53BP1 functions as a tumor suppressor in breast cancer via the inhibition of NF-κB through miR-146a

Identifying enhancer-driven subtype-specific prognostic markers in breast cancer based on multi-omics data

Breast cancer is a cancer of high complexity and heterogeneity, with differences in prognosis and survival among patients of different subtypes. Copy number variations (CNVs) within enhancers are crucial drivers of tumorigenesis by influencing expression of their targets. In this study, we performed an integrative approach to identify CNA-driven enhancers and their effect on expression of target genes in four breast cancer subtypes by integrating expression data, copy number data and H3K27ac data. We identified 672, 555, 531, 361 CNA-driven enhancer-gene pairs and 280, 189, 113 and 98 CNA-driven enhancer-lncRNA pairs in the Basal-like, Her2, LumA and LumB subtypes, respectively. We then reconstructed a CNV-driven enhancer-lncRNA-mRNA regulatory network in each subtype. Functional analysis showed CNA-driven enhancers play an important role in the progression of breast cancer subtypes by influencing P53 signaling pathway, PPAR signaling pathway, systemic lupus erythematosus and MAPK signaling pathway in the Basal-like, Her2, LumA and LumB subtypes, respectively. We characterized the potentially prognostic value of target genes of CNV-driven enhancer and lncRNA-mRNA pairs in the subtype-specific network. We identified MUM1 and AC016876.1 as prognostic biomarkers in LumA and Basal-like subtypes, respectively. Higher expression of MUM1 with an amplified enhancer exhibited poorer prognosis in LumA patients. Lower expression of AC016876.1 with a deleted enhancer exhibited poorer survival outcomes of Basal-like patients. We also identified enhancer-related lncRNA-mRNA pairs as prognostic biomarkers, including AC012313.2-MUM1 in the LumA, AC026471.4-PLK5 in the LumB, AC027307.2-OAZ1 in the Basal-like and AC022431.1-HCN2 in the Her2 subtypes. Finally, our results highlighted target genes of CNA-driven enhancers and enhancer-related lncRNA-mRNA pairs could act as prognostic markers and potential therapeutic targets in breast cancer subtypes.

Dissecting Molecular Heterogeneity of Circulating Tumor Cells (CTCs) from Metastatic Breast Cancer Patients through Copy Number Aberration (CNA) and Single Nucleotide Variant (SNV) Single Cell Analysis

Circulating tumor cells' (CTCs) heterogeneity contributes to counteract their introduction in clinical practice. Through single-cell sequencing we aim at exploring CTC heterogeneity in metastatic breast cancer (MBC) patients. Single CTCs were isolated using DEPArray NxT. After whole genome amplification, libraries were prepared for copy number aberration (CNA) and single nucleotide variant (SNV) analysis and sequenced using Ion GeneStudio S5 and Illumina MiSeq, respectively. CTCs demonstrate distinctive mutational signatures but retain molecular traces of their common origin. CNA profiling identifies frequent aberrations involving critical genes in pathogenesis: gains of 1q (CCND1) and 11q (WNT3A), loss of 22q (CHEK2). The longitudinal single-CTC analysis allows tracking of clonal selection and the emergence of resistance-associated aberrations, such as gain of a region in 12q (CDK4). A group composed of CTCs from different patients sharing common traits emerges. Further analyses identify losses of 15q and enrichment of terms associated with pseudopodium formation as frequent and exclusive events. CTCs from MBC patients are heterogeneous, especially concerning their mutational status. The single-cell analysis allows the identification of aberrations associated with resistance, and is a candidate tool to better address treatment strategy. The translational significance of the group populated by similar CTCs should be elucidated.

eEF2K Activity Determines Synergy to Cotreatment of Cancer Cells With PI3K and MEK Inhibitors

PI3K-mammalian target of rapamycin and MAPK/ERK kinase (MEK)/mitogen-activated protein kinase (MAPK) are the most frequently dysregulated signaling pathways in cancer. A problem that limits the success of therapies that target individual PI3K-MAPK members is that these pathways converge to regulate downstream functions and often compensate each other, leading to drug resistance and transient responses to therapy. In order to overcome resistance, therapies based on cotreatments with PI3K/AKT and MEK/MAPK inhibitors are now being investigated in clinical trials, but the mechanisms of sensitivity to cotreatment are not fully understood. Using LC-MS/MS-based phosphoproteomics, we found that eukaryotic elongation factor 2 kinase (eEF2K), a key convergence point downstream of MAPK and PI3K pathways, mediates synergism to cotreatment with trametinib plus pictilisib (which target MEK1/2 and PI3Kα/δ, respectively). Inhibition of eEF2K by siRNA or with a small molecule inhibitor reversed the antiproliferative effects of the cotreatment with PI3K plus MEK inhibitors in a cell model-specific manner. Systematic analysis in 12 acute myeloid leukemia cell lines revealed that eEF2K activity was increased in cells for which PI3K plus MEKi cotreatment is synergistic, while PKC potentially mediated resistance to such cotreatment. Together, our study uncovers eEF2K activity as a key mediator of responses to PI3Ki plus MEKi and as a potential biomarker to predict synergy to cotreatment in cancer cells.

