c-Rel is a cell cycle modulator in human melanoma cells.

Melanoma progression and resistance to therapy are associated with faulty regulation of signalling molecules including the central transcription factor NF-κB. Increased expression of the c-Rel subunit of NF-κB has been described in progressing melanoma, though mechanistic implications of this upregulation remain unclear. To elucidate the functional role of c-Rel in melanoma biology, we have assessed its expression in human melanoma as well as in melanoma cell lines. Suppression of c-Rel expression in four melanoma cell lines resulted in reduced growth and altered cell cycle regulation, namely G2/M and polyploid phase induction. Moreover, mitotic spindle morphology was profoundly altered in three of the cell lines with a predominance of monopolar structures. These findings suggest that c-Rel is involved in G2/M phase regulation, prevention of polyploidy and, consequently, chromosomal stability. Our results highlight a novel tumor-promoting function of c-Rel in human melanoma cells through governing cell cycle regulation.

Transient epidermal barrier deficiency and lowered allergic threshold in filaggrin-hornerin (FlgHrnr-/- ) double-deficient mice.

BACKGROUND: Filaggrin (Flg) and hornerin (Hrnr) share similar structural and functional features. Both proteins have been implicated as essential proteins for skin barrier maintenance. Loss-of-function mutations of these genes constitute a risk factor for atopic dermatitis and eczema-related asthma. Furthermore, both FLG and HRNR protein levels are downregulated in patients with atopic dermatitis. Thus, mice deficient for Flg and Hrnr provide a novel model to study skin barrier impairment and the susceptibility for cutaneous inflammation. METHODS: By using appropriate targeting vectors and breeding strategies, we established a homozygous FlgHrnr double-deficient (FlgHrnr-/- ) mouse model lacking both genes including the intergenomic sequence. RESULTS: Neonates appeared normal, but developed a transient scaly phenotype with overall flaky appearance, but no overt skin phenotype in adulthood, thereby reflecting a subclinical barrier defect seen in humans. Structurally, FlgHrnr-/- mice displayed a markedly reduced granular layer and a condensed cornified layer. Functionally, FlgHrnr-/- mice showed permeability abnormalities and metabolic aberrations regarding the production of natural moisturizing factors (NMFs) in the stratum corneum. Surprisingly, although the immune system revealed no aberrations under steady-state conditions, FlgHrnr-/- mice are predisposed to mount an allergic contact dermatitis, especially at hapten threshold levels eliciting allergic reactions. CONCLUSIONS: Together, our FlgHrnr-/- mouse model nicely reflects the epicutaneous sensitization susceptibilities and inflammatory reactions to environmental insults in humans with impaired skin barrier functions.

Comparative study of human-induced pluripotent stem cells derived from bone marrow cells, hair keratinocytes, and skin fibroblasts.

AIMS: Induced pluripotent stem cells (iPSCs) provide a unique opportunity for the generation of patient-specific cells for use in disease modelling, drug screening, and regenerative medicine. The aim of this study was to compare human-induced pluripotent stem cells (hiPSCs) derived from different somatic cell sources regarding their generation efficiency and cardiac differentiation potential, and functionalities of cardiomyocytes. METHODS AND RESULTS: We generated hiPSCs from hair keratinocytes, bone marrow mesenchymal stem cells (MSCs), and skin fibroblasts by using two different virus systems. We show that MSCs and fibroblasts are more easily reprogrammed than keratinocytes. This corresponds to higher methylation levels of minimal promoter regions of the OCT4 and NANOG genes in keratinocytes than in MSCs and fibroblasts. The success rate and reprogramming efficiency was significantly higher by using the STEMCCA system than the OSNL system. All analysed hiPSCs are pluripotent and show phenotypical characteristics similar to human embryonic stem cells. We studied the cardiac differentiation efficiency of generated hiPSC lines (n = 24) and found that MSC-derived hiPSCs exhibited a significantly higher efficiency to spontaneously differentiate into beating cardiomyocytes when compared with keratinocyte-, and fibroblast-derived hiPSCs. There was no significant difference in the functionalities of the cardiomyocytes derived from hiPSCs with different origins, showing the presence of pacemaker-, atrial-, ventricular- and Purkinje-like cardiomyocytes, and exhibiting rhythmic Ca2+ transients and Ca2+ sparks in hiPSC-derived cardiomyocytes. Furthermore, spontaneously and synchronously beating and force-developing engineered heart tissues were generated. CONCLUSIONS: Human-induced pluripotent stem cells can be reprogrammed from all three somatic cell types, but with different efficiency. All analysed iPSCs can differentiate into cardiomyocytes, and the functionalities of cardiomyocytes derived from different cell origins are similar. However, MSC-derived hiPSCs revealed a higher cardiac differentiation efficiency than keratinocyte- and fibroblast-derived hiPSCs.

