Cancer-targeted photoimmunotherapy induces antitumor immunity and can be augmented by anti-PD-1 therapy for durable anticancer responses in an immunologically active murine tumor model

The complex immunosuppressive nature of solid tumor microenvironments poses a significant challenge to generating efficacious and durable anticancer responses. Photoimmunotherapy is a cancer treatment strategy by which an antibody is conjugated with a non-toxic light-activatable dye. Following administration of the conjugate and binding to the target tumor, subsequent local laser illumination activates the dye, resulting in highly specific target cell membrane disruption. Here we demonstrate that photoimmunotherapy treatment elicited tumor necrosis, thus inducing immunogenic cell death characterized by the release of damage-associated molecular patterns (DAMPs). Photoimmunotherapy-killed tumor cells activated dendritic cells (DC), leading to the production of proinflammatory cytokines, T cell stimulation, priming antigen-specific T cells, and durable memory T cell responses, which led complete responder mice to effectively reject new tumors upon rechallenge. PD-1 blockade in combination with photoimmunotherapy enhanced overall anticancer efficacy, including against anti-PD-1-resistant tumors. The combination treatment also elicited abscopal anticancer activity, as observed by reduction of distal, non-illuminated tumors, further demonstrating the ability of photoimmunotherapy to harness local and peripheral T cell responses. With this work we therefore delineate the immune mechanisms of action for photoimmunotherapy and demonstrate the potential for cancer-targeted photoimmunotherapy to be combined with other immunotherapy approaches for augmented, durable anticancer efficacy. Moreover, we demonstrate responses utilizing various immunocompetent mouse models, as well as in vitro data from human cells, suggesting broad translational potential.

Development of an automated combined positive score prediction pipeline using artificial intelligence on multiplexed immunofluorescence images

Immunotherapy targeting immune checkpoint proteins, such as programmed cell death ligand 1 (PD-L1), has shown impressive outcomes in many clinical trials but only 20%-40% of patients benefit from it. Utilizing Combined Positive Score (CPS) to evaluate PD-L1 expression in tumour biopsies to identify patients with the highest likelihood of responsiveness to anti-PD-1/PD-L1 therapy has been approved by the Food and Drug Administration for several solid tumour types. Current CPS workflow requires a pathologist to manually score the two-colour PD-L1 chromogenic immunohistochemistry image. Multiplex immunofluorescence (mIF) imaging reveals the expression of an increased number of immune markers in tumour biopsies and has been used extensively in immunotherapy research. Recent rapid progress of Artificial Intelligence (AI)-based imaging analysis, particularly Deep Learning, provides cost effective and high-quality solutions to healthcare. In this article, we propose an imaging pipeline that utilizes three-colour mIF images (DAPI, PD-L1, and Pan-cytokeratin) as input and predicts the CPS using AI techniques. Our novel pipeline is composed of three modules employing algorithms of image processing, machine learning, and deep learning techniques. The first module of quality check (QC) detects and removes the image regions contaminated with sectioning and staining artefacts. The QC module ensures that only image regions free of the three common artefacts are used for downstream analysis. The second module of nuclear segmentation uses deep learning to segment and count nuclei in the DAPI images wherein our specialized method can accurately separate touching nuclei. The third module of cell phenotyping calculates CPS by identifying and counting PD-L1 positive cells and tumour cells. These modules are data-efficient and require only few manual annotations for training purposes. Using tumour biopsies from a clinical trial, we found that the CPS from the AI-based models shows a high Spearman correlation (78%, p = 0.003) to the pathologist-scored CPS.

Phase 1/2a, open-label, multicenter study of RM-1929 photoimmunotherapy in patients with locoregional, recurrent head and neck squamous cell carcinoma

Background

Recurrent head and neck squamous cell carcinoma (rHNSCC) represents a significant global health burden with an unmet medical need. In this study we determined the safety and efficacy of RM‐1929 photoimmunotherapy in patients with heavily pretreated rHNSCC.

Methods

RM‐1929 (anti‐EGFR–IR700 dye conjugate) was infused, followed by tumor illumination. We evaluated safety, tumor response, and pharmacokinetics.

Results

Nine patients were enrolled in Part 1 (dose‐finding) and 30 patients in Part 2 (safety and efficacy). No dose‐limiting toxicities were experienced in Part 1; 640 mg/m² with fixed light dose (50 J/cm² or 100 J/cm) was recommended for Part 2. Adverse events (AEs) in Part 2 were mostly mild to moderate but 19 (63.3%) patients had AE ≥Grade 3, including 3 (10.0%) with serious AEs leading to death (not treatment related). Efficacy in Part 2: unconfirmed objective response rate (ORR) 43.3% (95% CI 25.46%–62.57%); confirmed ORR 26.7% (95% CI 12.28%–45.89%); median overall survival 9.30 months (95% CI 5.16–16.92 months).

Conclusions

Treatment was well tolerated. Responses and survival following RM‐1929 photoimmunotherapy in heavily pretreated patients with rHNSCC were clinically meaningful and warrant further investigation.

Clinical Trial Information

NCT02422979.

