Myelopoiesis-associated immune suppressor cells in mice bearing metastatic Lewis lung carcinoma tumors: gamma interferon plus tumor necrosis factor alpha synergistically reduces immune suppressor and tumor growth-promoting activities of bone marrow cells and diminishes tumor recurrence and metastasis.

Metastatic Lewis lung carcinoma (LLC) tumors stimulate myelopoiesis and, consequently, induce bone marrow cells to become immune suppressive to T cell blastogenesis and macrophage activation for tumor necrosis factor alpha (TNF-alpha) secretion. The suppressor cells phenotypically resembled granulocytic-monocytic progenitor cells. In order to diminish the presence of these immune suppressor cells, LLC-bearing mice were treated with low doses of gamma interferon (IFN-gamma) (100 units/mouse) plus TNF-alpha (10 units/mouse). Treatment of LLC-bearing mice with these low doses of IFN-gamma plus TNF-alpha diminished the suppressive activity of their bone marrow cells, as measured by the effect on normal macrophage activation to secrete TNF-alpha. In in vivo adoptive transfer studies, bone marrow from placebo-treated LLC-bearers stimulated tumor establishment and metastasis, while the bone marrow of IFN-gamma-plus TNF-alpha-treated tumor-bearers diminished LLC establishment and metastasis. The effect of the low dose treatments with IFN-gamma and/or TNF-alpha on the recurrence of excised s.c. tumors was also assessed. Treatment of mice following tumor excision with either IFN-gamma, TNF-alpha, or the combination of IFN-gamma plus TNF-alpha reduced recurrence. However, in the animals with recurring tumors only the combined IFN-gamma plus TNF-alpha treatment effectively diminished the development of lung metastases. These results demonstrate that low dose IFN-gamma plus TNF-alpha treatment diminishes the presence of suppressor and tumor growth-promoting activities of bone marrow and reduces tumor recurrence and metastasis.     

Synergistic effects of granulocyte-colony stimulating factor and macrophage-colony stimulating factor on recovery of donor hematopoietic cells in allogeneic bone marrow transplantation

G-CSF and M-CSF are used clinically to augment hematopoiesis after bone marrow transplantation (BMT) and chemotherapy. In this paper, we examined the synergistic effect of G-CSF and M-CSF on hematopoietic recovery in allogeneic BMT as a model of human BMT. We performed BMT from eGFP-transgenic mice (C57BL/6 background; H-2b) into lethally-irradiated C3H (H-2k). From the day after BMT, G-CSF and/or M-CSF were injected for 5 consecutive days. Not only the numbers of day 12 CFU-S and spleen weight, but also white blood cell (WBC) counts in the peripheral blood (PB) and nuclear cells in the bone marrow (BM) increased in the mice treated with G-CSF and/or M-CSF 12 days after BMT. Moreover, the number of donor-type WBCs in the PB and donor-type nuclear cells in the BM also increased in the mice treated with G-CSF and/or M-CSF. The effects were pronounced when G-CSF and M-CSF were used together rather than independently. These results suggest that treatment with the combination of G-CSF and M-CSF has a synergistic effect on hematopoiesis in allogeneic BMT.     

Effects of cancer immunotherapy with indomethacin and interleukin-2 on murine hemopoietic stem cells.

