FADD phosphorylation is critical for cell cycle regulation in breast cancer cells

Identification of autoantibodies as potential non-invasive biomarkers for intrahepatic cholangiocarcinoma

Intrahepatic cholangiocarcinoma (iCCA) presents a challenging diagnosis due to its nonspecific early clinical manifestations, often resulting in late-stage detection and high mortality. Diagnosing iCCA is further complicated by its limited accuracy, often necessitating multiple invasive procedures for precise identification. Despite carbohydrate antigen 19-9 (CA19-9) having been investigated and employed for iCCA diagnosis, it demonstrates modest diagnostic performance. Consequently, the identification of novel biomarkers with improved sensitivity and specificity remains an imperative yet formidable task. Autoantibodies, as early indicators of the immune response against cancer, offer a promising avenue for enhancing diagnostic accuracy. Our study aimed to identify non-invasive blood-based autoantibody biomarkers capable of distinguishing iCCA patients from healthy individuals (CTRs). We profiled autoantibodies in 26 serum samples (16 iCCAs and 10 CTRs) using protein microarrays containing 1622 functional proteins. Leveraging machine learning techniques, we identified a signature composed of three autoantibody biomarkers (NDE1, PYCR1, and VIM) in conjunction with CA19-9 for iCCA detection. This combined signature demonstrated superior diagnostic performance with an AUC of 96.9%, outperforming CA19-9 alone (AUC: 83.8%). These results suggest the potential of autoantibody biomarkers to develop a complementary non-invasive diagnostic utility for routine iCCA screening.

FADD regulates adipose inflammation, adipogenesis, and adipocyte survival

Adipose tissue, aside from adipocytes, comprises various abundant immune cells. The accumulation of low-grade chronic inflammation in adipose tissue serves as a primary cause and hallmark of insulin resistance. In this study, we investigate the physiological roles of FADD in adipose tissue inflammation, adipogenesis, and adipocyte survival. High levels of Fadd mRNA were observed in mitochondrial-rich organs, particularly brown adipose tissue. To explore its metabolic functions, we generated global Fadd knockout mice, resulting in embryonic lethality, while heterozygous knockout (Fadd+/-) mice did not show any significant changes in body weight or composition. However, Fadd+/- mice exhibited reduced respiratory exchange ratio (RER) and serum cholesterol levels, along with heightened global and adipose inflammatory responses. Furthermore, AT masses and expression levels of adipogenic and lipogenic genes were decreased in Fadd+/- mice. In cellular studies, Fadd inhibition disrupted adipogenic differentiation and suppressed the expression of adipogenic and lipogenic genes in cultured adipocytes. Additionally, Fadd overexpression caused adipocyte death in vitro with decreased RIPK1 and RIPK3 expression, while Fadd inhibition downregulated RIPK3 in iWAT in vivo. These findings collectively underscore the indispensable role of FADD in adipose inflammation, adipogenesis, and adipocyte survival.

The adapter protein FADD provides an alternate pathway for entry into the cell cycle by regulating APC/C-Cdh1 E3 ubiquitin ligase activity

The E3 ubiquitin ligase APC/C-Cdh1 maintains the G0/G1 state, and its inactivation is required for cell cycle entry. We reveal a novel role for Fas-associated protein with death domain (FADD) in the cell cycle through its function as an inhibitor of APC/C-Cdh1. Using real-time, single-cell imaging of live cells combined with biochemical analysis, we demonstrate that APC/C-Cdh1 hyperactivity in FADD-deficient cells leads to a G1 arrest despite persistent mitogenic signaling through oncogenic EGFR/KRAS. We further show that FADDWT interacts with Cdh1, while a mutant lacking a consensus KEN-box motif (FADDKEN) fails to interact with Cdh1 and results in a G1 arrest due to its inability to inhibit APC/C-Cdh1. Additionally, enhanced expression of FADDWT but not FADDKEN, in cells arrested in G1 upon CDK4/6 inhibition, leads to APC/C-Cdh1 inactivation and entry into the cell cycle in the absence of retinoblastoma protein phosphorylation. FADD's function in the cell cycle requires its phosphorylation by CK1α at Ser-194 which promotes its nuclear translocation. Overall, FADD provides a CDK4/6-Rb-E2F-independent "bypass" mechanism for cell cycle entry and thus a therapeutic opportunity for CDK4/6 inhibitor resistance.

FADD phosphorylation contributes to development of renal fibrosis by accelerating epithelial-mesenchymal transition

FADD, a classical apoptotic signaling adaptor, has recently been reported to exhibit a series of non-apoptotic functions. Here, we report that FADD may play a critical role in the development of renal fibrosis. Neutrophil infiltration in the renal interstitial part, glomerular mesangial cell proliferation, and base-membrane thickening were observed in FADD-D mice by H&E, PAS, and PASM staining. Immunofluorescence analysis revealed that macrophage infiltration was significantly enhanced in FADD-D mice. Renal fibrosis might be induced by IgA nephritis in FADD-D mice as evidenced by increased Ki67 and type IV collagen. Additionally, the levels of α-SMA, Fibronectin, and Vimentin were also found to be elevated. Mechanism study indicated that the TLR4/myD88/NF-κB signaling pathway was activated in FADD-D mice. Moreover, FADD phosphorylation activated the mTOR and TGF-β/Smad pathway and accelerated the process of epithelial mesenchymal transition. Further studies indicated that the TGF-β1 pathway was also activated and the process of EMT was accelerated in both FADD-disrupted HEK293 cells and FADD-deficient MES cells. Thus, we concluded that FADD phosphorylation could lead to IgA nephritis and eventually result in renal fibrosis. Taken together, our study provides evidence, for the first time, that FADD, especially in its phosphorylated form, has an effect on the development of renal fibrosis.Abbreviations: FADD: FAS-associated protein with death domain; DED: death effector domain; DD: death domain; CKD: chronic kidney disease; ECM: extracellular matrix; ESRD: end-stage renal disease; RRT: renal replacement therapy; H&E: hematoxylin and eosin; PASM: periodic acid silver methenamine.

