Features of hpdODN B consist in a stretch of pyrimidines spanning nucleotides 1005 to 1012, a d step and a d step. To analyze meantime the possible effect of only one change in the sequence of hpdODN A, hpdODN C was designed by replacing dG with dC in position 1011. The kill ing efficiency of HpdODN C was lower than those of hpdODN A and hpdODN B, but in contrast with the latter, it showed a capacity to compete with IFNg induced mortality, suggesting that it interacts with STAT1. Ne t, by placing dG in 1003, dC in 1004, dC in 1011 and dG in 1017 we obtained hpdODN D, which corresponded with a sequence with a marked preference for STAT1 as previously shown by others using a reporter assay. hpdODN D did not induce SW480 cell mortality, but prevented IFNg induced killing.

Finally, hpdODN E, containing a mutated STAT3 binding site did not induce cell death and did not compete with IFNg induced cell death. A comparison of the different hpdODNs IFNg independent cell killing efficiency showed that hpdODN B was twice as efficient as hpdODN A and that the control mutated hpdODN E had no effect on cell death, as previously pub lished. The new STAT3 specific hpdODN B inhibits STAT3 but not STAT1 phosphorylation and inhibits cyclin D1 but not IRF1 e pression To detect the effect of the hpdODNs on STAT3 phos phorylation, IL 6 treated SW480 cells were used. In cells treated with hpdODN B and hpdODN A for 16 h, STAT3 phosphorylation was suppressed, the e pression of cyclin D1 and of STAT3 itself were con siderably diminished, in agreement with previous observations.

When cells were treated for 4 h with hpdODNs A and B, phos pho STAT3 was reduced without effect on STAT3, the control mutated hpdODN E had no effect. To confirm that hpdODN B was preferentially inhibiting STAT3 in SW480 cells, the induction of the STAT1 dependent IFNg target IRF1 was studied. In cells treated with IFNg, both phosphorylation of STAT1 and e pression of IRF1 increased. Treatment with hpdODN A, but not hpdODN B, strongly reduced IRF1 e pression. In IFNg treated cells, the addition of hpdODN A reduced IFNg induced IRF1 e pression whereas the addition of hpdODN B did not. Interestingly, STAT1 phosphorylation on tyrosine was inhibited following treatment with hpdODN A but not with hpdODN B. These data indicate that under these e perimental conditions hpdODN B does not inhi bit STAT1.

Biotinylated hpdODN B interacts preferentially with STAT3 Binding of STAT3 and STAT1 to hpdODNs has pre Carfilzomib viously been analyzed directly within cells using biotinylated versions of the different hpdODNs. To compare hpdODNs A and B, cells were treated, or not, with IFNg, transfected with biotinylated hpdODNs, and pull downs were performed. The pull down efficiencies of hpdODN A and B for STAT1 and STAT3 were very different. Indeed, compared with hpdODN A, hpdODN B brought down STAT3 very efficiently, but not STAT1, even in IFNg treated cells.