Immunotoxin therapy for cancer.
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ADP Ribose Transferases↗
Biomedical subjects
L H Pai
Publications and source records attributed to L H Pai.
The use of immunotoxins for cancer therapy.
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Humans↗
Evaluation of a new DTPA-derivative chelator: comparative biodistribution and imaging studies of 111In-labeled B3 monoclonal antibody in athymic mice bearing human epidermoid carcinoma xenografts.
Biodistribution and imaging characteristics of monoclonal antibody (MAb) B3 conjugated to either the 2-(p-isothiocyanatobenzyl)-cyclohexyl-DTPA (CHX-B) or 2-(p-isothiocyanatobenzyl)-6-methyl-DTPA (1B4M) and labeled with 111In, were evaluated in nude mice bearing A431 human epidermoid carcinoma xenografts. MAb B3, is a murine IgG1k reacting with a carbohydrate antigen abundantly expressed by most carcinomas. Both 111In-(CHX-B)-B3 and 111In-(1B4M)-B3 showed good tumor targeting with peak values observed at 72 h with 27.6 +/- 7.6 and 25.4 +/- 1.7% ID/g, respectively (P > 0.05). High tumor-to-organ ratios were also observed and, confirmed by the imaging results. In particular, tumor-to-liver ratios increased from 5.0 +/- 0.9 at 24 h to 9.2 +/- 2.0 at 168 h for 111In-(CHX-B)-B3 and from 4.5 +/- 0.6 to 8.9 +/- 3.5 for 111In-(1B4M)-B3. This was mainly the result of low liver accumulation of both 111In-(CHX-B)-B3 and 111In-(1B4M)-B3, with only 2.48 +/- 0.46 and 2.5 +/- 0.9% ID/g at 168 h, respectively (P > 0.05). Our findings indicate that either CHX-B or 1B4M can be successfully used for 111In-labeling of MAbs and that 111In-B3 may represent a promising radioimmunoimaging agent.
Animals↗
Pseudomonas exotoxin conjugated to monoclonal antibody MRK16 specifically kills multidrug resistant cells in cultured renal carcinomas and in MDR-transgenic mice.
Using renal carcinoma and prostate carcinoma cell lines, we investigated the concept of targeting and killing multidrug resistant cells in urogenital cancers. Renal carcinoma lines HTB44, 45, 46, and 47 expressed a relatively low, but detectable level of multidrug resistance (MDR)1 mRNA as indicated by Northern blot analysis, whereas prostate lines LNCaP and DU145 were found to be MDR1-negative. Anti-P-glycoprotein monoclonal antibody MRK16 was conjugated to Pseudomonas exotoxin (PE) by a stable thioether bond. Treatment with MRK16-PE resulted in a dose-dependent killing of multidrug resistant renal carcinoma cells, while non-MDR expressing prostate carcinoma cells were not affected. Addition of excess MRK16 blocked the effect of MRK16-PE. Furthermore, MOPC-PE, a non-MDR associated monoclonal antibody control conjugate, did not target and kill multidrug resistant renal carcinoma cells. Having established that MRK16-PE was active against and specific for multidrug resistant cells in culture, we also tested bioactivity in MDR-transgenic mice, whose bone marrow cells express the human MDR1 gene at a level approximately equal to that found in many human cancers. Again, MRK16-PE killed multidrug resistant bone marrow cells with high efficiency in an intact animal, and killing was blocked by unconjugated MRK16.
ADP Ribose Transferases↗
Cytotoxicity and antitumor effects of growth factor-toxin fusion proteins on human glioblastoma multiforme cells.
