Immunogenic cancer cell death selectively induced by near infrared photoimmunotherapy initiates host tumor immunity

A Wearable Fiberless Optical Sensor for Continuous Monitoring of Cerebral Blood Flow in Mice

Continuous and longitudinal monitoring of cerebral blood flow (CBF) in animal models provides information for studying the mechanisms and interventions of various cerebral diseases. Since anesthesia may affect brain hemodynamics, researchers have been seeking wearable devices for use in conscious animals. We present a wearable diffuse speckle contrast flowmeter (DSCF) probe for monitoring CBF variations in mice. The DSCF probe consists of a small low-power near-infrared laser diode as a point source and an ultra-small low-power CMOS camera as a 2D detector array, which can be affixed on a mouse head. The movement of red blood cells in brain cortex (i.e., CBF) produces spatial fluctuations of laser speckles, which are captured by the camera. The DSCF system was calibrated using tissue phantoms and validated in a human forearm and mouse brains for continuous monitoring of blood flow increases and decreases against the established technologies. Significant correlations were observed among these measurements (R² ≥ 0.80, p < 10^-5). This small fiberless probe has the potential to be worn by a freely moving conscious mouse. Moreover, the flexible source-detector configuration allows for varied probing depths up to ~8 mm, which is sufficient for transcranially detecting CBF in the cortices of rodents and newborn infants.

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 IgG_2b 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 2^nd 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.

Photothermal Ablation of Cancer Cells by Albumin-Modified Gold Nanorods and Activation of Dendritic Cells

Nanoparticle-mediated photothermal therapy has been widely studied for cancer treatment. It is important to disclose how photothermally ablated tumor cells trigger immune responses. In this study, bovine serum albumin (BSA)-coated gold nanorods (BSA-coated AuNRs) were prepared and used for photothermal ablation of breast tumor cells. The BSA-coated AuNRs showed high photothermal conversion efficiency and good photothermal ablation effect towards tumor cells. The ablated tumor cells were co-cultured with immature dendritic cells (DCs) through a direct cell contacting model and diffusion model to confirm the stimulatory effects of cell⁻cell interaction and soluble factors released from ablated tumor cells. The results indicated that photothermally ablated tumor cells induced immune-stimulatory responses of DCs through both cell⁻cell interaction and soluble factors. The results should be useful for synergistic photothermal-immunotherapy of primary and metastatic cancer.

Photoinduced Ligand Release from a Silicon Phthalocyanine Dye Conjugated with Monoclonal Antibodies: A Mechanism of Cancer Cell Cytotoxicity after Near-Infrared Photoimmunotherapy

Photochemical reactions can dramatically alter physical characteristics of reacted molecules. In this study, we demonstrate that near-infrared (NIR) light induces an axial ligand-releasing reaction, which dramatically alters hydrophilicity of a silicon phthalocyanine derivative (IR700) dye leading to a change in the shape of the conjugate and its propensity to aggregate in aqueous solution. This photochemical reaction is proposed as a major mechanism of cell death induced by NIR photoimmunotherapy (NIR-PIT), which was recently developed as a molecularly targeted cancer therapy. Once the antibody-IR700 conjugate is bound to its target, activation by NIR light causes physical changes in the shape of antibody antigen complexes that are thought to induce physical stress within the cellular membrane leading to increases in transmembrane water flow that eventually lead to cell bursting and necrotic cell death.

Sacrificial template-based synthetic approach of polypyrrole hollow fibers for photothermal therapy

In the present work, polypyrrole hollow fibers (PPy-HFs) were fabricated by sacrificial removal of soft templates of electrospun polycaprolactone (PCL) fibers with polypyrrole (PPy) coating through chemical polymerization of pyrrole monomer. Different physicochemical properties of as-fabricated PPy-HFs were then studied by Field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), Fourier transform infra-red (FT-IR) spectroscopy, Differential scanning calorimetry/Thermogravimetric analysis (DSC/TGA), and X-ray photoelectron spectroscopy (XPS). The photothermal activity of PPy-HF was studied by irradiating 808-nm near infra-red (NIR) light under different power values with various concentrations of PPy-HFs dispersed in phosphate buffer solution (PBS, pH 7.4). These PPy-HFs exhibited enhanced photothermal performance compared with polypyrrole nanoparticles (PPy-NPs). Furthermore, these PPy-HFs showed photothermal effect that was laser-power- and concentration-dependent. The photothermal toxicity of the resulting nanofiber was evaluated using cell counting kit-8 (CCK-8) and live and dead cell assays. Results showed that these PPy-HFs were more effective in killing cancer cells under NIR irradiation. In contrast, hollow-fiber showed no cytotoxicity without NIR exposure. Among different nanofiber formulations, PPy-160 exhibited the highest photothermal toxicity. It could be explained by its enhanced photothermal performance compared to other specimens. The resulting PPy-HFs showed superior drug-loading capacity to PPy-NPs. This might be attributed to adequate binding of the drug into both luminal and abluminal hollow-fiber surfaces. Fabrication of this substrate type opens a promising new avenue for architectural design of biocompatible organic polymer for biomedical field.

