Intraepithelial macrophage infiltration is related to a high number of regulatory T cells and promotes a progressive course of HPV‐induced vulvar neoplasia

Human papilloma virus (HPV)‐induced usual‐type vulvar intraepithelial neoplasia (uVIN) is infiltrated by myeloid cells but the type and role of these cells is unclear. We used triple immunofluorescent confocal microscopy to locate, identify and quantify myeloid cells based on their staining pattern for CD14, CD33 and CD163 in a cohort of 43 primary and 20 recurrent uVIN lesions, 21 carcinomas and 26 normal vulvar tissues. The progressive course of uVIN is characterized by an increase in both intraepithelial and stromal mature M1 and M2 macrophages. While the M2 macrophages outnumber M1 macrophages in healthy controls and uVIN, they are matched in number by M1 macrophages in cancer. Importantly, uVIN patients with a dense intraepithelial infiltration with mature CD14+ macrophages (irrespective of M1 or M2 type) displayed approximately a six times higher risk to develop a recurrence and a high number of these cells constituted an independent prognostic factor for recurrence. In addition, a dense intraepithelial CD14+ cell infiltration was associated with high numbers of intraepithelial CD4+ Tregs and low numbers of stromal CD8+TIM3+ T cells. Patients with low numbers of intraepithelial CD14+ cells and high numbers of stromal CD8+TIM3+ cells showed the best recurrence‐free survival. These data clearly show the importance of the local immune response in HPV‐induced vulvar neoplasia and may be of help in predicting the prognosis of patients or their response to immunotherapy.     

High infiltration of mast cells is associated with improved response to adjuvant chemotherapy in gallbladder cancer

Recent studies have reported that tumor‐infiltrating mast cells (TIM) play an important role in tumor regression, but the effect of TIM in gallbladder cancer (GBC) remains unclear. The present study aims to investigate the prognostic value of TIM in GBC patients and its responsiveness to gemcitabine‐based adjuvant chemotherapy (ACT). A total of 298 GBC patients from Zhongshan Hospital were recruited for this study. TIM infiltration was measured by immunohistochemical staining. Accumulation of TIM is significantly associated with prolonged overall survival in GBC patients. The benefit from gemcitabine‐based ACT was superior among patients with high infiltration of TIM with GBC. Multivariate analysis identified TIM infiltration as an independent prognostic factor for overall survival. A heatmap showed that TIM‐activated gene signatures were positively correlated with CD8+ T cells' gene signatures. Gene set enrichment analysis (GSEA) suggested that TIM was related to multiple T cell‐related processes and signaling pathways, including the interferon gamma signaling pathway and the leukocyte migration signaling pathway. It was confirmed that CD8+ T cell infiltration was positively correlated with high TIM infiltration in tissue microarray (TMA), suggesting that TIM infiltration was linked to the immune surveillance in GBC. TIM can be used as an independent prognostic factor and a predictor of therapeutic response of gemcitabine‐based ACT in GBC patients, which may mediate immune surveillance by recruiting and activating CD8+ T cells in GBC.     

PD‐1+ TIM‐3+ T cells in malignant ascites predict prognosis of gastrointestinal cancer

The liquid biopsy of ascites fluid could be an excellent source of tumor and microenvironment for the study of prognostic biomarkers because of its accessibility. Tumor‐infiltrating lymphocytes (TILs) can predict prognosis in multiple malignancies, including the response to immune checkpoint inhibitors, a breakthrough cancer therapy. However, TILs’ profiles from malignant ascites have not been extensively studied. Using flow cytometric analysis, we quantified the proportion of exhausted T cells and memory/naive/effector T‐cell subsets, among the CD4+ and CD8+ T‐cell populations of paired TILs and peripheral blood T cell samples (n = 22). The correlation between CD4+ and CD8+ subset profiles suggested that the combined analysis of CD4+ and CD8+ cells in malignant ascites was clinically significant. We found that cells positive for the exhaustion markers programmed cell death‐1 (PD‐1), and T‐cell immunoglobulin and mucin domain 3 (TIM‐3), and cells coexpressing PD‐1 and TIM‐3 abundantly exist among malignant ascites TILs. Furthermore, patients with high frequency of PD‐1+ TIM‐3+ cells among the CD4+ and CD8+ T‐cell population showed worse clinical outcome in multivariate analysis (n = 27). We propose that exhausted ascites TILs represent a clinically significant prognostic biomarker in advanced gastrointestinal cancer and represent an important target for immune checkpoint inhibitors.     

