BRCA1 augments transcription by the NF-kappaB transcription factor by binding to the Rel domain of the p65/RelA subunit

A high-throughput approach to identify BRCA1-downregulating compounds to enhance PARP inhibitor sensitivity

PARP inhibitors (PARPi) are efficacious in BRCA1-null tumors; however, their utility is limited in tumors with functional BRCA1. We hypothesized that pharmacologically reducing BRCA1 protein levels could enhance PARPi effectiveness in BRCA1 wild-type tumors. To identify BRCA1 downregulating agents, we generated reporter cell lines using CRISPR-mediated editing to tag endogenous BRCA1 protein with HiBiT. These reporter lines enable the sensitive measurement of BRCA1 protein levels by luminescence. Validated reporter cells were used in a pilot screen of epigenetic-modifying probes and a larger screen of more than 6,000 compounds. We identified 7 compounds that could downregulate BRCA1-HiBiT expression and synergize with olaparib. Three compounds, N-acetyl-N-acetoxy chlorobenzenesulfonamide (NANAC), A-443654, and CHIR-124, were validated to reduce BRCA1 protein levels and sensitize breast cancer cells to the toxic effects of olaparib. These results suggest that BRCA1-HiBiT reporter cells hold promise in developing agents to improve the clinical utility of PARPi.

Overview of angiogenesis and oxidative stress in cancer

Neoplasms can be considered as a group of aberrant cells that need more vascular supply to fulfill all their functions. Therefore, they promote angiogenesis through the same neovascularization pathway used physiologically. Angiogenesis is a process characterized by a heterogeneous distribution of oxygen caused by the tumor and oxidative stress; the latter being one of the most powerful stimuli of angiogenesis. As a result of altered tumor metabolism due to hypoxia, acidosis occurs. The angiogenic process and oxidative stress can be detected by measuring serum and tissue biomarkers. The study of the mechanisms underlying angiogenesis and oxidative stress could lead to the identification of new biomarkers, ameliorating the selection of patients with neoplasms and the prediction of their response to possible anti-tumor therapies. In particular, in the treatment of patients with similar clinical tumor phenotypes but different prognoses, the new biomarkers could be useful. Moreover, they may lead to a better understanding of the mechanisms underlying drug resistance. Experimental studies show that blocking the vascular supply results in antiproliferative activity in vivo in neuroendocrine tumor cells, which require a high vascular supply.

Noncanonical NF-κB factor p100/p52 regulates homologous recombination and modulates sensitivity to DNA-damaging therapy

Homologous recombination (HR) serves multiple roles in DNA repair that are essential for maintaining genomic stability, including double-strand DNA break (DSB) repair. The central HR protein, RAD51, is frequently overexpressed in human malignancies, thereby elevating HR proficiency and promoting resistance to DNA-damaging therapies. Here, we find that the non-canonical NF-κB factors p100/52, but not RelB, control the expression of RAD51 in various human cancer subtypes. While p100/p52 depletion inhibits HR function in human tumor cells, it does not significantly influence the proficiency of non-homologous end joining, the other key mechanism of DSB repair. Clonogenic survival assays were performed using a pair DLD-1 cell lines that differ only in their expression of the key HR protein BRCA2. Targeted silencing of p100/p52 sensitizes the HR-competent cells to camptothecin, while sensitization is absent in HR-deficient control cells. These results suggest that p100/p52-dependent signaling specifically controls HR activity in cancer cells. Since non-canonical NF-κB signaling is known to be activated after various forms of genomic crisis, compensatory HR upregulation may represent a natural consequence of DNA damage. We propose that p100/p52-dependent signaling represents a promising oncologic target in combination with DNA-damaging treatments.

The fellowship of the RING: BRCA1, its partner BARD1 and their liaison in DNA repair and cancer

The breast cancer type 1 susceptibility protein (BRCA1) and its partner - the BRCA1-associated RING domain protein 1 (BARD1) - are key players in a plethora of fundamental biological functions including, among others, DNA repair, replication fork protection, cell cycle progression, telomere maintenance, chromatin remodeling, apoptosis and tumor suppression. However, mutations in their encoding genes transform them into dangerous threats, and substantially increase the risk of developing cancer and other malignancies during the lifetime of the affected individuals. Understanding how BRCA1 and BARD1 perform their biological activities therefore not only provides a powerful mean to prevent such fatal occurrences but can also pave the way to the development of new targeted therapeutics. Thus, through this review work we aim at presenting the major efforts focused on the functional characterization and structural insights of BRCA1 and BARD1, per se and in combination with all their principal mediators and regulators, and on the multifaceted roles these proteins play in the maintenance of human genome integrity.

p50 mono-ubiquitination and interaction with BARD1 regulates cell cycle progression and maintains genome stability

p50, the mature product of NFKB1, is constitutively produced from its precursor, p105. Here, we identify BARD1 as a p50-interacting factor. p50 directly associates with the BARD1 BRCT domains via a C-terminal phospho-serine motif. This interaction is induced by ATR and results in mono-ubiquitination of p50 by the BARD1/BRCA1 complex. During the cell cycle, p50 is mono-ubiquitinated in S phase and loss of this post-translational modification increases S phase progression and chromosomal breakage. Genome-wide studies reveal a substantial decrease in p50 chromatin enrichment in S phase and Cycln E is identified as a factor regulated by p50 during the G1 to S transition. Functionally, interaction with BARD1 promotes p50 protein stability and consistent with this, in human cancer specimens, low nuclear BARD1 protein strongly correlates with low nuclear p50. These data indicate that p50 mono-ubiquitination by BARD1/BRCA1 during the cell cycle regulates S phase progression to maintain genome integrity.

p50 is a constitutively produced NF-κB subunit that modulates the response to DNA damage. Here, the authors show that activation of ATR during S phase induces p50 interaction with BARD1 resulting in p50 mono-ubiquitination, facilitating cell cycle progression and promoting chromosome integrity.

The Effects of Genetic and Epigenetic Alterations of BARD1 on the Development of Non-Breast and Non-Gynecological Cancers

Breast Cancer 1 (BRCA1) gene is a well-characterized tumor suppressor gene, mutations of which are primarily found in women with breast and ovarian cancers. BRCA1-associated RING domain 1 (BARD1) gene has also been identified as an important tumor suppressor gene in breast, ovarian, and uterine cancers. Underscoring the functional significance of the BRCA1 and BARD1 interactions, prevalent mutations in the BRCA1 gene are found in its RING domain, through which it binds the RING domain of BARD1. BARD1-BRCA1 heterodimer plays a crucial role in a variety of DNA damage response (DDR) pathways, including DNA damage checkpoint and homologous recombination (HR). However, many mutations in both BARD1 and BRCA1 also exist in other domains that significantly affect their biological functions. Intriguingly, recent genome-wide studies have identified various single nucleotide polymorphisms (SNPs), genetic alterations, and epigenetic modifications in or near the BARD1 gene that manifested profound effects on tumorigenesis in a variety of non-breast and non-gynecological cancers. In this review, we will briefly discuss the molecular functions of BARD1, including its BRCA1-dependent as well as BRCA1-independent functions. We will then focus on evaluating the common BARD1 related SNPs as well as genetic and epigenetic changes that occur in the non-BRCA1-dominant cancers, including neuroblastoma, lung, and gastrointestinal cancers. Furthermore, the pro- and anti-tumorigenic functions of different SNPs and BARD1 variants will also be discussed.

