Molecular aspects of growth control. An extended report on the first joint meeting of the AACR and the Japanese Cancer Association.
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Animals↗
Biomedical subjects
E Mihich
Publications and source records attributed to E Mihich.
Modification of host antitumor defense mechanisms in mice by progressively growing tumor.
The EL4 lymphoma in C57BL/6 mice was used as a model to examine the effect of progressive tumor growth on a variety of cell mediated cytolytic effector functions which have been shown in other systems to have antitumor potential. The functions examined were those of cytolytic T-lymphocyte, lymphokine activated killer cells, natural killer cells, and tumoricidal macrophage (MO). The kinetics of each function displayed a unique pattern as a consequence of tumor growth, but all were inhibited in animals bearing large tumors (late tumor bearers). In cell mixing experiments it was shown that spleen cells from individual late tumor bearers were suppressive for cytotoxic T-lymphocytes, lymphokine activated killer cells, and splenic MO but not peritoneal MO or splenic natural killer cells. The suppression was nonspecific and was mediated primarily by nonadherent cells and/or their soluble products. Suppression appeared to be mediated, in part, by tumor cells in the spleen since the degree of suppressor activity associated with a particular spleen cell preparation correlated with the number of tumor cells present. Furthermore, the direct addition of viable ascites EL4 cells to response cultures or assays had similar suppressive effects as late TBM spleen cells, i.e., inhibited cytotoxic T-lymphocytes, lymphokine activated killer cells, and splenic MO but had no effect on natural killer cells or peritoneal MO. The mechanism of suppression by ascites EL4 was not determined but it was mediated by viable cells only and not due to contaminating viruses or other microorganisms.
Animals↗
Role of tumor necrosis factor and interleukin 1 in gamma-interferon-promoted activation of mouse tumoricidal macrophages.
The purpose of this study was to determine if recombinant murine interleukin 1 beta (rMu-IL-1 beta) alone or in combination with recombinant murine gamma-interferon (rMu-IFN-gamma) could activate murine macrophages to be tumoricidal against tumor necrosis factor (TNF)-insensitive target cells and to evaluate the possible role of interleukin 1 (IL-1) in murine macrophage activation by recombinant murine tumor necrosis factor (rMu-TNF) plus rMu-IFN-gamma. rMu-IL-1 beta and rMu-TNF alone or in combination could neither directly lyse the TNF-insensitive P815 mastocytoma nor activate resident peritoneal macrophages to be tumoricidal for this target. A synergistic induction of tumoricidal macrophage activity against P815 occurred, however, when either of these monokines was combined with rMu-IFN-gamma. The tumoricidal activity obtained was transitory, and the level of activity was dependent upon the monokine concentration and the length of induction period. Murine macrophages stimulated under the same conditions used to induce tumoricidal activity with rMu-TNF plus rMu-IFN-gamma or with rMu-IL-1 plus rMu-IFN-gamma were shown to produce low concentrations of IL-1 or TNF, respectively. Thus, a bidirectional cross-induction of the production of the two monokines occurred. The monokine production was also quite transitory, and the time of peak production of the monokines (12 h) was found to precede the time of peak tumoricidal activation (24 h). Using neutralizing antisera specific for rMu-IL-1s and rMu-TNF, the cross-induced production of TNF was shown to be required for macrophage tumoricidal activation by rMu-IL-1 beta alone (TNF-sensitive targets) or in combination with rMu-IFN-gamma (TNF-insensitive targets). There was no evidence, however, that the production of IL-1 was required for macrophage activation by rMu-TNF in combination with rMu-IFN-gamma.
Animals↗
Effects of anticancer drugs on the immune system in humans.
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Adjuvants, Immunologic↗
Role of tumor necrosis factor in macrophage activation and tumoricidal activity.
