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Biomedical subjects

Bert Vogelstein

Publications and source records attributed to Bert Vogelstein.

At least 19 recordsLinked to original sources
PubMed2026

Comprehensive Genomic Analysis of Normal and Cancer Cells Elucidates the Elevated Mutation Burden in Cancer.

Self-renewing normal tissues generate several somatic mutations at each division. Previous studies have reported that cancer cells have more mutations than their normal counterparts. It is not obvious why dramatic differences in mutation burdens between normal tissues and cancers should exist. To fully understand human tumorigenesis, the increase of mutation burden in cancers will have to be understood. Here, we provided a systematic comparison of mutational burdens in normal and cancer cells from five different organs, revealing a four-fold increase of mutation burdens in cancerous vs. non-cancerous cells. Three proposed hypotheses that could account for the increased mutation burdens in cancer are: the classical hypothesis, where driver gene mutations explain the higher mutational burden; the catastrophic hypothesis, where extreme mutational events lead to large-scale genomic alterations; and the tail hypothesis, where differences in baseline mutation rates among individuals account for the differences. Testing through orthogonal observations showed that the observed medians and distributions of mutation burdens in cancers could be explained by the hypotheses to various degrees of significance, and only the tail hypothesis could easily explain the increase in median mutation burdens in the normal tissues of cancer patients compared to the normal tissues of non-cancer patients. Overall, this study characterizes an increased mutation burden across multiple types of cancer compared to normal tissue and provides insights into the contributing factors. A tenable hypothesis proposed in this study involving fundamental differences in baseline mutation rates among individuals could have implications for cancer prevention strategies.

Journal Article↗
PubMed2006

A bacterial protein enhances the release and efficacy of liposomal cancer drugs.

Clostridium novyi-NT is an anaerobic bacterium that can infect hypoxic regions within experimental tumors. Because C. novyi-NT lyses red blood cells, we hypothesized that its membrane-disrupting properties could be exploited to enhance the release of liposome-encapsulated drugs within tumors. Here, we show that treatment of mice bearing large, established tumors with C. novyi-NT plus a single dose of liposomal doxorubicin often led to eradication of the tumors. The bacterial factor responsible for the enhanced drug release was identified as a previously unrecognized protein termed liposomase. This protein could potentially be incorporated into diverse experimental approaches for the specific delivery of chemotherapeutic agents to tumors.

Amino Acid Sequence↗
PubMed2006

The genome and transcriptomes of the anti-tumor agent Clostridium novyi-NT.

Bacteriolytic anti-cancer therapies employ attenuated bacterial strains that selectively proliferate within tumors. Clostridium novyi-NT spores represent one of the most promising of these agents, as they generate potent anti-tumor effects in experimental animals. We have determined the 2.55-Mb genomic sequence of C. novyi-NT, identifying a new type of transposition and 139 genes that do not have homologs in other bacteria. The genomic sequence was used to facilitate the detection of transcripts expressed at various stages of the life cycle of this bacterium in vitro as well as in infections of tumors in vivo. Through this analysis, we found that C. novyi-NT spores contained mRNA and that the spore transcripts were distinct from those in vegetative forms of the bacterium.

Animals↗
PubMed2006

Facultative or obligate anaerobic bacteria have the potential for multimodality therapy of solid tumours.

Recent understanding of the unique pathology of solid tumours has shed light on the difficult and disappointing nature of their clinical treatment. All solid tumours undergo angiogenesis that results in biological changes and adaptive metabolisms, i.e. formation of defective vessels, appearance of hypoxic areas, and emergence of an heterogeneous tumour cell population. This micro-milieu provides a haven for anaerobic bacteria. The strictly anaerobic clostridia have several advantages over other facultative anaerobes such as salmonella or lactic acid-producing, Gram-positive, obligate, anaerobic bifidobacteria. Both pathogenic and non-pathogenic clostridia have been demonstrated to specifically colonise and destroy solid tumours. Early trials of non-pathogenic strains in humans had shown plausible safety. Genetic modifications and adaptation of pathogenic and non-pathogenic strains have further created improved features. However, these manipulations rarely generate strains that resulted in complete tumour control alone. Combined modalities of therapies with chemo and radiation therapies, on the other hand, often perform better, including 'cure' of solid tumours in a high percentage of animals. Considering that clostridia have unlimited capacities for genetic improvement, we predict that designer clostridia forecast a promising future for the development of potent strains for tumour destruction, incorporating mechanisms such as immunotherapy to overcome immune suppression and to elicit strong anti-tumour responses.

Angiogenesis Inhibitors↗
PubMed2006

The consensus coding sequences of human breast and colorectal cancers.

