Tasquinimod modulates suppressive myeloid cells and enhances cancer immunotherapies in murine models

PKCζ in prostate cancer cells represses the recruitment and M2 polarization of macrophages in the prostate cancer microenvironment

Tumor-associated macrophages are key regulators of the complex interplay between tumor and tumor microenvironment. M2 Macrophages, one type of tumor-associated macrophages, are involved in prostate cancer growth and progression. Protein kinase C zeta has been shown to suppress prostate cancer cell growth, invasion, and metastasis as a tumor suppressor; however, its role in chemotaxis and activation of tumor-associated macrophages remains unclear. Here, we investigated the role of protein kinase C zeta of prostate cancer cells in regulation of macrophage chemotaxis and M2 phenotype activation. Immunohistochemistry was performed to analyze the expression of protein kinase C zeta and the number of CD206+ M2 macrophages in human prostate tissue. Macrophage chemotaxis and polarization were examined using Transwell migration assays and a co-culture system. Quantitative real-time polymerase chain reaction, western blotting, and enzyme-linked immunosorbent assay were used to detect M2 markers, protein kinase C zeta, interleukin-4, and interleukin-10 expression. We found the expression of protein kinase C zeta increased in prostate cancer tissues, especially in the early stage, and was negatively associated with tumor grade and the number of CD206+ macrophages. Inhibition of protein kinase C zeta expression in prostate cancer cells promoted chemotaxis of peripheral macrophages and acquisition of M2 phenotypic features. These results were further supported by the finding that silencing of endogenous protein kinase C zeta promoted the expression of prostate cancer cell-derived interleukin-4 and interleukin-10. These results suggest that protein kinase C zeta plays an important role in reducing infiltration of tumor-associated macrophages and activation of a pro-tumor M2 phenotype, which may constitute an important mechanism by which protein kinase C zeta represses cancer progression.

Clinical development of immunotherapy for prostate cancer

Prostate cancer is the most common cancer in men, and the second leading cause of cancer-related death in Western countries. Prostate cancer-related death occurs in patients with metastatic castration-resistant prostate cancer. Although several new drugs for castration-resistant prostate cancer have been approved, each of these has prolonged survival by just a few months. Consequently, new therapies are sorely needed. Recently, it has been recognized that immunotherapy is an effective treatment for prostate cancer patients. Several strategies, such as cancer vaccines and immune checkpoint inhibitors, have been investigated in clinical studies for prostate cancer patients. In the present review, the results of the most recent clinical studies investigating immunotherapy in prostate cancer patients are reported, and the future clinical development of immunotherapy for prostate cancer is discussed.

Nanomedicine Strategies to Target Tumor-Associated Macrophages

In recent years, the influence of the tumor microenvironment (TME) on cancer progression has been better understood. Macrophages, one of the most important cell types in the TME, exist in different subtypes, each of which has a different function. While classically activated M1 macrophages are involved in inflammatory and malignant processes, activated M2 macrophages are more involved in the wound-healing processes occurring in tumors. Tumor-associated macrophages (TAM) display M2 macrophage characteristics and support tumor growth and metastasis by matrix remodeling, neo-angiogenesis, and suppressing local immunity. Due to their detrimental role in tumor growth and metastasis, selective targeting of TAM for the treatment of cancer may prove to be beneficial in the treatment of cancer. Due to the plastic nature of macrophages, their activities may be altered to inhibit tumor growth. In this review, we will discuss the therapeutic options for the modulation and targeting of TAM. Different therapeutic strategies to deplete, inhibit recruitment of, or re-educate TAM will be discussed. Current strategies for the targeting of TAM using nanomedicine are reviewed. Passive targeting using different nanoparticle systems is described. Since TAM display a number of upregulated surface proteins compared to non-TAM, specific targeting using targeting ligands coupled to nanoparticles is discussed in detail.

The ectonucleotidases CD39 and CD73: Novel checkpoint inhibitor targets

Cancers are able to grow by subverting immune suppressive pathways, to prevent the malignant cells as being recognized as dangerous or foreign. This mechanism prevents the cancer from being eliminated by the immune system and allows disease to progress from a very early stage to a lethal state. Immunotherapies are newly developing interventions that modify the patient's immune system to fight cancer, by either directly stimulating rejection-type processes or blocking suppressive pathways. Extracellular adenosine generated by the ectonucleotidases CD39 and CD73 is a newly recognized "immune checkpoint mediator" that interferes with anti-tumor immune responses. In this review, we focus on CD39 and CD73 ectoenzymes and encompass aspects of the biochemistry of these molecules as well as detailing the distribution and function on immune cells. Effects of CD39 and CD73 inhibition in preclinical and clinical studies are discussed. Finally, we provide insights into potential clinical application of adenosinergic and other purinergic-targeting therapies and forecast how these might develop in combination with other anti-cancer modalities.

