Transforming growth factor-alpha prevents detachment-induced inhibition of c-Src kinase activity, Bcl-XL down-regulation, and apoptosis of intestinal epithelial cells

Role of Membrane Cholesterol Levels in Activation of Lyn upon Cell Detachment

Cholesterol, a major component of the plasma membrane, determines the physical properties of biological membranes and plays a critical role in the assembly of membrane microdomains. Enrichment or deprivation of membrane cholesterol affects the activities of many signaling molecules at the plasma membrane. Cell detachment changes the structure of the plasma membrane and influences the localizations of lipids, including cholesterol. Recent studies showed that cell detachment changes the activities of a variety of signaling molecules. We previously reported that the localization and the function of the Src-family kinase Lyn are critically regulated by its membrane anchorage through lipid modifications. More recently, we found that the localization and the activity of Lyn were changed upon cell detachment, although the manners of which vary between cell types. In this review, we highlight the changes in the localization of Lyn and a role of cholesterol in the regulation of Lyn’s activation following cell detachment.

Oncogenic RAS-induced downregulation of ATG12 is required for survival of malignant intestinal epithelial cells

Activating mutations of RAS GTPase contribute to the progression of many cancers, including colorectal carcinoma. So far, attempts to develop treatments of mutant RAS-carrying cancers have been unsuccessful due to insufficient understanding of the salient mechanisms of RAS signaling. We found that RAS downregulates the protein ATG12 in colon cancer cells. ATG12 is a mediator of autophagy, a process of degradation and reutilization of cellular components. In addition, ATG12 can kill cells via autophagy-independent mechanisms. We established that RAS reduces ATG12 levels in cancer cells by accelerating its proteasomal degradation. We further observed that RAS-dependent ATG12 loss in these cells is mediated by protein kinases MAP2K/MEK and MAPK1/ERK2-MAPK3/ERK1, known effectors of RAS. We also demonstrated that the reversal of the effect of RAS on ATG12 achieved by the expression of exogenous ATG12 in cancer cells triggers both apoptotic and nonapoptotic signals and efficiently kills the cells. ATG12 is known to promote autophagy by forming covalent complexes with other autophagy mediators, such as ATG5. We found that the ability of ATG12 to kill oncogenic RAS-carrying malignant cells does not require covalent binding of ATG12 to other proteins. In summary, we have identified a novel mechanism by which oncogenic RAS promotes survival of malignant intestinal epithelial cells. This mechanism is driven by RAS-dependent loss of ATG12 in these cells.

Molecularly-targeted therapy for the oral cancer stem cells

Human cancer tissues are heterogeneous in nature and become differentiated during expansion of cancer stem cells (CSCs). CSCs initiate tumorigenesis, and are involved in tumor recurrence and metastasis. Furthermore, data show that CSCs are highly resistant to anticancer drugs. Cetuximab, a specific anti-epidermal growth factor receptor (EGFR) monoclonal antibody, is used in cancer treatment. Although development of resistance to cetuximab is well recognized, the underlying mechanisms remain unclear. Lapatinib, a dual inhibitor of epidermal growth factor receptor (EGFR)/ErbB2, has antiproliferative effects and is used to treat patients with ErbB2-positive metastatic breast cancer. In this review, cetuximab and lapatinib-resistant oral squamous cell carcinoma (OSCC) cells proliferation and migration signal transduction passway is discussed by introducing our research.

Loss of PRP4K drives anoikis resistance in part by dysregulation of epidermal growth factor receptor endosomal trafficking

Anoikis acts as a critical barrier to metastasis by inducing cell death upon cancer cell detachment from the extracellular matrix (ECM), thereby preventing tumor cell dissemination to secondary sites. The induction of anoikis requires the lysosomal-mediated downregulation of epidermal growth factor receptors (EGFRs) leading to termination of pro-survival signaling. In this study, we demonstrate that depletion of pre-mRNA splicing factor 4 kinase (PRP4K; also known as PRPF4B) causes dysregulation of EGFR trafficking and anoikis resistance. We also report a novel cytoplasmic localization of PRP4K at the late endosome, and demonstrate both nuclear and cytoplasmic localization in breast, lung and ovarian cancer tissue. Mechanistically, depletion of PRP4K leads to reduced EGFR degradation following cell detachment from the ECM and correlates with increased TrkB, vimentin and Zeb1 expression. As a result, PRP4K loss promotes sustained growth factor signaling and increased cellular resistance to anoikis in vitro and in a novel zebrafish xenotransplantation model of anoikis sensitivity, as well as increased metastasis in a mouse model of ovarian cancer. Thus, PRP4K may serve as a potential biomarker of anoikis sensitivity in ovarian and other epithelial cancers.

Regulation of antiapoptotic and cytoprotective pathways in colonic epithelial cells in ulcerative colitis

Ulcerative colitis is an inflammatory bowel disease involving the colon resulting in bloody diarrhea and increased risk of colorectal cancer in certain patient subgroups. Increased apoptosis in the epithelial cell layer causes increased permeability, especially during flares; this leads to translocation of luminal pathogens resulting in a continued inflammatory drive. The present work investigates how epithelial apoptosis is regulated in ulcerative colitis. The main results are that Fas mediated apoptosis is inhibited during flares of ulcerative colitis, probably by an upregulation of cellular inhibitor of apoptosis protein 2 (cIAP2) and cellular FLICE-like inhibitory protein. cIAP2 is upregulated in regenerative epithelial cells both in ulcerative colitis and in experimental intestinal wounds. Inhibition of cIAP2 decreases wound healing in vitro possibly through inhibition of migration. Altogether, it is shown that epithelial cells in ulcerative colitis responds to the hostile microenvironment by activation of cytoprotective pathways that tend to counteract the cytotoxic effects of inflammation. However, the present studies also show that epithelial cells produce increased amounts of reactive oxygen species during stimulation with tumor necrosis factor-α and interferon-γ resulting in DNA instability. The combined effect of increased DNA-instability and decreased apoptosis responses could lead to neoplasia.

