Up-regulation of macrophage inflammatory protein-3 alpha/CCL20 and CC chemokine receptor 6 in psoriasis

Autoimmunity plays a key role in the immunopathogenesis of psoriasis; however, little is known about the recruitment of pathogenic cells to skin lesions. We report here that the CC chemokine, macrophage inflammatory protein-3 alpha, recently renamed CCL20, and its receptor CCR6 are markedly up-regulated in psoriasis. CCL20-expressing keratinocytes colocalize with skin-infiltrating T cells in lesional psoriatic skin. PBMCs derived from psoriatic patients show significantly increased CCR6 mRNA levels. Moreover, skin-homing CLA+ memory T cells express high levels of surface CCR6. Furthermore, the expression of CCR6 mRNA is 100- to 1000-fold higher on sorted CLA+ memory T cells than other chemokine receptors, including CXCR1, CXCR2, CXCR3, CCR2, CCR3, and CCR5. In vitro, CCL20 attracted skin-homing CLA+ T cells of both normal and psoriatic donors; however, psoriatic lymphocytes responded to lower concentrations of chemokine and showed higher chemotactic responses. Using ELISA as well as real-time quantitative PCR, we show that cultured primary keratinocytes, dermal fibroblasts, and dermal microvascular endothelial and dendritic cells are major sources of CCL20, and that the expression of this chemokine can be induced by proinflammatory mediators such as TNF-alpha/IL-1 beta, CD40 ligand, IFN-gamma, or IL-17. Taken together, these findings strongly suggest that CCL20/CCR6 may play a role in the recruitment of T cells to lesional psoriatic skin.

The evolution of H5N1 influenza viruses in ducks in southern China

The pathogenicity of avian H5N1 influenza viruses to mammals has been evolving since the mid-1980s. Here, we demonstrate that H5N1 influenza viruses, isolated from apparently healthy domestic ducks in mainland China from 1999 through 2002, were becoming progressively more pathogenic for mammals, and we present a hypothesis explaining the mechanism of this evolutionary direction. Twenty-one viruses isolated from apparently healthy ducks in southern China from 1999 through 2002 were confirmed to be H5N1 subtype influenza A viruses. These isolates are antigenically similar to A/Goose/Guangdong/1/96 (H5N1) virus, which was the source of the 1997 Hong Kong "bird flu" hemagglutinin gene, and all are highly pathogenic in chickens. The viruses form four pathotypes on the basis of their replication and lethality in mice. There is a clear temporal pattern in the progressively increasing pathogenicity of these isolates in the mammalian model. Five of six H5N1 isolates tested replicated in inoculated ducks and were shed from trachea or cloaca, but none caused disease signs or death. Phylogenetic analysis of the full genome indicated that most of the viruses are reassortants containing the A/Goose/Guangdong/1/96-like hemagglutinin gene and the other genes from unknown Eurasian avian influenza viruses. This study is a characterization of the H5N1 avian influenza viruses recently circulating in ducks in mainland China. Our findings suggest that immediate action is needed to prevent the transmission of highly pathogenic avian influenza viruses from the apparently healthy ducks into chickens or mammalian hosts.

Loss of heterozygosity in normal tissue adjacent to breast carcinomas

Loss of heterozygosity (LOH) was detected in morphologically normal lobules adjacent to breast cancers. The most frequent aberration was at chromosome 3p22-25; of ten cases with this LOH in the carcinoma, six displayed the same LOH in adjacent normal lobules. This suggests that in a subset of sporadic breast cancers, a tumor suppresser gene at 3p22-25 may be important in initiation or early progression of tumorigenesis. Among sixteen breast cancers with LOH at 17p13.1 and five breast cancers with LOH at 11p15.5, one case each displayed the same LOH in adjacent normal lobules. Thus the molecular heterogeneity that characterizes invasive breast cancers may occur at the earliest detectable stages of progression.

Is plasminogen activator inhibitor-1 the molecular switch that governs urokinase receptor-mediated cell adhesion and release?

