Growth regulatory functions of IL6 and antitumour effects

Analysis of IL6-protein complexes in chondrosarcoma

Cytokines produced in the tumour microenvironment serve important roles in cancer pathogenesis or in the supression of disease progression. Metastatic chondrosarcoma is a cancer of the cartilage, and our group previously reported from a human ELISA assay that interleukin 6 (IL6) expression in JJ012 chondrosarcoma cells was 86-fold lower than that in C28 chondrocytes, indicating its role as an anti-inflammatory and anti-tumorigenic factor. Additionally, to the best of our knowledge, the study was the first to demonstrate downregulation of IL6 in a human chondrosarcoma cell line. To fully elucidate the effect of this IL6 downregulation, it is important to identify protein complexes and components that bind IL6 and potentially affect its gene expression directly or indirectly. To investigate IL6-protein interactions leading to these differences in IL6 expression, the current study performed a gel retardation electrophoretic mobility shift assay (EMSA), followed by 2D gel phoresis, in-gel trypsin digestion and proteomic mass spectral analysis. The results indicated a presence of ubiquitination enzymes in C28 chondrocytes, while none were identified in JJ012 chondrosarcoma cells. While it seems counterintuitive, it may be that the absence of ubiquitination of certain factors leads to the downregulation of IL6 expression in human chondrosarcoma. Therefore, dysregulated ubiquitination may be among the possible mechanisms for the markedly reduced IL6 expression in chondrosarcoma.

Effect of cytostatic proline rich polypeptide-1 on tumor suppressors of inflammation pathway signaling in chondrosarcoma

Cytokines produced in the tumour microenvironment exert an important role in cancer pathogenesis and in the inhibition of disease progression. Cancer of the cartilage is termed metastatic chondrosarcoma; however, the signaling events resulting in mesenchymal cell transformation to sarcoma have yet to be fully elucidated. The present study aimed to characterize the cytokine expression profile in the human JJ012 chondrosarcoma cell line, as well as the effect of cytostatic proline-rich polypeptide-1 (PRP-1). Western blot experiments demonstrated that the levels of suppressor of cytokine signaling 3 (SOCS3) were upregulated in chondrocytes compared with chondrosarcoma cells. Addition of PRP-1 restored the expression of the tumor suppressors, SOCS3 and ten-eleven-translocation methylcytosine dioxygenase 1 and 2 (TET1/2), in a dose-responsive manner. It is known that methylation of histone H3K9 was eliminated from the promoters of the inflammation-associated genes. PRP-1 inhibited H3K9 demethylase activity with an IC₅₀ (concentration required to give half-maximal inhibition) value of 3.72 µg/ml in the chondrosarcoma cell line. Data obtained from ELISA experiments indicated that the expression of interleukin-6 (IL-6) in chondrosarcoma cells was 86-fold lower compared with that in C28 chondrocytes. In the present study, a 53-fold downregulation of IL-6 expression in co-culture of chondrosarcoma cells and C28 chondrocytes was identified as well. Downregulation of IL-6 expression has been documented in numerous other tumor types, although the reasons for this have not been fully established. In chondrosarcoma, IL-6 manifests itself as an anti-inflammatory agent and, possibly, as an anti-tumorigenic factor. To explore protein-DNA interactions leading to such differences, a gel-shift chemiluminescent assay was performed. Gel shifts were observed for chondrosarcoma and chondrocytes in the lanes that contained nuclear cell extract and oligo-IL-6 DNA. Notably, the DNA-protein complexes in C28 chondrocytes were markedly larger compared with those in chondrosarcoma cells. The mechanisms that underpin such differences, and characterization of the interacting proteins, remain to be fully elucidated.

Macrophage activation for the production of immunostimulatory cytokines by delivering interleukin 1 via biodegradable microspheres

Interleukin 1alpha (IL-1alpha), a pleiotropic cytokine with multiple anti-tumour activities, has been investigated in our laboratory for its potential to serve as an immunotherapeutic agent. In the present study, an attempt was made to direct IL-1alpha to macrophages, in order to induce their immunoregulatory activities. For that purpose, IL-1alpha was encapsulated within biodegradable poly(lactic/glycolic acid) microspheres, 1-5 microm diameter in size. The microspheres were efficiently taken-up by macrophages in culture and after intraperitoneal injection into mice. In culture, phagocytosis of the microspheres reached saturation within 3 h and there was no apparent effect of polymer type on the extent of uptake. In vivo uptake of human IL-1alpha-microspheres by the macrophages lead to cell activation, as evidenced by the enhanced production of murine IL-1alpha, IL-6 and IL-12. Control microspheres, containing bovine serum albumin, induced only background to low levels of cytokine production. These cytokines, when expressed by or secreted from macrophages, may stimulate in situ diverse immune and inflammatory responses, including T cell-mediated immune responses, such as the development of Th(1)cells and cytotoxic lymphocytes. Thus, directing IL-1alpha into macrophages, via the appropriate microspheres, may serve as a unique mean to activate these cells to participate in anti-tumour immune responses in situ.

Response to IL-6 of HPV-18 cervical carcinoma cell lines

The human papillomavirus type 18 (HPV-18) upstream regulatory region (URR) controls cell type-specific expression of the viral oncoproteins E6 and E7. The HPV-18 URR is active in the cervical carcinoma cell line HeLa but inactive in the hepatoma cell line HepG2. C/EBPss (NF-IL-6) was shown to participate as an important regulator in HPV transcription dependent on the cell type. The finding that C/EPBss is critical for HPV-18 URR activity and that C/EPBss is induced by IL-6 offers the opportunity of manipulating HPV activity by specific cytokine treatment. In this report, we show that treatment with IL-6 results in activation of HPV-18 URR activity in HepG2 cells. In contrast, the HPV-18 URR is not inducible by IL-6 in three cervical carcinoma cell lines. In all three cell lines we found decreased expression of the IL-6 receptor compared to the IL-6-responsive HepG2 cells, whereas the level of expression of the signal transduction component gp130 is present in all cells. These results suggest that cervical carcinoma cells may circumvent the IL-6-induced cellular defense mechanism through downregulation of the IL-6-receptor.