Abstract 1798: CTLA-4 photoimmunotherapy depletes intratumoral regulatory T cells (Tregs) to augment local and systemic immunity for anticancer activity

Introduction: Photoimmunotherapy is an investigational cancer treatment platform that utilizes an antibody conjugated to a light activated dye IRDye® 700DX (IR700) combined with illumination with a non-thermal, red light for selective cell killing. CTLA-4 is a lymphocyte exhaustion marker targeted by anti-CTLA-4 checkpoint inhibitors to induce anticancer immune response and is highly expressed on intratumoral regulatory T cells (Tregs). In this study we used anti-CTLA-4-IR700 photoimmunotherapy (CTLA-4 photoimmunotherapy), which involves intratumoral Treg depletion with checkpoint inhibition, in syngeneic mouse models, including models refractory to immune checkpoint inhibition, to assess anticancer activity and immune response.

Methods: Mice inoculated with CT26, LL/2, MCA205, or 4T1 tumors were treated with CTLA-4 photoimmunotherapy. Tumor volume was determined by caliper measurements in target (illuminated) and distal (non-illuminated) tumors. Intratumoral immune responses were characterized by flow cytometry. To evaluate the activation of systemic immune responses, cytotoxic T lymphocyte assays were conducted with splenocytes derived from mice treated with CTLA-4 photoimmunotherapy. Tumor re-challenge studies were conducted to assess for tumor-specific immune memory responses.

Results: CTLA-4 photoimmunotherapy induced notable anticancer responses including complete responses (CRs), and enhanced survival of mice in multiple tumor models, including tumors resistant to anti-PD-1 or anti-CTLA-4 treatment. CTLA-4 photoimmunotherapy resulted in a reduction of intratumoral Tregs, an increase of the CD8/Treg ratio, and an increase of intratumoral NK and CD8 T cell activation in comparison to control groups. All CR mice (n=7) rejected new tumor inoculations, suggesting enhancement of systemic immune memory. Splenocytes derived from CTLA-4 photoimmunotherapy-treated mice displayed an expansion of tumor antigen-specific lymphocytes in comparison to control groups. In mice bearing bilateral CT26 tumors, tumor regression was observed in target and distal tumors after CTLA-4 photoimmunotherapy, demonstrating systemic anticancer immunity and potential abscopal effects.

Conclusion: CTLA-4 photoimmunotherapy elicited anticancer responses in a variety of tumor models, including tumors resistant to anti-PD-1 or anti-CTLA-4 treatment. Depletion of intratumoral Tregs by CTLA-4 photoimmunotherapy resulted in the local activation of CD8 T cell-mediated anticancer activity and systemic tumor specific immune response. These results indicate that treatment with CTLA-4 photoimmunotherapy can induce anticancer responses in checkpoint resistant mouse tumor models by combining rapid Treg depletion with anti-CTLA-4 checkpoint inhibition into a single method of treatment.

Citation Format: C. Daniel de Magalhaes Filho, Stephanie M. Okamura, Daniele M. Bergeron, Ahiram Rodriguez, Abram Lozano, Jerry J. Fong, Miguel Garcia-Guzman. CTLA-4 photoimmunotherapy depletes intratumoral regulatory T cells (Tregs) to augment local and systemic immunity for anticancer activity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1798.

Abstract 1796: PD-L1 photoimmunotherapy kills immunosuppressive myeloid cells to activate local and systemic antitumor immunity in syngeneic mouse models

Introduction: Photoimmunotherapy is an investigational anticancer treatment platform that combines the cell surface binding of an antibody conjugated to a light activatable dye (IRDye® 700DX, IR700) with non-thermal red light illumination for selective cell killing. PD-L1, the target of anti-PD-L1 inhibitors, is a suppressive checkpoint marker expressed on tumor cells and immunosuppressive myeloid cells in the tumor microenvironment. Here we examined the anticancer activity and immune activation elicited by anti-PD-L1-IR700 photoimmunotherapy (PD-L1 photoimmunotherapy).

Methods: CT26 or LL/2 tumors were used to assess antitumor immune response following PD-L1 photoimmunotherapy. CT26PD-L1-/- tumors were generated by CRISPR/Cas9. Tumor volume was determined by caliper measurements in illuminated and non-illuminated tumors. Intratumoral immune responses were assessed by flow cytometry. Complete responder (CR) mice were challenged with either CT26 or 4T1 tumors to evaluate immune memory.

Results: Mice bearing CT26 or LL/2 tumors treated with PD-L1 photoimmunotherapy exhibited a notable reduction of tumor growth compared to mice that received control treatments (saline, anti-PD-L1-IR700 conjugate alone without illumination, or multi-dosing with anti-PD-L1 antibody). Pre-treatment depletion of CD8+ T cells in the mice abrogated the antitumor activity of PD-L1 photoimmunotherapy, demonstrating a key role of CD8+ T-cell effector activity in the responses. PD-L1 photoimmunotherapy induced CRs in 7/15 mice, and all CR mice rejected CT26 tumor growth after re-challenge, indicating the generation of immunological memory. Furthermore, 6/8 mice rejected inoculation of 4T1 tumors, suggesting an enhanced ability to prime new T cells with tumor neoantigens. Intratumoral immune cell analysis showed a reduction of myeloid cells 2 hours following illumination, an increase of CD103+ dendritic cells 2 days following illumination, and an increase of non-exhausted PD-1-CD8+ T effector cells 8 days after illumination. In a bilateral tumor model, PD-L1 photoimmunotherapy resulted in tumor reduction in the non-illuminated tumor. Mice bearing CT26PD-L1-/- tumor cells similarly exhibited tumor reduction after PD-L1 photoimmunotherapy, suggesting that antitumor activity resulted from the elimination of PD-L1+ non-tumor cells.