DNA damage response and breast cancer development: Possible therapeutic applications of ATR, ATM, PARP, BRCA1 inhibition

Breast cancer is the most common and significant cancers in females regarding the loss of life quality. Similar to other cancers, one of the etiologic factors in breast cancer is DNA damage. A plethora of molecules are responsible for sensing DNA damage and mediating actions which lead to DNA repair, senescence, cell cycle arrest and if damage is unbearable to apoptosis. In each of these, aberrations leading to unrepaired damage was resulted in uncontrolled proliferation and cancer. Another cellular function is autophagy defined as a process eliminating of unnecessary proteins in stress cases involved in pathogenesis of cancer. Knowing their role in cancer, scholars have tried to develop strategies in order to target DDR and autophagy. Further, the interactions of DDR and autophagy plus their regulatory role on each other have been focused simultaneously. The present review study has aimed to illustrate the importance of DDR and autophagy in breast cancer according to the related studies and uncover the relation between DDR and autophagy and its significance in breast cancer therapy.

Oxidative Stress Down-Regulates MiR-20b-5p, MiR-106a-5p and E2F1 Expression to Suppress the G1/S Transition of the Cell Cycle in Multipotent Stromal Cells

Oxidative stress has been linked to senescence and tumorigenesis via modulation of the cell cycle. Using a hydrogen peroxide (H₂O₂)-induced oxidative stress-induced premature senescence (OSIPS) model previously reported by our group, this study aimed to investigate the effects of oxidative stress on microRNA (miRNA) expression in relation to the G1-to-S-phase (G1/S) transition of the cell cycle and cell proliferation. On global miRNA analysis of the OSIPS cells, twelve significantly up- or down-regulated miRNAs were identified, the target genes of which are frequently associated with cancers. Four down-regulated miR-17 family miRNAs are predicted to target key pro- and anti-proliferative proteins of the p21/cyclin D-dependent kinase (CDK)/E2F1 pathway to modulate G1/S transition. Two miR-17 miRNAs, miR-20-5p and miR-106-5p, were confirmed to be rapidly and stably down-regulated under oxidative stress. While H₂O₂ treatment hampered G1/S transition and suppressed DNA synthesis, miR-20b-5p/miR-106a-5p over-expression rescued cells from growth arrest in promoting G1/S transition and DNA synthesis. Direct miR-20b-5p/miR-106a-5p regulation of p21, CCND1 and E2F1 was demonstrated by an inverse expression relationship in miRNA mimic-transfected cells. However, under oxidative stress, E2F1 expression was down-regulated, consistent with hampered G1/S transition and suppressed DNA synthesis and cell proliferation. To explain the observed E2F1 down-regulation under oxidative stress, a scheme is proposed which includes miR-20b-5p/miR-106a-5p-dependent regulation, miRNA-E2F1 autoregulatory feedback and E2F1 response to repair oxidative stress-induced DNA damages. The oxidative stress-modulated expression of miR-17 miRNAs and E2F1 may be used to develop strategies to retard or reverse MSC senescence in culture, or senescence in general.

The role of inflammation and its related microRNAs in breast cancer: A narrative review

Breast cancer is recognized as the most common type of cancer among women with a high rate of mortality all over the world. Over the past years, growing attention has been regarded to realize more about the mechanisms underlying the disease process. It is revealed that the progression of breast cancer may be strongly linked to chronic inflammation owing to the role of inflammatory factors in genetic instability and subsequent cancer predisposition. Although the association between breast cancer and inflammatory pathways has been well-defined now, only recent evidence pointed towards the inflammation-related microRNAs (miRNAs) as potential biomarkers and therapeutic targets involved in the crosstalk of multiple pathways during breast cancer development. Moreover, the practical interactions between these miRNAs and inflammatory factors are also a little characterized. In this review, we intended to describe the effects of predominant inflammatory pathways such as cytokines, phosphoinositide 3-kinase/protein kinase B, and nuclear factor kappa B in association with tumor promoting and tumor suppressing miRNAs on breast cancer progression. Providing new studies in the field of combining biomarkers for early diagnosis, prognosis, and monitoring breast cancer are very important. Notably, understanding the underlying mechanisms of miRNAs as a possible link between inflammation and tumorigenesis may offer a novel insight for combating this epidemic.

Novel potential causative genes in carotid paragangliomas

Background

Carotid paragangliomas (CPGLs) are rare neuroendocrine tumors that arise from the paraganglion at the bifurcation of the carotid artery and are responsible for approximately 65% of all head and neck paragangliomas. CPGLs can occur sporadically or along with different hereditary tumor syndromes. Approximately 30 genes are known to be associated with CPGLs. However, the genetic basis behind the development of these tumors is not fully elucidated, and the molecular mechanisms underlying CPGL pathogenesis remain unclear.

Methods

Whole exome and transcriptome high-throughput sequencing of CPGLs was performed on an Illumina platform. Exome libraries were prepared using a Nextera Rapid Capture Exome Kit (Illumina) and were sequenced under 75 bp paired-end model. For cDNA library preparation, a TruSeq Stranded Total RNA Library Prep Kit with Ribo-Zero Gold (Illumina) was used; transcriptome sequencing was carried out with 100 bp paired-end read length. Obtained data were analyzed using xseq which estimates the influence of mutations on gene expression profiles allowing to identify potential causative genes.

Results

We identified a total of 16 candidate genes (MYH15, CSP1, MYH3, PTGES3L, CSGALNACT2, NMD3, IFI44, GMCL1, LSP1, PPFIBP2, RBL2, MAGED1, CNIH3, STRA6, SLC6A13, and ATM) whose variants potentially influence their expression (cis-effect). The strongest cis-effect of loss-of-function variants was found in MYH15, CSP1, and MYH3, and several likely pathogenic variants in these genes associated with CPGLs were predicted.

Conclusions

Using the xseq probabilistic model, three novel potential causative genes, namely MYH15, CSP1, and MYH3, were identified in carotid paragangliomas.

