Immunofluorescence detection with quantum dot bioconjugates for hepatoma in vivo

The use of highly specific and highly sensitive immunofluorescent probes is a promising approach for biomedical imaging in living tissue. We focus on immunofluorescence with quantum dot bioconjugates for hepatoma detection in vivo. We synthesized specific immunofluorescent probes by linking quantum dots to AFP (alpha-fetoprotein) antibody for specific binding AFP-an important marker for hepatocellular carcinoma cell lines. In in vivo studies, the characteristic quantum dot (QD) fluorescent property is exhibited by the QDs-Anti-AFP probes in tumor and they demonstrate active tumor targeting and spectroscopic hepatoma imaging with an integrated fluorescence imaging system. We investigate the inhomogeneous distribution of the QDs-Anti-AFP probes in tumor by using a site-by-site measurement method to test their ability for distribution studies of cancer cells. These results demonstrate the practicality of QD bioconjugates as attractive fluorescent probes for biomedical detection.     

Quantum dot loaded immunomicelles for tumor imaging

Background  

Optical imaging is a promising method for the detection of tumors in animals, with speed and minimal invasiveness. We have previously developed a lipid coated quantum dot system that doubles the fluorescence of PEG-grafted quantum dots at half the dose. Here, we describe a tumor-targeted near infrared imaging agent composed of cancer-specific monoclonal anti-nucleosome antibody 2C5, coupled to quantum dot (QD)-containing polymeric micelles, prepared from a polyethylene glycol/phosphatidylethanolamine (PEG-PE) conjugate. Its production is simple and involves no special equipment. Its imaging potential is great since the fluorescence intensity in the tumor is twofold that of non-targeted QD-loaded PEG-PE micelles at one hour after injection.     

量子点探针辅助的近红外荧光成像技术在肿瘤显影中的应用

肿瘤早期检测是精准并高效诊疗癌症的关键因素。荧光成像技术凭借其高灵敏度、高时空分辨率、无电离辐射和无创实时成像等优点,在生物医学领域,尤其在肿瘤检测方面展现出了广泛的应用前景。近红外光穿过生物组织时,受到的吸收和散射较少,因此在生物成像方面体现了高信噪比和强组织穿透能力。在众多荧光探针中,近红外发光的量子点探针因其量子产率高、抗光漂白性强、发射光可调和稳定性良好等特点在荧光成像方面显示出突出的优势。本文基于量子点探针的近红外荧光成像技术在肿瘤显影中的应用,介绍了量子点优异的光学性能,并重点讨论了硫化铅（PbS）和硫化银（Ag2S）近红外发光量子点探针在肿瘤成像方面的研究进展,并对近红外发光量子点探针的应用前景进行了展望。     

COMPARATIVE ANALYSIS OF DIRECT FLUORESCENCE,ZENON LABELING,AND QUANTUM DOT NANOCRYSTAL TECHNOLOGY IN IMMUNOFLUORESCENCE STAINING

A comparative analysis was performed to determine the sensitivity and efficiency of three fluorescent labeling techniques, including direct fluorescent-antibody staining (FA), Zenon labeling, and quantum dot (QD) nanocrystal technology. Two varicella-zoster virus immunoglobin (Ig) G forms, mAb 4F9 and mAb g62, were selected for these studies. The results indicated that: (1) All three methods demonstrated similar brightness and photostability; (2) the time required to conjugate the antibody varied, with Zenon labeling being the quickest; and (3) the stability of each conjugated complex was different, with FITC/rhodamine-conjugated antibody being the most stable.     

Multilayered, core/shell nanoprobes based on magnetic ferric oxide particles and quantum dots for multimodality imaging of breast cancer tumors