ErbB2-dependent downregulation of a pro-apoptotic protein Perp is required for oncogenic transformation of breast epithelial cells

The ability of breast cancer cells to resist anoikis, apoptosis caused by detachment of the non-malignant epithelial cells from the extracellular matrix (ECM), is thought to be critical for breast tumor growth, invasion and metastasis. ErbB2, an oncoprotein that is often overproduced in breast tumors, can block breast cancer cell anoikis via mechanisms that are understood only in part. In an effort to understand them better we found that detachment of the non-malignant human breast epithelial cells from the ECM upregulates a protein Perp in these cells. Perp is a component of the desmosomes, multiprotein complexes involved in cell-to-cell adhesion. Perp can cause apoptosis via unknown mechanisms. We demonstrated that Perp upregulation by cell detachment is driven by detachment-induced loss of epidermal growth factor receptor (EGFR). We also found that Perp knockdown by RNA interference (RNAi) rescues detached cells from death which indicates that Perp contributes to their anoikis. We observed that ErbB2, when overexpressed in detached breast epithelial cells, causes Perp downregulation. Furthermore, ErbB2-directed RNAi or treatment with lapatinib, an ErbB2/EGFR small-molecule inhibitor used for breast cancer therapy, upregulated Perp in ErbB2-positive human breast and ovarian carcinoma cells. We established that ErbB2 downregulates Perp by activating an ErbB2 effector protein kinase Mek that blocks detachment-induced EGFR loss in a manner that requires the presence of a signaling protein Sprouty-2. Finally, we observed that restoration of the wild-type Perp levels in ErbB2-overproducing breast epithelial cells increases their anoikis susceptibility and blocks their clonogenicity in the absence of adhesion to the ECM. In summary, we have identified a novel mechanism of ErbB2-mediated mechanism of anoikis resistance of ErbB2-overproducing breast epithelial cells. This mechanism allows such cells to grow without adhesion to the ECM and is driven by ErbB2-induced activation of Mek, subsequent EGFR upregulation and further EGFR-dependent Perp loss.

Verification and refinement of cellular glycosphingolipid profiles using HPLC

Glycosphingolipids (GSLs) are hybrid molecules consisting of the sphingolipid ceramide linked to a mono- or oligo-saccharide. In comparison to other membrane lipids, the family of GSLs stands out because of the extensive variation in the carbohydrate headgroup. GSLs are cell surface binding partners, in cis with growth factor receptors, and in trans with bacterial toxins and viruses, and are among the host-derived membrane components of viral particles, including those of HIV. In spite of their biological relevance, GSL profiles of commonly used cell lines have been analyzed to different degrees. Here, we directly compare the GSL complements from CHO-K1, COS-7, HeLa, HEK-293, HEPG2, Jurkat, and SH-SY5Y cells using an HPLC-based method requiring modest amounts of material. Compared to previous studies, the HPLC-based analyses provided more detailed information on the complexity of the cellular GSL complement, qualitatively as well as quantitatively. In particular for cells expressing multiple GSLs, we found higher numbers of GSL species, and different levels of abundance. Our study thus extends our knowledge of biologically relevant lipids in widely used cell lines.

Upregulation of ATG3 contributes to autophagy induced by the detachment of intestinal epithelial cells from the extracellular matrix, but promotes autophagy-independent apoptosis of the attached cells

Detachment of nonmalignant intestinal epithelial cells from the extracellular matrix (ECM) triggers their growth arrest and, ultimately, apoptosis. In contrast, colorectal cancer cells can grow without attachment to the ECM. This ability is critical for their malignant potential. We found previously that detachment-induced growth arrest of nonmalignant intestinal epithelial cells is driven by their detachment-triggered autophagy, and that RAS, a major oncogene, promotes growth of detached cells by blocking such autophagy. In an effort to identify the mechanisms of detachment-induced autophagy and growth arrest of nonmalignant cells we found here that detachment of these cells causes upregulation of ATG3 and that ATG3 upregulation contributes to autophagy and growth arrest of detached cells. We also observed that when ATG3 expression is artificially increased in the attached cells, ATG3 promotes neither autophagy nor growth arrest but triggers their apoptosis. ATG3 upregulation likely promotes autophagy of the detached but not that of the attached cells because detachment-dependent autophagy requires other detachment-induced events, such as the upregulation of ATG7. We further observed that those few adherent cells that do not die by apoptosis induced by ATG3 become resistant to apoptosis caused by cell detachment, a property that is critical for the ability of normal epithelial cells to become malignant. We conclude that cell-ECM adhesion can switch ATG3 functions: when upregulated in detached cells in the context of other autophagy-promoting events, ATG3 contributes to autophagy. However, when overexpressed in the adherent cells, in the circumstances not favoring autophagy, ATG3 triggers apoptosis.

Anoikis of colon carcinoma cells triggered by β-catenin loss can be enhanced by tumor necrosis factor receptor 1 antagonists

Detachment of non-malignant epithelial cells from the extracellular matrix causes their apoptosis, a phenomenon called anoikis. By contrast, carcinoma cells are anoikis-resistant, and this resistance is thought to be critical for tumor progression. Many oncogenes trigger not only anti- but also pr-apoptotic signals. The proapoptotic events represent an aspect of a phenomenon called oncogenic stress, which acts as a safeguard mechanism blocking tumor initiation. In cells that become malignant, oncogene-induced antiapoptotic signals outbalance the proapoptotic ones. It is now thought that treatments blocking the antiapoptotic events but preserving the proapoptotic signals can be particularly effective in killing tumor cells. Whether or not oncogenes induce any proanoikis signals that can be used for enhancing the efficiency of approaches aimed at triggering anoikis of cancer cells has never been explored. β-Catenin is a major oncoprotein that is often activated in colorectal cancer and promotes tumor progression via mechanisms that are understood only in part. We found here that β-catenin triggers both anti- and proanoikis signals in colon cancer cells. We observed that the antianoikis signals prevail and the cells become anoikis-resistant. We further established that one proanoikis signal in these cells is triggered by β-catenin-induced downregulation of an apoptosis inhibitor tumor necrosis factor receptor 1 (TNFR1) and subsequent reduction of the activity of a transcription factor NF-κB (nuclear factor-κB), a mediator of TNFR1 signaling. We also found that the effect of β-catenin on TNFR1 requires the presence of transcription factor TCF1, a β-catenin effector. We demonstrated that ablation of β-catenin in colon cancer cells triggers their anoikis and that this anoikis is enhanced even further if low TNFR1 or NF-κB activity is artificially preserved in the β-catenin-deprived cells. Thus, inhibition of TNFR1 or NF-κB activity can be expected to enhance the efficiency of approaches aimed at blocking β-catenin-driven anoikis resistance of colon carcinoma cells.

