[Differential invasion and metastasis capacities of methotrexate enantiomer-resistant A549 cell lines]

To study the differential in vitro motor and invasion capacities of methotrexate (MTX) enantiomer-resistant tumor cells.

The incremental concentrations and successive low-dose induction were employed to acquire the cell series resistant to 15 µmol/L MTX enantiomer, namely L-(+)-MTX/A549 and D-(-)-MTX/A549. Their drug-resistant indices were determined by MTT assay and their migration capacities by wound healing assay. Double soft-agar clone formation was used to detect the colony efficiency and size. And Transwell was employed to detect the in vitro movement and invasion capacity of three cell types.

The resistance indices of L-(+)-MTX/A549 and D-(-)-MTX/A549 were (6.1 ± 1.0) and (20.3 ± 1.8) respectively. At 72 hours after wound healing assay, the number of L-(+)-MTX/A549 entering scratch zone was fewer than that of D-(-)-MTX/A549; The numbers of colony formation in D-(-)-MTX/A549, L-(+)-MTX/A549 and parental cells were (50 ± 7), (44 ± 6), (52 ± 7) and the rates of colony formation (1.68% ± 0.23%), (1.49% ± 0.18%), (1.73% ± 0.23%) respectively. And there was no significant significance among three groups (P > 0.05). But the size of D-(-)-MTX/A549 was larger than that of L-(+)-MTX/A549. Transwell detected infiltration and invasion through artificial basement membrane Matrigel. The numbers of D-(-)-MTX/A549, L-(+)-MTX/A549 and parent cells were (267 ± 30), (106 ± 16) and (134 ± 16) respectively. The data were significant between D-(-)-MTX/A549 cells and L-(+)-MTX/A549 or parent cells (P < 0.05) but not significant between L-(+)-MTX/A549 and parent cells (P > 0.05).

The D-(-)-MTX-induced NSCLC A549 cells have greater motor and invasion capacities than those of L-(+)-MTX-induced ones. It suggests that MTX enantiomer has different capacities of tumor invasion and metastasis after acquiring resistance.