Tumor necrosis factor (TNF)-sensitive (LM) and -insensitive (P815) target cell lines were used to examine the role of TNF in both the activation and lytic phases of macrophage-mediated lysis. LM cells were lysed spontaneously by thioglycolate-elicited macrophages in an 18-h assay (media or activating agents added with targets) or 36-h assay (macrophages cultured with media or activating agents for 18 h, washed, and targets added for a subsequent 18 h). In contrast, P815 cells were lysed only in the 36-h assay by macrophages exposed to appropriate activation signals. Using antibody to murine TNF, it was shown that lysis of LM cells but not P815 cells was TNF mediated. The addition of lipopolysaccharide (LPS) to the 18-h assay resulted in augmented LM killing. This was probably due to the fact that LPS stimulates macrophages to produce TNF. Conversely, when macrophages were pretreated with LPS for 18 h, washed, and assessed for lytic activity during the subsequent 18 h, lysis of LM cells was reduced relative to the endogenous level. Although macrophage lysis of P815 was not mediated by TNF, the addition of TNF to macrophage activation cultures facilitated LPS triggering of cytolytic activity against P815. Similarly, the addition of TNF to the activation cultures partially prevented the LPS-induced reduction in macrophage-mediated LM cell lysis. Taken together, these data suggest that TNF may act as an autocrine signal during macrophage activation, in addition to being directly lytic to a select number of sensitive target cell lines.
Animals↗
Alterations in murine host defense functions by adriamycin or liposome-encapsulated adriamycin.
Peritoneal exudate cells (PEC) from C57BL/6 mice were collected on different days following an i.p. injection of Adriamycin (10 mg/kg) as free drug (ADM) or encapsulated in multilamellar liposomes (ADM/Lip). Macrophages harvested from mice at various times (Days 4-14) after either drug treatment were responsive to in vitro lipopolysaccharide induction of tumoricidal activity, maximum response being seen on Day 7. In addition, 18 days after treatment, significant macrophage tumoricidal activity was observed only in the ADM/Lip-treated group. When supernatants from cultures of PEC obtained 7 days after treatment were assayed for interleukin 1 following lipopolysaccharide stimulation, activity was found with both ADM- and ADM/Lip-treated cells. Without lipopolysaccharide stimulation, only PEC from ADM-treated mice elaborated factor(s) with interleukin 1-like activity. Both ADM and ADM/Lip induced significant PEC-natural killer (PEC-NK) activity by Day 4, while the ADM/Lip treatment sustained PEC-NK activity more effectively than free drug at later time points (7 or 11 days posttreatment). Drug-induced PEC-NK activity (Day 7) was (a) ablated by treatment in vitro with anti-asialo GM1 antibody and complement, and (b) associated with a population of PEC nonadherent to plastic. A transient suppression of splenic NK activity was seen 4 days following either ADM or ADM/Lip administration with recovery to control level by Day 7. These data demonstrate that following ADM or ADM/Lip administration some of the changes necessary for macrophage tumoricidal activation must have occurred in vivo. Liposome encapsulation of ADM extended the duration of ADM-induced augmentation of certain host defenses.
Animals↗
Comparison of adriamycin induced immunomodulation with that of the noncardiotoxic anthracycline 5-iminodaunorubicin.
Adriamycin (ADM) has been shown to modulate a variety of host immune responses. Although the mechanism(s) for this activity is not known, it has been suggested that free radical compounds generated during ADM metabolism act at the membrane level to alter immune cell function. The generation of free radical metabolites is also believed to be responsible for the cardiotoxic potential of ADM. 5-Iminodaunorubicin (IDM) is a non-cardiotoxic anthracycline analog which undergoes minimal free radical metabolism. In the present study the immunomodulatory capacity of IDM was compared to that of ADM. It was found that IDM and ADM had similar augmenting effects on cytolytic T-cell activity and that this correlated with: (1) Fc-dependent phagocytosis by spleen cells; and (2) the elimination or inhibition of an adherent regulatory cell in the spleen. The natural killer response was either unaffected (fresh NK) or slightly inhibited (cultured NK) by both drugs except moderate dose IDM which resulted in marked augmentation of cultured NK.
Adjuvants, Immunologic↗
Biological response modifiers in cancer therapeutics: potentialities and limitations.
