Development of the Gateway system for cloning and expressing genes in Entamoeba histolytica.

The early branching eukaryote Entamoeba histolytica is a human parasite that is the etiologic agent of amebic dysentery and liver abscess. The sequencing of the E. histolytica genome combined with the development of an E. histolytica microarray has resulted in the identification of several distinct gene expression profiles associated with virulence. The function of many modulated transcripts is unknown and their role in pathogenicity is unclear. They however represent a pool of potential virulence factors that could be targets for the development of novel therapeutics. Efficient tools and methods to characterize these novel virulence-associated genes and proteins would be beneficial. Here we report the use of the Gateway((R)) cloning system to generate the E. histolytica expression vector pAH-DEST. To test the usefulness of this system, the vector was used to construct a plasmid containing a recombinant version of the locus EHI_144490, which encoded a protein of unknown function. The recombinant gene was expressed and the recombinant protein, which was strep-myc-tagged, showed a cytoplasmic localization in transfected trophozoites. This expression vector with the Gateway((R)) system should facilitate investigation into the functions of novel proteins in E. histolytica.

Characterization of an Entamoeba histolytica high-mobility-group box protein induced during intestinal infection.

The unicellular eukaryote Entamoeba histolytica is a human parasite that causes amebic dysentery and liver abscess. A genome-wide analysis of gene expression modulated by intestinal colonization and invasion identified an upregulated transcript that encoded a putative high-mobility-group box (HMGB) protein, EhHMGB1. We tested if EhHMGB1 encoded a functional HMGB protein and determined its role in control of parasite gene expression. Recombinant EhHMGB1 was able to bend DNA in vitro, a characteristic of HMGB proteins. Core conserved residues required for DNA bending activity in other HMGB proteins were demonstrated by mutational analysis to be essential for EhHMGB1 activity. EhHMGB1 was also able to enhance the binding of human p53 to its cognate DNA sequence in vitro, which is expected for an HMGB1 protein. Confocal microscopy, using antibodies against the recombinant protein, confirmed its nuclear localization. Overexpression of EhHMGB1 in HM1:IMSS trophozoites led to modulation of 33 transcripts involved in a variety of cellular functions. Of these, 20 were also modulated at either day 1 or day 29 in the mouse model of intestinal amebiasis. Notably, four transcripts with known roles in virulence, including two encoding Gal/GalNAc lectin light chains, were modulated in response to EhHMGB1 overexpression. We concluded that EhHMGB1 was a bona fide HMGB protein with the capacity to recapitulate part of the modulation of parasite gene expression seen during adaptation to the host intestine.

Telomerase template antagonist GRN163L disrupts telomere maintenance, tumor growth, and metastasis of breast cancer.

PURPOSE: Maintenance of telomeres by telomerase is critical for the continuing proliferation of most advanced cancer cells. Telomerase activity has been detected in the vast majority of cancer cells but not most normal cells, making the enzyme an attractive target for anticancer therapy. The aim of this study was to address the breast cancer translational potential of the novel telomerase inhibitor, GRN163L. EXPERIMENTAL DESIGN: In the present study, we investigated the effects of GRN163L treatment on a panel of breast cancer cells representing different tumor subtypes with varying genetic backgrounds, including ER+, ER-, HER2+, BRCA1 mutant breast tumor cells as well as doxorubicin-resistant cancer cells. To investigate the in vivo effects of GRN163L, we employed a breast cancer xenograft and metastasis model that simulates a clinical situation in which a patient arrives with a primary tumor that may be then treated or surgically removed. RESULTS: GRN163L effectively inhibited telomerase activity in a dose-dependent fashion in all breast cancer cell lines resulting in progressive telomere shortening. A mismatch control oligonucleotide showed no effect on telomerase activity and GRN163L did not significantly affect telomere shortening in normal human mammary epithelial cells or in endothelial cells. Breast cancer cells that exhibited telomerase inhibition also exhibited significant reduction in colony formation and tumorigenicity. Furthermore, GRN163L suppressed tumor growth and lung metastases (P = 0.017) of MDA-MB-231 cells in vivo after 4 weeks of treatment. CONCLUSIONS: These results show in vivo effectiveness of GRN163L in breast cancer and support its promising clinical potential for breast cancer treatment.

Nonradioactive detection of telomerase activity using the telomeric repeat amplification protocol.

The telomeric repeat amplification protocol (TRAP) is a two-step process for analyzing telomerase activity in cell or tissue extracts. Recent modifications of this sensitive assay include elimination of radioactivity by using a fluorescently labeled primer instead of a radiolabeled primer. In addition, the TRAP assay has been modified for real-time, quantitative PCR analysis. Here, we describe cost-effective procedures for detection of telomerase activity using a fluorescent-based assay as well as by using real-time PCR. These modified TRAP assays can be accomplished within 4 h (from lysis of samples to analysis of telomerase products).