Dysfunction of nucleus accumbens-1 activates cellular senescence and inhibits tumor cell proliferation and oncogenesis

An overview of the co-transcription factor NACC1: Beyond its pro-tumor effects

Nucleus accumbens-associated protein 1 (NACC1) is a member of the broad complex, tramtrack, bric-a-brac/poxvirus and zinc finger (BTB/POZ) protein families, mainly exerting its biological functions as a transcription co-regulator. NACC1 forms homo- or hetero-dimers through the BTB/POZ or BANP, E5R, and NACC1 (BEN) domain with other transcriptional regulators to regulate downstream signals. Recently, the overexpression of NACC1 has been observed in various tumors and is positively associated with tumor progression, high recurrence rate, indicating poor prognosis. NACC1 also regulates biological processes such as embryonic development, stem cell pluripotency, innate immunity, and related diseases. Our review combines recent research to summarize advancements in the structure, biological functions, and relative molecular mechanisms of NACC1. The future development of NACC1 clinical appliances is also discussed.

Co-Targeting Nucleus Accumbens Associate 1 and NF-κB Signaling Synergistically Inhibits Melanoma Growth

Nucleus-accumbens-associated protein-1 (NAC1) is a cancer-related transcriptional factor encoded by the NACC1 gene, which is amplified and overexpressed in various human cancers and has been appreciated as one of the top potential cancer driver genes. NAC1 has therefore been explored as a potential therapeutic target for managing malignant tumors. Here, we show that NAC1 is a negative regulator of NF-κB signaling, and NAC1 depletion enhances the level of the nuclear NF-κB in human melanoma. Furthermore, the inhibition of NF-κB signaling significantly potentiates the antineoplastic activity of the NAC1 inhibition in both the cultured melanoma cells and xenograft tumors. This study identifies a novel NAC1-NF-κB signaling axis in melanoma, offering a promising new therapeutic option to treat melanoma.

Mechanistic Insights of NAC1 Nuclear Export and Its Role in Ovarian Cancer Resistance to Docetaxel

In this study, we uncovered the nuclear export of nucleus accumbens-associated protein-1 (NAC1) as a novel mechanism involved in ovarian cancer resistance to taxanes, the chemotherapeutic drugs commonly used in treatment of this malignancy. We showed that NAC1, a nuclear factor of the BTB/POZ gene family, has a nuclear export signal (NES) at the N terminus (aa 17-28), and this NES critically contributes to the NAC1 nuclear-cytoplasmic shuttling when tumor cells were treated with docetaxel. Mechanistically, the nuclear-exported NAC1 bound to cullin3 (Cul3) and Cyclin B1 via its BTB and BOZ domains respectively, and the cyto-NAC1-Cul3 E3 ubiquitin ligase complex promotes the ubiquitination and degradation of Cyclin B1, thereby facilitating mitotic exit and leading to cellular resistance to docetaxel. We also showed in in vitro and in vivo experiments that TP-CH-1178, a membrane-permeable polypeptide against the NAC1 NES motif, blocked the nuclear export of NAC1, interfered with the degradation of Cyclin B1 and sensitized ovarian cancer cells to docetaxel. This study not only reveals a novel mechanism by which the NAC1 nuclear export is regulated and Cyclin B1 degradation and mitotic exit are impacted by the NAC1-Cul3 complex, but also provides the nuclear-export pathway of NAC1 as a potential target for modulating taxanes resistance in ovarian cancer and other malignancies.

Expression of nucleus accumbens-1 in colon cancer negatively modulates antitumor immunity

BACKGROUND

Nucleus accumbens-1 (NAC-1) is highly expressed in a variety of tumors, including colon cancer, and is closely associated with tumor recurrence, metastasis, and invasion.

AIM

To determine whether and how NAC-1 affects antitumor immunity in colon cancer.

METHODS

NAC-1-siRNA was transfected into RKO colon cancer cells to knock down NAC expression; tumor cells with or without knockdown of NAC-1 were treated with CD8⁺ T cells to test their cytocidal effect. The level of the immune checkpoint programmed death receptor-1 ligand (PD-L1) in colon cancer cells with or without knockdown of NAC-1 was analyzed using Quantitative real-time polymerase chain reaction and Western blotting. A double luciferase reporter assay was used to examine the effects of NAC-1 on the transcription of PD-L1. Mice bearing MC-38-OVA colon cancer cells expressing NAC-shRNA or control-shRNA were treated with OT-I mouse CD8⁺ T cells to determine the tumor response to immunotherapy. Immune cells in the tumor tissues were analyzed using flow cytometry. NAC-1, PD-L1 and CD8⁺ T cells in colon cancer specimens from patients were examined using immunohistochemistry staining.

