Immune checkpoint inhibitors for cancer treatment

Computational Approach for the Development of pH-Selective PD-1/PD-L1 Signaling Pathway Inhibition in Fight with Cancer

Immunotherapy, particularly targeting the PD-1/PD-L1 pathway, holds promise in cancer treatment by regulating the immune response and preventing cancer cells from evading immune destruction. Nonetheless, this approach poses a risk of unwanted immune system activation against healthy cells. To minimize this risk, our study proposes a strategy based on selective targeting of the PD-L1 pathway within the acidic microenvironment of tumors. We employed in silico methods, such as virtual screening, molecular mechanics, and molecular dynamics simulations, analyzing approximately 10,000 natural compounds from the MolPort database to find potential hits with the desired properties. The simulations were conducted under two pH conditions (pH = 7.4 and 5.5) to mimic the environments of healthy and cancerous cells. The compound MolPort-001-742-690 emerged as a promising pH-selective inhibitor, showing a significant affinity for PD-L1 in acidic conditions and lower toxicity compared to known inhibitors like BMS-202 and LP23. A detailed 1000 ns molecular dynamics simulation confirmed the stability of the inhibitor-PD-L1 complex under acidic conditions. This research highlights the potential of using in silico techniques to discover novel pH-selective inhibitors, which, after experimental validation, may enhance the precision and reduce the toxicity of immunotherapies, offering a transformative approach to cancer treatment.

Non-viral expression of chimeric antigen receptors with multiplex gene editing in primary T cells

Efficient engineering of T cells to express exogenous tumor-targeting receptors such as chimeric antigen receptors (CARs) or T-cell receptors (TCRs) is a key requirement of effective adoptive cell therapy for cancer. Genome editing technologies, such as CRISPR/Cas9, can further alter the functional characteristics of therapeutic T cells through the knockout of genes of interest while knocking in synthetic receptors that can recognize cancer cells. Performing multiple rounds of gene transfer with precise genome editing, termed multiplexing, remains a key challenge, especially for non-viral delivery platforms. Here, we demonstrate the efficient production of primary human T cells incorporating the knockout of three clinically relevant genes (B2M, TRAC, and PD1) along with the non-viral transfection of a CAR targeting disialoganglioside GD2. Multiplexed knockout results in high on-target deletion for all three genes, with low off-target editing and chromosome alterations. Incorporating non-viral delivery to knock in a GD2-CAR resulted in a TRAC-B2M-PD1-deficient GD2 CAR T-cell product with a central memory cell phenotype and high cytotoxicity against GD2-expressing neuroblastoma target cells. Multiplexed gene-editing with non-viral delivery by CRISPR/Cas9 is feasible and safe, with a high potential for rapid and efficient manufacturing of highly potent allogeneic CAR T-cell products.

Exploring the safety profile of tremelimumab: an analysis of the FDA adverse event reporting system

BACKGROUND

Despite the approval of tremelimumab in 2022, there is a lack of pharmacovigilance studies investigating its safety profile in real-world settings using the FDA Adverse Event Reporting System (FAERS) database.

AIM

This pharmacovigilance study aimed to comprehensively explore the adverse events (AEs) associated with tremelimumab using data mining techniques on the FAERS database.

METHOD

The study utilized data from the FAERS database, covering the period from the first quarter of 2004 to the third quarter of 2022. Disproportionality analysis, the Benjamini Hochberg adjustment method and volcano plots were used to identify and evaluate AE signals associated with tremelimumab.

RESULTS

The study uncovered 233 AE cases associated with tremelimumab. Among these cases, pyrexia (n = 39), biliary tract infection (n = 23), and sepsis (n = 21) were the three main AEs associated with tremelimumab use. The study also investigated the system organ classes associated with tremelimumab-related AEs. The top three classes were gastrointestinal disorders (17.9%), infections and infestations (16.6%), and general disorders and administration site infections (11.2%). Several AEs were identified that were not listed on the drug label of tremelimumab. These AEs included pyrexia, biliary tract infection, sepsis, dyspnea, infusion site infection, hiccup, appendicitis, hypotension, dehydration, localised oedema, presyncope, superficial thrombophlebitis and thrombotic microangiopathy.

CONCLUSION

This pharmacovigilance study identified several potential adverse events signals related to tremelimumab including some adverse events not listed on the drug label. However, further basic and clinical research studies are needed to validate these results.

Advances in mRNA-Based Cancer Vaccines

Cancer is a leading cause of death worldwide, accounting for millions of deaths every year. Immunotherapy is a groundbreaking approach for treating cancer through harnessing the power of the immune system to target and eliminate cancer cells. Cancer vaccines, one immunotherapy approach, have shown promise in preclinical settings, but researchers have struggled to reproduce these results in clinical settings. However, with the maturity of mRNA technology and its success in tackling the recent coronavirus disease 2019 (COVID-19) pandemic, cancer vaccines are expected to regain attention. In this review, we focused on the recent progress made in mRNA-based cancer vaccines over the past five years. The mechanism of action of mRNA vaccines, advancements in neoantigen discovery, adjuvant identification, and delivery materials are summarized and reviewed. In addition, we also provide a detailed overview of current clinical trials involving mRNA cancer vaccines. Lastly, we offer an insight into future considerations for the application of mRNA vaccines in cancer immunotherapy. This review will help researchers to understand the advances in mRNA-based cancer vaccines and explore new dimensions for potential immunotherapy approaches.

IP-score correlated to endogenous tumour antigen peptide processing: A candidate clinical response score algorithm of immune checkpoint inhibitors therapy in multiple cohorts

