Spontaneous regression of neuroblastoma

Neuroblastomas are characterized by heterogeneous clinical behavior, from spontaneous regression or differentiation into a benign ganglioneuroma, to relentless progression despite aggressive, multimodality therapy. Indeed, neuroblastoma is unique among human cancers in terms of its propensity to undergo spontaneous regression. The strongest evidence for this comes from the mass screening studies conducted in Japan, North America and Europe and it is most evident in infants with stage 4S disease. This propensity is associated with a pattern of genomic change characterized by whole chromosome gains rather than segmental chromosome changes but the mechanism(s) underlying spontaneous regression are currently a matter of speculation. There is evidence to support several possible mechanisms of spontaneous regression in neuroblastomas: (1) neurotrophin deprivation, (2) loss of telomerase activity, (3) humoral or cellular immunity and (4) alterations in epigenetic regulation and possibly other mechanisms. It is likely that a better understanding of the mechanisms of spontaneous regression will help to identify targeted therapeutic approaches for these tumors. The most easily targeted mechanism is the delayed activation of developmentally programmed cell death regulated by the tropomyosin receptor kinase A (TrkA) pathway. Pan-Trk inhibitors are currently in clinical trials and so Trk inhibition might be used as the first line of therapy in infants with biologically favorable tumors that require treatment. Alternative approaches consist of breaking immune tolerance to tumor antigens but approaches to telomere shortening or epigenetic regulation are not easily druggable. The different mechanisms of spontaneous neuroblastoma regression are reviewed here, along with possible therapeutic approaches.

The "neuro" of neuroblastoma: Neuroblastoma as a neurodevelopmental disorder

Neuroblastoma is a childhood cancer derived from cells of neural crest origin. The hallmarks of its enigmatic character include its propensity for spontaneous regression under some circumstances and its association with paraneoplastic opsoclonus, myoclonus, and ataxia. The neurodevelopmental underpinnings of its origins may provide important clues for development of novel therapeutic and preventive agents for this frequently fatal malignancy and for the associated paraneoplastic syndromes. Ann Neurol 2016;80:13-23.

Mechanisms of neuroblastoma regression

Recent genomic and biological studies of neuroblastoma have shed light on the dramatic heterogeneity in the clinical behaviour of this disease, which spans from spontaneous regression or differentiation in some patients, to relentless disease progression in others, despite intensive multimodality therapy. This evidence also suggests several possible mechanisms to explain the phenomena of spontaneous regression in neuroblastomas, including neurotrophin deprivation, humoral or cellular immunity, loss of telomerase activity and alterations in epigenetic regulation. A better understanding of the mechanisms of spontaneous regression might help to identify optimal therapeutic approaches for patients with these tumours. Currently, the most druggable mechanism is the delayed activation of developmentally programmed cell death regulated by the tropomyosin receptor kinase A pathway. Indeed, targeted therapy aimed at inhibiting neurotrophin receptors might be used in lieu of conventional chemotherapy or radiation in infants with biologically favourable tumours that require treatment. Alternative approaches consist of breaking immune tolerance to tumour antigens or activating neurotrophin receptor pathways to induce neuronal differentiation. These approaches are likely to be most effective against biologically favourable tumours, but they might also provide insights into treatment of biologically unfavourable tumours. We describe the different mechanisms of spontaneous neuroblastoma regression and the consequent therapeutic approaches.

Simpson Golabi Behmel syndrome: progress toward understanding the molecular basis for overgrowth, malformation, and cancer predisposition