NF-кB c-Rel modulates pre-fibrotic changes in human fibroblasts.

Skin fibrosis is one central hallmark of the heterogeneous autoimmune disease systemic sclerosis. So far, there are hardly any standardized and effective treatment options. Pathogenic mechanisms underlying fibrosis comprise excessive and uncontrolled myofibroblast differentiation, increased extracellular matrix protein (ECM) synthesis and an intensification of the forces exerted by the cytoskeleton. A deeper understanding of fibroblast transformation could help to prevent or reverse fibrosis by specifically interfering with abnormally regulated signaling pathways. The transcription factor NF-κB has been implicated in the progression of fibrotic processes. However, the cellular processes regulated by NF-κB in fibrosis as well as the NF-κB isoforms preferentially involved are still completely unknown. In an in vitro model of fibrosis, we consistently observed the induction of the c-Rel subunit of NF-κB. Functional abrogation of c-Rel by siRNA resulted in diminished cell contractility of dermal fibroblasts in relaxed, but not in stressed 3D collagen matrices. Furthermore, directed migration was reduced after c-Rel silencing and total N-cadherin expression level was diminished, possibly mediating the observed cellular defects. Therefore, NF-кB c-Rel impacts central cellular adhesion markers and processes which negatively regulate fibrotic progression in SSc pathophysiology.

Protein Signatures of NK Cell-Mediated Melanoma Killing Predict Response to Immunotherapies.

Despite impressive advances in melanoma-directed immunotherapies, resistance is common and many patients still succumb to metastatic disease. In this context, harnessing natural killer (NK) cells, which have thus far been sidelined in the development of melanoma immunotherapy, could provide therapeutic benefits for cancer treatment. To identify molecular determinants of NK cell-mediated melanoma killing (NKmK), we quantified NK-cell cytotoxicity against a panel of genetically diverse melanoma cell lines and observed highly heterogeneous susceptibility. Melanoma protein microarrays revealed a correlation between NKmK and the abundance and activity of a subset of proteins, including several metabolic factors. Oxidative phoshorylation, measured by oxygen consumption rate, negatively correlated with melanoma cell sensitivity toward NKmK, and proteins involved in mitochondrial metabolism and epithelial-mesenchymal transition were confirmed to regulate NKmK. Two- and three-dimensional killing assays and melanoma xenografts established that the PI3K/AKT/mTOR signaling axis controls NKmK via regulation of NK cell-relevant surface proteins. A "protein-killing-signature" based on the protein analysis predicted NKmK of additional melanoma cell lines and the response of patients with melanoma to anti-PD-1 checkpoint therapy. Collectively, these findings identify novel NK cell-related prognostic biomarkers and may contribute to improved and personalized melanoma-directed immunotherapies. SIGNIFICANCE: NK-cell cytotoxicity assays and protein microarrays reveal novel biomarkers of NK cell-mediated melanoma killing and enable development of signatures to predict melanoma patient responsiveness to immunotherapies.