FADD as a key molecular player in cancer progression

Cancer is a leading disease-related cause of death worldwide. Despite advances in therapeutic interventions, cancer remains a major global public health problem. Cancer pathogenesis is extremely intricate and largely unknown. Fas-associated protein with death domain (FADD) was initially identified as an adaptor protein for death receptor-mediated extrinsic apoptosis. Recent evidence suggests that FADD plays a vital role in non-apoptotic cellular processes, such as proliferation, autophagy, and necroptosis. FADD expression and activity of are modulated by a complicated network of processes, such as DNA methylation, non-coding RNA, and post-translational modification. FADD dysregulation has been shown to be closely associated with the pathogenesis of numerous types of cancer. However, the detailed mechanisms of FADD dysregulation involved in cancer progression are still not fully understood. This review mainly summarizes recent findings on the structure, functions, and regulatory mechanisms of FADD and focuses on its role in cancer progression. The clinical implications of FADD as a biomarker and therapeutic target for cancer patients are also discussed. The information reviewed herein may expand researchers’ understanding of FADD and contribute to the development of FADD-based therapeutic strategies for cancer patients.

HIPK3 Inhibition by Exosomal hsa-miR-101-3p Is Related to Metabolic Reprogramming in Colorectal Cancer

Background

Exosomes are extracellular vesicles secreted by most cells to deliver functional cargoes to recipient cells. MicroRNAs (miRNAs) constitute a significant part of exosomal contents. The ease of diffusion of exosomes renders them speedy and highly efficient vehicles to deliver functional molecules. Cancer cells secrete more exosomes than normal cells. Reports have showed that exosomal miRNAs of cancer cells facilitate cancer progression. Yet the complexity of cancer dictates that many more functional exosomal miRNAs remain to be discovered.

Methods

In this study, we analyzed miRNA expression profiles of tissue and plasma exosome samples collected from 10 colorectal cancer (CRC) patients and 10 healthy individuals. We focused on hsa-miR-101-3p (101-3p), a profoundly up-regulated miRNA enriched in plasma exosomes of patients bearing CRC. We performed target analysis of 101-3p and pursued functional studies of this microRNA in two colorectal cancer cell lines, namely HCT116 and SW480.

Results

Our results indicated that inhibiting 101-3p slowed cell growth and retarded cell migration in vivo in two colorectal cancer cell lines. Target analysis showed that Homeodomain-interacting protein kinase (HIPK3) is a target of miR-101-3p. HCT116 and SW480 cells stably overexpressing HIPK3 showed increased level of phosphorylated FADD, as well as retarded cell growth, migration, and increased sensitivity to 5-FU. In-depth analysis revealed increased mitochondrial membrane potential upon HIPK3 overexpression along with increased production of reactive oxygen species, number of mitochondria, and expression of respiratory complexes. Measurements of glycolytic parameters and enzymes revealed decreased level of glycolysis upon HIPK3 overexpression in these two cell lines. Xenograft model further confirmed a profoundly improved potency of the synergistic treatment combining both 5-FU and 101-3p inhibitor compared to 5-FU alone.

Conclusion

This study unraveled an oncogenic nature of the exosomal 101-3p and suggested a relationship between the 101-3p-HIPK3 axis and metabolic homeostasis in colorectal cancer. Expression level of 101-3p is positively correlated with glycolytic capacity in CRC and therefore 101-3p itself is an oncomiR. Combining 101-3p inhibitor with chemotherapeutic agents is an effective strategy against CRC.

Metabolomic Identification of Anticancer Metabolites of Australian Propolis and Proteomic Elucidation of Its Synergistic Mechanisms with Doxorubicin in the MCF7 Cells

The combination of natural products with standard chemotherapeutic agents offers a promising strategy to enhance the efficacy or reduce the side effects of standard chemotherapy. Doxorubicin (DOX), a standard drug for breast cancer, has several disadvantages, including severe side effects and the development of drug resistance. Recently, we reported the potential bioactive markers of Australian propolis extract (AP-1) and their broad spectrum of pharmacological activities. In the present study, we explored the synergistic interactions between AP-1 and DOX in the MCF7 breast adenocarcinoma cells using different synergy quantitation models. Biochemometric and metabolomics-driven analysis was performed to identify the potential anticancer metabolites in AP-1. The molecular mechanisms of synergy were studied by analysing the apoptotic profile via flow cytometry, apoptotic proteome array and measuring the oxidative status of the MCF7 cells treated with the most synergistic combination. Furthermore, label-free quantification proteomics analysis was performed to decipher the underlying synergistic mechanisms. Five prenylated stilbenes were identified as the key metabolites in the most active AP-1 fraction. Strong synergy was observed when AP-1 was combined with DOX in the ratio of 100:0.29 (w/w) as validated by different synergy quantitation models implemented. AP-1 significantly enhanced the inhibitory effect of DOX against MCF7 cell proliferation in a dose-dependent manner with significant inhibition of the reactive oxygen species (p < 0.0001) compared to DOX alone. AP-1 enabled the reversal of DOX-mediated necrosis to programmed cell death, which may be advantageous to decline DOX-related side effects. AP-1 also significantly enhanced the apoptotic effect of DOX after 24 h of treatment with significant upregulation of catalase, HTRA2/Omi, FADD together with DR5 and DR4 TRAIL-mediated apoptosis (p < 0.05), contributing to the antiproliferative activity of AP-1. Significant upregulation of pro-apoptotic p27, PON2 and catalase with downregulated anti-apoptotic XIAP, HSP60 and HIF-1α, and increased antioxidant proteins (catalase and PON2) may be associated with the improved apoptosis and oxidative status of the synergistic combination-treated MCF7 cells compared to the mono treatments. Shotgun proteomics identified 21 significantly dysregulated proteins in the synergistic combination-treated cells versus the mono treatments. These proteins were involved in the TP53/ATM-regulated non-homologous end-joining pathway and double-strand breaks repairs, recruiting the overexpressed BRCA1 and suppressed RIF1 encoded proteins. The overexpression of UPF2 was noticed in the synergistic combination treatment, which could assist in overcoming doxorubicin resistance-associated long non-coding RNA and metastasis of the MCF7 cells. In conclusion, we identified the significant synergy and highlighted the key molecular pathways in the interaction between AP-1 and DOX in the MCF7 cells together with the AP-1 anticancer metabolites. Further in vivo and clinical studies are warranted on this synergistic combination.

