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Query: UMLS:C0027651 (tumor)
 685,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

EGFRvIII is a ligand-independent, constitutively active variant of the epidermal growth factor receptor (EGFR) that is specifically expressed in gliomas and various other human malignancies and has been proposed as a target for directed tumor therapy. We have recently constructed a highly potent single-chain antibody-toxin, scFv(14E1)-ETA, which consists of the variable domains of the antibody 14E1 specific for human full-length EGFR genetically fused to a truncated form of Pseudomonas exotoxin A. We demonstrate here binding of 14E1 antibody to both full-length and variant EGFR. In contrast to a recombinant toxin containing transforming growth factor-alpha (TGF-alpha) as a cell targeting domain, scFv(14E1)-ETA was highly active on cells expressing EGFRvIII. Surprisingly, scFv(14E1)-ETA displayed cell killing activity on EGFRvIII-expressing cells that was up to 100-fold higher than on control cells expressing full-length EGFR. No differences in the binding affinities of scFv(14E1)-ETA to full-length EGFR or EGFRvIII were observed, suggesting that events downstream of immunotoxin binding are responsible for the increased sensitivity of EGFRvIII-expressing cells. This might have implications for the development of therapeutic reagents simultaneously targeting different forms of the EGFR.
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PMID:Expression of an oncogenic mutant EGF receptor markedly increases the sensitivity of cells to an EGF-receptor-specific antibody-toxin. 950 33

In cancer chemotherapy, selective enhancement of drug delivery to tumor tissue is essentially important for increase of chemotherapeutic effects. An attenuated vasoconstrictive response to angiotensin II (Ang II) in tumors and a marked increase in tumor blood flow were observed compared with normal tissues during systemic hypertension induced by Ang II infusion. The phenomenon was absent when hypertension was provoked by endothelin-1 (ET-1). We assessed this response to characterize ET receptor and Ang II receptor density and affinity in normal and tumor tissues. The tumor cell line LY80 was transplanted to the skin in nude rats. Four weeks later the rats were sacrificed. [125I] ET-1 and [125I Sar1, Ile8]-Ang II were used to map the receptors for ET and Ang II in rat tissues using computerized in vitro autoradiography. A moderately high density of ET receptors, (ETB > ETA) was found in tumors. The Ang II receptors were markedly reduced in tumor tissues without changes in the affinity. These results suggest that the decrease in Ang II receptors but not ET receptors in tumors may explain the hemodynamic effect of Ang II-induced hypertension and ET-induced hypertension on tumor blood flow.
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PMID:Endothelin receptors and angiotensin II receptors in tumor tissue. 959 34

The production of endothelin 1 (ET-1) and its receptor-mediated actions on calcium signaling and growth responses were analyzed in human ovarian carcinoma cells. Immuno-reactive ET-1 was released from three of four ovarian tumor cell lines as a function of time in amounts ranging from 56 to 74 fmol/10(6) cells. Reverse-phase HPLC and radioimmuno-assay of conditioned media from tumor cells revealed a single peak coeluting with authentic ET-1. Radioligand binding studies showed that the ET-1-producing cell lines also expressed high-affinity ETA receptors (Kd < 0.1 nM) that ranged in abundance from 2,600 to 43,600 sites/cell. In fura-2-loaded ovarian carcinoma cells, ET-1 induced dose-dependent increases in cytoplasmic Ca2+ concentration. ET-1 also stimulated thymidine incorporation in the three cell lines that expressed ET receptors. In OVCA 433 cells, BQ 123 inhibited the stimulatory actions of ET-1 on thymidine incorporation and cell proliferation, and substantially reduced the basal growth rate of unstimulated ovarian tumor cells. These results demonstrate that ET-1 is produced in ovarian cancer cells and acts as an autocrine growth factor on ETA receptors to stimulate calcium signaling and proliferative responses. Such findings suggest that ET-1 participates in the progression of neoplastic growth in certain ovarian tumors.
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PMID:Autocrine actions of endothelin-1 as a growth factor in human ovarian carcinoma cells. 981 80

Recombinant immunotoxins (rITs) are highly specific anti-tumor agents composed of monoclonal antibody fragments or other specific carriers coupled to plant or bacterial toxins. A major problem in the purification of rITs is the low periplasmic yield in currently available expression systems. Thus, the aim of this study was the development of a new bacterial expression system for high-level production of rITs. We constructed a series of pET-based vectors for pelB-directed periplasmic secretion or cytoplasmic production under the control of the T7lac promoter. Expression in Escherichia coli BL21(DE3)pLysS allowed a tightly regulated isopropyl beta-d-thiogalactopyranoside (IPTG) induction of protein synthesis. An enterokinase-cleavable poly-histidine cluster was introduced into this setup for purification by affinity chromatography. A major modification resulted from the insertion of a specifically designed multiple cloning site. It contains only rare restriction enzyme recognition sites used for cloning of immunoglobulin variable region genes, as well as unique SfiI and NotI restriction sites for directed insertion of single-chain variable fragments (scFv) available from established bacteriophage systems. For this purpose, we deleted two naturally occurring internal SfiI consensus sites in a deletion mutant of Pseudomonas aeruginosa exotoxin A (ETA'). Each single structural element of the new vector (promoter, leader sequence, purification tag, scFv sequence, selectable marker, and toxin gene) was flanked by unique restriction sites allowing simple directional substitution. The fidelity of IPTG induction and high-level expression were demonstrated using an anti-CD30 scFv (Ki-4) fused to ETA'. These data confirm a bacterial vector system especially designed for efficient periplasmic expression of ETA'-based fusion toxins.
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PMID:A new series of pET-derived vectors for high efficiency expression of Pseudomonas exotoxin-based fusion proteins. 1009 14

