Gene Summary

Gene:XBP1; X-box binding protein 1
Aliases: XBP2, TREB5, XBP-1, TREB-5
Summary:This gene encodes a transcription factor that regulates MHC class II genes by binding to a promoter element referred to as an X box. This gene product is a bZIP protein, which was also identified as a cellular transcription factor that binds to an enhancer in the promoter of the T cell leukemia virus type 1 promoter. It may increase expression of viral proteins by acting as the DNA binding partner of a viral transactivator. It has been found that upon accumulation of unfolded proteins in the endoplasmic reticulum (ER), the mRNA of this gene is processed to an active form by an unconventional splicing mechanism that is mediated by the endonuclease inositol-requiring enzyme 1 (IRE1). The resulting loss of 26 nt from the spliced mRNA causes a frame-shift and an isoform XBP1(S), which is the functionally active transcription factor. The isoform encoded by the unspliced mRNA, XBP1(U), is constitutively expressed, and thought to function as a negative feedback regulator of XBP1(S), which shuts off transcription of target genes during the recovery phase of ER stress. A pseudogene of XBP1 has been identified and localized to chromosome 5. [provided by RefSeq, Jul 2008]
Databases:OMIM, HGNC, Ensembl, GeneCard, Gene
Protein:X-box-binding protein 1
Source:NCBIAccessed: 29 August, 2019


What does this gene/protein do?
Show (16)

Cancer Overview

Research Indicators

Publications Per Year (1994-2019)
Graph generated 29 August 2019 using data from PubMed using criteria.

Literature Analysis

Mouse over the terms for more detail; many indicate links which you can click for dedicated pages about the topic.

  • Neoplastic Cell Transformation
  • Estrogen Receptor alpha
  • B-Lymphocytes
  • Cell Proliferation
  • Western Blotting
  • Multiple Myeloma
  • Promoter Regions
  • Chromosome 22
  • Transcription Factor CHOP
  • regulatory factor X transcription factors
  • Antineoplastic Agents
  • Messenger RNA
  • Gene Expression Profiling
  • Gene Expression
  • Breast Cancer
  • Xenograft Models
  • Regulatory Elements, Transcriptional
  • eIF-2 Kinase
  • Apoptosis
  • Endoplasmic Reticulum Stress
  • Plasma Cells
  • Nuclear Proteins
  • Neoplasm Proteins
  • DNA-Binding Proteins
  • Cell Differentiation
  • Transfection
  • Protein-Serine-Threonine Kinases
  • Immunohistochemistry
  • RNA Splicing
  • Mutation
  • Cell Survival
  • Cancer Gene Expression Regulation
  • Endoplasmic Reticulum
  • Activating Transcription Factor 6
  • Liver Cancer
  • Endoribonucleases
  • Unfolded Protein Response
  • Drug Resistance
  • Signal Transduction
  • Oligonucleotide Array Sequence Analysis
Tag cloud generated 29 August, 2019 using data from PubMed, MeSH and CancerIndex

Specific Cancers (4)

Data table showing topics related to specific cancers and associated disorders. Scope includes mutations and abnormal protein expression.

Note: list is not exhaustive. Number of papers are based on searches of PubMed (click on topic title for arbitrary criteria used).

Latest Publications: XBP1 (cancer-related)

Dong H, Adams NM, Xu Y, et al.
The IRE1 endoplasmic reticulum stress sensor activates natural killer cell immunity in part by regulating c-Myc.
Nat Immunol. 2019; 20(7):865-878 [PubMed] Article available free on PMC after 13/11/2019 Related Publications
Natural killer (NK) cells are critical mediators of host immunity to pathogens. Here, we demonstrate that the endoplasmic reticulum stress sensor inositol-requiring enzyme 1 (IRE1α) and its substrate transcription factor X-box-binding protein 1 (XBP1) drive NK cell responses against viral infection and tumors in vivo. IRE1α-XBP1 were essential for expansion of activated mouse and human NK cells and are situated downstream of the mammalian target of rapamycin signaling pathway. Transcriptome and chromatin immunoprecipitation analysis revealed c-Myc as a new and direct downstream target of XBP1 for regulation of NK cell proliferation. Genetic ablation or pharmaceutical blockade of IRE1α downregulated c-Myc, and NK cells with c-Myc haploinsufficency phenocopied IRE1α-XBP1 deficiency. c-Myc overexpression largely rescued the proliferation defect in IRE1α

Sheng X, Nenseth HZ, Qu S, et al.
IRE1α-XBP1s pathway promotes prostate cancer by activating c-MYC signaling.
Nat Commun. 2019; 10(1):323 [PubMed] Article available free on PMC after 13/11/2019 Related Publications
Activation of endoplasmic reticulum (ER) stress/the unfolded protein response (UPR) has been linked to cancer, but the molecular mechanisms are poorly understood and there is a paucity of reagents to translate this for cancer therapy. Here, we report that an IRE1α RNase-specific inhibitor, MKC8866, strongly inhibits prostate cancer (PCa) tumor growth as monotherapy in multiple preclinical models in mice and shows synergistic antitumor effects with current PCa drugs. Interestingly, global transcriptomic analysis reveal that IRE1α-XBP1s pathway activity is required for c-MYC signaling, one of the most highly activated oncogenic pathways in PCa. XBP1s is necessary for optimal c-MYC mRNA and protein expression, establishing, for the first time, a direct link between UPR and oncogene activation. In addition, an XBP1-specific gene expression signature is strongly associated with PCa prognosis. Our data establish IRE1α-XBP1s signaling as a central pathway in PCa and indicate that its targeting may offer novel treatment strategies.

