Modulation of monocyte functions by muramyl tripeptide phosphatidylethanolamine in a phase II study in patients with metastatic melanoma

Inflammation and tumor progression: signaling pathways and targeted intervention

Cancer development and its response to therapy are regulated by inflammation, which either promotes or suppresses tumor progression, potentially displaying opposing effects on therapeutic outcomes. Chronic inflammation facilitates tumor progression and treatment resistance, whereas induction of acute inflammatory reactions often stimulates the maturation of dendritic cells (DCs) and antigen presentation, leading to anti-tumor immune responses. In addition, multiple signaling pathways, such as nuclear factor kappa B (NF-kB), Janus kinase/signal transducers and activators of transcription (JAK-STAT), toll-like receptor (TLR) pathways, cGAS/STING, and mitogen-activated protein kinase (MAPK); inflammatory factors, including cytokines (e.g., interleukin (IL), interferon (IFN), and tumor necrosis factor (TNF)-α), chemokines (e.g., C-C motif chemokine ligands (CCLs) and C-X-C motif chemokine ligands (CXCLs)), growth factors (e.g., vascular endothelial growth factor (VEGF), transforming growth factor (TGF)-β), and inflammasome; as well as inflammatory metabolites including prostaglandins, leukotrienes, thromboxane, and specialized proresolving mediators (SPM), have been identified as pivotal regulators of the initiation and resolution of inflammation. Nowadays, local irradiation, recombinant cytokines, neutralizing antibodies, small-molecule inhibitors, DC vaccines, oncolytic viruses, TLR agonists, and SPM have been developed to specifically modulate inflammation in cancer therapy, with some of these factors already undergoing clinical trials. Herein, we discuss the initiation and resolution of inflammation, the crosstalk between tumor development and inflammatory processes. We also highlight potential targets for harnessing inflammation in the treatment of cancer.

Soluble Intercellular Adhesion Molecule-1 and Serum Cytokines in Melanoma Patients Treated with Liposomes Containing Muramyl Tripeptide

Aims and Background

A soluble form of intercellular adhesion molecule-1 (sICAM-1) has been recently identified in patients with malignant melanoma. It has been demonstrated that inflammatory cytokines can modulate the cellular expression of ICAM-1 and the shedding of this molecule by cells. To our knowledge, few data exist on serum sICAM-1 levels in cancer patients treated with immunomodulators. Liposomes containing muramyl tripeptide (MLV MTP-PE) can activate monocytes from cancer patients in vitro and in vivo, making them cytotoxic such as tumor necrosis factor- α (TNF-α) and Interleukin-6 (IL-6). The purpose of the present study was to evaluate the levels of sICAM-1 and their possible correlation with serum inflammatory cytokine levels in melanoma patients treated with MLV MTP-PE.

Methods

The sera from 9 patients with metastatic melanoma treated with MLV MTP-PE, 4 mg i.v. twice a week for 12 weeks, were tested in ELISA system to detect sICAM-1, TNF-α, IL-6, Interleukin-1 β (IL- β) and Interferon-γ (IFN-γ) before, and 2 and 24 h after the 1st, 12th and 24th infusion of MLV MTP-PE.

Results

Baseline levels of sICAM-1 were elevated in all patients (median 540 ng/ml: range 400-1030 ng/ml). Twenty-four h after the 1st infusion of MLV MTP-PE, we observed 6 increases in sICAM-1 levels, 1 decrease and 2 stable values (median 720 ng/ml: range 410-1820; P = 0.060). Twenty-four h after the 12th infusion, sICAM-1 increased in 3 patients and did not change in 4 (median 790 ng/ml: range 495-1650 ng/ml; P = 0.069). At the 24th infusion, sICAM-1 increased in 4 of 6 evaluable patients and remained stable in 2 (median 802 ng/ml: range 510-1450 ng/ml; P = 0.045). To better analyze the variations in sICAM-1, the patients were arbitrarily divided into two groups according to their clinical behavior: 4 presented stabilization (all lesions, n = 2; some lesions, n = 2) (Group A); 5 presented progressive disease (Group B). In Group A, sICAM-1 levels remained stable or showed a modest increase during treatment (except in 1 patient, who exhibited a substantial variation after the 12th infusion). In contrast, in Group B very high levels of sICAM-1 were observed at the beginning of the study therapy in 1 patient and after the 1st infusion in 3 patients; these values remained high until the 24th infusion. In most of the patients, TNF-α and IL-6 increased after the 1st infusion, but not thereafter. IFN-γ was never detected; IL-1 β was detectable in a few cases, but only before the infusions.

