Major Vault Protein Expression Research Articles

The prognostic value and immunological role of MVP in pan-cancer study.

Major Vault Protein (MVP) has emerged as a potential prognostic and immunological biomarker in various cancer types. This pan-cancer study aimed to investigate expression of MVP and its correlation with clinical outcomes and immune infiltration across diverse cancer types. We conducted an analysis of extensive transcriptomic and clinical data from publicly available databases. Our findings unveiled a significant association between MVP expression and cancer progression, with higher expression levels predicting poorer overall survival in multiple cancer types. Importantly, MVP expression demonstrated a close relationship with immune infiltration in the tumor microenvironment, showing that higher expression levels were associated with increased immune cell infiltration. We further validated expression of MVP and function in cancer cell lines A549 and AGS. These compelling results suggest that MVP holds promise as a valuable biomarker for prognostic assessment and the development of immunotherapeutic strategies across various cancer types. Consequently, targeting MVP may offer a compelling therapeutic approach in the treatment of human cancers.

Dissecting the autism-associated 16p11.2 locus identifies multiple drivers in neuroanatomical phenotypes and unveils a male-specific role for the major vault protein

BackgroundUsing mouse genetic studies and systematic assessments of brain neuroanatomical phenotypes, we set out to identify which of the 30 genes causes brain defects at the autism-associated 16p11.2 locus.ResultsWe show that multiple genes mapping to this region interact to regulate brain anatomy, with female mice exhibiting far fewer brain neuroanatomical phenotypes. In male mice, among the 13 genes associated with neuroanatomical defects (Mvp, Ppp4c, Zg16, Taok2, Slx1b, Maz, Fam57b, Bola2, Tbx6, Qprt, Spn, Hirip3, and Doc2a), Mvp is the top driver implicated in phenotypes pertaining to brain, cortex, hippocampus, ventricles, and corpus callosum sizes. The major vault protein (MVP), the main component of the vault organelle, is a conserved protein found in eukaryotic cells, yet its function is not understood. Here, we find MVP expression highly specific to the limbic system and show that Mvp regulates neuronal morphology, postnatally and specifically in males. We also recapitulate a previously reported genetic interaction and show that Mvp+/−;Mapk3+/− mice exhibit behavioral deficits, notably decreased anxiety-like traits detected in the elevated plus maze and open field paradigms.ConclusionsOur study highlights multiple gene drivers in neuroanatomical phenotypes, interacting with each other through complex relationships. It also provides the first evidence for the involvement of the major vault protein in the regulation of brain size and neuroanatomy, specifically in male mice.

Correlation of expression of Major Vault Protein with androgen receptor and immune checkpoint protein B7-H3, and with poor prognosis in prostate cancer.

Prostate cancer diagnosis and early stratification is an important aspect to avoid undertreatment of high-risk prostate cancer patients. Major Vault Protein (MVP) has been proposed as a prognostic biomarker in prostate cancer. PTEN and the immune checkpoint protein B7-H3 interact with MVP and are important in prostate cancer progression and therapy response. We evaluated the expression of MVP by immunohistochemistry of tissue microarray samples from a retrospective cohort consisting of 119 prostate cancer patients. We correlated the protein expression of MVP with clinicopathological characteristics, and protein expression of androgen receptor (AR), PTEN, immune checkpoint proteins B7-H3 and PD-L1. We found MVP to be expressed in 53% of prostate tumors, and correlated positively with biochemical recurrence (ρ=0.211/p=0.021). Furthermore, we found positive correlation of MVP expression with expression of AR (ρ=0.244/p=0.009) and the immune checkpoint protein B7-H3 (ρ=0.200/p=0.029), but not with PD-L1 (ρ=0.152/p=0.117) or PTEN expression (ρ=-0.034/p=0.721). Our findings support the notion that expression of MVP is associated with poor prognosis in prostate cancer. The correlation between MVP and immune checkpoint protein B7-H3 in prostate cancer suggests a role for MVP in immunoregulation and drug resistance.

Major Vault Protein (MVP) Associated With BRAF V600E Mutation Is an Immune Microenvironment-Related Biomarker Promoting the Progression of Papillary Thyroid Cancer via MAPK/ERK and PI3K/AKT Pathways.

