Positive correlation between the levels of natural killer cells and the in vivo resistance to syngeneic tumor transplants as influenced by various routes of administration of Corynebacterium parvum bacteria

Combining the past and present to advance immuno-radiotherapy of cancer

Since its first clinical application, 120 years ago, radiotherapy evolved into a major anti-cancer treatment modality, offering high cure rates in many human malignancies. During the past ten years, the establishment of immune checkpoint inhibitors (ICIs) in cancer therapeutics has vigorously reintroduced the immune system's role in the outcome of radiotherapy and, conversely, the role of radio-vaccination in the efficacy of immunotherapy. The knowledge and clinical experience that founded the current era of immuno-radiotherapy started alongside with the birth of radiotherapy, and evolved through exhaustive experimental work, clinical trials on active specific immunotherapy, frustrating attempts to validate the importance of cytokine administration with radiotherapy, and, finally, the encouraging ICI-based clinical trials that opened the door to a far more encouraging perspective; radio-vaccination, through its old and new methods, is rising as a research field that promises to cure, previously incurable, disease. In this critical review, we focus on the scientific knowledge gathered through more than a century of research on radiotherapy interactions with the immune system. Understanding the origins of this promising therapeutic approach will substantially contribute to developing new immuno-radiotherapy policies in the fight against cancer.

Propionibacterium acnes Augments Antitumor, Anti-Angiogenesis and Immunomodulatory Effects of Melatonin on Breast Cancer Implanted in Mice

Breast cancer is one of the most invasive cancers with high mortality. The immune stimulating Propionibacterium acnes is a Gram positive bacterium that has the ability to cause inflammation and activate Th1-type cytokine immune response. Antitumor response was associated with the inflammation induced by P. acnes, but the antitumor effect of this bacterium was not evaluated in combination with other agents. The aim of this study was to test the antitumor potential of a combination of melatonin and P. acnes against breast cancer implanted in mice. Balb/C mice were transplanted with EMT6/P cell line and in vivo antitumor effect was assessed for P. acnes, melatonin, and a combination of melatonin and P. acnes. Tumor and organs sections were examined using hematoxylin/eosin staining protocol, and TUNEL colorimetric assay was used to detect apoptosis. The expression of vascular endothelial growth factor (VEGF) was measured in tumor sections and serum levels of INF-γ, and IL-4 were measured to evaluate the immune system function. To evaluate the toxicity of our combination, AST and ALT levels were measured in the serum of treated mice. The combination of melatonin and P. acnes has high efficiency in targeting breast cancer in mice. Forty percent of treated mice were completely cured using this combination and the combination inhibited metastasis of cancer cells to other organs. The combination therapy reduced angiogenesis, exhibited no toxicity, induced apoptosis, and stimulates strong Th1-type cytokine antitumor immune response. The combination of melatonin and P. acnes represents a promising option to treat breast cancer. However, carful preclinical and clinical evaluation is needed before considering this combination for human therapy.

Splenectomy inhibits non-small cell lung cancer growth by modulating anti-tumor adaptive and innate immune response

It has been shown that inhibitors of the immune system reside in the spleen and inhibit the endogenous antitumor effects of the immune system. We hypothesized that splenectomy would inhibit the growth of relatively large non-small lung cancer (NSCLC) tumors by modulating the systemic inhibition of the immune system, and in particular Myeloid Derived Suppressor Cells (MDSC). The effect of splenectomy was evaluated in several murine lung cancer models. We found that splenectomy reduces tumor growth and the development of lung metastases, but only in advanced tumors. In immune-deficient NOD-SCID mice the effect of splenectomy on tumor growth and metastatic spread disappeared. Splenectomy significantly reduced the presence of MDSC, and especially monocytic-MDSC in the circulation and inside the tumor. Specific reduction of the CCR2+ subset of monocytic MDSC was demonstrated, and the importance of the CCL2-CCR2 axis was further shown by a marked reduction in CCL2 following splenectomy. These changes were followed by changes in the macrophages contents of the tumors to become more antitumorigenic, and by increased activation of CD8⁺ Cytotoxic T-cells (CTL). By MDSC depletion, and adoptive transfer of MDSCs, we demonstrated that the effect of splenectomy on tumor growth was substantially mediated by MDSC cells. We conclude that the spleen is an important contributor to tumor growth and metastases, and that splenectomy can blunt this effect by depletion of MDSC, changing the amount and characteristics of myeloid cells and enhancing activation of CTL.

