c-myc, c-erbB-2, c-fms and bcl-2 oncoproteins. Expression in normal placenta, partial and complete mole, and choriocarcinoma.

Objective: To determine the expression of bcl-2, c-myc, c-fms and c-erbB-2 oncoproteins in normal placentas, partial and complete hydatidiform moles, and choriocarcinomas and to examine the possible presence of mutations in the K-ras gene in complete moles and choriocarcinomas.

Study Design: The expression of the above oncoproteins was determined immunohistochemically by specific antibodies for these proteins on formalin-fixed paraffin sections of 18 normal placentas, 17 partial moles, 25 complete moles and 11 choriocarcinomas. This was followed by polymerase chain reaction analysis (exons 12 and 13) of K-ras gene for possible mutations in complete moles and choriocarcinomas.

Results: Expression of c-fms oncoprotein appeared confined to the cytoplasm of syncytiotrophoblastic cells. The c-fms protein staining intensity of the syncytiotrophoblastic layer showed no significant difference among the four gestational tissues. c-erbB-2 antibody expression was confined to the cellular membrane of the extravillous trophoblast. When compared with normal placenta or partial mole, the expression of c-erbB-2 protein was significantly stronger in complete mole (P < .0001 and P < .0001, respectively) and choriocarcinoma (P < .0001 and P < .0001, respectively). Expression of bcl-2 protein was significantly stronger in the syncytiotrophoblast in complete mole and choriocarcinoma as compared to both normal placenta and partial mole (P < .0001 and P < .0001, respectively). Staining of c-myc of the syncytiotrophoblastic layer was significantly stronger in placenta, complete mole and choriocarcinoma than in partial mole (P < .0001, P < .0001 and P < .0001, respectively). Mutation in K-ras gene was not found in any of the 22 complete moles or 11 choriocarcinomas examined.

Conclusion: Our data suggest that c-myc, c-erbB-2, c-fms and bcl-2 oncoproteins may be important in the pathogenesis of complete mole and choriocarcinoma. However, while both complete mole and choriocarcinoma were characterized by overexpression of c-myc, c-erbB-2 and bcl-2, partial mole generally did not strongly express these three oncoproteins.