Antilymphoma activity of human gamma delta T-cells in mice with severe combined immune deficiency.

Human Burkitt lymphoma (Daudi) cells grow as disseminated tumors in mice with severe combined immune deficiency (SCID) after either i.v. or i.p. injection. These cells are lysed in vitro by human V gamma 9/V delta 2 T-cells that recognize the groEL homologue on the Daudi cell surface. We report that both Daudi cell-stimulated peripheral blood mononuclear cells (Daudi-PBMC) containing 41-95% of V gamma 9/V delta 2 T-cells and V gamma 9/V delta 2 T-cell clones prolong the survival of SCID mice given inoculations of a lethal dose of Daudi cells. Groups of 6-8-week-old SCID mice were given inoculations i.v. or i.p. of 10(5) Daudi cells followed (through different injection sites) by: (a) 10(7) Daudi-PBMC; or (b) 10(7) unstimulated PBMC; or (c) 0.9% saline solution. All animals in groups (b) and (c) died of disseminated lymphoma, and their survival was significantly shorter than that of mice in group (a) (P < 0.001 for both i.v. and i.p. routes). Significant antitumor effects were also detected when Daudi-PBMC were injected 4 days before or 4 days after Daudi cells (P < 0.05). In vivo depletion of murine natural killer cells by anti-asialo GM-1 rabbit antiserum did not affect survival, suggesting that these cells did not contribute to lymphoma killing. Daudi-PBMC did not exert in vivo antitumor activity against the control Raji lymphoma. Mice receiving i.p. injections of Daudi cells followed by cytotoxic V gamma 9/V delta 2 T-cell clones also survived significantly longer (P < 0.05 for 3 different clones) than animals given Daudi cells alone or Daudi cells followed by noncytotoxic gamma delta T-cell clones. Our results indicate that this model system can be used for studies of human antilymphoma T-cell responses in vivo.     

Pathogenesis of vertebral metastasis and epidural spinal cord compression

The authors have studied the sequential events in the process of vertebral metastasis that result in spinal cord compression. Different tumor cell lines were injected into the systemic arterial circulation of syngeneic or nude mice, and they were killed at timed intervals after injection or when they became paraplegic. The following observations were made. The tumor cells lodged and grew in the hematopoietic bone marrow of the vertebrae. Cancer cells in the vertebral marrow cavity invaded into the spinal canal through the foramina of the vertebral veins rather than destroying the cortical bone. Tumor cell lines that grew in an infiltrative fashion migrated toward a posterior location in the spinal canal, and compressed the spinal cord from a posterior direction. Tumor cell lines that grew as compact tumors formed a tumor mass at the same location from which the cells emerged from the vertebra, and compressed the cord predominantly from an anterior direction. Radiographic evidence of vertebral metastasis was a late event, and commonly associated with significant compression of the cord and extraosseous tumor. These experimental findings may help to establish better diagnostic and treatment strategies for patients with metastatic disease of the spine.     

Mechanisms of organ selective tumour growth by bloodborne cancer cells

The sites of tumour development for 6 rat tumours injected into syngeneic rats via different vascular routes was determined. Xenografts of human tumours were also injected intra-arterially (i.a.) into immunosuppressed rats. Following intravenous (i.v.) and intraportal (i.ptl.) injection of cells tumour colonies localized in lung and liver respectively due to tumour cell arrest. Arterially injected radiolabelled cells disseminated and arrested in a similar distribution to cardiac output and did not 'home' to any organs. Following arterial injection of unlabelled tumour cells colonies grew in many organs. While the pattern of growth for a particular tumour varied with the cell dose, the 'arterial patterns' for all of the tumours studied followed a similar pattern. Some organs (eg adrenals, ovaries and periodontal ligament) were consistently preferred, others (eg skin and skeletal muscle) only supported tumour growth following the delivery of large numbers of cells, while in some tissues (eg spleen and intestines) tumour never grew. Viable tumour cells could be demonstrated by bioassay in many organs for up to 24h after i.a. injection. However tumour growth only occurred in certain organs and the pattern of this growth was not related to the number of tumour cells arrested or their rate of autolysis. This site preference could be expressed quantitatively as the probability of an arrested cell developing into a tumour and was considered a 'soil effect'. Site preference was not directly related to organ vascularity. Organ colonisation was promoted by steroid treatment but the mechanism was unclear and was not secondary to T-cell immunosuppression or prostaglandin synthesis suppression. The adrenal glands were preferred sites of tumour growth but pharmacological manipulation of adrenal function did not alter tumour growth to this organ. Sites of injury and healing were preferred sites of tumour colonisation and this could not be accounted for by increased delivery of tumour cells to these regions. The possibility that the macrophage component of the inflammatory response promoted tumour growth was suggested from studies in which the interval between trauma and inoculation of tumour cells was varied as well as by promotion of intraperitoneal (i.p.) tumour growth by a macrophage infiltrate.     

