Expression and release of plasminogen activators, their inhibitors and receptor by human tumor cell lines

Plasminogen activators (PAs) and their inhibitors (PAIs) can be produced by tumor cells and surrounding inflammatory cells and fibroblasts. The present study evaluate both the expression and release of PAs (uPA and tPA) and PAIs (PAI-1 and PAI-2) from cultured cells, and also the expression of uPA receptor (uPAR). Immunocytochemistry showed that PAs, PAIs and uPAR were present to different extents on the surface of colon carcinoma cells (Caco-2, HT-29), malignant melanoma cells (LOX) and normal fibroblasts. uPA immunoreactivity was intermediate in Caco-2, HT-29 and LOX and weak in the fibroblasts. tPA immunoreactivity was intermediate in Caco-2 and LOX and weak in HT-29 and fibroblasts. PAI-1 and PAI-2 immunoreactivities were absent in HT-29, weak in Caco-2 and strong in fibroblasts. In LOX the immunoreactivity was intermediate for PAI-1 and strong for PAI-2. uPAR immunoreactivity was weak in Caco-2, HT-29 and LOX and negative in fibroblasts. ELISAs on conditioned medium detected that the colon carcinoma cells Caco-2 and HT-29 did not release any PAs or PAIs. LOX released tPA (median 9 ng/million cells at 72 hours), PAI-1 (1050 ng/million cells) and PAI-2 (245 ng/million cells), and fibroblasts released uPA (1 ng/million cells) and PAI-1 (910 ng/million cells). These results show that both tumor cells and fibroblasts express tissue destructive enzymes, PAs and PAIs, whereas only the tumor cells express the uPAR required for focalization and regulation of PA activity at the cell surface. The melanoma cells LOX and fibroblasts also released PAs and PAIs, in contrast to the colon carcinoma cells Caco-2 and HT-29.

MDM2 gene amplification and transcript levels in human sarcomas: relationship to TP53 gene status

BACKGROUND

Alterations of the TP53 tumor suppressor gene appear to be implicated in the tumorigenesis and progression of several types of human cancer, including different histologic subtypes of sarcomas. The MDM2 (murine double minute-2) gene encodes a nuclear phosphoprotein that may interact with both mutant and wild-type p53 proteins, thereby inhibiting p53-mediated transactivation in a dose-dependent manner. Recently it has been suggested that mdm2 and p53 proteins are components of an autoregulatory loop in which the MDM2 gene is transactivated by p53.

PURPOSE

Our purpose was to examine the frequency of MDM2 amplifications in larger panels of sarcomas, determine if the mRNA level could be elevated in tumors without concomitant gene amplification, and relate MDM2 findings to the TP53 status of the tumors.

METHODS

Sarcoma tissue of different histologic subtypes was obtained from 68 patients at the time of surgery and from 26 human xenografts in nude mice. In addition, two human sarcoma cell lines (OSA and U2OS) were studied. Genomic DNA from tumor tissue, in vitro cell lines, and peripheral blood cells were isolated by Southern-blot analysis methods to determine MDM2 gene amplification. Tumor DNA was analyzed for possible TP53 gene mutations in exons 5, 7, and 8 by constant denaturing gel electrophoresis. To determine the MDM2 and TP53 mRNA levels, Northern-blot analysis was performed.

RESULTS

Amplification of the MDM2 gene was detected in 10 tumors (10.3%). Whereas MDM2 amplification and/or over-expression were found only in two (U2OS and OSA cell lines) of 18 osteosarcomas, one of 20 malignant fibrous histiocytomas (MFHs), and in none of 14 leiomyosarcomas, such alterations were observed in two of two fibrosarcomas, three of six malignant schwannomas, three of 19 liposarcomas, and in the one hemangiopericytoma examined. MDM2 overexpression was found in all nine examined cases with and in three tumors without amplification. TP53 mutations were detected in 12 cases (five osteosarcomas, four MFHs, and three leiomyosarcomas), of which none showed amplification, but one had increased levels of MDM2 mRNA. None of the fibrosarcomas, malignant schwannomas, and liposarcomas examined had mutated TP53. The six sarcomas that showed high TP53 mRNA expression in the absence of gene mutation also had elevated levels of MDM2 mRNA.

CONCLUSIONS

The present data provide further indications that increased MDM2 expression level, caused by gene amplification or altered regulation of transcription, is involved in tumor progression of some, but not all, sarcoma subtypes.