Mechanisms involved in synergistic anticancer immunity of anti-4-1BB and anti-CD4 therapy

Anti-4-1BB-mediated anticancer effects were potentiated by depletion of CD4+ cells in B16F10 melanoma-bearing C57BL/6 mice. Anti-4-1BB induced the expansion and differentiation of polyclonal tumor-specific CD8+ T cells into IFN-gamma-producing CD11c+CD8+ T cells. The CD4+ cell depletion was responsible for facilitating immune cell infiltration into tumor tissues and removing some regulatory barriers such as T regulatory and indoleamine-2,3-dioxygenase (IDO)+ dendritic cells. Both monoclonal antibodies (mAb) contributed to the efficient induction of MHC class I molecules on the tumor cells in vivo. The effectors that mediated the anti-4-1BB effect were NKG2D+KLRG1+CD11c+CD8+ T cells that accumulated preferentially in the tumor tissues. Blocking NKG2D reduced the therapeutic effect by 20% to 26%, which may indicate that NKG2D contributes partially to tumor killing by the differentiated CD8+ T cells. Our results indicate that the combination of the two mAbs, agonistic anti-4-1BB and depleting anti-CD4, results in enhanced production of efficient tumor-killing CTLs, facilitation of their infiltration, and production of a susceptible tumor microenvironment.     

肺癌患者化疗前后T细胞抑制性分子的研究

  目的  研究晚期肺癌患者化疗5个周期T淋巴细胞表面抑制性分子（TIM3、PD-1、CTLA-4）的变化。  方法  应用流式细胞仪技术检测33例初治晚期肺癌患者化疗5个周期T淋巴细胞表面抑制性分子的表达变化。并与23例健康志愿者作对比。  结果  化疗前晚期肺癌患者外周血T淋巴细胞表面抑制性分子的表达明显高于健康对照组, 差异具有统计学意义（P < 0.05）。化疗后19例临床疗效评价为PR或SD的患者, 其外周血CD4+TIM3+T淋巴细胞、CD8+TIM3+T淋巴细胞、CD4+PD-1+T淋巴细胞、CD8+PD-1+ T淋巴细胞比例在化疗5个周期中降低, 差异有统计学意义（P < 0.05）; 而CD4+CTLA-4+T淋巴细胞、CD8+CTLA-4+T淋巴细胞比例呈现下降趋势, 与化疗前相比无显著性差异（P>0.05）。  结论  晚期肺癌患者的免疫功能处于抑制状态。有效的化疗可降低T淋巴细胞表面抑制性分子表达, 改善肿瘤对免疫功能的抑制。      

Plasmacytoid dendritic cells induce CD8+ regulatory T cells in human ovarian carcinoma

To directly dissect the role of each immune component in human tumor immunopathogenesis, we have studied the interaction between dendritic cells and T cells in the tumor environment of patients with ovarian carcinoma. We previously reported that functional plasmacytoid dendritic cells, but not functionally mature myeloid dendritic cells, accumulated in tumor microenvironments. We now show that tumor ascites macrophage-derived dendritic cells induced tumor-associated antigen-specific CD8+ T cells with effector functions. Strikingly, tumor ascites plasmacytoid dendritic cells induced interleukin-10+ CCR7+ CD45RO+ CD8+ regulatory T cells. Four characteristics have been identified in tumor plasmacytoid dendritic cell-induced CD8+ regulatory T cells: (a) induction of CD8+ regulatory T cells is independent of CD4+ CD25+ T cells; (b) CD8+ regulatory T cells significantly suppress myeloid dendritic cell-mediated tumor-associated antigen-specific T cell effector functions through interleukin-10; (c) repetitive myeloid dendritic cell stimulation can recover CD8+ regulatory T cell-mediated poor T cell proliferation, but not T cell effector function; (d) CD8+ regulatory T cells express functional CCR7, and efficiently migrate with lymphoid homing chemokine MIP-3beta. Primary suppressive CCR7+ CD45RO+ CD8+ T cells are found in the tumor environment of patients with ovarian cancers. Thus, tumor-associated plasmacytoid dendritic cells contribute to the tumor environmental immunosuppressive network. Collectively, tumors manipulate tumor microenvironmental dendritic cell subset distribution and function to subvert tumor immunity. The data are relevant to understanding tumor immunopathology as well as reevaluating tumor immunotherapeutic strategies.     

