Entry into a new class of potent proteasome inhibitors having high antiproliferative activity by structure-based design

Proteasome inhibition is a therapeutic concept of current interest in anticancer research. We report here the design, synthesis, and biological characterization of prototypes of a new class of noncovalent proteasome inhibitors showing high activity in biochemical and cellular assays.     

Interactions of nucleoside analogs, caffeine, and nicotine with human concentrative nucleoside transporters 1 and 2 stably produced in a transport-defective human cell line

Pharmacologically important drugs were examined as potential inhibitors or permeants of human concentrative nucleoside transporters 1 (hCNT1)- and 2 (hCNT2)-producing stable transfectants by assessing their abilities to inhibit uridine transport. hCNT1 exhibited high affinities for uridine analogs (5-fluorouridine, 2'-deoxyuridine, 5-fluoro-2'-deoxyuridine, and 5-fluoro-5'-deoxyuridine) with K(i) values of 22 to 33 microM, whereas hCNT2 exhibited moderate affinities for 5-fluoro-2'-deoxyuridine, high affinities for 2'-deoxyuridine and 5-fluorouridine, and low affinity for 5-fluoro-5'-deoxyuridine. The uridine analogs were transported at 2-fold higher rates (at 10 microM) by hCNT1 than by hCNT2. Enantiomeric configuration and the 3'-hydroxyl group of the ribose ring were important determinants for interaction with hCNTs, whereas the 2'-hydroxyl group was less important. Both transporters bound N(6)-(p-aminobenzyl)adenosine with affinities similar to those of adenosine (K(i) = 28-39 microM). Other adenosine receptor ligands, including caffeine, bound better to hCNT1 than to hCNT2 (K(i) = 46 versus 103 microM, respectively), whereas 2-chloroadenosine bound better to hCNT2 than to hCNT1 (K(i) = 37 and 101 microM, respectively). There was a greater than 3-fold difference in binding affinities between hCNT1 and hCNT2 for nicotine (K(i) = 63 versus 227 microM). However, direct measurements of nicotine and caffeine uptake rates (10 microM) failed to demonstrate mediated uptake by either transporter. Although hCNT1 bound several adenosine analogs relatively well, it did not transport 2-chloro-2'-deoxyadenosine (cladribine) or 2-fluoro-9-beta-d-arabinofuranosyladenine (fludarabine), whereas hCNT2 transported both, albeit with low activities. The results indicated that although hCNT1 and hCNT2 possess some overlap in transport of several uridine and adenosine analogs, they also exhibit distinct differences in capacity to interact with some adenosine receptor ligands, adenosine-based drugs, and nicotine.     

Prospective Clinical Trials of Brain Tumor Therapy: The Critical Role of Neurosurgeons

Prospective clinical trials are critical to the scientific evaluation of new treatments for brain tumors. This paper reviews basic concepts of early and late phase prospective clinical trials that are most relevant to neurosurgical oncologists, with an emphasis on the challenges associated with conducting clinical trials of brain tumor therapies. Novel clinical trial designs that meet these challenges by incorporating pretreatment 'molecular profiling' and post-treatment 'molecular endpoints' are described. Because of their ability to obtain brain tumor specimens from patients before and after treatment, neurosurgeons have been required to play an increasingly important role in the execution of these molecular-based clinical trials. Potential avenues for enhancing the participation of neurosurgeons in the design and development of clinical trials are discussed.     