Tumor cells as cellular vehicles to deliver gene therapies to metastatic tumors

A long-pursued goal in cancer treatment is to deliver a therapy specifically to metastases. As a result of the disseminated nature of the metastatic disease, carrying the therapeutic agent to the sites of tumor growth represents a major step for success. We hypothesized that tumor cells injected intravenously (i.v.) into an animal with metastases would respond to many of the factors driving the metastatic process, and would target metastases. Using a model of spontaneous metastases, we report here that i.v. injected tumor cells localized on metastatic lesions. Based on this fact, we used genetically transduced tumor cells for tumor targeting of anticancer agents such as a suicide gene or an oncolytic virus, with evident antitumoral effect and negligible systemic toxicity. Therefore, autologous tumor cells may be used as cellular vehicles for systemic delivery of anticancer therapies to metastatic tumors.     

Tumorigenicity and dissemination of primary and metastatic human melanomas implanted into different sites in athymic nude mice

In the present study, the growth features and metastatic capacity of human primary and metastatic melanomas transplanted by different routes in nude mice was examined. Eight different human melanoma early cell cultures derived from 3 primary tumors, 1 local recurrence and 4 metastatic lesions of 6 melanoma patients were characterized for cell surface HLA (class I and II) and melanoma-associated antigens and karyotype. These tumors were then transplanted in CD-1 outbred nude mice by subcutaneous, intraperitoneal and intrasplenic routes. It was found that 7 out of 8 melanomas were tumorigenic after subcutaneous implantation without giving rise to metastases; 5 out of 7 melanomas grew when injected intraperitoneally and 3 of them disseminated to peritoneal organs and infiltrated intraperitoneal lymph nodes, liver and pancreas; of 8 melanomas implanted intrasplenically 4 grew in the spleen or invaded intraperitoneal lymph nodes, liver, pancreas, ovaries or lungs. Primary and metastatic melanomas did not differ in the pattern of dissemination. In fact, 2 out of 4 metastases and 1 of 3 primary tumors and 1 recurrence disseminated after intrasplenic or intraperitoneal inoculation. Heterogeneity in the growth pattern of different metastases of the same melanoma patient was also found. No correlation could be detected between the metastatic ability of melanoma cells studied and clinical stage of patients, tumor cell karyotype abnormalities, modal number or with the antigenic phenotype.     

Antitumor activity of Fab' and IgG-anti-CD22 immunotoxins in disseminated human B lymphoma grown in mice with severe combined immunodeficiency disease: effect on tumor cells in extranodal sites

