Syngeneic Mouse Models of Oral Cancer Are Effectively Targeted by Anti-CD44-Based NIR-PIT

Fibroblast activation protein targeted near infrared photoimmunotherapy (NIR PIT) overcomes therapeutic resistance in human esophageal cancer

Cancer-associated fibroblasts (CAFs) have an important role in the tumor microenvironment. CAFs have the multifunctionality which strongly support cancer progression and the acquisition of therapeutic resistance by cancer cells. Near-infrared photoimmunotherapy (NIR-PIT) is a novel cancer treatment that uses a highly selective monoclonal antibody (mAb)-photosensitizer conjugate. We developed fibroblast activation protein (FAP)-targeted NIR-PIT, in which IR700 was conjugated to a FAP-specific antibody to target CAFs (CAFs-targeted NIR-PIT: CAFs-PIT). Thus, we hypothesized that the control of CAFs could overcome the resistance to conventional chemotherapy in esophageal cancer (EC). In this study, we evaluated whether EC cell acquisition of stronger malignant characteristics and refractoriness to chemoradiotherapy are mediated by CAFs. Next, we assessed whether the resistance could be rescued by eliminating CAF stimulation by CAFs-PIT in vitro and in vivo. Cancer cells acquired chemoradiotherapy resistance via CAF stimulation in vitro and 5-fluorouracil (FU) resistance in CAF-coinoculated tumor models in vivo. CAF stimulation promoted the migration/invasion of cancer cells and a stem-like phenotype in vitro, which were rescued by elimination of CAF stimulation. CAFs-PIT had a highly selective effect on CAFs in vitro. Finally, CAF elimination by CAFs-PIT in vivo demonstrated that the combination of 5-FU and NIR-PIT succeeded in producing 70.9% tumor reduction, while 5-FU alone achieved only 13.3% reduction, suggesting the recovery of 5-FU sensitivity in CAF-rich tumors. In conclusion, CAFs-PIT could overcome therapeutic resistance via CAF elimination. The combined use of novel targeted CAFs-PIT with conventional anticancer treatments can be expected to provide a more effective and sensible treatment strategy.

Near-infrared photoimmunotherapy of cancer: a new approach that kills cancer cells and enhances anti-cancer host immunity

Near-infrared photoimmunotherapy (NIR-PIT) is a recently developed hybrid cancer therapy that directly kills cancer cells as well as producing a therapeutic host immune response. Conventional immunotherapies, such as immune-activating cytokine therapy, checkpoint inhibition, engineered T cells and suppressor cell depletion, do not directly destroy cancer cells, but rely exclusively on activating the immune system. NIR-PIT selectively destroys cancer cells, leading to immunogenic cell death that initiates local immune reactions to released cancer antigens from dying cancer cells. These are characterized by rapid maturation of dendritic cells and priming of multi-clonal cancer-specific cytotoxic T cells that kill cells that escaped the initial direct effects of NIR-PIT. The NIR-PIT can be applied to a wide variety of cancers either as monotherapy or in combination with conventional immune therapies to further activate anti-cancer immunity. A global Phase 3 clinical trial (https://clinicaltrials.gov/ct2/show/NCT03769506) of NIR-PIT targeting the epidermal growth factor receptor (EGFR) in patients with recurrent head and neck cancer is underway, employing RM1929/ASP1929, a conjugate of anti-EGFR antibody (cetuximab) plus the photo-absorber IRDye700DX (IR700). NIR-PIT has been given fast-track recognition by regulators in the USA and Japan. A variety of imaging methods, including direct IR700 fluorescence imaging, can be used to monitor NIR-PIT. As experience with NIR-PIT grows, additional antibodies will be employed to target additional antigens on other cancers or to target immune-suppressor cells to enhance host immunity. NIR-PIT will be particularly important in patients with localized and locally advanced cancers and may help such patients avoid side-effects associated with surgery, radiation and chemotherapy.

Near-Infrared Photoimmunotherapy for Cancers of the Gastrointestinal Tract

BACKGROUND

Cancers of the gastrointestinal (GI) tract are the common leading cause of cancer-related death in the world. Recent advances in cancer therapies such as intensive multidrug chemotherapy and molecular targeted treatment have improved therapeutic efficacy; however, the outcomes are not satisfied. Moreover, these therapies also cause severe side effects. New type of cancer therapies is urgently needed to improve the outcomes and to reduce side effects of GI tract cancers.