The IKKα-dependent non-canonical pathway of NF-κB activation is constitutively active and modulates progression-related functions in a subset of human melanomas.

Owing to activation of several resistance-mediating pathways including NF-κB signaling, metastasized melanoma is almost universally resistant against chemotherapy. Given that blocking of NF-κB either by proteasome-, pan-IKK- or selective IKKß-inhibitors may increase the susceptibility of melanoma cells to chemotherapy, we have assessed the role of the second kinase within the IKK complex, IKKα. While expression of IKKα and overall activation of NF-κB were heterogeneous, the IKKα-specific p100/p52 processing was detected in a small subset of melanomas (1/9 primary and 1/12 metastatic melanomas) as well as in 1/8 melanoma cell lines. Down-modulation of IKKα by siRNA resulted in diminution of doxorubicin-induced NF-κB activation, constitutive and TNFα-stimulated expression of CXCL8 and ICAM-1, and cell migration. In contrast, overexpression of IKKα in melanoma cells did not significantly affect progression-related functions. Thus, IKKα may be a worthwhile target only in selected individualized therapies but not in general melanoma therapy.

c-Rel in Epidermal Homeostasis: A Spotlight on c-Rel in Cell Cycle Regulation.

To maintain proper skin barrier function, epidermal homeostasis requires a subtly governed balance of proliferating and differentiating keratinocytes. While differentiation takes place in the suprabasal layers, proliferation, including mitosis, is usually restricted to the basal layer. Only recently identified as an important regulator of epidermal homeostasis, c-Rel, an NF-κB transcription factor subunit, affects the viability and proliferation of epidermal keratinocytes. In human keratinocytes, decreased expression of c-Rel causes a plethora of dysregulated cellular functions including impaired cell viability, increased apoptosis, and abnormalities during mitosis and cell cycle regulation. On the other hand, c-Rel shows aberrant expression in many epidermal tumors. Here, in the context of its role in different cell types and compared with other NF-κB subunits, we discuss the putative function of c-Rel as a regulator of epidermal homeostasis and mitotic progression. In addition, implications for disease pathophysiology with perturbed c-Rel function and abnormal homeostasis, such as epidermal carcinogenesis, will be discussed.

The c-Rel subunit of NF-κB is a crucial regulator of phenotype and motility of HaCaT keratinocytes.

The transcription factor NF-κB exerts key functions in epidermal homeostasis and carcinogenesis. Its c-Rel subunit is expressed in squamous cell carcinoma, and c-Rel down-regulation results in increased apoptosis, G2/M cell cycle delay with reduced proliferation and aberrant mitotic spindle formation. To further study the impact of c-Rel on essential keratinocyte features such as migration and epithelial morphology, c-Rel was down-regulated in HaCaT keratinocytes by a siRNA approach. This inhibition of c-Rel impaired the keratinocyte-typical clustered growth leading to a more scattered appearance of the cultures. The cells were more spindle-shaped and elongated, albeit without expression changes of markers characteristic for epithelial mesenchymal transition. In addition, wound healing-related migration and adhesion to type I collagen, fibronectin, laminin and vitronectin were significantly impaired. On the sub-cellular level, these functional features were not associated with quantitatively altered adhesion receptor or Rho-GTPase expression, but rather with a significantly reduced length of cell-matrix adhesion complexes and altered appearance of filamentous actin. Thus, our studies support a role for c-Rel in processes crucial for keratinocyte integrity and malignant transformation such as adhesion and migration.

c-Rel downregulation affects cell cycle progression of human keratinocytes.

