TZD18 effect on cell proliferation is independent of PPARγ and PPARα. Cells (2 × 10⁵/mL) were incubated with antagonists for either PPARγ (GW9662, 2 μM) or PPARα (MK886, 2 μM) in the absence or presence of TZD18 (20 μM) for 4 days. Cell proliferation was measured by the MTT assay, as described in “Materials and methods.” Results are expressed as a percentage of control (without treatment). Values are mean ± SD of at least 3 experiments.