A novel E1A-E1B mutant adenovirus induces glioma regression in vivo

Malignant gliomas are the most frequently occurring primary brain tumors and are resistant to conventional therapy. Conditionally replicating adenoviruses are a novel strategy in glioma treatment. Clinical trials using E1B mutant adenoviruses have been reported recently and E1A mutant replication-competent adenoviruses are in advanced preclinical testing. Here we constructed a novel replication-selective adenovirus (CB1) incorporating a double deletion of a 24 bp Rb-binding region in the E1a gene, and a 903 bp deleted region in the E1b gene that abrogates the expression of a p53-binding E1B-55 kDa protein. CB1 exerted a potent anticancer effect in vitro in U-251 MG, U-373 MG, and D-54 MG human glioma cell lines, as assessed by qualitative and quantitative viability assays. Replication analyses demonstrated that CB1 replicates in vitro in human glioma cells. Importantly, CB1 acquired a highly attenuated replicative phenotype in both serum-starved and proliferating normal human astrocytes. In vivo experiments using intracranially implanted D-54 MG glioma xenografts in nude mice showed that a single dose of CB1 (1.5 x 10(8) PFU/tumor) significantly improved survival. Immunohistochemical analyses of expressed adenoviral proteins confirmed adenoviral replication within the tumors. The CB1 oncolytic adenovirus induces a potent antiglioma effect and could ultimately demonstrate clinical relevance and therapeutic utility.     

S-100B protein as a serum marker of secondary neurological complications in neurocritical care patients

There is growing evidence that S-100B protein measured by a simple blood test can be used as a novel biochemical marker of brain cell damage. The objective of our study was to investigate the potential of S-100B measurements to diagnose an acute neurological complication in the analgo-sedated and intubated intensive care patient and the impact on patient management. Serum S-100B levels were serially investigated in 246 neurocritical care patients. Venous blood samples for S-100B determination were obtained as soon as possible after admission and every 24 hours thereafter, for the duration of the stay at the neurocritical care unit. Blood samples were taken every morning as part of the routine laboratory investigation for analysis of S-100B using the immunoluminometric assay (AB Sangtec Medical, Bromma, Sweden) and a fully automated LIAISON system (Byk-Sangtec-Diagnostica, Dietzenbach, Germany) with a short time to result. The primary endpoint of our study was the occurrence of a severe neurological complication. Patients were admitted to the neurosurgical intensive care unit after routine major intracranial surgery in 116 cases (47%) and after a neurological or neurosurgical emergency in 130 cases (53%). Of the latter group, 79 patients (32%) underwent emergency surgery for evacuation or decompression of a space-occupying lesion before ICU admission. A severe neurological complication was defined as a new infarction, new hemorrhage or a newly developed progressive disease despite maximum therapy with a radiologically confirmed increase of mass lesion and midline shift. In 33 patients (13%) a complication with neurological deterioration occurred. All patients showed pathologically increased serum S-100B values (mean 2.00 microg/l, standard deviation 2.61 microg/l, range 0.31-9.66 microg/l). Twenty-eight of these patients (85%) showed S-100B increases >0.5 microg/l. In five cases (16%), the increase in S-100B was the first sign of neurological complication and prompted emergency computed tomography scanning. In another two cases, increasing S-100B values changed management decision towards a surgical intervention. The major finding of our study was the influence of serial S-100B measurement on actual management of the patient in 21% of cases with neurological complications.     

Cerebral microembolism during transcatheter closure of patent foramen ovale

BACKGROUND: Although transcatheter closure of patent foramen ovale (PFO) and atrial septal defect (ASD) has become a commonly performed intervention, the incidence of cerebral embolism with or without neurological deficits during such procedures has not been studied. METHODS: We monitored the middle cerebral artery in two different depths (48 mm and 53 mm) by continuous transcranial Doppler ultrasound during transcatheter PFO closure in 35 consecutive patients (F/M 20/15, mean age 47 +/- 11 years) and during ASD closure in 8 patients (F/M 7/1, mean age 45 +/- 5 years). All automatically detected high intensity transient signals (HITS) were manually reviewed to eliminate artifacts. RESULTS: HITS were detected in 33 of 35 patients (96%) with a median rate of 8 (interquartile range 4-19, range 2-29) HITS. The highest rates were observed when the septum was crossed with the guide wire (median 2; IQR 0-12; range 0-25) and when the left atrial disc was deployed (median 2; IQR 1-4; range 0-13). Despite this high rate of cerebral microembolism no clinically apparent neurological or neuropsychological deficit was observed. CONCLUSIONS: Silent cerebral embolism frequently occurs during transcatheter PFO and ASD closure. The peak of HITS at the time of crossing the septum with the guide wire may support the hypothesis that cerebral emboli in patients with PFO may originate from the septum itself. This may represent an alternative mechanism to the generally assumed paradoxical embolism.