同种异体LAK/IL-2经超声雾化吸入及胸腔内注射治疗晚期肺癌

将ＩＬ－２或ＩＦＮ－γ基因体内转染腹腔巨噬细胞（ＭΦ），其表达的基因产物能提高ＭΦ的细胞毒活性，并诱导ＭΦ分泌ＴＮＦ、ＩＬ－１和ＮＯ等抗肿瘤免疫介质，激发机体的非特异性免疫功能而产生抗肿瘤效应。特别是ＩＬ－２和ＩＦＮ－γ基因联合转染ＭΦ，其表达的产物既能使ＭΦ产生更强的细胞毒活性并发分泌高水平的ＴＮＦ、ＩＬ－１和ＮＯ，又能激活脾ＣＴＬ细胞，从而激发机体的非特异性和特异性免疫功能，产生更强的协同抗肿     

膜TNF—α在小鼠ConA—LAK细胞介导的MHC非限制性杀瘤效应 …

本文研究ＣｏｎＡ预刺激小鼠ＬＡＫ细胞的体外杀瘤活性，探讨膜ＴＮＦ－α在其杀瘤效应中的作用。结果表明，ＣｏｎＡ－ＬＡＫ可杀伤ＮＫ敏感的ＹＡＣ－１，ＴＮＦ敏感的１９２９及Ｈ－２低＝／无的ＨＣａ－Ｆ等肿瘤靶细胞，其杀瘤作用主要是直接杀伤，而效应细胞表面配体与靶细胞表面受体相互作用介导的非分泌途径起着重要的作用；ＣｏｎＡ－ＬＡＫ表达膜ＴＮＦ－α，后者参与杀伤ＴＮＦ敏感的肿瘤靶细胞，可能是介导ＭＨＣ非限制性     

抗APO-1单抗诱导人膀胱癌多药耐药细胞凋亡的研究

目的：研究巨噬细胞游抑制因子（ＭＩＦ）基因修饰的瘤苗诱导抗肿瘤免疫反应的机理。方法：ＭＩＦ基因修饰的ＦＢＬ３瘤苗小鼠免疫后,观察腹腔巨噬细胞数量和功能的变化。结果：ＭＩＦ基因修饰的瘤苗免疫后,小鼠腹腔巨噬细胞的数量,表面免疫相关分子的表达,以及ＴＮＦ－α和ＮＯ的分泌水平增高,吞哓功能、杀知性和抗原提呈功能增强。结论：ＭＩＦ基因修饰的瘤苗体内免疫后,其分泌的ＭＩＦ显著增强了巨噬细胞的功能,被活化的巨     

体内IL—2基因转染小鼠腹腔巨噬细胞的抗肿瘤作用

目的：研究ＩＬ２基因体内转染小鼠腹腔巨噬细胞，探讨基因的表达，抗肿瘤作用及其机理。方法：采用磷酸钙ＤＮＡ共沉淀法，将ｐＲＥＰ８ＩＬ２真核表达质粒直接注射至小鼠腹腔，转染腹腔巨噬细胞。结果：ＩＬ２基因可成功地转染腹腔巨噬细胞（ＭФ），并表达基因产物，能有效地抑制肿瘤的生长，转基因ＭФ及其表达产物可使脾ＮＫ活性和内源性ＬＡＫ活性增强，能增加腹腔ＭФ细胞毒活性并使ＭФ分泌ＴＮＦ、ＩＬ１和ＮＯ的水平增加。结论：本实验能有效地激活机体的非特异性免疫功能，从而发挥抗肿瘤效应。     

