Johannes Kleemann

Dimethylfumarate inhibits melanoma cell proliferation via p21 and p53 induction and bcl-2 and cyclin B1 downregulation

Recent evidence suggests that dimethylfumarate (DMF), known as a highly potent anti-psoriatic agent, might have anti-tumorigenic properties in melanoma. It has recently been demonstrated that DMF inhibits melanoma proliferation by apoptosis and cell cycle inhibition and therefore inhibits melanoma metastasis. Nonetheless, the underlying mechanisms remain to be evaluated. To elucidate the effects of DMF on melanoma cell lines (A375, SK-Mel), we first performed cytotoxicity assays. No significant lactatedehydogenase (LDH) release could be found. In further analysis, we showed that DMF suppresses melanoma cell proliferation in a concentration-dependent manner. To examine whether these effects are conveyed by apoptotic mechanisms, we studied the amount of apoptotic nucleosomes and caspase 3/7 activity using ELISA analysis. Significant apoptosis was induced by DMF in both cell lines, and this could be paralleled with bcl-2 downregulation and PARP-1 cleavage. We also performed cell cycle analysis and found that DMF induced concentration-dependent arrests of G0/G1 as well as G2/M. To examine the underlying mechanisms of cell cycle arrest, we analyzed the expression profiles of important cell cycle regulator proteins such as p53, p21, cyclins A, B1, and D1, and CDKs 3, 4, and 6. Interestingly, DMF induced p53 and p21 yet inhibited cyclin B1 expression in a concentration-dependent manner. Other cell cycle regulators were not influenced by DMF. The knockdown of DMF induced p53 via siRNA led to significantly reduced apoptosis but had no influence on cell cycle arrest. We examined the adhesion of melanoma cells on lymphendothelial cells during DMF treatment and found a significant reduction in interaction. These data provide evidence that DMF inhibits melanoma proliferation by reinduction of important cell cycle inhibitors leading to a concentration-dependent G0/G1 or G2/M cell cycle arrest and induction of apoptosis via downregulation of bcl-2 and induction of p53 and PARP-1 cleavage. Hence, DMF might be an interesting agent in the treatment of melanoma and is worth further investigation in vivo.

Dimethylfumarate effectively inhibits lymphangiogenesis via p21 induction and G1 cell cycle arrest

Different pathologies, such as lymphoedema, cancer or psoriasis, are associated with abnormal lymphatic vessel formation. Therefore, influencing lymphangiogenesis is an interesting target. Recent evidence suggests that dimethylfumarate (DMF), an antipsoriatic agent, might have antitumorigenic and antilymphangiogenic properties. To prove this assumption, we performed proliferation and functional assays with primary human dermal lymphendothelial cells (DLEC). We could demonstrated that DMF suppresses DLEC proliferation and formation of capillary‐like structures. Underlying apoptotic mechanisms could be ruled out. Cell cycle analysis demonstrated a pronounced G1‐arrest. Further evaluations revealed increases in p21 expression. In addition, DMF suppressed Cyclin D1 and Cyclin A expression in a concentration‐dependent manner. p21 knockdown experiments demonstrated a p21‐dependent mechanism of regulation. Further analysis showed an increased p21 mRNA expression after DMF treatment. This transcriptional regulation was enforced by post‐transcriptional and post‐translational mechanisms. In addition, we could demonstrate that the combination of a proteasomal inhibitor and DMF superinduced the p21 expression. Hence, DMF is a new antilymphangiogenic compound and might be used in various illnesses associated with increased lymphangiogenesis.

The histone deacetylase inhibitor trichostatin a decreases lymphangiogenesis by inducing apoptosis and cell cycle arrest via p21-dependent pathways