We examined: (a) whether in vitro-generated lymphocyte-activated killer (LAK) cells from normal mice and splenic killer cells from tumor-bearing mice subjected to interleukin-2 (IL-2) therapy alone or in combination with chronic indomethacin therapy have any detrimental effects on the spleen colony-forming units (CFU-S) of the normal bone marrow (BM); and (b) the effects of these immunotherapy protocols on CFU-S numbers in host hemopoietic organs. Effects of in vitro-generated LAK cells (normal C3H/HeN mouse splenocytes cultured with 1000 units IL-2/10(6) cells for 72 h) on BM CFU-S were examined by incubating macrophage-depleted BM cells with LAK cells at 1:2.5 and 1:5 BM:LAK cell ratios or with LAK cell supernatant for 4 h. The cells were washed and subsequently injected into irradiated mice. Irradiated mice were also reconstituted with BM cells or LAK cells incubated alone. Spleen colonies were scored macroscopically and microscopically on day 7 after reconstitution of lethally irradiated mice with the various cell combinations. A comparison of colony numbers produced by LAK and BM cell mixture revealed that LAK cells at either dose had no suppressive effect on the colony-forming ability of BM at the macroscopic and microscopic levels of analysis. The supernatant of cultured LAK cells had a minor suppressive effect on colony formation at the macroscopic but not the microscopic level of analysis, indicating the presence of one or more suppressive factors capable of mediating a short-term inhibitory effect. In the immunotherapy experiment, C3H/HeN mice transplanted s.c. with 5 x 10(5) C3L5 mammary adenocarcinoma cells received either vehicle alone (controls), IL-2 (1.5 x 10(4) Cetus units i.p. every 8 h on days 10-14 and days 20-25), or chronic indomethacin therapy (10 micrograms/ml in drinking water from day 5 onwards) plus IL-2 as above. Animals were killed 24-25 days after tumor transplantation to examine: (a) the number of metastatic lung nodules; (b) the effects of co-incubating therapy-generated splenic effector cells with normal BM cells for 4 h on BM CFU-S, and (c) the CFU-S content of host BM and spleen. Results revealed a drop in spontaneous lung metastases from a mean of 50 in control mice to 18 with IL-2 therapy alone, and to 5 with chronic indomethacin therapy plus IL-2 therapy. Splenocytes from normal and tumor-bearing control or treated mice, when incubated with normal BM, had no effect on spleen colony formation at the macroscopic level.(ABSTRACT TRUNCATED AT 400 WORDS)     

Combination Treatment with Irritant and Recombinant Interleukin 2 in the Peritoneal Cavity for Evoking Effective Anti-tumor Activity: Generation of Lymphokine-activated Killer Cells and Tumor-specific Killer Cells

Meth A sarcoma, growing in the subcutaneous tissue of syngeneic BALB/c mice, regressed completely after an intraperitoneal (ip) injection of protease peptone (PP) (on day 6) followed by 2 ip administrations (on days 7 and 8) of human recombinant interleukin-2 (IL-2, 25 μg/day), whereas one such treatment alone had little effect on the tumor growth. While this combination treatment was effective in anti-asialo GM1 antibody-treated mice, no such effect was noted in T cell-depleted ATXFL (thymectomized, irradiated and fetal liver cell-reconstituted) mice. These results show that T cells are mainly responsible for this antitumor effect. Treatment with a combination of PP and IL-2, but not with either PP or IL-2 alone, resulted in a marked increase in the T cell population in the peritoneal cavity after the treatment. At an early stage after the combination treatment, both peritoneal exudate cells (PEC) and spleen cells exhibited killing activity with a promiscuous specificity. However, at a later stage, 7 days after the treatment, Meth A-specific killer activity was observed in both PEC and the spleen. Meth A rechallenge was rejected by the mice in which the tumor had regressed, but the antigenically different Meth 1 was accepted by them. A similar result was obtained in Winn's neutralization test. These results suggest that this combination treatment, which is effective in the generation of lymphokine-activated killer cells in the peritoneal cavity, finally resulted in the induction of tumor-specific killer cells in the periphery. These results clearly show the anti-tumor efficacy of combination treatment with PP and rIL-2.     

Combination treatment with irritant and recombinant interleukin 2 in the peritoneal cavity for evoking effective anti-tumor activity: generation of lymphokine-activated killer cells and tumor-specific killer cells

Meth A sarcoma, growing in the subcutaneous tissue of syngeneic BALB/c mice, regressed completely after an intraperitoneal (ip) injection of proteose peptone (PP) (on day 6) followed by 2 ip administrations (on days 7 and 8) of human recombinant interleukin-2 (IL-2, 25 micrograms/day), whereas one such treatment alone had little effect on the tumor growth. While this combination treatment was effective in anti-asialo GM1 antibody-treated mice, no such effect was noted in T cell-depleted ATXFL (thymectomized, irradiated and fetal liver cell-reconstituted) mice. These results show that T cells are mainly responsible for this antitumor effect. Treatment with a combination of PP and IL-2, but not with either PP or IL-2 alone, resulted in a marked increase in the T cell population in the peritoneal cavity after the treatment. At an early stage after the combination treatment, both peritoneal exudate cells (PEC) and spleen cells exhibited killing activity with a promiscuous specificity. However, at a later stage, 7 days after the treatment, Meth A-specific killer activity was observed in both PEC and the spleen. Meth A rechallenge was rejected by the mice in which the tumor had regressed, but the antigenically different Meth 1 was accepted by them. A similar result was obtained in Winn's neutralization test. These results suggest that this combination treatment, which is effective in the generation of lymphokine-activated killer cells in the peritoneal cavity, finally resulted in the induction of tumor-specific killer cells in the periphery. These results clearly show the anti-tumor efficacy of combination treatment with PP and rIL-2.     

