P53, BAX AND BCL-2 EXPRESSION, AND APOPTOSIS IN GESTATIONAL TROPHOBLAST OF COMPLETE HYDATIDIFORM MOLE

This study investigates the extent of apoptosis in complete hydatidifo rm mole (CHM), using an in situ 3'-end DNA labelling (TUNEL) technique on formalin-fixed and paraffin-embedded sections. The sections were a lso immunostained with antibodies to p53, Bas and Bcl-2 proteins. In 1 0 normal placenta cases and 15 CHM cases, the apoptotic index was <1 a nd 2-4 per cent, respectively. The labelled trophoblastic cells posses sed pyknotic nuclei and densely eosinophilic cytoplasm which correspon ded well to the so-called apoptotic bodies by light and electron micro scopy. The p53 positive reaction was restricted to the nuclei of cytot rophoblasts and intermediate trophoblasts, while the syncytiotrophobla sts showed only rare immunolocalization. Strong p53 expression was see n most often in cytotrophoblasts of CHM (>30 per cent of nuclei) which also showed a higher apoptosis index, while cytotrophoblasts in norma l placentae were weakly and focally labelled (<10 per cent of nuclei). There were statistical differences between normal and CHM cases (P<0. 05). Bcl-2 accumulation, on the other hand, was observed predominantly in syncytiotrophoblasts of normal placentae, and cytotrophoblasts and intermediate trophoblasts did not express Bcl-2 in all cases. Interes tingly, syncytiotrophoblasts were found to be negative for Bax protein and positive in cytotrophoblast, which is consistent with the functio n of the protein in conveying increased apoptosis susceptibility to th is cell population. The results show that the level of apoptosis corre lates with the histological type of the gestational trophoblasts, and apoptosis index is higher in cytotrophoblasts in CHM. The fact that p5 3 quantitative expression and an increase in the Bax/Bcl-2 ratio were also observed in CHM suggested that they may contribute partly to the high level of apoptosis. (C) 1998 W. B. Saunders Company Ltd.