Induction by interleukin-15 of human killer cell activity against lung cancer cell lines and its regulatory mechanisms

Therapeutic approaches to enhance natural killer cell cytotoxicity

Enhancing the cytotoxicity of natural killer (NK) cells has emerged as a promising strategy in cancer immunotherapy, due to their pivotal role in immune surveillance and tumor clearance. This literature review provides a comprehensive overview of therapeutic approaches designed to augment NK cell cytotoxicity. We analyze a wide range of strategies, including cytokine-based treatment, monoclonal antibodies, and NK cell engagers, and discuss criteria that must be considered when selecting an NK cell product to combine with these strategies. Furthermore, we discuss the challenges and limitations associated with each therapeutic strategy, as well as the potential for combination therapies to maximize NK cell cytotoxicity while minimizing adverse effects. By exploring the wealth of research on this topic, this literature review aims to provide a comprehensive resource for researchers and clinicians seeking to develop and implement novel therapeutic strategies that harness the full potential of NK cells in the fight against cancer. Enhancing NK cell cytotoxicity holds great promise in the evolving landscape of immunotherapy, and this review serves as a roadmap for understanding the current state of the field and the future directions in NK cell-based therapies.

Intravesical interleukin-15 gene therapy in an orthotopic bladder cancer model

Interleukin-15 (IL-15) is known to stimulate the proliferation of CD8(+) T-cells and natural killer cells, and also to help to maintain memory CD8(+) T cells, suggesting that it may be of value in cytokine treatment of bladder cancer. In this experiment, we tested the efficiency of intravesical liposomal IL-15 gene delivery and its antitumor effect in a mouse orthotopic bladder cancer model. We established an orthotopic bladder cancer model by implanting 5×10(5) MBT-2 cells into female C3H/HeN mice through the urethra. The mice received repeated intravesical gene delivery injected with liposome-mediated plasmids (5 μg) transurethrally. On day 23, the bladder weights in the group receiving medium alone, the beta-galactosidase gene delivery control group, and the IL-15 gene therapy group were 196±36 mg, 201±35 mg, and 96±29 mg, respectively (p<0.05), demonstrating the antitumor effect of intravesical IL-15 gene therapy in this model. In the bladders treated with IL-15 gene plasmid instillation, histological analysis revealed that many inflammatory cells were induced around the tumors. Immunohistochemical analysis confirmed that there was predominant infiltration of CD8(+) T cells around the tumor nest. After the intravesical IL-15 gene therapy, the growth of rechallenged subcutaneous MBT-2 cells in surviving mice was inhibited again via tumor-specific cytotoxic T lymphocytes, although newly implanted FM3A cells in the same mice were not rejected. The present findings indicate that IL-15 gene therapy may be a promising new adjuvant therapy for bladder cancer.

Interleukin (IL-)15 has less activity than IL-2 to promote type 2 cytokine predominance in tumour-associated mononuclear cells from lung cancer patients

Deviation of type 1/type 2 cytokine balance to type 2 predominance may contribute to tumour progression. We investigated effect of interleukin (IL-)15 on modulation of type 1/type 2 balance in addition to non-major histo-compatibility complex (MHC)-restricted killer induction in the tumour-growing site. IL-15 induced significant killer activity in mononuclear cells (MNC) in malignant pleural effusion as well as those in peripheral blood. Pleural MNC produced more IFN-gamma (type 1 cytokine) by incubation with IL-15 or IL-2 than blood MNC. Moreover, IL-4 and IL-5 (type 2 cytokines) production by pleural MNC were observed only by incubation with IL-2, but not with IL-15. These observations suggest that IL-15 has a potent activity to restore type 1/type 2 balance in addition to killer induction in tumour-growing site.

Clinical implications of interleukin (IL)-10 induced by non-small-cell lung cancer

BACKGROUND

The type 2 cytokine interleukin (IL)-10 has been reported to inhibit the antitumour activity of the regional immunity against various neoplasms. Certain lung cancers produce IL-10, but the clinical significance of IL-10 expression is not well understood.

PATIENTS AND METHODS

We examined IL-10 and IL-10 receptor (IL-10R) mRNA expression in 82 non-small-cell lung cancers (NSCLC) by reverse transcription-polymerase chain reaction (RT-PCR) assay. Immunohistochemistry (IHC) and enzyme immunoassay (EIA) were applied to evaluate the cellular localisation and the serum levels of IL-10.

RESULTS

RT-PCR assay revealed IL-10 mRNA expression in 68 (83%) of 82 NSCLC surgical specimens (40 of 50 adenocarcinomas, 22 of 26 squamous cell carcinomas, 5 of 5 large-cell carcinomas, 1 of 1 adenosquamous-cell carcinoma). RT-PCR assay also revealed IL-10R mRNA expression in 79 cases of NSCLC (96.1%). IL-10 expression was confirmed within tumour cells by IHC. EIA showed no significant serum IL-10 elevation in the 12 NSCLC positive for IL-10 mRNA expression (0-2.99 pg/ml). The NSCLC patients with IL-10 production showed significantly poorer prognosis than those without IL-10 production (P < 0.05, Kaplan Meier, log-rank test).

