Truncation of the MSH2 C-terminal 60 amino acids disrupts effective DNA mismatch repair and is causative for Lynch syndrome.

Missense variants of DNA mismatch repair (MMR) genes pose a problem in clinical genetics as long as they cannot unambiguously be assigned as the cause of Lynch syndrome (LS). To study such variants of uncertain clinical significance, we have developed a functional assay based on direct measurement of MMR activity in mouse embryonic stem cells expressing mutant protein from the endogenous alleles. We have applied this protocol to a specific truncation mutant of MSH2 that removes 60 C-terminal amino acids and has been found in suspected LS families.

OATP1A/1B transporters affect irinotecan and SN-38 pharmacokinetics and carboxylesterase expression in knockout and humanized transgenic mice.

Organic anion-transporting polypeptides (OATP) mediate the hepatic uptake of many drugs, thus codetermining their clearance. Impaired hepatic clearance due to low-activity polymorphisms in human OATP1B1 may increase systemic exposure to SN-38, the active and toxic metabolite of the anticancer prodrug irinotecan. We investigated the pharmacokinetics and toxicity of irinotecan and SN-38 in Oatp1a/1b-null mice: Plasma exposure of irinotecan and SN-38 was increased 2 to 3-fold after irinotecan dosing (10 mg/kg, i.

Wnt5a promotes human colon cancer cell migration and invasion but does not augment intestinal tumorigenesis in Apc1638N mice.

Whereas aberrant activation of canonical Wnt/β-catenin signaling underlies the majority of colorectal cancer cases, the contribution of non-canonical Wnt signaling is unclear. As enhanced expression of the most extensively studied non-canonical Wnt ligand WNT5A is observed in various diseases including colon cancer, WNT5A is gaining attention nowadays. Numerous in vitro studies suggest modulating capacities of WNT5A on proliferation, differentiation, migration and invasion, affecting tumor and non-mutant cells.

Targeting BRAFV600E in an inducible murine model of melanoma.

The MAP kinase and PI3 kinase pathways have been identified as the most common pathways that mediate oncogenic transformation in melanoma, and the majority of compounds developed for melanoma treatment target one or the other of these pathways. In addition to such targeted therapies, immunotherapeutic approaches have shown promising results. A combination of these two treatment modalities could potentially result in further improvement of treatment outcome.

Induced Wnt5a expression perturbs embryonic outgrowth and intestinal elongation, but is well-tolerated in adult mice.

Wnt5a is essential during embryonic development, as indicated by mouse Wnt5a knockout embryos displaying outgrowth defects of multiple structures including the gut. The dynamics of Wnt5a involvement in these processes is unclear, and perinatal lethality of Wnt5a knockout embryos has hampered investigation of Wnt5a during postnatal stages in vivo. Although in vitro studies have suggested a relevant role for Wnt5a postnatally, solid evidence for a significant impact of Wnt5a within the complexity of an adult organism is lacking.

GFAP-Cre-mediated transgenic activation of Bmi1 results in pituitary tumors.

Bmi1 is a member of the polycomb repressive complex 1 and plays different roles during embryonic development, depending on the developmental context. Bmi1 over expression is observed in many types of cancer, including tumors of astroglial and neural origin. Although genetic depletion of Bmi1 has been described to result in tumor inhibitory effects partly through INK4A/Arf mediated senescence and apoptosis and also through INK4A/Arf independent effects, it has not been proven that Bmi1 can be causally involved in the formation of these tumors.

Evidence for complete epistasis of null mutations in murine Fanconi anemia genes Fanca and Fancg.

Fanconi anemia (FA) is a heritable disease characterized by bone marrow failure, congenital abnormalities, and cancer predisposition. The 15 identified FA genes operate in a molecular pathway to preserve genomic integrity. Within this pathway the FA core complex operates as an ubiquitin ligase that activates the complex of FANCD2 and FANCI to coordinate DNA repair.

Fancf-deficient mice are prone to develop ovarian tumours.

Fanconi anaemia (FA) is a rare recessive disorder marked by developmental abnormalities, bone marrow failure, and a high risk for the development of leukaemia and solid tumours. The inactivation of FA genes, in particular FANCF, has also been documented in sporadic tumours in non-FA patients. To study whether there is a causal relationship between FA pathway defects and tumour development, we have generated a mouse model with a targeted disruption of the FA core complex gene Fancf.

β-catenin tyrosine 654 phosphorylation increases Wnt signalling and intestinal tumorigenesis.

Objective Deregulation of the Wnt signalling pathway by mutations in the Apc or β-catenin genes underlies colorectal carcinogenesis. As a result, β-catenin stabilises, translocates to the nucleus, and activates gene transcription. Intestinal tumours show a heterogeneous pattern of nuclear β-catenin, with the highest levels observed at the invasion front.

Enriching lipid nanovesicles with short-chain glucosylceramide improves doxorubicin delivery and efficacy in solid tumors.

For amphiphilic anticancer drugs, such as the anthracyclin doxorubicin (Dox), uptake by tumor cells involves slow diffusion across the plasma membrane, a limiting factor in clinical oncology. Previously, we discovered that preinsertion of short-chain sphingolipids such as N-octanoyl-glucosylceramide (GC) in the tumor cell membrane enhances cellular Dox uptake. In the present study, we apply this strategy in vitro and in vivo by coadministering GC and Dox in a lipid nanovesicle (LNV).

Error-prone translesion replication of damaged DNA suppresses skin carcinogenesis by controlling inflammatory hyperplasia.

