Mesothelin-specific cell-based vaccine generates antigen-specific immunity and potent antitumor effects by combining with IL-12 immunomodulator

Efficacy evaluation of multi-immunotherapy in ovarian cancer: From bench to bed

Ovarian cancer, one of the most common gynecological malignancies, is characterized by high mortality and poor prognosis. Cytoreductive surgery and chemotherapy remain the mainstay of ovarian cancer treatment, and most women experience recurrence after standard care therapies. There is compelling evidence that ovarian cancer is an immunogenic tumor. For example, the accumulation of tumor-infiltrating lymphocytes is associated with increased survival, while increases in immunosuppressive regulatory T cells are correlated with poor clinical outcomes. Therefore, immunotherapies targeting components of the tumor microenvironment have been gradually integrated into the existing treatment options, including immune checkpoint blockade, adoptive cell therapy, and cancer vaccines. Immunotherapies have changed guidelines for maintenance treatment and established a new paradigm in ovarian cancer treatment. Despite single immunotherapies targeting DNA repair mechanisms, immune checkpoints, and angiogenesis bringing inspiring efficacy, only a subset of patients can benefit much from it. Thus, the multi-immunotherapy investigation remains an active area for ovarian cancer treatment. The current review provides an overview of various clinically oriented forms of multi-immunotherapy and explores potentially effective combinational therapies for ovarian cancer.

Synthetic multiepitope neoantigen DNA vaccine for personalized cancer immunotherapy

Neoantigen-based personalized vaccination has emerged as a viable method for tumor immunotherapy. Here we set up a DNA-based neoantigen vaccine platform with comprehensive identification of individual somatic mutations using whole-exome sequencing (WES) and RNA-seq, bioinformatic prediction of neo-epitopes, dendritic cell (DC)-based efficacy prevalidation of vaccine candidates, optimization of the DNA vaccine and its nanocarrier and adjuvant, and preparation of a liposome-encapsulated multiepitope DNA vaccine. The DNA vaccine was efficiently uptaken by DCs and induced effective immune response against mouse melanoma cells, leading to significant inhibition of melanoma tumor growth and reduction of lung metastasis in a mouse model. Numerous intratumoral infiltrated CD8+ T-cells with specific in vitro killing ability towards melanoma cells were identified. Our study offers evidence that a multiepitope neoantigen DNA vaccine in a nanocarrier can be exploited for personalized tumor immunotherapy and as a reliable prevalidation approach for rapid enrichment of effective neoantigens.

Generation of a Novel Mesothelin-Targeted Oncolytic Herpes Virus and Implemented Strategies for Manufacturing

Background: HER2-based retargeted viruses are in advanced phases of preclinical development of breast cancer models. Mesothelin (MSLN) is a cell-surface tumor antigen expressed in different subtypes of breast and non-breast cancer. Its recent identification as a marker of some triple-negative breast tumors renders it an attractive target, presently investigated in clinical trials employing antibody drug conjugates and CAR-T cells. The availability of MSLN-retargeted oncolytic viruses may complement the current immunotherapeutic panel of biological drugs against HER2-negative breast and non-breast tumors. Methods: A fully virulent, tumor-targeted oncolytic Herpes simplex virus-1 (MSLN-THV) with a selectivity for mesothelin-expressing cancer cells was generated. Recombineering technology was used to replace an essential moiety of the viral glycoprotein D with antibody fragments derived from clinically validated MSLN monoclonal antibodies, and to allow IL12 cargo expression in infected cells. Panels of breast and female reproductive system cell lines were used to verify the oncolytic potential of the viral constructs. A platform for production of the retargeted viruses was developed in HEK 293 cells, providing stable expression of a suitable chimeric receptor. Results: We demonstrated the selectivity of viral infection and cytotoxicity by MSLN-retargeted viruses in a panel of mesothelin-positive cancer cells, originating from breast and female reproductive system tumors. We also developed a second-generation oncolytic MSLN-THV, encoding IL12, to enhance the immunotherapeutic potential of the viral backbone. A non-tumor cell line expressing a chimeric MSLN/Nectin-1 receptor, de-sensitized from antiviral responses by genetic inactivation of the Stimulator of Interferon Genes (STING)-dependent pathway was engineered, to optimize viral yields. Conclusions: Our proof-of-concept study proposes MSLN-retargeted herpesviruses as potential cancer immunotherapeutics for assessments in preclinical models of MSLN-positive tumors, complementing the available panel of oncolytic viruses to HER2-negative breast tumors.

