Expression of the bric-a-brac tramtrack broad complex protein NAC-1 in cervical carcinomas seems to correlate with poorer prognosis

NAC1 promotes stemness and regulates myeloid-derived cell status in triple-negative breast cancer

Triple negative breast cancer (TNBC) is a particularly lethal breast cancer (BC) subtype driven by cancer stem cells (CSCs) and an immunosuppressive microenvironment. Our study reveals that nucleus accumbens associated protein 1 (NAC1), a member of the BTB/POZ gene family, plays a crucial role in TNBC by maintaining tumor stemness and influencing myeloid-derived suppressor cells (MDSCs). High NAC1 expression correlates with worse TNBC prognosis. NAC1 knockdown reduced CSC markers and tumor cell proliferation, migration, and invasion. Additionally, NAC1 affects oncogenic pathways such as the CD44-JAK1-STAT3 axis and immunosuppressive signals (TGFβ, IL-6). Intriguingly, the impact of NAC1 on tumor growth varies with the host immune status, showing diminished tumorigenicity in natural killer (NK) cell-competent mice but increased tumorigenicity in NK cell-deficient ones. This highlights the important role of the host immune system in TNBC progression. In addition, high NAC1 level in MDSCs also supports TNBC stemness. Together, this study implies NAC1 as a promising therapeutic target able to simultaneously eradicate CSCs and mitigate immune evasion.

miR-218-5p, miR-124-3p and miR-23b-3p act synergistically to modulate the expression of NACC1, proliferation, and apoptosis in C-33A and CaSki cells

Background

In cervical cancer (CC), miR-218-5p, -124-3p, and -23b-3p act as tumor suppressors. These miRNAs have specific and common target genes that modulate apoptosis, proliferation, invasion, and migration; biological processes involved in cancer.

Methods

miR-218-5p, -124-3p, and -23b-3p mimics were transfected into C-33A and CaSki cells, and RT-qPCR was used to quantify the level of each miRNA and NACC1. Proliferation was assessed by BrdU and apoptosis by Annexin V/PI. In the TCGA and The Human Protein Atlas databases, the level of NACC1 mRNA and protein (putative target of the three miRNAs) was analyzed in CC and normal tissue. The relationship of NACC1 with the overall survival in CC was analyzed in GEPIA2. NACC1 mRNA and protein levels were higher in CC tissues compared with cervical tissue without injury.

Results

An increased expression of NACC1 was associated with lower overall survival in CC patients. The levels of miR-218-5p, -124-3p, and -23b-3p were lower, and NACC1 was higher in C-33A and CaSki cells compared to HaCaT cells. The increase of miR-218-5p, -124-3p, and -23b-3p induced a significant decrease in NACC1 mRNA. The transfection of the three miRNAs together caused more drastic changes in the level of NACC1, in the proliferation, and in the apoptosis with respect to the individual transfections of each miRNA.

Conclusion

The results indicate that miR-218-5p, -124-3p, and -23b-3p act synergistically to decrease NACC1 expression and proliferation while promoting apoptosis in C-33A and CaSki cells. The levels of NACC1, miR-218-5p, -124-3p, and -23b-3p may be a potential prognostic indicator in CC.

NIPBL::NACC1 Fusion Hepatic Carcinoma

Several reports describing a rare primary liver tumor with histologic features reminiscent of follicular thyroid neoplasms have been published under a variety of descriptive terms including thyroid-like, solid tubulocystic, and cholangioblastic cholangiocarcinoma. Although these tumors are considered to represent histologic variants, they lack classic features of cholangiocarcinoma and have unique characteristics, namely immunoreactivity for inhibin and NIPBL::NACC1 fusions. The purpose of this study is to present clinicopathologic and molecular data for a large series of these tumors to better understand their pathogenesis. We identified 11 hepatic tumors with these features. Immunohistochemical and NACC1 and NIPBL fluorescence in situ hybridization assays were performed on all cases. Four cases had available material for whole-genome sequencing (WGS) analysis. Most patients were adult women (mean age: 42 y) who presented with abdominal pain and large hepatic masses (mean size: 14 cm). Ten patients had no known liver disease. Of the patients with follow-up information, 3/9 (33%) pursued aggressive behavior. All tumors were composed of bland cuboidal cells with follicular and solid/trabecular growth patterns in various combinations, were immunoreactive for inhibin, showed albumin mRNA by in situ hybridization, and harbored the NIPBL::NACC1 fusion by fluorescence in situ hybridization. WGS corroborated the presence of the fusion in all 4 tested cases, high tumor mutational burden in 2 cases, and over 30 structural variants per case in 3 sequenced tumors. The cases lacked mutations typical of conventional intrahepatic cholangiocarcinoma. In this report, we describe the largest series of primary inhibin-positive hepatic neoplasms harboring a NIPBL::NACC1 fusion and the first WGS analysis of these tumors. We propose to name this neoplasm NIPBL:NACC1 fusion hepatic carcinoma.

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.

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.

