Interleukin-6 enhances the induction of human lymphokine-activated killer cells

Intraperitoneal cancer-immune microenvironment promotes peritoneal dissemination of gastric cancer

A solid tumor consists of cancer and stromal cells, which comprise the tumor microenvironment (TME). Tumor-associated macrophages (TAMs) are usually abundant in the TME, contributing to tumor progression. In cases of peritoneal dissemination of gastric cancer (GC), the contribution of intraperitoneal TAMs remains unclear. Macrophages from peritoneal washings of GC patients were analyzed, and the link between intraperitoneal TAMs and GC cells was investigated to clarify the interaction between them in peritoneal dissemination. Macrophages were predominant among leukocytes constituting the microenvironment of the peritoneal cavity. The proportion of CD163-positive TAMs was significantly higher in stage IV than in stage I GC. Co-culture with TAMs potentiated migration and invasion of GC. IL-6 was the most increased in the medium of in vitro co-culture of macrophages and GC, and IL-6 elevation was also observed in the peritoneal washes with peritoneal dissemination. An elevated concentration of intraperitoneal IL-6 was correlated with a poor prognosis in clinical cases. In conclusion, intraperitoneal TAMs are involved in promoting peritoneal dissemination of GC via secreted IL-6. TAM-derived IL-6 could be a potential therapeutic target for peritoneal dissemination of GC.

T-cell mediated anti-tumor immunity after photodynamic therapy: why does it not always work and how can we improve it?

Photodynamic therapy (PDT) uses the combination of non-toxic photosensitizers and harmless light to generate reactive oxygen species that destroy tumors by a combination of direct tumor cell killing, vascular shutdown, and activation of the immune system. It has been shown in some animal models that mice that have been cured of cancer by PDT, may exhibit resistance to rechallenge. The cured mice can also possess tumor specific T-cells that recognize defined tumor antigens, destroy tumor cells in vitro, and can be adoptively transferred to protect naïve mice from cancer. However, these beneficial outcomes are the exception rather than the rule. The reasons for this lack of consistency lie in the ability of many tumors to suppress the host immune system and to actively evade immune attack. The presence of an appropriate tumor rejection antigen in the particular tumor cell line is a requisite for T-cell mediated immunity. Regulatory T-cells (CD25+, Foxp3+) are potent inhibitors of anti-tumor immunity, and their removal by low dose cyclophosphamide can potentiate the PDT-induced immune response. Treatments that stimulate dendritic cells (DC) such as CpG oligonucleotide can overcome tumor-induced DC dysfunction and improve PDT outcome. Epigenetic reversal agents can increase tumor expression of MHC class I and also simultaneously increase expression of tumor antigens. A few clinical reports have shown that anti-tumor immunity can be generated by PDT in patients, and it is hoped that these combination approaches may increase tumor cures in patients.

Interleukin-6 directly influences proliferation and invasion potential of head and neck cancer cells

Interleukin-6 (IL-6) is a multifunctional regulator of immune response and hematopoiesis. Recently, it has been reported that expression of IL-6 is correlated with prognosis in various cancer patients. In this study, we investigated whether the proliferation and invasion potential of head and neck squamous cell carcinomas (HNSCCs) were influenced by IL-6. All HNSCC cell lines, HEp-2, HSC-2, HSC-4, and SAS, were tested by reverse transcription-polymerase chain reaction (RT-PCR) and expressed the IL-6 receptor (IL-6R), and glycoprotein 130, which is responsible for signal transduction. HEp-2, HSC-2, and HSC-4 also produced IL-6. IL-6 inhibited the proliferation of HSC-2 and SAS, but the invasion potential of all the cell lines increased. Moreover, IL-6 down-regulated soluble IL-6R expression. Anti-IL-6R antibody abrogated the inhibited proliferation and increased invasion induced by IL-6. IL-6 stimulation also induced the extracellular regulated protein kinase 1/2 activation and increased vascular endothelial growth factor release. These results suggest that IL-6 can directly influence cell proliferation and the invasion potential as the first step of tumor metastasis.

Subpopulations of mononuclear leukocytes associated with inhibition of Ehrlich ascites tumor growth by treatment with Bothrops jararaca venom

Snake venoms have been used as antineoplastic substances in several experimental models. We demonstrated in previous studies that Bothrops jararaca venom (BjV) induces inhibition of Ehrlich ascites tumor (EAT) growth accompanied by an increase of mononuclear (MN) leukocytes in all groups inoculated with EAT and/or venom. The objective of the present study was to characterize the subpopulations of MN leukocytes involved in the inhibition of EAT growth by treatment with BjV. Swiss mice were inoculated with 1.0x10(3) EAT cells by the intraperitoneal route and treated with 0.4 mg/kg of BjV by the same route (Group TV). Treatment was started 24 h after tumor cell inoculation and consisted of five intraperitoneal injections performed at 72 h intervals. After 2, 8 and 14 days, groups of animals were sacrificed and the number of B, TCD4 and TCD8 lymphocytes, macrophages and natural killer cells present in the peritoneal cavity was determined by flow cytometry. The control group consisted of animals inoculated with EAT and treated with 0.1 ml of saline under the same conditions as the experimental group (Group T). Two additional control groups consisted of animals not inoculated with EAT and treated with saline or venom. Data were analyzed statistically by the Kruskal-Wallis non-parametric test for independent samples. On the 2nd and 8th day we observed a difference between groups T and TV (group T > group TV) for all cell types, except natural killer cells, that only differed on the 2nd day. However, on the 14th day there was no difference in MN cells among groups. These data suggest that the inhibition of EAT is related to the toxic action of BjV on tumor cells and/or to the proteolytic effect of the venom on the mediators produced by the cells for growth modulation.

