Nuclear beta-catenin and Ki-67 expression in choriocarcinoma and its pre-malignant form.
OBJECTIVE
To study the expression of nuclear beta-catenin and Ki-67 in patients with normal gestation products (NGP), complete hydatidiform moles (CHM), and choriocarcinoma to elucidate their roles in carcinogenesis and their interrelations.


METHODS
Expression of nuclear beta-catenin and Ki-67 was studied by immunohistochemistry using paraffin embedded blocks. Sixty NGP, 60 CHM, and 10 choriocarcinomas were analysed. In addition, approximately 400 trophoblasts each in 40 NGP, 40 CHM, and 10 choriocarcinomas from the same batch of samples were microdissected for quantitative reverse transcriptase polymerase chain reaction (Q-RT-PCR) to compare beta-catenin mRNA concentration among them.


RESULTS
In the chorionic villi of NGP, beta-catenin was consistently expressed in the nuclei of cytotrophoblasts but not syncytiotrophoblasts. Nuclear beta-catenin expression was comparatively reduced in CHM trophoblasts and was absent in choriocarcinoma. By contrast, Ki-67 expression was increased from cytotrophoblasts but not in syncytiotrophoblasts in the chorionic villi of NGP to CHM trophoblasts and choriocarcinoma. Using Q-RT-PCR, beta-catenin mRNA was detected in 10 NGP, 13 CHM, and three choriocarcinoma specimens, with median copy numbers of 43,230, 18,229, and 17,334 per 400 trophoblasts, respectively. A housekeeping gene glyceraldehyde-3-phosphate dehydrogenase (GAPDH) mRNA was detected as a control in the NGP, CHM, and choriocarcinoma specimens, with median copy numbers of 51,300, 54,270, and 97,150 per 400 trophoblasts, respectively. Thus median beta-catenin mRNA values after normalisation were 0.85 in NGP (n = 10), 0.31 in CHM (n = 13), and 0.16 in choriocarcinoma (n = 3).


CONCLUSIONS
Decreased nuclear beta-catenin expression and increased Ki-67 expression may be involved in choriocarcinoma carcinogenesis. The findings also suggest that nuclear beta-catenin may play a role in trophoblast differentiation during normal placental development.
Wong
S C C
SC
Department of Clinical Oncology, The Chinese University of Hong Kong, Prince of Wales Hospital, Hong Kong Special Administrative Region, China.
Chan
A T C
AT
Chan
J K C
JK
Lo
Y M D
YM
D014408:Biomarkers, Tumor / Q000032:analysis*; D002467:Cell Nucleus / Q000737:chemistry*; D002822:Choriocarcinoma / Q000737:chemistry*; D002824:Chorionic Villi / Q000737:chemistry; D004627:Embryonic Induction; D005260:Female; D006801:Humans; D006828:Hydatidiform Mole / Q000737:chemistry; D007150:Immunohistochemistry / Q000379:methods; D019394:Ki-67 Antigen / Q000032:analysis*; D016612:Paraffin Embedding; D011230:Precancerous Conditions / Q000378:metabolism; D011247:Pregnancy; D012333:RNA, Messenger / Q000032:analysis; D012189:Retrospective Studies; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014327:Trophoblasts / Q000737:chemistry; D014594:Uterine Neoplasms / Q000737:chemistry*; D014599:Uterus / Q000737:chemistry; D051176:beta Catenin / Q000032:analysis* / Q000235:genetics
D014408:Biomarkers, Tumor; D019394:Ki-67 Antigen; D012333:RNA, Messenger; D051176:beta Catenin