Kruppel-like factor 4 (KLF4) is required for maintenance of breast cancer stem cells and for cell migration and invasion

Kruppel-like factor 4 (KLF4) is highly expressed in more than 70% of breast cancers and functions as an oncogene. However, an exact mechanism by which KLF4 enhances tumorigenesis of breast cancer remains unknown. In this study, we show that KLF4 was highly expressed in cancer stem cell (CSC)-enriched populations in mouse primary mammary tumor and breast cancer cell lines. Knockdown of KLF4 in breast cancer cells (MCF-7 and MDA-MB-231) decreased the proportion of stem/progenitor cells as demonstrated by expression of stem cell surface markers such as aldehyde dehydrogenase 1 (ALDH1), side-population (SP), and by in vitro mammosphere assay. Consistently KLF4 overexpression led to an increase of the cancer stem cell population. KLF4 knockdown also suppressed cell migration and invasion in MCF-7 and MDA-MB-231 cells. Furthermore, knockdown of KLF4 reduced colony formation in vitro and inhibited tumorigenesis in immunocompromised NOD/SCID mice, supporting an oncogenic role for KLF4 in breast cancer development. Further mechanistic studies revealed that the Notch signaling pathway was required for KLF4-mediated cell migration and invasion, but not for CSC maintenance. Taken together, our study provides evidence that KLF4 plays a potent oncogenic role in mammary tumorigenesis likely by maintaining stem cell-like features and by promoting cell migration and invasion. Thus, targeting KLF4 may provide an effective therapeutic approach to suppress tumorigenicity in breast cancer.

Diffusion tensor MR imaging of cerebral gliomas: evaluating fractional anisotropy characteristics

BACKGROUND AND PURPOSE

FA correlation to glioma tumor grade has been mixed if not disappointing. There are several potential underlying fundamental issues that have contributed to these results. In an attempt to overcome these past shortfalls, we evaluated characteristics of FA of the solid tissue components of gliomas, including whether high-grade gliomas have a greater variation of FA than low-grade gliomas.

MATERIALS AND METHODS

Thirty-four patients with gliomas (9 grade II, 8 grade III, and 17 grade IV) underwent diffusion tensor imaging at 3T. Mean FA, maximum FA, and minimum FA values were measured within the solid tissue components of the tumors. The variations of FA were evaluated by determining the range of FA values and the maximum SDs of FA. The variations of FA values among different tumor grades were compared statistically. We also correlated FA variations with minimum FA and maximum FA.

RESULTS

The maximum FA, FA range, and maximum SD for grade II tumors were significantly lower than those for grade III and IV tumors (P < .0001 ∼ P = .0164). A very good correlation of maximum FA to FA range (r = 0.931) and maximum SD (r = 0.889) was observed.

CONCLUSIONS

The FA range and maximum SD appear useful for differentiating low- and high-grade gliomas. This analysis added value to the findings on conventional MR imaging. In addition, focal maximum FA is a key factor contributing to the larger FA variation within high-grade gliomas.

The reactive tumor microenvironment: MUC1 signaling directly reprograms transcription of CTGF

The MUC1 cytoplasmic tail (MUC1.CT) conducts signals from spatial and extracellular cues (growth factor and cytokine stimulation) to evoke a reprogramming of the cellular transcriptional profile. Specific phosphorylated forms of the MUC1.CT achieve this function by differentially associating with transcription factors and redirecting their transcriptional regulatory capabilities at specific gene regulatory elements. The specificity of interaction between MUC1.CT and several transcription factors is dictated by the phosphorylation pattern of the 18 potential phosphorylation motifs within the MUC1.CT. To better appreciate the scope of differential gene expression triggered by MUC1.CT activation, we performed microarray gene expression analysis and ChIP-chip promoter analysis and identified the genome-wide transcriptional targets of MUC1.CT signaling in pancreatic cancer. On a global scale, MUC1.CT preferentially targets genes relating to invasion, angiogenesis and metastasis, suggesting that MUC1.CT signaling contributes to establishing a reactive tumor microenvironment during tumor progression to metastatic disease. We examined in detail the molecular mechanisms of MUC1.CT signaling that induces expression of connective tissue growth factor (CTGF/CCN2), a potent mediator of ECM remodeling and angiogenesis. We demonstrate a robust induction of CTGF synthesis and secretion in response to serum factors that is enabled only when MUC1 is highly expressed. We demonstrate the requirement of phosphorylation at distinct tyrosine motifs within the MUC1.CT for MUC1-induced CTGF expression and demonstrate a phosphorylation-specific localization of MUC1.CT to the CTGF promoter. We found that MUC1 reorganizes transcription factor occupancy of genomic regions upstream of the CTGF gene, directing β-catenin and mutant p53 to CTGF gene regulatory elements to promote CTGF expression and destabilizing the interaction at these regions of the transcriptional repressor, c-Jun. With this example we illustrate the capacity of MUC1.CT to mediate transcription factor activity in a context-dependent manner to achieve widespread and robust changes in gene expression and facilitate creation of the reactive tumor microenvironment.

