A new acute transforming feline retrovirus and relationship of its oncogene v-kit with the protein kinase gene family

A new acute transforming feline retrovirus, the Hardy-Zuckerman 4 feline sarcoma virus (HZ4-FeSV), has been isolated from a feline fibrosarcoma. The viral genome of HZ4-FeSV contains a new oncogene designated v-kit, has the structure 5' delta gag-kit-delta pol-delta env 3' and specifies a gag-kit polyprotein of relative molecular mass 80,000. The predicted kit amino-acid sequence displays partial homology with tyrosine-specific protein kinase oncogenes. HZ4-FeSV appears to have been generated by transduction of feline c-kit sequences with feline leukaemia virus.     

Identification of ALK as a major familial neuroblastoma predisposition gene

Neuroblastoma is a childhood cancer that can be inherited, but the genetic aetiology is largely unknown. Here we show that germline mutations in the anaplastic lymphoma kinase (ALK) gene explain most hereditary neuroblastomas, and that activating mutations can also be somatically acquired. We first identified a significant linkage signal at chromosome bands 2p23-24 using a whole-genome scan in neuroblastoma pedigrees. Resequencing of regional candidate genes identified 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 showed somatically acquired mutations in the tyrosine kinase domain in 12.4% of samples. Nine of the ten mutations map to critical regions of the kinase domain and were predicted, with high probability, to be oncogenic drivers. Mutations resulted in constitutive phosphorylation, and 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. Our results demonstrate that heritable mutations of ALK are the main cause of familial neuroblastoma, and that germline or acquired activation of this cell-surface kinase is a tractable therapeutic target for this lethal paediatric malignancy.     

Amplified DNA with limited homology to myc cellular oncogene is shared by human neuroblastoma cell lines and a neuroblastoma tumour

Amplified cellular genes in mammalian cells frequently manifest themselves as double minute chromosomes (DMs) and homogeneously staining regions of chromosomes (HSRs). With few exceptions both karyotypic abnormalities appear to be confined to tumour cells. All vertebrates possess a set of cellular genes homologous to the transforming genes of RNA tumour viruses, and there is circumstantial evidence that these cellular oncogenes are involved in tumorigenesis. We have recently shown that DMs and HSRs in cells of the mouse adrenocortical tumour Y1 and an HSR in the human colon carcinoma COLO320 contain amplified copies of the cellular oncogenes c-Ki-ras and c-myc, respectively. Both DMs and HSRs are found with remarkable frequency in cells of human neuroblastomas. We show here that a DNA domain detectable by partial homology to the myc oncogene is amplified up to 140-fold in cell lines derived from different human neuroblastomas and in a neuroblastoma tumour, but not in other tumour cells showing cytological evidence for gene amplification. By in situ hybridization we found that HSRs are the chromosomal sites of the amplified DNA. The frequency with which this amplification appears in cells from neuroblastomas and its apparent specificity raise the possibility that one or more of the genes contained within the amplified domain contribute to tumorigenesis.