Case report: Atypical case of autoimmune glial fibrillary acidic protein astrocytopathy following COVID-19 vaccination refractory to immunosuppressive treatments.

A 54-year-old Japanese man presented with headache and fever the day after SARS-CoV-2 vaccination. He became deeply unconscious within a week. Brain MRI showed periventricular linear enhancements and a few spotty lesions in the cerebral white matter. Cerebrospinal fluid (CSF) testing showed mild pleocytosis. He was treated with intravenous methylprednisolone and plasma exchange. However, the white matter lesions enlarged to involve the brainstem and cerebellum, and long cord spinal lesions appeared. Anti-glial fibrillary acidic protein (GFAP) antibody was positive in the CSF and serum, and he was therefore diagnosed as autoimmune GFAP-astrocytopathy (GFAP-A). In addition, high-dose immunoglobulin therapy was administered twice, but his symptoms did not improve; the white matter lesions enlarged further, and modified Rankin Scale score increased to 5. A brain biopsy specimen showed infiltration of macrophages and CD4 + lymphocytes together with neuron and oligodendrocytic injuries and glial scar. Although GFAP-A generally responds well to steroids, the present case developed GFAP-A following SARS-CoV-2 vaccination, with refractory to intensive immunosuppressive therapy and atypical pathologic findings of infiltration of CD4 + lymphocytes and demyelination.

Current trends in the promising immune checkpoint inhibition and radiotherapy combination for locally advanced and metastatic urothelial carcinoma.

Locally advanced and metastatic urothelial carcinoma (UC) remains a challenging malignancy, though several novel therapeutic drugs have been developed in recent years. Over the past decade, immune checkpoint inhibitors (ICI) have shifted the paradigm of therapeutic strategies for UC; however, only a limited number of patients respond to ICI. Since radiotherapy (RT) is widely known to induce systemic immune activation, it may boost the efficacy of ICI. Conversely, RT also causes exhaustion of cytotoxic T cells, and the activation and recruitment of immunosuppressive cells; ICI may help overcome these immunosuppressive effects. Therefore, the combination of ICI and RT has attracted attention in recent years. The therapeutic benefits of this combination therapy and its optimal regimen have not yet been determined through prospective studies. Therefore, this review article aimed to provide an overview of the current preclinical and clinical studies that illustrate the underlying mechanisms and explore the optimization of the RT regimen along with the ICI and RT combination sequence. We also analyzed ongoing prospective studies on ICI and RT combination therapies for metastatic UC. We noted that the tumor response to ICI and RT combination seemingly differs among cancer types. Thus, our findings highlight the need for well-designed prospective trials to determine the optimal combination of ICI and RT for locally advanced and metastatic UC.

Proposal of recommended experimental protocols for in vitro and in vivo evaluation methods of boron agents for neutron capture therapy.

Recently, boron neutron capture therapy (BNCT) has been attracting attention as a minimally invasive cancer treatment. In 2020, the accelerator-based BNCT with L-BPA (Borofalan) as its D-sorbitol complex (Steboronine®) for head and neck cancers was approved by Pharmaceutical and Medical Devices Agency for the first time in the world. As accelerator-based neutron generation techniques are being developed in various countries, the development of novel tumor-selective boron agents is becoming increasingly important and desired. The Japanese Society of Neutron Capture Therapy believes it is necessary to propose standard evaluation protocols at each stage in the development of boron agents for BNCT. This review summarizes recommended experimental protocols for in vitro and in vivo evaluation methods of boron agents for BNCT based on our experience with L-BPA approval.

Evaluation of the Effectiveness of Boron Neutron Capture Therapy with Iodophenyl-Conjugated closo-Dodecaborate on a Rat Brain Tumor Model.