Mir-30 reduction maintains self-renewal and inhibits apoptosis in breast tumor-initiating cells

Accumulating evidence indicates that a sub-population of cancer cells with stem-like properties, termed tumor-initiating cells (T-ICs), exist in many different kinds of malignancies, which have a pivotal role in tumorigenesis, tumor progression, metastasis and post-treatment relapse. However, how the stem-like properties of T-ICs are regulated remains obscure. Our previous study showed that reduction of let-7 microRNA (miRNA) in breast tumor-initiating cells (BT-ICs) contributes to the maintenance of their self-renewal capacity and undifferentiated status. In this study we show the effect of mir-30 reduction on the stem-like features of BT-ICs. Similar to let-7, mir-30 is reduced in BT-ICs, and the protein level of Ubc9 (ubiquitin-conjugating enzyme 9) and ITGB3 (integrin beta3), the target genes of mir-30, is markedly upregulated. Enforced constitutive expression of mir-30 in BT-ICs inhibits their self-renewal capacity by reducing Ubc9, and induces apoptosis through silencing ITGB3. On the contrary, blocking the miRNA with a specific antisense oligonucleotide (ASO) in differentiated breast cancer cells revived their self-renewal capacity. Furthermore, ectopic expression of mir-30 in BT-IC xenografts reduces tumorigenesis and lung metastasis in nonobese diabetic/severe combined immunodeficient mice, whereas blocking mir-30 expression enhances tumorigenesis and metastasis. Together, our data suggest mir-30 as one of the important miRNAs in regulating the stem-like features of T-ICs.

Class IV-G and IV-S lupus nephritis in Chinese patients: a large cohort study from a single center

This study is to assess the difference between IV-G and IV-S in a large cohort of Chinese patients with lupus nephritis. The detailed data of patients with subclass IV-G and IV-S were retrospectively analyzed. Serum ANCA and anti-C1q antibodies were detected. A total of 172 cases were classified as class IV, including 152 cases with IV-G and 20 cases with IV-S. In IV-S, the level of haemoglobin was significantly higher (P = 0.024), proteinuria was milder (P = 0.003), serum creatinine was lower (P = 0.021), serum C3 was higher (P = 0.045) and the ratio of positive serum anti-cardiolipin antibodies was higher (P = 0.014). On pathological evaluation, the ratio of glomerular fibrinoid necrosis was significantly higher (P = 0.006) and the score of endocapillary hypercellualrity, interstitial inflammation and total activity indices was significantly lower (P < 0.001, P = 0.01, P = 0.006, respectively) in IV-S. The frequency of serum ANCA was significantly higher in IV-S than that in IV-G (20 vs 4.6%, P = 0.008). The frequencies of anti-C1q IgG1 and IgG3 subclass were significantly higher in IV-G (P = 0.006, P = 0.011, respectively). There are significant differences in clinical and pathological manifestations between IV-S and IV-G lupus nephritis which need further investigation.