Decreased Growth Rate of Lung Metastatic Lesions after Splenectomy in Mice

BACKGROUND

The effect of splenectomy on hematogenous metastases of malignant tumors remains controversial. The aim of this study was to clarify the effect of splenectomy on hematogenous metastases in an animal model.

METHODS

Colon 26 cancer cells were inoculated into the lateral tail vein of 90 mice. The mice were then assigned to a splenectomy group or a control group. Lung weight, number of lung metastases, size of metastatic nodules, and serum vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) levels after the surgical procedure were measured and compared between the two groups.

RESULTS

The lung nodules were significantly smaller in the splenectomy group than in the control group. In both groups, the serum VEGF levels increased on day 1 and then decreased. The serum VEGF levels on day 5 were significantly lower in the splenectomy group than in the control group. The serum bFGF levels were significantly lower in the splenectomy group than in the control group on days 1 and 5. Immunohistochemical study showed that bFGF was produced by reticuloendothelial cells of the spleen.

CONCLUSION

The growth rate of hematogenous metastatic lesions appears to decrease after splenectomy and may be associated with decreases in serum levels of VEGF and bFGF induced by splenectomy.

Synergistic anti-tumor activity of a novel immunomodulator, BCH-1393, in combination with cyclophosphamide

N,N-dimethylaminopurine pentoxycarbonyl D-arginine (BCH-1393) is a novel low molecular weight synthetic immunomodulator that has been shown to significantly stimulate cytotoxic T-lymphocyte responses both in vitro and in vivo (Zacharie B, Gagnon L, Attardo G, Connolly TP, St-Denis Y, Penney CL. Synthesis and activity of 6-substituted purine linker amine immunostimulants. J. Med. Chem. 1997;40:2883-94). Prompted by this evidence, we extended evaluation of BCH-1393 for anticancer activity in syngeneic mouse experimental tumor models. Consistent with previous findings, in vitro assessment of BCH-1393 activity demonstrated a significant increase in the CTL responses in the range of 10(-9)-10(-5) M. Treatment of mice with four consecutive daily intraperitoneal injections at 25 and 50 mg/kg resulted in a significant increase of the relative percentage of blood CD4+, CD8+, NK and monocyte subsets without any evidence of toxicity. In vivo anti-tumor activity of BCH-1393 was evaluated, either alone or in combination with subtherapeutic doses of cyclophosphamide (Cy), against weakly immunogenic mouse breast carcinoma DA-3 and strongly immunogenic colon adenocarcinoma MC38. Daily intraperitoneal injection of BCH-1393 at 50 mg/kg alone was well tolerated but produced a relatively weak anti-tumor effect in both tumor models. However, a significant inhibition of tumor outgrowth and suppression of established tumor growth was observed when BCH-1393 was administered in combination with subtherapeutic doses of Cy. Combination treatment of 50 mg/kg BCH-1393 with 100 mg/kg Cy (given as single intravenous bolus injection) starting 2 days prior to DA-3 tumor cell inoculation prevented tumor outgrowth in 70-80% of treated mice. In the remaining 20-30% of mice that had developed tumors, a nearly complete (90%) tumor growth inhibition was observed at days 22-24 post tumor implant. In the MC38 tumor model, combination treatment of established tumors with BCH-1393 and Cy (CTX) at 50 mg/kg resulted in a significant delay in tumor growth compared to CTX treatment alone. The observed concomitant anti-tumor activity of BCH-1393 with cyclophosphamide warrants further investigation of this immunomodulator as an adjunctive treatment of cancer.

7-Allyl-8-oxoguanosine (loxoribine) inhibits the metastasis of B16 melanoma cells and has adjuvant activity in mice immunized with a B16 tumor vaccine