SUMMARY

This account is a comprehensive review article on the newly developed, photochemistry-based cancer therapy named as near-infrared photoimmunotherapy (NIR-PIT). NIR-PIT is a highly selective tumor treatment that employs an antibody-photoabsorber conjugate, which is activated by near-infrared light. A world-wide phase 3 clinical trial of NIR-PIT against recurrent head and neck cancer patients is currently underway. NIR-PIT differs from conventional cancer therapies such as surgery, chemotherapy, and radiation in its selectivity for killing cancer cells and cells treated with NIR-PIT leading to immunogenic cell death. Preclinical research in animals with combining cancer-targeting NIR-PIT and other cancer immunotherapies could lead to responses not only in local tumor but also in distant metastases. NIR-PIT also leads to an immediate and dramatic increase in vascular permeability after therapy. From these aspects, NIR-PIT appears to be a promising new form of cancer therapy. NIR-PIT could be readily translated into clinical use for virtually any cancers in the near future provided suitable humanized antibodies are available. Here, we describe the specific advantages and applications of NIR-PIT in the GI tract. Key Messages: We believe that NIR-PIT with NIR excitation light, which can be delivered via a fiber optic diffuser through endoscopes, is a promising method for a new treatment of GI cancers.

Increased Immunogenicity of a Minimally Immunogenic Tumor after Cancer-Targeting Near Infrared Photoimmunotherapy

Near-infrared photoimmunotherapy (NIR-PIT) is a highly selective cancer treatment that employs an antibody photoabsorber conjugate (APC) composed of a targeting monoclonal antibody (mAb) conjugated with a photoactivatable phthalocyanine-derivative dye. Once injected and allowed to bind to a tumor, the APC is activated by local near-infrared light which kills cancer cells and induces a strong immune response in the tumor microenvironment by unmasking of new tumor antigens emerging from damaged tumor cells. Due to its ability to incite an immune reaction, even in poorly immunogenic tumors, NIR-PIT has the potential to enhance immunogenicity in tumors especially after immune checkpoint inhibition. In this study, we employ a poorly immunogenic MOC2-luc syngeneic tumor model and evaluate the efficacy of cancer-targeting CD44-targeted NIR-PIT. Increased infiltration of CD8+ T cells observed after NIR-PIT suggested an enhanced immune environment. Next, we evaluated tumor progression and survival after the combination of CD44-targeted NIR-PIT and short-term administration of an anti-PD1 immune checkpoint inhibitor (ICI) to further activate CD8+ T cells. Additionally, in mice in which the tumors were eradicated by this combination therapy, a re-challenge with fresh MOC2-luc cells demonstrated failure of tumor implantation implying acquired long-term immunity against the cancer cells. Combination therapy decreased tumor progression and prolonged survival significantly. Therefore, we concluded that NIR-PIT was able to convert a minimally immunogenic tumor unresponsive to anti-PD-1 ICI into a highly immunogenic tumor responsive to anti-PD-1 ICI, and this therapy was capable of inducing long-term immunity against the treated cancer.

Ligand-Targeted Delivery of Photosensitizers for Cancer Treatment

Photodynamic therapy (PDT) is a promising cancer treatment which involves a photosensitizer (PS), light at a specific wavelength for PS activation and oxygen, which combine to elicit cell death. While the illumination required to activate a PS imparts a certain amount of selectivity to PDT treatments, poor tumor accumulation and cell internalization are still inherent properties of most intravenously administered PSs. As a result, common consequences of PDT include skin photosensitivity. To overcome the mentioned issues, PSs may be tailored to specifically target overexpressed biomarkers of tumors. This active targeting can be achieved by direct conjugation of the PS to a ligand with enhanced affinity for a target overexpressed on cancer cells and/or other cells of the tumor microenvironment. Alternatively, PSs may be incorporated into ligand-targeted nanocarriers, which may also encompass multi-functionalities, including diagnosis and therapy. In this review, we highlight the major advances in active targeting of PSs, either by means of ligand-derived bioconjugates or by exploiting ligand-targeting nanocarriers.

Near-Infrared Photoimmunotherapy Combined with CTLA4 Checkpoint Blockade in Syngeneic Mouse Cancer Models

Near infrared photoimmunotherapy (NIR-PIT) is a newly developed and highly selective cancer treatment that induces necrotic/immunogenic cell death. It employs a monoclonal antibody (mAb) conjugated to a photo-absorber dye, IRDye700DX, which is activated by NIR light. Tumor-targeting NIR-PIT is also at least partly mediated by a profound immune response against the tumor. Cytotoxic T-lymphocyte antigen-4 (CTLA4) is widely recognized as a major immune checkpoint protein, which inhibits the immune response against tumors and is therefore, a target for systemic blockade. We investigated the effect of combining tumor-targeted NIR-PIT against the cell-surface antigen, CD44, which is known as a cancer stem cell marker, with a systemic CTLA4 immune checkpoint inhibitor in three syngeneic tumor models (MC38-luc, LL/2, and MOC1). CD44-targeted NIR-PIT combined with CTLA4 blockade showed greater tumor growth inhibition with longer survival compared with CTLA4 blockade alone in all tumor models. NIR-PIT and CTLA4 blockade produced more complete remission in MOC1 tumors (44%) than NIR-PIT and programmed cell death protein 1 (PD-1) blockade (8%), which was reported in our previous paper. However, the combination of NIR-PIT and CTLA4 blockade was less effective in MC38-luc tumors (11%) than the combination of NIR-PIT and PD-1 blockade (70%). Nonetheless, in many cases ineffective results with NIR-PIT and PD-1 blockade were reversed with NIR-PIT and CTLA4 blockade.

