BALB- and Harvey-murine sarcoma virus transformation of a novel lymphoid progenitor cell

Myeloid cell transformation by ras-containing murine sarcoma viruses

BALB and Harvey murine sarcoma viruses contain ras transforming genes capable of altering the proliferation and differentiation of cells within the erythroid and lymphoid lineages (W. D. Hankins and E. M. Scolnick, Cell 26:91-97, 1981; J. H. Pierce and S. A. Aaronson, J. Exp. Med. 156:873-887, 1982; E. M. Scolnick et al., Mol. Cell. Biol. 1:68-74). The present studies demonstrate hematopoietic targets of ras-containing viruses within the myeloid lineage. Diffuse colonies were induced by BALB or Harvey marine sarcoma virus infection of murine bone marrow cells. Generally, these colonies were made up of relatively mature macrophages which exhibited increased self-renewal capacity but eventually underwent terminal differentiation in culture. Cells from one BALB murine sarcoma virus-induced colony displayed phenotypic markers of more immature myelomonocytic cells. This colony, designated BAMC1, readily established as a continuous cell line and was highly malignant in vivo. Exposure of these cells to 12-O-tetradecanoylphorbol-13-acetate led to the induction of a more mature myeloid phenotype, which was associated with decreased growth potential in vitro and in vivo. The effects of the inducing agent were not mediated by an alteration in the level of expression of the ras-coded p21 transforming protein. Our present findings extend the spectrum of targets whose growth is altered by ras-containing retroviruses to cells at several stages of differentiation within each of the major hematopoietic lineages.

Cloning of terminal transferase cDNA by antibody screening

A cDNA library was prepared from a terminal deoxynucleotidyltransferase-containing thymoma in the lambda phage vector lambda gt11. By screening plaques with anti-terminal transferase antibody, positive clones were identified of which some had beta-galactosidase-cDNA fusion proteins identifiable after electrophoretic fractionation by immunoblotting with anti-terminal transferase antibody. The predominant class of cross-hybridizing clones was determined to represent cDNA for terminal transferase by showing that one representative clone hybridized to a 2200-nucleotide mRNA in close-matched enzyme-positive but not to enzyme-negative cells and that the cDNA selected a mRNA that translated to give a protein of the size and antigenic characteristics of terminal transferase. Only a small amount of genomic DNA hybridized to the longest available clone, indicating that the sequence is virtually unique in the mouse genome.

Hematopoietic cell transformation by a murine recombinant retrovirus containing the src gene of Rous sarcoma virus

A recombinant murine retrovirus (MRSV) containing the src gene of avian Rous sarcoma virus (RSV) was shown to induce hematopoietic colonies in infected mouse bone marrow. MRSV-induced colony formation followed single-hit kinetics and required mercaptoethanol in the agar medium. Cells from the colonies induced by MRSV could be established as continuous cell lines that demonstrated unrestricted self-renewal in vitro and tumorigenicity in vivo. The transformants, all of which expressed high levels of the Rous sarcoma virus transforming protein, pp60src, appeared to be at an early stage in lymphoid cell differentiation. They lacked Fc receptors and detectable immunoglobulin mu heavy chain synthesis, markers normally associated with committed B cells. The majority of the MRSV-transformed cell lines contained high levels of terminal deoxynucleotidyl transferase, an enzyme present in lymphoid progenitor cells committed to the T-cell lineage. One cell line expressed Thy-1 antigen, but none expressed Lyt-1 and Lyt-2, markers of more differentiated T cells. These findings demonstrate that the src gene is capable of transforming cells of hematopoietic origin.

Transforming genes of human hematopoietic tumors: frequent detection of ras-related oncogenes whose activation appears to be independent of tumor phenotype

We surveyed 22 human hematopoietic tumors and tumor cell lines for sequences capable of transforming NIH 3T3 cells by DNA transfection. A primary human acute myelogenous leukemia, a chronic myelogenous leukemia cell line, and cell lines derived from three independent acute lymphocytic leukemias demonstrated oncogenes capable of conferring the transformed phenotype to NIH 3T3 cells through serial cycles of transfection. One of three transforming genes associated with acute lymphocytic leukemia cells (classified as thymocyte developmental stage II) was identified as the activated cellular homologue of the Kirsten murine sarcoma virus onc gene, kis, a member of the ras family of onc genes. A transforming gene, which was demonstrated to be common to several human myeloid and lymphoid tumor cells, was shown to be a distantly related member of the ras gene family. Thus, the NIH 3T3 transfection assay commonly detects related oncogenes in human hematopoietic tumor cells. Moreover, the activation of these oncogenes appears to be independent of the specific stage of cell differentiation or tumor phenotype.