Near Infrared Photoimmunotherapy with Combined Exposure of External and Interstitial Light Sources

Near infrared photoimmunotherapy (NIR-PIT) is a new target-cell-specific cancer treatment that induces highly selective necrotic/immunogenic cell death after systemic administration of a photoabsorber antibody conjugate and subsequent NIR light exposure. However, the depth of NIR light penetration in tissue (approximately 2 cm) with external light sources limits the therapeutic effects of NIR-PIT. Interstitial light exposure using cylindrical diffusing optical fibers can overcome this limitation. The purpose in this study was to compare three NIR light delivery methods for treating tumors with NIR-PIT using a NIR laser system at an identical light energy; external exposure alone, interstitial exposure alone, and the combination. Panitumumab conjugated with the photoabsorber IRDye-700DX (pan-IR700) was intravenously administered to mice with A431-luc xenografts which are epithelial growth factor receptor (EGFR) positive. One and 2 days later, NIR light was administered to the tumors using one of three methods. Interstitial exposure alone and in combination with external sources showed the greatest decrease in bioluminescence signal intensity. Additionally, the combination of external and interstitial NIR light exposure showed significantly greater tumor size reduction and prolonged survival after NIR-PIT compared to external exposure alone. This result suggested that the combination of external and interstitial NIR light exposure was more effective than externally applied light alone. Although external exposure is the least invasive means of delivering light, the combination of external and interstitial exposures produces superior therapeutic efficacy in tumors greater than 2 cm in depth from the tissue surface.

Nanomaterials for modulating innate immune cells in cancer immunotherapy

Cancer immunotherapy has been intensively investigated in both preclinical and clinical studies. Whereas chemotherapies use cytotoxic drugs to kill tumor cells, cancer immunotherapy is based on the ability of the immune system to fight cancer. Tumors are intimately associated with the immune system: they can suppress the immune response and/or control immune cells to support tumor growth. Immunotherapy has yielded promising results in clinical practice, but some patients show limited responses. This may reflect the complexities of the relationship between a tumor and the immune system. In an effort to improve the current immunotherapies, researchers have exploited nanomaterials in creating new strategies to cure tumors via modulation of the immune system in tumor tissues. Although extensive studies have examined the use of immune checkpoint-based immunotherapy, rather less work has focused on manipulating the innate immune cells. This review examines the recent approaches and challenges in the use of nanomaterials to modulate innate immune cells.

In Vivo Molecular Imaging for Biomedical Analysis and Therapies

In vivo molecular imaging is a powerful tool to analyze the human body. Precision medicine is receiving high attention these days, and molecular imaging plays an important role as companion diagnostics in precision medicine. Nuclear imaging with PET or SPECT and optical imaging technologies are used for in vivo molecular imaging. Nuclear imaging is superior for quantitative imaging, and whole-body analysis is possible even for humans. Optical imaging is superior due to its ease of use, and highly targeted specific imaging is possible with activatable agents. However, with optical imaging using fluorescence, it is difficult to obtain a signal from deep tissue and quantitation is difficult due to the attenuation and scattering of the fluorescent signal. Recently, to overcome these issues, optoacoustic imaging has been used in in vivo imaging. In this article, we review in vivo molecular imaging with nuclear and optical imaging and discuss their utility for precision medicine.

Combination of NIR therapy and regulatory T cell modulation using layer-by-layer hybrid nanoparticles for effective cancer photoimmunotherapy

The efficacy of combined near-infrared (NIR) and immune therapies for inhibiting tumor growth and recurrence has gained increasing research attention. Regulatory T cells in the tumor microenvironment constitute a major obstacle in achieving robust CD8⁺ T cell antitumor immunotherapy. In the present study, we designed a photoimmunotherapy-based strategy involving a combination of photothermal and photodynamic therapies, followed by Treg cell suppression, for eliciting an immune response with IR-780- and imatinib-loaded layer-by-layer hybrid nanoparticles. Methods: The layer-by-layer hybrid nanoparticles were prepared through electrostatic interactions. Their photothermal effect, photodynamic effect as well as their effect on inhibiting Treg cells' suppressive function were investigated in vitro and in vivo. Their antitumor effect was evaluated using B16/BL6 and MC-38 tumor-bearing mice. Results: The layer-by-layer hybrid nanoparticles, which were pH-sensitive, enabled the release of IR-780 dye for NIR-induced photothermal and photodynamic effects, and the release of imatinib-loaded glucocorticoid-induced TNF receptor family-related protein/poly(lactic-co-glycolic acid) (GITR-PLGA) nanoparticles to initiate antitumor immunotherapy. The photothermal and photodynamic effects caused by IR-780 under NIR exposure resulted in direct tumor apoptosis/necrosis and the production of tumor-associated antigen, promoted dendritic cell maturation, and enhanced the presentation of tumor-associated antigen to T cells, while the imatinib-loaded GITR-PLGA cores reduced the suppressive function of Treg cells, and consequently activated effective CD8⁺ T cells towards tumors. Conclusion: With the significant photothermal, photodynamic and immunotherapies, the system successfully eradicated tumor growth, diminished tumor recurrence, and improved survival in vivo. The proposed nanoparticles provide a novel and versatile approach to boost antitumor photoimmunotherapy.

