Classification of current anticancer immunotherapies

Adoptive Cellular Therapy (ACT) for Cancer Treatment

Adoptive cellular therapy (ACT) with various lymphocytes or antigen-presenting cells is one stone in the pillar of cancer immunotherapy, which relies on the tumor-specific T cell. The transfusion of bulk T-cell population into patients is an effective treatment for regression of cancer. In this chapter, we summarize the development of various strategies in ACT for cancer immunotherapy and discuss some of the latest progress and obstacles in technical, safety, and even regulatory aspects to translate these technologies to the clinic. ACT is becoming a potentially powerful approach to cancer treatment. Further experiments and clinical trials are needed to optimize this strategy.

Resistance to anticancer vaccination effect is controlled by a cancer cell-autonomous phenotype that disrupts immunogenic phagocytic removal

Immunogenic cell death (ICD) is a well-established instigator of ‘anti-cancer vaccination-effect (AVE)’. ICD has shown considerable preclinical promise, yet there remain subset of cancer patients that fail to respond to clinically-applied ICD inducers. Non-responsiveness to ICD inducers could be explained by the existence of cancer cell-autonomous, anti-AVE resistance mechanisms. However such resistance mechanisms remain poorly investigated. In this study, we have characterized for the first time, a naturally-occurring preclinical cancer model (AY27) that exhibits intrinsic anti-AVE resistance despite treatment with ICD inducers like mitoxantrone or hypericin-photodynamic therapy. Further mechanistic analysis revealed that this anti-AVE resistance was associated with a defect in exposing the important ‘eat me’ danger signal, surface-calreticulin (ecto-CRT/CALR). In an ICD setting, this defective ecto-CRT further correlated with severely reduced phagocytic clearance of AY27 cells as well as the failure of these cells to activate AVE. Defective ecto-CRT in response to ICD induction was a result of low endogenous CRT protein levels (i.e. CRT^low-phenotype) in AY27 cells. Exogenous reconstitution of ecto-rCRT (recombinant-CRT) improved the phagocytic removal of ICD inducer-treated AY27 cells, and importantly, significantly increased their AVE-activating ability. Moreover, we found that a subset of cancer patients of various cancer-types indeed possessed CALR^low or CRT^low-tumours. Remarkably, we found that tumoural CALR^high-phenotype was predictive of positive clinical responses to therapy with ICD inducers (radiotherapy and paclitaxel) in lung and ovarian cancer patients, respectively. Furthermore, only in the ICD clinical setting, tumoural CALR levels positively correlated with the levels of various phagocytosis-associated genes relevant for phagosome maturation or processing. Thus, we reveal the existence of a cancer cell-autonomous, anti-AVE or anti-ICD resistance mechanism that has profound clinical implications for anticancer immunotherapy and cancer predictive biomarker analysis.

A core of kinase-regulated interactomes defines the neoplastic MDSC lineage

Myeloid-derived suppressor cells (MDSCs) differentiate from bone marrow precursors, expand in cancer-bearing hosts and accelerate tumor progression. MDSCs have become attractive therapeutic targets, as their elimination strongly enhances anti-neoplastic treatments. Here, immature myeloid dendritic cells (DCs), MDSCs modeling tumor-infiltrating subsets or modeling non-cancerous (NC)-MDSCs were compared by in-depth quantitative proteomics. We found that neoplastic MDSCs differentially expressed a core of kinases which controlled lineage-specific (PI3K-AKT and SRC kinases) and cancer-induced (ERK and PKC kinases) protein interaction networks (interactomes). These kinases contributed to some extent to myeloid differentiation. However, only AKT and ERK specifically drove MDSC differentiation from myeloid precursors. Interfering with AKT and ERK with selective small molecule inhibitors or shRNAs selectively hampered MDSC differentiation and viability. Thus, we provide compelling evidence that MDSCs constitute a distinct myeloid lineage distinguished by a “kinase signature” and well-defined interactomes. Our results define new opportunities for the development of anti-cancer treatments targeting these tumor-promoting immune cells.

Local Tumor Treatment in Combination with Systemic Ipilimumab Immunotherapy Prolongs Overall Survival in Patients with Advanced Malignant Melanoma

Immune checkpoint inhibition with ipilimumab has revolutionized cancer immunotherapy and significantly improved outcomes of patients with advanced malignant melanoma. Local peripheral treatments (LPT), such as radiotherapy or electrochemotherapy, have been shown to modulate systemic immune responses, and preliminary data have raised the hypothesis that the combination of LPT with systemic immune checkpoint blockade might be beneficial. Clinical data from 127 consecutively treated melanoma patients at four cancer centers in Germany and Switzerland were analyzed. Patients received either ipilimumab (n = 82) or ipilimumab and additional LPT (n = 45) if indicated for local tumor control. The addition of LPT to ipilimumab significantly prolonged overall survival (OS; median OS 93 vs. 42 weeks, unadjusted HR, 0.46; P = 0.0028). Adverse immune-related events were not increased by the combination treatment, and LPT-induced local toxicities were in most cases mild. In a multivariable Cox regression analysis, we show that the effect of added LPT on OS remained statistically significant after adjusting for BRAF status, tumor stage, tumor burden, and central nervous system metastases (adjusted HR, 0.56; 95% confidence interval, 0.31-1.01, P = 0.05). Our data suggest that the addition of LPT to ipilimumab is safe and effective in patients with metastatic melanoma irrespective of clinical disease characteristics and known risk factors. Induction of antitumor immune responses is most likely the underlying mechanism and warrants prospective validation. Cancer Immunol Res; 4(9); 744-54. ©2016 AACR.

Trial Watch: Immunotherapy plus radiation therapy for oncological indications

Malignant cells succumbing to some forms of radiation therapy are particularly immunogenic and hence can initiate a therapeutically relevant adaptive immune response. This reflects the intrinsic antigenicity of malignant cells (which often synthesize a high number of potentially reactive neo-antigens) coupled with the ability of radiation therapy to boost the adjuvanticity of cell death as it stimulates the release of endogenous adjuvants from dying cells. Thus, radiation therapy has been intensively investigated for its capacity to improve the therapeutic profile of several anticancer immunotherapies, including (but not limited to) checkpoint blockers, anticancer vaccines, oncolytic viruses, Toll-like receptor (TLR) agonists, cytokines, and several small molecules with immunostimulatory effects. Here, we summarize recent preclinical and clinical advances in this field of investigation.