Effects of interleukin 2 treatment combined with local hyperthermia in mice inoculated with Lewis lung carcinoma cells

Recombinant human (rhu) interleukin 2 (IL-2) was evaluated alone and in combination with local hyperthermia (LH) in mice inoculated s.c. with 5 x 10(5) Lewis lung carcinoma cells. Four treatment regimens were begun 6 days postinoculation at a time when the tumor had grown to approximately 8.0 mm in diameter. Treatments were: group 1, saline injected as control; group 2, LH; group 3, rhuIL-2; or group 4, LH combined with rhuIL-2. LH utilized hot water circulation by a Brann Thermomix 1420. The intratumor temperature was maintained at 43 +/- 0.2 degrees C for 30 min each on days 6 and 10 and rhuIL-2 was given s.c. at 5 x 10(4) units twice a day for 5 days. Thirty mice in each group were sacrificed 28 days after tumor inoculation. An additional 20 mice in each group were observed for survival time. The size of primary tumor and the number of lung metastases were reduced and the survival time was prolonged in mice treated by either LH or IL-2. However, a greater antitumor effect in Lewis lung carcinoma tumor-bearing mice was observed using IL-2 therapy combined with LH. Tumor growth was associated with increased splenic granulocyte-macrophage progenitor cells and an abnormal L3T4+/Lyt-2+ lymphocyte subset ratio (less than 1.0). Splenic granulocyte-macrophage progenitor cell numbers and the L3T4+/Lyt-2+ ratio returned to normal in the group treated with combination therapy, the best responder group. The L3T4+/Lyt-2+ ratio did not change in the groups treated with single therapy. These results suggest the efficacy and possible clinical relevance of combined therapy with rhuIL-2 and LH for certain metastatic tumors.     

Adoptive transfer of immunity induced by semi-allogeneic hybrid cells,against a murine fibrosarcoma

Semi-allogeneic somatic hybrid cells derived from the fusion of a C57BL/6 fibrosarcoma (MCB6–1) and A9 cells (C3H origin) were used to immunize C57BL/6 mice against the parental tumor cells. These hybrid cells expressed H-2 histocompatibility antigens of both parental cells (H-2_b and H-2^k), and failed to produce tumors in normal C57BL/6 mice. A single i.p. injection of hybrid cells induced anti-tumor immunity which could be transferred to normal C57BL/6 recipient mice by immune spleen or peritoneal cells; the efficient cells were T cells, as this activity was completely abrogated by treatment with anti-Thy-1–2 antiserum and complement. Among immune splenic T cells, only the light-density T cells, obtained after fractionation on Percoll gradient, were effective in the transfer of immunity. Immunity induced by the hybrid cells was specific for MCB6-1 parental tumor cells. This immunity could be transferred during two brief periods, 7 to 12 days, and 40 to 50 days, after hybrid cell injection; there appeared to be an intermediate period, 12 to 40 days after immunization, during which no immunity could be transferred. These results suggest a suppressive mechanism implicated during hybrid cell immunization and interacting with the anti-tumor immune response.     

Therapeutic effects of monoclonal antibody g250, interferons and tumor necrosis factor,in mice with renal-cell carcinoma xenografts

Because renal-cell carcinoma (RCC) is considered relatively resistant to radio-and chemotherapy, RCC patients may benefit from new treatment modalities, e.g. immunotherapy. In vitro and in vivo studies suggest that combinations of cytokines such as interferon γ or interferon a (IFN-γ, IFN-α) and tumor necrosis factor a (TNF-α) may act synergistically. In this study we tested whether a monoclonal antibody (MAb) G250, reactive with a RCC-associated antigen, showed anti-tumor effects in vivoin nude mice with established s.c. human RCC xenografts, and also whether this MAb could enhance the anti-tumor effect of combinations of IFNs and TNF-α. Treatment with combinations of IFN-α/TNF-α or IFN-γ/TNF-α, or with MAb G250 alone, resulted in a significant inhibition of tumor growth. Treatment with MAb G250, in combination with IFN-γ/TNF-α, did not result in an improve anti-tumor effect as compared to that of either treatment alone. In contrast, MAb G250 combined with IFN-α/TNF-α resulted in a significantly enhanced anti-tumor response. In one experiment, 3 out of 10 mice showed complete tumor regression, with no recurrence after 90 days. Large numbers of infiltrating macrophages were found surrounding viable and necrotic tumor tissue after treatment with G250 combined with IFN-α/TNF-α. These results suggest that combination therapy, consisting of IFN-α, TNF-α and MAbs, may have therapeutic value in the treatment of RCC.     