Dural Extranodal Marginal Zone Lymphoma in an XRCC2 Mutation Carrier

Dural extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue (MALT lymphoma) is a rare entity without an associated recurrent genetic abnormality. Only one case has been described in a woman with history of breast carcinoma without a known genetic predisposition. Here, we report a case of a 56-year-old woman heterozygous for XRCC2 mutation with a history of Graves’ disease and bilateral breast carcinomas, who was found to have a diffusely infiltrative extra-axial mass in the high parietal convexity with infiltration into the adjacent superior sagittal sinus. The morphologic, immunophenotypic, and molecular findings were diagnostic of MALT lymphoma. Staging bone marrow demonstrated involvement by the neoplasm. Although the study was limited to only the clinically significant laboratory evaluation, it may serve as an important addition to the current knowledge of the pathogenic potential of a loss of function mutation in this rarely reported cancer predisposition gene.

PI3K-AKT-mTOR and NFκB Pathways in Ovarian Cancer: Implications for Targeted Therapeutics

Ovarian cancer is the most lethal gynecologic malignancy in the United States, with an estimated 22,530 new cases and 13,980 deaths in 2019. Recent studies have indicated that the phosphoinositol 3 kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR), as well as the nuclear factor-κ light chain enhancer of activated B cells (NFκB) pathways are highly mutated and/or hyper-activated in a majority of ovarian cancer patients, and are associated with advanced grade and stage disease and poor prognosis. In this review, we will investigate PI3K/AKT/mTOR and their interconnection with NFκB pathway in ovarian cancer cells.

Genomic Signatures Predict the Immunogenicity of BRCA-Deficient Breast Cancer

PURPOSE

Breast cancers with BRCA1/2 alterations have a relatively high mutational load, suggesting that immune checkpoint blockade may be a potential treatment option. However, the degree of immune cell infiltration varies widely, and molecular features contributing to this variability remain unknown.

EXPERIMENTAL DESIGN

We hypothesized that genomic signatures might predict immunogenicity in BRCA1/2 breast cancers. Using The Cancer Genome Atlas (TCGA) genomic data, we compared breast cancers with (89) and without (770) either germline or somatic BRCA1/2 alterations. We also studied 35 breast cancers with germline BRCA1/2 mutations from Penn using WES and IHC.

RESULTS

We found that homologous recombination deficiency (HRD) scores were negatively associated with expression-based immune indices [cytolytic index (P = 0.04), immune ESTIMATE (P = 0.002), type II IFN signaling (P = 0.002)] despite being associated with a higher mutational/neoantigen burden, in BRCA1/2 mutant breast cancers. Further, absence of allele-specific loss of heterozygosity (LOH negative; P = 0.01) or subclonality (P = 0.003) of germline and somatic BRCA1/2 mutations, respectively, predicted for heightened cytolytic activity. Gene set analysis found that multiple innate and adaptive immune pathways that converge on NF-κB may contribute to this heightened immunogenicity. IHC of Penn breast cancers demonstrated increased CD45⁺ (P = 0.039) and CD8⁺ infiltrates (P = 0.037) and increased PDL1 expression (P = 0.012) in HRD-low or LOH-negative cancers. Triple-negative cancers with low HRD had far greater CD8⁺ T cells (P = 0.0011) and Perforin 1 expression (P = 0.014) compared with hormone receptor-positive HRD-high cancers.

CONCLUSIONS

HRD scores and hormone receptor subtype are predictive of immunogenicity in BRCA1/2 breast cancers and may inform the design of optimal immune therapeutic strategies.

Benzene metabolite hydroquinone promotes DNA homologous recombination repair via the NF-κB pathway

Benzene, a widespread environmental pollutant, induces DNA double-strand breaks (DSBs) and DNA repair, which may further lead to oncogenic mutations, chromosomal rearrangements and leukemogenesis. However, the molecular mechanisms underlying benzene-induced DNA repair and carcinogenesis remain unclear. The human osteosarcoma cell line (U2OS/DR-GFP), which carries a GFP-based homologous recombination (HR) repair reporter, was treated with hydroquinone, one of the major benzene metabolites, to identify the potential effects of benzene on DSB HR repair. RNA-sequencing was further employed to identify the potential key pathway that contributed to benzene-initiated HR repair. We found that treatment with hydroquinone induced a significant increase in HR. NF-κB pathway, which plays a critical role in carcinogenesis in multiple tumors, was significantly activated in cells recovered from hydroquinone treatment. Furthermore, the upregulation of NF-κB by hydroquinone was also found in human hematopoietic stem and progenitor cells. Notably, the inhibition of NF-κB activity by small molecule inhibitors (QNZ and JSH-23) significantly reduced the frequency of hydroquinone-initiated HR (−1.36- and −1.77-fold, respectively, P < 0.01). Our results demonstrate an important role of NF-κB activity in promoting HR repair induced by hydroquinone. This finding sheds light on the underlying mechanisms involved in benzene-induced genomic instability and leukemogenesis and may contribute to the larger exploration of the influence of other environmental pollutants on carcinogenesis.

BRCA1 Mutation Status and Follicular Fluid Exposure Alters NFκB Signaling and ISGylation in Human Fallopian Tube Epithelial Cells

Germline BRCA1 or BRCA2 mutations (mtBRCA1 and mtBRCA2) increase risk for high-grade serous ovarian cancer (HGSOC), the most commonly diagnosed epithelial ovarian cancer histotype. Other identified risk factors for this cancer, which originates primarily in the distal fallopian tube epithelium (FTE), implicate ovulation, during which the FTE cells become transiently exposed to follicular fluid (FF). To test whether mtBRCA1 or mtBRCA2 nonmalignant FTE cells respond differently to periovulatory FF exposure than control patient FTE cells, gene expression profiles from primary FTE cultures derived from BRCA1 or BRCA2 mutation carriers or control patients were compared at baseline, 24 hours after FF exposure, and 24 hours after FF replacement with culture medium. Hierarchical clustering revealed both FF exposure and BRCA mutation status affect gene expression, with BRCA1 mutation having the greatest impact. Gene set enrichment analysis revealed increased NFκB and EGFR signaling at baseline in mtBRCA1 samples, with increased interferon target gene expression, including members of the ISGylation pathway, observed after recovery from FF exposure. Gene set enrichment analysis did not identify altered pathway signaling in mtBRCA2 samples. An inverse relationship between EGFR signaling and ISGylation with BRCA1 protein levels was verified in an immortalized FTE cell line, OE-E6/E7, stably transfected with BRCA1 cDNA. Suppression of ISG15 and ISGylated protein levels by increased BRCA1 expression was found to be mediated by decreased NFκB signaling. These studies indicate that increased NFκB signaling associated with decreased BRCA1 expression results in increased ISG15 and protein ISGylation following FF exposure, which may be involved in predisposition to HGSOC.

