Lyn PTK is required for proliferation of CD45⁺ U266 cells enhanced by IL-6.

(A) BrdU incorporation was used to determine the DNA synthesis of CD45⁺ U266 cells treated with Lyn-specific sense (S, left 2 bars) or antisense (AS, right 2 bars) oligodeoxynucleotides (10 μM) in the presence (the second and fourth bars) or absence (the first and third bars) of IL-6. The results obtained from the experiments using 2 different oligodeoxynucleotides 1 and 2 are indicated on the left and right, respectively. (B) The PTK inhibitors PP2 (300 ng/mL, middle) and herbimycin A (1 μg/mL, right) reduce the BrdU incorporation of CD45⁺ U266 cells by IL-6 (right bars; left bars are without IL-6). Control DMSO is shown on the left. (C) Western blot analysis shows the effect of antisense (AS) or sense (S) oligodeoxynucleotides specific for Lyn on the expression of Lyn, STAT3, and MEK1/2 in CD45⁺ U266 cells. Western blot analysis is also used to examine the phosphorylation of STAT3 (Tyr705) and MEK1/2 (Ser217/221) in CD45⁺ U266 cells treated with either Lyn-specific antisense or sense oligodeoxynucleotides in the presence of IL-6. (D) Western blot analysis shows the phosphorylation and expression of STAT3 and MEK1/2 in CD45⁺ U266 cells treated with PP2 or herbimycin A prior to IL-6 stimulation. Values of BrdU incorporation are indicated by the means and SDs resulting from 3 independent experiments using triplicate samples (A,B).