Near-infrared photoimmunotherapy targeting PD-L1: Improved efficacy by preconditioning the tumor microenvironment.

Near-infrared photoimmunotherapy (NIR-PIT) is a new type of cancer therapy that employs antibody-IRDye700DX conjugates (AbPCs) and near-infrared (NIR) light at a wavelength of 689 nm, the excitation wavelength of IR700. Administered intravenously, injected AbPCs bind specifically to cells expressing the target antigen, whereupon NIR light exposure causes rapid, selective killing. This process induces an anticancer T cell response, leading to sustained anticancer host immune response. Programmed cell death ligand-1 (PD-L1) is a major inhibitory immune checkpoint molecule expressed in various cancers. In this study, we first assessed the efficacy of PD-L1-targeted NIR-PIT (αPD-L1-PIT) in immune-competent tumor mouse models. αPD-L1-PIT showed a significant therapeutic effect on the tumor models with high PD-L1 expression. Furthermore, αPD-L1-PIT induced an abscopal effect on distant tumors and long-term immunological memory. In contrast, αPD-L1-PIT was not as effective for tumor models with low PD-L1 expression. To improve the efficacy of PD-L1-targeted NIR-PIT, PEGylated interferon-gamma (IFNγ) was administered with αPD-L1-PIT. The combination therapy improved the treatment efficacy by increasing PD-L1 expression leading to more efficient cell killing by αPD-L1-PIT. Furthermore, the PEGylated IFNγ led to a CD8+ T cell-dominant tumor microenvironment (TME) with an enhanced anticancer T cell response after αPD-L1-PIT. As a result, even so-called cold tumors exhibited complete responses after αPD-L1-PIT. Thus, combination therapy of PEGylated IFNγ and PD-L1-targeted NIR-PIT has the potential to be an important future strategy for cancer immunotherapy.

Near-infrared photoimmunotherapy in the models of hepatocellular carcinomas using cetuximab-IR700.

Epidermal growth factor receptor (EGFR) has emerged as an important therapeutic target in many cancers, and overexpression of EGFR is frequently observed in hepatocellular carcinomas (HCCs). Near-infrared photoimmunotherapy (NIR-PIT) is a new anticancer treatment that selectively damages the cell membrane of cancer cells after NIR light-induced photochemical reaction of IR700, which is bound to a targeting antibody on the cell membrane. NIR-PIT using cetuximab-IR700 has already been approved in Japan, is under review by the US Food and Drug Administration (FDA) for advanced head and neck cancers, and its safety has been established. However, EGFR has not been investigated as a target in NIR-PIT in HCCs. Here, we investigate the application of NIR-PIT using cetuximab-IR700 to HCCs using xenograft mouse models of EGFR-expressing HCC cell lines, Hep3B, HuH-7, and SNU-449. In vitro NIR-PIT using EGFR-targeted cetuximab-IR700 killed cells in a NIR light dose-dependent manner. In vivo NIR-PIT resulted in a delayed growth compared with untreated controls. In addition, in vivo NIR-PIT in both models showed histological signs of cancer cell damage, such as cytoplasmic vacuolation and nuclear dysmorphism. A significant decrease in Ki-67 positivity was also observed after NIR-PIT, indicating decreased cancer cell proliferation. This study suggests that NIR-PIT using cetuximab-IR700 has potential for the treatment of EGFR-expressing HCCs.

Intercellular adhesion molecule-1-targeted near-infrared photoimmunotherapy of triple-negative breast cancer.

Triple-negative breast cancer (TNBC) is the most aggressive subtype of breast cancer, and conventional chemotherapy and molecular-targeted therapies show limited efficacy. Near-infrared photoimmunotherapy (NIR-PIT) is a new anticancer treatment that selectively damages the cell membrane of cancer cells based on NIR light-induced photochemical reactions of the antibody (Ab)-photoabsorber (IRDye700Dx) conjugate and the cell membrane. TNBC is known to express several adhesion molecules on the cell surface providing a potential new target for therapy. Here, we investigated the therapeutic efficacy of intercellular adhesion molecule-1 (ICAM-1)-targeted NIR-PIT using xenograft mouse models subcutaneously inoculated with two human ICAM-1-expressing TNBC cell lines, MDAMB468-luc and MDAMB231 cells. In vitro ICAM-1-targeted NIR-PIT damaged both cell types in a NIR light dose-dependent manner. In vivo ICAM-1-targeted NIR-PIT in both models showed early histological signs of cancer cell damage, such as cytoplasmic vacuolation. Even among the cancer cells that appeared to be morphologically intact within 2 h post treatment, abnormal distribution of the actin cytoskeleton and a significant decrease in Ki-67 positivity were observed, indicating widespread cellular injury reflected in cytoplasmic degeneration. Such damage to cancer cells by NIR-PIT significantly inhibited subsequent tumor growth and improved survival. This study suggests that ICAM-1-targeted NIR-PIT could have potential clinical application in the treatment of TNBC.