Detection of DNA Double Strand Breaks by γH2AX Does Not Result in 53bp1 Recruitment in Mouse Retinal Tissues

Gene editing is an attractive potential treatment of inherited retinopathies. However, it often relies on endogenous DNA repair. Retinal DNA repair is incompletely characterized in humans and animal models. We investigated recruitment of the double stranded break (DSB) repair complex of γH2AX and 53bp1 in both developing and mature mouse neuroretinas. We evaluated the immunofluorescent retinal expression of these proteins during development (P07-P30) in normal and retinal degeneration models, as well as in potassium bromate induced DSB repair in normal adult (3 months) retinal explants. The two murine retinopathy models used had different mutations in Pde6b: the severe rd1 and the milder rd10 models. Compared to normal adult retina, we found increased numbers of γH2AX positive foci in all retinal neurons of the developing retina in both model and control retinas, as well as in wild type untreated retinal explant cultures. In contrast, the 53bp1 staining of the retina differed both in amount and character between cell types at all ages and in all model systems. There was strong pan nuclear staining in ganglion, amacrine, and horizontal cells, and cone photoreceptors, which was attenuated. Rod photoreceptors did not stain unequivocally. In all samples, 53bp1 stained foci only rarely occurred. Co-localization of 53bp1 and γH2AX staining was a very rare event (< 1% of γH2AX foci in the ONL and < 3% in the INL), suggesting the potential for alternate DSB sensing and repair proteins in the murine retina. At a minimum, murine retinal DSB repair does not appear to follow canonical pathways, and our findings suggests further investigation is warranted.

Aurora kinase B dependent phosphorylation of 53BP1 is required for resolving merotelic kinetochore-microtubule attachment errors during mitosis

Defects in resolving kinetochore-microtubule attachment mistakes during mitosis is linked to chromosome instability associated with carcinogenesis as well as resistance to cancer therapy. Here we report for the first time that tumor suppressor p53-binding protein 1 (53BP1) is phosphorylated at serine 1342 (S1342) by Aurora kinase B both in vitro and in human cells, which is required for optimal recruitment of 53BP1 at kinetochores. Furthermore, 53BP1 staining normally localized on the outer kinetochore, extended to the whole kinetochore when it is merotelically-attached, in concert with mitotic centromere-associated kinesin. Kinetochore-binding of pS1342-53BP1 is essential for efficient resolving of merotelic attachment, a spontaneous kinetochore-microtubule connection error that usually causes aneuploidy. Consistently, loss of 53BP1 results in significant increase in lagging chromosome events, micronuclei formation and aneuploidy, due to the unresolved merotely in both cancer and primary cells, which is prevented by ectopic wild type 53BP1 but not by the nonphophorylable S1342A mutant. We thus document a novel DNA damage-independent function of 53BP1 in maintaining faithful chromosome segregation during mitosis.

Alterations in the expression of DNA damage response-related molecules in potentially preneoplastic oral epithelial lesions

OBJECTIVES

The aim of this study was to evaluate the expression levels of DNA damage response (DDR) markers in potentially preneoplastic oral epithelial lesions (PPOELs).

STUDY DESIGN

Immunohistochemical expression of DDR markers (γΗ2 ΑΧ, pChk2, 53 BP1, p53, and phosphorylated at Ser 15 p53) was assessed in 41 oral leukoplakias, ranging from hyperplasia (H) to dysplasia (D) and in comparison with oral squamous cell carcinoma (OSCC) and normal mucosa (NM). Statistical and receiver operating characteristic curve analysis were performed.

RESULTS

γH2 AX immunoexpression demonstrated a gradual increase and upper layer extension from NM to H to higher D degrees to OSCC. pChk2 expression was minimal in NM, relatively low in PPOELs, with an increasing tendency from H to D, and higher in OSCC. 53 BP1 demonstrated higher levels in OSCC than in NM, whereas its expression in PPOELs was heterogeneous, gradually increasing according to D. p53 demonstrated progressively higher levels and upper layer extension from H to D to OSCC. Phosphorylated p53 was absent in NM and relatively low in PPOELs and OSCC.

CONCLUSIONS

DDR markers' expression is variable in PPOELs, showing a tendency to increase along with dysplasia. Activated DDR mechanisms may play an important protective role at early stages of oral carcinogenesis, but probably suffer progressive deregulation, eventually failing to suppress malignant transformation.

Salivary Gland Cancer Patient-Derived Xenografts Enable Characterization of Cancer Stem Cells and New Gene Events Associated with Tumor Progression

Purpose: Salivary gland cancers (SGC) frequently present with distant metastases many years after diagnosis, suggesting a cancer stem cell (CSC) subpopulation that initiates late recurrences; however, current models are limited both in their availability and suitability to characterize these rare cells.Experimental Design: Patient-derived xenografts (PDX) were generated by engrafting patient tissue onto nude mice from one acinic cell carcinoma (AciCC), four adenoid cystic carcinoma (ACC), and three mucoepidermoid carcinoma (MEC) cases, which were derived from successive relapses from the same MEC patient. Patient and PDX samples were analyzed by RNA-seq and Exome-seq. Sphere formation potential and in vivo tumorigenicity was assessed by sorting for Aldefluor (ALDH) activity and CD44-expressing subpopulations.Results: For successive MEC relapses we found a time-dependent increase in CSCs (ALDH⁺CD44^high), increasing from 0.2% to 4.5% (P=0.033), but more importantly we observed an increase in individual CSC sphere formation and tumorigenic potential. A 50% increase in mutational burden was documented in subsequent MEC tumors, and this was associated with increased expression of tumor-promoting genes (MT1E, LGR5, and LEF1), decreased expression of tumor-suppressor genes (CDKN2B, SIK1, and TP53), and higher expression of CSC-related proteins such as SOX2, MYC, and ALDH1A1. Finally, genomic analyses identified a novel NFIB-MTFR2 fusion in an ACC tumor and confirmed previously reported fusions (NTRK3-ETV6 and MYB-NFIB)Conclusions: Sequential MEC PDX models preserved key patient features and enabled the identification of genetic events putatively contributing to increases in both CSC proportion and intrinsic tumorigenicity, which mirrored the patient's clinical course. Clin Cancer Res; 24(12); 2935-43. ©2018 AACR.