Gundamaraju R, Vemuri R, Chong WC, et al.
Bilirubin Attenuates ER Stress-Mediated Inflammation, Escalates Apoptosis and Reduces Proliferation in the LS174T Colonic Epithelial Cell Line.
Int J Med Sci. 2019; 16(1):135-144 [PubMed] Article available free on PMC after 13/11/2019 Related Publications
Mildly elevated serum unconjugated bilirubin (UCB) concentrations are associated with protection against disease conditions underpinned by cellular and metabolic stress. To determine the potential therapeutic efficacy of UCB we tested it in an

Ji H, Huang C, Wu S, Kasim V
XBP1-s promotes colorectal cancer cell proliferation by inhibiting TAp73 transcriptional activity.
Biochem Biophys Res Commun. 2019; 508(1):203-209 [PubMed] Related Publications
Endoplasmic reticulum (ER) stress activation could be found in a wide range of human tumors. ER stress induces the splicing of X-box binding protein 1 (XBP1) to form its splicing variant XBP1-s, which in turn activates various ER stress-related genes. XBP1-s is highly expressed in various tumors; however, its role in tumorigenesis is still largely unknown. Herein we showed that XBP1-s suppresses the expression of tumor suppressor TAp73, a member of p53 family with high homology with p53, by directly binds to TAp73 promoter and suppresses its transcriptional activity. We also found that overexpression of TAp73 cancelled the effect of XPB1-s on enhancing colorectal cancer cells proliferation and colony formation potential, indicating that TAp73 is critical for XBP1-s-induced tumorigenesis. Together, our findings not only reveal a novel mechanism of TAp73 aberrant regulation in tumor cells, but also link up tumor cells ER stress with tumor suppressive activity of TAp73.

Xin H, Deng Y, Cao J
Proviral insertion in murine lymphomas 2 promotes stomach cancer progression by regulating apoptosis via reactive oxygen species-triggered endoplasmic reticulum stress.
Biochem Biophys Res Commun. 2018; 506(1):145-152 [PubMed] Related Publications
Gastric cancer is one of the most fatal cancers worldwide. The incidence and death rates are still increasing for gastric cancer. Increasing studies have shown that proviral insertion in murine lymphomas 2 (PIM2) functions as critical regulator of multiple cancers. However, it remains unknown whether and how PIM2 regulates gastric cancer progression. In this study, PIM2 was increased in the gastric cancer tissues of patients. Patients with high PIM2 expression levels had significantly shorter survival than those with low PIM2 expression. PIM2 knockdown reduced proliferation, migration and invasion in vitro by up-regulating E-cadherin, and down-regulating N-cadherin and Vimentin. Knockdown of PIM2 induced apoptosis in gastric cancer cells, which was regulated by endoplasmic reticulum (ER) stress, as evidenced by the increased expression levels of Activating transcription factor (ATF) 6, ATF4, X-box- binding protein-1 (XBP-1) and C/EBP homologous protein (CHOP). In addition, our data showed that PIM2 silence induced reactive oxygen species (ROS) production, leading to the activation of c-Jun N-terminal kinase (JNK). Importantly, we found that PIM2 knockdown-induced apoptosis and ER stress could be abolished by reducing reactive oxygen species (ROS) generation. In vivo, PIM2 knockdown showed a significant reduction in SGC-7901 xenograft tumor size. In summary, our findings provided experimental evidence that PIM2 might function as an important oncogene in gastric cancer, which supplied promising target for developing new therapeutic strategy in gastric cancer.

Sbiera S, Kendl S, Weigand I, et al.
Hsp90 inhibition in adrenocortical carcinoma: Limited drug synergism with mitotane.
Mol Cell Endocrinol. 2019; 480:36-41 [PubMed] Related Publications
90 kDa heat shock proteins (Hsp90) act as protein chaperones and play a role in modulating endoplasmic reticulum (ER) stress. Hsp90 inhibitors are under clinical investigation as cancer treatment. Mitotane therapy of adrenocortical carcinoma (ACC) has been shown to act through lipid-induced ER-stress. To explore the potential of Hsp90 inhibitors in ACC as a single agent and in combination with mitotane, we analyzed two independent gene expression data sets of adrenal tumors in silico and treated the ACC cell line model NCI-H295 with Hsp90 inhibitors BIIB021 (B) and CCT18159 (C) alone and in combination with mitotane. ER-stress markers were monitored by immunoblotting. Drug synergism was quantified using the median effect model with cell viability as read-out. Cytosolic Hsp90 isoforms AA1 and AB1 were significantly overexpressed in ACC. Viability of H295 cells was impaired by B and C as single agents with an EC

Song M, Sandoval TA, Chae CS, et al.
IRE1α-XBP1 controls T cell function in ovarian cancer by regulating mitochondrial activity.
Nature. 2018; 562(7727):423-428 [PubMed] Article available free on PMC after 13/11/2019 Related Publications
Tumours evade immune control by creating hostile microenvironments that perturb T cell metabolism and effector function