Conclusions

baseline levels of sICAM-1 were elevated in all patients and further increased during treatment only in patients with more aggressive disease. No correlation was found between sICAM-1 and inflammatory cytokines. It would therefore seem that in patients with advanced disease, higher levels and a progressive increase in sICAM-1 may be unfavorable prognostic factors.

Inflammation as target in cancer therapy

Cells of the innate immunity infiltrating tumour tissues promote, rather than halt, cancer cell proliferation and distant spreading. Tumour-Associated Macrophages (TAMs) are abundantly present in the tumour milieu and here trigger and perpetrate a state of chronic inflammation which ultimately supports disease development and contributes to an immune-suppressive environment. Therapeutic strategies to limit inflammatory cells and their products have been successful in pre-clinical tumour models. Early clinical trials with specific cytokine and chemokine inhibitors, or with strategies designed to target TAMs, are on their way in different solid malignancies. Partial clinical responses and stabilization of diseases were observed in some patients, in the absence of significant toxicity. These encouraging results open new perspectives of combination treatments aimed at reducing cancer-promoting inflammation to maximize the anti-tumour efficacy.

Tumour-associated macrophages as treatment targets in oncology

Macrophages are crucial drivers of tumour-promoting inflammation. Tumour-associated macrophages (TAMs) contribute to tumour progression at different levels: by promoting genetic instability, nurturing cancer stem cells, supporting metastasis, and taming protective adaptive immunity. TAMs can exert a dual, yin-yang influence on the effectiveness of cytoreductive therapies (chemotherapy and radiotherapy), either antagonizing the antitumour activity of these treatments by orchestrating a tumour-promoting, tissue-repair response or, instead, enhancing the overall antineoplastic effect. TAMs express molecular triggers of checkpoint proteins that regulate T-cell activation, and are targets of certain checkpoint-blockade immunotherapies. Other macrophage-centred approaches to anticancer therapy are under investigation, and include: inhibition of macrophage recruitment to, and/or survival in, tumours; functional re-education of TAMs to an antitumour, 'M1-like' mode; and tumour-targeting monoclonal antibodies that elicit macrophage-mediated extracellular killing, or phagocytosis and intracellular destruction of cancer cells. The evidence supporting these strategies is reviewed herein. We surmise that TAMs can provide tools to tailor the use of cytoreductive therapies and immunotherapy in a personalized medicine approach, and that TAM-focused therapeutic strategies have the potential to complement and synergize with both chemotherapy and immunotherapy.

Mifamurtide: a review of its use in the treatment of osteosarcoma

Mifamurtide (liposomal muramyl tripeptide phosphatidyl ethanolamine; Mepact) is an immunomodulator with antitumor effects that appear to be mediated via activation of monocytes and macrophages. In the EU, mifamurtide is indicated in children, adolescents, and young adults for the treatment of high-grade, resectable, non-metastatic osteosarcoma after macroscopically complete surgical resection; it is administered by intravenous infusion in conjunction with postoperative multiagent chemotherapy. In the US, mifamurtide is currently an investigational agent that holds orphan drug status for the treatment of osteosarcoma. In a large, randomized, open-label, multicenter, phase III trial, the addition of adjuvant (postoperative) mifamurtide to three- or four-drug combination chemotherapy (doxorubicin, cisplatin, and high-dose methotrexate with, or without, ifosfamide) was associated with a statistically significant improvement in overall survival in patients with newly diagnosed, high-grade, non-metastatic, resectable osteosarcoma. The pattern of outcome was generally similar in a small cohort of patients with metastatic disease who were enrolled in this trial. Mifamurtide is generally well tolerated; adverse events attributed to administration of the drug include chills, fever, headache, nausea, and myalgias. Based on the available data, mifamurtide can be considered for inclusion in treatment protocols for localized osteosarcoma.