The antitumor effects of two anti-CD22 ricin A chain-containing immunotoxin (IT) constructs were compared in mice with severe combined immunodeficiency disease with human Daudi cell tumors (SCID-Daudi mice). SCID-Daudi mice develop disseminated lymphoma that clinically resembles African Burkitt's lymphoma, i.e., extranodal disease including infiltration of the vertebral column and spinal canal. In the absence of treatment, the mean survival time of SCID-Daudi mice was 45.9 +/- 4.3 days. The mice was given injections of a dose of IT equal to 40% of the 50% lethal dose. The ITs consisted of either IgG or Fab' fragments of mouse anti-CD22 antibody coupled to deglycosylated ricin A chain (dgA). Both ITs were potent and specific and inhibited protein synthesis in Daudi cells in vitro by 50% at concentrations of 1.2 x 10(-12) (IgG-dgA) and 1.3 x 10(-11) M (Fab'-dgA). When administered to mice beginning 1 day after inoculation with tumor cells, both ITs extended the mean survival time, to 87.2 +/- 18.9 days (IgG-dgA) or 57.9 +/- 3.8 days (Fab'-dgA). The latter represented the killing of 2 logs of Daudi cells, and the former 4 logs. IgG antibody alone killed 1 log of tumor cells. The IgG-dgA had an antitumor effect even when administered 20-23 days after tumor inoculation. Gross and histological examinations of IT-treated tumor-bearing mice showed a marked decrease in the number and size of neoplastic foci in both lymphoid organs and extranodal sites.     

Localization of radiolabelled F(ab')2 fragments of monoclonal antibodies in nude mice bearing intraperitoneally growing human ovarian cancer xenografts

The biodistribution and pharmacokinetics of 2 monoclonal antibodies (MAbs) specific for ovarian carcinoma, OC125 and OV-TL3, were studied in nude mice bearing intraperitoneally (i.p.) growing human ovarian carcinoma xenografts of NIH:OVCAR-3. The ovarian carcinoma xenografts grew as non-adherent cells in ascites and as solid implants in the peritoneal cavity of injected mice. The biodistribution and pharmacokinetics were determined by measurement of radioactivity in tumor masses, ascites, blood and other tissues after intravenous (i.v.) and i.p. injection of radioiodinated F(ab')2 fragments of MAbs. The specificity of the observed tumor localization was then evaluated by comparing the uptake of the anti-ovarian carcinoma antibodies OC125 and OV-TL3 with the uptake of a radioiodinated non-ovarian carcinoma-specific MAb A2C6. The results of the study indicate that uptake of the anti-ovarian carcinoma antibodies was highest in the non-adherent tumor cells in the ascites after i.p. injection. The observed uptake was 85% injected dose/g for OV-TL3 and 22% injected dose/g for OC125. This compares to the observed antibody uptake of 9% injected dose/g for OV-TL3 and less than 1% injected dose/g for OC125 in solid tumor masses after i.p. injection. After i.v. injection, uptake of OC125 and OV-TL3 was less than 3% injected dose/g, both for nonadherent tumor cells and for solid tumor masses. The data support the conclusion that OV-TL3 is superior to OC125 and that i.p. administration of radiolabelled MAb F(ab')2 fragments is superior to their i.v. administration for immunotherapy of ovarian carcinoma.     

A murine model of experimental metastasis to bone and bone marrow

Bone is a common site of metastasis in human cancer. A major impediment to understanding the pathogenesis of bone metastasis has been the lack of an appropriate animal model. In this paper, we describe an animal model in which B16 melanoma cells injected in the left cardiac ventricle reproducibly colonize specific sites of the skeletal system of mice. Injection of 10(5) cells resulted in melanotic tumor colonies in most organs, including the skeletal system. Injection of 10(4) or fewer cells resulted in experimental metastasis almost entirely restricted to the skeletal system and ovary. In contrast, i.v. injection of 10(5) cells resulted in tumor colonies in the lung only. Left cardiac injection of 10(2) cells caused bone colonization, but the same number of cells injected i.v. did not colonize the lung. The number of bones with tumor colonies increased with increasing number of cells injected. Melanotic tumor colonies in the bone were characteristically distributed in the metaphysis of long bones and in the periphery of flat bones. Most animals developed paraplegia due to spinal cord compression by bony metastasis to the spine. Tumor colonization of bone occurred only in regions of bone containing hematopoietic bone marrow. This suggests that the injected tumor cells lodge, survive in the hematopoietic bone marrow environment, and grow to destroy adjacent bone. This experimental model of metastasis to bone will facilitate future studies of the pathophysiology and treatment of bone and bone marrow metastasis.     

