance in cancer cells, its regulatory effects on cancer metabolism, and its relationships with other signaling pathways or microRNAs in cancer. This review aims to compile and summarize existing knowledge of the functions of HBXIP in cancer, which provides a comprehensive reference for future studies on the oncogenic mechanisms of HBXIP.

CLPTM1L induces estrogen receptor β signaling-mediated radioresistance in non-small cell lung cancer cells

INTRODUCTION

Radioresistance is a major challenge in lung cancer radiotherapy, and new radiosensitizers are urgently needed. Estrogen receptor β (ERβ) is involved in the progression of non-small cell lung cancer (NSCLC), however, the role of ERβ in the response to radiotherapy in lung cancer remains elusive. In the present study, we investigated the mechanism underlying ERβ-mediated transcriptional activation and radioresistance of NSCLC cells.

METHODS

Quantitative real-time PCR, western blot and immunohistochemistry were used to detect the expression of CLPTM1L, ERβ and other target genes. The mechanism of CLPTM1L in modulation of radiosensitivity was investigated by chromatin immunoprecipitation assay, luciferase reporter gene assay, immunofluorescence staining, confocal microscopy, coimmunoprecipitation and GST pull-down assays. The functional role of CLPTM1L was detected by function assays in vitro and in vivo.

RESULTS

CLPTM1L expression was negatively correlated with the radiosensitivity of NSCLC cell lines, and irradiation upregulated CLPTM1L in radioresistant (A549) but not in radiosensitive (H460) NSCLC cells. Meanwhile, IR induced the translocation of CLPTM1L from the cytoplasm into the nucleus in NSCLC cells. Moreover, CLPTM1L induced radioresistance in NSCLC cells. iTRAQ-based analysis and cDNA microarray identified irradiation-related genes commonly targeted by CLPTM1L and ERβ, and CLPTM1L upregulated ERβ-induced genes CDC25A, c-Jun, and BCL2. Mechanistically, CLPTM1L coactivated ERβ by directly interacting with ERβ through the LXXLL NR (nuclear receptor)-binding motif. Functionally, ERβ silencing was sufficient to block CLPTM1L-enhanced radioresistance of NSCLC cells in vitro. CLPTM1L shRNA treatment in combination with irradiation significantly inhibited cancer cell growth in NSCLC xenograft tumors in vivo.

CONCLUSIONS

The present results indicate that CLPTM1L acts as a critical coactivator of ERβ to promote the transcription of its target genes and induce radioresistance of NSCLC cells, suggesting a new target for radiosensitization in NSCLC therapy. Video Abstract.

DPEP1 promotes the proliferation of colon cancer cells via the DPEP1/MYC feedback loop regulation

DPEP1 is highly expressed in the colorectal carcinoma tissues and colon cancer cells. However, the function and underlying mechanism of DPEP1 in the colon cancer cells are still poorly understood. Here, we found that transcription factor MYC could occupy on the DPEP1 promoter and activate its activities, and DPEP1 was up-regulated by MYC proteins in mRNA and protein levels in a dose-dependent manner in colon cancer cells. The expression levels of DPEP1 were positively correlated with that of MYC in colorectal tumor tissues. Moreover, Laser confocal images and Co-immunoprecipitation (Co-IP) revealed that DPEP1 and MYC proteins could bind to each other in the colon cancer cells. In turn, DPEP1 could enhance the stability of MYC proteins by extending the half-life of MYC proteins in colon cancer cells. Thus, DPEP1 and MYC proteins might form a positive feedback loop to maintain their high expression levels in colon cancer cells. In function, the MTT, EdU, Clone Formation assays and xenograft tumors assays demonstrated that DPEP1 could boost the proliferation of colon cancer cells through the DPEP1/MYC positive feedback loop in vitro and in vivo. Theoretically, DPEP1 may serve as a colon cancer biomarker and a novel target of colorectal carcinogenesis therapy.

The oncoprotein HBXIP competitively binds KEAP1 to activate NRF2 and enhance breast cancer cell growth and metastasis

The nuclear factor E2-related factor 2 (NRF2)-Kelch-like ECH-associated protein 1 (KEAP1) signaling cascades is a key transcriptional pathway governing cellular oxidative stress and tumor development. Mammalian hepatitis B X-interacting protein (HBXIP) has critical roles in modulating cancer malignance and tumor progression. However, whether HBXIP interacts with KEAP1 and NRF2 is unclear. Here, we found that HBXIP can effectually compete with NRF2 for binding with KEAP1 protein via its highly conserved GLNLG motif. The HBXIP-mediated reduction in NRF2-KEAP1 complexes promotes NRF2 accumulation and nuclear entry, which facilities the activation of antioxidant response element (ARE)-dependent signaling cascades, thereby reducing the accumulation of endogenous cellular reactive oxygen species (ROS). We also found a strong positive correlation between HBXIP expression and NRF2 expression in breast cancer cells, tissue microarrays and clinical breast cancer tissues. Furthermore, this positive correlation was further confirmed via analysis of 1905 clinical cases of breast carcinoma provided by the cancer genomics database cBioPortal. Strikingly, disrupting the HBXIP-KEAP1 axis via mutating the GLNLG motif of HBXIP leads to potent inhibition of the malignancy of breast carcinoma both in vivo and in vitro. Our findings broaden our understanding of HBXIP as a modulation factor of cellular oxidative stress and address a novel regulatory mechanism governing redox homeostasis and the progression of breast carcinoma.