RESULTS

Knockdown of NAC-1 expression in colon cancer cells significantly enhanced the cytocidal effect of CD8⁺ T cells in cell culture experiments. The sensitizing effect of NAC-1 knockdown on the antitumor action of cytotoxic CD8⁺ T cells was recapitulated in a colon cancer xenograft animal model. Furthermore, knockdown of NAC-1 in colon cancer cells decreased the expression of PD-L1 at both the mRNA and protein levels, and this effect could be rescued by transfection of an RNAi-resistant NAC-1 expression plasmid. In a reporter gene assay, transient expression of NAC-1 in colon cancer cells increased the promoter activity of PD-L1, indicating that NAC-1 regulates PD-L1 expression at the transcriptional level. In addition, depletion of tumoral NAC-1 increased the number of CD8⁺ T cells but decreased the number of suppressive myeloid-derived suppressor cells and regulatory T cells.

CONCLUSION

Tumor expression of NAC-1 is a negative determinant of immunotherapy.

Tumorous expression of NAC1 restrains antitumor immunity through the LDHA-mediated immune evasion

BACKGROUND

T cell-mediated antitumor immunity has a vital role in cancer prevention and treatment; however, the immune-suppressive tumor microenvironment (TME) constitutes a significant contributor to immune evasion that weakens antitumor immunity. Here, we explore the relationship between nucleus accumbens-associated protein-1 (NAC1), a nuclear factor of the BTB (broad-complex, Tramtrack, bric a brac)/POZ (Poxvirus, and Zinc finger) gene family, and the TME.

METHODS

Adoptive cell transfer (ACT) of mouse or human tumor antigen (Ag)-specific CD8+ cytotoxic T lymphocytes (CTLs) was tested in an immunocompetent or immunodeficient mouse model of melanoma with or without expression of NAC1. The effects of NAC1 expression on immune evasion in tumor cells were assessed in vitro and in vivo. CRISPR/Cas9, glycolysis analysis, retroviral transduction, quantitative real-time PCR, flow cytometric analysis, immunoblotting, database analyses were used to screen the downstream target and underlying mechanism of NAC1 in tumor cells.

RESULTS

Tumorous expression of NAC1 negatively impacts the CTL-mediated antitumor immunity via lactate dehydrogenase A (LDHA)-mediated suppressive TME. NAC1 positively regulated the expression of LDHA at the transcriptional level, which led to higher accumulation of lactic acid in the TME. This inhibited the cytokine production and induced exhaustion and apoptosis of CTLs, impairing their cell-killing ability. In the immunocompetent and immunodeficient mice, NAC1 depleted melanoma tumors grew significantly slower and had an elevated infiltration of tumor Ag-specific CTLs following ACT, compared with the control groups.

CONCLUSIONS

Tumor expression of NAC1 contributes substantially to immune evasion through its regulatory role in LDHA expression and lactic acid production. Thus, therapeutic targeting of NAC1 warrants further exploration as a potential strategy to reinforce cancer immunotherapy, such as the ACT of CTLs.

Expression of NAC1 Restrains the Memory Formation of CD8+ T Cells during Viral Infection

Nucleus accumbens-associated protein 1 (NAC1) is a transcription co-factor that has been shown to possess multiple roles in stem cell and cancer biology. However, little is known about its roles in regulation of the immune system. In the current study, we observed that expression of NAC1 impacted the survival of CD8+ T cells in vitro. NAC1-/- CD8+ T cells displayed lower metabolism, including reduced glycolysis and oxidative phosphorylation. In vivo, compared with wild-type (WT) mice, NAC1-/- mice produced a lower response to vaccinia virus (VACV) infection, and viral antigen (Ag)-specific CD8+ T cells decreased more slowly. Additionally, we observed that the NAC1-/- mice demonstrated a stronger memory formation of viral Ag-specific CD8+ T cells post-viral infection. Mechanically, we identified that compared with WT CD8+ T cells, the Interferon Regulatory Factor 4 (IRF4), a key transcription factor in T cell development, was highly expressed in NAC1-/- CD8+ T cells, insinuating that IRF4 could be a critical regulatory target of NAC1 in the memory formation of CD8+ T cells. Our results indicate that NAC1 restrains the memory formation of CD8+ T cells by modulating IRF4, and targeting NAC1 may be exploited as a new approach to boosting CD8+ T cell memory.

FUS-induced circRHOBTB3 facilitates cell proliferation via miR-600/NACC1 mediated autophagy response in pancreatic ductal adenocarcinoma

Background

Circular RNAs (circRNAs) are becoming a unique member of non-coding RNAs (ncRNAs) with emerging evidence of their regulatory roles in various cancers. However, with regards to pancreatic ductal adenocarcinoma (PDAC), circRNAs biological functions remain largely unknown and worth investigation for potential therapeutic innovation.

