Cyclin D1 overexpression in thyroid carcinomas: Relation with clinico-pathological parameters, retinoblastoma gene product, and Ki67 labeling index

Cyclin D1 is a G1 cyclin participating in the control of cell cycle progres sion through interaction with the retinoblastoma gene product (pRB). The ov erexpression of positive regulators (such as cyclin D1) has been reported i n a variety of neoplasms, but their role in thyroid tumorigenesis is yet to be established. In our series of 54 thyroid carcinomas, cyclin D1 overexpr ession (detected by both immunohistochemistry and by Northern blotting) was correlated with prognostic variables, proliferative activity and pRB. Cycl in D1 overexpression was observed in 35% of thyroid carcinomas with a signi ficantly higher expression of this cyclin in neoplastic tissues than in mat ched normal parenchyma. In well-differentiated carcinomas, the cyclin D1 mR NA overexpression was inversely correlated with nodal status (p = 0.03), wh ile the protein product was higher in tumors from patients less than 40 tha n patients over 40 years of age. Inversely, there was no significant correl ation with gender and tumor status, pRB and with proliferative activity.