A Novel NIPBL-NACC1 Gene Fusion Is Characteristic of the Cholangioblastic Variant of Intrahepatic Cholangiocarcinoma

We report a novel NIPBL-NACC1 gene fusion in a rare primary hepatic neoplasm previously described as the "cholangioblastic variant of intrahepatic cholangiocarcinoma." The 2 index cases were identified within our consultation files as morphologically distinctive primary hepatic neoplasms in a 24-year-old female and a 54-year-old male. The neoplasms each demonstrated varied architecture, including trabecular, organoid, microcystic/follicular, and infiltrative glandular patterns, and biphasic cytology with large, polygonal eosinophilic cells and smaller basophilic cells. The neoplasms had a distinctive immunoprofile characterized by diffuse labeling for inhibin, and patchy labeling for neuroendocrine markers (chromogranin and synaptophysin) and biliary marker cytokeratin 19. RNA sequencing of both cases demonstrated an identical fusion of NIBPL exon 8 to NACC1 exon 2, which was further confirmed by break-apart fluorescence in situ hybridization assay for each gene. Review of a tissue microarray including 123 cases originally diagnosed as well-differentiated neuroendocrine neoplasm at one of our hospitals resulted in identification of a third case with similar morphology and immunophenotype in a 52-year-old male, and break-apart fluorescence in situ hybridization probes confirmed rearrangement of both NIPBL and NACC1. Review of The Cancer Genome Atlas (TCGA) sequencing data and digital images from 36 intrahepatic cholangiocarcinomas (www.cbioportal.org) revealed one additional case with the same gene fusion and the same characteristic solid, trabecular, and follicular/microcystic architectures and biphasic cytology as seen in our genetically confirmed cases. The NIPBL-NACC1 fusion represents the third type of gene fusion identified in intrahepatic cholangiocarcinoma, and correlates with a distinctive morphology described herein.

Nucleus Accumbens-Associated Protein 1 Binds DNA Directly through the BEN Domain in a Sequence-Specific Manner

Nucleus accumbens-associated protein 1 (NAC1) is a nuclear protein that harbors an amino-terminal BTB domain and a carboxyl-terminal BEN domain. NAC1 appears to play significant and diverse functions in cancer and stem cell biology. Here we demonstrated that the BEN domain of NAC1 is a sequence-specific DNA-binding domain. We selected the palindromic 6 bp motif ACATGT as a target sequence by using a PCR-assisted random oligonucleotide selection approach. The interaction between NAC1 and target DNA was characterized by gel shift assays, pull-down assays, isothermal titration calorimetry (ITC), chromatin-immunoprecipitation assays, and NMR chemical shifts perturbation (CSP). The solution NMR structure revealed that the BEN domain of human NAC-1 is composed of five conserved α helices and two short β sheets, with an additional hitherto unknown N-terminal α helix. In particular, ITC clarified that there are two sequential events in the titration of the BEN domain of NAC1 into the target DNA. The ITC results were further supported by CSP data and structure analyses. Furthermore, live cell photobleaching analyses revealed that the BEN domain of NAC1 alone was unable to interact with chromatin/other proteins in cells.

CRM197 reverses paclitaxel resistance by inhibiting the NAC-1/Gadd45 pathway in paclitaxel-resistant ovarian cancer cells

Heparin‐binding epidermal growth factor‐like growth factor (HB‐EGF) is a new promising target for the treatment of ovarian cancer. Our previous study showed that cross‐reacting material 197 (CRM197), a specific HB‐EGF inhibitor, significantly reverses resistance against paclitaxel in paclitaxel‐resistant ovarian cancer cells. However, the mechanism of the effect of CRM197 on the reversion of paclitaxel resistance was unclear. In this study, in vitro and in vivo data suggested that CRM197 treatment sensitized paclitaxel‐resistant ovarian cancer cells to paclitaxel, at least in part, via nucleus accumbens‐1 (NAC‐1) and its downstream pathway, DNA damage‐inducible 45‐γ interacting protein (Gadd45gip1)/growth arrest and DNA damage‐inducible 45 (Gadd45), in A2780/Taxol and SKOV3/Taxol cells. The results also showed that CRM197 activated the proapoptotic JNK/p38MAPK pathway to enhance caspase‐3 activity and apoptosis by downregulation of the NAC‐1/Gadd45gip1/Gadd45 pathway, leading to reversion of paclitaxel resistance in A2780/Taxol and SKOV3/Taxol cells. This study provides the first mechanism through which CRM197 significantly reverses resistance against paclitaxel by modulating the NAC‐1/Gadd45gip1/Gadd45 pathway in paclitaxel‐resistant ovarian cancer cells, and the mechanism of HB‐EGF inhibition as a novel therapeutic strategy for patients with paclitaxel‐resistant ovarian cancer.

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.

