CREB1 and melanoma: Incubation of melanoma cells (A375 and WM‐266‐4) with CM from replicative senescent fibroblasts but not with CM from non‐senescent fibroblasts resulted in a significant induction of phosphorylation of the cAMP‐responsive element binding protein (CREB), a member of the basic leucine zipper (bZIP) family of transcription factors (Shaywitz and Greenberg 1999; Vinson et al. 1989) at serine 133 (Figure 4A, Figure S12A).