The ectonucleotidases CD39 and CD73: Novel checkpoint inhibitor targets

Cancers are able to grow by subverting immune suppressive pathways, to prevent the malignant cells as being recognized as dangerous or foreign. This mechanism prevents the cancer from being eliminated by the immune system and allows disease to progress from a very early stage to a lethal state. Immunotherapies are newly developing interventions that modify the patient's immune system to fight cancer, by either directly stimulating rejection-type processes or blocking suppressive pathways. Extracellular adenosine generated by the ectonucleotidases CD39 and CD73 is a newly recognized "immune checkpoint mediator" that interferes with anti-tumor immune responses. In this review, we focus on CD39 and CD73 ectoenzymes and encompass aspects of the biochemistry of these molecules as well as detailing the distribution and function on immune cells. Effects of CD39 and CD73 inhibition in preclinical and clinical studies are discussed. Finally, we provide insights into potential clinical application of adenosinergic and other purinergic-targeting therapies and forecast how these might develop in combination with other anti-cancer modalities.

A comprehensive review of immunotherapies in prostate cancer

Prostate cancer is the second most common malignant neoplasm in men worldwide and the fifth cause of cancer-related death. Although multiple new agents have been approved for metastatic castration resistant prostate cancer over the last decade, it is still an incurable disease. New strategies to improve cancer control are needed and agents targeting the immune system have shown encouraging results in many tumor types. Despite being attractive for immunotherapies due to the expression of various tumor associated antigens, the microenvironment in prostate cancer is relatively immunosuppressive and may be responsible for the failures of various agents targeting the immune system in this disease. To date, sipuleucel-T is the only immunotherapy that has shown significant clinical efficacy in this setting, although the high cost and potential trial flaws have precluded its widespread incorporation into clinical practice. Issues with patient selection and trial design may have contributed to the multiple failures of immunotherapy in prostate cancer and provides an opportunity to tailor future studies to evaluate these agents more accurately. We have reviewed all the completed immune therapy trials in prostate cancer and highlight important considerations for the next generation of clinical trials.

The ectonucleotidases CD39 and CD73: Novel checkpoint inhibitor targets

Cancers are able to grow by subverting immune suppressive pathways, to prevent the malignant cells as being recognized as dangerous or foreign. This mechanism prevents the cancer from being eliminated by the immune system and allows disease to progress from a very early stage to a lethal state. Immunotherapies are newly developing interventions that modify the patient's immune system to fight cancer, by either directly stimulating rejection-type processes or blocking suppressive pathways. Extracellular adenosine generated by the ectonucleotidases CD39 and CD73 is a newly recognized "immune checkpoint mediator" that interferes with anti-tumor immune responses. In this review, we focus on CD39 and CD73 ectoenzymes and encompass aspects of the biochemistry of these molecules as well as detailing the distribution and function on immune cells. Effects of CD39 and CD73 inhibition in preclinical and clinical studies are discussed. Finally, we provide insights into potential clinical application of adenosinergic and other purinergic-targeting therapies and forecast how these might develop in combination with other anti-cancer modalities.

DNA vaccines for prostate cancer

DNA vaccines offer many advantages over other anti-tumor vaccine approaches due to their simplicity, ease of manufacturing, and safety. Results from several clinical trials in patients with cancer have demonstrated that DNA vaccines are safe and can elicit immune responses. However, to date few DNA vaccines have progressed beyond phase I clinical trial evaluation. Studies into the mechanism of action of DNA vaccines in terms of antigen-presenting cell types able to directly present or cross-present DNA-encoded antigens, and the activation of innate immune responses due to DNA itself, have suggested opportunities to increase the immunogenicity of these vaccines. In addition, studies into the mechanisms of tumor resistance to anti-tumor vaccination have suggested combination approaches that can increase the anti-tumor effect of DNA vaccines. This review focuses on these mechanisms of action and mechanisms of resistance using DNA vaccines, and how this information is being used to improve the anti-tumor effect of DNA vaccines. These approaches are then specifically discussed in the context of human prostate cancer, a disease for which DNA vaccines have been and continue to be explored as treatments.

The Role of Myeloid-Derived Suppressor Cells in Viral Infection

Myeloid-derived suppressor cells (MDSCs) are heterogeneous immature myeloid cells that are well described as potent immune regulatory cells during human cancer and murine tumor models. Reports of MDSCs during viral infections remain limited, and their association with immunomodulation of viral diseases is still being defined. Here, we provide an overview of MDSCs or MDSC-like cells identified during viral infections, including murine viral models and human viral diseases. Understanding the similarities and/or differences of virally induced versus tumor-derived MDSCs will be important for designing future immunotherapeutic approaches.