Papillary thyroid cancer (PTC) is the most common malignancy of the endocrine system, with an increase in incidence frequency. Major vault protein (MVP) is the main structural protein of the vault complex that has already been investigated in specific cancers. Yet the underlying biological functions and molecular mechanisms of MVP in PTC still remain considerably uncharacterized. Comprehensive analyses are predicated on several public datasets and local RNA-Seq cohort. Clinically, we found that MVP was upregulated in human PTC than in non-cancerous thyroid tissue and was correlated with vital clinicopathological parameters in PTC patients. MVP expression was associated with BRAF V600E, RAS, TERT, and RET status, and it was correlated with worse progression-free survival in PTC patients. Functionally, enrichment analysis provided new clues for the close relationship between MVP with cancer-related signaling pathways and the immune microenvironment in PTC. In PTC with high MVP expression, we found CD8+ T cells, regulatory T cells, and follicular helper T cells have a higher infiltration level. Intriguingly, MVP expression was positively correlated with multiple distinct phases of the anti-cancer immunity cycle. MVP knockdown significantly suppressed cell viability and colony formation, and promoted apoptosis. In addition, downregulated MVP markedly inhibited the migration and invasion potential of PTC cells. The rescue experiments showed that MVP could reverse the level of cell survival and migration. Mechanistically, MVP exerts its oncogenic function in PTC cells through activating PI3K/AKT/mTOR and MAPK/ERK pathways. These results point out that MVP is a reliable biomarker related to the immune microenvironment and provide a basis for elucidating the oncogenic roles of MVP in PTC progression.

Major vault protein attenuates cardiomyocyte injury in doxorubicin-induced cardiomyopathy through activating AKT

BackgroundDoxorubicin (DOX) has limited chemotherapy application for malignancies due to cardiotoxicity. The pathogenesis of DOX-induced cardiomyopathy (DiCM) is yet to be elucidated. Increasing studies proved that activation of AKT prevented cardiomyocyte apoptosis and cardiac dysfunction in response to DOX insult. Our previous studies indicated that major vault protein (MVP) deficiency was accompanied by suppressed phosphorylation of AKT in metabolic diseases. This study aimed to investigate the role and underlying mechanism of MVP on cardiomyocyte apoptosis in DiCM.MethodsMice were intraperitoneally injected with DOX 5 mg/kg, once a week for 5 weeks, the total cumulative dose was 25 mg/kg. Cardiomyocyte-specific MVP overexpression was achieved using an adeno-associated virus system under the cTnT promoter after the fourth DOX injection. Cardiac function was examined by echocardiography followed by euthanasia. Tissue and serum were collected for morphology analysis and biochemical examination.ResultsHerein, we found that MVP expression was upregulated in DOX-treated murine hearts. Cardiac-specific MVP overexpression alleviated DOX-induced cardiac dysfunction, oxidative stress and fibrosis. Mechanistically, MVP overexpression activated AKT signaling and decreased cardiomyocyte apoptosis in DiCM.ConclusionsBased on these findings, we supposed that MVP was a potential therapeutic agent against DiCM.

Major Vault Protein Inhibits Porcine Reproductive and Respiratory Syndrome Virus Infection in CRL2843CD163 Cell Lines and Primary Porcine Alveolar Macrophages.

Porcine reproductive and respiratory syndrome (PRRS), a significant viral infectious disease that commonly occurs among farmed pigs, leads to considerable economic losses to the swine industry worldwide. Major vault protein (MVP) is a host factor that induces type Ⅰ interferon (IFN) production. In this study, we evaluated the effect of MVP on PRRSV infection in CRL2843CD163 cell lines and porcine alveolar macrophages (PAMs). Our results showed that MVP expression was downregulated by PRRSV infection. Adenoviral overexpression of MVP inhibited PRRSV replication, whereas the siRNA knockdown of MVP promoted PRRSV replication. In addition, MVP knockdown has an adverse effect on the inhibitive role of MVP overexpression on PRRSV replication. Moreover, MVP could induce the expression of type Ⅰ IFNs and IFN-stimulated gene 15 (ISG15) in PRRSV-infected PAMs. Based on these results, MVP may be a potential molecular target of drugs for the effective prevention and treatment of PRRSV infection.