The oncoprotein HBXIP promotes human breast cancer growth through down-regulating p53 via miR-18b/MDM2 and pAKT/MDM2 pathways

Mammalian hepatitis B X-interacting protein (HBXIP) is an 18-kDa protein that regulates a large number of transcription factors such as TF-IID, E2F1, SP1, STAT3, c-Myc, and LXR by serving as an oncogenic transcription coactivator and plays an important role in the development of breast cancer. We previously showed that HBXIP as an oncoprotein could enhance the promoter activity of MDM2 through coactivating p53, promoting the MDM2 transcription in breast cancer. In this study we investigated the molecular mechanisms underlying the modulation of MDM2/p53 interaction by HBXIP in human breast cancer MCF-7 cells in vitro and in vivo. We showed that HBXIP could up-regulate MDM2 through inducing DNA methylation of miR-18b, thus suppressing the miR-18b expression, leading to the attenuation of p53 in breast cancer cells. In addition, HBXIP could promote the phosphorylation of MDM2 by increasing the level of pAKT and bind to pMDM2, subsequently enhancing the interaction between MDM2 and p53 for the down-regulation of p53 in breast cancer cells. In MCF-7 breast cancer xenograft nude mice, we also observed that overexpression of HBXIP promoted breast cancer growth through the miR-18b/MDM2 and pAKT/MDM2 pathways. In conclusion, oncoprotein HBXIP suppresses miR-18b to elevate MDM2 and activates pAKT to phosphorylate MDM2 for enhancing the interaction between MDM2 and p53, leading to p53 degradation in promotion of breast cancer growth. Our findings shed light on a novel mechanism of p53 down-regulation during the development of breast cancer.

N 6-Methyladenosine modification: a novel pharmacological target for anti-cancer drug development

N⁶-Methyladenosine (m⁶A) modification is the most pervasive modification of human mRNA molecules. It is reversible via regulation of m⁶A modification methyltransferase, demethylase and proteins that preferentially recognize m⁶A modification as “writers”, “erasers” and “readers”, respectively. Altered expression levels of the m⁶A modification key regulators substantially affect their function, leading to significant phenotype changes in the cell and organism. Recent studies have proved that the m⁶A modification plays significant roles in regulation of metabolism, stem cell self-renewal, and metastasis in a variety of human cancers. In this review, we describe the potential roles of m⁶A modification in human cancers and summarize their underlying molecular mechanisms. Moreover, we will highlight potential therapeutic approaches by targeting the key m⁶A modification regulators for cancer drug development.

Oncogenic mechanisms of Lin28 in breast cancer: new functions and therapeutic opportunities

The RNA binding protein Lin28 is best known for the critical role in cell development, recent researches also have implied its oncogenic function in various human cancers, including breast cancer. Specifically, aberrant Lin28 participates in multiple pathological processes, such as proliferation, metastasis, radiotherapy and chemotherapy resistance, metabolism, immunity and inflammation as well as stemness. In this review, we summarize the let-7-dependent and let-7-independent mechanism regulated by Lin28, focusing on its relation with tumor hallmarks in breast cancer, and subsequently discuss our present knowledge of Lin28 to develop a molecular-based therapeutic strategy against breast cancer.

The LPI/GPR55 axis enhances human breast cancer cell migration via HBXIP and p-MLC signaling

The G protein-coupled receptor 55 (GPR55) is expressed in multiple tissues, and has been implicated in cancer pathogenesis, but little is known about its role in the migratory behavior of cancer cells, particularly breast cancer cells. In this study we first showed that GPR55 expression levels in 38 metastatic lymph nodes of breast cancer patients were profoundly elevated, and were positively associated in human breast cancer cells with their migratory ability. Moreover, the plasma levels of GPR55 endogenous agonist L-a-lysophosphatidylinositol (LPI) were significantly increased in breast cancer patients compared with healthy individuals. In human breast cancer LM-MCF-7 and MDA-MB-231 cells, treatment with LPI (2.5 μmol/L) significantly increased filopodia formation and resulted in cell migration, which could be blocked either by the GPR55 antagonist CID16020046 or by siRNA-mediated GPR55 knockdown. Furthermore, dual-luciferase report gene assays showed that GPR55 upregulated HBXIP at the promoter; GPR55 expression levels were positively correlated with HBXIP expression levels in breast cancer tissues and 8 breast cancer cell lines. We also showed that the LPI/GPR55 axis promoted the migration of breast cancer cells via two mutually exclusive pathways - the HBXIP/p-ERK1/2/Capn4 and MLCK/MLC signaling pathways. In xenograft nude mouse model, loss of GPR55 mainly affected breast cancer cell metastasis and the formation of metastatic foci. Thus, GPR55 is involved in the migratory behavior of human breast cancer cells and could serve as a pharmacological target for preventing metastasis.

