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[Gene expression differences between high and low metastatic cells of adenoid cystic carcinoma].

OBJECTIVE: To investigate the complex differences between high metastatic and low metastatic cells of the Adenoid cystic Carcinoma. METHODS: Gene expression patterns were examined in high metastatic cell ACC-M strain and low metastatic ACC-2 strain with the method SSH (suppression subtractive hybridization). RESULTS: although extensive similarity was noted between the expression profiles, twelve genes were highly expressed of, in low metastatic cell ACC-2 tester, compared with driver, high metastatic cell ACC-M. These genes were cysteine-rich angiogenic-inducer protein (cyr61), chromosome7 clone RP11-52501, G protein, was family member Iferritin heavy polypeptide I, jumping translocation breakpoint, eukaryotic translation elongation, folate receptor, ribosomal proteins L7a, S21, P0 and other two novel genes-ACC metastasis-associated RNH and ACC metastasis-associated suspected protein. GenBank accession number were AF522024 and AF522025 respectively. CONCLUSIONS: the result suggests that the obtainment of the ability of metastasis is related to the low expression or mutation of these genes. These data provide insight into the extent of expression differences underlying metastasis-related genes that may prove useful as diagnostic or prognostic markers.

Base Sequence↗

Molecular and Clinical Determinants of Acquired Resistance and Treatment Duration for Targeted Therapies in Colorectal Cancer.

PURPOSE: Targeted therapies have improved outcomes for patients with metastatic colorectal cancer, but their impact is limited by rapid emergence of resistance. We hypothesized that an understanding of the underlying genetic mechanisms and intrinsic tumor features that mediate resistance to therapy will guide new therapeutic strategies and ultimately allow the prevention of resistance. EXPERIMENTAL DESIGN: We assembled a series of 52 patients with paired pretreatment and progression samples who received therapy targeting EGFR (n = 17), BRAF V600E (n = 17), KRAS G12C (n = 15), or amplified HER2 (n = 3) to identify molecular and clinical factors associated with time on treatment (TOT). RESULTS: All patients stopped treatment for progression and TOT did not vary by oncogenic driver (P = 0.5). Baseline disease burden (&#x2265;3 vs. <3 sites, P = 0.02), the presence of hepatic metastases (P = 0.02), and gene amplification on baseline tissue (P = 0.03) were each associated with shorter TOT. We found evidence of chromosomal instability (CIN) at progression in patients with baseline MAPK pathway amplifications and those with acquired gene amplifications. At resistance, copy-number changes (P = 0.008) and high number (&#x2265;5) of acquired alterations (P = 0.04) were associated with shorter TOT. Patients with hepatic metastases demonstrated both higher number of emergent alterations at resistance and enrichment of mutations involving receptor tyrosine kinases. CONCLUSIONS: Our genomic analysis suggests that high baseline CIN or effective induction of enhanced mutagenesis on targeted therapy underlies rapid progression. Longer response appears to result from a progressive acquisition of genomic or chromosomal instability in the underlying cancer or from the chance event of a new resistance alteration.

Humans↗

Relationship Between Cognitive Disorder and First-Line Targeted Therapy for Oncogene Driver-Positive Patients With Non-Small Cell Lung Cancer: Prospective Cohort Study.

BACKGROUND: Previous studies have found and confirmed a correlation between cognitive disorder and chemotherapy. As genetic testing becomes more routine in clinical practice, targeted therapies are increasingly gaining prominence. The relationship between targeted treatment and cognitive function is not yet clear. This study aimed to investigate the correlation between cognitive disorder and targeted treatment by evaluating the changes in cognitive function before and after targeted therapy. OBJECTIVE: This study aims to explore whether targeted therapy affects cognitive function in patients with advanced lung cancer and to explore the association between cognitive function, the inflammatory biomarker C-reactive protein, and psychological stress. METHODS: From the screened cohort of 150 patients with advanced non-small cell lung cancer (NSCLC) with gene mutations, 87 (58%) were rigorously selected for the study. The evaluation instruments used were the Mini-Mental State Examination scale, the Distress Thermometer, and the European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire Core 30 for assessing quality of life. RESULTS: A significantly lower progression-free survival (PFS) was observed in the group of patients surviving advanced NSCLC with cognitive disorder under targeted therapy in contrast to survivors in the group with no cognitive disorder (hazard ratio=0.347, 95% CI 0.209-0.578; P<.001). Furthermore, the objective response rate and disease control rate for the group with cognitive disorder were noted to be 37.8% and 86.7%, respectively, contrastingly lower than those in the group with no cognitive disorder, recorded at 78.6% and 97.6%, respectively. Significant variances were also noted in the Mini-Mental State Examination scores between patients with and without cognitive disorder both before and after targeted therapy (P<.001 in both cases), with a decreasing trend observed in both groups after targeted therapy. Noteworthy differences were found in quality of life scores both before and after targeted therapy (P<.001 in both cases). In addition, notable disparities were apparent in C-reactive protein levels among the 2 groups before and after treatment (P=.03 and P=.048 for each time point, respectively), with an upward trend observed in both groups after targeted therapy. The multivariate Cox regression analysis demonstrated that cognitive function is an independent risk factor for PFS in patients with NSCLC receiving targeted therapy. CONCLUSIONS: Cognitive disorder may lead to lower quality of life scores and shorter PFS in patients undergoing targeted therapy. Early screening and intervention for such patients could effectively improve clinical outcomes and quality of life.

