Unstable expression of E-cadherin adhesion molecules in metastatic ovarian tumor cells

E-Cadherin is a member of the cadherin family, which plays a key role in intercellular adhesion in various tumors as well as in normal tissues. Here, we examined the expression of this adhesion molecule in a murine ovarian tumor line OV2944, whose sublines show different degrees of spontaneous metastasis from subcutaneous sites; sublines LM-1 and LM-3 exhibit a low metastatic activity but a variant subline HM-1 has a high metastatic activity. When the expression of E-cadherin in these cells was examined by immunoblot analysis, the highly metastatic HM-1 cells was found to express an extremely small amount of this molecule, as compared with a high level of E-cadherin expression in the weakly metastatic LM-1 and LM-3 cells. Northern blot analysis showed that the amount of tanscripts from the E-cadherin gene is proportional to the amount of proteins detected in these cells. Immunofluorescence staining revealed that cells of the highly metastatic line were heterogeneous, that is, their cultures contained both E-cadherin-positive and negative cells. In contrast, cells of the weakly metastatic lines homogeneously expressed E-cadherin. When the highly metastatic line was subcloned, all the subclones consisted of E-cadherin-positive and negative cells. These results suggest that the expression of E-cadherin gene is not stably controlled in the highly metastatic line.