Gene Expression Alterations Associated with Oleuropein-Induced Antiproliferative Effects and S-Phase Cell Cycle Arrest in Triple-Negative Breast Cancer Cells

It is known that the Mediterranean diet is effective in reducing the risk of several chronic diseases, including cancer. A critical component of the Mediterranean diet is olive oil, and the relationship between olive oil consumption and the reduced risk of cancer has been established. Oleuropein (OL) is the most prominent polyphenol component of olive fruits and leaves. This compound has been shown to have potent properties in various types of cancers, including breast cancer. In the present study, the molecular mechanism of OL was examined in two racially different triple-negative breast cancer (TNBC) cell lines-African American (AA, MDA-MB-468) and Caucasian American (CA, MDA-MB-231). The data obtained showed that OL effectively inhibits cell growth in both cell lines, concomitant with S-phase cell cycle arrest-mediated apoptosis. The results also showed that OL-treated MDA-MB-468 cells were two-fold more sensitive to OL antiproliferative effect than MDA-MB-231 cells were. At lower concentrations, OL modified the expression of many apoptosis-involved genes. OL was more effective in MDA-MB-468, compared to MDA-MB-231 cells, in terms of the number and the fold-change of the altered genes. In MDA-MB-468 cells, OL induced a noticeable transcription activation in fourteen genes, including two members of the caspase family: caspase 1 (CASP1) and caspase 14 (CASP14); two members of the TNF receptor superfamily: Fas-associated via death domain (FADD) and TNF receptor superfamily 21 (TNFRSF21); six other proapoptotic genes: growth arrest and DNA damage-inducible 45 alpha (GADD45A), cytochrome c somatic (CYCS), BCL-2 interacting protein 2 (BNIP2), BCL-2 interacting protein 3 (BNIP3), BH3 interacting domain death agonist (BID), and B-cell lymphoma/leukemia 10 (BCL10); and the CASP8 and FADD-like apoptosis regulator (CFLAR) gene. Moreover, in MDA-MB-468 cells, OL induced a significant upregulation in two antiapoptotic genes: bifunctional apoptosis regulator (BFAR) and B-Raf proto-oncogene (BRAF) and a baculoviral inhibitor of apoptosis (IAP) repeat-containing 3 (BIRC3). On the contrary, in MDA-MB-231 cells, OL showed mixed impacts on gene expression. OL significantly upregulated the mRNA expression of four genes: BIRC3, receptor-interacting serine/threonine kinase 2 (RIPK2), TNF receptor superfamily 10A (TNFRSF10A), and caspase 4 (CASP4). Additionally, another four genes were repressed, including caspase 6 (CASP6), pyrin domain (PYD), and caspase recruitment domain (CARD)-containing (PAYCARD), baculoviral IAP repeat-containing 5 (BIRC5), and the most downregulated TNF receptor superfamily member 11B (TNFRSF11B, 16.34-fold). In conclusion, the data obtained indicate that the two cell lines were markedly different in the anticancer effect and mechanisms of oleuropein's ability to alter apoptosis-related gene expressions. The results obtained from this study should also guide the potential utilization of oleuropein as an adjunct therapy for TNBC to increase chemotherapy effectiveness and prevent cancer progression.

FADD Phosphorylation Modulates Blood Glucose Levels by Decreasing the Expression of Insulin-Degrading Enzyme

Our previous study revealed a novel role of Fas-associated death domain-containing protein (FADD) in islet development and insulin secretion. Insulin-degrading enzyme (IDE) is a zinc metalloprotease that selectively degrades biologically important substrates associated with type 2 diabetes (T2DM). The current study was designed to investigate the effect of FADD phosphorylation on IDE. We found that the mRNA and protein levels of IDE were significantly downregulated in FADD-D mouse livers compared with control mice. Quantitative real-time polymerase chain reaction analysis showed that FADD regulates the expression of IDE at the transcriptional level without affecting the stability of the mRNA in HepG2 cells. Following treatment with cycloheximide, the IDE protein degradation rate was found to be increased in both FADD-D primary hepatocytes and FADD-knockdown HepG2 cells. Additionally, IDE expression levels were reduced in insulin-stimulated primary hepatocytes from FADD-D mice compared to those from control mice. Moreover, FADD phosphorylation promotes nuclear translocation of FoxO1, thus inhibiting the transcriptional activity of the IDE promoter. Together, these findings imply a novel role of FADD in the reduction of protein stability and expression levels of IDE.

FADD in Cancer: Mechanisms of Altered Expression and Function, and Clinical Implications

FADD was initially described as an adaptor molecule for death receptor-mediated apoptosis, but subsequently it has been implicated in nonapoptotic cellular processes such as proliferation and cell cycle control. During the last decade, FADD has been shown to play a pivotal role in most of the signalosome complexes, such as the necroptosome and the inflammasome. Interestingly, various mechanisms involved in regulating FADD functions have been identified, essentially posttranslational modifications and secretion. All these aspects have been thoroughly addressed in previous reviews. However, FADD implication in cancer is complex, due to pleiotropic effects. It has been reported either as anti- or protumorigenic, depending on the cell type. Regulation of FADD expression in cancer is a complex issue since both overexpression and downregulation have been reported, but the mechanisms underlying such alterations have not been fully unveiled. Posttranslational modifications also constitute a relevant mechanism controlling FADD levels and functions in tumor cells. In this review, we aim to provide detailed, updated information on alterations leading to changes in FADD expression and function in cancer. The participation of FADD in various biological processes is recapitulated, with a mention of interesting novel functions recently proposed for FADD, such as regulation of gene expression and control of metabolic pathways. Finally, we gather all the available evidence regarding the clinical implications of FADD alterations in cancer, especially as it has been proposed as a potential biomarker with prognostic value.

