Characterisation of a mouse tumour cell line with in vitro derived resistance to verapamil.
We have established a subline (EMT6/VRP) of the mouse tumour cell line EMT6/P with acquired resistance to the calcium transport blocker verapamil (VRP). The subline was 4-fold resistant to the cytoxicity of VRP alone compared with the parent line but of similar sensitivity to adriamycin, vincristine or colchicine. EMT6/VRP cells growing in 75 micrograms ml-1 VRP were morphologically different from and larger in diameter than EMT6/P cells, but these two parameters reverted almost to normal within 3 days of VRP removal, although resistance was retained. Expression of an mRNA coding for P-glycoprotein was similar in EMT6/VRP and the parent cell line, although considerable hyperexpression was seen in a multidrug resistant subline, EMT6/AR1.0. Cellular accumulation of both 3H-daunorubicin and 3H-VRP were greater in EMT6/VRP than in the parent line. Sensitisation to adriamycin by 3.3 micrograms ml-1 VRP was, however, somewhat reduced in EMT6/VRP (i.e. to 6.1-fold) compared with the 11-fold sensitisation seen in the parent line. It is clear that resistance to VRP seen in this cell line occurs via a different mechanism from the resistance to drugs such as adriamycin, vincristine and colchicine seen in multidrug resistant cell lines.
Twentyman
P R
PR
MRC Clinical Oncology and Radiotherapeutics Unit, Cambridge, UK.
Wright
K A
KA
Fox
N E
NE
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000818:Animals; D002460:Cell Line; D003078:Colchicine / Q000494:pharmacology; D004273:DNA, Neoplasm / Q000032:analysis; D004317:Doxorubicin / Q000494:pharmacology; D004351:Drug Resistance; D004354:Drug Screening Assays, Antitumor; D008562:Membrane Glycoproteins / Q000235:genetics; D051379:Mice; D014407:Tumor Cells, Cultured / Q000187:drug effects* / Q000473:pathology; D014700:Verapamil / Q000494:pharmacology*; D014750:Vincristine / Q000494:pharmacology
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D004273:DNA, Neoplasm; D008562:Membrane Glycoproteins; D014750:Vincristine; D004317:Doxorubicin; D014700:Verapamil; D003078:Colchicine