Phase I clinical trial of a five-peptide cancer vaccine combined with cyclophosphamide in advanced solid tumors

Cancer vaccines: current status and future directions

Cancer continues to be a major global health burden, with high morbidity and mortality. Building on the success of immune checkpoint inhibitors and adoptive cellular therapy, cancer vaccines have garnered significant interest, but their clinical success remains modest. Benefiting from advancements in technology, many meticulously designed cancer vaccines have shown promise, warranting further investigations to reach their full potential. Cancer vaccines hold unique benefits, particularly for patients resistant to other therapies, and they offer the ability to initiate broad and durable T cell responses. In this review, we highlight the antigen selection for cancer vaccines, introduce the immune responses induced by vaccines, and propose strategies to enhance vaccine immunogenicity. Furthermore, we summarize key features and notable clinical advances of various vaccine platforms. Lastly, we delve into the mechanisms of tumor resistance and explore the potential benefits of combining cancer vaccines with standard treatments and other immunomodulatory approaches to improve vaccine efficacy.

Emerging Frontiers in Colorectal Cancer Therapy: From Targeted Molecules to Immunomodulatory Breakthroughs and Cell-Based Approaches

Colorectal cancer (CRC) is ranked as the second leading cause of cancer-related deaths globally, necessitating urgent advancements in therapeutic approaches. The emergence of groundbreaking therapies, including chimeric antigen receptor-T (CAR-T) cell therapies, oncolytic viruses, and immune checkpoint inhibitors, marks a transformative era in oncology. These innovative modalities, tailored to individual genetic and molecular profiles, hold the promise of significantly enhancing patient outcomes. This comprehensive review explores the latest clinical trials and advancements, encompassing targeted molecular therapies, immunomodulatory agents, and cell-based therapies. By evaluating the strengths, limitations, and potential synergies of these approaches, this research aims to reshape the treatment landscape and improve clinical outcomes for CRC patients, offering new found hope for those who have exhausted conventional options. The culmination of this work is anticipated to pave the way for transformative clinical trials, ushering in a new era of personalized and effective CRC therapy.

Immunotherapy in colorectal cancer: Statuses and strategies

Colorectal cancer (CRC) is widely recognized as the third most prevalent malignancy globally and the second leading cause of cancer-related mortality. Traditional treatment modalities for CRC, including surgery, chemotherapy, and radiotherapy, can be utilized either individually or in combination. However, these treatments frequently result in significant side effects due to their non-specificity and cytotoxicity affecting all cells. Moreover, a considerable number of patients face relapses following these treatments. Consequently, it is imperative to explore more efficacious treatment interventions for CRC patients. Immunotherapy, an emerging frontier in oncology, represents a novel therapeutic approach that leverages the body's immune system to target cancer cells. The principal advantage of immunotherapy is its capacity to selectively target cancer cells while minimizing damage to healthy cells. Its recent adoption as a neoadjuvant therapy presents significant potential to transform the treatment landscape for both primary resectable and metastatic CRC. This review endeavors to offer a comprehensive overview of current strategies in CRC immunotherapy, critically analyze existing literature, underscore anticipated outcomes from ongoing clinical trials, and deliberate on the challenges and impediments encountered within the field of immunotherapy.

Current status of vaccine immunotherapy for gastrointestinal cancers

Recent advances in tumor immunology and molecular drug development have ushered in a new era of cancer immunotherapy. Immunotherapy has shown promising results for several types of tumors, such as advanced melanoma, non-small cell lung cancer, renal cell carcinoma, bladder cancers, and refractory Hodgkin's lymphoma. Similarly, efforts have been made to develop immunotherapies such as adoptive T-cell transplantation, peptide vaccines, and dendritic cell vaccines, specifically for gastrointestinal tumors. However, before the advent of immune checkpoint inhibitors, immunotherapy did not work as well as expected. In this article, we review immunotherapy, focusing on cancer vaccines for gastrointestinal tumors, which generally target eliciting tumor-specific CD8 + cytotoxic T lymphocytes (CTLs). We also review various vaccine therapies and describe the relationship between vaccines and adjuvants. Finally, we discuss prospects for the combination of immunotherapy with immune checkpoint inhibitors.

A phase 3, randomized, double-blind, multicenter, placebo-controlled study of S-588410, a five-peptide cancer vaccine as an adjuvant therapy after curative resection in patients with esophageal squamous cell carcinoma

BACKGROUND

S-588410, a cancer peptide vaccine (CPV), comprises five HLA-A*24:02-restricted peptides from five cancer-testis antigens. In a phase 2 study, S-588410 was well-tolerated and exhibited antitumor efficacy in patients with urothelial cancer. Therefore, we aimed to evaluate the efficacy, immune response, and safety of S-588410 in patients with completely resected esophageal squamous cell carcinoma (ESCC).

METHODS

This phase 3 study involved patients with HLA-A*24:02-positive and lymph node metastasis-positive ESCC who received neoadjuvant therapy followed by curative resection. After randomization, patients were administered S-588410 and placebo (both emulsified with Montanide™ ISA 51VG) subcutaneously. The primary endpoint was relapse-free survival (RFS). The secondary endpoints were overall survival (OS), cytotoxic T-lymphocyte (CTL) induction, and safety. Statistical significance was tested using the one-sided weighted log-rank test with the Fleming-Harrington class of weights.

RESULTS

A total of 276 patients were randomized (N = 138/group). The median RFS was 84.3 and 84.1 weeks in the S-588410 and placebo groups, respectively (P = 0.8156), whereas the median OS was 236.3 weeks and not reached, respectively (P = 0.6533). CTL induction was observed in 132/134 (98.5%) patients who received S-588410 within 12 weeks. Injection site reactions (137/140 patients [97.9%]) were the most frequent treatment-emergent adverse events in the S-588410 group. Prolonged survival was observed in S-588410-treated patients with upper thoracic ESCC, grade 3 injection-site reactions, or high CTL intensity.

CONCLUSIONS

S-588410 induced immune response and had acceptable safety but failed to reach the primary endpoint. A high CTL induction rate and intensity may be critical for prolonging survival during future CPV development.

