Pull-Force Generated by the Revolving High-speed Drill Shaft Results in Unexpected Tissue Wrapping Around the Shaft.

BACKGROUND: Despite holding soft tissue away from high-speed drills during surgery, tissue can unexpectedly wrap around the drill shaft. We performed experiments to examine what precipitates such mishaps. METHODS: In a windless environment, a Signature Drill System (Stryker) featuring a 4-mm diameter coarse diamond or cutting bit was placed parallel to a suspended strip of polypropylene. The distance between the end of the strip and the drill shaft or bits was 4 or 8 mm. In another experiment, we placed the drill horizontally 10 mm above the top of dry-ice fog. The maximum drill speed was 75,000 rpm, and the horizontal motion of the polypropylene strip and the vertical motion of the dry-ice fog were recorded by a video camera. RESULTS: In the experiments, the strip parallel to the vertical shaft and the dry-ice fog were pulled toward the shaft; the higher the revolving drill speed, the faster its motion. On the other hand, in experiments where the end of the strip was next to either bit, no such motion was observed. CONCLUSIONS: The pulling force generated by revolving high-speed drill shafts may result in tissue wraparound even when soft tissue is held away from the shaft.

Convection-enhanced delivery of a synthetic retinoid Am80, loaded into polymeric micelles, prolongs the survival of rats bearing intracranial glioblastoma xenografts.

Prognosis for the patients with glioblastoma, the most common malignant brain tumor, remains dismal. A major barrier to progress in treatment of glioblastoma is the relative inaccessibility of tumors to chemotherapeutic agents. Convection-enhanced delivery (CED) is a direct intracranial drug infusion technique to deliver chemotherapeutic agents to the central nervous system, circumventing the blood-brain barrier and reducing systemic side effects. CED can provide wider distribution of infused agents compared to simple diffusion. We have reported that CED of a polymeric micelle carrier system could yield a clinically relevant distribution of encapsulated agents in the rat brain. Our aim was to evaluate the efficacy of CED of polymeric micellar Am80, a synthetic agonist with high affinity to nuclear retinoic acid receptor, in a rat model of glioblastoma xenografts. We also used systemic administration of temozolomide, a DNA-alkylating agent, which has been established as the standard of care for newly diagnosed malignant glioma. U87MG human glioma cells were injected into the cerebral hemisphere of nude rats. Rats bearing U87MG xenografts were treated with CED of micellar Am80 (2.4 mg/m(2)) on day 7 after tumor implantation. Temozolomide (200 mg/m(2)/day) was intraperitoneally administered daily for 5 days, starting on day 7 after tumor implantation. CED of micellar Am80 provided significantly longer survival than the control. The combination of CED of micellar Am80 and systemic administration of temozolomide provided significantly longer survival than single treatment. In conclusion, temozolomide combined with CED of micellar Am80 may be a promising method for the treatment of malignant gliomas.

Therapeutic efficacy of a polymeric micellar doxorubicin infused by convection-enhanced delivery against intracranial 9L brain tumor models.

Convection-enhanced delivery (CED) with various drug carrier systems has recently emerged as a novel chemotherapeutic method to overcome the problems of current chemotherapies against brain tumors. Polymeric micelle systems have exhibited dramatically higher in vivo antitumor activity in systemic administration. This study investigated the effectiveness of CED with polymeric micellar doxorubicin (DOX) in a 9L syngeneic rat model. Distribution, toxicity, and efficacy of free, liposomal, and micellar DOX infused by CED were evaluated. Micellar DOX achieved much wider distribution in brain tumor tissue and surrounding normal brain tissue than free DOX. Tissue toxicity increased at higher doses, but rats treated with micellar DOX showed no abnormal neurological symptoms at any dose tested (0.1-1.0 mg/ml). Micellar DOX infused by CED resulted in prolonged median survival (36 days) compared with free DOX (19.6 days; p = 0.0173) and liposomal DOX (16.6 days; p = 0.0007) at the same dose (0.2 mg/ml). This study indicates the potential of CED with the polymeric micelle drug carrier system for the treatment of brain tumors.

Convection-enhanced delivery of polyethylene glycol-coated liposomal doxorubicin: characterization and efficacy in rat intracranial glioma models.