Antitumor effect of Bothrops jararaca venom

Many experimental studies have been carried out using snake venoms for the treatment of animal tumors, with controversial results. While some authors have reported an antitumor effect of treatment with specific snake venom fractions, others have reported no effects after this treatment. The aim of this study was to evaluate the effect of Bothrops jararaca venom (BjV) on Ehrlich ascites tumor (EAT) cells in vivo and in vitro. In the in vivo study, Swiss mice were inoculated with EAT cells by the intraperitoneal (i.p.) route and treated with BjV venom (0.4 mg/kg, i.p.), on the 1st, 4th, 7th, 10th, and 13th days. Mice were evaluated for total and differential cells number on the 2nd, 5th, 8th, 11th and 14th days. The survival time was also evaluated after 60 days of tumor growth. In the in vitro study, EAT and normal peritoneal cells were cultivated in the presence of different BjV concentrations (2.5, 5.0, 10.0, 20.0, 40.0, and 80 microg) and viability was verified after 3, 6, 12 and 24 h of cultivation. Results were analyzed statistically by the Kruskal-Wallis and Tukey tests at the 5% level of significance. It was observed that in vivo treatment with BjV induced tumor growth inhibition, increased animal survival time, decreased mortality, increased the influx of polymorphonuclear leukocytes on the early stages of tumor growth, and did not affect the mononuclear cells number. In vitro treatment with BjV produced a dose-dependent toxic effect on EAT and peritoneal cells, with higher effects against peritoneal cells. Taken together, our results demonstrate that BjV has an important antitumor effect. This is the first report showing this in vivo effect for this venom.

Influence of peri-operative immunotherapy on serum cytokines and soluble cytokine receptors in patients undergoing surgery for colorectal cancer

OBJECTIVE

The cellular immune response is suppressed following surgery for colorectal cancer. As cytokines influence the patient's immunological responsiveness, we have measured serum cytokines and their soluble receptors in patients receiving peri-operative immunotherapy for colorectal cancer.

PATIENTS AND METHODS

Fifty-two patients were randomized to receive low dose recombinant IL-2 (rIL-2) alone; rIL-2 with interferon-alpha (IFN-α) or no immunotherapy. Serum cytokines and cytokine receptor levels were measured preoperatively and on post-operative days 1, 4, 7 and 10 using ELISA kits.

RESULTS

Circulating levels of IFN-γ were undetectable in the majority of patients, although IFN-γR levels were increased in all three groups on the first post-operative day (P < 0.05). Similarly, IL-2 was undetectable in most subjects and not enhanced by treatment. However, IL-2R was significantly induced in all patients (P < 0.001), and these levels were higher in both treatment groups when compared with control (P < 0.005). Tumour necrosis factor-alpha (TNF-α) was universally undetectable, but the TNF-R p55 and p75 subunits were induced in all patients (P < 0.005); and as with IL-2R, this was greater in the treatment groups (P < 0.01). Finally, IL-6 production was induced in all groups (P < 0.005), but this was only noted on day 1.

CONCLUSION

Soluble cytokine receptors are induced by surgery, and levels of IL-2R and TNF-R are enhanced by exogenous rIL-2 and rIL-2 with IFN-α. This augmentation suggests increased immunocompetence associated with low dose peri-operative immunotherapy.

Differential regulation of interleukin-12- and interleukin-15-induced natural killer cell activation by interleukin-4

The regulation of human natural killer (NK) cell activation is under the control of a network of regulatory signals provided by cytokines. In the present study, we investigated the functional interaction between interleukin (IL)-4 and two monocyte/macrophage-derived cytokines, IL-12 and IL-15, during the process of NK stimulation. Using freshly isolated human NK cells, we have demonstrated that IL-4 negatively regulates lymphokine-activated killer (LAK) activity induced by IL-15 against the NK-resistant Daudi target cells. In contrast, IL-4 had no effect on IL-12-stimulated LAK generation. The differential effect of IL-4 on NK cell activation by IL-12 and IL-15 correlates with its ability to increase or to down-regulate the level of tumor necrosis factor-alpha and interferon-gamma release by NK cells, respectively. In contrast, endogenous transforming growth factor-beta 1 does not appear to be involved in the IL-4 regulatory pathway. Furthermore, while IL-4 was found to decrease the basal expression of the IL-2 receptor beta subunit utilized by IL-15, it had no effect on the expression of the beta 1 chain of the IL-12 receptor compared to untreated cells. Northern blot analysis indicated that the IL-4 regulatory effect on NK lytic function was associated with its capacity to down-regulate granzyme B and perforin gene transcription in response to IL-15 and its failure to affect the expression of both gene's in response to IL-12. Together, these data suggest the existence of a distinct cross-talk between IL-4 and IL-15 or IL-12 signaling pathways during the regulation of human non-major histocompatibility complex-restricted cytotoxicity.

Natural killer cells and cancer

BACKGROUND

Natural cytotoxicity, mediated by natural killer (NK) cells and cell with lymphokine-activated killer (LAK) activity, is believed to play an important role in host anti-cancer mechanisms.

METHODS

The authors critically review recent publications on the role of natural cytotoxicity in patients with cancer.

RESULTS

In patients with cancer, several studies have noted variations in the numbers and activity of NK and cells with LAK activity in different body compartments. NK cell activity in the peripheral blood lymphocytes (PBLs) is higher than that found in lymph nodes and within tumors, and this appears to be due to the presence of suppressor factors. The natural cytotoxicity of PBLs in patients with different types of cancers varies. However, there appears to be a trend for natural cytotoxicity to be reduced in certain cancer patients, possibly related to tumor volume or dissemination. Anti-cancer treatments (e.g., surgery, hormonal modulation, radiotherapy and chemotherapy) can also result in suppression of natural cytotoxicity, although the long-term effect on response to treatment and development of metastases is at present unknown.

