mRNA expression pattern of retinoic acid and retinoid X nuclear receptor subtypes in human thyroid papillary carcinoma.

Retinoids have shown potential for the inhibition of tumour growth and progression. The objective of this study was to investigate retinoic acid nuclear receptor subtypes RAR/RXR and iodothyronine 5'-deiodinase, type I expression pattern in papillary thyroid tumour tissue of 26 patients in order to compare with those of the non-neoplastic thyroid tissue of the corresponding patients. The expression of selected parameters mRNA was examined by semi-quantitative RT-PCR. Papillary thyroid carcinoma (PTC) expressed RXRγ, when compared to non-neoplastic thyroid tissues of the corresponding patients that were lacking expression of RXRγ or its expression was very low. Moreover, we found significantly increased expression of RARα and RARγ in the overall group of PTC. This increase was detected in cases with positive lymph node metastasis (LNM), but not in cases with negative LNM. RARβ was significantly reduced in the subgroup of classic variant (CV). We also detected absence or significantly lower expression of hDIO1 mRNA in tumour tissue when compared to non-neoplastic tissue in both overall PTC cases and in the CV subgroup. However, the significantly decreased levels of hDIO1 mRNA were detected in cases with negative LNM but not in cases with positive LNM when compared to corresponding non-tumour tissue in both overall PTC cases and in the CV subgroup. Differences in RAR and RXR subtype mRNA expression patterns in various PTCs may contribute to the immunochemistry data available, and may thus find exploitation in clinical oncology, particularly in the differential diagnosis of thyroid neoplasms.