Changes in plasma membrane damage inducing cell death after treatment with near-infrared photoimmunotherapy

Near‐infrared photoimmunotherapy (NIR‐PIT) is a new cancer phototherapy modality using an antibody conjugated to a photosensitizer, IRDye700DX. When the conjugate binds to the plasma membrane and is exposed to NIR light, NIR‐PIT‐treated cells undergo swelling, and target‐selective necrotic/immunogenic cell death is induced. However, the cytotoxic mechanism of NIR‐PIT has not been elucidated. In order to understand the mechanism, it is important to elucidate how the damage to the plasma membrane induced by NIR light irradiation changes over time. Thus, in the present study, we investigated the changes in plasma membrane permeability using ions and molecules of various sizes. Na⁺ flowed into cells immediately after NIR light irradiation, even when the function of transporters or channels was blocked. Subsequently, fluorescent molecules larger than Na⁺ entered the cells, but the damage was not large enough for dextran to pass through at early time points. To assess these phenomena quantitatively, membrane permeability was estimated using radiolabeled ions and molecules: ¹¹¹InCl₃, ¹¹¹In‐DTPA, and ³H‐H₂O, and comparable results were obtained. Although minute plasma membrane perforations usually do not induce cell death, our results suggest that the minute damage induced by NIR‐PIT was irreversibly extended with time. In conclusion, minute plasma membrane damage is a trigger for the increase in plasma membrane permeability, cell swelling, and necrotic/immunogenic cell death in NIR‐PIT. Our findings provide new insight into the cytotoxic mechanism of NIR‐PIT.

Near-infrared photoimmunotherapy targeting EGFR-Shedding new light on glioblastoma treatment

Glioblastomas (GBMs) are high-grade brain tumors, differentially driven by alterations (amplification, deletion or missense mutations) in the epidermal growth factor receptor (EGFR), that carry a poor prognosis of just 12-15 months following standard therapy. A combination of interventions targeting tumor-specific cell surface regulators along with convergent downstream signaling pathways may enhance treatment efficacy. Against this background, we investigated a novel photoimmunotherapy approach combining the cytotoxicity of photodynamic therapy with the specificity of immunotherapy. An EGFR-specific affibody (ZEGFR:03115 ) was conjugated to the phthalocyanine dye, IR700DX, which when excited with near-infrared light produces a cytotoxic response. ZEGFR:03115 -IR700DX EGFR-specific binding was confirmed by flow cytometry and confocal microscopy. The conjugate showed effective targeting of EGFR positive GBM cells in the brain. The therapeutic potential of the conjugate was assessed both in vitro, in GBM cell lines and spheroids by the CellTiter-Glo® assay, and in vivo using subcutaneous U87-MGvIII xenografts. In addition, mice were imaged pre- and post-PIT using the IVIS/Spectrum/CT to monitor treatment response. Binding of the conjugate correlated to the level of EGFR expression in GBM cell lines. The cell proliferation assay revealed a receptor-dependent response between the tested cell lines. Inhibition of EGFRvIII+ve tumor growth was observed following administration of the immunoconjugate and irradiation. Importantly, this response was not seen in control tumors. In conclusion, the ZEGFR:03115 -IR700DX showed specific uptake in vitro and enabled imaging of EGFR expression in the orthotopic brain tumor model. Moreover, the proof-of-concept in vivo PIT study demonstrated therapeutic efficacy of the conjugate in subcutaneous glioma xenografts.

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.

3D mesoscopic fluorescence tomography for imaging micro-distribution of antibody-photon absorber conjugates during near infrared photoimmunotherapy in vivo

As a novel low-side-effect cancer therapy, photo-immunotherapy (PIT) is based on conjugating monoclonal antibody (mAb) with a near-infrared (NIR) phthalocyanine dye IRDye700DX (IR 700). IR700 is not only fluorescent to be used as an imaging agent, but also phototoxic. When illuminating with NIR light, PIT can induce highly-selective cancer cell death while leaving most of tumor blood vessels unharmed, leading to an effect termed super-enhanced permeability and retention (SUPR), which can significantly improve the effectiveness of anti-cancer drug. Currently, the therapeutic effects of PIT are monitored using 2D macroscopic fluorescence reflectance imager, which lacks the resolution and depth information to reveal the 3D distribution of mAb-IR700. In the study, we applied a multi-modal optical imaging approach including high-resolution optical coherence tomography (OCT) and high-sensitivity fluorescence laminar optical tomography (FLOT), to provide 3D tumor micro-structure and micro-distribution of mAb-IR700 in the tumor simultaneously during PIT in situ and in vivo. The multi-wavelength FLOT can also provide the blood vessels morphology of the tumor. Thus, the 3D FLOT reconstructed images allow us to evaluate the IR700 fluorescence distribution change with respect to the blood vessels and at different tumor locations/depths non-invasively, thereby enabling evaluation of the therapeutic effects in vivo and optimization of treatment regimens accordingly. The mAb-IR700 can access more tumor areas after PIT treatment, which can be explained by increased vascular permeability immediately after NIR-PIT. Two-photon microscopy was also used to record the mAb-IR700 on the tumor surface near the blood vessels to verify the results.