Integrative Bioinformatics and Functional Analyses of GEO, ENCODE, and TCGA Reveal FADD as a Direct Target of the Tumor Suppressor BRCA1

BRCA1 is a multifunctional tumor suppressor involved in several essential cellular processes. Although many of these functions are driven by or related to its transcriptional/epigenetic regulator activity, there has been no genome-wide study to reveal the transcriptional/epigenetic targets of BRCA1. Therefore, we conducted a comprehensive analysis of genomics/transcriptomics data to identify novel BRCA1 target genes. We first analyzed ENCODE data with BRCA1 chromatin immunoprecipitation (ChIP)-sequencing results and identified a set of genes with a promoter occupied by BRCA1. We collected 3085 loci with a BRCA1 ChIP signal from four cell lines and calculated the distance between the loci and the nearest gene transcription start site (TSS). Overall, 66.5% of the BRCA1-bound loci fell into a 2-kb region around the TSS, suggesting a role in transcriptional regulation. We selected 45 candidate genes based on gene expression correlation data, obtained from two GEO (Gene Expression Omnibus) datasets and TCGA data of human breast cancer, compared to BRCA1 expression levels. Among them, we further tested three genes (MEIS2, CKS1B and FADD) and verified FADD as a novel direct target of BRCA1 by ChIP, RT-PCR, and a luciferase reporter assay. Collectively, our data demonstrate genome-wide transcriptional regulation by BRCA1 and suggest target genes as biomarker candidates for BRCA1-associated breast cancer.

A BRCA1 deficient, NFκB driven immune signal predicts good outcome in triple negative breast cancer

Triple negative (TNBCs) and the closely related Basal-like (BLBCs) breast cancers are a loosely defined collection of cancers with poor clinical outcomes. Both show strong similarities with BRCA1-mutant breast cancers and BRCA1 dysfunction, or ‘BRCAness’, is observed in a large proportion of sporadic BLBCs. BRCA1 expression and function has been shown in vitro to modulate responses to radiation and chemotherapy. Exploitation of this knowledge in the treatment of BRCA1-mutant patients has had varying degrees of success. This reflects the significant problem of accurately detecting those patients with BRCA1 dysfunction. Moreover, not all BRCA1 mutations/loss of function result in the same histology/pathology or indeed have similar effects in modulating therapeutic responses. Given the poor clinical outcomes and lack of targeted therapy for these subtypes, a better understanding of the biology underlying these diseases is required in order to develop novel therapeutic strategies.

We have discovered a consistent NFκB hyperactivity associated with BRCA1 dysfunction as a consequence of increased Reactive Oxygen Species (ROS). This biology is found in a subset of BRCA1-mutant and triple negative breast cancer cases and confers good outcome. The increased NFκB signalling results in an anti-tumour microenvironment which may allow CD8+ cytotoxic T cells to suppress tumour progression. However, tumours lacking this NFκB-driven biology have a more tumour-promoting environment and so are associated with poorer prognosis. Tumour-derived gene expression data and cell line models imply that these tumours may benefit from alternative treatment strategies such as reprogramming the microenvironment and targeting the IGF and AR signalling pathways.

BRCA1-mimetic compound NSC35446.HCl inhibits IKKB expression by reducing estrogen receptor-α occupancy in the IKKB promoter and inhibits NF-κB activity in antiestrogen-resistant human breast cancer cells

PURPOSE

We previously identified small molecules that fit into a BRCA1-binding pocket within estrogen receptor-alpha (ERα), mimic the ability of BRCA1 to inhibit ERα activity ("BRCA1-mimetics"), and overcome antiestrogen resistance. One such compound, the hydrochloride salt of NSC35446 ("NSC35446.HCl"), also inhibited the growth of antiestrogen-resistant LCC9 tumor xenografts. The purpose of this study was to investigate the down-stream effects of NSC35446.HCl and its mechanism of action.

METHODS

Here, we studied antiestrogen-resistant (LCC9, T47DCO, MCF-7/RR, LY2), ERα-negative (MDA-MB-231, HCC1806, MDA-MB-468), and antiestrogen-sensitive (MCF-7) cell lines. Techniques utilized include RNA-seq, qRT-PCR, cell growth analysis, cell-cycle analysis, Western blotting, luciferase reporter assays, TUNEL assays, in silico analysis of the IKKB gene, and ChIP assays.

RESULTS

SC35446.HCl inhibited proliferation and induced apoptosis in antiestrogen-resistant LCC9, T47DCO, MCF-7/RR, and LY2 cells but not in ERα-negative breast cancer cell lines. IKKB (IKKβ, IKBKB), an upstream activator of NF-κB, was identified as a BRCA1-mimetic-regulated gene based on an RNA-seq analysis. NSC35446.HCl inhibited IKKB, IKKA, and IKKG/NEMO mRNA and protein expression in LCC9 cells. NSC35446.HCl also inhibited NF-κB activity and expression of NF-κB target genes. In silico analysis of the IKKB promoter identified nine estrogen response element (ERE) half-sites and one ERE-like full-site. ChIP assays revealed that ERα was recruited to the ERE-like full-site and five of the nine half-sites and that ERα recruitment was inhibited by NSC35446.HCl in LCC9 and T47DCO cells.

CONCLUSIONS

These studies identify functional EREs in the IKKB promoter and identify IKKB as an ERα and NSC35446.HCl-regulated gene, and they suggest that NF-κB and IKKB, which were previously linked to antiestrogen resistance, are targets for NSC35446.HCl in reversing antiestrogen resistance.

The DEAD-Box RNA Helicase DDX3 Interacts with NF-κB Subunit p65 and Suppresses p65-Mediated Transcription

RNA helicase family members exhibit diverse cellular functions, including in transcription, pre-mRNA processing, RNA decay, ribosome biogenesis, RNA export and translation. The RNA helicase DEAD-box family member DDX3 has been characterized as a tumour-associated factor and a transcriptional co-activator/regulator. Here, we demonstrate that DDX3 interacts with the nuclear factor (NF)-κB subunit p65 and suppresses NF-κB (p65/p50)-mediated transcriptional activity. The downregulation of DDX3 by RNA interference induces the upregulation of NF-κB (p65/p50)-mediated transcription. The regulation of NF-κB (p65/p50)-mediated transcriptional activity was further confirmed by the expression levels of its downstream cytokines, such as IL-6 and IL-8. Moreover, the binding of the ATP-dependent RNA helicase domain of DDX3 to the N-terminal Rel homology domain (RHD) of p65 is involved in the inhibition of NF-κB-regulated gene transcription. In summary, the results suggest that DDX3 functions to suppress the transcriptional activity of the NF-κB subunit p65.