High-grade gliomas present a significant challenge in neuro-oncology because of their aggressive nature and resistance to current therapies. Boron neutron capture therapy (BNCT) is a potential treatment method; however, the boron used by the carrier compounds-such as 4-borono-L-phenylalanine (L-BPA)-have limitations. This study evaluated the use of boron-conjugated 4-iodophenylbutanamide (BC-IP), a novel boron compound in BNCT, for the treatment of glioma. Using in vitro drug exposure experiments and in vivo studies, we compared BC-IP and BPA, with a focus on boron uptake and retention characteristics. The results showed that although BC-IP had a lower boron uptake than BPA, it exhibited superior retention. Furthermore, despite lower boron accumulation in tumors, BNCT mediated by BC-IP showed significant survival improvement in glioma-bearing rats compared to controls (not treated animals and neutrons only). These results suggest that BC-IP, with its unique properties, may be an alternative boron carrier for BNCT. Further research is required to optimize this potential treatment modality, which could significantly contribute to advancing the treatment of high-grade gliomas.

Pharmacokinetic Study of 14C-Radiolabeled p-Boronophenylalanine (BPA) in Sorbitol Solution and the Treatment Outcome of BPA-Based Boron Neutron Capture Therapy on a Tumor-Bearing Mouse Model.

BACKGROUND AND OBJECTIVE: Boron neutron capture therapy (BNCT) is a binary cancer treatment that combines boron administration and neutron irradiation. The tumor cells take up the boron compound and the subsequent neutron irradiation results in a nuclear fission reaction caused by the neutron capture reaction of the boron nuclei. This produces highly cytocidal heavy particles, leading to the destruction of tumor cells. p-boronophenylalanine (BPA) is widely used in BNCT but is insoluble in water and requires reducing sugar or sugar alcohol as a dissolvent to create an aqueous solution for administration. The purpose of this study was to investigate the pharmacokinetics of 14C-radiolabeled BPA using sorbitol as a dissolvent, which has not been reported before, and confirm whether neutron irradiation with a sorbitol solution of BPA can produce an antitumor effect of BNCT. MATERIALS AND METHODS: In this study, we evaluated the sugar alcohol, sorbitol, as a novel dissolution aid and examined the consequent stability of the BPA for long-term storage. U-87 MG and SAS tumor cell lines were used for in vitro and in vivo experiments. We examined the pharmacokinetics of 14C-radiolabeled BPA in sorbitol solution, administered either intravenously or subcutaneously to a mouse tumor model. Neutron irradiation was performed in conjunction with the administration of BPA in sorbitol solution using the same tumor cell lines both in vitro and in vivo. RESULTS: We found that BPA in sorbitol solution maintains stability for longer than in fructose solution, and can therefore be stored for a longer period. Pharmacokinetic studies with 14C-radiolabeled BPA confirmed that the sorbitol solution of BPA distributed through tumors in much the same way as BPA in fructose. Neutron irradiation was found to produce dose-dependent antitumor effects, both in vitro and in vivo, after the administration of BPA in sorbitol solution. CONCLUSION: In this report, we demonstrate the efficacy of BPA in sorbitol solution as the boron source in BNCT.

Multi-Targeted Neutron Capture Therapy Combined with an 18 kDa Translocator Protein-Targeted Boron Compound Is an Effective Strategy in a Rat Brain Tumor Model.

BACKGROUND: Boron neutron capture therapy (BNCT) has been adapted to high-grade gliomas (HG); however, some gliomas are refractory to BNCT using boronophenylalanine (BPA). In this study, the feasibility of BNCT targeting the 18 kDa translocator protein (TSPO) expressed in glioblastoma and surrounding environmental cells was investigated. METHODS: Three rat glioma cell lines, an F98 rat glioma bearing brain tumor model, DPA-BSTPG which is a boron-10 compound targeting TSPO, BPA, and sodium borocaptate (BSH) were used. TSPO expression was evaluated in the F98 rat glioma model. Boron uptake was assessed in three rat glioma cell lines and in the F98 rat glioma model. In vitro and in vivo neutron irradiation experiments were performed. RESULTS: DPA-BSTPG was efficiently taken up in vitro. The brain tumor has 16-fold higher TSPO expressions than its brain tissue. The compound biological effectiveness value of DPA-BSTPG was 8.43 to F98 rat glioma cells. The boron concentration in the tumor using DPA-BSTPG convection-enhanced delivery (CED) administration was approximately twice as high as using BPA intravenous administration. BNCT using DPA-BSTPG has significant efficacy over the untreated group. BNCT using a combination of BPA and DPA-BSTPG gained significantly longer survival times than using BPA alone. CONCLUSION: DPA-BSTPG in combination with BPA may provide the multi-targeted neutron capture therapy against HG.