MVP Expression Facilitates Tumor Cell Proliferation and Migration Supporting the Metastasis of Colorectal Cancer Cells.

Cancer cells show significant dysregulation of genes expression, which may favor their survival in the tumor environment. In this study, the cellular vault’s components MVP (major vault protein), TEP1 (telomerase-associated protein 1) and vPARP (vault poly(ADP-ribose) polymerase) were transiently or completely inhibited in U2OS cells (human bone osteosarcoma epithelial cells) to evaluate their impact on the cell proliferative and migratory capacity as well as on the development of their resistance to the drug vinorelbine. Comparative analysis of MVP protein expression level in normal colon tissue, primary colorectal tumor, and metastasis showed that the expression of this protein does not increase significantly in the primary tumor, but its expression increases in metastatic cells. Further comparative molecular analysis using the whole transcriptome microarrays for MVP-positive and MVP-negative cells showed that MVP is involved in regulating proliferation and migration of cancer cells. MVP may facilitate metastasis of colon cancer due to its impact on cell migration. Moreover, two vault proteins, MVP and TEP1, contribute the resistance to vinorelbine, while vPARP does not.

Novel cancer stem cell marker MVP enhances temozolomide-resistance in glioblastoma

The resistance of highly aggressive glioblastoma multiforme (GBM) to chemotherapy is a major clinical problem resulting in a poor prognosis. GBM contains a rare population of self-renewing cancer stem cells (CSCs) that proliferate, spurring the growth of new tumors, and evade chemotherapy. In cancer, major vault protein (MVP) is thought to contribute to drug resistance. However, the role of MVP as CSCs marker remains unknown and whether MVP could sensitize GBM cells to Temozolomide (TMZ) also is unclear. We found that sensitivity to TMZ was suppressed by significantly increasing the MVP expression in GBM cells with TMZ resistance. Also, MVP was associated with the expression of other multidrug-resistant proteins in tumorsphere of TMZ-resistant GBM cell, and was highly co-expressed with CSC markers in tumorsphere culture. On the other hands, knockdown of MVP resulted in reduced sphere formation and invasive capacity. Moreover, high expression of MVP was associated with tumor malignancy and survival rate in glioblastoma patients. Our study describes that MVP is a potentially novel maker for glioblastoma stem cells and may be useful as a target for preventing TMZ resistance in GBM patients.

Major vault protein (MVP) negatively regulates osteoclastogenesis via calcineurin-NFATc1 pathway inhibition.

Rationale: Bone homeostasis is maintained by a balanced interplay of osteoblasts and osteoclasts. Osteoclasts are derived from monocyte/macrophage lineage. Major vault protein (MVP) is known to promote apoptosis and prevent metabolic diseases in macrophage. However, whether MVP is involved in osteoclastogenesis is unknown. Here, we identified an important function of MVP as a negative regulator of osteoclastogenesis and its therapeutic potential in preventing bone loss.Methods: Expression of MVP in osteoclasts was investigated in human tumor tissues with immunohistochemical staining. Next, we generated total body (Mvp-/-) and monocyte-specific (Mvpf/fLyz2-Cre) MVP gene knockout mice to observe bone phenotype and osteoclastogenesis using micro-CT and bone histomorphometry. Moreover, we examined the effects of MVP on osteoclast differentiation, bone resorption, NFATc1 activation and calcium oscillations in vitro. Finally, we explored the clinical potential of targeting MVP in two osteoporosis mouse models and used an adeno-associated virus (AAV) gene to overexpress MVP locally in mice.Results: We found that Mvp-/- and Mvpf/fLyz2-Cre mice both exhibited osteoporosis-like phenotypes. MVP-deficiency also enhanced calcineurin-NFATc1 signaling and promoted NFATc1 activity, which led to enhanced osteoclastogenesis and bone resorption. Calcineurin inhibition using the small molecule inhibitor FK506 corrected the enhanced osteoclastogenesis in Mvpf/fLyz2-Cre group. Additionally, MVP reexpression in Mvpf/fLyz2-Cre group rescued calcineurin expression. MVP overexpression in wild-type mice prevented pathologic bone loss in mouse models of ovariectomized (OVX) and calvaria-adjacent lipopolysaccharide (LPS)-injected.Conclusions: Our data suggested that MVP negatively regulates osteoclast differentiation and bone resorption via inhibition of calcineurin-NFATc1 signaling. In osteoclast-related bone diseases such as osteoporosis, manipulation of MVP activity may be an attractive therapeutic target.