BRCA1 affects protein phosphatase 6 signalling through its interaction with ANKRD28

The tumour suppressor BRCA1 (breast and ovarian cancer-susceptibility gene 1) is implicated in several nuclear processes including DNA repair, transcription regulation and chromatin remodelling. BRCA1 also has some cytoplasmic functions including a pro-apoptotic activity. We identified ANKRD28 (ankyrin repeat domain 28) as a novel BRCA1-interacting protein in a yeast two-hybrid screen and confirmed this interaction by reciprocal immunoprecipitations of the two overexpressed proteins. Endogenous interaction between BRCA1 and ANKRD28 was also observed by co-immunoprecipitation and located in the cytoplasm by proximity ligation assay. The main site of interaction of ANKRD28 on BRCA1 is located in its intrinsically disordered scaffold central region. Whereas ANKRD28 silencing results in a destabilization of IκBε (inhibitor of nuclear factor κBε) through its activation of PP6 (protein phosphatase 6) co-regulator upon TNFα (tumour necrosis factor α) stimulation, BRCA1 overexpression stabilizes IκBε. A truncated form of BRCA1 that does not interact with ANKRD28 has no such effect. Our findings suggest that BRCA1 is a novel modulator of PP6 signalling via its interaction with ANKRD28. This new cytoplasmic process might participate in BRCA1 tumour-suppressor function.

Transcription Factor NF-κB: An Update on Intervention Strategies

The nuclear factor (NF)-κB family of transcription factors are ubiquitous and pleiotropic molecules that regulate the expression of more than 150 genes involved in a broad range of processes including inflammation, immunity, cell proliferation, differentiation, and survival. The chronic activation or dysregulation of NF-κB signaling is the central cause of pathogenesis in many disease conditions and, therefore, NF-κB is a major focus of therapeutic intervention. Because of this, understanding the relationship between NF-κB and the induction of various downstream signaling molecules is imperative. In this review, we provide an updated synopsis of the role of NF-κB in DNA repair and in various ailments including cardiovascular diseases, HIV infection, asthma, herpes simplex virus infection, chronic obstructive pulmonary disease, and cancer. Furthermore, we also discuss the specific targets for selective inhibitors and future therapeutic strategies.

Unirradiated cells rescue cells exposed to ionizing radiation: Activation of NF-κB pathway in irradiated cells

We studied the involvement of NF-κB pathway activation in the rescue effect in HeLa and NIH/3T3 cells irradiated by α particles. Firstly, upon irradiation by 5 cGy of α particles, for both cell lines, the numbers of 53BP1 foci/cell at 12 h post-irradiation were significantly smaller when only 2.5% of the cell population was irradiated as compared to 100% irradiation, which demonstrated the rescue effect. Secondly, we studied the effect of NF-κB on the rescue effect through the use of the NF-κB activation inhibitor BAY-11-7082. Novel experimental setup and procedures were designed to prepare the medium (CM) which had conditioned the bystander cells previously partnered with irradiated cells, to ensure physical separation between rescue and bystander signals. BAY-11-7082 itself did not inflict DNA damages in the cells or have effects on activation of the NF-κB response pathway in the irradiated cells through direct irradiation. The rescue effect was induced in both cell lines by the CM, which was abrogated if BAY-11-7082 was added to the CM. Thirdly, we studied the effect of NF-κB on the rescue effect through staining for phosphorylated NF-κB (p-NF-κB) expression using the anti-NF-κB p65 (phospho S536) antibody. When the fraction of irradiated cells dropped from 100% to 2.5%, the p-NF-κB expression in the cell nuclei of irradiated NIH/3T3 cells increased significantly, while that in the cell nuclei of irradiated HeLa cells also increased although not significantly. Moreover, the p-NF-κB expression in the cell nuclei of irradiated HeLa cells and NIH/3T3 cells treated with CM also increased significantly.

Interplay of Rad51 with NF-κB pathway stimulates expression of HIV-1

Transcription from the HIV-1 promoter is controlled by a series of ubiquitous and inducible cellular proteins with the ability to enter the nucleus and interact with the promoter. A DNA sequence spanning nucleotides −120 to −80, which supports the association of the inducible NF-κB transcription factor, has received much attention. Here we demonstrate that the interplay between Rad51, a key regulator of the homologous recombination pathway of DNA repair and whose level is induced upon HIV-1 infection, with the NF-κB pathway, augments transcription of the viral promoter. Evidently, stimulation of the NF-κB pathway by PMA and/or TSA promotes association of Rad51 with the LTR DNA sequence and that the p65 subunit of NF-κB is important for this event. Our results also demonstrate that, similar to p65, Rad51 utilizes the NF-κB pathway to position itself in the nucleus as ectopic expression of an IκB mutant impedes its nuclear appearance and transcriptional activity upon the HIV-1 LTR. Treatment of peripheral blood mononuclear cells with small molecules that inhibit Rad51 activity results in greater than 50% decrease in the HIV-1 infection of cells. These observations provide evidence for the involvement of DNA repair factors in control of HIV-1 gene activation and offer a new avenue for the development of anti-viral therapeutics that affect viral gene transcription in latently infected cells.

Acellular fraction of ovarian cancer ascites induce apoptosis by activating JNK and inducing BRCA1, Fas and FasL expression in ovarian cancer cells

Acellular fraction of ascites might play an active role in tumor development. Nevertheless the mechanisms involved in the tumor-modulating properties are still controversial. Here, we demonstrate that malignant ascites from 8 patients with epithelial ovarian cancer did not influence proliferative or invasive properties of ovarian cancer cells, but promoted H₂O₂-induced apoptosis and increased sensitivity to paclitaxel. Malignant ascites induced BRCA1, Fas and FasL expression and phosphorylation of JNK, but not the activation of caspase pathway. Ascites-induced apoptosis of ovarian cancer cells was strongly inhibited by a JNK inhibitor suggesting a critical role of JNK pathway in ascite-induced apoptosis. The use of siRNA JNK confirmed the importance of JNK in ascites-induced Fas and FasL expression. These results demonstrate that malignant ascites induce apoptosis of ovarian cancer cells and encourage us to think about the clinical management of ovarian cancer patients with malignant ascites.

