Engineering Synthetic Chromosomes by Sequential Loading of Multiple Genomic Payloads over 100 Kilobase Pairs in Size.

Gene delivery vehicles currently in the clinic for treatment of monogenic disorders lack sufficient carrying capacity to efficiently address complex polygenic diseases. Thus, to engineer multifaceted genetic circuits for bioengineering human cells as a therapeutic option for polygenic diseases, we require new tools that are currently in their infancy. Mammalian artificial chromosomes, or synthetic chromosomes, represent a viable approach for delivery of large genetic payloads that are mitotically stable and remain independent of the host genome.

AXL is a potential therapeutic target in dedifferentiated and pleomorphic liposarcomas.

Background: AXL is a well-characterized, protumorigenic receptor tyrosine kinase that is highly expressed and activated in numerous human carcinomas and sarcomas, including aggressive subtypes of liposarcoma. However, the role of AXL in the pathogenesis of well-differentiated (WDLPS), dedifferentiated (DDLPS), and pleomorphic liposarcoma (PLS) has not yet been determined.

Methods: Immunohistochemical analysis of AXL expression was conducted on two tissue microarrays containing patient WDLPS, DDLPS, and PLS samples.

Predictors of guideline treatment nonadherence and the impact on survival in patients with colorectal cancer.

Background: This study investigated the effect of comorbidity, age, health insurance payer status, and race on the risk of patient nonadherence to NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines) for Colon and Rectal Cancers. In addition, the prognostic impact of NCCN treatment nonadherence on overall survival was assessed.

Patients And Methods: Patients with CRC who received primary treatment at Memorial University Medical Center from 2003 to 2010 were eligible for this study.

Differential expression of cysteine dioxygenase 1 in complex karyotype liposarcomas.

Altered cysteine dioxygenase 1 (CDO1) gene expression has been observed in several cancers but has not yet been investigated in liposarcomas. The aim of this study was to evaluate CDO1 expression in a cohort of liposarcomas and to determine its association with clinicopathological features. Existing microarray data indicated variable CDO1 expression in liposarcoma subtypes.

Telomerase suppresses formation of ALT-associated single-stranded telomeric C-circles.

Telomere maintenance is an essential characteristic of cancer cells, most commonly achieved by activation of telomerase. Telomeres can also be maintained by a recombination-based mechanism, alternative lengthening of telomeres (ALT). Cells using ALT are characterized by the presence of ALT-associated promyelocytic leukemia (PML) bodies (APB), long, heterogeneously sized telomeres, extrachromosomal telomeric circular DNA, and elevated telomeric recombination.

Pleomorphic liposarcoma: clinical observations and molecular variables.

Background: Pleomorphic liposarcoma (PLS) is a rare high-grade sarcoma that has lipoblastic differentiation. In this study, the authors evaluated PLS natural history, patient outcomes, and commonly deregulated protein biomarkers.

Methods: Medical records from patients (n = 155) who had PLS from 1993 to 2010 were reviewed.

Doxorubicin resistance in a novel in vitro model of human pleomorphic liposarcoma associated with alternative lengthening of telomeres.

Soft tissue sarcomas are a diverse set of fatal human tumors where few agents have demonstrable clinical efficacy, with the standard therapeutic combination of doxorubicin and ifosfamide showing only a 25% to 30% response rate in large multi-institutional trials. Although liposarcomas are the most common histologic form of adult soft tissue sarcomas, research in this area is severely hampered by the lack of experimentally tractable in vitro model systems. To this end, here we describe a novel in vitro model for human pleomorphic liposarcoma.

MLL associates with telomeres and regulates telomeric repeat-containing RNA transcription.

Mammalian telomeres consist of TTAGGG repeats organized in nucleosomes and associated with a six-protein complex known as shelterin, which preserves telomere structure and protects chromosome ends from the cellular DNA damage response. Recent studies have found that telomeres are transcribed into telomeric UUAGGG repeat-containing RNA (TERRA) starting from subtelomeric regions. TERRA binding at telomeres appears to be involved in cis-based mechanisms of telomeric chromatin organization and maintenance.

Function, replication and structure of the mammalian telomere.

Telomeres are specialized structures at the ends of linear chromosomes that were originally defined functionally based on observations first by Muller (1938) and subsequently by McClintock (1941) that naturally occurring chromosome ends do not behave as double-stranded DNA breaks, in spite of the fact that they are the physical end of a linear, duplex DNA molecule. Double-stranded DNA breaks are highly unstable entities, being susceptible to nucleolytic attack and giving rise to chromosome rearrangements through end-to-end fusions and recombination events. In contrast, telomeres confer stability upon chromosome termini, as evidenced by the fact that chromosomes are extraordinarily stable through multiple cell divisions and even across evolutionary time.

The origin recognition complex localizes to telomere repeats and prevents telomere-circle formation.

