Metallothionein expression in renal cell carcinoma: subcellular localization and prognostic significance

We investigated the immunohistochemical localization of metallothionein (MT) in renal cell carcinoma and determined the potential role of MT expression as a possible prognostic variable for tumor proliferation and progression.

Tumor tissue blocks from 70 patients with renal cell carcinoma who underwent radical or partial nephrectomy were investigated. Mean followup plus or minus standard error was 36 +/- 3 months. Immunohistochemical testing was performed by the avidin-streptavidin method using a monoclonal mouse antiMT antibody. MT staining intensity in samples was evaluated semiquantitatively. The subcellular distribution of MT was also determined. Staining characteristics were compared with the clinicopathological results.

MT immunostaining was found in 39 of 70 tumors (55.7%) and subcellulary MT was localized in the cytoplasm, nucleus and cell membrane. The survival of patients with MT immunostaining was significantly worse than that of those with MT negative results (p = 0.02). A significant relationship of higher tumor grade and MT staining intensity was observed in grades I and III (p = 0.01), and grades II and III (p = 0.02) tumors. No association was found of MT expression and pathological stage. Sarcomatoid tumors showed significantly higher MT expression than clear cell, papillary, granular or chromophobe tumors (p = 0.02, 0.001, 0.01 and 0.01, respectively). MT expression was not an independent prognostic variable.

MT over expression seems to be associated with malignant behavior and poor prognosis in renal cell carcinoma. Therefore, MT expression may be considered a useful marker of less differentiated and more aggressive renal cell carcinoma.