Natural killer (NK) cell malignancies, particularly aggressive NK cell leukaemias and lymphomas, have poor prognoses. Although recent regimens with L-asparaginase substantially improved outcomes, novel therapeutic approaches are still needed to enhance clinical response. Resveratrol, a naturally occurring polyphenol, has been extensively studied for its anti-inflammatory, cardioprotective and anti-cancer activities. In this study, we investigated the potential anti-tumour activities of resveratrol against the NK cell lines KHYG-1, NKL, NK-92 and NK-YS. Resveratrol induced robust G0/G1 cell cycle arrest, significantly suppressed cell proliferation and induced apoptosis in a dose- and time-dependent manner for all four cell lines. In addition, resveratrol suppressed constitutively active STAT3 in all the cell lines and inhibited JAK2 phosphorylation but had no effect on other upstream mediators of STAT3 activation, such as PTEN, TYK2, and JAK1. Resveratrol also induced downregulation of the anti-apoptotic proteins MCL1 and survivin, two downstream effectors of the STAT3 pathway. Finally, resveratrol induced synergistic effect on the apoptotic and antiproliferative activities of L-asparaginase against KHYG-1, NKL and NK-92 cells. These results suggest that resveratrol may have therapeutic potential against NK cell malignancies. Furthermore, our finding that resveratrol is a bonafide JAK2 inhibitor extends its potential benefits to other diseases with dysregulated JAK2 signaling.

Preclinical studies have shown that resveratrol exerts immunomodulatory effects with potential clinical value in the amelioration of autoimmune disorders and cancer prevention; however, little is known about the in vivo effects of this naturally occurring polyphenol on human immune cells. We assessed the effects of repeated doses of resveratrol (1000 mg/day for 28 days) on circulating immune cells in healthy Japanese individuals. Resveratrol was safe and well tolerated and was associated with significant increases in the numbers of circulating γδ T cells and regulatory T cells and resulted in small, yet significant, decreases in the plasma levels of the proinflammatory cytokines TNF-α and MCP-1 and a significant increase in the plasma antioxidant activity compared with the corresponding antioxidant baseline activity and with that in four control individuals. In in vitro studies, resveratrol significantly improved the growth of γδ T cells and regulatory T cells. These findings demonstrate that resveratrol has some clear biological effects on human circulating immune cells. Further studies are necessary to interpret the long-term immunological changes associated with resveratrol treatment.

Human papillomavirus (HPV) is the most common sexually transmitted agent worldwide and is etiologically linked to several cancers, including cervical and genital cancers. NKG2D, an activating receptor expressed by NK cells, plays an important role in cancer immune-surveillance. We analyzed the impact of a NKG2D gene variant, rs1049174, on the incidence of HPV-related cancers in Vietnamese patients and utilized various molecular approaches to elucidate the mechanisms of NKG2D receptor regulation by rs1049174. In a group of 123 patients with HPV+ anogenital cancers, the low cytotoxicity allele LNK was significantly associated with increased cancer susceptibility (p = 0.016). Similar results were also observed in a group of 153 women with cervical cancer (p = 0.05). In functional studies, NK cells from individuals with LNK genotype showed a lower NKG2D expression and displayed less efficient NKG2D-mediated functions than NK cells with HNK genotype. Notably, the rs1049174 variant occurs within a targeting site for miR-1245, a negative regulator of NKG2D expression. Compared with the higher cytotoxicity allele HNK, the LNK allele was more efficiently targeted by miR-1245 and thus determined lower NKG2D expression in NK cells with the LNK genotype. The NKG2D variants may influence cancer immunosurveillance and thus determine susceptibility to various malignancies, including HPV-induced cancers.

