Intracellular doxorubicin concentrations and drug-induced DNA damage in a human colon adenocarcinoma cell line and in a drug-resistant subline.
The mechanisms of resistance to doxorubicin (DX) were investigated using a human colon adenocarcinoma cell line (LoVo) and a subline approximately 30 times less sensitive to doxorubicin. LoVo and LoVo/DX were similar in terms of DNA and protein content, cell volume, duration of S phase and the generation time, and proportion of cycling cells. LoVo/DX showed cross-resistance to other anthracyclines, to vinca alkaloids, epipodophyllotoxin derivatives, 4'-(9-acridinylamino-methanesulfon-m-aniside) and actinomycin D. LoVo/DX was equally sensitive to melphalan and showed collateral sensitivity to cis-platinum and 1-beta-D-arabinofuranosylcytosine. On exposing LoVo and LoVo/DX to 1.25 and 40 micrograms/ml DX respectively, for 4 hr, similar DX intracellular concentrations were reached in the two cell lines. In these treatment conditions protein associated DNA-single strand breaks or DNA-double strand breaks, assessed by alkaline elution methods were only slightly less in LoVo/DX than in LoVo cells. In LoVo/DX cells, however, DNA breaks disappeared very quickly after drug removal whereas they persisted longer in LoVo cells. This persistance is probably related to the much slower DX efflux from LoVo than LoVo/DX. When verapamil was combined with DX it inhibited the rapid DX efflux from LoVo/DX and reversed the resistance in this cell line, but it had no significant activity on LoVo cells. Verapamil also increased DX-induced DNA-single strand breaks and DNA-double strand breaks in LoVo/DX cells, but not in LoVo cells.
Broggini
M
M
Laboratory of Cancer Chemotherapy, Mario Negri Institute, Milan, Italy.
Grandi
M
M
Ubezio
P
P
Geroni
C
C
Giuliani
F C
FC
D'Incalci
M
M
D000230:Adenocarcinoma / Q000235:genetics / Q000473:pathology*; D002460:Cell Line / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002945:Cisplatin / Q000494:pharmacology; D003110:Colonic Neoplasms / Q000235:genetics / Q000473:pathology*; D003561:Cytarabine / Q000494:pharmacology; D004249:DNA Damage; D004273:DNA, Neoplasm / Q000187:drug effects*; D003609:Dactinomycin / Q000494:pharmacology; D004317:Doxorubicin / Q000494:pharmacology*; D004351:Drug Resistance; D005434:Flow Cytometry; D006801:Humans; D014700:Verapamil / Q000494:pharmacology
D004273:DNA, Neoplasm; D003561:Cytarabine; D003609:Dactinomycin; D004317:Doxorubicin; D014700:Verapamil; D002945:Cisplatin