Recombinant Origins of Pathogenic and Nonpathogenic Mouse Gammaretroviruses with Polytropic Host Range.

Ecotropic, xenotropic, and polytropic mouse leukemia viruses (E-, X-, and P-MLVs) exist in mice as infectious viruses and endogenous retroviruses (ERVs) inserted into mouse chromosomes. All three MLV subgroups are linked to leukemogenesis, which involves generation of recombinants with polytropic host range. Although P-MLVs are deemed to be the proximal agents of disease induction, few biologically characterized infectious P-MLVs have been sequenced for comparative analysis.

Sequence Diversity, Intersubgroup Relationships, and Origins of the Mouse Leukemia Gammaretroviruses of Laboratory and Wild Mice.

Unlabelled: Mouse leukemia viruses (MLVs) are found in the common inbred strains of laboratory mice and in the house mouse subspecies ofMus musculus Receptor usage and envelope (env) sequence variation define three MLV host range subgroups in laboratory mice: ecotropic, polytropic, and xenotropic MLVs (E-, P-, and X-MLVs, respectively). These exogenous MLVs derive from endogenous retroviruses (ERVs) that were acquired by the wild mouse progenitors of laboratory mice about 1 million years ago. We analyzed the genomes of seven MLVs isolated from Eurasian and American wild mice and three previously sequenced MLVs to describe their relationships and identify their possible ERV progenitors.

Phase I study of TP300 in patients with advanced solid tumors with pharmacokinetic, pharmacogenetic and pharmacodynamic analyses.

Background: A Phase I dose escalation first in man study assessed maximum tolerated dose (MTD), dose-limiting toxicity (DLT) and recommended Phase II dose of TP300, a water soluble prodrug of the Topo-1 inhibitor TP3076, and active metabolite, TP3011.

Methods: Eligible patients with refractory advanced solid tumors, adequate performance status, haematologic, renal, and hepatic function. TP300 was given as a 1-hour i.

Characterization of the human SNM1A and SNM1B/Apollo DNA repair exonucleases.

Human SNM1A and SNM1B/Apollo have both been implicated in the repair of DNA interstrand cross-links (ICLs) by cellular studies, and SNM1B is also required for telomere protection. Here, we describe studies on the biochemical characterization of the SNM1A and SNM1B proteins. The results reveal some fundamental differences in the mechanisms of the two proteins.

Evodiamine, a dual catalytic inhibitor of type I and II topoisomerases, exhibits enhanced inhibition against camptothecin resistant cells.

DNA topoisomerases are nuclear enzymes that are the targets for several anticancer drugs. In this study we investigated the antiproliferative activity against human leukaemia cell lines and the effects on topoisomerase I and II of evodiamine, which is a quinazolinocarboline alkaloid isolated from the fruit of a traditional Chinese medicinal plant, Evodia rutaecarpa. We report here the anti-proliferative activity against human leukaemia cells K562, THP-1, CCRF-CEM and CCRF-CEM/C1 and the inhibitory mechanism on human topoisomerases I and II, important anti-cancer drugs targets, of evodiamine.

Human SNM1A and XPF-ERCC1 collaborate to initiate DNA interstrand cross-link repair.

One of the major DNA interstrand cross-link (ICL) repair pathways in mammalian cells is coupled to replication, but the mechanistic roles of the critical factors involved remain largely elusive. Here, we show that purified human SNM1A (hSNM1A), which exhibits a 5'-3' exonuclease activity, can load from a single DNA nick and digest past an ICL on its substrate strand. hSNM1A-depleted cells are ICL-sensitive and accumulate replication-associated DNA double-strand breaks (DSBs), akin to ERCC1-depleted cells.

Measurement of DNA damage in individual cells using the Single Cell Gel Electrophoresis (Comet) assay.

The Single Cell Gel Electrophoresis (Comet) assay is a simple, versatile and sensitive method for measuring DNA damage in individual cells, allowing the determination of heterogeneity of response within a cell population. The basic alkaline technique described is for the determination of DNA strand break damage and its repair at a single cell level. Specific modifications to the method use a lower pH ('neutral' assay), or allow the measurement of DNA interstrand cross-links.

SG2285, a novel C2-aryl-substituted pyrrolobenzodiazepine dimer prodrug that cross-links DNA and exerts highly potent antitumor activity.

The pyrrolobenzodiazepines (PBD) are naturally occurring antitumor antibiotics, and a PBD dimer (SJG-136, SG2000) is in phase II trials. Many potent PBDs contain a C2-endo-exo unsaturated motif associated with the pyrrolo C-ring. The novel compound SG2202 is a PBD dimer containing this motif.

Anaplastic plasmacytomas: relationships to normal memory B cells and plasma cell neoplasms of immunodeficient and autoimmune mice.

Anaplastic plasmacytomas (APCTs) from NFS.V(+) congenic mice and pristane-induced plasmacytic PCTs from BALB/c mice were previously shown to be histologically and molecularly distinct subsets of plasma cell neoplasms (PCNs). Here we extended these comparisons, contrasting primary APCTs and PCTs by gene expression profiling in relation to the expression profiles of normal naïve, germinal centre, and memory B cells and plasma cells.