Cancer-related transcription regulator protein NAC1 forms a protein complex with CARM1 for ovarian cancer progression

NAC1 is a cancer-related transcription regulator protein that is overexpressed in various carcinomas, including ovarian, cervical, breast, and pancreatic carcinomas. NAC1 knock-down was previously shown to result in the apoptosis of ovarian cancer cell lines and to rescue their sensitivity to chemotherapy, suggesting that NAC1 may be a potential therapeutic target, but protein complex formation of intranuclear NAC1 in ovarian cancer cells remain poorly understood. In this study, analysis of ovarian cancer cell lysates by fast protein liquid chromatography on a sizing column showed that the NAC1 peak corresponded to an apparent molecular mass of 300–500 kDa, which is larger than the estimated molecular mass (58 kDa) of the protein. Liquid chromatography-tandem mass spectrometry analysis identified CARM1 as interacting with NAC1 in the protein complex. Furthermore, tissue microarray analysis revealed a significant correlation between CARM1 and NAC1 expression levels. Ovarian cancer patients expressing high levels of NAC1 and CARM1 exhibited poor prognosis after adjuvant chemotherapy. Collectively, our results demonstrate that high expression levels of NAC1 and its novel binding partner CARM1 may serve as an informative prognostic biomarker for predicting resistance to chemotherapy for ovarian cancer.

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.

Protein complex formation and intranuclear dynamics of NAC1 in cancer cells

Nucleus accumbens-associated protein 1 (NAC1) is a cancer-related transcription regulator protein that is also involved in the pluripotency and differentiation of embryonic stem cells. NAC1 is overexpressed in various carcinomas including ovarian, cervical, breast, and pancreatic carcinomas. NAC1 knock-down was previously shown to result in the apoptosis of ovarian cancer cell lines and to rescue their sensitivity to chemotherapy, suggesting that NAC1 may be a potential therapeutic target, but protein complex formation and the dynamics of intranuclear NAC1 in cancer cells remain poorly understood. In this study, analysis of HeLa cell lysates by fast protein liquid chromatography (FPLC) on a sizing column showed that the NAC1 peak corresponded to an apparent molecular mass of 300-500 kDa, which is larger than the estimated molecular mass (58 kDa) of the protein. Furthermore, live cell photobleaching analyses with green fluorescent protein (GFP)-fused NAC1 proteins revealed the intranuclear dynamics of NAC1. Collectively our results demonstrate that NAC1 forms a protein complex to function as a transcriptional regulator in cancer cells.

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.

Cullin 3 as a novel target in diverse pathologies

Recent evidence suggests that the malfunctioning disposal system of cell protein called ubiquitin–proteasome system (UPS) plays an important role in the development of disorders, including cancer and neurodegenerative diseases. Accumulating evidence suggests that the abnormal regulation of the E3 ubiquitin ligases, essential components of the UPS, contributes to uncontrolled proliferation, genomic instability and cancer, since these ligases and their substrates are involved in the regulation of cell cycle progression, gene transcription, signal transduction, DNA replication and others. Through selective degradation of specific substrates, E3 ligases regulate different biological processes. Cullins are a family of proteins that confer substrate specificity to multimeric complex of E3 ligases acting as scaffold proteins. So far, seven members of the cullin family of proteins have been identified. Interestingly, the data generated by several groups indicate that cullin 3 (Cul3) has begun to emerge as a protein involved in the etiopathology of multiple diseases. In this paper we examine the latest advances in basic research on the biology of Cul3 and how it could help to direct drug discovery efforts on this target.

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The most important system for protein degradation is the ubiquitin–proteasome system.

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The specific substrate for ubiquitination is highly specific and this activity can be provided by the E3 ubiquitin ligases.

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The E3 ubiquitin ligases based on cullins are the type of ubiquitin ligases more studied.

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The cullin 3 complex has emerged as a target due to its interaction with a wide range of BTB-proteins.

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Cullin 3 could be a molecule with a high therapeutic potential.

NAC1 is an actin-binding protein that is essential for effective cytokinesis in cancer cells

NAC1 is a transcriptional corepressor protein that is essential to sustain cancer cell proliferation and migration. However, the underlying molecular mechanisms of NAC1 function in cancer cells remain unknown. In this study, we show that NAC1 functions as an actin monomer-binding protein. The conserved BTB protein interaction domain in NAC1 is the minimal region for actin binding. Disrupting NAC1 complex function by dominant-negative or siRNA strategies reduced cell retraction and abscission during late-stage cytokinesis, causing multinucleation in cancer cells. In Nac1-deficient murine fibroblasts, restoring NAC1 expression was sufficient to partially avert multinucleation. We found that siRNA-mediated silencing of the actin-binding protein profilin-1 in cancer cells caused a similar multinucleation phenotype and that NAC1 modulated the binding of actin to profillin-1. Taken together, our results indicate that the NAC1/actin/profilin-1 complex is crucial for cancer cell cytokinesis, with a variety of important biologic and clinical implications.

Nuclear localization signal in a cancer-related transcriptional regulator protein NAC1

Nucleus accumbens-associated protein 1 (NAC1) might have potential oncogenic properties and participate in regulatory networks for pluripotency. Although NAC1 is described as a transcriptional regulator, the nuclear import machinery of NAC1 remains unclear. We found, using a point mutant, that dimer formation was not committed to the nuclear localization of NAC1 and, using deletion mutants, that the amino-terminal half of NAC1 harbored a potential nuclear localization signal (NLS). Wild type, but not mutants of this region, alone was sufficient to drive the importation of green fluorescent protein (GFP) into the nucleus. Bimax1, a synthetic peptide that blocks the importin α/β pathway, impaired nuclear localization of NAC1 in cells. We also used the binding properties of importin to demonstrate that this region is an NLS. Furthermore, the transcriptional regulator function of NAC1 was dependent on its nuclear localization activity in cells. Taken together, these results show that the region with a bipartite motif constitutes a functional nuclear import sequence in NAC1 that is independent of NAC1 dimer formation. The identification of an NAC1 NLS thus clarifies the mechanism through which NAC1 translocates to the nucleus to regulate the transcription of genes involved in oncogenicity and pluripotency.