Microenvironment revisited: time for reappraisal of some prevailing concepts of cancer metastasis

The development and biological characteristics of tumor metastasis are influenced by multiple cell and host-associated factors. To study these factors experimentally, the necessity of choosing adequate in vivo model systems for human tumor metastasis is emphasized. Recent research has provided results that highlight the role of the microenvironment in determining important characteristics of the metastatic cells, including their degree of differentiation and sensitivity to drugs. Furthermore, evidence is presented as background for discussing the general validity of the notion of clonal selection of metastatic cells, and whether the metastatic phenotype is acquired through the last of a series of mutational events occurring during tumor progression.

Helix pomatia agglutinin binding in human tumour cell lines: correlation with pulmonary metastases in nude mice

The extent of lectin binding by three human melanoma (LOX, FEMX-1 and SESX) and two sarcoma lines (MHMX and OHSX) was related to their potential for experimental metastasis formation in athymic nude mice. The Helix pomatia agglutinin (HPA), which recognises the N-acetyl-D-galactosamine ligand, showed differential binding to the cell lines in a manner that correlated with their ability to give lung colonies after i.v. injection in the mice (P < 0.005). The degree of HPA binding and lung colony formation of the cell lines studied was ranked in the following order, LOX > MHMX > OHSX > SESX > FEMX-I. Similar patterns were not observed with the other lectins used in this study (WGA, Con A, PNA and UEA-I). The high HPA reacting LOX melanoma line shows extensive pulmonary metastatic formation with no extrapulmonary colonies, whereas the low HPA reacting FEMX-I cells give only extrapulmonary metastases with no detectable colonies in the lungs. Precoating of tumour cells with HPA prior to injection did not reduce the ability of cells to give pulmonary metastases, suggesting that the HPA epitope was not functionally associated with the pulmonary metastatic potential observed in nude mice. These findings support recent human studies of a correlation between HPA binding and incidence of metastasis, however, our data indicate that there is no causal relationship. Further analyses are required to identify the specific HPA-binding glycoconjugates that may be involved.

Preclinical phase II studies in human tumor xenografts: a European multicenter follow-up study

BACKGROUND

The EORTC New Drug Development Office has initiated a multicenter collaborative program to evaluate the use of human tumor xenografts to predict phase II clinical activity. A first study confirmed the efficacy of doxorubicin and inactivity of amsacrine against human tumor xenografts (Boven et al., Cancer Res: 52, 5940, 1992). In the follow-up study reported here, the activities of cisplatin, AZQ (diaziquone), pazelliptine and retelliptine have been evaluated against a panel of 40 established tumor lines grown subcutaneously in nude mice.

DESIGN

The xenografts used represent carcinomas of the breast, colon, head+neck, ovary, small cell lung cancer (SCLC), non-small cell lung cancer (NSCLC) and melanoma. Drugs were administered intravenously on days 0 and 7. Doses were for cisplatin 5 mg/kg, AZQ 3-7 mg/kg, pazelliptine 20-80 mg/kg and retelliptine 6-12.5 mg/kg and were selected to give a median loss of about 10%-15% body weight.

RESULTS

When activity was defined as a specific growth delay > 1 and a tumor growth inhibition > 50%, then cisplatin demonstrated activity in 15 of 40 xenografts tested (3 of 5 breast, 1 of 6 colon, 0 of 5 head+neck, 2 of 6 NSCLC, 4 of 7 SCLC, 1 of 5 melanoma and 4 of 6 ovarian cancers); AZQ was active in 23 of 38 xenografts (2 of 3 breast, 2 of 7 colon, 4 of 5 head+neck, 3 of 6 NSCLC, 6 of 6 SCLC, 2 of 5 melanoma, 4 of 6 ovarian cancers); pazelliptine was active in 2 of 38 xenografts (1 of 5 breast cancers, 1 of 5 melanoma) while retelliptine was active in 1 of 39 xenografts (a breast cancer xenograft) tested.

CONCLUSIONS

These results are reasonably consistent with the clinical activity of cisplatin, but overpredict the clinical efficacy of AZQ. Since pazelliptine and retelliptine are investigational compounds, the clinical phase II studies will provide a prospective test for this model. The results of the present study and the previous one indicate that the human tumor xenograft model could be suitable for predicting the activity of novel compounds to be developed for treatment of cancer patients.

