Reduction of human chorionic gonadotropin beta subunit expression by modified U1 snRNA caused apoptosis in cervical cancer cells

BACKGROUND: Secretion of human chorionic gonadotropin, especially its beta subunit by malignant trophoblastic tumors and varieties of tumors of different origin is now well documented; however the role of hCG in tumorogenesis is still unknown. RESULTS: This study documents the molecular presence of human chorionic gonadotropin beta subunit in uterine cervix cancer tissues and investigates a novel technique to reduce hCGβ levels based on expression of a modified U1 snRNA as a method to study the hormone's role in biology of human cervical cancer cells cultured in vitro. The property of U1 snRNA to block the accumulation of specific RNA transcript when it binds to its donor sequence within the 3' terminal exon was used. The first 10 nucleotides of the human U1 snRNA gene, which normally binds to the 5'ss in pre-mRNA were replaced by a sequence complementary to a 10-nt segment in the terminal exon of the hCGβ mRNA. Three different 5' end-mutated U1 snRNA expression plasmids were tested, each targeting a different sequence in the hCGβ mRNA, and we found each one blocked the expression of hCGβ in HeLa cells, a cervix carcinoma cell line, as shown by immunohistochemistry and qRT-PCR. Reduction of hCGβ levels resulted in a significantly increased apoptosis rate with almost 90% of cells transfected with modified anti-hCGβ U1 snRNAs showing morphological changes characteristic of the apoptotic process. CONCLUSION: These data suggest that human chorionic gonadotropin beta subunit may act as a tumor growth-stimulating factor.