Selection of antibody and light exposure regimens alters therapeutic effects of EGFR-targeted near-infrared photoimmunotherapy.

Near-infrared photoimmunotherapy (NIR-PIT) is a cell-specific cancer therapy that uses an antibody-photoabsorber (IRDye700DX, IR700) conjugate (APC) and NIR light. Intravenously injected APC binds the target cells, and subsequent NIR light exposure induces immunogenic cell death only in targeted cells. Panitumumab and cetuximab are antibodies that target human epidermal growth factor receptor (hEGFR) and are suitable for NIR-PIT. In athymic nude mouse models, panitumumab-based NIR-PIT showed superior therapeutic efficacy compared to cetuximab-based NIR-PIT because of the longer half-life of panitumumab-IR700 (pan-IR700) compared with cetuximab-IR700 (cet-IR700). Two light exposures on two consecutive days have also been shown to induce superior effects compared to a single light exposure in the athymic nude mouse model. However, the optimal regimen has not been assessed in immunocompetent mice. In this study, we compared panitumumab and cetuximab in APCs for NIR-PIT, and single and double light exposures using a newly established hEGFR-expressing cancer cell line derived from immunocompetent C57BL/6 mice (mEERL-hEGFR cell line). Fluorescence imaging showed that the decline of pan-IR700 was slower than cet-IR700 confirming a longer clearance time. Among all the combinations tested, mice receiving pan-IR700 and double light exposure showed the greatest tumor growth inhibition. This group was also shown to activate CD8+ T lymphocytes in lymph nodes and accumulate CD8+ T lymphocytes to a greater extent within the tumor compared with the control group. These results showed that APCs with longer half-life and double light exposure lead to superior outcomes in cancer cell-targeted NIR-PIT in an immunocompetent mouse model.

Opening up new VISTAs: V-domain immunoglobulin suppressor of T cell activation (VISTA) targeted near-infrared photoimmunotherapy (NIR-PIT) for enhancing host immunity against cancers.

V-domain immunoglobulin suppressor of T cell activation (VISTA) is an inhibitory immune checkpoint molecule that is broadly expressed on lymphoid and myeloid cells, including regulatory T cells (Tregs) and myeloid-derived suppressor cells (MDSCs). Near-infrared photoimmunotherapy (NIR-PIT) is a cancer treatment that utilizes an antibody-photoabsorber (IRDye 700DX NHS ester) conjugate to selectively kill target cells after the local application of NIR light. Depletion of VISTA-expressing cells in the tumor microenvironment (TME) using NIR-PIT could enhance anti-tumor immune responses by removing immune suppressive cells. The purpose of this study was to evaluate the anti-tumor efficacy of VISTA-targeted NIR-PIT using two murine tumor models, MC38-luc and LL2-luc. VISTA was expressed on T cells including Tregs and MDSCs in the TME of these tumors. In contrast, CD45 - cells, including cancer cells, did not express VISTA. VISTA-targeted NIR-PIT depleted VISTA-expressing cells ex vivo. In vivo VISTA-targeted NIR-PIT inhibited tumor progression and prolonged survival in both models. After VISTA-targeted NIR-PIT, augmented CD8 + T cell and dendritic cell activation were observed in regional lymph nodes. In conclusion, VISTA-targeted NIR-PIT can effectively treat tumors by decreasing VISTA-expressing immune suppressor cells in the TME. Local depletion of VISTA-expressing cells in the tumor bed using NIR-PIT is a promising new cancer immunotherapy for treating various types of tumors.

Comparison of the Effectiveness of IgG Antibody versus F(ab')2 Antibody Fragment in CTLA4-Targeted Near-Infrared Photoimmunotherapy.