Induction of the urokinase type plasminogen activator receptor (uPAR) promotes cell adhesion through its interaction with vitronectin (VN) in the extracellular matrix, and facilitates cell migration and invasion by localizing uPA to the cell surface. We provide evidence that this balance between cell adhesion and cell detachment is governed by PA inhibitor-1 (PAI-1). First, we demonstrate that uPAR and PAI-1 bind to the same site in VN (i.e., the amino-terminal somatomedin B domain; SMB), and that PAI-1 competes with uPAR for binding to SMB. Domain swapping and mutagenesis studies indicate that the uPAR-binding sequence is located within the central region of the SMB domain, a region previously shown to contain the PAI-1-binding motif. Second, we show that PAI-1 dissociates bound VN from uPAR and detaches U937 cells from their VN substratum. This PAI-1 mediated release of cells from VN appears to occur independently of its ability to function as a protease inhibitor, and may help to explain why high PAI-1 levels indicate a poor prognosis for many cancers. Finally, we show that uPA can rapidly reverse this effect of PAI-1. Taken together, these results suggest a dynamic regulatory role for PAI-1 and uPA in uPAR-mediated cell adhesion and release.

Bax protein expression is increased in Alzheimer's brain: correlations with DNA damage, Bcl-2 expression, and brain pathology

We have shown that many neurons in Alzheimer's disease (AD) exhibit terminal deoxynucleotidyl transferase (TdT) labeling for DNA strand breaks, and upregulation of Bcl-2 is associated with neurons exhibiting nuclear DNA fragmentation, while downregulation of Bcl-2 is associated with tangle-bearing neurons in AD brains. Consequently, we examined the expression of bcl-associated X (Bax) protein in AD brain. Immunoreactivity for Bax was seen in neurons and microglia of the hippocampal formation, and was elevated in the majority of AD cases as compared to control cases. Interestingly, 3 transitional cases, which had mild degeneration changes, exhibited relatively high levels of Bax immunoreactivity. Most Bax-positive neurons showed either TdT-labeled nuclei or Bcl-2 immunoreactivity. Although Bax immunoreactivity was detected within most early tangle-bearing neurons, many Bax-positive neurons did not colocalize with later-stage tangle-bearing neurons. In regions containing relatively few tangles in mild AD brains, many TdT-labeled neurons were immunolabeled with Bax antibody and most of them lacked evidence of neurofibrillary changes. These findings suggest that Bax may contribute to neuronal cell death in AD. Furthermore, DNA damage and the upregulation of Bax appear to precede tangle formation or may represent an alternative pathway of cell death in AD.

An improved procedure for utilizing terminal transferase to add homopolymers to the 3' termini of DNA

Terminal deoxynucleotidyl transferase (E.C.2.7.7.3.1.) from calf thymus was used to add homopolymer tails to duplex DNA with 3' protruding, even, or 3' recessive ends. A gel electrophoresis method was employed to analyze the tail length and the percent of DNA with tails. In all the tailing reactions, dA, dT, and dC tails from CoCl2-containing buffer were longer than those from MnCl2 - or MgCl2 - containing buffers, whereas dG tails from MnCl2 -containing buffer were the longest. By varying the ratio of dNTP over DNA terminus and the concentration of terminal transferase, optimal conditions were found for adding dG or dC tails of 10-25 nucleotides in length and dA and dT tails of 20-40 nucleotides in length to duplex DNA with all types of 3' termini.

Neuronal DNA damage precedes tangle formation and is associated with up-regulation of nitrotyrosine in Alzheimer's disease brain

The relationship of neuronal DNA damage to tangle-bearing neurons and nitrotyrosine (NT) expression, a neurochemical marker of oxidative damage mediated by peroxynitrite, was examined in visual cortex of AD patients. Many terminal deoxynucleotidyl transferase (TdT)-positive neurons were detected and the majority (93%) of these TdT-labeled neurons lacked evidence of tangle formation. NT expression was elevated in AD cases and most TdT-labeled nuclei also showed strong NT immunoreactivity. These data suggest the hypothesis that the neurons with DNA damage in the absence of tangle formation may degenerate by tangle-independent mechanisms and that oxidative damage may contribute to such mechanisms in AD.

The functional significance of microRNA-145 in prostate cancer

Background:

MicroRNAs (miRNAs) are small noncoding RNAs that have important roles in numerous cellular processes. Recent studies have shown aberrant expression of miRNAs in prostate cancer tissues and cell lines. On the basis of miRNA microarray data, we found that miR-145 is significantly downregulated in prostate cancer.

