Correlation plot of the effect of EGF receptor inhibition. MEFs were treated with a mixture of two EGF receptor inhibitors (AG1478 and PD168393, 250 nM each) or DMSO (control) prior to stimulation with LPA (5 μM) for 4 hrs. Microarray hybridization was performed using the corresponding time-zero control with the same pretreatment. The 2log expression level of 528 LPA-regulated genes after 4 hrs is shown as a dot plot to correlate the effect of drug treatment on the expression level of individual genes. The expression level of 528 LPA-regulated genes in control cells was set at 100%. The overall reduction of LPA-induced expression by the inhibitors was approx. 35%, as inferred from the correlation coefficient.