The prognosis of glioblastoma multiforme remains poor despite advances in treatment by surgery, irradiation, and chemotherapy. Many malignant gliomas overexpress growth factor receptors. The possibility of targeting these receptors with selective cytotoxic molecules constructed by fusing deoxyribonucleic acid (DNA)-encoding mutant forms of Pseudomonas exotoxin A (PE) with complementary DNA-encoding growth factors was investigated. Several recombinant toxins have been produced, including those in which transforming growth factor (TGF)-alpha, insulin-like growth factor (IGF)-I, and acidic fibroblast growth factor (FGF) were fused to mutant forms of PE lacking the native cell-binding domain. These recombinant proteins are cytotoxic to cells that express specific cell-surface receptors. The cytotoxic activity of TGF-alpha, IGF-I, and acidic FGF chimeric toxins was tested in vitro against human glioblastoma cell lines. Each recombinant toxin exhibited potent and specific killing of cells. The TGF-alpha-PE40 construct was cytotoxic to seven of the eight cell lines and was active at concentrations as low as 0.5 ng/ml (1.1 x 10(-11) M). The acidic FGF-PE40 toxin was also active on seven of the eight cell lines but was 50-fold less active than the TGF-alpha-PE40. The IGF-I-PE40 construct was active on only two cell lines. To determine the possible therapeutic effect in animals, TGF-alpha-PE40 was administered to nude mice bearing subcutaneous human glioblastoma xenografts. The animals were treated for 7 days via a continuous infusion pump placed in the peritoneal cavity. A constant serum level of TGF-alpha-PE40 was achieved that was nontoxic to the mice yet caused a reduction in tumor volume and retarded growth beyond the treatment period. The overexpression of the epidermal growth factor receptor in glioblastomas multiforme and the potency and specificity of the TGF-alpha-PE40 construct designed to target this receptor suggests that TGF-alpha-PE40 has the potential to be an effective antitumor agent for the adjuvant therapy of these carcinomas.
ADP Ribose Transferases↗
Monoclonal antibody MRK16 reverses the multidrug resistance of multidrug-resistant transgenic mice.
Using multidrug-resistant (MDR)-transgenic mice, whose bone marrow cells express the human MDR1 gene at a level approximately equal to that found in many human cancers, we determined the efficacy of human-specific anti-P-glycoprotein monoclonal antibody MRK16 in overcoming multidrug resistance in an intact animal. MRK16 alone (2 mg) did not significantly affect the WBC counts of the MDR-transgenic mice, but MRK16, as well as the F(ab')2 fragments of MRK16, led to a dose-dependent circumvention of bone marrow resistance against daunomycin, doxorubicin, vincristine, vinblastine, etoposide, and taxol. This sensitizing effect could not be enhanced by combining MRK16 with low molecular weight chemosensitizing agents such as verapamil, quinine, quinidine, or cyclosporin A. We also investigated the concept of specifically targeting and killing multidrug-resistant cells by using MRK16 coupled to Pseudomonas exotoxin (PE). MRK16-PE resulted in a dose-dependent killing of bone marrow cells in MDR-transgenic mice, whereas no bone marrow toxicity was observed in normal control mice. Administration of excess MRK16 prior to injection of MRK16-PE successfully blocked the effect of MRK16-PE. MOPC-PE, a non-MDR-related control monoclonal antibody conjugate, did not target and kill multidrug-resistant bone marrow cells in MDR-transgenic mice. Thus, these immunological approaches to reversing multidrug resistance appear to be both specific and effective.
Alkaloids↗
Antitumor effects of B3-PE and B3-LysPE40 in a nude mouse model of human breast cancer and the evaluation of B3-PE toxicity in monkeys.
B3 is a tumor-reactive monoclonal antibody (mAb) that binds to a limited number of normal tissues. Immunotoxins made with B3 coupled to either Pseudomonas exotoxin (PE) or recombinant forms of PE with a deletion of the cell-binding domain (LysPE40) have been shown to cause complete tumor regression in nude mice bearing a rapidly growing A431 (L. H. Pai et al., Proc. Natl. Acad. Sci. USA, 88: 3358-3362, 1991) human epidermoid carcinoma. In this study we show that an immunotoxin composed of mAb B3 when chemically coupled to LysPE40 (B3-LysPE40) led to complete regression of a slowly growing breast cancer, MCF-7, in nude mice when given i.v. every other day for five doses. mAb B3 coupled to native PE also produced significant regression of the MCF-7 tumor. The reactivity of mAb B3 was evaluated using an immunohistochemical method on the two responsive tumors, MCF-7 and A431, and compared with a typical human colon carcinoma specimen that has B3 antigen on its surface. The results showed that both A431 and MCF-7 xenograft tumors have similar reactivity to B3 when compared with the human colon carcinoma specimen. To evaluate the toxicity of B3-PE in primates, Cynomolgus monkeys received escalating doses of B3-PE i.v. on Days 1, 3, and 5. Based on antibody localization studies using frozen sections of normal human and monkey tissue, gastric, trachea, and bladder mucosal injury could have occurred. However, no clinical signs of injury or histological damage to these organs were seen at the doses administered. Chemical hepatitis due to PE was transient and well tolerated at doses up to 50 micrograms/kg for three doses. The lethal dose was about 100 micrograms/kg, and the cause of death was liver necrosis, as shown by necropsy. We conclude that mAb B3, when coupled to PE40 or PE, can produce strong antitumor activity in vivo. The similar level of reactivity of the B3 antibody in our tumor models with a surgical specimen of a human colon carcinoma and the toxicity study in monkeys indicate that therapeutic doses of B3-PE and B3-LysPE40 can be delivered without causing toxicity to normal organs that express B3 antigen. Although both B3-PE and B3-LysPE40 have antitumor activity in nude mice bearing a human xenograft, B3-LysPE40 is better tolerated and should be further evaluated as a therapeutic agent for cancer patients.