Near infrared photoimmunotherapy targeting bladder cancer with a canine anti-epidermal growth factor receptor (EGFR) antibody

Anti-epidermal growth factor receptor (EGFR) antibody therapy is used in EGFR expressing cancers including lung, colon, head and neck, and bladder cancers, however results have been modest. Near infrared photoimmunotherapy (NIR-PIT) is a highly selective tumor treatment that employs an antibody-photo-absorber conjugate which is activated by NIR light. NIR-PIT is in clinical trials in patients with recurrent head and neck cancers using cetuximab-IR700 as the conjugate. However, its use has otherwise been restricted to mouse models. This is an effort to explore larger animal models with NIR-PIT. We describe the use of a recombinant canine anti-EGFR monoclonal antibody (mAb), can225IgG, conjugated to the photo-absorber, IR700DX, in three EGFR expressing canine transitional cell carcinoma (TCC) cell lines as a prelude to possible canine clinical studies. Can225-IR700 conjugate showed specific binding and cell-specific killing after NIR-PIT on EGFR expressing cells in vitro. In the in vivo study, can225-IR700 conjugate demonstrated accumulation of the fluorescent conjugate with high tumor-to-background ratio. Tumor-bearing mice were separated into 4 groups: (1) no treatment; (2) 100 µg of can225-IR700 i.v. only; (3) NIR light exposure only; (4) 100 µg of can225-IR700 i.v., NIR light exposure. Tumor growth was significantly inhibited by NIR-PIT treatment compared with the other groups (p < 0.001), and significantly prolonged survival was achieved (p < 0.001 vs. other groups) in the treatment groups. In conclusion, NIR-PIT with can225-IR700 is a promising treatment for canine EGFR-expressing cancers, including invasive transitional cell carcinoma in pet dogs, that could provide a pathway to translation to humans.

A Novel Theranostic Combination of Near-infrared Fluorescence Imaging and Laser Irradiation Targeting c-KIT for Gastrointestinal Stromal Tumors

It is difficult to distinguish gastrointestinal stromal tumors (GISTs) from other types of submucosal tumors under conventional gastrointestinal endoscopy. We aimed to detect GISTs by molecular fluorescence imaging using a near-infrared (NIR) photosensitizer (IR700)-conjugated anti-c-KIT antibody and to treat GISTs by photoimmunotherapy with NIR irradiation as a non-invasive theranostic procedure. We also investigated the therapeutic mechanisms. Methods: Human GIST cell lines GIST-T1 and GIST-882M were incubated with IR700-conjugated anti-c-KIT antibody, IR700-12A8, and observed by confocal laser microscopy. Mice with GIST-T1 xenografts or rats with orthotopic xenografts were injected with IR700-12A8 or AF488-conjugated antibody, and observed under IVIS or autofluorescence imaging (AFI) endoscopy. GIST cells were treated with IR700-12A8 and NIR light in vitro and vivo, and cell viability, histology and apoptosis were evaluated. Results: Strong red fluorescence of IR700-12A8 was observed on the cell membrane of GIST cells and was gradually internalized into the cytoplasm. Tumor-specific accumulation of IR700-12A8 was observed in GIST-T1 xenografts in mice. Under AFI endoscopy, a strong fluorescence signal was observed in orthotopic GIST xenografts in rats through the normal mucosa covering the tumor. The percentage of dead cells significantly increased in a light-dose-dependent manner and both acute necrotic and late apoptotic cell death was observed with annexin/PI staining. Cleaved PARP expression was significantly increased after IR700-12A8-mediated NIR irradiation, which was almost completely reversed by NaN₃. All xenograft tumors (7/7) immediately regressed and 4/7 tumors completely disappeared after IR700-12A8-mediated NIR irradiation. Histologic assessment and TUNEL staining revealed apoptosis in the tumors. Conclusion: NIR fluorescence imaging using IR700-12A8 and subsequent NIR irradiation could be a very effective theranostic technology for GIST, the underlying mechanism of which appears to involve acute necrosis and supposedly late apoptosis induced by singlet oxygen.