The elucidation of the human genome sequence has made it possible to identify genetic alterations in cancers in unprecedented detail. To begin a systematic analysis of such alterations, we determined the sequence of well-annotated human protein-coding genes in two common tumor types. Analysis of 13,023 genes in 11 breast and 11 colorectal cancers revealed that individual tumors accumulate an average of approximately 90 mutant genes but that only a subset of these contribute to the neoplastic process. Using stringent criteria to delineate this subset, we identified 189 genes (average of 11 per tumor) that were mutated at significant frequency. The vast majority of these genes were not known to be genetically altered in tumors and are predicted to affect a wide range of cellular functions, including transcription, adhesion, and invasion. These data define the genetic landscape of two human cancer types, provide new targets for diagnostic and therapeutic intervention, and open fertile avenues for basic research in tumor biology.

Amino Acid Substitution↗
PubMed2006

The colorectal microRNAome.

MicroRNAs (miRNAs) are a class of small noncoding RNAs that have important regulatory roles in multicellular organisms. The public miRNA database contains 321 human miRNA sequences, 234 of which have been experimentally verified. To explore the possibility that additional miRNAs are present in the human genome, we have developed an experimental approach called miRNA serial analysis of gene expression (miRAGE) and used it to perform the largest experimental analysis of human miRNAs to date. Sequence analysis of 273,966 small RNA tags from human colorectal cells allowed us to identify 200 known mature miRNAs, 133 novel miRNA candidates, and 112 previously uncharacterized miRNA* forms. To aid in the evaluation of candidate miRNAs, we disrupted the Dicer locus in three human colorectal cancer cell lines and examined known and novel miRNAs in these cells. These studies suggest that the human genome contains many more miRNAs than currently identified and provide an approach for the large-scale experimental cloning of novel human miRNAs in human tissues.

Base Sequence↗
PubMed2006

Tumor endothelial marker 1 (Tem1) functions in the growth and progression of abdominal tumors.

Tumor endothelial marker 1 (Tem1; endosialin) is the prototypical member of a family of genes expressed in the stroma of tumors. To assess the functional role of Tem1, we disrupted the Tem1 gene in mice by targeted homologous recombination. Tem1(-/-) mice were healthy, their wound healing was normal, and tumors grew normally when implanted in s.c. sites. However, there was a striking reduction in tumor growth, invasiveness, and metastasis after transplantation of tumors to abdominal sites in mice without functional Tem1 genes. These data indicate that the stroma can control tumor aggressiveness and that this control varies with anatomic site. Therefore, they have significant implications for the mechanisms underlying tumor invasiveness and for models that evaluate this process.

Abdominal Neoplasms↗
PubMed2006

Somatic mutations of GUCY2F, EPHA3, and NTRK3 in human cancers.

Tyrosine kinases are major regulators of signal transduction cascades involved in cellular proliferation and have important roles in tumorigenesis. We have recently analyzed the tyrosine kinase gene family for alterations in human colorectal cancers and identified somatic mutations in seven members of this gene family. In this study we have used high-throughput sequencing approaches to further evaluate this subset of genes for genetic alterations in other human tumors. We identified somatic mutations in GUCY2F, EPHA3, and NTRK3 in breast, lung, and pancreatic cancers. Our results implicate these tyrosine kinase genes in the pathogenesis of other tumor types and suggest that they may be useful targets for diagnostic and therapeutic intervention in selected patients.

Adenocarcinoma↗
PubMed2006

The role of companion diagnostics in the development and use of mutation-targeted cancer therapies.

Among all the known differences between cancer and normal cells, it is only the genetic differences that unequivocally distinguish the former from the latter. It is therefore not surprising that recent therapeutic advances are based on agents that specifically target the products of the genes that are mutated in cancer cells. The ability to identify the patients most likely to benefit from such therapies is a natural outgrowth of these discoveries. Development of companion diagnostic tests for this identification is proceeding but should receive much more attention than it currently does. These tests can simplify the drug discovery process, make clinical trials more efficient and informative, and be used to individualize the therapy of cancer patients.

Gene Targeting↗
PubMed2006

BEAMing up for detection and quantification of rare sequence variants.

BEAMing allows the one-to-one conversion of a population of DNA fragments into a population of beads. We used rolling circle amplification to increase the number of copies bound to such beads by more than 100-fold. This allowed enumeration of mutant and wild-type sequences even when they were present at ratios less than 1:10,000 and was sensitive enough to directly quantify the error rate of DNA polymerases used for PCR.

DNA↗
PubMed2005

Detection and quantification of mutations in the plasma of patients with colorectal tumors.

The early detection of cancers through analysis of circulating DNA could have a substantial impact on morbidity and mortality. To achieve this goal, it is essential to determine the number of mutant molecules present in the circulation of cancer patients and to develop methods that are sufficiently sensitive to detect these mutations. Using a modified version of a recently developed assay for this purpose, we found that patients with advanced colorectal cancers consistently contained mutant adenomatous polyposis coli (APC) DNA molecules in their plasma. The median number of APC DNA fragments in such patients was 47,800 per ml of plasma, of which 8% were mutant. Mutant APC molecules were also detected in >60% of patients with early, presumably curable colorectal cancers, at levels ranging from 0.01% to 1.7% of the total APC molecules. These results have implications for the mechanisms through which tumor DNA is released into the circulation and for diagnostic tests based on this phenomenon.

