Targeting cancer stem cells for treatment of glioblastoma multiforme.

Cancer stem cells (CSCs) in glioblastoma multiforme (GBM) are radioresistant and chemoresistant, which eventually results in tumor recurrence. Targeting CSCs for treatment is the most crucial issue. There are five methods for targeting the CSCs of GBM. One is to develop a new chemotherapeutic agent specific to CSCs. A second is to use a radiosensitizer to enhance the radiotherapy effect on CSCs. A third is to use immune cells to attack the CSCs. In a fourth method, an agent is used to promote CSCs to differentiate into normal cells. Finally, ongoing gene therapy may be helpful. New therapeutic agents for targeting a signal pathway, such as epidermal growth factor (EGF) and vascular epidermal growth factor (VEGF) or protein kinase inhibitors, have been used for GBM but for CSCs the effects still require further evaluation. Nonsteroidal anti-inflammatory drugs (NSAIDs) such as cyclooxygenase-2 (Cox-2) inhibitors have proven to be effective for increasing radiation sensitivity of CSCs in culture. Autologous dendritic cells (DCs) are one of the promising immunotherapeutic agents in clinical trials and may provide another innovative method for eradication of CSCs. Bone-morphogenetic protein 4 (BMP4) is an agent used to induce CSCs to differentiate into normal glial cells. Research on gene therapy by viral vector is also being carried out in clinical trials. Targeting CSCs by eliminating the GBM tumor may provide an innovative way to reduce tumor recurrence by providing a synergistic effect with conventional treatment. The combination of conventional surgery, chemotherapy, and radiotherapy with stem cell-orientated therapy may provide a new promising treatment for reducing GBM recurrence and improving the survival rate.

Adjuvant immunotherapy with whole-cell lysate dendritic cells vaccine for glioblastoma multiforme: a phase II clinical trial.

BACKGROUND: This study sought to evaluate effectiveness of autologous dendritic cell vaccine (immunotherapy) for glioblastoma multiforme (GBM). METHODS: Patients 14 to 70 years of age with newly diagnosed GBM and Karnofsky Performance Scale (KPS) score >70 who were receiving initial treatment were enrolled and were randomized into 2 groups during the 5-year study period. Eighteen patients underwent conventional treatment (surgery, radiotherapy, and chemotherapy) and received adjuvant autologous dendritic cell vaccine, and 16 patients (control group) underwent conventional treatment only. Administration of the vaccine was begun within 1 to 2 months postoperatively, with 10 inoculations given over 6 months. Outcome measures were overall survival (OS); progression-free survival (PFS); 1-, 2-, and 3-year survival rates, and quality of life (QoL). RESULTS: Follow-up time ranged from 14 to 56 months (median, 33 months). The 1-, 2-, and 3-year survival rates were 88.9%, 44.4%, and 16.7% for the vaccine group, respectively, and 75.0%, 18.8%, and 0%, respectively, for the control group, (P = 0.299, 0.0035, 0.0014, respectively). The median OS for the vaccine group was 31.9 months and for the control group was 15.0 months (P < 0.002). The median progression-free survival (PFS) for the vaccine group was 8.5 months, and 8.0 months for the control group (P = 0.075). The surviving fraction was significantly higher in the vaccine group based on Kaplan-Meier analysis. CONCLUSIONS: Adjuvant immunotherapy with whole-cell lysate dendritic cell vaccine may improve short-term survival. It seems to be safe, and its long-term effectiveness is worthy of further investigation.

The role of cancer stem cells (CD133(+)) in malignant gliomas.

Malignant gliomas, particularly glioblastoma multiforme (GBM) tumors, are very difficult to treat by conventional approaches. Although most of the tumor mass can be removed by surgical resection, radiotherapy, and chemotherapy, it eventually recurs. There is growing evidence that cancer stem cells (CSCs) play an important role in tumor recurrence. These stem cells are radioresistant and chemoresistant. The most commonly used tumor marker for CSCs is CD133. The amount of CSC component is closely correlated with tumor malignancy grading. Isolating, identifying, and treating CSCs as the target is crucial for treating malignant gliomas. CSC-associated vascular endothelial growth factor (VEGF) promotes tumor angiogenesis, tumor hemorrhage, and tumor infiltration. Micro-RNA (miRNA) plays a role in CSC gene expression, which may regulate oncogenesis or suppression to influence tumor development or progression. The antigenesis of CSCs and normal stem cells may be different. The CSCs may escape the T-cell immune response. Identifying a new specific antigen from CSCs for vaccine treatment is a key point for immunotherapy. On the other hand, augmented treatment with radiosensitizer or chemosensitizer may lead to reduction of CSCs and lead to CSCs being vulnerable to radiotherapy and chemotherapy. The control of signaling pathway and cell differentiation to CSC growth is another new hope for treatment of malignant gliomas. Although the many physiological behavioral differences between CSCs and normal stem cells are unclear, the more we know about these differences the better we will be able to treat CSCs effectively.

Recent advances of dendritic cells (DCs)-based immunotherapy for malignant gliomas.

Immunotherapy is a new light of hope for the treatment of malignant gliomas. The brain is no longer believed to be an immunologically privileged organ. The major advantage of immunotherapy is the tumor-specific cytotoxic effect on the tumor cells with minimal side effects. Autologous dendritic cells (DCs)-based immunotherapy is a promising and feasible method. DCs are the most potent antigen-presenting cells (APCs). DCs prime T lymphocytes by epitopic major histocompatibility (MHC) class I and II for CD8(+) cytotoxic T lymphocytes (CTLs) and CD4(+) T helper cells, respectively. From the tissue specimen examination after DCs-based immunotherapy, CD8(+) CTLs have replaced T regulatory cells (Tregs) as the major dominant tissue infiltrating lymphocytes (TILs). CD8(+) CTLs play a key role in the tumor response, which may also be effective against cancer stem cells. DCs themselves also produce many cytokines including interferon-gamma and interleukin (IL-2) to kill the tumor cells. From the preliminary better outcomes in the literature for malignant gliomas, DC-based immunotherapy may improve tumor response by increasing the survival rate and time. It is recommended that DC-based immunotherapy is applied as soon as possible with conjunctive radiotherapy and chemotherapy. Malignant gliomas have heterogeneity of tissue-associated antigens (TAAs). To find universal common antigens through different kinds of tumor culture may be the essential issue for tumor vaccine development in the future.