Cancer vaccines inducing antibody production: more pros than cons

Overview of Current Immunotherapies Targeting Mutated KRAS Cancers

The occurrence of somatic substitution mutations of the KRAS proto-oncogene is highly prevalent in certain cancer types, which often leads to constant activation of proliferative pathways and subsequent neoplastic transformation. It is often seen as a gateway mutation in carcinogenesis and has been commonly deemed as a predictive biomarker for poor prognosis and relapse when conventional chemotherapeutics are employed. Additionally, its mutational status also renders EGFR targeted therapies ineffective owing to its downstream location. Efforts to discover new approaches targeting this menacing culprit have been ongoing for years without much success, and with incidences of KRAS positive cancer patients being on the rise, researchers are now turning towards immunotherapies as the way forward. In this scoping review, recent immunotherapeutic developments and advances in both preclinical and clinical studies targeting K-ras directly or indirectly via its downstream signal transduction machinery will be discussed. Additionally, some of the challenges and limitations of various K-ras targeting immunotherapeutic approaches such as vaccines, adoptive T cell therapies, and checkpoint inhibitors against KRAS positive cancers will be deliberated.

An HER2-Displaying Virus-Like Particle Vaccine Protects from Challenge with Mammary Carcinoma Cells in a Mouse Model

Human epidermal growth factor receptor-2 (HER2) is upregulated in 20% to 30% of breast cancers and is a marker of a poor outcome. Due to the development of resistance to passive immunotherapy with Trastuzumab, active anti-HER2 vaccination strategies that could potentially trigger durable tumor-specific immune responses have become an attractive research area. Recently, we have shown that budded virus-like particles (VLPs) produced in Sf9 insect cells are an ideal platform for the expression of complex membrane proteins. To assess the efficacy of antigen-displaying VLPs as active cancer vaccines, BALB/c mice were immunized with insect cell glycosylated and mammalian-like glycosylated HER2-displaying VLPs in combination with two different adjuvants and were challenged with HER2-positive tumors. Higher HER2-specific antibody titers and effector functions were induced in mice vaccinated with insect cell glycosylated HER2 VLPs compared to mammalian-like glycosylated counterparts. Moreover, insect cell glycosylated HER2 VLPs elicited a protective effect in mice grafted with HER2-positive mammary carcinoma cells. Interestingly, no protection was observed in mice that were adjuvanted with Poly (I:C). Here, we show that antigen-displaying VLPs produced in Sf9 insect cells were able to induce robust and durable immune responses in vivo and have the potential to be utilized as active cancer vaccines.

Are mimotope vaccines a good alternative to monoclonal antibodies?

Utilizing immunotherapy as a potential therapeutic approach to boost the body's immune system for the fight against various diseases such as cancers, autoimmune diseases and also infections, is increasing day by day. Monoclonal antibodies, as effective therapeutic agents are used in cancer targeted therapies. However, these biologics have some disadvantages such as high costs and side effects. Therefore, emerging alternative immunotherapy strategies with high efficiency and low costs seems necessary. Mimotope vaccines, as epitope-mimicking structures, have shown to be effective therapeutic options, but are they really a good alternative to monoclonal antibodies, or are they just effective adjuvants?

Virus-like particle display of HER2 induces potent anti-cancer responses

Overexpression of human epidermal growth factor receptor-2 (HER2) occurs in 20–30% of invasive breast cancers. Monoclonal antibody therapy is effective in treating HER2-driven mammary carcinomas, but its utility is limited by high costs, side effects and development of resistance. Active vaccination may represent a safer, more effective and cheaper alternative, although the induction of strong and durable autoantibody responses is hampered by immune-tolerogenic mechanisms. Using a novel virus-like particle (VLP) based vaccine platform we show that directional, high-density display of human HER2 on the surface of VLPs, allows induction of therapeutically potent anti-HER2 autoantibody responses. Prophylactic vaccination reduced spontaneous development of mammary carcinomas by 50%-100% in human HER2 transgenic mice and inhibited the growth of HER2-positive tumors implanted in wild-type mice. The HER2-VLP vaccine shows promise as a new cost-effective modality for prevention and treatment of HER2-positive cancer. The VLP platform may represent an effective tool for development of vaccines against other non-communicable diseases.