Major Vault Protein Promotes Hepatocellular Carcinoma Through Targeting Interferon Regulatory Factor 2 and Decreasing p53 Activity.

Major vault protein (MVP) is up-regulated during infections with hepatitis B virus (HBV) and hepatitis C virus (HCV). Here, we found that MVP deficiency inhibited hepatocellular carcinoma (HCC) development induced by diethylnitrosamine, hepatitis B X protein, and HCV core. Forced MVP expression was sufficient to induce HCC in mice. Mechanistic studies demonstrate that the ubiquitin ligase human double minute 2 (HDM2) forms mutual exclusive complexes either with interferon regulatory factor 2 (IRF2) or with p53. In the presence of MVP, HDM2 is liberated from IRF2, leading to the ubiquitination of the tumor suppressor p53. Mouse xenograft models showed that HBV and HCV promote carcinogenesis through MVP induction, resulting in a loss of p53 mediated by HDM2. Analyses of clinical samples from chronic hepatitis B, liver cirrhosis, and HCC revealed that MVP up-regulation correlates with several hallmarks of malignancy and associates with poor overall survival. Taken together, through the sequestration of IRF2, MVP promotes an HDM2-dependent loss of p53 that promotes HCC development.

IL-25 promotes cisplatin resistance of lung cancer cells by activating NF-κB signaling pathway to increase of major vault protein.

As an inflammatory factor, IL‐25 has been studied in variouscancers, but it is rarely reported in cancer chemotherapy resistance. Major vault protein (MVP), as a gene associated with lung multidrug resistance, is associated with multiple chemotherapy resistances of lung cancer. However, the relationship between IL‐25 and MVP in lung cancer cells has not been studied. In this study, we found that both IL‐25 and MVP were elevated expressed in cisplatin‐resistant lung adenocarcinoma cell line (A549/CDDP). Silencing of IL‐25 resulted in down‐regulation of MVP expression and reduced cisplatin tolerance of A549/CDDP cells. Overexpression of IL‐25 resulted in increase of MVP expression and the cisplatin tolerance in A549 cells. In addition, we found that the extracellular IL‐25 could stimulate the expression of MVP and activate the NF‐κB signaling pathway. Further, animal models also confirmed that IL‐25 reduced the sensitivity of xenografts to chemotherapy. Taken together, we believe that the up‐regulation of IL‐25 induces MVP expression contributing to chemotherapy resistances of lung cancer cells. Our findings suggest that interference the expression of IL‐25 might be potential treatment strategies for the clinical reversing the chemotherapy resistance.

Adipocytes promote breast cancer resistance to chemotherapy, a process amplified by obesity: role of the major vault protein\xa0(MVP)

IntroductionClinical studies suggest that obesity, in addition to promoting breast cancer aggressiveness, is associated with a decrease in chemotherapy efficacy, although the mechanisms involved remain elusive. As chemotherapy is one of the main treatments for aggressive or metastatic breast cancer, we investigated whether adipocytes can mediate resistance to doxorubicin (DOX), one of the main drugs used to treat breast cancer, and the mechanisms associated.MethodsWe used a coculture system to grow breast cancer cells with in vitro differentiated adipocytes as well as primary mammary adipocytes isolated from lean and obese patients. Drug cellular accumulation, distribution, and efflux were studied by immunofluorescence, flow cytometry, and analysis of extracellular vesicles. Results were validated by immunohistochemistry in a series of lean and obese patients with cancer.ResultsAdipocytes differentiated in vitro promote DOX resistance (with cross-resistance to paclitaxel and 5-fluorouracil) in a large panel of human and murine breast cancer cell lines independently of their subtype. Subcellular distribution of DOX was altered in cocultivated cells with decreased nuclear accumulation of the drug associated with a localized accumulation in cytoplasmic vesicles, which then are expelled into the extracellular medium. The transport-associated major vault protein (MVP), whose expression was upregulated by adipocytes, mediated both processes. Coculture with human mammary adipocytes also induced chemoresistance in breast cancer cells (as well as the related MVP-induced DOX efflux) and their effect was amplified by obesity. Finally, in a series of human breast tumors, we observed a gradient of MVP expression, which was higher at the invasive front, where tumor cells are at close proximity to adipocytes, than in the tumor center, highlighting the clinical relevance of our results. High expression of MVP in these tumor cells is of particular interest since they are more likely to disseminate to give rise to chemoresistant metastases.ConclusionsCollectively, our study shows that adipocytes induce an MVP-related multidrug-resistant phenotype in breast cancer cells, which could contribute to obesity-related chemoresistance.