Near-infrared photoimmunotherapy: a comparison of light dosing schedules

Near infrared photoimmunotherapy (NIR-PIT) is a newly-developed cancer therapy in which a monoclonal antibody is conjugated to a near-infrared photoabsorber, IR700 to form an antibody photoabsorber conjugate (APC). After the APC binds to cancer cells expressing the cognate antigen, exposure to NIR light results in rapid, highly selective necrotic cell death of the cancer cells with minimal off-target effects. Several hours after NIR-PIT, the tumor vessels become supraphysiologically permeable and circulating APC can therefore readily leak into the already-treated tumor space where it can bind with viable cancer cells that is called super-enhanced permeability and retention effect. The presence of the SUPR effect after NIR-PIT has prompted regimens in which there is a repeat exposure of NIR light 24 hours after the initial NIR-PIT to take advantage of the leakage of additional APC deeper into the tumor. However, this post-treatment APC penetration was fully induced within 3 hours, therefore, it is possible that repeated exposures of NIR light could be administered much earlier than 24 hours and still produce the same effects. To test this idea, we compared several modes of delivering additional doses of light after initial NIR-PIT. We found that repeated exposures of NIR light starting 3 hours after initial NIR-PIT produced equal or superior results to more delayed exposures of NIR light. This finding has practical implications of an easy-to-perform regimen as repeated light exposures could be performed during a single day rather than extending the procedure over two days which is the current recommendation.

Molecular imaging of tumor photoimmunotherapy: Evidence of photosensitized tumor necrosis and hemodynamic changes

Near-infrared photoimmunotherapy (NIR PIT) employs the photoabsorbing dye IR700 conjugated to antibodies specific for cell surface epidermal growth factor receptor (EGFR). NIR PIT has shown highly selective cytotoxicity in vitro and in vivo. Cell necrosis is thought to be the main mode of cytotoxicity based mainly on in vitro studies. To better understand the acute effects of NIR PIT, molecular imaging studies were performed to assess its cellular and vascular effects. In addition to in vitro studies for cytotoxicity of NIR PIT, the in vivo tumoricidal effects and hemodynamic changes induced by NIR PIT were evaluated by ¹³C MRI using hyperpolarized [1,4-¹³C₂] fumarate, R₂* mapping from T₂*-weighted MRI, and photoacoustic imaging. In vitro studies confirmed that NIR PIT resulted in rapid cell death via membrane damage, with evidence for rapid cell expansion followed by membrane rupture. Following NIR PIT, metabolic MRI using hyperpolarized fumarate showed the production of malate in EGFR-expressing A431 tumor xenografts, providing direct evidence for photosensitized tumor necrosis induced by NIR PIT. R₂* mapping studies showed temporal changes in oxygenation, with an accompanying increase of deoxyhemoglobin at the start of light exposure followed by a sustained decrease after cessation of light exposure. This result suggests a rapid decrease of blood flow in EGFR-expressing A431 tumor xenografts, which is supported by the results of the photoacoustic imaging experiments. Our findings suggest NIR PIT mediates necrosis and hemodynamic changes in tumors by photosensitized oxidation pathways and that these imaging modalities, once translated, may be useful in monitoring clinical treatment response.

An Infrared Dye-Conjugated Virus-like Particle for the Treatment of Primary Uveal Melanoma

The work outlined herein describes AU-011, a novel recombinant papillomavirus-like particle (VLP) drug conjugate and its initial evaluation as a potential treatment for primary uveal melanoma. The VLP is conjugated with a phthalocyanine photosensitizer, IRDye 700DX, that exerts its cytotoxic effect through photoactivation with a near-infrared laser. We assessed the anticancer properties of AU-011 in vitro utilizing a panel of human cancer cell lines and in vivo using murine subcutaneous and rabbit orthotopic xenograft models of uveal melanoma. The specificity of VLP binding (tumor targeting), mediated through cell surface heparan sulfate proteoglycans (HSPG), was assessed using HSPG-deficient cells and by inclusion of heparin in in vitro studies. Our results provide evidence of potent and selective anticancer activity, both in vitro and in vivo AU-011 activity was blocked by inhibiting its association with HSPG using heparin and using cells lacking surface HSPG, indicating that the tumor tropism of the VLP was not affected by dye conjugation and cell association is critical for AU-011-mediated cytotoxicity. Using the uveal melanoma xenograft models, we observed tumor uptake following intravenous (murine) and intravitreal (rabbit) administration and, after photoactivation, potent dose-dependent tumor responses. Furthermore, in the rabbit orthotopic model, which closely models uveal melanoma as it presents in the clinic, tumor treatment spared the retina and adjacent ocular structures. Our results support further clinical development of this novel therapeutic modality that might transform visual outcomes and provide a targeted therapy for the early-stage treatment of patients with this rare and life-threatening disease. Mol Cancer Ther; 17(2); 565-74. ©2017 AACR.

