PATTERN OF RAS AND GSP ONCOGENE MUTATIONS IN RADIATION-ASSOCIATED HUMAN THYROID-TUMORS

The preferential activation of the Ki-ras oncogene in follicular radia tion-associated human thyroid carcinomas, has been suggested by Wright et al. (1991). However, only 12 thyroid tumors were analysed in this study. In order to confirm if radiation favours, in human thyroid tumo rigenesis, the appearance of a particular molecular lesion, we studied 33 benign and malignant human radiation-associated thyroid tumors. We used polymerase chain reaction (PCR) amplification and allele-specifi c hybridization with mutant-specific probes for the three ras genes an d the gsp oncogene. Compared to 85 'spontaneous' human thyroid tumors, the radiation-associated cases: (1) show a similar overall frequency of uas and gsp mutations (about 30% and 6% respectively); (2) present a similar frequency of mutation of the three ras genes without any pre dominance in adenomas and papillary carcinomas and (3) all Ki-ras muta tions were found in papillary carcinomas (4/15). ras and gsp genes wer e never found mutated simultaneously, suggesting an alternative role f or both oncogenes in the thyroid tumorigenic radiation-associated proc ess.