A MULTIDRUG-RESISTANT OVARIAN-CARCINOMA CELL-LINE WITH A MALIGNANT SUPPRESSED PHENOTYPE IS A CD44 GENE-EXPRESSION DEFECTIVE MUTANT

A multidrug-resistant cell subline [OV1/VCR] derived from an ovarian adenocarcinoma cell line [OV1/P] was characterized by a typical suppressed malignant phenotype and by a unique karyotypic change: del[11][p13]. In an attempt to discern some genetic alteration of 11p genes that may be relevant to the phenotypic shift, cells were analyzed with DNA probes mapped in the deleted region and with monoclonal antibodies [MoAbs] against 11p-encoded membrane molecules. Southern blot did not detect abnormal restriction patterns of the probed sequences. OV1/VCR cells did not express the CD44 epitope [11p13 MIC4 locus] recognized by the F1O-44 MoAb and did not accumulate RNAs of the CD44 [Hermes] core peptide. This defect was not detected in another OV1/P-derived drug-resistant subline that retained the malignant behavior and did not have the del(11p) marker. It may have contributed to phenotypic reversion because evidence shows that CD44 membrane molecule is involved in cell-cell interaction and growth regulation of cancer cells.