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Immunology |
Departments of 1 Immunology and Cell Biology and 2 Oncology, "Mario Negri" Institute; 3 Department of Obstetrics and Gynecology, University of Milano Bicocca, Hospital S. Gerardo; 4 START Project, European Institute of Oncology; 5 Southern Europe New Drugs Organization, Milan, Italy; and 6 Pharmamar, Madrid, Spain
Requests for reprints: Paola Allavena, Istituto Ricerche Farmacolgiche Mario Negri, Via Eritrea 62, 20152 Milano, Italy. Phone: 39-02-390141; Fax: 39-02-39014596; E-mail: allavena{at}marionegri.it.
| Abstract |
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Key Words: macrophages tumor-associated macrophages inflammatory cytokines Yondolis ovarian cancer
| Introduction |
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Although the precise mode of action of Yondelis has yet to be determined, there is strong biological and biochemical evidence that it is distinct from other anticancer drugs. Yondelis forms adducts in the minor groove of DNA and binds guanine at the N2 position, whereas most alkylating agents bind guanine at position N7 or O6 in the major groove (8, 9). This binding profoundly affects DNA structure, bending it toward the major groove, as shown by nuclear magnetic resonance spectroscopy. Moreover, Yondelis induces nonp53-dependent apoptosis and produces a cell cycle block in late S and G2-M phases (10).
A peculiar aspect of Yondelis is that the drug is less effective against cell lines deficient in nucleotide excision repair, which are hypersensitive to UV and other DNA-damaging agents (1012). In this respect, Yondelis is unique and different from all other DNA-interacting compounds investigated to date.
Early studies have identified that Yondelis interferes with transcriptional activation of the CCAAT box factor NF-Y in a promoter-specific manner (13, 14). More recently, other genes and transcriptional inducers indicate that Yondelis may be a more general inhibitor of activated but not basal transcription (15, 16). NF-Y is considered a transcription factor of major importance in the differentiation of monocytes to macrophages (17). Because it is unknown whether Yondelis affects these immune cells, this study was initiated to specifically investigate the effects of Yondelis on mononuclear phagocytes.
Monocyte/macrophages are recognized as important components of innate immunity. Circulating monocytes are versatile precursors with the ability to differentiate into the various forms of specialized macrophages (17). The cytokine milieu profoundly affects the differentiation and function of tissue macrophages. Recently, a functional polarization has been defined (18, 19). Macrophages activated by bacterial products and Th1 cytokines [e.g., lipopolysaccharide and IFN-
] are regarded as M1 or classically activated macrophages, with high bactericidal activity and cytotoxic function against tumor cells. On the other hand, macrophages activated by Th2 cytokines [e.g., interleukin (IL)-4 and IL-13] or immunosuppressors (e.g., corticosteroids, vitamin D3, and IL-10) are defined as M2 macrophages, with low cytotoxic functions but high tissue-remodeling activity. Schematically, whereas M1 cells have immunostimulatory properties and defend the host against pathogenic infections, M2 cells attenuate the acute inflammatory reaction, potently scavenge cellular debris, and secrete a variety of growth and angiogenic factors essential to repair the injured tissues. Thus, both polarized subsets serve important physiologic functions; however, when their activation (especially that of M1 macrophages) persists over time, pathologic conditions and tissue injury may occur. Indeed, the continuous production of proinflammatory mediators by mononuclear phagocytes has been implicated in the onset and progression of several chronic inflammatory diseases (1719).
Several lines of evidence suggest a strong association between chronic inflammation and increased susceptibility to cancer (2024). It has been estimated that up to 20% of all tumors arise from conditions of persistent inflammation due to chronic infections or other causes (20). The prominent role of inflammatory mediators has been shown in several studies. In mouse models of skin carcinogenesis, deletion of selected proinflammatory cytokines reduced tumor susceptibility (25). More recently, the activation of the transcription factor nuclear factor kB (NF
B) has been implicated in the formation and progression of inflammation-associated tumors (22).