Simpson Golabi Behmel syndrome (SGBS) is a complex congenital overgrowth syndrome with features that include macroglossia, macrosomia, and renal and skeletal abnormalities as well as an increased risk of embryonal cancers. Most cases of SGBS appear to arise as a result of either deletions or point mutations within the glypican-3 (GPC3) gene at Xq26, one member of a multigene family encoding for at least six distinct glycosylphophatidylinositol-linked cell surface heparan sulfate proteoglycans. As a class of molecules, heparan sulfate proteoglycans have been found to play essential roles in development by modulating cellular responses to growth factors and morphogens. Specifically, mutations in both the murine GPC3 gene and the Drosophila glypican, dally, have been found to modify cellular responses to bone morphogenetic proteins, providing important clues to the molecular basis of SGBS in humans. Despite these advances, there remains a paucity of information about the natural history of SGBS and optimal medical management strategies, and whether select mutations influence the SGBS phenotype and risk of cancer. To this end, an International SGBS Registry has been created and is being maintained to improve the clinical care and understanding of the pathogenesis of SGBS. Using an integrated approach employing epidemiology, molecular genetic characterization of specific GPC3 mutations, and the use of model organisms should rapidly expand the understanding of this complex disorder.

Survival of children with neuroblastoma. time trends and regional differences in Europe, 1978--1992

Neuroblastoma is one of the most common solid cancers in children. We present the data collected for the EUROCARE II study, describing survival patterns for children diagnosed in Europe 1985--1989 in detail, and exploring time trends from 1978 to 1992. On average, the mean 5-year survival rate was considerably higher in infants (79%) compared with older children (30--33%). The risk of death has dropped by 37% from 1978--1981 to 1990--1992. There is a pronounced difference between countries, with Scotland and England and Wales having two of the lowest survival rates (28% (95% confidence interval (CI) 14--48) and 36% (95% CI 31--41) 5-year survival rates, respectively). The survival rates in France, Germany and Italy (48--66% 5-year survival rate) were among the highest. This pattern corresponds to the incidence rates for these countries. It can be assumed that in neuroblastoma, both incidence and survival are related to the frequency of diagnosing asymptomatic cases with good prognosis among infants. However, one cannot ignore possible intercountry differences in the effectiveness of therapy.

Telomerase is a strong indicator for assessing the proneness to progression in neuroblastomas

BACKGROUND

As traditional parameters do not ensure completely accurate prognostic grouping in neuroblastoma (NB), new molecular markers are needed for assessing the individual patient's prognosis more precisely.

PROCEDURE, RESULTS, AND CONCLUSIONS

Based on 133 NB, we show that telomerase activity (TA) is a powerful, independent prognostic marker for all stages and is capable of differentiating between good and poor outcome in putative 'favorable' clinical or biological subgroups of NB patients. Analysis of gene and protein expression of telomerase subunits suggests that the presence or absence of TA in NB is strongly correlated with expression levels of both the catalytic subunit hTERT and the internal RNA component (hTR).

Stage-independent expression and genetic analysis of tp73 in neuroblastoma

The tp73 gene, a tp53 homologue, has been sub-regionally mapped at 1p36.3, a chromosomal region frequently deleted in neuroblastoma. Due to its chromosomal localization and to the mono-allelic expression observed in some neuroblastoma cell lines, it was proposed that tp73 might be involved in the pathogenesis of neuroblastoma. Functional assays have demonstrated that tp73 can inhibit cell proliferation and induce apoptosis. The role of this gene in tumorigenesis, however, is still unclear. We analyzed tp73 expression in 95 sporadic neuroblastoma samples by RT-PCR and we detected the tp73 transcript in 46 cases (48.4%), without significant correlation with age, clinical stage or 3-year overall survival. A genetic polymorphism in the 2nd exon of tp73 was utilized to identify the transcribed allele in tumor-cell samples. Expression from only one of the tp73 alleles was found in 13 out of 16 heterozygous tumors, while in 3 samples both alleles were present. Genotype analysis of 73 patients and 150 controls showed a significant deviation (p = 0.0308) from the Hardy-Weinberg equilibrium for a tp73 allele only among neuroblastoma patients. The absence of correlation between tp73 expression and clinical stage, age and survival suggests that this gene does not play an essential function in the clinical course of the disease. However, the distribution of genomic tp73 alleles in patients indicates that a role of this gene in the development of neuroblastoma cannot be completely ruled out. Int. J. Cancer (Pred. Oncol.) 84:365-369, 1999.