Integrating conventional and antibody-based targeted anticancer treatment into immunotherapy

In advanced cancer, current conventional therapies or immunotherapies cannot eradicate all tumor cells for most patients. Integration of these two treatments for synergistic effects could eradicate more tumor cells and increase overall survival rates. But proper integration is a challenge, partly due to a poor understanding of the impact of conventional treatment on immune responses. Intensive chemo/radiotherapy may impair ongoing immune responses whilst lower intensity of therapy might not kill enough tumor cells, both leading to tumor relapse. Current understanding of mechanisms of resistance to conventional and targeted cancer therapies has focused on cell intrinsic pathways that trigger DNA damage/repair or signaling pathways related to cell growth. Recent reports show that host T cells properly primed against tumor specific antigens after conventional treatment can integrate with direct cytotoxic effects induced by radiation or chemotherapy to profoundly control tumors. Following cytotoxic anticancer treatment, tumor derived DAMPs (damage-associated molecular patterns) can be sensed by innate cells which drives type I interferon (IFNs production) for cross priming of CD8⁺ T cells. Some types and protocols of chemotherapy or radiation can increase tumor infiltrating lymphocytes that overcome resistance to immunotherapy. As such, a deeper understanding to the immune mechanisms of conventional and targeted cancer therapies will lead toward novel combinatorial anticancer strategies with improved clinical benefit.

Human Leukocyte Antigen (HLA) Peptides Derived from Tumor Antigens Induced by Inhibition of DNA Methylation for Development of Drug-facilitated Immunotherapy

Treatment of cancer cells with anticancer drugs often fails to achieve complete remission. Yet, such drug treatments may induce alteration in the tumor's gene expression patterns, including those of Cancer/Testis Antigens (CTA). The degradation products of such antigens can be presented as HLA peptides on the surface of the tumor cells and be developed into anticancer immunotherapeutics. For example, the DNA methyl transferase inhibitor, 5-aza-2'-deoxycytidine (Decitabine) has limited antitumor efficacy, yet it induces the expression of many genes, including CTAs that are normally silenced in the healthy adult tissues. In this study, the presentation of many new HLA peptides derived from CTAs and induced by Decitabine was demonstrated in three human Glioblastoma cell lines. Such presentation of CTA-derived HLA peptides can be exploited for development of new treatment modalities, combining drug treatment with anti-CTA targeted immunotherapy. The Decitabine-induced HLA peptidomes include many CTAs that are not normally detected in healthy tissues or in cancer cells, unless treated with the drug. In addition, the study included large-scale analyses of the simultaneous effects of Decitabine on the transcriptomes, proteomes and HLA peptidomes of the human Glioblastoma cells. It demonstrates the poor correlations between these three levels of gene expression, both in their total levels and in their response to the drug. The proteomics and HLA peptidomics data are available via ProteomeXchange with identifier PXD003790 and the transcriptomics data are available via GEO with identifier GSE80137.

Molecular Profile of Tumor-Specific CD8+ T Cell Hypofunction in a Transplantable Murine Cancer Model

Mechanisms of self-tolerance often result in CD8(+) tumor-infiltrating lymphocytes (TIL) with a hypofunctional phenotype incapable of tumor clearance. Using a transplantable colon carcinoma model, we found that CD8(+) T cells became tolerized in <24 h in an established tumor environment. To define the collective impact of pathways suppressing TIL function, we compared genome-wide mRNA expression of tumor-specific CD8(+) T cells from the tumor and periphery. Notably, gene expression induced during TIL hypofunction more closely resembled self-tolerance than viral exhaustion. Differential gene expression was refined to identify a core set of genes that defined hypofunctional TIL; these data comprise the first molecular profile of tumor-specific TIL that are naturally responding and represent a polyclonal repertoire. The molecular profile of TIL was further dissected to determine the extent of overlap and distinction between pathways that collectively restrict T cell functions. As suggested by the molecular profile of TIL, protein expression of inhibitory receptor LAG-3 was differentially regulated throughout prolonged late-G1/early-S phase of the cell cycle. Our data may accelerate efficient identification of combination therapies to boost anti-tumor function of TIL specifically against tumor cells.

Tumor-associated macrophages and anti-tumor therapies: complex links

Myeloid cells infiltrating the tumor microenvironment, especially tumor-associated macrophages (TAMs), are essential providers of cancer-related inflammation, a condition known to accelerate tumor progression and limit the response to anti-tumor therapies. As a matter of fact, TAMs may have a dual role while interfering with cancer treatments, as they can either promote or impair their functionality. Here we review the connection between macrophages and anticancer therapies; moreover, we provide an overview of the different strategies to target or re-program TAMs for therapeutic purposes.

Muramyl dipeptide and anti-CD10 monoclonal antibody immunoconjugate enhances anti-leukemia immunity of T lymphocytes

It is necessary to completely eliminate minimal residual disease (MRD) to cure acute leukemia. Monoclonal antibodies (MAb) have been shown to be effective to eliminate MRD. In this study we aimed to investigate the effect of anti-CD10 MAb conjugated to muramyl dipeptide immunoconjugate (MDP-Ab) on the function of lymphocytes and activated lymphocytes using leukemia xenografts in nude mice as a model. Peripheral blood mononuclear cells were isolated from children with acute lymphoblastic leukemia and induced into dendritic cells (DCs) and lymphocytes. Cytotoxic activity of lymphocytes was detected by LDH release assay. Leukemia xenografts in nude mice were established to assess tumor growth. We found that the killing rate was significantly higher in MDP-Ab group, LPS group and MDP-Ab+LPS group than in control group, and was the highest in MDP-Ab+LPS group. Tumor-bearing mice in MDP-Ab group showed obvious coagulation necrosis. In conclusion, our data suggest that MDP-Ab could effectively prime DCs to improve the anti-tumor immunity of T lymphocytes and inhibit the tumor growth. MDP-Ab may be used as suitable candidate for eliminating residual leukemia cells to prevent relapse.

