Phosphorylation status of p70 S6 kinase in response to SDF-1. Immunoblot analysis of p70 S6 kinase phosphorylation of Ba/F3 and Ba/F3.p210 in response to SDF-1. SDF-1 induces serine 421/threonine 424 phosphorylation of p70 S6 kinase in normal Ba/F3 cells, but not in BCR/ABL-transformed cell lines. The same blot was stripped and probed with anti-S6 kinase showing that the amount of p70 S6 kinase is equivalent in all lanes.