BRCA1 and Oxidative Stress

The breast cancer susceptibility gene 1 (BRCA1) has been well established as a tumor suppressor and functions primarily by maintaining genome integrity. Genome stability is compromised when cells are exposed to oxidative stress. Increasing evidence suggests that BRCA1 regulates oxidative stress and this may be another mechanism in preventing carcinogenesis in normal cells. Oxidative stress caused by reactive oxygen species (ROS) is implicated in carcinogenesis and is used strategically to treat human cancer. Thus, it is essential to understand the function of BRCA1 in oxidative stress regulation. In this review, we briefly summarize BRCA1's many binding partners and mechanisms, and discuss data supporting the function of BRCA1 in oxidative stress regulation. Finally, we consider its significance in prevention and/or treatment of BRCA1-related cancers.

Genome-wide analysis reveals a role for BRCA1 and PALB2 in transcriptional co-activation

Breast and ovarian cancer susceptibility genes BRCA1 and PALB2 have enigmatic roles in cellular growth and mammalian development. While these genes are essential for growth during early developmental programs, inactivation later in adulthood results in increased growth and formation of tumors, leading to their designation as tumor suppressors. We performed genome-wide analysis assessing their chromatin residence and gene expression responsiveness using high-throughput sequencing in breast epithelial cells. We found an intimate association between BRCA1 and PALB2 chromatin residence and genes displaying high transcriptional activity. Moreover, our experiments revealed a critical role for BRCA1 and, to a smaller degree, PALB2 in transcriptional responsiveness to NF-κB, a crucial mediator of growth and inflammatory response during development and cancer. Importantly, we also uncovered a vital role for BRCA1 and PALB2 in response to retinoic acid (RA), a growth inhibitory signal in breast cancer cells, which may constitute the basis for their tumor suppressor activity. Taken together, our results highlight an important role for these breast cancer proteins in the regulation of diverse growth regulatory pathways.

NF-κB is a critical mediator of BRCA1-induced chemoresistance

BRCA1 mediates resistance to apoptosis in response to DNA damaging agents, causing BRCA1 wild-type tumours to be significantly more resistant to DNA damage than their mutant counterparts. In this study we demonstrate that following treatment with the DNA damaging agents etoposide or camptothecin, BRCA1 is required for the activation of NF-κB, and that BRCA1 and NF-κB cooperate to regulate the expression of the NF-κB antiapoptotic targets BCL2 and XIAP. We show that BRCA1 and the NF-κB subunit p65/RelA associate constitutively, whereas the p50 NF-κB subunit associates with BRCA1 only upon DNA damage treatment. Consistent with this BRCA1 and p65 are present constitutively on the promoters of BCL2 and XIAP whereas p50 is recruited to these promoters only in damage treated cells. Importantly, we demonstrate that the recruitment of p50 onto the promoters of BCL2 and XIAP is dependent upon BRCA1, but independent of its NF-κB partner subunit p65. The functional relevance of NF-κB activation by BRCA1 in response to etoposide and camptothecin is demonstrated by the significantly reduced survival of BRCA1 wild type cells upon NF-κB inhibition. This study identifies a novel BRCA1-p50 complex, and demonstrates for the first time that NF-κB is required for BRCA1 mediated resistance to DNA damage. It reveals a functional interdependence between BRCA1 and NF-κB, further elucidating the role played by NF-κB in mediating cellular resistance of BRCA1 wild-type tumours to DNA damaging agents.

Oxidative stress and cancer: an overview

Reactive species, which mainly include reactive oxygen species (ROS), are products generated as a consequence of metabolic reactions in the mitochondria of eukaryotic cells. In normal cells, low-level concentrations of these compounds are required for signal transduction before their elimination. However, cancer cells, which exhibit an accelerated metabolism, demand high ROS concentrations to maintain their high proliferation rate. Different ways of developing ROS resistance include the execution of alternative pathways, which can avoid large amounts of ROS accumulation without compromising the energy demand required by cancer cells. Examples of these processes include the guidance of the glycolytic pathway into the pentose phosphate pathway (PPP) and/or the generation of lactate instead of employing aerobic respiration in the mitochondria. Importantly, ROS levels can be used as a thermostat to monitor the damage that cells can bear. The implications for ROS regulation are highly significant for cancer therapy because commonly used radio- and chemotherapeutic drugs influence tumor outcome through ROS modulation. Moreover, the discovery of novel biomarkers that are able to predict the clinical response to pro-oxidant therapies is a crucial challenge to overcome to allow for the personalization of cancer therapies.

Essential role of cooperative NF-κB and Stat3 recruitment to ICAM-1 intronic consensus elements in the regulation of radiation-induced invasion and migration in glioma

Although radiotherapy improves survival in patients, glioblastoma multiformes (GBMs) tend to relapse with augmented tumor migration and invasion even after ionizing radiation (IR). Aberrant nuclear factor-κB (NF-κB) and signal transducer and activator of transcription factor 3 (Stat3) activation and interaction have been suggested in several human tumors. However, possible NF-κB/Stat3 interaction and the role of Stat3 in maintenance of NF-κB nuclear retention in GBM still remain unknown. Stat3 and NF-κB (p65) physically interact with one another in the nucleus in glioma tumors. Most importantly, glutathione S-transferase pull-down assays identified that Stat3 binds to the p65 transactivation domain and is present in the NF-κB DNA-binding complex. Irradiation significantly elevated nuclear phospho-p65/phospho-Stat3 interaction in correlation with increased intercellular adhesion molecule-1 (ICAM-1) and soluble-ICAM-1 levels, migration and invasion in human glioma xenograft cell lines 4910 and 5310. Chromatin immunopreicipitation and promoter luciferase activity assays confirmed the critical role of adjacent NF-κB (+399) and Stat3 (+479) binding motifs in the proximal intron-1 in elevating IR-induced ICAM-1 expression. Specific inhibition of Stat3 or NF-κB with Stat3.siRNA or JSH-23 severely inhibited IR-induced p65 recruitment onto ICAM-1 intron-1 and suppressed migratory properties in both the cell lines. On the other hand, Stat3C- or IR-induced Stat3 promoter recruitment was significantly decreased in p65-knockdown cells, thereby suggesting the reciprocal regulation between p65 and Stat3. We also observed a significant increase in NF-κB enrichment on ICAM-1 intron-1 and ICAM-1 transactivation in Stat3C overexpressing cells. In in vivo orthotopic experiments, suppression of tumor growth in Stat3.si+IR-treated mice was associated with the inhibition of IR-induced p-p65/p-Stat3 nuclear colocalization and ICAM-1 levels. To our knowledge, this is the first study showing the crucial role of NF-κB/Stat3 nuclear association in IR-induced ICAM-1 regulation and implies that targeting NF-κB/Stat3 interaction may have future therapeutic significance in glioma treatment.

