M.A. van der Valk

Mice bearing the E mu-myc and E mu-pim-1 transgenes develop pre-B-cell leukemia prenatally.

Previously, it has been shown that E mu-pim-1 transgenic mice are predisposed to T-cell lymphomas, whereas E mu-myc transgenic mice are predisposed to pre-B-cell lymphomas. Here we show that double-transgenic E mu-myc E mu-pim-1 mice exhibit pre-B-cell leukemia in utero. Upon transplantation into recipient mice, embryo-derived double-transgenic leukemic cells frequently progressed to highly malignant monoclonal tumors, indicating that additional (epi)genetic events had occurred during the progression of the disease.

Tiam1-deficiency impairs mammary tumor formation in MMTV-c-neu but not in MMTV-c-myc mice

BackgroundRho-like small GTPases, including RhoA, Rac1 and Cdc42, are crucial for the regulation of a large variety of biological processes such as the cytoskeletal organization and gene transcription. The activities of Rho GTPases are predominantly controlled by guanine nucleotide exchange factors (GEFs), which activate GTPases by catalyzing the exchange of bound GDP for GTP. Earlier, we have identified the Tiam1 gene as an invasion-inducing gene that encodes a specific activator (GEF) of the Rac GTPase. We found that Tiam1-mediated Rac signaling functions in various aspects of tumorigenicity including the formation and progression of Ras-induced skin tumors and Wnt-induced intestinal tumors. Here, we further distinguish the oncogenic pathways that depend on Tiam1 signaling in the mammary gland.Material and methods We crossed Tiam1 knockout mice with MMTV-c-myc and MMTV-c-neu transgenic mice, in which the expression of both oncogenes is targeted to the mammary gland leading to mammary tumorigenesis.ResultsWe found Tiam1 important for Neu-induced tumor formation and progression but not for Myc-induced tumors. Tiam1-deficiency delayed Neu-induced tumor initiation and reduced metastasis but had no effect on the growth of the MMTV-c-neu tumors.Conclusion Our data indicate that the Rac activator Tiam1 contributes to tumorigenicity induced by specific oncogenic signaling pathways only.

MHC and Non-MHC Genes in Lung Tumor Susceptibility in the Mouse: Implications for the Study of the Different Lung Tumor Types and Their Cell of Origin

Lung tumorigenesis in the mouse is controlled by multiple genes, which until now largely escaped detection because of the limitations of the available genetic tools. Therefore, we have developed the Recombinant Congenic Strains (RCS), which can be used to separate and map individual tumor susceptibility genes. The two strains, B10.O20/Dem and O20/A (used to produce the RCS series O20.c.B10.O20/Dem) differ in number, type, and degree of malignancy of lung tumors. Thus the genetic control of the different aspects of lung tumorigenesis can now be analyzed using RCS. The tests on the role of the Major Histocompatibility Complex (MHC; H-2 in mice) in lung tumorigenesis show that the H-2 influence is different for alveolar tumors and papillary tumors. In addition, only the development of papillary tumors is influenced by glucocorticoid administration concomitant with the transplacental carcinogen treatment. The MHC influence on lung tumor development is probably related to H-2 effects on the regulation of lung differentiation. In the H-2 congenic strains used papillary tumors developed early, whereas alveolar tumors appeared later, if at all. This differential impact of genetic and hormonal factors on the development of alveolar and papillary tumors suggests that they arise either from different cell types or from a common cell type at different stages of differentiation.