Interleukin-15 after Near-Infrared Photoimmunotherapy (NIR-PIT) Enhances T Cell Response against Syngeneic Mouse Tumors

Simple Summary

Near infrared photoimmunotherapy is a newly developed and highly selective cancer treatment that employs a monoclonal antibody conjugated to a photo-absorber dye, IRDye700DX, which is activated by 690 nm light. Cancer cell-targeted near infrared photoimmunotherapy selectively induces rapid necrotic/immunogenic cell death only on target cancer cells and this induces antitumor host immunity including re-priming and proliferation of multi-chronal T-cells that can react with cancer-specific antigens. Interleukin-15 is a type-I cytokine that activates natural killer-, B- and T-cells while having minimal effect on regulatory T-cells that lack the interleukin-15 receptor. Therefore, interleukin-15 administration combined with cancer cell-targeted near infrared photoimmunotherapy could further inhibit tumor growth by increasing antitumor host immunity. In tumor-bearing immunocompetent mice receiving this combination therapy, significant tumor growth inhibition and prolonged survival was demonstrated compared with either single therapy alone, and tumor infiltrating CD8+ T-cells increased in number in combination-treated mice. Interleukin-15 enhances therapeutic effects of cancer-targeted near infrared photoimmunotherapy.

Abstract

Near infrared photoimmunotherapy (NIR-PIT) is a newly developed and highly selective cancer treatment that employs a monoclonal antibody (mAb) conjugated to a photo-absorber dye, IRDye700DX, which is activated by 690 nm light. Cancer cell-targeted NIR-PIT induces rapid necrotic/immunogenic cell death (ICD) that induces antitumor host immunity including re-priming and proliferation of T cells. Interleukin-15 (IL-15) is a cytokine that activates natural killer (NK)-, B- and T-cells while having minimal effect on regulatory T cells (Tregs) that lack the IL-15 receptor. Here, we hypothesized that IL-15 administration with cancer cell-targeted NIR-PIT could further inhibit tumor growth by increasing antitumor host immunity. Three syngeneic mouse tumor models, MC38-luc, LL/2, and MOC1, underwent combined CD44-targeted NIR-PIT and short-term IL-15 administration with appropriate controls. Comparing with the single-agent therapy, the combination therapy of IL-15 after NIR-PIT inhibited tumor growth, prolonged survival, and increased tumor infiltrating CD8+ T cells more efficiently in tumor-bearing mice. IL-15 appears to enhance the therapeutic effect of cancer-targeted NIR-PIT.

P2Y2 receptors mediate nucleotide-induced EGFR phosphorylation and stimulate proliferation and tumorigenesis of head and neck squamous cell carcinoma cell lines

OBJECTIVES

To assess functional expression of the P2Y2 nucleotide receptor (P2Y2R) in head and neck squamous cell carcinoma (HNSCC) cell lines and define its role in nucleotide-induced epidermal growth factor receptor (EGFR) transactivation. The use of anti-EGFR therapeutics to treat HNSCC is hindered by intrinsic and acquired drug resistance. Defining novel pathways that modulate EGFR signaling could identify additional targets to treat HNSCC.

MATERIALS AND METHODS

In human HNSCC cell lines CAL27 and FaDu and the mouse oral cancer cell line MOC2, P2Y2R contributions to extracellular nucleotide-induced changes in intracellular free Ca2+ concentration and EGFR and extracellular signal-regulated kinase (ERK1/2) phosphorylation were determined using the ratiometric Ca2+ indicator fura-2 and immunoblot analysis, respectively. Genetic knockout of P2Y2Rs using CRISPR technology or pharmacological inhibition with P2Y2R-selective antagonist AR-C118925 defined P2Y2R contributions to in vivo tumor growth.

RESULTS

P2Y2R agonists UTP and ATP increased intracellular Ca2+ levels and ERK1/2 and EGFR phosphorylation in CAL27 and FaDu cells, responses that were inhibited by AR-C118925 or P2Y2R knockout. P2Y2R-mediated EGFR phosphorylation was also attenuated by inhibition of the adamalysin family of metalloproteases or Src family kinases. P2Y2R knockout reduced UTP-induced CAL27 cell proliferation in vitro and significantly reduced CAL27 and FaDu tumor xenograft volume in vivo. In a syngeneic mouse model of oral cancer, AR-C118925 administration reduced MOC2 tumor volume.