DNA repair genes PAXIP1 and TP53BP1 expression is associated with breast cancer prognosis

Despite remarkable advances in diagnosis, prognosis and treatment, advanced or recurrent breast tumors have limited therapeutic approaches. Many treatment strategies try to explore the limitations of DNA damage response (DDR) in tumor cells to selectively eliminate them. BRCT (BRCA1 C-terminal) domains are present in a superfamily of proteins involved in cell cycle checkpoints and the DDR. Tandem BRCT domains (tBRCT) represent a distinct class of these domains. We investigated the expression profile of 7 tBRCT genes (BARD1, BRCA1, LIG4, ECT2, MDC1, PAXIP1/PTIP and TP53BP1) in breast cancer specimens and observed a high correlation between PAXIP1 and TP53BP1 gene expression in tumor samples. Tumors with worse prognosis (tumor grade 3 and triple negative) showed reduced expression of tBRCT genes, notably, PAXIP1 and TP53BP1. Survival analyses data indicated that tumor status of both genes may impact prognosis. PAXIP1 and 53BP1 protein levels followed gene expression results, i.e., are intrinsically correlated, and also reduced in more advanced tumors. Evaluation of both genes in triple negative breast tumor samples which were characterized for their BRCA1 status showed that PAXIP1 is overexpressed in BRCA1 mutant tumors. Taken together our findings indicate that PAXIP1 status correlates with breast cancer staging, in a manner similar to what has been characterized for TP53BP1.

Writing, erasing and reading histone lysine methylations

Histone modifications are key epigenetic regulatory features that have important roles in many cellular events. Lysine methylations mark various sites on the tail and globular domains of histones and their levels are precisely balanced by the action of methyltransferases ('writers') and demethylases ('erasers'). In addition, distinct effector proteins ('readers') recognize specific methyl-lysines in a manner that depends on the neighboring amino-acid sequence and methylation state. Misregulation of histone lysine methylation has been implicated in several cancers and developmental defects. Therefore, histone lysine methylation has been considered a potential therapeutic target, and clinical trials of several inhibitors of this process have shown promising results. A more detailed understanding of histone lysine methylation is necessary for elucidating complex biological processes and, ultimately, for developing and improving disease treatments. This review summarizes enzymes responsible for histone lysine methylation and demethylation and how histone lysine methylation contributes to various biological processes.

53BP1 loss induces chemoresistance of colorectal cancer cells to 5-fluorouracil by inhibiting the ATM-CHK2-P53 pathway

PURPOSE

Loss of P53 binding protein 1 (53BP1) is considered a poor prognostic factor for colorectal cancer. However, its effect on chemosensitivity of colorectal cancer to 5-fluorouracil (5-FU) remains elusive. This study aimed to examine the association of 53BP1 expression with chemosensitivity of colorectal cancer cells to 5-FU.

METHODS

Immunohistochemistry was performed on 30 metastatic colorectal cancer samples to assess the associations of 53BP1 levels with clinical therapeutic effects. In vitro, IC₅₀ values for 5-FU and 53BP1 levels were determined by MTT assay and Western blot in 5 colorectal cancer cell lines. Then, 53BP1 was silenced in HCT116 and HT29 cells, and cell proliferation, apoptosis and cell cycle distribution were evaluated. Relative protein levels of ATM-CHK2-P53 pathway effectors and Bcl-2 family members were measured by Western blot. Finally, the effects of 53BP1 knockdown on tumor growth and 5-FU chemoresistance were investigated in vivo.

RESULTS

53BP1 expression was closely related to time to progression (TTP) after first-line chemotherapy. Namely, 53BP1 downregulation resulted in reduced TTP. In addition, 53BP1 silencing increased proliferation, inhibited apoptosis and induced S phase arrest in HCT116 and HT29 cells after 5-FU treatment. Moreover, 53BP1 knockdown also reduced the protein levels of ATM-CHK2-P53 apoptotic pathway effectors, caspase9 and caspase3, while increasing Bcl-2 expression. In vivo, 53BP1 silencing accelerated tumor proliferation in nude mice and enhanced resistance to 5-FU.

CONCLUSIONS

These findings confirmed that 53BP1 loss might be a negative factor for chemotherapy efficacy, promoting cell proliferation and inhibiting apoptosis by suppressing ATM-CHK2-P53 signaling, and finally inducing 5-FU resistance.