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

Nucleus accumbens-1 (NAC1), a nuclear factor belonging to the BTB/POZ gene family, has emerging roles in cancer. We report here that NAC1 acts as a negative regulator of cellular senescence in transformed and nontransformed cells, and dysfunction of NAC1 induces senescence and inhibits its oncogenic potential. We show that NAC1 deficiency markedly activates senescence and inhibits proliferation in tumor cells treated with sublethal doses of γ-irradiation. In mouse embryonic fibroblasts from NAC1 knockout mice, following infection with a Ras virus, NAC1-/- cells undergo significantly more senescence and are either nontransformed or less transformed in vitro and less tumorigenic in vivo when compared with NAC1+/+ cells. Furthermore, we show that the NAC1-caused senescence blunting is mediated by ΔNp63, which exerts its effect on senescence through p21, and that NAC1 activates transcription of ΔNp63 under stressful conditions. Our results not only reveal a previously unrecognized function of NAC1, the molecular pathway involved and its impact on pathogenesis of tumor initiation and development, but also identify a novel senescence regulator that may be exploited as a potential target for cancer prevention and treatment.

Fatty acid synthase expression associated with NAC1 is a potential therapeutic target in ovarian clear cell carcinomas

BACKGROUND

This study examined the clinical significance of NAC1 and the expression level of its potential downstream target fatty acid synthase (FASN) in ovarian clear cell carcinomas (OCCCs), and evaluated the NAC1/FASN pathway as a potential therapeutic target.

METHODS

NAC1 and FASN expression and NACC1 gene amplification were assessed in ovarian cancers by immunohistochemistry, fluorescence in situ hybridisation, and clinical data collected by a retrospective chart review. C75, a FASN inhibitor, was used to assess whether this pathway represented a therapeutic target in OCCC.

RESULTS

High NAC1 expression was most frequent in clear cell tumours (40.0%:24/60). NACC1 gene amplification was identified in none of the 58 OCCCs. The frequency of NACC1 gene amplification was significantly higher in the high-grade serous histology than in the clear cell histology (P<0.01). NAC1 expression was significantly correlated with FASN expression in both OCCC samples and OCCC cell lines. Either high NAC1 expression or high FASN expression significantly correlated with shorter progression-free and overall survival (P=0.002 and 0.0048). NAC1 overexpression stimulated FASN expression, and NAC1 silencing using siRNA decreased FASN expression in OCCC cell lines. Profound growth inhibition was observed in C75-treated carcinoma cells with FASN overexpression when compared with the response in carcinoma cells without FASN expression.

CONCLUSION

These findings indicate that NAC1/FASN overexpression is critical to the growth and survival of a subset of OCCC. The FASN silencing by the C75-induced phenotypes depends on the expression status of the targeted cell line. Therefore, NAC1/FASN pathway-targeted therapy may benefit selected OCCC patients.

Embryonic stem cell markers

Embryonic stem cell (ESC) markers are molecules specifically expressed in ES cells. Understanding of the functions of these markers is critical for characterization and elucidation for the mechanism of ESC pluripotent maintenance and self-renewal, therefore helping to accelerate the clinical application of ES cells. Unfortunately, different cell types can share single or sometimes multiple markers; thus the main obstacle in the clinical application of ESC is to purify ES cells from other types of cells, especially tumor cells. Currently, the marker-based flow cytometry (FCM) technique and magnetic cell sorting (MACS) are the most effective cell isolating methods, and a detailed maker list will help to initially identify, as well as isolate ESCs using these methods. In the current review, we discuss a wide range of cell surface and generic molecular markers that are indicative of the undifferentiated ESCs. Other types of molecules, such as lectins and peptides, which bind to ESC via affinity and specificity, are also summarized. In addition, we review several markers that overlap with tumor stem cells (TSCs), which suggest that uncertainty still exists regarding the benefits of using these markers alone or in various combinations when identifying and isolating cells.

Biological and clinical significance of NAC1 expression in cervical carcinomas: a comparative study between squamous cell carcinomas and adenocarcinomas/adenosquamous carcinomas

