HO-1 is a poor prognostic NSCLC predictor and its over-expression may increase the metastatic potential of NSCLC. Based on our findings and those of others, HO-1 may be considered as a novel NSCLC therapeutic target.

Communication between cancer cells and their microenvironment plays an important role in cancer development, but the precise mechanisms by which cancer-associated fibroblasts (CAF) impact anti-cancer immunity and cancer progression in lung cancer are poorly understood. Here, we report that lung fibroblasts when activated by lung cancer cells produce tryptophan metabolite kynurenine (Kyn) that inhibits dendritic cells' differentiation and induces cancer growth as well as migration. We identified TDO2 (tryptophan 2,3-dioxygenase) as the main enzyme expressed in fibroblasts capable of tryptophan metabolism. Mechanistically, condition medium of CAF or exogenous kynurenine stimulated AKT, with no lysine 1 (WNK1) and cAMP response element-bindingprotein (CREB) phosphorylation in lung cancer cells. Inhibition of the AKT/CREB pathway prevents cancer proliferation, while inhibition of the AKT/ WNK1 reverted epithelial-to-mesenchymal transition and cancer migration induced by kynurenine. Moreover, we also demonstrate that lung cancer-derived galectin-1 contributes to the upregulation of TDO2 in CAF through an AKT-dependent pathway. Immunohistochemical analysis of lung cancer surgical specimens revealed increased TDO2 expression in the fibroblasts adjacent to the cancer. Furthermore, in vivo studies showed that administration of TDO2 inhibitor significantly improves DCs function and T cell response, and decreases tumor metastasis in mice. Taken together, our data identify the feedback loop, consisting of cancer-derived galectin-1 and CAF-producing kynurenine, that sustains lung cancer progression. These findings suggest that targeting this pathway may be a promising therapeutic strategy.

High-mobility group box 1 (HMGB1) is a versatile protein with intranuclear and extracellular functions. It is involved in invasion and metastasis in various human malignancies. However, the role of HMGB1 in non-small cell lung cancer (NSCLC) is unclear. We hypothesized that HMGB1 expression is a determinant of cellular invasiveness and metastasis in lung cancer. We examined HMGB1 expression in 48 NSCLC specimens by quantitative real-time PCR. High HMGB1 expression was significantly associated with clinically advanced stages (stage III-IV) (P < 0.05) and was correlated to expression of matrix metalloproteinase-9 (MMP-9) (P < 0.05). Patients with high levels of HMGB1 expression had poorer clinical prognosis. The expression level of MMP-9 and metastatic ability in vitro were significantly higher in an HMGB1-overexpressing human NSCLC cell lines (A549 and H23). The treatment with HMGB1 small interfering RNA reduced MMP-9 expression and the cellular metastatic ability in NSCLC cells. We also demonstrated that phosphoinositide 3-kinase/Akt and NF-κB-related pathways contributed to the HMGB1-induced MMP-9 expression and cellular metastatic ability.