The processing of endogenous tumour antigen peptides was essential for anti-tumour immunity in the tumour microenvironment. A high degree of Endogenous tumour antigen peptide processing has been demonstrated to improve the prognosis of carcinoma patients. However, there is insufficient evidence to prove its effect on the clinical response to immune checkpoint inhibitor therapy. To undertake a more in-depth analysis of the effects of the aforementioned genes on immunotherapy, we constructed a gene set evaluation score system relevant to tumour endogenous antigen peptide therapy using the GSVA approach. This rating mechanism is known as IP score (IPs). Immediately afterwards, we used the TCGA pan-cancer cohorts to conduct a comprehensive analysis of 6 genes in the IPs, and the analysis results showed that these six genes were related to the proportion of CD8⁺ T lymphocytes in a variety of solid tumours. As a prognostic protective factor for solid tumours, patients had better prognosis outcomes in the group with high expression levels of the above genes. We analysed the differential expression of six genes between immune checkpoint inhibitor treatment response and disease progression groups using several treatment cohorts. The results revealed that after treatment with PD-1 or CTLA4 inhibitors, the expression levels of the above six genes were comparatively high in the effective group, but the expression of the signature genes was dramatically downregulated in the ICI-insensitive groups. This indicates that the 6 genes are related to the clinical response to ICI treatment. Finally, we used the GSVA method to evaluate the above signatures, and the results showed that PDCD1, CTAL4, CD274 and LAG3 were significantly higher expressed in the IPs high-expression group; therefore, based on the processing of endogenous antigenic peptides in tumours, a predictive score of clinical response to immune checkpoint inhibitor therapy composed of 6 genes(PSMB8/PSMB9/PSMB10/PSME1/PSME2/IRF1) was constructed, and the role of each independent variable in the signature in the solid tumour microenvironment and the impact on ICI treatment were comprehensively analysed. This study provides a candidate evaluation score for predicting clinical response to immune checkpoint inhibitor therapy.

Development of Anti-LRRC15 Small Fragments for Imaging Purposes Using a Phage-Display ScFv Approach

The human leucine-rich repeat-containing protein 15 (LRRC15) is a membrane protein identified as a marker of CAF (cancer-associated fibroblast) cells whose overexpression is positively correlated with cancer grade and outcome. Nuclear molecular imaging (i.e., SPECT and PET) to track LRRC15 expression could be very useful in guiding further therapeutic strategies. In this study, we developed an ScFv mouse phage-display library to obtain small fragment antibodies against human LRRC15 for molecular imaging purposes. Mice were immunized with recombinant human LRRC15 (hLRRC15), and lymph node cells were harvested for ScFv (single-chain variable fragment) phage-display analysis. The built library was used for panning on cell lines with constitutive or induced expression after transfection. The choice of best candidates was performed by screening various other cell lines, using flow cytometry. The selected candidates were reformatted into Cys-ScFv or Cys-diabody by addition of cysteine, and cloned in mammalian expression vectors to obtain batches of small fragments that were further used in site-specific radiolabeling tests. The obtained library was 1.2 × 107 cfu/µg with an insertion rate >95%. The two panning rounds performed on cells permittedenrichment of 2 × 10−3. Screening with flow cytometry allowed us to identify 28 specific hLRRC15 candidates. Among these, two also recognized murine LRCC15 and were reformatted into Cys-ScFv and Cys-diabody. They were expressed transiently in a mammalian system to obtain 1.0 to 4.5 mg of Cys fragments ready for bioconjugation and radiolabeling. Thus, in this paper, we demonstrate the relevance of the phage-display ScFv library approach for the fast-track development of small antibodies for imaging and/or immunotherapy purposes.

ICIs-Related Cardiotoxicity in Different Types of Cancer

Immune checkpoint inhibitors (ICIs) are rapidly developing immunotherapy cancer drugs that have prolonged patient survival. However, ICIs-related cardiotoxicity has been recognized as a rare, but fatal, consequence. Although there has been extensive research based on different types of ICIs, these studies have not indicated whether cardiotoxicity is specific to a type of cancer. Therefore, we conducted a systematic review to analyze a variety of ICIs-related cardiotoxicity, focusing on different types of cancer. We found that the incidence of ICIs-related cardiac adverse events (CAEs) and common cardiotoxic manifestations vary with cancer type. This inspired us to explore the underlying mechanisms to formulate targeted clinical strategies for maintaining the cardiovascular health of cancer patients.

Synthetic and Biodegradable Molybdenum (IV) Diselenide Triggers the Cascade Photo- and Immunotherapy of Tumor

In this study, a polyvinylpyrrolidone (PVP)-decorated MoSe₂ (MoSe₂ -PVP) nanoparticle with excellent photothermal transforming ability and chlorin E6 (Ce6) loading capacity is designed for combined tumor photothermal therapy (PTT), tumor photodynamic therapy (PDT), and immunotherapy. The light-to-heat conversion efficiency under irradiation with an 808 nm near-infrared laser is as high as 59.28%. The MoSe₂ -PVP NPs could function as an artificial catalase and catalyze the decomposition of H₂ O₂ . Their catalytic activity and thermal durability are higher than the native catalase, which relieve the tumor hypoxia status and sensitize the tumor PDT. The data show that the synthetic MoSe₂ -PVP is biodegradable, owing to the oxidation of the Mo⁴⁺ to Mo⁶⁺ . Moreover, its degradation products could increase the proportion of mature dendritic cells and CD8⁺ thymus (T) cells and promote the infiltration of active CD8⁺ T cells in tumors. The immune checkpoint inhibitor, programmed cell death protein 1 monoclonal antibody is combined with MoSe₂ -PVP and it is found that its degradation product could efficiently change the immune microenvironment of the tumor.

The Multifaceted Biology of PCSK9

This article reviews the discovery of PCSK9, its structure-function characteristics, and its presently known and proposed novel biological functions. The major critical function of PCSK9 deduced from human and mouse studies, as well as cellular and structural analyses, is its role in increasing the levels of circulating low-density lipoprotein (LDL)-cholesterol (LDLc), via its ability to enhance the sorting and escort of the cell surface LDL receptor (LDLR) to lysosomes. This implicates the binding of the catalytic domain of PCSK9 to the EGF-A domain of the LDLR. This also requires the presence of the C-terminal Cys/His-rich domain, its binding to the secreted cytosolic cyclase associated protein 1, and possibly another membrane-bound "protein X". Curiously, in PCSK9-deficient mice, an alternative to the downregulation of the surface levels of the LDLR by PCSK9 is taking place in the liver of female mice in a 17β-estradiol-dependent manner by still an unknown mechanism. Recent studies have extended our understanding of the biological functions of PCSK9, namely its implication in septic shock, vascular inflammation, viral infections (Dengue; SARS-CoV-2) or immune checkpoint modulation in cancer via the regulation of the cell surface levels of the T-cell receptor and MHC-I, which govern the antitumoral activity of CD8+ T cells. Because PCSK9 inhibition may be advantageous in these processes, the availability of injectable safe PCSK9 inhibitors that reduces by 50% to 60% LDLc above the effect of statins is highly valuable. Indeed, injectable PCSK9 monoclonal antibody or small interfering RNA could be added to current immunotherapies in cancer/metastasis.

