Double signal stimulation was required for full recovery of the autologous tumor-killing effect of effusion-associated lymphocytes

The role of PD-1/PD-L1 checkpoint in arsenic lung tumorigenesis

Chronic exposure to environmental arsenic promotes lung cancer. Emerging evidence indicates that compromised host immunity, particularly T cell anti-tumor immunity, may play a critical role in cancer development. However, there is a knowledge gap in terms of the effects of arsenic exposure on T cell anti-tumor immunity and how that may contribute to arsenic lung carcinogenicity. Immunosuppression has been known as a risk factor for many types of cancer, including lung cancer. The development of cancer indicates the success of immunosuppression and escape of cancer cells from host anti-tumor immunity in which T cells are the major component. The anti-tumor immunity is mainly executed by CD8 cytotoxic T cells through their anti-tumor effector function, which can be regulated by immune checkpoint pathways. Some inhibitory receptors on the T cell membrane and their ligands form these pathways, among which programmed death-1 (PD-1), a T cell inhibitory receptor, and its ligand, programmed death-ligand 1 (PD-L1), are best characterized. A/J mice are naturally sensitive to pulmonary carcinogens, prone to develop spontaneous lung tumors later in life and have been frequently used as an animal model for lung tumorigenesis research. Chronic arsenic administration through drinking water has been shown to enhance tumor formation in the lungs of A/J mice. In the current study, using this mouse model we want to determine whether PD-1/PD-L1 plays a role in arsenic-enhanced lung tumorigenesis. The results showed that prolonged arsenic exposure up-regulated PD-1/PD-L1, increased regulatory T cells (Tregs), decreased CD8/Treg ratio, inhibited T cell antitumor function in the lungs and enhanced lung tumor formation, while inhibition of PD-1/PD-L1 restored CD8/Treg ratio and T cell anti-tumor effector function, and mitigated arsenic-enhanced lung tumorigenesis. In addition, inhibition of PD-1/PD-L1 could be a potential preventive strategy to mitigate the tumorigenic action of chronic arsenic exposure.

Characteristics of Malignant Pleural Effusion Resident CD8+ T Cells from a Heterogeneous Collection of Tumors

While T cell-based cancer immunotherapies have shown great promise, there remains a need to understand how individual metastatic tumor environments impart local T cell dysfunction. At advanced stages, cancers that metastasize to the pleural space can result in a malignant pleural effusion (MPE) that harbors abundant tumor and immune cells, often exceeding 10⁸ leukocytes per liter. Unlike other metastatic sites, MPEs are readily and repeatedly accessible via indwelling catheters, providing an opportunity to study the interface between tumor dynamics and immunity. In the current study, we examined CD8⁺ T cells within MPEs collected from patients with heterogeneous primary tumors and at various stages in treatment to determine (1) if these cells possess anti-tumor activity following removal from the MPE, (2) factors in the MPE that may contribute to their dysfunction, and (3) the phenotypic changes in T cell populations that occur following ex vivo expansion. Co-cultures of CD8⁺ T cells with autologous CD45^- tumor containing cells demonstrated cytotoxicity (p = 0.030) and IFNγ production (p = 0.003) that inversely correlated with percent of myeloid derived suppressor cells, lactate, and lactate dehydrogenase (LDH) within the MPE. Ex vivo expansion of CD8⁺ T cells resulted in progressive differentiation marked by distinct populations expressing decreased CD45RA, CCR7, CD127, and increased inhibitory receptors. These findings suggest that MPEs may be a source of tumor-reactive T cells and that the cellular and acellular components suppress optimal function.

Induced Pluripotent Stem Cell-conditioned Medium Suppressed Melanoma Tumorigenicity Through the Enhancement of Natural-Killer Cellular Immunity

Induced pluripotent stem cells (iPSCs) can secrete cytokines that are involved in T-cell development and affect cytotoxic activity. To assess the effect of iPSC-conditioned medium on tumorigenicity, we retrieved splenocytes from B6 mice and cocultured them with or without irradiated B16 melanoma cells, mouse interleukin-2 (mIL-2), or iPSC-conditioned medium. Splenocyte cytotoxicity assays against B16 melanoma cells [as cytotoxic T lymphocyte (CTL) activity] and P815 cells [as natural killer (NK) activity] were performed. IL-10 and interferon-γ concentrations were measured. An in vivo subcutaneous B16 melanoma growth model was performed in B6 mice and treated with iPSC-conditioned medium. The lymphocyte subpopulation depletion test was performed to determine effectors against B16 melanoma cells. We found that unstimulated splenocytes had little cytotoxic activity. Without tumor cells, mIL-2 could augment iPSC-conditioned medium-treated CTL and NK activities (P<0.01). With irradiated tumor cells, mIL-2 treatment of splenocytes could not enhance CTL or NK activity, but iPSC-conditioned medium could enhance CTL and NK activity (P<0.001). Irradiated tumor cells induced mice splenocytes to secrete more IL-10, similar to mIL-2 treatment, but not iPSC-conditioned medium treatment. mIL-2 had better efficacy than conditioned medium in inducing splenocyte interferon-γ production. The CTL and NK cell depletion test showed that the immunostimulating effect of iPSC-conditioned medium on splenocytes was through the enhancement of NK cellular activity (P<0.05). The subcutaneous melanoma growth model showed that B16-bearing mice treated with an iPSC-conditioned medium intraperitoneal injection had a decreased tumor growth rate (P<0.01). Our study suggests that iPSC-conditioned medium had a protective effect against tumor-induced immunosuppression through the enhancement of host NK cellular activity.

