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.

[Reversal of multidrug resistance of gastric cancer cells by down-regulation of CIAPIN1 with CIAPIN1 siRNA]

The overexpression of a new cytokine-induced apoptosis inhibitor 1 (CIAPIN1) gene has been shown previously to promote a multidrug resistant phenotype in gastric cancer cells through the upregulation of MDR1 and MRP1. In the present study, we constructed the siRNA eukaryotic expression vectors of CIAPIN1 and transfected them into SGC7901/VCR cells to examine whether the down regulation of CIAPIN1 increased cell sensitivity towards chemotherapeutic drugs. After transfection, the expression of CIAPIN1 was dramatically decreased in CIAPIN1 siRNA transfectants compared with that in parental cells and empty vector control cells. The down-regulation of CIAPIN1 significantly enhanced the sensitivity of SGC7901/VCR cells to vincristine (VCR), adriamycin (ADR) and etoposide (VP-16), but not to 5-fluorouracil (5-FU) and cisplatin (CDDP). Cell capacity to efflux adriamycin decreased markedly in CIAPIN1 siRNA transfectants, and correlation between CIAPIN1 down regulation and decreased MDR1 transcriptional activity were observed. CIAPIN1 siRNA could significantly down regulate the expression of Bcl-2, and up-regulate the expression of Bax, but not alter the expression of PTEN in gastric cancer cells. These observations suggested that the siRNA constructs of CIAPIN1 we obtained could effectively down-regulate the expression of CIAPIN1 and reverse the resistant phenotype of gastric cancer cells. The further study of the biological functions of CIAPIN1 may be helpful for understanding the mechanisms of multidrug resistance of gastric cancer and developing possible strategies to treat gastric cancer.

Post-thaw viable CD34(+) cell count is a valuable predictor of haematopoietic stem cell engraftment in autologous peripheral blood stem cell transplantation

BACKGROUND AND OBJECTIVES

In peripheral blood stem cell transplantation, the number of CD34(+) cells infused is considered a predictor of haematopoietic engraftment. However, the currently accepted minimal threshold of CD34(+) cells/kg was determined by counting CD34(+) cells before freezing, and the loss of viable CD34(+) cells during freezing, cryopreservation or thawing prior to reinfusion has not been assessed.

MATERIALS AND METHODS

Total and viable CD34(+) cells were quantified using single platform flow cytometry and viability dye, 7-amino actinomycin D (7-ADD), at the time of collection and prior to reinfusion in 46 peripheral haematopoietic stem cell grafts from 36 patients. The time to engraftment of neutrophil and platelet was assessed by routine peripheral blood cell counts performed daily.

RESULTS

The median number of viable CD34(+) cells harvested was 3.6 x 10(6)/kg (range 0.05-21.2), and the median viability was 98% (range 70-100%) before freezing. After thawing, the median number of viable CD34(+) cells was reduced to 2.2 x 10(6)/kg (range 0.04-14.8) and the median viability was reduced to 71% (range 31-89%). The number of viable CD34(+) cells/kg before freezing and after thawing significantly correlated with engraftment of neutrophils (P < 0.0001 both) and platelets (P = 0.007 and 0.006, respectively). Although the minimum dose for engraftment (2.0 x 10(6) CD34(+) cells/kg) was harvested in 37 of 46 cases (85%), only 25 cases (54%) met this threshold at the time of reinfusion. For platelet engraftment, determination of viable CD34(+) cells prior to reinfusion was more important than enumeration at the time of collection.

CONCLUSION

Quantification of post-thaw viable CD34(+) cells better represents the actual composition of the graft and may be a more accurate predictor of haematopoietic engraftment than post-thaw total CD34(+) cell counts, or prefreeze determinations, especially for platelet engraftment. It is necessary to develop good quality controls for freezing and thawing procedures to minimize variance in cell viability.