We have shown previously that loxoribine exhibits adjuvant activity for B cells, activates natural killer (NK) cells, and enhances the activation of lymphokine-activated killer cells by interleukin-2 (IL-2). In this study, we examined loxoribine for protective effects in a B16 melanoma lung tumor metastasis model. Significant inhibition of B16 metastasis was seen in mice given a single injection of 2 mg loxoribine as late as day 3 of tumor growth but the greatest inhibition (96%) was seen in mice given four injections of loxoribine on alternate days starting the day before tumor injection. In experiments in which both IL-2 and loxoribine were administered, both agents were active when tested alone, but the combination of IL-2 and loxoribine gave significantly greater inhibition of metastasis. Loxoribine partially inhibited the development of tumors in mice that had been depleted of NK cells by the administration of anti-asialo-GM1 or anti-NK1.1 antibodies and in NK-deficient beige mice. In all cases, protection was seen only when smaller tumor inocula were injected. Taken together, these data suggest that both NK and non-NK cell populations or effector mechanisms with antitumor activity were activated by loxoribine. Since substituted guanosine analogs have been shown to have adjuvant activity in B cell systems, we evaluated whether loxoribine was active as an adjuvant in a tumor protection model. Mice immunized with both irradiated tumor cells and loxoribine developed a significantly lower number of lung tumors when challenged by live B16 tumor cells, whereas mice injected with either vaccine or loxoribine alone were not protected. There was a clear dose response seen with both loxoribine and the vaccine preparations. These data suggest that loxoribine may be useful in tumor therapy as an immunomodulator or as an adjuvant for use with tumor vaccines.

Effects of splenectomy on pulmonary metastasis and growth of SC42 carcinoma transplanted into mouse liver

The carcinoma SC42 was transplanted into the liver of its syngeneic mice DS, and the immunological integrity of the spleen and the effects of splenectomy on the growth and pulmonary metastasis of the liver tumor were assessed. On day 7 after liver tumor transplantation, the natural killer (NK) activity of the splenocytes was significantly elevated; it subsequently decreased at a later stage of the tumor. The response of the splenocytes to PHA and Con-A decreased significantly from the early stage of the tumor. However, the mixed lymphocyte-tumor cell reaction increased significantly from day 14 to day 28. The survival rate of the mice, which had undergone simultaneous splenectomy and liver tumor transplantation, was significantly lower than that of sham-operated control mice. The number of pulmonary metastases in splenectomized mice was significantly greater than in the control mice. There was, however, no difference between the two groups in the weight of the liver tumor. By contrast, splenectomies performed 14 days before or 14 days after tumor transplantation had no significant influence on the survival of the mice. Splenectomies performed on day 0 and on day 3 after tumor transplantation significantly increased the number of pulmonary metastases. Furthermore, the intravenous injection of anti-asialo GM1 antisera on day 0 and day 3 significantly increased the number of pulmonary metastases, but injection of anti-Thy 1.2 antisera had no effect. These results suggest that splenic NK cells may play an important role in the suppression of pulmonary metastasis at early stages of the liver tumor.

Antitumor activity of Streptococcus thermophilus against fibrosarcoma: role of T-cells

Antitumor activity induced by a heat-killed preparation of S. thermophilus against mouse fibrosarcoma was investigated. The treatment of Swiss mice with S. thermophilus prior to transplantation could not prevent tumors. However, animals cured by treatment with a S. thermophilus preparation failed to take up the tumor when rechallenged with fibrosarcoma. S. thermophilus did not induce antitumor activity in animals immunosuppressed by sublethal whole body gamma-irradiation (4 Gy) or hydrocortisone treatment prior to transplantation. Suppression of activity of macrophages by carrageenan had no effect on antitumor activity of the heat inactivated preparation of S. thermophilus. The intravenous administration of sera from cured animals was ineffective in curing the tumours. Spleen cells from cured animals could effectively transfer the antitumor activity to recipients transplanted with the tumor. This effect was abolished when the T-lymphocyte population in the inoculum was specifically depleted. The results thus suggest the involvement of T-lymphocytes in antitumor activity exhibited by S. thermophilus.

A novel guanosine analog, 7-thia-8-oxoguanosine, enhances macrophage and lymphocyte antibody-dependent cell-mediated cytotoxicity

Intraperitoneal treatment of mice with a novel guanosine analog, 7-thia-8-oxoguanosine (7-thia-8-oxoGuo), gives rise to activated splenic lymphocytes and peritoneal macrophages with enhanced capacity to mediate antibody-dependent cellular cytotoxicity (ADCC). ADCC activities against both chicken red blood cells and P815 murine plasmacytoma cells were enhanced, indicating that macrophages as well as lymphocytes functioning as K-cells in the two distinct cytolytic systems, were activated by 7-thia-8-oxoGuo. Furthermore, 7-thia-8-oxoGuo enhanced lymphocyte-mediated ADCC activity in beige (bgJ/bgJ) mice against P815, thus indicating the ability of 7-thia-8-oxoGuo to function as a potent immunomodulator even in an animal that is known to possess selective impairment of naturally occurring killer lymphocytes. These results suggest that 7-thia-8-oxoGuo could serve as an agent for immunomodulation and immunorestoration.