NF-κB regulates DNA double-strand break repair in conjunction with BRCA1-CtIP complexes

NF-κB is involved in immune responses, inflammation, oncogenesis, cell proliferation and apoptosis. Even though NF-κB can be activated by DNA damage via Ataxia telangiectasia-mutated (ATM) signalling, little was known about an involvement in DNA repair. In this work, we dissected distinct DNA double-strand break (DSB) repair mechanisms revealing a stimulatory role of NF-κB in homologous recombination (HR). This effect was independent of chromatin context, cell cycle distribution or cross-talk with p53. It was not mediated by the transcriptional NF-κB targets Bcl2, BAX or Ku70, known for their dual roles in apoptosis and DSB repair. A contribution by Bcl-xL was abrogated when caspases were inhibited. Notably, HR induction by NF-κB required the targets ATM and BRCA2. Additionally, we provide evidence that NF-κB interacts with CtIP-BRCA1 complexes and promotes BRCA1 stabilization, and thereby contributes to HR induction. Immunofluorescence analysis revealed accelerated formation of replication protein A (RPA) and Rad51 foci upon NF-κB activation indicating HR stimulation through DSB resection by the interacting CtIP-BRCA1 complex and Rad51 filament formation. Taken together, these results define multiple NF-κB-dependent mechanisms regulating HR induction, and thereby providing a novel intriguing explanation for both NF-κB-mediated resistance to chemo- and radiotherapies as well as for the sensitization by pharmaceutical intervention of NF-κB activation.

Pathway-based analysis using reduced gene subsets in genome-wide association studies

Background

Single Nucleotide Polymorphism (SNP) analysis only captures a small proportion of associated genetic variants in Genome-Wide Association Studies (GWAS) partly due to small marginal effects. Pathway level analysis incorporating prior biological information offers another way to analyze GWAS's of complex diseases, and promises to reveal the mechanisms leading to complex diseases. Biologically defined pathways are typically comprised of numerous genes. If only a subset of genes in the pathways is associated with disease then a joint analysis including all individual genes would result in a loss of power. To address this issue, we propose a pathway-based method that allows us to test for joint effects by using a pre-selected gene subset. In the proposed approach, each gene is considered as the basic unit, which reduces the number of genetic variants considered and hence reduces the degrees of freedom in the joint analysis. The proposed approach also can be used to investigate the joint effect of several genes in a candidate gene study.

Results

We applied this new method to a published GWAS of psoriasis and identified 6 biologically plausible pathways, after adjustment for multiple testing. The pathways identified in our analysis overlap with those reported in previous studies. Further, using simulations across a range of gene numbers and effect sizes, we demonstrate that the proposed approach enjoys higher power than several other approaches to detect associated pathways.

Conclusions

The proposed method could increase the power to discover susceptibility pathways and to identify associated genes using GWAS. In our analysis of genome-wide psoriasis data, we have identified a number of relevant pathways for psoriasis.

NF-κB addiction and its role in cancer: 'one size does not fit all'

Activation of nuclear factor (NF)-κB, one of the most investigated transcription factors, has been found to control multiple cellular processes in cancer including inflammation, transformation, proliferation, angiogenesis, invasion, metastasis, chemoresistance and radioresistance. NF-κB is constitutively active in most tumor cells, and its suppression inhibits the growth of tumor cells, leading to the concept of 'NF-κB addiction' in cancer cells. Why NF-κB is constitutively and persistently active in cancer cells is not fully understood, but multiple mechanisms have been delineated including agents that activate NF-κB (such as viruses, viral proteins, bacteria and cytokines), signaling intermediates (such as mutant receptors, overexpression of kinases, mutant oncoproteins, degradation of IκBα, histone deacetylase, overexpression of transglutaminase and iNOS) and cross talk between NF-κB and other transcription factors (such as STAT3, HIF-1α, AP1, SP, p53, PPARγ, β-catenin, AR, GR and ER). As NF-κB is 'pre-active' in cancer cells through unrelated mechanisms, classic inhibitors of NF-κB (for example, bortezomib) are unlikely to mediate their anticancer effects through suppression of NF-κB. This review discusses multiple mechanisms of NF-κB activation and their regulation by multitargeted agents in contrast to monotargeted agents, thus 'one size does not fit all' cancers.

NF-kappaB p65 subunit mediates lipopolysaccharide-induced Na(+)/I(-) symporter gene expression by involving functional interaction with the paired domain transcription factor Pax8

The Gram-negative bacterial endotoxin lipopolysaccharide (LPS) elicits a variety of biological responses. Na(+)/I(-) symporter (NIS)-mediated iodide uptake is the main rate-limiting step in thyroid hormonogenesis. We have recently reported that LPS stimulates TSH-induced iodide uptake. Here, we further analyzed the molecular mechanism involved in the LPS-induced NIS expression in Fisher rat thyroid cell line 5 (FRTL-5) thyroid cells. We observed an increase in TSH-induced NIS mRNA expression in a dose-dependent manner upon LPS treatment. LPS enhanced the TSH-stimulated NIS promoter activity denoting the NIS-upstream enhancer region (NUE) as responsible for the stimulatory effects. We characterized a novel putative conserved kappaB site for the transcription factor nuclear factor-kappaB (NF-kappaB) within the NUE region. NUE contains two binding sites for the transcription factor paired box 8 (Pax8), main regulator of NIS transcription. A physical interaction was observed between the NF-kappaB p65 subunit and paired box 8 (Pax8), which appears to be responsible for the synergic effect displayed by these transcription factors on NIS gene transcription. Moreover, functional blockage of NF-kappaB signaling and site-directed mutagenesis of the kappaB cis-acting element abrogated LPS stimulation. Silencing expression of p65 confirmed its participation as an effector of LPS-induced NIS stimulation. Furthermore, chromatin immunoprecipitation corroborated that NIS is a novel target gene for p65 transactivation in response to LPS. Moreover, we were able to corroborate the LPS-stimulatory effect on thyroid cells in vivo in LPS-treated rats, supporting that thyrocytes are capable of responding to systemic infections. In conclusion, our results reveal a new mechanism involving p65 in the LPS-induced NIS expression, denoting a novel aspect in thyroid cell differentiation.

BRCA1 represses amphiregulin gene expression

BRCA1, the breast cancer- and ovarian cancer-specific tumor suppressor, can be a transcriptional repressor or a transcriptional activator, depending on the promoter context. To identify the genes activated or repressed by BRCA1, we have analyzed microarray results from cells depleted of BRCA1 and revealed a number of genes regulated by BRCA1 on the level of transcription. Among the genes repressed by BRCA1, we have identified amphiregulin (AREG) and early growth response-1 (EGR1). Results indicate that BRCA1 regulates AREG transcription directly through binding to the AREG promoter, however, we could not detect BRCA1 on the EGR1 promoter, suggesting that EGR1 is indirectly regulated by BRCA1. In an attempt to identify the mechanism of the AREG transcriptional repression by BRCA1, we have mapped two independent BRCA1 response elements on the AREG located at positions -202/-182 and +19/+122. BRCA1 depletion leads to induction of the AREG protein. Taken together, our data build the connection between BRCA1 loss of function and AREG upregulation-a change in gene expression often observed in breast cancer.