CONCLUSIONS

NK and LAK cells, through the use of immune biologic modifiers, have been demonstrated to have a therapeutic role in the treatment of human cancers. Further studies are required to determine the optimal dosages and combinations of chemotherapeutic agents, the timing of surgery, and the adjuvant use of immune biologic response modifiers. An increasing awareness and understanding of this field, may allow for the future development of anti-cancer therapies.

Potential use of recombinant human interleukin-6 in clinical oncology

Recombinant human IL-6 (rhIL-6) is a pleiotropic cytokine with stimulatory actions on the hematopoietic system, the immune system and hepatocytes. Clinical interest in the use of this cytokine was raised because of its thrombopoietic properties and also because of its anti-tumor activity, which was shown in vitro and in the preclinical setting. Various studies show that doses up to 10 mu kg/kg/d rhIL-6 before and after chemotherapy are tolerable and the most frequent side-effects encountered consist of flu-like symptoms. Furthermore, a consistent decrease in hemoglobin was reported during rhIL-6 treatment. This was probably due to hemodilution, although a change in ferrokinetics, may also at least partly, explain the anemia. An evident increase of platelets has been observed in various studies. After chemotherapy, rh-IL6 seemed to hasten platelet recovery, without affecting platelet nadir. Preliminary data from studies investigating the value of rhIL-6 as an anti-tumor agent in renal cell carcinoma and melanoma reported low response rates, between 8 and 14%. The results of rhIL-6 in ameliorating chemotherapy induced bone-marrow depression and especially thrombocytopenia, are promising and merit further phase III studies.

Proliferation of IL-2 activated lymphocytes preferably occurs in aggregates by cells expressing the CD57 antigen

Aggregates of lymphocytes were investigated in long-term cultures of IL-2 stimulated peripheral blood mononuclear cells. Cells in clusters formed broad contact areas where coated pits and vesicles were often detectable. Proliferating cells were preferably found in aggregates indicating that the cell clusters represent proliferation centres in which cell division may be promoted by accessory signal transduction mediated by the close cell-to-cell contact. In bulk cultures CD57+ cells yielded increased proliferation capacity compared to CD57- cells. In addition, CD57+ cells were preferably localized in aggregates where they occupied the same position at the periphery of the clusters than the proliferating cells, suggesting that both cell types may be identical. It is discussed that the CD57 antigen represents a differentiation marker which is upregulated when CD57- cells start to proliferate assisted in cell aggregates.

Macrophage colony-stimulating factor enhancement of antibody-dependent cellular cytotoxicity against human colon carcinoma cells

Antibody-dependent cellular cytotoxicity (ADCC) has been suggested to be an important defense mechanism against tumors. The effects of recombinant human macrophage colony-stimulating factor (rhM-CSF) on ADCC activity of human monocytes were investigated. Human peripheral monocytes were pre-incubated for 72 h with rhM-CSF at various concentrations (50, 100, 200, 400 U/ml) and then used as effector cells in a 24-h 111-Indium release assay. Human carcinoma cell lines LS-174T, CBS, and KLE were used as targets to react with anti-carcinoma monoclonal antibodies (mAbs: murine D612, murine CC49, and chimeric CC49). A significant increase in ADCC activity was observed after monocytes were incubated in 100-400 U/ml of human rhM-CSF. Variation in ADCC activity of monocytes among donors was observed. The enhancement of ADCC activity was blocked by the addition of a neutralizing antibody to rhM-CSF. Less D612 mAb was required for the rhM-CSF-treated monocytes to mediate an equivalent level of ADCC activity as compared to the untreated monocytes. Because of the low levels of rhM-CSF required in these studies to enhance ADCC, treatment of monocytes alone with comparable levels of rhM-CSF did not enhance antibody-independent cytotoxicity. Moreover, it is demonstrated here that recombinant human interleukin-4 (rhIL-4) and rhM-CSF can have a synergistic effect of monocyte-mediated ADCC on human tumor cells. These results thus indicate that rhM-CSF augments ADCC of human peripheral blood monocytes using mAbs to human carcinomas, suggesting a potential role for rhM-CSF in cancer immunotherapy.

All trans retinoic acid enhances human LAK activity

All trans retinoic acid has various effects on normal and malignant cells. Lymphokine-activated killer (LAK) activity can be derived from T lymphocytes and natural killer cells. This study shows that all trans retinoic acid significantly enhances this activity by increasing production of tumour necrosis factor and gamma interferon, which results in enhanced expression of the p55 part of the interleukin 2 receptor. This effect is dependent on the concentration of all trans retinoic acid and the length of time of culture.