With increased knowledge of the mechanisms of host defenses against tumors, both immunological and nonimmunological in nature, and of the relationships between tumors and host cells, it becomes possible to develop agents aimed at modifying those relationships to therapeutic advantage. The task is facilitated by the advent of recombinant DNA technology, which makes it possible to produce biologicals in quantity and purity adequate for studies in vivo. The potentialities of biological response modifiers (BRMs) are primarily due to their specificity and/or selectivity of action, whether these attributes are related to receptors/antigens present on neoplastic cells or on cells of the immunological regulatory networks or to nonspecific activation of host defenses. The limitations are related to the fact that in certain cases treatments are too specific for a tumor cell within a heterogeneous cell population; these agents also show toxicities that, albeit usually unrelated to their antitumor action, can in some cases be severe.
Acetylmuramyl-Alanyl-Isoglutamine↗
Effect of recombinant tumor necrosis factor on tumoricidal activation of murine macrophages: synergism between tumor necrosis factor and gamma-interferon.
The activation of tumoricidal murine macrophages by recombinant human tumor necrosis factor (rH-TNF) alone or in combination with recombinant murine gamma-interferon (rM-IFN-gamma) was examined. When used alone, rH-TNF (10(-1)-10(5) units/ml) did not induce macrophage tumoricidal activity against TNF-insensitive P815 mastocytoma cells. Combining rH-TNF with rM-IFN-gamma resulted in the synergistic induction of tumoricidal activity in resident peritoneal macrophages. This synergistic effect was not due to contaminating bacterial lipopolysaccharide. A comparative study using recombinant murine tumor necrosis factor (rM-TNF) showed that rM-TNF alone also could not stimulate murine macrophages and there was no significant difference between effects of rM-TNF and rH-TNF on macrophage activation in the presence of rM-IFN-gamma. In experiments comparing sequential to simultaneous exposure of macrophages to rH-TNF and rM-IFN-gamma, it was found that: (a) when macrophages are primed with rM-IFN-gamma, rH-TNF serves only as a very weak triggering signal for tumoricidal activation; and (b) marked activation is obtained only when macrophages are exposed to the two cytokines simultaneously. These results suggest that TNF has an autocrine regulatory function in concert with lymphokines in macrophage-mediated host defense against tumors.
Animals↗
Effect of recombinant human tumor necrosis factor on the induction of murine macrophage tumoricidal activity.
The ability of recombinant human tumor necrosis factor (rH-TNF) alone or in combination with lymphokines (LK) to induce the in vitro activation of murine macrophages was evaluated. The treatment of C57BL/6 mouse resident peritoneal exudate cells (PEC) with rH-TNF and LK was found to induce the activation of macrophages to a tumoricidal state against P815 mastocytoma cells. Neither rH-TNF nor LK alone induced macrophage cytotoxic activity. Furthermore, the macrophage activation seen was not due to small amounts of contaminating lipopolysaccharide. The TNF plus LK-mediated macrophage activation could be totally ablated by rabbit antiserum to murine gamma-interferon, thus suggesting a role for gamma-interferon in this system. Since adherent cells (greater than or equal to 95% macrophages) only marginally responded to stimulation with rH-TNF plus LK and the addition of nonadherent PEC caused a marked augmentation of rH-TNF plus LK-mediated macrophage activation, the involvement of nonadherent PEC was suggested. In addition, using antibodies and complement to deplete subsets of cells from the nonadherent PEC, the requirement for cells bearing Thy 1.2 and asialo GM1 surface markers was demonstrated. These results suggest that TNF may play an autocrine regulatory role in concert with lymphokines in macrophage-mediated host defense against malignant neoplasia.
Animals↗
Low concentrations of thymidine modulate allogeneic responses.
The effect of the addition of low concentrations of thymidine on the development of primary allogeneic immune responses in culture was studied. It was found that, dependent upon day of addition to culture, allogeneic cytotoxic T-lymphocyte generation was augmented by thymidine in the concentration range of 10(-9) to 10(-8) M while specific T-suppressor cell development was inhibited by 10(-7) M thymidine. Based on the concentration of thymidine in serum, its addition in the concentration range of 10(-9) to 10(-7) M results in 0.1 to 10 fold concentration change in cultures supplemented with 10% serum. While the mechanism(s) by which such minor changes in thymidine concentrations induced the modulations seen have not been elucidated, it is clear that such changes are easily attainable. In fact, such variations in the concentration of thymidine could contribute to the variable results often observed with different lots of fetal calf serum and workers investigating immunomodulations in culture systems should be aware of this possibility.
