Expression of an exogenous interleukin 6 gene in human Epstein Barr virus B cells confers growth advantage and in vivo tumorigenicity.

Abstract

SummaryThe biological role of interleukin 6 (IL 6) molecules in human B cell tumorigenesis was studied by using an episomal expression vector, pHEBoSV IL6, to introduce stably the human IL6 gene into human Epstein Barr virus (EBV)-transformed B lymphoblasts . The gene was present in the IL6-transfected cells in a high copy number and was efficiently expressed, resulting in the secretion of consistent levels of 11,6 molecules. The constitutive expression of the IL6 gene led to an altered pattern of growth and to a malignant phenotype, as shown by clonogenicity in soft agar cultures and tumorigenicity in nude mice. These data suggest that the combined action of EBV, which exerts an immortalizing function, and of the growth-promoting activity of IIr6 molecules, can give rise to fully transformed B cell tumors in immunodeficient subjects. EBV is a herpes virus that preferentially infects B lymphocytes and induces proliferation, Ig secretion, and immortalization, giving rise to long-term lymphoblastoid B cell lines (LCL)t (1). EBV infection appears to play a pathogenetic role in the development of endemic Burkitt lymphoma (eBL) and in the recently identified AIDS-associated Burkitt lymphoma (AIDS-BL) (2-4). The nontumorigenic capabilities of LCL suggest that the neoplastic EBVinfected clones present in eBL and AIDS-BL may have acquired a malignant phenotype through additional pathogenetic events, possibly mediated by a deregulated expression of oncogenes (5, 6). As shown for a variety of neoplastic cell types, the continuous proliferation of EBVinfected B cells appears to depend on autocrine secretion of cytokines, including ILA and B cell growth factor-like molecules (7-10) . IL6 is a glycoprotein secreted by a variety ofcell types, e.g., monocytes, fibroblasts, certain T cell lines, and myeloma cells (11). Its biological action includes the growth stimulation of plasmacytomas and some EBV lymphoblastoid B cell lines (12, 13) . To investigate whether EBV infection, which exerts a typical immortalizing function, cooperates with the B cell growth-promoting activity of 11,6 in inducing B cell tumorigenesis, we transfected ROHA-9 MC3 cells, an EBV B cell line (8, 9), with an expression vector that allows a constitutive expression of the 1 Abbreviations used in this paper: BL, Burkitt lymphoma ; eBL, endemic BL; LCL, lymphoblastoid cell lines. human IL6 cDNA. Our results indicate that hyper-expression of an exogenous 11,6 gene in EBVimmortalized B cells results in a dramatic decrease in the requirement for exogenous growth factors with the development ofa fully tumorigenic phenotype. Materials and MethodsAnimals and Reagents . 4-wk-old Swiss female mice were purchased from Charles River Breeding Laboratories (Italy). LPS Escherichia coli 055 :B55 was obtained from Difco Laboratories (Detroit, MI); Plasmid pHEBoSV and pUC9 (3221 were obtained from R. Dalla Favera and P. B. Segal, respectively, hygromycin B was purchased from Boehringer Biochemica (Italy); F(ab)2 fragments of goat antibodies to human or mouse Igs and Leu 1...

Role of Epstein-Barr virus and interleukin 6 in the development of lymphomas of human origin in SCID mice engrafted with human tonsillar mononuclear cells

“…There is still controversy regarding whether the source of IL-6 in neoplasia is autocrine or paracrine (Kawano et al, 1988;Klein et al, 1989). With respect to B cells infected with EBV, IL-6 has been shown to enhance virus-induced B cell proliferation and Ig production in vitro 30-to 50-fold (Tosato et al, 1988), and to produce human B cell tumours in immunodeficient nude mice in vivo (Scala et al, 1990). The results of our study suggest that IL-6 potentiates EBV-associated lymphogenesis.…”

Constitutive cytokine production by primary effusion (body cavity-based) lymphoma-derived cell lines

“…31 While EBV-infected LCL are immortalized but not tumorigenic upon heterotransplantation, the overexpression of IL-6 in LCL cells led to the generation of lymphomas in nude mice. 32 As the effects of PEL cell line-produced IL-6 could be completely inhibited by a neutralizing antibody specific for huIL-6 and as it has been previously shown that vIL-6 was only active in high concentrations (and could not be blocked by the same antibody), 14 we assume that we measured production of huIL-6 in the supernatants of the PEL cell lines. It remains to be seen whether large quantities of vIL-6 are indeed produced physiologically in vivo and whether this is clinically relevant.…”

Induction of Chromosomal Aberrations and Growth-Transformation of Lymphoblastoid Cell Lines by Inhibition of Reactive Oxygen Species-Induced Apoptosis with Interleukin-6

“…These reports clearly indicate that IL-6 is important for the polyclonal proliferation of B-lineage cells and that the additional genetic changes must be required for the generation of monoclonal neoplasia. As for the transformation of LCLs, the enforced expression of human IL-6 induced colony formation on soft agar and tumorigenicity in nude mice (Scala et al, 1990). Inoculation of peripheral blood lymphocytes from EBV-seropositive donors into the severe combined immunodeficiency (SCID) mice Growth of OS sublines in medium supplemented with 10% (open bar) and 5% (shaded bar) FCS.…”