Conclusions: PD-L1photoimmunotherapy induces anticancer responses by killing PD-L1+ myeloid cells and possibly PD-L1+ cancer cells within the tumor, resulting in augmentation of local and systemic antitumor immunity. These results indicate that PD-L1 photoimmunotherapy can elicit anticancer immune responses in target and distal tumors, including syngeneic mouse models refractory to checkpoint inhibition.

Citation Format: Amy H. Thorne, Michelle H. Hsu, Daniel Mendoza, Jason Lapetoda, Christopher M. Parry, Jerry J. Fong, Miguel Garcia-Guzman. PD-L1 photoimmunotherapy kills immunosuppressive myeloid cells to activate local and systemic antitumor immunity in syngeneic mouse models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1796.

Abstract 480: Molecular mechanism of action of photoimmunotherapy with antibody-IR700 dye conjugates

INTRODUCTION: Cancer cell-targeted photoimmunotherapy (PIT) is a platform technology under development for the treatment of various cancers. PIT is a drug and device combination that utilizes an antibody conjugated to the IR700 (IRDye 700DX®) light-excitable dye, which upon antigen binding and illumination with non-thermal red light, leads to necrotic cell death. The objective of these studies was to characterize the molecular pharmacology and the underlying mechanism of action of PIT.

METHODS: In vitro PIT studies using human and mouse cancer cells were performed to evaluate conjugate (antibody + dye) binding, dose response and light dosimetry response. Mouse xenograft experiments assessed necrotic markers in tumor tissue and surrounding normal tissue post-PIT treatment. Oxidative damage to lipids was detected with a reporter dye. Mass spectrometry analysis was performed to assess protein oxidation, crosslinking and axial ligand dissociation from the dye.

RESULTS: Binding of the conjugate to the target cancer cells was required for PIT treatment to induce cell death as measured by antibody competition studies, however, internalization of the conjugate was not required for cytotoxic effects. Administration of non-thermal red light to the target cells bound with the conjugate led to morphologic changes and membrane disruption within minutes, and necrotic cell death was observed in a conjugate- and light-dose dependent manner. Requirement of conjugate binding to the cancer antigen provided high level of tumor specificity as demonstrated by lack of damage to normal surrounding tissue after PIT treatment. Light excitation of the conjugate generated 1O2 with high quantum yield. In vitro PIT treatment led to cell membrane lipid peroxidation, mediated by 1O2 as shown by abrogation with sodium azide, a selective 1O2 quencher. In addition, protein oxidation, cross-linking and aggregation of the conjugate was observed. In low oxygen concentrations and in the presence of ascorbate, photo-induced dissociation of axial ligands from the dye was detected.

CONCLUSIONS: These studies suggest the molecular mechanism of action of PIT includes generation of 1O2 that leads to lipid peroxidation and cell membrane disruption. Additional mechanisms may include protein oxidation and non-oxygen dependent mechanisms such as axial ligand loss of the IR700 dye. These results describe a biophysical process that damages and disrupts the cell membrane integrity resulting in necrotic cell death and immunogenic cell death.

Citation Format: Roger Heim, Lew Makings, Torsten Wiemann, Anthony Manibusan, Miguel Garcia-Guzman. Molecular mechanism of action of photoimmunotherapy with antibody-IR700 dye conjugates [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 480.

Abstract 949: Anti-cancer activity by photoimmunotherapy is driven by adaptive immune responses and vaccinates the host against the tumor

INTRODUCTION: Photoimmunotherapy (PIT) is an investigational anti-cancer treatment platform utilizing cell-targeted antibodies conjugated to the IR700 (IRDye 700DX®) light-excitable dye. Upon illumination with non-thermal red light, target cells bound with antibody-conjugates undergo rapid necrosis. Previous work demonstrated that PIT induces features of immunogenic cell death of tumor cells and ignites an immune response against the tumor. In these preclinical studies, we investigated the extent to which the immune response contributes to the in vivo anti-cancer activity using syngeneic cancer models.

METHODS: PIT treatment was applied to a panel of mouse and human cancer cell lines targeted by their respective antigen-binding conjugate in vitro, and the release of damage-associated molecular patterns (DAMPs) was measured from the cell supernatant. To determine the contribution of the immune response to PIT anti-cancer activity, PIT treatment was applied to immunocompetent animals with antibody-mediated CD8 T cell depletion, or blockade of CD40-CD40L axis concurrent with tumor implant or PIT treatment. To determine whether the immunogenic properties of PIT treatment induce vaccinal effects, immunocompetent animals were inoculated with in vitro PIT-treated cancer cells, and then challenged with live tumor cells in the contralateral flank one week later.

RESULTS: Cancer cells treated with PIT released significant amounts of immunogenic cell death markers including DAMPs such as ATP and Annexin A1. The anti-cancer activity of PIT treatment in immunocompetent animals was inhibited when 1) pre-existing immunity was abrogated by blockade of the CD40-CD40L interaction at time of tumor implant, and 2) CD8 T cells were depleted from the animals. Applying CD40-CD40L blockade concurrent with PIT treatment partially abrogated anti-cancer activity. When animals were inoculated with cancer cells treated by PIT ex vivo, tumor rejection was achieved in 8 out of 9 animals when challenged with live tumor cells on the contralateral flank.