Advanced Lewis Lung Carcinoma Cured by Tiazofurin as a System to Study Delayed Hemopoietic Effects of Cancer

Lewis lung carcinoma (LLC) induces a range ofhemopoietic alterations in its murine host including progressive anemia, thrombocytopenia, splenomegaly, neutrophilia, and marrow and splenic myeloid hyperplasia. Concentrations of both pluripotent and committed marrow hemopoietic progenitors is increased and the cycling fraction of granulocyte-macrophage progenitors is accelerated. We have developed a way to study whether these hemopoietic effects become long-term consequences of cancer, using LLC-bearing mice with advanced tumor treated with the antineoplastic agent tiazofurin, 2-β-D-ribofuranosyl-thiazole-4-carboxyamide, NSC 286193 (TZ). LLC mice were treated with a single dose of TZ either 150, 300, or 600 mg/kg, intraperitoneally on day 6 posttumor implant when lung metastases are present and all hemopoietic effects of the tumor are recognizable. Even a single dose of 150 mg/kg of TZ produced a significant survival advantage, and 600 mg/kg resulted in 30% of the animals remaining disease free during a 5-month follow-up. A 6-week treatment schedule was devised, administering TZ intraperitoneally, 600 mg/kg, weekly beginning on day 6. In this group, median survival was not reached after 9 months of follow-up. The only evidence of myelotoxicity produced by intermittent administration of TZ was a mild anemia which was fully reversible 2 weeks after discontinuance of the drug. No difference in white blood cell count, differential count, or platelet count was detected in tumor bearers and controls treated with TZ. Both pluripotent and committed marrow hemopoietic precursors remained unchanged in TZ-LLC, TZ-controb and untreated controls throughout treatment and 2 weeks thereafter. This study demonstrates that TZ-cured LLC mice are suitable to explore late hemopoietic effects of cancer.     

In vivo studies with Interleukin-12 alone and in combination with monocyte colony-stimulating factor and/or fractionated radiation treatment

Interleukin-12 (IL-12) was found to be an active anti-tumor agent in 3 established murine solid tumors: B16 melanoma, Lewis lung carcinoma and renal cell carcinoma (RenCa). IL-12 was well tolerated over a 100-fold dose range. Only the high-dose treatment of IL-12 resulted in a clear reduction in the number of lung metastases from B16 melanoma and Lewis lung carcinoma. Treatment of animals bearing Lewis lung carcinoma with IL-12 in combination with fractionated radiation therapy was markedly dose-modifying, indicating that IL-12 was acting synergistically with radiation. Treatment of animals bearing the same tumor with monocyte colony-stimulating factor (M-CSF) along with fractionated radiation therapy resulted in a parallel increase in tumor growth delay with increasing dose of M-CSF, indicating that M-CSF was affecting a subpopulation of tumor cells in addition to those killed by radiation therapy. The combination of IL-12 with M-CSF was most effective with radiation therapy, especially in the clinically relevant dosages of 2 and 3 Gy per fraction. By isobologram analysis, IL-12 and M-CSF, along with fractionated radiation therapy, resulted in a greater-than-additive (synergistic) tumor response. © 1996 Wiley-Liss, Inc.     

Does macrophage-colony stimulating factor stimulate rat haematopoietic cells?

It is known that colony stimulating factors (CSFs) stimulate the myeloid cells of bone marrow and splenic cells in rodents. The effects of macrophage (M)-CSF on the activities of thymidylate synthase and thymidine kinase, involved in de novo and salvage pathways for pyrimidine nucleotide synthesis, respectively, in haematopoietic cells of bone marrow and spleen were investigated in rats. A single M-CSF injection did not elevate the mRNA expression levels of the enzymes in bone marrow cells 6 h after treatment, but it enhanced the splenic thymidylate synthase mRNA expression. M-CSF stimulated the splenic thymidylate synthase activity without an increase of the peripheral granulocytes. The effect of M-CSF on granulocytes is considered to be weak compared with that of granulocyte (G)-CSF, because of the indirect secretion of endogenous G-CSF from the cells with M-CSF receptors stimulated by exogenous M-CSF. Since M-CSF was able temporarily to lead progenitor cells from long G1-phase into S-phase, M-CSF might accelerate the anticancer effects when used together with anticancer agents.     

