Interleukin-1β induces interleukin-6 regulated anti-apoptotic and immune suppressive pathways in non-small cell lung cancer cells

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Both interleukin-1β (IL-1β) and interleukin-6 (IL-6) levels are elevated in serum in lung cancer patients, and tumor-associated stromal and inflammatory cells have been demonstrated to secrete IL-1β. We found that IL-1β treatment induces IL-6 expression in non-small cell lung cancer (NSCLC) cells. Augmented IL-6 levels appear to contribute to tumor growth and survival through multiple pathways. We previously reported that cyclooxygenase-2 (COX-2) over-expression in NSCLC cell lines increases IL-6 expression 5 to 10-fold. Excessive IL-6 production resulted in phosphorylation of signal transducer and activator of transcription-3 (STAT-3) protein at Tyr706 and Ser727, which in turn elevated expression of the anti-apoptotic protein, survivin. In support of a role for IL-6 in tumor cell survival, exogenously added IL-6 protected NSCLC cells from staurosporine-induced apoptosis. IL-6 also increased expression of the angiogenic factor, VEGF through a pathway that does not require STAT-3 transcriptional activity. In addition, we found that IL-10 is induced in monocyte (U937) and T-cell (Jurkat) cell lines, but not in NSCLC cells after exposure to IL-6. In the presence of IL-10, monocytes and dendritic cells adopt a myelosuppressive phenotype, resulting in T-cell anergy and prevention of anti-tumor cell-mediated immune responses. Thus, IL-1β may promote an immune suppressive tumor microenvironment as well as pro-angiogenic and anti-apoptotic tumor phenotypes via IL-6. IL-1β also increases COX-2 expres sion in NSCLC cells and this has been linked to enhanced IL-6 production, however, neither pharmacological inhibitors of COX-2 nor an antisense COX-2 construct prevented IL-6 induction after IL-1β treatment. To determine the mechanism of IL-6 induction by IL-1β in NSCLC cells, we investigated the requirement for IL-1β intercellular effectors by treating A549 lung adenocarcinoma cells with small molecule inhibitors of JNK, MEK/ERK, and p38 MAPK. Pre-treatment with the p38 MAPK inhibitor, SB203580 caused a 2-fold decrease in IL-1β-induced IL-6 levels, and the JNK/SAPK inhibitor, SP600125 reduced IL-1β-mediated IL-6 induction by 25%. The MEK/ERK inhibitors, U0126 and PD98059 had no effect on IL-6 production. Therefore, IL-1β induces IL-6 through p38 MAPK, and to a lesser extent through JNK. These findings suggest that the capacity of IL-1β to induce IL-6 promotes the malignant phenotype in NSCLC. This may occur as a result of promotion of angiogenesis, apoptosis restistance, and degradation of cell-mediated immunity. Supported by: UCLA SPORE in lung cancer (P50 CA90388) and NIH Training Grant (T32HL072752)