In neonates S100A8/S100A9 alarmins prevent the expansion of a specific inflammatory monocyte population promoting septic shock

The high susceptibility of newborn infants to sepsis is ascribed to an immaturity of the neonatal immune system, but the molecular mechanisms remain unclear. Newborn monocytes massively release the alarmins S100A8/S100A9. In adults, these are major regulators of immunosuppressive myeloid-derived suppressor cells (MDSCs). We investigated whether S100A8/S100A9 cause an expansion of monocytic MDSCs (Mo-MDSCs) in neonates, thereby contributing to an immunocompromised state. Mo-MDSCs have been assigned to CD14⁺/human leukocyte antigen (HLA)-DR^-/low/CD33⁺ monocytes in humans and to CD11b⁺/Gr-1^int/Ly6G^-/Ly6C^hi cells in mice. We found monocytes with these phenotypes significantly expanded in their respective newborns. Functionally, however, they did not prove immunosuppressive but rather responded inflammatorily to microbial stimulation. Their expansion did not correlate with high S100A8/S100A9 levels in cord blood. Murine studies revealed an excessive expansion of CD11b⁺/Gr-1^int/Ly6G^-/Ly6C^hi monocytes in S100A9^-/- neonates compared to wild-type neonates. This strong baseline expansion was associated with hyperinflammatory responses during endotoxemia and fatal septic courses. Treating S100A9^-/- neonates directly after birth with S100A8/S100A9 alarmins prevented excessive expansion of this inflammatory monocyte population and death from septic shock. Our data suggest that a specific population of inflammatory monocytes promotes fatal courses of sepsis in neonates if its expansion is not regulated by S100A8/S100A9 alarmins.-Heinemann, A. S., Pirr, S., Fehlhaber, B., Mellinger, L., Burgmann, J., Busse, M., Ginzel, M., Friesenhagen, J., von Köckritz-Blickwede, M., Ulas, T., von Kaisenberg, C. S., Roth, J., Vogl, T., Viemann, D. In neonates S100A8/S100A9 alarmins prevent the expansion of a specific inflammatory monocyte population promoting septic shock.

Molecular Mechanisms and Metabolomics of Natural Polyphenols Interfering with Breast Cancer Metastasis

Metastatic cancers are the main cause of cancer-related death. In breast primary cancer, the five-year survival rate is close to 100%; however, for metastatic breast cancer, that rate drops to a mere 25%, due in part to the paucity of effective therapeutic options for treating metastases. Several in vitro and in vivo studies have indicated that consumption of natural polyphenols significantly reduces the risk of cancer metastasis. Therefore, this review summarizes the research findings involving the molecular mechanisms and metabolomics of natural polyphenols and how they may be blocking breast cancer metastasis. Most natural polyphenols are thought to impair breast cancer metastasis through downregulation of MMPs expression, interference with the VEGF signaling pathway, modulation of EMT regulator, inhibition of NF-κB and mTOR expression, and other related mechanisms. Intake of natural polyphenols has been shown to impact endogenous metabolites and complex biological metabolic pathways in vivo. Breast cancer metastasis is a complicated process in which each step is modulated by a complex network of signaling pathways. We hope that by detailing the reported interactions between breast cancer metastasis and natural polyphenols, more attention will be directed to these promising candidates as effective adjunct therapies against metastatic breast cancer in the clinic.

Adjunct Strategies for Tuberculosis Vaccines: Modulating Key Immune Cell Regulatory Mechanisms to Potentiate Vaccination