Methods

In our previous study, next-generation sequencing was used to identify differentially expressed circRNAs in 3 pairs of PDAC and adjacent normal tissues. Further validation of circRHOBTB3 expression in PDAC tissues and cell lines and gain-and-loss function experiments verified the oncogenic role of circRHOBTB3. The mechanism of circRHOBTB3 regulatory role was validated by pull-down assays, RIP, luciferase reporter assays. The autophagy response of PANC-1 and MiaPaca-2 cells were detected by mCherry-GFP-LC3B labeling and confocal microscopy, transmission electron microscopy and protein levels of LC3B or p62 via Western blot.

Results

circRHOBTB3 is highly expressed in PDAC cell lines and tissues, which also promotes PDAC autophagy and then progression in vitro and in vivo. Mechanistically, circRHOBTB3 directly binds to miR-600 and subsequently acts as a miRNA-sponge to maintain the expression level of miR-600-targeted gene NACC1, which facilitates the autophagy response of PDAC cells for adaptation of proliferation via Akt/mTOR pathway. Moreover, the RNA-binding protein FUS (FUS) directly binds to pre-RHOBTB3 mRNA to mediate the biogenesis of circRHOBTB3. Clinically, circRHOBTB3, miR-600 and NACC1 expression levels are correlated with the prognosis of PDAC patients and serve as independent risk factors for PDAC patients.

Conclusions

FUS-mediated circRHOBTB3 functions as a tumor activator to promote PDAC cell proliferation by modulating miR-600/NACC1/Akt/mTOR axis regulated autophagy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-021-02063-w.

NAC1 attenuates BCL6 negative autoregulation and functions as a BCL6 coactivator of FOXQ1 transcription in cancer cells

Background: Nucleus accumbens-associated protein 1 (NAC1) has multifaceted roles in cancer pathogenesis and progression, including the development of drug resistance, promotion of cytokinesis, and maintenance of “stem cell-like” phenotypes. NAC1 is a transcriptional co-regulator belonging to the bric-a-brac tramtrack broad (BTB) family of proteins, although it lacks the characteristic DNA binding motif of the BTB family. The formation of higher-order transcription complexes likely depends on its interaction with other DNA-binding co-factors.

Results: NAC1 interacts with BCL6 via its C-terminal BEN domain and forms a complex that binds the promoter region and activates transcription of the NAC1 target gene, FOXQ1. NAC1 and BCL6 were coordinately upregulated. Our analysis also identified a novel function of NAC1 in attenuating BCL6 auto-downregulation in ovarian cancer. Lastly, we found a significant overlap among NAC1- and BCL6-regulated genes in tumor cells, suggesting that NAC1 and BCL6 coordinately control transcription in cancer.

Conclusions: The results of this study provide a novel mechanistic insight into the oncogenic roles of NAC1 and underline the importance of developing the NAC1/BCL6-targeted cancer therapy.

Methods: Using the Cistrome database and Chromatin Immunoprecipitation (ChIP) analyses, we identified BCL6 as a potential NAC1- interacting molecule. Co-immunoprecipitation (Co-IP), luciferase reporter assay, immunohistochemistry and microarray analysis were performed to analyze the interaction between NAC1 and BCL6 and the mechanisms by which they regulate the downstream genes including FOXQ1.

DNA Methylation Influences miRNA Expression in Gonadotroph Pituitary Tumors

microRNAs are involved in pathogenesis of cancer. DNA methylation plays a role in transcription of miRNA-encoding genes and may contribute to changed miRNA expression in tumors. This issue was not investigated in pituitary neuroendocrine tumors (PitNETs) previously. DNA methylation patterns, assessed with HumanMethylation450K arrays in 34 PitNETs and five normal pituitaries, were used to determine differentially methylated CpGs located at miRNA genes. It showed aberrant methylation in regions encoding for 131 miRNAs. DNA methylation data and matched miRNA expression profiles, determined with next-generation sequencing (NGS) of small RNAs, were correlated in 15 PitNETs. This showed relationship between methylation and expression levels for 12 miRNAs. DNA methylation and expression levels of three of them (MIR145, MIR21, and MIR184) were determined in the independent group of 80 tumors with pyrosequencing and qRT-PCR and results confirmed both aberrant methylation in PitNETs and correlation between methylation and expression. Additionally, in silico target prediction was combined with analysis of established miRNA profiles and matched mRNA expression pattern, assessed with amplicon-based NGS to indicate putative target genes of epigenetically deregulated miRNAs. This study reveals aberrant DNA methylation in miRNA-encoding genes in gonadotroph PitNETs. Methylation changes affect expression level of miRNAs that regulate putative target genes with tumorigenesis-relevant functions.