The c-Rel protein, a member of the NF-κB transcription factor family, exerts unique and distinctive functions in various cell types. Although c-Rel is expressed in human epidermis, its functions in keratinocytes are poorly understood. Our small interfering RNA-based approach of c-Rel silencing in HaCaT keratinocytes induced altered cell morphology toward a spindle-shaped appearance. In addition, c-Rel downregulation resulted in increased apoptosis and significantly reduced proliferation towing to G2/M cell cycle delay, concomitant aberrant mitotic spindle formation, and induction of phospho-aurora A(Thr288). The relevance of c-Rel in epithelial carcinogenesis was further supported by detection of c-Rel expression in squamous cell carcinomas of the skin. Our studies indicate that c-Rel is a key regulator of cell fate decisions in keratinocytes such as cell growth and death and may have a role in epidermal carcinogenesis.

The two stem cell microRNA gene clusters C19MC and miR-371-3 are activated by specific chromosomal rearrangements in a subgroup of thyroid adenomas.

Thyroid adenomas are common benign human tumors with a high prevalence of about 5% of the adult population even in iodine sufficient areas. Rearrangements of chromosomal band 19q13.4 represent a frequent clonal cytogenetic deviation in these tumors making them the most frequent non-random chromosomal translocations in human epithelial tumors at all. Two microRNA (miRNA) gene clusters i.e. C19MC and miR-371-3 are located in close proximity to the breakpoint region of these chromosomal rearrangements and have been checked for a possible up-regulation due to the genomic alteration. In 4/5 cell lines established from thyroid adenomas with 19q13.4 rearrangements and 5/5 primary adenomas with that type of rearrangement both the C19MC and miR-371-3 cluster were found to be significantly overexpressed compared to controls lacking that particular chromosome abnormality. In the remaining cell line qRT-PCR revealed overexpression of members of the miR-371-3 cluster only which might be due to a deletion accompanying the chromosomal rearrangement in that case. In depth molecular characterization of the breakpoint in a cell line from one adenoma of this type reveals the existence of large Pol-II mRNA fragments as the most likely source of up-regulation of the C19MC cluster. The up-regulation of the clusters is likely to be causally associated with the pathogenesis of the corresponding tumors. Of note, the expression of miRNAs miR-520c and miR-373 is known to characterize stem cells and in terms of molecular oncology has been implicated in invasive growth of epithelial cells in vitro and in vivo thus allowing to delineate a distinct molecular subtype of thyroid adenomas. Besides thyroid adenomas rearrangements of 19q13.4 are frequently found in other human neoplasias as well, suggesting that activation of both clusters might be a more general phenomenon in human neoplasias.

ATROSAB, a humanized antagonistic anti-tumor necrosis factor receptor one-specific antibody.

Tumor necrosis factor (TNF) signals through two membrane receptors, TNFR1 and TNFR2, and TNFR1 is known to be the major pathogenic mediator of chronic and acute inflammatory diseases. Present clinical intervention is based on neutralization of the ligand TNF. Selective inhibition of TNF receptor 1 (TNFR1) provides an alternative opportunity to neutralize the pro-inflammatory activity of TNF while maintaining the advantageous immunological responses mediated by TNFR2, including immune regulation, tissue homeostasis and neuroprotection. We recently humanized a mouse anti-human TNFR1 monoclonal antibody exhibiting TNFR1-neutralizing activity. This humanized antibody has been converted into an IgG1 molecule (ATROSAB) containing a modified Fc region previously demonstrated to have greatly reduced effector functions. Purified ATROSAB, produced in CHO cells, showed strong binding to human and rhesus TNFR1-Fc fusion protein and mouse embryonic fibroblasts transfected with a recombinant TNFR1 fusion protein with an affinity identical to the parental mouse antibody H398. Using chimeric human/mouse TNFR1 molecules, the epitope of ATROSAB was mapped to the N-terminal region (amino acid residues 1-70) comprising the first cysteine-rich domain (CRD1) and the A1 sub-domain of CRD2. In vitro, ATROSAB inhibited typical TNF-mediated responses like apoptosis induction and activation of NFκB-dependent gene expression such as IL-6 and IL-8 production. These findings open the way to further analyze the therapeutic activity of ATROSAB in relevant disease models in non-human primates.