Incidence of apoptosis and metallothionein expression in renal cell carcinoma

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Abstract
Objective To investigate the frequency of apoptosis and expression of metallothionein (MT) protein and to clarify their roles in renal cell carcinoma (RCC). Materials and methods Apoptosis was detected by using the terminal deoxynucleotidyl transferase (TdT)‐mediated dUTP‐biotin nick‐end labelling (TUNEL) technique in 70 formalin‐fixed and paraffin‐embedded RCC specimens. The expression of MT was determined immunohistochemically. Results The incidence of apoptosis was significantly higher in grade 2 and 3 RCC than in grade 1. There were no significant differences amongst the other categories of RCC when grouped by tumour stage, cell type and growth pattern. The expression of MT was detected in 23 of 70 (33%) RCCs. Subcellularly, MT was localized in the cytoplasm, nucleus and cell membrane of RCC. Statistical analysis showed a close association of MT expression with the higher grades and invasive growth pattern of RCC. In addition, the incidence of apoptosis increased with increasing immunoreactivity of MT staining. There was a significant difference in the incidence of apoptosis between the diffuse staining and negative staining of MT. Conclusions There were close associations of higher grade RCC with both the incidence of apoptosis and the expression of MT, as well as a close relationship between MT expression and the invasive growth pattern of RCC. This suggests that the involvement of apoptotic cell death and MT expression should be considered an important factor in the process of the renal carcinogenesis and tumour progression.