Adenosine triphosphate-dependent transport of leukotriene C4 by membrane vesicles prepared from cisplatin-resistant human epidermoid carcinoma tumor cells.
BACKGROUND
Cisplatin accumulation is decreased in many cisplatin-resistant cells. An active efflux pump for cisplatin exists in cisplatin-resistant human epidermoid carcinoma cells (called KB cells). A previous study has suggested that the adenosine triphosphate (ATP)-dependent glutathione S-conjugate export pump (GS-X pump), which exports the bis-(glutathionato)-platinum (II) (GS-platinum) complex, could contribute to cellular resistance to cisplatin.


OBJECTIVE
In this study, we examined whether the active efflux pump for cisplatin in the cisplatin-resistant KB cells is the GS-X pump and tested its activity by using an endogenous substrate, [3H]leukotriene C4 ([3H]LTC4).


METHODS
Membrane vesicles were prepared from KB-3-1 (clone from parental KB cells) cells and from cisplatin-resistant KCP-4 (a mutant clone derived from KB-3-1 cells) cells. Using a filtration technique, we measured the uptake and transport of [3H]LTC4, a substrate for the GS-X pump, into membrane vesicles at 37 degrees C.


RESULTS
The uptake of [3H]LTC4 in the membrane vesicles from both the KB-3-1 and KCP-4 cells was ATP-dependent. In contrast, the ATP-dependent transport of [3H]LTC4 was observed only in KCP-4 membrane vesicles but not in KB-3-1 membrane vesicles. The ATP-dependent transport was vanadate sensitive and was inhibited by GS-platinum complex but only marginally by cisplatin and glutathione and not by vincristine or verapamil. The nucleotide triphosphates, guanosine triphosphate, cytidine triphosphate, uridine triphosphate, and deoxythymidine triphosphate could be substituted for ATP but were less efficient. A nonhydrolyzable ATP analogue, adenosine 5'-(beta,gamma-methylene) triphosphate, was not effective.


CONCLUSIONS
The transport of LTC4 in membrane vesicles prepared from KCP-4 cells was facilitated by an ATP-dependent pump that appeared very similar to the GS-X pump.


CONCLUSIONS
Our study suggests that the GS-X pump is involved in the decreased accumulation of cisplatin in KCP-4 cells.
Fujii
R
R
Department of Cancer Chemotherapy, Faculty of Medicine, Kagoshima University, Japan.
Mutoh
M
M
Sumizawa
T
T
Chen
Z S
ZS
Yoshimura
A
A
Akiyama
S
S
D000255:Adenosine Triphosphate / Q000502:physiology*; D001693:Biological Transport, Active; D002294:Carcinoma, Squamous Cell / Q000188:drug therapy / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D002945:Cisplatin / Q000627:therapeutic use; D004351:Drug Resistance; D005978:Glutathione / Q000378:metabolism*; D006801:Humans; D017997:Leukotriene C4 / Q000378:metabolism*; D014407:Tumor Cells, Cultured
D017997:Leukotriene C4; D000255:Adenosine Triphosphate; D005978:Glutathione; D002945:Cisplatin