Modeling antibody drug conjugate potential using a granzyme B antibody fusion protein.

BACKGROUND: Antibody drug conjugates (ADCs) constitute a promising class of targeted anti-tumor therapeutics that harness the selectivity of monoclonal antibodies with the potency of cytotoxic drugs. ADC development is best suited to initially screening antibody candidates for desired properties that potentiate target cell cytotoxicity. However, validating and producing an optimally designed ADC requires expertise and resources not readily available to certain laboratories. RESULTS: In this study, we propose a novel approach to help streamline the identification of potential ADC candidates by utilizing a granzyme B (GrB)-based antibody fusion protein (AFP) for preliminary screening. GrB is a non-immunogenic serine protease expressed by immune effector cells such as CD8 + T cells that induces apoptotic activity and can be leveraged for targeted cell killing. CONCLUSIONS: Our innovative model allows critical antibody parameters (including target cell binding, internalization, and cytotoxic potential) to be more reliably evaluated in vitro through the creation of an ADC surrogate. Successful incorporation of this AFP could also significantly expand and enhance ADC development pre-clinically, ultimately leading to the accelerated translation of ADC therapies for patients.

Listeria-based vaccination against the pericyte antigen RGS5 elicits anti-vascular effects and colon cancer protection.

Colorectal cancer (CRC) remains a leading cause of cancer-related mortality despite efforts to improve standard interventions. As CRC patients can benefit from immunotherapeutic strategies that incite effector T cell action, cancer vaccines represent a safe and promising therapeutic approach to elicit protective and durable immune responses against components of the tumor microenvironment (TME). In this study, we investigate the pre-clinical potential of a Listeria monocytogenes (Lm)-based vaccine targeting the CRC-associated vasculature. CRC survival and progression are reliant on functioning blood vessels to effectively mediate various metabolic processes and oxygenate underlying tissues. We, therefore, advance the strategy of initiating immunity in syngeneic mouse models against the endogenous pericyte antigen RGS5, which is a critical mediator of pathological vascularization. Overall, Lm-based vaccination safely induced potent anti-tumor effects that consisted of recruiting functional Type-1-associated T cells into the TME and reducing tumor blood vessel content. This study underscores the promising clinical potential of targeting RGS5 against vascularized tumors like CRC.

Targeting the pericyte antigen DLK1 with an alpha type-1 polarized dendritic cell vaccine results in tumor vascular modulation and protection against colon cancer progression.

Despite the availability of various treatment options, colorectal cancer (CRC) remains a significant contributor to cancer-related mortality. Current standard-of-care interventions, including surgery, chemotherapy, and targeted agents like immune checkpoint blockade and anti-angiogenic therapies, have improved short-term patient outcomes depending on disease stage, but survival rates with metastasis remain low. A promising strategy to enhance the clinical experience with CRC involves the use of dendritic cell (DC) vaccines that incite immunity against tumor-derived blood vessels, which are necessary for CRC growth and progression. In this report, we target tumor-derived pericytes expressing DLK1 with a clinically-relevant alpha type-1 polarized DC vaccine (αDC1) in a syngeneic mouse model of colorectal cancer. Our pre-clinical data demonstrate the αDC1 vaccine's ability to induce anti-tumor effects by facilitating cytotoxic T lymphocyte activity and ablating the tumor vasculature. This work, overall, provides a foundation to further interrogate immune-mediated mechanisms of protection in order to help devise efficacious αDC1-based strategies for patients with CRC.

Disrupting cancer angiogenesis and immune checkpoint networks for improved tumor immunity.

Immune checkpoint inhibitors (ICIs) have advanced the field of cancer immunotherapy in patients by sustaining effector immune cell activity within the tumor microenvironment. However, the approach in general is still faced with issues related to ICI response duration/resistance, treatment eligibility, and safety, which indicates a need for further refinements. As immune checkpoint upregulation is inextricably linked to cancer-induced angiogenesis, newer clinical efforts have demonstrated the feasibility of disrupting both tumor-promoting networks to mediate enhanced immune-driven protection. This review focuses on such key evidence stipulating the necessity of co-applying ICI and anti-angiogenic strategies in cancer patients, with particular interest in highlighting newer engineered antibody approaches that may provide theoretically superior multi-pronged and safe therapeutic combinations.