CONCLUSIONS

These results suggested that the cytoplasmic IL-10 correlated to clinical prognosis, and that IL-10 expression is a prognostic factor for NSCLC.

In vitro effect of lithium chloride on interleukin-15 production by monocytes from IL-breast cancer patients

Lithium salt compounds are used to limit the degree and duration of neutropenia in patients receiving chemotherapy for cancer. Interleukin-15 (IL-15) is a cytokine which possesses promoting activities on hematopoiesis and is also involved in antitumor response, activating NK, CTL and LAK cells. In this study we analyzed IL-15 production by monocyte cultures treated with lithium chloride (LiCl). Monocytes were obtained from patients affected by non-metastatic and metastatic breast cancer. LiCl treatment induced IL-15 production by monocytes mainly from non-metastatic patients. Combined lipopolysaccharide/LiCl treatment of monocyte cultures up-regulated IL-15 release compared to those treated with LPS alone (p<0.0001). The modulation of LiCl-induced IL-15 could counteract the immunosuppression state of cancer patients, which should be taken into account when developing new immunotherapeutic strategies.

Augmentation by interleukin-18 of MHC-nonrestricted killer activity of human peripheral blood mononuclear cells in response to interleukin-12

Interleukin (IL)-18 is a novel cytokine with pleiotropic functions. In the present study, we examined the induction of the killer activity of peripheral blood mononuclear cells (MNC) against lung cancer cell lines upon treatment with IL-18 in combination with IL-12. Cytotoxic activity was measured by standard (51)Cr release assay. IL-18 (100 ng/ml) was found to significantly augment IL-12-induced killer activity in a MHC-nonrestricted manner against allogeneic NK-resistant Daudi cells and lung cancer cell lines: SBC-3, RERF-LC-AI and A549. IL-18 could augment IL-12-induced killer activity both at the optimal as well as suboptimal doses of the latter. However, IL-18 was found to have little effect on the killer activity of MNC induced by optimal or suboptimal dose of IL-2 or IL-15. Treatment of MNC with IL-18 in combination with IL-12 for a period of more than 4 days was observed to optimally induce the killer activity. As for induction of IFN-gamma production by MNC, IL-18 augmented that induced by IL-2 and IL-15, as well as that induced by IL-12. These results show the potential of IL-18 in combination with IL-12 for clinical application in treatment of cancer.

Immunogene therapy of murine fibrosarcoma using IL-15 gene with high translation efficiency

We have recently found that translational efficiency is up-regulated by an alternative exon in IL-15 mRNA in mice. In a malignancy model using BALB/c mice and syngeneic Meth A fibrosarcoma (Meth A), we successfully applied immunological gene therapy with IL-15 protein using alternative IL-15 cDNA with high translational efficiency. Two expression vectors carrying the murine IL-15 gene were constructed for use in tumor immunotherapy, one utilizing IL-15 cDNA with alternative exon 5 and the second utilizing IL-15 cDNA with normal exon 5. The first vector induced the production of a large amount of IL-15 protein in Meth A cells, whereas tumor cells transfected by the second vector produced only a marginal level of IL-15 protein. Although cell growth of both transfectants in vitro remained unchanged, inoculation of clones transfected with normal IL-15 cDNA resulted in progressive tumor growth, while clones transfected with alternative IL-15 cDNA led to the rejection of the tumor. The clone producing high levels of IL-15 grew progressively in nude mice and mice treated with anti-CD4 monoclonal antibodies (mAb), whereas the growth of the transfectants was retarded in anti-CD8 mAb- or anti-asialo GM1 antibody-treated mice. Cured mice were shown to have generated immunity against a subsequent challenge with the wild type of Meth A but not against Meth 1 tumor cells, another type of fibrosarcoma derived from BALB/c mice. Thus, tumor therapy based on IL-15 gene transfection was effective against Meth A tumor cells, suggesting a possible application to human neoplasms.

Advances in cell separation: recent developments in counterflow centrifugal elutriation and continuous flow cell separation

Cell separation by counterflow centrifugal elutriation (CCE) or free flow electrophoresis (FFE) is performed at lower frequency than cell cloning and antibody-dependent, magnetic or fluorescence-activated cell sorting. Nevertheless, numerous recent publications confirmed that these physical cell separation methods that do not include cell labeling or cell transformation steps, may be most useful for some applications. CCE and FFE have proved to be valuable tools, if homogeneous populations of normal healthy untransformed cells are required for answering scientific questions or for clinical transplantation and cells cannot be labeled by antibodies, because suitable antibodies are not available or because antibody binding to a cell surface would induce the cell reaction which should be investigated on purified cells or because antibodies bound to the surface hamper the use of the isolated cells. In addition, the methods are helpful for studying the biological reasons for, or effects of, changes in cell size and cellular negative surface charge density. Although the value of the methods was confirmed in recent years by a considerable number of important scientific results, activities to further develop and improve the instruments have, unfortunately, declined.