Muramyl tripeptide (mifamurtide) for the treatment of osteosarcoma

Osteosarcoma is an ultraorphan disease. There are approximately 1000 new patients diagnosed with osteosarcoma each year in the USA and Europe. Current treatment for osteosarcoma utilizes multiagent chemotherapy and surgical resection of all clinically detectable disease. Current treatments for osteosarcoma achieve 60-70% event-free survival (EFS) for patients with localized disease and approximately 20% EFS for patients who present with metastasis. These results have been stable for two decades. The addition of muramyl tripeptide (mifamurtide) to chemotherapy resulted in a trend towards improved EFS and a one-third reduction in the risk of death from osteosarcoma. Mifamurtide has been approved in Europe for the treatment of newly diagnosed osteosarcoma in combination with chemotherapy.

Liposomal muramyl tripeptide phosphatidyl ethanolamine: a safe and effective agent against osteosarcoma pulmonary metastases

Osteosarcoma is the most common form of primary malignant bone tumor. The use of chemotherapy drugs with many side effects, including high-dose methotrexate, doxorubicin, cisplatin and ifosfamide, has greatly improved osteosarcoma survival compared with surgery alone. However, for 20 years, overall survival remained at a plateau of 60-70% in nonmetastatic disease and 20-30% in metastatic osteosarcoma owing to lung metastases. Liposomal muramyl tripeptide phosphatidyl ethanolamine (L-MTP-PE) is a new agent that improves overall osteosarcoma survival (chemotherapy without L-MTP-PE 70% versus with L-MTP-PE 78%; p = 0.03). L-MTP-PE offers additional benefit for osteosarcoma treatment in combination with chemotherapy, particularly ifosfamide-containing regimens. Clinical experience indicates that side effects such as fever are temporary and controlled or prevented with ibuprofen and/or acetoaminophen premedication; severe side effects are rare. Although surgery will remain the main approach for osteosarcoma treatment of lung metastases, L-MTP-PE combined with other modalities, including chemotherapy, appears to be of benefit in these patients as well.

Liposomal muramyl tripeptide phosphatidyl ethanolamine: ifosfamide-containing chemotherapy in osteosarcoma

Liposomal muramyl tripeptide phosphatidyl ethanolamine (L-MTP-PE) is a synthetic biological investigational agent used for treating osteosarcoma. It has been used in both canine and human osteosarcoma to reduce pulmonary metastases, the most common pattern of treatment failure for sarcomas. L-MTP-PE has been well tolerated using the concept of biological cancer therapy during chemotherapy. The use of L-MTP-PE with ifosfamide is the best studied combination with single agent chemotherapy. This may represent a new treatment choice for osteosarcoma patients receiving ifosfamide. Such patients include those with a poor initial histological response to primary therapy and/or metastatic disease including pulmonary metastases. Reduction of side effects of L-MTP-PE, such as fever and/or flu-like symptoms, with ibuprofen has not reduced efficacy. Since improved symptom control is possible using drug combinations that are especially effective for delayed nausea, outpatient high-dose ifosfamide chemotherapy combined with L-MTP-PE may lead to a safe and effective therapy while maintaining the patients’ quality of life.

Spontaneously occurring tumors of companion animals as models for human cancer

Spontaneous tumors in companion animals (dog and cat) offer a unique opportunity as models for human cancer biology and translational cancer therapeutics. The relatively high incidence of some cancers, similar biologic behavior, large body size, comparable responses to cytotoxic agents, and shorter overall lifespan are the factors that contribute to the advantages of the companion animal model. The tumor types that offer the best comparative interest include lymphoma/leukemia, osteosarcoma, STS, melanoma, and mammary tumors. With the increase in new therapeutic agents (traditional chemotherapy, gene therapy, biologic agents, etc.), the companion animal model can provide useful populations to test new agents where efficacy and toxicity can be examined.