Effect of intracerebrally injected Corynebacterium parvum on implanted brain tumor in mice

Experiments were performed to determine the effectiveness of Corynebacterium parvum on resistance to growth and development of tumor in the central nervous system. A syngeneic sarcoma was injected intracerebrally into C3H/HeN/MTV-negative female mice that had received intraperitoneal injections of C. parvum or saline prior to tumor inoculation or that received intraperitoneal C. parvum or saline after tumor inoculation. Groups then received an intracerebral injection of C. parvum or saline. Our results reveal that intracerebral C. parvum elicited an intracerebral inflammatory reaction which was enhanced by prior systemic priming with C. parvum. Any inflammatory reaction which was enhanced by prior systemic priming with C. parvum. Any inflammatory reaction produced by C. parvum retarded the growth of intracerebrally-implanted sarcoma and significantly increased the survival of mice bearing such tumors. These results suggest that C. parvum may be an effective therapeutic agent in the treatment of neoplasia of the central nervous system.

Biology of natural killer cells

Studies of cytotoxicity by human lymphocytes revealed not only that both allogeneic and syngeneic tumor cells were lysed in a non-MHC-restricted fashion, but also that lymphocytes from normal donors were often cytotoxic. Lymphocytes from any healthy donor, as well as peripheral blood and spleen lymphocytes from several experimental animals, in the absence of known or deliberate sensitization, were found to be spontaneously cytotoxic in vitro for some normal fresh cells, most cultured cell lines, immature hematopoietic cells, and tumor cells. This type of nonadaptive, non-MHC-restricted cellmediated cytotoxicity was defined as “natural” cytotoxicity, and the effector cells mediating natural cytotoxicity were functionally defined as natural killer (NK) cells. The existence of NK cells has prompted a reinterpretation of both the studies of specific cytotoxicity against spontaneous human tumors and the theory of immune surveillance, at least in its most restrictive interpretation. Unlike cytotoxic T cells, NK cells cannot be demonstrated to have clonally distributed specificity, restriction for MHC products at the target cell surface, or immunological memory. NK cells cannot yet be formally assigned to a single lineage based on the definitive identification of a stem cell, a distinct anatomical location of maturation, or unique genotypic rearrangements.

Antitumor activity of lactic acid bacteria on a solid fibrosarcoma, sarcoma-180 and Ehrlich ascites carcinoma

Antitumor activity of Leuconostoc mesenteroides, Streptococcus cremoris and Streptococcus lactis was investigated in solid mouse fibrosarcoma. Intratumor administration of lyophilised bacterial cells at a dose of 20 mg/kg body wt resulted in the regression of tumors in a maximum number of animals. Intraperitoneal injection at the same dose resulted in a significant increase in the survival time but was ineffective in curing the animals. Intratumor injection of Streptococcus thermophilus at a dose of 20 mg/kg body wt also inhibited the growth of fibrosarcoma accompanied by an increase in the survival time while intraperitoneal administration of S. thermophilus prolonged only the survival time and did not result in cure. In mice bearing the ascitic form of sarcoma-180 or Ehrlich ascites carcinoma, intraperitoneal administration of S. thermophilus resulted in complete cure in a very significant proportion of tumor-bearing mice. S. thermophilus was more effective in sarcoma-180 than in Ehrlich ascites carcinoma. The cured tumors did not recur.

Reduced risk of recurrent leukaemia in bone marrow transplant recipients after cytomegalovirus infection

The first 72 consecutive bone-marrow transplant recipients with haematological malignancies (29 with acute nonlymphoblastic leukaemia, 31 with acute lymphoblastic leukaemia, nine with CML and three with myelofibrosis, IgA myeloma and T-cell lymphoma, respectively) were investigated for the frequency of relapses 1 year or later after bone-marrow transplantation. Seven relapses occurred from 30 to 850 d after transplantation (median 180 d). All relapses occurred in patients with acute leukaemia less than or equal to 18 years of age with a high risk for relapse, i.e. transplanted in second or later remission or with more than 10% blasts in the marrow before transplantation. Among all patients the probability of relapse was increased in patients without cytomegalovirus (CMV) infection (P = 0.001) and in patients without chronic GVHD (P = 0.049). Among leukaemic patients less than or equal to 18 years of age with a high risk of relapse all relapses occurred in patients (n = 11) without CMV infection, whereas no relapses were seen in patients (n = 13) with CMV infection (P = 0.006). Known risk factors for leukaemic relapse were comparable in both groups.

