Comprehensive genomic profiles of small cell lung cancer

We have sequenced the genomes of 110 small cell lung cancers (SCLC), one of the deadliest human cancers. In nearly all the tumours analysed we found bi-allelic inactivation of TP53 and RB1, sometimes by complex genomic rearrangements. Two tumours with wild-type RB1 had evidence of chromothripsis leading to overexpression of cyclin D1 (encoded by the CCND1 gene), revealing an alternative mechanism of Rb1 deregulation. Thus, loss of the tumour suppressors TP53 and RB1 is obligatory in SCLC. We discovered somatic genomic rearrangements of TP73 that create an oncogenic version of this gene, TP73Dex2/3. In rare cases, SCLC tumours exhibited kinase gene mutations, providing a possible therapeutic opportunity for individual patients. Finally, we observed inactivating mutations in NOTCH family genes in 25% of human SCLC. Accordingly, activation of Notch signalling in a pre-clinical SCLC mouse model strikingly reduced the number of tumours and extended the survival of the mutant mice. Furthermore, neuroendocrine gene expression was abrogated by Notch activity in SCLC cells. This first comprehensive study of somatic genome alterations in SCLC uncovers several key biological processes and identifies candidate therapeutic targets in this highly lethal form of cancer

Regulation of Toll and Toll-like receptor signaling by the endocytic pathway

The Toll/TLR receptor family plays a central role in both vertebrate and insect immunity, driving the activation of humoral immunity in response to pathogens. In Drosophila, Toll is also responsible for directing the formation of the Dorsal/NFkappaB gradient specifying dorsoventral patterning of the embryo. Two recent studies have revealed that endocytosis and elements of the molecular machinery governing endosomal progression are required for Drosophila Toll signaling in development and immunity. We demonstrated that Toll is not only present at the plasma membrane but also in a Rab5+ early endosomal compartment in the embryo and that the distribution of constitutively active Toll10B is shifted towards endosomes. Localized inhibition of Rab5 function on the ventral side leads to a reduction of nuclear Dorsal levels, while locally increasing Rab5 function leads to potentiation of signaling. Independently, another laboratory identified the endosomal protein Mop as a potentiator of Toll signaling in Drosophila cell culture and fat-body tissue. Mop functions together with the ESCRT 0 component, Hrs, previously reported to stimulate endosomal progression and the signaling ability of internalized EGFR. We discuss these studies and briefly summarize the most significant findings concerning the role of intracellular localization and trafficking in mammalian TLR function

PICK1 Deficiency Impairs Secretory Vesicle Biogenesis and Leads to Growth Retardation and Decreased Glucose Tolerance

<div><p>Secretory vesicles in endocrine cells store hormones such as growth hormone (GH) and insulin before their release into the bloodstream. The molecular mechanisms governing budding of immature secretory vesicles from the trans-Golgi network (TGN) and their subsequent maturation remain unclear. Here, we identify the lipid binding BAR (Bin/amphiphysin/Rvs) domain protein PICK1 (protein interacting with C kinase 1) as a key component early in the biogenesis of secretory vesicles in GH-producing cells. Both PICK1-deficient <i>Drosophila</i> and mice displayed somatic growth retardation. Growth retardation was rescued in flies by reintroducing PICK1 in neurosecretory cells producing somatotropic peptides. PICK1-deficient mice were characterized by decreased body weight and length, increased fat accumulation, impaired GH secretion, and decreased storage of GH in the pituitary. Decreased GH storage was supported by electron microscopy showing prominent reduction in secretory vesicle number. Evidence was also obtained for impaired insulin secretion associated with decreased glucose tolerance. PICK1 localized in cells to immature secretory vesicles, and the PICK1 BAR domain was shown by live imaging to associate with vesicles budding from the TGN and to possess membrane-sculpting properties in vitro. In mouse pituitary, PICK1 co-localized with the BAR domain protein ICA69, and PICK1 deficiency abolished ICA69 protein expression. In the <i>Drosophila</i> brain, PICK1 and ICA69 co-immunoprecipitated and showed mutually dependent expression. Finally, both in a <i>Drosophila</i> model of type 2 diabetes and in high-fat-diet-induced obese mice, we observed up-regulation of PICK1 mRNA expression. Our findings suggest that PICK1, together with ICA69, is critical during budding of immature secretory vesicles from the TGN and thus for vesicular storage of GH and possibly other hormones. The data link two BAR domain proteins to membrane remodeling processes in the secretory pathway of peptidergic endocrine cells and support an important role of PICK1/ICA69 in maintenance of metabolic homeostasis.</p></div

Rescue of the phenotype of PICK1-deficient mice by GH administration.

<p>(A) Lean body mass was evaluated by MRI scanning before GH administration and subsequently once every week both in PICK1-deficient mice (black squares) and in saline-treated WT littermates (white circles). Before treatment the difference between the two groups was highly significant (**<i>p</i> = 0.0027), after a week the difference decreased but was still significant (*<i>p</i> = 0.050), and after 2 and 3 wk no significant difference were observed. (B) IGF-1 mRNA level in the liver as determined by RT-PCR was significantly lower in PICK1-deficient mice compared to untreated mice (*<i>p</i> = 0.0045), however this difference was not observed after GH-treatment for 3 wk. (C) OGTT and ITT on GH-treated PICK1-deficient mice (black circles) and the saline-treated WT littermate controls (white circles). Significant difference was observed in the OGTT, whereas no difference was observed in ITT. Data are expressed as mean ± SE and analyzed by two-way ANOVA in (A) and Student's <i>t</i> test in (B–D) (<i>n</i> = 4–8 in all the experiments). All experiments have been reproduced in another cohort of mice (<i>n</i> = 3–4), where the age of the mice was 4 wk higher.</p

Decreased GH storage and secretion in PICK1-deficient mice.

<p>(A) The livers of PICK-1-deficient mice had a significantly lower weight than those of WT mice (**<i>p</i><0.01). (B) PICK1-deficient mice exhibited a decreased level of plasma IGF-1 (*<i>p</i><0.05). (C) Decreased relative expression level of IGF-1 mRNA in the liver of PICK1-deficient mice versus WT mice (**<i>p</i> = 0.0045). Measurements in (A), (B), and (C) were performed in samples from 35–38-wk-old WT (+/+) or PICK1-deficient mice (−/−) after overnight fast. Data are means ± SE (<i>n</i> = 10–14). (D) PICK1-deficient mice display reduced femoral length. Measurements were done on 39–41-wk-old WT (+/+) and PICK1-deficient mice (−/−). Data are means ± SE (<i>n</i> = 4–5). *<i>p</i><0.05, compared to WT. (E) PICK1-deficient mice display decreased ghrelin-induced GH secretion. Basal plasma GH level and the level 5 min after ghrelin administration were determined in anesthetized WT (+/+) and PICK1-deficient mice (−/−) at the age of 7–9 wk. White bars, WT (+/+); black bars, PICK1-deficient mice (−/−). Data are means ± SE (<i>n</i> = 7–9). *<i>p</i><0.05, compared to WT. (F) PICK1-deficient mice display decreased GH content in the pituitary. Pituitaries were taken from 34-wk-old WT (+/+) or PICK1-deficient mice (−/−). Data are means ± SE (<i>n</i> = 4). **<i>p</i><0.01. (G) Relative expression levels of GH and GHR mRNA in pituitaries, determined by RT-PCR analysis (35–38-wk-old mice). White bars, PICK1 +/+: black bars, PICK1 −/−. Data are means ± SE (<i>n</i> = 7–8). *<i>p</i><0.05.</p