“VISA” Nanoparticles to Breast Cancer

Development of cancer gene therapy has been hampered by the fact that there are no effective cancer-specific expression vectors available, which is critical for improving therapeutic efficacy and reducing toxicity in clinics. To overcome this problem, we recently developed a safe and effective strategy fro targeting a potent pro-apoptotic gene (BikDD) to the pancreatic tumors (Xie et al. Cancer Cell, 2007). A VISA system (VP16-Gal4-WPRE integrated systemic amplifier) was engineered by using the two-step transcriptional amplification (TSTA) system and the posttranscriptional regulatory element of the woodchuck hepatitis virus (WPRE). The VISA system can boost the activity of cancer-specific promoters by an average of 600 folds compared to their basal levels. C-VISA (CCKAR-VISA) nanoparticles transcriptionally targets transgene expression effectively to pancreatic tumors in vivo. C-VISA-BikDD nanoparticles was shown to be highly effective in reducing tumor burden and increasing animal survival rate in orthotopic pancreatic cancer models which is moving into clinical trials at University of Texas M.D. Anderson Cancer Center, USA. In the current study, we identified hTERT(human telomerase reverse transcriptase), ß-cateinin, claudin-4, and FASN (fatty acid synthase) promoters as breast cancer-selective promoters, and amplified their activity to hundreds of folds greater by the “VISA” system without loss of their specificity. We further demonstrated significant antitumor activity of targeted BikDD expression driven by nanoparticles of the hTERT-VISA-BikDD vectors in Her-2-negative and -positive breast cancer cell lines and in multiple breast cancer models of living imaging by the Xenogen IVIS imaging system with limited toxicity. In addition, treatment with hTERT-VISA-BikDD nanoparticles plus lapatinib or produces evident combinational therapeutic efficacy, which is likely due to the ability of lapatinib to promote apoptosis of Her-2-overexpressing breast cancer cells. Thus, our newly developed hTERT-VISA-BikDD nanoparticles are an innovative strategy for targeted antitumor effects of both Her-2-negative and Her-2-positive breast cancer.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 5159.

Dosage compensation on the active X chromosome minimizes transcriptional noise of X-linked genes in mammals

Comparison of gene expression variation in autosomal and X-linked genes reveals that high transcriptional noise is not a necessary consequence of haploid expression.

Background

Theory predicts that haploid-expressed genes should have noisier expression than comparable diploid-expressed ones with the same expression level. However, in mammals there are several classes of gene that are monoallelically expressed, including X-linked genes, imprinted genes and some other autosomal genes. Does it follow that the evolution of X chromosomes in eukaryotes comes at the cost of increased transcriptional noise in the heterogametic sex? Moreover, is escaping X-inactivation in mammalian females associated with an increase in transcriptional variation? To address these questions, we analyze gene expression variation between replicate samples of diverse mammalian cell lines in steady-state using microarray data.

Results

We observe that transcriptional variation of X-linked genes is no different to that of autosomal genes both before and after control for transcript abundance. By contrast, autosomal genes subject to allelic exclusion do have unusually high noise levels even allowing for their low transcript abundance. The prior theory we suggest was insufficient, at least as regards X-chromosomes, as it failed to appreciate the regulatory complexity of gene expression, not least the effects of genomic neighborhood.

Conclusions

These results suggest that high noise is not a necessary consequence of haploid expression and emphasize the primacy of expression level as a determinant of noise. The latter has consequences for understanding the etiology of haplo-insufficiency and the evolution of gene expression levels. Given the coupling between expression level and noise on the X-chromosome, we suggest that part of the selective advantage of dosage compensation is noise abatement of X-linked genes.