The present status and future prospects of peptide-based cancer vaccines

Tumor cells commonly express several antigens, such as tumor-associated antigens (TAAs) or mutation-derived antigens (neoantigens), that can be regarded as foreign antigens and elicit anti-tumor immune responses in cancer patients. Various TAAs or neoantigens expressed in cancer cells have been identified and utilized as targets for cancer vaccines. One approach to elicit tumor-specific immune responses is termed peptide-based cancer vaccination; it involves administrating TAAs or neoantigen-derived peptide for treatment of cancers. There have been several forms of peptide-based cancer vaccines depending on which effector cells, such as CTLs or CD4(+) T-helper cells, are targeted to be activated. Many phase I and II clinical trials of peptide-based cancer vaccines using TAA-derived CTL epitopes, T-helper cell epitopes or dendritic cells loaded with TAA-derived peptides for various malignant tumors have been conducted and provide clinical benefits in a small fraction of patients. Nowadays, to improve the efficiency of peptide-based cancer vaccines, combination immunotherapy of peptide-based cancer vaccines with the immune-checkpoint blockade therapies using mAbs specific for CTLA-4, programmed cell death 1 (PD-1), or PD-1 ligand 1 (PD-L1) have been developed for clinical application. Furthermore, along with the recent technological progress in genetic and bioinformatic analysis, it has become easier to identify neoantigens from individual cancer patients. It is expected that peptide-based cancer vaccines targeting neoantigens as a personalized cancer immunotherapy will be developed.

Phase I/II clinical trial of dendritic-cell based immunotherapy (DCVAC/PCa) combined with chemotherapy in patients with metastatic, castration-resistant prostate cancer

PURPOSE

We conducted an open-label, single-arm Phase I/II clinical trial in metastatic CRPC (mCRPC) patients eligible for docetaxel combined with treatment with autologous mature dendritic cells (DCs) pulsed with killed LNCaP prostate cancer cells (DCVAC/PCa). The primary and secondary endpoints were safety and immune responses, respectively. Overall survival (OS), followed as a part of the safety evaluation, was compared to the predicted OS according to the Halabi and MSKCC nomograms.

EXPERIMENTAL DESIGN

Twenty-five patients with progressive mCRPC were enrolled. Treatment comprised of initial 7 days administration of metronomic cyclophosphamide 50 mg p.o. DCVAC/PCa treatment consisted of a median twelve doses of 1 × 107 dendritic cells per dose injected s.c. (Aldara creme was applied at the site of injection) during a one-year period. The initial 2 doses of DCVAC/PCa were administered at a 2-week interval, followed by the administration of docetaxel (75 mg/m2) and prednisone (5 mg twice daily) given every 3 weeks until toxicity or intolerance was observed. The DCVAC/PCa was then injected every 6 weeks up to the maximum number of doses manufactured from one leukapheresis.

RESULTS

No serious DCVAC/PCa-related adverse events have been reported. The median OS was 19 months, whereas the predicted median OS was 11.8 months with the Halabi nomogram and 13 months with the MSKCC nomogram. Kaplan-Meier analyses showed that patients had a lower risk of death compared with both MSKCC (Hazard Ratio 0.26, 95% CI: 0.13-0.51) and Halabi (Hazard Ratio 0.33, 95% CI: 0.17-0.63) predictions. We observed a significant decrease in Tregs in the peripheral blood. The long-term administration of DCVAC/PCa led to the induction and maintenance of PSA specific T cells. We did not identify any immunological parameter that significantly correlated with better OS.

CONCLUSIONS

In patients with mCRPC, the combined chemoimmunotherapy with DCVAC/PCa and docetaxel was safe and resulted in longer than expected survival. Concomitant chemotherapy did not preclude the induction of specific anti-tumor cytotoxic T cells.

Hypericin in the Light and in the Dark: Two Sides of the Same Coin

Hypericin (4,5,7,4',5',7'-hexahydroxy-2,2'-dimethylnaphtodianthrone) is a naturally occurring chromophore found in some species of the genus Hypericum, especially Hypericum perforatum L. (St. John's wort), and in some basidiomycetes (Dermocybe spp.) or endophytic fungi (Thielavia subthermophila). In recent decades, hypericin has been intensively studied for its broad pharmacological spectrum. Among its antidepressant and light-dependent antiviral actions, hypericin is a powerful natural photosensitizer that is applicable in the photodynamic therapy (PDT) of various oncological diseases. As the accumulation of hypericin is significantly higher in neoplastic tissue than in normal tissue, it can be used in photodynamic diagnosis (PDD) as an effective fluorescence marker for tumor detection and visualization. In addition, light-activated hypericin acts as a strong pro-oxidant agent with antineoplastic and antiangiogenic properties, since it effectively induces the apoptosis, necrosis or autophagy of cancer cells. Moreover, a strong affinity of hypericin for necrotic tissue was discovered. Thus, hypericin and its radiolabeled derivatives have been recently investigated as potential biomarkers for the non-invasive targeting of tissue necrosis in numerous disorders, including solid tumors. On the other hand, several light-independent actions of hypericin have also been described, even though its effects in the dark have not been studied as intensively as those of photoactivated hypericin. Various experimental studies have revealed no cytotoxicity of hypericin in the dark; however, it can serve as a potential antimetastatic and antiangiogenic agent. On the contrary, hypericin can induce the expression of some ABC transporters, which are often associated with the multidrug resistance (MDR) of cancer cells. Moreover, the hypericin-mediated attenuation of the cytotoxicity of some chemotherapeutics was revealed. Therefore, hypericin might represent another St. John's wort metabolite that is potentially responsible for negative herb-drug interactions. The main aim of this review is to summarize the benefits of photoactivated and non-activated hypericin, mainly in preclinical and clinical applications, and to uncover the "dark side" of this secondary metabolite, focusing on MDR mechanisms.

Current Challenges in Cancer Treatment

PURPOSE

In this review, we highlight the current concepts and discuss some of the current challenges and future prospects in cancer therapy. We frequently use the example of lung cancer.

METHODS

We conducted a nonsystematic PubMed search, selecting the most comprehensive and relevant research articles, clinical trials, translational papers, and review articles on precision oncology and immuno-oncology. Papers were prioritized and selected based on their originality and potential clinical applicability.

