IkappaB kinase beta (IKKbeta), required for NF-kappaB activation, links chronic inflammation with carcinogenesis. We investigated whether IKKbeta is involved in chemically induced liver cancer, a model not involving overt inflammation. Surprisingly, mice lacking IKKbeta only in hepatocytes (Ikkbeta(Deltahep) mice) exhibited a marked increase in hepatocarcinogenesis caused by diethylnitrosamine (DEN). This correlated with enhanced reactive oxygen species (ROS) production, increased JNK activation, and hepatocyte death, giving rise to augmented compensatory proliferation of surviving hepatocytes. Brief oral administration of an antioxidant around the time of DEN exposure blocked prolonged JNK activation and compensatory proliferation and prevented excessive DEN-induced carcinogenesis in Ikkbeta(Deltahep) mice. Decreased hepatocarcinogenesis was also found in mice lacking IKKbeta in both hepatocytes and hematopoietic-derived Kupffer cells. These mice exhibited reduced hepatocyte regeneration and diminished induction of hepatomitogens, which were unaltered in Ikkbeta(Deltahep) mice. IKKbeta, therefore, orchestrates inflammatory crosstalk between hepatocytes and hematopoietic-derived cells that promotes chemical hepatocarcinogenesis.

Metastatic progression depends on genetic alterations intrinsic to cancer cells as well as the inflammatory microenvironment of advanced tumors 1,2 . To understand how cancer cells affect the inflammatory microenvironment, we conducted a biochemical screen for macrophage activating factors secreted by metastatic carcinomas. Amongst the cell lines screened, Lewis lung carcinoma (LLC) 3 were the most potent macrophage activators leading to production of IL-6 and TNF-α through activation of the Toll-like receptor family members 4 TLR2 and TLR6. Both TNF-α and TLR2 were found to be required for LLC metastasis. Biochemical purification of LLC conditional medium (LCM) led to identification of the extracellular matrix proteoglycan versican, which is upregulated in many human tumors including lung cancer 5,6 , as a macrophage activator that acts via TLR2 and its co-receptors TLR6 and CD14. By activating TLR2:TLR6 complexes and inducing TNF-α secretion by myeloid cells, versican strongly enhances LLC metastatic growth. These results explain how advanced cancer cells usurp components of the host innate immune system, including bone marrow-derived myeloid progenitors 7 , to generate an inflammatory microenvironment hospitable for metastatic growth.Distant site metastases are the leading cause of cancer-associated mortality and depend on genetic and/or epigenetic alterations that are intrinsic to cancer cells or extrinsic factors provided by the tumor microenvironment 1 . For instance, cytokines produced by inflammatory cells can enhance metastatogenesis by repressing the metastasis suppressor maspin within primary prostate carcinoma cells 8 . Furthermore, tumor progression and metastasis positively correlate with presence of infiltrates containing myeloid and lymphoid cells 2,9 . It was shown that certain carcinomas secrete factors that upregulate fibronectin and recruit vascular endothelial growth factor receptor 1 (VEGFR1)-positive hematopoetic progenitors to sites of Correspondence and requests for materials should be addressed to M.K. future metastatic growth, termed the pre-metastatic niche 7 . To examine whether cancer cells secrete factors that directly activate myeloid cells to produce tumor promoting cytokines 10 , we collected serum free conditioned medium (CM) from different cancer cell lines, derived mainly from C57BL6 mice, and applied it to bone marrow (BM)-derived macrophages (BMDM), which were assayed for production of IL-1β, IL-6 and TNF-α. The screen included 1C1C7 and TrampC1, which are liver and prostate cancer cell lines, respectively, with little or no metastatic activity, and two metastatic breast and lung carcinomas, 4T1 and LLC, respectively. CM from metastatic cells, especially LLC, induced higher amounts of IL-6 and TNF-α secretion than CM from non-metastatic cells (Fig. 1A). IL-1β secretion was undetectable and the CM did not contain IL-6 or TNF-α (data not shown). LLC-CM (LCM) also induced expression of Il1β, Il6 and Tnfα mRNAs, whereas serum free medium (SFM) and NIH3T3 CM were inacti...

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Prostate cancer (CaP) progresses from prostatic intraepithelial neoplasia through locally invasive adenocarcinoma to castration resistant (CR) metastatic carcinoma 1 . Although radical prostatectomy, radiation and androgen ablation are effective therapies for androgen-dependent (AD) CaP, metastatic CR-CaP is a major complication with high mortality 2 . Androgens stimulate growth and survival of prostate epithelium and early CaP. Although most patients initially respond to androgen ablation, many develop CR-CaP within 12-18 months 2 . Despite extensive studies, the mechanisms underlying CR-CaP emergence remain poorly understood and their elucidation is critical for development of improved therapies. Curiously, CR-CaP remains androgen receptor (AR) dependent and potent AR antagonists induce tumor regression in castrated mice 3 . The role of inflammation in CR-CaP has not been addressed, although it was reported that intrinsic NF-κB activation supports its growth 4 . Inflammation is a localized protective reaction to injury or infection, but it also has a pathogenic role in many diseases, including cancer 5 . Whereas acute inflammation is critical for host defense, chronic inflammation contributes to tumorigenesis and metastatic progression. The inflammation-responsive IκB kinase (IKK) β and its target NF-κB have important tumor promoting functions within malignant cells and inflammatory cells 6 . The latter, including macrophages and lymphocytes, are important elements of the tumor microenvironment 7-9 , but the mechanisms underlying their recruitment remain obscure, although thought to depend on chemokine and cytokine production 10 . We found that CaP progression is associated with inflammatory infiltration and activation of IKKα, which stimulates metastasis by an NF-κB-independent, cell autonomous, mechanism 11 . We now show that androgen ablation causes infiltration of regressing AD tumors with leukocytes, including B cells, in which IKKβ activation results in production of cytokines that activate IKKα and STAT3 in CaP cells to enhance hormone-free survival.To determine whether IKKβ-driven NF-κB participates in development of CR-CaP, we conditionally deleted the Ikkβ gene in prostate epithelial cells of TRAMP mice, in which CaP is induced by prostate specific expression of SV40 T antigen 12 . Counter to previous expectations 4 , IKKβ ablation in prostate epithelial cells had no effect on genesis and progression of AD-CaP (Fig. S1) or development of CR-CaP after castration (Fig. S2). To facilitate mechanistic analysis of CR-CaP development we used subcutaneous (SC) allografts of the mouse AD-CaP cell line myc-CaP, which is derived from the FVB genetic