Methods and results:

We investigated the expression and functional significance of miR-145 in prostate cancer. The expression of miR-145 was low in all the prostate cell lines tested (PC3, LNCaP and DU145) compared with the normal cell line, PWR-1E, and in cancerous regions of human prostate tissue when compared with the matched adjacent normal. Overexpression of miR-145 in PC3-transfected cells resulted in increased apoptosis and an increase in cells in the G2/M phase, as detected by flow cytometry. Investigation of the mechanisms of inactivation of miR-145 through epigenetic pathways revealed significant DNA methylation of the miR-145 promoter region in prostate cancer cell lines. Microarray analyses of miR-145-overexpressing PC3 cells showed upregulation of the pro-apoptotic gene TNFSF10, which was confirmed by real-time PCR and western analysis.

Conclusion:

One of the genes significantly upregulated by miR-145 overexpression is the proapoptotic gene TNFSF10. Therefore, modulation of miR-145 may be an important therapeutic approach for the management of prostate cancer.

Suppression of apoptosis in a cytotoxic T-cell line by interleukin 2-mediated gene transcription and deregulated expression of the protooncogene bcl-2

Absence of interleukin 2 (IL-2) from IL-2-dependent cells, such as the cytotoxic T-cell line CTLL2, causes DNA fragmentation and programmed cell death (apoptosis). We found that, upon initiation, DNA degradation proceeds rapidly. IL-2-deprived CTLL2 cells can be rescued from apoptosis by the addition of IL-2 2 h prior to the onset of detectable DNA breakdown. Addition of inhibitors of transcription with IL-2 abolished the IL-2-mediated rescue of CTLL2 cells. Thus it appears that IL-2-mediated gene transcription is necessary for survival. Deregulated expression of a protooncogene, bcl-2, inhibits apoptosis of cells dependent on other hematopoietic growth factors. To determine whether bcl-2 was active in CTLL2 cells, we transfected CTLL2 cells with a plasmid containing bcl-2 cDNA expressed under the metallothionein promoter and observed prolonged survival of the transfected cells upon IL-2 deprivation. Cell growth, however, was arrested in the G0/G1 or G2/M phases of the cell cycle. The prolonged survival of bcl-2 transfectants allowed the analysis of endogenous bcl-2 mRNA levels by Northern blot analysis. The expression of endogenous bcl-2 was down-regulated within 8 h of IL-2 withdrawal and was not detected after 3 days. Addition of IL-2 induced endogenous bcl-2 expression within 8 h. Full recovery of bcl-2 expression was achieved by 24 h after IL-2 addition. We conclude that the survival of death-prone CTLL2 cells may be viewed as IL-2-dependent suppression of suicide, probably by the IL-2-induced expression of the cellular bcl-2 gene.

Adiponectin directly improves endothelial dysfunction in obese rats through the AMPK-eNOS Pathway

OBJECTIVE

Hypoadiponectinemia has been proved to be closely related to endothelial dysfunction in peripheral arteries and is thought to be an independent risk factor for cardiovascular disease. The objective of this study was to investigate whether adiponectin might independently improve endothelial dysfunction in aorta isolated from high-fat-diet-induced obese. Sprague-Dawley rat and to study the mechanism involved.

RESEARCH DESIGN AND SUBJECTS

Male Sprague-Dawley rats were fed with a regular or a high-fat diet for 6 weeks. The aorta was isolated, and vascular segments were incubated with vehicle or the globular adiponectin (globular domain (gAD); 2 mg ml(-1)) for 2 h. The effect of gAD on endothelial function and nitric oxide (NO) production was determined. Human aortic endothelial cells in primary culture were treated with vehicle or gAD (4 mg ml(-1)). The effect of gAD on the level of phosphorylation of endothelial nitric oxide synthase (eNOS) at Ser1177, AMPK at Thr176 and Akt at Ser473 in endothelial cells were determined.

RESULTS

Severe endothelial dysfunction was observed in high-fat diet fed rat aortic segments. After gAd incubation, the endothelium-dependent relaxation was partly improved and total production of nitric oxide as result of enhanced eNOS activity was also increased. In the cultured endothelial cell line HUVEC, globular adiponectin increased the activity of eNOS through activating AMPK by stimulating its phosphorylation at Thr176 but not Akt.