Correlation between the expression of LAT1 in cancer cells and the potential efficacy of boron neutron capture therapy.

Boron neutron capture therapy (BNCT) is a binary cancer therapy that involves boron administration and neutron irradiation. The nuclear reaction caused by the interaction of boron atom and neutron produces heavy particles with highly cytocidal effects and destruct tumor cells, which uptake the boron drug. p-Boronophenylalanine (BPA), an amino acid derivative, is used in BNCT. Tumor cells with increased nutrient requirements take up more BPA than normal tissues via the enhanced expression of LAT1, an amino acid transporter. The current study aimed to assess the correlation between the expression of LAT1 and the uptake capacity of BPA using genetically modified LAT1-deficient/enhanced cell lines. We conducted an in vitro study, SCC7 tumor cells wherein LAT1 expression was altered using CRISPR/Cas9 were used to assess BPA uptake capacity. Data from The Cancer Genome Atlas (TCGA) were used to examine the expression status of LAT1 in human tumor tissues, the potential impact of LAT1 expression on cancer prognosis and the potential cancer indications for BPA-based BNCT. We discovered that the strength of LAT1 expression strongly affected the BPA uptake ability of tumor cells. Among the histologic types, squamous cell carcinomas express high levels of LAT1 regardless of the primary tumor site. The higher LAT1 expression in tumors was associated with a higher expression of cell proliferation markers and poorer patient prognosis. Considering that BPA concentrate more in tumors with high LAT1 expression, the results suggest that BNCT is effective for cancers having poor prognosis with higher proliferative potential and nutritional requirements.

The mutual relationship between the host immune system and radiotherapy: stimulating the action of immune cells by irradiation.

The effects of irradiation on tumor tissue and the host immune system are interrelated. The antitumor effect of irradiation is attenuated in the immunocompromised hosts. In addition, radiation alone positively and negatively influences the host immune system. The positive effects of radiation are summarized by the ability to help induce and enhance tumor-antigen-specific immune responses. The cancer-immunity cycle is a multistep framework that illustrates how the tumor-antigen-specific immune responses are induced and how the induced antigen-specific immune cells exert their functions in tumor tissues. Irradiation affects each step of this cancer-immunity cycle, primarily in a positive manner. In contrast, radiation also has negative effects on the immune system. The first is that irradiation has the possibility to kill irradiated effector immune cells. The second is that irradiation upregulates immunosuppressive molecules in the tumor microenvironment, whereas the third is that irradiation to the tumor condenses immunosuppressor cells in the tumor microenvironment. When used in conjunction with radiotherapy, immune checkpoint inhibitors can further leverage the positive effects of radiation on the immune system and compensate for the negative effects of irradiation, which supports the rationale for the combination of radiotherapy and immune checkpoint inhibitors. In this review, we summarize the preclinical evidence for the reciprocal effects of radiation exposure and the immune system, and up-front topics of the combination therapy of immune checkpoint inhibitors and radiotherapy.

Anti-tumor effect of boron neutron capture therapy in pelvic human colorectal cancer in a mouse model.

Local recurrence of colorectal cancer (CRC) can occur in patients after curative resection, and additional surgical resection may therefore be required; however, this is a significant burden for patients, because additional surgical resection may necessitate the resection of other organs such as the bladder, prostate, uterus, or sacral bone. Therefore, there is a need for alternative therapeutic strategies. We focused on boron neutron capture therapy (BNCT) as a treatment modality that can selectively target tumor cells without excessive damage to normal tissues. The usefulness of BNCT to pelvic CRC remains unknown. This study investigated the anti-cancer effect of boronophenylalanine (BPA)-mediated BNCT in a previously established mouse model of pelvic recurrence of CRC. Uptake of BPA in CRC was observed both in vitro and in vivo, and the concentrations were sufficient for BNCT. Our results are the first to show that BPA-mediated BNCT prolonged the survival of experimental mice with pelvic tumors; moreover, it did not cause any obvious severe side effects in the treated animals. In conclusion, BPA-mediated BNCT could contribute to treating local recurrence of pelvic CRC.

