Cell type specific expression of the apoptosis stimulating protein (ASPP-2) in human tissues

Abstract

Apoptosis stimulating proteins of p53 (ASPP-l and ASPP-2) are a novel family of proteins that have been found to co-stimulate p53 activation of Bax (Bcl-2 associated protein X) inducing caspase-mediated apoptosis. Therefore, these proteins may play an important role in regulating apoptosis in normal and neoplastic cells. However, their cellular and tissue distribution has not been documented. The aim of this study was to determine the localization pattern of ASPP-2 in a variety of normal and malignant human tissues, including liver, lung, prostate, small intestine, kidney, ovary, bladder, cervix, breast, stomach, bowel, gallbladder, endometrium, pancreas, spleen and thyroid.The distribution and expression of ASPP-2 was assessed by immunohistochemistry in a range of formalin-fixed, paraffin embedded, benign and malignant human tissues, using a mouse monoclonal antibody against ASPP-2.The results showed a variable pattern of positivity of ASPP-2 within the tissues studied. ASPP-2 expression was localized in the cytoplasmic paranuclear granules in the epithelial cells of most of the organs we studied. The pattern of staining intensity of ASPP-2 correlated to the maturation state in benign tissue and to the differentiation state in the context of bladder cancer.This study indicates that ASPP-2 has a specific distribution pattern within tissues and cells in a way that appears to be related to differentiation. However, the patterns are neither simplistic nor straightforward and will require further investigation in order to appreciate fully their physiological/pathological significance.