Animals↗
In vitro effects of 4-hydroxyperoxycyclophosphamide on human immunoregulatory T subset function.
Treatment of T cells in vitro with low concentrations of 4-hydroperoxycyclophosphamide (4-HC) is known to result in immunopotentiation of both T and B cell effector function in a manner analogous to that of cyclophosphamide administered in vivo. A previous study demonstrated that augmentation of polyclonal immunoglobulin secretion occurs following pretreatment of autologous collaborating T cells with low concentrations of 4-HC as a result of blockade of suppressor effector induction from suppressor precursor, both of which share the identical T4+,8-phenotype. The present study was undertaken to examine the effects of 4-HC on regulatory T-T interactions in mixed lymphocyte culture (MLC) responses and for allospecific cytotoxic T lymphocyte (CTL) responses. Induction of CTL and MLC proliferation were found to be sensitive to as little as 40 microM 4-HC, whereas CTL effector function was resistant to greater than or equal to 80 microM. CTL effectors were restricted to the T4-,8+ subset and the cells showing sensitivity to low and intermediate 4-HC concentrations were found to be T4+,8-. Secondary MLC and CTL responses displayed a similar 4-HC concentration-dependent inhibition following drug treatment of the T4+ T subset which could only be detected at suboptimal responder to stimulator ratios. This suggests that the mechanisms of CTL induction by a T4+ inducer cell in primary and secondary MLC responses and the sensitivity of induction of 4-HC are qualitatively similar. Pretreatment of T cells with less than or equal to 20 microM 4-HC for one hour prior to Con A activation totally blocked suppressor effector induction both for MLC and CTL function. In contrast, treatment with 80 microM 4-HC following Con A induction was without effect on differentiated T suppressor effector activity. Studies utilizing monoclonal antibody/complement depletion and panning techniques demonstrated that the suppressor precursor and differentiated suppressors for T effector function were restricted to the T4+,8-subset. These results support the hypothesis that regulatory inducer T cell function is significantly more sensitive to the inhibitory effects of low to intermediate concentrations of 4-HC than either the suppressor-cytotoxic precursors themselves or suppressor/cytotoxic effectors. Con A inducible suppressor cell precursor induction (mediated by the T4+,8-subset) demonstrated the greatest sensitivity to 4-HC (less than or equal to 20 microM) followed by inducers of primary and secondary CTL (40-60 microM).(ABSTRACT TRUNCATED AT 400 WORDS)
Cells, Cultured↗
Modulation of antitumor immune responses.
Based on experimentation in animal model systems it is reasonable to expect immunomodulation by anticancer drugs and biological response modifiers to be instrumental in at least some of the antitumor effects of such agents. Even in the defined animal models, however, the immunomodulating effects of any given agent are in most cases correlated only with the therapeutic response to that agent, whereas causal relationships still evade unequivocal demonstration. The difficulties in this respect are magnified in humans, in whom the very nature and regulation of antitumor immunity, taken in a broad sense, are not yet well defined; thus at this time the basis on which to interpret the therapeutic or toxicological causative relevance of an immunomodulating effect is insufficient. Despite these limitations and uncertainties, or perhaps responding to the challenge they provide, experimentation evaluating the potential of immunomodulation is being carried out in a number of diversified areas. Salient findings from selected investigations of the actions of 1) drugs, 2) cytokines, and 3) combinations of agents or effectors are discussed as examples of the realization of the potential of this overall approach as well as to outline the requirements for future development of biological response modifiers.
Adjuvants, Immunologic↗
Inhibition of suppressor cell generation by mouse serum in culture.