53BP1 suppresses epithelial-mesenchymal transition by downregulating ZEB1 through microRNA-200b/429 in breast cancer

Epithelial–mesenchymal transition (EMT) is an important mechanism of cancer invasion and metastasis. Although p53 binding protein 1 (53BP1) has been implicated in several biological processes, its function in EMT of human cancers has not yet been reported. Here, we show that 53BP1 negatively regulated EMT by modulating ZEB1 through targeting microRNA (miR)-200b and miR-429. Furthermore, 53BP1 promoted ZEB1-mediated upregulation of E-cadherin and also inhibited the expressions of mesenchymal markers, leading to increased migration and invasion in MDA-MB-231 breast cancer cells. Consistently, in MCF-7 breast cancer cells, low 53BP1 expression reduced E-cadherin expression, resulting in increased migration and invasion. These effects were reversed by miR-200b and miR-429 inhibition or overexpression. Sections of tumor xenograft model showed increased ZEB1 expression and decreased E-cadherin expression with the downregulation of 53BP1. In 18 clinical tissue samples, expression of 53BP1 was positively correlated with miR-200b and mir-429 and negatively correlated with ZEB1. It was also found that 53BP1 was associated with lymph node metastasis. Taken together, these results suggest that 53BP1 functioned as a tumor suppressor gene by its novel negative control of EMT through regulating the expression of miR-200b/429 and their target gene ZEB1.

FOXP3 Controls an miR-146/NF-κB Negative Feedback Loop That Inhibits Apoptosis in Breast Cancer Cells

FOXP3 functions not only as the master regulator in regulatory T cells, but also as an X-linked tumor suppressor. The tumor-suppressive activity of FOXP3 has been observed in tumor initiation, but its role during tumor progression remains controversial. Moreover, the mechanism of FOXP3-mediated tumor-suppressive activity remains largely unknown. Using chromatin immunoprecipitation (ChIP) sequencing, we identified a series of potential FOXP3-targeted miRNAs in MCF7 cells. Notably, FOXP3 significantly induced the expression of miR-146a/b. In vitro, FOXP3-induced miR-146a/b prevented tumor cell proliferation and enhanced apoptosis. Functional analyses in vitro and in vivo revealed that FOXP3-induced miR-146a/b negatively regulates NF-κB activation by inhibiting the expression of IRAK1 and TRAF6. In ChIP assays, FOXP3 directly bound the promoter region of miR-146a but not of miR-146b, and FOXP3 interacted directly with NF-κB p65 to regulate an miR-146-NF-κB negative feedback regulation loop in normal breast epithelial and tumor cells, as demonstrated with luciferase reporter assays. Although FOXP3 significantly inhibited breast tumor growth and migration in vitro and metastasis in vivo, FOXP3-induced miR-146a/b contributed only to the inhibition of breast tumor growth. These data suggest that miR-146a/b contributes to FOXP3-mediated tumor suppression during tumor growth by triggering apoptosis. The identification of a FOXP3-miR-146-NF-κB axis provides an underlying mechanism for disruption of miR-146 family member expression and constitutive NF-κB activation in breast cancer cells. Linking the tumor suppressor function of FOXP3 to NF-κB activation reveals a potential therapeutic approach for cancers with FOXP3 defects.

Quercetin inhibits proliferation and invasion acts by up-regulating miR-146a in human breast cancer cells

Breast cancer is the most common female malignancies in the world which seriously impacts the female health. In recent years, various studies have been reported to determine the relevance of miRNAs to human cancer. One of these miRNAs, miR-146a has been down-regulated in multiple human cancer types, but up-regulation showed inducing apoptosis. To determine the role of quercetin treated on breast cancer, we investigated the effect of quercetin on cell proliferation in human breast cancer cell lines MCF-7 and MDA-MB-231 with/without transfection of miR-146a mimic or anti-miR-146a. Furthermore, the expressions of bax and cleaved-caspase-3, mainly were increased in control and overexpression miR-146a groups, however, the expression of EGFR was inverse. All the results demonstrated that quercetin exhibited excellent effect on inhibiting cell proliferation in human breast cancer cells, which was performed by up-regulating miR-146a expression, then via inducing apoptosis through caspase-3 activation and mitochondrial-dependent pathways, and inhibiting invasion through down-regulating the expression of EGFR.

Therapeutic microRNAs targeting the NF-kappa B signaling circuits of cancers

MicroRNAs (miRNAs) not only directly regulate NF-κB expression, but also up- or down-regulate NF-κB activity via upstream and downstream signaling pathways of NF-κB. In many cancer cells, miRNA expressions are altered accompanied with an elevation of NF-κB activity, which often plays a role in promoting cancer development and progression as well as hindering the effectiveness of chemo and radiation therapies. Thus NF-κB-targeting miRNAs have been identified and characterized as potential therapeutics for cancer treatment and sensitizers of chemo and radiotherapies. However, due to cross-targeting and instability of miRNAs, some limitations of using miRNA as cancer therapeutics still exist. In this review, the mechanisms for miRNA-mediated alteration of NF-κB expression and activation in different types of cancers will be discussed. The results of therapeutic use of NF-κB-targeting miRNA for cancer treatment will be examined. Some limitations, challenges and potential strategies in future development of miRNA as cancer therapeutics are also assessed.

microRNA and NF-kappa B

Nuclear Factor kappa B (NF-κB) plays important roles in regulation of countless cellular functions, including cell cycle and apoptosis. As a versatile transcription factor, NF-κB is a target of a large amount of miRNAs. Abnormal NF-κB activity is frequently associated with an abnormal level of miRNAs, which is found to play critical roles in disease progression including cancer. While the expression and activity of NF-κB can be directly or indirectly up-regulated or downregulated by various miRNAs, NF-κB can also regulate the expression of many miRNAs. Intriguingly, reciprocal regulation between miRNAs and NF-κB, which exists in the form of positive and negative feedback loops, is often observed in various cancers. In this chapter, the mechanisms and roles of miRNA-regulated NF-κB and NF-κB-regulated miRNAs in a variety of cancers will be discussed. The potential therapeutic use of miRNAs that are up- and down-stream of NF-κB signaling pathways as targets for cancer treatment will also be accessed.

