ACAGT‐007a, an anti‐cancer compound that modulates ERK MAPK signaling, induces nuclear enrichment of phosphorylated ERK in T3M4 pancreatic cancer cells

Abstract

AbstractThe extracellular‐signal‐regulated‐kinase (ERK) signaling pathway is essential for cell proliferation and is frequently deregulated in human tumors such as pancreatic cancers. ACAGT‐007a (GT‐7), an anti‐cancer compound, stimulates ERK phosphorylation, thereby inducing growth inhibition and apoptosis in T3M4 pancreatic cancer cells. However, how GT‐7 stimulates ERK phosphorylation and induces apoptosis in ERK‐active T3M4 cells remains unclear. To look into the mechanism, we performed a spatiotemporal analysis of ERK phosphorylation mediated by GT‐7 in T3M4 cells. The immunoblotting showed that GT‐7 stimulates ERK phosphorylation within 1 h, which was more remarkable after 2 h. Importantly, apoptosis induction as evaluated by the cleaved Caspase‐3 was observed only after 2‐h incubation with GT‐7. The immunofluorescence staining revealed the enrichment of phosphorylated ERK (phospho‐ERK) in the nucleus upon 1‐h incubation with GT‐7. Fractionation experiments showed that GT‐7 increases phospho‐ERK levels in the cytoplasm within 1 h, whereas nuclear phospho‐ERK accumulation is observed after 2‐h incubation with GT‐7. MEK inhibition by U0126 significantly diminishes nuclear phospho‐ERK distribution and apoptosis induction stimulated by GT‐7. Thus, GT‐7 may initiate the induction of ERK phosphorylation in the cytoplasm, which leads to phospho‐ERK enrichment in the nucleus. This nuclear phospho‐ERK accumulation by GT‐7 precedes and may underlie apoptosis induction in T3M4.