Macrophage Associated Immune Checkpoint CD47 Blocking Ameliorates Endometriosis

Peritoneal macrophages play a significant role in the progression of endometriosis (EM), but their functional differentiation is still unclear, and their phagocytic ability is weak. CD47-SIRPα and PD-L1-PD-1 are considered immune checkpoints associated with macrophage phagocytosis. A specific blockade of these two pathways had been shown to increase the phagocytic clearance of cancer cells by macrophages in most cancers. We hypothesized that targeting CD47/PD-L1 in EM could improve the phagocytosis of macrophages, thereby delaying the progression of EM. From localization to quantification, from mRNA to protein, we comprehensively evaluated the expression of CD47 and PD-L1 in EM. We demonstrated that the CD47 expression in ectopic endometrium from patients with EM was significantly increased, but PD-L1was not. We performed direct co-culture experiments of endometrial stromal cells with macrophages in vitro and in vivo to assess whether ectopic endometrial stromal cells escape macrophage phagocytosis through the CD47-SIRPα signaling pathway. The results showed that targeting CD47 increased the phagocytic capacity of macrophages. Interestingly, we also found that the reduction of CD47 expression promoted apoptosis of ESCs. In conclusion, these data suggested that targeting CD47 can effectively target ectopic endometrial stromal cells through a dual mechanism of increased phagocytosis of macrophages and induced apoptosis of ectopic endometrial stromal cells. Thus, immunotherapy based on the CD47-SIRPa signaling pathway has some potential in treating EM, but further mechanistic studies are needed to explore more effective and specific antibodies.

High expression of HHLA2 predicts poor prognosis in medullary thyroid carcinoma

Background

Human endogenous retrovirus-H long terminal repeat-associating protein 2 is a newly identified immune checkpoint molecule that was aberrantly expressed in many malignant tumors. However, its expression in medullary thyroid carcinoma is still unclear. This study aimed to investigate the human endogenous retrovirus-H long terminal repeat-associating protein 2 expression in medullary thyroid carcinoma tissues and to evaluate the relationships between its expression and clinicopathologic together with prognostic relevance.

Methods

Using 51 surgical specimens obtained from medullary thyroid carcinoma patients, the expression levels of the human endogenous retrovirus-H long terminal repeat-associating protein 2 protein in medullary thyroid carcinoma tumor tissues and adjacent noncancerous tissues were measured by immunohistochemistry, and its correlations with clinicopathologic and prognostic features were analyzed. Status of CD8+ tumor infiltrating lymphocytes was also investigated.

Results

The results showed that human endogenous retrovirus-H long terminal repeat-associating protein 2 was only detected in tumor tissues, and 31.4% of the medullary thyroid carcinoma patients had high expression of human endogenous retrovirus-H long terminal repeat-associating protein 2. High human endogenous retrovirus-H long terminal repeat-associating protein 2 expression was significantly associated with lymph node metastasis and advanced American Joint Committee on Cancer stages (P = 0.005). There existed an inverse trend between human endogenous retrovirus-H long terminal repeat-associating protein 2 expression and CD8+ tumor infiltrating lymphocytes infiltration in medullary thyroid carcinoma tumor samples (P = 0.042). The log-rank test showed a shorter disease-free survival in patients with high human endogenous retrovirus-H long terminal repeat-associating protein 2 expression (P = 0.002). The disease-free survival rates were also significantly low in cases of medullary thyroid carcinoma with lymph node metastasis, American Joint Committee on Cancer stages III–IV and multifocality. Multivariate Cox analysis confirmed that human endogenous retrovirus-H long terminal repeat-associating protein 2 acted as an independent predictive factor in the disease-free survival of medullary thyroid carcinoma patients (hazard ratio = 4.138, 95% confidence interval: 1.027–16.667, P = 0.046).

Conclusions

Taken together, human endogenous retrovirus-H long terminal repeat-associating protein 2 is highly expressed in medullary thyroid carcinoma patients and is a poor prognostic biomarker of disease-free survival of medullary thyroid carcinoma patients.

Metagenomics studies for the diagnosis and treatment of prostate cancer

AIM

Mutation occurs in the prostate cell genes, leading to abnormal prostate proliferation and ultimately cancer. Prostate cancer (PC) is one of the most common cancers amongst men, and its prevalence worldwide increases relative to men's age. About 16% of the world's cancers are the result of microbes in the human body. Impaired population balance of symbiosis microbes in the human reproductive system is linked to PC development.

DISCUSSION

With the advent of metagenomics science, the genome sequence of the microbiota of the human body has been unveiled. Therefore, it is now possible to identify a higher range of microbiome changes in PC tissue via the Next Generation Technique, which will have positive consequences in personalized medicine. In this review, we intend to question the role of metagenomics studies in the diagnosis and treatment of PC.

CONCLUSION

The microbial imbalance in the men's genital tract might have an effect on prostate health. Based on next-generation sequencing-generated data, Proteobacteria, Firmicutes, Actinobacteria, and Bacteriodetes are the nine frequent phyla detected in a PC sample, which might be involved in inducing mutation in the prostate cells that cause cancer.

The importance of immune checkpoints in immune monitoring: A future paradigm shift in the treatment of cancer

The growth and development of cancer are directly correlated to the suppression of the immune system. A major breakthrough in cancer immunotherapy depends on various mechanisms to detect immunosuppressive factors that inhibit anti-tumor immune responses. Immune checkpoints are expressed on many immune cells such as T-cells, regulatory B cells (Bregs), dendritic cells (DCs), natural killer cells (NKs), regulatory T (Tregs), M2-type macrophages, and myeloid-derived suppressor cells (MDSCs). Immune inhibitory molecules, including CTLA-4, TIM-3, TIGIT, PD-1, and LAG-3, normally inhibit immune responses via negatively regulating immune cell signaling pathways to prevent immune injury. However, the up-regulation of inhibitory immune checkpoints during tumor progression on immune cells suppresses anti-tumor immune responses and promotes immune escape in cancer. It has recently been indicated that cancer cells can up-regulate various pathways of the immune checkpoints. Therefore, targeting immune inhibitory molecules through antibodies or miRNAs is a promising therapeutic strategy and shows favorable results. Immune checkpoint inhibitors (ICIs) are introduced as a new immunotherapy strategy that enhance immune cell-induced antitumor responses in many patients. In this review, we highlighted the function of each immune checkpoint on different immune cells and therapeutic strategies aimed at using monoclonal antibodies and miRNAs against inhibitory receptors. We also discussed current challenges and future strategies for maximizing these FDA-approved immunosuppressants' effectiveness and clinical success in cancer treatment.