Hepatitis B X-interacting protein promotes the formation of the insulin gene-transcribing protein complex Pdx-1/Neurod1 in animal pancreatic β-cells

The activation of insulin gene transcription depends on multiple nuclear proteins, including the transcription factors PDX-1 and NEUROD1, which form a transcriptional complex. We recently reported that hepatitis B X-interacting protein (HBXIP, also termed LAMTOR5) can modulate glucose metabolism reprogramming in cancer cells. However, the physiological role of HBXIP in the modulation of glucose metabolism in normal tissues is poorly understood. Here, we report that Hbxip is an essential regulator of the effect of the Pdx-1/Neurod1 complex on insulin gene transcription in murine pancreatic β-cells in vitro and in vivo We found that pancreatic β-cell-specific Hbxip-knockout mice displayed higher fasting blood glucose levels and impaired glucose tolerance. Furthermore, Hbxip was involved in the regulation of insulin in the pancreas islets and increased insulin gene expression in rat pancreatic β-cells. Mechanistically, Hbxip stimulated insulin enhancer activity by interacting with Pdx-1 and recruiting Neurod1 to Pdx-1. Functionally, we provide evidence that Hbxip is required for Pdx-1/Neurod1-mediated insulin expression in rat pancreatic β-cells. Collectively, these results indicate that Hbxip is involved in the transcription of insulin by increasing the levels of the Pdx-1/Neurod1 complex in animal pancreatic β-cells. Our finding provides the insight into the mechanism by which Hbxip stimulates the transcription of the insulin gene.

HBXIP activates the PPARδ/NF-κB feedback loop resulting in cell proliferation

Hepatitis B X-interacting protein (HBXIP, also termed as LAMTOR5) plays a crucial role in regulation of cancer progression, while the mechanism is still unclear. Here we found that HBXIP increased the expression of PPARδ (peroxisome proliferator-activated receptor-δ) in gene and protein levels of SW480 or HT-29 colonic cancer cells. Chromatin immunoprecipitation and luciferase reporter assays showed that HBXIP occupied the core promoter (−1079/−239 nt) regions of PPARδ and that HBXIP activated the transcription activity of PPARδ in an NF-κB (p65)-dependent manner. Moreover, Co-immunoprecipitation and immunofluorescence analysis showed that HBXIP bound to NF-κB/p65 in the cells. Interestingly, we found that PPARδ could conversely increase the expression of NF-κB/p65 through activating its transcription activity. In addition, the clinical observations showed that both HBXIP and PPARδ were highly expressed in colonic carcinoma, and HBXIP expression was positively associated with that of PPARδ in the clinical specimen. Importantly, HBXIP expression levels were positively correlated with the clinical pathological parameters including lymph node metastasis and advanced TNM stage. These findings suggest that HBXIP served as a co-activator to activate the positive feedback regulations of NF-κB/PPARδ, which promoted the fast proliferation of the colonic cancer cells. Therapeutically, HBXIP may serve as a potential drug target of colonic cancer cells.

HBXIP-elevated methyltransferase METTL3 promotes the progression of breast cancer via inhibiting tumor suppressor let-7g

Methyltransferase-like 3 (METTL3) is involved in RNA metabolism through N6-methyladenosine (m⁶A) modification. However, whether METTL3 participates in the progression of breast cancer is unclear. Aberrant expression of Mammalian hepatitis B X-interacting protein (HBXIP) drives the aggressiveness of breast cancer. Here, we are interested in the potential links between HBXIP and METTL3 in breast cancer. We showed that the expression of METTL3 was positively related to that of HBXIP in clinical breast cancer tissues. Moreover, HBXIP could up-regulate METTL3 in breast cancer cells. Mechanistically, HBXIP modulated METTL3 by inhibiting miRNA let-7g, which down-regulated the expression of METTL3 by targeting its 3'UTR. Strikingly, we found that METTL3 promoted the expression of HBXIP through m⁶A modification. Furthermore, overexpressed HBXIP could rescue the inhibited-proliferation and enhanced-apoptosis induced by silencing of METTL3 in breast cancer cells. Thus, we conclude that HBXIP up-regulates METTL3 by suppressing let-7g, in which METTL3 increased HBXIP expression forming a positive feedback loop of HBXIP/let-7g/METTL3/HBXIP, leading to accelerated cell proliferation in breast cancer. Our finding provides new insights into the mechanism of the mutual regulation between HBXIP and METTL3 in the progression of breast cancer.

HBXIP suppression reduces cell proliferation and migration and its overexpression predicts poor prognosis in non-small-cell lung cancer

Emerging evidence has demonstrated that the high expression of HBXIP has been correlated with many cancers. With evaluation of the functional role of HBXIP in non-small-cell lung cancer, the primary aim of this study is to investigate the correlation between HBXIP expression and the prognosis of non-small-cell lung cancer patients. The protein levels of HBXIP were detected using western blotting in non-small-cell lung cancer cells. Cell proliferation and migration assays were measured to evaluate the function of HBXIP in non-small-cell lung cancer cells. A total of 120 non-small-cell lung cancer patients with strict follow-up and 60 adjacent non-tumor lung tissues were selected for immunohistochemical staining of the HBXIP protein. The localization of the HBXIP protein was detected in A549 non-small-cell lung cancer cells using immunofluorescence staining. The correlation between HBXIP expression and the clinicopathological features of non-small-cell lung cancer patients was analyzed by a chi-squared and Fisher’s exact test. The overall survival rates of all of the non-small-cell lung cancer patients were calculated using the Kaplan–Meier method, and univariate and multivariate analyses were performed using the Cox proportional hazards regression model. In function, we showed that suppression of HBXIP decreased A549 cell proliferation and migration. HBXIP protein showed a mainly cytoplasmic staining pattern in non-small-cell lung cancer using immunohistochemical staining in paraffin-embedded non-small-cell lung cancer tissues and immunofluorescence staining in A549 cells. The HBXIP protein had strong positive staining in the non-small-cell lung cancer tissues, which was significantly higher than the percentage of adjacent non-tumor tissues. The overexpression of HBXIP was closely correlated with histological grade, clinical stage, lymph node metastasis, and lower overall survival rates of patients with non-small-cell lung cancer. Moreover, multivariate analysis suggested that HBXIP emerged as a significant independent prognostic factor along with clinical stage in patients with non-small-cell lung cancer. In conclusion, a high level of expression of HBXIP is associated with the progression of non-small-cell lung cancer and may be a useful biomarker for poor prognostic evaluation and a potential molecular therapy target for patients with non-small-cell lung cancer.