Development of four donor-specific phenotypes in human long-term lymphokine-activated killer cell cultures

A series of 62 lymphokine-activated killer cell (LAK) cultures from 44 different donors was investigated for the distribution of various CD markers during a cultivation period of 3 weeks. Great differences in the phenotypic pattern were found between different donors, but similar changes of the subset pattern of various donors allowed a classification of the LAK cultures into four distinct LAK types. LAK type 1 was characterised by low numbers of CD3+ cells and high values for CD56+ cells. In LAK type 2 cultures gamma/delta TCR+ cells extensively proliferated, whereas in LAK type 3 cultures the CD57 and CD8 values increased considerably. LAK type 4 cultures did not show any of these characteristics. The resulting phenotype of a LAK culture was donor-specific, as LAK cultures established from the same peripheral blood mononuclear cells (PBMC), fresh or after cryopreservation, or from PBMC obtained from the same donor at different venous punctures, always developed the same phenotype. A clear correlation between phenotype and killing activity could only be found for LAK type 1 cultures, which always developed high lytic activity. Long-term IL-2 stimulation induced high levels of perforin-positive cells in LAK cultures but the perforin content did not correlate with the cytotoxicity. The transcription pattern for various cytokines only varied slightly between the cultures. Messenger RNA for granulocyte/macrophage- colony-stimulating factor, interferon gamma, tumour necrosis factor alpha, interleukin-4 (IL-4) and IL-5 were found in almost all cultures during the entire cultivation period, whereas mRNA for IL-2 was never detected. Most variations in the transcription pattern were observed for IL-6 and IL-7. However, no correlation could be found between the endogenous cytokine production and the phenotype or lytic activity of the LAK cultures. Further studies are required to determine the factors that cause lymphocyte subsets from a specific donor to proliferate preferentially under long-term IL-2 stimulation.

Immunomodulation in patients receiving intravenous Bryostatin 1 in a phase I clinical study: comparison with effects of Bryostatin 1 on lymphocyte function in vitro

Bryostatin 1 is a protein kinase C activator that inhibits growth of tumour cells and activates lymphocytes in vitro, properties that have encouraged its use in phase 1 clinical studies as an anticancer agent. We investigated interleukin-2(IL-2)-induced proliferation and lymphokine-activated killer (LAK) cell activity in peripheral blood mononuclear cells (PBMC) from cancer patients receiving Bryostatin intravenously. After Bryostatin administration both LAK generation and proliferation were enhanced when patients' PBMC were stimulated with IL-2 in vitro. However, when normal donors' PBMC were cultured in vitro in the presence Bryostatin and IL-2, LAK induction was inhibited while IL-2-driven proliferation was increased. These effects were also seen following only 2 h exposure to Bryostatin and could be elicited by conditioned medium from Bryostatin-pretreated cells. Neither IL-4 nor interferon gamma was detected in the conditioned medium. Bryostatin in vitro was found to increase expression of IL-2 receptors on CD4+, CD8+ and CD56+ cells and augment the proportion of CD8+ cells in conjunction with IL-2. We conclude that Bryostatin in combination with IL-2 in vitro enhances proliferation and IL-2 receptor expression on lymphocytes, favouring CD8+ cells while suppressing the generation of LAK activity. Intravenous administration of Bryostatin increases the potential of IL-2 to induce proliferation and LAK activity in lymphocytes which, taken together with its putative direct antitumour effect, makes Bryostatin an interesting candidate for clinical trials in combination with IL-2.

Lymphokine-activated killer cytotoxicity against pancreas adenocarcinoma cell lines and vascular endothelial cells

Eight pancreas carcinoma cell lines of duct cell origin (PCI-6, 10, 19, 24, 35, 43, 55, and 64) were established. Using one of these lines, PCI-24, human umbilical vein endothelial cells (HUVEC), and several recombinant cytokines, conditions and specificity of anti-PCI LAK induction were investigated, with the focus on a search for lymphokine-activated killer (LAK) activity that differentiates neoplastic (PCI) from non-neoplastic (HUVEC) cells. Interferon-gamma (IFN-gamma), IFN-alpha, IL-4, IL-6, and IL-7, but not tumor necrosis factor-alpha (TNF-alpha) or IL-1 beta, induced a weak LAK activity against PCI-24, whereas IL-2-induced (1000 U/mL) LAK exhibited a far more potent cytotoxicity. When these cytokines were added at the suboptimal dose IL-2 (100 U/mL), no significant augmentation in LAK activity was induced. Staphylococcal protein A (SpA) induced LAK activity as potent as that seen with IL-2 (1000 U/mL). Both IL-2-induced and SpA-induced LAK had a potent, dose-dependent cytotoxicity against HUVEC. HUVEC inhibited both IL-2- and SpA-induced LAK cytotoxicity against PCI-24 to almost the same extent as seen with PCI-24. Thus, two potent LAK-inducers did not generate LAK activity that differentiates neoplastic from non-neoplastic cells. Thus, in vitro cytotoxicity of LAK against non-neoplastic endothelial cells is unavoidable when handling cytokines in LAK induction.

Induction of lymphokine-activated killer activity in mice by prothymosin alpha

We have recently demonstrated that prothymosin alpha (ProT alpha) when administered intraperitoneally (i.p.) protects DBA/2 mice against the growth of syngeneic leukemic L1210 cells through the induction of tumoricidal peritoneal cells producing high levels of tumor necrosis factor alpha (TNF alpha) [Papanastasiou et al. (1992) Cancer Immunol Immunother 35: 145]. In this report we tested further immunological alterations that may be caused by the administration of ProT alpha in vivo. We demonstrate that i.p. injections of ProT alpha enhance natural killer (NK) cell activity and induce lymphokine-activated (LAK) activity in vivo. Thus, splenocytes from ProT alpha-treated DBA/2 animals exhibited significantly higher cytotoxic activity (up to threefold) against the NK-sensitive YAC cell line and the NK-resistant P815 and L1210 syngeneic tumor cells, as compared to splenocytes from syngeneic control mice. The enhancement of the cytotoxic profile of DBA/2 splenocytes was associated with increased percentages of CD8+ cells, NK cells and activated CD3+ cells. The ProT alpha-induced effect persisted for 30 days after the end of the ProT alpha treatment period and returned to normal levels 20 days later. Splenocytes from non-treated DBA/2 animals generated high NK and LAK activities in response to ProT alpha in vitro. The ProT alpha-induced NK and LAK activities reached 84% and 75% respectively of what was obtained with interleukin-2 (IL-2). High concentrations of TNF alpha and IL-2 were generated in response to ProT alpha in LAK cultures. These findings suggest that ProT alpha may provide an overall protective effect against tumor growth in vivo through induction of NK and LAK activities possibly indirectly via the production of IL-2 and TNF alpha in the spleen, peritoneal cavity and probably other lymphoid organs.