OBJECT: The characteristics of polyethylene glycol-coated liposomal doxorubicin (PLD), the only liposomal drug now clinically available for intravenous injection, were investigated after convection-enhanced delivery (CED) into the rat brain parenchyma. METHODS: The distribution, tissue retention, and toxicity profile were evaluated after CED into the rat brain parenchyma. The antitumor efficacy was also determined in rodent intracranial U-251MG and U-87MG glioma models. RESULTS: Convection-enhanced delivery of PLD achieved wider distributions and delayed onset of toxicity in the brain parenchyma compared with CED of free doxorubicin infusion. Fluorescence generated from doxorubicin infused as PLD was detected until at least 30 days after infusion. Local toxicity was not observed when a 10% dilution of the commercially available PLD solution was used (0.2 mg/ml doxorubicin), but was significant at higher concentrations. Results after 10% PLD was delivered locally with CED demonstrated significant survival prolongation in both intracranial U-251MG and U-87MG xenograft models. CONCLUSIONS: Convection-enhanced delivery of PLD achieved extensive tissue distribution and sustained drug release. Convection-enhanced delivery of PLD is a promising chemotherapy for the treatment of malignant gliomas.

The relationship among p53 oligomer formation, structure and transcriptional activity using a comprehensive missense mutation library.

Tumor suppressor p53 forms a homo-tetramer through its COOH-terminal oligomerization domain and acts as a sequence-specific transcription factor. We have analysed the interrelation among the transcriptional activities, the structure and the cancer-related mutations in the oligomerization domain by using a comprehensive missense mutation library. Here, we examined the ability of 184 mutant p53s in the domain to form an oligomer by expressing these mutant p53s in yeast, and compared the data with the previous information. We showed that specific residues in the alpha-helix and the beta-strand of the oligomerization domain were critical for both oligomer formation and sequence-specific transactivation, and the activities were closely related. In particular, the alpha-helix was more sensitive to amino-acid substitutions than the beta-strand. We found identity in the interrelation between the two activities, that is, monomer mutants were transcriptionally inactive whereas dimer and tetramer mutants retained their transcriptional activities. In TP53 mutation databases, a small number of mutations have been reported in this domain. Surprisingly, most do not encode p53s defective in functional properties. These results indicate that, although oligomer formation is essential for p53 transactivation function, the inactivation of oligomer formation and therefore the inactivation of transactivation may not be essential for tumor suppression by p53 because they do not lead to oncogenic proteins.

Peri-tumoral leakage during intra-tumoral convection-enhanced delivery has implications for efficacy of peri-tumoral infusion before removal of tumor.

In cases of malignant brain tumors, infiltrating tumor cells that exist at the tumor-surrounding brain tissue always escape from cytoreductive surgery and, protected by blood-brain barrier (BBB), survive the adjuvant chemoradiotherapy, eventually leading to tumor recurrence. Local interstitial delivery of chemotherapeutic agents is a promising strategy to target these cells. During our effort to develop effective drug delivery methods by intra-tumoral infusion of chemotherapeutic agents, we found consistent pattern of leakage from the tumor. Here we describe our findings and propose promising strategy to cover the brain tissue surrounding the tumor with therapeutic agents by means of convection-enhanced delivery. First, the intracranial tumor isograft model was used to define patterns of leakage from tumor mass after intra-tumoral infusion of the chemotherapeutic agents. Liposomal doxorubicin, although first distributed inside the tumor, distributed diffusely into the surrounding normal brain once the leakage happen. Trypan blue dye was used to evaluate the distribution pattern of peri-tumoral infusions. When infused intra- or peri-tumorally, infusates distributed robustly into the tumor border. Subsequently, volume of distributions with different infusion scheduling; including intra-tumoral infusion, peri-tumoral infusion after tumor resection, peri-tumoral infusion without tumor removal with or without systemic infusion of steroids, were compared with Evans-blue dye. Peri-tumoral infusion without tumor removal resulted in maximum volume of distribution. Prior use of steroids further increased the volume of distribution. Local interstitial drug delivery targeting tumor surrounding brain tissue before tumor removal should be more effective when targeting the invading cells.