Pathogenetic Features and Current Management of Glioblastoma.

Glioblastoma (GBM) is the most common form of primary malignant brain tumor with a devastatingly poor prognosis. The disease does not discriminate, affecting adults and children of both sexes, and has an average overall survival of 12-15 months, despite advances in diagnosis and rigorous treatment with chemotherapy, radiation therapy, and surgical resection. In addition, most survivors will eventually experience tumor recurrence that only imparts survival of a few months. GBM is highly heterogenous, invasive, vascularized, and almost always inaccessible for treatment. Based on all these outstanding obstacles, there have been tremendous efforts to develop alternative treatment options that allow for more efficient targeting of the tumor including small molecule drugs and immunotherapies. A number of other strategies in development include therapies based on nanoparticles, light, extracellular vesicles, and micro-RNA, and vessel co-option. Advances in these potential approaches shed a promising outlook on the future of GBM treatment. In this review, we briefly discuss the current understanding of adult GBM's pathogenetic features that promote treatment resistance. We also outline novel and promising targeted agents currently under development for GBM patients during the last few years with their current clinical status.

Dendritic cell vaccine therapy for colorectal cancer.

Colorectal cancer (CRC) remains a leading cause of cancer-related deaths in the United States despite an array of available treatment options. Current standard-of-care interventions for this malignancy include surgical resection, chemotherapy, and targeted therapies depending on the disease stage. Specifically, infusion of anti-vascular endothelial growth factor agents in combination with chemotherapy was an important development in improving the survival of patients with advanced colorectal cancer, while also helping give rise to other forms of anti-angiogenic therapies. Yet, one approach by which tumor angiogenesis may be further disrupted is through the administration of a dendritic cell (DC) vaccine targeting tumor-derived blood vessels, leading to cytotoxic immune responses that decrease tumor growth and synergize with other systemic therapies. Early generations of such vaccines exhibited protection against various forms of cancer in pre-clinical models, but clinical results have historically been disappointing. Sipuleucel-T (Provenge®) was the first, and to-date, only dendritic cell-based therapy to receive FDA approval after significantly increasing overall survival in prostate cancer patients. The unparalleled success of Sipuleucel-T has helped revitalize the clinical development of dendritic cell vaccines, which will be examined in this review. We also highlight the promise of these vaccines to instill anti-angiogenic immunity for individuals with advanced colorectal cancer.

Antibody-drug conjugates: an evolving approach for melanoma treatment.

Melanoma continues to be an aggressive and deadly form of skin cancer while therapeutic options are continuously developing in an effort to provide long-term solutions for patients. Immunotherapeutic strategies incorporating antibody-drug conjugates (ADCs) have seen varied levels of success across tumor types and represent a promising approach for melanoma. This review will explore the successes of FDA-approved ADCs to date compared to the ongoing efforts of melanoma-targeting ADCs. The challenges and opportunities for future therapeutic development are also examined to distinguish how ADCs may better impact individuals with malignancies such as melanoma.

Multi-parametric flow cytometry staining procedure for analyzing tumor-infiltrating immune cells following oncolytic herpes simplex virus immunotherapy in intracranial glioblastoma.

