Mutations in Liver Tumours

In an initial validation of SOMA for analysing the codon 249 mutation in p53, we analysed a series of 25 paired HCC tumour and normal samples that have previously been sequenced for mutations in the p53 gene [35], The oligonucleotides generated following amplification and restriction digestion for ESI-MS analysis are shown in Table 2. 

Allele Sequence Molecular Mass m/z of ion monitored m/z of daughter ions monitored 

For these oligonucleotides, the doubly charged parent ions were isolated sequentially and subjected to 30% coUision energy. The signals from one to three specific daughter ions were summed to provide a robust signal with a low background. 

A specific G- T mutation was detected in 10/25 (40%) of the tumour samples and 0 5 of the adjacent, histopathologically normal liver tissue samples analysed by SOMA [35]. The same 10 samples were found to contain a G- T mutation by DNA sequencing [36]. However, readable DNA sequence was not generated for one of the samples found to be negative by SOMA. No G- A mutations were found in any of the samples, either by DNA sequencing or SOMA. Thus, SOMA was found to have greater sensitivity compared with DNA sequencing for the measurement of codon 249 p53 mutations as data were obtained for all 25 patients. 

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Rumsby PC, Evans JG, Phillimore HE, et al. 1992. Search for Ka-ras codon 61 mutations in liver tumours caused by hexachlorobenzene and Aroclor 1254 in C57BL/10ScSn mice with iron overload. Carcinogenesis 13(10) 1917-1920. 

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