Predictors of sedation period for critical illness patients focusing on early rehabilitation on the bed.

There are various interventions of rehabilitation on the bed, but these are time-consuming and cannot be performed for all patients. The purpose of this study was to identify the patients who require early mobilization based on the level of sedation. We retrospectively evaluated the data of patients who underwent physical therapy, ICU admission of > 48 h, and were discharged alive. Sedation was defined as using sedative drugs and a Richmond Agitation-Sedation Scale score of < - 2. Multiple regression analysis was performed using sedation period as the objective variable, and receiver operating characteristic (ROC) curve and Spearman's rank correlation coefficient were performed. Of 462 patients admitted to the ICU, the data of 138 patients were analyzed. The Sequential Organ Failure Assessment (SOFA) score and non-surgery and emergency surgery cases were extracted as significant factors. The ROC curve with a positive sedation period of more than 3 days revealed the SOFA cutoff score was 10. A significant positive correlation was found between sedation period and the initial day on early mobilization. High SOFA scores, non-surgery and emergency surgery cases may be indicators of early mobilization on the bed in the ICU.

Boron neutron capture therapy using dodecaborated albumin conjugates with maleimide is effective in a rat glioma model.

Introduction Boron neutron capture therapy (BNCT) is a biologically targeted, cell-selective particle irradiation therapy that utilizes the nuclear capture reaction of boron and neutron. Recently, accelerator neutron generators have been used in clinical settings, and expectations for developing new boron compounds are growing. Methods and Results In this study, we focused on serum albumin, a well-known drug delivery system, and developed maleimide-functionalized closo-dodecaborate albumin conjugate (MID-AC) as a boron carrying system for BNCT. Our biodistribution experiment involved F98 glioma-bearing rat brain tumor models systemically administered with MID-AC and demonstrated accumulation and long retention of boron. Our BNCT study with MID-AC observed statistically significant prolongation of the survival rate compared to the control groups, with results comparable to BNCT study with boronophenylalanine (BPA) which is the standard use of in clinical settings. Each median survival time was as follows: untreated control group; 24.5 days, neutron-irradiated control group; 24.5 days, neutron irradiation following 2.5 h after termination of intravenous administration (i.v.) of BPA; 31.5 days, and neutron irradiation following 2.5 or 24 h after termination of i.v. of MID-AC; 33.5 or 33.0 days, respectively. The biological effectiveness factor of MID-AC for F98 rat glioma was estimated based on these survival times and found to be higher to 12. This tendency was confirmed in BNCT 24 h after MID-AC administration. Conclusion MID-AC induces an efficient boron neutron capture reaction because the albumin contained in MID-AC is retained in the tumor and has a considerable potential to become an effective delivery system for BNCT in treating high-grade gliomas.

Efficacy of Boron Neutron Capture Therapy in Primary Central Nervous System Lymphoma: In Vitro and In Vivo Evaluation.

BACKGROUND: Boron neutron capture therapy (BNCT) is a nuclear reaction-based tumor cell-selective particle irradiation method. High-dose methotrexate and whole-brain radiation therapy (WBRT) are the recommended treatments for primary central nervous system lymphoma (PCNSL). This tumor responds well to initial treatment but relapses even after successful treatment, and the prognosis is poor as there is no safe and effective treatment for relapse. In this study, we aimed to conduct basic research to explore the possibility of using BNCT as a treatment for PCNSL. METHODS: The boron concentration in human lymphoma cells was measured. Subsequently, neutron irradiation experiments on lymphoma cells were conducted. A mouse central nervous system (CNS) lymphoma model was created to evaluate the biodistribution of boron after the administration of borono-phenylalanine as a capture agent. In the neutron irradiation study of a mouse PCNSL model, the therapeutic effect of BNCT on PCNSL was evaluated in terms of survival. RESULTS: The boron uptake capability of human lymphoma cells was sufficiently high both in vitro and in vivo. In the neutron irradiation study, the BNCT group showed a higher cell killing effect and prolonged survival compared with the control group. CONCLUSIONS: A new therapeutic approach for PCNSL is urgently required, and BNCT may be a promising treatment for PCNSL. The results of this study, including those of neutron irradiation, suggest success in the conduct of future clinical trials to explore the possibility of BNCT as a new treatment option for PCNSL.