Rejection of murine ovarian cancer following treatment with regional immunotherapy: correlations with a neutrophil-mediated activation of cytostatic macrophages

Rejection of the murine ovarian teratocarcinoma (MOT) in C3HeB/FeJ mice, following intraperitoneal (ip) treatment with Corynebacterium parvum (C. parvum), is abrogated by injections of silica. We, therefore, investigated whether C. parvum-elicited macrophages affect MOT targets in vitro. Tumor-cytostatic, but not cytolytic, macrophages were detected in normal and tumor-challenged mice treated with C. parvum. The dose responsiveness and kinetics of macrophage activation strongly correlated with tumor rejection. A pyridine extract of C. parvum, possessing greatly diminished tumor rejection properties, was significantly less effective in activating macrophages. Cytostatic macrophage activation and prevention of tumor outgrowth also followed treatment in C3H/HEJ mice, a strain with a known deficiency in cytolytic macrophage function. Peritoneal neutrophils, obtained 6 hr after treatment with C. parvum, were capable of activating cytostatic macrophages when reinjected ip into normal mice. These results indicate a critical role for tumor cytostatic macrophages in this immunotherapy model and suggest their activation is mediated by inflammatory neutrophils.

Augmentation of mouse natural killer cell activity by Lactobacillus casei and its surface antigens

Lactobacillus casei YIT 9018 (LC 9018) augmented the natural killer (NK) cell activity of spleen cells from inbred BALB/c mice injected intravenously with LC 9018 or intraperitoneally with polyinosinate -polycytidylate. Augmentation of this activity by LC 9018 was also observed in male C3H/He, CBA/N, and C57BL/6 mice. The spleen cells exhibited no cytolytic activity against P815, a cell line insensitive to NK cells. The cytolytic activity of the spleen cells increased 2 days after the injection of 250 micrograms of LC 9018/mouse, peaked on day 3, and gradually declined thereafter. The increase caused by LC 9018 was also observed in normal and Meth A-bearing mice. In vitro treatment with anti-asialo GM1 antibody plus complement completely abrogated the LC 9018-augmented murine NK cell activity. The NK activity on the 3rd day after LC 9018 injection was reduced by in vitro treatment with anti-Thy 1.2 monoclonal antibody plus complement to half of that observed when treatment was with complement alone. This suggests that there were two populations of NK cells in the spleen cell suspension derived from LC 9018-treated mice. One population was asialo GM1-positive and Thy 1-negative, the other was asialo GM1-positive and Thy 1-positive.

Analysis of metastatic spread and growth of tumor cells in mice with depressed natural killer activity by anti-asialo GM1 antibody or anticancer agents

The mechanism of artificial and spontaneous metastases of tumor was analyzed in B16 melanoma cells and C57BL/6 mice by using anti-asialo GM1 antibody and anticancer agents. Single administrations of 500 micrograms anti-asialo GM1 antibody resulted in significantly decreased NK activity in spleen cells of C57BL/6 mice, lasting 10 days from the day following administration. Treatment with anti-asialo GM1 antibody never decreased the function of T lymphocytes measured by blastogenesis with phytohemagglutinin or T cell growth factor. The tumoricidal functions of activated macrophages but not of resident macrophages were decreased by in vivo treatment with anti-asialo GM1 antibody. The anti-asialo GM1 antibody was evaluated in terms of the enhancing effect on pulmonary metastases with regard to the timing of administration. Treatment with anti-asialo GM1 antibody 1 day before or on the day of tumor inoculation resulted in a substantial increase in the number of artificial pulmonary metastases. In the experimental system of spontaneous metastases, anti-asialo GM1 antibody most effectively increased the number of pulmonary metastases when administered 1-2 weeks before the removal of primary tumor, when the tumor cells are thought to be released into blood circulation from the primary site. In addition, accelerated growth of transplanted tumors at the primary site was observed in mice treated with anti-asialo GM1 antibody. These results strongly suggest that anti-asialo GM1 antibody enhances the incidence of in vivo tumor metastases and the growth of transplanted tumor mainly by suppressing the function of NK cells. The maximum effective dose (MED) of mitomycin C or its derivative (M-83) suppressed NK activity significantly, and pretreatment with these anticancer agents enhanced the growth of the artificial pulmonary and liver metastases. In contrast, the MED of cDDP showed no effect on the NK activity or the numbers of pulmonary and liver metastases. These results indicate that the depression of NK activity induced by chemotherapy results in the promotion of metastatic disease. From these studies it can be concluded that NK cells have a key role in the control of metastases of malignant disease, and that support of NK activity is very important for the prevention of metastases.