成纤维细胞介导的人α型干扰素基因疗法与过继免疫化疗联合治疗人肝癌的实验研究

作者以皮下接种人肝细胞癌细胞ＳＭＭＣ７７２１的裸鼠为荷瘤模型，由人外周血单个核细胞经体外ＩＬ－２和丝裂霉素Ｃ灭活的人肝癌细胞ＳＭＭＣ７７２１共同刺激培养后激活的杀伤细胞（ＡＫ），研究了将成纤维细胞介导的人ＩＦＮ－α基因疗法与ＩＬ－２／ＡＫ／阿霉素过继免疫化疗联合应用后对肝癌的治疗作用。结果表明：（１）给肝癌裸鼠单独腹腔埋植人ＩＦＮ－α基因转移的ＮＩＨ３Ｔ３成纤维细胞（ＮＩＨ３Ｔ３－ＩＦＮ－α￣＋）就能显著抑制肝癌（皮下）体内生长，使荷瘤裸鼠存活期明显延长；（２）在腹腔埋植ＮＩＨ３Ｔ３－ＩＦＮ－α￣＋之后再静脉注射ＡＫ细胞、腹腔内注射ＩＬ－２，发现荷瘤裸鼠的皮下肿瘤结节生长抑制作用更明显；（３）将ＮＩＨ３Ｔ３－ＩＦＮ－α￣＋与ＩＬ－２／ＡＫ／阿霉素联合应用后，对肝癌裸鼠的治疗效果更佳。     

新城鸡瘟病毒诱导小鼠腹腔巨噬细胞产生肿瘤坏死因子的细胞毒活性研究

目的观察新城鸡瘟病毒Ｌ系（ＮＤＶ－Ｌ）诱导小鼠腹腔巨噬细胞（ＰＥＭΦ）产生的肿瘤坏死因子－α（ＴＮＦ－α）对肿瘤细胞的细胞毒性作用。方法采用噻唑蓝（ＭＴＴ）和３Ｈ－脱氧胸苷（３Ｈ－ＴｄＲ）标记肿瘤细胞的方法。结果ＮＤＶ－Ｌ可诱导小鼠ＰＥＭΦ产生ＴＮＦ－α，其产生的量随ＮＤＶ－Ｌ感染量的增加而活性增强。当ＮＤＶ－Ｌ感染剂量一定时，ＴＮＦ－α释放量在ＮＤＶ－Ｌ作用ＰＥＭΦ２４ｈ时为最强（１００Ｕ／ｍｌ）。用３Ｈ－ＴｄＲ标记肿瘤细胞（小鼠乳腺癌细胞系Ｃａ７６１－８６和小鼠肥大细胞瘤Ｐ８１５）做ＴＮＦ－α的细胞毒试验，表明其具有明显的杀伤活性。结论ＮＤＶ－Ｌ诱导小鼠腹腔巨噬细胞产生的ＴＮＦ－α具有明显的细胞毒活性。     

M-CSF、IL-1和TNF-α在骨巨细胞瘤中的表达及其意义

目的：探讨巨噬细胞集落刺激因子（Ｍ－ＣＳＦ）,白细胞介素－１（ＩＬ－１）和肿瘤坏死因子－α（ＴＮＦ－α）在骨巨细胞瘤（ＧＣＴ）形成及其溶骨中的作用。方法：运用免疫组化方法和细胞增养技术,观察Ｍ－ＣＳＦ、ＩＬ－１和ＴＮＦ－α在１８例ＧＣＴ中的表达及对ＧＣＴ溶骨的影响。结果：在ＧＣＴ中,Ｍ－ＣＳＦ主要由纤维母细胞样基质细胞（ＦＣ）分泌;巨噬细胞样基质细胞（ＨＣ）主要分泌ＩＬ－１和ＴＮＦ－α,少数分泌Ｉ     

细胞因子上调大肠癌细胞Fas配体表达

目的：研究白介素１８（ＩＬ－１８）等内源性细胞因子对大肠癌细胞ＦａｓＬ表达水平的调控作用。方法：采用Ｗｅｓｔｅｒｎ蛋白印迹法测定细胞因子处理后大肠癌细胞的ＦａｓＬ表达水平。结果：在检测的６株大肠癌细胞中,全部表达ＦａｓＬ蛋白;ＴＮＦ－α和ＩＦＮ－γ显著上调ＤＬＤ－１ ＦａｓＬ蛋白的表达水平;ＴＮＦ－α和ＩＦＮ－γ以及乙酸肉豆佛波醇（ｐｈｏｔｂｏｌ１２－ｍｙｒｉｓｔａｔｅ １３－ａｃｅｔａｔｅ,ＰＭ     