Quantitative assessment of AKT activation in melanoma

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Background: Activating mutations of BRAF are highly prevalent in melanoma. However, multiple lines of evidence suggest that other pathways must also contribute to this disease. Activation of the PI3K-AKT pathway has been implicated in melanoma by mutations of NRAS and PTEN. Little direct information is known about the activation of the PI3K-AKT signaling pathway in melanoma, particularly in metastases. Methods: Proteins isolated from 99 frozen melanoma tumors were measured by reverse phase protein arrays (RRPA). A total of 53 proteins were assessed using validated antibodies. Activating mutations were assessed by mass spectroscopy-based genotyping. Activation of AKT (phospho-AKT) was compared to mutations and anatomic sites. Results: Samples from 75 regional metastases (LN or in-transit) and 24 distant metastases were analyzed. Technical replicates (same lysate) and biological replicates (same tumor, different lysates) demonstrated average Pearson correlation coefficients (r) of > 0.90, supporting the high technical quality of the analysis. A positive correlation was observed between levels of p-AKT and known AKT substrates p-GSK3 and p-TSC2 (p< 0.001 for both), and a negative correlation with PTEN (p < 0.01), supporting the maintenance of phosphorylation events during sample processing. Relative differences in p-AKT by RPPA were also confirmed by immunohistochemistry of representative tumors. Tumors with BRAF mutations had higher levels of p-AKT than tumors with NRAS mutations (p = 0.03). Indeed, tumors with NRAS mutations had p-AKT levels similar to tumors wild-type for BRAF and NRAS (p =0.73). Detailed analysis demonstrated that all tumors with elevated p-AKT had low PTEN expression. Similar results were seen in human melanoma cell lines. Analysis of distant metastases demonstrated that brain metastases had higher levels of p-AKT, p-GSK3, and p-TSC2, and lower levels of PTEN, compared to metastases to the lung or liver. Conclusions: AKT activation in melanoma correlates with PTEN expression, and does not correlate with NRAS mutation. Activation of the PI3K-AKT pathway may contribute to the aggressiveness of brain metastases. These findings have clinical implications for targeting this pathway, and demonstrate the feasibility and potential of RPPA analysis of signaling pathways in melanoma.

No significant financial relationships to disclose.

The impact of nucleosome positioning on the organization of replication origins in eukaryotes

The distribution of DNA replication origins (ORIs) on eukaryotic chromosomes is nonrandom, but the reasons behind this are not well understood. Previous studies have suggested a prominent role of transcriptional activity in determining the ORI organization. Here, we identify nucleosome occupancy as a likely candidate to set up ORI distribution. Combining genome-wide data on nucleosome positioning and ORI organization in yeast and humans, we demonstrate that open chromatin domains, characterized by nucleosome depletion, are preferentially permissive for replication. However, contrary to priori claims, the impact of transcriptional activity is considerably weaker than previously proposed and could partly be explained by our nucleosome exclusion model. We propose that the ORI organization imposed by nucleosome positioning is phylogenetically widespread in eukaryotes.

Evidence that the nonsense-mediated mRNA decay pathway participates in X chromosome dosage compensation in mammals

Current models of X chromosome dosage compensation are usually framed by reference to how regulation in transcriptional level elevates the gene expression of the active X chromosome. This framework, however, might be oversimplified because regulation of gene expression can also act at the post-transcriptional level. Here, after a genome-wide survey, we find that autosomal genes are more likely subject to nonsense-mediated mRNA decay (NMD) than X-linked genes. Furthermore, we demonstrate that after NMD inhibition, balanced gene expression between X chromosome and autosomes is corrupted such that the global mean X/autosome gene expression ratio is decreased by 10-15%. Our results identify NMD as a post-transcription-level regulatory mechanism that contributes to the observed fine-tuning of X chromosome dosage compensation in mammals.