The bright side of chemistry: Exploring synthetic peptide-based anticancer vaccines

The present review focuses on synthetic peptide-based vaccine strategies in the context of anticancer intervention, paying attention to critical aspects such as peptide epitope selection, adjuvant integration, and nuanced classification of synthetic peptide cancer vaccines. Within this discussion, we delve into the diverse array of synthetic peptide-based anticancer vaccines, each derived from tumor-associated antigens (TAAs), including melanoma antigen recognized by T cells 1 (Melan-A or MART-1), mucin 1 (MUC1), human epidermal growth factor receptor 2 (HER-2), tumor protein 53 (p53), human telomerase reverse transcriptase (hTERT), survivin, folate receptor (FR), cancer-testis antigen 1 (NY-ESO-1), and prostate-specific antigen (PSA). We also describe the synthetic peptide-based vaccines developed for cancers triggered by oncovirus, such as human papillomavirus (HPV), and hepatitis C virus (HCV). Additionally, the potential synergy of peptide-based vaccines with common therapeutics in cancer was considered. The last part of our discussion deals with the realm of the peptide-based vaccines delivery, highlighting its role in translating the most promising candidates into effective clinical strategies. Although this discussion does not cover all the ongoing peptide vaccine investigations, it aims at offering valuable insights into the chemical modifications and the structural complexities of anticancer peptide-based vaccines.

Efficacy of novel allogeneic cancer cells vaccine to treat colorectal cancer

Colorectal cancer (CRC) remains a significant global health burden, emphasizing the need for innovative treatment strategies. 95% of the CRC population are microsatellite stable (MSS), insensitive to classical immunotherapies such as anti-PD-1; on the other hand, responders can become resistant and relapse. Recently, the use of cancer vaccines enhanced the immune response against tumor cells. In this context, we developed a therapeutic vaccine based on Stimulated Tumor Cells (STC) platform technology. This vaccine is composed of selected tumor cell lines stressed and haptenated in vitro to generate a factory of immunogenic cancer-related antigens validated by a proteomic cross analysis with patient's biopsies. This technology allows a multi-specific education of the immune system to target tumor cells harboring resistant clones. Here, we report safety and antitumor efficacy of the murine version of the STC vaccine on CT26 BALB/c CRC syngeneic murine models. We showed that one cell line (1CL)-based STC vaccine suppressed tumor growth and extended survival. In addition, three cell lines (3CL)-based STC vaccine significantly improves these parameters by presenting additional tumor-related antigens inducing a multi-specific anti-tumor immune response. Furthermore, proteomic analyses validated that the 3CL-based STC vaccine represents a wider quality range of tumor-related proteins than the 1CL-based STC vaccine covering key categories of tumor antigens related to tumor plasticity and treatment resistance. We also evaluated the efficacy of STC vaccine in an MC38 anti-PD-1 resistant syngeneic murine model. Vaccination with the 3CL-based STC vaccine significantly improved survival and showed a confirmed complete response with an antitumor activity carried by the increase of CD8+ lymphocyte T cells and M1 macrophage infiltration. These results demonstrate the potential of this technology to produce human vaccines for the treatment of patients with CRC.

Immunotherapy for colorectal cancer: Rational strategies and novel therapeutic progress

There are increasing incidences and mortality rates for colorectal cancer in the world. It is common for chemotherapy and radiation given to patients with colorectal cancer to cause toxicities that limit their effectiveness and cause cancer cells to become resistant to these treatments. Additional targeted treatments are needed to improve patient's quality of life and outcomes. Immunotherapy has rapidly emerged as an incredibly exciting and promising avenue for cancer treatment in recent years. This innovative approach provides novel options for tackling solid tumors, effectively establishing itself as a new cornerstone in cancer treatment. Specifically, in the realm of colorectal cancer (CRC), there is great promise in developing new drugs that target immune checkpoints, offering a hopeful and potentially transformative solution. While immunotherapy of CRC has made significant advances, there are still obstacles and limitations. CRC patients have a poor response to treatment because of the immune-suppressing function of their tumor microenvironment (TME). In addition to blocking inhibitory immune checkpoints, checkpoint-blocking antibodies may also boost immune responses against tumors. The review summarizes recent advances in immune checkpoint inhibitors (ICIs) for CRC, including CTLA-4, PD-1, PD-L1, LAG-3, and TIM-3.

Chemical Strategies towards the Development of Effective Anticancer Peptides

Cancer is increasingly recognized as one of the primary causes of death and has become a multifaceted global health issue. Modern medical science has made significant advancements in the diagnosis and therapy of cancer over the past decade. The detrimental side effects, lack of efficacy, and multidrug resistance of conventional cancer therapies have created an urgent need for novel anticancer therapeutics or treatments with low cytotoxicity and drug resistance. The pharmaceutical groups have recognized the crucial role that peptide therapeutic agents can play in addressing unsatisfied healthcare demands and how these become great supplements or even preferable alternatives to biological therapies and small molecules. Anticancer peptides, as a vibrant therapeutic strategy against various cancer cells, have demonstrated incredible anticancer potential due to high specificity and selectivity, low toxicity, and the ability to target the surface of traditional "undruggable" proteins. This review will provide the research progression of anticancer peptides, mainly focusing on the discovery and modifications along with the optimization and application of these peptides in clinical practice.

Colorectal Cancer Immunotherapy: State of the Art and Future Directions

Cancer immunotherapy has become an indispensable mode of treatment for a multitude of solid tumor cancers. Colorectal cancer (CRC) has been one of the many cancer types to benefit from immunotherapy, especially in advanced disease where standard treatment fails to prevent recurrence or results in poor survival. The efficacy of immunotherapy in CRC has not been without challenge, as early clinical trials observed dismal responses in unselected CRC patients treated with checkpoint inhibitors. Many studies and clinical trials have since refined immunotherapies available for CRC, solidifying immunotherapy as a powerful asset for CRC treatment. This review article examines CRC immunotherapies, from their foundation, through emerging avenues for improvement, to future directions.

Peptide Vaccines as Therapeutic and Prophylactic Agents for Female-Specific Cancers: The Current Landscape

Breast and gynecologic cancers are significant global threats to women's health and those living with the disease require lifelong physical, financial, and social support from their families, healthcare providers, and society as a whole. Cancer vaccines offer a promising means of inducing long-lasting immune response against the disease. Among various types of cancer vaccines available, peptide vaccines offer an effective strategy to elicit specific anti-tumor immune responses. Peptide vaccines have been developed based on tumor associated antigens (TAAs) and tumor specific neoantigens which can also be of viral origin. Molecular alterations in HER2 and non-HER2 genes are established to be involved in the pathogenesis of female-specific cancers and hence were exploited for the development of peptide vaccines against these diseases, most of which are in the latter stages of clinical trials. However, prophylactic vaccines for viral induced cancers, especially those against Human Papillomavirus (HPV) infection are well established. This review discusses therapeutic and prophylactic approaches for various types of female-specific cancers such as breast cancer and gynecologic cancers with special emphasis on peptide vaccines. We also present a pipeline for the design and evaluation of a multiepitope peptide vaccine that can be active against female-specific cancers.