Activity and pharmacodynamics of 21-Day topotecan infusion in patients with ovarian cancer previously treated with platinum-based chemotherapy. New York Gynecologic Oncology Group

PURPOSE

Twenty-one-day topotecan infusion was administered as second-line therapy in patients with previously treated ovarian cancer (based on our prior favorable phase I experience) to determine its activity, time to progression, and pharmacodynamics.

PATIENTS AND METHODS

Ovarian cancer patients with measurable lesions and one prior platinum-containing regimen were eligible. Topotecan 0.4 mg/m(2)/d 21-day continuous ambulatory intravenous infusion, with appropriate dose modifications for toxicity, was administered every 28 days. Weekly blood levels of topotecan and topoisomerase-1 (topo-1) levels in peripheral-blood mononuclear cells (PBMCs) were determined for pharmacodynamic correlation.

RESULTS

Twenty-four patients were entered onto the study (six cisplatin-refractory, five relapsing within < 6 months and 13 relapsing > 6 months after platinum-based therapy). A total of 128 cycles of topotecan (median, four cycles per patient; range, one to 12 cycles) were administered. The major toxicity was neutropenia (29% grade 3 in all cycles and 4% grade 4). One episode of grade 4 thrombocytopenia (4%) occurred. Fifty-two percent of the patients had anemia that required transfusions. Eight of 23 patients with measurable disease (35%; 95% confidence interval [CI], 15% to 54%) had partial responses (PRs) lasting longer than 1 month. Two of these patients had minor residual computed tomographic changes but had clinical complete remissions that lasted up to 53 weeks while they were not undergoing further therapy. One patient with nonmeasurable disease had a PR (by CA-125 criteria) that lasted 6 months, for an overall response rate of 38% in nine of 24 patients (95% CI, 18% to 57%). The median time to progression was 26 weeks. Pharmacodynamic analysis demonstrated a statistically significant decrease in free PBMC topo-1 level at weeks 2 and 3 of drug administration. There was a strong statistical correlation between the decrease in free topo-1 levels and increasing area under the curve (AUC) for topotecan. This was confirmed in a pharmacodynamic model.

CONCLUSION

Twenty-one-day infusion is a well-tolerated method of administering topotecan. Pharmacodynamic studies demonstrate correlations between (1) the week of infusion and the PBMC topo-1 level, (2) the AUC of topotecan and the decrease in topo-1 levels, and (3) the change in topo-1 level and the neutrophil nadir. The objective response rate of 35% to 38% (95% CI, 15% to 57%) in this small multicenter study is at the upper level for topotecan therapy in previously treated ovarian cancer. Prolonged topotecan administration therefore warrants further investigation in larger, randomized studies comparing this 21-day schedule with the once-daily-for-5-days schedule.

Liposomes as delivery systems in the prevention and treatment of infectious diseases

Research on the potential application of liposomes in the prevention and treatment of infectious diseases has focussed on improvement of the therapeutic index of antimicrobial drugs and immunomodulators and on stimulation of the immune response to otherwise weak antigens in vaccines composed of purified micro-organism subunits. In this review current approaches in this field are outlined. The improved therapeutic index of antimicrobial drugs after encapsulation in liposomes is a result of enhanced drug delivery to infected tissue or infected cells and/or a reduction of drug toxicity of potentially toxic antibiotics. Liposomal encapsulation of immunomodulators that activate macrophages aims at reducing the toxicity of these agents and targeting them to the cells of the mononuclear phagocyte system in order to increase the nonspecific resistance of the host against infections. Studies on the immunogenicity of liposomal antigens have demonstrated that liposomes can potentiate the humoral and cell mediated immunity to a variety of antigens.

