[CANCER RESEARCH 5l. 612-618, January 15, 1991] In Vivo Acquisition of FcTRH Expression on Polyoma Virus-transformed Cells Derived from Tumors of Long Latency1 M. Ran, B. Katz, N. Kimchi, E. Halachmi, J-L. Teillaud, J. Even, Y. Berko-Flint, E. Atlas, W. H. Eridman, and I. P. Witz Department of Microbiology and the Moise and Frida Eskenasy Institute for Cancer Research, The (Jeorge S. Wise Faculty of Lije Sciences, Tel Aviv University . Tel Aviv 69978, Israel ¡M.R., B. A'., A/. A'., E. H., Y. B-F, E. A., I. P. W.], and Laboratoire d'Immunologie Cellulaire et Clinique, INSERM ('. 255, Institut Curie, Paris, France ¡J-L.T., J. E., W. H. F.] ABSTRACT BALB/c 3T3 cells transformed in vitro with polyoma virus »erecloned and passaged once in syngeneic mice. Resulting tumors from each clone were explanted and recultured. Expression of receptor for Fc of IgG (FcfRII) in the original in vitro maintained clones and in cells derived from tumors elicited by the respective cells was measured at the protein level as well as at the mRNA level. Clones were assayed in pairs. The ancestor in vitro maintained clones (designated cultured cells (C)| were compared with cells derived from the same clones after a single passage in vivo followed by cxplantation and reculturing [designated cultured- tumor-cultured cells (CTC)|. C cells of any of the tested clones did not express FcyRII. On the other hand, certain CTC cells were positive. The FcTRH-positive cells were derived from tumors appearing after a long precancer latency period (>140 days). CTC cells derived from tumors that appeared after shorter latency periods (<80 days) were !•'(•-> RII negative. These results were obtained both by using radioimmunoassay and monoclonal antibodies against mouse I i-~jRl1 as well as by Northern blot analysis using the I o KlI complementary DNA probe. The involve ment of macrophages as the Fc-yRII-expressing cells in CTC cells was excluded. 1 e->RII expression was down-regulated in CTC cells as a function of time following their explantation into culture. Io RII expression could be up-regulated in these cells and induced on C cells by maintaining the cultured cells in the presence of normal mouse serum or recombinant Interferon. We also tested the expression of Fc-yRII on CTC cells following their inoculation into syngeneic mice for a second time (CTCx2 cells). The results showed a positive correlation between FcfRII expres sion in the inoculated ancestor CTC cells and on the CTCx2 cell progeny. INTRODUCTION In experimental tumor systems the length of the precancer latency period can be precisely determined because it separates 2 measurable events. The First event is the exposure of the animal to an oncogenic agent or to an inoculum of transformed cells. The second event is the appearance of a tumor. In human cancer patients or in spontaneous animal tumor systems the duration of the precancer latency period cannot be determined because only the second event can be monitored. In both types of tumor systems the duration of the precancer latency period is primarily determined by the ability of the transformed cells to proliferate as well as by the fraction of proliferating cells and by their proliferation rate. The proliferation of transformed cells beyond a subthreshold mass may be halted due to intrinsic properties and/or to lack Received 5/30/90; accepted 10/26/90. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. 1 This work has been supported by the Israel Cancer Association. Tel Aviv: the National Council for Research and Development. Jerusalem; Association pour la Recherche sur le Cancer, Paris; Concern Foundation. Los Angeles: The Fainbarg Family Fund, Orange County; and the Mary A. Pikovski Fund, Jerusalem. Yehudit Berko-Flint is a fellow of the Israel Cancer Research Fund and Isaac P. Witz is the incumbent of Ihe David Furman Chair in Immunobiology of Cancer. of growth-promoting host-derived factors. The presence of growth-inhibiting host factors may also retard their prolifera tion. The persistence of transformed cells for prolonged periods of time without progressing toward a frank and overt tumor has been termed tumor dormancy (1, 2). Transformed cells may remain dormant until they acquire altered intrinsic properties and/or until the balance between host-derived inhibitory and growth-promoting factors changes. These cells may now prolif erate to form a tumor. Once a cellular variant within a dormant population has acquired the ability to proliferate in vivo and thus to exit the dormancy state, the remainder of the precancer latency period will by and large depend on the proliferation rate of this variant. In a previous study (3) we inoculated cloned BALB/c 3T3 cells transformed in vitro with PyV2 into syngeneic recipients. We demonstrated that the length of the precancer latency periods varied drastically in individual mice inoculated with an identical cell dose from the same clone (3). This was a general finding being more pronounced with low tumorigenic clones. In extreme cases the duration of the precancer latency of the first and the last tumor appearing in a group of syngeneic mice inoculated with a certain dose of cells from a particular clone differed by 8 months or more (3). Southern blot analysis re vealed identical integration sites of the PyV genome in the original in vitro transformed cells (that were never passaged in vivo) and in the cells from tumors which appeared after a short or a long latency period following the inoculation of the in vitro transformed cells.3 This clearly indicated that both the early tumors and late ones originated from the same population of in vitro transformed ancestor cells. Furthermore, these results suggested rather strongly that the cells from the late tumors were in a prolonged state of dormancy, some well over 1 year (3). In order to elucidate mechanisms responsible for tumor dor mancy and for its termination it may be helpful to dissect and identify genetic and phenotypic properties distinguishing tumor cells which underwent a long, a short, or no in vivo dormancy. The availability of cells derived from either early or late tumors while both types of tumors originated from the same ancestor clone of transformed cells makes such an analysis feasible. In previous publications we hypothesized that the "ectopie expression" of receptors for Fc7R by nonlymphoid tumor cells may be associated with cellular growth and progression patterns that may differ from those of similar tumor cells not expressing such receptors (4-6). In the present study we analyzed Fc7RII 1 The abbreviations used are: PyV, polyoma virus; C cells, cells maintained only in culture; CTC cells, cultured cells that were passaged once as tumors in syngeneic mice and recultured after explantation: Fc7R, receptor for Fc of IgG; GaM antibody, goat anti-mouse Ig antibody; mAb, monoclonal antibody: RIA, radioimmunoassay: r-IFN-p, recombinant Interferon 7; DMEM, Dulbecco's mod ified Eagle's medium; FCS. fetal calf serum; PBS, phosphate-buffered saline; NMS. normal mouse serum. 3 Y. Berko-Flint, personal communication. 612 Research. on August 17, 2017. © 1991 American Association for Cancer cancerres.aacrjournals.org Downloaded from