A4324

Abrin 42, 169, 171, 179 Abrus precatorius 169 accessory effector pathways, activation of 195 acute lymphocytic leukemia (ALL) 136 acute myeloid leukaemia (AML), treatment of 27 Adenia digitata 169 Adenia volkensii 169 adenine 42 dinucleotide 15 residue 86 adenocarcinoma 149, 158 cells 160, 163 types of cancers 143 adenovirus 57-8 adenylate cyclase 86 ADP-ribosylation of elongation factor-2 (EF-2) 86 reaction 181 adult T-cell leukaemia (ATL) 21, 120, 206 affinity chromatography 44 Ag barrier...

Retrograde transport to the ER

The first indication that toxins which do not translocate from endosomes may do so from the ER came from studies with PE. The C-terminal amino acid residues of the 37 kDa catalytic fragment of PE are ArgGluAspLeuLys (REDLK), a sequence homologous to ER retrieval sequence KDEL (Pelham, 1989). Soluble resident proteins of the ER lumen, such as BiP and protein disulfide isomerase, contain the tetrapeptide KDEL at the extreme C-terminus. Such resident proteins are known to escape from the ER by...

Protease sensitive loop

The C and T domains of DT are separated by a protease sensitive loop that is created by the disulfide bond between Cys 186 and 201. Upon binding to the receptors, the loop is nicked by the enzyme furin at the cell surface (Tsuneoka et al., 1993). At this stage the C and T domains remain associated by the disulfide bond that is reduced upon acidification of the early endosome. Papini et al. (1993) studied the kinetics of the disulfide bond reduction and discovered it to be the rate-limiting step...

Pseudomonas exotoxin

Pseudomonas exotoxin is a second bacterial toxin for which investigations have shed light on both its molecular mechanism of action and paved the way for sophisticated genetic engineering of therapeutic molecules. PE is a 66 kDa polypeptide possessing three domains (Allured et al., 1986 and Figure 1.3). Domain Ia consisting of amino acid residues 1-252 binds the heavy chain of the low density lipoprotein receptor-related protein (LRP) (Kounnas et al., 1992). After binding, the receptor-bound...

Suicide transport

Early experiments which led to the development of the suicide transport strategy using RIPs were driven by the issue of how to destroy vagal baroreceptor afferent neurons. Primary control over sudden changes in blood pressure involves reflexes which originate in baroreceptors that are sensitive to stretching. They send impulses via sensory neurons to centers in the brain that are responsible for coordinating information and regulating the cardiovascular system. To precisely identify the...

Other chimeric neurotoxins and novel approaches

To study the localization and function of neuronal targets of neuropeptide hormones, a variety of chimeric toxins of ricin A chain with oxytocin, atrial natriuretic peptide or gelonin with corticotrophin releasing factor have been prepared and characterized (Schwartz and Vale, 1989 Samson et al., 1992 1993 1995 Blackburn et al., 1995). Myelin basic protein (MBP) is an important component of myelinated neurons. Antibodies against MBP are generated in autoimmune diseases of the nervous system...

The ER as the site of toxin translocation

Why do toxins such as PE, ST and ricin need to reach the ER lumen in order to translocate into the cytosol The most likely explanation is that since they are unable to form their own membrane translocation channel, for example, in the way that DT does at low pH, they must reach a cellular location where such channels already exist. This entails some toxin reaching the TGN and being carried by retrograde vesicular transport through the Golgi stack to the ER. The ER membrane contains at least two...

Improving the therapeutic window of recombinant immunotoxins the balance of toxicity immunogenicity and efficacy

Although some of the problems, including design, large-scale production and stability, associated with the initial recombinant immunotoxins have been solved, other fundamental problems need to be addressed that are relevant to much of the immunotherapy field. Specificity, toxicity and immunogenicity are major factors that will determine the usefulness and success of recombinant immunotoxins. Immune responses and dose limiting toxicity As with any cytotoxic agent, side effects such as...

Applications and clinical trials of recombinant immunotoxins Recombinant Fvimmunotoxins against solid tumors

The treatment of solid tumors with immunotoxins is challenging due to their physiological nature of tight junctions between tumor cells, high interstitial pressure within tumors and heterogeneous blood supply and antigen expression (Jain, 1996). The greatest need for new therapies is in the treatment of metastatic epithelial cancers, and immuno-toxins can be a useful addition to the standard procedures of surgery, radiation and chemotherapy. As already described the use of recombinant fragments...

Non Hodgkins lymphoma

The initial clinical trials of diphtheria-based fusion protein toxins were conducted using DAB486IL-2 and DAB389IL-2 to establish their relative safety, pharmacokinetics, and potential efficacy in the treatment of non-Hodgkin's lymphoma. Non-Hodgkin's lymphoma represents a group of common neoplasms of lymphocytic origin, and are clonal expansions of lymphocytic elements blocked at particular stages of B- and T-cell differentiation. The malignant lymphomas comprise approximately 10 of all...

Ricin gene

Antibodies against RTA and antibodies against RTB precipitate a single polypeptide of Mr 60,500 during the in vitro translation of mRNA extracted from castor beans (Butterworth and Lord, 1983), revealing that RTA and RTB are synthesized in the form of a single precursor polypeptide (preproricin). Cloning of cDNA complementary to preproricin later confirmed that indeed, both subunits of ricin are coded as a single message and showed that preproricin begins with a 24-aa N-terminal signal sequence...

Introduction immunotoxins and their targets

Cancer immunotherapy and targeted cancer therapy combines rational drug design with the progress in understanding cancer biology. This approach takes advantage of some special properties of cancer cells many of them contain mutant or overexpressed oncogenes on their surface, and these proteins are attractive antigens for targeted therapy. It should be possible to use these molecular cell-surface markers as targets to eliminate the cancer cells while sparing the normal cells. The rapid progress...

Il13e13yr66ds69dpe38qqr

IL13 multiple mutant-based PE1E-containing cytotoxins showed the highest cytotoxicity towards glioma cells while PE38QQR-containing cytotoxins were slightly less cytotoxic. All novel cytotoxins tested showed cytotoxicity values that fell within the range of IL13.E13K-PE derivative cytotoxins previously tested by us (Debinski et al., 1995b 1996 1998a 1999a). These results are most encouraging because they indicate that the IL13 molecule's glioma-associated receptor...

Xso

Figure 12.1 PE and modified PEs with sequential deletion at carboxyl-terminal. Panel A shows a protein profile of PE and PE deletions. Panel B shows a simplified map and summary of PE and PE deletions. Panel C shows the relative ADP-ribosylation activity of PE and PE deletions. The full length PE is used as a positive control and stands for 100 of ADP-ribosylation activity. The relative ADP-ribosylation activity of various PE deletions was measured by comparing the specific ADP-ribosylation...

Receptor binding domain

In the DT-based fusion toxins the native R domain of DT has been replaced with various targeting ligands (Table 2.1). The resulting fusion toxin proteins can be used for receptor distribution studies and structure-function studies of the targeting ligands. For example, a gastrin releasing peptide (GRP)-directed fusion toxin, DAB389GRP and substance P (SP) fusion toxin, DAB389SP were used to assess distribution of GRP and SP receptors on various small cell lung cancer cell lines (vanderSpek et...