CONCLUSION

The demonstration in the current study that adiponectin reverses endothelial dysfunction through increasing NO production by eNOS phosphorylation, and decreasing NO inactivation by blocking superoxide production provides a new direction in the prevention of vascular injury in the obesity population.

Regulation of cell adhesion by PAI-1

Type I plasminogen activator inhibitor (PAI-1) is the primary inhibitor of tissue- and urokinase-type plasminogen activators. It circulates in plasma complexed with vitronectin (VN), the primary PAI-1 binding protein. The somatomedin B (SMB) domain of VN contains both the high affinity PAI-1 binding site and the specific site for urokinase plasminogen activator receptor (uPAR). PAI-1 is able to regulate uPAR-mediated cell adhesion by competing with uPAR for VN binding. Binding of PAI-1 to SMD may also affect integrin-mediated cell adhesion to VN by hindering integrin binding to the RGD sequence adjacent to the uPAR binding site.

KIAP, a novel member of the inhibitor of apoptosis protein family

We have identified a novel human gene, kiap (kidney inhibitor of apoptosis protein) that encodes a single BIR domain and a RING zinc finger domain. kiap has been assigned to the q13.3 region of human chromosome 20 by fluorescent in situ hybridization analysis. Northern blot analysis indicates that KIAP is expressed mainly in placenta, lymph node and fetal kidney. In this report, we show that overexpression of KIAP blocks apoptosis induced by menadione or by overexpression of BAX. In addition, we show that overexpression of KIAP enhances apoptosis induced by etoposide, and, that KIAP fails to block apoptosis induced by overexpression of Fas. Thus, KIAP, a new member of the inhibitor of apoptosis protein (IAP) family, has pleiotropic effects on apoptosis induced by various stimuli.

Alzheimer-associated presenilin-2 confers increased sensitivity to apoptosis in PC12 cells

Presenilin-2 is a gene of unknown function recently identified based upon linkage with some forms of familial Alzheimer's disease. To investigate potential effects of PS-2 on cell viability, rat pheochromocytoma (PC12) cells were stably transfected with cDNA constructs encoding either full-length human PS-2 or, for comparison, mouse Bcl-X(L). Overexpression of PS-2 conferred increased sensitivity to the apoptotic stimuli staurosporine and hydrogen peroxide. In contrast, Bcl-X(L) overexpression significantly reduced cell death induced by these stimuli. These results suggest that one function of PS-2 may involve modulation of cell viability.

Plasminogen activator inhibitor-1 regulates cell adhesion by binding to the somatomedin B domain of vitronectin

Plasminogen activator inhibitor-1 (PAI-1) binds to the somatomedin B (SMB) domain of vitronectin. It inhibits the adhesion of U937 cells to vitronectin by competing with the urokinase receptor (uPAR; CD87) on these cells for binding to the same domain. Although the inhibitor also blocks integrin-mediated cell adhesion, the molecular basis of this effect is unclear. In this study, the effect of the inhibitor on the adhesion of a variety of cells (e.g., U937, MCF7, HT-1080, and HeLa) to vitronectin was assessed, and the importance of the SMB domain in these interactions was determined. Although PAI-1 blocked the adhesion of all of these cells to vitronectin-coated wells, it did not block adhesion to a variant of vitronectin which lacked the SMB domain. Interestingly, HT-1080 and U937 cells attached avidly to microtiter wells coated with purified recombinant SMB (which does not contain the RGD sequence), and this adhesion was again blocked by the inhibitor. These results affirm that PAI-1 can inhibit both uPAR- and integrin-mediated cell adhesion, and demonstrate that the SMB domain of vitronectin is required for these effects. They also show that multiple cell types can employ uPAR as an adhesion receptor. The use of purified recombinant SMB should help to further define this novel adhesive pathway, and to delineate its relationship with integrin-mediated adhesive events.

Amino acid sequence of a new type of antifreeze protein, from the longhorn sculpin Myoxocephalus octodecimspinosis

A new type of fish antifreeze protein, designated here type IV, has been isolated from the longhorn sculpin, Myoxocephalus octodecimspinosis. Sequence analysis of the protein (LS-12) reveals that it contains 108 amino acids, is blocked at the N-terminus by a pyroglutamyl group and has a high (17%) content of glutamine; it is thus completely unrelated to the earlier described types I, II and III fish antifreeze proteins. Circular dichroism spectra and conformational analysis based on the sequence data indicate that LS-12 has a high helix content and probably folds as a four-helix bundle. LS-12 shows sequence similarity to certain plasma apolipoproteins known to have helix bundle structures, suggesting the possibility that LS-12 may have arisen by recruitment and mutation of a plasma apolipoprotein.