Let-7 Inverts the Chemoresistance of Breast Tumor-Initiating Cells

Background: Cancers may arise from rare self-renewing highly tumorigenic “stem” cells, which are thought not only to be the source of the tumor, but also to be responsible for resistance to cancer therapy and subsequent tumor recurrence. Our preliminary data strongly suggest that let-7 is a master regulator of BT-IC self-renewal and multipotency. It is likely that let-7 regulates many other genes/pathways during BT-IC differentiation. However, we do not know whether let-7 might also regulate other putative aspects of “stemness” such as chemoresistance.Material and Methods: Quantified qRT-PCR was used to test the expression of let-7a in chemoresistant breast tumor tissue from patients, as well as the chemosensitive samples. The location of let-7a in primary breast cancer samples from patients with chemoresistance were compared to the samples without chemoresistance by in situ hybridization analysis.SK-3rd Cells, which is a cell line enriched in breast tumor-initiating cells, were cultured in suspension to form mammosphere which could be induced to differentiation with adhesive culture. Lentivirus-mediated let-7a transduction was used to increase the expression level of let-7a.Let-7 target gene expression (HRAS and HMGA2) was determined by qRT-PCR and western blot. The response of BT-ICs to chemotherapy was determined by MTT, Annexin V and Tunel.Results: The expression level of let-7a microRNA in chemoresistant patients were significantly lower than the patients without chemoresistance (P&lt;0.05). The let-7a mimics can effectively enhance the expression of let-7a in mammospheric SK-3rd cells, and reduced the expression level of H-RAS and HMGA2 proteins, which are the targets of let-7. Mammospheric SK-3rd cells tranfected with let-7a mimics had a lower proliferation rate and a higher apoptosis rate under epirubicin treatment.Conclusion: Lack of expression of let-7 regulates BT-IC resistance to chemotherapy. Therefore, let-7a may be an effective maker to predict the response of tumor to chemotherapy.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 1136.

Proportion of Tumor Initiating Cells Contributes to Chemotherapeutic Resistance of Breast Cancers

Background: The mechanisms determining chemotherapeutic resistance of breast cancers are rather complicated with a variety of molecules involved. While targeting one single molecule or one signaling pathway are not sufficient to reverse chemo-resistance. Therefore, it is more important to identify and eliminate the subpopulations of tumor cells that are resistant to chemotherapy. Recently, accumulating evidence demonstrates that a wide variety of malignancies may be driven by a small subset of “tumor-initiating cells (T-ICs) displays a variety of drug-resisting mechanisms. Nevertheless, it remains obscure whether the proportion of breast tumor initiating cells (BT-ICs) correlates with chemotherapeutic sensitivity of breast cancers, and whether targeting BT-ICs may help to reverse chemo-resistance in the malignancy.Material and Methods: Using immunohistochemistry, we tested the expression level of ALDH1 in 192 human breast cancer samples before underwent neoadjuvant chemotherapy and analyzed the relationship between the ALDH1 level and clinical pathological features including clinical response and disease free survival (DFS). We tested the proportion of CD44+/CD24-, ALDH1+ and side population in primary cancer cells, wide type MCF7 and Adriamycin resistant (AdrR) MCF-7 by FACS. Compared the mammosphere formations in suspension culture. We further tested the drug sensitivity after treated with 1UM Lapatinib in AdrR MCF-7 mammospheric cells by MTT and AnnexinV staining. Results: In all 192 cases, there were 19.79% (38 of 192) cases with high ALDH1 expression (&gt;20% positive cancer cells) compared to 80.21% (154 of 192) cases with low expression (≤20% positives cells). The clinical response (PR and cCR) was only 52.63%% (20 of 38) in patients with high ALDH1 expression compared with 81.17% (125 of 154) in patients with low ALDH1 expression (x2=15.926; P=0.000). Patients with low ALDH1expression survived significantly longer than those with high ALDH1 expression (P = 0.006). In primary cancer cells, the percentage of ALDH1+ and CD44+/CD24-cells were up to 8.72% ±3.73% and 36% ±7.9% in the PD samples respectively, whereas only 1.42%±1.63% and 3.17 ±0.45% in PR samples (p=0.037 and 0.018). Moreover, mammosphere formation of primary human breast cancer cells was 10-20 fold higher in PD samples than in PR samples (p=0.01). Then we compared the proportion of BT-ICs between two breast cancer cell lines. The mammoshpere formation rate of the AdrR MCF-7 increased to 9.1%±1.01% compared with 1.03%±0.15% in the parent MCF-7 breast cancer cell (p=0.0046), meanwhile, the percentage of CD44+/CD24- cells was much higher in the AdrR MCF-7 cells(64.85%±1.3% vs than 1.3%±0.1%,p=0.01), the proportion of ALDH1+ cells was 15.9%±1.5% to 2.7%±0.3% (p=0.01),as well as the percentage of side population was 10.8%±1.4% to.0.25%±0.05% (p=0.001).After treated with Lapatinib, the sensitivity of passaged mammospheric AdrR MCF-7 cells to chemotherapy increased in the cell viability assay, while the dead cells increased from 50% ±2.8% to 75%±6.5% tested by FACS under chemotherapy pressure (p=012).Conclusion: Proportion of tumor initiating cells contributes to chemotherapeutic resistance of breast cancers.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 503.