Assessment of pharmacokinetic interaction of spirulina with glitazone in a type 2 diabetes rat model

The objective of the current study was to assess the possible pharmacokinetic interactions of spirulina with glitazones in an insulin resistance rat model. Wistar male albino rats were equally divided into five groups: insulin resistant rats+spirulina (500 mg/kg)+pioglitazone (10 mg/kg), insulin resistant rats+pioglitazone (10 mg/kg), insulin resistant rats+spirulina (500 mg/kg)+rosiglitazone (10 mg/kg), insulin resistant rats+rosiglitazone (10 mg/kg), and insulin resistant rats+spirulina (500 mg/kg). Described doses of pioglitazone, rosiglitazone, or spirulina were per orally administered and the plasma drug concentrations were determined. The pharmacokinetic parameters such as Tmax, Cmax, AUC(0-α), t1/2, and Kel were determined by plotting the drug concentration as a function of time. The data observed in this acute study indicated that there was no statistically significant difference in any of the pharmacokinetic parameters (Tmax, Cmax, AUC(0-α), t1/2, and Kel) of glitazones (pioglitazone, rosiglitazone) or spirulina, when they were coadministered. Given the promising results, this study concludes that the coadministration of spirulina does not influence the pharmacokinetics of glitazones in a type 2 diabetes rat model. Further chronic in vivo studies are recommended to assess the real time effect.

Cancer cell survival during detachment from the ECM: multiple barriers to tumour progression

Epithelial cells require attachment to the extracellular matrix (ECM) for survival. However, during tumour progression and metastasis, cancerous epithelial cells must adapt to and survive in the absence of ECM. During the past 20 years, several cellular changes, including anoikis, have been shown to regulate cell viability when cells become detached from the ECM. In this Opinion article, we review in detail how cancer cells can overcome or take advantage of these specific processes. Gaining a better understanding of how cancer cells survive during detachment from the ECM will be instrumental in designing chemotherapeutic strategies that aim to eliminate ECM-detached metastatic cells.

Dietary lutein modulates growth and survival genes in prostate cancer cells

Lutein is a carotenoid pigment present in fruits and vegetables that has anti-inflammatory and antitumor properties. In this study, we examined the effect of lutein on proliferation and survival-associated genes in prostate cancer (PC-3) cells. We found that in vitro culture of PC-3 cells with lutein induced mild decrease in proliferation that improved in combination treatment with peroxisome proliferator-activated receptor gamma (PPARγ) agonists and other chemotherapeutic agents. Flow cytometry analyses showed that lutein improved drug-induced cell cycle arrest and apoptosis in prostate cancer. Gene array and quantitative reverse transcription-polymerase chain reaction analyses showed that lutein altered the expression of growth and apoptosis-associated biomarker genes in PC-3 cells. These findings highlight that lutein modulates the expression of growth and survival-associated genes in prostate cancer cells.

Resveratrol and its metabolites bind to PPARs

Resveratrol, a modulator of several signaling proteins, can exert off-target effects involving the peroxisome proliferator-activated receptor (PPAR) transcription factors. However, evidence for the direct interaction between this polyphenol and PPARs is lacking. Here, we addressed the hypothesis that resveratrol and its metabolites control aspects of PPAR transcriptional activity through direct interaction with PPARs. Bioaffinity chromatographic studies with the immobilized ligand-binding domains (LBDs) of PPARγ and PPARα and isothermal titration calorimetry allowed the binding affinities of resveratrol, resveratrol 3-O-glucuronide, resveratrol 4-O-glucuronide, and resveratrol 3-O-sulfate to both PPAR-LBDs to be determined. Interaction of resveratrol, resveratrol 3-O-glucuronide, and resveratrol 4-O-glucuronide with PPARγ-LBD occurred with binding affinities of 1.4, 1.1, and 0.8 μM, respectively, although only resveratrol bound to the PPARα-LBD with a binding affinity of 2.7 μM. Subsequently, X-ray crystallographic studies were carried out to characterize resveratrol binding to the PPARγ-LBD at the molecular level. The electron density map from the crystal structure of the complex between PPARγ-LBD and resveratrol revealed the presence of one molecule of resveratrol bound to the LBD of PPARγ, with the ligand occupying a position close to that of other known PPARγ ligands. Transactivation assays were also performed in HepG2 cells, with the results showing that resveratrol was not a PPAR agonist but instead was able to displace rosiglitazone from PPARγ and Wy-14643 from PPARα with IC50 values of (27.4±1.8) μM and (31.7±2.5) μM, respectively. We propose that resveratrol acts as a PPAR antagonist through its direct interaction with PPARγ and PPARα.

Met receptor-induced Grb2 or Shc signals both promote transformation of intestinal epithelial cells, albeit they are required for distinct oncogenic functions

Background

Deregulation of receptor tyrosine kinases (RTK) contributes to the initiation and progression of intestinal-derived epithelial cancers, including colorectal cancer (CRC). However, the roles of the proximal signaling molecules engaged by RTKs in different oncogenic functions of CRC remain unclear.

Methods

Herein, the functional impact of expressing variant forms of the oncogenic Met receptor (Tpr-Met) that selectively recruit the adaptor proteins Grb2 or Shc was investigated in a model derived from normal intestinal epithelial cells (IEC-6). An RNA interference (RNAi) approach was used to define the requirement of Grb2 or Shc in Tpr-Met-transformed IEC-6 cells. Since Grb2 and Shc couple RTKs to the activation of the Ras/MEK/Erk and PI3K/Akt pathways, Erk and Akt phosphorylation/activation states were monitored in transformed IEC-6 cells, and a pharmacological approach was employed to provide insights into the roles of these pathways in oncogenic processes evoked by activated Met, and downstream of Grb2 and Shc.