Multilayered, core/shell nanoprobes (MQQ-probe) based on magnetic nanoparticles (MNPs) and quantum dots (QDs) have been successfully developed for multimodality tumor imaging. This MQQ-probe contains Fe(3)O(4) MNPs, visible-fluorescent QDs (600?nm emission) and near infrared-fluorescent QDs (780?nm emission) in multiple silica layers. The fabrication of the MQQ-probe involves the synthesis of a primer Fe(3)O(4) MNPs/SiO(2) core by a reverse microemulsion method. The MQQ-probe can be used both as a fluorescent probe and a contrast reagent of magnetic resonance imaging. For breast cancer tumor imaging, anti-HER2 (human epidermal growth factor receptor 2) antibody was conjugated to the surface of the MQQ-probe. The specific binding of the antibody conjugated MQQ-probe to the surface of human breast cancer cells (KPL-4) was confirmed by fluorescence microscopy and fluorescence-activated cell sorting analysis in?vitro. Due to the high tissue permeability of near-infrared (NIR) light, NIR fluorescence imaging of the tumor mice (KPL-4 cells transplanted) was conducted by using the anti-HER2 antibody conjugated MQQ-probe. In?vivo multimodality images of breast tumors were successfully taken by NIR fluorescence and T(2)-weighted magnetic resonance. Antibody conjugated MQQ-probes have great potential to use for multimodality imaging of cancer tumors in?vitro and in?vivo.     

Quantum dots thermal stability improves simultaneous phenotype-specific telomere length measurement by FISH-flow cytometry

Telomere length analysis has been greatly simplified by the quantitative flow cytometry technique FISH-flow. In this method, a fluorescein-labeled synthetic oligonucleotide complementary to the telomere terminal repeat sequence is hybridized to the telomere sequence and the resulting fluorescence measured by flow cytometry. This technique has supplanted the traditional laborious Southern blot telomere length measurement techniques in many laboratories, and allows single cell analysis of telomere length in high-throughput sample formats. Nevertheless, the harsh conditions required for telomere probe annealing (82 °C) has made it difficult to successfully combine this technique with simultaneous immunolabeling. Most traditional organic fluorescent probes (i.e. fluorescein, phycoerythrin, etc.) have limited thermal stability and do not survive the high temperature annealing process, despite efforts to covalently crosslink the antigen-antibody-fluorophore complex. This loss of probe fluorescence has made it difficult to measure FISH-flow in complex lymphocyte populations, and has generally forced investigators to use fluorescent-activated cell sorting to pre-separate their populations, a laborious technique that requires prohibitively large numbers of cells.In this study, we have substituted quantum dots (nanoparticles) for traditional fluorophores in FISH-flow. Quantum dots were demonstrated to possess much greater thermal stability than traditional low molecular weight and phycobiliprotein fluorophores. Quantum dot antibody conjugates directed against monocyte and T cell antigens were found to retain most of their fluorescence following the high temperature annealing step, allowing simultaneous fluorescent immunophenotyping and telomere length measurement. Since quantum dots have very narrow emission bandwidths, we were able to analyze multiple quantum dot antibody conjugates (Qdot 605, 655 and 705) simultaneously with FISH-flow measurement to assess the age-associated decline in telomere length in both human monocytes and T cell subsets. With quantum dot immunolabeling, the mean decrease rate in telomere length for CD4+ cells was calculated at 41.8 bp/year, very close to previously reported values using traditional flow-FISH and Southern blotting. This modification to the traditional flow-FISH technique should therefore allow simultaneous fluorescent immunophenotyping and telomere length measurement, permitting complex cell subset-specific analysis in small numbers of cells without the requirement for prior cell sorting.     

抗人PD-L1 单克隆抗体的制备及其应用

目的:获得能应用于临床诊断以及阻断PD-L1 与PD-1 结合的抗人PD-L1 单克隆抗体。方法:采用重组表达的人PD-L1 蛋白免疫BALB/ c 小鼠,通过杂交瘤细胞融合技术获得稳定分泌抗人PD-L1 单抗的阳性细胞株,ELISA 方法鉴定抗体的特异性、亲和力、亚型等方面特性;免疫印迹、间接免疫荧光方法对肿瘤细胞进行检测;肿瘤杀伤实验验证抗体阻断活性。结果:共获得2 株抗人PD-L1 单抗,抗体效价分别为1 2.56 106 和1 3 105 ,亲和力分别为1.5 109 L/ mol 和2.5 108 L/ mol,均与PD-L2 蛋白无交叉反应。免疫印迹、间接免疫荧光证实抗体有诊断作用。杀伤实验显示抗体有阻断作用。结论:共获得两株稳定分泌高效价、高特异性的抗人PD-L1 单抗的杂交瘤细胞株,能作为诊断抗体应用于肿瘤表型检测和预后有效性的评估。抗体的阻断功能可应用于联合CIK 细胞免疫治疗。     