Role of enhanced cellular adhesion in IL-6-augmented lymphokine-activated killer-cell function

The authors demonstrated previously that a short-term treatment with IL-6 of lymphokine-activated killer (LAK) cells produces an increase in cytotoxic activity of CD56+/CD3- effector cells generated from human PBL as well as from human thymocytes. In the study described here, the mechanisms by which IL-6 enhances LAK cytotoxicity were examined. Like untreated LAK cells, IL-6-treated LAK cells require Ca++ to initiate cytolysis. However, IL-6 treatment of LAK cells does not alter the rate of programming for lysis. Instead, IL-6 increases target-binding capacity of CD56+/CD3- LAK cells in association with the increased cytotoxicity. Similar to target-binding of untreated LAK cells, the binding between IL-6-treated LAK cells and target cells is dependent on Mg++. Cellular adhesion molecules (CAM), CD11a-c, CD18, CD54, CD56, CD58 and CD2 (T11(1) epitope), are up-regulated in LAK cells by culture with IL-2. Among MoAbs to these CAMs, only Abs to CD11a/CD18 (LFA-1) and CD54 (ICAM-1) decrease both target-binding and cytolysis by LAK cells. IL-6 treatment changes neither the proportion nor the intensity of CAM positive cells. However, MoAbs to CD11a/CD18 and CD54 reduce both target-conjugation and cytotoxicity of IL-6-enhanced LAK cells to the same level as control LAK cells treated with the MoAbs. IL-6-enhanced LAK functions (both target-conjugation and target-lysis) are not abrogated by MoAbs to other CAM which do not inhibit standard LAK functions. These results indicate that IL-6 up-regulates cellular events mediated by CD11a/CD18 and CD54 molecules which are involved in standard LAK functions. These events may result in activation of lytic effector cells, associated with an increase in target-binding and an increase in cytotoxicity.

Melanoma-derived interleukin 6 inhibits in vivo melanoma growth

Malignant melanomas are capable of producing a wide range of cytokines with multiple biologic functions, including interleukin 6 (IL-6). We have observed an inverse relationship between IL-6 production of three B16-derived murine melanoma cell lines (NP133, HFH18, and HFH(M)) and the tumorigenicity of these melanoma cells in syngeneic mice. To further test the effect of IL-6 on melanoma growth, a non-IL-6-producing murine B16-derived melanoma cell line (HFH18) was transfected with a murine IL-6 expression vector, resulting in stable transfectants (HFH18/IL-6(+)) that expressed significant amounts of IL-6 mRNA and secreted high levels of bioactive IL-6. Syngeneic C57BL/6 mice inoculated subcutaneously with HFH18/IL-6(+) cells developed tumors that reached a final mean diameter of less than half the size of tumors that developed in mice inoculated with either HFH18 parental or HFH18 cells transfected with the IL-6 cDNA in the non-coding 3'-5' orientation (HFH18/IL-6(-) cells). In addition, mice bearing IL-6-producing HFH18/IL-6(+) tumors survived twice as long as mice bearing HFH18 parental or HFH18/IL-6(-) tumors. The specificity of melanoma growth inhibition by IL-6 was confirmed by the reversal of the slow-growing phenotype of HFH18/IL-6(+) cells by local peritumoral administration of neutralizing alpha-murine IL-6 antibody. IL-6-producing melanoma cells exerted a growth-inhibitory effect on distant parental tumors in a dose-dependent manner. The growth of HFH18/IL-6(+) melanomas was also decreased in nude mice, suggesting that melanoma-derived IL-6 may mediate this anti-tumor effect independently of a normal host B- and T-cell immune response. Thus, melanoma-derived IL-6 exerts a significant inhibitory effect on cutaneous melanoma growth and progression. These results indicate that melanoma cytokines may have a profound effect on tumor pathogenesis.

Immune function of patients receiving recombinant human interleukin-6 (IL-6) in a phase I clinical study: induction of C-reactive protein and IgE and inhibition of natural killer and lymphokine-activated killer cell activity

Interleukin-6 (IL-6) is a cytokine that acts on a variety of cell types, including myeloid progenitor cells and B and T lymphocytes. It has been found to activate cytotoxic T cells and natural killer (NK) cells and to induce T-cell-mediated antitumour effects in animal models. In a phase I clinical trial of recombinant human IL-6, 20 patients with advanced cancer were entered to receive daily subcutaneous injections of IL-6 over 7 days followed by a 2-week observation period and another 4 weeks of daily IL-6 injections. Doses varied between 0.5 microgram/kg and 20 micrograms/kg body weight and immune functions were monitored throughout. At all dose levels IL-6 administration led to a marked increase in serum levels of C-reactive protein and a moderate rise in complement factor C3. The proportions of CD4, CD8 or HLA-DR lymphocytes in peripheral blood did not alter with IL-6 treatment nor did the in vitro proliferation of peripheral blood mononuclear cells induced by either phytohaemagglutinin, pokeweed mitogen or fixed Staphylococcus aureus. By contrast, NK cell activity, lymphokine-activated killer (LAK) cell activity and proliferation induced by in vitro culture with interleukin-2 (IL-2) were suppressed at doses exceeding 2.5 micrograms/kg. Serum IgE levels were consistently elevated over the IL-6 dose range but IgM, IgG and IgA levels were unaffected. In summary there is a dose-dependent induction of acute-phase proteins by in vivo IL-6 treatment. At higher IL-6 doses there is a suppressive effect on NK and LAK activity measured in vitro. IL-6 may thus be useful in combination cytokine therapies that seek to suppress LAK and favour cytotoxic T lymphocyte responses. The rise in IgE levels in response to IL-6 was unexpected and suggests a more pivotal role than previously known for the control of IgE production; this could include IgE-related diseases.

