Molecular mimicry of growth factors by products of tumor viruses.
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Biomedical subjects
Publications and source records attributed to J H Pierce.
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To determine the effect of oncogene expression on gamma radiation sensitivity of hematopoietic compared to fibroblastic cells, we selected clonal sublines of an interleukin-3 (IL-3)-dependent hematopoietic progenitor cell line 32D cl 3 and NIH/3T3 embryo fibroblastic cells following transfection with each oncogene linked to the mycophenolic acid resistance gene. Each mycophenolic acid-resistant subclone demonstrated high levels of specific poly(A)+ mRNA for each oncogene. The parent line 32D cl 3 demonstrated similar radiosensitivity at 116 cGy/min (D0 126, n 1.17) compared to 5 cGy/min (D0 123, n 1.65). This pattern was not altered in subclones of 32D cl 3 cells transfected with the epidermal growth factor (EGF) receptor gene and grown in EGF (at 116 cGy/min D0 104, n 0.998, at 5 cGy/min D0 115, n 1.09), or in 32D cl 3 cells expressing the v-sis oncogene (at 116 cGy/min D0 122.4, n 1.79, at 5 cGy/min D0 135, n 1.43). In contrast, expression of the transfected oncogenes v-erb-B, v-abl, or v-src conferred significant radioresistance at 5 cGy/min dose rate (D0 194, n 1.77; D0 165.5, n 1.56; D0 171, n 1.28, respectively). With the exception of v-sis, oncogene expression resulted in nonautocrine factor independence of 32D cl 3 subclones, and production of donor origin tumors in syngeneic new-born or adult mice. Two rare spontaneous factor-independent subclones of 32D cl 3 were also tested. Nonautocrine clone 32D cl 2 demonstrated significantly increased radioresistance at low dose rate (D0 186, n 1.63), while autocrine (IL-3 producing) subclone 32D cl 4 revealed no significant increase in radioresistance at 5 cGy/min. The parent fibroblast cell line NIH/3T3 showed an intrinsic relative radioresistance at low dose rate (at 5 cGy/min D0 157.3, n 1.81, compared to 116 cGy/min D0 134.3, n 1.57). Expression in NIH/3T3 of transfected oncogenes v-abl, v-fms, v-fos, or H-ras increased radioresistance at low dose rate (D0 208.6, n 1.61; D0 206.6, n 1.51; D0 167.5, n 1.85; and D0 206.8, n 1.08, respectively). Thus expression of each of several oncogenes induces resistance to gamma irradiation at 5 cGy/min in hematopoietic and fibroblast cell lines. These data may help explain the clinical recurrence of oncogene-expressing leukemia and lymphoma cells after marrow stem cell ablative doses of low-dose-rate total-body irradiation.
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Biochemical similarities and cellular distribution patterns of the early B lineage-specific BP-1 alloantigen and the B lineage transformation-associated 6C3 Ag prompted this comparative study of the reactivities of the BP-1 and 6C3 mAb. Both Ag were found to be expressed on the same cells in normal tissues, and on the same cell lines when a large panel was analyzed. The Ag are both phosphorylated and have identical m.w., which may vary in different cell types because of differences in glycosylation. Immunoprecipitation of pre-B cell lysates with the BP-1 antibody removed the 6C3-reactive molecules and vice versa. However, the 6C3 antibody did not inhibit binding of the BP-1 antibody to viable cells and, in fact, enhanced immunofluorescence staining was observed when both antibodies were added together. These results indicate that the BP-1 and 6C3 antibodies react with different epitopes on the same molecule that is expressed in relatively low levels on normal early B lineage cells, and in relatively high levels on most neoplastic pre-B cells, pre-B cells in long term bone marrow cultures and certain stromal cell lines.
