Mutation of K-ras Oncogene in Thyroid Tumor Tissue

다국어 초록 (Multilingual Abstract)

Point mutation of oncogene, one of the genetic alteration in cancer development, has been found in many malignant tumor tissues, Among those malignant tumors, the incidence of point mutation of K-ras oncogene was reported over 90% in pancreatic cancers, 40-50% in colotectal cancer, 25-30% in lung cancers and less than 10% in urogenital, breast or cervical cancers.
Several investigators have reported the incidence of point mutation of ras oncogene was 30-50% in benign thyroid tumors and 50-80% in malignant thyroid tumors with some difference by tumor cell differentiation. Also some reports suggested ras mutation may constitute early steps in thyroid tumorigenesis. But there if few report about relation between point mutation and characteristics of mutation.
In order to find out the incidence of k-ras oncogene point mutation and relation with characteristics of mutation in thyroid tumors, authors isolated DNA from each 10 normal tissue and benign and malignant tumor tissues. And then, point mutations of K-ras oncogene (four characteristics of codon 12 and one characteristic of codon 13) were detected by paired PCR with mutation-specific primer and agarose gel electrophoresis methods.
The resets are as follows;
1. Any mutation was not detected in normal thyroid tissues. While point mutations were detected 7/10 cases (70%) of benign thyroid tumor tissues and in 9/10 cases (90%) of malignant tumor tissues.
2. The incidence of GGT-AGT mutation was highest in benign thyroid tumors (60%) and lowest in malignant thyroid tumors (30%). The incidences of GGT-GAT, TGT-GTT and GGC-GAC mutations were high in malignant tumors (60%).
3. There were 8/9 cases (89%) in malignant tumors and 5/7 cases (71%) in benign tumors of positive mutations over two Hinds of mutation. And also 5/9 cases (56%) of malignant tumors and 4/7 case (51%) of benign tumors expressed positive mutations over 3 kinds. Moreover two cases of each benign and malignant turners expressed all of five mutations.
With above result, authors proposed that high incidence of point mutation of k-ras oncogene was detected in benign (70%) and malignant (90%) thyroid turners, and especially high incidence of GGT-AGT mutation (60%,) in benign tumors while high incidence of GGT-GAT, TGT, GTT and GGC-GAC mutations(60%) in malignant turners were noted. Also authors suggested that the point mutation may constitute early steps of thyroid tumorigenesis.