Germline hMSH2 promoter mutation in a Chinese HNPCC kindred: evidence for dual role of LOH

Hereditary non-polyposis colorectal cancer (HNPCC) is a dominantly inherited cancer predisposition syndrome that is caused by germline mutations in mismatch repair genes. By screening the core promoters of hMSH2, hMLH1, and hMSH6 in 37 Chinese suspected HNPCC families, a novel germline mutation c.-78_-79delGT was found in the hMSH2 promoter. Its pathogenic effects were supported by the following findings: (a) it co-segregated with HNPCC-related cancers and was not present in the 220 control subjects, (b) tumors harboring the mutation lacked the expression of hMSH2 and showed high microsatellite instability, (c) it significantly decreased the promoter activity, and (d) it abolished the binding ability of the transcription factor E1A-F. Loss of heterozygosity (LOH) was found in three of the tumors studied. Intriguingly, in the tumors from patients II:1 and III:1, LOH occurred in the wild-type allele and agreed well with the traditional 'two-hit' model. In contrast, in the tumor from patient III:3, LOH occurred in the mutant allele. A pathogenic somatic mutation (c.2210+1G>A) was also found in this tumor; therefore, we proposed that the 'second hit' was inactivated by somatic mutation, and the mutant allele was lost during tumor progression; this provided evidence for the new hypothesis for the dual role of LOH.

Aerosol-delivered programmed cell death 4 enhanced apoptosis, controlled cell cycle and suppressed AP-1 activity in the lungs of AP-1 luciferase reporter mice

The long-term survival of lung cancer patients treated with conventional therapies remains poor and therefore the need for novel approaches remains high. This has led to the re-emergence of aerosol delivery as a therapeutic intervention. In this study, glucosylated polyethylenimine (GPEI) was used as carrier to investigate programmed cell death 4 (PDCD4) and PDCD4 mutant (D418A), an eIF4A-binding mutant, on PDCD4-related signaling and activator protein-1 (AP-1) activity in the lungs of AP-1 luciferase reporter mice. After confirming the efficiency of GPEI as a carrier in lungs, the effects of aerosol-delivered PDCD4 were investigated in AP-1 luciferase reporter mice. Aerosol delivery of GPEI/PDCD4 through a nose-only inhalation facilitated the apoptosis of lungs whereas aerosol PDCD4 mutant did not. Also, such aerosol delivery regulated proteins relevant to cell-cycle control and suppressed AP-1 activity. Results obtained by western blot analysis, immunohistochemistry, luciferase assay and deoxynucleotidyl-transferase-mediated nick end labeling study suggest that combined actions such as facilitating apoptosis, controlling cell cycle and suppression of AP-1 activity by PDCD4 may provide useful tool for designing lung tumor prevention and treatment by which PDCD4 functions as a transformation suppressor in the future.

Drosha in primary microRNA processing

MicroRNA (miRNA)-mediated gene silencing is one of the major regulatory pathways in eukaryotes. Much effort has been made to identify the factors involved in the pathway, and our understanding of RNA silencing has significantly advanced in recent years. Our group has been working on some of the issues regarding miRNA biogenesis and, in this paper, we summarize what we and other workers in the field have learned thus far. The focus remains on the role of Drosha and DGCR8 in the early events of miRNA biogenesis in animals.

Altered chemotherapeutic response of primary human breast cancer epithelial cells (HBCEC) and breast cancer cell lines

11506

Background: A novel technique to obtain individual primary cultures of human breast cancer biopsies was filed for patent (PCT/DE 2006/000608). The different individualized HBCEC (human breast cancer epithelial cell) cultures will be characterized and chemotherapeutic effects will be compared to established breast cancer cell lines. Methods: Primary HBCEC from 20 different breast cancer patients were characterized for epithelial cell and tumor markers by immunofluorescence and PCR. Following treatment with 1μM epirubicin for 1h up to 72h differences in protein expression patterns were compared to the similarly treated MCF-7 cell line by 2D gel electrophoresis. Differentially expressed protein spots were identified by mass spectrometry and confirmed by appropriate Western blot analysis. Results: Characterization of primary HBCEC revealed continuous mitosis and cell cycle progression for more than one year in culture with no significant contamination by fibroblasts or other cell types. Whereby HBCEC underwent cell death within 72h of epirubicin treatment analysis by 2D gel and subsequent protein identification by MALDI-TOF/TOF mass spectrometry exhibited a variety of differences compared to MCF-7 cells including HSP27 and prohibitin. Appropriate Western blots confirmed these differences and revealed altered expression levels for HSP27 and prohibitin in the course of epirubicin exposure in HBCEC and MCF-7 cells, respectively, suggesting altered signalling pathways in either primary breast cancer cells or the tumor cell line. Conclusions: Individualized primary HBCEC from various patients could provide a cellular platform beyond breast cancer cell lines, which eventually meet the requirements for an appropriate breast cancer testing system including the characterization of biomarkers and the identification of potential molecular targets.