ADP Ribose Transferases↗
Alteration of a protease-sensitive region of Pseudomonas exotoxin prolongs its survival in the circulation of mice.
Pseudomonas exotoxin A (PE) is a single-chain 66-kDa polypeptide that kills eukaryotic cells by ADP-ribosylation of translational elongation factor 2. PE is composed of three major structural domains whose functions are binding of cells (I), translocation (II), and ADP-ribosylation (III). Here we describe a protease cleavage target that is located near arginine-490 on the surface of domain III. We made several different types of mutations near arginine-490. Deletion of arginine-490 or replacement of arginine-490 and -492 with serine and lysine or with two lysines resulted in protease-resistant molecules that were fully cytotoxic and had normal ADP-ribosylation activity. However, the half-life in mouse blood of the PE delta 490 mutant was 24 min whereas that of PE was 13 min. Furthermore, two PE mutants that were protease-hypersensitive, PEGlu246,247,249 and PEGlu57,246,247,249 (in which glutamate residues replace basic residues at the indicated positions), had very short half-lives. These data indicate that protease sensitivity is an important determinant in the half-life of PE in the circulation and suggest that the half-life of other proteins may be prolonged by removal of protease sites. Deletion of arginine-492 or the replacement of amino acids 486-491 with three glycines markedly diminished ADP-ribosylation activity and cytotoxicity, indicating that this region of domain III is also important for catalytic activity.
ADP Ribose Transferases↗
Characterization of the antigen (CAK1) recognized by monoclonal antibody K1 present on ovarian cancers and normal mesothelium.
K1 is a monoclonal antibody that reacts with a cell surface antigen (CAK1) found in human mesothelia and nonmucinous ovarian tumors. In this article, the characteristics of the CAK1 antigen have been examined in detail. Using immunofluorescence microscopy, we have found that the CAK1 signal is removed from the cell surface by treatment with proteases or by phosphatidylinositol-phospholipase C, but not by neuraminidase and beta-galactosidase. The phosphatidylinositol-phospholipase C-released material was found to contain the CAK1 antigen which was detected by a competition radioimmunoassay. The phosphatidylinositol-phospholipase C-released CAK1 antigen was examined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting and found to be approximately 40 kDa protein. The CAK1-K1 antibody complex remains on the cell surface and is poorly internalized, as shown by an acid wash immunofluorescence internalization assay. An immunotoxin composed of K1 and Lys-PE40, a mutant form of Pseudomonas exotoxin lacking the cell binding domain, was not cytotoxic, supporting the conclusion that the CAK1-K1 antibody complex is not internalized. However, an immunotoxin composed of K1 and native Pseudomonas exotoxin was selectively cytotoxic to cells expressing the CAK1 antigen. This cytotoxicity is due to the fact that domain I of Pseudomonas exotoxin promotes internalization of antigens which are not internalized or bound to antibody alone. Our results suggest that CAK1 is a polypeptide that is expressed on mesothelial cells and many ovarian cancers, and that K1 may be useful as a targeting agent for the immunotherapy of human ovarian cancer.
Antibodies, Monoclonal↗
Monoclonal antibody K1 reacts with epithelial mesothelioma but not with lung adenocarcinoma.