The pathologic features of neurocutaneous melanosis in a cynomolgus macaque

Neurocutaneous melanosis (NCM) is a rare phakomatosis characterized by proliferation of melanin-producing cells in both the skin and the brain. In this study, we describe the clinical and pathologic features of NCM in a 4.5-year-old female cynomolgus macaque. Histopathologically, skin lesions showed foci of nests and cords of pigmented cells in the dermis similar to blue nevi in humans. In the brain, focal pigmented cell infiltration was observed in the connective tissue under the leptomeninges and in the brain parenchyma. The pigmented cell was moderately reactive with a pan-melanoma antibody (melanoma(pan)) in the skin. In the brain, the pigmented cell was moderately to strongly positive for melanoma(pan) in subleptomeningeal areas and in the cerebral cortex. Melanosomes were observed in pigmented cells in the brain by electron microscopic examination. Based on the histologic, immunohistochemical, and electron microscopic results, the diagnosis of NCM was made. This case is possibly the first report of the condition in animals.

First observation of the Greisen-Zatsepin-Kuzmin suppression

The High Resolution Fly's Eye (HiRes) experiment has observed the Greisen-Zatsepin-Kuzmin suppression (called the GZK cutoff) with a statistical significance of five standard deviations. HiRes' measurement of the flux of ultrahigh energy cosmic rays shows a sharp suppression at an energy of 6 x 10(19) eV, consistent with the expected cutoff energy. We observe the ankle of the cosmic-ray energy spectrum as well, at an energy of 4 x 10(18) eV. We describe the experiment, data collection, and analysis and estimate the systematic uncertainties. The results are presented and the calculation of the statistical significance of our observation is described.

TGF-beta receptor II in epithelia versus mesenchyme plays distinct roles in the developing lung

Transforming growth factor (TGF)-beta signalling plays important roles in regulating lung development. However, the specific regulatory functions of TGF-beta signalling in developing lung epithelial versus mesenchymal cells are still unknown. By immunostaining, the expression pattern of the TGF-beta type II receptor (TbetaRII) was first determined in the developing mouse lung. The functions of TbetaRII in developing lung were then determined by conditionally knocking out TbetaRII in the lung epithelium of floxed-TbetaRII/surfactant protein C-reverse tetracycline transactivator/TetO-Cre mice versus mesenchyme of floxed-TbetaRII/Dermo1-Cre mice. TbetaRII was expressed only in distal airway epithelium at early gestation (embryonic day (E)11.5), but in both airway epithelium and mesenchyme from mid-gestation (E14.5) to post-natal day 14. Abrogation of TbetaRII in mouse lung epithelium resulted in retardation of post-natal lung alveolarisation, with markedly decreased type I alveolar epithelial cells, while no abnormality in prenatal lung development was observed. In contrast, blockade of TbetaRII in mesoderm-derived tissues, including lung mesenchyme, resulted in mildly abnormal lung branching and reduced cell proliferation after mid-gestation, accompanied by multiple defects in other organs, including diaphragmatic hernia. The primary lung branching defect was verified in embryonic lung explant culture. The novel findings of the present study suggest that transforming growth factor-beta type II receptor-mediated transforming growth factor-beta signalling plays distinct roles in lung epithelium versus mesenchyme to differentially control specific stages of lung development.

Microtubule breakage is not a major mechanism for resolving end-to-end chromosome fusions generated by telomere dysfunction during the early process of immortalization

Telomeres, the terminal chromosomal structure crucial for maintaining genomic integrity, shorten with deoxyribonucleic acid replications in most human somatic cells. Chromosomes carrying critically short telomeres tend to form end-to-end fusions, which are subject to breakage during cell division. However, it remains obscure how such telomere-mediated fusions are resolved during the process of immortalization, which is an early and indispensable step toward cancer. It has been hypothesized that the breakage could occur at either the microtubule or chromatid, causing numerical or structural chromosome instability, respectively. In this paper, we show that although the distributions of chromosomal segment losses or gains involved in structural aberrations were significantly correlated with the profiles of critically short telomeres in human epithelial cells undergoing immortalization, no such association was detected for whole-chromosome losses or gains in either metaphase or interphase cells. By distinguishing between homologues, we further showed that the specific homologues with critically short telomeres and frequent end-to-end fusions were not preferentially involved in respective whole-chromosome losses or gains. Our data therefore demonstrate that microtubule breakage is not a major mechanism for resolving chromosomal end-to-end fusions in human cells undergoing immortalization. An important implication of this finding is that microtubule-kinetochore attachment is stronger than the chromosome structure.