A novel immunogenic cell death signature for the prediction of prognosis and therapies in glioma

Glioma is a primary cranial malignancy with high recurrence rate, poor prognosis and high mortality. However, the roles of immunogenic cell death (ICD) in glioma remain unclear. Twenty ICD genes were analyzed to be differentially expressed between glioma tissues and non-tumor tissues in 371 glioma patients from The Cancer Genome Atlas (TCGA). Patients were classified into three subgroups via unsupervised clustering. Interestingly, the features of cell-infiltrating from three clusters were matched with three immune phenotypes. An applied scoring system was built depending on the expression of hub ICD-related genes. Notably, the ICD-related score was linked with immune checkpoints and the prognosis of glioma patients. In addition, the applied risk model could be used for the prediction of the effect of chemotherapy and immunotherapy for glioma patients. Furthermore, MYD88 was identified to play key roles in the risk model for glioma patients. MYD88 was specifically expressed in malignant cells and validated to correlate with cell proliferation and invasion. Ligand-receptor pairs are determined as novel communications indicating between immunocytes and malignant cells. Therefore, our research established an ICD-related score to investigate the potential effect to chemotherapy and immunotherapy for glioma patients and indicated that MYD88 was a key role in this risk model.

Establishing the applicability of cancer vaccines in combination with chemotherapeutic entities: current aspect and achievable prospects

Cancer immunotherapy is one of the recently developed cancer treatment modalities. When compared with conventional anticancer drug regimens, immunotherapy has shown significantly better outcomes in terms of quality of life and overall survival. It incorporates a wide range of immunomodulatory modalities that channel the effects of the immune system either by broadly modulating the host immune system or by accurately targeting distinct tumor antigens. One such treatment modality that has gained interest is cancer vaccine therapy which acts by developing antibodies against tumor cells. Cancer vaccines target individual peptides or groups of antigens that are released by tumor cells and presented by the APCs. This also initiates an effective process to activate the host immune responses. Studies on various types of cancer vaccines are conducted, out of which only few are approved by FDA for clinical uses. Despite of documented safety and efficacy of conventional chemotherapy and cancer vaccines, individually they did not produce substantial results in eradication of the cancer as a monotherapy. Hence, the combination approach holds the extensive potential to provide significant improvement in disease outcomes. Certain chemotherapy has immunomodulatory effects and is proven to synergize with cancer vaccines thereby enhancing their anti-tumor activities. Chemotherapeutic agents are known to have immunostimulatory mechanisms apart from its cytotoxic effect and intensify the anti-tumor activities of vaccines by various mechanisms. This review highlights various cancer vaccines, their mechanism, and how their activity gets affected by chemotherapeutic agents. It also aims at summarizing the evidence-based outcome of the combination approach of a cancer vaccine with chemotherapy and a brief on future aspects.

Colorectal cancer vaccines: The current scenario and future prospects

Colorectal cancer (CRC) is one of the most common cancers worldwide. Current therapies such as surgery, chemotherapy, and radiotherapy encounter obstacles in preventing metastasis of CRC even when applied in combination. Immune checkpoint inhibitors depict limited effects due to the limited cases of CRC patients with high microsatellite instability (MSI-H). Cancer vaccines are designed to trigger the elevation of tumor-infiltrated lymphocytes, resulting in the intense response of the immune system to tumor antigens. This review briefly summarizes different categories of CRC vaccines, demonstrates the current outcomes of relevant clinical trials, and provides particular focus on recent advances on nanovaccines and neoantigen vaccines, representing the trend and emphasis of CRC vaccine development.

Antitumor Peptide-Based Vaccine in the Limelight

The success of the immune checkpoint blockade has provided a proof of concept that immune cells are capable of attacking tumors in the clinic. However, clinical benefit is only observed in less than 20% of the patients due to the non-specific activation of immune cells by the immune checkpoint blockade. Developing tumor-specific immune responses is a challenging task that can be achieved by targeting tumor antigens to generate tumor-specific T-cell responses. The recent advancements in peptide-based immunotherapy have encouraged clinicians and patients who are struggling with cancer that is otherwise non-treatable with current therapeutics. By selecting appropriate epitopes from tumor antigens with suitable adjuvants, peptides can elicit robust antitumor responses in both mice and humans. Although recent experimental data and clinical trials suggest the potency of tumor reduction by peptide-based vaccines, earlier clinical trials based on the inadequate hypothesis have misled that peptide vaccines are not efficient in eliminating tumor cells. In this review, we highlighted the recent evidence that supports the rationale of peptide-based antitumor vaccines. We also discussed the strategies to select the optimal epitope for vaccines and the mechanism of how adjuvants increase the efficacy of this promising approach to treat cancer.

In Silico Model Estimates the Clinical Trial Outcome of Cancer Vaccines

Over 30 years after the first cancer vaccine clinical trial (CT), scientists still search the missing link between immunogenicity and clinical responses. A predictor able to estimate the outcome of cancer vaccine CTs would greatly benefit vaccine development. Published results of 94 CTs with 64 therapeutic vaccines were collected. We found that preselection of CT subjects based on a single matching HLA allele does not increase immune response rates (IRR) compared with non-preselected CTs (median 60% vs. 57%, p = 0.4490). A representative in silico model population (MP) comprising HLA-genotyped subjects was used to retrospectively calculate in silico IRRs of CTs based on the percentage of MP-subjects having epitope(s) predicted to bind ≥ 1–4 autologous HLA allele(s). We found that in vitro measured IRRs correlated with the frequency of predicted multiple autologous allele-binding epitopes (AUC 0.63–0.79). Subgroup analysis of multi-antigen targeting vaccine CTs revealed correlation between clinical response rates (CRRs) and predicted multi-epitope IRRs when HLA threshold was ≥ 3 (r = 0.7463, p = 0.0004) but not for single HLA allele-binding epitopes (r = 0.2865, p = 0.2491). Our results suggest that CRR depends on the induction of broad T-cell responses and both IRR and CRR can be predicted when epitopes binding to multiple autologous HLAs are considered.