S194-P-FADD as a marker of aggressiveness and poor prognosis in human T-cell lymphoblastic lymphoma

T-cell lymphoblastic lymphoma is a haematological disease with an urgent need for reliable prognostic biomarkers that allow therapeutic stratification and dose adjustment. The scarcity of human samples is responsible for the delayed progress in the study and the clinical management of this disease, especially compared with T-cell acute lymphoblastic leukaemia, its leukemic counterpart. In the present work, we have determined by immunohistochemistry that S194-P-FADD protein is significantly reduced in a cohort of 22 samples from human T-cell lymphoblastic lymphoma. Notably, the extent of such reduction varies significantly among samples and has revealed determinant for the outcome of the tumour. We demonstrate that Fas-associated protein with death domain (FADD) phosphorylation status affects protein stability, subcellular localization and non-apoptotic functions, specifically cell proliferation. Phosphorylated FADD would be more stable and preferentially localized to the cell nucleus; there, it would favour cell proliferation. We show that patients with higher levels of S194-P-FADD exhibit more proliferative tumours and that they present worse clinical characteristics and a significant enrichment to an oncogenic signature. This supports that FADD phosphorylation may serve as a predictor for T-cell lymphoblastic lymphoma aggressiveness and clinical status. In summary, we propose FADD phosphorylation as a new biomarker with prognostic value in T-cell lymphoblastic lymphoma.

FADD at the Crossroads between Cancer and Inflammation

Initially described as an adaptor molecule for death receptor (DR)-mediated apoptosis, Fas-associated death domain (FADD) was later implicated in nonapoptotic cellular processes. During the last decade, FADD has been shown to participate and regulate most of the signalosome complexes, including necrosome, FADDosome, innateosome, and inflammasome. Given the role of these signaling complexes, FADD has emerged as a new actor in innate immunity, inflammation, and cancer development. Concomitant to these new roles, a surprising number of mechanisms deemed to regulate FADD functions have been identified, including post-translational modifications of FADD protein and FADD secretion. This review focuses on recent knowledge of the biological roles of FADD, a pleiotropic molecule having multiple partners, and its impact in cancer, innate immunity, and inflammation.

Concordance between somatic copy number loss and down-regulated expression: A pan-cancer study of cancer predisposition genes

Cancer predisposition genes (CPGs) are a class of cancer genes in which germline variants lead to increased risk of cancer. Research has revealed that copy number variation (CNV) may be linked to cancer susceptibility in CPGs. In this pan-cancer analysis, we explored the relationship between somatic CNV and gene expression changes in CPGs. Based on curated 827 human CPGs from literature, we firstly identified 729 CPGs with precise CNV information from 5067 tumor samples using TCGA CNV data. Among them, 128 CPGs tended to have more frequent copy number losses (CNLs) compared with copy number gains (CNGs). Then by correlating these CNV data with TCGA gene expression data, we obtained 49 CPGs with concordant CNLs and gene down-regulation. Intriguingly, five CPGs showed concordance between CNL and down-regulation in 50 or more tumor samples: MTAP (216 samples), PTEN (143), MCPH1 (86), SMAD4 (63), and MINPP1 (51), which may represent the recurrent driving force for gene expression change during oncogenesis. Moreover, network analysis revealed that these 49 CPGs were tightly connected. In summary, this study provides the first observation of concordance between CNLs and down-regulation of CPGs in pan-cancer, which may help better understand the CPG biology in tumorigenesis and cancer progression.

FADD is a key regulator of lipid metabolism

FADD, a classical apoptotic signaling adaptor, was recently reported to have non‐apoptotic functions. Here, we report the discovery that FADD regulates lipid metabolism. PPAR‐α is a dietary lipid sensor, whose activation results in hypolipidemic effects. We show that FADD interacts with RIP140, which is a corepressor for PPAR‐α, and FADD phosphorylation‐mimic mutation (FADD‐D) or FADD deficiency abolishes RIP140‐mediated transcriptional repression, leading to the activation of PPAR‐α. FADD‐D‐mutant mice exhibit significantly decreased adipose tissue mass and triglyceride accumulation. Also, they exhibit increased energy expenditure with enhanced fatty acid oxidation in adipocytes due to the activation of PPAR‐α. Similar metabolic phenotypes, such as reduced fat formation, insulin resistance, and resistance to HFD‐induced obesity, are shown in adipose‐specific FADD knockout mice. Additionally, FADD‐D mutation can reverse the severe genetic obesity phenotype of ob/ob mice, with elevated fatty acid oxidation and oxygen consumption in adipose tissue, improved insulin resistance, and decreased triglyceride storage. We conclude that FADD is a master regulator of glucose and fat metabolism with potential applications for treatment of insulin resistance and obesity.

Anisomycin-induced GATA-6 degradation accompanying a decrease of proliferation of colorectal cancer cell

Transcription factor GATA-6 plays a key role in normal cell differentiation of the mesoderm and endoderm. On the other hand, GATA-6 is abnormally overexpressed in many clinical gastrointestinal cancer tissue samples, and accelerates cell proliferation or an anti-apoptotic response in cancerous tissues. We previously showed that activation of the JNK signaling cascade causes proteolysis of GATA-6. In this study, we demonstrated that anisomycin, a JNK activator, stimulates nuclear export of GATA-6 in a colorectal cancer cell line, DLD-1. Concomitantly, anisomycin remarkably inhibits the proliferation of DLD-1 cells via G2/M arrest in a plate culture. However, it did not induce apoptosis under growth arrest conditions. Furthermore, the growth of DLD-1 cells in a spheroid culture was suppressed by anisomycin. Although 5-FU showed only a slight inhibitory effect on 3D spheroid cultures, the same concentration of 5-FU together with a low concentration of anisomycin exhibited strong growth inhibition. These results suggest that the induction of GATA-6 dysfunction may be more effective for chemotherapy for colorectal cancer, although the mechanism underlying the synergistic effect of 5-FU and anisomycin remains unknown.