No significant financial relationships to disclose.

A novel zinc-chelating small molecule exhibits cancer cell growth inhibition in vitro and in vivo by induction of tumor suppressors early growth response 1 (Egr-1) and Krüppel-Like Factor 4 (KLF4)

14084

Background: Lead compound LT-253 was selected from a group of 2-indolyl imidazol [4,5-d] phenanthroline derivatives with anticancer activity. It shows potent and selective anti-proliferative activity against several human cancer types in vitro, and in vivo in xenograft mouse models of human colon carcinoma (HT-29) and non-small cell lung carcinoma (H460). Methods: The mechanism of cell growth inhibition of LT-253 was investigated in HT-29 colon cancer cells using the XTT cell proliferation assay, flow cytometry and apoptosis assays. In vitro and in vivo zinc chelation was determined by competition assays using fluorescent and chromophoric chelators. Gene expression studies were performed by human genome microarray analysis and confirmed by quantitative real- time PCR. The transcription factor activity profile of LT-253-treated cells was determined by a multiplex transcription factor array and electrophoretic mobility shift assays. The functional role of specific genes was evaluated by siRNA gene knock-down. Results: LT-253 functions as chelator of zinc in vitro, and of intracellular labile zinc in HT-29 cells. Moreover, LT-253-mediated HT-29 cell growth inhibition was reversed by zinc supplementation. Gene expression profiling confirmed sustained changes in zinc-sensitive genes such as metallothionine and several zinc transporters, but not copper-sensitive or iron-sensitive genes. LT-253 induces cancer cell growth inhibition primarily through G1/S phase cell cycle arrest. Gene expression and transcription factor activities of both Egr-1 and KLF4 are induced within 4 hr post LT-253 treatment. Moreover, increased expression of both Egr-1 and KLF4 is observed in LT-253-sensitive cancer cell lines of various origins. Importantly, Egr-1 and KLF4 gene knock-down by siRNA reversed the LT-253-mediated cell growth inhibition of HT-29 cells. Conclusion: Selective chelation of intracellular labile zinc pool by LT-253 triggers immediate induction of stress-responsive tumor suppressor Egr-1 and sustained induction of zinc-responsive tumor suppressor KLF4, leading to G1/S phase cell cycle arrest and inhibition of tumor growth.

No significant financial relationships to disclose.

An essential role for CCAAT/enhancer binding protein beta in bleomycin-induced pulmonary fibrosis

Pulmonary fibrosis is characterized by inflammation, genesis of myofibroblasts, and abnormal tissue repair. Despite extensive research, its pathogenesis remains incompletely understood. Previously, the transcription factor CCAAT/enhancer binding protein beta (C/EBPbeta) was found to be a key regulator of myofibroblast differentiation in vitro, and to be involved in the acute phase and inflammatory responses. In an attempt to test the role of C/EBPbeta in the development of pulmonary fibrosis, experiments using C/EBPbeta null mice and their wild-type littermates were conducted. Our findings indicated that, compared to wild-type mice, animals deficient in C/EBPbeta showed significantly reduced fibrotic lesions and collagen deposition in the lung upon endotracheal injection of bleomycin. Further studies on the mechanisms by which C/EBPbeta regulates fibrosis indicated that knockout of C/EBPbeta attenuates inflammatory cytokine expression in bleomycin-treated mice. The reduced alpha-smooth muscle actin gene expression in either isolated lung fibroblasts or lung tissue from bleomycin or saline-treated C/EBPbeta deficient mice suggests that C/EBPbeta regulates myofibroblast differentiation during fibrosis. Consistent with this finding, cells from C/EBPbeta deficient mice exhibited higher proliferative rates than those from wild-type mice. These data suggest that C/EBPbeta plays an essential role in pulmonary fibrosis and that this role appears to be multifactorial with respect to cytokine expression, cell differentiation, and proliferation.