Cytotoxic strategies which are directed to tumor-associated antigens might be most beneficial for cancer patients with minimal tumor load such as in an adjuvant setting after initial therapy. We have recently described a highly potent single chain antibody-toxin, scFv(14E1)-ETA, which consists of the variable domains of the antibody 14E1 genetically fused to a truncated form of Pseudomonas exotoxin A. ScFv(14E1)-ETA specifically recognizes the human epidermal growth factor receptor (EGFR) and the oncogenically activated receptor variant EGFRvIII, which have been implicated in the development of various human malignancies. Here we have investigated the antimetastatic activity of bacterially expressed scFv(14E1)-ETA and its disulfide-stabilized derivative ds-scFv(14E1)-ETA in a novel model for disseminated disease which is based on murine renal carcinoma cells subsequently transfected with the E. coli beta-galactosidase gene, and human full-length or variant EGFR cDNAs. Intravenous injection of these Renca-lacZ/EGFR and Renca-lacZ/EGFRvIII cells in syngenic Balb/c mice led to the formation of pulmonary metastases which were readily detectable upon excision of the lungs and X-gal staining. Systemic treatment of mice with scFv(14E1)-ETA resulted in the complete suppression of Renca-lacZ/EGFRvIII metastasis formation and drastically reduced the number of pulmonary Renca-lacZ/EGFR tumor nodules. The ds-scFv(14E1)-ETA derivative where the antibody variable regions are connected by an artificial disulfide bond displayed improved thermal stability at physiological temperature but due to reduced cytotoxic activity was less potent than the original scFv(14E1)-ETA in metastasis suppression.
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PMID:Suppression of metastasis formation by a recombinant single chain antibody-toxin targeted to full-length and oncogenic variant EGF receptors. 1020 32

The amplification and overexpression of the erbB-2 oncogene and its involvement in tumorigenesis makes this receptor an appropriate target for specific agents directed towards tumor cells. The purpose of this study was to evaluate the in vitro effect of the bacterially produced recombinant immunotoxin scFv(FRP5)-ETA on the protein synthesis and adenosine triphosphate (ATP) reduction in oral squamous cell carcinoma (OSCC) cells. This agent recognizes the erbB-2 receptor and inhibits protein synthesis in receptor-overexpressing cells. OSCC cells were selected for this study, and amplification and expression levels of the erbB-2 receptor were determined. Cell suspensions were cultured for 6 d with various concentrations of scFv(FRP5)-ETA (1-1000 ng/ml). A431 and MDA-MB468 cell lines were used as controls. Chemosensibility of tumor cells was measured by [3H]leucine incorporation assay and by an ATP luminescence assay. In OSCC cells with amplification and overexpression of erbB-2 inhibition, up to 92% of protein synthesis and 90% of ATP reduction was observed when cells were exposed to 1,000 ng/ml immunotoxin. In OSCC cells showing a deletion of erbB-2 and in erbB-2-negative MDA-MB468 cells, protein synthesis was inhibited by 22% and 8%, respectively. These results indicate that the effectiveness of a recombinant immunotoxin targeting erbB-2 receptors in OSCC cells depends on the level of erbB-2 amplification and expression, that it is highly specific for tumor cells expressing these receptors, and that a dose-dependency can be observed.
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PMID:Chemosensitivity testing of oral cancer cells treated with a p185neu-specific agent. 1051 98

Recombinant DNA technology makes it possible to genetically fuse V genes or cytokines to toxin domains, resulting in immunotherapeutics for selective destruction of tumor cells. Since recombinant immunotoxins can be easily manipulated in terms of affinity or cytotoxic potency and produced in large quantities, we have developed a new CD30 ligand-based fusion toxin (CD30L-ETA'). Human CD30L cDNA was ligated into a pET-based expression plasmid and thereby fused to a modified Pseudomonas aeruginosa exotoxin A (ETA') lacking its cell-binding domain I. After IPTG-indiced expression in E. coli strain BL21(DE3), the 60 kDa His-tagged fusion protein (CD30L-ETA') was isolated from inclusion bodies. Denatured protein was renatured in the presence of 0.4 M arginine and a glutathione redox system. Refolded protein was purified and concentrated by ion-exchange chromatography on a HiTrap Q column. The binding properties of CD30L-ETA' were evaluated by competitive ELISA, immunohistochemical staining, and FACS analysis on CD30-expressing cells. The in vitro toxicity of the fusion protein was then tested on the CD30+ Hodgkin-derived cell line L540cy and the Burkitt's lymphoma cell line BL38. CD30L-ETA' exhibited specific cytotoxicity against L540cy cells (IC50 = 24 ng/ml) as determined by [3H]leucine uptake assays. This is the first report on the specificity and cytotoxic potency of a chimeric CD30L fusion toxin against Hodgkin's disease-derived cells.
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PMID:CD30L-ETA': a new recombinant immunotoxin based on the CD30 ligand for possible use against human lymphoma. 1051 79

