Increased sensitivity to gemcitabine of P-glycoprotein and multidrug resistance-associated protein-overexpressing human cancer cell lines

Abstract

Gemcitabine (2 0 ,2 0 -difluorodeoxycytidine) is a deoxycytidine analogue that is activated by deoxycytidine kinase (dCK) to its monophosphate and subsequently to its triphosphate dFdCTP, which is incorporated into both RNA and DNA, leading to DNA damage. Multidrug resistance (MDR) is characterised by an overexpression of the membrane efflux pumps P-glycoprotein (P-gP) or multidrug resistance-associated protein (MRP). Gemcitabine was tested against human melanoma, non-small-cell lung cancer, smallcell lung cancer, epidermoid carcinoma and ovarian cancer cells with an MDR phenotype as a result of selection by drug exposure or by transfection with the mdr1 gene. These cell lines were nine-to 72-fold more sensitive to gemcitabine than their parental cell lines. The doxorubicin-resistant cells 2R120 (MRP1) and 2R160 (P-gP) were nine-and 28-fold more sensitive to gemcitabine than their parental SW1573 cells, respectively (Po0.01), which was completely reverted by 25 mM verapamil. In 2R120 and 2R160 cells, dCK activities were seven-and four-fold higher than in SW1573, respectively, which was associated with an increased dCK mRNA and dCK protein. Inactivation by deoxycytidine deaminase was 2.9-and 2.2-fold decreased in 2R120 and 2R160, respectively. dFdCTP accumulation was similar in SW1573 and its MDR variants after 24 h exposure to 0.1 mM gemcitabine, but dFdCTP was retained longer in 2R120 (Po0.001) and 2R160 (Po0.003) cells. 2R120 and 2R160 cells also incorporated four-and six-fold more [ 3 H]gemcitabine into DNA (Po0.05), respectively. P-glycoprotein and MRP1 overexpression possibly caused a cellular stress resulting in increased gemcitabine metabolism and sensitivity, while reversal of collateral gemcitabine sensitivity by verapamil also suggests a direct relation between the presence of membrane efflux pumps and gemcitabine sensitivity.

Isolation and characterization of gemcitabine-resistant human non-small cell lung cancer A549 cells

“…Cepharanthine reversed gemcitabine resistance in A549/GR cells. Although cepharanthine has been also reported to be an inhibitor of the P-gp efflux pump (16), NSCLC cell lines transfected with MDR1 gene had augmented sensitivity to gemcitabine (17). These findings suggest that cepharanthine might be effective in restoring the sensitivity of tumors to gemcitabine by inhibiting the drug efflux activity of MRP7 but not P-gp.…”

Gemcitabine, cisplatin and methylprednisolone (GEM-P) is an effective salvage regimen in patients with relapsed and refractory lymphoma

“…Gemcitabine is a novel nucleoside analogue, which is active in solid tumours such as pancreatic, ovarian and non-small cell lung cancer (Burris et al, 1997;Manegold et al, 1997). In vitro studies of gemcitabine have demonstrated its ability to circumvent multi-drug resistance (MDR) secondary to increased P-glycoprotein and MDR protein 1 overexpression (Bergman et al, 2003). These MDR cells are associated with increased deoxycytidine kinase activity and reduced deoxycytidine deaminase activity leading to accumulation and increase sensitivity to gemcitabine (Bergman et al, 2001).…”

Gemcitabine and oxaliplatin in the treatment of patients with immunotherapy‐resistant advanced renal cell carcinoma

“…Among more recent chemotherapeutic agents, gemcitabine appears to be the most promising drug available, in part because it is not a known substrate for P-glycoprotein, 24 which is responsible for the well known chemoresistance of RCC. 25 Recently, the combination of gemcitabine and 5-FU proved to be active against RCC, 14 but no further improvements were recorded when either cisplatin, 19 interferon, or IL-2 18 was added; furthermore, a Phase II study of gemcitabine, 5-FU, and oral thalidomide resulted in an unacceptably high incidence of thromboembolic complications.…”