Chromosome ends are maintained by telomere-repeat-binding factors (TRFs) that coordinate DNA end protection with telomere replication. The origin recognition complex (ORC) coordinates bidirectional DNA replication at most chromosomal sites, but it is also known to function in transcriptional silencing, heterochromatin formation, and sister-chromatid cohesion. We now show that ORC localizes to telomere repeats and contributes to telomere maintenance.

Whole-genome profiling in liposarcomas reveals genetic alterations common to specific telomere maintenance mechanisms.

Telomere attrition ultimately leads to the activation of protective cellular responses, such as apoptosis or senescence. Impairment of such mechanisms can allow continued proliferation despite the presence of dysfunctional telomeres. Under such conditions, high levels of genome instability are often engendered.

Telomere maintenance in sarcomas.

Purpose Of Review: To examine the activation of telomere maintenance in a variety of sarcoma subtypes, and to review the consequences of telomere maintenance with respect to genome stability and tumor progression.

Recent Findings: A hallmark of tumor cells is replicative immortality, which can be achieved, in part, by the activation of a telomere maintenance mechanism. A significant proportion of tumors show activation of telomerase, a specialized enzyme that adds telomeric repeats to pre-existing telomeres.

BRCC36 is essential for ionizing radiation-induced BRCA1 phosphorylation and nuclear foci formation.

We have previously reported the identification and characterization of a novel BRCA1/2 interacting protein complex, BRCC (BRCA1/2-containing complex). BRCC36, one of the proteins in BRCC, directly interacts with BRCA1, and regulates the ubiquitin E3 ligase activity of BRCC. Importantly, BRCC36 is aberrantly expressed in the vast majority of breast tumors, indicating a potential role in the pathogenesis of this disease.

p53 differentially inhibits cell growth depending on the mechanism of telomere maintenance.

Telomere stabilization is critical for tumorigenesis. A number of tumors and cell lines use a recombination-based mechanism, alternative lengthening of telomeres (ALT), to maintain telomere repeat arrays. Current data suggest that the mutation of p53 facilitates the activation of this pathway.

Chromosome 17p13.2 transfer reverts transformation phenotypes and Fas-mediated apoptosis in breast epithelial cells.

Transformation of the human breast epithelial cells (HBEC) MCF-10F with the carcinogen benz(a)pyrene (BP) into BP1-E cells resulted in the loss of the chromosome 17 p13.2 locus (D17S796 marker) and formation of colonies in agar-methocel (colony efficiency (CE)), loss of ductulogenic capacity in collagen matrix, and resistance to anti-Fas monoclonal antibody (Mab)-induced apoptosis. For testing the role of that specific region of chromosome 17 in the expression of transformation phenotypes, we transferred chromosome 17 from mouse fibroblast donors to BP1-E cells.

Telomerase is frequently activated in tumors with microsatellite instability.

Telomeres are specialized structures at the ends of eukaryotic chromosomes that are required for the complete replication and stability of naturally occurring chromosome ends. Telomere stabilization is critical for the unlimited cellular proliferation that is necessary for tumor formation. While most tumors achieve telomere stabilization through activation of telomerase, a subset of tumors utilize a recombination-based mechanism termed Alternative Lengthening of Telomeres (ALT) to maintain chromosome termini.

Telomere repeat binding factors TRF1, TRF2, and hRAP1 modulate replication of Epstein-Barr virus OriP.

Epstein-Barr virus OriP confers cell cycle-dependent DNA replication and stable maintenance on plasmids in EBNA1-positive cells. The dyad symmetry region of OriP contains four EBNA1 binding sites that are punctuated by 9-bp repeats referred to as nonamers. Previous work has shown that the nonamers bind to cellular factors associated with human telomeres and contribute to episomal maintenance of OriP.

Telomerase inhibition using azidothymidine in the HT-29 colon cancer cell line.

Background: We investigated the effects of telomerase inhibition by using the reverse transcriptase inhibitor azidothymidine (AZT) in the human colorectal cancer cell line HT-29 in the presence and absence of 5-fluorouracil (5-FU).

Methods: HT-29 cells were cultured in the presence of AZT. Telomerase activity was measured by using the telomerase repeat amplification protocol.

Putative telomere-recruiting domain in the catalytic subunit of human telomerase.

Telomerase, the enzyme that elongates telomeres, is essential to maintain telomere length and to immortalize most cancer cells. However, little is known about the regulation of this enzyme in higher eukaryotes. We previously described a domain in the hTERT telomerase catalytic subunit that is essential for telomere elongation and cell immortalization in vivo but dispensable for catalytic activity in vitro.

SV40 infection induces telomerase activity in human mesothelial cells.

Mesotheliomas are malignant tumors of the pleural and peritoneal membranes which are often associated with asbestos exposure and with Simian virus 40 (SV40) infection. Telomerase activity is repressed in somatic cells and tissues but is activated in immortal and malignant cells. We evaluated telomerase activity in seven primary malignant mesothelioma biopsies and matched lung specimens and 20 mesothelioma cell lines and eight corresponding primary tumor cultures.