a, rate of proliferation of PC3 prostate cancer cells is greatly reduced by treatment with oligomers containing CpG motifs, as assessed by (a) soft agar colony formation assay and (b and c) trypan blue exclusion. a, rate of proliferation of PC3 prostate cancer cells is greatly reduced by treatment with oligomers containing CpG motifs, as assessed by (a) soft agar colony formation assay and (b and c) trypan blue exclusion. G3139 and 2006 caused a dramatic inhibition in cloning efficiency and cellular proliferation after 6 days (a and b). b, G4126 and G4232 only slightly affected the proliferation rate, whereas the effect of 2009, a two-base longer oligomer, is intermediate. c, 84825 (C5 methylation outside the CpGs) inhibited cell proliferation to the same extent as G3139. However, oligonucleotides with only a single C5-methylated CpG (84822 and 84823) considerably lessen the inhibitory effect on cell proliferation. Lines, average; bars, SD (n = 3). *, P < 0.05, by Student's t test assuming unequal variances. (Control not included in analysis: All comparisons made to G4126 to eliminate nonspecific oligonucleotide treatment.) Jonathan C. Lai et al. Mol Cancer Ther 2003;2:1031-1043 ©2003 by American Association for Cancer Research