In the present study, expression and regulation of hCG receptor mRNA were analyzed in four established human ovarian cancer cell lines using different concentrations of hCG, EGF, and 8-bromo-cAMP for different periods between 6 and 72 h. The cells were examined for the hCG receptor using the reverse-transcriptase polymerase chain reaction with specific primers amplifying the hCG receptor gene. Receptor mRNA was found in all cell lines. In the line OVCAR-3, it was expressed in all samples independent of kind and concentration of the receptor agonist and incubation period. In the line COLO-704, the hCG receptor gene was expressed only in unstimulated samples, but not in the samples incubated with a receptor agonist. The cell line EFO-21 showed a downregulation of receptor mRNA after 24 h of treatment with 25 IU/ml hCG and after 6 h of treatment with 250 IU/ml hCG or 100 ng/ml EGF. The mRNA reappeared within 24-48 h. The cell line EFO-27 showed a downregulation of receptor mRNA after 6 h of incubation with 250 IU/ml hCG. Agarose gel electrophoresis and sequencing of the polymerase chain reaction products revealed four cDNA fragments resulting from an alternative splicing of the primary transcript. The results of the study demonstrate that the expression of hCG receptor mRNA in ovarian cancer cell lines varies considerably under different experimental conditions. We showed that ovarian cancer cells can produce hCG receptors when needed or wanted. The inherent mechanisms which rule this phenomenon need further evaluation.
Copyright 2003 S. Karger AG, Basel