G. Della Porta

Ret oncogene activation in human thyroid neoplasms is restricted to the papillary cancer subtype.

We have recently reported the activation of a new oncogene in human papillary thyroid carcinomas. This oncogene, papillary thyroid carcinoma (PTC), is a novel rearranged version of the ret tyrosine-kinase protooncogene. Thyroid neoplasms include a broad spectrum of malignant tumors, ranging from well-differentiated tumors to undifferentiated anaplastic carcinomas. To determine the frequency of ret oncogene activation, we analyzed 286 cases of human thyroid tumors of diverse histologic types. We found the presence of an activated form of the ret oncogene in 33 (19%) of 177 papillary carcinomas. By contrast, none of the other 109 thyroid tumors, which included 37 follicular, 15 anaplastic, and 18 medullary carcinomas, and 34 benign lesions, showed ret activation.

Gene p53 mutations are restricted to poorly differentiated and undifferentiated carcinomas of the thyroid gland.

The p53 gene was analyzed in tumor specimens obtained from 52 patients with various types of carcinoma of the thyroid gland by a combined molecular and immunocytochemical approach. The histologic types included 37 well-differentiated papillary and follicular carcinomas, 8 poorly differentiated, and 7 undifferentiated carcinomas. The p53 gene was shown to be unaffected in all differentiated tumors by single-strand conformation polymorphism analysis. However, in two out of eight (25%) of poorly differentiated carcinomas and five out of seven (71%) undifferentiated carcinomas, p53 mutations were identified and subsequently characterized by DNA sequencing. One undifferentiated carcinoma displayed two areas with varying degrees of differentiation. The comparative analysis of the p53 gene, in both the more and the less differentiated area of this tumor, clearly showed that the p53 mutation was confined to the latter component of the tumor specimen. These results indicate that mutations of the p53 gene are associated with the most aggressive histologic types of thyroid tumors, such as the undifferentiated carcinoma and, to a certain extent, the poorly differentiated carcinoma, and that the alterations of this gene represent a late genetic event in human thyroid carcinogenesis.

A t(2;3)(q12–13;p24–25) in follicular thyroid adenomas☆

We report the cytogenetic analysis of five cases of follicular thyroid adenoma. In two of them, we observed an identical t(2;3)(q12-13;p24-25) as a unique chromosome change. A third case showed a hyperdiploid karyotype with trisomies of chromosomes 7 and 12. Two cases had a normal diploid karyotype. These changes could define subgroups of follicular adenomas endowed with different malignant potential.

Cytogenetic abnormalities and overexpression of receptors for growth factors in normal bronchial epithelium and tumor samples of lung cancer patients.

A cytogenetic analysis was performed on direct preparations and short-term cell cultures of lung tumor and normal bronchial epithelium of 19 patients carrying either a first or a second primary lung cancer. In 9 tumors (6 squamous cell carcinomas, 1 adenocarcinoma, 1 mucoepidermoid carcinoma, and 1 small cell lung carcinoma) successfully analyzed, pseudodiploid and hyperdiploid karyotypes were observed with a heterogeneous pattern of chromosome abnormalities but with a consistent involvement (5 cases) of the short or the long arm of chromosome 3. The normal bronchial epithelial cells had a normal karyotype in 11 patients, whereas in 6 patients clonal and nonclonal chromosomal abnormalities were observed. Involvement of chromosome 7 was present in 4 cases. In addition, overexpression of the growth factor receptors, epidermal growth factor receptor and HER-2/neu, was found in 9 of 18 tumors and in 6 of 13 bronchial epithelium samples. These findings suggest that early genetic lesions could be present in the normal bronchial epithelial cells that are the target of further complex and multiple genetic changes occurring during the pathogenesis of lung cancer.