Development of an irradiation method for superficial tumours using a hydrogel bolus in an accelerator-based BNCT.

The aim of this study is the development of an irradiation method for the treatment of superficial tumours using a hydrogel bolus to produce thermal neutrons in accelerator-based Boron Neutron Capture Therapy (BNCT).To evaluate the neutron moderating ability of a hydrogel bolus, a water phantom with a hydrogel bolus was irradiated with an epithermal neutron beam from a cyclotron-based epithermal neutron source. Phantom simulating irradiation to the plantar position was manufactured using three-dimensional printing technology to perform an irradiation test of a hydrogel bolus. Thermal neutron fluxes on the surface of a phantom were evaluated and the results were compared with the Monte Carlo-based Simulation Environment for Radiotherapy Applications (SERA) treatment planning software. It was confirmed that a hydrogel bolus had the same neutron moderating ability as water, and the calculation results from SERA aligned with the measured values within approximately 5%. Furthermore, it was confirmed that the thermal neutron flux decreased at the edge of the irradiation field. It was possible to uniformly irradiate thermal neutrons by increasing the bolus thickness at the edge of the irradiation field, thereby successfully determining uniform dose distribution. An irradiation method for superficial tumours using a hydrogel bolus in the accelerator-based BNCT was established.

HIF-1α affects sensitivity of murine squamous cell carcinoma to boron neutron capture therapy with BPA.

Purpose To examine whether hypoxia and Hif-1α affect sensitivity of murine squamous cell carcinoma cells to boron neutron capture therapy (BNCT).Materials and methods SCC VII and SCC VII Hif-1α-deficient mouse tumor cells were incubated under normoxic or hypoxic conditions, and cell survival after BNCT was assessed. The intracellular concentration of the 10B-carrier, boronophenylalanine-10B (BPA), was estimated using an autoradiography technique. The expression profile of SLC7A5, which is involved in the uptake of BPA, and the amount of DNA damage caused by BNCT with BPA were examined. A cell survival assay was performed on cell suspensions prepared from tumor-bearing mice.Results Hypoxia ameliorated SCC VII cell survival after neutron irradiation with BPA, but not BSH. Hypoxia-treated SCC VII cells showed decreased intracellular concentrations of BPA and the down-regulated expression of the SLC7A5 protein. BPA uptake and the SLC7A5 protein were not decreased in hypoxia-treated Hif-1α-deficient cells, the survival of which was lower than that of SCC VII cells. More DNA damage was induced in SCC VII Hif-1α-deficient cells than in SCC VII cells. In experiments using tumor-bearing mice, the survival of SCC VII Hif-1α-deficient cells was lower than that of SCC VII cells.Conclusion. Hypoxia may decrease the effects of BNCT with BPA, whereas the disruption of Hif-1α enhanced sensitivity to BNCT with BPA.

[Human herpesvirus 8-unrelated primary effusion lymphoma-like lymphoma that developed during myelodysplastic syndrome].