Potentiation of natural killer cell activity and tumor immunity by diacetylputrescine

The objective of the present investigation was to evaluate the immunomodulating properties of tetramethylenebisacetamide (N,N' 1-diacetylputrescine, DAP), a known inducer of cellular differentiation. We examined the effect of DAP administration in vivo on splenic and nonadherent peritoneal natural killer (NK) cell activity. A single i.p. injection of DAP (100 mg/kg) enhanced cytolytic activity directed against YAC-1 and MCA-38 tumor target cells 2- to 3-fold. Cytolytic activity peaked 3 days following DAP injection. DAP treatment increased the frequency of asialo-GM1-positive splenocytes to 15% compared with 5% for vehicle treated controls. Furthermore, cytolytic activity could be eliminated by treatment with anti-asialo-GM1 antibodies and complement. Lysis of NK-resistant P815 and EL4 tumor target cells was not observed in leukocytes from DAP-treated mice. DAP treatment of mice given injections i.p. of MCA-38 tumor cells increased survival time of the mice by 37%, curing 10% of the animals of the tumor. DAP treatment of mice given injections intrasplenically of MCA-38 tumor cells reduced both the number and the size of the hepatic metastases. The antitumor effect of DAP in vivo could be eliminated by pretreating mice with anti-asialo-GM1 antibodies or utilizing NK cell deficient beige (bg/bg) mice. These results indicate that the observed anti-tumor activity of DAP is mediated, at least in part, by NK cells.     

Early hematopoietic events during tumor growth in mice

Lewis lung carcinoma (LLC) of C57BL/6 mice, a transplantable tumor widely metastatic by 6-7 days post implant (PI), caused hematopoietic alterations such as progressive anemia (hemoglobin: day 1 PI, 11.0 g/dl; day 19 PI, 7.8 g/dl), neutrophilia (neutrophils: day 1 PI, 2 X 10(3)/microliter; day 19 PI, 22 X 10(3)/microliter), and marrow and splenic myeloid hyperplasia (marrow myeloid-to-erythroid ratio: day 1 PI, 1:1; day 7 PI, 3:1). Accompanying these changes were an increased concentration of marrow granulocyte-macrophage colony-forming units (culture) (GM-CFUC) (day 3 PI, LLC 185 +/- 27% of control; day 19 PI, LLC 265 +/- 10% of control) and accelerated cycling of these myeloid progenitors [day 3 PI, LLC 45.3 +/- 6.5% GM-CFUC in cycle vs. sham (media) injected 17.5 +/- 10.5%; day 7 PI, LLC 52.2 +/- 2.5% vs. sham (media) injected 29.8 +/- 9.8%; day 11 PI, LLC 56.2 +/- 4.4% vs. sham (media) injected 22.2 +/- 14%]. This study questioned whether enhanced hematopoiesis was a result of progressive tumor growth or whether the injection of tumor cells could evoke the response. By use of groups of C57BL/6 mice given an injection of live LLC cells, x-irradiated killed LLC cells, or media, the hematopoietic response to live LLC cells versus dead LLC cells could be dissected. A biphasic colony-stimulating activity (CSA) response in the sera of tumor bearers was found to account for the myelopoietic changes. The first wave of CSA from days 1 to 3 PI stimulated 168 +/- 3.7% more GM-CFUC than control sera and was likely released by dead cells of the tumor inoculum; the second wave from day 7 onward stimulated 220 +/- 7.6% more colonies and was a result of the enlarging tumor mass. Tumor growth was necessary for GM-CFUC proliferation, and the declining growth fraction at day 19 in LLC-bearing mice suggested that hematopoietic exhaustion was a consequence of tumor growth.     