Development, characterization and therapy of a disseminated model of childhood neuroblastoma in SCID mice

PURPOSE: To develop a highly reproducible model of disseminated childhood neuroblastoma in mice to allow secondary evaluation of therapeutics against microscopic disseminated disease. METHODS: CB17/Icr SCID were injected i.v. with 10(3) to 5 x 10(6) human NB-1691 neuroblastoma cells. NB-1691 cells were detected by PCR for synaptophysin and tyrosine hydroxylase in peripheral blood, and bone marrow. Therapeutic studies evaluated topotecan and vincristine as single agents or in combination. Topotecan was administered i.v. daily for 5 days on two consecutive weeks. Courses were repeated every 21 days for three cycles. Vincristine (1 mg/kg) was administered i.v. every 7 days for nine consecutive weeks. Treatment started 11-21 days after tumor cell inoculation. RESULTS: Following injection of > or = 1 x 10(5) cells 100% of mice developed disease. Mice inoculated with 10(7) cells survived a median of 42 days. Survival time was a linear function of the cell inoculum. At autopsy, gross tumor was routinely detected in many organs in particular liver, ovaries, kidneys and adrenals. NB-1691 cells were detected by PCR in peripheral blood, and bone marrow. Immunohistochemical staining showed that lesions were strongly positive for synaptophysin, chromogranin A and negative for leukocyte common antigen. Topotecan (0.6 mg/kg) alone extended median survival from 44 days (controls) to 95 days. When treatment was started 21 days after inoculation of NB-1691 cells, topotecan extended median survival from 39 days (controls) to 91 and 99 days at dose levels of 0.3 and 0.6 mg/kg, respectively. Vincristine (1 mg/kg) extended survival by a median of 9.5 days. In combination with vincristine (1 mg/kg), median survival was increased to 141 days (topotecan 0.6 mg/kg) and 159 days (topotecan 1.0 mg/kg). CONCLUSION: This model of disseminated neuroblastoma is highly reproducible. As this model may more closely simulate childhood disease it may be a valuable adjunct in developing new approaches to advanced stage, poor prognosis neuroblastoma.     

Antitumor activity of idarubicin-monoclonal antibody conjugates in a disseminated thymic lymphoma model

Many of the experimental approaches used in the search for new targeted drug delivery systems ignore the disseminated nature of metastatic disease; the development of more relevant tumor models is therefore a priority. A reproducible and tumor-specific model has been generated by inoculating (C57BL/6 x BALB/c) F1 (Ly-2.2+) mice i.v. with the Ly-2.1+ murine ITT(1) 75NS E3 thymic lymphoma (E3). At a dose of 2 x 10(6) cells, E3 tumors grew in a disseminated fashion, arising initially and predominantly in the lung and kidney, and later and less often in the thymus, spleen, and other tissues. In addition, histopathological examination and flow cytometry of blood did not detect E3 tumor cells in most other organs or in the circulation throughout the course of disease. The mean survival time (MST) of untreated mice was both reproducible and proportional to the number of E3 tumor cells injected and was therefore used to demonstrate the suitability of this model for immunochemotherapeutic studies. When examining the antitumor efficacy of idarubicin-monoclonal antibody conjugates, it was observed that the survival times of treated mice were consistent within groups and between experiments. The disseminated E3 (Ly-2.1+) tumor model, like the s.c. E3 tumor model, demonstrated the dose-dependent efficacy of idarubicin-anti-Ly-2.1 conjugate treatment and illustrated both the negligible antitumor activity and toxicity of idarubicin alone. Furthermore, lung and kidney weight measurements formally demonstrated that the increased MST of treated mice represented a reduction of E3 tumor burden in these organs. This model provides a useful tool for study of the immunochemotherapy of disseminated tumors in mice and further illustrates the antitumor activity of idarubicin-monoclonal antibody conjugates.     

Bcl-2 antisense oligonucleotides are effective against systemic but not central nervous system disease in severe combined immunodeficient mice bearing human t(14;18) follicular lymphoma.