Targeted therapy with immunotoxins in a nude rat model for leptomeningeal growth of human small cell lung cancer

Metastasis to the central nervous system in patients with small cell lung cancer is not uncommon, and a fraction of the cases have leptomeningeal disease for which no effective therapy is available. To establish an experimental model for evaluation of new therapeutic approaches for such tumor lesions, 1 x 10(6) human H-146 cells were injected directly into the cerebrospinal fluid in the cisterna magna of nude rats. Small, superficial leptomeningeal tumors developed, consistently resulting in symptoms of central nervous system involvement after a mean latency of 20 days. The model was used to study the efficacy of intrathecal targeted therapy with immunotoxins. The monoclonal anti-carcinoma antibodies MOC-31 and NrLu10 and the growth factor transferrin were conjugated to Pseudomonas exotoxin A (PE), and 1 day after tumor cell inoculation instilled in the cisterna magna as a single bolus dose of 1.5 micrograms. The antibody conjugates, which were highly cytotoxic to target cells in a protein synthesis inhibition assay in vitro, increased the symptom-free latency by 35-46%. PE had no effect, reflecting a lower in vitro cytotoxicity and possibly also a down-regulation of transferrin-receptor expression in the meningeal H-146 tumors. Delayed or repeated treatment with MOC-31-PE was less effective than day 1 administration, whereas the addition of 10% glycerol to the injection solution increased the symptom-free period to 72%. The efficacy of MOC-31-PE is superior to reported effects obtained in similar models with other therapies, and the results support the development of this immunotoxin towards clinical evaluation in small cell lung cancer patients with leptomeningeal carcinomatosis.

In vivo efficacy of intrathecal transferrin-Pseudomonas exotoxin A immunotoxin against LOX melanoma

Neoplastic meningitis due to the dissemination of systemic cancer or primary central nervous system tumors through the cerebrospinal fluid carries a very poor prognosis. Current treatments for this disease are ineffective, and new therapeutic modalities such as immunotoxins may be beneficial. We created an animal model of human carcinomatous meningitis with LOX melanoma-derived tissue-culture cells in athymic rats for testing the efficacy of intrathecal therapy with transferrin-Pseudomonas exotoxin A (Tfn-PE) immunotoxin. An injection of 5 x 10(5) LOX cells into the intrathecal space through an indwelling catheter resulted in the reproducible development of lower-extremity paraplegia at 9.24 +/- 1.77 days because of focal deposits of tumor growth adjacent to the thoracic and lumbar spinal cord. A dose of 2.5 or 5 micrograms of intrathecal Tfn-PE immunotoxin was neurotoxic and resulted in the deaths of 8 of 10 animals within 24 hours. Histological evidence of central nervous system damage was seen as hemorrhagic degeneration around the central canal or a pathological cleft at the level of the cervical spinal cord. Because no neurotoxicity was seen with 1 microgram of intrathecal Tfn-PE immunotoxin, this dose was administered in treatment experiments. Twenty-four hours after the intrathecal instillation of LOX cells, 10 animals received intrathecally either 1 microgram of Tfn-PE or phosphate-buffered saline with 0.1% human serum albumin (control group).(ABSTRACT TRUNCATED AT 250 WORDS)

Validity and usefulness of human tumor models established by intratibial cell inoculation in nude rats

Intratibial injection in nude rats of 1 x 10(6) OHS, MHMX, and LOX human tumor cells resulted in each case in progressively growing bone tumors. When the diameter of the affected leg had increased by 2-3 mm, the animals were examined for uptake of 99mTc-methylenediphosphonate. The OHS osteosarcoma tumors caused sclerotic lesions with high and uniform isotope uptake, and the MHMX unclassified sarcoma showed a mixed pattern with both sclerotic and lytic areas, whereas the LOX melanoma caused lytic bone lesions with low uptake of the radionuclide. These findings were compared with the results of analogous investigations previously performed in the patients from whom the tumor lines originated. Striking similarities in both the morphology and the scintigraphic images were observed between corresponding tumors in rats and humans, with results supporting the clinical relevance of the model systems. When the LOX model was used for therapy experiments, doxorubicin had no effect on the growth of the tibial tumors, which in the control group appeared after a latency of 13.5 days. The alkylating agent mitozolomide increased the median tumor-free latency to 47 days in 7 rats, and 5 animals did not develop tumors within the observation period of 60 days. Doxorubicin was ineffective also against the OHS tumor, whereas ifosfamide and the radionuclide 89Sr-chloride showed significant antitumor activity. The disease-free latency increased from 20 days, in the control animals, to 45 and 28.5 days, respectively, in the 2 treated groups, in which 2 of 7 and 2 of 10 rats were without tumors at 60 days. The data demonstrate that the tibial models discriminated between the action of the different therapeutic agents, and suggest that they may be useful in selecting compounds with clinical activity against skeletal tumors.

