Consequences of antisense human chorionic gonadotrophin-alpha subunit cDNA expression in human choriocarcinoma JAR cells

Abstract

The biosynthesis of human chorionic gonadotrophin (hCG) is a hallmark endocrine function of human choriocarcinoma cells. The present study investigated the consequences of greatly diminishing this synthesis in JAR cells by stably transfecting them with pRSV-antisense hCG-alpha cDNA expression vector. The vector directs the synthesis of antisense hCG-alpha subunit mRNA which would then bind to sense hCG-alpha subunit mRNA, thus blocking its translation and consequently dimer hCG protein synthesis. The transfection with pRSV-antisense hCG-alpha cDNA resulted in a dramatic decrease in hCG secretion as compared with untransfected parental cells or those transfected with an empty vector used for the selection of clones. The decreased secretion was due to a decreased synthesis which in turn was due to a fall in steady-state hCG-alpha and -beta subunit mRNA levels. The decrease of hCG-beta subunit transcripts was unexpected and it was not due to contamination of antisense hCG-alpha cDNA construct with hCG-beta sequence. The transcription of hCG-alpha and -beta subunit genes was not altered in transfected cells suggesting that increased degradation was responsible for decreased steady-state hCG subunit mRNA levels. Despite the decreased hCG levels, the transfected cells maintained normal hCG receptor levels, responded to epidermal growth factor stimulation of hCG synthesis and secretion and grew at the same rate as the control parental cells and those transfected with an empty vector.