Mesothelin-targeted CAR-T cells for adoptive cell therapy of solid tumors

Significant progresses have been made in adoptive cell therapy with CAR-T cells for cancers, especially for hematological malignancies. However, the treatment of solid tumors still poses a tremendous challenge and remains an unmet medical need. Several factors are held responsible for the inadequate responses: tumor heterogeneity, inefficient homing of T cells to tumor tissues, immunosuppressive microenvironment and the shortage of specific antigens shortage. Mesothelin is a cell-surface glycoprotein highly expressed in many types of solid tumors. As such, it has attracted much attention as a molecular target in cancer immunotherapy. Here, we delineate the barriers imposed by solid tumors on CARs, outline the rationale of mesothelin as a target for immunotherapy, summarize the preclinical and clinical results of mesothelin-targeted therapies, and extrapolate the expected results of CAR-T cells directed against mesothelin for solid tumors.

Mesothelin-targeted CAR-T cell therapy for solid tumors

Introduction: Mesothelin (MSLN) is a tumor differentiation antigen normally restricted to the body's mesothelial surfaces, but significantly overexpressed in a broad range of solid tumors. For this reason, MSLN has emerged as an important target for the development of novel immunotherapies. This review focuses on anti-MSLN chimeric antigen receptor (CAR) T cell immunotherapy approaches.Areas covered: A brief overview of MSLN as a therapeutic target and existing anti-MSLN antibody-based drugs and vaccines is provided. A detailed account of anti-MSLN CAR-T cell approaches utilized in preclinical models is presented. Finally, a comprehensive summary of currently ongoing and completed anti-MSLN CAR-T cell clinical trials is discussed.Expert opinion: Initial trials using anti-MSLN CAR-T cells have been safe, but efficacy has been limited. Employing regional routes of delivery, introducing novel modifications leading to enhanced tumor infiltration and persistence, and improved safety profiles and combining anti-MSLN CAR-T cells with standard therapies, could render them more efficacious in the treatment of solid malignancies.

Towards Clinical Implementation of Adeno-Associated Virus (AAV) Vectors for Cancer Gene Therapy: Current Status and Future Perspectives

Adeno-associated virus (AAV) vectors have gained tremendous attention as in vivo delivery systems in gene therapy for inherited monogenetic diseases. First market approvals, excellent safety data, availability of large-scale production protocols, and the possibility to tailor the vector towards optimized and cell-type specific gene transfer offers to move from (ultra) rare to common diseases. Cancer, a major health burden for which novel therapeutic options are urgently needed, represents such a target. We here provide an up-to-date overview of the strategies which are currently developed for the use of AAV vectors in cancer gene therapy and discuss the perspectives for the future translation of these pre-clinical approaches into the clinic.

Preclinical and Clinical Immunotherapeutic Strategies in Epithelial Ovarian Cancer

In the past 20 years, the immune system has increasingly been recognized as a major player in tumor cell control, leading to considerable advances in cancer treatment. While promising with regards to melanoma, renal cancer and non-small cell lung cancer, immunotherapy provides, for the time being, limited success in other cancers, including ovarian cancer, potentially due to insufficient immunogenicity or to a particularly immunosuppressive microenvironment. In this review, we provide a global description of the immune context of ovarian cancer, in particular epithelial ovarian cancer (EOC). We describe the adaptive and innate components involved in the EOC immune response, including infiltrating tumor-specific T lymphocytes, B lymphocytes, and natural killer and myeloid cells. In addition, we highlight the rationale behind the use of EOC preclinical mouse models to assess resistance to immunotherapy, and we summarize the main preclinical studies that yielded anti-EOC immunotherapeutic strategies. Finally, we focus on major published or ongoing immunotherapy clinical trials concerning EOC.

From Malignant Progression to Therapeutic Targeting: Current Insights of Mesothelin in Pancreatic Ductal Adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC), accounting for 90% of all pancreatic tumors, is a highly devastating disease with poor prognosis and rising incidence. The lack of available specific diagnostics tests and the limited treatment opportunities contribute to this pejorative issue. Over the last 10 years, a growing interest pointing towards mesothelin (MSLN) as a promising PDAC-associated antigen has emerged. The limited expression of MSLN in normal tissues (peritoneum, pleura and pericardium) and its overexpression in 80 to 90% of PDAC make it an attractive candidate for therapeutic management of PDAC patients. Moreover, its role in malignant progression related to its involvement in tumor cell proliferation and resistance to chemotherapy has highlighted the relevance of its targeting. Hence, several clinical trials are investigating anti-MSLN efficacy in PDAC. In this review, we provide a general overview of the different roles sustained by MSLN during PDAC progression. Finally, we also summarize the different MSLN-targeted therapies that are currently tested in the clinic.