抑制性杀伤细胞受体在NK细胞和T细胞上的表达及其与急性移植物抗宿主病的关系

 目的 研究异基因造血干细胞移植（allo-HSCT）患者移植前后外周血NK及T细胞上4种抑制性杀伤细胞受体（CD158a、CD158b、NKB1和CD94／NKG2A）的表达及其与急性移植物抗宿主病（aGVHD）的关系。方法 采用流式细胞术检测NK及T细胞上抑制性杀伤细胞受体的表达。结果 NK细胞上CD158a和CD158b的表达于移植后3～4个月、NKB1和CD94／NKG2A的表达于移植后2个月恢复移植前水平。移植前后CD158a和NKB1在CD+3 T细胞上持续低水平表达;移植前CD158b和CD94／NKG2A在CD+3 T细胞上的表达水平较高,且主要表达于CD+8 T细胞上,移植后其在CD+8 T细胞上的表达增加。CD+8 T细胞上CD158b的表达在发生Ⅰ度aGVHD时显著增高,与无aGVHD组及Ⅱ~Ⅳ度aGVHD组相比,差异均有统计学意义（P均＜0.05）;在发生Ⅱ~Ⅳ度aGVHD时增高不明显,与无aGVHD组相比,差异无统计学意义（P＞0.05）。结论 CD158b在CD+8 T细胞上高表达可能有助于降低T细胞同种反应性,减轻aGVHD的程度。     

非小细胞肺癌EGFR基因突变异质性研究进展

 表皮生长因子受体（EGFR）酪氨酸激酶抑制剂（TKIs）在EGFR基因活化突变阳性晚期非小细胞肺癌（NSCLC）患者中疗效显著,然而,同样是EGFR活化突变阳性的NSCLC患者接受EGFR-TKIs治疗后,疗效仍有明显差异;同一个患者的不同瘤灶也会对EGFR-TKIs出现不同的反应,这些现象可能与EGFR基因突变异质性有关,同一瘤灶的不同部分、同一患者的不同瘤灶、以及同一瘤灶治疗前后EGFR突变状态都有可能不一致。本文将从这三个方面对EGFR突变异质性研究进展作一综述。     

Midgut carcinoid patients display increased numbers of regulatory T cells in peripheral blood with infiltration into tumor tissue

INTRODUCTION: Our aim was to investigate the immune status of midgut carcinoid patients. Cancer patients generally display suppressed Th1-type immunity that disables mounting of an efficient anti-tumor response. However, little is known about patients with neuroendocrine midgut carcinoids. MATERIAL AND METHODS: Circulating regulatory T cells were determined in patient blood by staining for CD4, CD25 and FoxP3 in flow cytometric analysis. T cell proliferation was measured by Alamar Blue in response to polyclonal activation and the regulatory phenotype of patient CD25+ cells was validated by allogeneic stimulation of CFSE labelled responders. Cytokine levels in patient peripheral blood were measured by ELISA and CBA. Tumor infiltrating T cells were analyzed by immunohistochemistry and immunofluorescence. RESULTS: The results demonstrate that midgut carcinoid patients exhibit increased frequencies of circulating Tregs and patient T cells have a decreased proliferative capacity compared to healthy donors. Systemic Th1-promoting cytokines are reduced. Midgut carcinoid tumors display CD4+ and CD8+ T cell infiltration, always in the presence of regulatory CD4+FoxP3+ cells. DISCUSSION: Midgut carcinoid patients display elevated T regulatory cell numbers and T cell dysfunction. Therapeutic strategies to overcome tumor-induced Th1 immunosuppression are required in combination with anti-tumor vaccinations.     

Prognostic significance of CD8+ T cell and macrophage peritumoral infiltration in colorectal cancer

The purpose of this study was to evaluate the prognostic significance of CD8+ T cell and macrophage peritumoral infiltration in patients with colorectal cancer. A total of 97 adenocarcinomas of the colon and rectum were examined. Immunohistochemical staining was performed by the standard avidin-biotin-peroxidase complex method using antibodies to CD8 and CD68. Peritumoral infiltration by CD8+ T cells or macrophages was evaluated along the invasive margin of the cancer in each specimen. The area with the most abundant infiltration was selected, and the number of immunoreactive positive cells counted at x400 magnification. Patients were divided into two groups based on the degree of infiltration by each cell type: namely those with a high level of infiltration (more than the mean number of positive cells) and those with a low level of infiltration (less than the mean number of positive cells). Patients with a low level of macrophage infiltration had a significantly deeper depth of invasion than patients with a high level of macrophage infiltration (P=0.027). The percentage of patients with a high level of macrophage infiltration was significantly higher in vascular invasion-negative cases (46.7%) than in vascular invasion-positive cases (22.7%; P=0.045), and in lymph node metastasis-negative cases (52.9%) than in lymph node metastasis-positive cases (28.3%; P=0.014). Overall survival was significantly shorter for patients with a low level of CD8+ T cell infiltration than those with a high level of CD8+ T cell infiltration (P=0.01). The survival rate for patients with a high level of both CD8+ T cell and macrophage infiltration was 100%. In conclusion, both CD8+ T cell and macrophage peritumoral infiltration indicates anti-tumoral action in patients with colorectal cancer.     