The t(14;18) is present in 85-90% of follicular lymphomas. It results in overexpression of the Bcl-2 protein, which inhibits apoptosis and plays a role in lymphomagenesis. Bcl-2 antisense oligonucleotides (ODNs) down-regulate Bcl-2 expression and inhibit growth of the follicular lymphoma cell line WSU-FSCCL. In this study, we have established a human lymphoma xenograft model in severe combined immunodeficient (SCID) mice using the WSU-FSCCL cell line. s.c., i.v., or i.p. injection of WSU-FSCCL cells into SCID mice results in the development of disseminated tumors, with the liver, spleen, bone marrow, and lymph nodes as major sites of disease. Tumors were fatal in 7-14 weeks, depending on cell inoculum and route of administration. Immunohistochemistry, flow cytometry, and cytogenetic analysis confirmed the human B-cell origin of tumor cells in the xenograft. Phosphorothioate ODNs against the translation initiation site of bcl-2 mRNA in the antisense and mismatched antisense sequences were administered i.v. or i.p. to the xenograft models three times a week for 2 weeks, starting on day 7 after tumor injections. Antisense-treated animals had significantly longer survival (mean, 11.6 weeks) compared with 7.6 weeks for the control group and 7.5 weeks for the mismatched antisense-treated animals (P = 0.002 and 0.004, respectively). More significantly, a pathological examination showed no tumor in the liver, spleen, or bone marrow of the antisense group. However, subsequent experiments showed that the central nervous system was involved, causing mice to die although other sites were disease free. We conclude that bcl-2 antisense ODN therapy is effective against systemic FSCCL disease in SCID mice xenografts; however, it does not prevent disease dissemination into the central nervous system causing animal death.     

Limitations of radiolabeled monoclonal antibodies for localization of human neoplasms

Tumor-associated monoclonal antibodies were radiolabeled with 125I and 131I and given i.v. in pairs to 19 patients 1-26 days prior to surgical excision of primary and metastatic breast, ovarian, and gastrointestinal tumors. For individual patients each monoclonal antibody was designated as specific or nonspecific according to prior immunoperoxidase staining results on the appropriate target neoplastic tissues. Quantitation of antibody uptake was performed on resected normal and neoplastic tissues. Although good tumor:non-tumor ratios were obtained with the specific antibodies (maximal tumor:blood ratio, 35.8:1 at 12 days postadministration), the absolute amount of radiolabel detected in tumors was small (mean value of 0.015% of total injected amount per g of tumor occurring 1 day postadministration). Furthermore, both specific and nonspecific antibodies accumulated in normal lymph nodes to a significant extent (mean value of 0.0026% of total injected amount per g of tissue occurring 1 day postadministration). Knowledge of such data is essential prior to considering therapeutic uses of radiolabeled monoclonal antibodies.     

Potentiation by interleukin 2 of Burkitt's lymphoma therapy with anti-pan B (anti-CD19) monoclonal antibodies in a mouse xenotransplantation model

To study the immunotherapeutic potential of monoclonal antibodies (mAbs) directed against the human pan-B-cell antigen CD19, a xenotransplantation model was developed in which the human Burkitt's cell line Daudi is s.c. transplanted into nude mice. IgG1, IgG2b, and IgG2a isotype variants of the anti-CD19 mAb (CLB-CD19) were tested for their capacity to inhibit the growth of 10 x 10(6) Daudi cells injected s.c. into nude mice. When mAb treatment was started 30 min after the injection of tumor cells, only the IgG2a isotype of CLB-CD19 had a marked antitumor effect in vivo. If treatment with IgG2a anti-CD19 mAb alone was delayed until Day 10 after tumor injection, no therapeutic effect was observed. However, the combination of this delayed mAb treatment with recombinant interleukin 2 (rIL-2) inhibited the growth of the Daudi cells in the nude mice, while treatment with rIL-2 alone was ineffective. The results of in vitro experiments showed that peritoneal exudate cells were able to inhibit the proliferation of Daudi cells in the presence of the IgG2a isotype variant of CLB-CD19 mAb but not in the presence of the other CLB-CD19 mAb isotype variants. Fresh nude mouse spleen cells did not mediate antibody-dependent cellular cytotoxicity against CLB-CD19 mAb-sensitized Daudi cells, irrespective of the isotype used for sensitization. However, preculture of these spleen cells with rIL-2 induced antibody-dependent cellular cytotoxicity against CD19+ target cells sensitized with CLB-CD19 mAb of all isotypes. These results indicate that it is possible to enhance mAb-dependent effector systems in vivo with the lymphokine rIL-2.     