Results

We show, for the first time, that constitutive activation of either Grb2 or Shc signals in IEC-6 cells, promotes morphological transformation associated with down-regulation of E-cadherin, as well as increased cell growth, loss of growth contact inhibition, anchorage-independent growth, and resistance to serum deprivation and anoikis. Oncogenic activation of Met was revealed to induce morphological transformation, E-cadherin down-regulation, and protection against anoikis by mechanisms dependent on Grb2, while Shc was shown to be partly required for enhanced cell growth. The coupling of activated Met to the Ras/MEK/Erk and PI3K/Akt pathways, and the sustained engagement of Grb2 or Shc in IECs, was shown to trigger negative feedback, limiting the extent of activation of these pathways. Nonetheless, morphological alterations and E-cadherin down-regulation induced by the oncogenic Tpr-Met, and by Grb2 or Shc signals, were blocked by MEK, but not PI3K, inhibitors while the enhanced growth and resistance to anoikis induced by Tpr-Met were nearly abolished by co-treatment with both inhibitors.

Conclusion

Overall, these results identify Grb2 and Shc as central signaling effectors of Met-driven progression of intestinal epithelial-derived cancers. Notably, they suggest that Grb2 may represent a promising target for the design of novel CRC therapies.

Gender, body mass index, and PPARγ polymorphism are good indicators in hyperuricemia prediction for Han Chinese

Hyperuricemia is closely associated with obesity and metabolic abnormalities, which is also an independent risk factor for cardiovascular diseases. The PPARγ gene, which is linked to obesity and metabolic abnormalities in Han Chinese, might be considered a top candidate gene that is involved in hyperuricemia. This study recruited 457 participants, aged 20-40 years old, to investigate the associations of the PPARγ gene and metabolic parameters with hyperuricemia. Three tag-single nucleotide polymorphisms, rs2292101, rs4684846, and rs1822825, of the PPARγ gene were selected to explore their association with hyperuricemia. Risk genotypes on rs1822825 of the PPARγ gene exhibited statistical significance with hyperuricemia (odds ratio: 1.9; 95% confidence interval: 1.05-3.57). Although gender, body mass index (BMI), serum total cholesterol concentration, or protein intake per day were statistically associated with hyperuricemia, the combination of BMI, gender, and rs1822825, rather than that of age, serum lipid profile, blood pressure, and protein intake per day, satisfied the predictability for hyperuricemia (sensitivity: 69.3%; specificity: 83.7%) in Taiwan-born obese Han Chinese. BMI, gender, and the rs1822825 polymorphism in the PPARγ gene appeared good biomarkers in hyperuricemia; therefore, these powerful indicators may be included in the prediction of hyperuricemia to increase the accuracy of the analysis.

PPARγ mediates the effects of WIN55,212-2, an synthetic cannabinoid, on the proliferation and apoptosis of the BEL-7402 hepatocarcinoma cells

Cannabis sativa has long been used as a traditional medicine in China. Among its effective compounds are cannabinoids. This study determined the effect of WIN55,212-2 (WIN), a synthetic cannabinoid, on the BEL-7402 human hepatocellular carcinoma (HCC) cell line. The results showed that WIN could decrease the proliferation of BEL-7402 cells. Moreover, WIN could cause apoptosis of the cells via up-regulation of Bax expression, down-regulation of Bcl-2 expression, induction of the mitochondrial membrane potential, increase of caspase-3, -8 and -9 activities, and induction of the cleavage of caspase-3 and poly-ADP-ribose polymerase (PARP). The WIN-induced apoptosis was accompanied by the up-regulation of PPARγ expression, the activation of PPARγ DNA binding activity, and a down-regulation of PPARγ target oncogene c-myc. Conversely, the effects of WIN could be attenuated by PPARγ antagonist GW9662, and the WIN induced PPARγ expression was partially attenuated by AM630, a cannabinoid receptor-2 antagonist, whereas the WIN-induced reduction of c-myc expression was partially restored by GW9662. Collectively, our results suggest that WIN can decrease the proliferation and cause apoptosis of the BEL-7402 cells via a mitochondrial-caspase pathway and mediated by PPARγ. These results may provide a basis for the application of WIN in HCC treatment.

Real-time monitoring of adipocyte differentiation using a capacitance sensor array

As obesity and its associated metabolic diseases become a worldwide epidemic, the demand for novel anti-obesity agents is increasing. We report a label-free and real-time monitoring method that uses a capacitance sensor array to screen anti-obesity agents. The results for the real-time capacitance of 3T3-L1 cells treated with 12 different chemicals extracted from natural products were consistent with the biochemical indicators of adipogenesis such as the expression of perilipin, the major protein coating the surface of lipid droplets in adipocytes. The data demonstrate that a capacitance change during adipocyte differentiation is closely associated with lipid accumulation in the cells, suggesting that adipocyte differentiation can be monitored in real time. This capacitance sensor might be used for label-free and real-time monitoring of adipocyte differentiation, and may facilitate the development of high throughput screening methods for anti-obesity drugs.

Osteoblast-adipocyte lineage plasticity in tissue development, maintenance and pathology

Osteoblasts and adipocytes share a common precursor in adult bone marrow and there is a degree of plasticity between the two cell lineages. This has important implications for the etiology of not only osteoporosis but also several other diseases involving an imbalance between osteoblasts and adipocytes. Understanding the process of differentiation of osteoblasts and adipocytes and their trans-differentiation is crucial in order to identify genes and other factors that may contribute to the pathophysiology of such diseases. Several transcriptional regulators have been shown to control osteoblast and adipocyte differentiation and function. Regulation of cell commitment occurs at the level of the progenitor cell through cross talk between complex signaling pathways and epigenetic mechanisms such as DNA methylation, chromatin remodeling, and microRNAs. Here we review the complex precursor cell microenvironment controlling osteoblastogenesis and adipogenesis during tissue development, maintenance, and pathology.