Suppression of the neoplastic phenotype in vivo by an anti-ras ribozyme

In this study, the efficacy of an anti-ras ribozyme in reversing the neoplastic phenotype was investigated. Murine NIH3T3 cells were transfected with cellular DNA from the FEMX-I human melanoma cell line expressing the activated H-ras gene. The transformed cells displayed the neoplastic phenotype in vitro and were tumorigenic in nude mice in vivo. When the transformants were transfected by a ribozyme designed to cleave only activated H-ras RNA, the transformed phenotype was abrogated. In contrast, expression of a mutant ribozyme, essentially acting only as antisense, into the transformed cells resulted in less dramatic changes in cell growth and tumorigenicity. These results reinforce the potential role of anti-oncogene ribozymes as suppressors of neoplastic growth, with possible implications for gene therapy.

TP53 allele loss, mutations and expression in malignant melanoma

p53 alterations at the DNA, mRNA and protein levels were studied in tumour metastases sampled from 30 patients with malignant melanoma. Paraffin-embedded sections from these and an additional 12 patients were examined for the presence of p53 protein. TP53 gene aberrations were found in 7 of 30 (23%) of the patients, six of which showed loss of heterozygosity (LOH). Point mutations were detected in only two cases, one of which had LOH whereas the other was non-informative. Increased levels of p53 mRNA were present in only one tumour with, but in six cases without, detectable DNA abnormalities. Four of the latter and six tumours with normal transcript levels had immunohistochemically detectable levels of p53 protein. In 25 cases in which corresponding primary and metastatic lesions could be compared, closely similar immunoreactivity patterns were observed. Increased expression of the MDM2 gene was found in only one tumour in parallel with overexpression of p53. Altogether, the data indicate that inactivation of the p53 regulatory pathway is not of major significance in the tumorigenesis of malignant melanoma. However, a significant association was found between p53 immunoreactivity and the relapse-free period in patients with superficial spreading melanoma. That increased protein expression was predominantly found in tumours without DNA alterations might suggest a role for the wild-type p53 protein in restricting malignant cell proliferation in these cases.

Expression of the neuroectodermal intermediate filament nestin in human melanomas

Nestin is a newly identified intermediate filament expressed in proliferating neuronal progenitor cells, but not in the adult brain. Nestin expression reappears in many tumors of the central nervous system and has in human glioblastomas been associated with a high degree of malignancy. Because melanocytes are of neuroectodermal origin, we studied nestin expression in benign and malignant cells of the melanocytic lineage using Northern blot and immunohistochemical analyses. Nestin mRNA was detected in 24 of 34 metastatic melanomas and in 1 of 4 benign nevi, whereas the protein was expressed in 10 of 15 primary melanomas, in 29 of 34 metastatic tumors, and in 3 of 4 nevi. Neither normal melanocytes nor any of 4 basal cell carcinomas showed detectable levels of the protein. The high fraction of melanocytic tumors which express nestin, particularly the metastatic melanomas, suggests that nestin may be a useful marker for such malignancies. Furthermore, although no significant correlation between nestin expression and tumor malignancy was observed, the protein was most abundantly expressed in the infiltrating part of the tumors, indicating a possible involvement of nestin in tumor invasion.

Comparison of two antibody-based methods for elimination of breast cancer cells from human bone marrow

Three monoclonal antibodies reactive with antigens abundantly expressed on human carcinoma cells were used to develop and compare the efficacy of immunotoxins (ITs) and immunobeads for purging breast cancer cells from bone marrow. ITs constructed as conjugates of the monoclonal antibodies and Pseudomonas exotoxin A showed high specific cytotoxicity against three breast cancer cell lines, inhibiting protein synthesis by 50% at concentrations of 4 x 10(-13) M to 1 x 10(-10) M. Tested in a reproducible clonogenic assay, two of the ITs used at a concentration of 0.1 microgram/ml killed > 5 log units of MCF7 cells, the maximal sensitivity for assessing cytotoxic effects, and 1.5 log of T-47D tumor cells. At 1 microgram/ml, each of the three ITs eliminated > 5 log of both cell lines. The immunobead procedure removed 2.0-4.1 log of tumor cells with one purging cycle and up to 6.0 log with two cycles. The mixture of the three ITs or immunobeads was not clearly superior in efficacy, compared to the use of individual molecules, probably reflecting an overlap in expression of the respective antigens in these cell lines. For both methods, the purging efficacy was not reduced when the tumor cells were admixed with normal bone marrow cells at a ratio of 1:10. The survival of colony-forming units, granulocyte/macrophage, was 49-86% with the immunobeads and 44-75% even at high concentrations (up to 2.5 micrograms/ml x 3) of the ITs. The results indicate that each of the two immunological methods can be safely used for effective elimination of tumor cells from the graft of breast cancer patients undergoing autologous bone marrow transplantation.

