Germline mutations in the anaplastic lymphoma kinase (ALK) gene explain most hereditary neuroblastomas, providing the first example of a pediatric cancer arising because of mutations in an oncogene.
Together with the reported common variations at chromosome band 6p22 predisposing to the development of sporadic neuroblastoma, the genetic etiology of this disease is now being defined and has clearly established ALK as a critical neuroblastoma oncogene.
Yael Mosse and co-workers from Philadelphia studied 20 probands with neuroblastoma and a family history of the disease.
A total of 176 individuals (49 affected with neuroblastoma) were genotyped genome-wide.
The researchers identified a significant linkage signal at chromosome bands 2p23-24 using a whole-genome scan in neuroblastoma pedigrees.
Resequencing of regional candidate genes showed three separate germline missense mutations in the tyrosine kinase domain of ALK that segregated with the disease in eight separate families.
Resequencing in 194 high-risk neuroblastoma samples revealed somatically acquired mutations in the tyrosine kinase domain in 12.4 per cent of samples.
Nine out of the 10 mutations map to critical regions of the kinase domain and were predicted, with high probability, to be oncogenic drivers.
Mutations resulted in constitutive phosphorylation.
Targeted knockdown of ALK messenger RNA resulted in profound inhibition of growth in all cell lines harbouring mutant or amplified ALK, as well as in two out of six wild-type cell lines for ALK.
The effects of SiRNA knockdown on substrate adherent growth were quantified using an RT-CES system, the forerunner model of the new Xcelligence cell analysis system from Roche Applied Science.
The discovery of highly penetrant, heritable ALK mutations as the cause of hereditary neuroblastoma is of immediate relevance to probands with a family history, as the researchers concluded.
Screening with non-invasive techniques such as sonography and measurement of urinary catecholamine metabolites should probably be implemented for unaffected children carrying an ALK mutation.
In addition, the germline or acquired activation of the cell-surface kinase provides a tractable therapeutic target for this lethal pediatric malignancy.
The Xcelligence system allows label-free dynamic monitoring of cell proliferation and viability in real-time.
The technique utilises an electronic readout of impedance to non-invasively quantify cellular status in real time.
Cells are seeded in e-plate microtiter plates, which are integrated with microelectronic sensor arrays.
The interaction of cells with the microelectrode surface generates a cell-electrode impedance response, which not only indicates cell viability but also correlates with the number of the cells seeded in the well.