Clinical study on the relationship between hepatitis B virus infection and risk of breast cancer: a large sized case-control and single center study in southwest of China

Purpose

Chronic hepatitis C virus (HCV) infection is reported to be associated with early-onset breast cancer, while, as a hepadnavirus, hepatitis B virus(HBV) infection is more common than HCV in China. In this article, it is aimed to study the relationship between HBV infection and risk of breast cancer in China.

Methods

The clinical data of 2452 cases of initially diagnosed breast cancer and 1926 cases of benign breast disease (as controls) with the consecutive reports of HBV serological markers and liver function tests, available in the Electronic Medical Records of the Breast Cancer Center of Chongqing, the southwest of China, from January 2011 to March 2015, were collected for analysis.

Results

The average age of the initially diagnosed breast cancer patients was 50.3±11.3 years with the age peaking about 40- 49yeaers (39.7%). The positive rate (8.2%) of hepatitis B surface antigen in breast cancer patients was relatively higher than that (7.8%) in controls (P>0.05). While, the positive rate (66.4%)of hepatitis B core antibody in breast cancer patients was significantly higher than that (53.7%) in controls (P<0.05), so were the similar results in the age groups of 40-49 years, after multiple layer analysis stratified by age and compare HBV markers adjusting age with binary logistic regression. Meanwhile, the status of albumin, aminotransferase and aspartate transaminase (41.4 g/L, 22.9 U/L, 22.0 U/L) in breast cancer patients were significantly poorer than those (44.1 g/L,16.8 U/L, 19.2 U/L) in controls (P<0.05).

Conclusions

Exposure to HBV infection may be a risk factor for breast cancer and may be also related to the earlier age onset of breast cancer (peaked around 40-49 years) among Chinese females.

HBXIP overexpression is correlated with the clinical features and survival outcome of ovarian cancer

Background

Accumulated evidence has demonstrated that Mammalian hepatitis B X-interacting protein (HBXIP) has broad roles in cancer. Although HBXIP is associated with a variety of cancers, the HBXIP protein expression level and its clinical significance in ovarian cancer have not yet been determined. The aim of this study is to investigate the association between HBXIP expression and the clinicopathological features of ovarian cancer patients to determine whether HBXIP may be correlated with a poor prognosis in ovarian cancer patients.

Methods

HBXIP protein expression was assessed in a well-characterized series of ovarian cancer tissue samples (n = 120) with long-term follow-up, using immunohistochemistry to determine the location pattern and expression of HBXIP in ovarian cancer. The localization of HBXIP was detected in SKOV-3 ovarian cancer cells using immunofluorescence (IF) staining. The relationship between high HBXIP expression and the clinicopathological features of ovarian cancer patients was analyzed by Chi-square and Fisher’s exact test. Overall survival (OS) rates of all the ovarian cancer patients were calculated using the Kaplan-Meier method, and univariate and multivariate analyses were performed using the Cox proportional hazards regression model.

Results

IF staining revealed strongly positive signals for HBXIP in both cytoplasm and nucleus, but mainly in the cytoplasm of SKOV-3 ovarian cancer cells. High HBXIP expression was predominantly observed in ovarian cancer tissues but not the adjacent non-tumor ovarian tissues. The strongly positive rate of HBXIP expression was 60.0% (72/120) in ovarian cancer and was significantly higher than in adjacent non-tumor tissues (17.4%, 4/23) (P = 0.000). High HBXIP expression was positively correlated with the occurrence of lymph node metastases (P = 0.025), histological grade (P = 0.036) and clinical stage (P = 0.003). The patients with high HBXIP expression had lower overall survival (OS) rates. Moreover, multivariate analysis indicated that HBXIP, in addition to the clinical stage, was a significant independent prognostic factor in patients with ovarian cancer.

Conclusions

High-level expression of HBXIP is associated with the progression of ovarian cancer and may be an effective biomarker for poor prognostic evaluation as well as a potential molecular therapy target for ovarian cancer patients.

Electronic supplementary material

The online version of this article (doi:10.1186/s13048-017-0322-7) contains supplementary material, which is available to authorized users.

Inflammatory factor TNF-α promotes the growth of breast cancer via the positive feedback loop of TNFR1/NF-κB (and/or p38)/p-STAT3/HBXIP/TNFR1

In the connection between inflammation and cancer development, tumor necrosis factor-alpha (TNF-α) contributes to the tumorigenesis. However, the underlying mechanism remains poorly understood. In this study, we report that TNF-α enhances the growth of breast cancer through up-regulation of oncoprotein hepatitis B X-interacting protein (HBXIP). Our data showed that the levels of TNF-α were positively related to those of HBXIP in clinical breast cancer tissues. Moreover, TNF-α could up-regulate HBXIP in breast cancer cells. Interestingly, silencing of TNF-α receptor 1 (TNFR1) blocked the effect of TNF-α on HBXIP. Mechanistically, we revealed that TNF-α could increase the activities of HBXIP promoter through activating transcriptional factor signal transducer and activator of transcription 3 (STAT3). In addition, nuclear factor kappa B (NF-κB) and/or p38 signaling increased the levels of p-STAT3 in the cells. Strikingly, HBXIP could also up-regulate TNFR1, forming a positive feedback loop of TNFR1/NF-κB (and/or p38)/p-STAT3/HBXIP/TNFR1. Notably, TNF-α was able to up-regulate TNFR1 through driving the loop. In function, we demonstrated that the knockdown of HBXIP remarkably abolished the growth of breast cancer mediated by TNF-α in vitro and in vivo. Thus, we conclude that TNF-α promotes the growth of breast cancer through the positive feedback loop of TNFR1/NF-κB (and/or p38)/p-STAT3/HBXIP/TNFR1.Our finding provides new insights into the mechanism by which TNF-α drives oncoprotein HBXIP in the development of breast cancer.