Adult↗
PubMed2005

Pharmacologic and toxicologic evaluation of C. novyi-NT spores.

Clostridium novyi-NT (C. novyi-NT) spores have been shown to be potent therapeutic agents in experimental tumors of mice and rabbits. In the present study, pharmacologic and toxicologic studies were performed to better understand the factors influencing the efficacy and toxicity of this form of therapy. We found that spores were rapidly cleared from the circulation by the reticuloendothelial system. Even after large doses were administered, no clinical toxicity was observed in healthy mice or rabbits. The spores were also not toxic in mice harboring poorly vascularized non-neoplastic lesions, including myocardial infarcts. In tumor-bearing mice, toxicity appeared related to tumor size and spore dose, as expected with any bacterial infection. However, there was no laboratory or histopathologic evidence of sepsis, and the toxicity could be effectively controlled by simple hydration.

Animals↗
PubMed2005

Colorectal cancer: mutations in a signalling pathway.

Protein kinases are enzymes that are important for controlling cellular growth and invasion, and their malfunction is implicated in the development of some tumours. We analysed human colorectal cancers for genetic mutations in 340 serine/threonine kinases and found mutations in eight genes, including in three members of the phosphatidylinositol-3-OH kinase (PI(3)K) pathway. The discovery of this mutational activation of a key cell-signalling pathway may provide new targets for therapeutic intervention.

Colorectal Neoplasms↗
PubMed2005

Discodermolide analogues as the chemical component of combination bacteriolytic therapy.

The marine natural product (+)-discodermolide (1) and several simplified analogues of this microtubule-stabilizing agent have proven to be potent in vitro cell growth inhibitory agents in several human cancer cell lines. Here, we demonstrate the in vivo efficacy of discodermolide and several simplified congeners, both as stand-alone anti-tumor agents and, in the case of (+)-2,3-anhydrodiscodermolide (3), as a chemical component of the combination bacteriolytic therapy. A single intravenous injection of (+)-3 plus genetically modified Clostridium novyi-NT spores caused rapid and complete regressions of tumors in mice bearing HCT116 colorectal cancer xenografts.

Alkanes↗
PubMed2005

Mutations in two short noncoding mononucleotide repeats in most microsatellite-unstable colorectal cancers.

DNA mismatch repair (MMR)-deficient cells typically accumulate mutations in short repetitive DNA tracts. This microsatellite instability (MSI) facilitates malignant transformation when affecting genes with growth-related and caretaker functions. To date, several putative MSI target genes have been proposed mainly based on high mutation frequency within their coding regions. However, some intronic repeat mutations have also been suggested to associate with MSI tumorigenesis, indicating the need for additional analyses on noncoding repeats. Here we have analyzed an intronic T9 repeat of semenogelin I (SEMG1) and report mutation frequencies of 51% (75 of 146) and 62% (8 of 13) in MMR-deficient primary colorectal cancers and cell lines, respectively. The putative effect of the SEMG1 mutations was assessed by RNA and protein level analyses, but no differences were detected between colorectal cancer cell lines with different SEMG1 status. Subsequently, the general background mutation frequency of MSI colorectal cancers was assessed by screening for intergenic T9 repeat alterations. One of 10 examined repeats was mutated in 70% (102 of 145) of the colorectal cancers evaluated. The frequencies observed here are notably higher than previously published in noncoding repeats shorter than 10 bp in MMR-deficient primary tumors. Our results indicate that high mutation frequencies, similar or higher than those observed in proposed and approved target genes, can be detected in repeat tracts of MSI tumors without any apparent selection pressure. These data call for urgent and thorough large-scale evaluation of mutation frequencies in neutral short repetitive sequences in MMR-deficient tumors.

Alleles↗
PubMed2005

Contribution of bone marrow-derived endothelial cells to human tumor vasculature.

It has been shown that bone marrow-derived stem cells can form a major fraction of the tumor endothelium in mouse tumors. To determine the role of such cells in human tumor angiogenesis, we studied six individuals who developed cancers after bone marrow transplantation with donor cells derived from individuals of the opposite sex. By performing fluorescence in situ hybridization (FISH) with sex chromosome-specific probes in conjunction with fluorescent antibody staining, we found that such stem cells indeed contributed to tumor endothelium, but at low levels, averaging only 4.9% of the total. These results illustrate substantial differences between human tumors and many mouse models with respect to angiogenesis and have important implications for the translation of experimental antiangiogenic therapies to the clinic.

Bone Marrow Cells↗