125 I标记的抗p185抗体的体外代谢与体内生物学分布

目的：研究^125Ⅰ标记的抗p185抗体（鼠mAb A21、人鼠嵌合抗体A21 scFv-Fc及单链抗体A21 seFv）在体外的细胞代谢和在体内的生物学分布，为其在诊断和治疗高表达p185肿瘤的临床应用提供依据。方法：通过FACS检测抗体是否与高表达膜表面抗原p185的SKOV，特异结合。采用氯胺T法进行碘标记抗体，用细胞放射免疫分析实验，检测抗体在SKOV、细胞中的代谢。建立荷SKOV，裸鼠模型，以观察抗体的体内生物学分布。结果：体外细胞代谢实验表明，抗体在与细胞膜表面结合后，进而被内吞入细胞，在细胞内降解和脱碘，最后被分泌出细胞外。体内药物代谢实验表明，抗体在动物体内肿瘤部位出现选择性放射性浓聚，而无关抗体未出现放射性浓聚，呈全身分布。结论：mAb A21，A21 seFv-Fc和A21 scFv对于高表达p185的卵巢癌在体内和体外都具有亲和力，可单用作高表挟D185肿瘤的诊断和治疗。     

~(125)I标记的抗p185抗体的体外代谢与体内生物学分布

目的:研究125I标记的抗p185抗体(鼠mAbA21、人鼠嵌合抗体A21scFv-Fc及单链抗体A21scFv)在体外的细胞代谢和在体内的生物学分布,为其在诊断和治疗高表达p185肿瘤的临床应用提供依据。方法:通过FACS检测抗体是否与高表达膜表面抗原p185的SKOV3特异结合。采用氯胺T法进行碘标记抗体,用细胞放射免疫分析实验,检测抗体在SKOV3细胞中的代谢。建立荷SKOV3裸鼠模型,以观察抗体的体内生物学分布。结果:体外细胞代谢实验表明,抗体在与细胞膜表面结合后,进而被内吞入细胞,在细胞内降解和脱碘,最后被分泌出细胞外。体内药物代谢实验表明,抗体在动物体内肿瘤部位出现选择性放射性浓聚,而无关抗体未出现放射性浓聚,呈全身分布。结论:mAbA21,A21scFv-Fc和A21scFv对于高表达p185的卵巢癌在体内和体外都具有亲和力,可望用作高表达p185肿瘤的诊断和治疗。     

量子点探针对人肝癌裸鼠模型的体内靶向成像研究

目的研究量子点标记靶向探针对人肝癌裸鼠模型的体内成像技术。方法将巯基乙酸修饰的水溶性量子点结合鼠抗人甲胎蛋白（AFP）单克隆抗体制备成水溶性量子点-AFP-Ab复合物探针。荧光、紫外光光谱分析及透射电镜研究其特性。通过直接免疫荧光法,用该复合物探针特异性识别肝癌细胞株HCCLM6 AFP抗原。将体外培养的肝癌细胞株HCCLM6通过皮下接种和尾静脉注射裸鼠分别建立人肝癌裸鼠模型和肺转移模型。尾静脉注射量子点-AFP-Ab探针,用蓝光二极管照射获得活体荧光成像;用掺Ti蓝宝石激光器照射,对肿瘤部位和正常部位进行光谱分析。取血清检测丙氨酸转氨酶、天冬氨酸转氨酶、尿素氮和肌苷水平。取裸鼠肝、脾、肾、肺、心和脑6种主要实质性器官行振荡切片,共聚焦显微镜观察,研究量子点-AFP-Ab探针在裸鼠体内的非特异性摄取。结果量子点-AFP-Ab复合物探针具有激发光谱宽、荧光强度高的特点,能特异性与肝癌细胞AFP抗原高亲和力结合,在体内能特异性靶向肿瘤组织进行活体成像,无明显急性毒性。光谱分析显示量子点-AFP-Ab复合物探针主要分布于肿瘤的外周部位,少数该探针被肝、脾和肺非特异性摄取。结论量子点-AFP-Ab复合物探针具有优良的光学特性和生物相容性,能够进行肝癌体内靶向成像,将有助于肝癌的分子靶向研究。     