Enhancing effect of natural killer cell stimulatory factor (NKSF/interleukin-12) on cell-mediated cytotoxicity against tumor-derived and virus-infected cells

Natural killer cell stimulatory factor (NKSF) or interleukin-12 (IL-12) is a heterodimeric cytokine with pleiomorphic effects on T and NK cells, including induction of lymphokine production, mitogenesis, and enhancement of spontaneous cytotoxic activity. Similarly to IL-2, NKSF/IL-12 enhances NK cell-mediated cytotoxicity within a few hours and independently from induced proliferation. This effect is independent from other induced cytokines, because it is not prevented by antibodies neutralizing interferon (IFN)-alpha, IFN-beta, IFN-gamma, IL-2 or tumor necrosis factor (TNF)-alpha and, unlike the induction of IFN-gamma production by peripheral blood lymphocytes, it does not require HLA class II-positive accessory cells. Enhanced cytotoxicity is accompanied by morphologic changes in NK cells, including a significant increase in the number of cytoplasmic granules. In addition to the previously described ability to enhance the cytotoxic activity of NK cells against tumor-derived target cells, NKSF/IL-12 is also a potent stimulator of cytotoxicity against virus-infected cells, either fibroblasts acutely infected with herpes viruses or T cell lines chronically infected with human immunodeficiency virus-1. NK cell-mediated antibody-dependent cytotoxicity or anti-CD16 antibody-redirected lysis is not significantly enhanced by NKSF/IL-12. However, the ability of resting peripheral blood T cells to mediate anti-CD3 antibody-redirected lysis is enhanced by 18-h incubation with NKSF/IL-12, indicating that this lymphokine can modulate the cytotoxic capability of both NK and T cells.

Transfer of the IL-6 gene into a human colorectal carcinoma cell line and consequent enhancement of tumor antigen expression

cDNA encoding the human IL gene (580 bp), inserted into a retroviral expression vector carrying neomycin resistance selective marker, was introduced into HT-29 human colon carcinoma cells by lipofection. Interleukin-6 activity was measured by ELISA and bioassay using B9 cells. Interleukin-6 secreted by transfected HT-29 cells was shown to be biologically active. The expression of the human tumor associated antigen CEA (carcinoembryonic antigen), HLA classes I and II, and ICAM-1 antigens in the transfected HT-29 cells were also analyzed by flow cytometry. Significant enhancement in the expression of CEA but not in the expression of HLA class I, HLA class II and ICAM-1 antigens, was observed in the transfected HT-29 cells as compared to the parental HT-29 cells. These results provide experimental evidence that enhancement of tumor antigen expression on tumor cells can be induced by IL-6 gene transfection, and suggest another potential role for the use of IL-6 gene transfer in the immunotherapy of human cancers.

Thymostimulin enhances the natural cytotoxic activity of patients with transitional cell carcinoma of the bladder

We have investigated the effect of thymostimulin on the major histocompatibility (MHC) unrestricted cytotoxic activity of peripheral blood mononuclear cells (PBMNC) from patients with superficial transitional cell carcinoma (TCC) of the bladder. PBMNC from patients and healthy controls were incubated in the presence of thymostimulin for varying periods of time (2 or 18 h or 5 days), and were used as effectors against 51Cr-radiolabeled natural killer (NK)-sensitive (K-562) and NK-resistant (JY) target cells in cytotoxic assays. In 6 out of 14 patients analyzed, thymostimulin enhanced the cytotoxic activity of PBMNC against NK-sensitive target cells in a dose-dependent manner. This cytotoxic inducer effect of thymostimulin was maximal after 18 h of culture. Thymostimulin failed to induce lytic activity in PBMNC from TCC patients against NK-resistant target cells. We also found that thymostimulin could synergize with interleukin-2 in inducing non-MHC restricted cytotoxic activity in PBMNC from TCC patients. In conclusion, we have demonstrated that thymostimulin can enhance the natural killer cytotoxic activity of PBMNC from patients with TCC of the bladder.

Temporal sequence and cellular origin of interleukin-2 stimulated cytokine gene expression

A study of activation of the cytokine network by interleukin 2, IL-2, may provide a rationale for devising cytokine combination and cytokine antagonist treatments with increased anti-tumour efficacy and decreased toxicity. We have investigated the expression of mRNA for 13 cytokines and three transcription factors during in vitro culture of peripheral blood mononuclear cells, PBMC, with IL-2. A consistent pattern of induction was seen in nine individuals, with early (2-24 h) induction of IL-1 beta, IL-6, tumour necrosis factor, TNF, lymphotoxin, LT, and gro. TNF and LT mRNA was expressed continually throughout culture, but levels of mRNA for IL-1 beta, IL-6, and gro declined by 24-48 h. After 48 h, PBMC began to express mRNA for IFN-gamma, IL-5, GM-CSF, and M-CSF. At 15 min to 1 h post IL-2 mRNA for c-fos, c-jun, and c-myc, and TNF was induced in three individuals studied. IL-4, IFN-alpha, and IL-1 alpha mRNA was not detected. Only a minority of cells expressed mRNA for TNF, IL-1 beta, IL-6 and IFN-gamma, and monocytes were the main source. Levels of cytokine protein in culture supernatants mirrored the pattern of mRNA induction. This in vitro model shows clear parallels with the reported in vivo production of cytokines during IL-2 therapy, and may prove useful in designing new therapeutic strategies.