Kim H, Moon JY, Burapan S, et al.
Induction of ER Stress-Mediated Apoptosis by the Major Component 5,7,4'-Trimethoxyflavone Isolated from Kaempferia parviflora Tea Infusion.
Nutr Cancer. 2018 Aug-Sep; 70(6):984-996 [PubMed] Related Publications
Kaempferia parviflora (KP) is a famous medicinal plant from Thailand, and is a rich source of various kinds of methoxyflavones (MFs). Many kinds of food products such as tea, capsule, and liquor are manufactured from the rhizomes of KP. In this study, KP infusions were prepared with different brewing conditions, and the amounts of three major methoxylflavones, 5,7-dimethoxyflavone (DMF), 5,7,4'-trimethoxyflavone (TMF), and 3,5,7,3',4'-pentamethoxyflavone (PMF), were analyzed. The antiproliferative activities of DMF, TMF, and PMF isolated from the brewed tea samples were evaluated. TMF was discovered to be significantly effective at inhibiting proliferation of SNU-16 human gastric cancer cells in a concentration dependent manner. TMF induced apoptosis, as evidenced by increments of sub-G1 phase, DNA fragmentation, annexin-V/PI staining, the Bax/Bcl-xL ratio, proteolytic activation of caspase-3,-7,-8, and degradation of poly (ADP-ribose) polymerase (PARP) protein. Furthermore, it was found that TMF induced apoptosis via ER stress, verified by an increase in the level of C/EBP homologous protein (CHOP), glucose regulated protein 78 (GRP78), inositol-requiring enzyme 1 α (IRE1α), activating transcription factor-4 (ATF-4), and the splice isoform of X-box-binding protein-1 (XBP-1) mRNA.

Arbel Rubinstein T, Shahmoon S, Zigmond E, et al.
Klotho suppresses colorectal cancer through modulation of the unfolded protein response.
Oncogene. 2019; 38(6):794-807 [PubMed] Related Publications
Klotho is an anti-aging transmembrane protein, which can be shed and function as a hormone. Accumulating data indicate klotho as a tumor suppressor in a wide array of malignancies and indicate the subdomain KL1 as the active region of the protein. We aimed to study the role of klotho as a tumor suppressor in colorectal cancer. Bioinformatics analyses of TCGA datasets indicated reduced klotho mRNA levels in human colorectal cancer, along with negative regulation of klotho expression by hypermethylation of the promoter and 1st exon, and hypomethylation of an area within the gene. Overexpression or treatment with klotho or KL1 inhibited proliferation of colorectal cancer cells in vitro. The in vivo activity of klotho and KL1 was examined using two models recapitulating development of tumors in the normal colonic environment of immune-competent mice. Treatment with klotho inhibited formation of colon polyps induced by the carcinogen azoxymethane, and KL1 treatment slowed growth of orthotopically-implanted colorectal tumors. Gene expression array revealed that klotho and KL1 expression enhanced the unfolded protein response (UPR) and this was further established by increased levels of spliced XBP1, GRP78 and phosphorylated-eIF2α. Furthermore, attenuation of the UPR partially abrogated klotho tumor suppressor activity. In conclusion, this study indicates klotho as a tumor suppressor in colorectal cancer and identifies, for the first time, the UPR as a pathway mediating klotho activities in cancer. These data suggest that administration of exogenous klotho or KL1 may serve as a novel strategy for prevention and treatment of colorectal cancer.

Liu S, Wang X, Qin W, et al.
Transcription Factors Contribute to Differential Expression in Cellular Pathways in Lung Adenocarcinoma and Lung Squamous Cell Carcinoma.
Interdiscip Sci. 2018; 10(4):836-847 [PubMed] Related Publications
Lung cancers are broadly classified into small cell lung cancers and non-small cell lung cancers (NSCLC). Lung adenocarcinoma (LUAD) and lung squamous cell carcinoma (LUSC) are two common subtypes of NSCLC, and despite the fact that both occur in lung tissues, these two subtypes show a number of different pathological characteristics. To investigate the differences and seek potential therapy targets, we used bioinformatics methods to analyze RNA-Seq data from different aspects. The previous studies and comparative pathway enrichment analysis on publicly available data showed that expressed or inhibited genes are different in two cancer subtypes through important pathways. Some of these genes could not only affect cell function through expression, but also could regulate other genes' expression by binding to a specific DNA sequence. This kind of genes is called transcription factor (TF) or sequence-specific DNA-binding factor. Transcription factors play important roles in controlling gene expression in carcinoma pathways. Our results revealed transcription factors that may cause differential expression of genes in cellular pathways of LUAD and LUSC, which provide new clues for study and treatment. Once such TF is NFE2l2 which may regulate genes in the Wnt signaling pathway, and the MAPK signaling pathway, thus leading to an increase the cell growth, cell division, and gene transcription. Another TF-XBP1 has high correlation with genes related to cell adhesion molecules and cytokine-cytokine receptor interaction pathways that may further affect the immune system. Moreover, the two TF and high correlated genes also show similar patterns in an independent GEO data set.

Sun Y, Jiang F, Pan Y, et al.
XBP1 promotes tumor invasion and is associated with poor prognosis in oral squamous cell carcinoma.
Oncol Rep. 2018; 40(2):988-998 [PubMed] Related Publications
X‑box‑binding protein 1 (XBP1) contributes to various types of cancer including breast, bladder cancer and esophageal squamous cell carcinoma. The aim of the study was to examine the metastatic role of XBP1 in oral squamous cell carcinoma (OSCC), and identify possible downstream molecules. Immunohistochemical staining was conducted on tissue microarrays comprising 96 OSCC cases to determine the expression level of XBP1 and analyze its association with metastasis, clinicopathological characteristics and survival prognosis. Compared with the adjacent normal tissues of OSCC, the expression of XBP1 was significantly increased in the tumor center and front area, and lymph nodes metastases (P<0.05). A relatively high XBP1 expression was associated with histological grades (P<0.05), advanced clinical stages (P<0.05), unfavorable 5‑year survival (P=0.027). Suppressed XBP1 expression caused a significant reduction of cell invasion capability (P<0.05). AXL and the downstream molecules, such as PI3K, MMP1, MMP3, and uPA were significantly suppressed when XBP1 expression was inhibited in OSCC cells. Once XBP1 was activated by Thapsigargin, AXL expression was restored. Moreover, aberrant AXL expression was associated with XBP1 overexpression in OSCC tissues (P<0.05). In conclusion, XBP1 is a potential target that is relevant to suppressing cell invasion and is associated with patient prognosis in OSCC.