斑点金免疫渗滤法检测肿瘤患者血清弓形虫IgG抗体的应用研究

为建立简便、快速的斑点金免疫渗滤法 (DIGFA)检测肿瘤患者血清弓形虫IgG抗体。本文将弓形虫抗原包被于硝酸纤维素薄膜上 ,用来检测肿瘤患者血清中的弓形虫IgG抗体 ,通过胶体金———SPA直接显色 ,阳性者出现红色斑点。用该法对 2 32名肿瘤患者血清和 2 6 0名正常体检者血清进行检测 ,阳性率分别为 11. 2 1%和 1. 92 %。与IHA法对比检测 ,其结果具有良好的一致性 ,总符合率为 99. 39%。结果显示 ,斑点金免疫渗滤法检测肿瘤患者血清中弓形虫抗体简便、快速 ,适于向基层推广。     

Induction of IgM, IgA and IgE Antibodies in Colorectal Cancer Patients Vaccinated with a Recombinant CEA Protein

Purpose

Previous clinical studies have indicated that natural IgM antibodies have the ability to induce apoptosis of tumor cells but IgE and IgA may also mediate tumor cell killing (in addition to IgG). The aim of the study was to analyse induction of IgM, IgA and IgE antibodies in patients vaccinated with the tumor associated antigen CEA.

Methods

Twenty-four resected CRC patients without macroscopic disease were immunized seven times with CEA?±?GM-CSF. Four different dose schedules were used over a 12-month period. IgM, IgA and IgE antibody responses against recombinant CEA were determined by ELISA. Patients were monitored immunologically for 36 months and clinically for 147 months.

Results

GM-CSF significantly augmented the anti-CEA response for all three antibody classes. Low dose of CEA tended to induce a higher IgM, IgA or IgE anti-CEA antibody response than higher. Anti-CEA IgA antibodies could lyse CEA positive tumor cells in antibody dependent cellular cytotoxicity (ADCC) as well as in complement dependent cytotoxicity (CDC). A significant correlation between survival and high IgA anti-CEA titers was noted (p?=?0.02) irrespective of GM-CSF treatment.

Conclusions

The observation that IgA anti-CEA antibodies were cytotoxic and associated with improved survival might indicate that also these antibodies may exert a clinical anti-tumor effect.     

The augmentation of tumor-specific immunity by virus help. II. Enhanced induction of cytotoxic T lymphocyte and antibody responses to tumor antigens by vaccinia virus-reactive helper T cells

The present study investigates the role of vaccinia virus-reactive helper T cells in causing enhanced induction of syngeneic tumor immunity. Vaccinia virus-reactive helper T cell activity capable of inducing the augmented generation of cytotoxic T lymphocyte (CTL) or antibody responses was generated in C3H/HeN mice by inoculating i.p. live virus. Immunization of these mice with vaccinia virus-infected syngeneic X5563 plasmacytoma or MH134 hapatoma cells led to augmented induction of immune resistance against the challenge with corresponding viable tumor cells when compared with the incidence of resistance observed in control mice not primed to vaccinia virus. In vitro cytotoxicity tests utilizing spleen cells and serum from mice which resulted in the augmented tumor resistance by virus help have revealed that spleen cells from C3H/HeN mice immune to the X5563 plasmacytoma exhibited appreciable anti-X5563 CTL activity, whereas serum from these mice failed to display any antibody response. In contrast, MH134-immune mice exhibited potent anti-MH134 antibody, but not CTL responses. Such an anti-tumor CTL or antibody response augmented by vaccinia virus-reactive helper T cells was found to be tumor specific. These results are discussed in the context of (a) the functional diversity of tumor antigens, and (b) mechanisms of virus help that are involved in various forms of augmented induction of syngeneic tumor immunity.     

Can oligomeric T-cell receptor be used as a tool to detect viral peptide epitopes on infected cells?

We have utilized soluble HIV Gag-specific T-cell receptor (TCR) D3 with low affinity and TCR-like antibody 25-D1.16 recognizing its natural peptide-MHC (pMHC) ligand with high affinity to determine how affinity and off-rate of the receptor-pMHC interactions affect the sensitivity of pMHC detection on the cell surface. We found that with soluble TCR cognate pMHCs can be detected only at relatively high cell surface densities when the TCR was oligomerized using either Streptavidin or quantum dot (QD) scaffolds. While the higher affinity probe led to a greater sensitivity of pMHC detection, monomers and oligomers of the probe showed essentially the same detection limit, which is restricted by the sensitivity of standard flow cytometry technique. We have also shown that imaging of QD/TCR specifically bound to cognate pMHC on the cell surface yielded a very bright fluorescent signal that can enhance the sensitivity of viral peptide detection on infected cells.     