FINDINGS

Two major revolutions have changed cancer treatment paradigms in the past few years: targeting actionable alterations in oncogene-driven cancers and immuno-oncology. Important challenges are still ongoing in both fields of cancer therapy. On the one hand, druggable genomic alterations are diverse and represent only small subsets of patients in certain tumor types, which limits testing their clinical impact in biomarker-driven clinical trials. Next-generation sequencing technologies are increasingly being implemented for molecular prescreening in clinical research, but issues regarding clinical interpretation of large genomic data make their wide clinical use difficult. Further, dealing with tumor heterogeneity and acquired resistance is probably the main limitation for the success of precision oncology. On the other hand, long-term survival benefits with immune checkpoint inhibitors (anti-programmed death cell protein-1/programmed death cell ligand-1[PD-1/L1] and anti-cytotoxic T lymphocyte antigen-4 monoclonal antibodies) are restricted to a minority of patients, and no predictive markers are yet robustly validated that could help us recognize these subsets and optimize treatment delivery and selection. To achieve long-term survival benefits, drug combinations targeting several molecular alterations or cancer hallmarks might be needed. This will probably be one of the most challenging but promising precision cancer treatment strategies in the future.

IMPLICATIONS

Targeting single molecular abnormalities or cancer pathways has achieved good clinical responses that have modestly affected survival in some cancers. However, this approach to cancer treatment is still reductionist, and many challenges need to be met to improve treatment outcomes with our patients.

Biomarkers for immunotherapy in genitourinary malignancies

Immunotherapy for genitourinary malignancies such as prostate, renal, and bladder cancers has experienced a resurgence since the development of 3 novel strategies: the autologous cellular product therapy, Sipuleucel-T for prostate cancer, the checkpoint inhibitors, anti-cytotoxic T-lymphocyte-associated protein 4 (anti-CTLA-4), anti-programmed cell death ligand 1 (anti-PD1), and anti-programmed cell death ligand 1), respectively. These agents have led to strikingly durable responses in several of these solid tumors, but their efficacy has been inconsistent. Why all solid tumors are not equal in their response to these therapies is unclear. More importantly, changes in humoral or cellular responses which may reflect changes in a tumor's biology have been limited due to differences in immune monitoring and lack of consistency in established reliable immunologic endpoints. How to design immunologic end points that reflect a meaningful effect on the cancer remains a challenge for clinical trial development. The issues faced by clinical investigators and the current state of immune monitoring are discussed.

MYC regulates the antitumor immune response through CD47 and PD-L1

The MYC oncogene codes for a transcription factor that is overexpressed in many human cancers. Here we show that MYC regulates the expression of two immune checkpoint proteins on the tumor cell surface: the innate immune regulator CD47 (cluster of differentiation 47) and the adaptive immune checkpoint PD-L1 (programmed death-ligand 1). Suppression of MYC in mouse tumors and human tumor cells caused a reduction in the levels of CD47 and PD-L1 messenger RNA and protein. MYC was found to bind directly to the promoters of the Cd47 and Pd-l1 genes. MYC inactivation in mouse tumors down-regulated CD47 and PD-L1 expression and enhanced the antitumor immune response. In contrast, when MYC was inactivated in tumors with enforced expression of CD47 or PD-L1, the immune response was suppressed, and tumors continued to grow. Thus, MYC appears to initiate and maintain tumorigenesis, in part, through the modulation of immune regulatory molecules.

Contribution of RIP3 and MLKL to immunogenic cell death signaling in cancer chemotherapy

Chemotherapy can reinstate anticancer immunosurveillance through inducing tumor immunogenic cell death (ICD). Here, we show that anthracyclines and oxaliplatin can trigger necroptosis in murine cancer cell lines expressing receptor-interacting serine-threonine kinase 3 (RIP3) and mixed lineage kinase domain-like (MLKL). Necroptotic cells featured biochemical hallmarks of ICD and stimulated anticancer immune responses in vivo. Chemotherapy normally killed Rip3 (-/-) and Mlkl (-/-) tumor cells and normally induced caspase-3 activation in such cells, yet was unable to reduce their growth in vivo. RIP3 or MLKL deficiency abolished the capacity of dying cancer cells to elicit an immune response. This could be attributed to reduced release of ATP and high mobility group box 1 (HMGB1) by RIP3 and MLKL-deficient cells. Measures designed to compensate for deficient ATP and HMGB1 signaling restored the chemotherapeutic response of Rip3 (-/-) and Mlkl (-/-) cancers. Altogether, these results suggest that RIP3 and MLKL can contribute to ICD signaling and tumor immunogenicity.

Immunogenic versus tolerogenic phagocytosis during anticancer therapy: mechanisms and clinical translation

Phagocytosis of dying cells is a major homeostatic process that represents the final stage of cell death in a tissue context. Under basal conditions, in a diseased tissue (such as cancer) or after treatment with cytotoxic therapies (such as anticancer therapies), phagocytosis has a major role in avoiding toxic accumulation of cellular corpses. Recognition and phagocytosis of dying cancer cells dictate the eventual immunological consequences (i.e., tolerogenic, inflammatory or immunogenic) depending on a series of factors, including the type of 'eat me' signals. Homeostatic clearance of dying cancer cells (i.e., tolerogenic phagocytosis) tends to facilitate pro-tumorigenic processes and actively suppress antitumour immunity. Conversely, cancer cells killed by immunogenic anticancer therapies may stimulate non-homeostatic clearance by antigen-presenting cells and drive cancer antigen-directed immunity. On the other hand, (a general) inflammatory clearance of dying cancer cells could have pro-tumorigenic or antitumorigenic consequences depending on the context. Interestingly, the immunosuppressive consequences that accompany tolerogenic phagocytosis can be reversed through immune-checkpoint therapies. In the present review, we discuss the pivotal role of phagocytosis in regulating responses to anticancer therapy. We give particular attention to the role of phagocytosis following treatment with immunogenic or immune-checkpoint therapies, the clinical prognostic and predictive significance of phagocytic signals for cancer patients and the therapeutic strategies that can be employed for direct targeting of phagocytic determinants.

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.

A Randomized Phase II/III Study of Naptumomab Estafenatox + IFNα versus IFNα in Renal Cell Carcinoma: Final Analysis with Baseline Biomarker Subgroup and Trend Analysis

PURPOSE

To prospectively determine the efficacy of naptumomab estafenatox (Nap) + IFNα versus IFN in metastatic renal cell carcinoma (RCC).