This study examined the biological and clinical significance of NAC1 (nucleus accumbens associated 1) expression in both cervical squamous cell carcinomas and adenocarcinomas/adenosquamous carcinomas. Using immunohistochemistry, the frequency of positive NAC1 expression in adenocarcinomas/adenosquamous carcinomas (31.0%; 18/58) was significantly higher than that in squamous cell carcinomas (16.2%; 12/74) (P = .043). NAC1 gene amplification was identified by fluorescence in situ hybridization in 5 (7.2%) of 69 squamous cell carcinomas. NAC1 amplification was not identified in the adenocarcinomas (0%; 0/58). Positive NAC1 expression was significantly correlated with shorter overall survival in squamous cell carcinomas (P < .0001). A multivariate analysis showed that positive NAC1 expression in squamous cell carcinomas was an independent prognostic factor for overall survival after standard radiotherapy (P = .0003). In contrast to squamous cell carcinomas, positive NAC1 expression did not correlate with shorter overall survival in adenocarcinomas/adenosquamous carcinomas (P = .317). Profound growth inhibition, increased apoptosis, decreased cell proliferation, and decreased cell migration and invasion were observed in silencing RNA-treated cancer cells with NAC1 overexpression compared with cancer cells without NAC1 expression. NAC1 overexpression stimulated proliferation, migration, and invasion in the cervical cancer cell lines TCS and Hela P3, which normally lack NAC1 expression. These findings indicate that NAC1 overexpression is critical to the growth and survival of cervical carcinomas irrespective of histologic type. Furthermore, they suggest that NAC1 silencing RNA-induced phenotypes depend on the expression status of the targeted cell line. Therefore, cervical carcinoma patients with NAC1 expression may benefit from a targeted therapy irrespective of histologic type.

NAC1 modulates sensitivity of ovarian cancer cells to cisplatin by altering the HMGB1-mediated autophagic response

Nucleus accumbens-1 (NAC1), a nuclear factor belonging to the BTB/POZ gene family, is known to play important roles in proliferation and growth of tumor cells and in chemotherapy resistance. Yet, the mechanisms underlying how NAC1 contributes to drug resistance remain largely unclear. We reported here that autophagy was involved in NAC1-mediated resistance to cisplatin, a commonly used chemotherapeutic drug in the treatment of ovarian cancer. We found that treatment with cisplatin caused an activation of autophagy in ovarian cancer cell lines, A2780, OVCAR3, and SKOV3. We further demonstrated that knockdown of NAC1 by RNAi or inactivation of NAC1 by inducing the expression of a NAC1 deletion mutant that contains only the BTB/POZ domain significantly inhibited the cisplatin-induced autophagy, resulting in increased cisplatin cytotoxicity. Moreover, inhibition of autophagy and sensitization to cisplatin by NAC1 knockdown or inactivation were accompanied by induction of apoptosis. To confirm that the sensitizing effect of NAC1 inhibition on the cytotoxicity of cisplatin was attributed to suppression of autophagy, we assessed the effects of the autophagy inhibitors, 3-MA and chloroquine, and siRNAs targeting beclin 1 or Atg5, on the cytotoxicity of cisplatin. Treatment with 3-MA, chloroquine or beclin 1 and Atg5-targeted siRNA also enhanced the sensitivity of SKOV3, A2780 and OVCAR3 cells to cisplatin, indicating that suppression of autophagy indeed renders tumor cells more sensitive to cisplatin. Regulation of autophagy by NAC1 was mediated via high mobility group box1 (HMGB1), as the functional status of NAC1 was associated with the expression, translocation and release of HMGB1. The results of our study not only revealed a new mechanism determining cisplatin sensitivity, but also identified NAC1 as a novel regulator of autophagy. Thus, the NAC1- mediated autophagy may be exploited as a new target for enhancing the efficacy of cisplatin against ovarian cancer and other types of malignancies.

Zinc finger protein ZBTB20 expression is increased in hepatocellular carcinoma and associated with poor prognosis

Background

Our previous studies showed that ZBTB20, a new BTB/POZ-domain gene, could negatively regulate α feto-protein and other liver-specific genes, concerning such as bio-transformation, glucose metabolism and the regulation of the somatotropic hormonal axis. The aim of this study is to determine the potential clinical implications of ZBTB20 in hepatocellular carcinoma (HCC).

Methods

Quantitative real-time RT-PCR and Western blot analyses were used to detect expression levels of ZBTB20 in 50 paired HCC tumorous and nontumorous tissues and in 20 normal liver tissues. Moreover, expression of ZBTB20 was assessed by immunohistochemistry of paired tumor and peritumoral liver tissue from 102 patients who had undergone hepatectomy for histologically proven HCC. And its relationship with clinicopathological parameters and prognosis was investigated.

Results

Both messenger RNA and protein expression levels of ZBTB20 were elevated significantly in HCC tissues compared with the paired non-tumor tissues and normal liver tissues. Overexpressed ZBTB20 protein in HCC was significantly associated with vein invasion (P = 0.016). Importantly, the recurrence or metastasis rates of HCCs with higher ZBTB20 expression were markedly greater than those of HCCs with lower expression (P = 0.003, P = 0.00015, respectively). Univariate and multivariate analyses revealed that ZBTB20 overexpression was an independent prognostic factor for HCC. The disease-free survival period and over-all survival period in patients with overexpressed ZBTB20 in HCC was significantly reduced.

Conclusions

The expression of ZBTB20 is increased in HCC and associated with poor prognosis in patients with HCC, implicating ZBTB20 as a candidate prognostic marker in HCC.