Humans↗

Emergentism as a default: cancer as a problem of tissue organization.

During the last fifty years the dominant stance in experimental biology has been reductionism. For the most part, research programs were based on the notion that genes were in 'the driver's seat' controlling the developmental program and determining normalcy and disease (genetic reductionism and genetic determinism). Philosophers were the first to realize that the belief that the Mendelian genes were reduced to DNA molecules was questionable. Soon after these pronouncements, experimental data confirmed their misgivings. The optimism of molecular biologists, fueled by early success in tackling relatively simple problems, has now been tempered by the difficulties found when attempting to understand complex biological problems. Here, we analyse experimental data that illustrate the shortcomings of this sort of reductionism. We also examine the prevailing paradigm in cancer research, the somatic mutation theory (SMT), the premises of which are: (i) cancer is derived from a single somatic cell that has accumulated multiple DNA mutations; (ii) the default state of cell proliferation in metazoa is quiescence; and (iii) cancer is a disease of cell proliferation caused by mutations in genes that control proliferation and the cell cycle. We challenge the notion that cancer is a cellular problem caused by mutated genes by assessing data gathered both from within the reductionist paradigm and from an alternative view that regards carcinogenesis as a developmental process gone awry. This alternative view, explored under the name of the tissue organization field theory (TOFT), is based on premises that place cancer in a different hierarchical level of complexity from that proposed by the SMT, namely: (i) carcinogenesis represents a problem of tissue organization comparable to organogenesis, and (ii) proliferation is the default state of all cells. We propose that the organicist view, in which the TOFT is based, is a good starting point from which to explore emergent phenomena. However, new theoretical concepts are needed in order to grapple with the apparent circular causality of complex biological phenomena in development and carcinogenesis.

Animals↗

Strategies and computational tools for improving randomized protein libraries.

In the last decade, directed evolution has become a routine approach for engineering proteins with novel or altered properties. Concurrently, a trend away from purely 'blind' randomization strategies and towards more 'semi-rational' approaches has also become apparent. In this review, we discuss ways in which structural information and predictive computational tools are playing an increasingly important role in guiding the design of randomized libraries: web servers such as ConSurf-HSSP and SCHEMA allow the prediction of sites to target for producing functional variants, while algorithms such as GLUE, PEDEL and DRIVeR are useful for estimating library completeness and diversity. In addition, we review recent methodological developments that facilitate the construction of unbiased libraries, which are inherently more diverse than biased libraries and therefore more likely to yield improved variants.

Algorithms↗

Lipid Metabolism-related lncRNA Model Identifies AC026412.3 as a Driver of Fatty Acid &#x3b2;-oxidation in Hepatocellular Carcinoma.