Tuberculosis (TB) remains a global health threat of alarming proportions, resulting in 1.5 million deaths worldwide. The only available licensed vaccine, Bacillus Calmette–Guérin, does not confer lifelong protection against active TB. To date, development of an effective vaccine against TB has proven to be elusive, and devising newer approaches for improved vaccination outcomes is an essential goal. Insights gained over the last several years have revealed multiple mechanisms of immune manipulation by Mycobacterium tuberculosis (Mtb) in infected macrophages and dendritic cells that support disease progression and block development of protective immunity. This review provides an assessment of the known immunoregulatory mechanisms altered by Mtb, and how new interventions may reverse these effects. Examples include blocking of inhibitory immune cell coreceptor checkpoints (e.g., programed death-1). Conversely, immune mechanisms that strengthen immune cell effector functions may be enhanced by interventions, including stimulatory immune cell coreceptors (e.g., OX40). Modification of the activity of key cell “immunometabolism” signaling pathway molecules, including mechanistic target of rapamycin, glycogen synthase kinase-3β, wnt/β-catenin, adenosine monophosophate-activated protein kinase, and sirtuins, related epigenetic changes, and preventing induction of immune regulatory cells (e.g., regulatory T cells, myeloid-derived suppressor cells) are powerful new approaches to improve vaccine responses. Interventions to favorably modulate these components have been studied primarily in oncology to induce efficient antitumor immune responses, often by potentiation of cancer vaccines. These agents include antibodies and a rapidly increasing number of small molecule drug classes that have contributed to the dramatic immune-based advances in treatment of cancer and other diseases. Because immune responses to malignancies and to Mtb share many similar mechanisms, studies to improve TB vaccine responses using interventions based on “immuno-oncology” are needed to guide possible repurposing. Understanding the regulation of immune cell functions appropriated by Mtb to promote the imbalance between protective and pathogenic immune responses may guide the development of innovative drug-based adjunct approaches to substantially enhance the clinical efficacy of TB vaccines.

Suppression of T cells by myeloid-derived suppressor cells in cancer

Myeloid-derived suppressor cells (MDSCs) are a population of immature myeloid cells defined by their immunosuppression. Elevated levels of certain soluble cytokines in tumor microenvironment, such as IL-6 and IL-10, contribute to the recruitment and accumulation of tumor-associated MDSCs. In turn, MDSCs secret IL-6 and IL-10 and form a positive self-feedback to promote self-expansion. MDSCs also release other soluble cytokines such as TGF-β and chemokines to exert their suppressive function by induction of regulatory T cells. Exhaustion of some amino acids by MDSCs with many secretory enzymes or membrane transporters as well as their metabolites leads to blockage of T cells development. The interaction of membrane molecules on MDSCs and T cells leads inactivation and apoptosis of T cells. There may be one or some dominant mechanism(s) by which MDSCs impair the immune system in different tumor microenvironment. Thus, it is important to identify the subpopulations of MDSCs and clarify the dominant mechanism(s) through which MDSCs inhibit antitumor immunity in order to establish a more individual immunotherapy by eliminating MDSCs-mediated suppression. Currently studies concentrated on therapeutic strategies targeting MDSCs have obtained promising results. However, more studies are needed to demonstrate their clinical safety and efficacy.

IL-4Rα aptamer-liposome-CpG oligodeoxynucleotides suppress tumour growth by targeting the tumour microenvironment

Tumour immunosuppressive microenvironments inhibit antigen-specific cellular responses and interfere with CpG-mediated immunotherapy. Overcoming tumour microenvironment (TME) immunosuppression is an important strategy for effective therapy. This study investigated the ability of a tumour-targeting IL-4Rα aptamer-liposome-CpG ODN delivery system to introduce CpG into tumours and overcome the immunosuppressive TME. The IL-4Rα-liposome-CpG delivery system was prepared. FAM-CpG visualisation was used to demonstrate tumour targeting in vitro and in vivo. Anti-tumour effects of this delivery system were evaluated in CT26 tumour-bearing mice. Mechanisms for conquering the TME were investigated. FAM-CpG was better distributed into the tumours upon treatment with IL-4Rα-liposome-FAM-CpG compared to distribution in the control group in vitro and in vivo. IL-4Rα-aptamer-liposome-CpG treatment inhibited distinct myeloid-derived suppressor cell populations in tumours and bone marrow. Similar profiles were observed for regulatory T cells in tumours. In CT26 tumour-bearing mice, IL-4Rα-liposome-CpG treatment exhibited enhanced anti-tumour activity. Increased mRNA levels of TNF-α, IL-2, and IL-12, and decreased mRNA levels of VEGF, IL-6, IL-10, MMP9, arginase-1, inducible NOS, CXCL9, p-Stat3, and NF-κB were observed in tumours upon IL-4R-liposome-CpG-treatment. The results suggested that pharmacologic targeting by the IL-4R aptamer-liposome-CpG system improves TME therapeutic benefit and provides a rationale for cancer immunotherapies.