EXPERIMENTAL DESIGN

In a randomized, open-label, multicenter, phase II/III study, 513 patients with RCC received Nap (15 μg/kg i. v. in three cycles of four once-daily injections) + IFN (9 MU s.c. three times weekly), or the same regimen of IFN monotherapy. The primary endpoint was overall survival (OS).

RESULTS

This phase II/III study did not meet its primary endpoint. Median OS/PFS for Nap + IFN patients was 17.1/5.8 months versus 17.5/5.8 months for the patients receiving IFN alone (P = 0.56; HR, 1.08/P = 0.41; HR, 0.92). Post hoc exploratory subgroup and trend analysis revealed that the baseline plasma concentrations of anti-SEA/E-120 (anti-Nap antibodies) for drug exposure and IL6 for immune status could be used as predictive biomarkers. A subgroup of patients (SG; n = 130) having concentrations below median of anti-SEA/E-120 and IL6 benefitted greatly from the addition of Nap. In SG, median OS/PFS for the patients treated with Nap + IFN was 63.3/13.7 months versus 31.1/5.8 months for the patients receiving IFN alone (P = 0.02; HR, 0.59/P = 0.02; HR, 0.62). Addition of Nap to IFN showed predicted and transient immune related AEs and the treatment had an acceptable safety profile.

CONCLUSIONS

The study did not meet its primary endpoint. Nap + IFN has an acceptable safety profile, and results from post hoc subgroup analyses showed that the treatment might improve OS/PFS in a baseline biomarker-defined RCC patient subgroup. The results warrant further studies with Nap in this subgroup. Clin Cancer Res; 22(13); 3172-81. ©2016 AACR.

Personalized chemotherapy of lung cancer: What the radiologist should know

Lung cancer is the leading cause of deaths due to cancer in France. More than half of lung cancers are discovered at an advanced-stage. New anticancer treatment strategies (i.e., the so-called personalized or targeted therapy) have recently been introduced and validated for non-small-cell lung cancer (NSCLC), in addition to or in association with standard chemotherapy. Personalized therapy includes tyrosine kinase inhibitors (TKIs), antiangiogenic treatments and immunotherapy. Because these treatments may be responsible for atypical thoracic adverse effects and responses as compared to standard chemotherapy, RECIST 1.1 criteria may be inadequate to evaluate the responses to these agents. The goal of this article was to review personalized treatment strategies for NSCLC, to consider the therapy-specific responses and thoracic complications induced by these new therapeutic agents and finally to discuss future directions for the personalized assessment of tumor response.

Trial Watch-Oncolytic viruses and cancer therapy

Oncolytic virotherapy relies on the administration of non-pathogenic viral strains that selectively infect and kill malignant cells while favoring the elicitation of a therapeutically relevant tumor-targeting immune response. During the past few years, great efforts have been dedicated to the development of oncolytic viruses with improved specificity and potency. Such an intense wave of investigation has culminated this year in the regulatory approval by the US Food and Drug Administration (FDA) of a genetically engineered oncolytic viral strain for use in melanoma patients. Here, we summarize recent preclinical and clinical advances in oncolytic virotherapy.

Immunotherapy in Chronic Lymphocytic Leukaemia (CLL)

Chronic lymphocytic leukaemia (CLL) is well known to generate impaired immune responses in the host, with the malignant clone residing in well-vascularized tissues and circulating in peripheral blood but also in close proximity to effector cells that are capable, if activated appropriately, of eliciting a cytotoxic response. These, combined with the fact that this is frequently a condition affecting older patients with co-morbidities often unfit for many "traditional" cytotoxic agents with their significant associated toxicities, make CLL an ideal candidate for the development of immunotherapy. The impressive results seen with the addition of a monoclonal antibody, rituximab, to a chemotherapy backbone, for example, is testament to how effective harnessing an immune-mediated response in CLL can be. This review serves to outline the available arsenal of immunotherapies-past and present-demonstrated to have potential in CLL with some perspectives on how the landscape in this disease may evolve in the future.

Natural and therapy-induced immunosurveillance in breast cancer

The immunosurveillance theory postulates that tumors evolve and progress in an uncontrolled fashion only when anticancer immune responses fail. Natural immunosurveillance clearly influences human breast cancer (BC) progression because the prognosis of BC patients is dictated by the density, composition and activity of the tumor immune infiltrate at diagnosis. Moreover, chemotherapeutic and radiotherapeutic regimens commonly employed for the treatment of BC affect the tumor immune infiltrate, and accumulating data suggest that the clinical efficacy of these treatments is largely determined by T cell-dependent tumor-specific immune responses. In addition, the mechanism of action of targeted anticancer therapeutics, such as the erb-b2 receptor tyrosine kinase 2 (ERBB2)-targeting agent trastuzumab, involves the innate and adaptive arms of the immune system. In this Review, we discuss these findings as well as preliminary evidence indicating that immunotherapy constitutes a promising option for the treatment of BC. Moreover, we point out that the successful implementation of immunotherapy to BC management requires the optimization of current immunotherapeutic regimens and the identification of immunological biomarkers that enable improved risk stratification and the design of personalized, dynamic treatment plans.

Mouse Models of Tumor Immunotherapy

Immunotherapy is now evolving into a major therapeutic option for cancer patients. Such clinical advances also promote massive interest in the search for novel immunotherapy targets, and to understand the mechanism of action of current drugs. It is projected that a series of novel immunotherapy agents will be developed and assessed for their therapeutic activity. In light of this, in vivo experimental mouse models that recapitulate human malignancies serve as valuable tools to validate the efficacy and safety profile of immunotherapy agents, before their transition into clinical trials. In this review, we will discuss the major classes of experimental mouse models of cancer commonly used for immunotherapy assessment and provide examples to guide the selection of appropriate models. We present some new data concerning the utility of a carcinogen-induced tumor model for comparing immunotherapies and combining immunotherapy with chemotherapy. We will also highlight some recent advances in experimental modeling of human malignancies in mice that are leading towards personalized therapy in patients.