TNFα影响LAK细胞、化疗药物抗胃癌细胞作用的实验研究

观察ＴＮＦα对ＬＡＫ细胞、化疗药物抗胃癌作用的影响。方法以不同浓度ＴＮＦα与ＩＬ┐２配伍培养ＬＡＫ细胞，并使ＴＮＦα单抗阻断试验；以ＴＮＦα预处理胃癌细胞，观察ＴＮＦα影响ＬＡＫ抗瘤活性的特性及胃癌细胞对ＰＢＭＣ及ＬＡＫ的敏感性变化；以ＴＮＦα联用５┐ＦＵ，ＡＤＭ或ＭＭＣ观察体外、ＴＮＦ联用ＭＭＣ观察荷胃癌裸鼠体内的抗胃癌效应。结果ＴＮＦα在低浓度ＩＬ┐２下增加ＬＡＫ活性，使ＩＬ┐２诱导同等ＬＡＫ活性的浓度下降约１０倍；ＴＮＦα预处理胃癌细胞使ＰＢＭＣ、ＬＡＫ对其的抗瘤活性提高约１０％、９％。ＴＮＦα与５┐ＦＵ、ＡＤＭ或ＭＭＣ联合组体外、ＴＮＦ与ＭＭＣ联用组体内抑制胃癌细胞生长效应明显优于单用组，差异显著。结论ＴＮＦα在低浓度ＩＬ┐２下增加ＬＡＫ抗胃癌活性，ＴＮＦα预处理使胃癌细胞对ＰＢＭＣ及ＬＡＫ的敏感性增加；ＴＮＦα联合化疗药物５┐ＦＵ、ＡＤＭ或ＭＭＣ可使抗胃癌效应提高     

福氏完全佐剂包裹白细胞介素2和肿瘤坏死因子对小鼠S180肿瘤的抑制作用

本文报道一种新的免疫治疗方法。用福氏完全佐剂（Ｆｒｅｕｎｄ＇ｓ　ｃｏｍｐｌｅｔｅ　ａｄｊｕｖｅｎｔ，ＦＣＡ）包裹白细胞介素２（ｌｎｔｅｒｌｅｕｋｉｎ　２，ＩＬ－２）及／或肿瘤坏死因子（Ｔｕｍｏｒ　Ｎｅｃｒｏｓｉｓ　Ｆａｃｔｏｒ，ＴＮＦ）作了抗Ｓ１８Ｏ肉瘤的体内抗瘤实验。结果表明：ＩＬ－２及／或ＴＮＦ经佐剂包裹后，可明显减轻其毒副作用，并显著提高ＩＬ－２及／或ＴＮＦ的抗瘤作用。     