Artemisia argyi Essential Oil Inhibits Hepatocellular Carcinoma Metastasis via Suppression of DEPDC1 Dependent Wnt/β-Catenin Signaling Pathway

The tumor metastasis is the major hurdle for the treatment of advanced hepatocellular carcinoma (HCC), due in part to the lack of effective systemic treatments. DEPDC1, a novel oncoantigen upregulated in HCC, is thought to be a molecular-target for novel therapeutic drugs. Artemisia argyi is a traditional Chinese medicine with anti-inflammatory and anti-tumor activities. This study investigated the potential therapeutic benefits of Artemisia argyi essential oil (AAEO) in suppressing metastasis of HCC by targeting DEPDC1. Assessment of AAEO cytotoxicity was performed by MTT assay. Anti-metastatic effects of AAEO were investigated in vitro using wound healing and transwell assays. The HepG2 cells were transduced with lentiviral vector containing luciferase (Luc). A metastasis model of nude mice was established by tail vein injection of HepG2-Luc cells. The nude mice were treated with AAEO (57.5, 115, and 230 mg/kg) or sorafenib (40 mg/kg). Metastasis of HCC cells was monitored via in vivo bioluminescence imaging. After treatment for 21 days, tissues were collected for histological examination and immunohistochemistry analysis. Gene and protein levels were determined by real-time quantitative PCR and western blotting. The results revealed that AAEO significantly inhibits the migration and invasion in vitro in a concentration-dependent manner. In vivo assays further confirmed that AAEO markedly inhibits HCC metastasis into lung, brain, and femur tissues and exhibits low toxicity. Our results suggested that AAEO significantly downregulates the mRNA and protein expression of DEPDC1. Also, AAEO attenuated Wnt/β-catenin signaling through reduction of Wnt1 and β-catenin production. Moreover, AAEO prevented epithelial-mesenchymal transition (EMT) by downregulation of vimentin and upregulation of E-cadherin. Furthermore, we found that DEPDC1 promoted HCC migration and invasion via Wnt/β-catenin signaling pathway and EMT. These results demonstrate that AAEO effectively inhibits HCC metastasis via attenuating Wnt/β-catenin signaling and inhibiting EMT by suppressing DEPDC1 expression. Thus, AAEO likely acts as a novel inhibitor of the DEPDC1 dependent Wnt/β-catenin signaling pathway.

Perspectives on Immunotherapy of Metastatic Colorectal Cancer

Colorectal cancer, especially liver metastasis, is still a challenge worldwide. Traditional treatment such as surgery, chemotherapy and radiotherapy have been difficult to be further advanced. We need to develop new treatment methods to further improve the poor prognosis of these patients. The emergence of immunotherapy has brought light to mCRC patients, especially those with dMMR. Based on several large trials, some drugs (pembrolizumab, nivolumab) have been approved by US Food and Drug Administration to treat the patients diagnosed with dMMR tumors. However, immunotherapy has reached a bottleneck for other MSS tumors, with low response rate and poor PFS and OS. Therefore, more clinical trials are underway toward mCRC patients, especially those with MSS. This review is intended to summarize the existing clinical trials to illustrate the development of immunotherapy in mCRC patients, and to provide a new thinking for the direction and experimental design of immunotherapy in the future.

Challenges and perspectives for immunotherapy in oesophageal cancer: A look to the future (Review)

Oesophageal cancer is one of the most aggressive malignancies with limited treatment options, thus resulting in a high morbidity and mortality. With 5‑year survival rates of only 5‑10%, oesophageal cancer holds a dismal prognosis for patients. In order to improve overall survival, the early diagnosis and tools for patient stratification for personalized treatment are urgent needs. A minority of oesophageal cancers belong to the spectrum of Lynch syndrome‑associated cancers and are characterized by microsatellite instability (MSI). Microsatellite instability is a consequence of defective mismatch repair protein functions and it has been well characterized in other gastrointestinal tumours, such as colorectal and gastric cancer. In the latter, high levels of MSI are associated with a better prognosis and with an increased benefit to immune‑based therapies. Therefore, similar therapeutic approaches could offer an opportunity of treatment for oesophageal cancer patients with MSI. Apart from immune checkpoint inhibitors, other immunotherapies such as adoptive T‑cell transfer, peptide vaccine and oncolytic viruses are under investigation in oesophageal cancer patients. In the present review, the rationale and current knowledge about immunotherapies in oesophageal cancer are summarised.

Related parameters of affinity and stability prediction of HLA-A*2402 restricted antigen peptides based on molecular docking

Background

Major histocompatibility complex class I (MHC-I) plays an important role in cell immune response, and stable interaction between polypeptides and MHC-I ensures efficient presentation of polypeptide-MHC-I (pMHC-I) molecular complexes to T cells. The aim of this study was to explore ways to improve the affinity and stability of the p-Human Leukocyte Antigen (HLA)-A*2402 complex.

Methods

The peptide sequences of the restricted antigen peptides for HLA-A*2402 and the results of the in vitro competitive binding test were retrieved from the literature. The affinity values were predicted using NetMHCpan v4.1 server, and the stability values were predicted using the NetMHCstab v1.0 server. Auto Vina was used to dock peptides to HLA-A*2402 protein in a flexible docking manner, while Flexpepdock was employed to optimize the docking morphology. Maestro was used to analyze the intermolecular forces and the binding affinity of the complex, while MM-GBSA was used to calculate the binding free energy values.

Results

The intermolecular interactions that maintained the affinity and stability of peptide-HLA-A*2402 complex relied mainly on HB, followed by pi stack. The binding affinity values of molecular docking were associated with the predicted values of affinity and stability, the binding affinity and the binding free energy, as well as the intermolecular force pi-stack. The pi stack had a significant negative correlation with binding affinity and binding free energy. The replacement of the residues of the polypeptides that did not form pi-stack interactions with HLA-A*2402 improved the affinity and/or stability compared to before replacement.

Conclusions

The generation and increase in the number of pi-stacks between peptides and HLA-A*2402 molecules may help improve the affinity and stability of p-HLA-A*2402 complexes. The prediction of intermolecular forces and binding affinity of peptide-HLA by means of molecular docking is a supplement to the current commonly used prediction databases.