CONCLUSION

P2Y2Rs mediate HNSCC cell responses to extracellular nucleotides and genetic or pharmacological blockade of P2Y2R signaling attenuates tumor cell proliferation and tumorigenesis, suggesting that the P2Y2R represents a novel therapeutic target in HNSCC.

Selective Photokilling of Colorectal Tumors by Near-Infrared Photoimmunotherapy with a GPA33-Targeted Single-Chain Antibody Variable Fragment Conjugate

Antibody-based near-infrared photoimmunotherapy (NIR-PIT) is an attractive strategy for cancer treatment. Tumor cells can be selectively and efficiently killed by the targeted delivery of an antibody-photoabsorber complex followed by exposure to NIR light. Glycoprotein A33 antigen (GPA33) is highly expressed in most human colorectal cancers (CRCs) and is an ideal diagnostic and therapeutic target. We previously produced a single-chain fragment of a variable antibody against GPA33 (A33scFv antibody). Here, we investigate the efficacy of NIR-PIT by combining A33scFv with the NIR photoabsorber IR700 (A33scFv-IR700). In vitro, recombinant A33scFv displayed specific binding and delivery of an NIR dye to GPA33-positive tumor cells. Furthermore, A33scFv-IR700-mediated NIR-PIT was successful in rapidly and specifically killing GPA33-positive colorectal tumor cells. NIR-PIT treatment induced the release of lactate dehydrogenase from tumor cells, followed by cell necrosis, rather than apoptosis, through the promotion of reactive oxygen species accumulation in tumor cells. In mice bearing LS174T tumor grafts, A33scFv selectively accumulated in GPA33-positive tumors. Following only a single injection of the conjugate and subsequent illumination, A33scFv-IR700-mediated NIR-PIT induced a significant increase in therapeutic response in LS174T-tumor mice compared with that in the non-NIR-PIT groups (p < 0.001). Because the GPA33 antigen is specifically expressed in CRC tumors, A33scFv-IR700 might be a promising antibody fragment-photoabsorber conjugate for NIR-PIT of CRC.

The current markers of cancer stem cell in oral cancers

Head and neck cancer (HNC) constitute 5% of all reported cancers. Among all, the oral cavity cancer is the most frequent type of HNC which accounts for over half of HNC cases. Mouth cancer ranks the sixth leading cause of cancer-related mortality. Generally, conventional chemotherapy has shown success at decreasing relapse and metastasis rates and improves the overall prognosis. Recently, target therapy and targeted drug delivery systems have been introduced as promising treatments. The elimination of efficiency of current therapeutic strategies due to the spared cancer stem cells that cause chemotherapy resistance, relapse and metastasis. Inefficiency methodologies in the elimination of all cancer cells in the body are a major problem that remained to be resolved before to confront the new cancer therapies. Many studies imply to cancer stem cell markers as important agents for targeted anti-cancer as well as improving chemotherapy efficiencies. The potentials of targeted cancer therapy led us to search for novel markers in the mouth cancer stem cells especially in rare cancers. The aimed of this research was, first a comprehensive critical review of the previous studies on the markers of cancer stem cells in oral cancers including oral squamous cell carcinoma, salivary gland cancers, and to highlight the most common cancer stem cell markers which have potential to be exploited as indicators for the preneoplastic lesion malignancy, oral cancer progression, and/or treatment prognosis.

Development and Radiation Response Assessment in A Novel Syngeneic Mouse Model of Tongue Cancer: 2D Culture, 3D Organoids and Orthotopic Allografts

Oral squamous cell carcinoma (OSCC) are aggressive cancers that contribute to significant morbidity and mortality in humans. Although numerous human xenograft models of OSCC have been developed, only a few syngeneic models of OSCC exist. Here, we report on a novel murine model of OSCC, RP-MOC1, derived from a tongue tumor in a C57Bl/6 mouse exposed to the carcinogen 4-nitroquinoline-1-oxide. Phenotypic characterization and credentialing (STR profiling, exome sequencing) of RP-MOC1 cells was performed in vitro. Radiosensitivity was evaluated in 2D culture, 3D organoids, and in vivo using orthotopic allografts. RP-MOC1 cells exhibited a stable epithelial phenotype with proliferative, migratory and invasive properties. Exome sequencing identified several mutations commonly found in OSCC patients. The LD₅₀ for RP-MOC1 cells in 2D culture and 3D organoids was found to be 2.4 Gy and 12.6 Gy, respectively. Orthotopic RP-MOC1 tumors were pan-cytokeratin+ and Ki-67+. Magnetic resonance imaging of orthotopic RP-MOC1 tumors established in immunocompetent mice revealed marked growth inhibition following 10 Gy and 15 Gy fractionated radiation regimens. This radiation response was completely abolished in tumors established in immunodeficient mice. This novel syngeneic model of OSCC can serve as a valuable platform for the evaluation of combination strategies to enhance radiation response against this deadly disease.

