MyD88-dependent BCG immunotherapy reduces tumor and regulates tumor microenvironment in bladder cancer murine model

Epigenetic changes associated with Bacillus Calmette-Guerin (BCG) treatment in bladder cancer

Bacillus Calmette-Guérin (BCG) treatment for non-muscle invasive bladder cancer (NMIBC) is an established immunotherapeutic, however, a significant portion of patients do not respond to treatment. Despite extensive research into the therapeutic mechanism of BCG, gaps remain in our understanding. This review specifically focuses on the epigenomic contributions in the immune microenvironment, in the context of BCG treatment for NMIBC. We also summarise the current understanding of NMIBC epigenetic characteristics, and discuss how future targeted strategies for BCG therapy should incorporate epigenomic biomarkers in conjunction with genomic biomarkers.

Path to bacteriotherapy: From bacterial engineering to therapeutic perspectives

The major reason for the failure of conventional therapies is the heterogeneity and complexity of tumor microenvironments (TMEs). Many malignant tumors reprogram their surface antigens to evade the immune surveillance, leading to reduced antigen-presenting cells and hindered T-cell activation. Bacteria-mediated cancer immunotherapy has been extensively investigated in recent years. Scientists have ingeniously modified bacteria using synthetic biology and nanotechnology to enhance their biosafety with high tumor specificity, resulting in robust anticancer immune responses. To enhance the antitumor efficacy, therapeutic proteins, cytokines, nanoparticles, and chemotherapeutic drugs have been efficiently delivered using engineered bacteria. This review provides a comprehensive understanding of oncolytic bacterial therapies, covering bacterial design and the intricate interactions within TMEs. Additionally, it offers an in-depth comparison of the current techniques used for bacterial modification, both internally and externally, to maximize their therapeutic effectiveness. Finally, we outlined the challenges and opportunities ahead in the clinical application of oncolytic bacterial therapies.

Bacillus Calmette-Guérin immunotherapy induces an efficient antitumor response to control murine melanoma depending on MyD88 signaling

Bacillus Calmette-Guérin (BCG) is the first line treatment for bladder cancer and it is also proposed for melanoma immunotherapy. BCG modulates the tumor microenvironment (TME) inducing an antitumor effective response, but the immune mechanisms involved still poorly understood. The immune profile of B16-F10 murine melanoma cells was assessed by infecting these cells with BCG or stimulating them with agonists for different innate immune pathways such as TLRs, inflammasome, cGAS-STING and type I IFN. B16-F10 did not respond to any of those stimuli, except for type I IFN agonists, contrasting with bone marrow-derived macrophages (BMDMs) that showed high production of proinflammatory cytokines. Additionally, we confirmed that BCG is able to infect B16-F10, which in turn can activate macrophages and spleen cells from mice in co-culture experiments. Furthermore, we established a subcutaneous B16-F10 melanoma model for intratumoral BCG treatment and compared wild type mice to TLR2-/-, TLR3-/-, TLR4-/-, TLR7-/-, TLR3/7/9-/-, caspase 1-/-, caspase 11-/-, IL-1R-/-, cGAS-/-, STING-/-, IFNAR-/-, MyD88-/-deficient animals. These results in vivo demonstrate that MyD88 signaling is important for BCG immunotherapy to control melanoma in mice. Also, BCG fails to induce cytokine production in the co-culture experiments using B16-F10 and BMDMs or spleen cells derived from MyD88-/- compared to wild-type (WT) animals. Immunotherapy with BCG was not able to induce the recruitment of inflammatory cells in the TME from MyD88-/- mice, impairing tumor control and IFN-γ production by T cells. In conclusion, MyD88 impacts on both innate and adaptive responses to BCG leading to an efficient antitumor response against melanoma.

