Rigosertib ameliorates the effects of oncogenic KRAS signaling in a murine model of myeloproliferative neoplasia.

Aberrant signaling triggered by oncogenic or hyperactive RAS proteins contributes to the malignant phenotypes in a significant percentage of myeloid malignancies. Of these, juvenile myelomonocytic leukemia (JMML), an aggressive childhood cancer, is largely driven by mutations in RAS genes and those that encode regulators of these proteins. The Mx1-cre kras+/G12D mouse model mirrors several key features of this disease and has been used extensively to determine the utility and mechanism of small molecule therapeutics in the context of RAS-driven myeloproliferative disorders. Treatment of disease-bearing KRASG12D mice with rigosertib (RGS), a small molecule RAS mimetic that is in phase II and III clinical trials for MDS and AML, decreased the severity of leukocytosis and splenomegaly and extended their survival. RGS also increased the frequency of HSCs and rebalanced the ratios of myeloid progenitors. Further analysis of KRASG12D HSPCs in vitro revealed that RGS suppressed hyperproliferation in response to GM-CSF and inhibited the phosphorylation of key RAS effectors. Together, these data suggest that RGS might be of clinical benefit in RAS-driven myeloid disorders.

A small molecule multi-kinase inhibitor reduces influenza A virus replication by restricting viral RNA synthesis.

Currently available drugs against influenza virus target the viral neuraminidase or the M2 ion channel. The emergence of viral strains resistant to these drugs has been widely described; therefore, there is an urgent need for novel antiviral drugs. Targeting of host factors required for viral replication is an attractive option for circumventing the problem of drug resistance. Several RNAi screens have demonstrated that host kinases are required for the replication of influenza virus. To determine whether compounds that inhibit these kinases can impair viral replication, we tested several kinase inhibitors for activity against influenza A virus. We demonstrate that the multi-kinase inhibitor ON108110 reduces replication of influenza A virus in a dose-dependent manner by suppressing viral RNA synthesis. In addition, ON108110 also inhibits other viruses including vesicular stomatitis virus and Newcastle disease virus, suggesting that this compound may represent a novel class of antiviral agents.

Inactivation of ELF/TGF-beta signaling in human gastrointestinal cancer.

TGF-beta/Smads regulate a wide variety of biological responses through transcriptional regulation of target genes. ELF, a beta-spectrin, plays a key role in the transmission of TGF-beta-mediated transcriptional response through Smads. ELF was originally identified as a key protein involved in endodermal stem/progenitor cells committed to foregut lineage. Also, as a major dynamic adaptor and scaffolding protein, ELF is important for the generation of functionally distinct membranes, protein sorting and the development of polarized differentiated epithelial cells. Disruption of elf results in the loss of Smad3/Smad4 activation and, therefore, a disruption of the TGF-beta pathway. These observations led us to pursue the function of ELF in gastrointestinal (GI) epithelial cell-cell adhesion and tumor suppression. Here, we show a significant loss of ELF and reduced Smad4 expression in human gastric cancer tissue samples. Also, of the six human gastric cancer cell lines examined, three show deficient ELF expression. Furthermore, we demonstrate the rescue of E-cadherin-dependent homophilic cell-cell adhesion by ectopic expression of full-length elf. Our results suggest that ELF has an essential role in tumor suppression in GI cancers.

Signaling by dual specificity kinases.

Dual specificity kinases that phosphorylate the Thr- and Tyr-residues within the TXY motif of MAP-kinases of play a central role in the regulation of various processes of cell growth. These dual specificity kinases also known as MAP kinase kinases are constituents of the sequential kinase signaling modules. Seven distinct mammalian MAP kinases kinases have been identified. Some of the unique signaling properties of these kinases are discussed here.

Genetics of xenotropic virus expression in mice. II. Expression of major virus structural proteins in crosses involving NZB/B1NJ, SWR/J, and 129/J strains of mice.

The expression of viral structural polypeptides and the production of infectious xenotropic virus were found to segregate together in NZB, 129/J, and SWR/J mice and in crosses between these strains. The viral p30 protein segregation pattern, as measured by competition radioimmunoassay using extracts of frozen spleens from backcross progeny, indicate that xenotropic murine leukemia virus expression is controlled by two dominant genes.

Nucleoside phosphorylase 2 (Np-2) of mice.

Isozyme patterns of nucleoside phosphorylase (NP) in 16 inbred strains, two recombinant inbred, one congenic, and three species of wild mice were studied. Evidence is provided for a genetic locus, Np-2, encoding an electrophoretic variant which is expressed exclusively in erythrocytes of certain inbred strains. This finding establishes the occurrence of genetic polymorphism of NP among inbred strains of mice. In addition, the Npla allele previously reported only in inbred strains has been observed in one of the species of wild mice (Mus musculus castaneus) studied.

Immunoglobulin production by lymphosarcomas induced by Abelson virus in mice.

A brief review of the origin and tumor-inducing properties of Abelson murine leukemia virus is given. The most common neoplasm induced by this virus in vivo is a nonthymic lymphocytic tumor of bone marrow and lymph node origin. Two morphologic types of lymphosarcomas are the undifferentiated lymphosarcoma (LS) and the plasmacytic lymphosarcoma (PL). With the electron microscope, both tumor cell types may be mixed and contain undifferentiated cells or cells with a moderate amount of rough endoplasmic reticulum and polysomes. PL tumors are composed predominantly of the latter. In biosynthetic studies, PL tumors produce more immunoglobulin (Ig) than LS and more of the Ig-heavy chain, which is thought to be the murine counterpart of IgD. PL-cells sensitized with rabbit antisera to mouse kappa chains formed rosettes with formalinized protein-A producing Staphylococcus aureus Cowan I strain. The rabbit antisera were specific for kappa chains by absorption. The failure of lymphosarcoma cells to secrete Ig indicates their differentiation is blocked by the transformation process. Lymphosarcoma cells appear then to be derived from B-lymphocytes.

Simplified radioimmunoassay for viral antigens: use of Staphylococcus aureus as an adsorbent for antigen-antibody complexes.

In a rapid method for the radioimmunoassay (RIA) of viral antigens, Staphylococcus aureus was used as the adsorbent for antigen-antibody complexes ("protein A" molecules on the cell walls of certain strains of staphylococci have a strong affinity toward IgG molecules). The results showed that this method could be used instead of the double-antibody technique, with the same or probably higher sensitivity in precipitation as well as competition RIA's.

Continuous culturing of murine splenic B-lumphocytes: synthesis and surface deposition of IgM and putative IgD molecules.

A method for the continuous culturing of mouse splenic lymphocytes is described. The method utilizes rat-tail collagen-coated glass or plastic surfaces which enhance the adherence and proliferation of B-lymphocytes. The cultured cells are shown to synthesize IgM and putative IgD molecules which are deposited on the cell membrane. The majority of the cells possessed Fc receptors and C' receptors, while none of them seemed to possess theta-antigen. It is concluded that these cells are functionally active B-lymphoid cells.