title: Isolation of highly multidrug-resistant P388 cells from drug-sensitive P388/S cells by flow cytometric cell sorting.
abstract: To investigate the spontaneous frequency of occurrence of stable multidrug-resistant cells in a population of drug-sensitive cells, we exposed drug sensitive P388/S cells to daunorubicin (dnr) for 1 h, then used fluorescence-activated cell sorting based on intracellular dnr fluorescence to isolate cells within P388/S having different intracellular content of drug. One of the sort windows chosen (low dnr content sort window) isolated only P388/S cells with intracellular drug content equal to or less than that of the known multidrug-resistant subline P388/adr. This sort window constituted approximately 3% of P388/S cells with lowest dnr content. By such a procedure we were able, on one of seven attempts, to isolate and cultivate stable, highly multidrug-resistant cells (comparable to that of P388/adr) from the P388/S cells obtained from the low dnr-content sort window. Net growth of cells in culture was observed 15-20 days after sorting, indicating that of the P388/S cells collected from the low dnr-content sort window, very few were actually highly drug-resistant. On no occasion could resistant cells be cultivated from cells sorted from P388/S with higher dnr content, as would be expected if mutation to a multidrug-resistant phenotype had occurred as a result of exposure to drug. The resistant cells isolated from P388/S by sorting (called P388/LoSort) displayed low intracellular accumulation of dnr that was enhanced by verapamil, were cross-resistant to vincristine and actinomycin-D, and distinct from P388/S, possessed a 150- to 160-kD membrane species identified by Vinca alkaloid photoaffinity labeling.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Laboratory of Developmental Therapeutics, University of Maryland Cancer Center, Baltimore 21201.
authors.forename: D D
authors.initials: DD
authors.lastname: Ross
authors.forename: J V
authors.initials: JV
authors.lastname: Ordóñez
authors.forename: C C
authors.initials: CC
authors.lastname: Joneckis
authors.forename: J R
authors.initials: JR
authors.lastname: Testa
authors.forename: B W
authors.initials: BW
authors.lastname: Thompson
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D002460:Cell Line; D002462:Cell Membrane / Q000032:analysis; D002469:Cell Separation; D003609:Dactinomycin / Q000494:pharmacology; D003630:Daunorubicin / Q000032:analysis / Q000378:metabolism / Q000494:pharmacology*; D004351:Drug Resistance; D005434:Flow Cytometry; D006801:Humans; D010641:Phenotype; D014700:Verapamil / Q000494:pharmacology; D014750:Vincristine / Q000494:pharmacology
chemical_list: D000970:Antineoplastic Agents; D003609:Dactinomycin; D014750:Vincristine; D014700:Verapamil; D003630:Daunorubicin