Pro-Tumoral Inflammatory Myeloid Cells as Emerging Therapeutic Targets

Since the observation of Virchow, it has long been known that the tumor microenvironment constitutes the soil for the infiltration of inflammatory cells and for the release of inflammatory mediators. Under certain circumstances, inflammation remains unresolved and promotes cancer development. Here, we review some of these indisputable experimental and clinical evidences of cancer related smouldering inflammation. The most common myeloid infiltrate in solid tumors is composed of myeloid-derived suppressor cells (MDSCs) and tumor-associated macrophages (TAMs). These cells promote tumor growth by several mechanisms, including their inherent immunosuppressive activity, promotion of neoangiogenesis, mediation of epithelial-mesenchymal transition and alteration of cellular metabolism. The pro-tumoral functions of TAMs and MDSCs are further enhanced by their cross-talk offering a myriad of potential anti-cancer therapeutic targets. We highlight these main pro-tumoral mechanisms of myeloid cells and give a general overview of their phenotypical and functional diversity, offering examples of possible therapeutic targets. Pharmacological targeting of inflammatory cells and molecular mediators may result in therapies improving patient condition and prognosis. Here, we review experimental and clinical findings on cancer-related inflammation with a major focus on creating an inventory of current small molecule-based therapeutic interventions targeting cancer-related inflammatory cells: TAMs and MDSCs.

Targeting Inflammation in Cancer Prevention and Therapy

Inflammation is associated with the development and malignant progression of most cancers. As most of the cell types involved in cancer-associated inflammation are genetically stable and thus are not subjected to rapid emergence of drug resistance, the targeting of inflammation represents an attractive strategy both for cancer prevention and for cancer therapy. Tumor-extrinsic inflammation is caused by many factors, including bacterial and viral infections, autoimmune diseases, obesity, tobacco smoking, asbestos exposure, and excessive alcohol consumption, all of which increase cancer risk and stimulate malignant progression. In contrast, cancer-intrinsic or cancer-elicited inflammation can be triggered by cancer-initiating mutations and can contribute to malignant progression through the recruitment and activation of inflammatory cells. Both extrinsic and intrinsic inflammation can result in immunosuppression, thereby providing a preferred background for tumor development. In clinical trials, lifestyle modifications including healthy diet, exercise, alcohol, and smoking cessation have proven effective in ameliorating inflammation and reducing the risk of cancer-related deaths. In addition, consumption of certain anti-inflammatory drugs, including aspirin, can significantly reduce cancer risk, suggesting that common nonsteroidal anti-inflammatory drugs (NSAID) and more specific COX2 inhibitors can be used in cancer prevention. In addition to being examined for their preventative potential, both NSAIDs and more potent anti-inflammatory antibody-based drugs need to be tested for their ability to augment the efficacy of more conventional therapeutic approaches on the basis of tumor resection, radiation, and cytotoxic chemicals. Cancer Prev Res; 9(12); 895-905. ©2016 AACR.

Clinical study of a survivin long peptide vaccine (SurVaxM) in patients with recurrent malignant glioma

Survivin is an anti-apoptotic protein that is highly expressed in many cancers, including malignant gliomas. Preclinical studies established that the conjugated survivin peptide mimic SurVaxM (SVN53-67/M57-KLH) could stimulate an anti-tumor immune response against murine glioma in vivo, as well as human glioma cells ex vivo. The current clinical study was conducted to test safety, immunogenicity and clinical effects of the vaccine. Recurrent malignant glioma patients whose tumors were survivin-positive, and who had either HLA-A*02 or HLA-A*03 MHC class I allele-positivity, were given subcutaneous injections of SurVaxM (500 μg) in Montanide ISA 51 with sargramostim (100 μg) at 2-week intervals. SurVaxM was well tolerated with mostly grade one adverse events (AE) and no serious adverse events (SAE) attributable to the study drug. Six patients experienced local injection site reactions; three patients reported fatigue (grades 1 and 2), and 2 patients experienced myalgia (grade 1). Six of eight immunologically evaluable patients developed both cellular and humoral immune responses to vaccine. The vaccine also stimulated HLA-A*02, HLA-A*03 and HLA-A*24 restricted T cell responses. Three patients maintained a partial clinical response or stable disease for more than 6 months. Median progression-free survival was 17.6 weeks, and median overall survival was 86.6 weeks from study entry with seven of nine patients surviving more than 12 months.

The anti-tumor effect of the quinoline-3-carboxamide tasquinimod: blockade of recruitment of CD11b(+) Ly6C(hi) cells to tumor tissue reduces tumor growth

Background

Previous work has demonstrated immunomodulatory, anti-tumor, anti-metastatic and anti-angiogenic effects of the small molecule quinoline-3-carboxamide tasquinimod in pre-clinical cancer models. To better understand the anti-tumor effects of tasquinimod in transplantable tumor models, we have evaluated the impact of the compound both on recruitment of myeloid cells to tumor tissue and on tumor-induced myeloid cell expansion as these cells are known to promote tumor development.