Tumor-induced changes in the phenotype of blood-derived and tumor-associated T cells of early stage breast cancer patients

Tumor‐induced immune suppression has mainly been studied in patients with advanced cancer. Despite the fact that they are most likely to benefit from immunotherapy, patients with early stage cancers were under‐represented in these studies. We analyzed blood and tumor‐derived T cells from patients with stage 1 (n = 20), stage 2 (n = 23) or stage 3 (n = 1) breast cancer and found that, even early stage tumors induced T cell differentiation. Breast cancer patients had significantly more circulating CD8+ memory and fewer CD8+ naïve T cells than healthy controls (n = 10). Up‐regulation of CD69 and PD1 on cancer patient T cells suggests previous activation, and increased expression of the chemokine receptors CCR5 and CXCR3 on CD8+ T cells indicates that their homing capacity differs from that of healthy individuals. Comparison of blood‐derived and tumor‐associated T cells from patients with different metastatic status and tumor grades revealed that tumor progression and aggressiveness seem to favor the expansion of memory T cells over naive T cells. We have previously shown that immunosuppression in this patient population is stronger in the tumor than in the blood. Here, we report signs of exhaustion, such as loss of CD28, on tumor‐associated as compared to blood‐derived CD8+ T cells, despite the fact that tumor‐associated T cells are predominantly effector memory cells and express high levels of CD69. The finding that the presence of a tumor potentially induces immunosenescence early during tumorigenesis indicates that efficient immunotherapy might be difficult even in patients with early stage cancer due to T cell exhaustion and tolerance.     

Impaired tumor rejection by memory CD8 T cells in mice with NKG2D dysfunction

Cytotoxic T cells are important effectors for robust antitumor immune responses. However, tumor-infiltrating CD8 T cells are often functionally impaired. Insufficient antitumor activity of CD8 T cells can be due to a lack of costimulatory signals. NKG2D is such a costimulatory receptor on CD8 T cells that facilitates immunorecognition of stressed and malignant cells, promotes tumor rejection by NK and CD8 T cells and contributes to immunosurveillance of spontaneous malignancies. Previous reports suggested an involvement of NKG2D in establishing CD8 T cell-mediated antitumor memory. However, the significance of NKG2D for the generation and effector phase of memory CD8 T cell responses is largely unknown. To address these issues, we made use of a transgenic mouse model (H2-K(b)-MICA mice) where the human NKG2D ligand MICA is ubiquitously and constitutively expressed resulting in a severe dysfunction of NKG2D. Both, ovalbumin (OVA)-specific (H2-K(b)/OVA(257-264)) memory CD8 T cells arisen from the endogenous T cell pool and adoptively transferred OVA-specific OT-I memory cells were unable to control growth of an OVA-expressing lymphoma in H2-K(b)-MICA mice. While expansion of memory T cells in these mice on antigen challenge was not different from controls, CD8 memory T cells of H2-K(b)-MICA mice did not effectively eliminate tumor cells in vivo. Altogether, our data suggest that NKG2D has no major role in the generation and expansion of memory CD8 T cells, but rather substantially enhances the cytolytic effector responses of reactivated memory T cells and thereby contributes to an efficacious tumor rejection.     

