Analysis of the cytotoxic activity of carboplatin and gemcitabine combination

Abstract

Aim: To determine if the drug doses and administration schedules of carboplatin and gemcitabine combination affect antitumor effects.

Materials and methods: The inhibition of cell viability was measured by MTT assay. Median effect analysis was conducted to determine the cytotoxicity activity of carboplatin and gemcitabine combination. Cell cycle changes were analyzed by flow cytometry.

Results: Synergism was observed when the bladder cancer cell line 5637 cells were treated with gemcitabine followed by carboplatin or concurrent carboplatin/gemcitabine. In contrast, moderate antagonism was observed when cells were treated with carboplatin followed by gemcitabine. Cell cycle analysis showed that the combined effect of these two drugs was cell cycle disturbance.

Conclusion: Different doses and administration schedules affect the antitumor effect of carboplatin/gemcitabine combination that may have clinical significance in the treatment for bladder cancer.

Figure 1

The anti-tumor activity of carboplatin, gemcitabine or in combination. A and B: Dose-dependent cytotoxic effects of 5637 cells exposed to carboplatin (A) or gemcitabine (B). C. Dose-effect curves for the carboplatin/gemcitabine combinations. 5637 cells were treated with: gemcitabine for 4 h followed by carboplatin for 4 h (square); carboplatin for 0.5 h followed by carboplatin plus gemcitabine for 3.5 h (circle); carboplatin for 4 h followed by gemcitabine for 4 h (triangle). Data are means ± SD of three independent experiments (each with samples in triplicate). *p<0.05, ***p<0.001. D. CI Plot. CI values are plotted as a function of the fractional inhibition (Fa) from 0.10 to 0.97. The CI values of <0.9 (below the lower dash line), =0.9–1.1, and <1.1 (above the upper dash line) represent synergism, additivity and antagonism, respectively.

Figure 2

Characteristic DNA histograms of 5637 cells treated with carboplatin, gemcitabine or in combination. The progressive cell cycle changes were observed after 24, 48 and 72 h of treatment, as compared with the untreated controls. Content of DNA is represented on the X axis; number of cells counted is represented on the Y axis.