Icotinib hydrochloride enhances the effect of radiotherapy by affecting DNA repair in colorectal cancer cells

The aim of the present study was to explore the efficacy and mechanism of the radiosensitisation of icotinib hydrochloride (IH), a novel oral epidermal growth factor receptor-tyrosine kinase activity inhibitor, by evaluating the changes in tumour cell double-strand breaks (DSBs) repair, cell cycle and apoptosis following a combination of IH and radiotherapy (RT) in human colorectal adenocarcinoma cell lines. The HT29 and HCT116 human CRC cell lines were treated with IH and/or radiation. Effects on cell viability and cell cycle progression were measured by MTT, a clonogenic survival assay, and flow cytometry. Immunofluorescent staining and western blot analysis were applied to detect the expression of γ-H2AX and 53BP1 in the different treatment groups. Finally, the in vivo effect on the growth of CRC xenografts was assessed in athymic nude mice. IH inhibited the proliferation and enhanced the radiosensitivity in HT29 and HCT116 CRC cells lines. IH combined with radiation increased cell cycle arrest in the G2/M phase compared to the other treatments in the HT29 cell line (P<0.05). Similarly, cell cycle arrest occurred in the HCT116 cell line, although this increase did not result in significant differences in the RT group (P>0.05). IH combined with radiation significantly inhibited the expression of γ-H2AX and 53BP1 based on results of immunofluorescent staining and western blot analysis. In vivo, IH plus radiation significantly inhibited the tumour growth compared to either agent independently. In conclusion, IH significantly increased the radiosensitivity of HT29 and HCT116 cells in vitro and in vivo. Radiation combined with EGFR blockade inhibited tumour proliferation, increased apoptosis, prolonged G2/M arrest and significantly enhanced DNA injury in colorectal cancer. These data support the clinical trials of biologically targeted and conventional therapies in the treatment of cancer.

Serum levels of miR-19b and miR-146a as prognostic biomarkers for non-small cell lung cancer

MicroRNA (miRNA) is a type of small non-coding RNA molecule that has important roles in cancer initiation, promotion and progression by negatively regulating gene expression. In this study, we explored the role of miRNAs in the prognosis of patients with non-small cell lung cancer (NSCLC). The miRNA expression profiles were determined in 5 pairs of NSCLC and paracancerous tissues (3 adenocarcinomas and 2 squamous cell carcinomas). Aberrantly expressed miRNAs were validated by quantitative real-time PCR (qRT-PCR) in 61 pairs of NSCLC and paracancerous tissues. Differentially expressed miRNAs were further analyzed in sera from 94 healthy subjects and 94 advanced NSCLC patients receiving platinum-based chemotherapy. Three miRNAs (miR-19b, miR-146a, and miR-223) were significantly dysregulated in NSCLC tissues (P < 0.05). High miR-19b and low miR-146a expression in NSCLC tissues were associated with higher TNM stage, lymph node metastasis and poorer survival (P < 0.05). The serum levels of miR-19b in NSCLC patients were significantly higher (P < 0.001), whereas serum levels of miR-146a were significantly lower (P < 0.001), compared with those in controls. Serum levels of miR-19b and miR-146a were associated with overall survival of NSCLC patients (P < 0.05). Patients with low serum level of miR-19b and high serum level of miR-146a achieved a higher overall response rate and longer survival time (P < 0.05). These data suggest that miR-19b and miR-146a are potential biomarkers for the prediction of survival and response to chemotherapy in NSCLC.

Novel roles of 1α,25(OH)2D3 on DNA repair provide new strategies for breast cancer treatment

Breast cancers classified as triple-negative (TNBC) and BRCA1-deficient, are particularly aggressive and difficult to treat. A major breakthrough was the finding that these tumors are exquisitely sensitive to inhibitors of poly(ADP-ribose) polymerase (PARPi). Phase II clinical trials have shown encouraging outcomes, with tolerable side effects. However, a significant fraction of these cancers acquire resistance. Elegant studies demonstrated that loss of the DNA repair protein 53BP1 contributes to the resistance of BRCA1-deficient cells and tumors to PARPi. Thus, raising the levels of 53BP1 in these aggressive tumors could potentially restore their sensitivity to PARPi and other genotoxic agents. We will review here our studies revealing that 1α,25(OH)2D3, an active form of vitamin D, stabilizes 53BP1 levels in tumor cells. Breast tumor cells that become BRCA1-deficient activate cathepsin L-mediated degradation of 53BP1 to ensure genome stability and proliferation. Importantly, 1α,25(OH)2D3 treatment restores the levels of 53BP1 as efficiently as cathepsin L inhibitors, which results in increased genomic instability in response to PARPi or radiation, and reduced proliferation. Furthermore, analysis of human breast tumors identified nuclear cathepsin L as a positive biomarker for TNBC, which correlates inversely with 53BP1 when vitamin D receptor (VDR) nuclear levels are low. The major findings of these studies are: (1) identification of a new pathway contributing to breast cancers with the poorest prognosis; (2) discovery of the ability of 1α,25(OH)2D3 to inhibit this pathway; and (3) discovery of a triple biomarker signature for identification of patients that could benefit from the treatment. This article is part of a Special Issue entitled '16th Vitamin D Workshop'.