FADD phosphorylation impaired islet morphology and function

Previous studies have indicated that Fas-FasL pathway and its downstream caspase-8 can regulate islet mass and insulin secretion. As a classical adaptor in Fas-FasL signaling, Fas-associated death domain-containing protein (FADD) takes part in many non-apoptosis processes regulated by its phosphorylation. However, its role in islets has not been evaluated to date. Here, through comparative proteomics and bioinformatic analysis on FADD phosphorylated (FADD-D) and wild-type (WT) MEFs, we found three proteins involved in islet differentiation and function were dysregulated due to FADD phosphorylation. The mouse model of FADD-D, which mimics constitutive phosphorylated FADD expression in mice, was further analyzed to address this issue. We confirmed the proteomic results by immunohistological analyses on pancreatic islets. In addition, we found that FADD-D mice displayed decreased islet area, and the glucose stimulated insulin secretion (GSIS) of FADD-D islets was impaired. These data suggest a novel role of FADD in islet development and insulin secretion.

Increased Expression of Phosphorylated FADD in Anaplastic Large Cell and Other T-Cell Lymphomas

FAS-associated protein with death domain (FADD) is a major adaptor protein involved in extrinsic apoptosis, embryogenesis, and lymphocyte homeostasis. Although abnormalities of the FADD/death receptor apoptotic pathways have been established in tumorigenesis, fewer studies have analyzed the expression and role of phosphorylated FADD (pFADD). Our identification of FADD as a lymphoma-associated autoantigen in T-cell lymphoma patients raises the possibility that pFADD, with its correlation with cell cycle, may possess role(s) in human T-cell lymphoma development. This immunohistochemical study investigated pFADD protein expression in a range of normal tissues and lymphomas, particularly T-cell lymphomas that require improved therapies. Whereas pFADD was expressed only in scattered normal T cells, it was detected at high levels in T-cell lymphomas (eg, 84% anaplastic large cell lymphoma and 65% peripheral T cell lymphomas, not otherwise specified). The increased expression of pFADD supports further study of its clinical relevance and role in lymphomagenesis, highlighting phosphorylation of FADD as a potential therapeutic target.

Tamoxifen integromics and personalized medicine: dynamic modular transformations underpinning response to tamoxifen in breast cancer treatment

Recent advances in pharmacogenomics technologies allow bold steps to be taken towards personalized medicine, more accurate health planning, and personalized drug development. In this framework, systems pharmacology network-based approaches offer an appealing way for integrating multi-omics data and set the basis for defining systems-level drug response biomarkers. On the road to individualized tamoxifen treatment in estrogen receptor-positive breast cancer patients, we examine the dynamics of the attendant pharmacological response mechanisms. By means of an "integromics" network approach, we assessed the tamoxifen effect through the way the high-order organization of interactome (i.e., the modules) is perturbed. To accomplish that, first we integrated the time series transcriptome data with the human protein interaction data, and second, an efficient module-detecting algorithm was applied onto the composite graphs. Our findings show that tamoxifen induces severe modular transformations on specific areas of the interactome. Our modular biomarkers in response to tamoxifen attest to the immunomodulatory role of tamoxifen, and further reveal that it deregulates cell cycle and apoptosis pathways, while coordinating the proteasome and basal transcription factors. To the best of our knowledge, this is the first report that informs the fields of personalized medicine and clinical pharmacology about the actual dynamic interactome response to tamoxifen administration.

Comparative proteomics analysis reveals roles for FADD in the regulation of energy metabolism and proteolysis pathway in mouse embryonic fibroblast

Fas-associated death domain-containing protein (FADD) is a classical apoptotic pathway adaptor. Further studies revealed that it also plays essential roles in nonapoptotic processes, which is assumed to be regulated by its phosphorylation. However, the exact mechanisms are still poorly understood. To study the nonapoptotic effects of FADD, a comprehensive strategy of proteomics identification combined with bioinformatic analysis was undertaken to identify proteins differentially expressed in three cell lines containing FADD and its mutant, FADD-A and FADD-D. The cell lines were thought to bear wild-type FADD, unphosphorylated FADD mimic and constitutive phosphorylated FADD mimic, respectively. A total of 47 proteins were identified to be significantly changed due to FADD phosphorylation. Network analysis using MetaCore™ identified a number of changed proteins that were involved in cellular metabolic process, including lipid metabolism, fatty acid metabolism, glycolysis, and oxidative phosphorylation. The finding that FADD-D cell line showed an increase in fatty acid oxidation argues that it could contribute to the leaner phenotype of FADD-D mice as reported previously. In addition, six proteins related to the ubiquitin-proteasome pathway were also specifically overexpressed in FADD-D cell line. Finally, the c-Myc gene represents a convergent hub lying at the center of dysregulated pathways, and was upregulated in FADD-D cells. Taken together, these studies allowed us to conclude that impaired mitochondrial function and proteolysis might play pivotal roles in the dysfunction associated with FADD phosphorylation-induced disorders.

Role of Fas-associated death domain-containing protein (FADD) phosphorylation in regulating glucose homeostasis: from proteomic discovery to physiological validation

Fas-associated death domain-containing protein (FADD), a classical apoptotic signaling adaptor, participates in different nonapoptotic processes regulated by its phosphorylation. However, the influence of FADD on metabolism, especially glucose homeostasis, has not been evaluated to date. Here, using both two-dimensional electrophoresis and liquid chromatography linked to tandem mass spectrometry (LC/MS/MS), we found that glycogen synthesis, glycolysis, and gluconeogenesis were dysregulated because of FADD phosphorylation, both in MEFs and liver tissue of the mice bearing phosphorylation-mimicking mutation form of FADD (FADD-D). Further physiological studies showed that FADD-D mice exhibited lower blood glucose, enhanced glucose tolerance, and increased liver glycogen content without alterations in insulin sensitivity. Moreover, investigations on the molecular mechanisms revealed that, under basal conditions, FADD-D mice had elevated phosphorylation of Akt with alterations in its downstream signaling, leading to increased glycogen synthesis and decreased gluconeogenesis. Thus, we uncover a novel role of FADD in the regulation of glucose homeostasis by proteomic discovery and physiological validation.

