Evaluating the Role of Mitochondrial Function in Cancer-related Fatigue

Fatigue is a common and debilitating condition that affects most cancer patients. To date, fatigue remains poorly characterized with no diagnostic test to ...

National Institutes of Health

Chromosomal aneuploidy is a defining feature of carcinomas. For instance, in colon cancer, an additional copy of Chromosome 7 is not only observed in early pre-malignant polyps, but is faithfully maintained throughout progression to metastasis. These copy number changes show a positive correlation with average transcript levels of resident genes. An independent line of research has also established that specific chromosomes occupy a well conserved 3D position within the interphase nucleus.

Artificially introduced aneuploid chromosomes assume a conserved position in colon cancer cells.

The nonrandom positioning of chromosome territories in eukaryotic cells is largely correlated with gene density and is conserved throughout evolution. Gene-rich chromosomes are predominantly central, while gene-poor chromosomes are peripherally localized in interphase nuclei. We previously demonstrated that artificially introduced human chromosomes assume a position equivalent to their endogenous homologues in the diploid colon cancer cell line DLD-1. These chromosomal aneuploidies result in a significant increase in transcript levels, suggesting a relationship between genomic copy number, gene expression, and chromosome position. We previously proposed that each chromosome is marked by a "zip code" that determines its nonrandom position in the nucleus. In this paper, we investigated (1) whether mouse nuclei recognize such determinants of nuclear position on human chromosomes to facilitate their distinct partitioning and (2) if chromosome positioning and transcriptional activity remain coupled under these trans-species conditions. Using three-dimensional fluorescence in situ hybridization, confocal microscopy, and gene expression profiling, we show (1) that gene-poor and gene-rich human chromosomes maintain their divergent but conserved positions in mouse-human hybrid nuclei and (2) that a foreign human chromosome is actively transcribed in mouse nuclei. Our results suggest a species-independent conserved mechanism for the nonrandom positioning of chromosomes in the three-dimensional interphase nucleus.

Position of human chromosomes is conserved in mouse nuclei indicating a species-independent mechanism for maintaining genome organization.

To evaluate the mechanisms and consequences of chromosomal aberrations in colorectal cancer (CRC), we used a combination of spectral karyotyping, array comparative genomic hybridization (aCGH), and array-based global gene expression profiling on 31 primary carcinomas and 15 established cell lines. Importantly, aCGH showed that the genomic profiles of primary tumors are recapitulated in the cell lines. We revealed a preponderance of chromosome breakpoints at sites of copy number variants (CNVs) in the CRC cell lines, a novel mechanism of DNA breakage in cancer. The integration of gene expression and aCGH led to the identification of 157 genes localized within high-level copy number changes whose transcriptional deregulation was significantly affected across all of the samples, thereby suggesting that these genes play a functional role in CRC. Genomic amplification at 8q24 was the most recurrent event and led to the overexpression of MYC and FAM84B. Copy number dependent gene expression resulted in deregulation of known cancer genes such as APC, FGFR2, and ERBB2. The identification of only 36 genes whose localization near a breakpoint could account for their observed deregulated expression demonstrates that the major mechanism for transcriptional deregulation in CRC is genomic copy number changes resulting from chromosomal aberrations.

Integrative genomics reveals mechanisms of copy number alterations responsible for transcriptional deregulation in colorectal cancer.

Colorectal carcinomas (CRC) might be organized hierarchically and contain a subpopulation of tumorigenic, putative cancer stem cells that are CD133 positive. We studied the biological and genetic characteristics of such cells in CRC cell lines and primary tumors. Three CRC cell lines were sorted in CD133 positive and negative fractions. The respective genetic aberration profiles were studied using array comparative genomic hybridization (aCGH) and expression profiling. Tumorigenicity for each cellular population was tested by injection into nude mice. Additionally, we compared CD133+ and CD133- cells of 12 primary colorectal tumors using laser capture microdissection and aCGH. Three of five CRC cell lines displayed both CD133+ and CD133- cells, but tumorigenicity of these subfractions did not differ significantly and aCGH revealed essentially identical genomic imbalances. However, 96 genes were differentially expressed between the two populations. Array comparative genomic hybridization analysis after laser capture microdissection of CD133+ and CD133- areas in primary colorectal tumors revealed genetic differences in 7 of 12 cases. The use of cell lines for studying genomic alterations that define cancer stem cell characteristics, therefore, seems questionable. In contrast, CD133+ cells in primary cancer samples showed a unique genomic aberration profile. In conclusion, our data suggest that CD133 positivity defines a genetically distinct cellular compartment in primary CRC, which potentially includes tumor initiating cells.

Genome and transcriptome profiles of CD133-positive colorectal cancer cells.

Chromosomal copy number alterations (aneuploidy) define the genomic landscape of most cancer cells, but identification of the oncogenic drivers behind these imbalances remains an unfinished task. In this study, we conducted a systematic analysis of colorectal carcinomas that integrated genomic copy number changes and gene expression profiles. This analysis revealed 44 highly overexpressed genes mapping to localized amplicons on chromosome 13, gains of which occur often in colorectal cancers (CRC). RNA interference (RNAi)-mediated silencing identified eight candidates whose loss-of-function reduced cell viability 20% or more in CRC cell lines. The functional space of the genes NUPL1, LNX2, POLR1D, POMP, SLC7A1, DIS3, KLF5, and GPR180 was established by global expression profiling after RNAi exposure. One candidate, LNX2, not previously known as an oncogene, was involved in regulating NOTCH signaling. Silencing LNX2 reduced NOTCH levels but also downregulated the transcription factor TCF7L2 and markedly reduced WNT signaling. LNX2 overexpression and chromosome 13 amplification therefore constitutively activates the WNT pathway, offering evidence of an aberrant NOTCH-WNT axis in CRC.