Major vault protein is a direct target of Notch1 signaling and contributes to chemoresistance in triple-negative breast cancer cells

Resistance to chemotherapy remains a significant problem in the treatment of breast cancer, especially for triple-negative breast cancer (TNBC), in which standard systemic therapy is currently limited to chemotherapeutic agents. Our study aimed to better understand the molecular mechanisms that lead to failure of chemotherapy in TNBC. Herein, we observed elevated expression of Notch1 and major vault protein (MVP) in MDA-MB-231DDPR cells compared to their parental counterparts. We demonstrated that Notch1 could positively regulate the expression of MVP. Also, Notch1 intracellular domain (ICD) was capable of binding to CBF-1 on the promoter of MVP to drive its transcription, resulting in activation of AKT pathway and promoting the progress of epithelial to mesenchymal transition (EMT). Conversely, silencing of Notch1 and MVP suppressed AKT pathway, reduced EMT and enhanced the sensitivity of TNBC cells to cisplatin and doxorubicin. Survival analysis indicated that the MVP was closely related to shorter recurrence-free survival (RFS) in patients with TNBC. Collectively, this study provides evidence that Notch1 activates AKT pathway and promotes EMT partly through direct activation of MVP. Targeting Notch1/MVP pathway appears to have potential in overcoming chemoresistance in TNBC.

Major Vault Protein, a Candidate Gene in 16p11.2 Microdeletion Syndrome, Is Required for the Homeostatic Regulation of Visual Cortical Plasticity.

Microdeletion of a region in chromosome 16p11.2 increases susceptibility to autism. Although this region contains exons of 29 genes, disrupting only a small segment of the region, which spans five genes, is sufficient to cause autistic traits. One candidate gene in this critical segment is MVP, which encodes for the major vault protein (MVP) that has been implicated in regulation of cellular transport mechanisms. MVP expression levels in MVP+/- mice closely phenocopy those of 16p11.2 mutant mice, suggesting that MVP+/- mice may serve as a model of MVP function in 16p11.2 microdeletion. Here we show that MVP regulates the homeostatic component of ocular dominance (OD) plasticity in primary visual cortex. MVP+/- mice of both sexes show impairment in strengthening of open-eye responses after several days of monocular deprivation (MD), whereas closed-eye responses are weakened as normal, resulting in reduced overall OD plasticity. The frequency of miniature EPSCs (mEPSCs) in pyramidal neurons is decreased in MVP+/- mice after extended MD, suggesting a reduction of functional synapses. Correspondingly, upregulation of surface GluA1 AMPA receptors is reduced in MVP+/- mice after extended MD, and is accompanied by altered expression of STAT1 and phosphorylated ERK, which have been previously implicated in OD plasticity. Normalization of STAT1 levels by introducing STAT1 shRNA rescues surface GluA1 and open-eye responses, implicating STAT1 as a downstream effector of MVP. These findings demonstrate a specific role for MVP as a key molecule influencing the homeostatic component of activity-dependent synaptic plasticity, and potentially the corresponding phenotypes of 16p11.2 microdeletion syndrome.SIGNIFICANCE STATEMENT Major vault protein (MVP), a candidate gene in 16p11.2 microdeletion syndrome, has been implicated in the regulation of several cellular processes including transport mechanisms and scaffold signaling. However, its role in brain function and plasticity remains unknown. In this study, we identified MVP as an important regulator of the homeostatic component of experience-dependent plasticity, via regulation of STAT1 and ERK signaling. This study helps reveal a new mechanism for an autism-related gene in brain function, and suggests a broader role for neuro-immune interactions in circuit level plasticity. Importantly, our findings might explain specific components of the pathophysiology of 16p11.2 microdeletion syndrome.