Breast Cancer Initiating Cells Promote Chemoresistance by Pre-Activation of the DNA Damage Repair

Background: Breast tumor initiating cells (BT-ICs) display a variety of drug-resisting mechanisms including overxpression of ATP binding cassette (ABC) transporters and anti-apoptotic molecules. Unfortunately, application of P-glycoprotein inhibitors has not been successful in several clinical trials .Based on the tumor initiating cell concept, an alternative model posits that the T-ICs are naturally resistant to chemotherapy through their quiescence and their capacity for DNA repair. Gaining a better insight into the mechanisms of BT-IC resistance to chemotherapy might therefore lead to new therapeutic targets and better anticancer strategies.Material and Methods: We generated large numbers of BT-IC-enriched cells (SK-3rd) by in vivo passage of breast cancer cells SKBR3 in NOD/SCID mice treated with epirubicin, then enriched BT-ICs again by isolating spherical clusters of self-replicating cells (“mammospheres”) from suspension cultures. Under chemotherapy pressure, compared the apoptosis between BT-IC and non BT-IC by MTT, Annexin V, DNA ladder and hochest 33342 staining, and analyzed the cell cycles by Flow cytometry. We tested the DNA repair capacity after chemo-induced DNA damage between BT-IC and non BT-IC by single cell gel electrophoresis and tested the expression of DNA damage checkpoint protein by immunoblot.Results:SK-3rd formed 40-fold more mammospheres than SKBR3 (16.7%±2.6% vs 0.5%±0.2%; P&lt;0.001). Compared with non BT-IC, BT-IC treated with epirubicin showed more viability as assessed by MTT assay. After treated with 0.3ug/ml Epirubicin for 24 hours, withdrew the drug, and then repaired for 12, 24 hours respectively, analyzed the Annexin V positive cells in BT-IC were less than n non BT-IC(17.27%±2.3% vs 56%±6.7%; P=0.026), hochest staining also showed the similar results.SK-3rd mammospheric cells treated with or without Epirubicin arrested in G0/1 stage. Breast T-IC can repair chemo-induced DNA damage more efficiently than non BT-IC. Treated with or without Epirubicin, Sk-3rd mammospheric cells can pre-activated phosphorylated DNA chk2checkpoint (Thr68),but not in non BT-IC.Dicussion: The discovery of cancer initiating cells in solid tumors has changed our view of carcinogenesis and chemotherapy. In our study, we found that, BT-IC was more resistant than non BT-IC under the same chemotherapy pressure Although initiating cells can self-renew, they are generally quiescent, spending most of their time in G0. BT-IC treated with or without Epirubicin activated DNA checkpoint phosphorylated chk2 and arrested in G0/1 stage, which implied that BT-IC can target itself to arrest in G0/1 stage and pre-active chk2. When treated with DNA damage, BT-IC has enough time and quickly responses to repair damaged DNA, and at last contributes to the failure of chemotherapy. The new insight into the mechanisms of initiating -cell chemoresistance might allow the development of new strategies to improve targeted therapies in breast cancer.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 1121.