Mesothelin as a biomarker for targeted therapy

CAR-T cell therapy targeting CD19 has achieved remarkable success in the treatment of B cell malignancies, while various solid malignancies are still refractory for lack of suitable target. In recent years, a large number of studies have sought to find suitable targets with low “on target, off tumor” concern for the treatment of solid tumors. Mesothelin (MSLN), a tumor-associated antigen broadly overexpressed on various malignant tumor cells, while its expression is generally limited to normal mesothelial cells, is an attractive candidate for targeted therapy. Strategies targeting MSLN, including antibody-based drugs, vaccines and CAR-T therapies, have been assessed in a large number of preclinical investigations and clinical trials. In particular, the development of CAR-T therapy has shown great promise as a treatment for various types of cancers. The safety, efficacy, doses, and pharmacokinetics of relevant strategies have been evaluated in many clinical trials. This review is intended to provide a brief overview of the characteristics of mesothelin and the development of strategies targeting MSLN for solid tumors. Further, we discussed the challenges and proposed potential strategies to improve the efficacy of MSLN targeted immunotherapy.

Immune checkpoint Ab enhances the antigen-specific anti-tumor effects by modulating both dendritic cells and regulatory T lymphocytes

We determined the anti-tumor effects and possible mechanisms of an antigen-specific DNA vaccine combined with PD-1 or CTLA-4 blockade. Using the HPV16 E6/E7⁺ syngeneic mouse tumor model, we investigated whether anti-CTLA-4 antibody (Ab) or anti-PD-1 Ab increases the antigen-specific anti-tumor effects and immune response induced by CTGF/E7 chimeric DNA vaccine and the possible mechanisms. Anti-PD-1 Ab or anti-CTLA-4 Ab combined with E7-specific DNA vaccine generated more potent antigen-specific immunity, including anti-E7 Abs and the number and cytotoxic activity of E7-specific cytotoxic CD8⁺ T lymphocytes, and anti-tumor effects than E7-specific DNA vaccine alone. In addition, the number of systemic and intratumoral Tregs was lower with the anti-PD-1 or anti-CTLA-4 Ab and E7-specific DNA vaccine. Furthermore, anti-PD-1 and anti-CTLA-4 Abs could enhance the maturation and abilities of intratumoral DCs to activate E7-specific cytotoxic CD8⁺ T cells. Immune checkpoint blockade overcomes the immunosuppressive status of the tumor-microenvironment to enhance the antigen-specific immunity and anti-tumor effects generated by an antigen-specific DNA vaccine. Antigen-specific immunotherapy combined with immune checkpoint blockade can be a novel strategy in clinical cancer therapy.

Immuno-modulators enhance antigen-specific immunity and anti-tumor effects of mesothelin-specific chimeric DNA vaccine through promoting DC maturation

As a tumor antigen, mesothelin (MSLN) can be identified in various malignancies. MSLN is potential for antigen-specific cancer vaccines. We generated a novel chimeric DNA vaccine using antigen-specific connective tissue growth factor lined with MSLN (CTGF/MSLN). The anti-tumor effects of the CTGF/MSLN DNA vaccine combined with anti-CD40 Ab and toll-like receptor 3 ligand-poly(I:C) were validated in an MSLN-expressing model. CTGF/MSLN DNA with anti-CD40Ab and poly(I:C) vaccinated mice demonstrated potent anti-tumor effects with longer survival and less tumor volumes. An increase in MSLN-specific CD8⁺ T cells and anti-MSLN Ab titers was also noted in CTGF/MSLN DNA with anti-CD40Ab and poly(I:C) vaccinated mice. The CTGF/MSLN DNA vaccine combined with immuno-modulator EGCG also generated potent anti-tumor effects. Immuno-modulators could enhance the antigen-specific anti-tumor effects of CTGF/MSLN DNA vaccine through promoting the DC maturation. In addition, MSLN-specific cell-based vaccine with AAV-IL-12 and the CTGF/MSLN DNA vaccine with anti-CD40Ab/polyp(I:C) generated more potent anti-tumor effects than the other combinational regimens. The results indicate that an MSLN-specific DNA vaccine combined with immuno-modulators may be an effective immunotherapeutic strategy to control MSLN-expressing tumors including ovarian and pancreastic cancers, and malignant mesothelioma.