Nucleus accumbens-associated 1 contributes to cortactin deacetylation and augments the migration of melanoma cells

We investigated the prognostic significance and post-transcriptional acetylation-modification of cortactin (CTTN) via the nucleus accumbens-associated 1 (NACC1)-histone deacetylase 6 (HDAC6) deacetylation system in primary melanomas and melanoma cell lines. Overexpression of CTTN protein was observed in 56 (73%) of 77 stage I-IV melanomas, and was significantly correlated with tumor thickness, lymph node metastasis, distant metastasis, and disease outcome. The patients whose tumors exhibited CTTN overexpression had a poorer outcome than patients without this feature (P=0.028, log-rank test). NACC1 and CTTN proteins, but not HDAC6, were overexpressed in four melanoma cell lines in comparison with a primary culture of normal human epidermal melanocytes. Knockdown of both NACC1 and HDAC6 markedly downregulated the migration activity of all melanoma cell lines (P<0.05), and induced a gain of CTTN protein acetylation status. Confocal microscopy showed that hyperacetylation of CTTN modulated by depletion of both NACC1 and HDAC6 induced disappearance of CTTN protein at the leading edge of migrating cells, resulting in stabilization of the focal adhesion structure and development of actin stress fibers. These data suggest that the acetylation status of CTTN modulated by the NACC1-HDAC6 deacetylation system induces acceleration of melanoma cell migration activity via an actin-dependent cellular process, possibly contributing to aggressive behavior (invasion/metastasis) of the melanoma cells.

Amplification of the ch19p13.2 NACC1 locus in ovarian high-grade serous carcinoma

On the basis of digital karyotyping, we have identified a new, discrete amplified region at ch19p13.2 in a high-grade ovarian serous carcinoma. To further characterize this region, we determined the frequency and biological significance of ch19p13.2 amplification by analyzing 341 high-grade serous carcinomas from The Cancer Genome Atlas (TCGA) and found an increased DNA copy number at this locus in 18% of cases. We correlated the DNA and RNA copy number by analyzing the TCGA data set for all amplified genes and detected seven genes within ch19p13.2 that were significantly correlated (R≥0.54) and were, in fact, listed as the top 100 potential 'driver' genes at a genome-wide scale. Interestingly, one of the seven genes, NACC1, encoding NAC1 was previously reported to be involved in the development of tumor recurrence in ovarian serous carcinoma and to have a causal role in the development of paclitaxel resistance. Therefore, we selected NACC1 for validation in an independent cohort. On the basis of fluorescence in situ hybridization, we found that 35 (20%) of 175 high-grade serous carcinomas had an increased DNA copy number at the NACC1 locus, and those amplified cases were associated with early disease recurrence within 6 months (P=0.013). A significantly high level of NAC1 protein expression based on immunohistochemistry was detected in amplified tumors as compared with non-amplified tumors (P<0.005). In summary, our data suggest that amplification at the ch19p13.2 NACC1 locus, leading to NAC1 overexpression, is one of the molecular genetic alterations associated with early tumor recurrence in ovarian cancer.

MKK4 acts as a potential tumor suppressor in ovarian cancer

Our previous studies indicate that loss of MKK4 expression is associated with the progression of ovarian cancer. However, direct evidence that MKK4 inhibits the malignant phenotype of ovarian cancer cells is limited. In the current study, we investigated the mechanism relating loss of MKK4 expression to the development of ovarian cancer. Using cell growth and anchorage-independent assays, we determined that both the growth and colony-forming ability of MKK4-transfected TOV-21G cells, a line with a homozygous deletion of MKK4, were significantly reduced compared to control vector-transfected cells. Overexpression of the MKK4 gene in TOV-21G cells resulted in reduced proliferative activity and increased apoptosis. To confirm that MKK4 expression related to tumor suppress function, we used two independent but complementary approaches. MKK4 gene knockdown in OVK18#2 and MDAH2774 cells, which overexpressed MKK4, increased proliferation activity. Additionally, the engineered expression of MKK4 in SKOV3 cells, a line with low endogenous MKK4 expression, produced a phenotype similar to that of TOV-21G. Similar results were produced in tumor xenografts in nude mice. These results indicated that MKK4 acts as a tumor suppressor and may represent an important therapeutic target for the treatment of ovarian cancer.

Overexpression of LAPTM4B-35 in cervical carcinoma: a clinicopathologic study

Lysosome-associated protein transmembrane 4β-35 (LAPTM4B-35) is a member of the mammalian 4-tetratransmembrane spanning protein superfamily, which is overexpressed in several solid malignancies. However, the expression of LAPTM4B-35 and its role in the progression of cervical carcinoma is unknown. The aim of this study was to determine the level of expression of LAPTM4B-35 in cervical carcinoma. Immunohistochemistry was used to determine the expression of LAPTM4B-35 protein in 53 cervical intraepithelial neoplasias (CINs) and 113 cervical carcinomas in comparison with 20 normal cervical specimens. The correlation between the expression of the LAPTM4B-35 protein and the clinicopathologic characteristics of patients with cervical carcinoma was analyzed. Statistical analysis showed that LAPTM4B-35 expression was significantly elevated in CINII/III and cervical carcinoma but not in CINI compared with the normal controls (P=0.002, P<0.001 and P=0.289, respectively). In addition, the LAPTM4B-35 expression was significantly higher in both the CINII/III and cervical carcinoma cases than in the CINI cases (P=0.021 and P=0.002, respectively). High LAPTM4B-35 staining was present in 72.57% (82 of 113) of all the cases with cervical carcinoma. The overexpression of LAPTM4B-35 was significantly associated with the International Federation of Gynecology and Obstetrics stage (P=0.014), tumor histologic grade (P=0.033), lymph node metastasis (P=0.045), and recurrence (P=0.010). The Kaplan-Meier survival analysis showed that the high expression of LAPTM4B-35 was related to the poor overall survival and disease-free survival of patients with cervical carcinoma (P=0.004 and P=0.005, respectively). Multivariate Cox analysis showed that LAPTM4B-35 was an independent factor for both overall survival and disease-free survival (P=0.015 and P=0.016, respectively). Overexpression of LAPTM4B-35 may be associated with tumor progression in cervical carcinoma and thus may serve as a new molecular marker to predict the prognosis of cervical carcinoma patients.

