Natural killer (NK) cells play a key role in tumor immune surveillance. However, adoptive immunotherapy protocols using NK cells have shown limited clinical efficacy to date, possibly due to tumor escape mechanisms that inhibit NK cell function. In this study, we analyzed the effect of coculturing melanoma cells and NK cells on their phenotype and function. We found that melanoma cells inhibited the expression of major NK receptors that trigger their immune function, including NKp30, NKp44, and NKG2D, with consequent impairment of NK cell–mediated cytolytic activity against various melanoma cell lines. This inhibitory effect was primarily mediated by indoleamine 2,3-dioxygenase (IDO) and prostaglandin E2 (PGE2). Together, our findings suggest that immunosuppressive barriers erected by tumors greatly hamper the antitumor activity of human NK cells, thereby favoring tumor outgrowth and progression. Cancer Res; 72(6); 1407–15. ©2012 AACR.

Neutrophils play an essential role in host defense and inflammation, but the latter may trigger and sustain the pathogenesis of a range of acute and chronic diseases. Green tea has been claimed to exert anti-inflammatory properties through unknown molecular mechanisms. We have previously shown that the most abundant catechin of green tea, (−)epigallocatechin-3-gallate (EGCG), strongly inhibits neutrophil elastase. Here we show that 1) micromolar EGCG represses reactive oxygen species activity and inhibits apoptosis of activated neutrophils, and 2) dramatically inhibits chemokine-induced neutrophil chemotaxis in vitro; 3) both oral EGCG and green tea extract block neutrophil-mediated angiogenesis in vivo in an inflammatory angiogenesis model, and 4) oral administration of green tea extract enhances resolution in a pulmonary inflammation model, significantly reducing consequent fibrosis. These results provide molecular and cellular insights into the claimed beneficial properties of green tea and indicate that EGCG is a potent anti-inflammatory compound with therapeutic potential.

Tertiary lymphoid structures (TLSs) are a common finding in non-small cell lung cancer (NSCLC) and are predictors of favourable clinical outcome. Here we show that NCR⁺ innate lymphoid cell (ILC)-3 are present in the lymphoid infiltrate of human NSCLC and are mainly localized at the edge of tumour-associated TLSs. This intra-tumoral lymphocyte subset is endowed with lymphoid tissue-inducing properties and, on activation, produces IL-22, TNF-α, IL-8 and IL-2, and activates endothelial cells. Tumour NCR⁺ILC3 may interact with both lung tumour cells and tumour-associated fibroblasts, resulting in the release of cytokines primarily on engagement of the NKp44-activating receptor. In patients, NCR⁺ILC3 are present in significantly higher amounts in stage I/II NSCLC than in more advanced tumour stages and their presence correlate with the density of intratumoral TLSs. Our results indicate that NCR⁺ILC3 accumulate in human NSCLC tissue and might contribute to the formation of protective tumour-associated TLSs.

BACKGROUND Given the association of consumption of green tea with prevention of cancer development, metastasis, and angiogenesis, the effect of the main flavanol present, epigallocatechin‐3‐gallate (EGCG), on two gelatinases most frequently overexpressed in cancer and angiogenesis (MMP‐2 and MMP‐9) and on tumor cell invasion and chemotaxis were examined. METHODS Zymography, Western blotting, and enzyme linked immuoadsorbent assay were used to analyze the effect of EGCG on MMP‐2 and MMP‐9 activity, whereas its effect on tumor cell invasion and chemotaxis was examined using modified Boyden chamber assays. RESULTS A Zn²⁺ chelation‐independent, dose‐dependent, noncompetitive inhibition by EGCG of both gelatinases was found at concentrations 500 times lower than that reported to inhibit urokinase. Tumor cell invasion of a reconstituted basement membrane matrix, but not chemotaxis, was reduced by 50% with EGCG concentrations equivalent to that in the plasma of moderate green tea drinkers, and 2 orders of magnitude below those of tissue inhibitors of MMPs. Although higher concentrations of EGCG were associated with increased levels of both cell‐associated gelatinases and their activator MT1‐MMP, no increased gelatinase activation was found, and TIMP‐1 and TIMP‐2 inhibitors were up‐regulated. Finally, concentrations of EGCG active in restraining proliferation and inducing apoptosis of transformed cells were more than 100 times lower than those reported for normal cells. CONCLUSIONS Epigallocatechin‐3‐gallate is a potent inhibitor of gelatinases and an orally available pharmacologic agent that may confer the antiangiogenic and antimetastatic activity associated with green tea. Cancer 2001;91:822–32. © 2001 American Cancer Society.

The HIV-1 Tat protein is a potent chemoattractant for monocytes. We observed that Tat shows conserved amino acids corresponding to critical sequences of the chemokines, a family of molecules known for their potent ability to attract monocytes. Synthetic Tat and a peptide (CysL_24–51) encompassing the “chemokine-like” region of Tat induced a rapid and transient Ca²⁺influx in monocytes and macrophages, analogous to β-chemokines. Both monocyte migration and Ca²⁺mobilization were pertussis toxin sensitive and cholera toxin insensitive. Cross-desensitization studies indicated that Tat shares receptors with MCP-1, MCP-3, and eotaxin. Tat was able to displace binding of β-chemokines from the β-chemokine receptors CCR2 and CCR3, but not CCR1, CCR4, and CCR5. Direct receptor binding experiments with the CysL_24–51peptide confirmed binding to cells transfected with CCR2 and CCR3. HIV-1 Tat appears to mimic β-chemokine features, which may serve to locally recruit chemokine receptor-expressing monocytes/macrophages toward HIV producing cells and facilitate activation and infection.