Combination Chemotherapy and IL-15 Administration Induce Permanent Tumor Regression in a Mouse Lung Tumor Model: NK and T Cell-Mediated Effects Antagonized by B Cells

Previous studies have demonstrated that IL-15 administration after cyclophosphamide (CY) injection of C57BL/6J mice bearing the i.m. 76-9 rhabdomyosarcoma resulted in a significant prolongation of life. In the present study, we investigated the immune response against the 76-9 experimental lung metastases after CY + IL-15 therapy. Administration of CY + IL-15, but not IL-15 alone, induced prolongation of life and cures in 32% of mice bearing established experimental pulmonary metastases of 76-9 tumor. The CY + IL-15 therapy resulted in increased levels of NK1.1+/LGL-1+ cells, and CD8+/CD44+ T cells in PBL. In vitro cytotoxic assay of PBL indicated the induction of lymphokine-activated killer cell activity, but no evident tumor-specific class I-restricted lytic activity. Survival studies showed that the presence of NK and T lymphocytes is necessary for successful CY + IL-15 therapy. Experiments using knockout mice implied that either αβ or γδ T cells were required for an antitumor effect induced by CY + IL-15 therapy. However, mice lacking in both αβ and γδ T cells failed to respond to combination therapy. Cured B6 and αβ or γδ T cell-deficient mice were immune to rechallenge with 76-9, but not B16LM tumor. B cell-deficient mice showed a significant improvement in the survival rate both after CY and combination CY + IL-15 therapy compared with normal B6 mice. Overall, the data suggest that the interaction of NK cells with tumor-specific αβ or γδ T lymphocytes is necessary for successful therapy, while B cells appear to suppress the antitumor effects of CY + IL-15 therapy.

Comparative analysis of interleukin 15 and interleukin 2 for induction of killer activity and of type 2 cytokine production by mononuclear cells from lung cancer patients

Interleukin (IL) 15 is a novel cytokine with IL-2-like activity. In this study, we examined the effect of IL-15 on induction of non major histocompatibility complex (MHC)-restricted killer activity and of type 2 cytokine production by peripheral blood and pleural mononuclear cells (MNCs), from 34 lung cancer patients and 20 control subjects. IL-15 induced significant killer activity in blood MNCs from lung cancer patients as well as control subjects against a small-cell lung cancer cell line (SBC-3). Effective killer induction by IL-15 was observed even in blood MNCs and pleural MNCs from the site of tumour growth in advanced lung cancer patients. IL-12 had an additive effect with a suboptimal dose of IL-15 in induction of killer activity. In the case of MNCs from lung cancer patients, IL-10 production was more prominent when cells were incubated with IL-2 than with IL-15. IL-5 production was observed in MNCs from lung cancer patients stimulated with IL-2, but not with IL-15. These observations suggest that IL-15, by virtue of its lesser induction of type 2 cytokine, may be a better candidate than IL-2 for lung cancer immunotherapy.

In vivo regulation of replicative Legionella pneumophila lung infection by endogenous interleukin-12

The in vivo role of endogenous interleukin 12 (IL-12) in modulating intrapulmonary growth of Legionella pneumophila was assessed by using a murine model of replicative L. pneumophila lung infection. Intratracheal inoculation of A/J mice with virulent bacteria (10(6) L. pneumophila cells per mouse) resulted in induction of IL-12, which preceded clearance of the bacteria from the lung. Inhibition of endogenous IL-12 activity, via administration of IL-12 neutralizing antiserum, resulted in enhanced intrapulmonary growth of the bacteria within 5 days postinfection (compared to untreated L. pneumophila-infected mice). Because IL-12 has previously been shown to modulate the expression of cytokines, including gamma interferon (IFN-gamma), tumor necrosis factor alpha (TNF-alpha), and IL-10, which regulate L. pneumophila growth, immunomodulatory effects of endogenous IL-12 on intrapulmonary levels of these cytokines during replicative L. pneumophila lung infection were subsequently assessed. Results of these experiments demonstrated that TNF-alpha activity was significantly lower, while protein levels of IFN-gamma and IL-10 in the lung were similar, in L. pneumophila-infected mice administered IL-12 antiserum, compared to similarly infected untreated mice. Together, these results demonstrate that IL-12 is critical for resolution of replicative L. pneumophila lung infection and suggest that regulation of intrapulmonary growth of L. pneumophila by endogenous IL-12 is mediated, at least in part, by TNF-alpha.