Immunoscintigraphy of bone sarcomas--results in 5 patients

The feasibility of using the murine monoclonal antibody, TP-1, for clinical immunoscintigraphy was examined in a pilot study involving 5 patients with bone sarcomas. 131I-labelled F(ab')2 antibody fragments were injected in doses of 0.8-1.0 mg (90-130 MBq), and the accumulation of radioactivity was examined by scintigraphy, and assessed by direct measurements on biopsied tumour and normal tissue. One osteosarcoma patient had a primary tumour in the femur, whereas the other 4 had single lung metastases detected by other diagnostic methods. Immunoscintigraphy of the femoral primary was optimally visualised after 22 h. In 2 patients, the method failed to detect lung metastasis, in 1 of the cases possibly related to less than optimal methodological conditions. In 2 other patients, increased accumulation of radioactivity indicated one and three lung tumours, in addition to the single metastasis observed by X-ray and CT scanning, tumours that were later confirmed and removed surgically. The concentration of radioactivity in tumour and normal tissues 44-72 h after antibody injection could be measured in 4 patients. The tumour to blood ratios were in the range of 1.2-4.2, compared to 0.1-0.8 for various normal tissues. The results indicate that immunoscintigraphy with TP-1 antibody fragments have a potential for early detection of lung metastases in patients with bone sarcoma.

Nude rat models for human tumor metastasis to CNS. Procedures for intracarotid delivery of cancer cells and drugs

Models for hematogenous spread of human cancer to the central nervous system (CNS) were established by injecting human tumor cells into the internal carotid artery of nude rats. With 4 out of 10 cell lines, belonging to four different tumor types, metastases developed in all injected animals. Tumor growth manifested clinically as neurological symptoms which appeared after a median latency ranging from 19-87 days for the different tumors. The H-146 and DMS-273 small cell lung cancers and the LOX melanoma almost exclusively gave meningeal tumors, whereas with FEMX-I melanoma cells bone metastases in the skull dominated. For these tumor types a correlation was found between the capacity for experimental metastasis formation and the s.c. tumorigenicity. In agreement with clinical experience, none of the 2 sarcoma and 2 glioblastoma lines gave CNS metastases. With a modified microsurgical technique, allowing for repeated ipsilateral intracarotid injections, we analyzed the drug concentrations obtained in tumor and surrounding brain tissue after i.v. treatment with doxorubicin. The concentration in the LOX tumor reached therapeutic levels and was approximately 100 x higher than in normal brain tissue, both with and without intraarterial pretreatment with arabinose. In the same model, the tissue concentrations of 9.2.27-abrin immunotoxin 10 min after intracarotid injection were examined. Although the levels were low, a tumor to brain concentration ratio of up to 9 was achieved. The data demonstrate that clinically relevant tumor models can be established with the techniques described, and these models may successfully be used to evaluate the pharmacokinetics and effect of intravenous or intraarterial therapy.

Mapping of amplification units in the q13-14 region of chromosome 12 in human sarcomas: some amplica do not include MDM2

Amplification of cellular oncogenes may be important for the development and progression of malignant tumors. In human sarcomas, amplification of several genes located to the q13-14 region of chromosome 12 has been reported. Because the mdm2 protein seems to inactivate the tumor suppressor protein p53, a selective growth advantage of 12q13-14 amplification has previously been assigned to increased copy number and expression of the MDM2 gene. We have analyzed a panel of 98 human sarcomas of different subtypes to characterize the 12q13-14 amplica and determine which of the genes GLI, A2MR, SAS, MDM2, and GADD153 (CHOP) in this region was most consistently amplified. MDM2 was amplified in 9 of the tumors, SAS in 10, GADD153 in 4, GLI in 2, and A2MR in 2. Amplification was, in most cases, associated with increased expression of the corresponding gene. SAS and MDM2 were coamplified in 8 of the tumors, whereas GADD153, GLI, and A2MR were only amplified together with SAS. One liposarcoma showed amplification of MDM2 alone, whereas two osteosarcomas and a rhabdomyosarcoma cell line showed amplification of SAS and GADD153 (CHOP) but not MDM2. It is suggested that the selective target for these amplica may be an as yet unidentified gene localized between SAS and MDM2.