HBXIP up-regulates ACSL1 through activating transcriptional factor Sp1 in breast cancer

The oncoprotein hepatitis B X-interacting protein (HBXIP) results in the dysregulation of lipid metabolism to enhance the development of breast cancer. Acyl-CoA synthetase long-chain family member 1 (ACSL1) is required for thioesterification of long-chain fatty acids into their acyl-CoA derivatives. In this study, we present a hypothesis that HBXIP might be involved in the regulation of ACSL1 in breast cancer. Interestingly, we found that the overexpression of HBXIP was able to up-regulate ACSL1 at the levels of mRNA and protein in a dose-dependent manner in breast cancer cells. Conversely, silencing of HBXIP led to the opposite results. Mechanistically, HBXIP as a coactivator interacted with transcriptional factor Sp1 through binding to the promoter of ACSL1 by ChIP assays analysis, leading to the transcription of ACSL1 in breast cancer cells. Immunohistochemistry staining revealed that the positive rate of ACSL1 was 71.4% (35/49) in clinical breast cancer tissues, HBXIP 79.6% (39/49), in which the positive rate of ACSL1 was 76.9% (30/39) in the HBXIP-positive specimens. But, few positive rate of ACSL1 10% (1/10) was observed in normal breast tissues. The mRNA levels of ACSL1 were significantly higher in clinical breast cancer tissues than those in their corresponding peritumor tissues. The mRNA levels of ACSL1 were positively associated with those of HBXIP in clinical breast cancer tissues. Thus, we conclude that the oncoprotein HBXIP is able to up-regulate ACSL1 through activating the transcriptional factor Sp1 in breast cancer.

The oncoprotein HBXIP suppresses gluconeogenesis through modulating PCK1 to enhance the growth of hepatoma cells

Hepatitis B X-interacting protein (HBXIP) as an oncoprotein plays crucial roles in the development of cancer, involving glucose metabolism reprogramming. In this study, we are interested in whether the oncoprotein HBXIP is involved in the modulation of gluconeogenesis in liver cancer. Here, we showed that the expression level of phosphoenolpyruvate carboxykinase (PCK1), a key enzyme of gluconeogenesis, was lower in clinical hepatocellular carcinoma (HCC) tissues than that in normal tissues. Mechanistically, HBXIP inhibited the expression of PCK1 through down-regulating transcription factor FOXO1 in hepatoma cells, and up-regulated miR-135a targeting the 3'UTR of FOXO1 mRNA in the cells. In addition, HBXIP increased the phosphorylation levels of FOXO1 protein by activating PI3K/Akt pathway, leading to the export of FOXO1 from nucleus to cytoplasm. Strikingly, over-expression of PCK1 could abolish the HBXIP-promoted growth of hepatoma cells in vitro and in vivo. Thus, we conclude that the oncoprotein HBXIP is able to depress the gluconeogenesis through suppressing PCK1 to promote hepatocarcinogenesis, involving miR-135a/FOXO1 axis and PI3K/Akt/p-FOXO1 pathway. Our finding provides new insights into the mechanism by which oncoprotein HBXIP modulates glucose metabolism reprogramming in HCC.

The oncoprotein HBXIP promotes glucose metabolism reprogramming via downregulating SCO2 and PDHA1 in breast cancer

The glucose metabolism reprogramming is a hallmark of cancer. The oncoprotein hepatitis B X-interacting protein (HBXIP) functions in the development of breast cancer. In this study, we supposed that HBXIP might be involved in the glucose metabolism reprogramming in breast cancer. We showed that HBXIP led to increases in generation of intracellular glucose and lactate, as well as decreases in generation of reactive oxygen species. Expression of synthesis of cytochrome c oxidase 2 (SCO2) and pyruvate dehydrogenase alpha 1 (PDHA1), two factors of metabolic switch from oxidative phosphorylation to aerobic glycolysis, was suppressed by HBXIP. In addition, miR-183/182 and miR-96 directly inhibited the expression of SCO2 and PDHA1 through targeting their mRNA coding sequences (CDSs), respectively. Interestingly, HBXIP elevated the miR-183/96/182 cluster expression through hypoxia-inducible factor 1α (HIF1α). The stability of HIF1α was enhanced by HBXIP through disassociating interaction of von Hippel-Lindau protein (pVHL) with HIF1α. Moreover, miR-183 increased the levels of HIF1α protein through directly targeting CDS of VHL mRNA, forming a feedback loop of HIF1α/miR-183/pVHL/HIF1α. In function, HBXIP-elevated miR-183/96/182 cluster enhanced the glucose metabolism reprogramming in vitro. HBXIP-triggered glucose metabolism reprogramming promoted the growth of breast cancer in vivo. Thus, we conclude that the oncoprotein HBXIP enhances glucose metabolism reprogramming through suppressing SCO2 and PDHA1 in breast cancer.

miRNA-548p suppresses hepatitis B virus X protein associated hepatocellular carcinoma by downregulating oncoprotein hepatitis B x-interacting protein

AIM

miR-548p is a recently identified and poorly characterized miRNA. However, its role of miR-548p in tumorigenesis and progression remains poorly understood. Here, we aimed to investigate the biofunction of miR-548p in hepatocellular carcinogenesis.