Step-by-Step Immune Activation for Suicide Gene Therapy Reinforcement

Gene-directed enzyme prodrug gene therapy (GDEPT) theoretically represents a useful method to carry out chemotherapy for cancer with minimal side effects through the formation of a chemotherapeutic agent inside cancer cells. However, despite great efforts, promising preliminary results, and a long period of time (over 25 years) since the first mention of this method, GDEPT has not yet reached the clinic. There is a growing consensus that optimal cancer therapies should generate robust tumor-specific immune responses. The advent of checkpoint immunotherapy has yielded new highly promising avenues of study in cancer therapy. For such therapy, it seems reasonable to use combinations of different immunomodulators alongside traditional methods, such as chemotherapy and radiotherapy, as well as GDEPT. In this review, we focused on non-viral gene immunotherapy systems combining the intratumoral production of toxins diffused by GDEPT and immunomodulatory molecules. Special attention was paid to the applications and mechanisms of action of the granulocyte-macrophage colony-stimulating factor (GM–CSF), a cytokine that is widely used but shows contradictory effects. Another method to enhance the formation of stable immune responses in a tumor, the use of danger signals, is also discussed. The process of dying from GDEPT cancer cells initiates danger signaling by releasing damage-associated molecular patterns (DAMPs) that exert immature dendritic cells by increasing antigen uptake, maturation, and antigen presentation to cytotoxic T-lymphocytes. We hypothesized that the combined action of this danger signal and GM–CSF issued from the same dying cancer cell within a limited space would focus on a limited pool of immature dendritic cells, thus acting synergistically and enhancing their maturation and cytotoxic T-lymphocyte attraction potential. We also discuss the problem of enhancing the cancer specificity of the combined GDEPT–GM–CSF–danger signal system by means of artificial cancer specific promoters or a modified delivery system.

TIGIT and PD-1 Immune Checkpoint Pathways Are Associated With Patient Outcome and Anti-Tumor Immunity in Glioblastoma

Glioblastoma (GBM) remains an aggressive brain tumor with a high rate of mortality. Immune checkpoint (IC) molecules are expressed on tumor infiltrating lymphocytes (TILs) and promote T cell exhaustion upon binding to IC ligands expressed by the tumor cells. Interfering with IC pathways with immunotherapy has promoted reactivation of anti-tumor immunity and led to success in several malignancies. However, IC inhibitors have achieved limited success in GBM patients, suggesting that other checkpoint molecules may be involved with suppressing TIL responses. Numerous IC pathways have been described, with current testing of inhibitors underway in multiple clinical trials. Identification of the most promising checkpoint pathways may be useful to guide the future trials for GBM. Here, we analyzed the The Cancer Genome Atlas (TCGA) transcriptomic database and identified PD1 and TIGIT as top putative targets for GBM immunotherapy. Additionally, dual blockade of PD1 and TIGIT improved survival and augmented CD8+ TIL accumulation and functions in a murine GBM model compared with either single agent alone. Furthermore, we demonstrated that this combination immunotherapy affected granulocytic/polymorphonuclear (PMN) myeloid derived suppressor cells (MDSCs) but not monocytic (Mo) MDSCs in in our murine gliomas. Importantly, we showed that suppressive myeloid cells express PD1, PD-L1, and TIGIT-ligands in human GBM tissue, and demonstrated that antigen specific T cell proliferation that is inhibited by immunosuppressive myeloid cells can be restored by TIGIT/PD1 blockade. Our data provide new insights into mechanisms of GBM αPD1/αTIGIT immunotherapy.

Immuno-profiling and cellular spatial analysis using five immune oncology multiplex immunofluorescence panels for paraffin tumor tissue

Multiplex immunofluorescence (mIF) has arisen as an important tool for immuno-profiling tumor tissues. We updated our manual protocol into an automated protocol that allows the use of up to seven markers in five mIF panels to apply to formalin-fixed paraffin-embedded tumor tissues. Using a tyramide signal amplification system, we optimized five mIF panels that included cytokeratin to characterize malignant cells (MCs), immune checkpoint markers (i.e., PD-L1, B7-H3, B7-H4, IDO-1, VISTA, LAG3, ICOS, TIM3, and OX40), tumor-infiltrating lymphocytic markers (i.e., CD3, CD8, CD45RO, granzyme B, PD-1, and FOXP3), and markers to characterize myeloid-derived suppressor cells (i.e., CD68, CD66b, CD14, CD33, Arg-1, and CD11b). To determine analytical reproducibility and the impact of those panels for immuno-profiling tumor tissues, we performed an exploratory analysis in a set of non–small cell lung cancer (NSCLC) samples. The slides were scanned, and the different cell phenotypes were quantified by simultaneous co-localizations with the markers using image analysis software. Comparison between the time points of staining showed high analytical reproducibility. The analysis of NSCLC cases showed an immunosuppressive microenvironment with PD-L1/PD-1 expression as a predominant axis. Interestingly, high density of MCs expressing B7-H4 was correlated with recurrence. Unexpectedly, MCs expressing OX40 were also detected, and those cells were a closer distance to CD3+T-cells than were MCs expressing other immune checkpoints. Two different cellular patterns of spatial distribution were determined according the CD3 distribution, and the predominant pattern was related with active immunosuppressive interaction with MCs. Our study shows that these five mIF panels can identify multiple targets in a single cell with high reproducibility. The study of different cell populations and their spatial relationship can open new ideas for therapeutic approaches.

A functional antibody cross-reactive to both human and murine cytotoxic T-lymphocyte-associated protein 4 via binding to an N-glycosylation epitope

Cytotoxic T-lymphocyte-associated protein 4 (CTLA-4, CD152) is a receptor on T cells that inhibits the cell’s functions. Blocking CTLA-4 with an antibody has proven effective for the treatment of cancer patients. Anti-CTLA-4 antibodies currently approved for clinical use can bind to human CTLA-4, but do not cross-react to murine CTLA-4. Here, we report the generation and characterization of a functional humanized antibody, mAb146, against both human and murine CTLA-4. Alanine scanning of CTLA-4 using mammalian cell expression cassette identified the unique epitopes of this novel antibody. In addition to the amino acid residues interacting with ligands CD80 and CD86, an N-glycosylation site on N110, conserved in CTLA-4 of human, monkey, and mouse, was identified as the specific epitope that might contribute to the cross-species binding and function of this antibody. This finding may also contribute to the understanding of the glycosylation of CTLA-4 and its related biologic function. In addition to facilitating preclinical development of anti-CTLA-4 antibodies, mAb146 may be useful as a therapeutic agent.