NACC-1 regulates hepatocellular carcinoma cell malignancy and is targeted by miR-760

Hepatocellular carcinoma (HCC) is the most prominent form of presentation in liver cancer. It is also the fourth most common cause of cancer-associated deaths globally. The role of nucleus accumbens associated protein-1 (NACC-1) has been evaluated in several cancers. This protein is a transcriptional regulator that regulates a number of significant cellular processes. In the current study, we aimed to understand the role of NACC-1 in HCC. Primarily, we measured the expression of NACC-1 using quantitative real time polymerase chain reaction and western blot analysis. We knocked down the expression of NACC-1 in HCC cell lines Huh7 and HepG2 by transferring a commercially synthesized small interfering RNA and explored the impact of NACC-1 knockdown on cellular growth, migration, invasion, and chemoresistance to doxorubicin. Through bioinformatic analysis, we identified NACC-1 as a potential target of miR-760. Using a dual reporter luciferase assay, we confirmed the predicted target and assessed miR-760-mediated regulation of NACC-1 and rescue of tumorigenic phenotypes. We observed increased expression of NACC-1 in HCC. Furthermore, knockdown of NACC-1 resulted in reduced cell proliferation and invasion and increased susceptibility to doxorubicin-mediated chemosensitivity. Overexpression of miR-760 in HCC cell lines rescued NACC-1-mediated migration and invasion. We revealed that miR-760 regulated NACC-1 expression in HCC. Our data indicated that both miR-760 and NACC-1 could be used as prognostic markers, and miR-760 may have therapeutic benefits for HCC and other cancers.

Identification of a small-molecule compound that inhibits homodimerization of oncogenic NAC1 protein and sensitizes cancer cells to anticancer agents

Nucleus accumbens-associated protein-1 (NAC1) is a transcriptional repressor encoded by the NACC1 gene, which is amplified and overexpressed in various human cancers and plays critical roles in tumor development, progression, and drug resistance. NAC1 has therefore been explored as a potential therapeutic target for managing malignant tumors. However, effective approaches for effective targeting of this nuclear protein remain elusive. In this study, we identified a core unit consisting of Met⁷ and Leu⁹⁰ in NAC1's N-terminal domain (amino acids 1-130), which is critical for its homodimerization and stability. Furthermore, using a combination of computational analysis of the NAC1 dimerization interface and high-throughput screening (HTS) for small molecules that inhibit NAC1 homodimerization, we identified a compound (NIC3) that selectively binds to the conserved Leu-90 of NAC1 and prevents its homodimerization, leading to proteasomal NAC1 degradation. Moreover, we demonstrate that NIC3-mediated down-regulation of NAC1 protein sensitizes drug-resistant tumor cells to conventional chemotherapy and enhances the antimetastatic effect of the antiangiogenic agent bevacizumab both in vitro and in vivo These results suggest that small-molecule inhibitors of NAC1 homodimerization may effectively sensitize cancer cells to some anticancer agents and that NAC1 homodimerization could be further explored as a potential therapeutic target in the development of antineoplastic agents.

NACC1, as a Target of MicroRNA-331-3p, Regulates Cell Proliferation in Urothelial Carcinoma Cells

The nucleus accumbens-associated protein 1 (NACC1) is a transcription factor constitutively expressed in the urothelium, where it regulates cell growth, senescence, autophagy, and epithelial-mesenchymal transition. microRNA (miRNA) constitutes a class of small non-coding RNAs which are involved in cell proliferation, differentiation, and progression of tumors. miRNAs and their target molecules are utilized for molecular diagnosis of urothelial carcinoma. NACC1 is one of several putative target molecules of miR-331-3p, and is associated with cell proliferation in cancers such as prostate and cervical cancer. Functional experiments involving miR-331-3p and its target molecule NACC1 were conducted using the urothelial carcinoma (UC) cell lines, T24, UMUC6, and KU7. Furthermore, quantitative reverse transcription polymerase chain reaction and immunostaining were performed to evaluate the expression of NACC1 in UC derived from transurethral resection of bladder tumor (TUR-Bt) specimens. The methane thiosulfonate (MTS) assay revealed that cell proliferation was significantly reduced after transient transfection of miR-331-3p precursor and/or NACC1 siRNA in UC cells. Cell senescence via cell cycle arrest at the G1 phase was induced by NACC1 inhibition. On the other hand, suppression of NACC1 induced cell migration and invasion abilities. Immunohistochemical analysis of TUR-Bt specimens revealed that over 70% of UC cells presented strongly positive results for NACC1. In contrast, normal urothelial cells were weakly positive for NACC1. It was also found that NACC1 expression was lower in invasive UC cells than in non-invasive UC cells. Loss of NACC1 induced vessel invasion in invasive UC tissues. The present results indicate that NACC1 regulated by miR-331-3p contributes to cell proliferation, and is involved in cell migration and invasion. This suggests that NACC1 can serve as a potential target molecule for the prediction and prognosis of UC, and can contribute to effective treatment strategies.