Methods

Mice bearing subcutaneous 4 T1 mammary carcinoma tumors were treated with tasquinimod in the drinking water. A BrdU-based flow cytometry assay was utilized to assess the impact of short-term tasquinimod treatment on myeloid cell recruitment to tumors. Additionally, long-term treatment was performed to study the anti-tumor effect of tasquinimod as well as its effects on splenic myeloid cells and their progenitors. Myeloid cell populations were also immune-depleted by in vivo antibody treatment.

Results

Short-term tasquinimod treatment did not influence the proliferation of splenic Ly6C^hi and Ly6G^hi cells, but instead reduced the influx of Ly6C^hi cells to the tumor. Treatment with tasquinimod for various periods of time after tumor inoculation revealed that the anti-tumor effect of this compound mainly operated during the first few days of tumor growth. Similar to tasquinimod treatment, antibody-mediated depletion of Ly6C^hi cells within that same time frame, caused reduced tumor growth, thereby confirming a significant role for these cells in tumor development. Additionally, long-term tasquinimod treatment reduced the splenomegaly and expansion of splenic myeloid cells during a later phase of tumor development. In this phase, tasquinimod normalized the tumor-induced alterations in myeloerythroid progenitor cells in the spleen but had only limited impact on the same populations in the bone marrow.

Conclusions

Our results indicate that tasquinimod treatment reduces tumor growth by operating early after tumor inoculation and that this effect is at least partially caused by reduced recruitment of Ly6C^hi cells to tumor tissue. Long-term treatment also reduces the number of splenic myeloid cells and myeloerythroid progenitors, but these effects did not influence established rapidly growing tumors.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-016-2481-0) contains supplementary material, which is available to authorized users.

A Perspective of Immunotherapy for Prostate Cancer

In cancer patients, the immune system is often altered with an excess of inhibitory factors, such as immunosuppressive cytokines, produced by regulatory T cells (Treg) or myeloid-derived suppressor cells (MDSC). The manipulation of the immune system has emerged as one of new promising therapies for cancer treatment, and also represents an attractive strategy to control prostate cancer (PCa). Therapeutic cancer vaccines and immune checkpoint inhibitors have been the most investigated in clinical trials. Many trials are ongoing to define the effects of immune therapy with established treatments: androgen deprivation therapy (ADT) and chemotherapy (CT) or radiotherapy (RT). This article discusses some of these approaches in the context of future treatments for PCa.

Randomized, Double-Blind, Placebo-Controlled Phase III Study of Tasquinimod in Men With Metastatic Castration-Resistant Prostate Cancer

PURPOSE

Tasquinimod, a novel oral therapy targeting the tumor microenvironment, significantly improved progression-free survival (PFS) in a randomized, placebo-controlled phase II trial in men with metastatic castration-resistant prostate cancer (mCRPC). This phase III study was conducted to confirm the phase II results and to detect an overall survival (OS) benefit.

PATIENTS AND METHODS

Men with chemotherapy-naïve mCRPC and evidence of bone metastases were assigned (2:1) to receive tasquinimod once per day or placebo until progression or toxicity. The primary end point was radiographic PFS (rPFS; time from random assignment to radiologic progression or death) per Prostate Cancer Working Group 2 criteria and RECIST 1.1. The study had 99.9% power to detect an rPFS hazard ratio (HR) of 0.6 with a two-sided alpha error of .05 and 80% power to detect a target HR of 0.8 for OS, the key secondary end point.

RESULTS

In all, 1,245 patients were randomly assigned to either tasquinimod (n = 832) or placebo (n = 413) between March 2011 and December 2012 at 241 sites in 37 countries. Baseline characteristics were balanced between groups: median age, 71 years; Karnofsky performance status ≥ 90%, 77.3%; and visceral metastases, 21.1%. Estimated median rPFS by central review was 7.0 months (95% CI, 5.8 to 8.2 months) with tasquinimod and 4.4 months (95% CI, 3.5 to 5.5 months) with placebo (HR, 0.64; 95% CI, 0.54 to 0.75; P < .001). Median OS was 21.3 months (95% CI, 19.5 to 23.0 months) with tasquinimod and 24.0 months (95% CI, 21.4 to 26.9 months) with placebo (HR, 1.10; 95% CI, 0.94 to 1.28; P = .25). Grade ≥ 3 adverse events were more frequent with tasquinimod (42.8% v 33.6%), the most common being anemia, fatigue, and cancer pain.

CONCLUSION

In chemotherapy-naïve men with mCRPC, tasquinimod significantly improved rPFS compared with placebo. However, no OS benefit was observed.