FADD expression is associated with regional and distant metastasis in squamous cell carcinoma of the head and neck

AIMS

The Fas-associated death domain gene (FADD) is often overexpressed in squamous cell carcinoma of the head and neck (HNSCC), and is considered to be a driver gene in amplification of the chromosomal 11q13.3 region. Amplification of 11q13.3 is associated with increased metastasis in HNSCC and breast cancer. The aim of this study was to investigate the association between FADD protein expression in advanced-stage HNSCC and clinicopathological features and outcome.

METHODS AND RESULTS

Tumour tissues of 177 HNSCC patients uniformly treated with primary surgery and postoperative radiotherapy were collected. FADD expression was assessed on pretreatment tumour biopsies using immunohistochemistry. High FADD expression was detected in 44% of the HNSCC patients. High expression was associated with an increased rate of lymph node metastasis (P = 0.001) and with a shorter distant metastasis-free interval (DMFI) (HR 2.6, 95% CI 1.0-6.7, P = 0.046) when lymph node metastases were present.

CONCLUSIONS

Our data show that an increase in FADD expression is associated with a higher incidence of lymph node metastasis at presentation, and with shorter DMFI when lymph node metastases are present. High FADD expression in the primary tumour could be a useful marker to select patients for systemic treatment strategies that reduce the risk of distant metastases.

Functional specific roles of FADD: comparative proteomic analyses from knockout cell lines

Comparative proteomics identification combined with bioinformatic analyses and cell biology validation revealed novel non-apoptotic functions of FADD in energy metabolism and proteolysis.

Regulation of protein kinase C inactivation by Fas-associated protein with death domain

Protein kinase C (PKC) plays important roles in diverse cellular processes. PKC has been implicated in regulating Fas-associated protein with death domain (FADD), an important adaptor protein involved in regulating death receptor-mediated apoptosis. FADD also plays an important role in non-apoptosis processes. The functional interaction of PKC and FADD in non-apoptotic processes has not been examined. In this study, we show that FADD is involved in maintaining the phosphorylation of the turn motif and hydrophobic motif in the activated conventional PKC (cPKC). A phosphoryl-mimicking mutation (S191D) in FADD (FADD-D) abolished the function of FADD in the facilitation of the turn motif and hydrophobic motif dephosphorylation of cPKC, suggesting that phosphorylation of Ser-191 negatively regulates FADD. We show that FADD interacts with PP2A, which is a major phosphatase involved in dephosphorylation of activated cPKC and FADD deficiency abolished PP2A mediated dephosphorylation of cPKC. We show that FADD deficiency leads to increased stability and activity of cPKC, which, in turn, promotes cytoskeleton reorganization, cell motility, and chemotaxis. Collectively, these results reveal a novel function of FADD in a non-apoptotic process by modulating cPKC dephosphorylation, stability, and signaling termination.

Methylseleninic acid enhances paclitaxel efficacy for the treatment of triple-negative breast cancer

A major challenge in breast cancer therapy is the lack of an effective therapeutic option for a particularly aggressive subtype of breast cancer, triple-negative breast cancer. Here we provide the first preclinical evidence that a second-generation selenium compound, methylseleninic acid, significantly enhances the anticancer efficacy of paclitaxel in triple-negative breast cancer. Through combination-index value calculation, we demonstrated that methylseleninic acid synergistically enhanced the growth inhibitory effect of paclitaxel in triple-negative breast cancer cells. The synergism was attributable to more pronounced induction of caspase-mediated apoptosis, arrest of cell cycle progression at the G2/M checkpoint, and inhibition of cell proliferation. Treatment of SCID mice bearing MDA-MB-231 triple-negative breast cancer xenografts for four weeks with methylseleninic acid (4.5 mg/kg/day, orally) and paclitaxel (10 mg/kg/week, through intraperitoneal injection) resulted in a more pronounced inhibition of tumor growth compared with either agent alone. The attenuated tumor growth correlated with a decrease in tumor cell proliferation and an induction of apoptosis. The in vivo study also indicated the safety of using methylseleninic acid in the combination regime. Our findings thus provide strong justification for the further development of methylseleninic acid and paclitaxel combination therapy for the treatment of triple-negative breast cancer.

Carbon monoxide inhibits Fas activating antibody-induced apoptosis in endothelial cells

Background

The extrinsic apoptotic pathway initiates when a death ligand, such as the Fas ligand, interacts with its cell surface receptor (ie., Fas/CD95), forming a death-inducing signaling complex (DISC). The Fas-dependent apoptotic pathway has been implicated in several models of lung or vascular injury. Carbon monoxide, an enzymatic product of heme oxygenase-1, exerts antiapoptotic effects at low concentration in vitro and in vivo.

Methods

Using mouse lung endothelial cells (MLEC), we examined the antiapoptotic potential of carbon monoxide against apoptosis induced by the Fas/CD95-activating antibody (Jo2). Carbon monoxide was applied to cell cultures in vitro. The expression and/or activation of apoptosis-related proteins and signaling intermediates were determined using Western Immunoblot and co-immunoprecipitation assays. Cell death was monitored by lactate dehydrogenase (LDH) release assays. Statistical significance was determined by student T-test and a value of P < 0.05 was considered significant.

Results

Treatment of MLEC with Fas-activating antibody (Jo2) induced cell death associated with the formation of the DISC, and activation of caspases (-8, -9, and -3), as well as the pro-apoptotic Bcl-2 family protein Bax. Exposure of MLEC to carbon monoxide inhibited Jo2-induced cell death, which correlated with the inhibition of DISC formation, cleavage of caspases-8, -9, and -3, and Bax activation. Carbon monoxide inhibited the phosphorylation of the Fas-associated death domain-containing protein, as well as its association with the DISC. Furthermore, carbon monoxide induced the expression of the antiapoptotic protein FLIP and increased its association with the DISC.