BACKGROUND AND AIMS: Dysregulated lipid metabolism contributes to hepatocellular carcinoma (HCC) progression, but the prognostic value and mechanistic roles of lipid metabolism-related long noncoding RNAs (LRLs) remain insufficiently characterized. This study aimed to construct and validate an LRL-based prognostic model and to investigate the biological function and metabolic mechanism of AC026412.3 in HCC. METHODS: Transcriptomic and clinical data from the The Cancer Genome Atlas Liver Hepatocellular Carcinoma cohort were analyzed to identify LRLs based on their correlation with curated lipid metabolism genes. Differential expression, univariate Cox, least absolute shrinkage and selection operator (LASSO), and multivariate Cox analyses were performed to construct a prognostic signature, which was evaluated using Kaplan-Meier survival and time-dependent receiver operating characteristic (ROC) analyses. Functional enrichment analyses Gene Ontology [GO], Kyoto Encyclopedia of Genes and Genomes [KEGG] and gene set enrichment analysis [GSEA], mutation profiling, tumor mutational burden, immune infiltration estimation, and consensus clustering were applied to characterize associated features. A key LRL was identified through integrated bioinformatic screening and prioritization. Its biological role was assessed by quantitative reverse transcription polymerase chain reactionq (RT-PCR), western blotting, BODIPY staining, colony formation, Transwell assays, and xenograft models. RNA sequencing followed by pathway enrichment analysis was conducted to explore underlying mechanisms. RESULTS: A three-LRL signature (AL031985.3, NRAV, and AC026412.3) stratified HCC patients into distinct risk groups with significantly different survival outcomes and demonstrated independent prognostic value. AC026412.3 was markedly upregulated in HCC and associated with poor prognosis. Functional assays demonstrated that AC026412.3 promoted proliferation, invasion, and tumor growth while reducing lipid accumulation. Mechanistically, AC026412.3 upregulated solute carrier family 22 member 5 (SLC22A5), enhanced fatty acid &#x3b2;-oxidation, and increased adenosine triphosphate (ATP) production, thereby driving metabolic reprogramming. CONCLUSIONS: This study establishes a robust LRL-based prognostic model and identifies AC026412.3 as a key regulator of lipid metabolic reprogramming via the SLC22A5-fatty acid &#x3b2;-oxidation axis, highlighting its potential as a biomarker and therapeutic target in HCC.

HCC↗

Turning behavior in Drosophila larvae: a role for the small scribbler transcript.

The Drosophila larva is extensively used for studies of neural development and function, yet the mechanisms underlying the appropriate development of its stereotypic motor behaviors remain largely unknown. We have previously shown that mutations in scribbler (sbb), a gene encoding two transcripts widely expressed in the nervous system, cause abnormally frequent episodes of turning in the third instar larva. Here we report that hypomorphic sbb mutant larvae display aberrant turning from the second instar stage onwards. We focus on the smaller of the two sbb transcripts and show that its pan-neural expression during early larval life, but not in later larval life, restores wild type turning behavior. To identify the classes of neurons in which this sbb transcript is involved, we carried out transgenic rescue experiments. Targeted expression of the small sbb transcript using the cha-GAL4 driver was sufficient to restore wild type turning behavior. In contrast, expression of this sbb transcript in motoneurons, sensory neurons or large numbers of unidentified interneurons was not sufficient. Our data suggest that the expression of the smaller sbb transcript may be needed in a subset of neurons for the maintenance of normal turning behavior in Drosophila larvae.

Age Factors↗

Relevant molecular markers and targets.

Ovarian cancer is a heterogeneous disease with extensive cytogenetic and molecular heterogeneity including aneuploidy, chromosomal alterations, mutations and overexpression as well as a natural propensity to disseminate and spread, making it difficult to diagnose at an early stage. Insights into the molecular mechanisms operative in cancer development, progression and metastasis have uncovered a wide array of targets for therapeutic intervention. In the absence of a common driving oncogene in ovarian cancer, single targeted therapy for this disease is unlikely to yield significant clinical benefit. Tailored approaches that combine molecular targeting agents with cytotoxic regimens hold great promise when used in primary treatment, during consolidation and maintenance therapy, and in the treatment of persistent or recurrent disease. The most promising treatment strategies are those that target the drivers of tumorigenesis and enhance the activity of cytotoxic agents. Receptor tyrosine kinases, non-receptor tyrosine kinases, serine/threonine kinases, transferases, proteases and deacetylases are among the relevant molecular markers and targets for ovarian cancer that are discussed. Collaboration, coordination, creativity and aggressive outreach to patients and their advocates are essential for success in running the concurrent trials with multiple clinical end points and embedded translational research that are needed to evaluate the array of promising targeted therapeutics and combinations. Validated biomarkers, surrogate specimens and end points, and additional clinically relevant in vitro and in vivo models for ovarian cancer are needed to facilitate the drug development and evaluation process, and ultimately to make meaningful improvements in the diagnosis, prevention and management of ovarian cancer.

Biomarkers, Tumor↗

Long-read sequencing of single cell-derived melanoma subclones reveals divergent and parallel genomic and epigenomic evolutionary trajectories.

