Suppression of natural killer cell activity by adherent effusion cells of cancer patients. Suppression of motility, binding capacity and lethal hit of NK cells

Expanded human NK cells from lung cancer patients sensitize patients' PDL1-negative tumors to PD1-blockade therapy

Lung cancer remains the leading cause of cancer death worldwide despite the significant progress made by immune checkpoint inhibitors, including programmed death receptor-1 (PD1)/PD ligand 1 (PDL1)-blockade therapy. PD1/PDL1-blockade has achieved unprecedented tumor regression in some patients with advanced lung cancer. However, the majority of patients fail to respond to PD1/PDL1 inhibitors. The high rate of therapy non-response results from insufficient PDL1 expression on most patients' tumors and the presence of further immunosuppressive mechanisms in the tumor microenvironment. Here, we sensitize non-responding tumors from patients with lung cancer to PD1-blockade therapy using highly cytotoxic expanded natural killer (NK) cells. We uncover that NK cells expanded from patients with lung cancer dismantle the immunosuppressive tumor microenvironment by maintaining strong antitumor activity against both PDL1+ and PDL1- patient tumors. In the process, through a contact-independent mechanism involving interferon γ, expanded NK cells rescued tumor killing by exhausted endogenous TILs and upregulated the tumor proportion score of PDL1 across patient tumors. In contrast, unexpanded NK cells, which are susceptible to tumor-induced immunosuppression, had no effect on tumor PDL1. As a result, combined treatment of expanded NK cells and PD1-blockade resulted in robust synergistic tumor destruction of initially non-responding patient tumors. Thus, expanded NK cells may overcome the critical roadblocks to extending the prodigious benefits of PD1-blockade therapy to more patients with lung cancer and other tumor types.

Influence of natural killer cells and perforin‑mediated cytolysis on the development of chemically induced lung cancer in A/J mice

One alternative approach for the treatment of lung cancer might be the activation of the immune system using vaccination strategies. However, most of clinical vaccination trials for lung cancer did not reach their primary end points, suggesting that lung cancer is of low immunogenicity. To provide additional experimental information about this important issue, we investigated which type of immune cells contributes to the protection from lung cancer development. Therefore, A/J mice induced for lung adenomas/ adenocarcinomas by the tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) were depleted of CD4+ or CD8+ T cells, CD11b+ macrophages, Gr-1+ neutrophils and asialo GM1+ natural killer (NK) cells. Subsequent analysis of tumour growth showed an increase in tumour number only in mice depleted of NK cells. Further asking by which mechanism NK cells suppressed tumour development, we neutralized several death ligands of the tumour necrosis factor (TNF) family known to be involved in NK cell-mediated cytotoxicity. However neither depletion of TNF-α, TNF-related apoptosis-inducing ligand, TNF-like weak inducer of apoptosis or FasL alone nor in combination induced an augmentation of tumour burden. To show whether an alternative cell death pathway is involved, we next generated A/J mice deficient for perforin. After challenging with NNK, mice deficient for perforin showed an increase in tumour number and volume compared to wild-type A/J mice. In summary, our data suggest that NK cells and perforin-mediated cytolysis are critically involved in the protection from lung cancer giving promise for further immunotherapeutic strategies for this disease.

Vimentin in cancer and its potential as a molecular target for cancer therapy

Vimentin, a major constituent of the intermediate filament family of proteins, is ubiquitously expressed in normal mesenchymal cells and is known to maintain cellular integrity and provide resistance against stress. Vimentin is overexpressed in various epithelial cancers, including prostate cancer, gastrointestinal tumors, tumors of the central nervous system, breast cancer, malignant melanoma, and lung cancer. Vimentin's overexpression in cancer correlates well with accelerated tumor growth, invasion, and poor prognosis; however, the role of vimentin in cancer progression remains obscure. In recent years, vimentin has been recognized as a marker for epithelial-mesenchymal transition (EMT). Although EMT is associated with several tumorigenic events, vimentin's role in the underlying events mediating these processes remains unknown. By virtue of its overexpression in cancer and its association with tumor growth and metastasis, vimentin serves as an attractive potential target for cancer therapy; however, more research would be crucial to evaluate its specific role in cancer. Our recent discovery of a vimentin-binding mini-peptide has generated further impetus for vimentin-targeted tumor-specific therapy. Furthermore, research directed toward elucidating the role of vimentin in various signaling pathways would reveal new approaches for the development of therapeutic agents. This review summarizes the expression and functions of vimentin in various types of cancer and suggests some directions toward future cancer therapy utilizing vimentin as a potential molecular target.