Multi-color flow cytometry is a standard laboratory protocol, which is regularly used to analyze tumor-infiltrating immune cell subsets. Oncolytic herpes simplex virus has shown promise in treating various types of cancers, including deadly glioblastoma. Intracranial/intratumoral treatment with oncolytic herpes simplex virus expressing interleukin 12, i.e., immunovirotherapy results in induction of anti-tumor immune responses and tumor infiltration of a variety of immune cells. Multi-color flow cytometry is employed to characterize immune cells in the tumor microenvironment. Here, we describe a step-by-step 11-color flow cytometry protocol to stain tumor-infiltrating immune cells in glioblastoma following oncolytic herpes virotherapy. We also describe a method to identify HSV-1 glycoprotein-B-specific CD8+ T cells using fluorochrome-conjugated major histocompatibility complex multimers. The multimers carry major histocompatibility peptide complexes, which have the ability to interact and bind to T cell receptors present on the surface of T cells; allowing identification of T cells (e.g., CD8+) reactive to a desired antigen. This multimer staining can be used in conjunction with the multi-parametric flow cytometry staining. Brain tumor quadrants are harvested, minced, enzymatically digested, immune cells are isolated by positive selection, single cells are counted and blocked for Fc receptors, cells are incubated with dye and/or color-conjugated antibodies, and flow cytrometry is performed using a BD LSRII flow cytometer. The protocol described herein is also applicable to stain immune cells in other mouse and human tumors or in any desired tissues.

Expression and characterization of soluble epitope-defined major histocompatibility complex (MHC) from stable eukaryotic cell lines.

MHC class I-specific reagents such as fluorescently-labeled multimers (e.g., tetramers) have greatly advanced the understanding of CD8+ T cells under normal and diseased states. However, recombinant MHC class I components (comprising MHC class I heavy chain and ß2 microglobulin) are usually produced in bacteria following a lengthy purification protocol that requires additional non-covalent folding steps with exogenous peptide for complete molecular assembly. We have provided an alternative and rapid approach to generating soluble and fully-folded MHC class I molecules in eukaryotic cell lines (such as CHO cells) using a Sleeping Beauty transposon system. Importantly, this method culminates in generating stable cell lines that reliably secrete epitope-defined MHC class I molecules into the tissue media for convenient purification and eventual biotinylation/multimerization. Additionally, MHC class I components are covalently linked, providing the opportunity to produce a diverse set of CD8+ T cell-specific reagents bearing peptides with various affinities to MHC class I.

TCR-like antibody drug conjugates mediate killing of tumor cells with low peptide/HLA targets.

The currently marketed antibody-drug conjugates (ADC) destabilize microtubule assembly in cancer cells and initiate apoptosis in patients. However, few tumor antigens (TA) are expressed at high densities on cancer lesions, potentially minimizing the therapeutic index of current ADC regimens. The peptide/human leukocyte antigen (HLA) complex can be specifically targeted by therapeutic antibodies (designated T cell receptor [TCR]-like antibodies) and adequately distinguish malignant cells, but has not been the focus of ADC development. We analyzed the killing potential of TCR-like ADCs when cross-linked to the DNA alkylating compound duocarmycin. Our data comprise proof-of-principle results that TCR-like ADCs mediate potent tumor cytotoxicity, particularly under common scenarios of low TA/HLA density, and support their continued development alongside agents that disrupt DNA replication. Additionally, TCR-like antibody ligand binding appears to play an important role in ADC functionality and should be addressed during therapy development to avoid binding patterns that negate ADC killing efficacy.

Immune Checkpoint Inhibitors: New Insights and Current Place in Cancer Therapy.

The treatment of cancer has largely relied on killing tumor cells with nonspecific cytotoxic therapies and radiotherapy. This approach, however, has limitations including severe systemic toxicities, bystander effects on normal cells, recurrence of drug-resistant tumor cells, and the inability to target micrometastases or subclinical disease. An increased understanding of the critical role of the immune system in cancer development and progression has led to new treatment strategies using various immunotherapies. It is now recognized that established tumors have numerous mechanisms of suppressing the antitumor immune response including production of inhibitory cytokines, recruitment of immunosuppressive immune cells, and upregulation of coinhibitory receptors known as immune checkpoints. This review focuses on the immune checkpoint inhibitors, a novel class of immunotherapy first approved in 2011. Our objective is to highlight similarities and differences among the three immune checkpoint inhibitors approved by the U.S. Food and Drug Administration-ipilimumab, pembrolizumab, and nivolumab-to facilitate therapeutic decision making. We conducted a review of the published literature and conference proceedings and present a critical appraisal of the clinical evidence supporting their use in the treatment of metastatic melanoma and advanced squamous non-small cell lung cancer (NSCLC). We also compare and contrast their current place in cancer therapy and patterns of immune-related toxicities, and discuss the role of dual immune checkpoint inhibition and strategies for the management of immune-related adverse events. The immune checkpoint inhibitors have demonstrated a dramatic improvement in overall survival in patients with advanced melanoma and squamous NSCLC, along with acceptable toxicity profiles. These agents have a clear role in the first-line treatment of advanced melanoma and in the second-line treatment of advanced squamous NSCLC.