Relationship between immune checkpoint proteins, tumour microenvironment characteristics, and prognosis in primary operable colorectal cancer

The tumour microenvironment is an important factor for colorectal cancer prognosis, affecting the patient's immune response. Immune checkpoints, which regulate the immune functions of lymphocytes, may provide prognostic power. This study aimed to investigate the prognostic value of the immune checkpoints TIM‐3, LAG‐3 and PD‐1 in patients with stage I–III colorectal cancer. Immunohistochemistry was employed to detect TIM‐3, LAG‐3, PD‐1 and PD‐L1 in 773 patients with stage I–III colorectal cancer. Immune checkpoint protein expression was assessed in tumour cells using the weighted histoscore, and in immune cells within the stroma using point counting. Scores were analysed for associations with survival and clinical factors. High tumoural LAG‐3 (hazard ratio [HR] 1.45 95% confidence interval [CI] 1.00–2.09, p = 0.049) and PD‐1 (HR 1.34 95% CI 1.00–1.78, p = 0.047) associated with poor survival, whereas high TIM‐3 (HR 0.60 95% CI 0.42–0.84, p = 0.003), LAG‐3 (HR 0.58 95% CI 0.40–0.87, p = 0.006) and PD‐1 (HR 0.65 95% CI 0.49–0.86, p = 0.002) on immune cells within the stroma associated with improved survival, while PD‐L1 in the tumour (p = 0.487) or the immune cells within the stroma (p = 0.298) was not associated with survival. Furthermore, immune cell LAG‐3 was independently associated with survival (p = 0.017). Checkpoint expression scores on stromal immune cells were combined into a Combined Immune Checkpoint Stromal Score (CICSS), where CICSS 3 denoted all high, CICSS 2 denoted any two high, and CICSS 1 denoted other combinations. CICSS 3 was associated with improved patient survival (HR 0.57 95% CI 0.42–0.78, p = 0.001). The results suggest that individual and combined high expression of TIM‐3, LAG‐3, and PD‐1 on stromal immune cells are associated with better colorectal cancer prognosis, suggesting there is added value to investigating multiple immune checkpoints simultaneously.

The safety and efficacy of immune checkpoint inhibitors in patients with advanced cancers and pre-existing chronic viral infections (Hepatitis B/C, HIV): A review of the available evidence

The treatment paradigm of several cancers has dramatically changed in recent years with the introduction of immunotherapy. Most oncology trials involving immune checkpoint inhibitors (ICIPs) have routinely excluded patients with HIV infection and chronic viral hepatitis B (HBV) and C (HCV) due to concerns about viral reactivation, fears of increased toxicity, and the potential lack of efficacy in these patient subgroups. However, with current antiviral therapies, HIV and HBV infections have become chronic diseases and HCV infections can even be cured. Broadening cancer trial eligibility criteria in order to include cancer patients with chronic viral infections can maximize the ecological validity of study results and the ability to understand the ICPIs' benefit-risk profile in patients with these comorbidities. In this review, we examined the evidence on the efficacy and safety of using ICPIs in cancer patients with concurrent chronic viral infections.

Immune-related adverse events in cancer patients treated with immune checkpoint inhibitors: A single-center experience

Immune checkpoint inhibitors (ICIs) like cytotoxic T-lymphocyte-associated protein 4 (anti-CTLA4) and programmed death cell protein 1 (anti-PD1) have revolutionized cancer treatment. As ICI use becomes widespread, more immune-related adverse events (irAE's) are being reported. Our aim was to investigate the frequency and nature of new irAE's as well as report the frequency of flare-ups of pre-existing autoimmune conditions occurring after ICI therapy.We performed a retrospective chart review of all patients treated for cancer with anti-PD1 or anti-CTLA4 or combination therapy at our tertiary care center from January 2014 to April 2016. Demographic data, cancer type and stage, irAE's (new immune disorders and disease flares of pre-existing autoimmune disorders on ICI therapy), and drug treatment information were extracted.We identified 220 patients treated with ICI therapy during the study period out of which 27% (60/220) developed irAE's. 11% in anti-CTLA4 group and 16% among anti-PD1 treated patients developed irAE's. IrAE's resulted in discontinuation of cancer therapy in 28% of those who developed irAE's. 21.4% had a flare of their autoimmune disease but only 1 required discontinuation of immunotherapy.IrAE's are an important emerging clinical disease entity for specialists to be aware of. Our study shows that ICI's can be safely used in patients with pre-existing autoimmune conditions with close monitoring. However, there is still a large unmet need to have a better understanding of how to systematically evaluate and manage patients with irAE's as well as for identifying the predictors of irAE's.

Soluble fibrinogen-like protein 2 promotes the growth of hepatocellular carcinoma via attenuating dendritic cell-mediated cytotoxic T cell activity

BACKGROUND

Soluble fibrinogen-like protein 2 (sFGL2), a secretory protein expressed by regulatory T cells (Tregs) with immunosuppressive activity, is highly expressed in both the peripheral blood and tumor tissue of patients with hepatocellular carcinoma (HCC); however, sFGL2 function in HCC remains largely unknown. Here, we elucidated the potential role of sFGL2 in HCC progression.

METHODS

T cells, dendritic cells (DCs), and related cytokines in the tumor microenvironment were comparatively analyzed in BALB/c and C57BL/6 mice bearing transplanted hepatomas harboring Fgl2-knockout or receiving sFGL2-antibody treatment. Additionally, the effects of sFGL2 on DCs and T cells were evaluated in vivo and ex vivo.

RESULTS

The growth of both subcutaneously and orthotopically transplanted hepatomas was inhibited in Fgl2-knockout mice and those treated with the sFGL2 antibody, respectively, as compared with controls. Moreover, sFGL2 depletion enhanced the proportion and cytotoxicity of cytotoxic T cells, promoted DC maturation, and improved DC activity to proliferate T cells in the tumor microenvironment. Furthermore, we detected lower levels of interleukin (IL)-35 in both types of transplanted hepatomas and higher level of IL-6 in orthotopically transplanted hepatomas following sFGL2 depletion. Mechanistically, we found that sFGL2 impaired bone-marrow-derived DC (BMDCs) function by inhibiting phosphorylation of Akt, nuclear factor-kappaB, cAMP response element binding protein, and p38 and downregulating the expression of major histocompatibility complex II, CD40, CD80, CD86, and CD83 on BMDCs in vitro.

CONCLUSIONS

Our data suggest that sFGL2 promotes hepatoma growth by attenuating DC activity and subsequent CD8+ T cell cytotoxicity, suggesting sFGL2 as a novel potential therapeutic target for HCC treatment.