Breaking Barriers: Modulation of Tumor Microenvironment to Enhance Bacillus Calmette-Guérin Immunotherapy of Bladder Cancer

The clinical management of bladder cancer continues to present significant challenges. Bacillus Calmette-Guérin (BCG) immunotherapy remains the gold standard of treatment for non-muscle invasive bladder cancer (NMIBC), but many patients develop recurrence and progression to muscle-invasive disease (MIBC), which is resistant to BCG. This review focuses on the immune mechanisms mobilized by BCG in bladder cancer tumor microenvironments (TME), mechanisms of BCG resistance, the dual role of the BCG-triggered NFkB/TNFα/PGE2 axis in the regulation of anti-tumor and tumor-promoting aspects of inflammation, and emerging strategies to modulate their balance. A better understanding of BCG resistance will help develop new treatments and predictive biomarkers, paving the way for improved clinical outcomes in bladder cancer patients.

Cytosolic bacterial pathogens activate TLR pathways in tumors that synergistically enhance STING agonist cancer therapies

Bacterial pathogens that invade the eukaryotic cytosol are distinctive tools for fighting cancer, as they preferentially target tumors and can deliver cancer antigens to MHC-I. Cytosolic bacterial pathogens have undergone extensive preclinical development and human clinical trials, yet the molecular mechanisms by which they are detected by innate immunity in tumors is unclear. We report that intratumoral delivery of phylogenetically distinct cytosolic pathogens, including Listeria, Rickettsia, and Burkholderia species, elicited anti-tumor responses in established, poorly immunogenic melanoma and lymphoma in mice. We were surprised to observe that although the bacteria required entry to the cytosol, the anti-tumor responses were largely independent of the cytosolic sensors cGAS/STING and instead required TLR signaling. Combining pathogens with TLR agonists did not enhance anti-tumor efficacy, while combinations with STING agonists elicited profound, synergistic anti-tumor effects with complete responses in >80% of mice after a single dose. Small molecule TLR agonists also synergistically enhanced the anti-tumor activity of STING agonists. The anti-tumor effects were diminished in Rag2-deficient mice and upon CD8 T cell depletion. Mice cured from combination therapy developed immunity to cancer rechallenge that was superior to STING agonist monotherapy. Together, these data provide a framework for enhancing the efficacy of microbial cancer therapies and small molecule innate immune agonists, via the co-activation of STING and TLRs.

The Urinary Microbiome in Health and Disease: Relevance for Bladder Cancer

Bladder cancer (BC) constitutes one of the most diagnosed types of cancer worldwide. Advancements in and new methodologies for DNA sequencing, leading to high-throughput microbiota testing, have pinpointed discrepancies in urinary microbial fingerprints between healthy individuals and patients with BC. Although several studies suggest an involvement of microbiota dysbiosis in the pathogenesis, progression, and therapeutic response to bladder cancer, an established direct causal relationship remains to be elucidated due to the lack of standardized methodologies associated with such studies. This review compiles an overview of the microbiota of the human urinary tract in healthy and diseased individuals and discusses the evidence to date on microbiome involvement and potential mechanisms by which the microbiota may contribute to the development of BC. We also explore the potential profiling of urinary microbiota as a biomarker for risk stratification, as well as the prediction of the response to intravesical therapies and immunotherapy in BC patients. Further investigation into the urinary microbiome of BC patients is imperative to unravel the complexities of the role played by host-microbe interactions in shaping wellness or disease and yield valuable insights into and strategies for the prevention and personalized treatment of BC.

NMAAP1 regulated macrophage polarizion into M1 type through glycolysis stimulated with BCG