The induction of skin cancer involves both mutagenic and proliferative responses of the epidermis to ultraviolet (UV) light. It is believed that tumor initiation requires the mutagenic replication of damaged DNA by translesion synthesis (TLS) pathways. The mechanistic basis for the induction of proliferation, providing tumor promotion, is poorly understood.

Lack of CD200 enhances pathological T cell responses during influenza infection.

Influenza virus infection can be accompanied by life-threatening immune pathology most likely due to excessive antiviral responses. Inhibitory immune receptors may restrain such overactive immune responses. To study the role of the inhibitory immune receptor CD200R and its ligand CD200 during influenza infection, we challenged wild-type and CD200(-/-) mice with influenza virus.

A targeted constitutive mutation in the APC tumor suppressor gene underlies mammary but not intestinal tumorigenesis.

Germline mutations in the adenomatous polyposis coli (APC) gene are responsible for familial adenomatous polyposis (FAP), an autosomal dominant hereditary predisposition to the development of multiple colorectal adenomas and of a broad spectrum of extra-intestinal tumors. Moreover, somatic APC mutations play a rate-limiting and initiating role in the majority of sporadic colorectal cancers. Notwithstanding its multifunctional nature, the main tumor suppressing activity of the APC gene resides in its ability to regulate Wnt/beta-catenin signaling.

Fancm-deficient mice reveal unique features of Fanconi anemia complementation group M.

The Fanconi anemia (FA) core complex member FANCM remodels synthetic replication forks and recombination intermediates. Thus far, only one FA patient with FANCM mutations has been described, but the relevance of these mutations for the FA phenotype is uncertain. To provide further experimental access to the FA-M complementation group we have generated Fancm-deficient mice by deleting exon 2.

Analysis of CD97 expression and manipulation: antibody treatment but not gene targeting curtails granulocyte migration.

The heptahelical receptor CD97 is a defining member of the EGF-TM7 family of adhesion class receptors. In both humans and mice, CD97 isoforms are expressed with variable numbers of tandemly arranged N-terminal epidermal growth factor-like domains that facilitate interactions with distinct cellular ligands. Results from treatment of mice with mAbs in various disease models have suggested a role for CD97 in leukocyte trafficking.

A conditional mouse model for malignant mesothelioma.

Malignant mesothelioma is a devastating disease that has been associated with loss of Neurofibromatosis type 2 (NF2) and genetic lesions affecting RB and P53 pathways. We introduced similar lesions in the mesothelial lining of the thoracic cavity of mice. Mesothelioma developed at high incidence in Nf2;Ink4a/Arf and Nf2;p53 conditional knockout mice with median survival times of approximately 30 and 20 weeks, respectively.

Knockout of cytochrome P450 3A yields new mouse models for understanding xenobiotic metabolism.

Cytochrome P450 3A (CYP3A) enzymes constitute an important detoxification system that contributes to primary metabolism of more than half of all prescribed medications. To investigate the physiological and pharmacological roles of CYP3A, we generated Cyp3a-knockout (Cyp3a-/-) mice lacking all functional Cyp3a genes. Cyp3a-/- mice were viable, fertile, and without marked physiological abnormalities.

p15Ink4b is a critical tumour suppressor in the absence of p16Ink4a.

The CDKN2b-CDKN2a locus on chromosome 9p21 in human (chromosome 4 in mouse) is frequently lost in cancer. The locus encodes three cell cycle inhibitory proteins: p15INK4b encoded by CDKN2b, p16INK4a encoded by CDKN2a and p14ARF (p19Arf in mice) encoded by an alternative reading frame of CDKN2a (ref. 1).

Targeting self-antigens through allogeneic TCR gene transfer.

Adoptive transfer of T-cell receptor (TCR) genes has been proposed as an attractive approach for immunotherapy in cases where the endogenous T-cell repertoire is insufficient. While there are promising data demonstrating the capacity of TCR-modified T cells to react to foreign antigen encounter, the feasibility of targeting tumor-associated self-antigens has not been addressed. Here we demonstrate that T-cell receptor gene transfer allows the induction of defined self-antigen-specific T-cell responses, even when the endogenous T-cell repertoire is nonreactive.

An inducible mouse model of melanoma expressing a defined tumor antigen.

Cancer immunotherapy based on vaccination with defined tumor antigens has not yet shown strong clinical efficacy, despite promising results in preclinical models. This discrepancy might result from the fact that available preclinical models rely on transplantable tumors, which do not recapitulate the long-term host-tumor interplay that occurs in patients during progressive tumor development and results in tumor tolerance. To create a faithful preclinical model for cancer immunotherapy, we generated a transgenic mouse strain developing autologous melanomas expressing a defined tumor antigen recognized by T cells.

Mice lacking Mrp3 (Abcc3) have normal bile salt transport, but altered hepatic transport of endogenous glucuronides.

Background/aim: Multidrug Resistance Protein 3 (MRP3) transports bile salts and glucuronide conjugates in vitro and is postulated to protect the liver in cholestasis. Whether the absence of Mrp3 affects these processes in vivo is tested.

Methods: Mrp3-deficient mice were generated and the contribution of Mrp3 to bile salt and glucuronide conjugate transport was tested in (1): an Ussing-chamber set-up with ileal explants (2), the liver during bile-duct ligation (3), liver perfusion experiments, and (4) in vitro vesicular uptake experiments.

Cutting edge: CD95 maintains effector T cell homeostasis in chronic immune activation.

The elimination of activated T cells is important to maintain homeostasis and avoid immunopathology. CD95 (Fas/APO-1) has been identified as a death mediator for activated T cells in vitro but the function of CD95 in death of mature T cells in vivo is still controversial. Here we show that triggering of the costimulatory TNF receptor family member CD27 sensitized T cells for CD95-induced apoptosis.