CONCLUSIONS: Cancer treatment by PIT induces necrotic and immunogenic cell death resulting in local and systemic immune response. These preclinical data indicate that adaptive immune responses induced by PIT treatment drive the anti-cancer effects and can also provide vaccinal effects due to the release of DAMPs and cancer antigens.

Citation Format: C. Daniel De Magalhaes Filho, Michelle A. Hsu, Stephanie M. Okamura, Dany Gitnick, Estela Solis, Jerry J. Fong, Miguel Garcia-Guzman. Anti-cancer activity by photoimmunotherapy is driven by adaptive immune responses and vaccinates the host against the tumor [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 949.

Abstract 2255: Combination treatment of cancer cell-targeted photoimmunotherapy plus anti-PD1 leads to synergistic anticancer activity in an immunocompetent mouse model

INTRODUCTION: Photoimmunotherapy (PIT) is a new cancer-targeted platform technology that utilizes a photoactivatable dye (IRDye 700DX) conjugated to a cancer-targeting antibody. Binding of the antibody- dye conjugate to cancer cells followed by photoactivation with nonthermal red light elicits rapid necrosis of the cancer cells bound to the antibody conjugate. In previous studies using immunocompetent mouse models, intratumoral innate and adaptive immune cell activation was observed after PIT treatment. We hypothesized that combination therapy with PIT plus anti-PD1 may enhance the activity of anticancer immune activation elicited by PIT treatments and in this study we evaluated the effects of the combination treatment in an immunocompetent mouse model.

METHODS: Immunocompetent mice implanted with CT26 tumor cells engineered to overexpress specific recombinant mouse antigens, received PIT treatment alone, anti-PD1, or combination therapy and were assessed for tumor growth inhibition and complete response rate. In animals achieving a complete response, the specificity of the response was evaluated by tumor re-challenge experiments. Animals with residual disease had their tumors excised and assessed for intratumoral immune activation. Splenocytes from treated animals were harvested and evaluated for cytotoxic activity against the cancer cells.

RESULTS: Of the mice that received combination treatment, 7 of 14 achieved complete response compared to 0 of 14 and 1 of 14 when treated with anti-PD1 monotherapy and PIT monotherapy, respectively. All tumor-free animals from combination treatment also rejected formation of new tumors following inoculation with the same tumor type (CT26), but not tumors from a different cancer cell type (4T1). Splenocytes derived from animals that received combination treatment had the greatest cytotoxic activity against CT26 cells when compared to single agent controls. In addition, splenocytes derived from animals that received combination treatment had increased total CD3+ CD8+ cells, as well as increased CD62L-CD44+ effector memory CD8+ cells, in comparison to splenocytes derived from animals that received single agent therapies.

CONCLUSION: In this study, combination cancer-targeted PIT plus anti-PD1 treatment in immunocompetent mice resulted in synergistic anticancer activity due to enhanced adaptive immune activation, as demonstrated by tumor rejection and increased systemic, tumor-specific cytotoxic T cells, and effector memory CD8+ cells. The results of this study warrant the clinical evaluation of combination treatment of cancer-targeted PIT plus anti-PD1 therapies.

Citation Format: Stephanie M. Okamura, Michelle A. Hsu, Daniele M. Bergeron, Estela Solis, Deepak Yadav, Jerry J. Fong, Roger Heim, Miguel Garcia-Guzman. Combination treatment of cancer cell-targeted photoimmunotherapy plus anti-PD1 leads to synergistic anticancer activity in an immunocompetent mouse model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2255.

Abstract 3734: Cancer cell-targeted photoimmunotherapy elicits immunogenic cell death and activates the innate and adaptive immune response in the tumor microenvironment

INTRODUCTION: Cancer cell-targeted photoimmunotherapy (PIT) is a platform technology under development for the treatment of various cancers. PIT is a drug + device combination that utilizes monoclonal antibodies conjugated to a dye (IRDye 700DX) that are activated with nonthermal red light illumination to induce rapid cell death by necrosis. Binding of the antibody-dye conjugate to cancer cells followed by photoactivation with nonthermal red light elicits rapid necrosis of the cancer cells bound to the antibody conjugate, providing very high cancer cell specificity. Given the rapid cell necrosis induced by PIT treatment, we hypothesized that PIT also induces immunogenic cell death (ICD) as a step to activate immune cells in the tumor microenvironment. The objective of this study was to evaluate, through in vitro and in vivo experiments, whether PIT results in ICD of targeted cancer cells and activation of the innate and adaptive immune response.

METHODS: Human cancer cells (A431 and FaDu cells) were targeted by PIT, and evaluated for ICD markers in vitro. Human dendritic cells exposed to supernatants of PIT-killed cancer cells were evaluated for activation markers and cytokine production. An immunocompetent mouse model for PIT was also developed to determine intratumoral immune activation after treatment with PIT.