Studies on natural killer cell activity and the influence of Corynebacterium parvum on murine T-cell leukemogenesis induced by butylnitrosourea

Butylnitrosourea (BNU) was used to induce thymic lymphomas in BDF1 mice. During and after the 12-week BNU exposure the spontaneous NK cell activity against YAC-1 cells and that arising 4 days after stimulation with Corynebacterium parvum (CP) were measured, as were the mitogen responses of splenic T and B cells. In addition to BNU, groups of mice received multiple injections of the interferon inducer CP during or after the BNU exposure period. The results show a slight impairment of the NK cell activity by BNU and also after the injections of CP depending heavily on the treatment protocol. After the multiple injections of CP, either into BNU-treated mice or into controls, no further stimulation by CP was possible. The mitogen responses, reduced after BNU, were further reduced after the additional treatment. Both effects can be explained by the known induction of suppressor cells by CP. Although these treatments had pronounced effects on the parameters tested in vitro there was no significant influence on the development of thymic lymphomas in vivo.

Protection of mice against influenza virus infection: enhancement of nonspecific cellular responses by Corynebacterium parvum

Groups of C57BL/6J, BALB/c, BALB/c, nu+/nu+ mice, inoculated intranasally with Corynebacterium parvum (350 micrograms/mouse) were protected from death by an otherwise lethal dose of influenza virus, A/WSN (H1N1) inoculated 3 days later. The lungs of C. parvum-treated, virus-infected C57BL/6J, BALB/c, or BALB/c nu+/nu+ mice contained significantly less infectious virus than did controls, and this reduction was apparent as soon as 24 hr after virus inoculation. The maximum protective effect correlated with increased lung interferon levels. C. parvum treatment caused an increase in the lung cell number which was in part due to a large increase (ca. 10-fold) in macrophage content, and the natural killer cell activity was also enhanced, though not as markedly as occurred 3 days after infection. Most (greater than 85%) of the resident macrophages in normal lungs were susceptible to infection by virus (as indicated by hemadsorption), whereas most of those recovered from the lungs of C. parvum-treated mice resisted infection. Despite the increase in macrophage content, the level of specific immune responses to infection, such as cytotoxic T-cell activity, DTH reaction, and antihemagglutinin antibody, remained unchanged by C. parvum treatment so that the major if not only effect of this treatment was on the level of the less-specific components of the immune system.

Selective depletion of NK cell activity in vivo and its effect on the growth of NK-sensitive and NK-resistant tumor cell variants

Intravenous injection of rabbit anti-asialo-GM1 serum, an antiserum previouslY shown to eliminate splenic natural killer (NK) activity in vitro, profoundly depressed NK activity in CBA, DBA/2 and BALB/c nu/nu mice. The effect on NK activity was selective, as treatment of mice with anti-asialo-GM1 serum did not affect the development of other cytotoxic cells including cytotoxic macrophages following injection of poly I:C, or cytotoxic T cells in response to allogeneic cells. The role of NK cells in controlling tumor cell growth was investigated using an NK-sensitive (cl 27v-1C2) and an NK-resistant (cl 27av) subline of the murine lymphoma L5178Y. Initial studies showed that cl 27v-1C2 cells were at least 100 times less tumorigenic than were cl 27av cells in both syngeneic DBA/2 mice and BALB/c nu/nu mice. In addition, treatment of DBA/2 mice with poly I:C, which boosted NK activity, markedly depressed the growth of cl 27v-1C2 cells, but not of cl 27av cells. On the other hand, treatment of DBA/2 mice and BALB/c nu/nu mice with anti-asialo-GM1 serum led to a marked increase in tumorigenicity of cl 27v 1C2 cells, but had no effect on the tumorigenicity of cl 27av cells. In addition, the protection against cl 27v-1C2 growth afforded by poly-I:C treatment was abrogated by injection oif anti-asialo-GM1 serum. The possibility that the effects observed were caused by binding of the injected antibodies to the tumor cells was minimized by: (1) using a clone of tumor cells (cl 27v-1C2) that lacks chemically detectable asialo-GM1, and (2) pretreating animals with anti-asialo-GM1 rather than administering antiserum and tumor cells concurrently. These studies provided compelling evidence that NK cells could play an active role in controlling tumor growth. Selective depletion of NK activity by injection of anti-asialo-GM1 serum is a method which would be generally applicable to studying the role of NK cells in disease processes.

