AJUBA: A regulator of epidermal homeostasis and cancer.

The epidermis, outermost layer of the skin, is constantly renewing itself through proliferative and differentiation processes. These processes are vital to maintain proper epidermal integrity during skin development and homeostasis and for preventing skin diseases and cancers. The biological mechanisms that permit this balancing act are vast, where individual pathway regulators are known, but the exact regulatory control and cross-talk between simultaneously turning one biological pathway on and an opposing one off remain elusive. This review explores the diverse roles the scaffolding protein AJUBA plays during epidermal homeostasis and cancer. Initially identified for its role in promoting meiotic progression in oocytes through Grb2 and MAP kinase activity, AJUBA also maintains cytoskeletal tension permitting epidermal tissue development and responds to retinoic acid committing cells to initiate development of surface epidermal layer. AJUBA regulates proliferation of skin stem cells through Hippo and Wnt signalling and encourages mitotic commitment through Aurora-A, Aurora-B and CDK1. In addition, AJUBA also induces epidermal differentiation to maintain appropriate epidermal thickness and barrier function by activating Notch signalling and stabilizing catenins and actin during cellular remodelling. AJUBA also plays an imperative context-dependent tumor-promoting and tumor-suppressive role within epithelial cancers. AJUBA's abundant roles within the epidermis signify its importance as a molecular switchboard, vetting multiple signalling pathways to control epidermal biology.

Rare driver mutations in head and neck squamous cell carcinomas converge on NOTCH signaling.

In most human cancers, only a few genes are mutated at high frequencies; most are mutated at low frequencies. The functional consequences of these recurrent but infrequent "long tail" mutations are often unknown. We focused on 484 long tail genes in head and neck squamous cell carcinoma (HNSCC) and used in vivo CRISPR to screen for genes that, upon mutation, trigger tumor development in mice. Of the 15 tumor-suppressor genes identified, ADAM10 and AJUBA suppressed HNSCC in a haploinsufficient manner by promoting NOTCH receptor signaling. ADAM10 and AJUBA mutations or monoallelic loss occur in 28% of human HNSCC cases and are mutually exclusive with NOTCH receptor mutations. Our results show that oncogenic mutations in 67% of human HNSCC cases converge onto the NOTCH signaling pathway, making NOTCH inactivation a hallmark of HNSCC.

Functional screening of FGFR4-driven tumorigenesis identifies PI3K/mTOR inhibition as a therapeutic strategy in rhabdomyosarcoma.

Rhabdomyosarcoma (RMS) is the most common pediatric soft tissue sarcoma and outcomes have stagnated, highlighting a need for novel therapies. Genomic analysis of RMS has revealed that alterations in the receptor tyrosine kinase (RTK)/RAS/PI3K axis are common and that FGFR4 is frequently mutated or overexpressed. Although FGFR4 is a potentially druggable receptor tyrosine kinase, its functions in RMS are undefined. This study tested FGFR4-activating mutations and overexpression for the ability to generate RMS in mice. Murine tumor models were subsequently used to discover potential therapeutic targets and to test a dual PI3K/mTOR inhibitor in a preclinical setting. Specifically, we provide the first mechanistic evidence of differential potency in the most common human RMS mutations, V550E or N535K, compared to FGFR4wt overexpression as murine myoblasts expressing FGFR4V550E undergo higher rates of cellular transformation, engraftment into mice, and rapidly form sarcomas that highly resemble human RMS. Murine tumor cells overexpressing FGFR4V550E were tested in an in vitro dose-response drug screen along with human RMS cell lines. Compounds were grouped by target class, and potency was determined using average percentage of area under the dose-response curve (AUC). RMS cells were highly sensitive to PI3K/mTOR inhibitors, in particular, GSK2126458 (omipalisib) was a potent inhibitor of FGFR4V550E tumor-derived cell and human RMS cell viability. FGFR4V550E-overexpressing myoblasts and tumor cells had low nanomolar GSK2126458 EC50 values. Mass cytometry using mouse and human RMS cell lines validated GSK2126458 specificity at single-cell resolution, decreasing the abundance of phosphorylated Akt as well as decreasing phosphorylation of the downstream mTOR effectors 4ebp1, Eif4e, and S6. Moreover, PI3K/mTOR inhibition also robustly decreased the growth of RMS tumors in vivo. Thus, by developing a preclinical platform for testing novel therapies, we identified PI3K/mTOR inhibition as a promising new therapy for this devastating pediatric cancer.

Biological effects of tritium on fish cells in the concentration range of international drinking water standards.

PURPOSE: To evaluate whether the current Canadian tritium drinking water limit is protective of aquatic biota, an in vitro study was designed to assess the biological effects of low concentrations of tritium, similar to what would typically be found near a Canadian nuclear power station, and higher concentrations spanning the range of international tritium drinking water standards. MATERIALS AND METHODS: Channel catfish peripheral blood B-lymphoblast and fathead minnow testis cells were exposed to 10-100,000 Bq l(-1) of tritium, after which eight molecular and cellular endpoints were assessed. RESULTS: Increased numbers of DNA strand breaks were observed and ATP levels were increased. There were no increases in γH2AX-mediated DNA repair. No differences in cell growth were noted. Exposure to the lowest concentrations of tritium were associated with a modest increase in the viability of fathead minnow testicular cells. Using the micronucleus assay, an adaptive response was observed in catfish B-lymphoblasts. CONCLUSIONS: Using molecular endpoints, biological responses to tritium in the range of Canadian and international drinking water standards were observed. At the cellular level, no detrimental effects were noted on growth or cycling, and protective effects were observed as an increase in cell viability and an induced resistance to a large challenge dose.

Draft Whole-Genome Sequences of 25 Salmonella enterica Strains Representing 24 Serovars.

We report the draft genome sequences of 25 Salmonella enterica strains representing 24 different serotypes, many of which were not available in public repositories during our selection process. These draft genomes will provide useful reference for the genetic variation between serotypes and aid in the development of molecular typing tools.