RESULTS: After photoactivation, PIT-targeted human cancer cells upregulated cell surface ICD markers Hsp70, Hsp90, and calreticulin, as well as release of intracellular HMGB1. Human dendritic cells exposed to PIT-killed cell supernatants exhibited markers of immune activation (CD86 and MHCII), and secreted proinflammatory cytokines including TNF, IP-10, IL-1β, MIP-1a, MIP-1b, and IL-8. In an immunocompetent mouse model, tumors treated by PIT displayed increased percentage of intratumoral CD11c+ dendritic cells with activation markers MHCIIhigh, CD80, and PD-L1. In addition, intratumoral natural killer cells from PIT treated tumors displayed increased cytotoxic activity (CD3-DX5+CD69+ and CD3-DX5+CD107a+), as well as an increased population of total CD3+ CD8+ T cells, compared to non-PIT treated tumors.

CONCLUSION: Cancer cells killed by PIT undergo ICD, which results in the activation of intratumoral innate and adaptive immune response in a preclinical mouse model. Combination studies with PIT and immune modulators are warranted to explore potential synergistic anticancer effects.

Citation Format: Michelle A. Hsu, Stephanie M. Okamura, Daniele M. Bergeron, Deepak Yadav, Jerry J. Fong, Roger Heim, Miguel Garcia-Guzman. Cancer cell-targeted photoimmunotherapy elicits immunogenic cell death and activates the innate and adaptive immune response in the tumor microenvironment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3734.

Second-Generation Non-Covalent NAAA Inhibitors are Protective in a Model of Multiple Sclerosis

Palmitoylethanolamide (PEA) and oleoylethanolamide (OEA) are endogenous lipid mediators that suppress inflammation. Their actions are terminated by the intracellular cysteine amidase, N-acylethanolamine acid amidase (NAAA). Even though NAAA may offer a new target for anti-inflammatory therapy, the lipid-like structures and reactive warheads of current NAAA inhibitors limit the use of these agents as oral drugs. A series of novel benzothiazole-piperazine derivatives that inhibit NAAA in a potent and selective manner by a non-covalent mechanism are described. A prototype member of this class (8) displays high oral bioavailability, access to the central nervous system (CNS), and strong activity in a mouse model of multiple sclerosis (MS). This compound exemplifies a second generation of non-covalent NAAA inhibitors that may be useful in the treatment of MS and other chronic CNS disorders.

Abstract 2019: Photoimmunotherapy with an anti-EGFR antibody conjugated to an IRDye700 results in extensive and rapid cell death in vitro and in vivo in human pancreatic cancer cell lines

Photoimmunotherapy (PIT) of cancer utilizes tumor-specific monoclonal antibodies conjugated to a photosensitizer phthalocyanine dye IR700 which becomes cytotoxic upon irradiation with near infrared light. In this study, we aimed to evaluate the efficacy of PIT on human pancreatic cancer cells in vitro and in vivo in a nude mouse model. An in vitro cytotoxicity assay was used to determine cell death following treatment with PIT for Panc-1, MiaPaCa2, and BxPC-3 human pancreatic cancer cells. For in vivo determination of PIT efficacy, nude mice were implanted with BxPC-3 pancreatic tumors expressing green fluorescent protein (GFP). After tumor engraftment, the mice were divided into two groups: treatment with anti-EGFR-IR700 + 690 nm laser and treatment with 690 nm laser only. Anti-EGFR-IR700 (100 μg) was administered to the treatment group via tail vein injection 24 hours prior to therapy. Tumors were then exposed and treated with phototherapy at an intensity of 150 mW/cm2 for 30 minutes. Whole body imaging was done using an OV-100 small animal imaging system. Anti-EGFR-IR700 antibody bound to the BxPC3 cells to a high degree based on image co-localization. Anti-EGFR-IR700 caused extensive cancer cell killing after light activation compared to control cells in cytotoxicity assays. In the mouse experiments, the treatment group had significantly smaller tumors as measured by GFP than the control after just 96 hours. The present results indicate the high potential of PIT for pancreatic cancer therapy.

Citation Format: Nzola de Magalhães, Takashi Murakami, Roger Heim, Lew Makings, Miguel Garcia-Guzman, Hisataka Kobayashi, Robert M. Hoffman, Michael Bouvet. Photoimmunotherapy with an anti-EGFR antibody conjugated to an IRDye700 results in extensive and rapid cell death in vitro and in vivo in human pancreatic cancer cell lines. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2019. doi:10.1158/1538-7445.AM2015-2019

Photoimmunotherapy lowers recurrence after pancreatic cancer surgery in orthotopic nude mouse models

BACKGROUND

Photoimmunotherapy (PIT) is based on the use of a monoclonal antibody specific to cancer epitopes conjugated to a photosensitizer near-infrared phthalocyanine dye (IR700). In this study, PIT with IR700 conjugated to anti-carcinoembryonic antigen (CEA) was used as an adjunct to surgery in orthotopically-implanted human pancreatic cancer in a nude mouse model to eliminate microscopic disease in the post-surgical tumor bed and prevent local as well as metastatic recurrence.

MATERIALS AND METHODS

Athymic nude mice were orthotopically implanted with the human pancreatic cancer cell line BxPC3 expressing green fluorescent protein. After tumor engraftment, the mice were divided into two groups as follows: bright light surgery (BLS) + anti-CEA-IR700 + 690 nm laser (PIT); and BLS only. Anti-CEA-IR700 (100 μg) was administered to the treatment group via tail-vein injection 24 h before therapy. Tumors were resected, and the surgical bed was treated with intraoperative phototherapy at an intensity of 150 mW/cm(2) for 30 min. Mice were imaged noninvasively for 8 wk using an OV-100 small animal fluorescence imager.