Human mesenchymal stem cells express neuronal markers after osteogenic and adipogenic differentiation

Mesenchymal stem cells (MSCs) are multipotent cells that are able to differentiate into mesodermal lineages (osteogenic, adipogenic, chondrogenic), but also towards non-mesodermal derivatives (e.g. neural cells). Recent in vitro studies revealed that, in the absence of any kind of differentiation stimuli, undifferentiated MSCs express neural differentiation markers, but the literature data do not all concur. Considering their promising therapeutic potential for neurodegenerative diseases, it is very important to expand our knowledge about this particular biological property of MSCs. In this study, we confirmed the spontaneous expression of neural markers (neuronal, glial and progenitor markers) by undifferentiated human MSCs (hMSCs) and in particular, we demonstrated that the neuronal markers βIII-tubulin and NeuN are expressed by a very high percentage of hMSCs, regardless of the number of culture passages and the culture conditions. Moreover, the neuronal markers βIII-tubulin and NeuN are still expressed by hMSCs after in vitro osteogenic and adipogenic differentiation. On the other hand, chondrogenically differentiated hMSCs are negative for these markers. Our findings suggest that the expression of neuronal markers could be common to a wide range of cellular types and not exclusive for neuronal lineages. Therefore, the expression of neuronal markers alone is not sufficient to demonstrate the differentiation of MSCs towards the neuronal phenotype. Functional properties analysis is also required.

Toward the goal of personalized therapy in pancreatic cancer by targeting the molecular phenotype

The purpose of this article is to provide a critical review of the molecular alterations in pancreatic cancer that are clinically investigated as therapeutic targets and their potential impact on clinical outcomes. Adenocarcinoma of exocrine pancreas is generally associated with poor prognosis and the conventional therapies are marginally effective. Advances in understanding the genetic regulation of normal and neoplastic development of pancreas have led to development and clinical evaluation of new therapeutic strategies that target the signaling pathways and molecular alterations in pancreatic cancer. Applications have begun to utilize the genetic targets as biomarkers for prediction of therapeutic responses and selection of treatment options. The goal of accomplishing personalized tumor-specific therapy with tolerable side effects for patients with pancreatic cancer is hopefully within reach in the foreseeable future.

Histone H3K9 methyltransferase G9a represses PPARγ expression and adipogenesis

PPARγ promotes adipogenesis while Wnt proteins inhibit adipogenesis. However, the mechanisms that control expression of these positive and negative master regulators of adipogenesis remain incompletely understood. By genome-wide histone methylation profiling in preadipocytes, we find that among gene loci encoding adipogenesis regulators, histone methyltransferase (HMT) G9a-mediated repressive epigenetic mark H3K9me2 is selectively enriched on the entire PPARγ locus. H3K9me2 and G9a levels decrease during adipogenesis, which correlates inversely with induction of PPARγ. Removal of H3K9me2 by G9a deletion enhances chromatin opening and binding of the early adipogenic transcription factor C/EBPβ to PPARγ promoter, which promotes PPARγ expression. Interestingly, G9a represses PPARγ expression in an HMT activity-dependent manner but facilitates Wnt10a expression independent of its enzymatic activity. Consistently, deletion of G9a or inhibiting G9a HMT activity promotes adipogenesis. Finally, deletion of G9a in mouse adipose tissues increases adipogenic gene expression and tissue weight. Thus, by inhibiting PPARγ expression and facilitating Wnt10a expression, G9a represses adipogenesis.

Anoikis resistance: an essential prerequisite for tumor metastasis

Metastasis is a multistep process including dissociation of cancer cells from primary sites, survival in the vascular system, and proliferation in distant target organs. As a barrier to metastasis, cells normally undergo an apoptotic process known as “anoikis,” a form of cell death due to loss of contact with the extracellular matrix or neighboring cells. Cancer cells acquire anoikis resistance to survive after detachment from the primary sites and travel through the circulatory and lymphatic systems to disseminate throughout the body. Because recent technological advances enable us to detect rare circulating tumor cells, which are anoikis resistant, currently, anoikis resistance becomes a hot topic in cancer research. Detailed molecular and functional analyses of anoikis resistant cells may provide insight into the biology of cancer metastasis and identify novel therapeutic targets for prevention of cancer dissemination. This paper comprehensively describes recent investigations of the molecular and cellular mechanisms underlying anoikis and anoikis resistance in relation to intrinsic and extrinsic death signaling, epithelial-mesenchymal transition, growth factor receptors, energy metabolism, reactive oxygen species, membrane microdomains, and lipid rafts.

Cell surface adhesion molecules and adhesion-initiated signaling: understanding of anoikis resistance mechanisms and therapeutic opportunities

Cells express various cell surface adhesion molecules (receptors) that not only mechanically serve as contacting sites between the cell and extracellular matrix (ECM) or adjacent cells, but also initiate intracellular signaling pathways modulating important cellular events including survival and proliferation. Normal cells undergo apoptosis when lacking ECM attachment. This type of cell death has been termed anoikis. Anoikis can be viewed as a normal process which ensures tissue homeostasis and failure to execute the anoikis program or resistance to anoikis could result in adherent cells surviving under suspension condition and proliferating at ectopic sites where the matrix proteins are different from those the cells originally contact. Resistance to anoikis is emerging as a hallmark of metastatic cancers which enables cancer cells to disseminate to distant organs through systemic circulation. In this review, we will discuss the molecular basis of adhesion-initiated signaling, the impact of loss of cell-ECM adhesion on normal cell survival, the role of cancer cell aggregate formation via intercellular adhesion under non-adherent condition, and mechanisms of anoikis resistance developed in metastatic cancer cells. Understanding of these aspects will provide opportunities to find new potential molecular targets, and therapeutic strategies based on these findings will likely prove to be more specific and effective.

Oncogenic ras-induced down-regulation of pro-apoptotic protease caspase-2 is required for malignant transformation of intestinal epithelial cells

Resistance of carcinoma cells to anoikis, apoptosis that is normally induced by loss of cell-to-extracellular matrix adhesion, is thought to be essential for the ability of these cells to form primary tumors, invade adjacent tissues, and metastasize to distant organs. Current knowledge about the mechanisms by which cancer cells evade anoikis is far from complete. In an effort to understand these mechanisms, we found that ras, a major oncogene, down-regulates protease caspase-2 (which initiates certain steps of the cellular apoptotic program) in malignant human and rat intestinal epithelial cells. This down-regulation could be reversed by inhibition of a protein kinase Mek, a mediator of Ras signaling. We also found that enforced down-regulation of caspase-2 in nonmalignant intestinal epithelial cells by RNA interference protected them from anoikis. Furthermore, the reversal of the effect of Ras on caspase-2 achieved by the expression of exogenous caspase-2 in detached ras-transformed intestinal epithelial cells promoted well established apoptotic events, such as the release of the pro-apoptotic mitochondrial factors cytochrome c and HtrA2/Omi into the cytoplasm of these cells, significantly enhanced their anoikis susceptibility, and blocked their long term growth in the absence of adhesion to the extracellular matrix. Finally, the blockade of the effect of Ras on caspase-2 substantially suppressed growth of tumors formed by the ras-transformed cells in mice. We conclude that ras-induced down-regulation of caspase-2 represents a novel mechanism by which oncogenic Ras protects malignant intestinal epithelial cells from anoikis, promotes their anchorage-independent growth, and allows them to form tumors in vivo.