Paquinimod reduces skin fibrosis in tight skin 1 mice, an experimental model of systemic sclerosis

BACKGROUND

Systemic Sclerosis (SSc) is an autoimmune disease characterized by vascular and immune dysfunction. A hallmark of SSc is the excessive accumulation of extracellular matrix in the skin and in internal organs. There is a high and unmet medical need for novel therapies in this disease. The pathogenesis of SSc is complex and still poorly understood, but the innate immune system has emerged as an important factor in the disease. SSc patients show increased numbers of macrophages/monocytes in the blood and in the skin compared to healthy individuals and these cells are important sources of profibrotic cytokines and chemokines. Paquinimod belongs to a class of orally active quinoline-3-carboxamide (quinoline) derivatives with immunomodulatory properties and has shown effects in several models of autoimmune/inflammatory disorders. Paquinimod is currently in clinical development for treatment of SSc. The immunomodulatory effects of paquinimod is by targeting the myeloid cell compartment via the S100A9 protein.

OBJECTIVE

In this study we investigate whether targeting of myeloid cells by paquinimod can effect disease development in an experimental model of SSc, the tight skin 1 (Tsk-1) mouse model.

METHODS

Seven weeks old female B6.Cg-Fbn1(Tsk)/J (Tsk-1) mice were treated with vehicle or paquinimod at the dose of 5 or 25mg/kg/day in the drinking water for 8 weeks. The effect of paquinimod on the level of skin fibrosis and on different subpopulations within the myeloid cell compartment in skin biopsies were evaluated by using histology, immunohistochemisty, a hydroxyproline assay and real-time PCR. Furthermore, the level of IgG in serum from treated animals was also analysed. The statistical analyses were performed using Mann-Whitney nonparametric two tailed rank test.

RESULTS

The results show that treatment with paquinimod reduces skin fibrosis measured as reduction of skin thickness and decreased number of myofibroblasts and total hydroxyproline content. The effect on fibrosis was associated with a polarization of macrophages in the skin from a pro-fibrotic M2 to a M1 phenotype. Paquinimod treatment also resulted in a reduced TGFβ-response in the skin and an abrogation of the increased auto-antibody production in this SSc model.

CONCLUSIONS

Paquinimod reduces skin fibrosis in an experimental model of SSc, and this effect correlates with local and systemic effects on the immune system.

Tasquinimod inhibits prostate cancer growth in bone through alterations in the bone microenvironment

BACKGROUND

Tasquinimod (ABR-215050) is an orally active quinoline-3-carboxamide analog that inhibits occurrence of experimental metastasis and delays disease progression of castration resistant prostate cancer in humans. Its mechanism of action is not fully elucidated, but previous studies show immunomodulatory and anti-angiogenic effects. The aim of the present study was to investigate the tumor inhibiting effect of tasquinimod in bone of castrated mice as well as to elucidate its working mechanism related to bone microenvironment.

METHODS

Effects of tasquinimod on prostate cancer metastasis to bone was studied in an intratibial xenograft model. Animals were treated with tasquinimod and tumor establishment and growth, immunological status, as well as markers for bone remodeling were analyzed. Direct effects of tasquinimod on osteoblasts were studied in vitro.

RESULTS

Establishment and growth of tumors in the bone after intratibial implantation in castrated mice was suppressed by tasquinimod treatment. The treatment effect was linked to decreased potential for immunosuppression in the pre-metastatic niche in bone (lower levels of CD206 and Arg1 expression in combination with increased iNOS expression) as well as in the tumor microenvironment (less Gr1 and CD206 staining). The shift to a pro-inflammatory, anti-tumorigenic milieu was also reflected in serum by increased levels of IFN-γ, CCL4, IL-5, LIX, IP-10, and MCP-1 as well as decreased TGF-β. Tasquinimod treatment also affected expression of factors involved in the pre-metastatic niche in the bone microenvironment (Lox, Cdh2, Cdh11, and Cxcl12). In addition, tasquinimod treatment caused a decreased osteogenic response indicated by decreased expression of Ocn, Runx2, and Col1a2 and increased expression of osteoclast stimulating CSF2. In vitro studies on mouse osteoblasts showed impaired osteoblast mineralization upon tasquinimod treatment.

CONCLUSIONS

The present study shows that tasquinimod reduces establishment and progression of tumor growth in bone likely through a combination of effects on the pre-metastatic niche, homing, immunological status, and osteogenesis. It was concluded that tasquinimod interferes with the metastatic process, presumably by inhibition of tumor establishment. Hence, our data suggest that tasquinimod might be most effective in inhibiting the occurrence of new metastatic lesions.

