De novo expression of transfected human class 1 aldehyde dehydrogenase (ALDH) causes resistance to oxazaphosphorine anti-cancer alkylating agents in hamster V79 cell lines. Elevated class 1 ALDH activity is closely correlated with reduction in DNA interstrand cross-linking and lethality.
Human class 1 aldehyde dehydrogenase (hALDH-1) can oxidize aldophosphamide, a key aldehyde intermediate in the activation pathway of cyclophosphamide and other oxazaphosphorine (OAP) anti-cancer alkylating agents. Overexpression of class 1 ALDH (ALDH-1) has been observed in cells selected for survival in the presence of OAPs. We used transfection to induce de novo expression of human ALDH-1 in V79/SD1 Chinese hamster cells to clearly quantitate the role of hALDH-1 expression in OAP resistance. Messenger RNA levels correlated well with hALDH-1 protein levels and enzyme activities (1.5-13.6 milliunits/mg with propionaldehyde/NAD+ substrate, compared to < 1 milliunit/mg in controls) in individual clonal transfectant lines, and slot blot analysis confirmed the presence of the transfected cDNA. Expressed ALDH activity was closely correlated (r = 0.99) with resistance to mafosfamide, up to 21-fold relative to controls. Transfectants were cross-resistant to other OAPs but not to phosphoramide mustard, ifosfamide mustard, melphalan, or acrolein. Resistance was completely reversed by pretreatment with 25 microM diethylaminobenzaldehyde, a potent ALDH inhibitor. Alkaline elution studies showed that expression of ALDH-1 reduced the number of DNA cross-links commensurate with mafosfamide resistance, and this reduction in cross-links was fully reversed by the inhibitor. Thus, overexpression of human class 1 ALDH alone is sufficient to confer OAP-specific drug resistance.
Bunting
K D
KD
Biochemistry Department, Bowman Gray School of Medicine, Wake Forest University Comprehensive Cancer Center, Winston-Salem, North Carolina 27157, USA.
Townsend
A J
AJ
D000444:Aldehyde Dehydrogenase / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D000818:Animals; D018906:Antineoplastic Agents, Alkylating / Q000494:pharmacology*; D001483:Base Sequence; D002460:Cell Line; D006224:Cricetinae; D003412:Cricetulus; D003520:Cyclophosphamide / Q000031:analogs & derivatives / Q000494:pharmacology; D004247:DNA / Q000378:metabolism*; D004351:Drug Resistance; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D007527:Isoenzymes / Q000502:physiology*; D008969:Molecular Sequence Data; D010752:Phosphoramide Mustards / Q000494:pharmacology; D014162:Transfection
D018906:Antineoplastic Agents, Alkylating; D004791:Enzyme Inhibitors; D007527:Isoenzymes; D010752:Phosphoramide Mustards; C030090:phosphoramide mustard; C048341:mafosfamide; D003520:Cyclophosphamide; D004247:DNA; D000444:Aldehyde Dehydrogenase