Inhibition of pulmonary metastasis by Nocardia rubra cell wall skeleton, with special reference to macrophage activation

The antimetastatic activity of Nocardia rubra cell wall skeleton (N-CWS) with or without cyclophosphamide was examined in an experimental model of pulmonary metastasis induced by Lewis lung carcinoma in C57BL/6 mice. Lewis lung carcinoma cells were implanted into the footpads of mice, and the implanted tumors were removed 9 to 10 days later. Pulmonary metastatic nodules began to develop a few days after the implanted tumor was removed. The inhibitory effect of N-CWS was evaluated from the number of pulmonary surface nodules about 3 weeks after tumor implantation. The antimetastatic activity of N-CWS depended upon the dose, time, and route of its injection. Injection of N-CWS i.v. after removal of the implanted tumor caused the greatest inhibition of development of pulmonary metastases. Therapy with N-CWS plus cyclophosphamide prolonged significantly the survival of mice with metastases. The cytotoxic activities of peritoneal macrophages and macrophages in the lung against Lewis lung carcinoma cells were enhanced in mice treated with N-CWS. Injection i.v. of peritoneal macrophages activated with N-CWS inhibited pulmonary metastases. The role of macrophages in inhibition of micrometastasis in the lung is discussed.     

Co-treatment with therapeutic neural stem cells expressing carboxyl esterase and CPT-11 inhibit growth of primary and metastatic lung cancers in mice

In this study, neural stem cells (NSCs)-derived enzyme/prodrug therapy (NDEPT) was used to treat primary lung cancer or metastatic lung cancer in the brain. To confirm the anti-tumor effect of NSCs expressing carboxyl esterase (CE), A549 lung cancer cells were treated with HB1.F3.CE cells and CPT-11. A significant decrease in the viability/proliferation of lung cancer cells was observed compared to negative controls or cells treated with CPT-11 alone. To produce a mouse model of primary lung cancer or lung cancer metastasis to the brain, A549 cells were implanted in the dorsal area of the mouse or right hemisphere. CM-DiI pre-stained stem cells were implanted near the primary lung cancer tumor mass or in the contralateral brain. Two days after stem cells injection, mice were inoculated with CPT-11 (13.5 kg/mouse/day) via intraperitoneal injection. In the primary lung cancer mouse models, tumor mass was 80% lower in response to HB1.F3.CE in conjunction with CPT-11, while it was only reduced by 40% in the group treated with CPT-11 alone. Additionally, therapeutic efficacy of co-treatment with stem cells and CPT-11 was confirmed by detection of apoptosis and necrosis in primary and metastatic lung cancer tissues. By secreting VEGF, tumor cells modulate Erk1/2 and Akt signaling and migration of stem cells. This further increased tumor-selectivity of stem cell/prodrug co-therapy. Overall, these results indicate that NSCs expressing the therapeutic gene may be a powerful tool for treatment of primary lung cancer or metastasis of lung cancer to the brain.     

Local low-dose interleukin-2 induces systemic immunity when combined with radiotherapy of cancer. A pre-clinical study

Tumor recurrence and outgrowth of metastases limit the therapeutical effect of radiotherapy. We have tested whether these problems can be overcome by supplementing radiotherapy with locoregional interleukin-2 (IL-2) treatment. The SL2 lymphoma and the M8013 mammary carcinoma were used. Mice bearing a 10-day-old s.c. tumor were locally irradiated and were treated daily with IL-2 peritumorally for 5 or 10 days. Low-dose IL-2 therapy improved local response (LR) and increased disease-free survival (DFS) in both tumor models following either single-dose irradiation or fractionated irradiation. For example, 93% of SL2-bearing mice treated with single-dose irradiation and 10 days of IL-2 experienced long-term DFS, compared with 17% for irradiation alone (p < 0.0001). Additionally, treatment of one tumor with irradiation +IL-2 led to anti-tumor effects in a second, untreated tumor in 80% of SL2-bearing mice. LR was increased to 100% and DFS to 70% when the second, non-irradiated tumor was also treated with peritumoral IL-2. We conclude that supplementing local radiotherapy with low doses of IL-2 results in increased local tumor control and regression of distant, non-irradiated tumors. This type of radioimmunotherapy is a promising new approach for the clinic. Int. J. Cancer 72:1003–1007, 1997. © 1997 Wiley-Liss, Inc.     