The cross-linkage of high affinity Fc epsilon receptors (Fc epsilon RI) on mast cells and basophils is central to the induction of allergic inflammatory responses. As a result of such cross-linkage, mast cells secrete a variety of preformed biologically active substances, such as histamine, and newly synthesized arachidonic acid metabolites. Here we show that cross-linkage of Fc epsilon RI on a series of nontransformed murine mast cell lines, or treatment of these cells with calcium ionophores, stimulates increased messenger RNA levels and secretion of a group of lymphokines classically produced by a subset of murine T cell lines (TH2 cells). These factors include interleukin-3 (a mast cell growth factor)s interleukin-4 (an IgE 'switch factor'), interleukin-5 (an eosinophil differentiation factor) and interleukin-6 (a factor controlling immunoglobulin secretion). The production of these polypeptide factors by mast cells may have great importance in the induction of allergic and anti-parasite inflammatory responses.
The effects of murine recombinant IL-3 (multi-CSF) and murine recombinant GM-CSF (granulocyte-macrophage colony stimulating factor) on the radiation biology of clonal hematopoietic progenitor cell lines were evaluated. Four clonal cell lines with growth response to either IL-3 or GM-CSF (FDCP-1JL26, and bg/bg d64) or exclusively dependent on IL-3 (32D cl 3 and B6SUtA), were pre-incubated in IL-3, or GM-CSF, for 7 days prior to gamma irradiation, then washed and irradiated at 5 cGy/min, or 116 cGy/min, and transferred to semisolid medium supplemented with either IL-3, or GM-CSF, for assay of 7 day greater than or equal to 50 cell colonies. The cell lines demonstrated similar radiosensitivity and lack of a detectable dose-rate effect when grown in IL-3 (FDCP-1JL26: D0 154, n 1.05 at 5 cGy/min, and D0 138, n 1.16 at 116 cGy/min; bg/bg d64: D0 95.7, n 1.16 at 5 cGy/min, and D0 97.7 n .993 at 116 cGy/min; B6SUtA: D0 101, n 1.29 at 5 cGy/min, D0 100, n 1.27 at 116 cGy/min; and cell line 32D cl 3: D0 123, n 1.65 at 5 cGy/min, and D0 126, n 1.17 at 116 cGy/min). In contrast, FDCP-1JL26 cells demonstrated a significant relative radioresistance at low-dose-rate when grown in recombinant GM-CSF, (D0 217, n 1.27 at 5 cGy/min, D0 138, n 1.34 at 116 cGy/min, p less than .005). The increase in radioresistance of FDCP-1 cells at low-dose-rate was induced either by preincubation in GM-CSF with transfer to IL-3, or by preincubation in IL-3 and transfer to recombinant GM-CSF. Growth factor independent malignant subclones of lines B6SUtA and FDCP-1JL26 demonstrated a significant increase in radioresistance at low-dose-rate (B6SUtA EL4JL: D0 187, n 1.39 at 5 cGy/min, and D0 133, n 1.73 at 116 cGy/min (p. less than .05); and FDCP-1JL26 F7 cl 2: D0 191, n 1.17 at 5 cGy/min, and D0 150, n 1.31 at 116 cGy/min [p less than .05]). Thus, some hematopoietic progenitor cell lines are induced by GM-CSF to grow after irradiation at low-dose-rate similar to the growth of clonal malignant cell lines. The data may have implications for the radiation biology of normal hematopoietic progenitor cells in two circumstances: (a) selective survival of GM-CSF responsive cells after total body irradiation, and (b) selective survival of some hematopoietic progenitors in vivo during clinical recombinant GM-CSF infusion.
Distinct genes encode alpha and beta platelet-derived growth factor (PDGF) receptors that differ in their abilities to be triggered by three dimeric forms of the PDGF molecule. We show that PDGF-receptor mitogenic function can be reconstituted in a naive hematopoietic cell line by introduction of expression vectors for either alpha or beta PDGF receptor cDNAs. Thus, each receptor is independently capable of coupling with mitogenic signal-transduction pathways inherently present in these cells. Activation of either receptor also resulted in chemotaxis, alterations in inositol lipid metabolism, and mobilization of intracellular Ca2+. The magnitude of these functional responses correlated well with the binding properties of the different PDGF isoforms to each receptor. Thus, availability of specific PDGF isoforms and relative expression of each PDGF-receptor gene product are major determinants of the spectrum of known PDGF responses.