Combined CD44- and CD25-Targeted Near-Infrared Photoimmunotherapy Selectively Kills Cancer and Regulatory T Cells in Syngeneic Mouse Cancer Models

Near-infrared photoimmunotherapy (NIR-PIT) is a newly developed and selective cancer treatment that induces necrotic and immunogenic cell death and utilizes a mAb conjugated to a photo-absorber dye, IR700DX, activated by NIR light. Although CD44 is a surface cancer marker associated with drug resistance, anti-CD44-IR700 NIR-PIT results in inhibited cell growth and prolonged survival in multiple tumor types. Meanwhile, CD25-targeted NIR-PIT has been reported to achieve selective and local depletion of FOXP3⁺CD25⁺CD4⁺ regulatory T cells (Treg), which are primary immunosuppressive cells in the tumor microenvironment (TME), resulting in activation of local antitumor immunity. Combined NIR-PIT with CD44- and CD25-targeted agents has the potential to directly eliminate tumor cells and also amplify the immune response by removing FOXP3⁺CD25⁺CD4⁺ Tregs from the TME. We investigated the difference in therapeutic effects of CD44-targeted NIR-PIT alone, CD25-targeted NIR-PIT alone, and the combination of CD44- and CD25-targeted NIR-PIT in several syngeneic tumor models, including MC38-luc, LL/2, and MOC1. The combined NIR-PIT showed significant tumor growth inhibition and prolonged survival compared with CD44-targeted NIR-PIT alone in all tumor models and showed prolonged survival compared with CD25-targeted NIR-PIT alone in MC38-luc and LL/2 tumors. Combined CD44- and CD25-targeted NIR-PIT also resulted in some complete remissions. Therefore, combined NIR-PIT simultaneously targeting cancer antigens and immunosuppressive cells in the TME may be more effective than either type of NIR-PIT alone and may have potential to induce prolonged immune responses in treated tumors.

Near-Infrared Photoimmunotherapy: Photoactivatable Antibody-Drug Conjugates (ADCs)

Cancer treatment has been founded traditionally on the three approaches of surgery, radiation, and chemotherapy with the latter recognized as the obvious systemic treatment approach applicable to disease that has spread. Although significant progress has been made over nearly 100 years of developing systemic treatments, it remains clear that use of the toxic agents involved is a two-edged sword with normal organ toxicities always needing to be balanced with and against administration of relevant therapeutic doses. With the advent of monoclonal antibodies targeted against tumor-associated antigens that could be used as carriers of potently toxic chemotherapy drugs, it was thought that such antibody-drug conjugates (ADCs) could engender the answer to the toxicity/therapeutic equation by shifting the equation more toward beneficial therapeutic efficacy. However, over 40 or so years, antibody-drug conjugates have not significantly affected the toxicity/therapy balance paradigm in most cancer indications, especially in solid tumors. Ideally, a further step may be required in that a non-tumor-targeted antibody-drug conjugate should be essentially nontoxic in its native administered form, with toxic effects unleashed only at the site of targeted tumors. A new approach that employs this principle is the use of an antibody-drug conjugate that is essentially nontoxic to normal tissues by virtue of requiring an extra step of light activation to become potent. We describe the preclinical data and first clinical results gained over the past few years by use of antibody-drug conjugates wherein the drug comprises a near-infrared photoactivatable dye delivered to tumors by a monoclonal antibody and is subsequently activated to a toxic entity solely at sites of tumors.

Mouse Tumor-Bearing Models as Preclinical Study Platforms for Oral Squamous Cell Carcinoma

Preclinical animal models of oral squamous cell carcinoma (OSCC) have been extensively studied in recent years. Investigating the pathogenesis and potential therapeutic strategies of OSCC is required to further progress in this field, and a suitable research animal model that reflects the intricacies of cancer biology is crucial. Of the animal models established for the study of cancers, mouse tumor-bearing models are among the most popular and widely deployed for their high fertility, low cost, and molecular and physiological similarity to humans, as well as the ease of rearing experimental mice. Currently, the different methods of establishing OSCC mouse models can be divided into three categories: chemical carcinogen-induced, transplanted and genetically engineered mouse models. Each of these methods has unique advantages and limitations, and the appropriate application of these techniques in OSCC research deserves our attention. Therefore, this review comprehensively investigates and summarizes the tumorigenesis mechanisms, characteristics, establishment methods, and current applications of OSCC mouse models in published papers. The objective of this review is to provide foundations and considerations for choosing suitable model establishment methods to study the relevant pathogenesis, early diagnosis, and clinical treatment of OSCC.