Near-infrared photoimmunotherapy (NIR-PIT) is a novel cancer treatment modality that utilizes antibody-photoabsorber conjugates (APCs) and selectively kills target cells after irradiation with NIR light. Originally, NIR-PIT was targeted against cancer cell surface antigens, but as it became clear that NIR-PIT induced a strong immune response, an effort was made to target selected immune cell populations in the tumor microenvironment to encourage an even stronger immune response. Thus, CD25-targeted NIR-PIT and cytotoxic T-lymphocyte associated protein 4 (CTLA4)-targeted NIR-PIT were developed to kill regulatory T cells (Tregs) in conjunction with cancer-cell-targeted NIR-PIT, in order to amplify the host immune response. It was found that CD25-targeted NIR-PIT, using an antibody with the Fc portion removed, led to better results than the unmodified anti-CD25 antibody-directed NIR-PIT presumably because of a negative effect on activated T cells. The aim of this study was to compare the efficacy of an antibody fragment [anti-CTLA4-F(ab')2] and a whole antibody (anti-CTLA4-IgG) for NIR-PIT. There was no significant difference in NIR-PIT-induced Treg killing between the anti-CTLA4-F(ab')2 and anti-CTLA4-IgG antibodies. Although both the antibody and the antibody fragment resulted in significant tumor growth inhibition, the antibody induced more robust CD8+ T cell activation in ipsilateral lymph nodes and was more effective compared to the antibody fragment. The slower clearance of the anti-CTLA4-IgG APC enhanced antitumor immunity by promoting T cell priming in lymph nodes. In conclusion, unlike the results with CD25 where modified antibodies produced superior results to unmodified antibodies, anti-CTLA4-IgG antibody-based NIR-PIT proved more effective in reducing tumor growth than anti-CTLA4-F(ab')2 antibody-based NIR-PIT.

Evaluation and management of esophageal varices by through-the-scope endoscopic Doppler probe method.

OBJECTIVES: Objective assessments of esophageal varices (EVs) are inadequate. The recurrence of variceal bleeding after endoscopic variceal ligation (EVL) is associated with residual blood flow underlying EVL or incomplete treatment of a perforating vein by EVL. We aimed to assess our novel through-the-scope endoscopic Doppler probe method (DOP) for the evaluation and management of EVs. METHODS: This study included 20 patients (54 varices) with a history of esophageal variceal rupture from June 2019 to May 2021 who underwent DOP at a tertiary hospital. Variceal velocities were compared based on the size and endoscopic variceal findings. Additionally, we performed EVL assisted by DOP (EVL + DOP) in nine patients. RESULTS: Doppler imaging of EVs was observed in all 20 patients. The velocity of varices was significantly higher in EVs with a larger size, greater form, blue color, and red color sign positive. Perforating veins connecting to the EVs were identified in six out of nine patients who underwent EVL + DOP. Eight out of nine patients underwent repeat EVL. Repeat EVL was performed until the variceal velocity reached absent. No recurrence of variceal bleeding occurred during the follow-up period (mean 8.7 ± 3.2 months). No adverse events associated with DOP were observed. CONCLUSION: The evaluation of EVs using DOP is feasible and accurate. EV velocities are related to the variceal size, form, blue color, and red color sign. EVL + DOP may be a more reliable treatment for EVs. Further large-scale, long-term comparative studies are warranted.

Endoscopic near-infrared photoimmunotherapy in an orthotopic head and neck cancer model.

Near-infrared photoimmunotherapy (NIR-PIT) is a cell selective cancer therapy that uses an antibody-photoabsorber (IRDye700DX, IR700) conjugate (APC) and NIR light. NIR-PIT targeting epidermal growth factor receptor (EGFR) in head and neck cancer (HNC) was conditionally approved in Japan in 2020. APC-bound tumors can be detected using endoscopic fluorescence imaging, whereas NIR light can be delivered using endoscopic fiber optics. The aims of this study were: (1) to assess the feasibility of endoscopic NIR-PIT in an orthotopic HNC model using a CD44-expressing MOC2-luc cell line; and (2) to evaluate quantitative fluorescence endoscopic imaging prior to and during NIR-PIT. The results were compared in 3 experimental groups: (1) untreated controls, (2) APC injection without light exposure (APC-IV), and (3) APC injection followed by NIR light exposure (NIR-PIT). APC injected groups showed significantly higher fluorescence signals for IR700 compared with the control group prior to therapeutic NIR light exposure, and the fluorescence signal significantly decreased in the NIR-PIT group after light exposure. After treatment, the NIR-PIT group showed significantly attenuated bioluminescence compared with the control and the APC-IV groups. Histology demonstrated diffuse necrotic death of the cancer cells in the NIR-PIT group alone. In conclusion, endoscopically delivered light combined with quantitative fluorescence imaging can be used to "see and treat" HNC. This method could also be applied to other types of cancer approachable with endoscopy.