Rapid detection of transferrin receptor expression on glioma cell lines by using magnetic microspheres

A rapid method for detecting the presence of transferrin receptors (TR) on human glioblastoma-derived cell lines is presented. The development of new treatment modalities, such as immunotoxins for central nervous system cancer, requires the identification of appropriate surface antigens on tumor cells. Seven established human glioblastoma-derived cell lines were assayed for the presence of TR with antibody-coated magnetic microspheres (immunobeads). The immunobeads bound to glioblastoma cells in the presence of human anti-TR monoclonal antibodies to a significantly greater degree than to control cell lines (P < 0.0001). The expression of TR was confirmed by standard immunocytochemical techniques. A 9L rat gliosarcoma cell line was used as a nonhuman control and did not demonstrate TR expression by either the immunobead assay or immunocytochemistry. This assay represents a simple, sensitive way to detect TR expression on malignant cells, which may be useful for the identification of other cell surface antigens that can be exploited by targeted therapies.

Eradication of small cell lung cancer cells from human bone marrow with immunotoxins

The potential of autologous bone marrow transplantation to improve the treatment results for patients with small cell lung cancer (SCLC) may be limited by the presence of tumor cells in the graft. We constructed immunotoxins (ITs) involving 4 monoclonal antibodies and Pseudomonas exotoxin A and investigated the cytotoxicity of the ITs to H-146 SCLC cells in the presence and absence of normal human bone marrow (BM) cells. The Pseudomonas exotoxin A conjugate with the MOC-1 antibody, which recognizes an NCAM antigen, was inactive, as tested in a reproducible soft agar assay. Conjugates involving the monoclonal antibodies MOC-31, NrLu10, and MLuC1 killed about 3.5 log tumor cells at 0.1 microgram/ml and > 5.0 log at 1 microgram/ml. In the absence of BM cells, the combination of the 3 ITs was not superior to each IT used individually. However, when H-146 cells were admixed to nucleated BM cells at the ratio of 1:10, > 5 log tumor cell kill was obtained at a concentration as low as 0.1 microgram/ml of each IT. Survival of normal BM progenitor cells was only moderately reduced by the IT treatment, even in experiments in which the 3 IT3s were used at 2.5 micrograms/ml each. Freezing and thawing of the BM, as required in a clinical setting, reduced the colony-forming unit, granulocyte-macrophage, and colony-forming unit, granulocyte-erythroid-macrophage-megakaryocyte, by 30-60% in both treated and untreated cultures. We conclude that the use of a mixture of the 3 ITs provides a safe, rapid, and effective method for eradicating SCLC cells from BM used for autologous bone marrow transplantation following high-dose chemotherapy.

Effective removal of SCLC cells from human bone marrow. Use of four monoclonal antibodies and immunomagnetic beads

High dose chemotherapy with autologous bone marrow transplantation (ABMT) has shown promise in several types of cancer. There is, however, a risk of transfusing contaminating tumour cells with the bone marrow cells, e.g. in patients with small cell lung carcinoma (SCLC). To eliminate SCLC cells from normal human bone marrow, four monoclonal antibodies reactive with SCLC cells were used with immunomagnetic beads in model experiments. With two cycles of immunomagnetic elimination the individual antibodies removed 2.5-4.4 log of H-146 tumour cells from a single cell suspension, as assessed in a highly reproducible soft agar assay. Different combinations of two antibodies were only marginally more effective than the individual MAbs, whereas 5-6 log removal was obtained with a combination of all four antibodies. The method was equally effective when the tumour cells were mixed with bone marrow cells at a ratio of 1:10. The immunomagnetic procedure did not significantly affect the survival of normal progenitor cells, assessed in CFU-GM and CFU-GEMM assays. The results indicate that the procedure safely and effectively can be used to eliminate tumour cells from the bone marrow in conjunction with ABMT in patients with SCLC.