Macrophages infiltrating the tumor tissue, or tumor-associated macrophages (TAM), constitute a peculiar macrophage population. The role of TAMs in the tumor microenvironment and tumor development is complex and multifaceted, as suggested in the "macrophage balance hypothesis" (26). Unlike M1 macrophages, there is limited evidence that TAMs can be directly tumoricidal and induce tumor-reactive T cells. On the contrary, a growing body of evidence indicates that TAMs are skewed toward M2 macrophages and produce a variety of growth and angiogenic factors as well as immunosuppressive molecules [e.g., IL-10 and transforming growth factor ß (19, 2629)]. Thus, the presence of TAMs at the tumor site and the continuous expression of their products may favor, rather than antagonize, tumor progression.
In view of these findings, there is increasing interest in defining new therapies aimed at reducing the persistent activation of macrophages and their release of proinflammatory and protumor mediators. In this study we show that blood monocytes are selectively susceptible and undergo apoptosis at therapeutic concentrations of Yondelis, a novel and original antitumor agent. In addition, at subcytotoxic concentrations, this compound significantly inhibits the in vitro macrophage differentiation and the production of two inflammatory mediators, IL-6 and CCL2. These anti-inflammatory properties of Yondelis may be an extended mechanism of its antitumor activity.
| Materials and Methods |
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(500 IU/mL), or IL-4 (20 ng/mL; Schering Plough, Kenilworth, NJ) for 24 hours. TAMs and tumor cells were isolated from the ascitic fluid of patients with diagnosed ovarian adenocarcinoma who were admitted to the Clinical of Obstetrics and Gynecology of the University of Milan Bicocca, Milan, Italy. Cells contained in the ascitic fluid were centrifuged and isolated by Ficoll and Percoll gradients as previously described (31). Purity of TAM and tumor cell preparations was usually >65 ± 10% as defined by morphology and phenotype analysis. Cells were treated with Yondelis at the indicated concentrations and cultured for 1 to 5 days, as specified. At the end of the incubation period cells were collected, washed, and used for DNA analysis or functional assays.
Determination of cell viability. Cell viability was analyzed by DNA content in flow cytometry. Cells exposed to treatments were fixed with 70% ethanol, washed in PBS, and stained with propidium iodide (PI) solution containing 10 µg/mL PI in PBS and 25 µL RNase (10,000 units) overnight in the dark. PI incorporation was evaluated on at least 20,000 cells per sample using a FACS Calibur instrument (Becton Dickinson, Sunnyvale, CA), with a band-pass filter at 620 nm. Apoptosis was detected by staining with Annexin V and PI. Fluorescence-activated cell-sorting analysis was done using a band-pass filter, 530 and 620 nm for green (Annexin V) and red (PI) fluorescence, respectively, in combination with a 570-nmol/L dichroic mirror.
Phenotype analysis. Expression of cell membrane markers was done by immunofluorescence and analyzed by flow cytometry. Cells were incubated with anti-CD16 (clone B73.1), anti-CD68 (clone KP1, DAKO), anti-CD206/mannose receptor (clone PAM-1; ref. 30), and FITC-goat anti-mouse immunoglobulin. At least 10,000 cells were analyzed.
Antineoplastic agents. Yondelis was obtained from Pharmamar SA (Madrid, Spain), cisplatin from Sigma Chemical Co. (St. Louis, MI), doxorubicin from Pfizer (Milan, Italy), and taxol from Bristol-Myers Squibb (New York, NY).
Cytokine production. Supernatants of untreated cells or cells treated with Yondelis or other antineoplastic agents were collected after 16 hour culture and frozen. Monocytes, macrophages, and TAMs were stimulated with 100 ng/mL lipopolysaccharide to induce maximal cytokine production. Determination of cytokine CCL2, tumor necrosis factor (TNF
), and IL-6 was done by specific ELISA following the manufacturer's instructions (R&D Systems, Minneapolis, MN).