Pommier A, Anaparthy N, Memos N, et al.
Unresolved endoplasmic reticulum stress engenders immune-resistant, latent pancreatic cancer metastases.
Science. 2018; 360(6394) [PubMed] Article available free on PMC after 13/11/2019 Related Publications
The majority of patients with pancreatic ductal adenocarcinoma (PDA) develop metastatic disease after resection of their primary tumor. We found that livers from patients and mice with PDA harbor single disseminated cancer cells (DCCs) lacking expression of cytokeratin 19 (CK19) and major histocompatibility complex class I (MHCI). We created a mouse model to determine how these DCCs develop. Intraportal injection of immunogenic PDA cells into preimmunized mice seeded livers only with single, nonreplicating DCCs that were CK19

Dai W, Li Q, Liu BY, et al.
Differential networking meta-analysis of gastric cancer across Asian and American racial groups.
BMC Syst Biol. 2018; 12(Suppl 4):51 [PubMed] Article available free on PMC after 13/11/2019 Related Publications
BACKGROUND: Gastric Carcinoma is one of the most lethal cancer around the world, and is also the most common cancers in Eastern Asia. A lot of differentially expressed genes have been detected as being associated with Gastric Carcinoma (GC) progression, however, little is known about the underlying dysfunctional regulation mechanisms. To address this problem, we previously developed a differential networking approach that is characterized by involving differential coexpression analysis (DCEA), stage-specific gene regulatory network (GRN) modelling and differential regulation networking (DRN) analysis.
RESULT: In order to implement differential networking meta-analysis, we developed a novel framework which integrated the following steps. Considering the complexity and diversity of gastric carcinogenesis, we first collected three datasets (GSE54129, GSE24375 and TCGA-STAD) for Chinese, Korean and American, and aimed to investigate the common dysregulation mechanisms of gastric carcinogenesis across racial groups. Then, we constructed conditional GRNs for gastric cancer corresponding to normal and carcinoma, and prioritized differentially regulated genes (DRGs) and gene links (DRLs) from three datasets separately by using our previously developed differential networking method. Based on our integrated differential regulation information from three datasets and prior knowledge (e.g., transcription factor (TF)-target regulatory relationships and known signaling pathways), we eventually generated testable hypotheses on the regulation mechanisms of two genes, XBP1 and GIF, out of 16 common cross-racial DRGs in gastric carcinogenesis.
CONCLUSION: The current cross-racial integrative study from the viewpoint of differential regulation networking provided useful clues for understanding the common dysfunctional regulation mechanisms of gastric cancer progression and discovering new universal drug targets or biomarkers for gastric cancer.

Jiang S, Song C, Gu X, et al.
Ubiquitin-Specific Peptidase 22 Contributes to Colorectal Cancer Stemness and Chemoresistance via Wnt/β-Catenin Pathway.
Cell Physiol Biochem. 2018; 46(4):1412-1422 [PubMed] Related Publications
BACKGROUND/AIMS: Two major barriers to the successful treatment of colorectal cancer (CRC) are the development of stem cell-like characteristics (stemness) and chemoresistance. Ubiquitin-specific peptidase 22 (USP22) is a deubiquitinating enzyme and putative CRC marker that has emerged as a potential cause of both phenomena in CRC. There is evidence that USP22 acts through the Wnt/β-catenin pathway and that downregulation of the latter may reduce chemoresistance.
METHODS: In this study, we used CRC tissue specimens from human patients as well as human CRC cell lines to evaluate the role of USP22 in CRC stemness and chemoresistance in vitro and in vivo. RT-PCR and western blot were used for gene expression analyses. Immunohistochemistry was performed for USP22 expression in clinical samples. CD133 levels were analyzed by flow cytometry. Sphere formation and MTT assays were used for self-renewal and proliferation analysis. Chemoresistance was evaluated by cell viability and sphere formation assays.
RESULTS: We found a significant increase of USP22 in recurrent CRC and chemoresistant CRC cells as compared to primary CRC and non-chemoresistant CRC cells, respectively. We then demonstrated that USP22 mediates CRC cell chemoresistance through the Wnt/β-catenin pathway and that reducing USP22 in CRC cells diminishes chemoresistance.
CONCLUSIONS: Having established the crucial role of USP22 in CRC stemness and chemoresistance, this study suggests that USP22 may be an ideal genetic target in the treatment of chemoresistant CRC.