Peptide-based therapeutic cancer vaccine: Current trends in clinical application

The peptide‐based therapeutic cancer vaccines have attracted enormous attention in recent years as one of the effective treatments of tumour immunotherapy. Most of peptide‐based vaccines are based on epitope peptides stimulating CD8⁺ T cells or CD4⁺ T helper cells to target tumour‐associated antigens (TAAs) or tumour‐specific antigens (TSAs). Some adjuvants and nanomaterials have been exploited to optimize the efficiency of immune response of the epitope peptide to improve its clinical application. At present, numerous peptide‐based therapeutic cancer vaccines have been developed and achieved significant clinical benefits. Similarly, the combination of peptide‐based vaccines and other therapies has demonstrated a superior efficacy in improving anti‐cancer activity. We delve deeper into the choices of targets, design and screening of epitope peptides, clinical efficacy and adverse events of peptide‐based vaccines, and strategies combination of peptide‐based therapeutic cancer vaccines and other therapies. The review will provide a detailed overview and basis for future clinical application of peptide‐based therapeutic cancer vaccines.

Cancer Vaccines: Adjuvant Potency, Importance of Age, Lifestyle, and Treatments

Although the discovery and characterization of multiple tumor antigens have sparked the development of many antigen/derived cancer vaccines, many are poorly immunogenic and thus, lack clinical efficacy. Adjuvants are therefore incorporated into vaccine formulations to trigger strong and long-lasting immune responses. Adjuvants have generally been classified into two categories: those that ‘depot’ antigens (e.g. mineral salts such as aluminum hydroxide, emulsions, liposomes) and those that act as immunostimulants (Toll Like Receptor agonists, saponins, cytokines). In addition, several novel technologies using vector-based delivery of antigens have been used. Unfortunately, the immune system declines with age, a phenomenon known as immunosenescence, and this is characterized by functional changes in both innate and adaptive cellular immunity systems as well as in lymph node architecture. While many of the immune functions decline over time, others paradoxically increase. Indeed, aging is known to be associated with a low level of chronic inflammation—inflamm-aging. Given that the median age of cancer diagnosis is 66 years and that immunotherapeutic interventions such as cancer vaccines are currently given in combination with or after other forms of treatments which themselves have immune-modulating potential such as surgery, chemotherapy and radiotherapy, the choice of adjuvants requires careful consideration in order to achieve the maximum immune response in a compromised environment. In addition, more clinical trials need to be performed to carefully assess how less conventional form of immune adjuvants, such as exercise, diet and psychological care which have all be shown to influence immune responses can be incorporated to improve the efficacy of cancer vaccines. In this review, adjuvants will be discussed with respect to the above-mentioned important elements.

Vaccine candidate designed against carcinoembryonic antigen-related cell adhesion molecules using immunoinformatics tools

Carcinoembryonic antigen-related cell adhesion (CEACAM) molecules belong to a family of membrane glycoproteins that mediate intercellular interactions influencing cellular growth, immune cell activation, apoptosis, and tumor suppression. Several family members (CEACAM1, CEACAM5, and CEACAM6) are highly expressed in cancers, and they share a conserved N-terminal domain that serves as an attractive target for cancer immunotherapy. A multi-epitope vaccine candidate against this conserved domain has been developed using immunoinformatics tools. Specifically, several epitopes predicted to interact with MHC class I and II molecules were linked together with appropriate linkers. The tertiary structure of the vaccine is generated by homology and ab initio modeling. Molecular docking of epitopes to MHC structures have revealed that the lowest energy conformations are the epitopes bound to the antigen-binding groove of the MHC molecules. Subsequent molecular dynamics simulation has confirmed the stability of the binding conformations in solution. The predicted vaccine has relatively high antigenicity and low allergenicity, suggesting that it is an ideal candidate for further refinement and development.Communicated by Ramaswamy H. Sarma.

Exploratory open-label clinical study to determine the S-588410 cancer peptide vaccine-induced tumor-infiltrating lymphocytes and changes in the tumor microenvironment in esophageal cancer patients

Cancer vaccines induce cancer-specific T-cells capable of eradicating cancer cells. The impact of cancer peptide vaccines (CPV) on the tumor microenvironment (TME) remains unclear. S-588410 is a CPV comprising five human leukocyte antigen (HLA)-A*24:02-restricted peptides derived from five cancer testis antigens, DEPDC1, MPHOSPH1, URLC10, CDCA1 and KOC1, which are overexpressed in esophageal cancer. This exploratory study investigated the immunologic mechanism of action of subcutaneous S-588410 emulsified with MONTANIDE ISA51VG adjuvant (median: 5 doses) by analyzing the expression of immune-related molecules, cytotoxic T-lymphocyte (CTL) response and T-lymphocytes bearing peptide-specific T-cell receptor (TCR) sequencing in tumor tissue or blood samples from 15 participants with HLA-A*24:02-positive esophageal cancer. Densities of CD8+, CD8+ Granzyme B+, CD8+ programmed death-1-positive (PD-1+) and programmed death-ligand 1-positive (PD-L1+) cells were higher in post- versus pre-vaccination tumor tissue. CTL response was induced in all patients for at least one of five peptides. The same sequences of peptide-specific TCRs were identified in post-vaccination T-lymphocytes derived from both tumor tissue and blood, suggesting that functional peptide-specific CTLs infiltrate tumor tissue after vaccination. Twelve (80%) participants had treatment-related adverse events (AEs). Injection site reaction was the most frequently reported AE (grade 1, n = 1; grade 2, n = 11). In conclusion, S-588410 induces a tumor immune response in esophageal cancer. Induction of CD8+ PD-1+ tumor-infiltrating lymphocytes and PD-L1 expression in the TME by vaccination suggests S-588410 in combination with anti-PD-(L)1 antibodies may offer a clinically useful therapy.Trial registration UMIN-CTR registration identifier: UMIN000023324.

Cancer-Testis Antigen Peptide Vaccine for Cancer Immunotherapy: Progress and Prospects

Cancer vaccines, including peptide-based vaccines, have been considered a key tool of effective and protective cancer immunotherapy because of their capacity to provide long-term clinical benefit for tumors. Among a large number of explorations of peptide antigen-based vaccines, cancer-testis antigens (CTAs), which are activated in cancers but silenced in normal tissues (except testis tissue), are considered as ideal targets. Currently, personalized treatment for cancer has become a trend due to its superior clinical efficacy. Thus, we envisage rational selection of CTA peptides to design "personalized" CTA peptide vaccines. This review summarizes the advances in CTA peptide vaccine research and discusses the feasibility of establishing "personalized" CTA peptide vaccines.