Tumor patients. Patients with ovarian cancer undergoing phase II trial with Yondelis were admitted to the European Oncology Institute, Milan, Italy. Patients received Yondelis (1,300 µg/m2) in a 3-hour infusion. Dexamethasone was also administered to reduce drug toxicity (4-10 mg). Blood withdrawal was done under informed consent following procedures approved by the ethical board. Blood samples (40 mL) were collected immediately before treatment and at the end of the infusion (+3 hours). Blood samples were immediately processed and Percoll-purified monocytes (usually 106 cells) were cultured with M-CSF (20 ng/mL) for 5 days. Differentiated cells were harvested, counted, and analyzed for phenotype expression. Results are presented as absolute numbers of marker-positive cells per 10,000 cells. Significant inhibition of macrophage differentiation was considered at least 50% reduction of marker-positive cells relative to cells collected before therapy.
Real-time PCR. Total RNA extraction was done with Trizol. cDNA was synthesized by random priming from 1 µg of total RNA with GeneAmp RNA PCR kit (Applied Biosystems, Foster City, CA) according to the manufacturer's instructions. Real-time PCR was done using SYBR Green dye and GeneAmp 5700 Sequence Detection System (PE Applied Biosystems, Foster City CA) as described (32). The sequences of primer pairs specific for each gene (Invitrogen, San Diego, CA) were designed with Primer Express Software (Applied Biosystems). For each gene, mRNA was normalized to ß-actin mRNA by subtracting the cycle threshold (Ct) value of ß-actin mRNA from the Ct value of the gene (
Ct). Fold difference (2
Ct) was calculated by comparing the
Ct with the
Ct of unstimulated cells (32).
| Results |
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To confirm these findings, we tested whether the in vivo administration of Yondelis in tumor patients could affect the differentiating capacity of monocytes into macrophages. Tumor patients selected for these experiments were treated with Yondelis at 1,300 µg/m2 in the same phase II study as described above. Blood samples were drawn immediately before drug administration and at the end of a 3-hour infusion. Purified monocytes were cultured for 5 days with M-CSF and then tested for phenotype analysis. Of 12 patients tested, monocytes from 6 subjects showed marked inhibition of macrophage differentiation compared with cells collected before drug infusion, evaluated as at least 50% decrease in the number of cells expressing CD68, CD16, and CD206 (Table 1). Possible association between the clinical response to drug treatment and the reduced differentiation activity in vitro is being investigated and will require a larger number of cases.
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(M1) or by IL-4 (M2) were also susceptible to drug treatment (Fig. 4C, middle). TAMs isolated from the ascites of nontreated patients with ovarian adenocarcinoma were also tested. TAMs were significantly susceptible in vitro to Yondelis. Results from three different patients show 40% to 60% reduction of cell viability at 10 nmol/L (Fig. 4C, right). Yondelis inhibits the production of inflammatory mediators. Production of selected inflammatory mediators was tested in monocytes/macrophages, TAMs, and freshly isolated tumor cells, upon in vitro treatment with Yondelis. Cells were treated for 16 hours and supernatants collected for ELISA measurements; under these treatment conditions, cell viability was usually >85% for all drug concentrations tested.
Yondelis dose-dependently reduced the production of the inflammatory chemokine CCL2. Mean inhibition at 5 nmol/L was 65% (n = 7) for lipopolysaccharide-stimulated monocytes and 60% for in vitro differentiated macrophages (n = 5; Fig. 5). IL-6 production was also reduced, with an overall inhibition at 5 nmol/L of 54% (n = 4) and 59% (n = 4) in monocytes and macrophages, respectively (Fig. 5). By contrast, and quite surprisingly, the production of TNF
by monocytes/macrophages was never inhibited (Fig. 5), suggesting that this compound interferes only with selected genes. This result further indicates that under these conditions cells were not damaged by the treatment.