Monoclonal antibody accumulation in experimental and spontaneous lung metastases of human malignant melanoma in rodents

Monoclonal antibody (mAb) uptake in metastatic lung lesions was depicted and evaluated by digital autoradiography. The models examined were experimental metastases of a human melanoma in nude mice and spontaneous metastases of human melanoma in immunocompromised young rats. By comparing uptake patterns in local (s.c.) tumours and in lung processes of various sizes it was found that patterns were essentially similar in both types of malignant tissue. From the point of view of visualization, however, the high blood content of lung tissue resulted in high background and low contrast. This could be overcome by the use of rapidly cleared antibody fragments.

[Transgenic mice as animal model of Cushing's syndrome]

Transgenic mice were generated with the polyoma early region promoter linked to cDNA encoding polyoma large T antigen (PyLT). Light microscopic examination showed up to 5 mm large pituitary adenomas in clinically ill transgenic mice. The tumour cells showed positive ACTH immuno-reactivity. The adrenal glands of clinically ill mice showed an increase in weight and exhibited medullary hyperplasia. These findings were unexpected, and might have been caused by transgene expression in the neuroendocrine cells of the adrenal medulla. Plasma ACTH measurements showed significantly increased levels in clinically ill PyLT-1 transgenic mice.

Preclinical antitumour activity and animal toxicology studies of rhizoxin, a novel tubulin-interacting agent

Rhizoxin is a 16-membered antifungal macrocyclic lactone isolated from the plant pathogenic fungus Rhizopus chinensis. The compound binds to tubulin, preventing microtubule formation, and inhibiting mitosis. It possesses antitumour activity in vivo against various preclinical murine models, both leukaemias and solid tumours model, as well as in vincristine- and doxorubicin-resistant leukaemia lines. In the present study, cytotoxic activity was observed in human tumour cell lines in vitro at very low concentrations (+/- 10(-10) M) particularly against melanoma, colon, renal, non-small cell and small cell lung cancer. In vivo antitumour activity was demonstrated in murine P388 and L1210 murine leukaemias, solid tumour models B16 melanoma and M5076 sarcoma, and in 5 out of 9 human solid tumour xenografts: LOX melanoma, MX-1 breast cancer, non-small cell lung cancer A549, and small cell lung cancers LXFS 605 and LXFS 650. The absence of cross-resistance to vinca alkaloids was confirmed in vivo against the vincristine-resistant P388 leukaemia subline and the vincristine-resistant human small cell lung cancer LXFS 650. In addition, the antitumour activity of rhizoxin was improved by prolonged or repeated drug administration indicating a schedule dependency. In animal toxicology studies, transient changes in erythrocyte and leukocyte numbers, local phlebitis, diarrhea, and spermatogenic arrest were observed. The LD10 value of rhizoxin after a single intravenous injection was 2.8 mg/kg (8.4 mg/m2). One-tenth of the mouse equivalent LD10 (0.84 mg/m2), the starting dose for clinical phase I studies, was considered to be safe in rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Phase II preclinical drug screening in human tumor xenografts: a first European multicenter collaborative study

In a European joint project carried out in 6 laboratories a disease-oriented program was set up consisting of a panel of 7 tumor types, each represented by 4 to 8 different human tumor lines, for secondary screening of promising anticancer drugs. Human tumor lines were selected on the basis of differences in histology, growth rate, and sensitivity to conventional cytostatic agents. Xenografts were grown s.c. in nude mice, and treatment was started when tumors reached a mean diameter of 6 mm in groups of mice where at least 6 tumors were evaluable. Drugs were given at the maximum tolerated dose. For evaluation of drug efficacy, median tumor growth curves were drawn, and specific growth delay and treated/control x 100% were calculated. Doxorubicin (8 mg/kg i.v. days 1 and 8) was effective (treated/control < 50%, and specific growth delay > 1.0) in 0 of 2 breast cancers, 1 of 3 colorectal cancers, 2 of 5 head and neck cancers, 3 of 6 non-small cell lung cancers, 4 of 6 small cell lung cancers, 0 of 3 melanomas, and 3 of 6 ovarian cancer lines. Amsacrine (8 mg/kg i.v. days 1 and 8) was not effective, while datelliptium (35 mg/kg i.p. days 1 and 8) was active against 2 of 6 small cell lung cancer lines. Brequinar sodium (50 mg/kg i.p. days 1-5) showed efficacy in 4 of 5 head and neck cancers, 5 of 8 non-small cell lung cancers, and 4 of 5 small cell lung cancer lines. The project has been shown to be a feasible approach. Clinical activity for doxorubicin and inactivity for amsacrine against solid tumor types was confirmed in the human tumor xenograft panel. Additional anticancer drugs will be studied in the European joint project to further define the reliability of this novel, promising screening approach.