Concentration rather than dose defines the local brain toxicity of agents that are effectively distributed by convection-enhanced delivery.

BACKGROUND: Convection-enhanced delivery (CED) has been developed as a potentially effective drug-delivery strategy into the central nervous system. In contrast to systemic intravenous administration, local delivery achieves high concentration and prolonged retention in the local tissue, with increased chance of local toxicity, especially with toxic agents such as chemotherapeutic agents. Therefore, the factors that affect local toxicity should be extensively studied. NEW METHOD: With the assumption that concentration-oriented evaluation of toxicity is important for local CED, we evaluated the appearance of local toxicity among different agents after delivery with CED and studied if it is dose dependent or concentration dependent. RESULTS: Local toxicity profile of chemotherapeutic agents delivered via CED indicates BCNU was dose-dependent, whereas that of ACNU was concentration-dependent. On the other hand, local toxicity for doxorubicin, which is not distributed effectively by CED, was dose-dependent. Local toxicity for PLD, which is extensively distributed by CED, was concentration-dependent. COMPARISON WITH EXISTING METHOD: Traditional evaluation of drug induced toxicity was dose-oriented. This is true for systemic intravascular delivery. However, with local CED, toxicity of several drugs exacerbated in concentration-dependent manner. From our study, local toxicity of drugs that are likely to distribute effectively tended to be concentration-dependent. CONCLUSION: Concentration rather than dose may be more important for the toxicity of agents that are effectively distributed by CED. Concentration-oriented evaluation of toxicity is more important for CED.

A multicenter phase I/II study of the BCNU implant (Gliadel(®) Wafer) for Japanese patients with malignant gliomas.

Carmustine (BCNU) implants (Gliadel(®) Wafer, Eisai Inc., New Jersey, USA) for the treatment of malignant gliomas (MGs) were shown to enhance overall survival in comparison to placebo in controlled clinical trials in the United States and Europe. A prospective, multicenter phase I/II study involving Japanese patients with MGs was performed to evaluate the efficacy, safety, and pharmacokinetics of BCNU implants. The study enrolled 16 patients with newly diagnosed MGs and 8 patients with recurrent MGs. After the insertion of BCNU implants (8 sheets maximum, 61.6 mg BCNU) into the removal cavity, various chemotherapies (including temozolomide) and radiotherapies were applied. After placement, overall and progression-free survival rates and whole blood BCNU levels were evaluated. In patients with newly diagnosed MGs, the overall survival rates at 12 months and 24 months were 100.0% and 68.8%, and the progression-free survival rate at 12 months was 62.5%. In patients with recurrent MGs, the progression-free survival rate at 6 months was 37.5%. There were no grade 4 or higher adverse events noted due to BCNU implants, and grade 3 events were observed in 5 of 24 patients (20.8%). Whole blood BCNU levels reached a peak of 19.4 ng/mL approximately 3 hours after insertion, which was lower than 1/600 of the peak BCNU level recorded after intravenous injections. These levels decreased to less than the detection limit (2.00 ng/mL) after 24 hours. The results of this study involving Japanese patients are comparable to those of previous studies in the United States and Europe.

Apoptotic DNA endonuclease (DNase-gamma) gene transfer induces cell death accompanying DNA fragmentation in human glioma cells.

AIMS: Both the genetic restoration of the apoptotic pathway and the introduction of proapoptotic molecules are now drawing attention. Concerning apoptosis of human glioma cells induced by human interferon-beta protein, we found that DNA endonuclease (DNase-gamma) acts as an executive molecule. The authors investigated whether gene transfer of this DNase-gamma exerts some therapeutic effects on human glioma cells. METHODS: We transduced U251SP, U251MG, and T98G human glioma cells with DNase-gamma gene via multilamellar cationic liposomes, monitored the growth of those cells, and carefully observed the cell-death pattern. RESULTS: DNase-gamma gene transfer resulted in an overexpression of DNase-gamma protein and induced DNA fragmentation in gene-transferred cells. The cytotoxic effect rose with multiple inoculations of the liposome, suggesting a relationship between its expression and the therapeutic effect. CONCLUSIONS: These results demonstrate that DNase-gamma gene transfer can induce apoptosis in human glioma cells, indicating its potential to become a future gene therapy strategy.