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| Discussion |
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Of interest, other chemotherapeutic agents, including cisplatin and taxol did not show, in vitro, appreciable cytotoxicity on mononuclear phagocytes, whereas doxorubicin did affect monocyte viability but less potently than Yondelis. Thus, the cytotoxic effect of Yondelis on monocytes is a peculiar characteristic of this compound, not generally shared by other antitumor drugs.
The differentiation of macrophages in vitro, induced by M-CSF, was inhibited at subcytotoxic concentrations of the drug. We have confirmed these results with monocytes from tumor-bearing patients undergoing Yondelis therapy. In 6 of 12 patients tested, monocytes collected after 3 hours of drug infusion (1,300 µg/m2) showed >50% inhibition of macrophage differentiation, compared with monocytes collected just before therapy. These results indicate that a brief in vivo exposure to Yondelis is sufficient to provide a measurable effect on monocytes. This is also supported by in vitro results that short exposure (1 hour) to the drug was sufficient to affect cell viability after 48 hours (not shown).
It should be noted that even in the presence of M-CSF, monocytes never underwent cell cycle progression, as checked by DNA analysis with flow cytometry (not shown). The toxic effect of Yondelis on monocytes is, therefore, independent of cell cycle and provides the unique opportunity to study the biological effects of this drug on nonreplicating cells.
A major finding of this work was the inhibitory activity of Yondelis on the production of inflammatory cytokines. Among various macrophage-derived products, we have tested CCL2, IL-6, and TNF. CCL2 is a chemoattractant for monocytes and lymphocytes and is produced both by mononuclear phagocytes and by tumor cells. Tumor-derived CCL2 attracts circulating monocytes at the tumor site (26, 29). In ovarian and pancreatic carcinomas, serum levels of CCL2 significantly correlate with the macrophage content of tumors (3537); thus, CCL2 is a major determinant of the monocyte recruitment within the tumor tissue. Yondelis significantly reduced CCL2 release by lipopolysaccharide-activated monocytes, macrophages, and TAM. Most importantly, Yondelis strongly inhibited the constitutive release of CCL2 by unstimulated TAM and freshly isolated ovarian tumor cells at concentrations as low as 2.5 nmol/L. Lower levels of CCL2 produced in the tumor microenvironment are likely to effectively reduce macrophage accumulation at the tumor site. Interestingly, doxorubicin and taxol did not inhibit CCL2 production, whereas cisplatin showed a modest inhibition only at high concentrations (10 µmol/L, not shown).
Several lines of evidence indicate that in the tumor stroma a symbiotic relationship between cancer cells and TAM takes place, whereby cancer cells attract TAM and sustain their survival, and TAM respond to tumor-derived molecules by producing important growth factors and matrix enzymes that stimulate tumor proliferation, angiogenesis, and invasion of the surrounding tissues (2628, 38) . The relationship of TAM infiltration and prognosis in tumor patients has been investigated in several studies (3941). As pointed out in a recent review (27), 10 of 15 studies concluded that the greater the macrophage infiltration, the worse the prognosis, whereas the opposite was found in three studies and no clear association in the remaining two. Therefore, the presence of high numbers of TAM at the tumor site is more frequently associated with poor prognosis. In this study, we found that TAM viability was significantly reduced in vitro. The toxic effect of Yondelis on TAM, as well as the inhibition of chemoattractant release, is likely to bear particular relevance for its antitumor activity.