Expression of the Major Vault Protein (MVP) and Cellular Vault Particles in Fish.

Cellular vaults are ubiquitous 13 mega Da multi-subunit ribonuceloprotein particles that may have a role in nucleocytoplasmic transport. Seventy percent of the vault's mass consists of a ≈100 kDa protein, the major vault protein (MVP). In humans, a drug resistance-associated protein, originally identified as lung resistance protein in metastatic lung cancer, was ultimately shown to be the previously described MVP. In this study, a partial MVP sequence was cloned from channel catfish. Recombinant MVP (rMVP) was used to generate a monoclonal antibody that recognizes full length protein in distantly related fish species, as well as mice. MVP is expressed in fish spleen, liver, anterior kidney, renal kidney, and gills, with a consistent expression in epithelial cells, macrophages, or endothelium at the interface of the tissue and environment or vasculature. We show that vaults are distributed throughout cells of fish lymphoid cells, with nuclear and plasma membrane aggregations in some cells. Protein expression studies were extended to liver neoplastic lesions in Atlantic killifish collected in situ at the Atlantic Wood USA-EPA superfund site on the southern branch of the Elizabeth River, VA. MVP is highly expressed in these lesions, with intense staining at the nuclear membrane, similar to what is known about MVP expression in human liver neoplasia. Additionally, MVP mRNA expression was quantified in channel catfish ovarian cell line following treatment with different classes of pharmacological agents. Notably, mRNA expression is induced by ethidium bromide, which damages DNA. Anat Rec, 2017. © 2017 Wiley Periodicals, Inc. Anat Rec, 300:1981-1992, 2017. © 2017 Wiley Periodicals, Inc.

Abstract 1966: Cell-surface major vault protein is a novel marker for circulating tumor cells with nonepithelial phenotypes in hepatocellular carcinoma

Abstract Hepatocellular carcinoma (HCC) is currently is the fifth most common malignancy worldwide and the poor because of frequent metastasis and resistance to chemotherapy. Circulating tumor cells (CTCs) in blood have attracted attention as potential seeds for metastasis and an important indicator of treatment outcome. However, the biological properties of CTCs are largely unknown due to rarity and lack of CTC-specific surface markers. Major vault protein (MVP) is upregulated during malignant progression and drug resistance development in various cancer cells, although it is ubiquitously expressed in many normal tissues. Here, we found for the first time that MVP was expressed on the surface of various cancer cells including HCC cell lines, although MVP has been known as a cytoplasmic and nuclear protein. To investigate the role of cell-surface MVP (csMVP) on HCC cell lines, MVP expression was knocked down in Huh7 cells by small interfering RNA. MVP knockdown decreased cell growth and increased apoptotic cell death. When Huh7 cells were treated with a polyclonal anti-MVP antibody (α-MVP) recognizing csMVP, Huh7 cell proliferation was decreased without apoptotic cell death. Cell sorting revealed that csMVP-positive Huh7 cells showed a higher proliferation and survival rate than csMVP-negative Huh7 cells under the stress of low density seeding. Huh7 cells treated with α-MVP also inhibited cell invasion and migration in vitro. Thus, csMVP is positively associated with HCC cell proliferation, survival, invasion and migration. Analysis of signaling molecules showed that MVP knockdown caused a significant decrease in the levels of phosphorylation of FAK, ERK, AKT and S6K. MVP knockdown also increased E-cadherin but decreased vimentin, indicating that MVP promotes the process of epithelial-to-mesenchymal transition. To further analyze the role of csMVP during HCC metastasis, blood samples from 62 HCC patients and 10 healthy volunteers were stained with csMVP, EpCAM, HSA, EGFR, CK, and/or vimentin antibodies after the depletion of red blood cells and CD45-positive cells. csMVP-positive CTCs were detected in approximately 85.5% (> 0.46CTCs/ml) of patients, and the cell count measured in ml of blood ranged between 0.48 and 37.8. Double staining showed that almost all csMVP-positive cells were panCK-negative while approximately one fifth of csMVP-positive CTCs was HSA-positive. Triple staining further showed that among csMVP-positive cells, EpCAM+Vimentin-, EpCAM+Vimentin+, EpCAM-Vimentin+ and EpCAM-Vimentin- cells were approximately 0, 0, 49 and 51%, respectively, suggesting that a half of csMVP-positive cells are EMT-phenotypic cells and the rest of them are both EpCAM- and vimentin-negative cells. The results suggest that csMVP is a novel marker on CTCs in patients with HCCs, where it is expressed predominantly on EMT phenotypic and EpCAM-vimentin- intermediate CTCs. Citation Format: Hyun Min Lee, Jae Won Joh, Won Tae Kim, Min Kyu Kim, Se Ri Seo, Hong Seo Choi, Hee Jin Chang, Young Joo Jang, Dae Shick Kim, Chun Jeih Ryu. Cell-surface major vault protein is a novel marker for circulating tumor cells with nonepithelial phenotypes in hepatocellular carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1966. doi:10.1158/1538-7445.AM2017-1966