RESULTS

BLS + PIT reduced local recurrence to 1/7 mice from 7/7 mice with BLS-only (P = 0.001) and metastatic recurrence to 2/7 mice compared with 6/7 mice with BLS-only (P = 0.03). Local tumor growth continued at a rapid rate after BLS-only compared with BLS + PIT where almost no local growth occurred. There was a significant difference in tumor size between mice in the BLS + PIT (2.14 mm(2), 95% confidence interval [CI] [-2.06 to 6.34] and BLS-only groups (115.2 mm(2), 95% CI [88.8-141.6]) at 6 wk after surgery (P < 0.001). There was also a significant difference in tumor weight between the BLS + PIT group (6.65 mg, 95% CI [-6.35 to 19.65] and BLS-only group (1100 mg, 95% CI [794-1406] at 8 wk after surgery (P < 0.001).

CONCLUSIONS

PIT holds promise in the treatment of pancreatic cancer and may serve as a useful adjunct to surgery in the eradication of microscopic residual disease that can lead to both local and metastatic recurrence. Further studies are warranted to investigate the potential toxicities of PIT, especially with regard to anastomoses, such as those involved in pancreaticoduodenectomy.

Muscarinic pain pharmacology: realizing the promise of novel analgesics by overcoming old challenges

The antinociceptive and analgesic effects of muscarinic receptor ligands in human and nonhuman species have been evident for more than half a century. In this review, we describe the current understanding of the roles of different muscarinic subtypes in pain modulation and their mechanism of action along the pain signaling pathway, including peripheral nociception, spinal cord pain processing, and supraspinal analgesia. Extensive preclinical and clinical validation of these mechanisms points to the development of selective muscarinic agonists as one of the most exciting and promising avenues toward novel pain medications.

Refolding and characterization of a soluble ectodomain complex of the calcitonin gene-related peptide receptor

The calcitonin gene-related peptide (CGRP) receptor is a heterodimer of two membrane proteins: calcitonin receptor-like receptor (CLR) and receptor activity-modifying protein 1 (RAMP1). CLR is a class B G-protein-coupled receptor (GPCR), possessing a characteristic large amino-terminal extracellular domain (ECD) important for ligand recognition and binding. Dimerization of CLR with RAMP1 provides specificity for CGRP versus related agonists. Here we report the expression, purification, and refolding of a soluble form of the CGRP receptor comprising a heterodimer of the CLR and RAMP1 ECDs. The extracellular protein domains corresponding to residues 23-133 of CLR and residues 26-117 of RAMP1 were shown to be sufficient for formation of a stable, monodisperse complex. The binding affinity of the purified ECD complex for the CGRP peptide was significantly lower than that of the native receptor (IC(50) of 12 microM for the purified ECD complex vs 233 pM for membrane-bound CGRP receptor), indicating that other regions of CLR and/or RAMP1 are important for peptide agonist binding. However, high-affinity binding to known potent and specific nonpeptide antagonists of the CGRP receptor, including olcegepant and telcagepant (K(D) < 0.02 muM), as well as N-terminally truncated peptides and peptide analogues (140 nM to 1.62 microM) was observed.

Organization of functional domains in the docking protein p130Cas

The docking protein p130Cas becomes phosphorylated upon cell adhesion to extracellular matrix proteins, and is thought to play an essential role in cell transformation. Cas transmits signals through interactions with the Src-homology 3 (SH3) and Src-homology 2 domains of FAK or v-Crk signaling molecules, or with 14-3-3 protein, as well as phosphatases PTP1B and PTP-PEST. The large (130kDa), multi-domain Cas molecule contains an SH3 domain, a Src-binding domain, a serine-rich protein interaction region, and a C-terminal region that participates in protein interactions implicated in antiestrogen resistance in breast cancer. In this study, as part of a long-term goal to examine the protein interactions of Cas by X-ray crystallography and nuclear magnetic resonance spectroscopy, molecular constructs were designed to express two adjacent domains, the serine-rich domain and the Src-binding domain, that each participate in intermolecular contacts dependent on protein phosphorylation. The protein products are soluble, homogeneous, monodisperse, and highly suitable for structural studies to define the role of Cas in integrin-mediated cell signaling.

Genetic selection for modulators of the MAP kinase and beta-catenin growth-control pathways in mammalian cells

Transdominant genetic selections can yield protein fragment and peptide modulators of specific biochemical pathways. In yeast, such screens have been highly successful in targeting the MAP (mitogen-activated protein) kinase growth-control pathway. We performed a similar type of selection aimed at recovery of modulators of the mammalian MAP kinase cascade. Two pathway activators were identified, fragments of the TrkB and Raf-1 kinases. In a second selection directed at the beta-catenin growth-control pathway, three different clones encoding cadherin fragments were recovered. In neither selection were peptide inhibitors observed. We conclude that some transdominant selections in mammalian cells can readily yield high-penetrance protein fragments, but may be less amenable to isolation of peptide inhibitors.