Biological role and prognostic significance of NAC1 in ovarian cancer

OBJECTIVE

This study examined the biological and clinical significance of NAC1 expression in ovarian cancer and assessed whether NAC1 has the potential to be a therapeutic target.

METHODS

NAC1 expression and gene amplification were assessed in ovarian cancers by immunohistochemistry, fluorescence in situ hybridization, and clinical data collected by a retrospective chart review. NAC1 gene knockdown using silencing RNA and a NAC1 gene transfection system were used to assess NAC1 function in ovarian cancer tissue samples.

RESULTS

The frequency of positive NAC1 expression in serous adenocarcinomas (50.0%:22/44) was significantly higher than that in the other histological subtypes (33.3%: 10/30). NAC1 gene amplification was identified in seven (9.5%) of 74 ovarian carcinomas. Positive NAC1 expression significantly correlated with shorter disease-free and overall survival (P = 0.002, P = 0.0048). A multivariate analysis showed that positive NAC1 expression was an independent prognostic factor for disease-free and overall survival after standard platinum-taxane chemotherapy (P = 0.0027, P = 0.0302). Profound growth inhibition, increased apoptosis, decreased cell proliferation, and decreased cell migration and invasion were observed in silencing RNA-treated cancer cells with NAC1 overexpression compared with cancer cells without NAC1 expression. NAC1 overexpression stimulated proliferation, migration, and invasion in ovarian cancer cell lines KF28 and TOV-21G, which normally lacked NAC1 expression.

CONCLUSION

These findings indicate that NAC1 over-expression is critical to the growth and survival of ovarian cancers. Furthermore, they suggest that NAC1 silencing RNA-induced phenotypes depend on the expression status of the targeted cell line. Therefore, NAC1-targeted therapy may benefit ovarian cancer patients with NAC1 expression.

Expression of nuclear Notch3 in cervical squamous cell carcinomas and its association with adverse clinical outcomes

OBJECTIVE

The aim of this study was to clarify the functional role of Notch3 in human cervical carcinomas.

METHODS

Notch3 expression in cervical cancer was assessed by immunohistochemistry, and data on clinical variables were collected by retrospective chart review. We used dual-color fluorescence in situ hybridization (FISH) to analyze DNA copy number alterations in cervical cancer. Inactivation of Notch3 and knocking down Notch3 gene were done using gamma-secretase inhibitor and Notch 3 specific SiRNA to asses Notch3 function in cervical cancer either in vivo or in vitro.

RESULTS

Immunohistochemical analysis revealed that Notch3 was significantly overexpressed in cervical squamous cell carcinomas compared with adenocarcinomas. In contrast to normal cervical tissue and cervical intraepithelial neoplasms [CINs], squamous cell carcinomas demonstrated higher nuclear Notch3 immunoreactivity. Notch3 amplification was not found in any cervical carcinomas using FISH analysis. Notch3 nuclear expression was significantly correlated with Jagged-1, a putative Notch3 ligand, and Pbx1b, a potential Notch3 downstream target (P<0.05).Patients with cervical carcinomas positive for nuclear Notch3 expression had significantly shorter overall survival than their peers whose tumors did not express nuclear Notch3. Inactivation of Notch3 decreased cell proliferation and induced apoptosis in ME180 and SKGIIIb cell lines that overexpressed Notch3. Injection of a gamma-secretase inhibitor into ME180 cell tumors established on mice, demonstrated a reduction in tumor growth.

CONCLUSION

Our findings suggest that Notch3 might play important role for the proliferation and survival of Notch3 overexpressing tumors and that inactivation of Notch3 may represent a new therapeutic avenue for cervical squamous cell carcinomas.