Mir-128 Regulates the Self-Renewal of Breast Tumor-Initiating Cells through HTERT

Background: hTERT (human telomerase reverse transcriptase), which maintains telomere ends by addittion of the telomere repeat sequence TTAGGG, is increased in cancer cells and embryonic stem cells. However, whether hTERT has a role in regulating breast tumor-initiating cells remains unknown. Therefore, the regulation of hTERT in breast tumor initiating cells (BT-IC) would potentially facilitate our understanding of the etiology of breast cancer.Material and Methods: Enrichment for BT-ICs was performed by mammospheres from suspension cultures. The capacity of self-renewal and differentiation of BT-ICs were determined by mammosphere formation, immunohistochemical analysis of epithelial markers and FACS, respectively. TRAP assay was used to detect telomerase activity. The expression levels of hTERT in BT-ICs, with or without lentivirus-mediated mir-128 transduction, were determined by qRT-PCR and western blot. hTERT siRNA or lentivirus-shTERT were used to silence the expression of hTERT in BT-ICs. Differentially expressed mir-128 in BT-ICs was quantified by qRT-PCR and Northern Blot. The expression of BMI1 was determined by Western Blot.Results: hTERT, as well as telomerase activity, had a higher expression in BT-ICs, compared to the differentiated breast cancer cells. BMI1, the target of mir-128, is increased in BT-ICs. Conversely, the expression level of mir-128 is lower in BT-ICs, compared to the differentiated cells. Mir-128 over-expressing reduced the level of BMI1,as well as hTERT, in BT-ICs. Silencing BMI1 by lentivirus-shRNA transfection in BT-ICs leads to the decrease of hTERT protein level. Furthermore, BT-ICs, with hTERT knockdown, lost its ability to form mammospheres and proliferated poorly under differentiating conditions.Conclutions: mir-128 miRNA is reduced in mammospheric BT-ICs, resulting in up-regulation of BMI1, which further brought on the up-regulation of hTERT. And hTERT promotes self-renewal and blocks epithelial differentiation of BT-ICs. Therefore, mir-128 regulates BT-IC stem-cell like properties by BMI1 and hTERT.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 5157.

Strong association of socioeconomic status with genetic ancestry in Latinos: implications for admixture studies of type 2 diabetes

AIMS/HYPOTHESIS

Type 2 diabetes is more prevalent in US American minority populations of African or Native American descent than it is in European Americans. However, the proportion of this epidemiological difference that can be ascribed to genetic or environmental factors is unknown. To determine whether genetic ancestry is correlated with diabetes risk in Latinos, we estimated the proportion of European ancestry in case-control samples from Mexico and Colombia in whom socioeconomic status had been carefully ascertained.

METHODS

We genotyped 67 ancestry-informative markers in 499 participants with type 2 diabetes and 197 controls from Medellín (Colombia), as well as in 163 participants with type 2 diabetes and 72 controls from central Mexico. Each participant was assigned a socioeconomic status scale via various measures.

RESULTS

Although European ancestry was associated with lower diabetes risk in Mexicans (OR [95% CI] 0.06 [0.02-0.21], p = 2.0 x 10(-5)) and Colombians (OR 0.26 [0.08-0.78], p = 0.02), adjustment for socioeconomic status eliminated the association in the Colombian sample (OR 0.64 [0.19-2.12], p = 0.46) and significantly attenuated it in the Mexican sample (OR 0.17 [0.04-0.71], p = 0.02). Adjustment for BMI did not change the results.

CONCLUSIONS/INTERPRETATION

The proportion of non-European ancestry is associated with both type 2 diabetes and lower socioeconomic status in admixed Latino populations from North and South America. We conclude that ancestry-directed search for genetic markers associated with type 2 diabetes in Latinos may benefit from information involving social factors, as these factors have a quantitatively important effect on type 2 diabetes risk relative to ancestry effects.

Association between polymorphisms in the FCGRT gene and lupus nephritis in Chinese patients

OBJECTIVE

Studies on mouse models have indicated that the neonatal Fc receptor (FcRn) plays important roles in a variety of autoimmune diseases. A variable number of tandem repeat (VNTR) polymorphisms within the FCGRT gene have been detected, and were found to affect the expression and functioning of FcRn. This study investigated the possible association of FCGRT VNTR polymorphisms with susceptibility and clinical manifestations in patients with lupus nephritis (LN).

METHODS

A total of 404 Han Chinese subjects, comprising 200 patients with LN and 204 geographically-matched healthy controls, participated in the study. The FCGRT VNTR polymorphism was genotyped by DNA amplification using a touchdown polymerase chain reaction followed by polyacrylamide gel electrophoresis.