Nac1 promotes self-renewal of embryonic stem cells through direct transcriptional regulation of c-Myc

The pluripotency transcriptional network in embryonic stem cells (ESCs) is composed of distinct functional units including the core and Myc units. It is hoped that dissection of the cellular functions and interconnections of network factors will aid our understanding of ESC and cancer biology. Proteomic and genomic approaches have identified Nac1 as a member of the core pluripotency network. However, previous studies have predominantly focused on the role of Nac1 in psychomotor stimulant response and cancer pathogenesis. In this study, we report that Nac1 is a self-renewal promoting factor, but is not required for maintaining pluripotency of ESCs. Loss of function of Nac1 in ESCs results in a reduced proliferation rate and an enhanced differentiation propensity. Nac1 overexpression promotes ESC proliferation and delays ESC differentiation in the absence of leukemia inhibitory factor (LIF). Furthermore, we demonstrated that Nac1 directly binds to the c-Myc promoter and regulates c-Myc transcription. The study also revealed that the function of Nac1 in promoting ESC self-renewal appears to be partially mediated by c-Myc. These findings establish a functional link between the core and c-Myc-centered networks and provide new insights into mechanisms of stemness regulation in ESCs and cancer.

NAC1 promotes the migration of prostate cancer cells and participates in osteoclastogenesis by negatively regulating IFNβ

Nucleus accumbens-associated protein 1 (NAC1), a transcriptional co-regulator, is overexpressed in advanced prostate cancer. However, the NAC1-regulated transcriptome has not been completely explored. In the present study, the functional silencing of NAC1 blocked the migration of prostate cancer cells and suppress osteoclastogenesis. The present study also determined that NAC1 was overexpressed in the highly aggressive prostate cancer cell lines PC-3, DU-145 and LNCaP. NAC1 small interfering RNA treatment of DU-145 cells decreased cell migration, but interestingly had no significant effects on cell proliferation. Furthermore, microarray analysis showed that a group of genes may be associated with the development of prostate cancer after NAC1 knockdown, including interferon-β (IFNβ), which is reported to be involved in osteoclastogenesis, an important factor affecting bone metastasis. The mechanisms of NAC1 function were further explored by co-culture studies using PC-3 and RAW264.7 osteoclast precursor cells, which demonstrated that silencing NAC1 downregulated the genes associated with the activation of osteoclasts. Furthermore, it was revealed that NAC1 had the ability to affect the release of IFNβ into the extracellular environment. Together, these findings indicated that NAC1 promoted cell migration, and that NAC1 may have a key role in osteoclastogenesis.

Silencing of NAC1 Expression Induces Cancer Cells Oxidative Stress in Hypoxia and Potentiates the Therapeutic Activity of Elesclomol

In order to survive under conditions of low oxygen, cancer cells can undergo a metabolic switch to glycolysis and suppress mitochondrial respiration in order to reduce oxygen consumption and prevent excessive amounts of reactive oxygen species (ROS) production. Nucleus accumbens-1 (NAC1), a nuclear protein of the BTB/POZ gene family, has pivotal roles in cancer development. Here, we identified that NAC1-PDK3 axis as necessary for suppression of mitochondrial function, oxygen consumption, and more harmful ROS generation and protects cancer cells from apoptosis in hypoxia. We show that NAC1 mediates suppression of mitochondrial function in hypoxia through inducing expression of pyruvate dehydrogenase kinase 3 (PDK3) by HIF-1α at the transcriptional level, thereby inactivating pyruvate dehydrogenase and attenuating mitochondrial respiration. Re-expression of PDK3 in NAC1 absent cells rescued cells from hypoxia-induced metabolic stress and restored the activity of glycolysis in a xenograft mouse model, and demonstrated that silencing of NAC1 expression can enhance the antitumor efficacy of elesclomol, a pro-oxidative agent. Our findings reveal a novel mechanism by which NAC1 facilitates oxidative stress resistance during cancer progression, and chemo-resistance in cancer therapy.

Overexpression of NAC1 confers drug resistance via HOXA9 in colorectal carcinoma cells