Anti-inflammatory therapy for diabetic retinopathy

Diabetic retinopathy (DR) is one of the most common complications of diabetes. This devastating disease is a leading cause of blindness in people of working age in industrialized countries and affects the daily lives of millions of people. Despite tight glycemic control, blood pressure control and lipid-lowering therapy, the number of DR patients keeps growing and therapeutic approaches are limited. Moreover, there are significant limitations and side effects associated with the current therapies. Thus, there is a great need for development of new strategies for prevention and treatment of DR. Studies have shown that DR has prominent features of chronic, subclinical inflammation. This article focuses on the role of inflammation in DR and summarizes the progress of studies of anti-inflammatory strategies for DR.

FAK regulates intestinal epithelial cell survival and proliferation during mucosal wound healing

Background

Following damage to the intestinal epithelium, restoration of epithelial barrier integrity is triggered by a robust proliferative response. In other tissues, focal adhesion kinase (FAK) regulates many of the cellular processes that are critical for epithelial homeostasis and restitution, including cell migration, proliferation and survival. However, few studies to date have determined how FAK contributes to mucosal wound healing in vivo.

Methodology and Principal Findings

To examine the role of FAK in intestinal epithelial homeostasis and during injury, we generated intestinal epithelium (IE)-specific conditional FAK knockout mice. Colitis was induced with dextran-sulfate-sodium (DSS) and intestinal tissues were analyzed by immunohistochemistry and immunoblotting. While intestinal development occurred normally in mice lacking FAK, FAK-deficient animals were profoundly susceptible to colitis. The loss of epithelial FAK resulted in elevated p53 expression and an increased sensitivity to apoptosis, coincident with a failure to upregulate epithelial cell proliferation. FAK has been reported to function as a mechanosensor, inducing cyclin D1 expression and promoting cell cycle progression under conditions in which tissue/matrix stiffness is increased. Collagen deposition, a hallmark of inflammatory injury resulting in increased tissue rigidity, was observed in control and FAK knockout mice during colitis. Despite this fibrotic response, the colonic epithelium in FAK-deficient mice exhibited significantly reduced cyclin D1 expression, suggesting that proliferation is uncoupled from fibrosis in the absence of FAK. In support of this hypothesis, proliferation of Caco-2 cells increased proportionally with matrix stiffness in vitro only under conditions of normal FAK expression; FAK depleted cells exhibited reduced proliferation concomitant with attenuated cyclin D1 expression.

Conclusions

In the colon, FAK functions as a regulator of epithelial cell survival and proliferation under conditions of mucosal injury and a mechanosensor of tissue compliance, inducing repair-driven proliferation in the colonic epithelium through upregulation of cyclin D1.

A Role for PPARgamma in the Regulation of Cytokines in Immune Cells and Cancer

Peroxisome proliferator-activated receptor γ (PPARγ) is a ligand-activated transcription factor and a member of the nuclear receptor superfamily. PPARγ and its ligands appear to serve diverse biological functions. In addition to the well-studied effects of PPARγ on metabolism and cellular differentiation, abundant evidence suggests that PPARγ is an important regulator of the immune system and cancers. Since cytokines are not only key modulators of inflammation with pro- and anti-inflammatory functions but they also can either stimulate or inhibit tumor growth and progression, this review summarizes the role for PPARγ in the regulation of cytokine production and cytokine-mediated signal transduction pathways in immune cells and cancer.

Curcumin suppresses intestinal polyps in APC Min mice fed a high fat diet

Colorectal cancer (CRC) is a leading cause of cancer deaths in the United States. Various risk factors have been associated with CRC including increasing age and diet. Epidemiological and experimental studies have implicated a diet high in fat as an important risk factor for colon cancer. High fat diets can promote obesity resulting in insulin resistance and inflammation and the development of oxidative stress, increased cell proliferation, and suppression of apoptosis. Because of the high consumption of dietary fats, especially saturated fats, by Western countries, it is of interest to see if non-nutrient food factors might be effective in preventing or delaying CRC in the presence of high saturated fat intake. Curcumin (Curcuma longa), the main yellow pigment in turmeric, was selected to test because of its reported anti-tumor activity. APC Min mice, which develop intestinal polyps and have many molecular features of CRC, were fed a diet containing 35% pork fat, 33% sucrose, and a protein and vitamin mineral mixture (HFD) with or without 0.5% curcumin. These cohorts were compared to APC Min mice receiving standard rodent chow (RC) with 8% fat. APC Min mice fed the HFD for 3 months had a 23% increase in total number of polyps compared to APC Min mice on RC. Curcumin was able to significantly reverse the accelerated polyp development associated with the HFD suggesting it may be effective clinically in helping prevent colon cancer even when ingesting high amounts of fatty foods. The anti-tumor effect of curcumin was shown to be associated with enhanced apoptosis and increased efficiency of DNA repair. Since curcumin prevented the gain in body weight seen in APC Min mice ingesting the HFD, modulation of energy metabolism may also be a factor.