METHODS

The expression levels of miR-548p were detected by quantitative reverse transcription polymerase chain reaction (qRT-PCR). The role of miR-548p in hepatocellular carcinoma (HCC) was determined by colony formation, flow cytometry assay and nude mice xenograft experiments. miR-548p target genes were analyzed by miRNA target predication programs and verified by qRT-PCR, western blotting assay and dual-luciferase reporter assay.

RESULTS

miR-548p is repressed by hepatitis B virus X protein (HBx) in HCC tumor tissues and hepatoma cells, and inhibited cell growth by inhibiting cell proliferation and promoting cell apoptosis. miR-548p directly downregulated the expression of hepatitis B x-interacting protein (HBXIP) by binding to the 3'-untranslated region of HBXIP mRNA. Further study showed that hepatocyte nuclear factor-4a (HNF4A) promoted the expression of miR-548p and inhibited the transcription of HBXIP. HNF4A is a dominant transcriptional regulator of hepatocyte differentiation and hepatocellular carcinogenesis, and is shown to be repressed by HBx.

CONCLUSION

We proposed the model for HBx/HNF4A/miR-548p/HBXIP pathway that controls hepatoma cell growth and tumorigenesis of HCC. miR-548p was identified as a tumor-suppressor in HBx-associated hepatocellular carcinogenesis.

Oncoprotein HBXIP Modulates Abnormal Lipid Metabolism and Growth of Breast Cancer Cells by Activating the LXRs/SREBP-1c/FAS Signaling Cascade

Abnormal lipid metabolism is a hallmark of tumorigenesis. Accumulating evidence demonstrates that fatty acid synthase (FAS, FASN) is a metabolic oncogene that supports the growth and survival of tumor cells and is highly expressed in many cancers. Here, we report that the oncoprotein, hepatitis B X-interacting protein (HBXIP, LAMTOR5) contributes to abnormal lipid metabolism. We show that high expression of HBXIP in 236 breast cancer patients was significantly associated with decreased overall survival and progression-free survival. Interestingly, the expression of HBXIP was positively related to that of FAS in clinical breast cancer tissues, and HBXIP overexpression in breast cancer cells resulted in FAS upregulation. Mechanistically, HBXIP upregulated SREBP-1c (SREBF1), which activates the transcription of FAS, by directly interacting with and coactivating nuclear receptor (NR) liver X receptors (LXR). Physiologically, LXRs are activated via a coactivator containing NR motif in a ligand-dependent manner. However, in breast cancer cells, HBXIP containing the corepressor/nuclear receptor motif with special flanking sequence could coactivate LXRs independent of ligand. Moreover, overexpressed SREBP-1c was able to activate the transcription of HBXIP, forming a positive-feedback loop. Functionally, HBXIP enhanced lipogenesis, resulting in the growth of breast cancer cells in vitro and in vivo Thus, we conclude that the oncoprotein HBXIP contributes to the abnormal lipid metabolism in breast cancer through LXRs/SREBP-1c/FAS signaling, providing new insights into the mechanisms by which cancer cells reprogram lipid metabolism in their favor. Cancer Res; 76(16); 4696-707. ©2016 AACR.

The oncoprotein HBXIP up-regulates FGF4 through activating transcriptional factor Sp1 to promote the migration of breast cancer cells

We have reported that the oncoprotein hepatitis B X-interacting protein (HBXIP) is able to promote migration of breast cancer cells. Fibroblast growth factor 4 (FGF4) is a multipotent growth factor and is highly expressed in various human cancers. However, the regulatory mechanism of FGF4 in breast cancer remains poorly understood. In the present study, we report that HBXIP is able to up-regulate FGF4 to enhance the migration of breast cancer cells. Immunohistochemistry staining showed that HBXIP and FGF4 were highly expressed in clinical metastatic lymph nodes of breast tumor. The expression levels of HBXIP were positively related to those of FGF4 in clinical breast cancer tissues. Then, we validated that HBXIP up-regulated the expression of FGF4 at the levels of promoter, mRNA and protein by luciferase reporter gene assays, reverse transcription-polymerase chain reaction and Western blot analysis. Moreover, we found that HBXIP was able to activate FGF4 promoter through transcriptional factor Sp1 by luciferase reporter gene assays. Chromatin immunoprecipitation assays confirmed that HBXIP coactivated Sp1 to stimulate FGF4 promoter. In function, we showed that HBXIP promoted breast cancer cell migration through FGF4 by wound healing and transwell cell migration assays. Thus, we conclude that the oncoprotein HBXIP up-regulates FGF4 through activating transcriptional factor Sp1 to promote the migration of breast cancer cells. Therapeutically, HBXIP may serve as a novel target in breast cancer.