Structural and functional analysis of the plasminogen activator inhibitor-1 binding motif in the somatomedin B domain of vitronectin

Plasminogen activator inhibitor 1 (PAI-1) binds to the somatomedin B (SMB) domain of vitronectin (VN), a domain present in at least seven other proteins. In this study, we investigate the PAI-1 binding activity of these SMB homologs and attempt to more specifically localize the PAI-1 binding site within this domain. SMBVN and several of its homologs were expressed in Escherichia coli, purified, and tested for PAI-1 binding activity in a competitive ligand binding assay. Although recombinant SMBVN was fully active in this assay, none of the homologs bound to PAI-1 or competed with VN for PAI-1 binding. These inactive homologs are structurally related to SMBVN, having 33-45% sequence identity and containing all 8 cysteines at conserved positions. Thus, homolog-scanning experiments were conducted by exchanging progressively larger portions of the NH2- or COOH-terminal regions of active SMBVN with the corresponding regions of the inactive homologs. These experiments revealed that the minimum PAI-1-binding sequence was present in the central region (residues 12-30) of SMBVN. Alanine scanning mutagenesis further demonstrated that each of the 8 cysteines as well as Gly12, Asp22, Leu24, Try27, Tyr28, and Asp34 were critical for PAI-1 binding and were required to stabilize PAI-1 activity. These results indicate that the PAI-1 binding motif is localized to residues 12-30 of SMBVN and suggest that this motif is anchored in the active conformation by disulfide bonds.

Hepatic HDL receptor, SR-B1 and Apo A-I expression in chronic renal failure

BACKGROUND

Chronic renal failure (CRF) is associated with hypertriglyceridaemia and depressed plasma high-density lipoprotein (HDL)-cholesterol and apolipoprotein A-I (Apo A-I) concentrations. Uraemic hypertriglyceridaemia is due, in part, to lipoprotein lipase and hepatic lipase deficiencies, which are causally linked to excess parathormone (PTH). This study was designed to test the hypothesis that depressed plasma concentration and abnormal composition of HDL in CRF may be due to dysregulation of hepatic expression of Apo A-I and/or the newly discovered HDL receptor.

METHODS

Hepatic Apo A-I and HDL receptor mRNA abundance (Northern blot), and HDL receptor protein mass (Western blot) were determined in CRF rats (5/6 nephrectomy), parathyroidectomized CRF rats (CRF-PTx) and sham-operated controls.

RESULTS

The CRF group exhibited normal hepatic HDL receptor mRNA and HDL receptor protein abundance coupled with reduced hepatic Apo A-I mRNA. Hepatic Apo A-I mRNA, HDL receptor mRNA and protein abundance were not affected by PTx.

CONCLUSIONS

CRF results in the down-regulation of hepatic Apo A-I gene expression, which accounts for the known reduction in plasma Apo A-I concentration. However, CRF does not affect HDL receptor mRNA or protein expression in this model. Neither Apo A-I nor HDL receptor expression were modified by PTx in CRF rats.

Methylation of hMLH1 promoter correlates with the gene silencing with a region-specific manner in colorectal cancer

Microsatellite instability is present in over 80% of the hereditary non-polyposis colorectal carcinoma and about 15-20% of the sporadic cancer. Microsatellite instability is caused by the inactivation of the mismatch repair genes, such as primarily hMLH1, hMSH2. To study the mechanisms of the inactivation of mismatch repair genes in colorectal cancers, especially the region-specific methylation of hMLH1 promoter and its correlation with gene expression, we analysed microsatellite instability, expression and methylation of hMLH1 and loss of heterozygosity at hMLH1 locus in these samples. Microsatellite instability was present in 17 of 71 primary tumours of colorectal cancer, including 14 of 39 (36%) mucinous cancer and three of 32 (9%) non-mucinous cancer. Loss of hMLH1 and hMSH2 expression was detected in nine and three of 16 microsatellite instability tumours respectively. Methylation at CpG sites in a proximal region of hMLH1 promoter was detected in seven of nine tumours that showed no hMLH1 expression, while no methylation was present in normal mucosa and tumours which express hMLH1. However, methylation in the distal region was observed in all tissues including normal mucosa and hMLH1 expressing tumours. This observation indicates that methylation of hMLH1 promoter plays an important role in microsatellite instability with a region-specific manner in colorectal cancer. Loss of heterozygosity at hMLH1 locus was present in four of 17 cell lines and 16 of 54 tumours with normal hMLH1 status, while loss of heterozygosity was absent in all nine cell lines and nine tumours with abnormal hMLH1 status (mutation or loss of expression), showing loss of heterozygosity is not frequently involved in the inactivation of hMLH1 gene in sporadic colorectal cancer.