Tumor evolution is driven by various mutational processes, ranging from single-nucleotide variants (SNVs) to large structural variants (SVs) to dynamic shifts in DNA methylation. Current short-read sequencing methods struggle to accurately capture the full spectrum of these genomic and epigenomic alterations due to inherent technical limitations. To overcome that, here we introduce an approach for long-read sequencing of single-cell derived subclones, and use it to profile 23 subclones of a mouse melanoma cell line, characterized with distinct growth phenotypes and treatment responses. We develop a computational framework for harmonization and joint analysis of different variant types in the evolutionary context. Uniquely, our framework enables detection of recurrent amplifications of putative driver genes, generated by independent SVs across different lineages, suggesting parallel evolution. In addition, our approach revealed gradual and lineage-specific methylation changes associated with aggressive clonal phenotypes. We also show our set of phylogeny-constrained variant calls along with openly released sequencing data can be a valuable resource for the development of new computational methods.

Journal Article↗

Structural genome variation drives adaptation of the xylose-fermenting yeast Scheffersomyces stipitis to lignocellulosic hydrolysates.

Second-generation (2G) bioethanol from lignocellulosic feedstocks is a sustainable alternative to fossil fuels. However, its production is constrained by the poor performance of industrial microbes in hydrolysates that are generated during biomass pretreatment. Scheffersomyces stipitis is a native xylose fermenting yeast and a promising platform for 2G bioethanol production, and adaptive evolution under hydrolysate stress has yielded strains with enhanced performance. However, the chromosomal basis of this adaptation is unknown. Here, we demonstrate that chromosome scale structural variation, rather than point mutations, underlies the improved phenotype of the evolved strains. By integrating long- and short-read genome sequencing, we identify two major chromosomal rearrangements in the top performing isolate: a reciprocal translocation between chromosomes 1 and 2 that disrupts the NUDIX hydrolase gene YSA1, and the formation of a mitotically stable 175&#xa0;kb minichromosome derived from chromosome 5. Functional analyses show that disruption of YSA1 enhances xylose utilisation and ethanol yield, while the minichromosome contributes to improved performance in hydrolysate conditions. These findings provide direct evidence that balanced rearrangements and minichromosome formation can be selected during prolonged stress and can generate adaptive phenotypes. Taken together, our study establishes genome reorganisation as a key driver of adaptation in S. stipitis.

Xylose↗

Mitotic microhomology-mediated break-induced replication promotes chromoanasynthesis.

Chromoanasynthesis is a form of complex chromosomal rearrangement (CCR) commonly detected in cancers and congenital disorders, but the mechanism underlying its generation remain elusive. Here we develop a single-molecule long-read DNA sequencing approach to characterise ultra-complex mutational events, consistent with chromoanasynthesis, occurring at shortened telomeres and sub-telomeric DNA double-strand breaks in human cells. Our data reveal that chromoanasynthesis is generated by microhomology-mediated break-induced replication (MM-BIR), occurring specifically in mitosis. Surprisingly, this mitotic pathway involves a collaboration between microhomology-mediated end-joining (MMEJ) and BIR, where MMEJ proteins initiate a Pol&#x3b4;-dependent BIR pathway that is regulated by PIF1, POLD3 and PCNA. This pathway is highly prone to template switching and can generate dramatic amplification of genomic loci in a single event. Our findings help explain the extreme mutagenic nature of chromoanasynthesis and establish mitotic MM-BIR as a key driver of CCRs, with important implications for the origin of cancers and congenital disorders.

Humans↗

Climate-driven co-evolution of antimicrobial resistance and virulence in Escherichia coli on dairy farms: unraveling adaptive genetic signatures with novel SSCP-PCR.

This study addresses a critical One Health challenge by investigating the epidemiological and genetic drivers of antimicrobial resistance (AMR) in E. coli from 290 clinical bovine samples. On Egyptian dairy farms, our findings revealed that while calf diarrhea peaked during the winter, a higher rate of multidrug resistance was consistently observed in isolates from the summer, directly linking seasonal pressures to AMR dissemination. Strikingly, a mastitis isolate was confirmed as the highly virulent E. coli O157:H7 serotype, harboring the Shiga toxin genes stx1 and stx2, underscoring a direct and significant public health risk. To dissect the molecular basis of these trends, we pioneered the use of a novel Single-Strand Conformation Polymorphism Polymerase Chain Reaction (SSCP-PCR) assay on 33 selected isolates. This high-throughput approach revealed prevalent mutations in resistance genes (blaTEM and gyrB) and the virulence gene (fimH). Crucially, sequencing confirmed that mutations in the highly conserved 16S rRNA gene significantly co-occurred with mutations in blaTEM, fimH, and lacI, providing compelling evidence for co-selected adaptive pathways and clonal expansion. Our research demonstrates that climate-driven environmental pressures fuel the co-evolution of AMR and virulence on farms, championing SSCP-PCR as a robust tool for tracking microbial evolution and advocating for integrated, molecularly-informed One Health strategies.