Genetics of susceptibility to radiation-induced apoptosis in colon: two loci on Chromosomes 9 and 16

Apoptosis, a mechanism for removal of genetically damaged cells and for maintenance of desired size of cell populations, has been implicated in tumor development. Previously, we defined polymorphic loci for susceptibility to apoptosis of thymocytes Rapop1, Rapop2, and Rapop3 on mouse Chromosomes 16, 9, and 3, respectively, using recombinant congenic CcS/Dem strains, each of which contains a random set of 12.5% STS/A genome in the genetic background of BALB/cHeA. The STS/A alleles at these loci confer lower susceptibility to radiation-induced apoptosis of thymocytes than the BALB/cHeA. In the present study, we tested susceptibility of colon crypt cells to radiationinduced apoptosis. In contrast to apoptosis in thymus, the STS/A mice were more susceptible to apoptosis in colon than the BALB/ cHeA. Among the CcS/Dem strains, CcS-4, CcS-7, and CcS-16 were more susceptible to apoptosis in colon than the BALB/cHeA; in thymus, the CcS-7 mice are less susceptible, and the CcS-4 and CcS-16 are not different from the BALB/cHeA. Thus, individual CcS/Dem strains showed different apoptosis susceptibility in the two organs. Analysis of (CcS-7 × BALB/cHeA)F2 hybrids revealed linkage of susceptibility to radiation-induced apoptosis of colon crypt cells to two loci on Chrs 9 and 16, to which Rapop2 and Rapop1 are mapped. The STS/A allele at the locus on chromosome 9 results in high susceptibility to apoptosis of colon crypt cells in mice homozygous for the BALB/cHeA allele at the locus on Chr 16. Although these two loci may be identical to Rapop1 and Rapop2, they affect apoptosis in colon in a way different from that in thymus.

Stem cell carcinoma in the small intestine of mice treated transplacentally with N-ethyl-N-nitrosourea: Some quantitative and histological aspects

A high incidence of tumours of the small intestine occurred in mice of the B10.A/SgSnA strain treated transplacentally with N-ethyl-N-nitrosourea (ENU). In these adenocarcinomas, histologically different tumour cells which resembled the 4 cell types of the normal intestinal epithelium were present. Since normal intestinal epithelial cells are thought to originate from common stem cells, the tumours seem to be derived from these stem cells.

Early morbidity encountered in the dietary-related mouse model of Barrett’s esophagus: a question of zinc?

Recently, a mouse model for Barretts esophagus based on a zinc-deficient diet supplemented with deoxycholic bile acids has been published. The aim of this study was to attempt to reproduce these data and extend them by employing genetically modified mice and intraperitoneal iron supplementation. The study design encompassed six experimental groups (wild type, Apc-mutant and Smad4-mutant mice, with or without iron injections), with all animals fed with the zinc-deficient diet supplemented with deoxycholic bile acids. All treatments were started at 3-5 weeks of age (the majority [78%] at 5 weeks). Animals were scheduled for euthanasia at two distinct time points, namely at 3 and 6 months of age. All mice showed signs of considerable distress already 4 weeks after the start of the modified diets, and had to be euthanized before the first evaluation time point (mean age 9.3 weeks, range 5-15 weeks). No differences were observed between wild type and genetically modified mice, or between animals with or without iron supplementation. On histological examination, we could not detect any lesions (Barretts esophagus-like or tumors) other than esophagitis. In the currently presented experimental settings, we were not able to reproduce the mouse model according to which Barretts-like lesions could be detected in animals fed with the zinc-deficient diet supplemented with deoxycholic bile acids.

Triploidy and intersexuality in adult commercial layers.

The cause of masculinisation of the left ovary and the outgrowth of the vestigial right gonad was investigated in intersexual hens. Tumour-like cell masses, resembling mouse tubular adenomas of the ovary, were observed in the majority of masculinised left gonads. Except for one male and two intersexuals, testosterone concentrations were below detectable levels. For oestrogen, progesterone and the oestrogen : progesterone ratio all differences were significant, except for the difference between the intersex and the male. Histochemically this cell mass showed weak androgen-synthesising activity. These intersexual gonads showed similarities to normal testicular tissue. Karyotyping revealed 3n-autosomes and a ZZW sex chromosome constitution. The early and almost complete absence of cortical follicular structures was most notable and may have been the cause of the sex reversal.