VPARP Adjusts MVP Expression in Drug-resistant Cell Lines in Conjunction with MDR Proteins.

The definition of vault (ribonucleoprotein particles) function remains highly complex. Vaults may cooperate with multidrug resistance (MDR) proteins, supporting their role in drug resistance. This topic is the main theme of this publication. The cell viability was determined by an MTT assay. The protein expression was detected by western blot analysis. The proteins were knocked-down using siRNA. No major vault protein (MVP) in the LoVo/Dx and W1PR cell lines after tunicamycin treatment was shown. In W1PR cells with knocked-down MVP, a statistically significant decrease in cell viability was noted. In LoVo/Dx, W1TR and A2780TR cells were vault poly-ADP-ribose polymerase (vPARP) was knockdown, a decrease in cell viability was shown. Also, MVP silencing induced an increase in glycoprotein P (Pgp) expression in LoVo/Dx cells. MVP is important for the drug resistance of cancer cells, but it probably requires the presence of vPARP for full activation. Some correlations between MDR proteins and vaults exist.

Abstract 1591: Identification and characterization of surface major vault protein on circulating tumor cells in patients with hepatocellular carcinoma

Abstract The prognosis of patients with hepatocellular carcinoma (HCC) is poor because of frequent metastasis and resistance to chemotherapy. Circulating tumor cells (CTCs) in blood have attracted attention as potential seeds for metastasis and an important indicator of treatment outcome. However, the biological properties of CTCs are largely unknown due to rarity and lack of CTC-specific surface markers. Previously, we produced monoclonal antibodies (MAbs) against surface molecules on human embryonic stem cells. We found that some of them bound to surface antigens on HCC cell lines but not to normal primary cells. MAb 63-B6, one of the MAbs, recognized CD45-negative CTCs in 6 out of 8 patients with HCCs, suggesting that 63-B6-reactive antigen may be a novel surface marker on CTCs. In a subsequent study, we found that 63-B6 recognized major vault protein (MVP) on the surface of cancer cells, although MVP has been known as a cytoplasmic and nuclear protein. To investigate the role of surface MVP on HCC cell lines, MVP expression was knocked down in Huh7 cells by small interfering RNA. MVP depletion decreased cell growth and increased apoptotic cell death. When Huh7 cells were treated with a polyclonal anti-MVP antibody recognizing surface MVP, Huh7 cell proliferation was decreased without apoptotic cell death, suggesting that surface MVP regulates cell proliferation. Huh7 cells treated with 63-B6 or the anti-MVP antibodies also inhibited Huh7 cell invasion and migration in vitro. Thus, surface MVP is positively associated with HCC cell proliferation, invasion and migration. To further dissect the functional role of surface MVP during HCC metastasis, blood samples from 60 HCC patients and 6 normal adults were stained with 63-B6, HSA, and/or EMT-related antibodies after the depletion of red blood cells and CD45-positive cells. CTCs were detected with 63-B6 in approximately 92% (≥2 CTCs) of patients, and the cell count measured in 7.5 ml of blood ranged between 2 and 1032. Double staining showed that 80% of HSA-positive CTCs was 63-B6-positive. Seventy-six% of EpCAM-positive CTCs was 63-B6-positive while 95% of vimentin-positive CTCs was 63-B6-positive, suggesting that 63-B6-reactive-surface MVP is more expressed on mesenchymal-phenotypic CTCs. Triple staining further showed that 36% of 63-B6-positive CTCs was EpCAM(-)Vimentin(+) and 19% of 63-B6-positive CTCs was EpCAM(+)Vimentin(+) while 3% of 63-B6-positive CTCs was EpCAM(+)Vimentin(-). Interestingly, 42% of 63-B6-positive CTCs was EpCAM(-)Vimentin(-). These results suggest that 63-B6-reactive surface MVP is a novel surface marker on CTCs in patients with HCCs, where it is expressed predominantly on mesenchymal phenotypic and EpCAM(-)Vimentin(-) CTCs. Citation Format: Hyun Min Lee, Jae Won Joh, Hong Seo Choi, Won Tae Kim, Se Ri Seo, Min Kyu Kim, Hee Jin Chang, Dae Shick Kim, Chun Jeih Ryu. Identification and characterization of surface major vault protein on circulating tumor cells in patients with hepatocellular carcinoma. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1591.