Eicosanoids and the immunology of cancer

Studies in both cancer patients and in animal tumor models have shown that immune defenses can mediate destruction of tumor, but these defenses are often functioning at a suppressed or suboptimal level. Frequently, prostaglandins, mainly PGE2, have been implicated in this tumor-associated subversion of immune function, with immune reactivities to tumor typically being enhanced by prostaglandin synthesis inhibitor. Both the tumor and tumor-induced host immune suppressive macrophages have the capacity to suppress immune functions through their production of PGE2. Although the inhibitory functions have been more widely studied, recent evaluations of the effects of PGE2 have led to the surprising realization that not all of the PGE2's effects are inhibitory to immune function. Summarized below are some of the well characterized inhibitory effects of PGE2, as well as the lesser studied stimulatory effects of PGE2 toward the effector cells that are considered to be important in the immune defense against cancer.

In vitro TNF-alpha production and in vivo alteration of TNF-alpha RNA in mouse peritoneal macrophages after treatment with different bacterial derived agents

Since muramyl dipeptide (MDP) was recognized as a potent monocyte/macrophage activating agent, many MDP analogues were synthesized and tested for their ability to augment the host immune defence system against neoplasms. This study was performed to determine whether the newly synthesized desmuramyl N-acyl dipeptides LK 409 and LK 410 were also capable of affecting the immune system. For this purpose, the peritoneal macrophages were incubated in vitro with these two agents and TNF-alpha production was measured. In addition, the effect of LK 409 and LK 410 on TNF-alpha and IL-1 RNA levels in in vivo stimulated macrophages was determined by quantitative polymerase chain reaction (RT-PCR). None of the LK 409 and LK 410 concentrations tested were able to render macrophages in vitro to excrete a detectable amount of TNF-alpha in the supernatant fluid. However, the TNF-alpha and IL-1 RNA levels in macrophages of in vivo treated mice (C57Bl/6) were increased in comparison to mock-treated mice. The results indicate that LK 409 and LK 410 are capable of inducing an increase in TNF-alpha and IL-1 RNA levels, yet in vitro TNF-alpha production remains under detectable levels (40 U/ml).

Current studies of liposome muramyl tripeptide (CGP 19835A lipid) therapy for metastasis in spontaneous tumors: a progress review

Targeted delivery of macrophage activating agents is an attractive approach to treat micrometastatic disease. Liposome-encapsulated muramyl tripeptide phosphatidylethanolamine (L-MTP-PE) is a potent activator of monocytes/macrophages in humans, mice, and dogs. We have conducted clinical trials in dogs with malignant and highly metastatic spontaneous tumors. Presented are results of our trials evaluating L-MTP-PE in combination with surgery and chemotherapy in dogs with spontaneous osteosarcoma and hemangiosarcoma, particularly relevant malignancies having having many similarities to human cancer. Osteosarcoma dogs received chemotherapy following surgery (cisplatin q 28 days x 4). At completion of chemotherapy, dogs were randomized to receive L-MTP-PE or placebo. The L-MTP-PE group had a significantly longer median survival time compared to the placebo group (p < 0.021). Dogs with splenic hemangiosarcoma received combination chemotherapy following surgery (doxorubicin and cyclophosphamide q 21 days x 4). At the first chemotherapy, dogs were randomized to receive L-MTP-PE or placebo. The L-MTP-PE group had a significantly longer median survival time compared to the placebo group (p < 0.03). These studies show that L-MTP-PE is an effective agent for treatment of metastasis and can be safely administered in combination with chemotherapy.