Normal C57BL/6 mouse spleen cells cultured for five days in the presence of fetal calf serum (FCS-induced suppressor generation culture) were shown, in mixing experiments, to suppress the primary humoral response of freshly explanted C57BL/6 spleen cells against sheep erythrocytes (SRBC). This suppressor cell generation was largely dependent on the FCS concentration in the suppressor generation culture. Ten or 5% FCS effectively supported the generation of suppressor cells, but 1% FCS only marginally supported it. When mouse serum (MS) from normal C57BL/6 mice was added to the suppressor generation culture, it inhibited the generation of the suppressor cells. Sera from allogeneic mice and athymic nude mice were also effective. The effect of MS was resistant to heat treatment (56 degrees C, 30 min). The inhibitory activity of MS was not dialyzable, and concentrated into the fraction which was not precipitated by 50% saturation of ammonium sulfate and which was eluted at a concentration of about 0.2 M NaCl from a DEAE-Sephadex A-50 column. The active fraction of MS also effectively inhibited the growth of Ehrlich tumor cells in culture. Further, MS also inhibited the generation of Con A-induced suppressor cells. The inhibition by MS of FCS-induced suppressor generation was eliminated by an interleukin 2-containing preparation.
Animals↗
Future perspectives for biological response modifiers: a viewpoint.
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Adjuvants, Immunologic↗
Selective modulation by alpha-difluoromethylornithine of T-lymphocyte and antibody-mediated cytotoxic responses to mouse tumor allografts.
alpha-Difluoromethylornithine (DFMO), an inhibitor of polyamine biosynthesis, has been shown to be growth inhibitory in a wide variety of normal and tumor cell systems. Since cells of the host defense system are among the most rapidly proliferating cells in the body, DFMO may inhibit certain components of this system. In order to assess this possibility, four randomized groups of C57BL/6 mice were maintained either on water throughout (controls) or on 2% DFMO in drinking water for various periods of time. Mice were given DFMO from Days -4 to 0, Days 0 to +4, or Day 0 to day of assay. On Day 0 randomly selected mice from each group received P815 tumor allografts. Daily from Days +3 to +14, pools of spleen cells from three mice per group were assessed for allospecific cytolytic T-lymphocyte, antibody formation, natural killer cell, and phagocytic cell activities. While natural killer cell and phagocytic cell activities remained essentially unchanged under all conditions, both cytotoxic T-lymphocyte and antibody responses were modified. Somewhat similar effects were seen with both responses and involved to varying degrees: (a) a delay of the initiation of rapid increase in the response but not in the onset of first detectable response; (b) delay in the time of peak response; (c) increased level of maximal response; (d) two peaks of maximal response. The data indicate that DFMO treatment of whole animals, dependent upon schedule of administration and time of assay, induces very selective effects on both cytotoxic T-lymphocyte and antibody responses, without apparent modification of nonspecific host defense mechanisms, with the overall effect being a prolongation of the period of specific response.
Animals↗
Correlation between adriamycin-induced augmentation of interleukin 2 production and of cell-mediated cytotoxicity in mice.
Based on the observation that spleen cells from Adriamycin-treated mice could develop augmented levels of cytotoxic T-lymphocyte activity in response to heat-treated and/or X-irradiated alloantigens, it was postulated that modulations in soluble mediators could be involved in this phenomenon. In fact, in this study Adriamycin-induced increases in the levels of prostaglandin E2 and interleukin 2 activity have been observed with isolated cells. The "interleukin 2-like" activity was indistinguishable from that of partially purified interleukin 2 in terms of ability to restore responsiveness to experimentally inhibited primary alloantigen response cultures and to maintain long-term cultures of activated T-cells. Furthermore this latter activity was completely ablated by antiinterleukin 2 monoclonal antibody. While the modification in prostaglandin E2 production did not appear to play a role in determining augmentation of cytotoxic T-cell activity, the modification in interleukin 2 production was consistent with the possibility that this is a primary mechanism of Adriamycin-induced augmented cell-mediated cytotoxicity.
Animals↗
Biological response modifiers: their potential and limitations in cancer therapeutics.
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Adjuvants, Immunologic↗