Levels of nm23 messenger RNA in metastatic malignant melanomas: inverse correlation to disease progression

Data obtained in experimental murine tumors and in clinical specimens of human breast cancer have suggested that the nm23 gene may function as a metastasis suppressor gene. In this report we examined the nm23 mRNA level in tumor tissue obtained from distant metastases in 33 patients with malignant melanoma. The gene was differentially expressed in the tumors with a 20-fold range in hybridization intensities. The levels of nm23 mRNA in benign nevi obtained from 12 of the 33 patients were relatively low, with a mean value of 17% of that in the melanomas. In attempts to relate the level of nm23 expression in the tumor metastases to progression of the disease, the time from biopsy of the primary tumor to the appearance of metastases was used as a clinical end point. It was found that patients developing metastases during the first 2 years after diagnosis had significantly lower levels of tumor nm23 expression (56% of the mean value) compared to patients with less aggressive disease (164%) (P < 0.0004). In concordance with previous data the association found here between low levels of nm23 mRNA and the malignant potential of melanomas suggests that the nm23 gene may be implicated in the mechanism of disease progression in some types of human cancer.

Immunotoxins directed against the high-molecular-weight melanoma-associated antigen. Identification of potent antibody-toxin combinations

To study factors influencing the cytotoxicity of immunotoxins (ITs), we compared the in vitro cytotoxicity of conjugates in which the plant toxin abrin and the bacterial toxin Pseudomonas exotoxin A (PE) were coupled by 2 different procedures to 2 MAbs, 9.2.27 and NR-ML-05, which bind to different epitopes on the melanoma-associated antigen p250. The individual target cell lines differed widely in sensitivity to the different ITs, as assessed by measurement of protein synthesis inhibition. The action of the ITs was highly specific, as the toxicity of abrin and PE conjugates was respectively 20-540 and 2,200-550,000 times higher in antigen-positive cell lines (FEMX, SESX, OHS) than in the antigen-negative line KPDX. The PE conjugates prepared with the 2 different MAbs differed in potency by factors of 16-126 in the target-cell lines, but were consistently more toxic than the abrin ITs. The results demonstrate that the cytotoxicity of ITs varies with the nature of both of its moieties and that optimal results require that toxins and MAbs be matched. Moreover, the 2 coupling procedures affected differentially the binding and potency of some ITs. Each of the 2 toxins was conjugated to a sheep anti-mouse antibody (SAM) and the toxicity of these 2 conjugates was tested in an indirect approach using 9.2.27 and NR-ML-05 as primary MAbs. The results showed that the indirect procedure would have correctly predicted the most potent antibody-toxin pair, indicating that the approach may be valid for selecting suitable combinations of MAbs and toxins for use as direct ITs.

Detection of bone marrow metastases in small cell lung cancer patients. Comparison of immunologic and morphologic methods

An immunocytochemical method, involving four monoclonal antibodies (MAbs) previously selected for their specific binding to small cell lung cancer (SCLC) cells in human bone marrow, was used for detection of bone marrow metastases in 81 patients with diagnosed SCLC. This procedure was compared with two routine morphologic methods with regard to diagnostic efficiency and sensitivity. Bone marrow involvement was found in 26 patients (32%), one of which had limited disease according to conventional clinical criteria. Eight of the positive cases were exclusively diagnosed by immunocytochemistry, whereas the histologic and cytologic methods separately identified two patients each. Immunocytochemistry had a detection level of tumor cells in the mononuclear cell fraction of approximately 1-2%, whereas no patients with less than 10% immunocytologically detectable tumor cells were diagnosed by cytomorphologic examination of bone marrow aspirates. Evidence was obtained that the diagnostic efficiency of any method increased with the number of samples examined. Of the four MAbs used, the anti-NCAM antibody, MOC-1, labeled tumor cells in all immunologically positive patients, and in all but one of these patients all cytologically confirmed tumor cells were stained. The antibodies MOC-31, which recognize a cluster-2 antigen, and NrLu10 bound nearly all tumor cells in most cases, whereas MLuC1 only diagnosed tumor cells in a fraction of the patients. The results show that the immunocytochemical application of these antibodies is superior to morphologic techniques in detecting SCLC bone marrow metastases. Further use of the method might provide prognostically and therapeutically useful information.