Analysis of natural killer activity and antibody-dependent cellular cytotoxicity in healthy volunteers and in patients with primary lung cancer and metastatic pulmonary tumors

To clarify the contribution of ADCC and NK activities to host immune response against cancer, the characteristics of cells mediating these activities were examined in the peripheral blood lymphocytes of normal volunteers, and the changes of these activities were also evaluated in patients with lung cancer and metastatic pulmonary tumors before and after chemotherapy. OAT cells derived from small cell carcinoma of the lung and K-562 cells derived from erythroleukemia were used as target cells of ADCC and/or NK assay. ADCC and NK activities were not changed according to age, sex, and blood type. Mild and marked personal difference were observed in ADCC and NK activity, respectively. These activities were also influenced by environment. ADCC and NK activities of normal adult volunteers were diversely correlated at the coefficient of gamma-0.426. NK activities were high against K-562 and CCRF-CEM cells, and low against BALL and OAT cells. NK activity against K-562 cells was strongly inhibited by K-562 or CCRF-CEM cells with high NK sensitivity, on the other hand, it was slightly inhibited by OAT and BALL cells with low NK sensitivity. NK activity against OAT cells was strongly inhibited by OAT, K-562 and CCRF-CEM cells, but not inhibited by BALL cells. The effector cells mediating NK activity were identified as non-adherent, E-receptor-positive, Fc-receptor-positive small lymphocytes. NK activity was not decreased before chemotherapy in patients with stage III primary lung cancer and metastatic pulmonary tumors. It was decreased only in patients of bad performance status, and it was significantly decreased in all patients after chemotherapy. ADCC also exhibited the tendency to decrease after chemotherapy in tumor-bearing patients. The recovery of NK-activity after chemotherapy well correlated with the effect of chemotherapy.

Corynebacterium parvum stimulation of adherent and non-adherent cytotoxic cells in mice

Two naturally occurring cytotoxic cell populations have been identified in the peritoneal cavity of mice inoculated with C. parvum (CP), and are distinguishable on the basis of target-cell reactivity and intrinsic properties. The first effector cell was non-adherent to nylon wool and glass and non-phagocytic. These cells were selectively cytotoxic to the NK-sensitive target cell line K562, and present in the peritoneal cavity of mice 2 days after treatment with 700 micrograms of CP. The second cytotoxic effector cell was adherent to nylon wool and glass, and killed EL4 lymphoma cells derived from in vivo tumour transplants; these target cells are susceptible to phagocytic cell killing, but not NK-cell cytotoxicity in short-term (4h) assays. The adherent cytotoxic population of effector cells was present 4 days after inoculation of CP. In vivo studies showed that CP injected i.p. induced resistance to i.p. challenge with lymphoma EL4 cells, but no resistance was evident when the challenge dose was administered s.c. Adoptive-transfer studies showed that the effector cell type responsible for inhibiting tumour growth was nylon-wool adherent, probably CP-activated macrophages.

Mechanisms of anti-tumor action of Corynebacterium parvum. I. Potentiated tumor-specific immunity and its therapeutic limitations

The anti-tumor mechanism in mice induced by a subcutaneous injection of syngeneic tumor cells admixed with Corynebacterium parvum was investigated. When mice were implanted in a hind footpad with x 2 1096) tumor cells admixed with 100 microgram C. parvum, the tumor that emerged grew progressively for about 9 d and then underwent progressive and complete regression. It was found that this C. parvum-induced regression was associated with the acquisition of a systemic, T cell-mediated mechanism of immunity to tumor-specific transplantation antigens, which enabled the host to cause the regression of an untreated test tumor growing simultaneously at a distant site. The generation of a C. parvum-potentiated anti-tumor response was dependent on the presence of tumor cells in close association with C. parvum, tumor immunogenicity, and the quantity of tumor antigen in the admixture. The anti-tumor immunity was specific for the tumor in the therapeutic admixture and could be adoptively transferred to normal recipients with Thy-1.2-positive lymphocytes, but not with serum. Complete regression of a distant test tumor by the C. parvum-tumor admixture was limited to tumors below a certain critical size.