Association between the Frequency of Daily Toothbrushing and Development of Nonalcoholic Fatty Liver Disease.

Background & Aim: This study aimed to evaluate the association between the frequency of daily toothbrushing and the development of nonalcoholic fatty liver disease (NAFLD). METHODS: A retrospective longitudinal study was conducted from 2005 to 2012 at the Center for Preventive Medicine at St. Luke's International Hospital, Japan. Data on all participants who underwent a health checkup during the study period were collected. NAFLD was diagnosed by abdominal ultrasonography, and all participants who were diagnosed with NAFLD at the time of their initial visit, consumed alcohol in any amount, or had received only one health checkup were excluded. The questionnaire for the frequency of daily toothbrushing was conducted as part of health checkups. The primary outcome was the risk of developing NAFLD according to the frequency of daily toothbrushing (1-2 times a day or 3 times a day) compared to those who brush teeth once or less than once a day. RESULTS: Data were collected from 25,804 people. A total of 3,289 (12.7%) participants developed NAFLD. The mean age was 45.2 years, and 6,901 (26.7%) of the participants were male. The risk of developing NAFLD significantly decreased with increased frequency of daily toothbrushing. Adjusted odds ratios (ORs) are as follows: brushing teeth 1-2 times a day (OR: 0.85, 95% confidence interval [CI]: 0.77-0.95) and 3 times a day (OR: 0.74, 95% CI: 0.67-0.82). CONCLUSION: Frequent toothbrushing was shown to significantly reduce the risk of developing NAFLD.

The association between non-alcoholic fatty liver disease (with or without metabolic syndrome) and extrahepatic cancer development.

BACKGROUND AND AIM: This study was designed to determine whether non-alcoholic fatty liver disease (NAFLD), with or without metabolic syndrome (MetS), is a risk factor for cancer development. METHODS: We conducted a retrospective longitudinal study at the Center for Preventive Medicine, St. Luke's International Hospital. Among all participants who underwent a health checkup between 2005 and 2019, cancer development tendencies were compared between those who were diagnosed with NAFLD and those who were not. Further evaluation was conducted among NAFLD-diagnosed participants with versus without MetS in the same manner. Those with a history of a specific liver disease, any type of cancer, or alcohol consumption in any amount at the time of the initial visit were excluded from the study. RESULTS: Data were collected from 30 172 participants who underwent health checkups, among whom 4394 (14.6%) had NAFLD. Over the 14-year follow-up period, 2086 participants (6.9%) developed cancer. Participants with NAFLD had a higher incidence of digestive organ neoplasms (odds ratio [OR]: 1.34, 95% confidence interval [CI]: 1.07-1.67), especially in the stomach (OR: 1.40, 95% CI: 1.02-1.94) and small intestine (OR: 2.80, 95% CI: 0.87-8.96), than did those without NAFLD. Participants with NAFLD and MetS had significantly lower rates of neoplasms in respiratory and intrathoracic organs (OR: 0.35 95% CI: 0.14-0.88) and male genital organs (OR: 0.46 95% CI: 0.24-0.87) than did individuals without NAFLD. CONCLUSIONS: Non-alcoholic fatty liver disease is associated with the development of gastrointestinal malignancies, while MetS is a negative risk factor for lung and prostate cancer.

Safety and Effectiveness of Endoscopic Band Ligation for Colonic Diverticular Bleeding in Elderly Patients.