In vivo activation of nude mouse macrophages by human melanoma cells

Human melanoma cell lines inoculated ip in outbred nude mice were found to activate locally macrophages, which became tumoricidal for the EL 4 target cells in a 48-hour [3H]thymidine cytotoxicity assay. However, the kinetics of this activation largely depended on the tumorigenicity of the cell line used. One week after inoculation with a poorly tumorigenic cell line (PTCL), peritoneal macrophages showed a maximal tumoricidal activity, which then slowly declined to disappear on the 4th week. Macrophages obtained after inoculation of a highly tumorigenic cell line (HTCL) were also activated, but the level of their tumoricidal activity was somewhat lower and decreased more rapidly. Irradiated melanoma cells were also able to activate peritoneal macrophages. The inoculation of a higher number of melanoma cells (less than or equal to 8 X 10(7) cells) resulted in a parallel increase in the cytotoxicity of peritoneal macrophages when activated by PTCL and in a parallel decrease when activated by HTCL. Activated macrophages taken 1 week after tumor cell inoculation and further kept in vitro without additional stimulation progressively lost their tumoricidal activity, within 48 hours after being harvested from PTCL-inoculated mice and within 24 hours after being collected from HTCL-inoculated animals. These data allied to the in vivo capacity of peritoneal cells rich in activated macrophages to prevent the growth of HTCL in nude mice strongly leaned toward the idea that macrophages are involved in the tumor growth control in the absence of a specific immune response. In addition, tumor-macrophage interactions are likely to vary from tumor to tumor and may contribute to the expression of the xenografting capacity of human tumor cells.     

Interactions with host macrophages and ability of human melanoma cell lines to grow in nude mice

The interactions of nude mouse macrophages with five human melanoma cell lines, characterized by their resistance to mouse NK activity and varying in their ability to grow s.c. in nude mice, were investigated. These lines were equally susceptible in vitro to both cytostatic and tumoricidal activities of activated peritoneal macrophages collected from nude mice inoculated 3 days previously with Brucella abortus B19R strains. I.p. injection of a poorly tumorigenic melanoma cell line (PTCL) in nude mice was followed by the local appearance of macrophages able to kill these cells in a 48-hr 3H-thymidine cytotoxicity assay. The level of tumoricidal macrophages was maximum for the first week and then slowly declined to disappear by the 4th week following PTCL inoculation. The use of an HTCL instead of a PTCL also induced macrophages able to kill HTCL cells, but the cytotoxicity level was lower and the activity disappeared more rapidly. In cross-experiments using PTCL-activated macrophages as effectors on HTCL targets, these cells were found to be less sensitive than PTCL cells when macrophages were taken at weeks 2 and 3 following PTCL inoculation. To investigate whether tumoricidal macrophages activated in vivo with human melanoma cells could also act in vivo, we inoculated these s.c. into nude mice, simultaneously with live HTCL cells. Peritoneal cells rich in melanoma-activated macrophages prevented HTCL growth in most recipients, whereas spleen cells from the same donor mice did not modify the tumor take. These data indicate that xenogeneic tumors could activate nude mouse macrophages in vivo and suggest that the ability of human tumors to grow in nude mice could be related to their capacity to activate host macrophages locally and to the susceptibility of human tumor cells to the tumoricidal activity of activated macrophages.     

Differential effect of recombinant granulocyte macrophage colony-stimulating factor on human monocytes and alveolar macrophages

The effect of granulocyte-macrophage colony-stimulating factor (GM-CSF), a pluripotent cytokine, on tumoricidal activity of alveolar macrophages and monocytes from nonsmoking normal volunteers was compared using [3H]thymidine-labeled human tumor cells (SK-MEL-28, melanoma) as targets. A dose-response study (500-5000 units/ml) of recombinant GM-CSF indicated dramatic differences between cytotoxicity of alveolar macrophages and blood monocytes. Macrophages exhibited significant (P less than 0.01) tumoricidal activity at all GM-CSF doses tested. In contrast, monocytes showed no significant tumoricidal activity at 500 units/ml and significantly (P less than 0.01) less activity than alveolar macrophages at doses of 1000-5000 units/ml. Maximal activity in alveolar macrophages occurred 72-96 h after exposure to 1000-5000 units/ml GM-CSF. Tumoricidal activity may be related to the state of maturation, because monocytes matured in vitro for 7 days displayed enhanced tumoricidal activity after GM-CSF exposure. Tumor necrosis factor alpha and interleukin 1 beta were measured in supernatant fluids of 24-h GM-CSF-treated cells. No significant increase in either cytokine was detected after GM-CSF treatment of alveolar macrophages. Monocyte interleukin 1 beta secretion was not enhanced by GM-CSF; however, tumor necrosis factor alpha secretion was enhanced in some donors (three of five). Superoxide anion production of alveolar macrophages was not enhanced by GM-CSF. These data suggest that alveolar macrophage tumoricidal activity is induced by GM-CSF and is not dependent on oxidative metabolism or secreted forms of interleukin 1 beta or tumor necrosis factor alpha.     