腹腔内注射IL-2重组腺病毒、IL-3重组腺病毒增强化疗药物抗白血病作用的研究

对实验性白血病小鼠模型大剂量化疗后,直接腹腔注射IL-2重组腺病毒(Ad-IL-2)和/或IL-3重组腺病毒(Ad-IL-3),发现腹腔注射对照腺病毒载体小鼠虽经大剂量化疗,仍有大量白血病细胞浸润至骨髓、血管、肝脏及脾脏。而腹腔注射Ad-IL-2或Ad-IL-3组小鼠肿瘤生长缓慢,注射Ad-IL-2组小鼠脾NK、CTL活性显著提高,注射Ad-IL-3组小鼠腹腔巨噬细胞数量及杀伤活性明显提高,联合应用Ad-IL-2,Ad-IL-3组小鼠抗白血病作用最为明显,骨髓中虽然仍见白血病细胞,但可见较多正常造血细胞,且肝、脾中未见白血病细胞浸润。表明腹腔内注射Ad-IL-2和Ad-IL-3可显著增强大剂量化疗对白血病的治疗效果。     

Selective localization and growth of Bifidobacterium bifidum in mouse tumors following intravenous administration

A strain of domestic bacteria, Bifidobacterium bifidum (Lac B), which is nonpathogenic and anerobic, selectively localized and proliferated in several types of mouse tumors following i.v. administration. None of the same bacilli could be detected in the tissues of healthy organs such as the liver, spleen, kidney, lung, blood, bone marrow, and muscle 48 or 96 hr after i.v. administration into tumor-bearing mice. Proliferation of Lac B in the tumor was artifically stimulated by i.p. administration of DDD-H-2s mice of a synthesized disaccharide, lactulose (4-O-beta-D-galactopyranosyl-D-fructofuranose), a sugar which is not metabolized by mammalian tissue cells. Lac B, which survices and proliferates selectively in the tumor following i.v. administration into the tumor-bearing host, should aid in diagnosis and selective therapy for cancer.     

B细胞非霍奇金淋巴瘤小鼠模型的建立

背景与目的：近年来非霍奇金淋巴瘤（non-Hodgkin’slymphoma,NHL）发病率呈上升趋势,其中侵袭性NHL占了很大的比例,然而传统化疗方案提高NHL疗效的空间有限。本研究旨在建立淋巴瘤小鼠模型,为探讨治疗NHL新方案并研究其药物作用机制提供动物模型。方法：应用人弥漫大B细胞NHL细胞株SU-DHL-4及人Burkitt淋巴瘤细胞株Daudi,经尾静脉注射人SCID小鼠体内．探索建立淋巴瘤小鼠模型的条件及特点。Daudi淋巴瘤小鼠分为对照组及美罗华治疗组．观察小鼠的发病情况及生存时间。结果：SU-DHL-4淋巴瘤小鼠在中位时间39．5d后开始发病,主要表现为精神萎靡、消瘦、竖毛、活动迟缓,于小鼠腹腔、尾部或后肢部位出现肿块,未发现肝脏、脾脏、骨髓等脏器出现淋巴瘤细胞浸润。Daudi淋巴瘤小鼠于中位时间30．5d发病,出现双后肢瘫痪,于瘫痪后9．5d左右死亡。Daudi淋巴瘤小鼠的脏器大多受淋巴瘤细胞的累及,骨髓中出现大量Daudi细胞浸润。美罗华治疗使小鼠骨髓中的Daudi细胞呈现明显的凋亡形态。对照组Daudi淋巴瘤小鼠的中位瘫痪时间及生存时间分别为30．5d及40d,美罗华治疗组的小鼠分别为52．5d及76．5d,美罗华治疗组小鼠的中位瘫痪时间及生存时间显著延长（P〈0．05）。结论：应用SU—DHL-4细胞及Daudi细胞均可以成功建立B细胞NHL小鼠模型。     