The proto-oncogene c-Cbl is a positive regulator of Met-induced MAP kinase activation: a role for the adaptor protein Crk

Hepatocyte growth factor triggers a complex biological program leading to invasive cell growth by activating the c-Met receptor tyrosine kinase. Following activation, Met signaling is elicited via its interactions with SH2-containing proteins, or via the phosphorylation of the docking protein Gab1, and the subsequent interaction of Gab1 with additional SH2-containing effector molecules. We have previously shown that the interaction between phosphorylated Gab1 and the adaptor protein Crk mediates activation of the JNK pathway downstream of Met. We report here that c-Cbl, which is a Gab1-like docking protein, also becomes tyrosine-phosphorylated in response to Met activation and serves as a docking molecule for various SH2-containing molecules, including Crk. We further show that Cbl is similarly capable of enhancing Met-induced JNK activation, and several lines of experimentation suggests that it does so by interacting with Crk. We also show that both Cbl and Gab1 enhance Met-induced activation of another MAP kinase cascade, the ERK pathway, in a Crk-independent manner. Taken together, our studies demonstrate a previously unidentified functional role for Cbl in Met signaling and suggest that Met utilizes at least two docking proteins, Gab1 and Cbl, to activate downstream signaling pathways. Oncogene (2000) 19, 4058 - 4065.

Met-induced JNK activation is mediated by the adapter protein Crk and correlates with the Gab1 - Crk signaling complex formation

Constitutive activation of the Met tyrosine kinase results in transformation of cells of diverse origin. Recent studies have demonstrated a role for the c-Jun N-terminal kinase (JNK) in Met-induced transformation, but little is known about the molecular mechanisms that connect Met to JNK activation. Our studies show that activated Met associates with, and phosphorylates, the docking protein Gab1, which in turn binds to the src homology 2 (SH2)-domain of the adapter protein Crk and recruits Crk to the Met signaling complex. Formation of the Gab1 - Crk complex correlates with Met-induced JNK activation, and mutant forms of Met that fail to induce the complex formation also fail to activate JNK. Importantly, expression of a loss-of-function mutant of Crk severely impairs activation of the JNK pathway by Met. We also show here that Met controls the transcription of the matrix metalloproteinase-1 (MMP-1) gene in carcinoma cells and that this transcriptional regulation occurs in a Crk - JNK-dependent manner through an AP-1 element in the MMP-1 promoter. Taken together, our data implicate the Gab1 - Crk signaling complex in Met-induced JNK activation and suggest that the Gab1 - Crk complex formation may be an important event in regulating the tumorigenic phenotype of Met-transformed cells.

Cell adhesion regulates the interaction between the docking protein p130(Cas) and the 14-3-3 proteins

Integrin ligand binding induces a signaling complex formation via the direct association of the docking protein p130(Cas) (Cas) with diverse molecules. We report here that the 14-3-3zeta protein interacts with Cas in the yeast two-hybrid assay. We also found that the two proteins associate in mammalian cells and that this interaction takes place in a phosphoserine-dependent manner, because treatment of Cas with a serine phosphatase greatly reduced its ability to bind 14-3-3zeta. Furthermore, the Cas-14-3-3zeta interaction was found to be regulated by integrin-mediated cell adhesion. Thus, when cells are detached from the extracellular matrix, the binding of Cas to 14-3-3zeta is greatly diminished, whereas replating the cells onto fibronectin rapidly induces the association. Consistent with these results, we found that the subcellular localization of Cas and 14-3-3 is also regulated by integrin ligand binding and that the two proteins display a significant co-localization during cell attachment to the extracellular matrix. In conclusion, our results demonstrate that 14-3-3 proteins participate in integrin-activated signaling pathways through their interaction with Cas, which, in turn, may contribute to important biological responses regulated by cell adhesion to the extracellular matrix.

The adaptor protein Crk connects multiple cellular stimuli to the JNK signaling pathway

c-Jun N-terminal kinases (JNKs) are potently activated by a number of cellular stimuli. Small GTPases, in particular Rac, are responsible for initiating the activation of the JNK pathways. So far, the signals leading from extracellular stimuli to the activation of Rac have remained elusive. Recent studies have demonstrated that the Src homology 2 (SH2)- and Src homology 3 (SH3)-containing adaptor protein Crk is capable of activating JNK when ectopically expressed. We found here that transient expression of Crk induces JNK activation, and this activation was dependent on both the SH2- and SH3-domains of Crk. Expression of p130(Cas) (Cas), a major binding protein for the Crk SH2-domain, also induced JNK activation, which was blocked by the SH2-mutant of Crk. JNK activation by Cas and Crk was effectively blocked by a dominant-negative form of Rac, suggesting for a linear pathway from the Cas-Crk-complex to the Rac-JNK activation. Many of the stimuli that activate the Rac-JNK pathway enhance engagement of the Crk SH2-domain. JNK activation by these stimuli, such as epidermal growth factor, integrin ligand binding and v-Src, was efficiently blocked by dominant-negative mutants of Crk. A dominant-negative form of Cas in turn blocked the integrin-, but not epidermal growth factor - nor v-Src-mediated JNK activation. Together, these results demonstrate an important role for Crk in connecting multiple cellular stimuli to the Rac-JNK pathway, and a role for the Cas-Crk complex in integrin-mediated JNK activation.