Tumor-induced CD8+ T-cell dysfunction in lung cancer patients

Lung cancer is the leading cause of cancer deaths worldwide and one of the most common types of cancers. The limited success of chemotherapy and radiotherapy regimes have highlighted the need to develop new therapies like antitumor immunotherapy. CD8+ T-cells represent a major arm of the cell-mediated anti-tumor response and a promising target for developing T-cell-based immunotherapies against lung cancer. Lung tumors, however, have been considered to possess poor immunogenicity; even so, lung tumor-specific CD8+ T-cell clones can be established that possess cytotoxicity against autologous tumor cells. This paper will focus on the alterations induced in CD8+ T-cells by lung cancer. Although memory CD8+ T-cells infiltrate lung tumors, in both tumor-infiltrating lymphocytes (TILs) and malignant pleural effusions, these cells are dysfunctional and the effector subset is reduced. We propose that chronic presence of lung tumors induces dysfunctions in CD8+ T-cells and sensitizes them to activation-induced cell death, which may be associated with the poor clinical responses observed in immunotherapeutic trials. Getting a deeper knowledge of the evasion mechanisms lung cancer induce in CD8+ T-cells should lead to further understanding of lung cancer biology, overcome tumor evasion mechanisms, and design improved immunotherapeutic treatments for lung cancer.

Characterization of novel transforming growth factor-beta type I receptors found in malignant pleural effusion tumor cells

Background

Tumors expressing a transforming growth factor-beta type I receptor (TβRI) mutant with sequence deletions in a nine-alanine (9A) stretch of the signal peptide are reported to be highly associated with disease progression. Expression of this mutant could interfere with endogenous TGFβ signaling in the cell. However, little is known about the importance of the remaining part of the signal peptide on the cellular function of TβRI.

Results

We cloned and identified four new in-frame deletion variants of TβRI, designated DM1 to DM4, in pleural effusion-derived tumor cells. Intriguingly, DM1 and DM2, with a small region truncated in the putative signal peptide of TβRI, had a serious defect in their protein expression compared with that of the wild-type receptor. Using serial deletion mutagenesis, we characterized a region encoded by nucleotides 16–51 as a key element controlling TβRI protein expression. Consistently, both DM1 and DM2 have this peptide deleted. Experiments using cycloheximde and MG132 further confirmed its indispensable role for the protein stability of TβRI. In contrast, truncation of the 9A-stretch itself or a region downstream to the stretch barely affected TβRI expression. However, variants lacking a region C-terminal to the stretch completely lost their capability to conduct TGFβ-induced transcriptional activation. Intriguingly, expression of DM3 in a cell sensitive to TGFβ made it significantly refractory to TGFβ-mediated growth inhibition. The effect of DM3 was to ablate the apoptotic event induced by TGFβ.

Conclusion

We identified four new transcript variants of TβRI in malignant effusion tumor cells and characterized two key elements controlling its protein stability and transcriptional activation. Expression of one of variants bestowed cancer cells with a growth advantage in the presence of TGFβ. These results highlight the potential roles of some naturally occurring TβRI variants on the promotion of tumor malignancy.

Identification of alpha-enolase as an autoantigen in lung cancer: its overexpression is associated with clinical outcomes

PURPOSE

Although existence of humoral immunity has been previously shown in malignant pleural effusions, only a limited number of immunogenic tumor-associated antigens (TAA) have been identified and associated with lung cancer. In this study, we intended to identify more TAAs in pleural effusion-derived tumor cells.

EXPERIMENTAL DESIGN

Using morphologically normal lung tissues as a control lysate in Western blotting analyses, 54 tumor samples were screened with autologous effusion antibodies. Biochemical purification and mass spectrometric identification of TAAs were done using established effusion tumor cell lines as antigen sources. We identified a p48 antigen as alpha-enolase (ENO1). Semiquantitative immunohistochemistry was used to evaluate expression status of ENO1 in the tissue samples of 80 patients with non-small cell lung cancer (NSCLC) and then correlated with clinical variables.

RESULTS

Using ENO1-specifc antiserum, up-regulation of ENO1 expression in effusion tumor cells from 11 of 17 patients was clearly observed compared with human normal lung primary epithelial and non-cancer-associated effusion cells. Immunohistochemical studies consistently showed high level of ENO1 expression in all the tumors we have examined thus far. Log-rank and Cox's analyses of ENO1 expression status revealed that its expression level in primary tumors was a key factor contributing to overall- and progression-free survivals of patients (P < 0.05). The same result was also obtained in the early stage of NSCLC patients, showing that tumors expressing relatively higher ENO1 level were tightly correlated with poorer survival outcomes.

CONCLUSIONS

Our data strongly support a prognostic role of ENO1 in determining tumor malignancy of patients with NSCLC.