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-α cDNA expression vector. The vector directs the synthesis of antisense hCG-α subunit mRNA which would then bind to sense hCG-α subunit mRNA, thus blocking its translation and consequently dimer hCG protein synthesis.
The transfection with pRSV-antisense hCG-α 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-α and -β subunit mRNA levels. The decrease of hCG-β subunit transcripts was unexpected and it was not due to contamination of antisense hCG-α cDNA construct with hCG-β sequence. The transcription of hCG-α and -β subunit genes was not altered in transfected cells suggesting that increased degradation was responsible for decreased steadystate 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.