HBXIP and LSD1 Scaffolded by lncRNA Hotair Mediate Transcriptional Activation by c-Myc

c-Myc is regarded as a transcription factor, but the basis for its function remains unclear. Here, we define a long noncoding RNA (lncRNA)/protein complex that mediates the transcriptional activation by c-Myc in breast cancer cells. Among 388 c-Myc target genes in human MCF-7 breast cancer cells, we found that their promoters could be occupied by the oncoprotein HBXIP. We confirmed that the HBXIP expression correlated with expression of the c-Myc target genes cyclin A, eIF4E, and LDHA. RNAi-mediated silencing of HBXIP abolished c-Myc-mediated upregulation of these target genes. Mechanistically, HBXIP interacted directly with c-Myc through the leucine zippers and recruited the lncRNA Hotair along with the histone demethylase LSD1, for which Hotair serves as a scaffold. Silencing of HBXIP, Hotair, or LSD1 was sufficient to block c-Myc-enhanced cancer cell growth in vitro and in vivo. Taken together, our results support a model in which the HBXIP/Hotair/LSD1 complex serves as a critical effector of c-Myc in activating transcription of its target genes, illuminating long-standing questions on how c-Myc drives carcinogenesis.

Deacetylation of tumor-suppressor MST1 in Hippo pathway induces its degradation through HBXIP-elevated HDAC6 in promotion of breast cancer growth

Reduction or loss of tumor-suppressor mammalian STE20-like kinase 1 (MST1) in Hippo pathway contributes to the tumorigenesis. However, the mechanism leading to reduction of MST1 in cancers remains poorly understood. In this study, we explored the hypothesis that the oncoprotein hepatitis B X-interacting protein (HBXIP) is involved in the reduction of MST1 in breast cancer. Immunohistochemical analysis of tissue microarrays revealed that the expression of HBXIP was negatively associated with that of MST1 in 98 clinical breast tissue samples. Then we found that HBXIP could posttranslationally downregulate MST1 in breast cancer cells. Mechanistically, we identified that MST1 could be acetylated on its lysine 35 residue in the cells. Strikingly, the treatment with trichostatin A, an inhibitor of histone deacetylases (HDACs), markedly increased the levels of MST1 acetylation and protein in the cells. Interestingly, the oncoprotein HBXIP could significantly inhibit acetylation of MST1, resulting in the reduction of MST1 protein. Notably, we revealed that the HDAC6 could reduce the protein levels of MST1 through deacetylation modification of MST1 in the cells. Moreover, our data revealed that HBXIP upregulated HDAC6 at the levels of mRNA and protein by activating transcription factor nuclear factor-κB. Deacetylation of MST1 promoted the interaction of MST1 with HSC70 in the cells, resulting in a lysosome-dependent degradation of MST1 via chaperone-mediated autophagy (CMA). Functionally, the reduction of tumor-suppressor MST1 mediated by HBXIP promoted the growth of breast cancer cells in vitro and in vivo. Thus we conclude that the deacetylation of MST1 mediated by HBXIP-enhanced HDAC6 results in MST1 degradation in a CMA manner in promotion of breast cancer growth. Our finding provides new insights into the mechanism of tumor-suppressor MST1 reduction in breast cancer.

The oncoprotein HBXIP modulates the feedback loop of MDM2/p53 to enhance the growth of breast cancer

MDM2 and p53 form a negative feedback loop, in which p53 as a transcription factor positively regulates MDM2 and MDM2 negatively regulates tumor suppressor p53 through promoting its degradation. However, the mechanism of the feedback loop is poorly understood in cancers. We had reported previously that the oncoprotein hepatitis B X-interacting protein (HBXIP) is a key oncoprotein in the development of cancer. Thus, we supposed that HBXIP might be involved in the event. Here, we observed that the expression levels of HBXIP were positively correlated to those of MDM2 in clinical breast cancer tissues. Interestingly, HBXIP was able to up-regulate MDM2 at the levels of mRNA and protein in MCF-7 breast cancer cells. Mechanically, HBXIP increased the promoter activities of MDM2 through directly binding to p53 in the P2 promoter of MDM2. Strikingly, we identified that the acetyltransferase p300 was recruited by HBXIP to p53 in the promoter of MDM2. Moreover, we validated that HBXIP enhanced the p53 degradation mediated by MDM2. Functionally, the knockdown of HBXIP or/and p300 inhibited the proliferation of breast cancer cells in vitro, and the depletion of MDM2 or overexpression of p53 significantly blocked the HBXIP-promoted growth of breast cancer in vitro and in vivo. Thus, we concluded that highly expressed HBXIP accelerates the MDM2-mediated degradation of p53 in breast cancer through modulating the feedback loop of MDM2/p53, resulting in the fast growth of breast cancer cells. Our findings provide new insights into the mechanism of the acceleration of the MDM2/p53 feedback loop in the development of cancer.

The oncoprotein HBXIP promotes migration of breast cancer cells via GCN5-mediated microtubule acetylation

We have documented that the oncoprotein hepatitis B X-interacting protein (HBXIP) is able to promote migration of breast cancer cells. A subset of acetylated microtubules that accumulates in the cell leading edge is necessary for cell polarization and directional migration. In this study, we explored the hypothesis that HBXIP contributes to migration of breast cancer cells by supporting microtubule acetylation in breast cancer cells. We found that HBXIP could induce acetylated microtubules accumulating into the leading protrusion in wound-induced directional migration in breast cancer cells by immunofluorescence staining analysis. Interestingly, HBXIP was able to increase the acetylation of α-tubulin in the cells by immunofluorescence staining and Western blot analysis. Furthermore, we observed that acetyltransferase GCN5 was involved in the event that HBXIP induced increase of acetylated microtubules and their expansion in protrusions in breast cancer cells by Western blot analysis and immunofluorescence staining. Moreover, GCN5 was required for the HBXIP-enhanced migration of breast cancer cells by wound healing assay. Thus, we conclude that HBXIP promotes the migration of breast cancer cells through modulating microtubule acetylation mediated by GCN5. Therapeutically, HBXIP may serve as a novel target in breast cancer.