Suppression by human placental protein 14 of natural killer cell activity

Human decidua of early pregnancy contains considerable numbers of CD3-CD56+ natural killer (NK) cells. In this study, two major protein products of the decidua, placental protein 14 (PP14) and placental protein 12 (PP12), were tested for the ability to regulate human NK cell activity. In vitro overnight exposure to PP14 of blood lymphocytes or purified large granular lymphocytes (LGL) resulted in suppression of cytotoxicity against K562 target cells in a 4-h 51Cr release assay. The NK inhibition was dependent on concentrations of PP14, being detectable at 5 micrograms/ml and reaching maximum at 50 micrograms/ml. Manifestation of PP14-induced NK suppression required 18-h contact with NK cells. The suppression of NK activity by PP14 was not abolished by indomethacin. In a target binding assay the number of PP14-treated LGL binding to K562 was comparable to that of untreated ones. By contrast with PP14, PP12 produced no effects on NK cells. These results indicate that PP14 suppresses the function of NK cells, which might be involved in prevention of maternal immune rejection of fetus at the fetomaternal interface.

Effects of X-ray irradiation on natural killer (NK) cell system. II. Increased sensitivity to natural killer cytotoxic factor (NKCF)

Irradiation with low-doses of X-rays of tumor cells elevated their susceptibility to lysis by natural killer (NK) cells in an accompanying paper. Cytotoxicity assays conducted at the single cell level revealed that X-ray irradiation of K562 cells did not affect the number of effector-target conjugates but increased the frequency of dead conjugated target cells. During interaction with K562 cells large granular lymphocytes released a soluble cytotoxic factor (NKCF) that killed the target cells. X-ray irradiation did not affect the NKCF stimulatory ability of K562 cells, while it elevated their sensitivity to the lytic effect of NKCF. In contrast to X-rays, exposure to ultraviolet (UV) radiation of K562 cells did not elevate their NK sensitivity but rather reduced it. Treatment with mitomycin C produced no effect on NK sensitivity. These results indicate that X-ray irradiation elevates the target sensitivity to NKCF, which may be involved in the increased NK sensitivity, and that the X-ray effect may be different from that of UV radiation or DNA synthesis inhibition.

Lymphokine activated killer (LAK) cells in patients with gastrointestinal cancer

Lymphokine activated killer (LAK) cells are a recently described cellular immune phenomenon with exciting potential for the treatment of tumours arising from solid organs. A comparison of some aspects of LAK cell precursors and LAK cell function was undertaken in 44 control subjects and 44 preoperative patients suffering from gastrointestinal cancer (20 localised and 24 advanced). Lymphokine activated killer cell precursor (natural killer (NK) cell) activity was significantly diminished in patients with advanced tumours (p less than 0.02) as was fully mature LAK cell activity against an NK resistant target cell (p less than 0.012). T-lymphocyte responses were not significantly different between the three groups. The reduced LAK cell generation was associated with a significantly diminished proliferative response of LAK precursors to stimulation with high dose IL-2 in vitro (p less than 0.012). Impaired LAK cell generation may explain the failure of adoptive cellular immunotherapy with LAK cells in some patients with advanced gastrointestinal cancer and prompts the search for means of augmenting this activity in such patients.