Colorectal carcinoma (CRC) is one of the most common types of malignancy worldwide. Recently, neoadjuvant chemotherapy has become an important treatment strategy for CRC. However, treatment frequently fails due to the development of chemoresistance, which is a major obstacle for positive prognosis. However, the underlying mechanisms of chemoresistance remain unclear. The present study assessed the functions of nucleus accumbens-associated protein 1 (NAC1), an important transcriptional regulator, in CRC progression. Reverse transcription-quantitative polymerase chain reaction, western blot analysis and immunohistochemistry were performed to detect the expression levels of NAC1. It was identified that NAC1 was significantly overexpressed in CRC compared with non-tumorous tissues, indicating an oncogenic role. Following this, gain and loss of function analyses were performed in vitro to further investigate the function of NAC1. Cell viability and caspase-3/7 activity assays were used to assess chemotherapy-induced apoptosis. These results indicated that overexpression of NAC1 in CRC cells increased resistance to chemotherapy and inhibited apoptosis. Additionally, RNA interference-mediated knockdown of NAC1 restored the chemosensitivity of CRC cells. Furthermore, mechanistic investigation revealed that NAC1 increased drug resistance via inducing homeobox A9 (HOXA9) expression, and that knockdown of HOXA9 abrogated NAC1-induced drug resistance. In conclusion, the results of the present study demonstrated that NAC1 may be a critical factor in the development of chemoresistance, offering a potential novel target for the treatment of CRC.

Nucleus accumbens-1/GADD45GIP1 axis mediates cisplatin resistance through cellular senescence in ovarian cancer

Nucleus accumbens-1 (NAC1), a nuclear factor belonging to the bric-a-brac-tramtrack-broad complex/pox virus and zinc finger gene family, is known to serve important roles in the proliferation and growth of tumor cells, and in chemotherapy resistance. However, the underlying molecular mechanisms through which NAC1 contributes to drug resistance remain unclear. In the present study, the role of NAC1 in drug resistance in ovarian cancer was investigated. NAC1 expression was markedly negatively associated with growth arrest and DNA-damage-inducible 45γ-interacting protein 1 (GADD45GIP1) expression in ovarian cancer. Increased NAC1 expression or decreased GADD45GIP1 expression was significantly associated with decreased progression-free survival (P=0.0041). Multivariate analysis demonstrated that NAC1/GADD45GIP1 expression was an independent prognostic factor of progression-free survival (P=0.0405). It was investigated whether cellular senescence was involved in NAC1-mediated resistance to cisplatin, a commonly used chemotherapeutic drug in the treatment of ovarian cancer. Treatment with cisplatin activated cellular senescence in ovarian cancer cell lines (SKOV3 and TOV-21G cells). Furthermore, knockdown of NAC1 by RNA interference significantly increased GADD45GIP1 expression and inhibited cisplatin-induced cellular senescence, resulting in increased cisplatin cytotoxicity in SKOV3 cells, which express increased levels of NAC1. To investigate whether the sensitizing effect of NAC1 inhibition on cisplatin-induced cytotoxicity may be attributed to the suppression of cellular senescence, the effects of NAC1 overexpression were assessed in TOV-21G cells, which do not express endogenous NAC1. Transfection with NAC1 in TOV-21G cells reduced the sensitivity of TOV-21G cells to cisplatin, indicating that suppression of cellular senescence was induced by GADD45GP1 activation. The results of the present study suggest that NAC1 is a negative regulator of cellular senescence and that NAC1-dependent suppression of senescence, mediated through GADD45GIP1, serves an important role in promoting cisplatin resistance. Therefore, the NAC1/GADD45GIP1 axis may be a potential target for the treatment of ovarian cancer, particularly in platinum-resistant cancers.

Nucleus accumbens-associated protein-1 promotes glycolysis and survival of hypoxic tumor cells via the HDAC4-HIF-1α axis

Nucleus accumbens-associated protein-1 (NAC1), a nuclear factor of the BTB/POZ gene family, has emerging roles in cancer. In this study, we identified the NAC1-HDAC4-HIF-1α axis as an important pathway in regulating glycolysis and hypoxic adaptation in tumor cells. We show that nuclear NAC1 binds to histone deacetylase type 4 (HDAC4), hindering phosphorylation of HDAC4 at Ser²⁴⁶ and preventing its nuclear export that leads to cytoplasmic degradation of the deacetylase. Accumulation of HDAC4 in the nuclei results in an attenuation of HIF-1α acetylation, enhancing the stabilization and transcriptional activity of HIF-1α and strengthening adaptive response of cells to hypoxia. We also show the role of NAC1 in promoting glycolysis in a mouse xenograft model, and demonstrate that knockdown of NAC1 expression can reinforce the antitumor efficacy of bevacizumab, an inhibitor of angiogenesis. Clinical implication of the NAC1-HDAC4-HIF-1α pathway is suggested by the results showing that expression levels of these proteins are significantly correlative in human tumor specimens and associated with the disease progression. This study not only reveals an important function of NAC1 in regulating glycolysis, but also identifies the NAC1-HDAC4-HIF-1α axis as a novel molecular pathway that promotes survival of hypoxic tumor cells.