肺癌患者外周血CD+8 自然杀伤T细胞表面受体NKG2D和NKG2A表达的临床意义

 【摘要】　目的　检测肺癌患者外周血CD+8 自然杀伤（NK）T细胞表面受体NKG2D和NKG2A的表达,探讨二者表达失衡与肺癌免疫逃逸的关系。方法　选择95例原发未治疗的肺癌患者,采用流式细胞术检测CD+8 NKT细胞表面受体NKG2D和NKG2A的表达,以50名健康人为对照。结果　肺癌组CD+8 NKT细胞NKG2D+表达率[（77.07±5.77）%]明显低于对照组[（84.13±4.49）%],差异有统计学意义（t＝8.14,P＜0.05）;在TNM分期中,Ⅰ～ⅢA、ⅢB、Ⅳ期患者CD+8 NKT细胞NKG2D+表达率依次为（81.07±5.02）%、（76.95±4.70）%、（72.80±5.16）%,差异有统计学意义（F＝18.74,P＜0.05）。肺癌组CD+8 NKT细胞NKG2A+表达率[（33.58±8.82）%]明显高于对照组[（25.31±8.38）%],差异有统计学意义（t＝-5.46,P＜0.05）;在TNM分期中,Ⅰ～ⅢA、ⅢB、Ⅳ期患者CD+8 NKT细胞NKG2A+的表达率依次为（25.10±6.93）%、（33.24±3.76）%、（43.64±6.10）%,差异有统计学意义（F＝75.73,P＜0.05）。结论　肺癌患者CD+8 NKT细胞表面NKG2A和NKG2D表达失衡可能抑制该细胞的杀伤功能,而这可能是肿瘤免疫逃逸的机制之一。     

A high proportion of bone marrow T cells with regulatory phenotype (CD4+CD25hiFoxP3+) in Ewing sarcoma patients is associated with metastatic disease

Immunosuppressive CD4+CD25^hiFoxP3+ T cells (T_reg cells) have been found at increased densities within the tumor microenvironment in many malignancies and interfere with protective antitumor immune responses. Osseous Ewing sarcomas (ESs) are thought to derive from a bone marrow (BM) mesenchymal cell of origin, and microscopic marrow involvement defines a subpopulation of patients at a high risk of relapse. We hypothesized that BM‐resident T cells may contribute to a permissive milieu for immune escape of ESs. Using 6‐color‐flow cytometry, we investigated the pattern of immune cell subset distribution including NK cells, γδ T cells, central and effector memory CD8+ and CD4+ T cells as well as T cells with regulatory phenotype (T_reg cells) in BM obtained at diagnosis from 45 primary or relapsed ES patients treated within standardized protocols. Although patients at relapse had an inverted CD4:CD8 T‐cell ratio, neither CD8+ effector/memory T‐cell subsets nor T_reg cells significantly differed from patients at diagnosis. No significant associations of innate and effector/memory T‐cell subpopulations with known risk factors were found, including age, gender, tumor site, primary metastases and histological tumor response. By contrast, T_reg cells were found at significantly higher frequencies in patients with primary metastatic disease compared with localized ESs (5.0 vs. 3.3%, p = 0.01). Thus, increased BM T_reg cells in patients with metastasized ES may reflect an immune escape mechanism that contributes to the development of metastatic disease. Immunotherapeutic strategies will have to adequately consider the regulatory milieu within areas of Ewing tumor‐immune interactions. © 2009 UICC     

FOXP3+ regulatory T cells affect the development and progression of hepatocarcinogenesis.

PURPOSE: Tumor-infiltrating lymphocytes represent the host immune response to cancer. CD4+CD25+FOXP3+ regulatory T cells (Tregs) suppress the immune reaction. The aim of the present study was to investigate the clinicopathologic significance and roles of Tregs and CD8+ T cells during hepatocarcinogenesis. EXPERIMENTAL DESIGN: We examined the infiltration of FOXP3+ Tregs and CD8+ T cells in the tumor stroma and nontumorous liver parenchyma using 323 hepatic nodules including precursor lesions, early hepatocellular carcinoma (HCC), and advanced HCC, along with 39 intrahepatic cholangiocarcinomas and 59 metastatic liver adenocarcinomas. We did immunohistochemical comparative studies. RESULTS: The prevalence of Tregs was significantly higher in HCC than in the nontumorous liver (P<0.001). The patient group with a high prevalence of Tregs infiltrating HCC showed a significantly lower survival rate (P=0.007). Multivariate analysis revealed that the prevalence of Tregs infiltrating HCC was an independent prognostic factor. The prevalence of Tregs increased in a stepwise manner (P<0.001) and that of CD8+ T cells decreased during the progression of hepatocarcinogenesis (P<0.001). Regardless of the presence of hepatitis virus infection or histopathologic evidence of hepatitis, the prevalence of Tregs was significantly increased in nontumorous liver bearing primary hepatic tumors. CONCLUSIONS: Tregs play a role in controlling the immune response to HCC during the progression of hepatocarcinogenesis. It has been suggested that primary hepatic cancers develop in liver that is immunosuppressed by a marked infiltration of Tregs. A high prevalence of Tregs infiltrating HCC is thought to be an unfavorable prognostic indicator.     