Another cytokine whose production was reduced by Yondelis was IL-6. IL-6 and related members of its cytokine family are strongly involved in immune and inflammatory response by regulating a variety of biological processes including cell division, differentiation, and survival (42). Moreover, IL-6 is a cofactor for the production of CCL2 (43). Several studies have showed that IL-6 can directly act as a growth and survival factor in several tumors, in particular, in multiple myeloma and ovarian cancer (44, 45). In addition, IL-6 and related cytokines are involved in tumor-induced cachexia and in metastasis-induced osteolysis (42). In vitro treatment with Yondelis dose-dependently reduced IL-6 production by lipopolysaccharide-stimulated monocytes/macrophages. The lipopolysaccharide-induced as well as the constitutive release by TAM and freshly isolated tumor cells was also inhibited. In view of its ability to sustain tumor cell growth and survival, the drug-mediated reduction of IL-6 may be an important antitumor mechanism.
Quite surprisingly, Yondelis had no significant effect on TNF production, another important inflammatory cytokine. The release of TNF by lipopolysaccharide-stimulated monocytes/macrophages and TAM was completely unaffected by Yondelis, even at high drug concentrations. The effect on the constitutive production by unstimulated TAM and tumor cells was difficult to evaluate because both cell types released very low amounts of TNF in the absence of stimuli (not shown). The reason why TNF transcription is intact after drug treatment is not clear at the moment. It was already known that Yondelis binds DNA with some sequence specificity. Our results extend this observation by indicating that the compound interferes only with the transcription of selected cytokine genes. TNF transcription in myeloid cells stimulated by lipopolysaccharide is primarily activated by NF
B (46), although other factors could be involved. CCL2 and IL-6 transcription is also under the control of NF
B but can be activated by other transcription factors, such as activator protein (AP-1), SP-1, Smad3 for CCL2 (47) and AP-1, cFOS, and CCAAT/NF-IL-6 for IL-6 (48). Of these, AP-1 activates also TNF. The search for transcription factors common to CCL2 and IL-6 and not to TNF has been unsuccessful, up to now, and will require further study.
TNF has been strongly implicated as a promoter of carcinogenesis in mouse tumor models (25). Moreover, TNF activates NF
B, which, in addition to inducing cytokine production, is important to controlling cell proliferation and survival. Recently, activation of NF
B has been implicated in the neoplastic transformation of precancerous cells (22, 24). In ovarian cancer, TNF has been shown to increase tumor cell growth and angiogenesis and to promote the adhesion of ascitic cancer cells to the peritoneal wall (49). Therefore, the inability of Yondelis to interfere with TNF production should be considered. TNF antagonists are currently being tested in the clinic in patients with autoimmune diseases and, more recently, tumors (50). Combination therapies with chemotherapeutic drugs and TNF antagonists could be considered.
Because tumor patients undergoing Yondelis therapy are also treated with corticosteroids to prevent drug-induced hepatotoxicity, it was of interest to evaluate whether the in vitro treatment of monocytes with the combination Yondelis + dexamethasone affected TNF production. As expected, dexamethasone inhibited TNF production by 50%, and the drug combination resulted in a similar inhibition (not shown). The association of decreased TNF levels with the corticosteroid-induced protection from hepatotoxicity remains to be investigated.
In conclusion, the antineoplastic agent Yondelis showed a selective cytotoxic effect on monocytes and macrophages including TAM. At subcytotoxic concentrations, it significantly reduced the production of two proinflammatory cytokines, IL-6 and CCL2, which have a major role in host-tumor relationship and in cancer progression. In view of the protumoral role of TAM and the enlarging link between inflammation and cancer, these properties of Yondelis may contribute to its antitumor activity. This compound can be seen as the prototype of a new class of anticancer agents possessing high anti-inflammatory activity as well as selectivity for macrophages.
| Acknowledgments |
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The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
We thank Prof. Alberto Mantovani and Dr. Antonio Sica (Istituto Mario Negri, Milano) for helpful discussion and suggestions, Dr. Carla Paganin for pilot studies in this project, and Southern Europe New Drugs Organization for efficient assistance in collecting information and samples from patients with cancer.
Received 11/10/04. Revised 12/22/04. Accepted 1/18/05.
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