High doses of bone morphogenetic protein 2 induce structurally abnormal bone and inflammation in vivo

The major Food and Drug Association-approved osteoinductive factors in wide clinical use are bone morphogenetic proteins (BMPs). Although BMPs can promote robust bone formation, they also induce adverse clinical effects, including cyst-like bone formation and significant soft tissue swelling. In this study, we evaluated multiple BMP2 doses in a rat femoral segmental defect model and in a minimally traumatic rat femoral onlay model to determine its dose-dependent effects. Results of our femoral segmental defect model established a low BMP2 concentration range (5 and 10 μg/mL, total dose 0.375 and 0.75 μg in 75 μg total volume) unable to induce defect fusion, a mid-range BMP2 concentration range able to fuse the defect without adverse effects (30 μg/mL, total dose 2.25 μg in 75 μg total volume), and a high BMP2 concentration range (150, 300, and 600 μg/mL, total dose 11.25, 22.5, and 45 μg in 75 μg total volume) able to fuse the defect, but with formation of cyst-like bony shells filled with histologically confirmed adipose tissue. In addition, compared to control, 4 mg/mL BMP2 also induced significant tissue inflammatory infiltrates and exudates in the femoral onlay model that was accompanied by increased numbers of osteoclast-like cells at 3, 7, and 14 days. Overall, we consistently reproduced BMP2 side effects of cyst-like bone and soft tissue swelling using high BMP2 concentration approaching the typical human 1500 μg/mL.

Skeletal aging and the adipocyte program: New insights from an "old" molecule

Aging is associated with profound changes in bone mass and body composition. Emerging evidence supports the hypothesis that alterations in mesenchymal stromal cell fate are a critical etiologic factor. In addition, time-keeping at the cellular level is affected as aging progresses, particularly in the adipocyte. In this Extra View we discuss the interactive role of three molecules, PPARγ, nocturnin and IGF-I in regulating stem cell fate in the marrow and the potential implications of this network for understanding cellular aging.

Rosiglitazone inhibits proliferation of renal proximal tubular cells via down-regulation of ERK and Akt

Rosiglitazone has been reported to exert the protective effect against acute renal failure in animal models. However, the underlying mechanisms by which it protects the damaged kidney cells are poorly understood. The present study was therefore undertaken to examine the effect of rosiglitazone on cell proliferation and to determine its molecular mechanism in opossum kidney (OK) cells, an established renal proximal tubular cell line. Rosiglitazone treatment inhibited cell proliferation in a dose- and time-dependent manner, and such effects were not associated with induction of cell death. The anti-proliferative effect of rosiglitazone was accompanied by the cell cycle arrest at the G1 phase. Western blot analysis data showed that rosiglitazone caused down-regulation of extracellular signal-regulated kinase (ERK) and Akt pathway. Transfection of constitutively active forms of MEK (an upstream kinase of ERK) and Akt prevented the proliferation inhibition induced by rosiglitazone. Rosiglitazone facilitated the recovery of cells after cisplatin-mediated injury. Taken together, these data suggest that rosiglitazone induces inhibition of cell proliferation through ERK and Akt-dependent cell cycle arrest at the G1 phase. The cell cycle arrest may play a protective role in kidney cells by preventing injured cells from progressing in the cell cycle.

Intestinal epithelial cancer cell anoikis resistance: EGFR-mediated sustained activation of Src overrides Fak-dependent signaling to MEK/Erk and/or PI3-K/Akt-1

Herein, we investigated the survival roles of Fak, Src, MEK/Erk, and PI3-K/Akt-1 in intestinal epithelial cancer cells (HCT116, HT29, and T84), in comparison to undifferentiated and differentiated intestinal epithelial cells (IECs). We report that: (1) cancer cells display striking anoikis resistance, as opposed to undifferentiated/differentiated IECs; (2) under anoikis conditions and consequent Fak down-activation, cancer cells nevertheless exhibit sustained Fak-Src interactions and Src/MEK/Erk activation, unlike undifferentiated/differentiated IECs; however, HCT116 and HT29 cells exhibit a PI3-K/Akt-1 down-activation, as undifferentiated/differentiated IECs, whereas T84 cells do not; (3) cancer cells require MEK/Erk for survival, as differentiated (but not undifferentiated) IECs; however, T84 cells do not require Fak and HCT116 cells do not require PI3-K/Akt-1, in contrast to the other cells studied; (4) Src acts as a cornerstone in Fak-mediated signaling to MEK/Erk and PI3-K/Akt-1 in T84 cells, as in undifferentiated IECs, whereas PI3-K/Akt-1 is Src-independent in HCT116, HT29 cells, as in differentiated IECs; and (5) EGFR activity inhibition abrogates anoikis resistance in cancer cells through a loss of Fak-Src interactions and down-activation of Src/MEK/Erk (T84, HCT116, HT29 cells) and PI3-K/Akt-1 (T84 cells). Hence, despite distinctions in signaling behavior not necessarily related to undifferentiated or differentiated IECs, intestinal epithelial cancer cells commonly display an EGFR-mediated sustained activation of Src under anoikis conditions. Furthermore, such sustained Src activation confers anoikis resistance at least in part through a consequent sustenance of Fak-Src interactions and MEK/Erk activation, thus not only overriding Fak-mediated signaling to MEK/Erk and/or PI3-K/Akt-1, but also the requirement of Fak and/or PI3-K/Akt-1 for survival.

Primary human colonic epithelial cells are transiently protected from anoikis by a Src-dependent mechanism

Complete loss of cell anchorage triggers apoptosis in primary human colonic epithelial cells (CEC), a phenomenon known as anoikis. Besides the induction of pro-apoptotic events, activation of survival pathways was observed in detached intestinal epithelial cell lines, providing a transient apoptosis protection. However, nothing is known about molecular mechanisms protecting primary CEC from anoikis. In this study intact CEC crypts were isolated and kept in suspension, a condition which leads to the loss of cell-cell anchorage and induces anoikis. To reconstitute cell-cell contacts, cells were centrifuged to form cell aggregates. Induction of apoptosis was assessed by caspase-3 activity assay; activation of survival pathways was analyzed by Western blot. Immediately after loss of cell anchorage a rapid activation of survival proteins was observed before active caspase-3 could be detected. Src hyperactivation significantly contributed to transient protection from anoikis in CEC because its inhibition reversed the protecting effect of re-establishment of cell contacts. Basal levels of active Src in CEC from patients with inflammatory bowel disease were markedly reduced compared to control patients. These results demonstrate that loss of cell anchorage activates survival pathways in primary human CEC providing transient anoikis protection. Src is an important mediator of this mechanism and therefore constitutes a key regulatory molecule coordinating survival signals mediated by cell adhesion in primary human CEC.

