Friend murine leukemia virus and spleen focus-forming virus expression in highly malignant interferon-sensitive and interferon-resistant friend leukemia cells

Role of endogenous alpha/beta interferon in the selection of virus nonproducer Friend leukemia cells after serial intraperitoneal passages in syngeneic mice

“…Most (83 to 91%) of the clones derived from 745 cells recovered from untreated mice or mice treated with normal gamma globulins did not produce any detectable RT activity in the culture supernatants, indicating that a selection of virus nonproducer tumor cell variants had occurred in the course of in vivo passages. The virus nonproducer phenotype of these clones persisted after at least 12 in vitro subcultivations (data not shown) and thus was a stable characteristic of these clones, in agreement with our previous observations (22) indicating that clones derived from in vivo-passaged 745 cells lack the expression of the F-MuLV component of the FV comhplex. In contrast, 96% of the clones (26 of 27) derived from 745 cells recovered from mice serially treated with antibodies to MuIFN-a/, were still capable of releasing high levels of RT activity in the culture medium ( Table 2), indicating that endogenous MuIFN-a/, was indeed an important host component for the in vivo selection of virus nonproducer tumor cell variants.…”

“…Immunofluorescence technique. Indirect immunofluorescence techniques to detect gp7O antigens on FLC membranes were performed by using a monospecific goat serum as previously described (22). The expression of H-2 (class I) antigens on the FLC membrane was also determined by indirect immunofluorescence techniques by using a mouse monoclonal antibody to H-2 (Kd) antigens prepared in our laboratory from ascitic fluids of BALB/c nude mice injected with anti-H-2 (Kd) hybridoma cell lines (purchased from the American Type Culture Collection; cell line 31-3-4S).…”

“…with high efficiency and metastasizing to the spleen and to the liver after subcutaneous injection (5). We recently demonstrated that the in vivo-passaged IFN-sensitive 745 cells, as well as the clones derived thereof, did not release FV, since the replication-competent F-MuLV was not expressed (22). In contrast, the in vivo-passaged IFNresistant 3Cl-8 FLCs continued to produce FV and to express F-MuLV to an extent similar to that of the original in vitro-passaged FLCs (22).…”

“…We recently demonstrated that the in vivo-passaged IFN-sensitive 745 cells, as well as the clones derived thereof, did not release FV, since the replication-competent F-MuLV was not expressed (22). In contrast, the in vivo-passaged IFNresistant 3Cl-8 FLCs continued to produce FV and to express F-MuLV to an extent similar to that of the original in vitro-passaged FLCs (22). In the present study, we show that the in vivo selection of virus nonproducer tumor cells also occurred by using other retrovirus producer tumor cells exhibiting an IFN-sensitive phenotype and that this phenomenon was mediated by endogenous IFN-ot/a.…”

Wheat germ agglutinin-binding protein changes in highly malignant Friend leukemia cells metastasizing to the liver

“…Friend murine leukemia virus (F-MuLV)) and in particular the gp 69-70 virus antigen, although in vivo passaged interferon-resistant 3C1-8 cells did continue to express gp 70 and to produce F-MuLV to the same extent as the original in vitro passaged FLC [25]. In contrast to in vitro passaged FLC we have recently demonstrated that in vivo passaged interferonsensitive 745 cells did not express the replication-competent ecotropic component of the FV complex (i.e.…”