Anti-cancer activity of dose-fractioned mPE +/- bevacizumab regimen is paralleled by immune-modulation in advanced squamous NSLC patients

Background

Results from the BEVA2007 trial, suggest that the metronomic chemotherapy regimen with dose-fractioned cisplatin and oral etoposide (mPE) +/- bevacizumab, a monoclonal antibody to the vascular endothelial growth factor (VEGF), shows anti-angiogenic and immunological effects and is a safe and active treatment for metastatic non-small cell lung cancer (mNSCLC) patients. We carried out a retrospective analysis aimed to evaluate the antitumor effects of this treatment in a subset of patients with squamous histology.

Methods

Retrospective analysis was carried out in a subset of 31 patients with squamous histology enrolled in the study between September 2007 and September 2015. All of the patients received chemotherapy with cisplatin (30 mg/sqm, days 1-3q21) and oral etoposide (50 mg, days 1-15q21) (mPE) and 14 of them also received bevacizumab 5 mg/kg on the day 3q21 (mPEBev regimen).

Results

This treatment showed a disease control rate of 71% with a mean progression free survival (PFS) and overall survival (OS) of 13.6 and 17 months respectively. After 4 treatment courses, 6 patients showing a remarkable tumor shrinkage, underwent to radical surgery, attaining a significant advantage in term of survival (P=0.048). Kaplan-Meier and log-rank test identified the longest survival in patients presenting low baseline levels in neutrophil-to-lymphocyte ratio (NLR) (P=0.05), interleukin (IL) 17A (P=0.036), regulatory-T-cells (T_regs) (P=0.020), and activated CD83+ dendritic cells (DCs) (P=0.03).

Conclusions

These results suggest that the mPE +/- bevacizumab regimen is feasible and should be tested in comparative trials in advanced squamous-NSCLC (sqNSCLC). Moreover, its immune-biological effects strongly suggest the investigation in sequential combinations with immune check-point inhibitors.

Why man's best friend, the dog, could also benefit from an anti-HER-2 vaccine

Human epidermal growth factor receptor-2 (HER-2) is a well-established target for anticancer anticancerprecision medicine in humans. A HER-2 homologue with 92% amino acid identity has been described in canine mammary tumors, which whichis termed here as ‘dog epidermal growth factor receptor-2 (DER-2)’, with similar biological implications as those in human breast cancer. Both antigens can principally be immunologically targeted by anti-HER-2 antibodies, such as trastuzumab; however, the in vivo application applicationof humanized antibodies to other species would lead to specific hypersensitivity reactions. Therefore, HER-2 mimotope vaccines that actively induce autologous trastuzumab-like immunoglobulins represent a novel and economic treatment option to overcome species-specific limitations. Thus, the present review proposes the implementation of clinical trials with HER-2 vaccines in canine cancer model modelpatients with spontaneous DER-2 positive mammary gland carcinomas in order to assess their safety and efficacy. This approach would not only pave the way into the veterinary oncology market, but would also similarly generate robust data for human trials and facilitate the testing of novel combinatorial treatments.

Proof of concept study with an HER-2 mimotope anticancer vaccine deduced from a novel AAV-mimotope library platform

Background: Anticancer vaccines could represent a valuable complementary strategy to established therapies, especially in settings of early stage and minimal residual disease. HER-2 is an important target for immunotherapy and addressed by the monoclonal antibody trastuzumab. We have previously generated HER-2 mimotope peptides from phage display libraries. The synthesized peptides were coupled to carriers and applied for epitope-specific induction of trastuzumab-like IgG. For simplification and to avoid methodological limitations of synthesis and coupling chemistry, we herewith present a novel and optimized approach by using adeno-associated viruses (AAV) as effective and high-density mimotope-display system, which can be directly used for vaccination. Methods: An AAV capsid display library was constructed by genetically incorporating random peptides in a plasmid encoding the wild-type AAV2 capsid protein. AAV clones, expressing peptides specifically reactive to trastuzumab, were employed to immunize BALB/c mice. Antibody titers against human HER-2 were determined, and the isotype composition and functional properties of these were tested. Finally, prophylactically immunized mice were challenged with human HER-2 transfected mouse D2F2/E2 cells. Results: HER-2 mimotope AAV-vaccines induced antibodies specific to human HER-2. Two clones were selected for immunization of mice, which were subsequently grafted D2F2/E2 cells. Both mimotope AAV clones delayed the growth of tumors significantly, as compared to controls. Conclusion: In this study, a novel mimotope AAV-based platform was created allowing the isolation of mimotopes, which can be directly used as anticancer vaccines. The example of trastuzumab AAV-mimotopes demonstrates that this vaccine strategy could help to establish active immunotherapy for breast-cancer patients.

