- Cytosolic phospholipase A 2 α (cPLA 2 α) up-regulation has been reported in human colorectal cancer cells, thus we aimed to elucidate its role in the proliferation of the human colorectal cancer cell line, HT-29. EGF caused a rapid activation of cPLA 2 α which coincided with a significant increase in cell proliferation. The inhibition of cPLA 2 α activity by pyrrophenone or by antisense oligonucleotide against cPLA 2 α (AS) or inhibition of prostaglandin E 2 (PGE 2 ) production by indomethacin resulted with inhibition of cell proliferation, that was restored by addition of PGE 2 . The secreted PGE 2 activated both protein kinase A (PKA) and PKB/Akt pathways via the EP2 and EP4 receptors. Either, the PKA inhibitor (H-89) or the PKB/Akt inhibitor (Ly294002) caused a partial inhibition of cell proliferation which was restored by PGE 2 . But, inhibited proliferation in the presence of both inhibitors could not be restored by addition of PGE 2 . AS or H-89, but not Ly294002, inhibited CREB activation, suggesting that CREB activation is mediated by PKA. AS or Ly294002, but not H-89, decreased PKB/Akt activation as well as the nuclear localization of β-catenin and cyclin D1 and increased the plasma membrane localization of β-catenin with E-cadherin, suggesting that these processes are regulated by the PKB pathway. Similarly, Caco-2 cells exhibited cPLA 2 α dependent proliferation via activation of both PKA and PKB/Akt pathways. In conclusion, our findings suggest that the regulation of HT-29 proliferation is mediated by cPLA 2 α-dependent PGE 2 production. PGE 2 via EP induces CREB phosphorylation by the PKA pathway and regulates β-catenin and cyclin D1 cellular localization by PKB/Akt pathway.