Gene expression profiling upon PI3K inhibition using different inhibitors

Activation of the phosphoinositide 3-kinase (PI3K)/Akt signaling pathway is one the most frequent genetic events in human cancer. Therefore, the development of PI3K inhibitors has attracted much attention. We previously described the pyrazolopyrimidine derivative ETP-45658 as a potent inhibitor of PI3K p110α in vitro and in vivo. Here we report the gene expression signatures of MCF7 cells treated with ETP-45658 or the reference PI3K inhibitor PI-103. Both compounds potently inhibited proliferation of a wide range of human cancer cells. ETP-45658 most potently suppressed the growth of PIK3CA (E545K)-mutated MCF7 breast cancer cells. Treatment with ETP-45658 or PI-103 resulted in a time and concentration-dependent decrease in phosphorylation of AKT Ser473 in MCF7 cells. We conducted microarray analysis examining the gene expression profile in MCF7 cells at six hours post ETP-45658 or PI-103 incubation. Both compounds induced the expression of negative cell cycle regulators including Cyclin G2, p27kip1 and ING4 and decreased positive regulators such as Cyclin D1 without significantly affecting the expression of pro-apoptotic genes. We found FOXO transcription factor binding sites over-represented in both up- and down-regulated genes but not in those without significant changes. The expression of the breast cancer tumor suppressor Nischarin was found to be induced by ETP-45658 but not after PI-103 treatment while several genes differentially expressed specifically after ETP-45658 treatment are functionally associated with the focal adhesion pathway. Twelve samples have been analyzed in six different conditions. Two replicates have been included for each condition.