Oncogenic ras-induced down-regulation of autophagy mediator Beclin-1 is required for malignant transformation of intestinal epithelial cells

Detachment of non-malignant epithelial cells from the extracellular matrix causes their growth arrest and, ultimately, death. By contrast, cells composing carcinomas, cancers of epithelial origin, can survive and proliferate without being attached to the extracellular matrix. These properties of tumor cells represent hallmarks of malignant transformation and are critical for cancer progression. Previously we identified several mechanisms by which ras, a major oncogene, blocks detachment-induced apoptosis of intestinal epithelial cells, but mechanisms by which Ras promotes proliferation of those cells that remain viable following detachment are unknown. We show here that detachment of non-malignant intestinal epithelial cells promotes formation of autophagosomes, vacuole-like structures that mediate autophagy (a process of cellular self-cannibalization), and that oncogenic ras prevents this autophagosome formation. We also found that ras activates a GTPase RhoA, that RhoA promotes activation of a protease calpain, and that calpain triggers degradation of Beclin-1, a critical mediator of autophagy, in these cells. The reversal of the effect of ras on Beclin-1 (achieved by expression of exogenous Beclin-1) promoted autophagosome formation following cell detachment, significantly reduced the fraction of detached cells in the S phase of the cell cycle and their rate of proliferation without affecting their viability. Furthermore, RNA interference-induced Beclin-1 down-regulation in non-malignant intestinal epithelial cells prevented detachment-dependent reduction of the fraction of these cells in the S phase of the cell cycle. Thus, ras oncogene promotes proliferation of those malignant intestinal epithelial cells that remain viable following detachment via a distinct novel mechanism that involves Ras-induced down-regulation of Beclin-1.

Cellular aggregation facilitates anoikis in MDCK cells

Anoikis is a specific type of apoptosis caused by the detachment of anchorage-dependent cells from their supportive matrix. Aggregation of suspended cells is believed to suppress anoikis. Here we describe the effects of cellular aggregation on anoikis in Madin-Darby canine kidney (MDCK) cells. Suspension cultures of MDCK cells grown under conditions known to induce extensive cellular aggregation were less able to reattach to culture dishes, exhibited higher caspase-8 activity, and contained more sub-G(1) cells than suspension cultures did with less cellular aggregation. When suspension cultures of MDCK cells were separated into aggregated cells and single cells, the aggregated cells had low caspase-8 activity regardless of suspension conditions, whereas the single cells had higher caspase-8 activity that increased with an increasing degree of aggregation. These results suggest that cell-cell interactions in cellular aggregates of suspended MDCK cells facilitate anoikis, causing more apoptosis in individual cells than when these interactions are absent.

Peroxisome proliferator-activated receptors in diabetic nephropathy

Diabetic nephropathy is a leading cause of end-stage renal disease, which is increasing in incidence worldwide, despite intensive treatment approaches such as glycemic and blood pressure control in patients with diabetes mellitus. New therapeutic strategies are needed to prevent the onset of diabetic nephropathy. Peroxisome proliferator-activated receptors (PPARs) are ligand-activated nuclear transcription factors that play important roles in lipid and glucose homeostases. These agents might prevent the progression of diabetic nephropathy, since PPAR agonists improve dyslipidemia and insulin resistance. Furthermore, data from murine models suggest that PPAR agonists also have independent renoprotective effects by suppressing inflammation, oxidative stress, lipotoxicity, and activation of the renin-angiotensin system. This review summarizes data from clinical and experimental studies regarding the relationship between PPARs and diabetic nephropathy. The therapeutic potential of PPAR agonists in the treatment of diabetic nephropathy is also discussed.

Characterization of a novel polymorphism in PPARG regulatory region associated with type 2 diabetes and diabetic retinopathy in Italy

Peroxisome proliferator-activated receptor gamma polymorphisms have been widely associated with type 2 diabetes, although their role in the pathogenesis of vascular complications is not yet demonstrated. In this study, a cohort of 211 type 2 diabetes, 205 obese, and 254 control individuals was genotyped for Pro12Ala, C1431T, C-2821T polymorphisms, and for a newly identified polymorphism (A-2819G). The above-mentioned polymorphisms were analyzed by gene-specific PCR and direct sequencing of all samples. A significant difference was found for -2819G frequency when patients with type 2 diabetes—particularly diabetic women with the proliferative retinopathy—were compared with healthy control individuals. In conclusion, we identified a novel polymorphism, A-2819G, in PPARG gene, and we found it to be associated with type 2 diabetes and proliferative retinopathy in diabetic females. In the analyzed population, this variant represents a genetic risk factor for developing the diabetic retinopathy, whereas Pro12Ala and C1431T do not.

PPARgamma-2 and BMPR2 genes were differentially expressed in peripheral blood of SLE patients with osteonecrosis

Most researchers believe that the peroxisome proliferative activated receptor gamma (PPARgamma-2) and bone morphogenetic protein receptor type II (BMPR2) play important roles in steroid-induced osteonecrosis (ON). However, the molecular mechanism of this process is still unclear. Recent studies indicate that steroid treatments cause adipocyte formation due to differentiation of mesenchymal stem cells, which then prevents osteoblast formation. This study examined PPARgamma-2, bone morphogenetic protein 2 (BMP2), and BMPR2 in patients with systemic lupus erythromatosus (SLE) who eventually developed ON after prolonged steroid treatment. The subjects of this experiment included 220 SLE patients who had undergone steroid treatment for at least 2 years. Fifty-five of the 220 patients were ON patients, and 165 were non-ON patients. Real-time PCR was performed to analyze the expression of the PPARgamma-2, BMP2, and BMPR2 mRNA in the peripheral blood of these patients. The results indicated that the expression of PPARgamma-2 mRNA increased 37% in the ON patients' peripheral blood, but the expression of BMPR2 mRNA decreased 57%. The average expression of the PPARgamma-2 mRNA in the ON patients was significantly higher than that in the non-ON patients (p = 0.044). Conversely, the expression of BMPR2 mRNA was significantly lower than that in non-ON patients (p = 0.036), but the expression of BMP2 mRNA did not significantly differ. This study demonstrated that the PPARgamma-2 and BMPR2 have important roles in the ON process after prolonged steroid administration in SLE patients; however, the detailed molecular mechanisms of this process require further study.