Immunoperoxidase histochemical staining of cryostat sections from human tumor tissues revealed that a murine monoclonal antibody (MAb), K1, can distinguish epithelial mesotheliomas from lung adenocarcinomas. All of 15 epithelial-type mesotheliomas and all four mixed type mesothelioma samples, but none of 23 lung adenocarcinomas with different degrees of histologic differentiation demonstrated reactivity with antibody K1. Of the cell populations in each mesothelioma tested, 80% to 100% showed strong and homogeneous staining with MAb K1. Immunofluorescence analysis of live cultured cells from an epithelioid mesothelioma (H-meso) and several lung carcinoma cell lines as well as a pleural effusion of a patient with mesothelioma also showed selective reactivity of K1 with the mesothelioma cells. These data indicate that K1 can be useful as a mesothelial cell marker for the differential pathological diagnosis of the epithelial form of mesothelioma; K1 may also be useful in the study of the pathogenesis, immunodiagnosis, and immunotherapy of epithelial-type and mixed-type human malignant mesothelioma.
Adenocarcinoma↗
Therapy of patients with metastatic breast cancer with 5-fluorouracil, leucovorin and carboplatin.
Thirty-four women with metastatic breast cancer were treated at the National Cancer Institute of the National Institutes of Health, with a regimen of leucovorin (L), 500 mg/m2 i.v. over 30 min, followed in 1 h by 5-fluorouracil (5-FU), 375 mg/m2 i.v. bolus on days 1-5, and carboplatin (CBDCA), 50-100 mg/m2 i.v. bolus on days 2-4, every 28 days. All patients had received previous combination chemotherapy with at least one regimen (29 patients with 5-FU-containing regimens). CBDCA, 100 mg/m2 on days 2-4, resulted in grade 4 neutropenia in 10 out of 11 patients associated with sepsis in all 10 patients. CBDCA, 75 mg/m2 (seven patients) and 50 mg/m2 (15 patients), resulted in grade 4 neutropenia in six and eight patients, and neutropenic sepsis in five and two cases, respectively. Grade 4 thrombocytopenia occurred in 10, five and two patients receiving 100, 75 and 50 mg/m2 of CBDCA, respectively. Other toxicities included grade 3/4 mucositis in 18 patients and grade 3/4 diarrhea in 10 patients. Twenty nine patients were evaluable for response, with one pathologic complete response (3%), two partial responses (6%), 18 stable disease (53%) and eight (24%) progressive disease. Sites of response included bone, viscera and soft tissue. The median time from entry on study to progression, for responders, was 15 months. When platinum-DNA adduct formation in peripheral white blood cells was analyzed in 27 patients at 24 h after drug administration, a significant correlation between adduct level and CBDCA cumulative dose was found.(ABSTRACT TRUNCATED AT 250 WORDS)
Adult↗
B3(Fv)-PE38KDEL, a single-chain immunotoxin that causes complete regression of a human carcinoma in mice.
The genes encoding the heavy- and light-chain Fv regions of the monoclonal murine antibody B3, which recognizes a carbohydrate antigen on the surface of many human carcinomas, were cloned by PCR techniques and used to generate single-chain immunotoxins containing Pseudomonas exotoxin (PE). The light and heavy chains were connected by a flexible linker to form a single-chain antigen-binding protein, B3(Fv), which was in turn fused to truncated forms of PE lacking the cell-binding domain. The single-chain Fv and two different B3(Fv) immunotoxins, B3(Fv)-PE40 and B3(Fv)-PE38KDEL, were expressed in Escherichia coli and the single-chain immunotoxins were purified to near homogeneity. Both recombinant immunotoxins were shown to be cytotoxic specifically to carcinoma cell lines that express the B3 antigen on their surface; B3(Fv)-PE38KDEL was significantly more active. Furthermore, intravenous administration of B3(Fv)-PE38KDEL caused complete regression of human epidermoid carcinomas growing subcutaneously in immunodeficient mice.
ADP Ribose Transferases↗
Antitumor activity of a transforming growth factor alpha-Pseudomonas exotoxin fusion protein (TGF-alpha-PE40).