INTRODUCTION: Colonic diverticulosis increases with age, leading to a higher risk of colonic diverticular bleeding (CDB) in the elderly. As life expectancy continues to increase, the need for endoscopic hemostasis for CDB in the elderly can also be expected to increase. However, there have been no reports to date on the feasibility of endoscopic hemostasis for elderly CDB patients. Several recent studies have addressed the effectiveness of endoscopic band ligation (EBL) for CDB. In this study, we evaluate the safety and effectiveness of EBL in elderly CDB patients compared to younger CDB patients. METHODS: We retrospectively analyzed the medical records of consecutive patients treated with EBL for the first time at a tertiary referral center between March 2011 and November 2017. Patients were grouped according to age into those at least 75 years old (the Elderly) and those <75 years old (the Nonelderly). Patient characteristics, technical success, and complications were compared between the two groups. RESULTS: EBL was performed in 153 patients during the study period (49 Elderly patients and 104 Nonelderly patients). Elderly patients were less likely to be male (p < 0.001) and had lower hemoglobin levels on admission (p < 0.001). Bleeding on the right side of the splenic flexure was observed more frequently in the Nonelderly (p = 0.002). Charlson Comorbidity Index (CCI) and use of antithrombotic agents were significantly higher in the Elderly (p < 0.001 and p < 0.001, respectively). Active bleeding tended to be observed more frequently in the Elderly (p = 0.054), while the difference was not significant. There were no significant differences in the shock index, procedure time, or units of packed red blood cells transfused between the 2 groups. No significant differences in the technical success rate (97.1 vs. 98%, p = 0.76), early rebleeding rate (10.2 vs. 14.4%, p = 0.47), or other complications (2 vs. 1%, p = 0.58) were observed. Perforation and abscess formation were not observed in either group. Female gender, left-sidedness, higher CCI, and lower hemoglobin level were all significantly more frequently observed in the Elderly on multiple logistic regression analysis. DISCUSSION/CONCLUSION: EBL may be similarly safe and effective for the treatment of CDB in the elderly as in the nonelderly.

Effectiveness of risk scoring systems in predicting endoscopic treatment in colonic diverticular bleeding.

BACKGROUND AND AIMS: The identification of stigmata of recent hemorrhage (SRH) in colonic diverticular bleeding (CDB) enables an endoscopic treatment and can improve the clinical outcome. However, SRH identification rate remains low. This study aims to investigate whether NOBLADS and Strate scoring systems are useful for predicting SRH identification rate of CDB pre-procedurally via colonoscopy. METHODS: In this single-center retrospective observational study, 302 patients who experienced their first episode of CDB from April 2008 to March 2018 were included. Patients were classified into SRH-positive and SRH-negative groups. The primary outcome was SRH identification rate. The secondary outcomes were active bleeding in SRH and early rebleeding rates. The usefulness of the NOBLADS and Strate scores as predicted values of SRH identification was evaluated using the area under the receiver operating characteristic curve. RESULTS: There were 126 and 176 patients in the SRH-positive and SRH-negative groups, respectively. The area under the receiver operating characteristic curve for SRH identification using the NOBLADS score was 0.74 (95% confidence interval, 0.69-0.80) and that using the Strate score was 0.74 (95% confidence interval, 0.68-0.79). Active bleeding and early rebleeding rates increased according to each score. By setting the cut-off of the NOBLADS score to four points, treatment was possible in 70.2% (66/94) patients. Addition of extravasation at computed tomography to a NOBLADS score of ≧ 4 points allowed treatment of all patients (24/24). CONCLUSIONS: Severity scoring in acute lower gastrointestinal bleeding was effective for predicting SRH identification in CDB. We suggest that combination of these scorings and CT findings could offer a new therapeutic strategy.

Near-infrared photoimmunotherapy through bone.

Near-infrared photoimmunotherapy (NIR-PIT) is a molecularly targeted cancer phototherapy that is based on injecting a conjugate of a silicon-phthalocyanine derivative, IRdye 700DX (IR700), and a monoclonal antibody that targets an expressed antigen on the cancer cell surface. Subsequent local exposure to NIR light results in the rapid and highly selective immunogenic cell death of targeted cancer cells. Because many cancers grow in bones through which light does not penetrate well, the goal of this study was to determine if NIR-PIT can effectively treat cancers in bone. A bovine rib was used as a bone sample. Because the sample's NIR light transmittance was shown to be approximately 4.52% in preliminary tests, it was hypothesized that a maximum radiation dosage of 128 and 1500 J/cm2 would be sufficient to induce cell death in in vitro target cells and in vivo mouse tumor models, respectively. Cell viability was measured through bioluminescence studies comparing relative luciferase activity, as well as a cytotoxicity assay. In the in vitro model, tumor cell viability was significantly decreased after 64 and 128 J/cm2 NIR light irradiation through the bone. An in vivo mouse tumor model also showed that 1500 J/cm2 NIR light irradiation through the bone significantly reduced tumor viability at both 24 and 48 hours posttreatment compared to the control group (P = .026 and .040 respectively). Therefore, despite limitations in light transmission, NIR-PIT nevertheless is capable of effectively treating cancers within bone.