RESULTS

The distribution of VNTR polymorphisms within the FCGRT gene in Chinese subjects was different to that in Caucasians. Analysis of allele and genotype frequencies revealed no significant difference between LN patients and controls. There was no significant difference in the clinical features or prognosis in LN patients when stratified by VNTR polymorphism.

CONCLUSION

Our results suggest that VNTR polymorphisms within the FCGRT promoter are not associated with LN in the Chinese population.

Fusion protein encoded by a CTLA-4 targeted DNA construct binds to human dendritic cells

Fusing antigens to cytotoxic T-lymphocyte antigen 4 (CTLA-4) represents an effective approach to enhance DNA vaccine efficacy. It has been speculated that the direct targeting of CTLA-4 fusion antigens to antigen-presenting cells (APCs) causes antigens to be processed and presented to T cells more efficiently, leading to a stronger immune response. In the present study, dendritic cells (DCs), the most potent APCs, were generated from human monocytes. The specific binding of CTLA-4 fusion protein to DCs was investigated by flow cytometry. The results showed that the CTLA-4 fusion protein was capable of binding to the B7 molecules on human DCs with specificity.

Search for maximal flavor violating scalars in same-charge lepton pairs in pp collisions at sqrt[s]=1.96 TeV

Models of maximal flavor violation (MxFV) in elementary particle physics may contain at least one new scalar SU(2) doublet field Phi(FV)=(eta(0),eta(+)) that couples the first and third generation quarks (q_(1), q_(3)) via a Lagrangian term L(FV)=xi(13)Phi(FV)q(1)q(3). These models have a distinctive signature of same-charge top-quark pairs and evade flavor-changing limits from meson mixing measurements. Data corresponding to 2 fb(-1) collected by the Collider Dectector at Fermilab II detector in pp[over ] collisions at sqrt[s]=1.96 TeV are analyzed for evidence of the MxFV signature. For a neutral scalar eta(0) with m_(eta;(0))=200 GeV/c(2) and coupling xi(13)=1, approximately 11 signal events are expected over a background of 2.1+/-1.8 events. Three events are observed in the data, consistent with background expectations, and limits are set on the coupling xi(13) for m(eta(0)=180-300 GeV/c(2).

Ovocleidin (OC 116) is present in avian skeletal tissues

Ovocleidin (OC-116), a protein identified in eggshell matrix, was found to be expressed in avian growth plate chondrocytes. Because OC-116 has been reported to be a member of a family of related phosphoprotein genes clustered on avian chromosome 4, we expanded our search to other skeletal tissues. Using Western blotting, we found OC-116 in the matrix of chick cortical bone and laying hen medullary bone as well as in hypertrophic chondrocyte lysates. Furthermore, other members of this family (bone sialoprotein, dental matrix protein-1, and osteopontin) were also present in the eggshell matrix. Reverse transcription-PCR was used to confirm the presence of the OC-116 gene in bone tissues as well as the expression of bone sialoprotein and dental matrix protein-1 in uterine tissue. These results, in combination with those of other laboratories, show that this family of phosphoproteins is found in a wide variety of avian mineralized tissues.

An antibiotic complex from Lysobacter enzymogenes strain C3: antimicrobial activity and role in plant disease control

Lysobacter enzymogenes C3 is a bacterial biological control agent that exhibits antagonism against multiple fungal pathogens. Its antifungal activity was attributed in part to lytic enzymes. In this study, a heat-stable antifungal factor (HSAF), an antibiotic complex consisting of dihydromaltophilin and structurally related macrocyclic lactams, was found to be responsible for antagonism by C3 against fungi and oomycetes in culture. HSAF in purified form exhibited inhibitory activity against a wide range of fungal and oomycetes species in vitro, inhibiting spore germination, and disrupting hyphal polarity in sensitive fungi. When applied to tall fescue leaves as a partially-purified extract, HSAF at 25 mug/ml and higher inhibited germination of conidia of Bipolaris sorokiniana compared with the control. Although application of HSAF at 12.5 mug/ml did not reduce the incidence of conidial germination, it inhibited appressorium formation and suppressed Bipolaris leaf spot development. Two mutant strains of C3 (K19 and DeltaNRPS) that were disrupted in different domains in the hybrid polyketide synthase-nonribosomal peptide synthetase gene for HSAF biosynthesis and had lost the ability to produce HSAF were compared with the wild-type strain for biological control efficacy against Bipolaris leaf spot on tall fescue and Fusarium head blight, caused by Fusarium graminearum, on wheat. Both mutant strains exhibited decreased capacity to reduce the incidence and severity of Bipolaris leaf spot compared with C3. In contrast, the mutant strains were as efficacious as the wild-type strain in reducing the severity of Fusarium head blight. Thus, HSAF appears to be a mechanism for biological control by strain C3 against some, but not all, plant pathogenic fungi.