The Effect of Antibody Fragments on CD25 Targeted Regulatory T Cell Near-Infrared Photoimmunotherapy

Regulatory T (Treg) cells play a major role in immune suppression permitting tumors to evade immune surveillance. Depletion of intratumoral Treg cells can result in tumor regression. However, systemic depletion of Tregs may also induce autoimmune adverse events. Near-infrared photoimmunotherapy (NIR-PIT) is a newly developed cell-specific cancer therapy that locally kills specific cells in the tumor. Antibody-photoabsorber (IRDye700DX) conjugates (APC) are injected and bind to the tumor, and subsequent administration of NIR light to the tumor results in rapid cell death only in targeted cells. CD25-targeted NIR-PIT has been shown to induce spatially selective depletion of tumor-associated Treg cells. In this study, we compared the efficacy of an antibody fragment, anti-CD25-F(ab')₂, and a full antibody, anti-CD25-IgG, as agents for NIR-PIT. Tumor-bearing mice were divided into four groups: (1) no treatment; (2) anti-CD25-IgG-IR700 i.v. only; (3) anti-CD25-F(ab')₂-IR700 i.v. with NIR light exposure; and (4) anti-CD25-IgG-IR700 i.v. with NIR light exposure. Although both CD25-targeted NIR-PITs resulted in significant tumor growth inhibition, the anti-CD25-F(ab')₂-IR700 based NIR-PIT was superior to the anti-CD25-IgG-IR700 NIR-PIT. The anti-CD25-F(ab')₂-IR700 demonstrated faster clearance from the body than the anti-CD25-IgG-IR700. Sustained circulation of anti-CD25-IgG-IR700 may block IL-2 binding on the activated effector T-cells decreasing immune response. In conclusion, anti-CD25-F(ab')₂ based NIR-PIT was more effective in reducing tumor growth than anti-CD25-IgG based NIR-PIT. Absence of the Fc portion of the APC leads to faster clearance and therefore promotes a superior activated T cell response in tumors.

Near-Infrared Photoimmunotherapy of Cancer

This Account is the first comprehensive review article on the newly developed, photochemistry-based cancer therapy near-infrared (NIR) photoimmunotherapy (PIT). NIR-PIT is a molecularly targeted phototherapy for cancer that is based on injecting a conjugate of a near-infrared, water-soluble, silicon-phthalocyanine derivative, IRdye700DX (IR700), and a monoclonal antibody (mAb) that targets an expressed antigen on the cancer cell surface. Subsequent local exposure to NIR light turns on this photochemical "death" switch, resulting in the rapid and highly selective immunogenic cell death (ICD) of targeted cancer cells. ICD occurs as early as 1 min after exposure to NIR light and results in irreversible morphologic changes only in target-expressing cells based on the newly discovered photoinduced ligand release reaction that induces physical changes on conjugated antibody/antigen complex resulting in functional damage on cell membrane. Meanwhile, immediately adjacent receptor-negative cells are totally unharmed. Because of its highly targeted nature, NIR-PIT carries few side effects and healing is rapid. Evaluation of the tumor microenvironment reveals that ICD induced by NIR-PIT results in rapid maturation of immature dendritic cells adjacent to dying cancer cells initiating a host anticancer immune response, resulting in repriming of polyclonal CD8⁺T cells against various released cancer antigens, which amplifies the therapeutic effect of NIR-PIT. NIR-PIT can target and treat virtually any cell surface antigens including cancer stem cell markers, that is, CD44 and CD133. A first-in-human phase 1/2 clinical trial of NIR-PIT using cetuximab-IR700 (RM1929) targeting EGFR in inoperable recurrent head and neck cancer patients successfully concluded in 2017 and led to "fast tracking" by the FDA and a phase 3 trial ( https://clinicaltrials.gov/ct2/show/NCT03769506 ) that is currently underway in 3 countries in Asia, US/Canada, and 4 countries in EU. The next step for NIR-PIT is to further exploit the immune response. Preclinical research in animals with intact immune systems has shown that NIT-PIT targeting of immunosuppressor cells within the tumor, such as regulatory T-cells, can further enhance tumor-cell-selective systemic host-immunity leading to significant responses in distant metastatic tumors, which are not treated with light. By combining cancer-targeting NIR-PIT and immune-activating NIR-PIT or other cancer immunotherapies, NIR-PIT of a local tumor, could lead to responses in distant metastases and may also inhibit recurrences due to activation of systemic anticancer immunity and long-term immune memory without the systemic autoimmune adverse effects often associated with immune checkpoint inhibitors. Furthermore, NIR-PIT also enhances nanodrug delivery into tumors up to 24-fold superior to untreated tumors with conventional EPR effects by intensively damaging cancer cells behind tumor vessels. We conclude by describing future advances in this novel photochemical cancer therapy that are likely to further enhance the efficacy of NIR-PIT.