Bacillus Calmette Guerin (BCG) perfusion is widely used as cancer adjuvant therapy, in which macrophages play an important role. Novel macrophage activated associated protein 1 (NMAAP1), upregulated after BCG's activation, was proved to promote macrophage polarization to the M1 type. We found that BCG could stimulate mice BMDM to the M1 type and kill tumor cells. After the deletion of NMAAP1, the tumor volume of mice became larger, and the number of M1 type macrophages in the tumor decreased significantly. When macrophages were induced into the M1 type, aerobic glycolysis, the Warburg effect manifested in the increased uptake of glucose and the conversion of pyruvate to lactic acid. NMAAP1 could bind with IP3R and regulate macrophage polarization to the M1 type. However, the specific mechanism of how NMAAP1 regulates macrophage polarization towards the M1 type and plays an antitumor role must be clarified. NMAAP1 could promote the release of lactic acid and pyruvate, enhance the glycolysis of macrophages, and affect the expression of HIF-1α. After inhibition of glycolysis by 2-DG and lactic acid generation by FX11, the effects of NMAAP1 promoting macrophage polarization to the antitumor M1 type were weakened. Furthermore, NMAAP1 upregulated the expression of HIF-1α, which is associated with glycolysis. Moreover, the Ca2+/NF-κB pathway regulated HIF-1α expression by NMAAP1 in the macrophages. NMAAP1 promotes the polarization of macrophages towards the M1 type by affecting the Warburg effect stimulated by BCG.

BCG vaccination stimulates integrated organ immunity by feedback of the adaptive immune response to imprint prolonged innate antiviral resistance

Bacille Calmette-Guérin (BCG) vaccination can confer nonspecific protection against heterologous pathogens. However, the underlying mechanisms remain mysterious. We show that mice vaccinated intravenously with BCG exhibited reduced weight loss and/or improved viral clearance when challenged with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2 B.1.351) or PR8 influenza. Protection was first evident between 14 and 21 d post-vaccination and lasted ∼3 months. Notably, BCG induced a biphasic innate response and robust antigen-specific type 1 helper T cell (TH1 cell) responses in the lungs. MyD88 signaling was essential for innate and TH1 cell responses, and protection against SARS-CoV-2. Depletion of CD4+ T cells or interferon (IFN)-γ activity before infection obliterated innate activation and protection. Single-cell and spatial transcriptomics revealed CD4-dependent expression of IFN-stimulated genes in lung myeloid and epithelial cells. Notably, BCG also induced protection against weight loss after mouse-adapted SARS-CoV-2 BA.5, SARS-CoV and SHC014 coronavirus infections. Thus, BCG elicits integrated organ immunity, where CD4+ T cells feed back on tissue myeloid and epithelial cells to imprint prolonged and broad innate antiviral resistance.

Current Understanding of Bacillus Calmette-Guérin-Mediated Trained Immunity and Its Perspectives for Controlling Intracellular Infections

The bacillus Calmette-Guérin (BCG) is an attenuated bacterium derived from virulent Mycobacterium bovis. It is the only licensed vaccine used for preventing severe forms of tuberculosis in children. Besides its specific effects against tuberculosis, BCG administration is also associated with beneficial non-specific effects (NSEs) following heterologous stimuli in humans and mice. The NSEs from BCG could be related to both adaptive and innate immune responses. The latter is also known as trained immunity (TI), a recently described biological feature of innate cells that enables functional improvement based on metabolic and epigenetic reprogramming. Currently, the mechanisms related to BCG-mediated TI are the focus of intense research, but many gaps are still in need of elucidation. This review discusses the present understanding of TI induced by BCG, exploring signaling pathways that are crucial to a trained phenotype in hematopoietic stem cells and monocytes/macrophages lineage. It focuses on BCG-mediated TI mechanisms, including the metabolic-epigenetic axis and the inflammasome pathway in these cells against intracellular pathogens. Moreover, this study explores the TI in different immune cell types, its ability to protect against various intracellular infections, and the integration of trained innate memory with adaptive memory to shape next-generation vaccines.