Combinatorial Approach to Improve Cancer Immunotherapy: Rational Drug Design Strategy to Simultaneously Hit Multiple Targets to Kill Tumor Cells and to Activate the Immune System

Cancer immunotherapy, including immune checkpoint blockade and adoptive CAR T-cell therapy, has clearly established itself as an important modality to treat melanoma and other malignancies. Despite the tremendous clinical success of immunotherapy over other cancer treatments, this approach has shown substantial benefit to only some of the patients while the rest of the patients have not responded due to immune evasion. In recent years, a combination of cancer immunotherapy together with existing anticancer treatments has gained significant attention and has been extensively investigated in preclinical or clinical studies. In this review, we discuss the therapeutic potential of novel regimens combining immune checkpoint inhibitors with therapeutic interventions that (1) increase tumor immunogenicity such as chemotherapy, radiotherapy, and epigenetic therapy; (2) reverse tumor immunosuppression such as TAMs, MDSCs, and Tregs targeted therapy; and (3) reduce tumor burden and increase the immune effector response with rationally designed dual or triple inhibitory chemotypes.

Recent Advances in Polymeric Nanomedicines for Cancer Immunotherapy

Immunotherapy has emerged as a promising approach to treat cancer, since it facilitates eradication of cancer by enhancing innate and/or adaptive immunity without using cytotoxic drugs. Of the immunotherapeutic approaches, significant clinical potentials are shown in cancer vaccination, immune checkpoint therapy, and adoptive cell transfer. Nevertheless, conventional immunotherapies often involve immune-related adverse effects, such as liver dysfunction, hypophysitis, type I diabetes, and neuropathy. In an attempt to address these issues, polymeric nanomedicines are extensively investigated in recent years. In this review, recent advances in polymeric nanomedicines for cancer immunotherapy are highlighted and thoroughly discussed in terms of 1) antigen presentation, 2) activation of antigen-presenting cells and T cells, and 3) promotion of effector cells. Also, the future perspectives to develop ideal nanomedicines for cancer immunotherapy are provided.

Rational combination immunotherapeutic approaches for effective cancer treatment

Immunotherapy is an important mode of cancer treatment. Over the past decades, immunotherapy has improved the clinical outcome for cancer patients. However, in many cases, mutations in cancer cells, lack of selectivity, insufficiency of tumor-reactive T cells, and host immunosuppression limit the clinical benefit of immunotherapy. Combination approaches in immunotherapy may overcome these obstacles. Accumulating evidence demonstrates that combination immunotherapy is the future of cancer treatment. However, designing safe and rational combinations of immunotherapy with other treatment modalities is critical. This review will discuss the optimal immunotherapy-based combinations mainly with respect to the mechanisms of action of individual therapeutic agents that target multiple steps in evasion and progression of tumor.

Clinicopathological Significance and Antitumor Effect of MPHOSPH1 in Testicular Germ Cell Tumor

MPHOSPH1, which is one of the kinesin superfamily proteins, has been reported to play an essential role in the carcinogenesis and progression of several kinds of cancers. MPHOSPH1 has also been suggested to be involved in STAT3 phosphorylation in hepatocellular carcinoma. However, the biological behavior of MPHOSPH1 in testicular germ cell tumors (TGCTs) is unclear at present. The purposes of this study were to investigate the correlation between the expression of MPHOSPH1 and clinicopathological factors and to examine the efficacy of MPHOSPH1 target therapy in TGCTs. We investigated 75 formalin-fixed paraffin-embedded TGCT samples, containing a total of 86 germ cell tumor components, by immunohistochemistry and 12 frozen samples by Western blotting. Moreover, we carried out in vitro studies to clarify the antitumor effect of MPHOSPH1 knockdown in embryonal carcinoma cell lines, NEC8 and NEC14, using small interference RNA (siRNA). A significantly high expression of MPHOSPH1 was recognized in embryonal carcinoma and yolk sac tumor components compared to the seminoma component (p<0.001, respectively). Clinically, non-seminoma cases are known to have worse prognosis than pure-seminoma cases. Interestingly, high MPHOSPH1 expression was associated with distant metastasis (p=0.001), and thus with advanced-stage disease in this study. High expression of MPHOSPH1 interacted with high expression of phosphorylated STAT3 (p=0.01). The in vitro experiments demonstrated that MPHOSPH1 interruption by siRNA resulted in a significant reduction of cell migration, invasion, proliferation and colony formation in both embryonal carcinoma cell lines (p<0.001, respectively). In conclusion, MPHOSPH1 may be a potential treatment option for TGCTs, and its expression may be a novel biomarker of poor prognosis.

Inferior survival for patients with malignant peripheral nerve sheath tumors defined by aberrant TP53

Malignant peripheral nerve sheath tumor is a rare and aggressive disease with poor treatment response, mainly affecting adolescents and young adults. Few molecular biomarkers are used in the management of this cancer type, and although TP53 is one of few recurrently mutated genes in malignant peripheral nerve sheath tumor, the mutation prevalence and the corresponding clinical value of the TP53 network remains unsettled. We present a multi-level molecular study focused on aberrations in the TP53 network in relation to patient outcome in a series of malignant peripheral nerve sheath tumors from 100 patients and 38 neurofibromas, including TP53 sequencing, high-resolution copy number analyses of TP53 and MDM2, and gene expression profiling. Point mutations in TP53 were accompanied by loss of heterozygosity, resulting in complete loss of protein function in 8.2% of the malignant peripheral nerve sheath tumors. Another 5.5% had MDM2 amplification. TP53 mutation and MDM2 amplification were mutually exclusive and patients with either type of aberration in their tumor had a worse prognosis, compared to those without (hazard ratio for 5-year disease-specific survival 3.5, 95% confidence interval 1.78-6.98). Both aberrations had similar consequences on the gene expression level, as analyzed by a TP53-associated gene signature, a property also shared with the copy number aberrations and/or loss of heterozygosity at the TP53 locus, suggesting a common "TP53-mutated phenotype" in as many as 60% of the tumors. This was a poor prognostic phenotype (hazard ratio = 4.1, confidence interval:1.7-9.8), thus revealing a TP53-non-aberrant patient subgroup with a favorable outcome. The frequency of the "TP53-mutated phenotype" warrants explorative studies of stratified treatment strategies in malignant peripheral nerve sheath tumor.

Immunogenic cell death in anticancer chemotherapy and its impact on clinical studies

The traditional view holds that apoptosis is non-immunogenic and does not induce an inflammatory response. However, recent studies have suggested that certain chemotherapeutic drugs that induce tumor cell apoptosis can induce immunogenic cell death (ICD) in cancer cells. This process is characterized by not only up-regulation of a series of signaling molecules in cancer cells, including expose of calreticulin (CRT), secretion of adenosine triphosphate (ATP) and release of high mobility group box 1 (HMGB1). In this review, we summarize recent progress in identifying and classifying ICD inducers; concepts and molecular mechanisms of ICD; and the impact and potential applications of ICD in clinical studies. We also discuss the contributions of ICD inducers in combination with other anticancer drugs in clinical applications.

