Analysis of splice variants of the fibronectin gene in thyroid carcinomas by reverse transcription-polymerase chain reaction: Increased expression ofoncofetal fibronectin mRNA in papillary carcinomas is not caused by the alternation in splicing

The expression levels of each splice variant of the fibronectin gene in the normal thyroid and in thyroid tumors were examined by reverse transcriptio n-polymerase chain reaction (RT-PCR). In thyroid papillary carcinomas, inse rtion of a variant exon in the ED-A and EDB domains, and three of five type s of splice variants in the IIICS domain were observed. In spite of the mar ked increase in the expression of oncofetal fibronectin mRNA with the IIICS sequence in papillary and anaplastic carcinomas in the previous reports, t he relative expression levels of each splice variant with or without the II ICS sequence showed no difference among all the tumor types. Therefore, the much increased expression of oncofetal fibronectin mRNA in these carcinoma s is not caused by the alternation in splicing, but may be caused by an inc rease in promoter activity or stability of mRNA of the fibronectin gene. (J . Endocrinol. Invest. 22: 18-22, 1999) (C)1999, Editrice Kurtis.