Two-Round Mixed Lymphocyte Reaction for Evaluation of the Functional Activities of Anti-PD-1 and Immunomodulators

Immune checkpoint inhibitors (ICIs), such as anti-PD-1 and anti-PD-L1 Abs, have shown efficacy for the treatment of various cancers. Although research has actively sought to develop new ICIs and immunomodulators, no efficient in vitro assay system is available to evaluate their functional activities. In the present study, we established a two-round MLR with human PBMCs for evaluation of the T cell-activating capacity of anti-PD-1 and other immunomodulators. We initially performed conventional MLR for this purpose. However, anti-PD-1 blocking Abs could not increase the proliferation of allo-reactive T cells in conventional MLR because PD-L1⁺ and PD-L2⁺ cells disappeared gradually during MLR. Therefore, we re-applied the same stimulator PBMCs to the allo-stimulated responder cells as a second-round MLR on day 6 when anti-PD-1 or immunomodulators were also added. In this two-round MLR, the proliferation of allo-reactive T cells was enhanced by anti-PD-1 in a dose-dependent manner or by immunomodulators, such as lenalidomide and galunisertib, a TGF-β receptor-1 inhibitor. Proliferation was further increased by the combination of immunomodulators with anti-PD-1. Here, we established a modified two-round MLR method with human PBMCs for evaluation of the functional activities of anti-PD-1 and immunomodulators.

Pomalidomide increases immune surface marker expression and immune recognition of oncovirus-infected cells

Most chronic viruses evade T-cell and natural killer (NK) immunity through downregulation of immune surface markers. Previously we showed that Pomalidomide (Pom) increases surface expression of major histocompatibility complex class I (MHC-I) in Kaposi sarcoma-associated herpesvirus-infected latent and lytic cells and restores ICAM-1 and B7-2 in latent cells. We explored the ability of Pom to increase immune surface marker expression in cells infected by other chronic viruses, including human T-cell leukemia virus type-1 (HTLV-1), Epstein-Barr virus (EBV), human papilloma virus (HPV), Merkel cell polyoma virus (MCV), and human immunodeficiency virus type-1 (HIV-1). Pom increased MHC-1, ICAM-1, and B7-2/CD86 in immortalized T-cell lines productively infected with HTLV-1 and also significantly increased their susceptibility to NK cell-mediated cytotoxicity. Pom enhancement of MHC-I and ICAM-1 in primary cells infected with HTLV-1 was abrogated by knockout of HTLV-1 orf-1. Pom increased expression of ICAM-1, B7-2 and MHC class I polypeptide related sequence A (MICA) surface expression in the EBV-infected Daudi cells and increased their T-cell activation and susceptibility to NK cells. Moreover, Pom increased expression of certain of these surface markers on Akata, Raji, and EBV lymphoblastic cell lines. The increased expression of immune surface markers in these virus-infected lines was generally associated with a decrease in IRF4 expression. By contrast, Pom treatment of HPV, MCV and HIV-1 infected cells did not increase these immune surface markers. Pom and related drugs may be clinically beneficial for the treatment of HTLV-1 and EBV-induced tumors by rendering infected cells more susceptible to both innate and adaptive host immune responses.

Soluble immune checkpoints in cancer: production, function and biological significance

Immune checkpoints play important roles in immune regulation, and blocking immune checkpoints on the cell membrane is a promising strategy in the treatment of cancer. Based on this, monoclonal antibodies are having much rapid development, such as those against CTLA-4 (cytotoxic T lymphocyte antigen 4) and PD-1 (programmed cell death protein 1).But the cost of preparation of monoclonal antibodies is too high and the therapeutic effect is still under restrictions. Recently, a series of soluble immune checkpoints have been found such as sCTLA-4 (soluble CTLA-4) and sPD-1 (soluble PD-1). They are functional parts of membrane immune checkpoints produced in different ways and can be secreted by immune cells. Moreover, these soluble checkpoints can diffuse in the serum. Much evidence has demonstrated that these soluble checkpoints are involved in positive or negative immune regulation and that changes in their plasma levels affect the development, prognosis and treatment of cancer. Since they are endogenous molecules, they will not induce immunological rejection in human beings, which might make up for the deficiencies of monoclonal antibodies and enhance the utility value of these molecules. Therefore, there is an increasing need for investigating novel soluble checkpoints and their functions, and it is promising to develop relevant therapies in the future. In this review, we describe the production mechanisms and functions of various soluble immune checkpoint receptors and ligands and discuss their biological significance in regard to biomarkers, potential candidate drugs, therapeutic targets, and other topics.

Unsolvable Problems of Biology: It Is Impossible to Create Two Identical Organisms, to Defeat Cancer, or to Map Organisms onto Their Genomes

The review is devoted to unsolvable problems of biology. 1) Problems unsolvable due to stochastic mutations occurring during DNA replication that make it impossible to create two identical organisms or even two identical complex cells (Sverdlov, E. D. (2009) Biochemistry (Moscow), 74, 939-944) and to "defeat" cancer. 2) Problems unsolvable due to multiple interactions in complex systems leading to the appearance of unpredictable emergent properties that prevent establishment of unambiguous relationships between the genetic architecture and phenotypic manifestation of the genome and make impossible to predict with certainty responses of the organism, its parts, or pathological processes to external factors. 3) Problems unsolvable because of the uncertainty principle and observer effect in biology, due to which it is impossible to obtain adequate information about cells in their tissue microenvironment by isolating and analyzing individual cells. In particular, we cannot draw conclusions on the properties of stem cells in their niches based on the properties of stem cell cultures. A strategy is proposed for constructing the pattern most closely approximated to the relationship of genotypes with their phenotypes by designing networks of intermediate phenotypes (endophenotypes).

Cost effectiveness vs. affordability in the age of immuno-oncology cancer drugs

INTRODUCTION

After years of setback, cancer immunotherapy has begun to yield clinical dividends, which are changing the treatment landscape and offering cancer patients the potential for long-term survival, reduced treatment-related toxicity and improved quality-of-life. Using the immune system to treat cancer is known as 'Immuno-oncology' (IO) and agents are sub-classified by their ability to enhance anti-tumor response or to direct the immune system to attack cancer cells via tumor-associated antigens. Areas covered: Clinical trials have demonstrated the effectiveness of several IO agents in many disease sites such as early and advanced stage melanoma, advanced non-small cell lung cancer, bladder, head and neck, gastric, kidney as well as Hodgkin's lymphoma. Notwithstanding the therapeutic excitement generated for patients and clinicians alike, an important consideration is treatment cost, which can reach more than $US100,000 per patient annually. The cost of the drugs, coupled with high disease prevalence and the ever-expanding number of indications, means the current cost trajectory is untenable for most healthcare systems to sustain. Expert commentary: In this paper, the approved IO drugs and those in clinical development are reviewed. The issue of cost effectiveness vs. affordability is then addressed and suggestions that facilitate patient access and long-term sustainability are presented.

