Recent advances in the treatment of central nervous system germ cell tumors

Convection-enhanced delivery of SN-38-loaded polymeric micelles (NK012) enables consistent distribution of SN-38 and is effective against rodent intracranial brain tumor models

Convection-enhanced delivery (CED) of therapeutic agents is a promising local delivery technique that has been extensively studied as a treatment for CNS diseases over the last two decades. One continuing challenge of CED is accurate and consistent delivery of the agents to the target. The present study focused on a new type of therapeutic agent, NK012, a novel SN-38-loaded polymeric micelle. Local delivery profiles of NK012 and SN-38 were studied using rodent brain and intracranial rodent brain tumor models. First, the cytotoxicity of NK012 against glioma cell lines was determined in vitro. Proliferations of glioma cells were significantly reduced after exposure to NK012. Then, the distribution and local toxicity after CED delivery of NK012 and SN-38 were evaluated in vivo. Volume of distribution of NK012 after CED was much larger than that of SN-38. Histological examination revealed minimum brain tissue damage in rat brains after delivery of 40 µg NK012 but severe damage with SN-38 at the same dose. Subsequently, the efficacy of NK012 delivered via CED was tested in 9L and U87MG rodent orthotopic brain tumor models. CED of NK012 displayed excellent efficacy in the 9L and U87MG orthotopic brain tumor models. Furthermore, NK012 and gadolinium diamide were co-delivered via CED to monitor the NK012 distribution using MRI. Volume of NK012 distribution evaluated by histology and MRI showed excellent agreement. CED of NK012 represents an effective treatment option for malignant gliomas. MRI-guided CED of NK012 has potential for clinical application.

Single-fraction γ-60Co radiation induces apoptosis in cultured rat C6 cells

BACKGROUND AND OBJECTIVES

Radiotherapy is frequently applied in the treatment of malignant gliomas, but it is unclear if radiotherapy exerts its effects via induction of apoptosis. The present study was designed to determine whether a single-fraction γ-60Co radiation can induce apoptosis.

DESIGN AND SETTING

In vitro cytological controlled study performed at a military medical university from October 2006 to June 2008.

METHODS

C6 cells were treated with a single fraction of ?-60Co radiation at various doses (0, 4, 16, and 64 Gy). The 3-(4,5)-dimethylthiazol-2)-2,5-diphenyl tetrazolium bromide (MTT) assay, apoptosis assays using Annexin V-fluorescein isothiocyanate /propidium iodide or Hoechst 33258 staining, and the cell cycle assay were performed, and the expression of p53 and p21 proteins was evaluated.

RESULTS

The C6 cell numbers in the 16 Gy and 64 Gy groups were much lower than in the control group at 48, 96, and 144 hours after irradiation. The irradiated cells underwent apoptosis in a dose-dependent manner. Irradiation also impacted cell cycle progression, arresting cells in the G1 phase. The p53 protein expression was shown in both the nucleus and the cytoplasm of irradiated cells, whereas p53 was only expressed in the nucleus of control (untreated) cells. The p21 protein was expressed in irradiated cells but not in control cells.

CONCLUSIONS

Single-fraction ?-60Co radiation inhibited C6 cell growth by inducing apoptosis and G1 arrest, which correlated with the up-regulation of the p53-p21 pathway. The extent of apoptosis and G1 arrest was positively correlated with the dose of radiation. Better understanding of apoptosis induced by radiation therapy will help design optimal dosing schedules for radiation therapy, especially in combination with chemotherapy.

Current advances in the diagnosis and management of intracranial germ cell tumors

Central nervous system (CNS) germ cell tumors (GCT) account for less than 5% of primary brain tumors in children and young adults, but they continue to attract much attention. Over the past decade, two advances have led to re-evaluation of what constitutes conventional therapy for CNS GCT. For pure germinomas, the challenge remains the determination of the optimal field and dose of irradiation and whether or not the use of chemotherapy can lead to a reduced dose or elimination of irradiation altogether without compromising disease control or survival. For non-germinomatous germ cell tumors, an improvement in the current dismal prognosis is imperative.