TGF-alpha-PE40 is a chimeric protein composed of transforming growth factor alpha (TGF-alpha) linked to a modified Pseudomonas toxin from which the cell recognition domain has been deleted (PE40). TGF-alpha-PE40 has been shown to have cytotoxic effects on human cancer cell lines that express the epidermal growth factor (EGF) receptor on their surface, and when given i.p., it prolongs the survival of nude mice bearing i.p. tumors. Because several normal tissues, including liver, express EGF receptors on their surfaces, it has not been clear that this agent can be used systemically to treat EGF receptor-bearing tumors. In this study, we have delivered TGF-alpha-PE40 for 7 days by continuous infusion through a miniosmotic pump placed in the peritoneal cavity of nude immunodeficient mice. Two different human cancer cell lines that express EGF receptors on their surface were implanted s.c. One was A431, an epidermoid carcinoma; the other was DU-145, a prostate carcinoma. By using this mode of continuous i.p. delivery, we were able to achieve a constant serum level of TGF-alpha-PE40 that was nontoxic to the mice and yet delayed the growth of both tumors implanted s.c. and caused partial regression of one. We conclude that it is possible to deliver TGF-alpha-PE40 systemically and achieve a therapeutic serum level in mice without major toxicity. Although side effects may be expected, this study establishes that there is a therapeutic window for this agent in the therapy of cancers with high numbers of EGF receptors.
Animals↗
Anti-tumor activities of immunotoxins made of monoclonal antibody B3 and various forms of Pseudomonas exotoxin.
B3 is a monoclonal antibody that reacts with a carbohydrate epitope present on a variety of proteins located on the surface of many cancer cells and a limited number of normal tissues. We evaluated the cytotoxic activity of immunotoxins composed of monoclonal antibody B3 coupled to native Pseudomonas exotoxin (PE) or two recombinant forms of Pseudomonas exotoxin, PEArg57 or LysPE40, a form of PE with a deletion of the cell binding domain. All three conjugates were cytotoxic to human cell lines expressing the B3 antigen on their surface. The survival of each of the three immunotoxins in the circulation of mice was determined after administering the immunotoxin i.v. The half-life in blood of B3-PE and B3-PEArg57 was 20 hr, whereas the half-life of B3-LysPE40 was 4 hr. The short half-life of B3-LysPE40 may be due to the absence of domain I of PE. To determine the therapeutic effects of the three immunotoxins, they were given intraperitoneally to nude mice bearing subcutaneous A431 tumors. All three immunotoxins caused complete regression of 50-mm3 tumors with no toxic effects to the animals at therapeutic doses. Furthermore, substantial regression was also noted with much larger tumors. Our data indicate that the monoclonal antibody B3, when coupled to PE or recombinant forms of PE, may be useful for the treatment of tumors expressing B3 antigen. The therapeutic window was largest with B3-LysPE40, which can be administered in higher doses because it lacks sequences in domain I of PE that enable PE to bind to nontarget cells.
ADP Ribose Transferases↗
Clinical evaluation of intraperitoneal Pseudomonas exotoxin immunoconjugate OVB3-PE in patients with ovarian cancer.
OVB3-PE is an immunotoxin composed of a murine monoclonal antibody reactive with human ovarian cancer and conjugated to Pseudomonas exotoxin (PE). Twenty-three patients with refractory ovarian cancer were treated intraperitoneally (IP) with escalating doses of OVB3-PE to study toxicity, pharmacokinetics, antiimmunotoxin antibody formation, and antitumor response. Dose-limiting CNS toxicity occurred after repeated doses at 5 and 10 micrograms/kg. Other non-dose-limiting toxicities included transient elevation of liver enzymes, fever, and gastrointestinal toxicity. Pharmacokinetics of IP and serum OVB3-PE were determined in 16 patients. Peak peritoneal fluid levels exceeded the in vitro median effective dose at all doses tested. At doses of 1 to 2 micrograms/kg, the immunotoxin concentration in the peritoneal fluid remained constant for up to 8 hours and dropped to negligible levels after 12 hours. At the 5 and 10 micrograms/kg doses, levels remained high for up to 24 hours (greater than 100 ng/mL) and then gradually decreased and became undetectable (less than 4 ng/mL) after 72 hours. Serum levels of OVB3-PE were also analyzed in 16 patients. At doses of 1 micrograms/kg and 2 micrograms/kg, serum levels were not detectable (less than 5 ng/mL). However, after doses of 5 or 10 micrograms/kg, peak serum level occurred at 24 hours after each dose and dropped to negligible levels by 72 hours. Sera from 12 patients were analyzed for anti-PE antibodies and antibodies to mouse immunoglobulin (HAMA). All patients developed antibodies against PE within 14 days of therapy. Domain II of PE appeared to be the most immunogenic portion of the PE molecule. HAMA was detected on day 14 of therapy in nine patients, on day 21 in two, and on day 28 in one patient. No clinical antitumor responses were observed. We conclude that IP OVB3-PE at dose levels of 5 micrograms/kg (x 3) and 10 micrograms/kg (x 2) is accompanied by dose-limiting toxic encephalopathy. Neurologic toxicity is likely to be due to crossreactivity of OVB3 to normal human brain tissue, which was not appreciated during preclinical screening.
