Hemoglobin synthesis in murine virus-induced leukemic cells in vitro: stimulation of erythroid differentiation by dimethyl sulfoxide

Erythropoietic differentiation in colonies of cells transformed by Friend virus

Cells transformed by Friend virus in liquid suspension culture respond to low concentrations of dimethylsulfoxide by initiating hemoglobin synthesis. The kinetics of appearance of such differentiated erythroid cells is consistent with either the induction of differentiation in a uniformly susceptible population of transformed cells or selection for the growth of a distinct erythropoietic subpopulation. The dimethylsulfoxide response of individual colonies of cells transformed by Friend virus grown in semisolid medium was studied in order to distinguish between these alternatives. The data do not support a selective effect of dimethylsulfoxide on the growth of a unique erythropoietic subpopulation; they indicate, rather, that the 745A strain of cells transformed by Friend virus consists of a relatively uniform population of dimethylsulfoxide-sensitive erythropoietic cells.

An association between globin messenger RNA and 60S RNA derived from Friend leukemia virus

The association between certain cellular RNAs and purified RNA tumor viruses prompted us to examine the possibility that specific host messenger RNAs might also be incorporated into RNA tumor viruses. Using a mouse cell line infected with Friend leukemia virus, T-3-Cl-2, which can be induced to accumulate mouse-globin messenger RNA, we show that mouse-globin messenger RNA sequences are present in viral particles purified from the culture medium of globin-producing cells. These globin messenger RNA sequences are absent from viral particles derived from T-3-Cl-2 cells that are not producing globin messenger RNA. Virus-associated globin messenger RNA sequences sediment in association with the 60S viral RNA complex as well as in free, 9S form. However, under mild denaturing conditions which result in the conversion of viral 60S RNA to 30S and smaller forms, all the globin sequences sediment as 9S RNA. Appropriate control experiments indicate that the virus-associated globin messenger RNA is resistant to degradation by exogenous ribonuclease; that exogenously added globin messenger RNA does not become associated with the 60S viral RNA complex; and that globin messenger RNA can be detected in virions derived from cells both induced for and constitutively synthesizing globin messenger RNA.

The absence of globin gene sequences from friend leukaemia virus RNA

Complementary DNA to mouse globin mRNA was prepared using viral reverse transcriptase. Molecular hybridisation of this cDNA to Friend virus RNA demonstrates the absence of globin gene sequences.

Effects of 5-bromo-2' -deoxyuridine on production of globin messenger RNA in dimethyl sulfoxide-stimulated Friend leukemia cells

Friend leukemia cells grown in the presence of dimethyl sulfoxide show enhanced erythroid differentiation and hemoglobin synthesis. The effects of dimethyl sulfoxide stimulation are inhibited by BrdU. To determine the effect of BrdU on the amount of globin mRNA present in cells treated and not treated with dimethyl sulfoxide, molecular hybridization between total cell RNA and [(3)H]DNA complementary to mouse globin mRNA was used. Cells treated with BrdU and dimethyl sulfoxide had 70% less globin mRNA than cells treated with dimethyl sulfoxide alone. The size and base sequence of the residual globin mRNA in the cultures treated with BrdU and dimethyl sulfoxide were unaltered. Cells treated with BrdU alone contained slightly more globin mRNA than did the untreated controls, suggesting that BrdU may have a dual effect in transcription of messenger RNA.

Dimethyl sulfoxide-induced reversion of several features of polyoma transformed baby hamster kidney cells (BHK-21). Alterations in growth and morphology

Cells of a polyoma virus transformed clonal line (Cl-I) of baby hamster kidney fibroblasts (BHK-21) were grown in medium containing 2 percent dimethylsulfoxide (DMSO). Unlike the untransformed BHK-21 cells, Cl-I cells adapted to replication in the presence of DMSO, and they exhibited a rapidly reversible phenotypic reversion of a number of properties characteristic of the transformed state. Restoration of density dependent growth inhibition with accumulation of cells in the G(1) phase of the cell cycle occurred and was associated with restoration of contact dependent behavior and with reversion of histological and ultrastructural features towards those which characterize untransformed cells. Concomitantly, Cl-I cells grown in 2 percent DMSO lost the ability to form colonies in semisolid medium. The data presented suggest that DMSO alters the expression of cellular functions which were altered as a result of viral transformation and which may be involved in cell tumorigenicity.

Globin messenger-RNA induction during erythroid differentiation of cultured leukemia cells

A cloned line of murine proerythroblastoid cells (T-3-Cl-2), transformed by Friend leukemia virus, undergoes changes associated with erythroid differentiation when treated with dimethylsulfoxide in culture. This line, which does not undergo spontaneous differentiation, develops specific erythrocyte-membrane antigen and accumulates detectable amounts of heme within four days of dimethylsulfoxide treatment. In the present study, we have followed the phenotypic expression of the globin genes by measuring globin mRNA in differentiating cells. Our hybridization probe for this purpose is [(3)H]DNA, which is complementary to purified globin mRNA, synthesized by viral RNA-directed DNA polymerase. This probe is sufficiently sensitive to detect less than 1 ng of globin mRNA. Using it, we find little or no hybridizable globin mRNA in either uninduced cells or in treated control lymphoid cells. In contrast, globin mRNA can be detected in T-3-Cl-2 cell 2 days after induction by dimethylsulfoxide; it reaches a maximum concentration four days after induction. At this time, cells that stain positively for heme appear. The hybridizable cytoplasmic RNA induced in these cells has the sedimentation properties of 9S globin mRNA. Considering the stable character of globin mRNA, our results are most readily explained in terms of a transcriptional activation of the globin genes.

A factor that can be used to regulate an in vitro primary immune response

A factor has been isolated that supports the stimulation of an immune response against heterologous erythrocyte antigens in mouse spleen cells cultured in a medium that contains deficient serum. The factor is secreted by certain spleen cells that are obtained in permanent culture after leukemia virus infection. The factor permits antigen-sensitive cells derived from bone marrow to mature to antibody-forming cells. This factor can be used in controlling the initiation of a primary immune response in vitro.

Myeloperoxidase and crystalline bodies in the granules of DMBA-induced rat chloroma cells

Chloroma (chloroleukemia) was induced in a splenectomized rat by repeatedly administering dimethylbenz(a)anthracene (DMBA) and was serially transplanted thereafter. Composed of immature myeloid cells, the tumor imparted a green discoloration to the tissues that it infiltrated extensively. Chloroma cells fluoresced red in ultraviolet light, produced a characteristic curve in spectrophotometry, and contained large amounts of myeloperoxidase. They included numerous intracytoplasmic granules of both types A and B, which contained occasional crystalline bars. Permanent lines of chloroma cells were established in tissue culture. These cells, while maintaining their initial morphology, ceased producing myeloperoxidase and subsequently induced white tumors when they were isotransplanted.