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Alterations affecting the epidermal growth factor (EGF)/transforming growth factor alpha (TGF alpha)-responsive mitogenic pathway are frequently detected in malignancies. In particular, the EGF-receptor (EGFR) molecule has been found overexpressed in a number of human tumors, and TGF alpha is produced by a large array of tumor cells. Gene transfer experiments have previously demonstrated that expression of either TGF alpha or EGFR alone is not sufficient to induce the transformed phenotype in NIH3T3 cells. In this study we sought to investigate the biological effect of expression of TGF alpha and high levels of EGFR in this model system. We demonstrate that the gene for TGF alpha acts as a potent oncogene in NIH3T3 cells overexpressing EGFR (NIH-EGFR, greater than 10(6) EGFR). We further show that TGF alpha directly stimulates proliferation of the cell in which it is produced and provide evidence that the extracellular compartment of the transformed cell is the major site of interaction between TGF alpha and EGFR. Analysis of human tumor cell lines revealed a strong correlation between expression of TGF alpha and overexpression of EGFR. Moreover, high levels of EGF-independent tyrosine phosphorylation of the EGFR were detected both in NIH-EGFR expressing TGF alpha and in high EGFR and TGF alpha coexpressing human tumor cell lines. Thus, the two events instituting the EGFR/TGF alpha autocrine loop responsible for transformation in vitro may play a role in the development of some human malignancies.
To define the action of the retroviral src gene on hematopoietic stem cells, C57BL/6 x DBA/2 (B6D2F1) mouse long-term marrow cultures were infected at initiation with Moloney murine leukemia virus (MuLV) pseudotypes of src-recombinant retroviruses with the src gene inserted in the env region of an amphotropic MuLV (src-Ampho), or in the gag region of Moloney MuLV (src-Mo). Other cultures were infected with Friend spleen focus-forming virus polycythemia-inducing strain (SFFVp), Moloney MuLV, or amphotropic MuLV, or were uninfected controls. Harvested nonadherent cells were tested weekly for multilineage, granulocyte-erythroid-megakaryocyte macrophage (CFU-GEMM) colony formation in vitro in recombinant murine IL-3 and erythropoietin, and individual colonies were removed, split 1:2, with half of each replated for in vitro self-renewal and the other half examined morphologically for number of hematopoietic cellular lineages, or tested for release of MuLV and src virus. Cultures infected with src-Ampho, src-Mo, or SFFVp demonstrated a significant increase in cumulative nonadherent cell and CFU-GEMM production. There was prolonged self-renewal over seven serial transfers of individual CFU-GEMM from src virus-infected cultures over seven serial transfers, and five of 61 individual colonies from the second or third generations contained detectable v-src gene sequences, but none released detectable src virus. Self-renewal of CFU-GEMM was similar to that with permanent IL-3-dependent cell line B6SUtA. In contrast, MuLV-infected or control uninfected cultures produced fewer cells, and self-renewal of CFU-GEMM did not exceed three generations. IL-3-dependent clonal hematopoietic progenitor cell lines, derived from each culture group, formed no detectable tumors in vivo; however, each released the original helper and/or transforming virus. Adherent cell lines, derived from src-Ampho-infected cultures released src virus and formed fibro-sarcomas in vivo. The data support the conclusion that src-recombinant virus expression in long-term marrow cultures increases the self-renewal capacity of multilineage hematopoietic stem cells.
A cell line, HAFTL-1, derived by in vitro transformation of fetal liver cells with v-Ha-ras, was found to have molecular and phenotypic characteristics of pro-B cells recently committed to the Ly-1+ B cell differentiation pathway. Stimulation of these cells with LPS resulted in their differentiation within either the B or myelomonocytic lineages. Thus, lines derived from LPS-stimulated HAFTL-1 cells were shown to be clonally related, as evidenced by common v-ras integrations, but to exhibit characteristics of pre-B cells (ThB expression, continuing DJ heavy chain rearrangements) or mature macrophages (expression of Mac-1 and Mac-2, lysozyme and nonspecific esterase production, phagocytosis) while maintaining their Ly-1+ phenotype. These results suggest that events resulting in the irrevocable commitment to a single lineage occur late in differentiation, at least within the pathway yielding Ly-1+ B cells and a proposed subpopulation of Ly-1+ monocytes and macrophages. Final commitment to these lineages is carefully orchestrated, as evidenced by restricted expression of Ly-5 isoforms and production of IgH transcripts.