Current status and future directions of cancer immunotherapy

In the past decades, our knowledge about the relationship between cancer and the immune system has increased considerably. Recent years' success of cancer immunotherapy including monoclonal antibodies (mAbs), cancer vaccines, adoptive cancer therapy and the immune checkpoint therapy has revolutionized traditional cancer treatment. However, challenges still exist in this field. Personalized combination therapies via new techniques will be the next promising strategies for the future cancer treatment direction.

Generation of Discriminative Human Monoclonal Antibodies from Rare Antigen-specific B Cells Circulating in Blood

Monoclonal antibodies (mAbs) are powerful tools useful for both fundamental research and in biomedicine. Their high specificity is indispensable when the antibody needs to distinguish between highly related structures (e.g., a normal protein and a mutated version thereof). The current way of generating such discriminative mAbs involves extensive screening of multiple Ab-producing B cells, which is both costly and time consuming. We propose here a rapid and cost-effective method for the generation of discriminative, fully human mAbs starting from human blood circulating B lymphocytes. The originality of this strategy is due to the selection of specific antigen binding B cells combined with the counter-selection of all other cells, using readily available Peripheral Blood Mononuclear Cells (PBMC). Once specific B cells are isolated, cDNA (complementary deoxyribonucleic acid) sequences coding for the corresponding mAb are obtained using single cell Reverse Transcription-Polymerase Chain Reaction (RT-PCR) technology and subsequently expressed in human cells. Within as little as 1 month, it is possible to produce milligrams of highly discriminative human mAbs directed against virtually any desired antigen naturally detected by the B cell repertoire.

YAP-Induced PD-L1 Expression Drives Immune Evasion in BRAFi-Resistant Melanoma

Activation of YAP, a Hippo pathway effector, is an important resistance mechanism to BRAF inhibitor (BRAFi) in melanoma. Emerging evidence also suggests that YAP is involved in suppression of the antitumor immune response. However, the potential direct impact of YAP activity on cytotoxic T-cell immune responses has not been explored yet. Here, we show that BRAFi-resistant melanoma cells evade CD8⁺ T-cell immune responses in a PD-L1-dependent manner by activating YAP, which synchronously supports melanoma cell survival upon BRAF inhibition. PD-L1 expression is elevated in BRAFi-resistant melanoma cells, in which YAP is robustly activated, and YAP knockdown decreases PD-L1 expression. In addition, constitutively active YAP (YAP-5SA) increases PD-L1 expression by binding to an upstream enhancer of the PD-L1 gene and potentiating its transcription. Both BRAFi-resistant and YAP-5SA-expressing melanoma cells suppress the cytotoxic function and cytokine production of Melan-A-specific CD8⁺ T cells, whereas anti-PD-1 antibody reverses the YAP-mediated T-cell suppression. Moreover, nuclear enrichment of YAP in clinical melanoma samples correlates with increased PD-L1 expression. Our findings show that YAP directly mediates evasion of cytotoxic T-cell immune responses in BRAFi-resistant melanoma cells by upregulating PD-L1, and targeting of YAP-mediated immune evasion may improve prognosis of melanoma patients. Cancer Immunol Res; 6(3); 255-66. ©2018 AACR.

Clinical Interventions in HIV Cure Research

Research over the past decade has resulted in a much-improved understanding of how and where HIV persists in patients on otherwise suppressive antiretroviral therapy (ART). It has become clear that the establishment of a latent infection in long-lived cells is the key barrier to curing HIV or allowing for sustained ART-free remission. Informed by in vitro and ex vivo studies, several therapeutic approaches aimed at depleting the pool of latently infected cells have been tested in small-scale experimental clinical trials including studies of ART intensification, genome editing, ART during acute/early infection and latency reversal. Many studies have focused on the use of latency-reversing agents (LRAs) to induce immune- or virus-mediated elimination of virus-producing cells. These trials have been instrumental in establishing safety and have shown that it is possible to impact the state HIV latency in patients on suppressive ART. However, administration of LRAs alone has thus far not demonstrated an effect on the frequency of latently infected cells or the time to virus rebound during analytical interruption of ART. More recently, there has been an enhanced focus on immune-based therapies in the onwards search for an HIV cure including therapeutic vaccines, toll-like receptor agonists, broadly neutralising antibodies, immune checkpoint inhibitors, interferon-α and interleukin therapy. In ongoing studies immunotherapy interventions are also tested in combination with latency reversal. In this chapter, the overall results of these clinical interventions ultimately aimed at a cure for HIV are presented and discussed.

Intratumoural PD-L1 expression is associated with worse survival of patients with Epstein-Barr virus-associated gastric cancer

BACKGROUND

This study investigated the clinical relevance and prognostic impact of the overall expression of programmed cell death protein ligand-1 (PD-L1) and programmed cell death protein ligand-2 (PD-L2), in patients with Epstein-Barr virus-associated gastric cancer (EBVaGC).

METHODS

After reviewing 1318 consecutive cases of surgically resected or endoscopic submucosal dissected gastric cancers, the expression status of PD-L1 and PD-L2 in 120 patients with EBVaGC identified by EBV-encoded RNA in situ hybridisation was retrospectively analysed using immunohistochemistry (IHC). For each IHC marker, positivity was separately in intraepithelial tumour cells (iTu-) and immune cells in the tumour stroma area (str-).

RESULTS

Among 116 eligible patients, 57 (49.1%) and 66 patients (56.9%) were determined as iTu-PD-L1-positive and str-PD-L1-positive, respectively, whereas 23 (21.6%) and 45 patients (38.8%) were determined as iTu-PD-L2 positive and str-PD-L2 positive, respectively. Intraepithelial tumour cell PD-L1 positivity was found to be significantly associated with lymph node (LN) metastasis (P=0.012) and a poor disease-free survival (DFS) (P=0.032), yet not overall survival (P=0.482). In a multivariate analysis, iTu-PD-L1 positivity was independently associated with a poor DFS (P=0.006, hazard ratio=12.085). In contrast, str-PD-L2-positivity was related to a lower T category (P=0.003), absence of LN metastasis (P=0.032) and perineural invasion (P=0.028). Intraepithelial tumour cell and str-PD-L2 positivity showed a trend towards an improved DFS, although not significant (P=0.060 and P=0.073, respectively).