Bcl-2 facilitates recovery from DNA damage after oxidative stress

Oxidative stress is a major factor affecting the brain during aging and neurodegenerative diseases such as Alzheimer's disease (AD). Understanding the mechanisms by which neurons can be protected from oxidative stress, therefore, is critical for the prevention and treatment of such degeneration. Previous studies have shown that bcl-2 expression is increased in neurons with DNA damage in AD and bcl-2 has an antioxidant effect. The goal of this study is to document the effects of oxidative insults on mitochondrial and nuclear DNA in PC12 cells and determine the extent to which bcl-2 prevents damage or facilitates repair. Using extralong PCR to amplify nuclear and mitochondrial DNA, the time course of DNA damage and repair was determined. Within minutes after exposure of cells to low concentrations of hydrogen peroxide and peroxynitrite, significant mitochondrial and nuclear DNA damage was evident. Mitochondrial DNA was damaged to a greater degree than nuclear DNA. Expression of bcl-2 in PC12 cells inhibited nitric oxide donor (sodium nitroprusside)- and peroxynitrite-induced cell death. Although oxidative insults caused both genomic and mitochondrial DNA damage in cells expressing bcl-2, recovery from DNA damage was accelerated in these cells. These results suggest that neuronal up-regulation of bcl-2 may facilitate DNA repair after oxidative stress.

Transneuronal degeneration in the spread of Alzheimer's disease pathology: immunohistochemical evidence for the transmission of tau hyperphosphorylation

Neurofibrillary tangles and dystrophic neurites appear to develop in a highly characteristic spatial and temporal sequence in AD. In order to examine the nature of the cellular progression we have studied the trisynaptic entorhinal, dentate gyrus, CA3/4 circuit, using an antibody to hyperphosphorylated tau which is a biochemical marker for tangle formation. In early AD cases, we found numerous ATB-stained boutons in the outer molecular layer of the dentate gyrus, the termination field of neurons from the entorhinal cortex. These AT8-stained boutons co-labeled with synaptophysin, indicating that they represent synaptic boutons in an early state of degeneration. Since the labeled boutons were apposed to or clustered around dendrites or soma that lacked or had less intense staining for AT8 or PHF-1, it appeared that presynaptic events preceded postsynaptic neurofibrillary tangle formation. Furthermore, as a function of disease progression, the pattern of degeneration moved through the circuit. In this progression tau, which is normally localized to axons, becomes redistributed into dendrites and hyperphosphorylated. These observations support the hypothesis that the presynaptic terminal changes may promote the formation of initial neurofibrillary pathology in the postsynaptic neurons via anterograde transneuronal mechanisms and that this initiates a breakdown of routing and sorting mechanisms for the cytoskeletal protein tau.

Methylation in hMLH1 promoter interferes with its binding to transcription factor CBF and inhibits gene expression

Microsatellite instability (MSI) is caused by the dysfunction of mismatch repair genes, such as hMLH1, hMSH2. Loss of hMLH1 expression and methylation of CpG sites in hMLH1 promoter are frequently present in sporadic colorectal cancer with MSI. In this study, by transient transfection assay with constructs containing different lengths of hMLH1 promoter and a luciferase reporter gene, we located a proximal region of hMLH1 promoter, which plays a main role in regulating the gene. The fact that luciferase activities were high in all host cell lines regardless of their hMLH1 expression levels indicates that the transcription machinery is intact even in non-expressing cells. When hMLH1 promoter was in vitro methylated before transfection, the luciferase activities in the transfectants were significantly reduced. This observation indicates that methylation causes the inhibition of hMLH1 promoter activity. By electrophoretic mobility shift assay (EMSA), we identified a CCAAT box in this region, which specifically bound transcription factor CBF. Mutations in CCAAT box not only inhibited its binding to CBF factor, but also reduced its ability to drive the expression of luciferase gene. The role of CBF in activating transcription was further substantiated by inhibition of promoter activity with a plasmid expressing a dominant negative CBF-B mutant. Methylation at a CpG site two base pairs upstream of the CCAAT box inhibited the binding of CBF to CCAAT box. We conclude that methylation of an adjacent CpG site inhibits binding of the CBF transcription to the corresponding CCAAT box, and is one of the causes of hMLH1 gene silencing in colon cancer cells.