Liposome-encapsulated muramyl tripeptide up-regulates monocyte chemotactic and activating factor gene expression in human monocytes at the transcriptional and post-transcriptional levels

Liposome-encapsulated muramyl tripeptide phosphatidylethanolamine (L-MTP-PE) is a novel immune modulator that is now under investigation against metastatic melanoma and osteosarcoma. We have already reported that L-MTP-PE induced monocyte-mediated tumoricidal activity and up-regulation of the tumor necrosis factor and interleukin-1 (IL-1) in vivo and in vitro. We now demonstrate that L-MTP-PE also induces monocyte chemotactic and activating factor (MCAF) mRNA expression at both the transcriptional and post-transcriptional levels. Monocyte chemotactic activity was also present in the supernatants of L-MTP-PE-stimulated cells. In monocytes, the increased expression of MCAF was induced rapidly (by 2 h) but was short-lived. By 4 h, MCAF mRNA had decreased to background level. We found no change in MCAF mRNA levels in lymphocytes exposed to L-MTP-PE. We therefore conclude that L-MTP-PE selectively up-regulates MCAF expression in monocytes and that MCAF may play a role in the tumoricidal and immune-stimulating activity of L-MTP-PE.

Combination therapy with a synthetic peptide of C-reactive protein and interleukin 2: augmented survival and eradication of pulmonary metastases

A synthetic peptide (RS-83277) derived from the structure of human C-reactive protein (CRP) was previously shown to have antitumor activity in three different murine tumor models when administered in multilamellar vesicles (MLV). The therapeutic effects were comparable to those seen with MLV-encapsulated native CRP. The present study evaluated the therapeutic and immunomodulatory effects of administering CRP peptide RS-83277 MLV simultaneously with low-dose recombinant interleukin-2 (IL-2) to C57Bl/6 mice bearing established pulmonary metastases of fibrosarcoma T241. Results demonstrated that the capacity of RS-83277 MLV to inhibit tumor metastases and prolong survival was significantly augmented by combination with 10,000 U/day IL-2 i.p. Treated animals showed no evidence of toxicity. By immunohistochemistry, increased Thy 1.2+ cells were detectable in lungs of RS-83277 MLV/IL-2-treated animals compared to those receiving RS-83277 MLV alone. Circulating tumor necrosis factor alpha (TNF) and interferon (IFN) were not detectable in animals receiving RS-83277 MLV alone, but TNF was significantly elevated in animals receiving IL-2. In the presence of combination therapy, however, circulating TNF was not detectable. Results suggest that the combination of synthetic CRP peptide RS-83277 MLV and low-dose IL-2 offers a therapeutic advantage over either agent alone.

Pharmacokinetics and immunomodulatory effects on monocytes during prolonged therapy with liposomal muramyltripeptide

The macrophage activator muramyl tripeptide-phosphatidyl ethanolamine (MTP-PE) was infused in liposomal form in 14 metastatic cancer patients (4 mg i.v. during 30 min twice weekly for 12 weeks). Clinical, pharmacokinetic and immunological parameters were studied before and 0.5, 2, 4, 24 and 72h after start of drug infusion in week 1, 4, 8 and 12. No tumor regressions were seen. Tumors progressed in 11 patients, in 4 of them within 2 months; 3 patients had stable disease. The intensity and frequency of side effects (fever and nausea) diminished from week 1 to 12. The rate of disappearance of total and free MTP-PE from blood was rapid and mean serum concentration-time curves remained unchanged throughout 12 study weeks. MTP-PE caused a marked increase of serum TNFa, IL-1 receptor antagonist (IL-1ra) and IL-6 in week 1, but not thereafter. In contrast, MTP-PE caused a persistent, 2-fold increase in serum neopterin and young forms of granulocytes (bands) during week 1 to 12. Before therapy, monocyte tumor cytotoxicity and in-vitro monocyte derived TNFa, IL-1 beta and IL-6 production were low in 9 patients (group L, < 15%) and high in 5 patients (group H, > 40%). Monocyte cytotoxicity and in-vitro cytokine production was transiently enhanced in week 1 in group L, it declined under therapy in group H. In conclusion, MTP-PE induced marked initial immunomodulation; the extent of the ex vivo monocyte cytokine and tumor cytotoxic response was dependent on pre-therapy cell activity. A decrease of the cytokine and IL-1ra response during prolonged therapy contrasted with a persistent increase of neopterin and juvenile blood granulocytes. The long lasting biologic effects may be relevant to direct future clinical studies with liposomal MTP-PE in an adjuvant setting.