Aberrant quality control in the endoplasmic reticulum impairs the biosynthesis of pulmonary surfactant in mice expressing mutant BiP

Accumulation of misfolded proteins in the endoplasmic reticulum (ER) induces the unfolded protein response (UPR), which alleviates protein overload in the secretory pathway. Although the UPR is activated under diverse pathological conditions, its physiological role during development and in adulthood has not been fully elucidated. Binding immunoglobulin protein (BiP) is an ER chaperone, which is central to ER function. We produced knock-in mice expressing a mutant BiP lacking the retrieval sequence to cause a defect in ER function without completely eliminating BiP. In embryonic fibroblasts, the UPR compensated for mutation of BiP. However, neonates expressing mutant BiP suffered respiratory failure due to impaired secretion of pulmonary surfactant by alveolar type II epithelial cells. Expression of surfactant protein (SP)-C was reduced and the lamellar body was malformed, indicating that BiP plays a critical role in the biosynthesis of pulmonary surfactant. Because pulmonary surfactant requires extensive post-translational processing in the secretory pathway, these findings suggest that in secretory cells, such as alveolar type II cells, the UPR is essential for managing the normal physiological ER protein overload that occurs during development. Moreover, failure of this adaptive mechanism may increase pulmonary susceptibility to environmental insults, such as hypoxia and ischemia, ultimately leading to neonatal respiratory failure.

Prevention of Mantle Lymphoma Tumor Establishment by Routing Transferrin Receptor toward Lysosomal Compartments

Mantle cell lymphoma (MCL) is one of the most frequent of the newly recognized non-Hodgkin's lymphomas. The major problem of MCL therapy is the occurrence of relapse and subsequent resistance to chemotherapy and immunotherapy in virtually all cases. Here, we show that one injection of anti-human transferrin receptor (TfR) monoclonal antibody A24 totally prevented xenografted MCL tumor establishment in nude mice. It also delayed and inhibited tumor progression of established tumors, prolonging mice survival. In vitro, A24 induced up to 85% reduction of MCL cell proliferation (IC(50) = 3.75 nmol/L) independently of antibody aggregation, complement-dependent or antibody-dependent cell-mediated cytotoxicity. A24 induced MCL cell apoptosis through caspase-3 and caspase-9 activation, either alone or synergistically with chemotherapeutic agents. A24 induced TfR endocytosis via the clathrin adaptor protein-2 complex pathway followed by transport to lysosomal compartments. Therefore, A24-based therapies alone or in association with classic chemotherapies could provide a new alternative strategy against MCL, particularly in relapsing cases.

Zinc ribbon domain containing 1 protein: modulator of multidrug resistance, tumorigenesis and cell cycle

Zinc ribbon domain containing 1 (ZNRD1) gene encoding a protein consisting of two zinc ribbon domains was recently cloned from the human HLA locus. So far, ZNRD1 has been found implicated in transcription regulation and might play potential roles in mediating several biological processes, including multidrug resistance, tumorigenesis and cell cycle. This article reviewed these recent findings and provided additional information to support the role of ZNRD1 gene as a novel candidate DNA damage repair related gene.

Proteomic analysis of hypoxia-induced responses in the syncytialization of human placental cell line BeWo

Syncytiotrophoblast formation is affected by a number of pathological conditions and suppressed syncytiotrophoblast formation due to hypoxia may play a role in the pathogenesis of preeclampsia. However, the molecular basis of hypoxia-inhibited trophoblast syncytialization is poorly understood. To determine the effect of hypoxia on trophoblast syncytialization, a proteomic analysis was performed in the human cytotrophoblast cell line BeWo using two-dimensional electrophoresis and MALDI-TOF-TOF-MS. Hypoxia induced marked inhibition of BeWo cell fusion and differentiation. The proteomic profiling was established under hypoxia in BeWo cell syncytialization. The results showed that twenty proteins were significantly up-or down-regulated under hypoxia, compared with cells under normoxia. In response to hypoxia, three antioxidants, peroxiredoxin 1, peroxiredoxin 2 and 1-Cys peroxiredoxin, were down-regulated, two proteins involved in glycolysis pathway (malate dehydrogenase and enolase) were up-regulated. The expression of two members of the annexin family (annexin A2 and annexin A5) increased. We also found a decreased expression of 14-3-3 tau protein in hypoxia treated cells. Proteins implied in protein degradation and folding were also identified. The expression of two cytoskeleton components (keratin 1 and beta-actin) was found to be down-regulated. In addition, galectin-3 was up-regulated. These proteins have been implicated in regulating cellular oxidative stress, glycolysis, signal transduction, protein folding and degradation, cell mobility and cytoskeletal structure formation. Western blot analysis revealed that the levels of peroxiredoxin 1 and 14-3-3 tau decreased, whereas the levels of annexin A5 and annexin A2 increased in BeWo cells under hypoxia. These findings provided new insights into the molecular mechanisms in mediating cellular response to hypoxia in trophoblast syncytialization.