Molecularly Targeted Cancer Combination Therapy with Near-Infrared Photoimmunotherapy and Near-Infrared Photorelease with Duocarmycin-Antibody Conjugate

Near-infrared photoimmunotherapy (NIR-PIT) is a highly selective tumor treatment that uses an antibody-photoabsorber conjugate (APC). However, the effect of NIR-PIT can be enhanced when combined with other therapies. NIR photocaging groups, based on the heptamethine cyanine scaffold, have been developed to release bioactive molecules near targets after exposure to light. Here, we investigated the combination of NIR-PIT using panitumumab-IR700 (pan-IR700) and the NIR-releasing compound, CyEt-panitumumab-duocarmycin (CyEt-Pan-Duo). Both pan-IR700 and CyEt-Pan-Duo showed specific binding to the EGFR-expressing MDAMB468 cell line in vitro In in vivo studies, additional injection of CyEt-Pan-Duo immediately after NIR light exposure resulted in high tumor accumulation and high tumor-background ratio. To evaluate the effects of combination therapy in vivo, tumor-bearing mice were separated into 4 groups: (i) control, (ii NIR-PIT, (iii) NIR-release, (iv) combination of NIR-PIT and NIR-release. Tumor growth was significantly inhibited in all treatment groups compared with the control group (P < 0.05), and significantly prolonged survival was achieved (P < 0.05 vs. control). The greatest therapeutic effect was shown with NIR-PIT and NIR-release combination therapy. In conclusion, combination therapy of NIR-PIT and NIR-release enhanced the therapeutic effects compared with either NIR-PIT or NIR-release therapy alone. Mol Cancer Ther; 17(3); 661-70. ©2017 AACR.

Evaluation of Early Therapeutic Effects after Near-Infrared Photoimmunotherapy (NIR-PIT) Using Luciferase-Luciferin Photon-Counting and Fluorescence Imaging

Near-infrared photoimmunotherapy (NIR-PIT) is a newly developed cancer treatment that induces highly selective immunogenic cell death. It is based on an antibody-photoabsorber conjugate (APC) that is activated by NIR light. The purpose of this study was to investigate the effects of NIR-PIT as measured by luciferase-luciferin photon-counting and fluorescence imaging. Six days after subcutaneous injection of A431-luc-GFP cells tumors formed in a xenograft mouse model. The EGFR-targeting antibody, panitumumab, was conjugated to the photoabsorber, IRDye-700DX (pan-IR700), and was intravenously administered to tumor-bearing mice. Serial luciferase-luciferin photon-counting images and both green fluorescent protein (GFP) and IR700 fluorescence images were obtained from the same mice before and after NIR-PIT treatment (0, 10, 20, 30 min (early phase), and 24, 48 h (late phase) after NIR light exposure). Optical signal intensities were compared for each modality. IR700 fluorescence and luciferase-luciferin photon-counting images showed decreased intensities in both the early and late phases after NIR-PIT (p < 0.01). On the other hand, GFP fluorescence images showed decreased intensities only in the late phase (p < 0.01). In the early phase, GFP fluorescence images showed smaller intensity reductions compared to IR700 fluorescence and luciferase-luciferin photon-counting (p < 0.01), while in the late phase, IR700 fluorescence showed smaller intensity reductions than luciferase-luciferin photon-counting and GFP fluorescence (p < 0.05), due to redistribution of pan-IR700 within the tumor bed. In conclusion, luciferase-luciferin photon-counting imaging is suitable to evaluate early phase NIR-PIT effects, while both luciferase-luciferin photon-counting and GFP reflected later phase effects.

Dynamic changes in the cell membrane on three dimensional low coherent quantitative phase microscopy (3D LC-QPM) after treatment with the near infrared photoimmunotherapy

Near infrared photoimmunotherapy (NIR-PIT) is a newly developed cancer therapy that relies on the binding of a near-infrared antibody photoabsorber conjugate (APC) to a cancer cell. Subsequent exposure to NIR light selectively induces rapid necrotic cell death on target-expressing cells with minimal off-target effects. When treated with NIR-PIT, targeted cells become swollen, develop blebs and burst within minutes of light exposure. Detailed spatial and temporal morphological changes of the cellular membrane of targeted cells treated with NIR-PIT have not been fully explored with state-of-the-art microscopic methods. In this study, we investigated the morphologic and kinetic effects of PIT on two types of cells, a spindle-shaped 3T3/Her cell and a spheric-shaped MDA-MB468 cell, after NIR-PIT using three-dimensional low-coherent quantitative phase microscopy (3D LC-QPM). Adhesive cells treated with NIR-PIT demonstrated region-specific cell membrane rupture occurring first on the distal free edge of the cell near the site of adhesion, in a process that was independent of cell shape. The results show that the peripheral portions of the cell membrane near the site of adhesion are particularly vulnerable to the effects of NIR-PIT, likely because these sites exhibit higher baseline surface tension.

