The cell line TE671 has been widely used as a model of human medulloblastoma. In the present study we have demonstrated that transfection of DNA from this cell line into NIH 3T3 cells reveals the presence of an activated N-ras gene. Using oligonucleotide probes we have shown that the N-ras gene is activated by a point mutation at the third base of codon 61 resulting in the substitution of histidine for glutamine in the p21 ras gene product. We noted that this relatively uncommon activating mutation is also present in the human rhabdomyosarcoma cell line RD. Based on this finding and on the observation that several of the phenotypic characteristics of TE671, such as the presence of muscle-type nicotinic acetylcholine receptors and the intermediate filament protein desmin, are suggestive of myoid origin we investigated the possible identity of these two cell lines. Cytogenetic analysis revealed the presence of marker chromosomes common to both TE671 and RD. DNA fingerprinting using both locus specific and multilocus core probes showed indistinguishable band patterns in the two cell lines. Taken together our data show that TE671 and RD are derivatives of the same cell line and we conclude that the properties of the TE671 line should be ascribed to rhabdomyosarcoma rather than medulloblastoma cells.

The human and mouse met protooncogenes encode proteins that have the characteristics of growth factor receptors. Thus, the 1408 amino acid human met protein (Park et al., 1987) can be divided into several putative domains, including an intracellular protein tyrosine kinase (PTK) domain, a transmembrane domain and a 926 amino acid extracellular domain that possesses a cysteine-rich region. An activa-ed form of the met gene that is present in the chemicallytransformed human cell line (MNNG-HOS) was originally detected by its ability to transform NIH3T3 mouse fibroblasts in DNA transfection experiments (Cooper et al., 1984a, b). Activation of met involves a chromosomal rearrangement in which the regions of the met gene encoding the transmembrane and extracellular domain are replaced by a portion of an unrelated gene that has been designated tpr (Park et al., 1986a; Tempest et al., 1986a). The chimaeric gene is transcribed to produce a 5.0 kb hybrid mRNA that is in turn translated to form a fusion protein. DNA sequence analysis of cDNA clones prepared from transcripts of the activated human met gene reveal that all of the met PTK domain is retained in the product of the activated gene and that the region of the fusion protein encoded by the tpr gene exhibits weak homology to laminin Bi (Chan et al., 1987). Alterations of met were also observed in lines of spontaneously transformed mouse fibroblasts where a modest (4-8 fold) amplification of the protooncogene is accompanied by dramatic (50-100 fold) increase in the level of an 8.5 kb met transcript (Cooper et al., 1986).Northern analysis of mRNAs from a series of human cell lines has revealed a complex pattern of transcription of the met protooncogene (Park et al., 1986). Many cell lines, including a human fibroblast cell line, contain a single 9.0 kb mRNA species. Other cell lines such as the CaLu-I lung tumour line contain both 9.0 kb and 7.0 kb mRNAs while the most complex pattern of transcription of the normal met gene is present in MNNG-HOS cells and in the parent HOS cell line, which both contain 9.0 kb, 7.0 kb and 6.0 kb mRNA species. Most B-cell and T-cell tumour lines do not contain detectable levels of met transcripts.Antibodies raised against synthetic peptides corresponding to the carboxyl terminus of the predicted met gene product have been used to detect proteins encoded by the activated and normal met genes (Park et al., 1986b;Tempest et al., 1986b Tempest et al. (1986b), although in this particular study of low level of phosphorylation of a 165 kD protein, which probably corresponds to the 160 kD protein detected by Park et al. (1986b), was also observed.As a first step in determining whether alterations in met can be implicated in the induction of human tumours we have used antipeptide antibodies to examine met protein kinase activity in a series of human tumour cell lines. In addition, to help understand the large quantitative and qualitative variations in met kinase activity observed in these experiments, we have used SDS-polyacrylamide gel electr...

Summary Of patients being treated by radiotherapy for cancer, a small proportion develop marked long-term radiation damage. It is believed that this is due. at least in part, to intrinsic individual differences in radiosensitivity, but the underlying mechanism is unknown. Individuals affected by the recessive disease ataxia telangiectasia (AT) exhibit extreme sensitivity to ionizing radiation. Cells from such individuals are also radiosensitive in in vitro assays, and cells from AT heterozygotes are reported to show in vitro radiosensitivity at an intermediate level between homozygotes and control subjects. In order to examine the possibility that a defect in the ATM gene may account for a proportion of radiotherapy complications, 41 breast cancer patients developing marked changes in breast appearance after radiotherapy and 39 control subjects who showed no clinicalty detectable reaction after radiotherapy were screened for mutations in the ATM gene. One out of 41 cases showing adverse reactions was heterozygous for a mutation (insertion A at NT 898) that is predicted to generate a truncated protein of 251 amino acids. No truncating mutations were detected in the control subjects. On the basis of this result, the estimated percentage (950o confidence interval) of AT heterozygous patients in radiosensitive cases was 2.4% (0.1-12.9%) and in control subjects (0-9.0%). We conclude that ATM gene defects are not the major cause of radiotherapy complications in women with breast cancer.

Summary:A carcinoid tumour presenting as Cushing's syndrome is reported. Although no tumour mass could be initially identified the patient returned with first a liver and subsequently a cerebellar mass both of which were resected. Only at post-mortem was the lung primary discovered. ACTH, gastrinreleasing peptide (GRP) and calcitonin gene-related peptide were elevated in plasma before resection of the hepatic tumour. These peptides were demonstrated in both the hepatic and cerebellar tumours by immunocytochemistry and radioimmunoassay. This case illustrates the occasional tendency of primary lung carcinoids to remain small and clinically undetectable while generating secondary tumours which are symptomatic. It is suggested that immunological demonstration of GRP may be diagnostically helpful in directing attention to the lung as a primary site in neuroendocrine tumours which present in this fashion.

No abstract