Oncogenic activation of c-Abl in non-small cell lung cancer cells lacking FUS1 expression: inhibition of c-Abl by the tumor suppressor gene product Fus1

In lung cancer, frequent loss of one allele of chromosome 3p is seen in both small cell lung cancer and non-small cell lung cancer (NSCLC), providing evidence of tumor suppressor genes (TSGs) in this chromosomal region. The mechanism of Fus1 tumor suppressor activity is unknown. We have found that a Fus1 peptide inhibits the Abl tyrosine kinase in vitro (IC(50) 35 microM). The inhibitory Fus1 sequence was derived from a region that was deleted in a mutant FUS1 gene (FUS1 (1-80)) detected in some lung cancer cell lines. Importantly, a stearic acid-modified form of this peptide was required for the inhibition, but stearic acid alone was not inhibitory. Two NSCLC cell lines, which lack expression of wild-type Fus1, contain activated c-Abl. Forced expression of an inducible FUS1 cDNA in H1299 NSCLC cells decreased levels of activated c-Abl and inhibited its tyrosine kinase activity. Similarly, treatment of c-Abl immune complexes with the inhibitory Fus1 peptide also reduced the level of c-Abl in these immune complexes. The size and number of colonies of the NSCLC cell line, H1,299, in soft agar was strongly inhibited by the Abl kinase inhibitor imatinib mesylate. Co-expression of FUS1 and c-ABL in COS1 cells blocked activation of c-Abl tyrosine kinase. In contrast, co-expression of mutant FUS1 (1-80) with c-ABL had little inhibitory activity against c-Abl. These findings provide strong evidence that c-Abl is a possible target in NSCLC patients that have reduced expression of Fus1 in their tumor cells.

The role of dynamin 3 in the testis

We report here that dynamin 3 in the testis is associated with structures termed tubulobulbar complexes that internalize intact intercellular junctions during sperm release and turnover of the blood-testis barrier. The protein lies adjacent to an actin-Arp2/3 network that cuffs the double plasma membrane tubular invagination at the core of each complex. To explore the possible relationship between dynamin 3 and nectin-based adhesion junctions, we transiently transfected DsRed-tagged dynamin 3 into MDCK cells stably transfected with eGFP-tagged nectin 2, one of the adhesion molecules known to be expressed in Sertoli cells at adhesion junctions. Cells transfected with the dynamin 3 construct had less uniformly distributed nectin 2 at intercellular contacts when compared to control cells expressing only nectin 2 or transfected with the DsRed plasmid alone. Significantly, tubular extensions positive for nectin 2 were visible projecting into the cells from regions of intercellular contact. Our findings are consistent with the conclusion that dynamin 3 is involved with tubulobulbar morphogenesis. Dynamin 3 also occurs in concentrated deposits around the capitulum and striated columns in the connecting piece of sperm tails suggesting that the protein in these cells may function to stabilize the base of the tail or serve as a reservoir for use during or after fertilization.

Core promoter elements recognized by transcription factor IIB

The general transcription factor TFIIB (transcription factor IIB) plays a critical role in the assembly of the RNA polymerase II pre-initiation complex. TFIIB can make sequence-specific DNA contacts both upstream and downstream of the TATA box. This has led to the definition of two core promoter BREs (TFIIB-recognition elements), one upstream [BRE(u) (upstream BRE)] and one downstream of TATA box [BRE(d) (downstream BRE)]. TFIIB-BRE(u) and TFIIB-BRE(d) contacts are mediated by two independent DNA-recognition motifs within the core domain of TFIIB. Both the BRE(u) and the BRE(d) modulate the transcriptional potency of a promoter. However, the net effect of the BREs on promoter activity is dependent on the specific blend of elements present within a core promoter.