Vascular anatomy and organ-specific tumor growth as critical factors in the development of metastases and their distribution among organs

We have examined with 19 tumor cell lines the discrete roles that vascular anatomy and tumor-cell-organ-affinity play in the development of metastases and their distribution among organs. Spontaneous metastases of B16-G3.26 melanoma cells from a primary tumor growing in the foot pad of mice, or experimental metastases 21 days after intravenous tumor-cell injection resulted in tumor colonies only in the lungs. In contrast, when the lung microvasculature was bypassed, and the same cells given by systemic intra-arterial (s.i.a.) injection, large tumor colonies developed selectively in the ovaries, adrenal glands and bones, but rarely in the lungs. When animals injected i.v. were allowed to live with lung metastases for a long period of time, small tumor colonies began to develop in extra-pulmonary organs with a distribution identical to that seen after s.i.a. injection. Seven murine tumor cell lines (previously characterized by their ability to colonize primarily the lungs after i.v. injection) and 7 of the 8 studied human tumor cell lines colonized different specific extra-pulmonary organs after s.i.a. injection, frequently producing metastatic syndromes commonly described in patients with cancer, but rarely seen in animal models of metastasis. These results suggest that metastatic cells, even those capable of colonizing specific organs, do not freely circulate in the blood stream and lodge in specific tissues. In contrast, the cells must establish a vascular route of access to the target organ, e.g., through the systemic circulation from metastatic tumors in the lungs. Two cell lines considered to be tumorigenic but non-metastatic failed to colonize the lungs or extra-pulmonary organs after i.v. injection, but readily colonized specific organs after s.i.a. injection. Thus, tumor cells considered to be non-metastatic may be indeed metastatic if they are provided with vascular access to an organ more congenial to their growth requirements.     

Cytotoxic effect of anti-Mr 67,000 protein immunotoxins on human tumors in a nude mouse model

We have studied the potential use of immunotoxins (ITs) for therapeutic treatment of human tumors in an experimental model of human neoplasia. We tested intact ricin IT for its antitumor activity against established tumors. CEM, a human T-cell leukemia line expressing an Mr 67,000 cell surface antigen, and Daudi, a human B-cell lymphoma line which does not express the antigen, were found to be consistently tumorigenic in nude mice. ITs were synthesized using T101, a high-affinity monoclonal antibody reacting with the Mr 67,000 protein determinant and intact ricin. We have shown for the first time that established CEM solid tumors in nude mice will regress following intratumoral injection of T101-ricin IT, while Daudi tumors will not. Selective activity of T101-ricin is dependent on systemic i.v. administration of lactose and local intratumoral injection of the T101-ricin IT with lactose. Intact ricin ITs require the presence of lactose to block native ricin binding and render them antigen specific when linked to monoclonal antibody. Killing of target was cell specific since (a) nonspecific (irrelevant) ITs did not cause the regression of CEM tumors, and (b) injection of large amounts of free T101 antibody prior to T101-ricin IT blocked antitumor activity. Selectivity was not absolute, since regression occurred in one of six animals given irrelevant IT, and blocking was observed in two of four mice. Intratumoral IT treatment with 1 or 2 micrograms of T101-ricin IT plus lactose was not harmful to mice in contrast to intratumoral ricin treatment, which killed all treated tumor-bearing mice at a dose of 0.3 micrograms. Without i.v. injection of lactose, intratumoral injection of T101-ricin IT was also effective in eliminating established tumors. However, this treatment did not result in the selective elimination of tumor, since Daudi tumors also regressed following T101-ricin IT treatment. IT, made with ricin A chain only (T101-A chain IT), was also tested against established CEM tumors. We found that high dosages of T101-A chain IT did not destroy CEM tumors when injected intratumorally, even in the presence of activating agents such as NH4Cl or the carboxylic ionophore X-537 A. In contrast, in vitro experiments demonstrated that T101-A chain IT plus activating agents had potent and selective cytotoxic effect against CEM cells. We conclude that ITs are specifically toxic to established tumors. Although selectivity is not absolute, ITs exhibit potential as a new class of antitumor reagents.