An expression vector for the epidermal growth factor (EGF) receptor was introduced into the 32D myeloid cell line, which is devoid of EGF receptors and absolutely dependent on interleukin-3 (IL-3) for its proliferation and survival. Expression of the EGF receptor conferred the ability to utilize EGF for transduction of a mitogenic signal. When the transfected cells were propagated in EGF, they exhibited a more mature myeloid phenotype than was observed under conditions of IL-3-directed growth. Moreover, exposure to EGF led to a rapid stimulation of phosphoinositide metabolism, while IL-3 had no detectable effect on phosphoinositide turnover either in control or EGF receptor-transfected 32D cells. Although the transfected cells exhibited high levels of functional EGF receptors, they remained nontumorigenic. In contrast, transfection of v-erbB, an amino-terminal truncated form of the EGF receptor with constitutive tyrosine kinase activity, not only abrogated the IL-3 growth factor requirement of 32D cells, but caused them to become tumorigenic in nude mice. These results show that a naïve hematopoietic cell expresses all of the intracellular components of the EGF-signaling pathway necessary to evoke a mitogenic response and sustain continuous proliferation.
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In contrast to the dose-rate independent X ray killing observed with human bone marrow hematopoietic stem cells, bone marrow adherent stromal cells from the same fresh marrow harvests demonstrate increased radiation resistance at low dose rate (LDR) (5 cGy/min), compared to high dose rate (HDR) irradiation (120-200 cGy/min). Physiologic changes observed in plateau phase bone marrow cells after LDR irradiation in vivo and in vitro suggested that marrow stromal cells might be heterogeneous in LDR irradiation repair. Five permanent clonal bone marrow stromal lines were derived from a single human marrow donor. Each cell line was positive for markers of fibroblasts including: immunohistochemically detectable fibronectin, collagen, acid phosphatase, and nonspecific esterase, and was negative for Factor VIII, alkaline phosphatase, lysozyme and several markers of marrow macrophages. The x-irradiation survival curve of each cell line was determined at LDR and HDR in vitro. Cell lines KM102, KM103, KM104, and KM105 each demonstrated a significant (p less than .05) increase in radioresistance at LDR (D0 = 142, n = 2.9; D0 = 131, n = 2.5; D0 = 145, n = 2.1 and D0 = 127, n = 2.1 respectively) compared to HDR: (D0 = 111, n = 2.1; D0 = 94, n = 3.5; D0 = 99, n = 3.5 and D0 = 95, n = 2.1 respectively). In contrast, cell line KM101 demonstrated no significant change in radiosensitivity relative to dose rate at LDR (D0 = 113, n = 3.3) compared to HDR, D0 = 114, n = 3.3. Cell line KM101 was more supportive than the other lines of cocultivated hemopoietic cells in vitro. Subclones of KM101 and KM104 selected by retroviral vector transfer of the neor gene for growth in the antibiotic neomycin-analogue G418, maintained the stably associated radiobiologic properties of each parent clonal line. These data indicate significant heterogeneity in the LDR irradiation response of clonal stromal cell lines derived from human bone marrow.
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Compared with normal erbB-2 gp185, mutant erbB-2 proteins generated by mutations either in the transmembrane domain or by NH2-terminal deletion are able to transform NIH 3T3 cells at a 10- to 100-fold greater efficiency. Mutant proteins of both classes show increased tyrosine kinase activity, suggesting that an abnormal level of receptor-associated tyrosine kinase activity is a major determinant of erbB-2 oncogenic potential.