Protein products of
cyclin D1 and
retinoblastoma (Rb) genes play crucial roles in regulation of G1/S transition in the cell cycle. In this study we analyzed, using immunohistochemical methods, the expression of
cyclin D1 and Rb
proteins in material from medical archives (12 cases of
follicular thyroid carcinoma, 57 cases of
follicular adenoma and 17
nodular goiter cases). A positive nuclear reaction for
cyclin D1 was observed in 83.3% (10/12) of the follicular
carcinomas, in 96.5% (55/57) of the
follicular adenomas and in 23.5% (4/17) of
nodular goiters. Overexpression of
cyclin Dl (more than 50% of positively staining cells) was noted in 25% (3/12) of the follicular
carcinomas and in 22.8% (13/57) of the
follicular adenomas. No overexpression of
cyclin D1 was noted among
nodular goiters. The number of
carcinoma cases with
cyclin D1 overexpression did not differ statistically in any significant way from the
follicular adenoma group (p = 1.000). A positive nuclear reaction for
Rb protein was noted in 100% of the follicular
carcinomas (12/12), in 96.5% of the
follicular adenomas (55/57) and in 47.1% of the cases (8/17) of
nodular goiter.
Rb protein overexpression (more than 50% of positively staining cells) was found in 83.3% (10/12) of the follicular
carcinomas, in 68.4% (39/57) of the
follicular adenomas and in 11.8% (2/17) of the
nodular goiters. The number of cases with
Rb protein overexpression in the follicular
carcinoma group did not differ significantly from that in the
follicular adenoma group (p = 0.486). A positive correlation was found in the groups studied between the expressions of
Rb protein and
cyclin D1. However, the correlation was statistically significant only in the
nodular goiter group (Rs = 0.567; p = 0.018). In the follicular
carcinoma group, that correlation was borderline (Rp = 0.437; p = 0.072) and, in the
follicular adenoma group, it was statistically insignificant (Rs = 0.217; p = 0.105). Our results confirm the existence of mutual regulation mechanisms of Rb and
cyclin D1 protein expressions, which are observed in cells from various
carcinomas.