Responses of simple and complex cells to random dot patterns: a quantitative comparison

1. There are several reports that random dot patterns are potent stimuli for cortical complex cells but not for simple cells. This finding is regarded as evidence against Hubel and Wiesel's hierarchical model of cortical circuitry, in which simple cells are the principal input to complex cells. We have reinvestigated the question quantitatively by recording responses to dot patterns from 106 cells in area 17 and the 17/18 border region of normal adult cats. 2. The cells were classified as simple (n = 62) or complex (n = 40) (4 were end stopped or hypercomplex) on the basis of whether they gave modulated (AC) or unmodulated (DC) responses to drifting sine gratings. 3. Although there are large within-group differences, we found both simple and complex cells that respond to bright random dots on a dark background, drifted across the receptive field at 3 degrees/s. The responses at the optimal direction averaged 6.2 and 18.1 spikes/s (spontaneous activity subtracted) for simple and complex cells, respectively. 4. We also recorded responses to drifting sine gratings. Complex cells were also found to respond more than simple cells to these stimuli. For each cell, we calculated a dot index expressing the dot response relative to grating response. The dot index averaged 0.43 for simple cells and 0.55 for complex cells. It therefore appears that much of the difference in response to dot patterns reflects a difference in general responsivity. 5. In subsamples of cells, we examined the effects of varying dot density, dot size, and drift velocity. These variables affect different cells in a manner largely independent of cell class. Most simple cells in our sample responded well to random dot patterns at several velocities, at two different dot sizes and at both 3 and 50% dot densities. 6. Our results agree with previous studies in showing that complex cells respond more vigorously than simple cells to dot patterns, but the fact that many simple cells also respond to these stimuli makes our results consistent with a hierarchical model of cortical circuitry.     

Monoclonal antibody enzyme-linked immunosorbent assay for specific identification and typing of subgroup F adenoviruses.

Monoclonal antibody specific for subgroup F enteric adenoviruses (EAds) was prepared by fusing P3-NS1/Ag4-1 mouse myeloma cells with lymphocytes from BALB/c mice immunized with G1105, an adenovirus type 41 (Ad41) strain. Monoclone 3F11/2H9, which specifically recognized Ad41, was successfully used as detector antibody in an enzyme-linked immunosorbent assay (ELISA). Additionally, previously prepared monoclones 5D8/2C2 and 2H6/1E11, recognizing Ad40 plus Ad41 and Ad40 alone, respectively, were used to study stool and/or tissue culture specimens from 106 patients with adenovirus-positive gastroenteritis. By ELISA, 91 had EAds (22 were Ad40 and 69 were Ad41) and 15 had non-EAds. ELISA results were in concordance with restriction endonuclease results for 38 of 39 specimens, with dot blot data for 19 of 20 specimens, and with neutralization test results for 74 of 78 specimens. ELISA was at least 10-fold more sensitive than direct electron microscopy was for the detection of EAds in stool specimens.     

Downstream characterization of anti-TNF-α single chain variable fragment antibodies

Using phage display technology (PDT), we have recently isolated single-chain variable fragment (scFv) antibodies (Ab) against some pivotal molecular markers involved in malignancies and systemic inflammation including human tumor necrosis factor-alpha (TNF-α, GI:367465798). Downstream purification and characterization of scFv antibodies is a challenging issue, which may impose substantial impacts on quality of the final product(s). Of various purification methods, affinity chromatography has widely been used in the pharmaceutical grade downstream processing (PGDP) of proteins (e.g., monoclonal antibody (mAb) and scFvs). To pursue an optimized PGDP, in the current study, we have capitalized PDT for upstream selection of anti-TNF-α scFvs and protein A affinity chromatography (PAAC) for downstream extraction and purification of the scFvs from the crude medium secreted and periplasmic fractions of HB2151 cells. The versatility of the PDT selection was validated using SDS-PAGE electrophoresis, western blot, dot blot, ELISA and fluorescence microscopy. SDS-PAGE western blot analyses displayed a 17 kDa scFv with high purity (> 98%), while dot blot and ELISA analyses showed high specificity and binding affinity of the purified scFv antibody fragments toward human TNF-α at nM range. Fluorescence microscopy further confirmed detection of TNF-α in Raji B lymphoblast cells. Finally, based on our findings, we believe that these PDT selected and PAAC processed scFvs may be used as targeting and/or therapy agent for TNF-α mediated diseases. Further, to increase the production yield, downstream purification techniques need to be optimized for the large scale production of scFv antibodies.     

