Fig. 2

The combination of DCA and PX-478 shows significantly lower effects on the non-cancerous cell line HEK-293 than on the six PX-478-sensitive cancer cell lines (A549, HeLa, HEPG2, MCF-7, U251 and H441). HEK-293 cells were seeded in 96-well plates and treated with 15 mM DCA and 15 μM PX-478 or the combination at a confluence of approximately 50%. Forty-eight hours later, an SRB assay was performed. The combination had no significant effect (97% protein mass) compared to the control (p = 0.3). The effect of the combination of 15 mM DCA and 15 μM PX-478 on HEK-293 cells was compared to the effect of similar or lower concentrations of the combination on the tested cancer cell lines (A549: 15 mM and 16.5 μM, HeLa: 15.5 mM and 10 μM, HEPG2: 10.5 mM and 8 μM, MCF-7: 10 mM and 4 μM, U251: 10 mM and 18.5 μM and H-441: 9 mM and 12.5 μM respectively). Data points used to generate the dose-response curves in Fig. 1 were used for comparison. The bars are marked with an asterisk when the effect on a cancer cell line was significantly stronger than that on HEK-293 cells. All six PX-478-sensitive cancer cell lines were significantly more sensitive than HEK-293 cells to the combination of DCA and PX-478. HT-29 and MDA-MB-231 cells were not compared, since due to the described resistance, no doses of PX-478 close to 15 μM were used. This figure is not applicable for comparing effects between the different cancer cell lines, since different concentrations of the compounds were used. For comparisons of synergism, please see Fig. 1 and Table 2