Deregulation of miR-146a expression in a mouse model of pancreatic cancer affecting EGFR signaling

Aberrant expression of microRNAs (miRNAs) plays important roles in the development and progression of pancreatic cancer (PC). Expression analysis of miR-146a in human PC tissues showed decreased expression in about 80% of samples compared to corresponding non-cancerous tissue. Moreover, expression of miR-146a in eight PC cell lines, and in pancreatic tissues obtained from transgenic mouse models of K-Ras (K), Pdx1-Cre (C), K-Ras;Pdx1-Cre (KC) and K-Ras;Pdx1-Cre;INK4a/Arf (KCI), showed down-regulation of miR-146a expression in KCI mice which was in part led to over-expression of its target gene, epidermal growth factor receptor (EGFR). Treatment of PC cells with CDF, a novel synthetic compound, led to re-expression of miR-146a, resulting in the down-regulation of EGFR expression. Moreover, re-expression of miR-146a by stable transfection or treatment with CDF in vivo (xenograft animal model) resulted in decreased tumor growth which was consistent with reduced EGFR, ERK1, ERK2, and K-Ras expression. Further knock-down of miR-146a in AsPC-1 cells led to the up-regulation of EGFR expression and showed increased clonogenic growth. In addition, knock-down of EGFR by EGFR siRNA transfection of parental AsPC-1 cells and AsPC-1 cells stably transfected with pre-miR-146a resulted in decreased invasive capacity, which was further confirmed by reduced luciferase activity in cells transfected with pMIR-Luc reporter vector containing miR-146a binding site. Collectively, these results suggest that the loss of expression of miR-146a is a fundamental mechanism for over-expression of EGFR signaling and that re-expression of miR-146a by CDF treatment could be useful in designing personalized strategy for the treatment of human PC.

Aberrant BLID expression is associated with breast cancer progression

In our previous study, we have found that BH3-like motif containing, cell death inducer (BLID) was a tumor suppressor in breast cancer, and its downregulation was correlated with both poor disease-free and overall survival. In the present study, we aimed to explore the possible role of BLID in breast cancer progression. We found that BLID was strongly expressed in all normal breast tissues, and it became lower and wreaker gradually in the progression from normal, UDH (usual ductal hyperplasia), ADH (atypical ductal hyperplasia), and DCIS (ductal carcinoma in situ) to breast cancer. Statistical analysis demonstrated significant different BLID expressions between proliferative and cancerous breast lesions. Our data suggested that loss of BLID may contribute to the progression of intraductal proliferation lesions to breast cancer. Our finding gives a new clue that BLID might be a potential indicator for progression of breast cancer in the future.

Licochalcone A suppresses migration and invasion of human hepatocellular carcinoma cells through downregulation of MKK4/JNK via NF-κB mediated urokinase plasminogen activator expression

Hepatocellular cell carcinoma (HCC) is one of the most commonly diagnosed cancers worldwide and in Taiwan. Chemoprevention of cancer with dietary bioactive compounds could potentially reverse, suppress, or prevent cancer progression. Licochalcone A (LicA) is a characteristic chalcone of licorice, which is the root of Glycyrrhiza inflate. It had been reported that LicA has anti-inflammatory, anti-microbial, and anti-tumor properties. However, the effects of LicA on the migration and invasion of human HCC cells have not yet been reported. In the present study, it was found that LicA inhibits the migratory and invasion ability of SK-Hep-1 and HA22T/VGH cells in a dose-dependent manner, as assessed by the cell migration and Matrigel cell invasion assay. Using casein zymography, Western blotting, reverse transcriptase polymerase chain reaction, and an immunofluorescence assay, it was found that LicA induces a dose-dependent inhibition of uPA activity and expression, as well as reduces mRNA levels in SK-Hep-1 and HA22T/VGH cells. LicA was also found to inhibit the expression of phosphor-JNK and phosphor-MKK4 in SK-Hep-1 cells. Furthermore, LicA significantly decreased uPA levels in SP600125-treated or si-MKK4-transfected cells alongside a marked reduction in cell migration and invasion, which supports the notion that an inhibition of MKK4/JNK results in anti-metastatic effects. Moreover, LicA inhibited the expression of nuclear NF-κB, as well as the binding ability of NF-κB to the uPA promoter. These findings further our understanding of the role of LicA in suppressing tumor metastasis and its underlying molecular mechanisms, as well as suggest that LicA may be a promising anti-metastatic agent.

Association of miR-146a gene polymorphism with risk of nasopharyngeal carcinoma in the central-southern Chinese population

This case-control study focused on estimating the association between miR-146a polymorphism and risk of nasopharyngeal carcinoma (NPC) in central-south China. In total, 160 patients with NPC and 200 healthy controls in central-south China were genotyped using polymerase chain reaction-restriction fragment length polymorphism assay. Chi-square test was used to assess the different distribution of miR-146a polymorphism between NPC patients and controls; and logistic regression analysis was applied to analyze the associations between miR-146a polymorphism with cancer risk in different contrast models. Significant differences between NPC patients and controls were found in genotype (P=0.033 for GG versus CG versus CC; and odds ratio (OR)=0.568, 95% confidence interval (CI)=0.354-0.912, P=0.019 for CG versus CC; and OR=0.503, 95% CI=0.261-0.971, P=0.041 for CG versus CC; and OR=0.564, 95% CI=0.360-0.884, P=0.012 for GG+CG versus CC, respectively) and allelic analysis (P=0.025 for G versus C). Our findings suggested that polymorphism of mir-146a was associated with NPC in the central-southern Chinese population.