Measurement of DNA interstrand crosslinking in naked DNA using gel-based methods.

Bifunctional DNA damaging agents continue to be the mainstay in various chemotherapeutic regimens used in the clinic. DNA interstrand crosslinks are considered to be the critical cytotoxic lesions for the biological activity of such agents. Gel-based electrophoretic assays can efficiently separate denatured single-stranded DNA from double-stranded, covalently-linked DNA resulting from the presence of an interstrand crosslink.

Measurement of DNA interstrand crosslinking in individual cells using the Single Cell Gel Electrophoresis (Comet) assay.

The Single Cell Gel Electrophoresis (Comet) assay, originally developed to allow visualisation of DNA strand break damage in individual cells, has been adapted to measure DNA interstrand cross-links. DNA interstrand cross-links are formed in cells by a number of commonly used cancer chemotherapy agents and are considered to be the critical lesion formed by such agents. This technique allows the analysis of DNA interstrand cross-link formation and repair at a single cell level, requires few cells, allows the determination of heterogeneity of response within a cell population and is sensitive enough to measure DNA interstrand cross-links at pharmacologically relevant doses.

Expression of infectious murine leukemia viruses by RAW264.7 cells, a potential complication for studies with a widely used mouse macrophage cell line.

The mouse macrophage-like cell line RAW264.7, the most commonly used mouse macrophage cell line in medical research, was originally reported to be free of replication-competent murine leukemia virus (MuLV) despite its origin in a tumor induced by Abelson MuLV containing Moloney MuLV as helper virus. As currently available, however, we find that it produces significant levels of ecotropic MuLV with the biologic features of the Moloney isolate and also MuLV of the polytropic or MCF class.

Functionalised cyclopentadienyl titanium compounds as potential anticancer drugs.

A number of new ionic titanocene compounds have been isolated and characterised, which exhibit excellent cytotoxicity against different human tumour cell lines including a defined cisplatin resistant cell line. A range of biological assays have been carried out to determine levels of cytotoxicity and levels of DNA interstrand crosslinking.

Novel nitrogen mustard-armed combi-molecules for the selective targeting of epidermal growth factor receptor overexperessing solid tumors: discovery of an unusual structure-activity relationship.

To enhance the potency of "combi-molecules", we designed 6a-d and 18 to release an inhibitor of EGFR TK and a bifunctional alkylator. The combi-molecules blocked EGFR TK with potency increasing with the basicity of the mustard moiety. They selectively killed cells transfected with EGFR and were potent against the DU145 prostate cancer cells.

Anaplastic, plasmablastic, and plasmacytic plasmacytomas of mice: relationships to human plasma cell neoplasms and late-stage differentiation of normal B cells.

We have compared histologic features and gene expression profiles of newly identified plasmacytomas from NFS.V(+) congenic mice with plasmacytomas of IL6 transgenic, Fasl mutant, and SJL-beta2M(-/-) mice. NFS.

Modulation of topoisomerase IIalpha expression by a DNA sequence-specific polyamide.

Topoisomerase IIalpha (topo IIalpha) is an important target for several chemotherapeutic agents, including etoposide and doxorubicin. Confluent cells express low levels of topo IIalpha and are resistant to etoposide treatment. Repression of transcription in confluent cells is mediated by binding of the transcription factor NF-Y to inverted CCAAT motifs within the topo IIalpha promoter.

Histologic and molecular characterizations of megakaryocytic leukemia in mice.

Six cases of megakaryocytic leukemia (MKL) were identified and analyzed for morphology and molecular features. MKL were composed of megakaryocyte lineage cells ranging from immature to quite mature cells. VWF, GATA1 and RUNX1 were strongly expressed in megakaryocytes in both normal spleen and MKL as analyzed by immunohistochemistry (IHC).

Expression of the cyclin-dependent kinase inhibitor p27 and its deregulation in mouse B cell lymphomas.

CDKN1B (p27) regulates cell-cycle progression at the G1-S transition by suppressing the cyclin E/CDK2 kinase complex. In normal lymphocytes and most human B cell non-Hodgkin lymphomas (NHL), there is an inverse correlation between proliferative activity and expression of p27; however, a subset of NHL with high mitotic indices expresses p27, which is inactive due to sequestration in nuclear protein complexes or due to cytoplasmic retention. Our studies of mouse B cell NHL also identified cases with high proliferative activity and high levels of p27 at a surprisingly high frequency.

High-throughput retroviral tagging for identification of genes involved in initiation and progression of mouse splenic marginal zone lymphomas.

Human B-cell lymphomas are frequently associated with specific genetic changes caused by chromosomal translocations that activate proto-oncogenes. For lymphomas of mice expressing murine leukemia virus, mutagenic proviral insertions are thought to play a similar role. Here we report studies designed to determine whether specific retroviral integration sites might be associated with a specific subset of mouse B-cell lymphomas and if the genes associated with these sites are regularly altered in expression.

Characterization of a novel murine retrovirus mixture that facilitates hematopoiesis.

A new virus previously arose in BALB/c females mated repeatedly to C57BL/6 (B6) males and then injected with fixed, activated B6 male spleen cells (V. S. Ter-Grigorov, O.