Biomedical subjects

D C Radisky

Publications and source records attributed to D C Radisky.

6 recordsLinked to original sources

PubMed2005

Microenvironmental regulators of tissue structure and function also regulate tumor induction and progression: the role of extracellular matrix and its degrading enzymes.

It is now widely accepted that elements of the cellular and tissue microenvironment are crucial regulators of cell behavior in culture and homeostasis in vivo, and that many of the same factors influence the course of tumor progression. Less well established is the extent to which extracellular factors actually cause cancer, and the circumstances under which this may occur. Using physiologically relevant three-dimensional culture assays and transgenic animals, we have explored how the environmental and architectural context of cells, tissues, and organs controls mammary-specific gene expression, growth regulation, apoptosis, and drug resistance and have found that loss of tissue structure is a prerequisite for cancer progression. Here we summarize this evidence and highlight two of our recent studies. Using mouse mammary epithelial cells, we show that exposure to matrix metalloproteinase-3 (MMP-3) stimulates production of reactive oxygen species (ROS) that destabilize the genome and induce epithelial-mesenchymal transition, causing malignant transformation. Using a human breast cancer progression series, we find that ADAM-dependent growth factor shedding plays a crucial role in acquisition of the malignant phenotype. These findings illustrate how normal tissue structure controls the response to extracellular signals so as to preserve tissue specificity and growth status.

Animals↗

PubMed2000

Integrating naive Bayes models and external knowledge to examine copper and iron homeostasis in S. cerevisiae.

A novel suite of analytical techniques and visualization tools are applied to 78 published transcription profiling experiments monitoring 5,687 Saccharomyces cerevisiae genes in studies examining cell cycle, responses to stress, and diauxic shift. A naive Bayes model discovered and characterized 45 classes of gene profile vectors. An enrichment measure quantified the association between these classes and specific external knowledge defined by four sets of categories to which genes can be assigned: 106 protein functions, 5 stages of the cell cycle, 265 transcription factors, and 16 chromosomal locations. Many of the 38 genes in class 42 are known to play roles in copper and iron homeostasis. The 17 uncharacterized open reading frames in this class may be involved in similar homeostatic processes; human homologs of two of them could be associated with as yet undefined disease states arising from aberrant metal ion regulation. The Met4, Met31, and Met32 transcription factors may play a role in coregulating genes involved in copper and iron metabolism. Extensions of the simple graphical model used for clustering to learning more complex models of genetic networks are discussed.

Bayes Theorem↗

PubMed1999

The yeast frataxin homologue mediates mitochondrial iron efflux. Evidence for a mitochondrial iron cycle.

Mutations in the nuclear gene encoding the mitochondrial protein frataxin are responsible for the neurological disorder Friedreich ataxia (FA). Yeast strains with a deletion in the frataxin homologue YFH1 accumulate excess iron in mitochondria and demonstrate mitochondrial damage. We show that in the absence of YFH1, mitochondrial damage is proportional to the concentration and duration of exposure to extracellular iron, establishing mitochondrial iron accumulation as causal to mitochondrial damage. Reintroduction of YFH1 results in the rapid export of accumulated mitochondrial iron into the cytosol as free, non-heme bound iron, demonstrating that mitochondrial iron in the yeast FA model can be made bioavailable. These results demonstrate a mitochondrial iron cycle in which Yfh1p regulates mitochondrial iron efflux.

Biological Transport↗

PubMed1998

Iron in cytosolic ferritin can be recycled through lysosomal degradation in human fibroblasts.

Examination of the mechanism of intracellular iron recovery from lysosomally-degraded ferritin in vivo has been complicated by the continuous flux of cellular iron through ferritin molecules. Here we incubated human fibroblasts with cationic ferritin, a derivative of horse spleen ferritin, as a technique for delivering immunologically distinct ferritin molecules directly to lysosomes. Using this method, we found increased endogenous ferritin levels after the cellular degradation of cationic ferritin, demonstrating that cells can utilize lysosomal ferritin to produce increased cytosolic ferritin levels. Further, using an in vitro assay, we showed that isolated lysosomes degrade endogenous ferritin in a time- and temperature-dependent manner. These results are consistent with a model in which cytosolic ferritin is taken into the lysosomes and degraded. The solubilized iron from the ferric core could then be transported across the lysosomal membrane back into the cytosol.

Cells, Cultured↗

PubMed1997

Characterization of VPS41, a gene required for vacuolar trafficking and high-affinity iron transport in yeast.

Mutations in the yeast gene VPS41 give rise to poor growth on low iron medium, severe alterations in vacuolar morphology, and cause the missorting of membranous and soluble vacuolar proteins. Our studies predict that VPS41 encodes a hydrophilic protein of 992 amino acids that contains no obvious signal sequence or hydrophobic domains. The deduced Vps41p sequence contains a domain rich in glutamic and aspartic residues, as well as a domain with resemblance to a region of clathrin heavy chain. We have also identified and sequenced putative VPS41 homologues from Caenorhabditis elegans, plants, and humans. The VPS41 homologues (but not the yeast VPS41 itself) contain a conserved cysteine-rich RING-H2 zinc finger at their COOH termini. Biochemical experiments suggest that VPS41 functions in post-Golgi protein processing: the deletion mutant exhibits defective high affinity transport due to impaired Fet3p activity and also exhibits defects in the processing and sorting of multiple vacuolar hydrolases.

Amino Acid Sequence↗

PubMed1993

Makaluvamines, marine natural products, are active anti-cancer agents and DNA topo II inhibitors.

The makaluvamines were isolated from a sponge of the genus Zyzzya by following bioactivity against the human colon carcinoma cell line, HCT 116. These compounds have considerable cytotoxic activity. The makaluvamines appear to be acting through inhibition of DNA topoisomerase II. The compounds show enhanced toxicity toward a topoisomerase II-cleavable complex-sensitive cell line, they inhibit topoisomerase II decatenation of kinetoplast DNA in vitro. Makaluvamine C was shown to produce protein-linked DNA double-strand breaks, and makaluvamine A produced DNA double-strand breaks by neutral filter elution in a dose-dependent fashion similar to 4'-(9-acridinylamino)methanesulfon-m-anisidide (m-AMSA). The makaluvamines also increased the life span of nude mice bearing solid tumors of human ovarian cancer cells.

Animals↗