May 17, 1985 - Nati. Acad. Sci. USA. Vol. 82, pp. 6255-6259, September 1985. Immunology. The specific induction of myc protooncogene expression in normal.
Proc. Nati. Acad. Sci. USA
Vol. 82, pp. 6255-6259, September 1985
Immunology
The specific induction of myc protooncogene expression in normal human B cells is not a sufficient event for acquisition of competence to proliferate (activation by surface antigens/B-cell growth factor/cell cycle)
ERLEND SMELAND*t, ToRE GODALt, ERIK RUUDt, KLAUS BEISKEt, STEINAR FUNDERUDt, EDWARD A. CLARKf, SUSAN PFEIFER-OHLSSON§, AND ROLF OHLSSON§ tLaboratory of Immunology, Department of Pathology and the Norwegian Cancer Society, Norsk Hydro's Institute for Cancer Research, The Norwegian Radiumhospital, Montebello, Oslo 3, Norway; tDepartment of Microbiology and Immunology, University of Washington, Seattle, WA 98195; and §Department of Oncology, University of Ume&, S-901 87 Umel, Sweden
Communicated by E. Donnall Thomas, May 17, 1985
ABSTRACT Resting human B cells can be activated to proliferate in the presence of both polyclonal antibodies to immunoglobulin pA heavy chains and B-cell growth factor (BCGF). This process appears to be temporally controlled in that the initial activation of the B cells and their responsiveness to BCGF'is carried out by polyclonal anti-p-chain antibodies alone. We have used this system to investigate the role of the c-myc gene in the cell cycle of normal human peripheral blood B cells. Our results show that the polyconal anti-pt-chain antibody-induced B-cell activation is accompanied by a specific induction of c-myc gene expression without promoting subsequent entry into the S phase unless BCGF is added. Monoclonal antibodies to either pu chain or the pan-B-cell antigen Bp35 also revealed a similar Go-to-G1 transition and activation of c-myc gene expression. However, unlike activation with polyclonal anti-p-chain antibodies, cells stimulated with these monoclonal antibodies do not acquire responsiveness to BCGF. The results imply that additional inducible functions must be present to potentiate the myc-specific function in order for the B cells to acquire the capacity to proliferate in response to BCGF. These findings are discussed in relation to the origin of B-cell malignancies.
Through studies on acutely transforming retroviruses, viral oncogenes and their cellular progenitors, protooncogenes, have been implicated in the control of proliferative processes in both malignant and normal cells (1-4). This notion has gained considerable support recently through the identification of the v-erbB and v-sis oncogenes as the retroviral versions of epidermal growth factor (EGF) receptor and platelet-derived growth factor (PDGF) B-chain genes, respectively (5-8). Several lines of evidence strongly suggest that the myc protooncogene functions as a key correlate in the induction pathway to competence for cell proliferation (9-12). In murine B and T cells, Kelly et al. demonstrated that c-myc gene expression could be induced by mitogens prior to DNA synthesis (9). Moreover, c-myc gene expression in quiescent murine 3T3 fibroblasts by PDGF indicates that such a link is not direct because these cells need an additional and subsequent exposure to EGF for an entry into the S phase (13). In this system EGF itself has no significant effect on the pattern of c-myc gene expression (9). Furthermore, 3T3 cells carrying a stably integrated conjugate between the mouse mammary tumor (MMTV) promoter and coding myc sequences acquire, when activated by hormones, a competence to respond to EGF in the absence of PDGF (12). Data like these imply that The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.
one function of the myc protein product may be to promote an acquisition of competence to respond to exogenously added growth factors. To further study the influence of transcriptionally activated c-myc genes upon normal human phenotypes, we utilized the activation pathway of human B cells, purified from peripheral blood, as a model system of choice. Under certain conditions the stimulation of B cells from quiescence to proliferation can be divided into at least two distinct steps. Thus, the cells can be activated initially by cognate interaction with T cells or by crosslinking of surface immunoglobulin (sIg) by antigen or anti-Ig (14-16). This treatment renders the cells responsive to accessory cell-derived "progression" factors such as the B-cell growth factor (BCGF); one important event possibly modulates the presence of receptors for these factors (14-16). As shown in this report, the experimental dissociation of the activation and subsequent proliferation processes can be dissected further by using certain monoclonal antibodies. Thus, this system provides us with the means to penetrate in some depth the link between c-myc expression and cell proliferation.
MATERIALS AND METHODS B-Cell Purification and in Vitro Maintenance. Human B lymphocytes were highly enriched from peripheral blood mononuclear cells of normal donors as described (17). Briefly, two monoclonal pan-B-cell antibodies were used in a direct panning technique, followed by lysis of remaining T cells by OKT 3 and OKT 11 (Ortho Diagnostics) and rabbit complement. The highly enriched B cells contained