PD-1 Blockade Unleashes Effector Potential of Both High- and Low-Affinity Tumor-Infiltrating T Cells

Antitumor T cell responses involve CD8⁺ T cells with high affinity for mutated self-antigen and low affinity for nonmutated tumor-associated Ag. Because of the highly individual nature of nonsynonymous somatic mutations in tumors, however, immunotherapy relies often on an effective engagement of low-affinity T cells. In this study, we studied the role of T cell affinity during peripheral priming with single-peptide vaccines and during the effector phase in the tumor. To that end, we compared the antitumor responses after OVA_257-264 (N4) peptide vaccination of CD8⁺ T cells carrying TCRs with high (OT-1) and low (OT-3) avidity for the N4 peptide in B16.N4 tumor-bearing C57BL/6 mice. Additionally, we assessed the response of OT-1 cells to either high-affinity (B16.N4) or low-affinity (B16.T4) Ag-expressing tumors after high-affinity (N4) or low-affinity (T4) peptide vaccination. We noticed that although low-affinity tumor-specific T cells expand less than high-affinity T cells, they express lower levels of inhibitory receptors and produce more cytokines. Interestingly, tumor-infiltrating CD8⁺ T cells show similar in vivo re-expansion capacity to their counterparts in secondary lymphoid organs when transferred to tumor-free hosts, suggesting that T cells in tumors may be rekindled upon relief of tumor immunosuppression. Moreover, our results show that αPD-1 treatment enhances tumor control of high- and low-affinity ligand-expressing tumors, suggesting that combination of high-affinity peripheral priming by altered peptide ligands and checkpoint blockade may enable tumor control upon low-affinity Ag recognition in the tumor.

A phase I/Ib study of OTSGC-A24 combined peptide vaccine in advanced gastric cancer

Background

We conducted a phase I/Ib, open-label, single-arm trial to assess the safety, tolerability and optimal scheduling regimen of OTSGC-A24 cancer vaccine in patients with advanced gastric cancer.

Methods

Patients with advanced gastric cancer with HLA-A*24:02 haplotype were included in this study. OTSGC-A24 was administered at 1 mg in 3-weekly (3w), 2-weekly (2w), and weekly (1w) cohorts to evaluate the safety, immunological response and schedule. Based on the highest specific cytotoxic T lymphocyte (CTL) induction rate at 4 weeks, using the ELISPOT test, cohorts were expanded to define the optimal dosing schedule for OTSGC-A24.

Results

In this study, 24 advanced gastric cancer patients with HLA-A*24:02 haplotype were enrolled and treated in 3 cohorts (3w cohort: 3; 2w cohort: 11 and 1w cohort: 10 patients). The most common adverse events were decreased appetite (29%), diarrhea (21%), myalgia (25%). The most common treatment-related adverse event was injection site erythema (25%). No dose-limiting toxicities were observed in any cohort and OTSGC-A24 was well tolerated. Positive CTL responses after vaccination were observed in 15 patients (75%) at 4 weeks: 3w cohort (33%), 2w cohort (88%), 1w cohort (78%). At 12 weeks, 18 patients had responded (90%); 3w cohort (100%), 2w cohort (100%), 1w cohort (78%). The best radiological was stable disease (40%). Median progression free survival was 1.7 months (95% CI: 1.4 to 3.5) and median overall survival was 5.7 months (95% CI 3.8 to 8.6).

Conclusions

OTSGC-A24 combined peptide cancer vaccine was well tolerated. Significant responses in CTL were observed and the recommended phase 2 dose is 1 mg OTSGC-A24 sub-cutaneous, every 2 weeks. Although no radiological response was observed, a respectable overall survival was achieved, consistent with other immunotherapy agents being investigated in gastric cancer.

Trial registration

ClinicalTrials.gov Identifier: NCT01227772, Date registered: 21 Oct 2010.

A phase I clinical trial of RNF43 peptide-related immune cell therapy combined with low-dose cyclophosphamide in patients with advanced solid tumors

The objective of this study was to investigate the safety and the tolerability of combined cellular immunotherapy with low-dose cyclophosphamide (CPA) in patients with advanced solid tumors. This study targeted a novel tumor-associated antigen, ring finger protein 43 (RNF43). Eligible patients were resistant to standard therapy, HLA-A*24:02- or A*02:01-positive and exhibiting high RNF43 expression in their tumor cells. They were administered 300 mg/m2 CPA followed by autologous lymphocytes, preliminarily cultured with autologous RNF43 peptide-pulsed dendritic cells (DCs), RNF43 peptide-pulsed DCs and systemic low dose interleukin-2. The primary endpoint was safety whereas the secondary endpoint was immunological and clinical response to treatment. Ten patients, in total, were enrolled in this trial. Primarily, no adverse events greater than Grade 3 were observed. Six out of 10 patients showed stable disease (SD) on day 49, while 4 other patients showed progressive disease. In addition, one patient with SD exhibited a partial response after the second trial. The frequency of regulatory T cells (Tregs) in patients with SD significantly decreased after CPA administration. The ratio of interferon-γ-producing, tumor-reactive CD8+ T cells increased with time in patients with SD. We successfully showed that the combination of immune cell therapy and CPA was safe, might induce tumor-specific immune responses and clinical efficacy, and was accompanied by a decreased ratio of Tregs in patients with RNF43-positive advanced solid tumors.

Trial watch: Immunogenic cell death induction by anticancer chemotherapeutics

The expression "immunogenic cell death" (ICD) refers to a functionally unique form of cell death that facilitates (instead of suppressing) a T cell-dependent immune response specific for dead cell-derived antigens. ICD critically relies on the activation of adaptive responses in dying cells, culminating with the exposure or secretion of immunostimulatory molecules commonly referred to as "damage-associated molecular patterns". Only a few agents can elicit bona fide ICD, including some clinically established chemotherapeutics such as doxorubicin, epirubicin, idarubicin, mitoxantrone, bleomycin, bortezomib, cyclophosphamide and oxaliplatin. In this Trial Watch, we discuss recent progress on the development of ICD-inducing chemotherapeutic regimens, focusing on studies that evaluate clinical efficacy in conjunction with immunological biomarkers.