Inhibition of spleen cell cytotoxic capacity toward tumor by elevated prostaglandin E2 levels in mice bearing Lewis lung carcinoma

The capacity to generate cytotoxic cells toward Lewis lung carcinoma (LLC) in mixed cultures of stimulator LLC and responder spleen cells of LLC-bearing C57BL/6 mice was monitored during the course of tumor growth. The cytotoxic response of mice bearing tumors that were not yet palpable was enhanced. However, as palpable tumors developed and tumor growth progressed, their cytotoxic capacity became suppressed. Concurrent with this decline in cytotoxic capacity, there was an increase in systemic immunoreactive prostaglandin E2 (PGE2) concentrations in tumor-bearing mice. Administration of indomethacin, a prostaglandin synthesis inhibitor, to LLC-bearing mice prevented the rise in PGE2 concentrations and the suppression in cytotoxic capacity toward LLC. A relationship between the elevated immunoreactive PGE2 levels, suppression in cytotoxic capacity, and progressive tumor growth was indicated when administration of indomethacin to tumor-bearing mice also reduced the rate of tumor development.     

Inhibition of tumor growth and metastases in mice with Lewis lung tumors by vitamin A and BCG]

The anti-tumor effect of vitamin A and/or BCG was investigated in Lewis lung tumor system. Tumor growth and lung metastases were significantly suppressed, when tumor cells were mixed with BCG and inoculated subcutaneously into vitamin A-treated animals. Survival time was also prolonged by the same treatment. Vitamin A alone, without BCG, showed no effect on tumor growth, lung metastases or survival time.     

3-(5'羟甲基-2'呋喃基)-1苯甲基吲唑联合放疗治疗Lewis移植瘤小鼠的实验研究

目的 观察3-(5'羟甲基-2'呋喃基)-1苯甲基吲唑(YC-1)联合不同放射治疗方式对Lewis肺癌移植瘤的疗效,并对其机制进行初步探讨.方法 对Lewis肺癌荷瘤C57BL/6小鼠进行随机分组后,Yc-1按照每天10 μg/g连续7 d腹腔注射,放疗采用6 MeV(3.0 Gy/min)电子线连续3 d照射,单次剂量5 Gy,照射总剂量为15 Gy.分别测量各组肿瘤长短径绘制抑瘤曲线,记录各组小鼠的体重变化;免疫组织化学法对低氧诱导因子1 α(HIF-1α)和血管内皮生长因子(VEGF)蛋白表达进行半定量分析,TUNEL凋亡试剂盒检测各组的细胞凋亡情况;Kaplan-Meier法比较各远期组的生存时间.结果 YC-1+放疗(R)组和R+YC-1组的肿瘤生长较YC-1组、R组及空白组(NS组和DMSO组)明显延缓.YC-1+R组抑瘤效果较R+YC-1组强,其差异有统计学意义.YC-1和放疗联合后能增强对HIF-1α、VEGF表达的抑制,提高凋亡率,延长荷瘤小鼠的生存时间.结论 YC-1与放疗联合应用能明显增强放疗的抑瘤作用,且先放疗再给予YC-1抑瘤效果更为明显,而单独应用YC-1效果不明显.     

Dysfunction of sinus macrophages in tumor-bearing host induces resistance to immunotherapy

Sinus macrophages in draining lymph nodes (DLNs) are involved in anti-tumor immune reactions. CD169 (Sialoadhesin, Siglec-1) is expressed on sinus macrophages and is considered a surrogate marker for the immunostimulatory phenotype of macrophages. In this study, the significance of sinus macrophages in immunotherapy was evaluated using mouse models. Treatment with anti-programmed death-ligand 1 (PD-L1) antibody suppressed the subcutaneous tumor growth of MC38 and E0771 cells but was not effective against MB49 and LLC tumors. Decreased cytotoxic T-lymphocyte (CTL) infiltration in tumor tissues and CD169 expression in sinus macrophages were observed in MB49 and LLC cells compared to corresponding parameters in MC38 and E0771 cells. The anti-tumor effects of the anti-PD-L1 antibody on MC38 and E0771 cells were abolished when sinus macrophages in DLNs were depleted, suggesting that sinus macrophages are involved in the therapeutic effect of the anti-PD-L1 antibody. Naringin activated sinus macrophages. Naringin inhibited tumor growth in MB49- and LLC-bearing mice but did not affect that in MC38- and E0771-bearing mice. The infiltration of CTLs in tumor tissues and their activation were increased by naringin, and this effect was impaired when sinus macrophages were depleted. Combination therapy with naringin and anti-PD-L1 antibody suppressed MB49 tumor growth. In conclusion, CD169-positive sinus macrophages in DLNs are critical for anti-tumor immune responses, and naringin suppresses tumor growth by activating CD169-positive sinus macrophages and anti-tumor CTL responses. The activation status of sinus macrophages has been suggested to differ among tumor models, and this should be investigated in future studies.