GalNAcalpha1-3Gal, a new prognostic marker for cervical cancer

Cancer cells undergo significant changes in carbohydrate expression, and these alterations can be useful as biomarkers and therapeutic targets. In this study, we investigated the expression of carbohydrate antigens containing a terminal GalNAcalpha1-3Gal or GalNAcalpha1-6Gal on human cervix and cervical carcinoma. Monoclonal antibodies to each of these carbohydrates were generated by immunizing rabbits with the corresponding antigen conjugated to KLH followed by hybridoma production. Antibodies were screened and evaluated using a combination of carbohydrate microarray profiling, ELISA, dot blot and immunohistochemical staining to verify specificity. Antibody 132-3 was found to selectively recognize GalNAcalpha1-3Gal with little cross-reactivity to other structurally similar antigens such as GalNAcalpha1-6Gal, blood group A, Forssman antigen and the Tn antigen on both solution assays and human tissue. Although GalNAcalpha1-6Gal expression was not detected, GalNAcalpha1-3Gal expression was found on 55% of squamous cell carcinomas. Expression in normal tissue was observed but was restricted to the suprabasal epithelial layer. Importantly, we found expression of the antigen on cervical cancer had a statistically significant correlation with the 5-year survival rate of the patients (48 vs. 85% for antigen negative vs. positive, p = 0.017). Expression of GalNAcalpha1-3Gal did not correlate with other clinical factors including tumor stage, size and lymph node metastasis, indicating the antigen is a new, independent biomarker for the prognosis of cervical cancer.

Expression of a BTB/POZ protein, NAC1, is essential for the proliferation of normal cyclic endometrial glandular cells and is up-regulated by estrogen

PURPOSE

The purpose of this study was to investigate the expression and localization of NAC1, a member of the BTB/POZ gene family in the human cyclic endometrium.

EXPERIMENTAL DESIGN

NAC1 expression in normal cyclic endometrium was assessed by immunohistochemistry, and data on clinical variables were collected by retrospective chart review. To elucidate the molecular mechanisms of NAC1 expression in the normal endometrium endometrial carcinoma cell lines (Ishikawa, HHUA; ER+, PR+) and primary cultured normal endometria were tested in a sex steroid induction assay and a NAC1 knockdown assay using siRNA.

RESULTS

Expression of NAC1 in glandular cells was significantly higher in the early and mid proliferative phases than in the other menstrual phases. Both NAC1 RNA and protein expression were up-regulated by treatment with 10 nmol/L 17beta-Estradiol (E2) in Ishikawa, HHUA and primary cultured normal endometrial cells. The estrogen receptor antagonist ICI 182,780 significantly attenuated E2-induced NAC1 expression. NAC1 gene knockdown inhibited cell growth and induced apoptosis in Ishikawa, HHUA, and normal endometria, all of which expressed NAC1. Furthermore, NAC1 siRNA significantly abrogated estrogen-driven cellular proliferation in Ishikawa, HHUA, and primary cultured normal endometrial cells, whereas the control siRNA had no effect on cell growth in any of these cells.

CONCLUSIONS

These findings suggest that NAC1 is functionally involved in E2-induced cell growth of the normal endometrial glandular cells. Because NAC1 is thought to have oncogenic potential, the current findings may provide new insight into the mechanism of estrogen induced endometrial carcinogenesis.

NAC-1, a potential stem cell pluripotency factor, contributes to paclitaxel resistance in ovarian cancer through inactivating Gadd45 pathway

Nucleus accumbens-1 (Nac1 or NAC-1) belongs to the BTB/POZ (Pox virus and Zinc finger/Bric-a-brac Tramtrack Broad complex) transcription factor family and is a novel protein that potentially participates in self-renewal and pluripotency in embryonic stem cells. In human cancer, NAC-1 is upregulated in several types of neoplasms, but particularly in recurrent chemoresistant ovarian carcinomas, suggesting a biological role for NAC-1 in the development of drug resistance in ovarian cancer. We have assessed this possibility and shown a correlation between NAC-1 expression and ex vivo paclitaxel resistance in ovarian serous carcinoma tissues and cell lines. We found that expression of Gadd45-gamma-interacting protein 1 (Gadd45gip1), a downstream target negatively regulated by NAC-1, was reduced in paclitaxel-resistant cells. Ectopic expression of NAC-1 or knockdown of Gadd45gip1 conferred paclitaxel resistance, whereas NAC-1 knockdown or ectopic expression of Gadd45gip1 increased paclitaxel sensitivity. Furthermore, silencing NAC-1 expression or disrupting NAC-1 homodimerization by a dominant negative NAC-1 protein that contained only the BTB/POZ domain induced the expression of Gadd45gamma, which interacted with Gadd45gip1. Reducing Gadd45gamma expression by small hairpin RNAs partially enhanced paclitaxel resistance. Thus, this study provides new evidence that NAC-1 upregulation and homodimerization contribute to tumor recurrence by equipping ovarian cancer cells with the paclitaxel-resistant phenotype through negative regulation of the Gadd45 pathway.

Structure of the human Nac1 POZ domain

Nac1 is a POZ-domain transcription factor that is involved in the self-renewal of embryonic stem cells. It is overexpressed in ovarian serous carcinoma and targeting the interactions of its POZ domain is a potential therapeutic strategy. Nac1 lacks a zinc-finger DNA-binding domain and thereby differs from most other POZ-domain transcription factors. Here, the crystal structure of the Nac1 POZ domain at 2.1 A resolution is reported. The Nac1 POZ domain crystallized as a dimer in which the interaction interfaces between subunits resemble those found in the POZ-zinc finger transcription factors. The organization of the Nac1 POZ-domain core resembles reported POZ-domain structures, whereas the C-terminus differs markedly. The C-terminal alpha-helix of the Nac1 POZ domain is shorter than that observed in most other POZ-domain transcription factors; variation in the organization of this region may be a general feature of POZ-domain structures.