Multi-target chimaeric VLP as a therapeutic vaccine in a model of colorectal cancer

Background

Colorectal cancer is responsible for almost 700,000 deaths annually worldwide. Therapeutic vaccination is a promising alternative to conventional treatment for colorectal cancer, using vaccines to induce targeted immune responses against tumour-associated antigens. In this study, we have developed chimaeric virus-like particles (VLP), a form of non-infectious non-replicative subunit vaccine consisting of rabbit haemorrhagic disease virus (RHDV) VP60 capsid proteins containing recombinantly inserted epitopes from murine topoisomerase IIα and survivin. These vaccines were developed in mono- (T.VP60, S.VP60) and multi-target (TS.VP60) forms, aiming to elucidate the potential benefits from multi-target vaccination.

Methods

Chimaeric RHDV VLP were developed by recombinantly inserting immune epitopes at the N-terminus of VP60. Vaccines were tested against a murine model of colorectal cancer by establishing MC38-OVA tumours subcutaneously. Unmethylated CpG DNA oligonucleotides (CpGs) were used as a vaccine adjuvant. Statistical tests employed included the Mantel-Cox log-rank test, ANOVA and unpaired t-tests depending on the data analysed, with a post hoc Bonferroni adjustment for multiple measures.

Results

Chimaeric RHDV VLP were found to form a composite particle in the presence of CpGs. Overall survival was significantly improved amongst mice bearing MC38-OVA tumours following vaccination with T.VP60 (60%, 9/15), S.VP60 (60%, 9/15) or TS.VP60 (73%, 11/15). TS.VP60 significantly prolonged the vaccine-induced remission period in comparison to each mono-therapy.

Conclusions

Chimaeric VLP containing multiple epitopes were found to confer an advantage for therapeutic vaccination in a model of colorectal cancer based on the prolongation of remission prior to tumour escape.

Electronic supplementary material

The online version of this article (doi:10.1186/s40425-017-0270-1) contains supplementary material, which is available to authorized users.

Identification of a HLA-A*0201-restricted immunogenic epitope from the universal tumor antigen DEPDC1

The identification of universal tumor-specific antigens shared between multiple patients and/or multiple tumors is of great importance to overcome the practical limitations of personalized cancer immunotherapy. Recent studies support the involvement of DEPDC1 in many aspects of cancer traits, such as cell proliferation, resistance to induction of apoptosis and cell invasion, suggesting that it may play key roles in the oncogenic process. In this study, we report that DEPDC1 expression is upregulated in most types of human tumors, and closely linked to a poorer prognosis; therefore, it might be regarded as a novel universal oncoantigen potentially suitable for targeting many different cancers. In this regard, we report the identification of a HLA-A*0201 allele-restricted immunogenic DEPDC1-derived epitope, which is able to induce cytotoxic T lymphocytes (CTL) exerting a strong and specific functional response in vitro toward not only peptide-loaded cells but also triple negative breast cancer (TNBC) cells endogenously expressing the DEPDC1 protein. Such CTL are also therapeutically active against human TNBC xenografts in vivo upon adoptive transfer in immunodeficient mice. Overall, these data provide evidence that this DEPDC1-derived antigenic epitope can be exploited as a new tool for developing immunotherapeutic strategies for HLA-A*0201 patients with TNBC, and potentially many other cancers.

Current status and future prospects of peptide-based cancer vaccines

Cancer immunotherapy has attracted attention worldwide owing to the recent development of immune checkpoint inhibitors. However, these therapies have shown limited efficacy, and further advancements are needed before these modalities can progress to widespread use. Immune checkpoint inhibitors are a type of nonspecific cancer immunotherapy, and antitumor effects are only observed when cancer-specific T cells are found within the nonspecifically activated T-cell group. In order to facilitate the development of potent immunotherapies, selective enhancement of cancer-specific T cells is essential. In this report, we discuss current and future perspectives, including the latest clinical trials of cancer-specific immunotherapies, particularly cancer peptide vaccines.

The importance of correctly timing cancer immunotherapy

INTRODUCTION

The treatment options for cancer-surgery, radiotherapy and chemotherapy-are now supplemented with immunotherapy. Previously underappreciated but now gaining strong interest are the immune modulatory properties of the three conventional modalities. Moreover, there is a better understanding of the needs and potential of the different immune therapeutic platforms. Key to improved treatment will be the combinations of modalities that complete each other's shortcomings. Area covered: Tumor-specific T-cells are required for optimal immunotherapy. In this review, the authors focus on the correct timing of different types of chemotherapeutic agents or immune modulators and immunotherapeutic drugs, not only for the activation and expansion of tumor-specific T-cells but also to support and enhance their anti-tumor efficacy. Expert opinion: At an early phase of disease, clinical success can be obtained using single treatment modalities but at later disease stages, combinations of several modalities are required. The gain in success is determined by a thorough understanding of the direct and indirect immune effects of the modalities used. Profound knowledge of these effects requires optimal tuning of immunomonitoring. This will guide the appropriate combination of treatments and allow for correct sequencing the order and interval of the different therapeutic modalities.

Immunogenic FEAT protein circulates in the bloodstream of cancer patients

BACKGROUND

FEAT is an intracellular protein that potently drives tumorigenesis in vivo. It is only weakly expressed in normal human tissues, including the testis. In contrast, FEAT is aberrantly upregulated in most human cancers. The present study was designed to investigate whether FEAT is applicable to tumor immunotherapy and whether FEAT is discernible in the bloodstream as a molecular biomarker of human cancers.

METHODS

Two mouse FEAT peptides with predicted affinities for major histocompatibility complex H-2Kb and H-2Db were injected subcutaneously into C57BL/6 mice before subcutaneous transplantation of isogenic B16-F10 melanoma cells. Intracellular localization of FEAT was determined by immunogold electron microscopy. Immunoprecipitation was performed to determine whether FEAT was present in blood from cancer patients. A sandwich enzyme-linked immunosorbent assay was used to measure FEAT concentrations in plasma from 30 cancer patients and eight healthy volunteers.

RESULTS

The vaccination experiments demonstrated that FEAT was immunogenic, and that immune responses against FEAT were induced without deleterious side effects in mice. Electron microscopy revealed localization of FEAT in the cytoplasm, mitochondria, and nucleus. Immunoprecipitation identified FEAT in the blood plasma from cancer patients, while FEAT was not detected in plasma exosomes. Plasma FEAT levels were significantly higher in the presence of cancers.

CONCLUSIONS

These findings suggest that FEAT is a candidate for applications in early diagnosis and prevention of some cancers.