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.     

Tumoricidal activation of murine resident peritoneal macrophages by interleukin 2 and tumor necrosis factor alpha.

The capacity of recombinant human interleukin 2 (rH-IL2), alone or in combination with recombinant tumor necrosis factor (r-TNF alpha), to activate murine resident peritoneal macrophages to a tumoricidal state was examined. Resident peritoneal exudate cells from C57BL/6 mice were cultured for 18 h with activating agents and washed and the adherent cells (macrophages) were assessed for cytolytic activity against radiolabeled target tumor cells (EL4, P815). Under these conditions, rH-IL2 alone activated macrophages to a tumoricidal state in a concentration dependent fashion. Neither murine nor human r-TNF alpha alone had any activating effect but, when combined with rH-IL2, further stimulated rH-IL2-inducible responses. Using polymyxin B, it was shown that macrophage activation was not due to an inadvertent lipopolysaccharide contamination of the r-TNF alpha or rH-IL2 preparations. It was also unlikely that target cell lysis was a direct result of increased TNF alpha production by rH-IL2 stimulated macrophages since P815 is totally resistant to lysis by r-TNF alpha. Although the lytic effector function was mediated by adherent cells, nonadherent peritoneal exudate cells were required for activation to occur. Furthermore, antisera against murine gamma-interferon, when added to activation cultures, reduced the level of cytolytic activity which developed. These data suggest that rH-IL2-induced peritoneal macrophage activation requires stimulation of nonadherent cells and is dependent upon gamma-interferon mediated mechanisms.     

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.     

Suppression of macrophage nitric oxide production by melanoma: mediation by a melanoma-derived product

The tumour-bearing state is known to induce immune dysfunction that contributes to increased infectious complications and tumour progression. However, the mechanisms underlying this immunosuppression remain unclear. This study investigated in a murine model the effects of melanoma growth on nitric oxide (NO) production by peritoneal macrophages in vivo and in vitro. B16 and K1735 melanoma cells were inoculated subcutaneously into C57BL/6 and C3H/HeN mice, respectively. Stimulated NO production by elicited peritoneal macrophages was examined in control and melanoma- bearing mice. An in vitro system was established to assess the effects of co-culturing melanoma cells (B16 and K1735) or melanoma-conditioned medium with normal peritoneal macrophages on subsequent NO production. NO production was significantly suppressed in macrophages from melanoma-bearing mice. Co-culture of normal macrophages with melanoma cells in a transwell system or with melanoma-conditioned media in vitro reproduced the defects observed in vivo without affecting macrophage viability, pointing to a melanoma-derived product as the basis for the observed suppression of NO production. This inhibition required RNA and protein synthesis and was dose and time dependent. Using inhibition profiles and neutralizing antibodies, it was demonstrated that this melanoma inhibitory activity was distinct from known NO inhibitors. Preliminary characterization attributed this activity to a melanoma-secreted protein moiety.     

Evidence for the production of nitric oxide by activated macrophages treated with the antitumor agents flavone-8-acetic acid and xanthenone-4-acetic acid