Antitumor effects of recombinant interleukin-6 expressed in eukaryotic cells

In the present study we evaluate the antitumor efficacy of a glycosylated molecule of interleukin-6 (IL-6), which was cloned and expressed in Chinese hamster ovary cells. When tested with two syngeneic murine tumors, the MC38 adenocarcinoma and the MCA106 fibrosarcoma, recombinant IL-6 (rIL-6) significantly reduced the number of day-3 established MC38 lung metastases, but had no effect on MCA106 lung metastases. A similar effect of rIL-6 was seen on day-3 MC38 liver metastases. The antitumor activity mediated by rIL-6 was achieved at doses of the cytokine ranging from 6 micrograms to 150 micrograms/day. There was no correlation between the responsiveness to rIL-6 of these two tumors and their susceptibility, in vitro, to a direct cytostatic effect of the cytokine or the increase in the expression of major histocompatibility complex (MHC) antigens after exposure to rIL-6. However, a correlation was seen between the antitumor response to rIL-6 and the initial number of tumor cells expressing MHC antigens. The possible role of MHC antigens expressed on tumor cells, the generation of MHC-restricted cytotoxic cells and the responsiveness to IL-6 are discussed.

Tumour cell inhibition of macrophage cytokine activity

Macrophages elaborate both effector and regulatory immune functions. It was hypothesised that tumours can exert a local alteration of macrophage function. Murine peritoneal macrophage-derived cytokines were assayed in the presence and absence of cells, cytosol fractions or conditioned media (TCCM) from established murine tumour lines. Interleukin-1 beta, interleukin-6 and tumour necrosis factor-alpha activities were significantly inhibited by tumour cells or their products, as were the corresponding recombinant human cytokines. Intracellular protein kinase C activation was also measured and was significantly inhibited by murine TCCM, thus suggesting one possible site of inhibitor action. Data analyses indicate that the inhibitory factor(s) is probably not an already well-characterised macrophage inhibitor.

IL-6 enhances the cytotoxic activity of thymocyte-derived CD56+ cells

Thymocyte-derived lymphokine-activated killer (LAK) cells were used as a model for the study of the cytokine driven development of cytotoxicity. These cells are devoid of initial cytotoxic activity but upon culture in IL-2 they develop into cytotoxic effectors. The parameters of the response of thymocytes to IL-6 are similar to that of PBL in that IL-6, at concentrations as low as 1 mu/ml, increases cytotoxicity of thymocyte-LAK cells when generated in low doses (25-50 mu/ml) of IL-2. IL-6-enhanced thymocyte-LAK cytotoxicity is observed when tested against both NK-resistant and NK-sensitive tumor cell lines. IL-6 alone does not induce any cytotoxicity from thymocytes nor does IL-6 change the time course of thymocyte-LAK cell generation in IL-2 culture. IL-6 does not affect DNA synthesis, total cell number, proportion of CD56+ cells, or the expression of IL-2R (both P55 and P75 glycoproteins) in IL-2-cultured thymocytes. Instead, IL-6 used to treat mature thymocyte-LAK effector cells for as little as 1 hr prior to 51Cr-release assay increases LAK cytotoxicity. This enhancement is abrogated by pretreatment of effector cells with cycloheximide, suggesting that protein synthesis is required for IL-6 to enhance LAK cell activity. The precursor phenotypes of IL-6-responsive thymocyte-LAK cells are CD3-/CD5-. The effector phenotypes of IL-6-enhanced thymocyte-LAK cells are CD5-/CD56+. Thus, IL-6 depends on synthesis of rapid-turnover proteins to act on mature CD56+/CD5- LAK cells to increase their cytotoxic function.

Treatment of malignant melanoma and renal cell carcinoma with recombinant human interleukin-2: analysis of cytokine levels in sera and culture supernatants

In this study we evaluated the clinical response of 12 patients with malignant melanoma and renal cell carcinoma (RCC) following administration of recombinant human interleukin-2 (rhIL-2) by continuous infusion. Serum samples taken before, during and following sequential courses of IL-2 were assayed for the presence of tumour necrosis factor alpha (TNF-alpha) IL-1 alpha, IL-6 and interferon gamma (IFN-gamma) and the presence or changes in these cytokines were examined with respect to clinical response data: our results did not show any direct correlation between the parameters measured and clinical outcome. In addition, peripheral blood mononuclear cells (PBMC) derived from 3 RCC patients were cultured in a serum-free environment and the resulting supernatants assayed for the production of these cytokines and compared to the corresponding serum levels. During one or more courses of treatment only 1 patient, who had metastatic bone disease, demonstrated detectable serum TNF-alpha; serum IL-6 levels were elevated in a proportion of all patients studied and a sustained IL-6 response occurred in a patient who had complete disease remission; IL-1 alpha was detected in the serum of 3 RCC patients; IFN-gamma could not be detected in any serum sample tested. Cytokine levels in sera and supernatants derived from 3 RCC patients were compared but no correlation was found: TNF-alpha and IL-6 were shown to be present at much higher concentrations in supernatants when compared to sera whereas the levels of IL-1 alpha were almost undetectable. This lack of correlation is probably due to the presence of "interfering" proteins in sera which either depress or enhance the ability to detect cytokines in sera using enzyme immunoassays.