Afrin S, Giampieri F, Gasparrini M, et al.
The inhibitory effect of Manuka honey on human colon cancer HCT-116 and LoVo cell growth. Part 1: the suppression of cell proliferation, promotion of apoptosis and arrest of the cell cycle.
Food Funct. 2018; 9(4):2145-2157 [PubMed] Related Publications
Numerous investigations have been made on plant phenolic compounds and cancer prevention in recent decades. Manuka honey (MH) represents a good source of phenolic compounds such as luteolin, kaempferol, quercetin, gallic acid and syringic acid. The aim of this work was to evaluate the chemopreventive effects of MH on human colon cancer HCT-116 and LoVo cells. Both cells were exposed to different concentrations of MH (0-20 mg mL-1 for HCT-116 cells and 0-50 mg mL-1 for LoVo cells) for 48 h to measure apoptosis and cell cycle arrest as well as apoptosis and cell cycle regulatory gene and protein expression. MH exhibited profound inhibitory effects on cellular growth by reducing the proliferation ability, inducing apoptosis and arresting the cell cycle in a dose-dependent manner. Interestingly, MH treatment in non-malignant cells did not exert any significant toxicity at similar concentrations. The apoptosis event was associated with the increasing expression of p53, cleaved-PARP and caspase-3 and with the activation of both intrinsic (caspase-9) and extrinsic (caspase-8) apoptotic pathways. MH induced cell cycle arrest in the S phase in HCT-116 cells, and simultaneously, in LoVo cells, it occurred in the G2/M phase through the modulation of cell cycle regulator genes (cyclin D1, cyclin E, CDK2, CDK4, p21, p27 and Rb). The expression of p-Akt was suppressed while the expression of p-p38MAPK, p-Erk1/2 and endoplasmic stress markers (ATF6 and XBP1) was increased for apoptosis induction. Overall, these findings indicate that MH could be a promising preventive or curative food therapy for colon cancer.

Wu S, Du R, Gao C, et al.
The role of XBP1s in the metastasis and prognosis of hepatocellular carcinoma.
Biochem Biophys Res Commun. 2018; 500(3):530-537 [PubMed] Related Publications
Tumor metastasis and recurrence are the primary contributors to poor prognosis in patients with hepatocellular carcinoma (HCC). The epithelial-mesenchymal transition (EMT) of tumor cells is the predominant mechanism of HCC progression. XBP1s is a newly discovered molecule involved in the endoplasmic reticulum (ER) stressresponse, which is an adaptive response and defense mechanism in cells that enablessurvival under adverse conditions. Abnormally high XBP1sexpression has been found in tumor cells, but the role of XBP1sin HCC progression remains unclear. We found that the expression of XBP1s in HCC cell lines and tissuesamples was higher than that in control cells and tissuesamples. Clinicopathological analysis showed that the expression of XBP1s was closely correlated with distant metastasis and poor prognosis in HCC. In vivo and invitro experiments confirmed that the overexpression of XBP1s promoted EMT and metastasis in HCC cells. XBP1ssilencing attenuated cellular migration and development of the EMT phenotypein vitro. Through further study to elucidate the molecular mechanism underlying the promotion ofEMT by XBP1s in HCC cells, we confirmed that XBP1s could mediate the expression of Twist. In HCC cells, XBP1s enhanced the expression of Twist and Snail, resulting in a subsequent reduction in the expression of E-cadherin, a contributor to cell-cell adhesion. Overall, this study reveals a novel XBP1s/Twist/Snail axis that mediates EMT in HCC cells and the invasion and metastasis of HCC.

Lee M, Song IH, Heo SH, et al.
Expression of Immunoproteasome Subunit LMP7 in Breast Cancer and Its Association with Immune-Related Markers.
Cancer Res Treat. 2019; 51(1):80-89 [PubMed] Article available free on PMC after 13/11/2019 Related Publications
PURPOSE: In the presence of interferon, proteasome subunits are replaced by their inducible counterparts to form an immunoproteasome (IP) plays a key role in generation of antigenic peptides presented by MHC class I molecules, leading to elicitation of a T cell‒mediated immune response. Although the roles of IP in other cancers, and inflammatory diseases have been extensively studied, its significance in breast cancer is unclear.
Materials and Methods: We investigated the expression of LMP7, an IP subunit, and its relationship with immune system components in two breast cancer cohorts.
RESULTS: In 668 consecutive breast cancer cohort, 40% of tumors showed high level of LMP7 expression, and tumors with high expression of LMP7 had more tumor-infiltrating lymphocytes (TILs) in each subtype of breast cancer. In another cohort of 681 triple-negative breast cancer patients cohort, the expression of LMP7 in tumor cells was significantly correlated with the amount of TILs and the expression of interferon-associated molecules (MxA [p < 0.001] and PKR [p < 0.001]), endoplasmic reticulum stress-associated molecules (PERK [p=0.012], p-eIF2a [p=0.001], and XBP1 [p < 0.001]), and damage-associated molecular patterns (HMGN1 [p < 0.001] and HMGB1 [p < 0.001]). Patients with higher LMP7 expression had better disease-free survival outcomes than those with no or low expression in the positive lymph node metastasis group (p=0.041).
CONCLUSION: Close association between the TIL levels and LMP7 expression in breast cancer indicates that better antigen presentation through greater LMP7 expression might be associated with more TILs.

