Synergistic interaction of gemcitabine and paclitaxel by modulating acetylation and polymerization of tubulin in non-small cell lung cancer cell lines

Background: The combination of gemcitabine (GEM) and paclitaxel (PTX) was appealing for clinical exploration due to different mechanisms of action and partially non-overlapping toxicities. Purpose: The aim of this study was to elucidate a potential effect of this combination on the proliferation of two non-small cell lung cancer (NSCLC) cell lines, A549 and H520. Materials and methods: Cell lines were treated with GEM and PTX for 48 hours to evaluate the half maximal inhibitory concentration (IC50). To determine the combination index (CI), cell lines were exposed to GEM and PTX, in a constant ratio of IC50, by various combination treatments. GEM`s effect on tubulin was assessed by western blotting and immunofluorescent staining. GEM was combined with nanoparticle albumin-bound-paclitaxel (NP) in evaluating tumor growth inhibition. Results: The IC50 of GEM and PTX in A549 and H520 were 6.6 nM and 46.1 nM, and 1.35 nM and 7.59 nM, respectively. Among the sequences explored (GEM→PTX, PTX→GEM, and GEM plus PTX simultaneously [GEM+PTX]), GEM→PTX produced a mean CI <1 in both cell lines. Western blotting and immunofluorescent staining revealed the intention expressions of acetylated tubulin protein and enhancement of tubulin polymerization within GEM→PTX group. A combination order GEM→NP also worked synergistically to suppress tumor growth. Conclusion: The GEM→PTX sequence may represent a promising candidate regimen for the treatment of NSLCL.