Corynebacterium parvum treatment of P388 tumor-bearing mice. I. Lysosomal enzyme levels in adherent peritoneal cells and peritoneal lavage fluid

BDF1 mice treated with Corynebacterium parvum (C. parvum) 2 days before an implant of 106 P388 leukemic cells had up to an 110% increase in survival time above control; Bacillus Calmette-Guérin (BCG) treatment was ineffective. Acid phosphatase and beta-glucuronidase were measured in adherent peritoneal lavage cells and beta-glucuronidase in peritoneal lavage fluid form mice treated with C. parvum or BCG 2 days before the implant of P388 cells. In the presence of the tumor, adherent peritoneal cells from C. parvum-treated animals had a 250-300% increased specific lysosomal enzyme activity above control values (cells form animals receiving tumor implant alone). Peak enzyme activity which occurred on day 3 was not present in adherent cells from BCG-treated tumor-bearing animals or the control animals. The beta-glucuronidase activity in peritoneal lavage fluid was elevated by the tumor cells, BCG, or C. parvum. Peak levels occurred on day 5 regardless of the treatment with an additive effect present on day 5 in animals receiving the combination of tumor with C. parvum. The evidence indicated the development of a different pattern of enhanced lysosomal enzyme activity if the immunopotentiator protected against the P388 tumor vs one that did not. Protection was associated with an increase in lysosomal enzyme activity in adherent cells with no increase in lavage fluid in the presence of tumor cells. Changes in cellular enzyme activity may prove to be diagnostic for antitumor activity by an immunostimulant.

Effect of leucocyte interferon on natural killer cells in healthy volunteers

The effect of partially purified human leucocyte interferon on natural killer activity (NK activity) of peripheral blood in six healthy volunteers was tested in this study. After 4 h of intradermal injection of interferon, a rapid transient decline in NK activity and in the number of NK cells (large granular lymphocytes) in peripheral blood was observed. The decline was most distinct at 20 h and recovered at 72 h. Since no clear activation of Nk cells in peripheral blood was detected, the results suggest an extravasation of NK cells as a result of interferon injection. NK cells did not accumulate at the injection site on the skin, because the suction blister fluids over the injection sites did not contain increased numbers of NK cells.

Factors affecting stimulation of natural cytotoxicity to a rat lymphoma by Corynebacterium parvum

Differences were seen in the ability of 2 strains of C. parvum to augment cytotoxicity attributable to NK cells towards a rat lymphoma. Furthermore, 2 batches of the same strain of C. parvum prepared by different methods also differed in their ability to augment cytotoxicity. Other factors influencing cytotoxicity were dose, route of inoculation and time after injection at which the assay was performed. Although all preparations of C. parvum augmented the cytotoxicity of peritoneal-exudate cells when injected i.p., only the most stimulatory preparation consistently augmented splenic cytotoxicity when given by this route. I.v. administration of 1 mg of C. parvum produced peak levels of splenic cytotoxicity 2-3 days later, but this response was strictly dose-dependent, since 1 microgram depressed splenic cytotoxicity. This dose-dependent effect also extended to ADCC, since 1 mg stimulated cytotoxicity towards antibody-coated P815 cells, whilst 1 microgram depressed it in a manner similar to its effect on natural cytotoxicity. Whilst the cytotoxic cells of stimulated rats closely resembled the NK cells of normal rats, BN rats responded differently to C. parvum from W/Fu or WAG rats, in that marked lysis of P815 or RBL-5 cells was observed, though these targets are usually resistant to lysis by rat NK cells in short-term assays.

Optimal conditions for antitumor activity of C. parvum against the ascites form of sarcoma 180

Single and multiple doses of Corynebacterium parvum (C. parvum) ranging from 0.1--60 mg/kg were tested for antitumor activity against 10(6) sarcoma 180 cells in male CD1 mice. Determinations were made of the optimal dose and time of treatment needed to produce maximum suppression of the tumor using both median survival time and percent survival to day 90 as endpoints. A dose of 1 mg/kg given 3 days before sarcoma 180 transplant produced complete protection (100% survival). All other treatment regimens produced less of an effect. Single doses of 1, 10 and 60 mg/kg had significant antitumor activity when administered either on day 3, 2, or 1 before tumor implant, 0.1 mg/kg protected only when given on day 3. All single doses given 5 or 8 days before and anytime after tumor were ineffective. Multiple doses were only of advantage over single doses when treatments were after tumor cell inoculation. In vitro cytotoxicity studies demonstrated that both 1 and 60 mg/kg enhanced tumor cell killing by cells isolated from the peritoneal cavity, with the 1 mg/kg dose producing a greater effect. It was concluded that dose and time of administration of C. parvum, in relation to tumor implant, were important in determining optimal antitumor activity against sarcoma 180.