Bae J, Hideshima T, Tai YT, et al.
Histone deacetylase (HDAC) inhibitor ACY241 enhances anti-tumor activities of antigen-specific central memory cytotoxic T lymphocytes against multiple myeloma and solid tumors.
Leukemia. 2018; 32(9):1932-1947 [PubMed] Article available free on PMC after 13/11/2019 Related Publications
Histone deacetylases (HDAC) are therapeutic targets in multiple cancers. ACY241, an HDAC6 selective inhibitor, has shown anti-multiple myeloma (MM) activity in combination with immunomodulatory drugs and proteasome inhibitors. Here we show ACY241 significantly reduces the frequency of CD138

Liang H, Xiao J, Zhou Z, et al.
Hypoxia induces miR-153 through the IRE1α-XBP1 pathway to fine tune the HIF1α/VEGFA axis in breast cancer angiogenesis.
Oncogene. 2018; 37(15):1961-1975 [PubMed] Article available free on PMC after 13/11/2019 Related Publications
It is well documented that hypoxia activates the hypoxia-inducible factor 1-alpha (HIF1α)/vascular endothelial growth factor A (VEGFA) axis to promote angiogenesis in breast cancer. However, it is unclear how this axis is negatively regulated. In this study, we demonstrated that miR-153 directly inhibits expression of HIF1α by binding to the 3'UTR of HIF1A mRNA, as well as suppresses tube formation of primary human umbilical vein endothelial cells (HUVECs) and breast cancer angiogenesis by decreasing the secretion of VEGFA. Importantly, expression of miR-153 was induced by hypoxia-stimulated ER stress, which activates IRE1α and its downstream transcription factor X-box binding protein 1 (XBP1). X-box binding protein 1 directly binds to the promoter of the miR-153 host gene PTPRN and activates transcription. These results indicate that hypoxia induces miR-153 to fine tune the HIF1α/VEGFA axis in breast cancer angiogenesis and miR-153 could be used for breast cancer anti-angiogenesis therapy.

Zhang X, Carlisle SM, Doll MA, et al.
High N-Acetyltransferase 1 Expression Is Associated with Estrogen Receptor Expression in Breast Tumors, but Is not Under Direct Regulation by Estradiol, 5
J Pharmacol Exp Ther. 2018; 365(1):84-93 [PubMed] Article available free on PMC after 13/11/2019 Related Publications
N-acetyltransferase 1 (NAT1) is an enzyme that metabolizes carcinogens, which suggests a potential role in breast carcinogenesis. High

Li XM, Liu J, Pan FF, et al.
Quercetin and aconitine synergistically induces the human cervical carcinoma HeLa cell apoptosis via endoplasmic reticulum (ER) stress pathway.
PLoS One. 2018; 13(1):e0191062 [PubMed] Article available free on PMC after 13/11/2019 Related Publications
Up till now, studies have not been conducted on how the combination of Quercetin (Q), Aconitine (A) and apoptosis induction affects human cervical carcinoma HeLa cells. The result of our findings shows that the combination of Q and A (QA) is capable of synergistically inhibiting the proliferation of HeLa cells in a number of concentrations. QA synergistically inhibits the proliferation of MDR1 gene in the HeLa cells. It is concluded based on our result that QA induces apoptosis and ER stress just as QA-induced ER stress pathway may mediate apoptosis by upregulating mRNA expression levels of eIF2α, ATF4, IRE1, XBP1, ATF6, PERK and CHOP in the HeLa cells. The up-regulating of mRNA expression level of GRP78 and activation of UPR are a molecular basis of QA-induced ER stress.

Herroon MK, Rajagurubandara E, Diedrich JD, et al.
Adipocyte-activated oxidative and ER stress pathways promote tumor survival in bone via upregulation of Heme Oxygenase 1 and Survivin.
Sci Rep. 2018; 8(1):40 [PubMed] Article available free on PMC after 13/11/2019 Related Publications
Metastatic tumor cells engage the local tumor microenvironment and activate specific pro-survival mechanisms to thrive and progress in the harsh bone marrow niche. Here we show that the major contributors to the survival of carcinoma cells that have colonized the bone marrow are the adipocyte-induced oxidative stress and ER stress pathways. We demonstrate that upon exposure to adipocyte-rich environments in vitro or in vivo, bone-trophic prostate and breast tumor cells upregulate the oxidative stress enzyme, HO-1. We also show that HO-1 levels are significantly increased in human metastatic prostate cancer tissues and that stable HO-1 overexpression in tumor cells promotes growth and invasiveness. Co-incident with the adipocyte-induced expression of HO-1, there is an upregulation of ER chaperone BIP and splicing of XBP1, indicating adipocyte-driven unfolded protein response, a process that we show to be sensitive to antioxidant treatment. Importantly, we also demonstrate that triggering of the oxidative stress and ER stress responses, or HO-1 induction by adipocyte exposure result in the activation of pro-survival pathways, involving survivin. Collectively, our findings reveal a new link between HO-1 and survivin expression in tumor cells, and provide a new insight into potentially targetable survival pathways in bone-metastatic disease.

Lhomond S, Avril T, Dejeans N, et al.
Dual IRE1 RNase functions dictate glioblastoma development.
EMBO Mol Med. 2018; 10(3) [PubMed] Article available free on PMC after 13/11/2019 Related Publications
Proteostasis imbalance is emerging as a major hallmark of cancer, driving tumor aggressiveness. Evidence suggests that the endoplasmic reticulum (ER), a major site for protein folding and quality control, plays a critical role in cancer development. This concept is valid in glioblastoma multiform (GBM), the most lethal primary brain cancer with no effective treatment. We previously demonstrated that the ER stress sensor IRE1α (referred to as IRE1) contributes to GBM progression, through XBP1 mRNA splicing and regulated IRE1-dependent decay (RIDD) of RNA Here, we first demonstrated IRE1 signaling significance to human GBM and defined specific IRE1-dependent gene expression signatures that were confronted to human GBM transcriptomes. This approach allowed us to demonstrate the antagonistic roles of XBP1 mRNA splicing and RIDD on tumor outcomes, mainly through selective remodeling of the tumor stroma. This study provides the first demonstration of a dual role of IRE1 downstream signaling in cancer and opens a new therapeutic window to abrogate tumor progression.