Gene expression profiling integrated into network modelling reveals heterogeneity in the mechanisms of BRCA1 tumorigenesis

BACKGROUND

Gene expression profiling has distinguished sporadic breast tumour classes with genetic and clinical differences. Less is known about the molecular classification of familial breast tumours, which are generally considered to be less heterogeneous. Here, we describe molecular signatures that define BRCA1 subclasses depending on the expression of the gene encoding for oestrogen receptor, ESR1.

METHODS

For this purpose, we have used the Oncochip v2, a cancer-related cDNA microarray to analyze 14 BRCA1-associated breast tumours.

RESULTS

Signatures were found to be molecularly associated with different biological processes and transcriptional regulatory programs. The signature of ESR1-positive tumours was mainly linked to cell proliferation and regulated by ER, whereas the signature of ESR1-negative tumours was mainly linked to the immune response and possibly regulated by transcription factors of the REL/NFkappaB family. These signatures were then verified in an independent series of familial and sporadic breast tumours, which revealed a possible prognostic value for each subclass. Over-expression of immune response genes seems to be a common feature of ER-negative sporadic and familial breast cancer and may be associated with good prognosis. Interestingly, the ESR1-negative tumours were substratified into two groups presenting slight differences in the magnitude of the expression of immune response transcripts and REL/NFkappaB transcription factors, which could be dependent on the type of BRCA1 germline mutation.

CONCLUSION

This study reveals the molecular complexity of BRCA1 breast tumours, which are found to display similarities to sporadic tumours, and suggests possible prognostic implications.

The DEAD-box RNA helicase DDX1 interacts with RelA and enhances nuclear factor kappaB-mediated transcription

DEAD-box RNA helicases constitute the largest family of RNA helicases and are involved in many aspects of RNA metabolism. In this study, we identified RelA (p65), a subunit of nuclear factor-kappaB (NF-kappaB), as a cellular co-factor of DEAD-box RNA helicase DDX1, through mammalian two hybrid system and co-immunoprecipitation assay. Additionally, confocal microscopy and chromatin immunoprecipitation assays confirmed this interaction. In NF-kappaB dependent reporter gene assay, DDX1 acted as a co-activator to enhance NF-kappaB-mediated transcription activation. The functional domains involved were mapped to the carboxy terminal transactivation domain of RelA and the amino terminal ATPase/helicase domain of DDX1. The DDX1 trans-dominant negative mutant lacking ATP-dependent RNA helicase activity lost it transcriptional inducer activity. Moreover, depletion of endogenous DDX1 by specific small interfering RNAs significantly reduced NF-kappaB-dependent transcription. Taken together, the results suggest that DDX1 may play an important role in NF-kappaB-mediated transactivation, and revelation of this regulatory pathway may help to explore the novel mechanisms for regulating NF-kappaB transcriptional activity.

HCV NS3/4A protein activates HIV-1 transcription from its long terminal repeat

Approximately 30-40% of patients infected with the human immunodeficiency virus (HIV) in the U.S. are also infected with the hepatitis C virus (HCV). Studies have shown that HIV can worsen hepatitis C, while the impact of hepatitis C on HIV disease is less clear. In this study, we described that HCV NS3/4A protein can activate HIV-1 transcription from its long terminal repeat (LTR) region, while the serine protease-inactive mutant of NS3/4A fails to do so. The activation effect of NS3/4A to HIV-1 transcription can be explained by its ability to enhance DNA binding activities of the transcription factor AP-1. These results have provided insights into the mechanism involved in the co-infection of HCV and HIV.

Mullerian-inhibiting substance induces Gro-beta expression in breast cancer cells through a nuclear factor-kappaB-dependent and Smad1-dependent mechanism

Mullerian-inhibiting substance (MIS), a transforming growth factor-beta family member, activates the nuclear factor-kappaB (NF-kappaB) pathway and induces the expression of B-cell translocation gene 2 (BTG2), IFN regulatory factor-1 (IRF-1), and the chemokine Gro-beta. Inhibiting NF-kappaB activation with a phosphorylation-deficient IkappaBalpha mutant abrogated MIS-mediated induction of all three genes. Expression of dominant-negative Smad1, in which serines at the COOH-terminal SSVS motif are converted to alanines, suppressed MIS-induced Smad1 phosphorylation and impaired MIS-stimulated Gro-beta promoter-driven reporter expression and Gro-beta mRNA. Suppressing Smad1 expression using small interfering RNA also mitigated MIS-induced Gro-beta mRNA, suggesting that regulation of Gro-beta expression by MIS was dependent on activation of NF-kappaB as well as Smad1. However, induction of IRF-1 and BTG2 mRNAs by MIS was independent of Smad1 activation. Characterization of kappaB-binding sequences within Gro-beta, BTG2, and IRF-1 promoters showed that MIS stimulated binding of p50 and p65 subunits to all three sites, whereas phosphorylated Smad1 (phospho-Smad1) protein was detectable only in the NF-kappaB complex bound to the kappaB site of the Gro-beta promoter. Consistent with these observations, chromatin immunoprecipitation assays showed recruitment of both phospho-Smad1 and p65 to the Gro-beta promoter in vivo, whereas p65, but not phospho-Smad1, was recruited to the BTG2 promoter. These results show a novel interaction between MIS-stimulated Smad1 and NF-kappaB signaling in which enhancement of NF-kappaB DNA binding and gene expression by phospho-Smad1 is dependent on the sequence of the kappaB consensus site within the promoter.

Current insights into the regulation of programmed cell death by NF-kappaB

The nuclear factor-kappaB (NF-kappaB) transcription factors have emerged as major regulators of programmed cell death (PCD) whether via apoptosis or necrosis. In this context, NF-kappaB's activity has important ramifications for normal tissue development, homoeostasis and the physiological functions of various cell systems including the immune, hepatic, epidermal and nervous systems. However, improper regulation of PCD by NF-kappaB can have severe pathologic consequences, ranging from neurodegeneration to cancer, where its activity often precludes effective therapy. Although NF-kappaB generally protects cells by inducing the expression genes encoding antiapoptotic and antioxidizing proteins, its role in apoptosis and necrosis can vary markedly in different cell contexts, and NF-kappaB can sensitize cells to death-inducing stimuli in some instances. This article describes our current knowledge of the role of NF-kappaB in apoptosis and necrosis, and focuses on the many advances since we last reviewed this rapidly evolving topic in Oncogene 3 years ago. There has been substantial progress in understanding NF-kappaB's mode of action in apoptosis and necrosis and the mechanisms that regulate its anti- vs proapoptotic activities. These recent developments shed new light on the role of NF-kappaB in many disease conditions including tumor development, tumor progression and anticancer treatment.