Role of 53BP1 in the regulation of DNA double-strand break repair pathway choice

The p53-binding protein 1 (53BP1) is a well-known DNA damage response (DDR) factor, which is recruited to nuclear structures at the site of DNA damage and forms readily visualized ionizing radiation (IR) induced foci. Depletion of 53BP1 results in cell cycle arrest in G2/M phase as well as genomic instability in human as well as mouse cells. Within the DNA damage response mechanism, 53BP1 is classified as an adaptor/mediator, required for processing of the DNA damage response signal and as a platform for recruitment of other repair factors. More recently, specific 53BP1 contributions to DSB repair pathway choice have been recognized and are being characterized. In this review, we have summarized recent advances in understanding the role of 53BP1 in regulating DNA DSBs repair pathway choice, variable diversity joining [V(D)J] recombination and class-switch recombination (CSR).

53BP1 sensitizes breast cancer cells to 5-fluorouracil

Chemoresistance of breast cancer is a worldwide problem for breast cancer and the resistance to chemotherapeutic agents frequently led to the subsequent recurrence and metastasis. In our previous study, we have found that 53BP1 showed a gradual decrease during the progression of breast cancer and loss of 53BP1 was associated with metastasis and poor prognosis in breast cancer. Here we aimed to reveal whether 53BP1 could sensitize breast cancer to 5-Fu. We found that ectopic expression of 53BP1 can significantly sensitize breast cancer cells to 5-Fu while knockdown of 53BP1 conferred the resistance. The in vivo experiments confirmed that overexpression of 53BP1 in combination with 5-Fu markedly inhibited growth of xenotransplanted tumors in nude mice when compared to either agent alone. Furthermore, we demonstrated that 53BP1 regulated the sensitivity to 5-Fu through thymidylate synthase (TS) and dihydropyrimidine dehydrogenase (DPYD). The present studies provide a new clue that combination of 5-Fu and 53BP1 could be a potential novel targeted strategy for overcoming breast cancer chemoresistance.

53BP1 is a novel regulator of angiogenesis in breast cancer

In our previous study, we found that 53BP1 was a tumor suppressor and was associated with prognosis in breast cancer. However, little is known about its role in angiogenesis. In the present study, we aimed to reveal the role of 53BP1 in angiogenesis of breast cancer. With RNA interference and ectopic expression strategies to elucidate the detailed function of 53BP1 in angiogenesis, we observed that ectopic expression of 53BP1 inhibited cellular angiogenesis and 53BP1 RNA interference led to an increase in angiogenesis both in vitro and in vivo. In clinical breast cancer samples, 53BP1 was inversely correlated with CD31, MMP-2 and MMP-9 by immunohistochemistry analysis. Furthermore, we showed that the Akt pathway was involved in the antiangiogenesis function of 53BP1. Overall, our findings demonstrate that 53BP1 plays a vital role in inhibiting angiogenesis. These findings suggest that 53BP1 might provide a viable target therapy for breast cancer.

BRCC2 inhibits breast cancer cell growth and metastasis in vitro and in vivo via downregulating AKT pathway

In our previous study, we demonstrated that the BRCC2 (breast cancer cell 2) gene is a proapoptotic molecule that interacts with Bcl-X_L. BRCC2 downregulation is associated with poor disease-free and overall survival in breast cancer. In this study, we aimed to investigate the role of BRCC2 in tumor suppression in breast cancer. In clinical breast cancer samples, we found that BRCC2 expression was significantly downregulated in cancer lesions compared with paired normal breast tissues. By silencing or overexpressing BRCC2 in breast cancer cells, we found that BRCC2 could inhibit cell growth and metastasis in vitro. An in vivo assay showed that BRCC2 not only dramatically inhibited breast cancer cell xenograft formation and growth but also inhibited breast cancer cell metastasis in a lung metastasis model. Moreover, we demonstrated that BRCC2 inhibited breast cancer metastasis via regulation of the Akt pathway. Thus, our study provided evidence that BRCC2 functions as a novel tumor suppressor in breast cancer and may be a potential therapeutic target for breast cancer management.

53BP1 is limiting for NHEJ repair in ATM-deficient model systems that are subjected to oncogenic stress or radiation

The DNA damage response (DDR) factors ataxia telangiectasia mutated (ATM) and p53 binding protein 1 (53BP1) function as tumor suppressors in humans and mice, but the significance of their mutual interaction to the suppression of oncogenic translocations in vivo has not been investigated. To address this question, the phenotypes of compound mutant mice lacking 53BP1 and ATM (Trp53bp1(-/-)/Atm(-/-)), relative to single mutants, were examined. These analyses revealed that loss of 53BP1 markedly decreased the latency of T-lineage lymphomas driven by RAG-dependent oncogenic translocations in Atm(-/-) mice (average survival, 14 and 23 weeks for Trp53bp1(-/-)/Atm(-/-) and Atm(-/-) mice, respectively). Mechanistically, 53BP1 deficiency aggravated the deleterious effect of ATM deficiency on nonhomologous end-joining (NHEJ)-mediated double-strand break repair. Analysis of V(D)J recombinase-mediated coding joints and signal joints in Trp53bp1(-/-)/Atm(-/-) primary thymocytes is, however, consistent with canonical NHEJ-mediated repair. Together, these findings indicate that the greater NHEJ defect in the double mutant mice resulted from decreased efficiency of rejoining rather than switching to an alternative NHEJ-mediated repair mechanism. Complementary analyses of irradiated primary cells indicated that defects in cell-cycle checkpoints subsequently function to amplify the NHEJ defect, resulting in more frequent chromosomal breaks and translocations in double mutant cells throughout the cell cycle. Finally, it was determined that 53BP1 is dispensable for the formation of RAG-mediated hybrid joints in Atm(-/-) thymocytes but is required to suppress large deletions in a subset of hybrid joints.

IMPLICATIONS

The current study uncovers novel ATM-independent functions for 53BP1 in the suppression of oncogenic translocations and in radioprotection.