Detection of human leukocyte antigen biomarkers in breast cancer utilizing label-free biosensor technology.

According to the American Cancer Society, more than 200,000 women will be diagnosed with invasive breast cancer each year and approximately 40,000 will die from the disease. The human leukocyte antigen (HLA) class I samples peptides derived from proteasomal degradation of cellular proteins and presents these fragments on the cell surface for interrogation by circulating cytotoxic T lymphocytes (CTL). Generation of T-cell receptor mimic (TCRm) monoclonal antibodies (mAbs) which recognize breast cancer specific peptide/HLA-A*02:01 complexes such as those derived from macrophage migration inhibitory factor (MIF19-27) and NY-ESO-1157-165 enable detection and destruction of breast cancer cells in the absence of an effective anti-tumor CTL response. Intact class I HLA/peptide complexes are shed by breast cancer cells and represent potentially relevant cancer biomarkers. In this work, a breakthrough biomarker screening system for cancer diagnostics incorporating T-cell receptor mimic monoclonal antibodies combined with a novel, label-free biosensor utilizing guided-mode resonance (GMR) sensor technology is presented. Detection of shed MIF/HLA-A*02:01 complexes in MDA-MB-231 cell supernatants, spiked human serum, and patient plasma is demonstrated. The impact of this work could revolutionize personalized medicine through development of companion disease diagnostics for targeted immunotherapies.

Monitoring antigen-specific T cell responses using real-time PCR.

Flow cytometry-, ELISA-, and ELISpot-based in vitro assays have played important roles in assessing the frequencies and functional competence of antigen-specific T cells in the setting of infectious disease and cancer. Such methods have helped in the development of antigen-specific vaccines for human disease prevention/treatment and have also served as a foundation for the monitoring of patients' immune responsiveness based on antigen-induced T cell expression of effector molecules (such as cytokines, chemokines, or proteins associated with cytolysis) as a consequence of therapeutic intervention. The following method outlines a protocol employing quantitative real-time PCR (qRT-PCR) with SYBR(®) green technology to examine antigen-specific CD8(+) T cell responses based on their rapid up-regulation of IFN-γ mRNA transcription following in vitro stimulation with peptide (antigen)-loaded, autologous peripheral blood mononuclear cells (PBMCs). The advantages of the current qRT-PCR approach over protein-based detection methods include the sensitivity to distinguish resident CD8(+) T cell responses against multiple antigens without the need to artificially pre-expand T cell numbers ex vivo, as is commonly required for the latter in vitro assay systems. Following qRT-PCR setup and run, the level of human IFN-γ transcript is normalized to CD8 transcript expression level, with data reported as the relative fold change in this index versus a patient-matched PBMC sample stimulated with a negative control peptide (e.g., HIV NEF).

Dasatinib promotes the expansion of a therapeutically superior T-cell repertoire in response to dendritic cell vaccination against melanoma.