High frequency of genetic instability of microsatellites in human prostatic adenocarcinoma

In order to investigate the genomic instability associated with prostate cancer, 36 microsatellite marker loci on chromosomes 1p, 3p, 5q, 8p, 8q, 9p, 11q and 13q were analyzed using microdissected samples from prostate cancer and adjoining microscopically normal tissues from the same slide. DNA was extracted from the normal and tumor cells of 40 microdissected prostate-cancer samples, amplified by PCR, and analyzed for microsatellite instability (MSI) using 36 different polymorphic DNA markers. In the present study, we have utilized a highly refined technique of PCR product separation on a sequencing gel, developed in our laboratory, which clearly shows high-quality results for the microsatellite instability in prostate cancer. The results of this study suggest that 45% (18 out of 40) showed genomic instability at a minimum of 1 locus; 4 cases each showed MSI at one and 2 loci, 4 cases had MSI at 3 loci, 3 cases showed MSI at 5 loci, while one case each showed MSI at 7, 8 and 15 loci. There was no significant correlation between the MSI and stage or grade of the tumors. This extensive study on genomic instability in prostate cancer found the occurrence of MSI to be very high, which suggests a role of MSI in the pathophysiology of prostate cancer.

Isolation and characterization of an antifreeze protein from the longhorn sculpin, Myoxocephalus octodecimspinosis

A new type of antifreeze protein was isolated from the serum of the longhorn sculpin, Myoxocephalus octodecimspinosis, by gel filtration and high-performance liquid chromatography. This protein (LS-12) exhibits freezing point depression activity (thermal hysteresis) and ice crystal modification properties similar to those seen for other types of fish antifreeze polypeptide, except that ice crystals grow as hexagonal trapezohedra in the presence of LS-12, rather than hexagonal bipyramids usually seen. Ice crystal etching studies demonstrate that LS-12 does not bind to the hexagonal bipyramidal or secondary prism surfaces reported for the antifreeze polypeptides from winter flounder and shorthorn sculpin, respectively. Circular dichroism studies indicate that LS-12 has an alpha-helix content of about 60% at 1 degreesC, which is in good agreement with a value of about 70% predicted from the amino acid sequence. Limited proteolysis studies and further analysis of the amino acid sequence suggest that LS-12 consists of four amphipathic alpha-helices of similar length which are folded into a four-helix bundle. Based on its size (Mr=12299) and predicted tertiary structure, LS-12 can be regarded as the first example of a new class (type IV) of fish antifreeze protein.

Exosomes promote cetuximab resistance via the PTEN/Akt pathway in colon cancer cells

Cetuximab is widely used in patients with metastatic colon cancer expressing wildtype KRAS. However, acquired drug resistance limits its clinical efficacy. Exosomes are nanosized vesicles secreted by various cell types. Tumor cell-derived exosomes participate in many biological processes, including tumor invasion, metastasis, and drug resistance. In this study, exosomes derived from cetuximab-resistant RKO colon cancer cells induced cetuximab resistance in cetuximab-sensitive Caco-2 cells. Meanwhile, exosomes from RKO and Caco-2 cells showed different levels of phosphatase and tensin homolog (PTEN) and phosphor-Akt. Furthermore, reduced PTEN and increased phosphorylated Akt levels were found in Caco-2 cells after exposure to RKO cell-derived exosomes. Moreover, an Akt inhibitor prevented RKO cell-derived exosome-induced drug resistance in Caco-2 cells. These findings provide novel evidence that exosomes derived from cetuximab-resistant cells could induce cetuximab resistance in cetuximab-sensitive cells, by downregulating PTEN and increasing phosphorylated Akt levels.