Assessment of cyclin D1 gene expression as a prognostic factor in benign and malignant thyroid lesions

Cyclin D1, encoded by CCND1 (cyclin D1) gene with locus in chromosome 11q13, is a protein that plays the key role in the passage through the restriction point in G1 phase of cell cycle. The aim of the study were: 1) an assessment of CCND1 gene expression level in benign and malignant thyroid lesions and 2) the evaluation of possible correlations between gene expression and the histopathological variants of papillary thyroid carcinoma (PTC), or tumour size, classified according to TNM definition of primary tumours (in case of PTC only) or patient's sex or age.

Thirty five (35) tissue samples were analysed: 24 cases of PTC, 4 cases of medullary thyroid carcinoma (MTC), 4 cases of follicular adenoma (FA) and 3 cases of nodular goitre (NG). In real-time polymerase chain reaction (real-time PCR), two-step RT-PCR (reverse transcriptase-polymerase chain reaction) in an ABI PRISM 7500 Sequence Detection System was employed. Cyclin D1 gene expression level was assessed, calculating the mean relative quantification rate (RQ rate) increase for each sample.

The level of cyclin D1 gene expression was significantly higher in malignant thyroid tumours (PTC, MTC), as compared with that in macroscopically unchanged thyroid tissue, FA and/or NG groups. However, the differences of RQ rate value between different PTC variants were statistically insignificant. No correlation was found between RQ values and patients' sex or age. On the other hand, the correlation was observed between RQ values and tumour size.

Cyclin D1 gene expression in various thyroid lesions may be helpful in diagnostically doubtful cases. However, our results--mostly due to the small numbers of cases in the groups other than PTC--do not yet allow considering cyclin D1 gene as a molecular prognostic marker.