Dasatinib (DAS) is a potent inhibitor of the BCR-ABL, SRC, c-KIT, PDGFR, and ephrin tyrosine kinases that has demonstrated only modest clinical efficacy in melanoma patients. Given reports suggesting that DAS enhances T cell infiltration into the tumor microenvironment, we analyzed whether therapy employing the combination of DAS plus dendritic cell (DC) vaccination would promote superior immunotherapeutic benefit against melanoma. Using a M05 (B16.OVA) melanoma mouse model, we observed that a 7-day course of orally-administered DAS (0.1 mg/day) combined with a DC-based vaccine (VAC) against the OVA257-264 peptide epitope more potently inhibited tumor growth and extended overall survival as compared with treatment with either single modality. The superior efficacy of the combinatorial treatment regimen included a reduction in hypoxic-signaling associated with reduced levels of immunosuppressive CD11b+Gr1+ myeloid-derived suppressor cells (MDSC) and CD4+Foxp3+ regulatory T (Treg) populations in the melanoma microenvironment. Furthermore, DAS + VAC combined therapy upregulated expression of Type-1 T cell recruiting CXCR3 ligand chemokines in the tumor stroma correlating with activation and recruitment of Type-1, vaccine-induced CXCR3+CD8+ tumor-infiltrating lymphocytes (TILs) and CD11c+ DC into the tumor microenvironment. The culmination of this bimodal approach was a profound "spreading" in the repertoire of tumor-associated antigens recognized by CD8+ TILs, in support of the therapeutic superiority of combined DAS + VAC immunotherapy in the melanoma setting.

The role of gamma interferon in DNA vaccine-induced tumor immunity targeting simian virus 40 large tumor antigen.

The central role of CD4+ T lymphocytes in mediating DNA vaccine-induced tumor immunity against the viral oncoprotein simian virus 40 (SV40) large tumor antigen (Tag) has previously been described by our laboratory. In the present study, we extend our previous findings by examining the roles of IFN-γ and Th1-associated effector cells within the context of DNA immunization in a murine model of pulmonary metastasis. Immunization of BALB/c mice with plasmid DNA encoding SV40 Tag (pCMV-Tag) generated IFN-γ-secreting T lymphocytes that produced this cytokine upon in vitro stimulation with mKSA tumor cells. The role of IFN-γ as a mediator of protection against mKSA tumor development was assessed via in vivo IFN-γ neutralization, and these experiments demonstrated a requirement for this cytokine in the induction immune phase. Neutralization of IFN-γ was associated with a reduction in Th1 cytokine-producing CD4+ and CD8+ splenocytes, as assessed by flow cytometry analysis, and provided further evidence for the role of CD4+ T lymphocytes as drivers of the cellular immune response. Depletion of NK cells and CD8+ T lymphocytes demonstrated the expendability of these cell types individually, but showed a requirement for a resident cytotoxic cell population within the immune effector phase. Our findings demonstrate the importance of IFN-γ in the induction of protective immunity stimulated by pCMV-Tag DNA-based vaccine and help to clarify the general mechanisms by which DNA vaccines trigger immunity to tumor cells.

Shock block for improved immunotherapy.

Cancer cells use heat shock proteins (HSP) to stabilize growth/survival-associated client proteins such as receptor tyrosine kinases (RTKs), in vivo. Our recent work suggests that chemical HSP90 inhibitors combined with a vaccination strategy targeting HSP90 client proteins that are (over)expressed in the tumor microenvironment yields superior therapeutic benefit.

Combined vaccine+axitinib therapy yields superior antitumor efficacy in a murine melanoma model.

Axitinib, a tyrosine kinase inhibitor of vascular endothelial growth factor receptors, has demonstrated modest efficacy when applied as a single agent in the setting of advanced-stage melanoma. On the basis of the reported ability of axitinib to 'normalize' the tumor vasculature, we hypothesize that combination therapy using axitinib plus specific peptide-based vaccination would promote superior activation and recruitment of protective T cells into the melanoma microenvironment, leading to enhanced treatment benefit. Using a subcutaneous M05 (B16.OVA) melanoma model, we observed that a treatment regimen consisting of a 7-day course of axitinib (0.5 mg/day provided orally) combined with a subcutaneous vaccine [ovalbumin (OVA) peptide-pulsed syngenic dendritic cells adenovirally engineered to produce IL-12p70] yielded superior protection against melanoma growth and extended overall survival when compared with animals receiving either single modality therapy. Treatment benefits were associated with: (a) a reduction in suppressor cell (myeloid-derived suppressor cells and Treg) populations in the tumor, (b) activation of tumor vascular endothelial cells, and (c) activation and recruitment of type-1, vaccine-induced CD8 T cells into tumors. These results support the therapeutic superiority of combined vaccine+axitinib immunotherapy and the translation of such approaches into the clinic for the treatment of patients with advanced-stage melanoma.

