Abstract
Our previous studies have identified that silencing oncoprotein 18 (Op18)/stathmin via RNA interference (RNAi) inhibited autocrine interleukin‑10 (IL‑10) and enhanced the sensitivity to Taxol in NCI‑H1299 non‑small cell lung cancer cells. In this study, whether autocrine IL‑10 regulates Op18/stathmin signaling in NCI‑H1299 cells was examined by neutralizing IL‑10 using a targeted antibody. In vitro neutralization of IL‑10 by anti‑IL‑10 antibody impaired the capacities of the NCI‑H1299 cells to proliferate, form colonies and migrate. Furthermore, the expression levels of caspase‑3 and ‑8, and sensitivity to Taxol were increased. Neutralizing IL‑10 downregulated Op18/stathmin expression and its phosphorylation at Ser25 and Ser63 sites, and suppressed the activities of upstream kinases, extracellular signal‑regulated kinase (ERK) and cyclin‑dependent kinase 1 (CDK1). In addition, neutralizing IL‑10 also reduced the expression levels of the transcription factor nuclear factor‑κB (NF‑κB) and phosphorylation of its active subunit, p65 (Ser536). Furthermore, blocking NF‑κB signaling with PDTC also decreased the activities of ERK and CDC2 kinases, and decreases levels of autocrine released IL‑10 and its protein expression. Additionally, knocking down Op18/stathmin by RNAi reduced the expression levels of NF‑κB and IL‑10. Further animal experiments revealed that the number of neutrophils, lymphocytes and monocytes were all decreased in the blood of tumor‑bearing mice with NCI‑H1299 cell xenografts. Thus, the data suggested that autocrine IL‑10 regulates Op18/stathmin signaling via an IL‑10‑NF‑κB‑ERK/CDC2 axis, which regulates the malignant behaviors of NCI‑H1299 cells. A feedback regulation also exists between Op18/stathmin and autocrine IL‑10 signaling pathways in non‑small cell lung cancer cells.