Effect of taxol on the expression of FoxM1 ovarian cancer-associated gene

The incidence of ovarian cancer in women has been on the increase in recent years. The aim of the present study was to examine the effects of taxol on the expression of ovarian cancer-associated gene forkhead box transcription factor M1 (FoxM1) and its therapeutic effects for ovarian cancer. The expression of FoxM1 gene was examined in patients with or without ovarian cancer. RNA and protein levels of FoxM1 gene of ovarian cancer patients were detected at different time periods (1, 3, 6, 8, 12 and 24 months) after treatment with taxol. The results showed that the mRNA level of FoxM1 gene in patients with ovarian cancer was significantly higher than that in normal women (P<0.05). With time and progression of the disease, the expression of FoxM1 gene significantly increased in the patients not being administered taxol, whereas the expression of FoxM1 in the patients administered taxol was significantly lower comparatively (P<0.05). In conclusion, an asssociation was identified between the FoxM1 gene and ovarian cancer. The FoxM1 gene therefore promotes the generation and deterioration of ovarian cancer, whereas taxol reduces it. These findings provide a certain theoretical basis for the later treatment of ovarian cancer disease.

miR-339-5p inhibits migration and invasion in ovarian cancer cell lines by targeting NACC1 and BCL6

This study aimed to explore the role of miR-339-5p in ovarian cancer. The expression of miR-339-5p in seven ovarian cancer cell lines (Hey, SKOV3, OVCAR5, SKOV3-IP, A2780, CAOV3, and OVCA433) was detected by quantitative real-time polymerase chain reaction (qRT-PCR). The miR-339-5p mimic and inhibitor were used to regulate its expression. Migration, invasion, and proliferation were examined. A bioinformatics analysis was used to predict targets, and a dual-luciferase reporter system was applied for validation, along with Western blot verification. Additionally, the association of miR-339-5p and its target genes with ovarian cancer was analyzed based on The Cancer Genome Atlas (TCGA) database. OVCAR5 and SKOV3 had the highest and lowest miR-339-5p expression, respectively. Inhibition of miR-339-5p expression increased the migration and invasion of OVCAR5 cells, while in SKOV3 cells, upregulated miR-339-5p attenuated the migration and invasion ability. Modulation of miR-339-5p had no effect on proliferation. The genes nucleus accumbens associated 1(BEN and BTB (POZ) domain containing) (NACC1) and B cell lymphoma-6 (bcl6) were validated to be targets of miR-339-5p. Clinically, patients with a high expression of NACC1 had a high risk in the survival analysis. miR-339-5p inhibits migration and invasion in ovarian cancer by targeting NACC1 and BCL6. miR-339-5p may be a biomarker of metastasis in ovarian cancer; NACC1 had a predictive value for ovarian cancer progression.

Zerumbone inhibits growth of hormone refractory prostate cancer cells by inhibiting JAK2/STAT3 pathway and increases paclitaxel sensitivity

Zerumbone, a phytochemical isolated from Zingiber zerumbet has been shown previously to exhibit antineoplastic activity. But, the effect of zerumbone in prostate cancer has not been evaluated. Prostate cancer is frequently associated with elevated levels of interleukin-6 (IL-6), which exerts its oncogenic effects through activation of Janus kinase 2 (JAK2) followed by activation of the transcription factor STAT3 (signal transducer and activator of transcription 3). Here, we investigated whether the anticancer effects of zerumbone are mediated through inhibition of the JAK2/STAT3 signaling pathway and whether zerumbone can increase the paclitaxel (PTX) sensitivity of prostate cancer cells. Zerumbone exerted significant cytotoxicity of DU145 versus PC3 prostate cancer cells through cell cycle arrest at G0/G1 phase followed by apoptosis. Zerumbone selectively inhibited JAK2 in both DU145 and PC3 cells. However, the biological axis of IL-6/JAK2/STAT3 was inhibited only in DU145 cells as no STAT3 phosphorylation was detected in PC3 cells even after IL-6 stimulation. Other signaling pathways in DU145 cells remained unaffected. The expression of prostate cancer-associated genes, including cyclin D1, IL-6, COX2, and ETV1, was blocked. Zerumbone also synergistically increased the sensitivity to PTX. Further preclinical study might reveal the potential use of zerumbone as a chemotherapeutic agent for hormone refractory prostate cancer where IL-6/JAK2/STAT3 signaling is aberrantly active and may be combined with PTX.

Targeting NAMPT for Therapeutic Intervention in Cancer and Inflammation: Structure-Based Drug Design and Biological Screening

Nicotinamide phosphoribosyltransferase (NAMPT) is a rate limiting enzyme that plays an important role in the synthesis of nicotinamide adenine dinucleotide (NAD) via a salvage pathway. Along with a role in bioenergetics, NAMPT regulates the activity of proteins such as SIRT-1 that utilize NAD as a cofactor. As NAD metabolism is usually high in diseased conditions, it has been hypothesized and proven that NAMPT is over expressed in various cancers and inflammatory disorders. Inhibitors targeting NAMPT could therefore be useful in treating disorders arising from aberrant NAMPT signalling. In this study, inhibitors against NAMPT were designed using an energy-based pharmacophore strategy and evaluated for efficacy in cellular assays. Besides reducing cellular pools of NAD and NMN, NAMPT inhibitors decreased concentrations of reactive oxygen species as well as mRNA levels of TNFα and IL6, thereby implicating their potential in alleviating the inflammatory process. In addition, reduced NAD levels corroborated with an induction of apoptosis in prostate cancer cell lines.

