Changes in the balance between proliferation and apoptosis during the progression of malignancy in thyroid tumours

The aim of this study was to gain better insight into molecular changes which reflect disturbances in the balance between proliferation and apoptosis during progression of thyroid malignancy from papillary microcarcinoma (PMC) via clinically manifest papillary carcinoma (PTC) to anaplastic carcinoma (ATC). The apoptosis related molecules (Bcl-2, Bax) and proliferation related marker (PCNA) were analysed immunohistochemically in 120 archival cases comprising PMC (n=34), PTC (n=52) and ATC (n=34). In addition, in situ apoptotic cell death was analysed by the TUNEL method. The average Bcl-2 staining score did not differ between PMC and PTC (p>0.05), but was significantly lower in ATC (p<0.05).The Bax score was higher in PTCs and ATCs than in PMCs (p<0.05). Due to these changes, the Bcl-2/Bax ratio showed a marked decrease from PMC to ATC (p<0.05), while proliferation activity increased significantly from PTC to ATC (p<0.05). Despite high Bax expression, the rate of apoptotic cell death was low in the investigated carcinomas, especially in ATC, i.e. the increase in proliferative activity was not counterbalanced with appropriate cell death. Differences were found in the expression of apoptotic molecules (Bcl-2 and Bax), their ratio (Bcl-2 /Bax) and in the rate of apoptotic cell death and proliferative activity between PMC, PTC and ATC, indicating that disturbances in the balance between apoptosis and proliferation, in favour of the latter, occur gradually during the progression of malignancy in thyroid tumours.

Changes in the balance between proliferation and apoptosis during the progression of malignancy in thyroid tumours

The aim of this study was to gain better insight into molecular changes which reflect disturbances in the balance between proliferation and apoptosis during progression of thyroid malignancy from papillary microcarcinoma (PMC) via clinically manifest papillary carcinoma (PTC) to anaplastic carcinoma (ATC). The apoptosis related molecules (Bcl-2, Bax) and proliferation related marker (PCNA) were analysed immunohistochemically in 120 archival cases comprising PMC (n=34), PTC (n=52) and ATC (n=34). In addition, in situ apoptotic cell death was analysed by the TUNEL method. The average Bcl-2 staining score did not differ between PMC and PTC (p>0.05), but was significantly lower in ATC (p<0.05).The Bax score was higher in PTCs and ATCs than in PMCs (p<0.05). Due to these changes, the Bcl-2/Bax ratio showed a marked decrease from PMC to ATC (p<0.05), while proliferation activity increased significantly from PTC to ATC (p<0.05). Despite high Bax expression, the rate of apoptotic cell death was low in the investigated carcinomas, especially in ATC, i.e. the increase in proliferative activity was not counterbalanced with appropriate cell death. Differences were found in the expression of apoptotic molecules (Bcl-2 and Bax), their ratio (Bcl-2 /Bax) and in the rate of apoptotic cell death and proliferative activity between PMC, PTC and ATC, indicating that disturbances in the balance between apoptosis and proliferation, in favour of the latter, occur gradually during the progression of malignancy in thyroid tumours.

Galectin-3 and proliferating cell nuclear antigen (PCNA) expression in papillary thyroid carcinoma

BACKGROUND AND AIM

To examine the relationship between galectin-3 and cell proliferation in thyroid tumor tissue. Galectin-3, a beta-galactoside binding protein, has recently been recognized as a promising molecular marker of thyroid malignancy, due to its high expression in thyroid carcinomas and absence from normal or benign thyroid tissue. However, its exact role in thyroid tumor biology is still unknown.

PATIENTS AND METHODS

We examined the relationship between galectin-3 and cell proliferation by comparative immunostaining for galectin-3 and proliferating cell nuclear antigen (PCNA) in paraffin-embedded tissues from 126 cases of papillary thyroid carcinoma.

RESULTS

Positive cytoplasmic immunostaining for galectin-3 was found in 115 (91.3%) cases. Nuclear staining for PCNA was detectable in 93 (74.4%) cases. A low level of PCNA staining (less than 10% positive cells) was found in 36 (28.6%) cases, moderate staining for PCNA (more than 10% but less than 30% positive cells) in 35 cases (27.8%), while highly increased PCNA expression (more than 30% positive cells) was found in 32 (25.4%) cases. Moderate or strong galectin-3 expression, found in 99 cases, was associated with highly increased PCNA staining in 28.3% of them but with no detectable PCNA expression in 24.3% of them.

CONCLUSION

These results suggest that overexpression of galectin-3 is not clearly related to proliferative activity of papillary thyroid carcinoma cells as assessed by PCNA immunostaining.