Activated peritoneal macrophages, obtained from mice pretreated with Bacillus Calmette-Guérin, after exposure in vitro to flavone-8-acetic acid (FAA; NSC 347512) at a concentration of 890 microM, produce nitrite (3.7 nmol/10(6) cells), as measured 20 h later by the Griess reaction. Stimulation of nitrite production was inhibited at least 90% by NG-monomethylarginine (125 microM), suggesting that nitrite was formed via nitric oxide as a product of arginine metabolism. Stimulation was only partially inhibited by dexamethasone (0.1 microM). The ability of xanthenone-4-acetic acid (XAA) and three of its analogues to stimulate nitrite production was also investigated. 5,6-Dimethyl-XAA stimulated nitrite production (12.6 nmol/10(6) cells) at an optimal concentration of 80 microM, 8-methyl-XAA was without effect, and XAA and 5-methyl-XAA showed intermediate activity. The optimal in vitro drug concentrations for stimulation by FAA, XAA, and active XAA analogues correlated with the optimal in vivo dose required for the induction of either hemorrhagic necrosis or growth delay of s.c. Colon 38 tumors. These results strongly imply that FAA and active XAA derivatives function as low molecular weight stimulators of nitric oxide formation in macrophages, possibly acting on the same differentiation pathway as do endotoxin and tumor necrosis factor alpha. We suggest that nitric oxide, which is known to be toxic to tumor cells, contributes to the cytotoxic action of FAA and its analogues.     

抗表皮生长因子受体单克隆抗体在胶质瘤导向治疗的实验研究

目的观察同位素标记的抗表皮生长因子单克隆抗体ＥＱ７５对胶质瘤细胞的亲和力及杀伤力。方法体外实验：采用荧光显微镜及流式细胞仪荧光强度定量分析进行ＥＱ７５对人胶质瘤细胞株ＢＴ３２５表面抗原特异性鉴定。体内试验：建立裸小鼠移植性胶质瘤模型，随机分组，经尾静脉分别注入１１１Ｉｎ┐ＥＱ７５和１１１Ｉｎ┐ＩｇＧ，４８ｈ后测定各脏器组织Ｔ／ＮＴ放射性比值，连续２周观测肿瘤移植物的大小，比较荷瘤小鼠的生存时间。结果体外试验：ＥＱ７５对ＢＴ３２５有高度的亲和性。体内试验：ＥＱ７５组Ｔ／ＮＴ、肿瘤移植物的抑制率以及荷瘤小鼠的生存时间均高于对照组（Ｐ＜０．０１）。结论１１１Ｉｎ┐ＥＱ７５对胶质瘤细胞有良好的亲和力及杀伤力。     

Macrophage arginase promotes tumor cell growth and suppresses nitric oxide-mediated tumor cytotoxicity

Macrophages use L-arginine to synthesize nitric oxide (NO) and polyamines through the inducible NO synthase (iNOS) and arginase, respectively. The released NO contributes to the tumoricidal activity of macrophages, whereas polyamines may promote the growth of tumor cells. Both the tumoricidal and growth-promoting activities from macrophages have been reported; however, the underlying mechanisms for switching between this dual function of macrophages remain unclear. Here, we test the hypothesis that arginase participates in the switching between the cytotoxic and growth-promoting activities of macrophages toward tumor cells. To alter arginase activity in macrophages, cells (murine macrophage cell line J774A.1) were transfected with the rat liver arginase gene or treated with an arginase inhibitor, L-norvaline. The effects of macrophage arginase activity on the growth-promoting and cytotoxic activities of macrophages toward breast tumor cells (ZR-75-1) were investigated in a coculture system. The results demonstrated that overexpression of arginase in macrophages enhanced L-ornithine and putrescine production and consequently promoted tumor cell proliferation. This proliferative effect was down-regulated by the arginase inhibitor L-norvaline. Furthermore, increases in arginase activity also attenuated NO production by the lipopolysaccharide-activated macrophages and thus reduced the cytotoxic effect on cocultured tumor cells. Inhibiting arginase activity by L-norvaline effectively reversed the suppression of NO-mediated tumor cytotoxicity. Together, these results suggest that arginase induction in macrophages can enhance tumor cell growth by providing them with polyamines and suppress tumor cytotoxicity by reducing NO production. It appears that L-arginine metabolism through the arginase and iNOS pathways in macrophages can have very different influences on the growth of nearby tumor cells depending on which pathway is prevailing.