Gli1 acts through Snail and E-cadherin to promote nuclear signaling by beta-catenin

The Hedgehog pathway transcription factor Gli1 induces transformation of epithelial cells via induction of Snail, a repressor of E-cadherin (E-cad). E-cad is normally complexed with beta-catenin at the cell membrane. Loss of E-cad during developmental epithelial-mesenchymal transitions can switch beta-catenin from its role at adherens junctions to its role in nuclear transcription. During tumorigenesis it is unclear which pathways trigger this switch. In the current study, gain- and loss-of-function approaches identified E-cad as a selective inhibitor of transformation by Gli1, and Snail knockdown was rescued by downregulation of E-cad. Gli1 induced relocalization of beta-catenin from the cell membrane to the nucleus. The ability of wild-type or mutant alleles of E-cad to modulate transformation by Gli1 correlated with their ability to regulate localization of beta-catenin. Inhibition of Wnt-beta-catenin signaling by dominant negative Tcf4 selectively blocked in vitro transformation by Gli1. In Gli1-transgenic mice, infiltrating skin tumor cells expressed active, unphosphorylated beta-catenin. Our studies identify E-cad as a selective suppressor of transformation by Gli1 and point to the Sonic Hedgehog-Gli1 pathway as a key regulator of the beta-catenin switch in epithelial cells and cancers.

Pressor responses to ephedrine are not impaired in dopamine beta-hydroxylase knockout mice

BACKGROUND AND PURPOSE

Ephedrine and amphetamine can cause substantial increases in systemic arterial pressure. However, the role of endogenous noradrenaline release in mediating the pressor response to ephedrine is controversial. Studies using pharmacologic agents to decrease the synthesis, storage, and release of catecholamines have supported both a direct and an indirect mechanism of action for ephedrine. The purpose of the present study was to determine if endogenous noradrenaline release is required for cardiovascular responses to ephedrine and amphetamine using a genetic mouse model.

EXPERIMENTAL APPROACH

Increases in systemic arterial pressure and heart rate in response to ephedrine and amphetamine were investigated and compared in dopamine beta-hydroxylase knockout (Dbh -/-) mice that cannot synthesize noradrenaline. Dbh +/- littermates have normal noradrenaline and adrenaline tissue levels, and served as controls in all experiments.

KEY RESULTS

In Dbh -/- mice the increases in systemic arterial pressure and heart rate in response to i.v. injections of ephedrine were not impaired whereas responses to amphetamine were markedly reduced, when compared with responses in Dbh +/- mice. The pressor response to tyramine was abolished whereas pressor responses to noradrenaline, phenylephrine, dopamine, and angiotensin II were similar in Dbh -/- and Dbh +/- mice.

CONCLUSIONS AND IMPLICATIONS

The present results in Dbh -/- mice provide support for the hypothesis that pressor responses to ephedrine are directly mediated whereas responses to amphetamine are dependent on the release of noradrenaline and suggest that Dbh +/- and Dbh -/- mice are useful for the study of direct and indirect mechanisms.

Molecular and cytogenetic changes involved in the immortalization of nasopharyngeal epithelial cells by telomerase