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

Oral cavity squamous cell carcinoma (OSCC) is considered one of the most aggressive subtypes of cancer. Anti-CD44 monoclonal antibodies (mAb) are a potential therapy against CD44 expressing OSCC; however, to date the therapeutic effects have been disappointing. Here, a new cancer treatment is described, near-infrared photoimmunotherapy (NIR-PIT), that uses anti-CD44 mAbs conjugated to the photoabsorber IR700DX. This conjugate is injected into mice harboring one of three CD44 expressing syngeneic murine oral cancer cell (MOC) lines, MOC1 (immunogenic), MOC2 mKate2 (moderately immunogenic), and MOC2-luc (poorly immunogenic). Binding of the anti-CD44-IR700 conjugate was shown to be specific and cell-specific cytotoxicity was observed after exposure of the cells to NIR light in vitro The anti-CD44-IR700 conjugate, when assessed in vivo, demonstrated deposition within the tumor with a high tumor-to-background ratio. Tumor-bearing mice were separated into four cohorts: no treatment; 100 μg of anti-CD44-IR700 i.v. only; NIR light exposure only; and 100 μg of anti-CD44-IR700 i.v. with NIR light exposure. NIR-PIT therapy, compared with the other groups, significantly inhibited tumor growth and prolonged survival in all three cell model systems. In conclusion, these data reveal that anti-CD44 antibodies are suitable as mAb-photoabsorber conjugates for NIR-PIT in MOC cells.Implications: This study using syngeneic mouse models, which better model the disease in humans than conventional xenografts, suggests that NIR-PIT with anti-CD44-IR700 is a potential candidate for the treatment of OSCC. Mol Cancer Res; 15(12); 1667-77. ©2017 AACR.

Avoiding thermal injury during near-infrared photoimmunotherapy (NIR-PIT): the importance of NIR light power density

Near-infrared photoimmunotherapy (NIR-PIT) is a newly-established cancer treatment which employs the combination of an antibody-photoabsorber conjugate (APC) and NIR light. When NIR light is absorbed by APC-bound tissues, a certain amount of heat is generated locally. For the most part this results in a subclinical rise in skin temperature, however, excessive light exposure may cause non-specific thermal damage. In this study, we investigated the potential for thermal damage caused by NIR-PIT by measuring surface temperature. Two sources of light, laser and light emitting diode (LED), were compared in a mouse tumor model. First, we found that the skin was heated rapidly by NIR light regardless of whether laser or LED light sources were used. Air cooling at the surface reduced the rise in temperature. There were no associations between the rise of skin temperature and tumor volume of the treated tumor, or APC concentration. Second, we investigated the extent of thermal damage to the skin at various light doses. We detected burn injuries 1 day after NIR-PIT, when the NIR light was at a power density higher than 600 mW/cm². Successful treatments at lower power density could be achieved if the total light energy absorbed by the tumor was the same, i.e. by extending the duration of light exposure. In conclusion, this study demonstrates that thermal injury after NIR-PIT can be avoided by either employing a cooling system or by lowering the power density of the light source and prolonging the exposure time such that the total energy is constant. Thus, thermal damage is preventable side effect of NIR-PIT.

Applying near-infrared photoimmunotherapy to B-cell lymphoma: comparative evaluation with radioimmunotherapy in tumor xenografts

Objective

Radioimmunotherapy (RIT) has proven effective for patients with relapsed and refractory lymphoma. However, new types of therapy are strongly desired as B-cell lymphoma remains incurable for many patients. Photoimmunotherapy (PIT) is an emerging targeted cancer therapy that uses photosensitizer (IR700)-conjugated monoclonal antibodies (mAbs) to specifically kill cancer cells. To evaluate the usefulness and potential role of PIT for treating B-cell lymphoma in a comparison with RIT, we performed in vivo PIT and RIT studies with an IR700 or ⁹⁰Y-conjugated anti-CD20 mAb, NuB2.

Methods

IR700 or ⁹⁰Y were conjugated to NuB2. Since cell aggressiveness greatly affects the therapeutic effect, we selected both an indolent (RPMI 1788) and an aggressive (Ramos) type of B-cell lymphoma cell line. The in vitro therapeutic effect of PIT and the biodistribution profiles of IR700–NuB2 were evaluated. In vivo PIT and RIT studies were performed with 100 or 500 μg of IR700–NuB2 and 150 μCi/20 μg of ⁹⁰Y-NuB2, respectively, in two types of B-cell lymphoma-bearing mice.

Results

The in vitro studies revealed that Ramos was more sensitive than RPMI 1788 to PIT. The therapeutic effect of PIT with 500 µg IR700–NuB2 was superior to any other therapies against aggressive Ramos tumors, whereas RIT showed the highest therapeutic effect in indolent RPMI 1788 tumors. Since the uptake levels and intratumoral distribution of IR700–NuB2 were comparable in both tumors, a possible cause of this difference is the tumor growth rate. The PIT with 500 µg (IR700–NuB2) group showed a significantly greater therapeutic effect than the PIT with 100 µg group due to the higher and more homogeneous tumor distribution of IR700–NuB2.

Conclusions

PIT was effective for both indolent and aggressive B-cell lymphoma, and the higher dose provided a better therapeutic effect. In aggressive tumors, PIT was more effective than RIT. Thus, PIT would be a promising strategy for the locoregional treatment or control of B-cell lymphoma. Since PIT and RIT have distinctive advantages over each other, they could play complementary rather than competitive roles in B-cell lymphoma treatment.