Phase I trial of thymidylate synthase poly-epitope peptide (TSPP) vaccine in advanced cancer patients

Thymidylate synthase (TS) poly-epitope peptide (TSPP) is a 27-mer peptide vaccine containing the amino acidic sequences of three epitopes with HLA-A2.1-binding motifs of TS, an enzyme overexpressed in cancer cells, which plays a crucial role in DNA repair and replication. Based on the results of preclinical studies, we designed a phase Ib trial (TSPP/VAC1) to investigate, in a dose escalation setting, the safety and the biological activity of TSPP vaccination alone (arm A) or in combination with GM-CSF and IL-2 (arm B) in cancer patients. Twenty-one pretreated metastatic cancer patients, with a good performance status (ECOG ≤ 1) and no severe organ failure or immunological disease, were enrolled in the study (12 in arm A, nine in arm B) between April 2011 and January 2012, with a median follow-up of 28 months. TSPP resulted safe, and its maximal tolerated dose was not achieved. No grade 4 toxicity was observed. The most common adverse events were grade 2 dermatological reactions to the vaccine injection, cough, rhinitis, fever, poly-arthralgia, gastro-enteric symptoms and, to a lesser extent, moderate hypertension and hypothyroidism. We detected a significant rise in auto-antibodies and TS-epitope-specific CTL precursors. Furthermore, TSPP showed antitumor activity in this group of pretreated patients; indeed, we recorded one partial response and seven disease stabilizations (SD) in arm A, and three SD in arm B. Taken together, our findings provide the framework for the evaluation of the TSPP anti-tumor activity in further disease-oriented clinical trials.

Vaccination with Melanoma Helper Peptides Induces Antibody Responses Associated with Improved Overall Survival

PURPOSE

A melanoma vaccine incorporating six peptides designed to induce helper T-cell responses to melanoma antigens has induced Th1-dominant CD4(+) T-cell responses in most patients, and induced durable clinical responses or stable disease in 24% of evaluable patients. The present study tested whether this vaccine also induced antibody (Ab) responses to each peptide, and whether Ab responses were associated with T-cell responses and with clinical outcome.

EXPERIMENTAL DESIGN

Serum samples were studied from 35 patients with stage III-IV melanomas vaccinated with 6 melanoma helper peptides (6MHP). IgG Ab responses were measured by ELISA. Associations with immune response and overall survival were assessed by log-rank test and χ(2) analysis of Kaplan-Meier data.

RESULTS

Ab responses to 6MHP were detected by week 7 in 77% of patients, and increased to peak 6 weeks after the last vaccine and persisted to 6 months. Ab responses were induced most frequently to longer peptides. Of those with T-cell responses, 82% had early Ab responses. Survival was improved for patients with early Ab response (P = 0.0011) or with early T-cell response (P < 0.006), and was best for those with both Ab and T-cell responses (P = 0.0002).

CONCLUSIONS

Vaccination with helper peptides induced both Ab responses and T-cell responses, associated with favorable clinical outcome. Such immune responses may predict favorable clinical outcome to guide combination immunotherapy. Further studies are warranted to understand mechanisms of interaction of these Abs, T-cell responses, and tumor control.

CD8(+) T cell response to adenovirus vaccination and subsequent suppression of tumor growth: modeling, simulation and analysis

BACKGROUND

Using immune checkpoint modulators in the clinic to increase the number and activity of cytotoxic T lymphocytes that recognize tumor antigens can prolong survival for metastatic melanoma. Yet, only a fraction of the patient population receives clinical benefit. In short, these clinical trials demonstrate proof-of-principle but optimizing the specific therapeutic strategies remains a challenge. In many fields, CAD (computer-aided design) is a tool used to optimize integrated system behavior using a mechanistic model that is based upon knowledge of constitutive elements. The objective of this study was to develop a predictive simulation platform for optimizing anti-tumor immunity using different treatment strategies.