Bacillus Calmette-Guérin-Trained Macrophages Elicit a Protective Inflammatory Response against the Pathogenic Bacteria Brucella abortus

The bacillus Calmette-Guérin (BCG) can elicit enhanced innate immune responses against a wide range of infections, known as trained immunity. Brucella abortus is the causative agent of brucellosis, a debilitating disease that affects humans and animals. In this study, we demonstrate that C57BL/6 mouse bone marrow-derived macrophages under BCG training enhance inflammatory responses against B. abortus. BCG-trained macrophages showed increased MHC class II and CD40 expression on the cell surface and higher IL-6, IL-12, and IL-1β production. The increase in IL-1β secretion was accompanied by enhanced activation of canonical and noncanonical inflammasome platforms. We observed elevated caspase-11 expression and caspase-1 processing in BCG-trained macrophages in response to B. abortus compared with untrained cells. In addition, these BCG-trained cells showed higher NLRP3 expression after B. abortus infection. From a metabolic point of view, signaling through the Akt/mammalian target of rapamycin/S6 kinase pathway was also enhanced. In addition, BCG training resulted in higher inducible NO synthase expression and nitrite production, culminating in an improved macrophage-killing capacity against intracellular B. abortus. In vivo, we monitored a significant reduction in the bacterial burden in organs from BCG-trained C57BL/6 mice when compared with the untrained group. In addition, previous BCG immunization of RAG-1-deficient mice partially protects against Brucella infection, suggesting the important role of the innate immune compartment in this scenario. Furthermore, naive recipient mice that received BM transfer from BCG-trained donors showed greater resistance to B. abortus when compared with their untrained counterparts. These results demonstrate that BCG-induced trained immunity in mice results in better control of intracellular B. abortus in vivo and in vitro.

Plants against cancer: the immune-boosting herbal microbiome: not of the plant, but in the plant. Basic concepts, introduction, and future resource for vaccine adjuvant discovery

The presence of microorganism communities (MOCs) comprised of bacteria, fungi, archaea, algae, protozoa, viruses, and the like, are ubiquitous in all living tissue, including plant and animal. MOCs play a significant role in establishing innate and acquired immunity, thereby influencing susceptibility and resistance to disease. This understanding has fostered substantial advancements in several fields such as agriculture, food science/safety, and the development of vaccines/adjuvants, which rely on administering inactivated-attenuated MOC pathogens. Historical evidence dating back to the 1800s, including reports by Drs Busch, Coley, and Fehleisen, suggested that acute febrile infection in response to "specific microbes" could trigger spontaneous tumor remission in humans. This discovery led to the purposeful administration of the same attenuated strains, known as "Coley's toxin," marking the onset of the first microbial (pathogen) associated molecular pattern (MAMPs or PAMPs)-based tumor immunotherapy, used clinically for over four decades. Today, these same MAMPS are consumed orally by billions of consumers around the globe, through "specific" mediums (immune boosting "herbal supplements") as carriers of highly concentrated MOCs accrued in roots, barks, hulls, sea algae, and seeds. The American Herbal Products Association (AHPA) mandates microbial reduction in botanical product processing but does not necessitate the removal of dead MAMP laden microbial debris, which we ingest. Moreover, while existing research has focused on the immune-modulating role of plant phytochemicals, the actual immune-boosting properties might instead reside solely in the plant's MOC MAMP laden biomass. This assertion is logical, considering that antigenic immune-provoking epitopes, not phytochemicals, are known to stimulate immune response. This review explores a neglected area of research regarding the immune-boosting effects of the herbal microbiome - a presence which is indirectly corroborated by various peripheral fields of study and poses a fundamental question: Given that food safety focuses on the elimination of harmful pathogens and crop science acknowledges the existence of plant microbiomes, what precisely are the immune effects of ingesting MAMPs of diverse structural composition and concentration, and where are these distributed in our botanicals? We will discuss the topic of concentrated edible MAMPs as acid and thermally stable motifs found in specific herbs and how these would activate cognate pattern recognition receptors (PPRs) in the upper gut-associated lymphoid tissue (GALT), including Peyer's patches and the lamina propria, to boost antibody titers, CD8+ and CD4+ T cells, NK activity, hematopoiesis, and facilitating M2 to M1 macrophage phenotype transition in a similar manner as vaccines. This new knowledge could pave the way for developing bioreactor-grown/heat-inactivated MOC therapies to boost human immunity against infections and improve tumor surveillance.

