Regulation of adenovirus and cellular gene expression and of cellular transformation by the E1B-encoded 175-amino-acid protein.

Mutants of type 5 adenovirus that fail to express the E1B-gene-encoded 175-amino-acid (175R) protein are unable to morphologically transform primary or continuous cultures of rat embryo fibroblast cells. This phenotype could result from a direct effect of this E1B polypeptide (along with E1A polypeptides) on cellular gene expression resulting in a pathway leading to altered cell growth or from an indirect role of the 175R protein made possible by its ability to modulate viral early-gene (most likely E1A) expression. To distinguish between these two models, viruses were constructed that expressed the individual E1A 13S and 12S genes in the presence of either the E1B 175R or 495R protein.

Effect of methyl methanesulfonate on type 5 adenovirus DNA integration and the phenotypic properties of cold-sensitive type 5 adenovirus-transformed cloned rat embryo fibroblast cells.

Pretreatment of a cloned rat embryo fibroblast cell line (CREF) with methyl methanesulfonate (MMS) prior to infection with a specific cold-sensitive type 5 adenovirus mutant, H5hr1, results in a unique carcinogen enhancement of transformation phenotype. MMS induces a dose-dependent increase in the absolute number of transformed foci in comparison with solvent-treated controls as well as an increase in transformation frequency when normalized for carcinogen-induced cell toxicity. To determine if the carcinogen enhancement of transformation phenotype was a consequence of the carcinogen altering the pattern of type 5 adenovirus (Ad5) DNA integration into the genome of CREF cells and/or if carcinogen treatment modified the phenotype of established H5hr1-transformed CREF cells, we have analyzed a series of single cell-derived H5hr1-transformed CREF cultures which were isolated from cultures pretreated with carcinogen-solvent or MMS prior to infection with H5hr1.

Unique carcinogen enhancement of transformation phenotype displayed by cloned rat embryo fibroblast (CREF) cells treated with methyl methanesulfonate and infected with a specific host-range mutant of type 5 adenovirus.

Pretreatment of cloned rat embryo fibroblast (CREF) cells with methyl methanesulfonate (MMS) prior to infection with wild-type 5 adenovirus (H5wt) or a temperature-sensitive mutant of Ad5 (H5ts125) results in an MMS dose-dependent enhancement of viral transformation. With both viral isolates, MMS enhanced the transformation frequency when normalized for cell toxicity but did not induce a carcinogen dose-dependent increase in the absolute number of foci above solvent-treated controls. In contrast, pretreatment of CREF cells with MMS prior to infection with a host-range mutant of Ad5 (H5hr1) which contains a single basepair deletion in the E1a-transforming region of Ad5 and displays a cold-sensitive transformation phenotype, results in an MMS dose-dependent increase in the absolute number of transformed foci in comparison with solvent-treated controls as well as an increase in transformation frequency when normalized for cell toxicity.

Effect of recombinant human fibroblast interferon and mezerein on growth, differentiation, immune interferon binding and tumor associated antigen expression in human melanoma cells.

The combination of recombinant human fibroblast interferon (INF-delta) and the antileukemic compound mezerein (MEZ) results in a synergistic suppression in the growth of human melanoma cells and a concomitant increase in melanin synthesis. In the present study we have further analyzed this synergistic interaction and have also evaluated the effect of IFN-delta and MEZ, alone and in combination, on recombinant human gamma interferon (IFN-gamma) binding and Class I HLA and melanoma associated antigen (MAA) expression in the HO-1 human melanoma cell line. Single cell clones isolated from the HO-1 cell line varied in their sensitivity to the antiproliferative effects of IFN-delta and MEZ.

Effects of combined treatment with interferon and mezerein on melanogenesis and growth in human melanoma cells.

We have analyzed the effects of various human interferons produced in bacteria and the antileukemic compound mezerein (MEZ) on growth and melanogenesis in human melanoma cells. In four human melanoma cell lines, recombinant human fibroblast interferon (IFN-beta) was more active than recombinant human leukocyte interferons (IFN-alpha A, IFN-alpha D, or IFN-alpha A/D (Bgl] in inhibiting cellular proliferation. When monolayer cultures were exposed to 1000 IU/ml IFN-beta for four days the degree of growth inhibition in the different melanoma cell lines varied between 94 and 26%.

Hybrid recombinant human leukocyte interferon inhibits differentiation in murine B-16 melanoma cells.

We have investigated the effects of recombinant human leukocyte interferons (IFN-alpha A and IFN-alpha D) and various hybrid recombinant human leukocyte interferons on differentiation in B-16 mouse melanoma cells. Inhibition of both spontaneous and melanocyte hormone stimulated differentiation was observed with one hybrid construct, IFN-alpha A/D (Bgl) consisting of amino acids 1 to 62 from IFN-alpha A and amino acids 64 to 166 from IFN-alpha D. In contrast, the parental human interferons, IFN-alpha A and IFN-alpha D, when used alone or in combination, as well as other hybrid human leukocyte interferons, did not cause significant inhibition of melanogenesis in B-16 mouse cells.