Approaches to Treatment of Children with Advanced Neuroblastoma
Abstract: Children with advanced neuroblastoma are at high risk for relapse of multidrug resistant disease, despite initial response to intensive multimodality treatment. Neuroblastomas have similarities with immature neuroblasts seen during embryonic development of the sympathetic nervous system (the origin of these tumors). Chemotherapeutic drugs have various mechanisms of action and successfully treated cancer cells eventually undergo programmed cell death (apoptosis). Hence, impaired apoptotic pathways can be one explanation for drug resistance, but also represent causes for tumor initiation, progression and metastatic spread. Tumor hypoxia (low oxygen levels) due to rapid cell overgrowth and impaired vascularization is another obstacle in cancer treatment, especially recognized by radiotherapists. Recent studies have revealed that tumor hypoxia affect malignant potential of tumor cells through increased genomic instability and metastatic ability. We have identified that the embryonic transcription factor dHAND is exclusively expressed in neuroblastomas, and this protein/gene might represent a potential diagnostic marker and target for future therapy. In addition, we have found that hypoxia alters neuroblastoma cells toward an immature phenotype and we hypothesize that hypoxic cells de-differentiate and thereby retain their migration capacities, which could be an explanation for tumor progression. Hypoxic neuroblastoma cells were found resistant to cytotoxic drugs but not to mitomycin C, and we propose that this compound might be useful for targeting the hypoxic cells in the initial treatment of neuroblastoma. Arsenic trioxide, a newly re-introduced drug in the treatment of relapsed and drug-resistant acute promyelocytic leukemia, induces a p53-independent apoptotic cell death in neuroblastoma cells, which is in contrast to conventional cytotoxic agents. We suggest that arsenic trioxide could be useful in the clinical setting in the treatment of children with advanced neuroblastoma.
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