P-glycoprotein targeted photodynamic therapy of chemoresistant tumors using recombinant Fab fragment conjugates

P-glycoprotein (Pgp) has been considered as a major cause of cancer multidrug resistance; however, clinical solutions to overcome this drug resistance do not exist despite the tremendous endeavors. The lack of cancer specificity is a main reason for clinical failure of conventional approaches. Targeted photodynamic therapy (PDT) is highly cancer specific by combining antibody targeting and locoregional light irradiation. We aimed to develop Pgp-targeted PDT using antibody-photosensitizer conjugates made of a recombinant Fab fragment. We prepared the photosensitizer conjugates by expressing a recombinant Fab fragment and specifically linking IR700-maleimide at the C-terminal of the Fab heavy chain. In vitro studies showed that the Fab conjugates specifically bind to Pgp. Their phototoxicity was comparable to full antibody conjugates when assayed with conventional 2-D cell culture, but they outperformed the full antibody conjugates in a 3-D tumor spheroid model. In a mouse xenograft model of chemoresistant tumors, Fab conjugates showed Pgp specific delivery to chemoresistant tumors. Upon irradiation with near-infrared light, they caused rapid tumor shrinkage and significantly prolonged the survival of tumor-bearing mice. Compared to the full antibody conjugates, Fab conjugates took a shorter time to reach peak tumor levels and achieved a more homogeneous tumor distribution. This allows light irradiation to be initiated at a shorter time interval after the conjugate injection, and thus may facilitate clinical translation. We conclude that our targeted PDT approach provides a highly cancer-specific approach to combat chemoresistant tumors, and that the conjugates made of recombinant antibody fragments are superior to full antibody conjugates for targeted PDT.

Near infrared photoimmunotherapy using a fiber optic diffuser for treating peritoneal gastric cancer dissemination

BACKGROUND

Peritoneal dissemination (PD) of abdominal malignancies is a common form of metastasis and its presence signals a poor prognosis. New treatment is required for patients with PD. Near infrared photoimmunotherapy (NIR-PIT) is a highly selective tumor treatment that employs an antibody-photo-absorber conjugate (APC). In this study, we investigate in vitro and in vivo efficacy of trastuzumab (tra)-IR700DX NIR-PIT on a human epidermal growth factor receptor type 2 (HER2)-positive gastric cancer cell line.

METHODS

NIR-PIT effects were investigated in vitro and in vivo. Disseminated peritoneal implants mice were separated into 5 groups: (1) no treatment; (2) tra-IR700 i.v. only; (3) NIR light only; (4) NIR-PIT; (5) repeated NIR-PIT. The peritoneal cavity was irradiated with NIR light using a fiber optic diffuser delivered through the catheter.

RESULTS

Specific binding and cell-specific killing was observed after NIR-PIT in vitro. In the in vivo study, fluorescence endoscopy showed high tumor accumulation of tra-IR700 within tumors. Significantly prolonged survival was achieved in the three treatment groups (tra-IR700 i.v. only, NIR-PIT, and repeated NIR-PIT groups) compared with control and NIR light only group (p < 0.05 for tra-IR700 i.v. only, p < 0.01 for NIR-PIT, and p < 0.0001 for repeated NIR-PIT). Moreover, most prolonged survival was shown for the repeated NIR-PIT group (p < 0.0001 vs tra-IR700 i.v. only, p < 0.01 vs NIR-PIT).

CONCLUSION

NIR-PIT using a fiber optic diffuser to deliver light is a promising candidate for the treatment of disseminated peritoneal metastases and could be readily translated to humans.

Host Immunity Following Near-Infrared Photoimmunotherapy Is Enhanced with PD-1 Checkpoint Blockade to Eradicate Established Antigenic Tumors

Near-infrared photoimmunotherapy (NIR-PIT) induces immunogenic cell death but has mostly failed to induce durable antitumor responses in syngenic tumor mouse models. We hypothesized that adaptive immune resistance could be limiting durable responses after treatmemt with NIR-PIT. We investigated the effects of combining NIR-PIT targeting cell-surface CD44 and PD-1 blockade in multiple syngeneic tumor models. In two of three models, NIR-PIT monotherapy halted tumor growth, enhanced dendritic cell tumor infiltration, and induced de novo tumor antigen-specific T-cell responses absent at baseline. The addition of PD-1 blockade reversed adaptive immune resistance, resulting in both enhanced preexisting tumor antigen-specific T-cell responses and enhanced de novo T-cell responses induced by NIR-PIT. Enhanced immune responses correlated with shared tumor antigen expression, suggesting that antigenicity is a major determinant of response to combination NIR-PIT and PD-1 blockade. Combination treatment induced complete rejection of MC38 tumors treated with NIR-PIT, as well as untreated, distant tumors. Accordingly, tumor antigen-specific T-cell responses were measured in both treated and untreated tumors, validating the development of systemic antitumor immunity. Mice that cleared tumors resisted subsequent tumor challenge, indicating the presence of systemic immune memory. Cumulatively, these results demonstrate reversal of adaptive immune resistance following induction of innate and adaptive immunity by NIR-PIT, resulting in high rates of tumor rejection and/or significant tumor growth control in antigenic syngeneic models of cancer.

