BACKGROUND Sentinel-lymph-node biopsy is associated with increased melanoma-specific survival (i.e., survival until death from melanoma) among patients with node-positive intermediate-thickness melanomas (1.2 to 3.5 mm). The value of completion lymph-node dissection for patients with sentinel-node metastases is not clear. METHODS In an international trial, we randomly assigned patients with sentinel-node metastases detected by means of standard pathological assessment or a multimarker molecular assay to immediate completion lymph-node dissection (dissection group) or nodal observation with ultrasonography (observation group). The primary end point was melanoma-specific survival. Secondary end points included disease-free survival and the cumulative rate of nonsentinel-node metastasis. RESULTS Immediate completion lymph-node dissection was not associated with increased melanoma-specific survival among 1934 patients with data that could be evaluated in an intention-to-treat analysis or among 1755 patients in the per-protocol analysis. In the per-protocol analysis, the mean (±SE) 3-year rate of melanoma-specific survival was similar in the dissection group and the observation group (86±1.3% and 86±1.2%, respectively; P=0.42 by the log-rank test) at a median follow-up of 43 months. The rate of disease-free survival was slightly higher in the dissection group than in the observation group (68±1.7% and 63±1.7%, respectively; P=0.05 by the log-rank test) at 3 years, based on an increased rate of disease control in the regional nodes at 3 years (92±1.0% vs. 77±1.5%; P<0.001 by the log-rank test); these results must be interpreted with caution. Nonsentinel-node metastases, identified in 11.5% of the patients in the dissection group, were a strong, independent prognostic factor for recurrence (hazard ratio, 1.78; P=0.005). Lymphedema was observed in 24.1% of the patients in the dissection group and in 6.3% of those in the observation group. CONCLUSIONS Immediate completion lymph-node dissection increased the rate of regional disease control and provided prognostic information but did not increase melanoma-specific survival among patients with melanoma and sentinel-node metastases. (Funded by the National Cancer Institute and others; MSLT-II ClinicalTrials.gov number, NCT00297895.)

IntroductionRegulatory T (Treg) cells play a central role in controlling immune tolerance and homeostasis of the immune system, preventing autoimmune diseases, and limiting chronic inflammatory diseases. 1,2 However, Treg cells can also inhibit effective immune responses against cancer and various pathogen infections. [3][4][5] Therefore, it is critical to better define the suppressive mechanisms used by Treg cells in order to develop effective approaches for their clinical manipulation for therapeutic intervention. Significant progress has been made in delineating the molecules and mechanisms that Treg cells use to mediate suppression. [6][7][8] These mechanisms include suppression by inhibitory cytokines and secreted molecules, 9 by cytolysis or apoptosis of target cells, [10][11][12] by consumption of limiting growth factors and metabolic disruption, [12][13][14] and/or by affecting dendritic cell functions. 15 The majority of previous studies were performed in animal models, so whether these mechanisms are also used by human Treg cells is still under investigation. In addition, the fate and function of responder T cells suppressed by Treg cells is unclear.Cellular senescence was described initially more than 40 years ago in human fibroblasts with limited passages in cell culture. 16 It is now well known that senescent cells have permanent cell-cycle arrest but remain viable and metabolically active and possess unique transcriptional profiles and gene-regulation signatures. 17 There are 2 major categories of cellular senescence: replicative senescence (also known as telomere-dependent senescence) [18][19][20] and premature senescence (also known as extrinsic senescence or telomere-independent senescence). 17,[21][22][23] Recent studies suggest that replicative senescence also occurs in the human immune system. Accumulation of senescent CD8 ϩ T cells has been found in persons during normal aging, in younger persons with chronic viral infections, and in patients with certain types of cancers. [24][25][26][27] Senescent CD8 ϩ T cells show functional changes and have defective killing abilities due to the loss of perforin and granzyme or have defects in signaling of granule exocytosis. 28,29 Furthermore, senescent CD8 ϩ T cells have negative regulatory functions that reduce the effects of immunization and vaccinations and prolong the survival of allografts. 26,30 Improved understanding of the molecular mechanisms used in the generation of senescent T cells and their functional alterations will open new avenues to restoring T-cell function and will help in the design of novel vaccines for infectious diseases and cancers.In the present study, we explored the suppressive mechanisms used by human Treg cells and investigated the fate of Treg-treated responder T cells and found that treatment with CD4 ϩ CD25 hi naturally occurring Treg cells can induce naive/effector T-cell senescence. We further identified the molecular signaling that controls the process of T-cell senescence and characterized these senescent T cells....

Although Th17 cells play critical roles in the pathogenesis of many inflammatory and autoimmune diseases, their prevalence among tumor-infiltrating lymphocytes (TILs) and function in human tumor immunity remains largely unknown. We have recently demonstrated high percentages of Th17 cells in TILs from ovarian cancer patients, but the mechanisms of accumulation of these Th17 cells in the tumor microenvironment are still unclear. In this study, we further showed elevated Th17 cell populations in the TILs obtained from melanoma and breast and colon cancers, suggesting that development of tumor-infiltrating CD4+ Th17 cells may be a general feature in cancer patients. We then demonstrated that tumor microenvironmental RANTES and MCP-1 secreted by tumor cells and tumor-derived fibroblasts mediate the recruitment of Th17 cells. In addition to their recruitment, we found that tumor cells and tumor-derived fibroblasts produce a proinflammatory cytokine milieu as well as provide cell–cell contact engagement that facilitates the generation and expansion of Th17 cells. We also showed that inflammatory TLR and nucleotide oligomerization binding domain 2 signaling promote the attraction and generation of Th17 cells induced by tumor cells and tumor-derived fibroblasts. These results identify Th17 cells as an important component of human TILs, demonstrate mechanisms involved in the recruitment and regulation of Th17 cells in tumor microenvironments, and provide new insights relevant for the development of novel cancer immunotherapeutic approaches.

Defining the suppressive mechanisms used by regulatory T (Treg) cells is critical for the development of effective strategies for treating tumors and chronic infections. The molecular processes that occur in responder T cells that are suppressed by Treg cells are unclear. Here we show that human Treg cells initiate DNA damage in effector T cells caused by metabolic competition during cross-talk, resulting in senescence and functional changes that are molecularly distinct from anergy and exhaustion. ERK1/2 and p38 signaling cooperate with STAT1 and STAT3 to control Treg-induced effector T-cell senescence. Human Treg-induced T-cell senescence can be prevented via inhibition of the DNA damage response and/or STAT signaling in T-cell adoptive transfer mouse models. These studies identify molecular mechanisms of human Treg cell suppression and indicate that targeting Treg-induced T-cell senescence is a checkpoint for immunotherapy against cancer and other diseases associated with Treg cells.

Accumulating evidence suggests the immunosuppressive microenvironments created by malignant tumors represent a major obstacle for effective anti-tumor immunity. A better understanding of the suppressive mechanisms mediated by tumor microenvironments and the development of strategies to reverse the immune suppression are major challenges for the success of tumor immunotherapy. Here, we report that human tumor cells can induce senescence in naïve/effector T cells, exhibiting potent suppressive function in vitro and in vivo. We further show that tumor-derived endogenous cyclic adenosine monophosphate (cAMP) is responsible for the induction of T-cell senescence. Importantly, activation of TLR8 signaling in tumor cells can block the induction and reverse the suppression of senescent naïve and tumor-specific T cells in vitro and in vivo, resulting in enhanced anti-tumor immunity. These studies identify a novel mechanism of human tumor-mediated immune suppression and provide a new strategy to reverse tumor immunosuppressive effects for tumor immunotherapy.