抗ssDNA单克隆抗体的研制和在检测凋亡细胞中的应用

为了制备抗单链DNA单克隆抗体和建立检测细胞凋亡的新方法 ,采用杂交瘤细胞融合技术用于筛选分泌抗单链DNA抗体的单克隆杂交瘤细胞株 ,并用斑点印迹和竞争ELISA法鉴定单抗的特异性 ,进而结合免疫组织化学和免疫荧光方法用于检测凋亡细胞。通过筛选得到单克隆杂交瘤细胞株B17,其分泌的抗体与单链DNA结合而与双链DNA无交叉反应 ,用此单抗建立的凋亡细胞检测方法能够检测出凋亡细胞 ,区分非凋亡细胞和坏死细胞。实验结果表明 ,成功地获得一株分泌特异性抗单链DNA抗体的单克隆杂交瘤细胞株 ,以此建立的凋亡细胞检测方法特异性高、敏感性强     

点免疫金渗滤法筛选胶体金标记抗人IgG 的研究

目的:应用点免疫金渗滤法筛选适宜胶体金标记的抗人IgG(以下简称二抗),并运用多个评价指标进行比较和分析。方法:选择三个不同公司的二抗用胶体金标记,根据棋盘滴定法确定最佳标记条件;运用点免疫金渗滤法对三种二抗的胶体金标记后检测效能进行比较,采用包虫病人和健康对照血清,用包虫病特异性抗原检测包虫病患者血清中的特异性抗体,评价最优的二抗,并与酶联免疫吸附测定法进行比较。结果:A、B、C 三种二抗标记的最佳标记条件为:pH 均为8.5,加入量分别为38.4、24、19.2 g/ ml,综合评价二抗B 检测效能最优。将其与酶联免疫吸附测定法检测效能进行比较,两种方法检测结果的Kappa=0.895(P<0.05),吻合度较强。结论:应用点免疫金渗滤法,以及本文提出的评价指标,能够筛选出最佳二抗,对检测试剂盒中二抗的选择具有重要的参考价值。     

Immunotherapy of human ovarian carcinoma with OvaRex MAb-B43.13 in a human-PBL-SCID/BG mouse model

The monoclonal antibody (MAb) B43.13, binding to the ovarian cancer-associated antigen CA125, has been injected into more than 200 patients with ovarian cancer to detect recurrence of the disease. The follow-up of the patients revealed surprisingly long survival spans for several patients despite high CA125 levels. To investigate the therapeutic effectiveness of OvaRex MAb-B43.13 (AltaRex, Edmonton, Canada) under well-controlled conditions, the antibody was tested in a human-PBL-SCID/BG mouse model with CA125 positive human ovarian cancer cells. Mice were reconstituted with human peripheral blood lymphocytes (PBL, normal donors) by intraperitoneal (IP) injection of 2 to 3 x 10(7) PBL/mouse. OvaRex MAb-B43.13 was administered at 100 microg/mouse in phosphate buffered saline (PBS), in three different experimental set-ups. An isotype-matched control antibody (MOPC21 or MAb-170) and PBS injection served as controls. The ovarian cancer cell line NIH:OVCAR-NU-3 was injected IP at 1 x 10(6) cells/mouse or subcutaneously (SC) at 4 x 10(6) cells/mouse. Human-PBL-SCID/BG mice were either immunized before injection of tumor cells, along with tumor cells or after small tumors were established (2 weeks after transplantation). Antibody injections were repeated twice in 2-week intervals. Functional and cellular characterization of serum and PBL from these mice demonstrated the successful engraftment of a human immune system in those mice. All three experiments showed that OvaRex MAb-B43.13 treatment could (a) delay or prevent development of tumors; (b) reduce the size of small established tumors (SC tumor injection) or suppress ascites formation; (c) delay tumor growth when injected prior to tumor implantation; and (d) prolong the survival of the mice (i.p. tumor injection).