PTGS2 and infection: Second, we demonstrated that shCOX-2-expressing vectors (pSH1, pSCOX−2 and pSTBE) can be efficiently delivered into HT-29 and HCA-7 CRC cell lines after infection with InvColi strains (MOI 1:1000), thus promoting a strong COX-2 downregulation (both at mRNA and protein levels) mediated by RNAi and a prolonged reduction in PGE2 levels.