Nac1 interacts with the POZ-domain transcription factor, Miz1

Nac1 (nucleus accumbens 1) is a POZ (poxvirus and zinc finger)-domain transcriptional repressor that is expressed at high levels in ovarian serous carcinoma. Here we identify Nac1 as a novel interacting partner of the POZ-domain transcriptional activator, Miz1 (Myc-interacting zinc-finger protein 1), and using chemical crosslinking we show that this association is mediated by a heterodimeric interaction of the Nac1 and Miz1 POZ domains. Nac1 is found in discrete bodies within the nucleus of mammalian cells, and we demonstrate the relocalization of Miz1 to these structures in transfected HeLa cells. We show that siRNA (small interfering RNA)-mediated knockdown of Nac1 in ovarian cancer cells results in increased levels of the Miz1 target gene product, p21^Cip1. The interaction of Nac1 with Miz1 may thus be relevant to its mechanism of tumourigenesis in ovarian cancer.

Nac1 is a transcriptional repressor that has been implicated in ovarian serous carcinoma. Here we show that Nac1 interacts with the transcription factor Miz1, and suggest that this interaction may contribute to tumourigenesis.

Identification of the NAC1-regulated genes in ovarian cancer

Nucleus accumbens-associated protein 1 (NAC1), encoded by the NACC1 gene, is a transcription co-regulator that plays a multifaceted role in promoting tumorigenesis. However, the NAC1-regulated transcriptome has not been comprehensively defined. In this study, we compared the global gene expression profiles of NAC1-overexpressing SKOV3 ovarian cancer cells and NAC1-knockdown SKOV3 cells. We found that NAC1 knockdown was associated with up-regulation of apoptotic genes and down-regulation of genes involved in cell movement, proliferation, Notch signaling, and epithelial-mesenchymal transition. Among NAC1-regulated genes, FOXQ1 was further characterized because it is involved in cell motility and epithelial-mesenchymal transition. NAC1 knockdown decreased FOXQ1 expression and promoter activity. Similarly, inactivation of NAC1 by expression of a dominant-negative construct of NAC1 suppressed FOXQ1 expression. Ectopic expression of NAC1 in NACC1 null cells induced FOXQ1 expression. NAC1 knockdown resulted in decreased cell motility and invasion, whereas constitutive expression of FOXQ1 rescued motility in cells after NAC1 silencing. Moreover, in silico analysis revealed a significant co-up-regulation of NAC1 and FOXQ1 in ovarian carcinoma tissues. On the basis of transcription profiling, we report a group of NAC1-regulated genes that may participate in multiple cancer-related pathways. We further demonstrate that NAC1 is essential and sufficient for activation of FOXQ1 transcription and that the role of NAC1 in cell motility is mediated, at least in part, by FOXQ1.

Loss of NAC1 expression is associated with defective bony patterning in the murine vertebral axis

NAC1 encoded by NACC1 is a member of the BTB/POZ family of proteins and participates in several pathobiological processes. However, its function during tissue development has not been elucidated. In this study, we compared homozygous null mutant Nacc1^-/- and wild type Nacc1^+/+ mice to determine the consequences of diminished NAC1 expression. The most remarkable change in Nacc1^-/- mice was a vertebral patterning defect in which most knockout animals exhibited a morphological transformation of the sixth lumbar vertebra (L6) into a sacral identity; thus, the total number of pre-sacral vertebrae was decreased by one (to 25) in Nacc1^-/- mice. Heterozygous Nacc1^+/- mice had an increased tendency to adopt an intermediate phenotype in which L6 underwent partial sacralization. Nacc1^-/- mice also exhibited non-closure of the dorsal aspects of thoracic vertebrae T10-T12. Chondrocytes from Nacc1^+/+ mice expressed abundant NAC1 while Nacc1^-/- chondrocytes had undetectable levels. Loss of NAC1 in Nacc1^-/- mice was associated with significantly reduced chondrocyte migratory potential as well as decreased expression of matrilin-3 and matrilin-4, two cartilage-associated extracellular matrix proteins with roles in the development and homeostasis of cartilage and bone. These data suggest that NAC1 participates in the motility and differentiation of developing chondrocytes and cartilaginous tissues, and its expression is necessary to maintain normal axial patterning of murine skeleton.