Modeling, analysis, and validation of a novel HIV integrase structure provide insights into the binding modes of potent integrase inhibitors

It has been shown that L-731988, a potent integrase inhibitor, targets a conformation of the integrase enzyme formed when complexed to viral DNA, with the 3'-end dinucleotide already cleaved. It has also been shown that diketo acid inhibitors bind to the strand transfer complex of integrase and are competitive with the host target DNA. However, published X-ray structures of HIV integrase do not include the DNA; thus, there is a need to develop a model representing the strand transfer complex. In this study, we have constructed an active-site model of the HIV-1 integrase complexed with viral DNA using the crystal structure of DNA-bound transposase and have identified a binding mode for inhibitors. This proposed binding mechanism for integrase inhibitors involves interaction with a specific Mg(2+) in the active site, accentuated by a hydrophobic interaction in a cavity formed by a flexible loop upon DNA binding. We further validated the integrase active-site model by selectively mutating key residues predicted to play an important role in the binding of inhibitors. Thus, we have a binding model that is applicable to a wide range of potent integrase inhibitors and is consistent with the available resistant mutation data.

Evaluation of a new algorithm in classification of systemic vasculitis

OBJECTIVE

Recently, a new consensus algorithm for classification of ANCA-associated vasculitis (AAV) and PAN had been proposed by Watt et al. for epidemiological studies. In order to evaluate this algorithm, the current study used the algorithm to reclassify the patients with AAV and PAN in our centre.

METHODS

Five hundred and fifty Chinese patients with primary systemic vasculitis diagnosed in our referral diagnostic centre during the past 10 years were retrospectively studied. Four hundred and ninety-three out of 550 were ANCA positive. We compared the new consensus algorithm and the 1994 Chapel Hill Consensus Conference (CHCC) definitions supplemented with surrogate parameters, in the same cohort of patients with primary systemic vasculitis.

RESULTS

Applying the CHCC definitions with surrogate parameters, the diagnoses were Churg-Strauss syndrome (CSS) (n = 0), WG (n = 127), microscopic polyangiitis (MPA) (n = 363), PAN (n = 4) and unclassified (n = 56). Using the new consensus algorithm, the diagnoses were CSS (n = 2), WG (n = 199), MPA (n = 329), PAN (n = 0) and unclassified (n = 20).

CONCLUSIONS

Watts' algorithm was a useful method to classify patients into a single category, with less unclassified patients and without overlapping diagnosis, which allows their use in epidemiological studies.

Biosynthesis of sphinganine-analog mycotoxins

Sphinganine-analog mycotoxins (SAMT) are polyketide-derived natural products produced by a number of plant pathogenic fungi and are among the most economically important mycotoxins. The toxins are structurally similar to sphinganine, a key intermediate in the biosynthesis of ceramides and sphingolipids, and competitive inhibitors for ceramide synthase. The inhibition of ceramide and sphingolipid biosynthesis is associated with several fatal diseases in domestic animals and esophageal cancer and neural tube defects in humans. SAMT contains a highly reduced, acyclic polyketide carbon backbone, which is assembled by a single module polyketide synthase. The biosynthesis of SAMT involves a unique polyketide chain-releasing mechanism, in which a pyridoxal 5'-phosphate-dependent enzyme catalyzes the termination, offloading and elongation of the polyketide chain. This leads to the introduction of a new carbon-carbon bond and an amino group to the polyketide chain. The mechanism is fundamentally different from the thioesterase/cyclase-catalyzed polyketide chain releasing found in bacterial and other fungal polyketide biosynthesis. Genetic data suggest that the ketosynthase domain of the polyketide synthase and the chain-releasing enzyme are important for controlling the final product structure. In addition, several post-polyketide modifications have to take place before SAMT become mature toxins.