Acquisition of transforming properties by alternative point mutations within c-bas/has human proto-oncogene

The transforming gene of a human lung carcinoma-derived cell line, Hs242, has been cloned in biologically active form, and identified as c-bas/has (otherwise known as c-Ha-ras). The genetic lesion responsible for the transforming activity of the Hs242 oncogene has been localized to a point mutation in the second exon which results in the substitution of leucine for glutamine as amino acid 61 of the predicted protein. No changes were observed in the first exon, the region of c-bas/has in which a point mutation is responsible for activation of the T24 and EJ bladder carcinoma oncogenes.

In vitro transformation of murine pre-B lymphoid cells by Snyder-Theilen feline sarcoma virus

Snyder-Theilen feline sarcoma virus (ST-FeSV) codes for a protein kinase with specificity for tyrosine residues (Barbacid et al., Proc. Natl. Acad. Sci. U.S.A. 77:5158-5163, 1980), properties analogous to those of the transforming gene product of Abelson murine leukemia virus (Witte et al., Nature (London) 283:826-831, 1980). In the present report, ST-FeSV was demonstrated to transform murine hematopoietic cells under in vitro assay conditions which detect lymphoid cell transformation by Abelson murine leukemia virus. Bone marrow colony formation was shown to require ST-FeSV, follow single-hit kinetics, and require the presence of mercaptoethanol in the agar medium. ST-FeSV-induced colonies could be established in culture as continuous cell lines that demonstrated unrestricted self-renewal capacity and leukemogenicity in vivo. The hematopoietic blast cells transformed by ST-FeSV in culture appeared to be at an early stage of B cell differentiation. They possessed Lyb 2 surface antigens, were dependent on mercaptoethanol for growth, and contained only low levels of terminal deoxynucleotidyl transferase. Moreover, a large fraction of the lines synthesized immunoglobulin mu chain in the absence of light chains. Thus, the phenotype of ST-FeSV hematopoietic transformants was indistinguishable from that of the pre-B lymphoblast transformants induced by Abelson murine leukemia virus. These findings indicate that the in vitro functional similarities in the onc gene products of ST-FeSV and Abelson murine leukemia virus may reflect a common pathway by which they exert their oncogenic potential.

Frequent activation of c-kis as a transforming gene in fibrosarcomas induced by methylcholanthrene

The DNA's from two of four methylcholanthrene-induced mouse fibrosarcomas contained transforming genes that were identical in their pattern of restriction endonuclease resistance to inactivation of biologic activity. This transforming gene was identified as the activated homolog of the Kirsten murine sarcoma virus onc gene, v-kis. The finding that a defined carcinogen reproducibly leads to activation of kis as a transforming gene should be of value in elucidating the role of oncogenes in the neoplastic process.

Construction and isolation of a transforming murine retrovirus containing the src gene of Rous sarcoma virus

Recombinant murine retroviruses containing the src gene of the avian retrovirus Rous sarcoma virus were isolated. Such viruses were isolated from cells after transfection with DNAs in which the src gene was inserted into the genome of the amphotropic murine retrovirus 4070A. The isolated viruses had functional gag and pol genes, but they were all env defective since the src gene was inserted in the middle of the env gene coding region. Infectious transforming virus could be isolated only from cells transfected with DNA constructions in which the src gene was in the same polarity as that of a long terminal repeat of the amphotropic viral genome. These recombinant viruses encoded a pp60src protein with a molecular weight similar to that of the Schmidt-Ruppin strain of Rous sarcoma virus. In addition, the src protein(s) of these recombinant viruses was as active as protein kinases in the immune complex protein kinase assay. Intravenous injection of helper-independent Moloney and Friend murine leukemia virus pseudotypes of the src recombinant viruses into 6-week-old NIH Swiss mice resulted in the appearance of splenic foci within 2 weeks, splenomegaly and, later after infection (8 to 10 weeks), anemia. Infectious transforming virus could be recovered from the spleens of diseased animals. Such viruses encoded pp60src but not p21ras or mink cell focus-forming virus-related glycoproteins.

BALB and Kirsten murine sarcoma viruses alter growth and differentiation of EGF-dependent balb/c mouse epidermal keratinocyte lines

Clonal BALB/c mouse epidermal keratinocyte (BALB/MK) cell lines were established in tissue culture. Despite their aneuploid nature, the lines were nontumorigenic, and retained in vitro properties similar to those of primary diploid keratinocytes. These included the constitutive expression of keratin and terminal differentiation in response to a calcium concentration greater than 1.0 mM in the medium. The cells also demonstrated an absolute requirement for nanomolar concentrations of epidermal growth factor (EGF) for their proliferation. BALB or Kirsten murine sarcoma viruses are acute transforming retroviruses, which have been shown to transform fibroblastic and hematopoietic cells. Infection of BALB/MK or its clonal sublines with either virus leads to the rapid acquisition of EGF-independent growth. The cells concomitantly lose their sensitivity to calcium-induced terminal differentiation. Thus these retroviruses can rapidly confer upon epithelial keratinocytes in culture growth properties that resemble those of malignant epidermoid carcinoma cells.