Characterization of reemergent anti-B red blood cell antibodies in a patient with recurrent acute myeloid leukemia with ABO-incompatible allogeneic peripheral blood stem cell transplantation.

BACKGROUND: Isohemagglutinins against ABO antigens absent on both recipient and donor red blood cells (RBCs) increase or decrease after ABO-incompatible hematopoietic stem cell transplantation (HSCT). However, few reports have described the changes in the isohemagglutinin titers and the characteristics in patients with recurrent hematologic conditions after ABO-incompatible HSCT. CASE REPORT: A 59-year-old female with acute erythroid leukemia received a peripheral blood stem cell transplant from her HLA-haploidentical daughter. The patient was typed as group O with anti- A (4+) and B (4+) isohemagglutinins, while the donor was typed as group B. The bone marrow cells achieved complete donor cell chimerism on Day 13 after HSCT. On Day 120, the patient showed 97% B RBC type with persistent anti-A (3+) and without anti-B antibodies. On Day 375, her leukemia relapsed, and recipient type O RBCs and anti-B antibodies sequentially reemerged. However, clinicolaboratory hemolysis and erythroid aplasia were not detected in the patient. RESULTS: The post-HSCT sera agglutinated the allo B RBCs, but not the donor B RBCs, while the pre-HSCT sera agglutinated both RBCs. The burst-forming/colony-forming units of erythroid formation from the donor peripheral blood stem cells were impaired by only the pre-HSCT sera and not by the post-HSCT sera. CONCLUSION: To our knowledge, this is the first report investigating the characteristic changes of isohemagglutinins between the pre- and post-HSCT sera in a patient with recurrent acute myeloid leukemia. The present study suggests that the plasma cells producing anti-donor B RBCs in the patient have been selectively eliminated or induced into an anergic state by the post-HSCT immunologic reconstruction.

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

BACKGROUND: Peritoneal dissemination (PD) of abdominal malignancies is a common form of metastasis and its presence signals a poor prognosis. New treatment is required for patients with PD. Near infrared photoimmunotherapy (NIR-PIT) is a highly selective tumor treatment that employs an antibody-photo-absorber conjugate (APC). In this study, we investigate in vitro and in vivo efficacy of trastuzumab (tra)-IR700DX NIR-PIT on a human epidermal growth factor receptor type 2 (HER2)-positive gastric cancer cell line. METHODS: NIR-PIT effects were investigated in vitro and in vivo. Disseminated peritoneal implants mice were separated into 5 groups: (1) no treatment; (2) tra-IR700 i.v. only; (3) NIR light only; (4) NIR-PIT; (5) repeated NIR-PIT. The peritoneal cavity was irradiated with NIR light using a fiber optic diffuser delivered through the catheter. RESULTS: Specific binding and cell-specific killing was observed after NIR-PIT in vitro. In the in vivo study, fluorescence endoscopy showed high tumor accumulation of tra-IR700 within tumors. Significantly prolonged survival was achieved in the three treatment groups (tra-IR700 i.v. only, NIR-PIT, and repeated NIR-PIT groups) compared with control and NIR light only group (p < 0.05 for tra-IR700 i.v. only, p < 0.01 for NIR-PIT, and p < 0.0001 for repeated NIR-PIT). Moreover, most prolonged survival was shown for the repeated NIR-PIT group (p < 0.0001 vs tra-IR700 i.v. only, p < 0.01 vs NIR-PIT). CONCLUSION: NIR-PIT using a fiber optic diffuser to deliver light is a promising candidate for the treatment of disseminated peritoneal metastases and could be readily translated to humans.

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.

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.

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.