BackgroundThe formation of new lymphatic vessels provides an additional route for tumour cells to metastasize. Therefore, inhibiting lymphangiogenesis represents an interesting target in cancer therapy. First evidence suggests that histone deacetylase inhibitors (HDACi) may mediate part of their antitumor effects by interfering with lymphangiogenesis. However, the underlying mechanisms of HDACi induced anti-lymphangiogenic properties are not fully investigated so far and in part remain unknown.MethodsHuman lymphatic endothelial cells (LEC) were cultured in vitro and treated with or without HDACi. Effects of HDACi on proliferation and cell cycle progress were analysed by BrdU assay and flow cytometry. Apoptosis was measured by quantifying mono- and oligonucleosomes in the cytoplasmic fraction of cell lysates. In vitro lymphangiogenesis was investigated using the Matrigel short term lymphangiogenesis assay. The effects of TSA on cell cycle regulatory proteins and apoptosis-related proteins were examined by western blotting, immunofluorescence staining and semi-quantitative RT-PCR. Protein- and mRNA half-life of p21 were analysed by western blotting and quantitative RT-PCR. The activity of the p21 promoter was determined using a dual luciferase assay and DNA-binding activity of Sp1/3 was investigated using EMSA. Furthermore, siRNA assays were performed to analyse the role of p21 and p53 on TSA-mediated anti-lymphangiogenic effects.ResultsWe found that HDACi inhibited cell proliferation and that the pan-HDACi TSA induced G0/G1 arrest in LEC. Cell cycle arrest was accompanied by up-regulation of p21, p27 and p53. Additionally, we observed that p21 protein accumulated in cellular nuclei after treatment with TSA. Moreover, we found that p21 mRNA was significantly up-regulated by TSA, while the protein and mRNA half-life remained largely unaffected. The promoter activity of p21 was enhanced by TSA indicating a transcriptional mechanism. Subsequent EMSA analyses showed increased constitutive Sp1/3-dependent DNA binding in response to HDACi. We demonstrated that p53 was not required for TSA induced p21 expression and growth inhibition of LECs. Interestingly, siRNA-mediated p21 depletion almost completely reversed the anti-proliferative effects of TSA in LEC. In addition, TSA induced apoptosis by cytochrome c release contributed to activating caspases-9, −7 and −3 and downregulating the anti-apoptotic proteins cIAP-1 and −2.ConclusionsIn conclusion, we demonstrate that TSA - a pan-HDACi - has distinct anti-lymphangiogenic effects in primary human lymphatic endothelial cells by activating intrinsic apoptotic pathway and cell cycle arrest via p21-dependent pathways.

Peroxisome proliferator-activated receptor (PPAR) α and δ activators induce ICAM-1 expression in quiescent non stimulated endothelial cells

BackgroundPeroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors that are implicated in the regulation of lipid and glucose homeostasis. PPAR agonists have been shown to control inflammatory processes, in part by inhibiting the expression of distinct proinflammatory genes such as vascular cell adhesion molecule-1 (VCAM-1), IL-8, and intercellular adhesion molecule-1 (ICAM-1). ICAM-1 is an important endothelial membrane receptor that facilitates the transmigration of leukocytes across the endothelium. To date, the influence of PPARα and δ activators on the expression of ICAM-1 in non-induced, quiescent endothelial cells has been unclear. Therefore, we examined the effects of various PPARα and δ agonists on the expression of ICAM-1 in non-stimulated primary human endothelial cells.ResultsWe found that PPARα and PPARδ agonists significantly induced ICAM-1 surface, intracellular protein, and mRNA expression in a time and concentration-dependent manner. The PPARδ induced ICAM-1 expression could be paralleled with a significantly increased T-cell adherence to the endothelial cells whereas PPARα failed to do so. Transcriptional activity studies using an ICAM-1 reporter gene constructs revealed that PPARδ, but not PPARα agonists induced gene expression by stimulating ICAM-1 promoter activity via an Sp1 transcription factor binding site and inhibit the binding of the transcription factors Sp1 and Sp3. Furthermore, we performed mRNA stability assays and found that PPARα and PPARδ agonists increased ICAM-1 mRNA stability.ConclusionTherefore, our data provide the first evidence that PPARα and PPARδ agonists induce ICAM-1 expression in non-stimulated endothelial cells via transcriptional and posttranscriptional mechanisms.

STAT6-Dependent Collagen Synthesis in Human Fibroblasts Is Induced by Bovine Milk

Since the domestication of the urus, 10.000 years ago, mankind utilizes bovine milk for different purposes. Besides usage as a nutrient also the external application of milk on skin has a long tradition going back to at least the ancient Aegypt with Cleopatra VII as a great exponent. In order to test whether milk has impact on skin physiology, cultures of human skin fibroblasts were exposed to commercial bovine milk. Our data show significant induction of proliferation by milk (max. 2,3-fold, EC50: 2,5% milk) without toxic effects. Surprisingly, bovine milk was identified as strong inducer of collagen 1A1 synthesis at both, the protein (4-fold, EC50: 0,09% milk) and promoter level. Regarding the underlying molecular pathways, we show functional activation of STAT6 in a p44/42 and p38-dependent manner. More upstream, we identified IGF-1 and insulin as key factors responsible for milk-induced collagen synthesis. These findings show that bovine milk contains bioactive molecules that act on human skin cells. Therefore, it is tempting to test the herein introduced concept in treatment of atrophic skin conditions induced e.g. by UV light or corticosteroids.

