Ganglioside composition and histology of a spontaneous metastatic brain tumour in the VM mouse

Glycosphingolipid abnormalities have long been implicated in tumour malignancy and metastasis. Gangliosides are a family of sialic acid-containing glycosphingolipids that modulate cell–cell and cell–matrix interactions. Histology and ganglioside composition were examined in a natural brain tumour of the VM mouse strain. The tumour is distinguished from other metastatic tumour models because it arose spontaneously and metastasizes to several organs including brain and spinal cord after subcutaneous inoculation of tumour tissue in the flank. By electron microscopy, the tumour consisted of cells (15 to 20 μm in diameter) that had slightly indented nuclei and scant cytoplasm. The presence of smooth membranes with an absence of junctional complexes was a characteristic ultrastructural feature. No positive immunostaining was found for glial or neuronal markers. The total ganglioside sialic acid content of the subcutaneously grown tumour was low (12.6 ± 0.9 μg per 100 mg dry wt, n= 6 separate tumours) and about 70% of this was in the form of N-glycolylneuraminic acid. In contrast, the ganglioside content of the cultured VM tumour cells was high (248.4 ± 4.4 μg, n= 3) and consisted almost exclusively of N-acetylneuraminic acid. The ganglioside pattern of the tumour grown subcutaneously was complex, while GM3, GM2, GM1, and GD1a were the major gangliosides in the cultured tumour cells. This tumour will be a useful natural model for evaluating the role of gangliosides and other glycolipids in tumour cell invasion and metastasis. © 2001 Cancer Research Campaign http://www.bjcancer.co

Population Genomics on the Fly: Recent Advances in Drosophila

Drosophila melanogaster, a small dipteran of African origin, represents one of the best-studied model organisms. Early work in this system has uniquely shed light on the basic principles of genetics and resulted in a versatile collection of genetic tools that allow to uncover mechanistic links between genotype and phenotype. Moreover, given its worldwide distribution in diverse habitats and its moderate genome-size, Drosophila has proven very powerful for population genetics inference and was one of the first eukaryotes whose genome was fully sequenced. In this book chapter, we provide a brief historical overview of research in Drosophila and then focus on recent advances during the genomic era. After describing different types and sources of genomic data, we discuss mechanisms of neutral evolution including the demographic history of Drosophila and the effects of recombination and biased gene conversion. Then, we review recent advances in detecting genome-wide signals of selection, such as soft and hard selective sweeps. We further provide a brief introduction to background selection, selection of noncoding DNA and codon usage and focus on the role of structural variants, such as transposable elements and chromosomal inversions, during the adaptive process. Finally, we discuss how genomic data helps to dissect neutral and adaptive evolutionary mechanisms that shape genetic and phenotypic variation in natural populations along environmental gradients. In summary, this book chapter serves as a starting point to Drosophila population genomics and provides an introduction to the system and an overview to data sources, important population genetic concepts and recent advances in the field

Genomics of gallbladder cancer: the case for biomarker-driven clinical trial design

BACKGROUND AND AIMS: Gallbladder carcinoma is a rare, aggressive malignancy of the biliary tract associated with a poor prognosis. Despite the deployment of targeted therapies that have demonstrated marked survival benefits in many tumor types, traditional cytotoxic chemotherapy has remained the mainstay of treatment for unresectable and metastatic gall-bladder cancer. METHODS: Systematic review of ongoing and prior clinical studies shows a paucity of biomarker-driven therapeutic trials using targeted agents in gallbladder cancer. In fact, over the past 6 years, of the 38 therapeutic biliary tract protocols listed on clinicaltrials.gov, only 6 (21 %) utilized targeted therapies based upon tumor biomarkers or genomics. Now that we have entered the era of next-generation sequencing and precision medicine, we are beginning to identify common and specific genetic alterations in gallbladder carcinomas. RESULTS: A review of the literature reveals alterations in ARID1A, BRAF, CDKN2A/B, EGFR, ERBB2-4, HKN-RAS, PIK3CA, PBRM1, and TP53. Given the widespread use of tumor genomic profiling and the fact that most of the aforementioned alterations are pharmacologically tractable, these observations suggest the potential for new therapeutic strategies in this aggressive malignancy. CONCLUSIONS: Taken together, further understanding of the genomic landscape of gallbladder cancer coupled with biomarker-driven clinical trials that match therapies to targets are urgently needed