Huang C, Wu S, Ji H, et al.
Identification of XBP1-u as a novel regulator of the MDM2/p53 axis using an shRNA library.
Sci Adv. 2017; 3(10):e1701383 [PubMed] Article available free on PMC after 13/11/2019 Related Publications
Cell cycle progression is a tightly controlled fundamental process in living cells, with any defects being closely linked to various abnormalities. The tumor suppressor p53/p21 axis is a core pathway controlling cell cycle progression; however, its regulatory mechanism has not been fully elucidated. In an effort to unravel this crucial network, we screened a short hairpin RNA expression vector library and identified unspliced X-box binding protein 1 (XBP1-u) as a novel and critical regulator of the p53/p21 axis. Specifically, XBP1-u negatively regulates the p53/p21 axis by enhancing p53 ubiquitination, which in turn down-regulates p21 expression. We show that XBP1-u suppression induces G

Dunlop RA, Powell JT, Metcalf JS, et al.
L-Serine-Mediated Neuroprotection Includes the Upregulation of the ER Stress Chaperone Protein Disulfide Isomerase (PDI).
Neurotox Res. 2018; 33(1):113-122 [PubMed] Related Publications
The unfolded protein response (UPR) is a highly evolutionarily conserved response to endoplasmic reticulum (ER) stress, which functions to return cells to homeostasis or send them into apoptosis, depending on the degree of cellular damage. β-N-methylamino-L-alanine (L-BMAA) has been shown to induce ER stress in a variety of models and has been linked to several types of neurodegenerative disease including Guamanian amyotrophic lateral sclerosis/Parkinsonism dementia complex (ALS/PDC). L-Serine, an amino acid critical for cellular metabolism and neurological signaling, has been shown to be protective against L-BMAA-induced neurotoxicity in both animal and cell culture models. While the mechanisms of L-BMAA neurotoxicity have been well characterized, less is known about L-serine neuroprotection. We recently reported that L-serine and L-BMAA generate similar differential expression profiles in a human ER stress/UPR array, despite L-serine being neuroprotective and L-BMAA being linked to neurodegenerative disease. Here, we further investigate the mechanism(s) of L-serine-induced UPR dysregulation by examining key genes and proteins in the ER stress/UPR pathways. We report that L-serine selectively increased protein disulfide isomerase (PDI) protein translation, an ER chaperone involved in refolding misfolded proteins, suggesting it may be modulating the UPR to favor recovery from ER stress. This constitutes a new mechanism for L-serine-mediated neuroprotection and has implications for its use as a therapy for neurodegenerative illnesses.

Guglielmi V, Nowis D, Tinelli M, et al.
Bortezomib-Induced Muscle Toxicity in Multiple Myeloma.
J Neuropathol Exp Neurol. 2017; 76(7):620-630 [PubMed] Related Publications
Multiple myeloma (MM) accounts for ∼13% of all hematologic malignancies. Bortezomib treatment is effective in MM, but can be complicated with neurological side effects. We describe a patient with symptomatic MM who had a reversible metabolic myopathy associated with bortezomib administration and pathologically characterized by excessive storage of lipid droplets together with mitochondrial abnormalities. In a single-center prospective study, 14 out of 24 patients with symptomatic MM were treated with bortezomib and, among these, 7 developed muscular signs and/or symptoms. The myopathy was characterized by a proximal muscle weakness involving lower limbs and was an early complication. Complete resolution of muscle weakness occurred after treatment discontinuation. Conversely, none of the patients who received a treatment without bortezomib developed muscular symptoms. Experimental studies demonstrate that in primary human myoblasts bortezomib at low concentrations leads to excessive storage of lipid droplets together with structural mitochondrial abnormalities, recapitulating the pathologic findings observed in patient's muscle. Our data suggest that patients treated with bortezomib should be monitored for muscular signs and/or symptoms and muscle weakness should alert the clinician to the possibility of myopathy. Bortezomib-induced metabolic myopathy is a potentially reversible entity with important implications for management and treatment of patients with MM.

Gugliotta G, Sudo M, Cao Q, et al.
Valosin-Containing Protein/p97 as a Novel Therapeutic Target in Acute Lymphoblastic Leukemia.
Neoplasia. 2017; 19(10):750-761 [PubMed] Article available free on PMC after 13/11/2019 Related Publications
B acute lymphoblastic leukemia (B-ALL) cells are distinctively vulnerable to endoplasmic reticulum (ER) stress. Recently, inhibition of p97 was shown to induce ER stress and subsequently cell death in solid tumors and in multiple myeloma. We investigated the role of a novel, orally available, p97 inhibitor (CB-5083; Cleave Biosciences) in B-ALL. CB-5083 induced a significant reduction in viability in 10 human B-ALL cell lines, harboring the most common fusion-genes involved in pediatric and adult B-ALL, with IC50s ranging from 0.34 to 0.76 μM. Moreover, CB-5083 significantly reduced the colony formation of OP1 and NALM6 cells. Early and strong induction of apoptosis was demonstrated in BALL1 and OP1 cells, together with a robust cleavage of PARP. CB-5083 induced ER stress, as documented through: 1) prominent expression of chaperones (GRP78, GRP94, PDI, DNAJC3, and DNAJB9); 2) increased activation of IRE1-alpha, as demonstrated by the splicing of XBP1; and 3) activation of PERK, which resulted in a significant overexpression of CHOP, and its downstream genes. CB-5083 reduced the viability also in GRP78

