Adenovirus E1a-mediated tumor suppression by a c-erbB-2/neu-independent mechanism.

We reported previously that the adenovirus E1a gene reversed the transformed phenotype of one human melanoma and one fibrosarcoma cell line (S. Frisch, Proc. Natl. Acad. Sci. USA, 88: 9077-9081, 1991). To determine the generality of the tumor suppression effects of E1a, a diversity of tumor cell lines, including A204 rhabdomyosarcoma, RD rhabdomyosarcoma, Saos-2 osteosarcoma, NCI-H23 non-small cell lung carcinoma, MDA-MB435S breast carcinoma, and ras-transformed MDCK kidney epithelial cells, were infected with a retrovirus bearing the 12S E1a coding sequence. We demonstrate here that the expression of E1a severely reduced the anchorage-independent and tumorigenic growth of these cell lines without affecting their growth under normal culture conditions. The parental tumor cells used in this study did not overexpress c-erbB-2/neu, and E1a did not affect its expression in these cells. Thus, tumor suppression by E1a can operate in a wide variety of human tumor cells by c-erbB-2/neu-independent mechanisms. E1a also sensitized these cell lines to the cytotoxic effects of the anticancer drugs etoposide and cisplatin. The results suggest that E1a could prove useful for the gene therapy of a wide variety of human cancers.

Small-sample total RNA purification: laser capture microdissection and cultured cell applications.

Gene expression studies require analysis of RNA, but isolation of total RNA from very small samples by traditional methods can be difficult and inefficient. The Absolutely RNA microprep kit provides a convenient method for isolating total RNA from small numbers of cells such as those harvested by laser capture microdissection (LCM). The protocol includes binding of RNA to a solid support, thus eliminating the need for organic extraction and alcohol precipitation. DNase digestion on the solid support reduces or eliminates DNA contamination and minimizes RNA handling. Efficient washing removes contaminants, and elution in a small volume of buffer results in high-purity RNA at a concentration appropriate for demanding applications such as RT-PCR. RNA isolated from as few as 200 laser capture microdissected brain tumor cells resulted in detection of low, medium, and highly expressed genes by conventional and real-time RT-PCR.

Production of activin A and its roles in inflammation and hematopoiesis.

Activin A, a member of the transforming growth factor beta (TGF-beta) superfamily, is a protein consisting of two homodimeric beta A subunits. It was originally isolated from follicular fluid as a factor stimulating the release of follicle-stimulating hormone from the pituitary gland. Increasing evidence suggests that activin A is broadly distributed and regulates multiple functions in various biological systems by autocrine/paracrine mechanisms. In this review, we discuss the effects of activin A on hematopoiesis, especially the enhancement of erythropoiesis, and the production of activin A within the bone marrow microenvironment and in peripheral blood monocytes. The regulatory control of activin A expression by its 5' promoter region is also discussed. Furthermore, we consider that the expression of activin A is modulated by different agents, including proinflammatory cytokines, glucocorticoids and retinoic acid, suggesting new roles for activin A in inflammation reactions. Recently, this role in inflammation was further strengthened by the findings that activin A expression is elevated in inflammatory arthropathies, is regulated by inflammation-associated cytokines in synoviocyte and articular chondrocyte cultures, and is able to counteract many of the interleukin-6 (IL-6)-induced biological activities. Therefore it is likely that activin A may also act as a paracrine/autocrine moderator in diverse functions, including host defenses.

Incorporation of CD4 into virions by a recombinant herpes simplex virus.

Two herpes simplex virus type 1 (HSV-1) recombinants were constructed by inserting the human CD4 gene into the HSV-1 genome between the gC promoter and the gC structural gene. These viruses, designated K delta T/CD4 and K082/CD4, synthesized a significant quantity of CD4. CD4 was expressed on the surface of infected cells at levels substantially higher than on the surface of HUT78 cells, a CD4+ cell line. Most significantly, a small but detectable quantity of CD4 was incorporated into virions produced by the recombinant viruses. This was demonstrated both by immunoprecipitation of CD4 from purified virions and by neutralization of the recombinant virions by OKT4 and complement. These results suggest that specific virion incorporation signals are not strictly required for inclusion of glycoproteins into HSV-1 virions. It may be possible to utilize this ability to alter the host range or tissue specificity of HSV-1.

Syncytial mutations in the herpes simplex virus type 1 gK (UL53) gene occur in two distinct domains.

Syncytial (syn) mutants of herpes simplex virus cause cell fusion. Many syn mutations map to the syn1 locus, which has been identified with the gK (UL53) gene. In this work, the gK genes of eight syn mutants derived from the KOS strain were sequenced to identify residues and, possibly, domains important for the fusion activity of mutant gK. DNA sequencing showed that six mutants (syn30, syn31, syn32, syn102, syn103, and syn105) had single missense mutations in the gK gene. Two of these, syn31 and syn32, had identical mutations that caused the introduction of a potential site for N-linked glycosylation. syn31 gK was analyzed by in vitro translation and found to utilize the novel glycosylation site. Two other mutants, syn8 and syn33, had three mutations each, resulting in three amino acid substitutions in syn8 and two substitutions in syn33. Of the 10 gK syn mutant sequences known, 8 have mutations in the N-terminal domain of gK, suggesting that this domain, which is likely to be an ectodomain, is important for the function of the protein. The other two mutants, syn30 and syn103, have mutations near the C terminus of gK.

Genetic analysis of type-specific antigenic determinants of herpes simplex virus glycoprotein C.