A new anti-mesothelin antibody targets selectively the membrane-associated form

Mesothelin is a glycosylphosphatidylinositol (GPI)-anchored membrane protein that shows promise as a target for antibody-directed cancer therapy. High levels of soluble forms of the antigen represent a barrier to directing therapy to cellular targets. The ability to develop antibodies that can selectively discriminate between membrane-bound and soluble conformations of a specific protein, and thus target only the membrane-associated antigen, is a substantive issue. We show that use of a tolerance protocol provides a route to such discrimination. Mice were tolerized with soluble mesothelin and a second round of immunizations was performed using mesothelin transfected P815 cells. RNA extracted from splenocytes was used in phage display to obtain mesothelin-specific antigen-binding fragments (Fabs) that were subsequently screened by flow cytometry and ELISA. This approach generated 147 different Fabs in 34 VH-CDR3 families. Utilizing competition assays with soluble protein and mesothelin-containing serum obtained from metastatic cancer patients, 10 of these 34 VH-CDR3 families were found to bind exclusively to the membrane-associated form of mesothelin. Epitope mapping performed for the 1H7 clone showed that it does not recognize GPI anchor. VH-CDR3 sequence analysis of all Fabs showed significant differences between Fabs selective for the membrane-associated form of the antigen and those that recognize both membrane bound and soluble forms. This work demonstrates the potential to generate an antibody specific to the membrane-bound form of mesothelin. 1H7 offers potential for therapeutic application against mesothelin-bearing tumors, which would be largely unaffected by the presence of the soluble antigen.

Irradiation Enhances Abscopal Anti-tumor Effects of Antigen-Specific Immunotherapy through Regulating Tumor Microenvironment

Ionizing radiation therapy is a well-established method of eradicating locally advanced tumors. Here, we examined whether local RT enhanced the potency of an antigen-specific DNA vaccine, and we investigated the possible underlying mechanism. Using the HPV16 E6/E7⁺ syngeneic TC-1 tumor, we evaluated the combination of CTGF/E7 vaccination with local irradiation with regard to synergistic antigen-specific immunity and anti-tumor effects. Tumor-bearing mice treated with local RT (6 Gy twice weekly) and CTGF/E7 DNA vaccination exhibited dramatically increased numbers of E7-specific CD8⁺ cytotoxic T cell precursors, higher titers of anti-E7 Abs, and significantly reduced tumor size. The combination of local RT and CTGF/E7 vaccination also elicited abscopal effects on non-irradiated local subcutaneous and distant pulmonary metastatic tumors. Local irradiation induced the expression of high-mobility group box 1 protein (HMGB-1) in apoptotic tumor cells and stimulated dendritic cell (DC) maturation, consequently inducing antigen-specific immune responses. Additionally, local irradiation eventually increased the effector-to-suppressor cell ratio in the tumor microenvironment. Overall, local irradiation enhanced the antigen-specific immunity and anti-tumor effects on local and distant metastatic tumors generated by an antigen-specific DNA vaccine. These findings suggest that the combination of irradiation with antigen-specific immunotherapy is a promising new clinical strategy for cancer therapy.

The Protective and Immunomodulatory Effects of Fucoidan Against 7,12-Dimethyl benz[a]anthracene-Induced Experimental Mammary Carcinogenesis Through the PD1/PDL1 Signaling Pathway in Rats

Fucoidan is a sulfated polysaccharide that is extracted from brown algae seaweed. This study was designed to evaluate the protective and immunomodulatory effects of dietary fucoidan on 7,12-dimethyl benz[a]anthracene (DMBA)-induced experimental mammary carcinogenesis in rats. Sixty Sprague-Dawley rats were randomly assigned to four equal groups: the control group (control group), the cancer model group (model group), and the F1 and F2 groups, which were fed fucoidan at concentrations of 200 and 400 mg/kg·body weight, respectively. We found that fucoidan treatment decreased the tumor incidence and mean tumor weight and prolonged the tumor latency. Flow cytometric analyses revealed that the number of blood natural killer cells was higher after fucoidan treatment and that the proportions of CD4 and CD8 T cells were also increased. The serum levels of interleukin (IL)-6, IL-12p40, and interferon (IFN)-γ were higher in the rats treated with fucoidan compared to those of model rats. Moreover, the percentage of CD3+ Foxp3+ regulatory T cells in the blood and the levels of IL-10 and transforming growth factor β in the serum were lower in the rats treated with fucoidan. Furthermore, fucoidan treatment decreased the expression of Foxp3 and programmed cell death 1 ligand 1 (PDL1) in tumor tissues. The levels of p-phosphatidyl inositol kinase 3 and p-AKT in tumor tissues were also lower than those of model rats. These results suggest that a fucoidan-supplemented diet can inhibit DMBA-induced tumors in rats. This study provides experimental evidence toward elucidating the immune enhancement induced by fucoidan through the programmed cell death 1/PDL1 signaling pathway. The immunomodulatory effect is one of the possible mechanisms of the protective effect of fucoidan against mammary carcinogenesis.