METHODS

To better understand the therapeutic role that cytotoxic CD8(+) T cells can play in controlling tumor growth, we developed a multi-scale mechanistic model of the biology using impulsive differential equations and calibrated it to a self-consistent data set.

RESULTS

The multi-scale model captures the activation and differentiation of naïve CD8(+) T cells into effector cytotoxic T cells in the lymph node following adenovirus-mediated vaccination against a tumor antigen, the trafficking of the resulting cytotoxic T cells into blood and tumor microenvironment, the production of cytokines within the tumor microenvironment, and the interactions between tumor cells, T cells and cytokines that control tumor growth. The calibrated model captures the modest suppression of tumor cell growth observed in the B16F10 model, a transplantable mouse model for metastatic melanoma, and was used to explore the impact of multiple vaccinations on controlling tumor growth.

CONCLUSIONS

Using the calibrated mechanistic model, we found that the cytotoxic CD8(+) T cell response was prolonged by multiple adenovirus vaccinations. However, the strength of the immune response cannot be improved enough by multiple adenovirus vaccinations to reduce tumor burden if the cytotoxic activity or local proliferation of cytotoxic T cells in response to tumor antigens is not greatly enhanced. Overall, this study illustrates how mechanistic models can be used for in silico screening of the optimal therapeutic dosage and timing in cancer treatment.

Diepitope multiple antigen peptide of hTERT trigger stronger anti-tumor immune responses in vitro

Rapid advances in immune system knowledge have led to the exploration of immunologic approaches for eliminating tumor cells. Human telomerase reverse transcriptase (hTERT) is considered to be an ideal universal target for novel immunotherapies against cancers. Thus far, studies of effective antitumor immunotherapies have focused on the quantity and quality of the effector function of the CD8 compartment. However, increasing evidence has demonstrated that CD4+ T cells play important roles in generating and maintaining antitumor immune responses in animal models. The aim of this work was to verify whether diepitope multiple antigen peptides (MAPs) that were composed of the cytotoxic T lymphocyte (CTL) epitope of hTERT and the T-helper epitope of hTERT could improve upon the immunogenicity of a monoepitope MAP of hTERT. Dendritic cells (DCs) pulsed with diepitope MAPs composed of the CTL epitope hTERT-540 and the T-helper epitope hTERT-766 were used to evaluate immune responses against various tumor cells. A standard in vitro 4-h ⁵¹Cr-release assay was employed in this study. The results demonstrated that CTLs activated by the diepitope MAP that consisted of hTERT-540 and hTERT-766 could cause 8.56% more lysis than CTLs activated by the monoepitope MAP containing hTERT-540. Moreover, the activated CTLs could kill neither hTERT-negative tumor cells, such as U2OS cells, nor HLA-A2 negative cells, such as HepG2 cells. Our results indicate that diepitope MAPs that are generated from hTERT can be exploited for cancer immunotherapy.

Meta-analysis of clinical data using human meiotic genes identifies a novel cohort of highly restricted cancer-specific marker genes

Identifying cancer-specific biomarkers represents an ongoing challenge to the development of novel cancer diagnostic, prognostic and therapeutic strategies. Cancer/testis (CT) genes are an important gene family with expression tightly restricted to the testis in normal individuals but which can also be activated in cancers. Here we develop a pipeline to identify new CT genes. We analysed and validated expression profiles of human meiotic genes in normal and cancerous tissue followed by meta-analyses of clinical data sets from a range of tumour types resulting in the identification of a large cohort of highly specific cancer biomarker genes, including the recombination hot spot activator PRDM9 and the meiotic cohesin genes SMC1beta and RAD21L. These genes not only provide excellent cancer biomarkers for diagnostics and prognostics, but may serve as oncogenes and have excellent drug targeting potential.

For breast cancer prognosis, immunoglobulin kappa chain surfaces to the top

The stromal immunoglobulin kappa chain (IGKC) has been validated as an immunologic biomarker of prognosis and response to therapy in human breast cancer and other cancers. This validation emphasizes the key role of humoral immunity in control of cancer progression and has major implications for determining prognosis of patients with cancer.