Vaccines targeting tumor blood vessel antigens promote CD8(+) T cell-dependent tumor eradication or dormancy in HLA-A2 transgenic mice.

We have recently shown that effective cytokine gene therapy of solid tumors in HLA-A2 transgenic (HHD) mice lacking murine MHC class I molecule expression results in the generation of HLA-A2-restricted CD8(+) T effector cells selectively recognizing tumor blood vessel-associated pericytes and/or vascular endothelial cells. Using an HHD model in which HLA-A2(neg) tumor (MC38 colon carcinoma or B16 melanoma) cells are not recognized by the CD8(+) T cell repertoire, we now show that vaccines on the basis of tumor-associated blood vessel Ags (TBVA) elicit protective Tc1-dependent immunity capable of mediating tumor regression or extending overall survival. Vaccine efficacy was not observed if (HLA-A2(neg)) wild-type C57BL/6 mice were instead used as recipient animals. In the HHD model, effective vaccination resulted in profound infiltration of tumor lesions by CD8(+) (but not CD4(+)) T cells, in a coordinate reduction of CD31(+) blood vessels in the tumor microenvironment, and in the "spreading" of CD8(+) T cell responses to alternate TBVA that were not intrinsic to the vaccine. Protective Tc1-mediated immunity was durable and directly recognized pericytes and/or vascular endothelial cells flow-sorted from tumor tissue but not from tumor-uninvolved normal kidneys harvested from these same animals. Strikingly, the depletion of CD8(+), but not CD4(+), T cells at late time points after effective therapy frequently resulted in the recurrence of disease at the site of the regressed primary lesion. This suggests that the vaccine-induced anti-TBVA T cell repertoire can mediate the clinically preferred outcomes of either effectively eradicating tumors or policing a state of (occult) tumor dormancy.

Combined Tbet and IL12 gene therapy elicits and recruits superior antitumor immunity in vivo.

We have recently shown that intratumor (i.t.) injection of syngenic dendritic cells (DC) engineered to express the transcription factor Tbet (TBX21) promotes protective type-1 T cell-mediated immunity via a mechanism that is largely interleukin (IL)-12p70-independent. Since IL-12 is a classical promoter of type-1 immunity, the current study was undertaken to determine whether gene therapy using combined Tbet and IL-12 complementary DNA (cDNA) would yield improved antitumor efficacy based on the complementary/synergistic action of these biologic modifiers. Mice bearing established subcutaneous (s.c.) tumors injected with DC concomitantly expressing ectopic Tbet and IL12 (i.e., DC.Tbet/IL12) displayed superior (i) rates of tumor rejection and extended overall survival, (ii) cross-priming of Tc1 reactive against antigens expressed within the tumor microenvironment, and (iii) infiltration of CD8(+) T cells into treated tumors in association with elevated locoregional production of CXCR3 ligand chemokines. In established bilateral tumor models, i.t. delivery of DC.Tbet/IL12 into a single lesion led to slowed growth or regression at both tumor sites. Furthermore, DC.Tbet/IL12 pulsed with tumor antigen-derived peptides and injected as a therapy distal to the tumor site prevented tumor growth and activated robust antigen-specific Tc1 responses. These data support the translation use of combined Tbet and IL-12p70 gene therapy in the cancer setting.

Chronic inflammation and immunologic-based constraints in malignant disease.

Acute inflammatory reactions benefit the host by supporting the effective clearance of pathogens and fostering wound healing, in addition to other self-preservative processes. However, when the inflammatory program is not resolved, becoming chronic in nature, it creates an environment conducive to cancer development and progression. Therefore, minimizing exposure to risk factors that contribute to chronic inflammation and reconditioning the host towards a state of (at least locoregional) acute inflammation would meaningfully impact cancer incidence and its treatment, respectively. Regarding cancer therapy, combinational treatments that both disrupt chronic inflammation and install specific adaptive type I immunity are predicted to enhance quality of life and extend the overall survival of patients.