Herpes simplex virus type 1 (HSV-1) glycoprotein C (gC-1) elicits a largely serotype-specific immune response directed against previously described determinants designated antigenic sites I and II. To more precisely define these two immunodominant antigenic regions of gC-1 and to determine whether the homologous HSV-2 glycoprotein (gC-2) has similarly situated antigenic determinants, viral recombinants containing gC chimeric genes which join site I and site II of the two serotypes were constructed. The antigenic structure of the hybrid proteins encoded by these chimeric genes was studied by using gC-1- and gC-2-specific monoclonal antibodies (MAbs) in radioimmunoprecipitation, neutralization, and flow cytometry assays. The results of these analyses showed that the reactivity patterns of the MAbs were consistent among the three assays, and on this basis, they could be categorized as recognizing type-specific epitopes within the C-terminal or N-terminal half of gC-1 or gC-2. All MAbs were able to bind to only one or the other of the two hybrid proteins, demonstrating that gC-2, like gC-1, contains at least two antigenic sites located in the two halves of the molecule and that the structures of the antigenic sites in both molecules are independent and rely on limited type-specific regions of the molecule to maintain epitope structure. To fine map amino acid residues which are recognized by site I type-specific MAbs, point mutations were introduced into site I of the gC-1 or gC-2 gene, which resulted in recombinant mutant glycoproteins containing one or several residues from the heterotypic serotype in an otherwise homotypic site I background. The recognition patterns of the MAbs for these mutant molecules demonstrated that (i) single amino acids are responsible for the type-specific nature of individual epitopes and (ii) epitopes are localized to regions of the molecule which contain both shared and unshared amino acids. Taken together, the data described herein established the existence of at least two distinct and structurally independent antigenic sites in gC-1 and gC-2 and identified subtle amino acid sequence differences which contribute to type specificity in antigenic site I of gC.

Suppression of IL-6 biological activities by activin A and implications for inflammatory arthropathies.

Activin A is a cytokine whose multiple functions have yet to be fully determined. In this study, the role of proinflammatory cytokines in regulatory control of activin A production was shown in synoviocytes and chondrocytes. Additional facets of functional inflammation-related activities of activin A were also determined. Results showed that activin A concentrations in the synovial fluid of patients with rheumatoid arthritis and gout were elevated relative to those in patients with osteoarthritis. Further studies showed that production of activin A by synoviocytes and chondrocytes in culture was stimulated by cytokines such as IL-1, transforming growth factor-beta (TGF-beta), interferon-gamma (IFN-gamma), and IL-8, consistent with previous studies in regard to the control of activin A production in marrow stromal cells and monocytes by cytokines, glucocorticoids and retinoic acid. In addition, the relationship of activin A to IL-6-induced biological activities was investigated. Three major IL-6 activities involved in inflammatory responses were found to be suppressed by activin A. In a dose-dependent manner, activin A efficiently suppressed IL-6-induced proliferation of 7TD1 B lymphoid cells, phagocytic activity of monocytic M1 cells, and fibrinogen production in HepG2. Therefore, it is likely that activin A serves as a suppressor for IL-6, dampening inflammatory responses, and has the potential to perform some previously unrecognized roles in inflammation.

Analysis of activin A gene expression in human bone marrow stromal cells.

Activin A, a member of the TGF-beta superfamily, plays roles in differentiation and development, including hematopoiesis. Our previous studies indicated that the expression of activin A by human bone marrow cells and monocytes is highly regulated by inflammatory cytokines and glucocorticoids. The present study was undertaken to investigate the regulation of activin A gene expression in the human bone marrow stromal cell lines L87/4 and HS-5, as well as in primary stromal cells. Northern blots demonstrated that, like primary stromal cells, the cell lines expressed four activin A RNA transcripts (6.4, 4.0, 2.8, and 1.6 kb), although distribution of the RNA among the four sizes varied. The locations of the 5' ends of the RNAs were investigated by Northern blots and RNase protection assays. The results identified a transcription start site at 212 nucleotides upstream of the translation start codon. In addition, luciferase expression assays of a series of deletion constructs were used to identify regulatory sequences upstream of the activin A gene. A 58 bp upstream sequence exhibits promoter activity. However, severalfold higher expression requires a positive element consisting of an additional 71 bp of the upstream region. Promoter activity was also identified between 2.5 and 3.6 kb upstream of the start codon. These findings suggest that expression of activin A at the transcriptional level follows complex patterns of regulation.

Serologic type conversion of a herpes simplex virus type 1 (HSV-1) to an HSV-2 epitope caused by a single amino acid substitution in glycoprotein C.

A monoclonal antibody to herpes simplex virus type 2 glycoprotein C (gC-2) did not recognize wild-type herpes simplex virus type 1 gC (gC-1) but did recognize a mutant gC-1 molecule. This conversion from a type 1 to a type 2 epitope was shown to be due to a single amino acid substitution in gC-1.

Resistance of herpes simplex virus type 2 to neomycin maps to the N-terminal portion of glycoprotein C.

Entry of herpes simplex virus (HSV) into cells is believed to be mediated by specific binding of envelope proteins to a cellular receptor. Neomycin specifically blocks this initial step in infection by HSV-1 but not HSV-2. Resistance of HSV-2 to this compound maps to a region of the genome encoding glycoprotein C (gC-2). We have studied the function of gC-2 in the initial interaction of the virus with the host cell, using HSV-2 mutants deleted for gC-2 and gC-2-rescued recombinants. Resistance to neomycin was directly linked to the presence of gC-2 within the viral genome. In addition, deletion of the gC-2 gene caused a marked delay in adsorption to cells relative to the wild-type virus. HSV-1 recombinants containing chimeric gC genes composed of HSV-1 and HSV-2 sequences were used to localize neomycin resistance within the N-terminal 223 amino acids of gC-2. This region of the glycoprotein comprises an important domain responsible for binding of HSV-2 to cell receptors in the presence of neomycin. A gC-2-negative mutant is still infectious, indicating that HSV-2 also has an alternative pathway of adsorption.