CONCLUSIONS

Intraepithelial tumour cells PD-L1 expression can be used to predict a poor outcome in patients with EBVaGC and can represent a rational approach for PD-1/PD-L pathway-targeted immunotherapy.

B-cell populations are expanded in breast cancer patients compared with healthy controls

BACKGROUND

Historically, humoral immunity was considered unimportant in anti-tumor immunity, and the differentiation and anti-tumor activity of B cells in breast cancer are poorly understood. However, it was recently discovered that B cells participate in tumor immunity through both antibody production and immunosuppressive mechanisms. We analyzed the expression of B-cell differentiation markers in detail using fluorescence-activated cell sorting to investigate the relationship between B-cell subsets and breast cancer etiology.

METHODS

Blood samples were taken from breast cancer patients and healthy donors, and peripheral blood mononuclear cells were collected. B cells at various stages of differentiation were identified by the expression of combinations of the cell surface markers CD5, CD19, CD21, CD24, CD27, CD38, CD45, and IgD. Statistical analysis of the proportions of each B-cell subtype in the different patient groups was then performed.

RESULTS

Twenty-seven breast cancer patients and 12 controls were considered. The proportion of total B cells was significantly higher in cancer patients than in controls (11.51 ± 2.059 vs 8.905 ± 0.379%, respectively; p = 0.001). Breast cancer patients were then classified as High-B or Low-B for further analysis. A significantly higher proportion of memory B cells was found in the High-B group than in the Low-B or control groups (p = 0.003 and p = 0.043, respectively).

CONCLUSIONS

Breast cancer patients generally have a higher proportion of B cells than healthy controls, but this is highly variable. Analysis of the major B-cell surface markers indicates that memory B cells in particular are significantly expanded, or more robust, in breast cancer patients.

Harness the synergy between targeted therapy and immunotherapy: what have we learned and where are we headed?

Since the introduction of imatinib for the treatment of chronic myelogenous leukemia, several oncogenic mutations have been identified in various malignancies that can serve as targets for therapy. More recently, a deeper insight into the mechanism of antitumor immunity and tumor immunoevasion have facilitated the development of novel immunotherapy agents. Certain targeted agents have the ability of inhibiting tumor growth without causing severe lymphocytopenia and amplifying antitumor immune response by increasing tumor antigenicity, enhancing intratumoral T cell infiltration, and altering the tumor immune microenvironment, which provides a rationale for combining targeted therapy with immunotherapy. Targeted therapy can elicit dramatic responses in selected patients by interfering with the tumor-intrinsic driver mutations. But in most cases, resistance will occur over a relatively short period of time. In contrast, immunotherapy can yield durable, albeit generally mild, responses in several tumor types via unleashing host antitumor immunity. Thus, combination approaches might be able to induce a rapid tumor regression and a prolonged duration of response. We examine the available evidence regarding immune effects of targeted therapy, and review preclinical and clinical studies on the combination of targeted therapy and immunotherapy for cancer treatment. Furthermore, we discuss challenges of the combined therapy and highlight the need for continued translational research.

Clinical significance of tumor-infiltrating lymphocytes for gastric cancer in the era of immunology

Immunotherapy has begun to revolutionize cancer treatment, by introducing therapies that target the host immune system instead of the tumor, therapies that possess unique adverse event profiles, and therapies that may cure certain types of cancer. The immune microenvironment of tumors is emerging as the most important means of understanding the relationship between a patient' immune system and their cancer, informing prognosis, and guiding immunotherapy, such as an antibody blockade of immune checkpoints. For some solid tumors, simple quantitation of lymphocyte infiltration would seem to have prognostic significance, suggesting that lymphocyte infiltration is not passive but may actively promote or inhibit tumor growth. For gastric cancers, several studies have provided strong evidence that immune cells contribute to determining prognosis. However, the exact role of immune cells in gastric cancer remains unclear. Therefore, this review focuses on the clinical significance of immune cells, especially tumor-infiltrating lymphocytes, in gastric cancer.

MafB silencing in macrophages does not influence the initiation and growth of lung cancer induced by urethane

An increased number of tumor-associated macrophages (TAMs) that exhibit the M2 macrophage phenotype is related to poorer prognosis in cancer patients. MafB is a transcription factor regulating the differentiation of macrophages. However, involvement of MafB for the development of TAMs is unknown. This study was designed to investigate the role of MafB in a murine urethane-induced lung cancer model. Urethane was injected intraperitoneally into wild-type and dominant-negative MafB transgenic mice. Twenty-four weeks later, mice were sacrificed and their lungs removed for pathological analysis. The numbers and mean areas of lung cancer were evaluated. In addition, the numbers of Mac-3-positive macrophages were evaluated in each tumor. The numbers and mean areas of lung cancer induced by urethane administration were not significantly different between wild-type and dominant-negative MafB transgenic mice. The numbers of TAMs in lung cancer tissue were not significantly different between the two groups. MafB silencing using dominant-negative MafB did not influence the initiation and growth of lung cancer in mice exposed to urethane. These data suggest that MafB may not be related to the development of TAMs.

FAP positive fibroblasts induce immune checkpoint blockade resistance in colorectal cancer via promoting immunosuppression

Immune checkpoint blockades that significantly prolonged survival of melanoma patients have been less effective on colorectal cancer (CRC) patients. Growing evidence suggested that fibroblast activation protein-alpha (FAP) on cancer associate fibroblasts (CAFs) has critical roles in regulating antitumor immune response by inducing tumor-promoting inflammation. In this study, we explored the roles of FAP in regulating the tumor immunity and immune checkpoint blockades resistance in CRC experimental systems. We found that CAFs with high FAP expression could induce immune checkpoint blockade resistance in CRC mouse model. Mechanistically, CAFs with high FAP expression promoted immunosuppression in the CRC tumor immune microenvironment by up-regulating CCL2 secretion, recruiting myeloid cells, and decreasing T-cell activity. In human CRC samples, FAP expression was proportional to myeloid cells number, but inversely related to T-cell number. High FAP expression also predicted poor survival of CRC patients. Taken together, our study suggested that high FAP expression in CAFs is one reason leading to immune checkpoint blockades resistance in CRC patients and FAP is an optional target for reversing immune checkpoint blockades resistance.