Near-Infrared Photoimmunotherapy Targeting Prostate Cancer with Prostate-Specific Membrane Antigen (PSMA) Antibody

Prostate-specific membrane antigen (PSMA) is a membrane protein that is overexpressed manifold in prostate cancer and provides an attractive target for molecular therapy. Near-infrared photoimmunotherapy (NIR-PIT) is a highly selective tumor treatment that employs an antibody-photoabsorber conjugate (APC). Here, we describe the efficacy of NIR-PIT, using a fully human IgG₁ anti-PSMA monoclonal antibody (mAb), conjugated to the photoabsorber, IR700DX, in a PSMA-expressing PC3 prostate cancer cell line. Anti-PSMA-IR700 showed specific binding and cell-specific killing was observed after exposure of the cells to NIR light in vitro In the in vivo study, anti-PSMA-IR700 showed high tumor accumulation and high tumor-background ratio. Tumor-bearing mice were separated into 4 groups: (i) no treatment; (ii) 100 μg of anti-PSMA-IR700 i.v.; (iii) NIR light exposure; (iv) 100 μg of anti-PSMA-IR700 i.v., NIR light exposure was administered. These were performed every week for up to 3 weeks. Tumor growth was significantly inhibited by NIR-PIT treatment compared with the other control groups (P < 0.001), and significantly prolonged survival was achieved (P < 0.0001 vs. other control groups). More than two thirds of tumors were cured with NIR-PIT. In conclusion, the anti-PSMA antibody is suitable as an APC for NIR-PIT. Furthermore, NIR-PIT with the anti-PSMA-IR700 antibody is a promising candidate of the treatment of PSMA-expressing tumors and could be readily translated to humans.Implications: NIR-infrared photoimmunotherapy (NIR-PIT) using a fully human anti-PSMA-IR700 conjugate showed potential therapeutic effects against a PSMA-expressing prostate cancer that is readily translated to humans. Mol Cancer Res; 15(9); 1153-62. ©2017 AACR.

Cerenkov Radiation-Induced Photoimmunotherapy with 18F-FDG

Near-infrared photoimmunotherapy (NIR-PIT) is a new cancer treatment that combines the specificity of antibodies for targeting tumors with toxicity induced by photoabsorbers after irradiation with NIR light. A limitation of NIR-PIT is the inability to deliver NIR light to a tumor located deep inside the body. Cerenkov radiation (CR) is the ultraviolet and blue light that is produced by a charged particle traveling through a dielectric medium faster than the speed of light in that medium and is commonly produced during radioactive decay. Here, we demonstrate the feasibility of using CR generated by ¹⁸F-FDG accumulated in tumors to induce photoimmunotherapy. Methods: Using A431-luc cells, we evaluated the therapeutic effects of CR-PIT in vitro and in vivo using bioluminescence imaging. Results: CR-PIT showed significant suppression of tumor size, but the decrease of bioluminescence after CR-PIT was not observed consistently over the entire time course. Conclusion: Although CR-PIT can induce tumor killing deep within body, it is less effective than NIR-PIT, possibly related to the relatively lower efficiency of short wavelength light than NIR.

Near infrared photoimmunotherapy of B-cell lymphoma

Near infrared photoimmunotherapy (NIR-PIT) is a new, highly-selective cancer theranostics that employs an antibody-photo absorber conjugate (APC). NIR-PIT has successfully treated preclinical tumor models with APCs and is now in the first-in-human phase 1 clinical trial for head and neck cancer patients against EGFR. CD20 is highly expressed in many B-cell lymphomas and is emerging as a molecular target for this disease. Here, we describe the use of the anti-CD20 monoclonal antibody (mAb), rituximab-IR700 APC for NIR-PIT of B-cell lymphoma in two CD20-expressing lymphoma mouse models. CD20 expressing B-cell lymphoma cell lines (Daudi and Ramos) were used in this study. Rituximab-IR700, rituximab conjugated with IRDye700DX, showed specific binding, and cell-specific killing only after exposure of NIR light to both cells in vitro. To evaluate effects of NIR-PIT in vivo, tumor-bearing mice were separated into 4 groups: (1) control; (2) APC i.v. only; (3) NIR light exposure only; (4) APC and NIR light (NIR-PIT). These were performed every week for up to 3 weeks. Rituximab-IR700 showed high tumor accumulation and high target-to-background ratio in vivo. Tumor growth was significantly inhibited by NIR-PIT in comparison with the other groups (p < 0.001 for both tumors), and survival was significantly prolonged in both tumors (p < 0.001 for Daudi tumors and p < 0.0001 for Ramos tumors vs other groups). More than half of tumors were cured with this single regimen of NIR-PIT. In conclusion, anti-CD20 rituximab-IR700 works as a highly effective APC for NIR-PIT against B-cell lymphoma.