CO-dependent cytoprotection against Fas mediated apoptosis in MLEC depended in part on activation of ERK1/2-dependent signaling.

Conclusions

Carbon monoxide has been proposed as a potential therapy for lung and other diseases based in part on its antiapoptotic effects in endothelial cells. In vitro, carbon monoxide may inhibit both Fas/caspase-8 and Bax-dependent apoptotic signaling pathways induced by Fas-activating antibody in endothelial cells. Strategies to block Fas-dependent apoptotic pathways may be useful in development of therapies for lung or vascular disorders.

Expression of serine 194-phosphorylated Fas-associated death domain protein correlates with proliferation in B-cell non-Hodgkin lymphomas

Fas-associated death domain protein is a key component of the extrinsic apoptotic pathway. In addition, in animal models, Fas-associated death domain protein phosphorylation at serine 194 has been shown to affect cell proliferation, especially in T lymphocytes. The importance of Fas-associated death domain protein phosphorylation at serine 194 for the proliferation of B lymphocytes, however, is uncertain. Here we show in reactive lymph nodes that serine 194 phosphorylated Fas-associated death domain protein is expressed predominantly in the dark (proliferative) zone of germinal centers. In B-cell non-Hodgkin lymphoma cell lines, serine 194 phosphorylated Fas-associated death domain protein levels are substantially higher in highly proliferating cells and lower in serum-starved cells. We also used immunohistochemical analysis to assess Fas-associated death domain protein phosphorylation at serine 194 expression in 122 B-cell non-Hodgkin-type lymphomas. The mean percentage of serine 194 phosphorylated Fas-associated death domain protein positive tumor cells was 81% in Burkitt lymphoma, 41% in diffuse large B-cell lymphoma, 18% in follicular lymphoma, 18% in plasma cell myeloma, 12% in extranodal marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue, 11% in mantle cell lymphoma, and 2% in chronic lymphocytic leukemia/small lymphocytic lymphoma (P < .0001, Kruskal-Wallis test). Furthermore, in chronic lymphocytic leukemia/small lymphocytic lymphoma, serine 194 phosphorylated Fas-associated death domain protein was detected predominantly in proliferation centers. In the entire study group, the percentage of cells positive for serine 194 phosphorylated Fas-associated death domain protein correlated significantly with the proliferation index Ki-67 (Spearman R = 0.9, P < .0001). These data provide evidence that serine 194 phosphorylated Fas-associated death domain protein is involved in the proliferation of normal and neoplastic B cells and has features of a novel proliferation marker.

Phosphorylation by polo-like kinase 1 induces the tumor-suppressing activity of FADD

Phosphorylation of the Fas-associated death domain (FADD) protein sensitizes cancer cells to various chemotherapeutics. However, the molecular mechanism underlying chemosensitization by phosphorylated FADD (P-FADD) is poorly understood. In this study, we describe the physical interactions and functional interplay between Polo-like kinase 1 (Plk1) and FADD. Plk1 phosphorylates FADD at Ser-194 in response to treatment with taxol. Overexpression of a phosphorylation-mimicking mutant, FADD S194D, caused degradation of Plk1 in an ubiquitin-independent manner, and delayed cytokinesis, consistent with the expected cellular phenotype of Plk1 deficiency. This demonstrates that Plk1 is regulated via a negative feedback loop by its substrate, FADD. Overexpression of FADD S194D sensitized HeLa cells to a low dose of taxol independently of caspase activation, whereas overexpression of FADD S194D resulted in caspase activation in response to a high dose of taxol. Therefore, we examined whether the death potential of P-FADD affected Plk1-mediated tumorigenesis. Transfection of FADD S194D inhibited colony formation by Plk1-overexpressing HeLa cells (HeLa-Plk1). Moreover, overexpression of FADD S194D suppressed tumorigenesis in nude mice xenografted with HeLa-Plk1. Therefore, this study reports the first in vivo validation of tumor-suppressing activity of P-FADD. Collectively, our data demonstrate that in response to taxol, Plk1 endows death-promoting and tumor-suppressor functions to its substrate, FADD.

DNA amplification and expression of FADD in oral squamous cell carcinoma

BACKGROUND

The Fas-associated death domain-containing protein, FADD, is an adaptor for relaying apoptotic signals. However, recent studies have shown that FADD also plays an important role in the growth and regulation of the cell cycle. The purpose of this study was to elucidate the role of FADD in oral squamous cell carcinoma (SCC).

METHODS

The DNA amplification of FADD from 30 samples of tongue SCC was analyzed using real-time PCR and the protein expression of FADD from 60 samples of tongue SCC was analyzed using immunohistochemistry.

RESULTS

The DNA amplifications of FADD were observed in 13 cases (44.3%) and were significantly correlated with the histopathological differentiation grade of SCCs (P = 0.009). FADD expression levels compared with the matched adjacent epithelium increased significantly (P = 0.000). Additionally, the positive expressions of FADD were significantly correlated with lymph node metastasis of SCCs (P = 0.029) and the 5-year disease-specific survival rates (P = 0.049). A positive association between FADD expression level and the histopathological differentiation grade was found to be limited to T1 SCCs (P = 0.019). DNA amplification was moderately correlated (correlation coefficient = 0.406, P = 0.026) with expression of FADD in 30 samples of tongue SCC.

CONCLUSION

In tongue SCCs, the expression of FADD was higher when compared with that of adjacent areas, which might be determined via genomic amplification in 11q13.3. Thus, SCC cells with the expression of FADD are possibly more likely to become metastatic and to worsen survival rates.

