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[Development and characterization of a gemcitabine-resistant variant of human lung adenocarcinoma cell line A549].

BACKGROUND & OBJECTIVE
Gemcitabine (2',2-difluorodeo- xycytide) has antitumor activity in both experimental and clinical treatment of solid tumors. Although resistance to gemcitabine in ovarian cancer cell line and erythroleukemic cell line was described, there was no report on the lung cancer resistant variant. In order to elucidate the mechanism by which gemcitabine induce resistance in lung cancer, we have established the resistance to gemcitabine in human lung adenocarcinoma cell line A549 and described the characteristics of its resistant variant.


METHODS
Resistance to gemcitabine was established by exposing A549 cells to increasing concentration of gemcitabine, which was designated as A549-Gem. The IC(50) and resistance index(RI) were tested by MTT assay and colony formation test. The growth curve and cell cycle of A549 and A549-Gem were compared. The cross-resistance profile of A549-Gem was also tested.


RESULTS
The IC(50) increased from 6.56+/-1.19 micromol/L in A549 to 921.09+/-225.27 micromol/L in A549-Gem as tested by MTT assay at 72h exposure, the RI was 140.52 (P=0.019 5). The RI of colony formation test was 132.95. Double time of A549 and A549-Gem were 29.7 h and 36.4 h, respectively, as evaluated by the growth curve. A549-Gem was cross-resistant to vincristine and etoposide(54.38-fold and 6.18-fold)(P< 0.01), but not to adriamycin, cisplatin, cytarabine, and paclitaxel.


CONCLUSION
A549-Gem, the gemcitabine resistant phenotype, is stable and suitable for the study of gemcitabine resistance in lung cancer. A549-Gem is cross-resistant to vincristine and etoposide, but not resistant to adriamycin, cisplatin, cytarabine and paclitaxel.