Nasopharyngeal carcinoma (NPC) is a common disease in Hong Kong and southern provinces of China. EBV infection is believed to play a critical role in the development of NPC. Previous studies on the transformation mechanism of EBV genes were mostly performed in either NPC or nonnasopharyngeal epithelial cells which may not be representative of premalignant nasopharyngeal epithelial cells. Establishment of a representative cell system would greatly facilitate the elucidation of the role of EBV infection in the development of NPC. Using telomerase alone, we were able to establish an immortalized nasopharyngeal epithelial cell line from primary nonmalignant nasopharyngeal biopsies. The telomerase-immortalized nasopharyngeal epithelial cells are largely diploid in karyotype. Interestingly, this newly immortalized nasopharyngeal epithelial cell line, referred as NP460hTert, harbors genetic alterations previously identified in premalignant and malignant nasopharyngeal epithelial cells. These include inactivation of p16 by homozygous deletion of the p16(INK4A) locus and downregulation of RASSF1A expression. The deletion of the p16(INK4A) locus appears to be the most crucial event for the immortalization of nasopharyngeal epithelial cells by telomerase and precedes RASSF1A downregulation. In addition, detailed analysis of the cytogenetic changes by conventional cytogenetics, spectral karyotyping (SKY) and array-based CGH revealed a gain of a 17q21-q25 fragment on 11p15 chromosome in all NP460hTert cells which occurred before deletion of the p16(INK4A) locus. Gain of 17q has been previously reported in NPC. In addition, activation of NF-kappaB was observed in immortalized NP460hTert cells at the later population doublings, and may play a role in the survival of immortalized NP epithelial cells. Id1 which is commonly expressed in various human cancers, including NPC, was also upregulated in the immortalized NP460hTert cells. Thus, the establishment of an immortalized nasopharyngeal epithelial cell line harboring common genetic alterations present in premalignant and cancerous nasopharyngeal epithelial cells may provide a valuable cell system to examine for early events involved in NPC carcinogenesis, particularly in elucidating the role of EBV infection in NPC development.

Gene and stem cell therapy for erectile dysfunction

Erectile dysfunction (ED) is defined as the inability to attain and/or maintain penile erection sufficient for satisfactory sexual performance. ED is a highly prevalent health problem with considerable impact on the quality of life of men and their partners. Although the treatment of ED with oral phosphodiesterase type V (PDE5) inhibitors is effective in a wide range of individuals, it is not efficacious in all patients. The failure of PDE5 inhibitors happens mainly in men with diabetes, non-nerve sparing radical prostatectomy, and high disease severity. Therefore, improved therapies based on a better understanding of the fundamental issues in erectile physiology and pathophysiology have recently been proposed. Here, we summarize studies on ED treatment using gene and stem cell therapies. Adenoviral-mediated intracavernosal transfer of therapeutic genes, such as endothelial nitric oxide synthase (eNOS), calcitonin gene-related peptide (CGRP), superoxide dismutase (SOD), and RhoA/Rho kinase and mesenchymal stem cell-based cell and gene therapy strategy for the treatment of age- and diabetes-related ED are the focus of this review.

Identifying potential risk haplotypes for schizophrenia at the DTNBP1 locus in Han Chinese and Scottish populations

The dystrobrevin-binding protein 1 (DTNBP1) gene on chromosome 6p has emerged as a potential susceptibility gene for schizophrenia. Although a number of attempts to replicate the original association finding have been successful, they have not identified any obvious pathogenic variants or a single at risk haplotype common to all populations studied. In the present study we attempted further replication in an independent sample of 638 nuclear families from the Han Chinese population of Sichuan Province, SW China. We also examined 580 Scottish schizophrenic cases and 620 controls. We genotyped 10 single-nucleotide polymorphisms (SNPs) in DTNBP1 that were used in the original report of association, plus rs2619538 (SNP 'A') in the putative promoter region, which has also been associated with schizophrenia. In the Chinese trios we found that two SNPs (P1635 and P1765) were significantly overtransmitted, but with alleles opposite to those reported in the original studies. SNPs P1757 and P1765 formed a common haplotype, which also showed significant overtransmission. In the Scottish cases and controls, no individual markers were significantly associated with schizophrenia. A single haplotype, which included rs2619538 and P1583, and one rare haplotype, composed of P1320 and P1757, were significantly associated with schizophrenia, but no previously reported haplotypes were associated. Based on the data from the Chinese population, our results provide statistical support for DTNBP1 as a susceptibility gene for schizophrenia, albeit with haplotypes different from those of the original study. However, our lack of replication in the Scottish samples also indicates that caution is warranted when evaluating the robustness of the evidence for DTNBP1 as genetic risk factor for schizophrenia.