The Role of Immunotherapy in Multiple Myeloma

Multiple myeloma is the second most common hematologic malignancy. The treatment of this disease has changed considerably over the last two decades with the introduction to the clinical practice of novel agents such as proteasome inhibitors and immunomodulatory drugs. Basic research efforts towards better understanding of normal and missing immune surveillence in myeloma have led to development of new strategies and therapies that require the engagement of the immune system. Many of these treatments are under clinical development and have already started providing encouraging results. We, for the second time in the last two decades, are about to witness another shift of the paradigm in the management of this ailment. This review will summarize the major approaches in myeloma immunotherapies.

Novel cancer antigens for personalized immunotherapies: latest evidence and clinical potential

The clinical success of monoclonal antibody immune checkpoint modulators such as ipilimumab, which targets cytotoxic T lymphocyte-associated antigen 4 (CTLA-4), and the recently approved agents nivolumab and pembrolizumab, which target programmed cell death receptor 1 (PD-1), has stimulated renewed enthusiasm for anticancer immunotherapy, which was heralded by Science as 'Breakthrough of the Year' in 2013. As the potential of cancer immunotherapy has been recognized since the 1890s when William Coley showed that bacterial products could be beneficial in cancer patients, leveraging the immune system in the treatment of cancer is certainly not a new concept; however, earlier attempts to develop effective therapeutic vaccines and antibodies against solid tumors, for example, melanoma, frequently met with failure due in part to self-tolerance and the development of an immunosuppressive tumor microenvironment. Increased knowledge of the mechanisms through which cancer evades the immune system and the identification of tumor-associated antigens (TAAs) and negative immune checkpoint regulators have led to the development of vaccines and monoclonal antibodies targeting specific tumor antigens and immune checkpoints such as CTLA-4 and PD-1. This review first discusses the established targets of currently approved cancer immunotherapies and then focuses on investigational cancer antigens and their clinical potential. Because of the highly heterogeneous nature of tumors, effective anticancer immunotherapy-based treatment regimens will likely require a personalized combination of therapeutic vaccines, antibodies and chemotherapy that fit the specific biology of a patient's disease.

The oncolytic virus dl922-947 reduces IL-8/CXCL8 and MCP-1/CCL2 expression and impairs angiogenesis and macrophage infiltration in anaplastic thyroid carcinoma

Anaplastic thyroid carcinoma (ATC) is one of the most aggressive human solid tumor and current treatments are ineffective in increasing patients' survival. Thus, the development of new therapeutic approaches for ATC is needed. We have previously shown that the oncolytic adenovirus dl922-947 induces ATC cell death in vitro and tumor regression in vivo. However, the impact of dl922-947 on the pro-tumorigenic ATC microenvironment is still unknown. Since viruses are able to regulate cytokine and chemokine production from infected cells, we sought to investigate whether dl922-947 virotherapy has such effect on ATC cells, thereby modulating ATC microenvironment. dl922-947 decreased IL-8/CXCL8 and MCP-1/CCL2 production by the ATC cell lines 8505-c and BHT101-5. These results correlated with dl922-947-mediated reduction of NF-κB p65 binding to IL8 promoter in 8505-c and BHT101-5 cells and CCL2 promoter in 8505-c cells. IL-8 stimulates cancer cell proliferation, survival and invasion, and also angiogenesis. dl922-947-mediated reduction of IL-8 impaired ATC cell motility in vitro and ATC-induced angiogenesis in vitro and in vivo. We also show that dl922-947-mediated reduction of the monocyte-attracting chemokine CCL2 decreased monocyte chemotaxis in vitro and tumor macrophage density in vivo. Interestingly, dl922-947 treatment induced the switch of tumor macrophages toward a pro-inflammatory M1 phenotype, likely by increasing the expression of the pro-inflammatory cytokine interferon-γ. Altogether, we demonstrate that dl922-947 treatment re-shape the pro-tumorigenic ATC microenvironment by modulating cancer-cell intrinsic factors and the immune response. An in-depth knowledge of dl922-947-mediated effects on ATC microenvironment may help to refine ATC virotherapy in the context of cancer immunotherapy.

STAT3 inhibition for cancer therapy: Cell-autonomous effects only?

A paper recently published in Science Translational Medicine describes a next-generation antisense oligonucleotide that specifically downregulates the expression of human signal transducer and activator of transcription 3 (STAT3). Such an oligonucleotide, AZD9150, exerts antineoplastic effects on a selected panel of STAT3-dependent human cancer cells growing in vitro and in vivo (as xenografts in immunodeficient mice). Moreover, preliminary data from a Phase I clinical trial indicate that AZD9150 may cause partial tumor regression in patients with chemorefractory lymphoma and non-small cell lung carcinoma. STAT3 not only participates in cell-autonomous processes that are required for the survival and growth of malignant cells, but also limits their ability to elicit anticancer immune responses. Moreover, STAT3 contribute to the establishment of an immunosuppressive tumor microenvironment. Thus, the inhibition of STAT3 may promote immunosurveillance by a dual mechanism: (1) it may increase the immunogenicity of cancer cells via cell-autonomous pathways; and (2) it may favor the reprogramming of the tumor microenvironment toward an immunostimulatory state. It will therefore be important to explore whether immunological biomarkers predict the efficacy of AZD9150 in the clinic. This may ameliorate patient stratification and it may pave the way for rational combination therapies involving classical chemotherapeutics with immunostimulatory effects, AZD9150 and immunotherapeutic agents such as checkpoint blockers.

First oncolytic virus approved for melanoma immunotherapy

On 2015, October 27th, the US Food and Drug Administration (FDA) has officially approved talimogene laherparepvec (T-VEC, also known as OncoVEX^GM-CSF) for use in melanoma patients with injectable but non-resectable lesions in the skin and lymph nodes. T-VEC (which is commercialized by Amgen, Inc. under the name of Imlygic®) becomes therefore the first oncolytic virus approved for cancer therapy in the US.