Recombination signal sequence binding protein Jkappa is constitutively bound to the NF-kappaB site of the interleukin-6 promoter and acts as a negative regulatory factor

Analysis by electrophoretic mobility shift assays (EMSA) of the different proteins associated with the kappaB sequence of the interleukin-6 (IL-6) promoter (IL6-kappaB) allowed us to detect a specific complex formed with the recombination signal sequence binding protein Jkappa (RBP-Jkappa). Single-base exchanges within the oligonucleotide sequence defined the critical base pairs involved in the interaction between RBP-Jkappa and the IL6-kappaB motif. Binding analysis suggests that the amount of RBP-Jkappa protein present in the nucleus is severalfold higher than the total amount of inducible NF-kappaB complexes but that the latter bind DNA with a 10-fold-higher affinity. A reporter gene study was performed to determine the functional implication of this binding; we found that the constitutive occupancy of the IL6-kappaB site by the RBP-Jkappa protein was responsible for the low basal levels of IL-6 promoter activity in L929sA fibrosarcoma cells and that RBP-Jkappa partially blocked access of NF-kappaB complexes to the IL-6 promoter. We propose that such a mechanism could be involved in the constitutive repression of the IL-6 gene under normal physiological conditions.

Interleukin 6 gene-transfected mouse mammary adenocarcinoma: tumour cell growth and metastatic potential

Cells from the spontaneous metastatic TSA mammary adenocarcinoma of BALB/C mouse were transfected with the murine (interleukin-6) IL6 gene. The clone (TSA-IL6) secreting the largest amount of IL6 displayed an in vitro increased growth rate compared with that of TSA cells transfected with the neomycin resistance gene only (TSA-neo). TSA-IL6 cell colonies consisted mainly of fusiform cells and TSA-neo colonies of polygonal cells. When subcutaneously (s.c.) injected in syngeneic mice, TSA-IL6 cells gave rise to tumours that grew significantly slower than TSA-neo cell tumours. Microscopically, TSA-IL6 tumours displayed a fascicular pattern of growth, associated with a very scanty macrophage infiltrate. S.c. TSA-IL6 tumours were significantly less metastatic than TSA-neo tumours. By contrast, following intravenous (i.v.) challenge, TSA-IL6 cells produced 5-7 times more lung metastases than TSA-neo cells. The i.v. TSA-IL6 cell lung metastases showed a marked macrophage infiltrate and a rich vascularization. The high in vitro TSA-IL6 cell growth rate is attributable to the IL6-induced production of growth factors, some of which possess heparin-binding properties, such as amphiregulin. The differences in vascularization and macrophage infiltrate may underlie the observed differences between s.c. TSA-IL6 tumour growth with low spontaneous metastatic potential and the widespread growth of i.v. metastasis.

Recombinant human interleukin 6 in metastatic renal cell cancer: a phase II trial

A phase II trial investigating the anti-tumour effects of recombinant human interleukin 6 (rhIL-6) in patients with metastatic renal cell cancer was carried out. RhIL-6 (150 microgram) was administered as a daily subcutaneous injection for 42 consecutive days on an outpatient basis. Forty-nine patients were studied, 12 with and 37 without previous immunotherapy. Forty patients were evaluable for response. A partial remission was noted in two patients, stable disease in 17 and progressive disease in 21. Toxicity was moderate and reversible and consisted mainly of fever, flu-like symptoms, nausea, weight loss and hepatotoxicity. Anaemia, leucocytosis and thrombocytosis and induction of acute phase protein synthesis were noted in most patients. In 15% of the patients anti-IL-6 antibodies developed, and were neutralising in only one patient. Baseline plasma IL-6 concentrations did not correlate with tumour behaviour before or after rhIL-6 treatment. In conclusion, rhIL-6 can be safely administered on an outpatient basis for prolonged period of time and has moderate, reversible toxicity. Its administration induces IL-6-antibody production in only a minority of patients. Antitmour effects of rhIL-6 in metastatic renal cancer are limited.

In vivo cytokine gene transfer by gene gun reduces tumor growth in mice

Implantation of tumor cells modified by in vitro cytokine gene transfer has been shown by many investigators to result in potent in vivo antitumor activities in mice. Here we describe an approach to tumor immunotherapy utilizing direct transfection of cytokine genes into tumor-bearing animals by particle-mediated gene transfer. In vivo transfection of the human interleukin 6 gene into the tumor site reduced methylcholanthrene-induced fibrosarcoma growth, and a combination of murine tumor necrosis factor alpha and interferon gamma genes inhibited growth of a renal carcinoma tumor model (Renca). In addition, treatment with murine interleukin 2 and interferon gamma genes prolonged the survival of Renca tumor-bearing mice and resulted in tumor eradication in 25% of the test animals. Transgene expression was demonstrated in treated tissues by ELISA and immunohistochemical analysis. Significant serum levels of interleukin 6 and interferon gamma were detected, demonstrating effective secretion of transgenic proteins from treated skin into the bloodstream. This in vivo cytokine gene therapy approach provides a system for evaluating the antitumor properties of various cytokines in different tumor models and has potential utility for human cancer gene therapy.