Endocrine Abstracts

Background

Recent knowledge implicates a differential expression of the insulin-like growth factor-1 (IGF-1) mRNA splice variants (i.e., IGF-1Ea, IGF-1Eb and IGF-1Ec) in cancerous tissues, implying possible specific roles of the encoded IGF-1 protein isoforms in cancer biology. In particular, there is growing evidence that IGF-1Ec isoform may plays a distinct biological role in various types of cancer. The aim of the present study was to investigate whether IGF-1Ec isoform expression is associated with a particular type of thyroid cancer.

Materials and Methods

Formalin-fixed paraffin-embedded tissue specimens of different types of thyroid cancer from 92 patients were assessed for IGF-1Ec expression profile by immunohistochemistry. In addition, thyroid cancer biopsies of different TNM staging histological types were evaluated for mRNA expression of the IGF-1Ec transcript by real-time polymerase chain reaction (rt-PCR).

Results

From the total number of 92 samples, 2 were anaplastic, 10 medullary, 4 hyperplasia of C-cell, 11 follicular, 5 hurtle cell carcinoma, 2 poor differentiated, 5 nodular hyperplasia, 1 lymphoma and 52 were papillary thyroid carcinomas. The age of the patients at the time of diagnosis or the tumor size did not affect significantly the IGF-1Ec expression. Among all types of cancer, IGF-1Ec was expressed in papillary differentiated thyroid carcinoma. Its expression/localization was mainly cytoplasmic and significantly positively associated with TNM staging and the presence of muscular and capsule cancerous invasion (P <0.05), while no differences were found regarding vascular or regional lymph node infiltration. Similarly, a differential profile was revealed regarding the mRNA expression of the IGF-1Ec transcript, which exhibited a higher expression in advanced papillary thyroid carcinoma.

Conclusion

The present data demonstrate that the expression of IGF-1Ec isoform in thyroid cancer is positively associated with more advanced stages of papillary thyroid carcinoma.