Evaluating the Effectiveness of Intravesical Instillation of BCG by Modified Maintenance Method in Patients With High-Risk Ta and T1 Bladder Cancer: A Randomized Clinical Trial

Background

It is estimated that 75% of urothelial bladder cancers are non-muscle-invasive cancers (NMIBCs). The development of more effective methods for optimizing the management of this subset of patients is of paramount importance. This study aimed to evaluate the effectiveness and side effects of modified maintenance Bacillus Calmette-Guérin (BCG) therapy in patients with high-risk NMIBC.

Methods

A total of 84 patients with NMIBC who met the inclusion criteria were randomly divided into 2 groups of 42 patients after receiving intravesical BCG weekly, 1 month after transurethral resection of the bladder tumor (TURT) for 6 weeks as the induction. In group I, patients continued monthly intravesical instillation of BCG for 6 months as maintenance, whereas group II patients did not. All patients were followed up for recurrence and progression for 2 years.

Results

Although the recurrence rate was lower in group I (16.7% vs 31%), there was no significant difference among groups (P = .124). Pathology progression was also lower in group I (7.1% vs 11.9%) with no significant difference among groups (P = .713). Complications were not statistically different among groups (P = .651). A statistically significant difference was not observed between the groups in the acceptance rate of patients (97.6% in group I vs 100% in group II).

Conclusions

The recurrence rate and progression rate in NMIBC patients with maintenance-free induction therapy after TURT were almost twice as high as those with 6-month maintenance therapy; however, it was not statistically significant. Modified BCG maintenance protocol made favorable compliance for patients.

Trial registration

This study was retrospectively registered at Iranian Registery of Clinical Trials with the code IRCT20220302054165N1.

Engineering live attenuated vaccines: Old dogs learning new tricks

Autoimmune diseases such as rheumatoid arthritis and type 1 diabetes are increasingly common global problems. Concerns about increases in the prevalence of such diseases and the limited efficacy of conventional treatment regimens necessitates new therapies to address these challenges. Autoimmune disease severity and dysbiosis are interconnected. Although probiotics have been established as a therapy to rebalance the microbiome and suppress autoimmune symptoms, these microbes tend to lack a number of advantageous qualities found in non-commensal bacteria. Through attenuation and genetic manipulation, these non-commensal bacteria have been engineered into recombinant forms that offer malleable platforms capable of addressing the immune imbalances found in RA and T1D. Such bacteria have been engineered to express valuable gene products known to suppress autoimmunity such as anti-inflammatory cytokines, autoantigens, and enzymes synthesizing microbial metabolites. This review will highlight current and emerging trends in the field and discuss how they may be used to prevent and control autoimmune diseases.

Bacteria and macrophages in the tumor microenvironment

Cancer and microbial infections are significant worldwide health challenges. Numerous studies have demonstrated that bacteria may contribute to the emergence of cancer. In this review, we assemble bacterial species discovered in various cancers to describe their variety and specificity. The relationship between bacteria and macrophages in cancer is also highlighted, and we look for ample proof to establish a biological basis for bacterial-induced macrophage polarization. Finally, we quickly go over the potential roles of metabolites, cytokines, and microRNAs in the regulation of the tumor microenvironment by bacterially activated macrophages. The complexity of bacteria and macrophages in cancer will be revealed as we gain a better understanding of their pathogenic mechanisms, which will lead to new therapeutic approaches for both inflammatory illnesses and cancer.

Targeting hypoxia-induced tumor stemness by activating pathogen-induced stem cell niche defense

