c-myc oncogene alterations in human thyroid carcinomas.

A possible role of the c-myc oncogene in the neoplastic transformation of the human thyroid has been investigated. The structure, the methylation status, and the copy number of this oncogene have been analyzed in normal and in tumor thyroid DNAs by Southern blotting technique and dot blot hybridization. Among six carcinomas, four presented abnormal c-myc DNA structure: Three cases showed a mutation in the 5' flanking region of the gene, originating a new EcoRI site; the other case showed a deletion of 5 kb involving the first exon of the gene. This deletion was also observed in the white blood cells of the same individual. In addition, in three carcinomas a double dose of the oncogene has been demonstrated. In all the carcinomas examined, undermethylation of the c-myc oncogene has been observed. These findings suggest that c-myc oncogene alterations might be involved in the malignant transformation of the human thyroids and can be considered as tumor markers.