Glioblastoma—a moving target

The slow development of effective treatment of glioblastoma is contrasted by the rapidly advancing research on the molecular mechanisms underlying the disease. Amplification and overexpression of receptor tyrosine kinases, particularly EGFR and PDGFRA, are complemented by mutations in the PI3K, RB1, and p53 signaling pathways. In addition to finding effective means to target these pathways, we may take advantage of the recent understanding of the hierarchical structure of tumor cell populations, where the progressive expansion of the tumor relies on a minor subpopulation of glioma stem cells, or glioma-initiating cells. Finding ways to reprogram these cells and block their self-renewal is one of the most important topics for future research

Biocompatibility of a novel avidin-agarose adsorbent for extracorporeal removal of redundant radiopharmaceutical from the blood.

The use of monoclonal antibodies (MAbs) in cytotoxic conjugates (radionuclides, toxins, or drugs) for targeting tumor cells is restricted due to toxicity in vital organs. Through improved tumor targeting, it is possible to administer larger amounts of such labeled MAbs, thus improving the ability to eradicate tumor cells without increased normal organ toxicity. Extracorporeal affinity adsorption treatment (ECAT) has therefore been developed using an avidin-agarose (AA) adsorbent with high binding affinity for the biotinylated radiolabeled MAb, rituximab. During ECAT, excess radioimmunoconjugates, not bound to the tumor cells, can be removed improving tumor targeting. The present study was performed to estimate the biocompatibility of the AA adsorber. Seven patients with B-cell lymphoma not responding to conventional treatment were studied. During the ECAT procedure, blood (B) components, plasma (P) complement fragments C3a, C5a, and P-bradykinin were analyzed, and other laboratory tests were carried out. Slight decreases in B-hemoglobin (8.3%), B-thrombocytes (11.4%), and P-albumin (14.3%) were observed, and could be explained by the dilution of the blood with normal saline and acid citrate dextrose. The AA adsorbent had no effect on the blood cells, immunological status or P-bradykinin level. The AA adsorber demonstrated good hemocompatibility and biocompatibility, without any side effects in the patients

The interaction between different domains of staphylococcal protein A and human polyclonal IgG, IgA, IgM and F(ab')2: separation of affinity from specificity

Binding properties of staphylococcal protein A (SpA) to different human immunoglobulins have been investigated. In this analysis, intact SpA as well as SpA-derived fragments containing one to five IgG-binding domains of different compositions, were used. The affinity binding constants of the different proteins to human polyclonal IgG, IgA, IgM and F(ab')2-fragments as well as their binding capacity to the immunoglobulin molecules were determined. The results show that although all the proteins bound to IgG, regardless of size or composition, the binding strength differed significantly. Proteins containing five domains have a stronger affinity for IgG than those containing one or two. There were no marked differences in binding strength between different domains. However, the binding ability to IgA and IgM showed a marked difference between the various SpA-derived proteins of different compositions. This discrepancy was correlated to differences in their relative binding properties to isolated F(ab')2-fragments of IgG. Hence, we conclude that the binding affinity is mainly affected by the number of domains, whereas the binding specificity is to a large extent determined by which domains are selected

Trifunctional conjugation reagents. Reagents that contain a biotin and a radiometal chelation moiety for application to extracorporeal affinity adsorption of radiolabeled antibodies

A method of removing radiolabeled monoclonal antibodies (mAbs) from blood using a device external to the body, termed extracorporeal affinity-adsorption (EAA), is being evaluated as a means of decreasing irradiation of noncancerous tissues in therapy protocols. The EAA device uses an avidin column to capture biotinylated-radiolabeled mAbs from circulated blood. In this investigation, three trifunctional reagents have been developed to minimize the potential deleterious effect on antigen binding brought about by the combination of radiolabeling and biotinylation of mAbs required in the EAA approach. The studies focused on radiolabeling with (111)In and (90)Y, so the chelates CHX-A' '-DTPA and DOTA, which form stable attachments to these radionuclides, were incorporated in the trifunctional reagents. The first trifunctional reagent prepared did not incorporate a group to block the biotin cleaving enzyme biotinidase, but the two subsequent reagents coupled aspartic acid to the biotin carboxylate for that purpose. All three reagents used 4,7,10-trioxa-1,13-tridecanediamine as water-soluble spacers between an aminoisophthalate core and the biotin or chelation group. The mAb conjugates were radioiodinated to evaluate cell binding as a function of substitution. Radioiodination was used so that a direct comparison with unmodified mAb could be made. Evaluation of the number of conjugates per antibody versus cell binding immunoreactivities indicated that minimizing the number of conjugates was best. Interestingly, a decrease of radioiodination yield as a function of the number of isothiocyanate containing conjugates per mAb was noted. The decreased yields were presumably due to the presence of thiourea functionality formed in the conjugation reaction. Radiolabeling with (111)In and (90)Y was facile at room temperature for conjugates containing the CHX-A' ', but elevated temperature (e.g., 45 degrees C) was required to obtain good yields with the DOTA chelate. Stability of (90)Y labeled mAb in serum, and when challenged with 10 mM EDTA, was high. However, challenging the (90)Y labeled mAb with 10 mM DTPA demonstrated high stability for the DOTA containing conjugate, but low stability for the CHX-A' ' containing conjugate. Thus, the choice between these two chelating moieties might be made on requirements for facile and gentle labeling versus very high in vivo stability. Application of the trifunctional biotinylation reagents to the blood clearance of labeled antibodies in EAA is under investigation. The new reagents may also be useful for other applications

Peripheral leucocyte count variations in rectal cancer treatment.

AIM: Mortality after curative surgery for rectal cancer is increased if surgery is not performed within a week of completed short course radiotherapy. A link to the suppression of leucocytes after neoadjuvant radiotherapy has been suggested. This study investigates the effects of radiotherapy on peripheral leucocyte counts, complications and survival. METHOD: Patient data variables from a retrospective database (Local and National Swedish Registries) of a total of 926 consecutive patients treated for rectal cancer disease at two surgical units (1993-2004) were analysed for leucocyte counts and mortality. In all 310 patients received radiotherapy. Mean follow-up time was 2.8 years. RESULTS: There was a marked suppression of leucocytes in the irradiated groups coupled with a reduction in leucocyte response to surgery (p<0.05) compared to non-irradiated patients. Long course radiotherapy resulted in a better postoperative leucocyte response. Irradiated patients with a low post/preoperative leucocyte ratio had higher complication rates. No association between leucocyte response and survival was seen in the irradiated group. CONCLUSIONS: Postoperative leucocytosis is impaired after neoadjuvant radiotherapy, independent of latency period to surgery. Irradiated patients with a suppression of leucocyte response had significantly higher complication rates. The true extent of survival could not be measured in radiotherapy groups due to the short median follow-up period