Characteristics of interleukin-6-enhanced lymphokine-activated killer cell function

To study the effect of IL-6 on the development of cytotoxic cells, we examined lymphokine-activated killer (LAK) activity generated from human nonadherent PBL. Addition of rIL-6 at the initiation of 5-day PBL cultures significantly increases LAK activity in the presence of low concentrations (between 5 and 25 u/ml) of rIL-2. RIL-6 alone induces no PBL LAK activity but at doses as low as 0.8 u/ml rIL-6 enhances LAK activity with optimal enhancement of LAK at 5.0 u/ml of rIL-6. This enhancement is independent of effects on cells growth as rIL-6 did not affect the cell recovery of PBL cultured in rIL-2. RIL-6-enhanced LAK is mediated by the same type of effector cells as those of LAK from rIL-2 alone with effector cells primarily generated from large granular CD3-negative E rosetting lymphocytes. RIL-6 does not change the time course of LAK development and pretreatment of PBL with rIL-6 has no effect on the PBL response to subsequent rIL-2 induction of LAK. Addition of rIL-6 to LAK cultures 2 hr before the cytotoxicity assay shows equal enhancement as addition at the initiation of the culture. However, rIL-6 requires the presence of both rIL-2 and another factor in the supernatant from LAK cultures in order to enhance LAK. Our results indicate that IL-6 can modulate LAK activity at a very late stage of LAK development, and that the enhancement by IL-6 is dependent on the presence of IL-2 and another soluble factor generated during rIL-2 culture.

Interleukin-6 does not support interleukin-2 induced generation of human lymphokine-activated killer cells

The activity of lymphokine-activated killer (LAK) cells is supported by various cytokines. The objective of this study was to see if recombinant interleukin-6 (IL-6) either alone or in combination with interleukin-2 (IL-2) has any effect on the generation of LAK cells. Peripheral blood mononuclear cells of healthy donors were cultured for 4 or 6 days with both cytokines either alone or in combination. LAK activity against K562 and natural killer-resistant Daudi cells was assessed by a 4-h and an 18-h 51Cr-release assay at various effector to target ratios. IL-6 alone in increasing concentrations did not induce LAK cell activity. Neither additive nor synergistic effects of IL-6 with IL-2 were observed. Immunofluorescence analysis with phycoerythrin-conjugated anti-CD56 antibody demonstrated that IL-6 could not maintain or increase the number of CD56-positive cells over a 6-day culture period. These results suggest that IL-6 does not support LAK cell generation by itself or increase LAK cell activity in combination with IL-2.

Human recombinant interleukin-6 enhances antibody-dependent cellular cytotoxicity of human tumor cells mediated by human peripheral blood mononuclear cells

The effects of human recombinant interleukin-6 (hrIL-6) on antibody-dependent cellular cytotoxicity (ADCC) activity mediated by human peripheral blood mononuclear cells (PMNC) were investigated. Human PMNC were preincubated for 24 h with various concentrations of hrIL-6 and were used as effector cells in a 4-h 51Cr-release assay. The ability of hrIL-6 to augment ADCC was measured using anti-colorectal carcinoma mAbs D612, 17.1A and 31.1 (each directed against a distinct tumor antigen) and using three human colorectal carcinoma cell lines, LS-174T, WiDr and HT-29, as targets. A significant increase in ADCC activity was observed after PMNC were preincubated in 100-400 U/ml but not in lower concentrations of hrIL-6. Variations in activities of PMNC among donors were observed. Non-specific mAb showed no effect in augmenting ADCC activity. hrIL-6 treatment did not augment non-specific (non-mAb-mediated) cytotoxicity. The enhancement of ADCC activity was blocked by the addition of an antibody against hrIL-6 but not by an antibody to the IL-2 receptor (capable of blocking the induction of lymphokine-activated killer cell cytotoxicity by IL-2), suggesting that hrIL-6 augmentation of ADCC activity may not be mediated through IL-2. These results demonstrate that hrIL-6 augments ADCC activity of human PMNC using mAbs to human tumor antigens and human tumor cells as targets, suggesting a potential role for IL-6 in combination with anti-cancer antibodies for cancer immunotherapy.

Suppression of lymphokine-activated killer (LAK) cell induction mediated by interleukin-4 and transforming growth factor-beta 1: effect of addition of exogenous tumour necrosis factor-alpha and interferon-gamma, and measurement of their endogenous production

Recombinant human interleukin-4 (rhIL-4) and transforming growth factor-beta 1 (TGF-beta 1) suppressed the induction of lymphokine-activated killer (LAK) activity induced by recombinant human interleukin-2 (rhIL-2) in peripheral blood lymphocytes. DNA synthesis and the expression of the p55 alpha chain of the IL-2 receptor (Tac antigen) were also inhibited. The inhibitory effect was greatest when these factors were added during the first 48 h of a 4-day culture, with reduced cytolytic activity against both natural killer (NK) resistant and NK-sensitive tumour cell line targets. The suppressive action of both cytokines was accompanied by a reduction in tumour necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma) levels in lymphocyte culture supernatants. Recombinant human IFN-gamma (rhIFN-gamma), but not recombinant human TNF-alpha (rhTNF-alpha) was able to overcome the inhibitory effect of recombinant human interleukin-4 (rhIL-4) on LAK induction and DNA synthesis but not Tac antigen expression. However, cytotoxicity induced by rhIFN-gamma alone was also suppressed by rhIL-4 and TGF-beta 1, inferring that rhIFN-gamma-mediated abrogation of rhIL4 suppression was not simply a direct IL-2-independent effect on cytotoxicity. In addition, rhIL-4 did not increase TGF-beta production from rhIL-2-activated peripheral blood mononuclear cells, suggesting that rhIL-4 did not mediate reduction of rhIL-2 responses through the induction of TGF-beta release.