title: Circumvention of pleiotropic drug resistance in subcutaneous tumours in vivo with verapamil and clomipramine.
abstract: The development of pleiotropic drug resistance (PDR) in vivo in solid tumour models suggests that a similar process may occur in the clinic. A subline of the Ridgway osteogenic sarcoma (ROS)--a murine subcutaneously-growing solid tumour--with moderate resistance (1.5 fold) to actinomycin D was selected by repeated suboptimal treatment with this drug in vivo. This subline (ROS/ADX/G2) showed cross-resistance to vincristine (3.5 fold) and etoposide (over 5.1 fold) but not to doxorubicin. The resistance could in all cases be partly or completely overcome by treatment with non-cytotoxic doses of verapamil or clomipramine. Resistance to actinomycin in this model was associated with lower (up to 3.2 fold) drug accumulation into tumours which could be increased (up to 2.8 fold) by treatment with 25 micrograms/g verapamil. These data support clinical trials of the use of membrane-active agents to overcome PDR.
authors.affiliation: Imperial Laboratories Ltd., Andover, Hampshire, U.K.
authors.forename: S
authors.initials: S
authors.lastname: Merry
authors.forename: T G
authors.initials: TG
authors.lastname: Hamilton
authors.forename: P
authors.initials: P
authors.lastname: Flanigan
authors.forename: R I
authors.initials: RI
authors.lastname: Freshney
authors.forename: S B
authors.initials: SB
authors.lastname: Kaye
mesh_terms: D000818:Animals; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use; D002997:Clomipramine / Q000627:therapeutic use*; D003609:Dactinomycin / Q000627:therapeutic use; D004317:Doxorubicin / Q000627:therapeutic use; D004351:Drug Resistance; D005047:Etoposide / Q000627:therapeutic use; D005260:Female; D008297:Male; D051379:Mice; D008806:Mice, Inbred AKR; D012516:Osteosarcoma / Q000188:drug therapy* / Q000473:pathology; D014700:Verapamil / Q000627:therapeutic use*; D014750:Vincristine / Q000627:therapeutic use
chemical_list: D003609:Dactinomycin; D014750:Vincristine; D005047:Etoposide; D004317:Doxorubicin; D014700:Verapamil; D002997:Clomipramine