The oncoprotein HBXIP up-regulates SCG3 through modulating E2F1 and miR-509-3p in hepatoma cells

Hepatitis B X-interacting protein (HBXIP) is an important oncoprotein in hepatocarcinogenesis. Here, we found that the expression levels of HBXIP were positively associated with those of Secretogranin III (SCG3) in clinical hepatocellular carcinoma tissues. We identified that HBXIP up-regulated the expression of SCG3 through modulating both E2F transcription factor 1 (E2F1) and miR-509-3p. HBXIP suppressed miR-509-3p through activating NF-κB. In function, we showed that SCG3 increased the proliferation of hepatoma cells and HBXIP enhanced the proliferation of the cells via SCG3 in vitro and in vivo. Thus, we conclude that HBXIP facilitates the proliferation of hepatoma cells through up-regulating SCG3.

Hepatitis B virus X protein accelerates hepatocarcinogenesis with partner survivin through modulating miR-520b and HBXIP

BACKGROUND

Hepatitis B virus X protein (HBx) plays crucial roles in hepatocarcinogenesis. However, the underlying mechanism remains elusive. We have reported that HBx is able to up-regulate survivin in hepatocellular carcinoma tissues. The oncopreotein hepatitis B X-interacting protein (HBXIP), a target of miR-520b, is involved in the development of cancer. In this study, we focus on the investigation of hepatocarcinogenesis mediated by HBx.

METHODS

The expression of HBx and survivin was examined in the liver tissues of HBx-Tg mice. The effect of HBx/survivin on the growth of LO2-X-S cells was determined by colony formation and transplantation in nude mice. The effect of HBx/survivin on promoter of miR-520b was determined by Western blot analysis, luciferase reporter gene assay, co-immunoprecipitation (co-IP) and chromatin immunoprecipitation (ChIP), respectively. The expression of HBx, survivin and HBXIP was detected by immunohistochemistry and real-time PCR in clinical HCC tissues, respectively. The DNA demethylation of HBXIP promoter was examined. The functional influence of miR-520b and HBXIP on proliferation of hepatoma cells was analyzed by MTT, colony formation, EdU and transplantation in nude mice in vitro and in vivo.

RESULTS

In this study, we provided evidence that HBx up-regulated survivin in the liver cancer tissues of HBx-Tg mice aged 18 M. The engineered LO2 cell lines with survivin and/or HBx were successfully established, termed LO2-X-S. MiR-520b was down-regulated in LO2-X-S cells and clinical HCC tissues. Our data revealed that HBx survivin-dependently down-regulated miR-520b through interacting with Sp1 in the cells. HBXIP was highly expressed in LO2-X-S cells, liver cancer tissues of HBx-Tg mice aged 18 M and clinical HCC tissues (75.17%, 112/149). The expression level of HBXIP was positively associated with those of HBx or survivin in clinical HCC tissues. In addition, we showed that HBx survivin-dependently up-regulated HBXIP through inducing demethylation of HBXIP promoter in LO2-X-S cells and clinical HCC tissues. In function, low level miR-520b and high level HBXIP mediated by HBx with partner survivin contributed to the growth of LO2-X-S cells in vitro and in vivo.

CONCLUSION

HBx accelerates hepatocarcinogenesis with partner survivin through modulating tumor suppressor miR-520b and oncoprotein HBXIP.

The nuclear import of oncoprotein hepatitis B X-interacting protein depends on interacting with c-Fos and phosphorylation of both proteins in breast cancer cells

Aberrant nuclear localization of oncogenic transcription factors and coactivators always leads to the development of cancer. We have reported that the oncoprotein hepatitis B X-interacting protein (HBXIP) acts as a novel transcriptional coactivator to promote proliferation and migration of breast cancer cells. However, the mechanism of regulating the nuclear import of HBXIP remains unclear. In the present study, we found that HBXIP interacted with c-Fos through their leucine zipper domains in vitro and in vivo. Interestingly, the leucine zipper mutant of HBXIP (or c-Fos) was unavailable to bind to c-Fos (or HBXIP), resulting in the disappearance of nuclear localization of HBXIP. Moreover, we revealed that the nuclear import of HBXIP was required for phosphorylation of c-Fos at Thr(232), Thr(325), Thr(331), and Ser(374) by ERK1/2. In addition, the mutant of HBXIP at the Ser(108) phosphorylation site failed to import into the nucleus. Strikingly, we found that the kinase ataxia telangiectasia mutated (ATM) phosphorylated HBXIP at Ser(108). The knockdown of ATM by siRNA remarkably decreased the levels of serine phosphorylation and blocked the nuclear import of HBXIP. Then, we identified that ATM could bind to HBXIP. Moreover, we validated that the nuclear import of HBXIP contributed to its nuclear function. Therefore, we conclude that the nuclear import of the oncoprotein HBXIP requires interaction with c-Fos through their leucine zipper domains and phosphorylation of both proteins in breast cancer cells. Thus, our findings provide new insights into the mechanism of the nuclear import of HBXIP. Therapeutically, the block of the nuclear import of HBXIP is significant in breast cancer.