BackgroundEpstein Barr virus-associated lymphoproliferative disease is an increasing complication in patients with immunosuppressive conditions. Although the current therapies for this disorder are effective, they are also associated with significant toxicity. In an attempt to identify newer therapeutic agents, this study investigated the effects of Resveratrol, a naturally occurring polyphenolic compound, on the EBV transformation of human B cells.Methodology/Principal FindingsThis study demonstrates that resveratrol prevents EBV transformation in human B cells. These effects are mediated by specific cytotoxic activities of resveratrol against EBV-infected B cells that are associated with the downregulation of the anti-apoptotic proteins Mcl-1 and survivin. This occurs as a consequence of the inhibition of EBV-induced NFκB and STAT-3 signaling pathways and a resveratrol-induced decrease in the expression of the oncogenic viral product LMP1 in EBV-infected B cells. In addition, resveratrol decreased the expression of miR-155 and miR-34a in EBV-infected B cells, blocked the expression of the anti-apoptotic viral gene BHRF1, and thus interrupted events that are critical for EBV transformation and the survival of EBV-transformed cells.Conclusions/SignificanceThese results suggest that resveratrol may therefore be a potentially effective therapeutic alternative for preventing EBV-associated lymphoproliferative diseases in immune compromised patients.

The powerful activating receptor NKG2D is expressed by natural killer (NK) cells and promotes cytotoxic lysis of cancer cells expressing NKG2D ligands (NKG2D-Ls). We report the effective induction of NKG2D-Ls, achieved with the naturally occurring polyphenol resveratrol, in a broad range of leukemia cells. In this study, resveratrol upregulated the NKG2D-Ls MHC class I chain-related proteins MICA and MICB, and UL16-binding proteins ULBP1, ULBP2, and ULBP3 in most of the leukemia cells analyzed. Ligand upregulation induced by resveratrol was impaired by pharmacological and genetic disruption of ataxiatelangiectasia mutated kinase, the main regulator of NKG2D-L expression. Leukemia cells treated with resveratrol were more susceptible to killing by NK cells than untreated cells, and the enhanced cytotoxicity of NK cells was blocked by treatment of NK cells with anti-NKG2D mAbs. Interestingly, resveratrol consistently upregulated the NKG2D receptor expression and enhanced NKG2D-mediated functions in resting NK cells obtained from healthy individuals. Therefore, resveratrol has attractive immunotherapeutic potential. (Cancer Sci 2013; 104: 657-662) T he potent activating receptor NKG2D is expressed on effector cells of both the innate and adaptive immune system such as natural killer (NK) cells, NK T cells, cd T cells, and some subsets of CD8 + T cells. The NKG2D receptor plays pivotal roles in immunosurveillance of viral infections and cancer.(1) NKG2D recognizes diverse and structurally different ligands, including the MHC class I chain-related proteins (MICA and MICB), the UL16-binding proteins (ULBP1 to 5) and retinoic acid early transcript.(2) The NKG2D ligand (NKG2D-L) transcripts are detectable in numerous normal healthy tissues; however, they are either absent or poorly expressed at the protein level.(3) In response to a variety of cell stress stimuli, such as viral infections and tumorigenesis, NKG2D-Ls are upregulated on the cell surface rendering ligands expressing cells more sensitive to destruction by NK cells through the NKG2D receptor.(1,2) Stress signals, particularly those associated with double-strand breaks in DNA, upregulate the NKG2D ligand expression through the activation of ataxia-telangiectasia mutated (ATM) signals.(4) Therefore, ATM has been postulated to be the most important regulator of NKG2D-L expression. (4) Resveratrol is a polyphenol found in grapes and other sources that possesses numerous health benefits, including anti-inflammatory, anti-aging, and antitumor activities.(5) Resveratrol is a multitarget agent capable of modulating several proteins, including those in the nuclear factor-jB, JAK2 ⁄ signal transducer and activator of transcription-3 (STAT3), and protein kinase B pathways.(5-8) Interestingly, resveratrol induces non-mutagenic DNA damage and direct activation of ATM in tumor cells (9,10) ; however, it is unknown whether ATM activation induced by resveratrol is associated with the induction of NKG2D-Ls in malignant cells.This study showed that resveratrol not only acti...