Song J, Kim BC, Nguyen DT, et al.
Levodopa (L-DOPA) attenuates endoplasmic reticulum stress response and cell death signaling through DRD2 in SH-SY5Y neuronal cells under α-synuclein-induced toxicity.
Neuroscience. 2017; 358:336-348 [PubMed] Related Publications
Parkinson's disease (PD) is characterized by the formation of Lewy bodies (LBs) in dopaminergic neurons. α-Synuclein (α-syn), a major protein component of LBs, is known to regulate synaptic plasticity, with a crucial role in memory and motor function in the central nervous system. Levodopa (L-3,4-dihydroxyphenylalanine; also known as L-DOPA) is considered the most effective medication for controlling the symptoms of PD. However, it is unclear whether L-DOPA improves the neuropathology of PD. In the present study, we investigated the effect of L-DOPA on SH-SY5Y neuronal cells under α-syn-induced toxicity. We assessed the protein and mRNA levels of endoplasmic reticulum (ER) stress and cell death markers using western blot analysis and reverse transcription-PCR. Our data showed that L-DOPA could attenuate ER stress markers, including the levels of activating transcription factor 4 (ATF4), C/EBPhomologous protein expression (CHOP), immunoglobulin-heavy-chain-binding protein (BiP), sliced X-box-binding protein 1 (XBP-1), and reduce nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) signaling through dopamine receptor D2 (DRD2) in SH-SY5Y neuronal cells under α-syn-induced toxicity. In conclusion, we suggest that L-DOPA may attenuate the neuropathology of PD by regulating signaling related to DRD2 in neuronal cells under α-syn-induced toxicity. Our study, therefore, indicates an additional role for L-DOPA in the treatment of PD.

Siyo V, Schäfer G, Hunter R, et al.
The Cytotoxicity of the Ajoene Analogue BisPMB in WHCO1 Oesophageal Cancer Cells Is Mediated by CHOP/GADD153.
Molecules. 2017; 22(6) [PubMed] Article available free on PMC after 13/11/2019 Related Publications
Garlic is a food and medicinal plant that has been used in folk medicine since ancient times for its beneficial health effects, which include protection against cancer. Crushed garlic cloves contain an array of small sulfur-rich compounds such as ajoene. Ajoene is able to interfere with biological processes and is cytotoxic to cancer cells in the low micromolar range. BisPMB is a synthetic ajoene analogue that has been shown in our laboratory to have superior cytotoxicity to ajoene. In the current study we have performed a DNA microarray analysis of bisPMB-treated WHCO1 oesophageal cancer cells to identify pathways and processes that are affected by bisPMB. The most significantly enriched biological pathways as assessed by gene ontology, KEGG and ingenuity pathway analysis were those involving protein processing in the endoplasmic reticulum (ER) and the unfolded protein response. In support of these pathways, bisPMB was found to inhibit global protein synthesis and lead to increased levels of ubiquitinated proteins. BisPMB also induced alternate splicing of the transcription factor XBP-1; increased the expression of the ER stress sensor GRP78 and induced expression of the ER stress marker CHOP/GADD153. CHOP expression was found to be central to the cytotoxicity of bisPMB as its silencing with siRNA rendered the cells resistant to bisPMB. The MAPK proteins, JNK and ERK1/2 were activated following bisPMB treatment. However JNK activation was not critical in the cytotoxicity of bisPMB, and ERK1/2 activation was found to play a pro-survival role. Overall the ajoene analogue bisPMB appears to induce cytotoxicity in WHCO1 cells by activating the unfolded protein response through CHOP/GADD153.

Sowmya Shree G, Yogendra Prasad K, Arpitha HS, et al.
β-carotene at physiologically attainable concentration induces apoptosis and down-regulates cell survival and antioxidant markers in human breast cancer (MCF-7) cells.
Mol Cell Biochem. 2017; 436(1-2):1-12 [PubMed] Related Publications
Although β-carotene is known for its anti-carcinogenic and antioxidant properties, a few recent epidemiological and experimental evidence show that at higher concentration it acts as pro-oxidant and induces cancer. Since the global burden of breast cancer exceeds all other types of cancer, and its incidence rates is also in increasing trend, the present study attempted to evaluate the anti-cancer molecular mechanism of β-carotene (at 1 µM concentration) isolated from Spinacia oleracea in human breast cancer (MCF-7) cells. The carotenoid was purified by open column chromatography and identified by LC-MS. The anti-proliferative effect of β-carotene at different concentrations was evaluated by WST-1 assay and the changes in cell morphology were examined by microscopic observation. The induction of apoptosis by β-carotene was observed by DAPI staining and colorimetric caspase-3 assay. The expression of cell survival, apoptotic, and antioxidant marker proteins was measured by western blot analysis. Purified β-carotene inhibited the viability of MCF-7 cells in a dose-dependent manner, which was well correlated with changes in cell morphology. Increased apoptotic cells were observed in β-carotene (1 µM)-treated cells. This apoptosis induction was associated with increased caspase-3 activity. The protein expression studies showed that β-carotene at 1 µM concentration effectively decreases the expression of the anti-apoptotic protein, Bcl-2 and PARP, and survival protein, NF-kB. It also inhibited the activation of intracellular growth signaling proteins, Akt and ERK1/2. The inhibition of Akt activation by β-carotene results in decreased phosphorylation of Bad. Further, it down-regulated antioxidant enzyme, SOD-2, and its transactivation factor (Nrf-2), and endoplasmic reticulum (ER) stress marker, XBP-1, at protein levels. These findings exhibit the key role of β-carotene even at a low physiological concentration in MCF-7 cells which further explains its predominant anti-cancer activity.

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