Activation of PKB/Akt and p44/42 by mechanical stretch utilizes desmosomal structures and the keratin filament

BACKGROUND Mechanical stress is an ubiquitous challenge of human cells with fundamental impact on cell physiology. Previous studies have shown that stretching promotes signalling cascades involved in proliferation and tissue enlargement. OBJECTIVE The present study is dedicated to learn more about cellular structures contributing to perception and signal transmission of cell stretch. In particular, we hypothesized that desmosmal contacts and the adjacent keratin filament build an intercellular matrix providing information about the mechanical load. METHODS Epidermal cells with different keratin equipment were seeded on flexible silicon dishes and stretched. As read out parameter the activation of PKB/Akt and p44/42 was monitored by Western blotting. Likewise desomosomal contacts were manipulated by depletion or addition of calcium. Moreover, desmoglein 3 and desmocollin 3 were blocked by either specific antibodies or siRNA. RESULTS It was found that the omission of calcium from the medium, a necessary cofactor for desmosomal cadherins, inhibited stretch mediated activation of PKB/Akt and p44/42. The relevance of desmosomes in this context was further substantiated by experiments using a desmoglein 3 blocking antibody (AK23) and siRNA against desmocollin 3. Moreover, disruption of the keratin filament by sodium orthovanadate also abrogates PKB/Akt and p44/42 activation in response to stretch. Likewise, KEB-7 keratinocytes harbouring a mutation in the keratin 14 gene and genetically modified keratinocytes devoid of any keratin show an altered signalling after stretch indicating the relevance of the keratin filament in this context. CONCLUSION Besides their important role in cell architecture our results identify desmosomes and keratins as mechanosensing structures.

Tumor Neoangiogenesis and Flow Congestion: A Parallel to the Braess Paradox?

Although tumor angiogenesis is considered as a critical parameter in tumor growth, antiangiogenic monotherapy lags far behind expectations. Applying a mathematical model from route planning, known as the Braess paradox, provides an explanation by showing that in some constellations, more roads can lead to more traffic jams. It is one of the most widely accepted paradigms in tumor biology that growth of solid tumors is restricted to the ample supply of nutrients. Accordingly, it is assumed that passive diffusion is sufficient for tumor growth only to a size of ≈2 mm in diameter; thus, the tumor connects to capillaries to satisfy its hunger. It was Folkman1 who first established in 1971 the concept of a tumor that actively attracts capillaries sprouting into the tumor tissue. In this model, the hypoxia-inducible factor 1, a heterodimeric transcription factor consisting of the constitutively hypoxia-inducible factor 1β and the oxygen-sensitive hypoxia-inducible factor 1α subunit, plays a key role. Under normoxic conditions, hypoxia-inducible factor 1α is proteasomally degraded, whereas hypoxia stabilized the dimer allowing transcription of a set of genes. Among those, members of the vascular endothelial growth factor (VEGF) family are of particular importance as they direct endothelial cell migration along the hypoxic gradient.2 Together with the proliferation-inducing properties of VEGF, new blood vessels are formed connecting the tumor to the blood circulation. These findings inspired the development of antiangiogenic tumor therapy as an effective tool to combat the growth of solid tumors. As a result, >60 antiangiogenic compounds of different origin have been identified and tested in patients to date.3 In particular, antibodies directed against VEGF-A (bevacizumab) and VEGF receptor 2 (ramucirumab), as well as endogenous inhibitors of angiogenesis, such as angiostatin and endostatin, are viewed as highly potential drugs to halt vessel growth.4,5 Furthermore, regimens utilizing …

Directing adipose‐derived stem cells into keratinocyte‐like cells: impact of medium composition and culture condition

Adipose‐derived stem cells (ASC) are known to transdifferentiate into a wide range of different cell species in vitro including along the epidermal lineage. This property makes them a promising tool for regenerative medicine to restore the epidermal barrier.

Acting without Central Agent—Considerations for a Self-Model at the Cellular Level

Fossil discoveries suggest that life began on earth about 3.8 billion years ago. At first there were single-celled organisms with no nuclei (prokaryotes), later ∼2.7 billion years ago, protozoa developed which are cells with a nucleus (eukaryotes). Only since about 800 million years have multicellular organisms (eumetazoa) emerged and with that the ability to evolve specialized cells, such as nerve cells. The function of nerve cells is to receive information from both the internal and external environment, interpret and translate it into body reactions e.g., muscle contractions which change the body’s position. In radially symmetric multicellular organisms such as jellyfish, there is a loose network of nerves which condenses in higher organisms with bilateral symmetry to a central nervous system. In bilateria the main axis is mostly in the direction of movement, where, at the front, uptake of nutrients takes place. This defines the starting point for cephalization with the emergence of a cerebral ganglion. Later in evolution, according to the prosomeric model the morphology of the vertebrate forebrain emerges from segmental structures, the number, and interconnections of ganglia increased forming a brain, the place where we assume cognition and intelligence is located. The everyday neuro-fixation ignores indications that already single cells show complex behavior patterns with a kind of basal intelligence and the ability to memorize. How do single cells accomplish this? In the following we hypothesize that cells may have a kind of self-model, a representation of themselves.