Amplicon mapping and expression profiling identify the Fas-associated death domain gene as a new driver in the 11q13.3 amplicon in laryngeal/pharyngeal cancer

PURPOSE

Amplification of the 11q13 region is a frequent event in human cancer. The highest incidence (36%) is found in head and neck squamous cell carcinomas. Recently, we reported that the amplicon size in 30 laryngeal and pharyngeal carcinomas with 11q13 amplification is determined by unique genomic structures, resulting in the amplification of a set of genes rather than a single gene.

EXPERIMENTAL DESIGN

To investigate which gene(s) drive the 11q13 amplicon, we determined the smallest region of overlap with amplification and the expression levels of all genes within this amplicon.

RESULTS

Using array-based comparative genomic hybridization analysis, we detected a region of approximately 1.7 Mb containing 13 amplified genes in more than 25 of the 29 carcinomas. Quantitative reverse transcription-PCR revealed that overexpression of 8 potential driver genes including, cyclin D1, cortactin, and Fas-associated death domain (FADD), correlated significantly with DNA amplification. FADD protein levels correlated well with DNA amplification, implicating that FADD is also a candidate driver gene in the 11q13 amplicon. Analysis of 167 laryngeal carcinomas showed that increased expression of FADD (P = 0.007) and Ser(194) phosphorylated FADD (P = 0.011) were associated with a worse disease-specific survival. FADD was recently reported to be involved in cell cycle regulation, and cancer cells expressing high levels of the Ser(194) phosphorylated isoform of FADD proved to be more sensitive to Taxol-induced cell cycle arrest.

CONCLUSION

Because of the frequent amplification of the 11q13 region and concomitant overexpression of FADD in head and neck squamous cell carcinomas, we hypothesize that FADD is a marker to select patients that might benefit from Taxol-based chemoradiotherapy.

Prostate cancer antigen-1 contributes to cell survival and invasion though discoidin receptor 1 in human prostate cancer

A novel gene, prostate cancer antigen (PCA)-1, was recently reported to be expressed in the prostate; however, its biological roles remain unclear. Knockdown of the PCA-1 gene by small interfering RNA transfection induced apoptosis through reducing the expression of the anti-apoptotic molecule Bcl-xl and cytoplasmic release of cytochrome c in the androgen-independent prostate cancer cell line PC3. Moreover, in vitro matrigel and in vivo chorioallantoic membrane assays showed that silencing of PCA-1 significantly downregulated discoidin receptor (DDR)-1 expression, resulting in suppression of cancer-cell invasion. Transfection with PCA-1 increased the levels of both Bcl-xl and DDR1, which made the cells more invasive through the upregulation of matrix metalloproteinase 9 in DU145. Interestingly, long-term culture using androgen-free medium increased the level of PCA-1 and the related expression of Bcl-xl and DDR-1 in the androgen-sensitive cancer cell line LNCaP, suggesting that PCA-1 signaling is associated with androgen independence. Immunohistochemical analysis in a series of 169 prostate carcinomas showed that PCA-1 and DDR1 were strongly expressed in prostate cancer cells, including preneoplastic lesions, but there was little or no expression in normal epithelium. Moreover, the expression of PCA-1 and DDR-1 was associated with a hormone-independent state of prostate cancer. Taken together, we propose that PCA-1-DDR-1 signaling is a new important axis involved in malignant potential prostate cancer associated with hormone-refractory status.

Expression of nuclear and cytoplasmic phosphorylated FADD in gastric cancers

Fas-associated death domain (FADD) plays a crucial role during death receptor-mediated apoptosis. In addition, FADD possesses apoptosis-independent activities, including cell-cycle regulation and cell proliferation regulated by the phosphorylation of FADD at Ser194. The aim of this study was to explore the possibility whether alteration of phosphorylated FADD (p-FADD) expression might be a characteristic of gastric cancer. We analyzed the expression of p-FADD protein in 60 gastric adenocarcinomas by immunohistochemistry using a tissue microarray approach. In the normal gastric mucosal cells, surface and glandular epithelial cells evenly expressed p-FADD in the nuclei but not in the cytoplasm. In the cancers, p-FADD expression was detected in 38 cases (63%) of the gastric carcinomas, but there was no p-FADD immunostaining in the remaining 22 cancers (37%). Of note, p-FADD immunostaining was observed in cytoplasm/nuclei (20 cancers; 33%) and cytoplasm (18 cancers; 30%). There was no significant association of p-FADD expression with clinocopathological characteristics, including invasion, metastasis, and stage. Our data showed that the expression of p-FADD in gastric cancers was heterogenous in its location compared to the uniform nuclear expression of p-FADD in normal gastric cells. Many of the cancers (67%) were devoid of nuclear p-FADD, suggesting that p-FADD functions in the nucleus may be perturbed in the cancers. Also, p-FADD expression in the cytoplasm in a large fraction of the cancers (63%), not seen in the normal cells, suggested that the cell death functions of p-FADD could be altered in the cancer cells.

Bcl-2 phosphorylation has pathological significance in human breast cancer

The anti-apoptotic molecule, Bcl-2, is well known to play an important role in the chemoresistance of breast cancer. We have previously demonstrated that phosphorylation of Fas-associated death domain-containing protein (FADD) at 194 serine through c-jun NH2-terminal kinase (JNK) activation sensitizes breast cancer cells to chemotherapy through accelerating cell cycle arrest at G2/M, and that Bcl-2 phosphorylation downstream of JNK/FADD plays an important role in cell growth suppression by paclitaxel. In this study, the clinicopathological association of phosphorylated Bcl-2 (P-Bcl-2) with estrogen, progesterone, c-erbB-2 receptors, p53 expressions and phosphorylated FADD/JNK (P-FADD/JNK) was analyzed immunohistochemically using 107 human breast cancer specimens. Expression of P-Bcl-2 was found to significantly correlate with lymphatic invasion, lymph node metastasis, but not histological differentiation, tumor grade or vascular and fatty invasion. The positivity of P-Bcl-2 was also significantly correlated to that of P-FADD/JNK. Thus, P-Bcl-2 as well as the P-FADD/JNK parameter might be useful markers for cancer progression, independent of the hormone receptor status, in human breast cancers.