Near-infrared photoimmunotherapy of pancreatic cancer using an indocyanine green-labeled anti-tissue factor antibody

AIM

To investigate near-infrared photoimmunotherapeutic effect mediated by an anti-tissue factor (TF) antibody conjugated to indocyanine green (ICG) in a pancreatic cancer model.

METHODS

Near-infrared photoimmunotherapy (NIR-PIT) is a highly selective tumor treatment that utilizes an antibody-photosensitizer conjugate administration, followed by NIR light exposure. Anti-TF antibody 1849-ICG conjugate was synthesized by labeling of rat IgG2b anti-TF monoclonal antibody 1849 (anti-TF 1849) to a NIR photosensitizer, ICG. The expression levels of TF in two human pancreatic cancer cell lines were examined by western blotting. Specific binding of the 1849-ICG to TF-expressing BxPC-3 cells was examined by fluorescence microscopy. NIR-PIT-induced cell death was determined by cell viability imaging assay. In vivo longitudinal fluorescence imaging was used to explore the accumulation of 1849-ICG conjugate in xenograft tumors. To examine the effect of NIR-PIT, tumor-bearing mice were separated into 5 groups: (1) 100 μg of 1849-ICG i.v. administration followed by NIR light exposure (50 J/cm2) on two consecutive days (Days 1 and 2); (2) NIR light exposure (50 J/cm2) only on two consecutive days (Days 1 and 2); (3) 100 μg of 1849-ICG i.v. administration; (4) 100 μg of unlabeled anti-TF 1849 i.v. administration; and (5) the untreated control. Semiweekly tumor volume measurements, accompanied with histological and immunohistochemical (IHC) analyses of tumors, were performed 3 d after the 2nd irradiation with NIR light to monitor the effect of treatments.

RESULTS

High TF expression in BxPC-3 cells was observed via western blot analysis, concordant with the observed preferential binding with intracellular localization of 1849-ICG via fluorescence microscopy. NIR-PIT-induced cell death was observed by performing cell viability imaging assay. In contrast to the other test groups, tumor growth was significantly inhibited by NIR-PIT with a statistically significant difference in relative tumor volumes for 27 d after the treatment start date [2.83 ± 0.38 (NIR-PIT) vs 5.42 ± 1.61 (Untreated), vs 4.90 ± 0.87 (NIR), vs 4.28 ± 1.87 (1849-ICG), vs 4.35 ± 1.42 (anti-TF 1849), at Day 27, P < 0.05]. Tumors that received NIR-PIT showed evidence of necrotic cell death-associated features upon hematoxylin-eosin staining accompanied by a decrease in Ki-67-positive cells (a cell proliferation marker) by IHC examination.

CONCLUSION

The TF-targeted NIR-PIT with the 1849-ICG conjugate can potentially open a new platform for treatment of TF-expressing pancreatic cancer.

Endoscopic near infrared photoimmunotherapy using a fiber optic diffuser for peritoneal dissemination of gastric cancer

Near infrared photoimmunotherapy (NIR‐PIT) is a highly selective tumor treatment that employs an antibody‐photo‐absorber conjugate (APC) which is activated by near infrared light. Here, we describe the efficacy of endoscopic NIR‐PIT using the APC trastuzumab‐IR700DX (tra‐IR700) in the setting of human epidermal growth factor 2 positive (HER2 + ) gastric carcinoma with peritoneal disseminations. In this in vivo study, fluorescence endoscopy showed high tumor accumulation of tra‐IR700 within disseminated peritoneal implants. Mice with disseminated peritoneal gastric cancer were separated into 4 groups: (i) control (no treatment); (ii) tra‐IR700 i.v. only; (iii) NIR light only; and (iv) endoscopic NIR‐PIT. NIR light irradiation was carried out through a fiber optic diffuser under endoscopic guidance. In vivo bioluminescence images showed significantly greater therapeutic effect in the endoscopic NIR‐PIT group than that in the control groups (P < .01 vs other control groups). Histological analysis showed diffuse cancer cell death in NIR‐PIT‐treated tumors. In conclusion, NIR‐PIT with NIR light delivered via an endoscopic fiber optic diffuser is a promising method for the treatment of peritoneal dissemination of gastric cancer. Moreover, this technique could be readily used in other types of cancers with peritoneal dissemination provided that suitable antibodies could be found.