肺腺癌浸润CD8+T细胞表达CD39的机制

目的：探讨肿瘤浸润CD8⁺T细胞表达CD39的可能机制。方法：通过TCGA数据库的肺腺癌(LUAD)组织及正常肺组织转录组数据分析CD39在LUAD组织和正常肺组织中的表达差异及其对患者预后的影响,分析CD39表达与T细胞浸润、激活的关系。用小鼠LUAD Lewis细胞建立小鼠皮下移植瘤模型,FCM检测淋巴结、脾脏以及移植瘤组织中CD8⁺CD39⁺T细胞。收集Lewis细胞培养上清液作为条件培养基(CCM),免疫磁珠法(MACS)分选CD8⁺T细胞、CD11b⁺细胞;在培养基中分别加入CCM、IL-6和采取非接触或接触培养方式进行培养,探索CD8⁺T细胞表达CD39的可能机制。结果：CD39在LUAD组织中呈低表达(P<0.01),其表达水平与LUAD患者OS、T细胞浸润和激活水平均呈正相关(P<0.05或P<0.001)。FCM检测结果显示,在移植瘤组织中CD8+CD39⁺T细胞的比例明显高于淋巴结及脾脏(P<...     

Low miR-16 expression induces regulatory CD4+NKG2D+ T cells involved in colorectal cancer progression

MiR-15a/16 is a member of the miRNA cluster that exhibits tumor suppression and immune modulation via targeting multiple genes. Decreased miR-15a/16 expression is involved in many cancer cells. Here, miR-16 had decreased expression in NK1.1^-CD4⁺NKG2D⁺ T cells and bound with the 3’-UTR of NKG2D gene. MiR-15a/16-deficient mice had many CD4⁺NKG2D⁺ T cells, which produced TGF-β1 and IL-10 and inhibited the IFN-γ production of CD8⁺ T cells. Adoptive transfer of NK1.1^-CD4⁺NKG2D⁺ T cells from miR-15a/16-deficient mice promoted tumor growth in vivo. However, no changes for NK1.1^-CD4⁺NKG2D⁺ T cells were found in the miR-15a/16-transgenic mice. Although the miR-15a/16 transgenic mice transplanted with B16BL6 or MC38 cells exhibited rapid growth, these tumor-bearing mice did not show changes in NK1.1^-CD4⁺NKG2D⁺ T cell distributions in either spleens or tumors. When NK1.1^-CD4⁺ T cells were stimulated by α-CD3/sRAE-1 ex vivo, the NKG2D expression was difficult to induce in the T cells of miR-15a/16-transgenic mice. Finally, increased frequencies of regulatory CD4⁺NKG2D⁺ T cells with low miR-16 levels were observed in patients with late-stage colorectal cancer (Duke’s C, D). Thus, miR-16 modulates NK1.1^-CD4⁺NKG2D⁺ T cell functions via targeting NKG2D. Low miR-16 expression in CD4⁺ T cells induces the regulatory CD4⁺NKG2D⁺ T subpopulation, which promotes tumor evasion via the secretion of immune-suppressive molecules.     

Ovarian carcinoma expresses the NKG2D ligand Letal and promotes the survival and expansion of CD28- antitumor T cells

The role of the NKG2D immunoreceptor and its ligands in antitumor immune response is incompletely understood. Here, we report that effector immune cells infiltrating ovarian carcinoma are mostly CD8+ lymphocytes lacking CD28 but expressing the NKG2D costimulatory receptor. Human ovarian carcinoma expresses the novel NKG2D ligand lymphocyte effector cell toxicity-activating ligand (Letal). Letal was found to be an independent prognosticator of improved survival in advanced ovarian cancer. Higher levels of tumor-derived Letal were associated with stronger lymphocyte infiltration. Letal exerted marked costimulatory effects and induced type-1 polarization in CD8+CD28- tumor-infiltrating lymphocytes ex vivo. Letal engagement increased the expression of the glucose transporter Glut-1, enhanced glucose up-take, and protected CD8+ lymphocytes from cisplatin-induced killing. Letal also down-regulated the expression of Fas in CD8+ cells and rendered them resistant to Fas ligand-induced apoptosis. Our results indicate that Letal promotes tumor immune surveillance by promoting the survival and intratumoral expansion of antitumor cytotoxic lymphocytes. We propose that Letal could be used for the ex vivo expansion of apoptosis-resistant tumor-reactive cytotoxic lymphocytes for adoptive transfer.