Primary effusion lymphoma (PEL) is a large B-cell lymphoma that only proliferates proliferating effusion in the body cavity. It is associated with human herpesvirus 8 (HHV8).HHV8 negative effusion lymphoma, which is different from PEL in many ways, has also been reported and is referred to as HHV8-unrelated PEL-like lymphoma. This lymphoma is very rare and its clinical characteristics have not been fully clarified.A 79-year-old male developed HHV8-negative primary effusion lymphoma during treatment for myelodysplastic syndrome.Abdominal computed tomography revealed abdominal effusion, but did not show any evidence of a tumor mass or lymph node enlargement. A cytological analysis of his pleural effusion revealed atypical lymphoid cells that were negative for CD10, and positive for CD19 and CD20. Corticosteroids were administered to treat the abdominal effusion; however, the patient died of an exacerbation of lymphoma on the 20th day after the initiation of corticosteroid therapy. We herein report the case of an HIV seronegative elderly patient with HHV8-unrelated PEL-like lymphoma.

Quantitative autoradiography in boron neutron capture therapy considering the particle ranges in the samples.

PURPOSE: Boron neutron capture therapy is a cellular-scale particle therapy exploiting boron neutron capture reactions in boron compounds distributed in tumour cells. Its therapeutic effect depends on both the accumulation of boron in tumour cells and the neutron fluence. Autoradiography is used to visualise the micro-distribution of boron compounds. METHODS: Here, we present an equation for the relationship between boron concentration and pit density on the solid-state nuclear track detector, taking into consideration the particle ranges in the samples. This equation is validated using liver-tissue sections and boron standard solutions. Moreover, we present a simple co-localisation system for pit and tissue-section images that requires no special equipment. RESULTS: The equation reproduces the experimentally observed trends between boron concentration and pit density. This equation provides a theoretical explanation for the widely used calibration curve between pit density and boron concentration; it also provides a method to correct for differences of tissue-section thickness in quantitative autoradiography. CONCLUSIONS: Using the equation together with this co-localisation system could improve micro-scale quantitative estimation in tissue sections.

The Therapeutic Effects of Dodecaborate Containing Boronophenylalanine for Boron Neutron Capture Therapy in a Rat Brain Tumor Model.

BACKGROUND: The development of effective boron compounds is a major area of research in the study of boron neutron capture therapy (BNCT). We created a novel boron compound, boronophenylalanine-amide alkyl dodecaborate (BADB), for application in BNCT and focused on elucidating how it affected a rat brain tumor model. METHODS: The boron concentration of F98 rat glioma cells following exposure to boronophenylalanine (BPA) (which is currently being utilized clinically) and BADB was evaluated, and the biodistributions in F98 glioma-bearing rats were assessed. In neutron irradiation studies, the in vitro cytotoxicity of each boron compound and the in vivo corresponding therapeutic effect were evaluated in terms of survival time. RESULTS: The survival fractions of the groups irradiated with BPA and BADB were not significantly different. BADB administered for 6 h after the termination of convection-enhanced delivery ensured the highest boron concentration in the tumor (45.8 µg B/g). The median survival time in the BADB in combination with BPA group showed a more significant prolongation of survival than that of the BPA group. CONCLUSION: BADB is a novel boron compound for BNCT that triggers a prolonged survival effect in patients receiving BNCT.

Deep abscopal response to radiotherapy and anti-PD-1 in an oligometastatic melanoma patient with unfavorable pretreatment immune signature.

Radiotherapy can elicit abscopal effects in non-irradiated metastases, particularly under immune checkpoint blockade (ICB). We report on two elderly patients with oligometastatic melanoma treated with anti-PD-1 and stereotactic body radiation therapy (SBRT). Before treatment, patient 1 showed strong tumor infiltration with exhausted CD8+ T cells and high expression of T cell-attracting chemokines. This patient rapidly mounted a complete response, now ongoing for more than 4.5 years. Patient 2 exhibited low CD8+ T cell infiltration and high expression of immunosuppressive arginase. After the first SBRT, his non-irradiated metastases did not regress and new metastases occurred although neoepitope-specific and differentiation antigen-specific CD8+ T cells were detected in the blood. A second SBRT after 10 months on anti-PD-1 induced a radiologic complete response correlating with an increase in activated PD-1-expressing CD8 T cells. Apart from a new lung lesion, which was also irradiated, this deep abscopal response lasted for more than 2.5 years. However, thereafter, his disease progressed and the activated PD-1-expressing CD8 T cells dropped. Our data suggest that oligometastatic patients, where a large proportion of the tumor mass can be irradiated, are good candidates to improve ICB responses by RT, even in the case of an unfavorable pretreatment immune signature, after progression on anti-PD-1, and despite advanced age. Besides repeated irradiation, T cell epitope-based immunotherapies (e.g., vaccination) may prolong antitumor responses even in patients with unfavorable pretreatment immune signature.