Escherichia coli↗

Mechanisms of Disease: the first kiss-a crucial role for kisspeptin-1 and its receptor, G-protein-coupled receptor 54, in puberty and reproduction.

Although the hypothalamic secretion of gonadotropin-releasing hormone (GnRH) is the defining hormonal event of puberty, the physiologic mechanisms that drive secretion of GnRH at the time of sexual maturation have been difficult to identify. After puberty is initiated, the factors that modulate the frequency and amplitude of GnRH secretion in rapidly changing sex-steroid environments (i.e. the female menstrual cycle) also remain unknown. The discovery that, in both humans and mouse models, loss-of-function mutations in the gene that encodes G-protein-coupled receptor 54 result in phenotypes of hypogonadotropic hypogonadism with an absence of pubertal development has unearthed a novel pathway regulating GnRH secretion. Ligands for G-protein-coupled receptor 54 (KiSS-1R), including metastin (derived from the parent compound, kisspeptin-1) and metastin's C-terminal peptide fragments, have been shown to be powerful stimulants for GnRH release in vivo via their stimulation of G-protein-coupled receptor 54. This article reviews the discovery of the GPR54 gene, places it into the appropriate biological context, and explores the data from in vitro and in vivo studies that point to this ligand-receptor system as a major driver of GnRH secretion.

Animals↗

Clonotypic characterization defines B-cell drivers of clonal expansion and intratumor heterogeneity in IgM monoclonal gammopathies.

Waldenstr&#xf6;m macroglobulinemia (WM) and IgM monoclonal gammopathy of undetermined significance (MGUS) share the same cell of origin but differ in clonal size. Compared with other B-cell neoplasms, the lymphoplasmacytic clone in WM can be rather small, limiting our understanding of clonal expansion. We applied an integrative approach using single-cell RNA with B-cell receptor (BCR) sequencing, the assay for transposase-accessible chromatin, and whole-genome sequencing to characterize the tumor clone in patients with IgM MGUS, smoldering WM (SWM), and symptomatic WM (WM). IgM MGUS and low- or intermediate-risk SWM harbored multiple B-cell clones compared to WM. CD9, JCHAIN, RASSF6, and DUSP22 were the main markers of the dominant B-cell clone at gene expression and chromatin activity levels, with CD9 preferentially expressed in plasma cell-like tumor cells. POU2F2 had high activity in the tumor clone and was linked to CD9 regulatory regions. MYD88 and IGLL5 mutations, mainly associated with the mutational signature SBS5, were present in minor clones, whereas the MYD88 mutation was also detected in nonexpanded B-cells. The 6q deletion was present in tumor cells from high-risk patients, which harbored fitness advantage over copy-neutral tumor cells. Coding mutations clustered tumor and minor clones from oligoclonal patients and were associated with abnormal transcriptional programs. The B-cell clones also showed enriched predicted interactions with monocytes. Our integrative single-cell approach reveals the importance of clone size in IgM gammopathy and identifies key markers promoting clonal expansion.

Journal Article↗

The fruitless gene is required for the proper formation of axonal tracts in the embryonic central nervous system of Drosophila.

The fruitless (fru) gene in Drosophila melanogaster is a multifunctional gene that has sex-specific functions in the regulation of male sexual behavior and sex-nonspecific functions affecting adult viability and external morphology. While much attention has focused on fru's sex-specific roles, less is known about its sex-nonspecific functions. We have examined fru's sex-nonspecific role in embryonic neural development. fru transcripts from sex-nonspecific promoters are expressed beginning at the earliest stages of neurogenesis, and Fru proteins are present in both neurons and glia. In embryos that lack most or all fru function, FasII- and BP102-positive axons have defasciculation defects and grow along abnormal pathways in the CNS. These defects in axonal projections in fru mutants were rescued by the expression of specific UAS-fru transgenes under the control of a pan-neuronal scabrous-GAL4 driver. Our results suggest that one of fru's sex-nonspecific roles is to regulate the pathfinding ability of axons in the embryonic CNS.