Molecular and Translational Classifications of DAMPs in Immunogenic Cell Death

The immunogenicity of malignant cells has recently been acknowledged as a critical determinant of efficacy in cancer therapy. Thus, besides developing direct immunostimulatory regimens, including dendritic cell-based vaccines, checkpoint-blocking therapies, and adoptive T-cell transfer, researchers have started to focus on the overall immunobiology of neoplastic cells. It is now clear that cancer cells can succumb to some anticancer therapies by undergoing a peculiar form of cell death that is characterized by an increased immunogenic potential, owing to the emission of the so-called “damage-associated molecular patterns” (DAMPs). The emission of DAMPs and other immunostimulatory factors by cells succumbing to immunogenic cell death (ICD) favors the establishment of a productive interface with the immune system. This results in the elicitation of tumor-targeting immune responses associated with the elimination of residual, treatment-resistant cancer cells, as well as with the establishment of immunological memory. Although ICD has been characterized with increased precision since its discovery, several questions remain to be addressed. Here, we summarize and tabulate the main molecular, immunological, preclinical, and clinical aspects of ICD, in an attempt to capture the essence of this phenomenon, and identify future challenges for this rapidly expanding field of investigation.

A quantitative analysis of therapeutic cancer vaccines in phase 2 or phase 3 trial

Despite the progress that has been made in other forms of cancer therapy, Provenge® (Sipuleucel-T) is the only FDA-approved vaccine for the treatment of cancer. To understand the current landscape of therapeutic oncology vaccines we performed a quantitative analysis of phase 2 and phase 3 therapeutic cancer vaccine trials. We highlight shifts in trends for the vaccine platforms examined, common adjuvant use, target indications, antibody or treatment combinations between past and recent trials as well as discuss the relationship between these trends and ratio between the number of phase 3: phase 2 for different vaccine platforms. Despite the poor success rate in vaccine approvals, registration of phase 3 trials between 2010 and 2014 were stable indicating continued investment and efforts towards development of immunotherapeutic vaccines.

Immunotherapies for bladder cancer: a new hope

PURPOSE OF REVIEW

We review recent data on immunotherapies for bladder cancer and discuss strategies to maximize the antitumor effect of immunotherapy in solid tumors.

RECENT FINDINGS

Anti-programmed death ligand 1 has shown promise in advanced bladder cancer. Clinical trials of immune checkpoint inhibitors as monotherapy or in combination are underway. Here we review strategies for enhancing antitumor immunity using immunomodulating agents or combination treatments that may increase tumor response.

SUMMARY

Combining immune checkpoint inhibitors with other treatment modalities may lead to the development of new treatment strategies in advanced bladder cancer; however, identifying predictive biomarkers is essential for appropriate patient selection.

Immunotherapy for Head and Neck Squamous Cell Carcinoma

Although head and neck squamous cell carcinoma has traditionally been considered to be a very immunosuppressive, or at least nonimmunogenic, tumor type, recent results from clinical studies of immune checkpoint blockade strategies have led to resurgence in the enthusiasm for immunotherapeutic approaches. Additional strategies for immunotherapy that are under active investigation include enhancement of cetuximab-mediated antibody-dependent cell-mediated cytotoxicity, tumor vaccines, and engineered T cells for adoptive therapy. All of these studies have early-phase clinical trials under way, and the next several years will be exciting as the results of these studies are reported.

Targeting tumor vasculature: expanding the potential of DNA cancer vaccines

Targeting the tumor vasculature with anti-angiogenesis modalities is a bona fide validated approach that has complemented cancer treatment paradigms. Tumor vasculature antigens (TVA) can be immunologically targeted and offers multiple theoretical advantages that may enhance existing strategies against cancer. We focused on tumor endothelial marker 1 (TEM1/CD248) as a model TVA since it is broadly expressed on many different cancers. Our DNA-based vaccine approach demonstrated that CD248 can be effectively targeted immunologically; anti-tumor responses were generated in several mouse models; and CD8(+)/CD4(+) T cell responses were elicited against peptides derived from CD248 protein. Our work supports our contention that CD248 is a novel immunotherapeutic target for cancer treatment and highlights the efficient, safe and translatable use of DNA-based immunotherapy. We next briefly highlight ongoing investigations targeting CD248 with antibodies as a diagnostic imaging agent and as a therapeutic antibody in an early clinical trial. The optimal approach for generating effective DNA-based cancer vaccines for several tumor types may be a combinatorial approach that enhances immunogenicity such as combination with chemotherapy. Additional combination approaches are discussed and include those that alleviate the immunosuppressive tumor microenvironment induced by myeloid-derived suppressor cells and T regulatory cells. Targeting the tumor vasculature by CD248-based immunological modalities expands the armamentarium against cancer.

The Relationship of Immune Cell Signatures to Patient Survival Varies within and between Tumor Types

Enhancing pre-existing anti-tumor immunity leads to therapeutic benefit for some patients, but why some tumors are more immunogenic than others remains unresolved. We took a unique systems approach to relate patient survival to immune gene expression in >3,500 tumor RNAseq profiles from a dozen tumor types. We found significant links between immune gene expression and patient survival in 8/12 tumor types, with tumors partitioned by gene expression comprising distinct molecular subtypes. T/NK cell genes were most clearly survival-related for melanoma, head and neck, and bladder tumors, whereas myeloid cell genes were most clearly survival-related with kidney and breast tumors. T/NK or myeloid cell gene expression was linked to poor prognosis in bladder and kidney tumors, respectively, suggesting tumor-specific immunosuppressive checkpoints. Our results suggest new biomarkers for existing cancer immunotherapies and identify targets for new immunotherapies.

Negative prognostic value of high levels of intracellular poly(ADP-ribose) in non-small cell lung cancer

BACKGROUND

Cisplatin-resistant non-small cell lung cancer (NSCLC) cells are often characterized by alterations in vitamin B-related metabolic processes, including the overexpression and hyperactivation of poly(ADP-ribose) polymerase 1 (PARP1) and the downregulation of pyridoxal kinase (PDXK), correlating with elevated apoptosis resistance. Low PDXK expression is an established negative prognostic factor in NSCLC.

PATIENTS AND METHODS

We determined by immunohistochemistry the expression of PARP1 and the level of its product, poly(ADP-ribose) (PAR), in two independent cohorts of patients with resected NSCLC.

RESULTS

Intratumoral high levels (above median) of PAR (but not PARP1 protein levels) had a negative prognostic impact in both the training (92 stage I subjects) and validation (133 stage I and II subjects) cohorts, as determined by univariate and multivariate analyses. The simultaneous assessment of PAR and PDXK protein levels improved risk stratification.