Tumor hypoxia and oxidative stress reprograms cancer stem cells (CSCs) to a highly aggressive and inflammatory phenotypic state of tumor stemness. Previously, we characterized tumor stemness phenotype in the ATP Binding Cassette Subfamily G Member 2 (ABCG2)–positive migratory side population (SPm) fraction of CSCs exposed to extreme hypoxia followed by reoxygenation. Here, we report that post-hypoxia/reoxygenation SPm+/ABCG2+ CSCs exerts defense against pathogen invasion that involves bystander apoptosis of non-infected CSCs. In an in vitro assay of cancer cell infection by Bacillus Calmette Guerin (BCG) or mutant Mycobacterium tuberculosis (Mtb) strain 18b (Mtb-m18b), the pathogens preferentially replicated intracellular to SPm+/ABCG2+ CSCs of seven cell lines of diverse cancer types including SCC-25 oral squamous cancer cell line. The conditioned media (CM) of infected CSCs exhibited direct anti-microbial activity against Mtb and BCG, suggesting niche defense against pathogen. Importantly, the CM of infected CSCs exhibited marked in vitro bystander apoptosis toward non-infected CSCs. Moreover, the CM-treated xenograft bearing mice showed 10- to 15-fold reduction (p < 0.001; n = 7) in the number of CSCs residing in the hypoxic niches. Our in vitro studies indicated that BCG-infected SPm+/ABCG2+ equivalent EPCAM+/ABCG2+ CSCs of SCC-25 cells underwent pyroptosis and released a high mobility group box protein 1 (HMGB1)/p53 death signal into the tumor microenvironment (TME). The death signal can induce a Toll-like receptor 2/4–mediated bystander apoptosis in non-infected CSCs by activating p53/MDM2 oscillation and subsequent activation of capase-3–dependent intrinsic apoptosis. Notably, SPm+/ABCG2+ but not SP cells undergoing bystander apoptosis amplified the death signal by further release of HMGB1/p53 complex into the TME. These results suggest that post-hypoxia SPm+/ABCG2+ CSCs serve a functional role as a tumor stemness defense (TSD) phenotype to protect TME against bacterial invasion. Importantly, the CM of TSD phenotype undergoing bystander apoptosis may have therapeutic uses against CSCs residing in the hypoxic niche.

The future clinical implications of trained immunity

INTRODUCTION

Trained Immunity (TI) refers to the long-term modulation of the innate immune response, based on previous interactions with microbes, microbial ligands or endogenous substances. Through metabolic and epigenetic reprogramming, monocytes, macrophages and neutrophils develop an enhanced capacity to mount innate immune responses to subsequent stimuli and this is persistent due to alterations at the myeloid progenitor compartment.

AREAS COVERED

The purpose of this article is to review the current understanding of the TI process and discuss about its potential clinical implications in the near future. We address the evidence of TI involvement in various diseases, the currently developed new therapy, and discuss how TI may lead to new clinical tools to improve existing standards of care.

EXPERT OPINION

The state of art in this domain has made considerable progress, linking TI-related mechanisms in multiple immune-mediated pathologies, starting with infections to autoimmune disorders and cancers. As a relatively new area of immunology, it has seen fast progress with many of its applications ready to be investigated in clinical settings.

Lipopolysaccharide sensitizes the therapeutic response of breast cancer to IAP antagonist

Inhibitor of apoptosis protein (IAP) is a class of E3 ubiquitin ligases functioning to support cancer survival and growth. Many small-molecule IAP antagonists have been developed, aiming to degrade IAP proteins to kill cancer. We have evaluated the effect of lipopolysaccharide (LPS), a component of the bacterial outer membrane, on IAP antagonists in treating breast cancer in a mouse model to guide future clinical trials. We show that LPS promotes IAP antagonist-induced regression of triple-negative breast cancer (TNBC) from MDA-MB-231 cells in immunodeficient mice. IAP antagonists such as SM-164, AT-406, and BV6, do not kill MDA-MB-231 cells alone, but allow LPS to induce cancer cell apoptosis rapidly. The apoptosis caused by LPS plus SM-164 is blocked by toll-like receptor 4 (TLR4) or MyD88 inhibitor, which inhibits LPS-induced TNFα production by the cancer cells. Consistent with this, MDA-MB-231 cell apoptosis induced by LPS plus SM-164 is also blocked by the TNF inhibitor. LPS alone does not kill MDA-MB-231 cells because it markedly increases the protein level of cIAP1/2, which is directly associated with and stabilized by MyD88, an adaptor protein of TLR4. ER⁺ MCF7 breast cancer cells expressing low levels of cIAP1/2 undergo apoptosis in response to SM-164 combined with TNFα but not with LPS. Furthermore, TNFα but not LPS alone inhibits MCF7 cell growth in vitro. Consistent with these, LPS combined with SM-164, but not either of them alone, causes regression of ER⁺ breast cancer from MCF7 cells in immunodeficient mice. In summary, LPS sensitizes the therapeutic response of both triple-negative and ER⁺ breast cancer to IAP antagonist therapy by inducing rapid apoptosis of the cancer cells through TLR4- and MyD88-mediated production of TNFα. We conclude that antibiotics that can reduce microbiota-derived LPS should not be used together with an IAP antagonist for cancer therapy.