Abstract 4419: The role of ABC transporters in PhIP-induced colon carcinogenesis

Proceedings: AACR 103rd Annual Meeting 2012‐‐ Mar 31‐Apr 4, 2012; Chicago, IL ABC transporters such as BCRP, P-gp, Mrp2 and Mrp3 are thought to protect organisms from xenobiotics, including dietary carcinogens and anticancer drugs. These multidrug transporters reduce the oral uptake, systemic availability and tissue or cellular accumulation of transported substrates by mediating their extrusion from cells and the body in general. Therefore, they could have very important roles in the distribution of carcinogens to certain tissues and cell types, and carcinogen susceptibility. In this study, we aimed to investigate the role of ABC transporters in the tumorigenicity of a dietary carcinogen, PhIP (2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine), which is produced during high-temperature cooking of meat. We have performed a pharmacokinetic experiment in wild-type FVB and ABC transporter knockout strains (Bcrp;Mrp2;Mrp3-/- and Bcrp;Mdr1a/1b;Mrp2-/-) with 200 mg/kg orally administered PhIP and observed that ABC transporters have an impact on the distribution of PhIP metabolites to several organs. There was an accumulation of N-OH-PhIP, a potentially carcinogenic metabolite, in the liver of Bcrp;Mrp2;Mrp3-/- mice and a decrease in the levels of PhIP-5-sulfate, a surrogate marker for DNA exposure to reactive compound, in small intestine of Bcrp;Mrp2;Mrp3-/- and Bcrp;Mdr1a/1b;Mrp2-/- mice compared to wild-type FVB. For carcinogenesis experiments, we used a chemically-induced colon carcinogenesis model where wild-type FVB and ABC transporter compound knock-out mice received a single, oral administration of 200 mg/kg PhIP for initiation and seven days administration of Dextran Sodium Sulfate (DSS) in drinking water for promotion of the tumorigenesis process via colonic inflammation. During the whole experiment, mice were closely checked for their body weight loss, diarrhea and rectal bleeding. Our results showed that PhIP and DSS treatment together induced colonic tumors in all strains over 180 days. No tumor formation could be found in only PhIP-treated, only DSS-treated and negative control groups that received vehicle. Tumor incidence was lower in both knock-outs compared to the wild-type FVB when inflammation levels between the groups were corrected. Our results suggest that these ABC transporters are not protecting the intestinal tract from PhIP-induced carcinogenesis upon oral ingestion in mice, and perhaps even partially enhance PhIP-induced carcinogenesis. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4419. doi:1538-7445.AM2012-4419

Influence of MHC and Non-MHC Genes on Tumorigenesis and the Use of the Recombinant Congenic Strains as a Novel Tool for the Genetic Analysis of Tumor Susceptibility

One of the main developments in the contemporary biology is the rapid progress in the structural analysis of the mammalian genome, concentrated mainly on two species - the human and the mouse. A specific potential of the analysis of the mouse genome resides in the possibility of combining the structural analysis with the study of the genetic determination of various functional traits. This contribution of mouse studies is especially valuable in view of the limited possibilities of direct biological experiments in humans.

Mammary tumorigenicities of three chemically induced mouse kidney cell lines in syngeneic female hosts

Three chemically induced, mammary tumour virus (MMTV) and leukemia virus (MuLV) producing, baby mouse kidney (BMK) cell lines derived from respectively strains BALB/c (-/HeA and -/CrglA) and C57BL/LiA were investigated for their mammary tumour (MT) evoking potentials in syngeneic female hosts. An i.p. inoculated virus-enriched fraction from A3 cells (BALB/c/HeA) had a similar oncogenic effect as i.p. and s.c. inoculated whole A3 cells. The average MT ages were reduced in all 3 groups. Cell lines BBM (BALB/c/CrglA) and BB (C57BL/LiA) were tested as i.p. inoculated whole cells. Again, the average MT age was reduced in thus treated BALB/c/Crgl females. In the case of C57BL/LiA the percentage of animals with MT was strongly increased in the BB cell inoculated group (1 MT in control group). Bioassay results corrected for intercurrent death cases (including leukosis) were statistically significant. It is concluded that the endogenous MMTV variants of the 3 mouse (sub-)strains are virulent MT evoking viruses in autologous hosts when they are induced.