CONCLUSION

NSCLC patients with high intratumoral PARP1 activity (i.e. elevated PAR levels above median) and low PDXK expression (below median) had a dismal prognosis, while patients with low PARP1 activity and high PDXK expression had a favorable outcome. Altogether, these results underscore the clinical potential and possible therapeutic relevance of these biomarkers.

Targeting Transcriptional Regulators of CD8+ T Cell Dysfunction to Boost Anti-Tumor Immunity

Transcription is a dynamic process influenced by the cellular environment: healthy, transformed, and otherwise. Genome-wide mRNA expression profiles reflect the collective impact of pathways modulating cell function under different conditions. In this review we focus on the transcriptional pathways that control tumor infiltrating CD8+ T cell (TIL) function. Simultaneous restraint of overlapping inhibitory pathways may confer TIL resistance to multiple mechanisms of suppression traditionally referred to as exhaustion, tolerance, or anergy. Although decades of work have laid a solid foundation of altered transcriptional networks underlying various subsets of hypofunctional or “dysfunctional” CD8+ T cells, an understanding of the relevance in TIL has just begun. With recent technological advances, it is now feasible to further elucidate and utilize these pathways in immunotherapy platforms that seek to increase TIL function.

Cytotoxic effects of chemotherapy on cancer and immune cells: how can it be modulated to generate novel therapeutic strategies?

The first objective to use chemotherapy is to kill cancer cells. However, it is common knowledge that these drugs can also damage healthy host cells, especially immune cells, and thus impair the endogenous antitumor response. Here, we focus on the cytotoxic effects of chemotherapy on tumor cells and immune cells. It is not enough to simply kill cancer cells, and causing immunogenic cell death will impair the adaptive immune system's ability to fight the remaining cancer cells. On the other hand, the killing of immune cells can also enhance tumor growth. A study of the repercussions of the cytotoxic effects of chemotherapy is of great importance to evaluate the antitumor response. Strategies can be proposed to promote the 'good way' for cancer cells to die and to avoid the adverse side effects of chemotherapy on immune cells in order to strengthen the role of the immune system in the antitumor response.

Irradiation of necrotic cancer cells, employed for pulsing dendritic cells (DCs), potentiates DC vaccine-induced antitumor immunity against high-grade glioma

Dendritic cell (DC)-based immunotherapy has yielded promising results against high-grade glioma (HGG). However, the efficacy of DC vaccines is abated by HGG-induced immunosuppression and lack of attention toward the immunogenicity of the tumor lysate/cells used for pulsing DCs. A literature analysis of DC vaccination clinical trials in HGG patients delineated the following two most predominantly applied methods for tumor lysate preparation: freeze-thaw (FT)-induced necrosis or FT-necrosis followed by X-ray irradiation. However, from the available clinical evidence, it is unclear which of both methodologies has superior immunogenic potential. Using an orthotopic HGG murine model (GL261-C57BL/6), we observed that prophylactic vaccination with DCs pulsed with irradiated FT-necrotic cells (compared to FT-necrotic cells only) prolonged overall survival by increasing tumor rejection in glioma-challenged mice. This was associated, both in prophylactic and curative vaccination setups, with an increase in brain-infiltrating Th1 cells and cytotoxic T lymphocytes (CTL), paralleled by a reduced accumulation of regulatory T cells, tumor-associated macrophages (TAM) and myeloid-derived suppressor cells (MDSC). Further analysis showed that irradiation treatment of FT-necrotic cells considerably increased the levels of carbonylated proteins — a surrogate-marker of oxidation-associated molecular patterns (OAMPs). Through further application of antioxidants and hydrogen peroxide, we found a striking correlation between the amount of lysate-associated protein carbonylation/OAMPs and DC vaccine-mediated tumor rejection capacity thereby suggesting for the first time a role for protein carbonylation/OAMPs in at least partially mediating antitumor immunity. Together, these data strongly advocate the use of protein oxidation-inducing modalities like irradiation for increasing the immunogenicity of tumor lysate/cells used for pulsing DC vaccines.

Spatial distribution of B cells predicts prognosis in human pancreatic adenocarcinoma

B-cell responses are emerging as critical regulators of cancer progression. In this study, we investigated the role of B lymphocytes in the microenvironment of human pancreatic ductal adenocarcinoma (PDAC), in a retrospective consecutive series of 104 PDAC patients and in PDAC preclinical models. Immunohistochemical analysis revealed that B cells occupy two histologically distinct compartments in human PDAC, either scatteringly infiltrating (CD20-TILs), or organized in tertiary lymphoid tissue (CD20-TLT). Only when retained within TLT, high density of B cells predicted longer survival (median survival 16.9 mo CD20-TLT^hi vs. 10.7 mo CD20-TLT^lo; p = 0.0085). Presence of B cells within TLT associated to a germinal center (GC) immune signature, correlated with CD8-TIL infiltration, and empowered their favorable prognostic value. Immunotherapeutic vaccination of spontaneously developing PDAC (Kras^G12D-Pdx1-Cre) mice with α-enolase (ENO1) induced formation of TLT with active GCs and correlated with increased recruitment of T lymphocytes, suggesting induction of TLT as a strategy to favor mobilization of immune cells in PDAC. In contrast, in an implanted tumor model devoid of TLT, depletion of B cells with an anti-CD20 antibody reinstated an antitumor immune response. Our results highlight B cells as an essential element of the microenvironment of PDAC and identify their spatial organization as a key regulator of their antitumor function. A mindfully evaluation of B cells in human PDAC could represent a powerful prognostic tool to identify patients with distinct clinical behaviors and responses to immunotherapeutic strategies.

Trial Watch: Immunostimulation with Toll-like receptor agonists in cancer therapy

Accumulating preclinical evidence indicates that Toll-like receptor (TLR) agonists efficiently boost tumor-targeting immune responses (re)initiated by most, if not all, paradigms of anticancer immunotherapy. Moreover, TLR agonists have been successfully employed to ameliorate the efficacy of various chemotherapeutics and targeted anticancer agents, at least in rodent tumor models. So far, only three TLR agonists have been approved by regulatory agencies for use in cancer patients. Moreover, over the past decade, the interest of scientists and clinicians in these immunostimulatory agents has been fluctuating. Here, we summarize recent advances in the preclinical and clinical development of TLR agonists for cancer therapy.