Inducible Major Vault Protein Plays a Pivotal Role in Double-Stranded RNA- or Virus-Induced Proinflammatory Response.

Pathogen invasion triggers robust antiviral cytokine production via different transcription factor signaling pathways. We have previously demonstrated that major vault protein (MVP) induces type I IFN production during viral infection; however, little is known about the role of MVP in proinflammatory responses. In this study, we found in vitro that expression of MVP, IL-6, and IL-8 was inducible upon dsRNA stimulation or viral infection. Moreover, MVP was essential for the induction of IL-6 and IL-8, as impaired expression of IL-6 and IL-8 in MVP-deficient human PBMCs, human lung epithelial cells (A549), and THP-1 monocytes, as well as in murine splenocytes, peritoneal macrophages, and PBMCs from MVP-knockout (MVP(-/-)) mice, was observed. Upon investigation of the underlying mechanisms, we demonstrated that MVP acted in synergy with AP-1 (c-Fos) and CCAAT/enhancer binding protein (C/EBP)β-liver-enriched transcriptional activating protein to activate the IL6 and IL8 promoters. Introduction of mutations into the AP-1 and C/EBPβ binding sites on the IL6 and IL8 promoters resulted in the loss of synergistic activation with MVP. Furthermore, we found that MVP interacted with both c-Fos and C/EBPβ. The interactions promoted nuclear translocation and recruitment of these transcription factors to IL6 and IL8 promoter regions. In the MVP(-/-) mouse model, significantly decreased expression of early antiviral cytokines resulted in higher viral titer in the lung, higher mortality, and heavier lung damage after infection with lethal influenza A virus. Taken together, our findings help to delineate a novel role of MVP in host proinflammatory response.

Correlation between Expression of MVP, Index of p53 and AgNOR Value with Chemoradiotherapy Clinical Response of Cervical Cancer

Cervical cancer is the most frequent cancer found in Indonesia. The primary treatment of cervical cancer at the locally advanced stage is usually performed by using radiotherapy and chemotherapy. The combination of the two techniques is often called chemoradioherapy. The response to chemoradiotherapy is influenced by biological and physical factors. Major vault protein (MVP) is a ribonucleoprotein which contributes to drug resistance in some cancers. The purposes of this research were: (1) to determine the correlation between the expression of MVP and the index of p53, including AgNOR values and index of MIB-1; and (2) between MVP and chemoradiotherapy clinical response of cervical cancer. Twenty-one microscopic slides taken from biopsy tissues of cervical cancer patients before undergoing treatment were stained to identify MVP, p53, and MIB-1 by means of immunohistochemistry techniques and AgNORs staining. After undergoing chemoradiotherapy treatment, the patients’ clinical responses were observed by pelvic control method. Experimental results showed that there was a correlation between MVP and AgNOR value (P=0.05), but no correlation between MVP and index of p53 (P=0.729), including MIB-1 LI (P=0.63), in untreated cervical cancer. In addition, there was no association between MVP and chemoradioterapy response. In conclusion, MVP expression correlates with the process of cell proliferation before the G2 phase of cell cycle in untreated cancer cells. Those have no association with clinical responses after the completion of treatment. Received: 20 November 2013; Revised: 18 July 2014; Accepted: 28 September 2014