Immunohistochemical study of metallothionein isoform ii in hyperplastic, dysplastic and neoplastic prostatic lesions

ABSTRACT

Metallothioneins [MTs] constitute a family of several intracellular, low molecular-weight proteins with a high affinity to various heavy metals. They are involved in metalloregulatory functions such as cell proliferation, growth, and differentiation. The goals of the present study were to investigate the expression of MT in hyperplastic, dysplastic and neoplastic prostatic lesions and to correlate its expression with histologic grade of prostatic carcinoma. This study was performed on Formalin fixed and paraffin embedded tissue blocks from 8 patients with benign prostatic hyperplasia [BPH], 6 patients with prostatic intraepithelial neoplasia [PIN] and 30 patients with prostatic carcinoma [PC] using streptavidin-biotin technique. The histologic grade was defined and the carcinoma cases were divided into 8 low grade [Gleason 2-4], 12 moderate grade [Gleason 5-6] and 10 high grade [Gleason 7-10] carcinoma. Normal and benign prostatic tissues showed patchy MT staining of epithelial cells. All cases of PIN, 20 out of 30 PC cases [66.7%] showed positive staining for MT. MT expression significantly increased from low to high grade tumours. The proportion of MT positively stained cells was directly correlated with histologic grade of PC. The epithelial cells lack uniformity in staining intensity, but the percentage of strongly positive cells increased with increasing the histologic grade of PC. The high incidence of MT expression in PIN in this study suggests that it is associated with early prostate tumorigenesis. Also MT expression was directly correlated with histologic grade of PC suggesting that MT may be a useful marker for predicting prognosis of cancer prostate