The endothelins (ET1, ET2, ET3) are a family of peptides that exert vasoactive and mitogenic effects. ETs bind to at least two subtypes of receptors: the ETA subtype is ET1 selective whereas the ETB subtype binds ET1, ET2 and ET3. By RT-PCR, we detected ETA receptor mRNA and ETB receptor mRNA in leiomyoma and in homologous myometrium distal from the tumor. Despite the presence of four spliced variants of ETA receptors, we identified a single class of ETA-binding sites. The level of ETB receptor mRNA was found to be higher in myometrium versus leiomyomas. Using complementary pharmacologic approach, we demonstrated the predominance of ETA receptors in normal myometrium (75% of total receptors). Both ETA and ETB transcripts coexist in leiomyomas, but we have reported only ETA binding sites. Because of growth properties of ET1, we suggest a role for this peptide in the tumoral development of human uterine smooth muscle.
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PMID:[Endothelin receptors in benign human tumours of uterine muscle]. 1051 70

Since clinical phase-I/II trials in patients with resistant Hodgkin's lymphoma treated with the chemically linked anti-CD25 ricin-A-chain immunotoxin RFT5-SMPT-dgA indicate promising results for patients with minimal residual disease, we constructed a new immunotoxin by fusing the RFT5 single-chain variable fragment to a deletion mutant of Pseudomonas exotoxin A (ETA'). The recombinant protein was directed into the periplasmic space of E. coli by means of the pET-derived expression vector pBM1.1 and our newly developed expression/purification method. Biologically active RFT5(scFv)-ETA' was isolated by freezing/thawing and purified by immobilized metal-ion affinity and molecular-size-chromatography. RFT5(scFv)-ETA' was subsequently used for the treatment of disseminated human Hodgkin's lymphoma in a SCID-mouse model. The mean survival time (MST) of L540rec-challenged SCID mice was 38.1 days. A single i.v. injection of 40 microg recombinant immunotoxin (rIT) 1 day after tumor inoculation resulted in 100% tumor-free mice, extending the MST to more than 220 days (p < 0.0001). The blood-distribution time T(1/2)alpha was 39.65 min, the serum elimination time T(1/2)alpha, 756.6 min. All animals were assessed for soluble interleukin-2 receptor alpha, which is directly correlated to tumor burden. Soluble CD25 was not detectable in mice treated with the rIT. Our findings, concerning potent anti-tumor effects of a recombinant anti-CD25 immunotoxin against disseminated Hodgkin's lymphoma in SCID mice reported here demonstrate that RFT5(scFv)-ETA' might be suitable for further evaluation against Hodgkin's lymphoma in humans.
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PMID:Recombinant anti-CD25 immunotoxin RFT5(SCFV)-ETA' demonstrates successful elimination of disseminated human Hodgkin lymphoma in SCID mice. 1079 96

The human lymphocyte activation marker CD30 is highly overexpressed on Hodgkin/Reed-Sternberg cells and represents an ideal target for selective immunotherapy. We used the murine anti-CD30 hybridoma Ki-4 to construct a new recombinant immunotoxin (rIT) for possible clinical use in patients with CD30(+) lymphoma. Hybridoma V genes were polymerase chain reaction-amplified, assembled, cloned, and expressed as a mini-library for display on filamentous phage. Functional Ki-4 scFv obtained by selection of binding phage on the CD30-expressing Hodgkin lymphoma cell line L540cy was inserted into the bacterial expression vector pBM1.1 and fused to a deletion mutant of Pseudomonas exotoxin A (ETA'). Periplasmically expressed Ki-4(scFv)-ETA' demonstrated specific activity against a variety of CD30(+) lymphoma cells as assessed by different in vitro assays. To evaluate in vivo antitumor activity, severe combined immunodeficient mice challenged with human lymphoma cell lines were treated with the immunotoxin. The blood distribution time t(1/2)alpha of Ki-4(scFv)-ETA' was 19 minutes, and its serum elimination time t(1/2)alpha was 193 minutes. A single intravenous injection of 40 microg rIT 1 day after tumor inoculation rendered 90% of the mice tumor free, extending the mean survival time to more than 200 days compared with 38.1 days in the phosphate-buffered saline control group (P <.001). This new rIT is a promising candidate for further clinical evaluation in patients with Hodgkin lymphoma or other CD30(+) malignancies. (Blood. 2000;95:3909-3914)
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PMID:Ki-4(scFv)-ETA', a new recombinant anti-CD30 immunotoxin with highly specific cytotoxic activity against disseminated Hodgkin tumors in SCID mice. 1084 27


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