Molecular characterization and pharmacological properties of the human P2X3 purinoceptor

Using PCR and library screening techniques, a cDNA encoding an ATP ligand-gated channel has been isolated from human heart. The full-length cDNA encodes a protein 397 amino acids long which shows a high amino-acid sequence identity with the rat P2X3 purinoceptor (93%). By fluorescence in situ hybridization, the human P2X3 gene has been mapped to region q12 of chromosome 11. Tissue distribution analysis of human P2X3 receptor mRNA shows a restricted expression pattern, i.e. transcripts are limited to the spinal cord and heart. This result contrasts with the distribution of the rat P2X3 receptor which was detected exclusively in sensory neurons of trigeminal, dorsal root and nodose ganglia. Heterologous expression of human P2X3 cRNA in Xenopus oocytes generates a fast desensitizing ATP-activated channel with pharmacological properties resembling the profile of the rat homologue receptor. Thus, the order of agonist potency is 2MeSATP > ATP > alphabeta-meATP > CTP > betagamma-meATP approximately ADP. Moreover, ATP-evoked currents on human P2X3 receptor are efficiently blocked in a reversible manner by the purinoceptor antagonists, suramin and PPADS.

Characterization of recombinant human P2X4 receptor reveals pharmacological differences to the rat homologue

We isolated a cDNA from human brain encoding a purinergic receptor that shows a high degree of homology to the rat P2X4 receptor (87% identity). By fluorescence in situ hybridization, the human P2X4 gene has been mapped to region q24.32 of chromosome 12. Tissue distribution analysis of human P2X4 transcripts demonstrates a broad expression pattern in that the mRNA was detected not only in brain but also in all tissues tested. Heterologous expression of the human P2X4 receptor in Xenopus laevis oocytes and human embryonic kidney 293 cells evoked an ATP-activated channel. Simultaneous whole-cell current and Fura-2 fluorescence measurements in human embronic kidney 293 cells transfected with human P2X4 cDNA allowed us to determine the fraction of the current carried by Ca2: this was approximately 8%, demonstrating a high Ca2+ permeability. Low extracellular Zn2+ concentrations (5-10 microM) increase the apparent gating efficiency of human P2X4 by ATP without affecting the maximal response. However, raising the concentration of the divalent cation (> 100 microM) inhibits the ATP-evoked current in a non-voltage-dependent manner. The human P2X4 receptor displays a very similar agonist potency profile to that of rat P2X4 (ATP > > 2-methylthio-ATP > or = CTP > alpha, beta-methylene-ATP > dATP) but has a notably higher sensitivity for the antagonists suramin, pyridoxal-phosphate-6-azophenyl-2',4'-disulfonic acid, and bromphenol blue. Chimeric constructs between human and rat isoforms as well as single-point mutations were engineered to map the regions responsible for the different sensitivity to suramin and pyridoxal-phosphate-6-azophenyl-2'4'-disulfonic acid.

Molecular cloning and functional expression of a novel rat heart P2X purinoceptor

Here we describe a novel purinergic receptor, the P2X5 receptor, cloned from rat heart. The full-length cDNA encodes a protein 455 amino acids long which shares an overall identity of 40-47% with other members of the P2X purinergic receptor family. P2X5 mRNA transcripts are found predominantly in rat heart but are also present in brain, spinal cord and adrenal gland. Functional expression of the recombinant receptor in HEK-293 cells shows a current that resembles mostly the P2X2 phenotype: the ATP-activated current reveals little agonist desensitization, is not activated by alpha,beta-meATP and is completely blocked by suramin and PPADS.

Cloning and tissue distribution of a novel P2X receptor from rat brain

We have isolated the cDNA for a novel member (P2X6) of the ATP-gated ion channel family. The rat P2X6 nucleotide sequence encodes a 379 amino acid protein that conserves all the structural features of previously cloned P2X receptors, including the two putative transmembrane domains predicted by hydrophobicity plots. In situ hybridization analysis of rat brain sections showed a wide pattern of mRNA expression that is virtually identical to that already described for P2X4. Injection of P2X6 cRNA in Xenopus oocytes did not give rise to ATP-activated channels. Coexpression of P2X6 with P2X4 subunits produced currents which were not discernibly different from those of P2X4 expressed alone.

P2X4: an ATP-activated ionotropic receptor cloned from rat brain

Extracellular ATP exerts pronounced biological actions in virtually every organ or tissue that has been studied. In the central and peripheral nervous system, ATP acts as a fast excitatory transmitter in certain synaptic pathways [Evans, R.J., Derkach, V. & Surprenant, A. (1992) Nature (London) 357, 503-505; Edwards, F.A., Gigg, A.J. & Colquhoun, D. (1992) Nature (London) 359, 144-147]. Here, we report the cloning and characterization of complementary DNA from rat brain, encoding an additional member (P2X4) of the emerging multigenic family of ligand-gated ATP channels, the P2X receptors. Expression in Xenopus oocytes gives an ATP-activated cation-selective channel that is highly permeable to Ca2+ and whose sensitivity is modulated by extracellular Zn2+. Surprisingly, the current elicited by ATP is almost insensitive to the common P2X antagonist suramin. In situ hybridization reveals the expression of P2X4 mRNA in central nervous system neurons. Northern blot and reverse transcription-PCR (RT-PCR) analysis demonstrate a wide distribution of P2X4 transcripts in various tissues, including blood vessels and leukocytes. This suggests that the P2X4 receptor might mediate not only ATP-dependent synaptic transmission in the central nervous system but also a wide repertoire of biological responses in diverse tissues.