The interaction between
cancer cells and their microenvironment is a paradoxical cycle that exacerbates
cancer progression and results in
metastasis. Our study investigated the mechanism underlying the synergistic enhancement of release of soluble factors from
tumor-associated dendritic cells and its effect on
cancer development. The combination of
HB-EGF (
heparin-binding EGF-like growth factor) and CXCL5 (CXCL5/epithelial neutrophil-activating
peptide-78) produced a strong synergistic effect on
cancer proliferation, epithelial-mesenchymal transition, migration and invasion. CXCL5 not only potentiated the classical EGFR pathway and the AKT and ERK/RSK1/2 signaling pathways but also increased the phosphorylation of
heat shock protein 27 (HSP27), which was slightly increased in A549 cells treated with either
HB-EGF or CXCL5 only. Phosphorylated HSP27 stabilized sustained AKT activity by direct interaction, leading to enhanced
tumor spheroid formation. Knockdown of HSP27 by
shRNA decreased
HB-EGF plus CXCL5-mediated
tumor spheroid formation in a three-dimensional culture system, suggesting that AKT/HSP27 was required for
HB-EGF/CXCL5-mediated
cancer progression. Inhibiting RSK also reduces the modulation of c-Fos phosphorylation, Snail upregulation and cell migration by
HB-EGF plus CXCL5, suggesting a synergistic effect of ERK/RSK and
HB-EGF plus CXCL5 on cell migration. In mice, CXCL5 antibody synergistically enhances the efficiency of the
tyrosine kinase inhibitor,
gefitinib, without increasing its toxicity. These results provide evidence that elucidates potential cross-points between extracellular signals affecting
lung cancer progression. Targeting CXCL5 may provide therapeutic benefits for
lung cancer chemotherapy or
immunotherapy.