Depressed natural killer cell activity in acute myocardial infarction

Natural killer (NK) cell activity against K562 target cells was measured in patients within 24 h of acute myocardial infarction (AMI) and regularly thereafter for 6 weeks. NK cell activity was suppressed on days 1, 3, and 7 (P less than 0.01), day 14 (P less than 0.05) and at 6 weeks (P = 0.05) when compared to controls. Interferon, interleukin 2 and indomethacin enhanced NK cell activity on all days measured, but did not completely restore the defective NK cell activity. Serum from the patients did not suppress the NK cell activity of healthy mononuclear cells. The number of NK cells, identified as large granular lymphocytes (LGL), measured on days 1, 3, and 14 and at 6 weeks was not reduced in comparison to that of controls. Thus, the defective NK cell activity can be characterized as functional.

Kinetic analysis of the inhibition of natural killer (NK) activity by multiple populations of tumor-activated suppressor cells

Previous studies have shown that the progressive growth of the M-1 fibrosarcoma in DBA/2J mice is associated with the activation of suppressor cells which inhibit both mitogen-induced proliferative responses and antibody synthesis. In this study, we have analyzed the effect of tumor growth on NK cell activity. Mice in the advanced stages of tumor growth did have a significant depression in NK activity, and this depression could not be overcome by the injection of the interferon inducer, polyinosinic-polycytidylic acid (Poly I:C). The decline in NK activity was associated with the presence in the spleens of suppressor cells capable of inhibiting the NK activity of spleen cells from Poly I:C-treated syngeneic mice. In order to characterize the suppressor cells, we used a combination of negative selection procedures and kinetic analysis. These studies demonstrated that the spleens of tumor-bearing mice contained two distinct populations of suppressor cells which were not evident in normal mice. One population was non-adherent to nylon wool, Thy-1-, non-phagocytic, did not bind target cells, and had a non-competitive mechanism of suppression. The second population was adherent, Thy-1-, phagocytic, and had a competitive mechanism of suppression. In addition, the spleens of both normal and tumor-bearing mice contained an adherent, non-competitive suppressor cell population which was enriched following negative selection procedures removing T cells or phagocytic cells.

In vitro modulation of human natural killer cell activity by interferon: generation of adherent suppressor cells

The in vivo and in vitro effects of human alpha-interferon (IFN) on blood natural killer (NK) cell activity were studied in patients with malignant melanoma. The initial response to an i.m. injection of IFN was a depression of blood NK cell activity, being detectable at 4 h and reaching a nadir at 12 h. Blood NK cell activity returned to or exceeded pretreatment levels within 24 h. The frequency of large granular lymphocytes among peripheral blood lymphocytes (PBL), however, remained unchanged during the first 24 h of IFN treatment. In a single cell cytotoxicity assay in agarose the number of lymphocytes forming conjugates with K562 target cells was not affected at 12-h points of IFN treatment, while the frequency of lytic conjugates with dead target cells was decreased by 12 h. Thus, the number of active NK cells was reduced by IFN administration. While in vitro exposure to IFN resulted in an augmentation of NK cell activity of PBL from untreated patients, IFN failed to enhance the activity of PBL obtained 12 h post IFN injection. When PBL obtained 12 h after IFN injection were cultured overnight, they recovered their responsiveness to NK-boosting effects of IFN. Blood monocytes obtained at 12-h points from IFN-treated patients suppressed IFN-induced enhancement of NK cell activity, although these monocytes did not inhibit the base line level of NK cell activity. In contrast, the streptococcal preparation OK432 was able to augment NK cell activity of PBL obtained 12 h post IFN administration and of control PBL even in the presence of suppressor monocytes. PBL obtained 24 h post IFN injection expressing enhanced NK cell activity were also unresponsive to IFN in vitro. However, monocytes obtained 24 h after IFN injection were no longer able to inhibit IFN-induced augmentation of NK cell activity. These results indicate that in vivo administration of IFN-alpha to cancer patients results in rapid and transient generation of suppressor monocytes capable of inhibiting IFN-dependent development of functional NK cell activity, which could be responsible for the initial and transient decline in blood NK cell activity.