Figure 1

APE1 overexpression in melphalan-resistant MM cell lines RPMI-8226/LR5 and U266/LR6. (A) CCK-8 assay indicated that RPMI-8226/LR5 and U266/LR6 show more resistance to melphalan than their parental cell lines RPMI-8226 and U266. All cell lines were treated with three different doses of melphalan for 48 hours then cell viability was assayed using the CCK-8 assay. Results are shown as mean ± SD and were from three separate experiments. The significance was analyzed by Student t test. Stars (*) represent that the differences between RPMI-8226/LR5 and RPMI-8226 or between U266/LR6 and U266 are statistically significant (p < 0.01). Differential APE1 expression at the mRNA (B) and protein (C) level was assayed using quantitative RT-PCR and Western blots, respectively. The bar graph showing the quantitative results of APE1 mRNA levels was from three independent experiments. Representative blot images are shown and β-actin was used as a loading control.