Characterization of the catecholamine extraneuronal uptake2 carrier in human glioma cell lines SK-MG-1 and SKI-1 in relation to (2-chloroethyl)-3-sarcosinamide-1-nitrosourea (SarCNU) selective cytotoxicity.
Transport of (2-chloroethyl)-3-sarcosinamide-1-nitrosourea (SarCNU) and (-)-norepinephrine was investigated in SarCNU-sensitive SK-MG-1 and -resistant SKI-1 human glioma cell lines. [3H]SarCNU influx was inhibited by SarCNU, sarcosinamide, and (+/-)-epinephrine in SK-MG-1 cells with competitive inhibition observed by (+/-)-epinephrine (Ki = 140 +/- 12 microM) and (+/-)-norepinephrine (Ki = 255 +/- 41 microM). No effect on influx was detected in SKI-1 cells. [3H](-)-Norepinephrine influx was linear to 15 sec in both cell lines and temperature dependent only in SK-MG-1 cells. Influx of [3H](-)-norepinephrine was found to be saturable in SK-MG-1 (K(m) = 148 +/- 28 microM, Vmax = 1.23 +/- 0.18 pmol/microL intracellular water/sec) but not in SKI-1 cells. In SK-MG-1 cells, [3H](-)-norepinephrine influx was found to be inhibited competitively by (-)-epinephrine (Ki = 111 +/- 7 microM) and SarCNU (Ki = 1.48 +/- 0.22 mM). Ouabain and KCl were able to inhibit the [3H](-)-norepinephrine influx in SK-MG-1 cells, consistent with influx being driven by membrane potential. Several catecholamine uptake2 inhibitors were able to reduce significantly the influx of [3H](-)-norepinephrine and [3H]SarCNU with no inhibition by a catecholamine uptake1 inhibitor. These findings suggest that increased sensitivity of SK-MG-1 to SarCNU is secondary to enhanced accumulation of SarCNU mediated via the catecholamine extraneuronal uptake2 transporter, which is not detectable in SKI-1 cells. The introduction of SarCNU into clinical trials will confirm if increased uptake via the catecholamine extraneuronal uptake2 transporter will result in increased antitumor activity.
Noë
A J
AJ
Lady Davis Institute for Medical Research, Sir Mortimer B. Davis-Jewish General Hospital, Montréal, Québec, Canada.
Marcantonio
D
D
Barton
J
J
Malapetsa
A
A
Panasci
L C
LC
D000970:Antineoplastic Agents / Q000494:pharmacology*; D002330:Carmustine / Q000031:analogs & derivatives* / Q000494:pharmacology; D002395:Catecholamines / Q000378:metabolism*; D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D004837:Epinephrine / Q000378:metabolism; D005910:Glioma / Q000188:drug therapy* / Q000378:metabolism*; D006801:Humans; D009638:Norepinephrine / Q000378:metabolism; D013997:Time Factors
D000970:Antineoplastic Agents; D002395:Catecholamines; C044565:2-((((2-chloroethyl)nitrosoamino)carbonyl)amino)propanamide; D002330:Carmustine; D009638:Norepinephrine; D004837:Epinephrine