Quantitative and qualitative assessment of CA‐125 production by human endometrial epithelial cells: Comparison of eutopic and heterotopic epithelial cells

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Abstract
We have established an in vitro system for the culture of epithelial cells (ECs) from human uterine endometrium to examine the production of CA 125 and to characterize the CA‐125 antigen purified from the conditioned media. CA‐125 secretion was higher in heterotopic ECs than in eutopic ECs and it was more significant after heterotopic ECs reached confluence than during the logarithmic growth phase. CA‐125 expression was observed mainly in the G0/G,‐phase. CA‐125 expression on cell membranes did not correlate with the volume of CA 125 released per cell, and there was no amplification of CA‐125 expression in heterotopic EC membranes. Treatment of the purified CA‐125 antigen with 6 M urea yielded a much lower molecular‐mass peak (200 kDa). The results of Western blot indicated the presence of a single polydisperse band of 200 kDa in the conditioned media from eutopic ECs, whereas 2 major CA‐125 isoforms of 200 kDa and 110 kDa, as well as 2 minor forms of 100 kDa and 70 kDa, were observed in the conditioned media of the heterotopic ECs. We conclude that, in heterotopic ECs, the 1 10‐kDa CA‐125 is more prominent than the 200‐kDa antigen, and that the elevation of CA‐125 levels in the conditioned media could be attributed to significantly increased release of I 10‐kDa CA‐125 from heterotopic ECs.