Genetic amplification of the NOTCH modulator LNX2 upregulates the WNT/β-catenin pathway in colorectal cancer.

In the process of human hematopoiesis, precise regulation of the expression of lineage-specific gene products is critical for multiple cell-fate decisions that govern cell differentiation, proliferation, and self-renewal. Given the important role of microRNAs (miRNAs) in development and differentiation, we examined the global expression of miRNA in CD34(+) cells during lineage specific hematopoiesis and found 49 miRNAs to be differentially expressed, with functional roles in cellular growth and proliferation, and apoptosis. miR-18a was upregulated during erythropoiesis and downregulated during megakaryopoiesis. miR-145 was upregulated during granulopoiesis and down regulated during erythropoiesis. Megakaryopoitic differentiation resulted in significant alteration in the expression of many miRNAs that are believed to play critical roles in the regulation of B and T cell differentiation. Target prediction analyses on three different miRNA databases indicated that TargetScan outperformed microCosm and miRDB in identifying potential miRNA targets associated with hematopoietic differentiation process. An integrated analysis of the observed miRNAs and messenger RNAs (mRNAs) resulted in 87 highly correlated miRNA-mRNA pairs that have major functional roles in cellular growth and proliferation, hematopoietic system development, and Wnt/B-catenin and Flt 3 signaling pathways. We believe that this study will enhance our understanding on the regulatory roles of miRNA in hematopoiesis by providing a library of mRNA-miRNA networks.

Integrated analysis of miRNA and mRNA during differentiation of human CD34+ cells delineates the regulatory roles of microRNA in hematopoiesis.

Although improving health systems promises important benefits, most developing nations lack the resources to support nationally driven clinical research. Strengthened clinical research capacity can advance national health goals by supporting greater autonomy in aligning research with national priorities. From March through June 2010, we assessed six elements of clinical research capacity in Vietnam: research agenda; clinical investigators and biostatisticians; donors and sponsors; community involvement; scientific, ethical, safety, and quality oversight; and clinical research institutions. Assessments were drawn from interviews with investigators, Ministry of Health staff members, nongovernment organizations, and U.S. Mission staff members, and document review. Observations and recommendations were shared with collaborators. Reassessment in 2015 found growth in the number of clinical trials, improved regulation in human subjects protection and community engagement, and modest advances in research agenda setting. Training and investment in institutions remain challenging. A framework for assessing clinical research capacity can affirm strengths and weaknesses and guide the coordination of capacity-building efforts.

Assessing Clinical Research Capacity in Vietnam: A Framework for Strengthening Capability for Clinical Trials in Developing Countries.

Histone methyltransferases EZH1 and EZH2 catalyse the trimethylation of histone H3 at lysine 27 (H3K27), which serves as an epigenetic signal for chromatin condensation and transcriptional repression. Genome-wide associated studies have implicated EZH2 in the control of height and mutations in EZH2 cause Weaver syndrome, which includes skeletal overgrowth. Here we show that the combined loss of Ezh1 and Ezh2 in chondrocytes severely impairs skeletal growth in mice. Both of the principal processes underlying growth plate chondrogenesis, chondrocyte proliferation and hypertrophy, are compromised. The decrease in chondrocyte proliferation is due in part to derepression of cyclin-dependent kinase inhibitors Ink4a/b, while ineffective chondrocyte hypertrophy is due to the suppression of IGF signalling by the increased expression of IGF-binding proteins. Collectively, our findings reveal a critical role for H3K27 methylation in the regulation of chondrocyte proliferation and hypertrophy in the growth plate, which are the central determinants of skeletal growth.

EZH1 and EZH2 promote skeletal growth by repressing inhibitors of chondrocyte proliferation and hypertrophy.

Identification of single nucleotide polymorphisms (SNPs) associated with gene expression levels, known as expression quantitative trait loci (eQTLs), may improve understanding of the functional role of phenotype-associated SNPs in genome-wide association studies (GWAS). The small sample sizes of some previous eQTL studies have limited their statistical power. We conducted an eQTL investigation of microarray-based gene and exon expression levels in whole blood in a cohort of 5257 individuals, exceeding the single cohort size of previous studies by more than a factor of 2.

Integrated genome-wide analysis of expression quantitative trait loci aids interpretation of genomic association studies.

Elevated blood pressure is a major risk factor for cardiovascular disease and has a substantial genetic contribution. Genetic variation influencing blood pressure has the potential to identify new pharmacological targets for the treatment of hypertension. To discover additional novel blood pressure loci, we used 1000 Genomes Project-based imputation in 150 134 European ancestry individuals and sought significant evidence for independent replication in a further 228 245 individuals. We report 6 new signals of association in or near , , , , , and , and provide new replication evidence for a further 2 signals in  and  Combining large whole-blood gene expression resources totaling 12 607 individuals, we investigated all novel and previously reported signals and identified 48 genes with evidence for involvement in blood pressure regulation that are significant in multiple resources. Three novel kidney-specific signals were also detected. These robustly implicated genes may provide new leads for therapeutic innovation.

Quang Nguyen

National Institute of Nursing Research

National Institutes of Health

Evaluating the Role of Mitochondrial Function in Cancer-related Fatigue

Quang Nguyen

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National Institutes of Health

Evaluating the Role of Mitochondrial Function in Cancer-related Fatigue

National Institute of Nursing Research