Expression of HOX gene products in normal and abnormal trophoblastic tissue

Objective. The expression pattern of three homeobox genes products, HOX All, HOX B6, and HOX C6, was examined in normal human placental tissue and abnormal trophoblastic tissue derived from complete hydatidiform moles and choriocarcinoma tumors. We sought to determine whether expression of these gene products during different states of trophoblastic differentiation and proliferation is constant or demonstrates variation. Variation in expression of these respective homeobox genes may provide insight into predicting which molar tissues are likely to develop into choriocarcinoma tumors. Methods. Tissue sections from a total of 12 samples were studied. Among these, six full-term human placentas, three complete hydatidiform moles, and three choriocarcinoma tumors were examined for expression of the homeobox HOX A 11, HOX B6, and HOX C6 gene products, using immunohistochemistry staining methods. Results. Expression of HOX homeobox gene products, HOX A11, HOX B6, and HOX C6, was detected in full-term human placenta and tissue from complete hydatiform moles. Abnormal trophoblasts from complete moles demonstrated an immunoreactivity expression pattern comparable to that of normal trophoblasts from term pregnancies. However, definitive expression of these respective homeobox genes was not identified in tissue obtained from choriocarcinoma tumors. Conclusion. Variation in expression of HOX homeobox gene products, HOX A11, HOX B6, and HOX C6, was established in trophoblast tissue obtained from full-term human placentas, complete hydatiform moles, and choriocarcinoma tumors. This finding indicates that normal full-term trophoblasts and abnormal molar trophoblasts may share similar fundamental regulatory control mechanisms. The absence of definitive expression of these HOX gene products in trophoblastic cells derived from choriocarcinoma tumors indicates that while HOX A11, HOX B6, and HOX C6 genes may be involved in maintenance of some trophoblastic cell states, they may be either downregulated or have alterations in their expression in trophoblasts from choriocarcinoma tumors. (C) 2003 Elsevier Science (USA). All rights reserved.