Animals↗

The Genomic Landscape of MYC-, MYCL-, and MYCN-Amplified Solid Tumors.

PURPOSE: MYC, MYCN, and MYCL amplifications are recurrent oncogenic events across solid tumors. Currently, no standardized selection biomarker is available to identify patients with MYC-dependent tumors. EXPERIMENTAL DESIGN: We analyzed copy-number alterations of MYC family genes and their features in more than 68,000 tumor-normal paired samples from pediatric and adult patients sequenced with MSK-IMPACT (Memorial Sloan Kettering-Integrated Mutation Profiling of Actionable Cancer Targets) and annotated with FACETS (Fraction and Allele-Specific Copy Number Estimates from Tumor Sequencing). The relationship between amplification features and MYC mRNA expression levels were evaluated in more than 10,000 samples from The Cancer Genome Atlas (TCGA). RESULTS: Across MSK Cancer Center samples, MYC amplifications were most common, found in 2,949 samples compared with 310 in MYCL and 217 in MYCN. Although MYCN and MYCL amplifications were predominantly focal (<10 Mb, 79% and 93%, respectively), MYC amplifications were frequently broader (>10 Mb, 62%). Although most tumor types showed similar features between broad and focal amplifications of MYC, in select cancer types, we identified differing co-occurrence and mutual exclusivity patterns with other disease-specific drivers. Furthermore, although MYC-amplified TCGA samples showed higher mRNA expression than wild-type ones, the focality of MYC amplification was seen to have limited influence on expression levels. CONCLUSIONS: Our results suggest that MYC dependency likely depends on many factors, including, but not limited to, total copy number of the detected amplification, lineage-specific factors, concomitant presence or absence of additional oncogenic alterations, and in some cases amplification focality.

Humans↗

Deciphering Clonal Hematopoiesis of Indeterminate Potential: Methods, Mechanisms, and Implications for Kidney Diseases.

CKD afflicts over 10% of US adults, with its prevalence increasing sharply with age. Clonal hematopoiesis of indeterminate potential (CHIP) is a common, genetically heterogeneous blood cell disorder characterized by the age-related clonal expansion of hematopoietic cells driven by leukemogenic somatic mutations yet without hematologic malignancy or dysplasia. While CHIP is a strong risk factor of future hematologic malignancy (estimated at approximately 0.5% per year, compared with <0.1% for those without CHIP), it is also linked to two-fold higher cardiovascular disease in epidemiologic, cell-based, and murine studies. However, more recent work has implicated CHIP with kidney outcomes, such as CKD as well as AKI, independent of traditional risk factors. This review covers the observations and proposed hypotheses linking CHIP and kidney disease. The review also underscores the need for further research to elucidate the distinct pathways through which CHIP may contribute to CKD and its comorbidities, considering the heterogeneity within CKD stages and etiologies, as well as whether CHIP is a causal driver of kidney disease or a marker of aging and comorbidity. Finally, we discuss the potential of anti-inflammatory treatments to mitigate CHIP's adverse effects on kidney health, aiming to improve management strategies for patients with CHIP-associated kidney diseases.

Humans↗

Identification of sample-specific sequences in mammalian cDNA and genomic DNA by the novel ligation-mediated subtraction (Limes).

The representational difference analysis (RDA) and other subtraction techniques are used to enrich sample-specific sequences by elimination of ubiquitous sequences existing in both the sample of interest (tester) and the subtraction partner (driver). While applying the RDA to genomic DNA of cutaneous lymphoma cells in order to identify tumor relevant alterations, we predominantly isolated repetitive sequences and artificial repeat-mediated fusion products of otherwise independent PCR fragments (PCR hybrids). Since these products severely interfered with the isolation of tester-specific fragments, we developed a considerably more robust and efficient approach, termed ligation-mediated subtraction (Limes). In first applications of Limes, genomic sequences and/or transcripts of genes involved in the regulation of transcription, such as transforming growth factor beta stimulated clone 22 related gene (TSC-22R), cell death and cytokine production (caspase-1) or antigen presentation (HLA class II sequences), were found to be completely absent in a cutaneous lymphoma line. On the assumption that mutations in tumor-relevant genes can affect their transcription pattern, a protocol was developed and successfully applied that allows the identification of such sequences. Due to these results, Limes may substitute/supplement other subtraction/comparison techniques such as RDA or DNA microarray techniques in a variety of different research fields.

Animals↗