BCG in Bladder Cancer Immunotherapy

BCG is a live attenuated strain of Mycobacterium bovis that is primarily used as a vaccine against tuberculosis. In the past four decades, BCG has also been used for the treatment of non-muscle invasive bladder cancer (NMIBC). In patients with NMIBC, BCG reduces the risk of tumor recurrence and decreases the likelihood of progression to more invasive disease. Despite the long-term clinical experience with BCG, its mechanism of action is still being elucidated. Data from animal models and from human studies suggests that BCG activates both the innate and adaptive arms of the immune system eventually leading to tumor destruction. Herein, we review the current data regarding the mechanism of BCG and summarize the evidence for its clinical efficacy and recommended indications and clinical practice.

Intratumoral immunotherapy using a TLR2/3 agonist, L-pampo, induces robust antitumor immune responses and enhances immune checkpoint blockade

BACKGROUND

Toll-like receptors (TLRs) are critical innate immune sensors that elicit antitumor immune responses in cancer immunotherapy. Although a few TLR agonists have been approved for the treatment of patients with early-stage superficial cancers, their therapeutic efficacy is limited in patient with advanced invasive cancers. Here, we identified the therapeutic role of a TLR2/3 agonist, L-pampo (LP), which promotes antitumor immunity and enhances the immune checkpoint blockade.

METHODS

We generated LP by combining a TLR2 agonist, Pam3CSK4, with a TLR3 agonist, Poly (I:C). Immune responses to stimulation with various TLR agonists were compared. Tumor-bearing mice were intratumorally treated with LP, and their tumor sizes were measured. The antitumor effects of LP treatment were determined using flow cytometry, multiplexed imaging, and NanoString nCounter immune profiling. The immunotherapeutic potential of LP in combination with α-programmed cell death protein-1 (PD-1) or α-cytotoxic T-lymphocytes-associated protein 4 (CTLA-4) was evaluated in syngeneic MC38 colon cancer and B16F10 melanoma.

RESULTS

The LP treatment induced a potent activation of T helper 1 (Th1) and 2 (Th2)-mediated immunity, tumor cell apoptosis, and immunogenic tumor cell death. Intratumoral LP treatment effectively inhibited tumor progression by activating tumor-specific T cell immunity. LP-induced immune responses were mediated by CD8⁺ T cells and interferon-γ, but not by CD4⁺ T cells and CD25⁺ T cells. LP simultaneously activated TLR2 and TLR3 signaling, thereby extensively changing the immune-related gene signatures within the tumor microenvironment (TME). Moreover, intratumoral LP treatment led to systemic abscopal antitumor effects in non-injected distant tumors. Notably, LP treatment combined with ɑPD-1 and ɑCTLA-4 further enhanced the efficacy of monotherapy, resulting in complete tumor regression and prolonged overall survival. Furthermore, LP-based combination immunotherapy elicited durable antitumor immunity with tumor-specific immune memory in colon cancer and melanoma.

CONCLUSIONS

Our study demonstrated that intratumoral LP treatment improves the innate and adaptive antitumor immunity within the TME and enhances the efficacy of αPD-1 and αCTLA-4 immune checkpoint blockade.