Adding Indoximod to Hypofractionated Radiotherapy with Anti-PD-1 Checkpoint Blockade Enhances Early NK and CD8+ T-Cell-Dependent Tumor Activity.

PURPOSE: There is growing interest in combinations of immunogenic radiotherapy (RT) and immune checkpoint blockade, but clinical responses are still limited. Therefore, we tested the triple therapy with an inhibitor of the indoleamine 2,3-dioxygenase pathway, which like immune checkpoints, downregulates the antitumor immune response. EXPERIMENTAL DESIGN: Triple treatment with hypofractionated RT (hRT) + anti-PD-1 antibody (αPD1) + indoximod was compared with the respective mono- and dual therapies in two syngeneic mouse models. RESULTS: The tumors did not regress following treatment with hRT + αPD1. The αPD1/indoximod combination was not effective at all. In contrast, triple treatment induced rapid, marked tumor regression, even in mice with a large tumor. The effects strongly depended on CD8+ T cells and partly on natural killer (NK) cells. Numbers and functionality of tumor-specific CD8+ T cells and NK cells were increased, particularly early during treatment. However, after 2.5-3 weeks, all large tumors relapsed, which was accompanied by increased apoptosis of tumor-infiltrating lymphocytes associated with a non-reprogrammable state of exhaustion, terminal differentiation, and increased activation-induced cell death, which could not be prevented by indoximod in these aggressive tumor models. Some mice with a smaller tumor were cured. Reirradiation during late regression (day 12), but not after relapse, cured almost all mice with a large B16-CD133 tumor, and strongly delayed relapse in the less immunogenic 4T1 model, depending on CD8+ T cells. CONCLUSIONS: Our findings may serve as a rationale for the clinical evaluation of this triple-combination therapy in patients with solitary or oligometastatic tumors in the neoadjuvant or the definitive setting.

Cisplatin Facilitates Radiation-Induced Abscopal Effects in Conjunction with PD-1 Checkpoint Blockade Through CXCR3/CXCL10-Mediated T-cell Recruitment.

PURPOSE: Localized radiotherapy can cause T-cell-mediated abscopal effects on nonirradiated metastases, particularly in combination with immune checkpoint blockade (ICB). However, results of prospective clinical trials have not met the expectations. We therefore investigated whether additional chemotherapy can enhance radiotherapy-induced abscopal effects in conjunction with ICB. EXPERIMENTAL DESIGN: In three different two-tumor mouse models, triple therapy with radiotherapy, anti-PD-1, and cisplatin (one of the most widely used antineoplastic agents) was compared with double or single therapies. RESULTS: In these mouse models, the response of the nonirradiated tumor and the survival of the mice were much better upon triple therapy than upon radiotherapy + anti-PD-1 or cisplatin + anti-PD-1 or the monotherapies; complete regression of the nonirradiated tumor was usually only observed in triple-treated mice. Mechanistically, the enhanced abscopal effect required CD8+T cells and relied on the CXCR3/CXCL10 axis. Moreover, CXCL10 was found to be directly induced by cisplatin in the tumor cells. Furthermore, cisplatin-induced CD8+T cells and direct cytoreductive effects of cisplatin also seem to contribute to the enhanced systemic effect. Finally, the results show that the abscopal effect is not precluded by the observed transient radiotherapy-induced lymphopenia. CONCLUSIONS: This is the first report showing that chemotherapy can enhance radiotherapy-induced abscopal effects in conjunction with ICB. This even applies to cisplatin, which is not classically immunogenic. Whereas previous studies have focused on how to effectively induce tumor-specific T cells, this study highlights that successful attraction of the induced T cells to nonirradiated tumors is also crucial for potent abscopal effects.