ADP Ribose Transferases↗
Inhibition of antibody response to Pseudomonas exotoxin and an immunotoxin containing Pseudomonas exotoxin by 15-deoxyspergualin in mice.
Immunotoxins are potent cell-killing agents that may be useful in the treatment of cancer. The early production of neutralizing antibodies to immunotoxins is one of the major limiting factors for their use in humans. 15-Deoxyspergualin (DSG), a derivative of spergualin, which is a metabolite of Bacillus laterosporus, has been found to have immunosuppressive activity in rodents, dogs, and primates. We examined the suppressive activity of DSG on the antibody response to Pseudomonas exotoxin in mice by enzyme-linked immunosorbent assay. Male BDF1 mice were immunized with a single dose of a nontoxic mutant of Pseudomonas exotoxin (40 micrograms) and then treated with i.p. injections of DSF at a dose of 10 mg/kg for 3 days. Although antibodies to Pseudomonas exotoxin were observed within 7 days in the control group, there was complete suppression of antibody production in the DSG-treated group. Immunosuppression has also been observed in animals immunized with multiple doses (10 mg x 7 d) of Pseudomonas exotoxin and treated with DSG at a dose of 5 mg/kg for 21 days. Similar immunosuppression was observed in mice given multiple doses of the immunotoxin, anti-Tac-LysPE40. We conclude that the immunosuppressive activity of DSG may be useful in increasing the duration of immunotoxin treatment.
ADP Ribose Transferases↗
Relationship between patient response in ovarian and breast cancer and platinum drug-DNA adduct formation.
Nucleated blood cell DNA samples from ovarian (n = 27) and breast (n = 25) cancer patients receiving either cis-diamminedichloroplatinum II (cisplatin) and/or diamminecyclobutanecarboxylatoplatinum II were examined for the presence of platinum drug bound to DNA during several cycles of therapy. Platinum-DNA adducts were quantitated by cisplatin-DNA enzyme-linked immunosorbent assay (ELISA) and atomic absorbance spectroscopy, techniques that measure either a fraction of the intrastrand cis-diammineplatinum-d(ApG) and -d(GpG) adducts (ELISA) or the total platinum bound to DNA (atomic absorbance spectroscopy), respectively. For either the complete study, or for samples obtained during the early cycles, individuals with progressive disease had severalfold lower overall cisplatin-DNA ELISA-measurable adduct levels than the individuals with more favorable clinical responses (complete response, partial response, or stable disease), who were grouped together and termed nonprogressive disease. In the case of the ovarian cancer patients, who experienced a 59% rate of complete and partial response, the correlation of high adduct values with disease response was statistically significant by the Wilcoxon rank-sum test (P = 0.028). In contrast, the breast cancer patients achieved only an 11.5% rate of complete and partial response, and the correlation of high adduct formation with disease response was not statistically significant. Levels of total DNA-bound platinum, measured by atomic absorbance spectroscopy, showed no correlation with disease response for either cancer by any analysis. The study supports previous observations demonstrating a consistent correlation between high cisplatin-DNA ELISA measurements and positive clinical outcome in ovarian cancer patients.(ABSTRACT TRUNCATED AT 250 WORDS)
Biological Assay↗