Tasquinimod modulates tumor-infiltrating myeloid cells and improves the antitumor immune response to PD-L1 blockade in bladder cancer

The infiltration of myeloid cells helps tumors to overcome immune surveillance and imparts resistance to cancer immunotherapy. Thus, strategies to modulate the effects of these immune cells may offer a potential therapeutic benefit. We report here that tasquinimod, a novel immunotherapy which targets S100A9 signaling, reduces the immunosuppressive properties of myeloid cells in preclinical models of bladder cancer (BCa). As single anticancer agent, tasquinimod treatment was effective in preventing early stage tumor growth, but did not achieve a clear antitumor effect in advanced tumors. Investigations of this response revealed that tasquinimod induces an increase in the expression of a negative regulator of T cell activation, Programmed-death-ligand 1 (PD-L1). This markedly weakens its antitumor immunity, yet provokes an "inflamed" milieu rendering tumors more prone to T cell-mediated immune attack by PD-L1 blockade. Interestingly, the combination of tasquinimod with an Anti-PD-L1 antibody enhanced the antitumor immune response in bladder tumors. This combination synergistically modulated tumor-infiltrating myeloid cells, thereby strongly affecting proliferation and activation of effector T cells. Together, our data provide insight into the rational combination of therapies that activate both innate and adaptive immune system, such as the association of S100A9-targeting agents with immune checkpoints inhibitors, to improve the response to cancer immunotherapeutic agents in BCa.

Role of S100 Proteins in Colorectal Carcinogenesis

The family of S100 proteins represents 25 relatively small (9-13 kD) calcium binding proteins. These proteins possess a broad spectrum of important intracellular and extracellular functions. Colorectal cancer is the third most common cancer in men (after lung and prostate cancer) and the second most frequent cancer in women (after breast cancer) worldwide. S100 proteins are involved in the colorectal carcinogenesis through different mechanisms: they enable proliferation, invasion, and migration of the tumour cells; furthermore, S100 proteins increase angiogenesis and activate NF-κβ signaling pathway, which plays a key role in the molecular pathogenesis especially of colitis-associated carcinoma. The expression of S100 proteins in the cancerous tissue and serum levels of S100 proteins might be used as a precise diagnostic and prognostic marker in patients with suspected or already diagnosed colorectal neoplasia. Possibly, in the future, S100 proteins will be a therapeutic target for tailored anticancer therapy.

Tasquinimod triggers an early change in the polarization of tumor associated macrophages in the tumor microenvironment

Background

Tasquinimod (a quinoline-3-carboxyamide) is a small molecule immunotherapy with demonstrated effects on the tumor microenvironment (TME) involving immunomodulation, anti-angiogenesis and inhibition of metastasis. A target molecule of tasquinimod is the inflammatory protein S100A9 which has been shown to affect the accumulation and function of suppressive myeloid cell subsets in tumors. Given the major impact of myeloid cells to the tumor microenvironment, manipulation of this cell compartment is a desirable goal in cancer therapeutics.

Methods

To understand the consequences of tasquinimod treatment on the TME, we evaluated early treatment effects in tumor infiltrating myeloid cells. Cellular phenotypes were studied by flow cytometry while gene expression both in tumor tissue and in isolated CD11b⁺ cells or tumor cells were measured by real time-PCR. Effects on angiogenesis were monitored by changes in CD31 levels and by gene expression in tumor tissue. Effects on cytokine levels in tumor tissue and serum were determined by multiplex analysis.

Results

The MC38-C215 colon carcinoma tumors showed a substantial infiltration of primarily myeloid cells that were dominated by Ly6C^lowF4/80⁺CD206⁺ M2-polarized tumor associated macrophages (TAMs), an immuno-suppressive and pro-angiogenic cell population. Here, we show that tasquinimod treatment induces an anti-tumor effect which is subsequent to a reduction in tumor infiltrating CD206⁺ M2 macrophages and a simultaneous increase in M1 macrophages expressing MHC class II and CD86. The tasquinimod-induced changes in TAM polarization were evident within 24 h of exposure, emphasizing the ability of tasquinimod to rapidly reprogram the tumor microenvironment. This change in the tumor associated myeloid compartment preceded an increased IL12-production within the tumor and a decrease in tumor neovascularization. The switch in TAM polarization by tasquinimod was confirmed in the 4T1 breast cancer model where tasquinimod also reduce lung metastasis development.

Conclusion

Our data show that tasquinimod affects tumor infiltrating myeloid cells early after exposure, leading to a change in phenotype from pro-angiogenic and immunosuppressive M2-like TAMs to pro-inflammatory M1-like macrophages. These changes are consistent with the effects of tasquinimod seen on tumor vascularization, immune suppression and metastasis giving further insights to the anti-tumor mechanism of action of tasquinimod.

Electronic supplementary material

The online version of this article (doi:10.1186/s40425-015-0098-5) contains supplementary material, which is available to authorized users.

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