NF-kappa B activation as a pathological mechanism of septic shock and inflammation

The pathophysiology of sepsis and septic shock involves complex cytokine and inflammatory mediator networks. NF-kappaB activation is a central event leading to the activation of these networks. The role of NF-kappaB in septic pathophysiology and the signal transduction pathways leading to NF-kappaB activation during sepsis have been an area of intensive investigation. NF-kappaB is activated by a variety of pathogens known to cause septic shock syndrome. NF-kappaB activity is markedly increased in every organ studied, both in animal models of septic shock and in human subjects with sepsis. Greater levels of NF-kappaB activity are associated with a higher rate of mortality and worse clinical outcome. NF-kappaB mediates the transcription of exceptional large number of genes, the products of which are known to play important roles in septic pathophysiology. Mice deficient in those NF-kappaB-dependent genes are resistant to the development of septic shock and to septic lethality. More importantly, blockade of NF-kappaB pathway corrects septic abnormalities. Inhibition of NF-kappaB activation restores systemic hypotension, ameliorates septic myocardial dysfunction and vascular derangement, inhibits multiple proinflammatory gene expression, diminishes intravascular coagulation, reduces tissue neutrophil influx, and prevents microvascular endothelial leakage. Inhibition of NF-kappaB activation prevents multiple organ injury and improves survival in rodent models of septic shock. Thus NF-kappaB activation plays a central role in the pathophysiology of septic shock.

Is there more to BARD1 than BRCA1?

It has been over a decade since mutations in BRCA1 and BRCA2 were found to be associated with a small number of familial breast cancer cases. BRCA1 is a large protein that interacts with many other proteins that have diverse functions, so it has been a challenge to determine how defects in its function could lead to cancer. One particular protein, BARD1, seems to be an important regulator of the tumour-suppressor function of BRCA1, as well as acting as a tumour suppressor itself. BARD1 is indispensable for cell viability, so loss-of-function mutations are rare, but mutations and truncations that alter its function might be involved in the pathogenesis of breast cancer.

A novel mechanism of nuclear factor-kappaB regulation by adenoviral protein 14.7K

Viruses have evolved many different ways to evade immune attacks. The adenoviral E3 protein 14.7K effectively inhibits antiviral immunity and inflammation. However, the underlying mechanism for this effect is unclear. Here we show that 14.7K is a potent inhibitor of nuclear factor (NF)-kappaB transcriptional activity following Toll-like receptor (TLR) or tumour necrosis factor (TNF) receptor signalling. The inhibition of the NF-kappaB activity occurs downstream of IkappaBalpha degradation and NF-kappaB translocation into the nucleus. Analysis of NF-kappaB DNA binding reveals that 14.7K specifically inhibits p50 homodimer DNA binding and that this inhibition is mediated through the interaction of 14.7K with p50. We propose that 14.7K inhibits NF-kappaB activity through directly blocking p50 binding to DNA and that this is the basis for its anti-inflammatory properties. Our data also indicate a role for p50 homodimer-dependent transcription in inflammation.

FAK-dependent regulation of myofibroblast differentiation

Fibroblasts and myofibroblasts both participate in wound healing. Transforming growth factor beta (TGFbeta) induces fibroblasts to differentiate into myofibroblasts, whereas fibroblast growth factor and heparin (FGF/h) induce myofibroblasts to "de-differentiate" into fibroblasts. TGFbeta induces expression of smooth muscle alpha actin (SMalphaA) and incorporation into in stress fibers, a phenotype of differentiated myofibroblasts. Additionally, TGFbeta induces the expression of fibronectin and fibronectin integrins. Fibronectin-generated signals contribute to the TGFbeta-mediated myofibroblast differentiation. Because fibronectin signals are transmitted through focal adhesion kinase (FAK), it was predicted that FAK would be essential to TGFbeta-mediated myofibroblast differentiation. To determine whether the FAK signaling pathway is required for myofibroblast differentiation, we used two approaches to decrease FAK in mouse embryo fibroblasts (MEFs): 1) FAK +/+ MEFs, in which FAK protein expression was greatly decreased by short hairpin RNA (shRNA), and 2) FAK -/- MEFs, which lack FAK. In both cases, the majority of cells were myofibroblasts, expressing SMalphaA in stress fibers even after treatment with FGF/h. Furthermore, both the surface expression of FGFRs and FGF signaling were greatly reduced in FAK -/- [corrected]MEFs. We conclude that FAK does not contribute to TGFbeta-dependent myofibroblast differentiation. Instead, FAK was necessary for FGF/h signaling in down-regulating expression of SMalphaA, which is synonymous with myofibroblast differentiation. FAK activation could contribute to regulating myofibroblast differentiation, thereby ameliorating fibrosis.

IKK/NF-kappaB signaling: balancing life and death--a new approach to cancer therapy

IkappaB kinase/NF-kappaB (IKK/NF-kappaB) signaling pathways play critical roles in a variety of physiological and pathological processes. One function of NF-kappaB is promotion of cell survival through induction of target genes, whose products inhibit components of the apoptotic machinery in normal and cancerous cells. NF-kappaB can also prevent programmed necrosis by inducing genes encoding antioxidant proteins. Regardless of mechanism, many cancer cells, of either epithelial or hematopoietic origin, use NF-kappaB to achieve resistance to anticancer drugs, radiation, and death cytokines. Hence, inhibition of IKK-driven NF-kappaB activation offers a strategy for treatment of different malignancies and can convert inflammation-induced tumor growth to inflammation-induced tumor regression.

Identification of Novel and Cell Type Enriched Cofactors of the Transcription Activation Domain of RelA (p65 NF-κB)

RelA (NF-kappaB) is a transcription factor inducible by distinct stimuli in many different cell types. To find new cell type specific cofactors of NF-kappaB dependent transcription, we isolated RelA transcription activation domain binding proteins from the nuclear extracts of three different cell types. Analysis by electrophoresis and liquid chromatography tandem mass spectrometry identified several novel putative molecular partners. Some were strongly enriched in the complex formed from the nuclear extracts of specific cell types.

BRCA1 regulation of transcription

BRCA1, a tumor suppressor gene on chromosome 17q21, was identified in 1994 based on its linkage to hereditary breast and ovarian cancer syndromes. The BRCA1 gene encodes a 220 kDa nuclear phosphoprotein. Studies aimed at elucidating the mechanisms of its tumor suppressor activity have revealed, in part, that BRCA1 participates in the DNA damage response and acts to maintain the integrity of the genome. This activity is generic and does not account for the propensity of BRCA1 mutation carriers to develop specific tumor types rather than a broad spectrum of cancers. In addition to genome maintenance, BRCA1 has been found to broadly regulate gene transcription, even though it is not itself a sequence-specific DNA-binding transcription factor. The ability of BRCA1 to function as a coregulator of transcription may underlie some of its tumor suppressor activity and may explain the tissue-specific nature of this activity. This review will focus on how BRCA1 selectively regulates transcription and how this regulatory function may relate to tumor suppression.