Immune-mediated Abscopal Effects Research Articles

Bioactivable STING Nanoagonists to Synergize NIR-II Mild Photothermal Therapy Primed Robust and Long-Term Anticancer Immunity.

Pharmacological activation of the stimulator of interferon genes (STING) pathway has become a promising strategy for cancer immunotherapy. However, the insufficient tumorous accumulation, rapid clearance, and short duration of drug efficacy in the tumor microenvironment of small structural STING agonists greatly compromise the therapeutic efficacy. Herein, a tumorous extracellular matrix (ECM) is presented anchoring STING agonist-based photoimmunothernostic nanomedicine (SAPTN) that can be activated by mild-temperature photothermal therapy (mild PTT) induced neutrophilic inflammation. The SAPTN owns second window near-infrared (NIR-II) photonics properties fitting for NIR-II fluorescence and photoacoustic imaging-guided cancer therapy. The aggregates SAPTN targeting to the ECM provide slow and continuous release of potent STING agonists diABZIs. The mild PTT and long-lasting STING agonists released in the ECM synergisticallyprime systematic, robust, and long-term anticancer immunity. In a tumor model, this approach leads to complete tumor eradication in about 100% of mice with orthotopic breast tumors, and the mice regained tumor-free survival of at least 2 months. In addition, the immune-mediated abscopal effect shows inhibition of the distant solid tumor growth by intratumoral administration of SAPTN with laser irradiation. Overall, this approach represents a generalized photoactivable nanomedicine to prime anticancer immunity for improved cancer theranostics.

Shifting the Immune-Suppressive to Predominant Immune-Stimulatory Radiation Effects by SBRT-PArtial Tumor Irradiation Targeting HYpoxic Segment (SBRT-PATHY).

Simple SummaryThis review presents and summarizes the key components and outcomes of a novel, unconventional radiation approach aimed to exploit immune-stimulatory radiation effects which, being added to direct radiation tumor cell killing, may improve the therapeutic ratio of radiotherapy. This technique, as a product of translational oncology research, was intentionally developed for the induction of immune-mediated bystander and abscopal effects in the treatment of unresectable bulky tumors which have much fewer therapeutic options and show poor prognoses after conventional treatments. This review offers insights into a unique unconventional radiotherapy technique which, due to its higher immunogenic potential, may improve the prognosis of patients affected by highly complex malignancies, providing additional opportunities for future research in terms of combining novel immuno-modulating agents with more modern radiotherapy approaches.Radiation-induced immune-mediated abscopal effects (AE) of conventional radiotherapy are very rare. Whole-tumor irradiation leads to lymphopenia due to killing of immune cells in the tumor microenvironment, resulting in immunosuppression and weak abscopal potential. This limitation may be overcome by partial tumor irradiation sparing the peritumoral immune-environment, and consequent shifting of immune-suppressive to immune-stimulatory effect. This would improve the radiation-directed tumor cell killing, adding to it a component of immune-mediated killing. Our preclinical findings showed that the high-single-dose irradiation of hypoxic tumor cells generates a stronger bystander effect (BE) and AE than the normoxic cells, suggesting their higher “immunogenic potential”. This led to the development of a novel Stereotactic Body RadioTherapy (SBRT)-based PArtial Tumor irradiation targeting HYpoxic segment (SBRT-PATHY) for induction of the immune-mediated BE and AE. Encouraging SBRT-PATHY-clinical outcomes, together with immunohistochemical and gene-expression analyses of surgically removed abscopal-tumor sites, suggested that delivery of the high-dose radiation to the partial (hypoxic) tumor volume, with optimal timing based on the homeostatic fluctuation of the immune response and sparing the peritumoral immune-environment, would significantly enhance the immune-mediated anti-tumor effects. This review discusses the current evidence on the safety and efficacy of SBRT-PATHY in the treatment of unresectable hypoxic bulky tumors and its bystander and abscopal immunomodulatory potential.

Ionizing radiation results in a mixture of cellular outcomes including mitotic catastrophe, senescence, methuosis, and iron-dependent cell death

Radiotherapy is commonly used as a cytotoxic treatment of a wide variety of tumors. Interestingly, few case reports underlined its potential to induce immune-mediated abscopal effects, resulting in regression of metastases, distant from the irradiated site. These observations are rare, and apparently depend on the dose used, suggesting that dose-related cellular responses may be involved in the distant immunogenic responses. Ionizing radiation (IR) has been reported to elicit immunogenic apoptosis, necroptosis, mitotic catastrophe, and senescence. In order to link a cellular outcome with a particular dose of irradiation, we performed a systematic study in a panel of cell lines on the cellular responses at different doses of X-rays. Remarkably, we observed that all cell lines tested responded in a similar fashion to IR with characteristics of mitotic catastrophe, senescence, lipid peroxidation, and caspase activity. Iron chelators (but not Ferrostatin-1 or vitamin E) could prevent the formation of lipid peroxides and cell death induced by IR, suggesting a crucial role of iron-dependent cell death during high-dose irradiation. We also show that in K-Ras-mutated cells, IR can induce morphological features reminiscent of methuosis, a cell death modality that has been recently described following H-Ras or K-Ras mutation overexpression.

Marginless Radiotherapy (MRT): Leveraging The Abscopal Effect Toward The Treatment Of Metastatic Castration Resistant Prostate Cancer

Marginless Radiotherapy (MRT) is a new radiotherapy approach whereby only the gross tumor volume (GTV) or sub-volume (sv) is irradiated. We sought to investigate the potential of MRT in combination with in-situ delivered anti-CD40 to generate a robust abscopal effect in metastatic castration resistant prostate cancer. Using an aggressive castration resistant prostrate adenocarcinoma cell line derived from TRAMP-C1, two contralateral tumors were implanted in each mouse either subcutaneously (SQ) in two flanks or one SQ and one orthotopic to anterior prostate lobe. In both cases one SQ tumor was chosen to be treated. The mice were randomly assigned to different cohorts (n = 5-8) for image-guided radiotherapy (IGRT) of a single dose of 2, 5, 8, or 10 Gy using Small Animal Radiation Research Platform (SARRP). Following the IGRT, each cohort was treated with 20 μg of intratumoral mouse antiCD40 antibody loaded in a smart radiotherapy biomaterial (srbAntiCD40) for sustain release. These cohorts were then compared with a control group with no treatment. Tumor volume of both treated (treated site) and untreated tumors (abscopal site) were then measured and survival percent was calculated to determine the most potent RT dose which was then used for the PTV vs. GTV/sv of IGRT study. PTV of IGRT was delivered with 10x10 mm2 field size collimators whereas 1x1, 3x3, or 5x5 mm2 field size collimators were used for GTV/sv. Statistical analyses for tumor volume and Kaplan–Meier survival assay were then analyzed. A single fraction IGRT dose of 5 Gy to the PTV with srbAntiCD40 shows the highest survival fraction (****) compare with other radiation doses. Further analysis of 5 Gy of IGRT in PTV or GTV/sv along with srbAntiCD40 (intratumoral) demonstrates non-significant difference of the survival rate with PTV (80%**) compare to GTV/sv in SQ model (100%***) or orthotopic model (80%***). Similarly, fold increase of tumor volume (from day of treatment) in treated sides were 91 (+/- 11.5), 11* (+/- 6.5), 6* (+/-2.5), and 6* (+/- 2.5) respectively for Control, RT-PTV, RT-GTVsv (SQ), and RT-GTVsv (orthotopic) cohorts. Untreated, abscopal side tumors also shown similar effects (60 (+/- 17.4), 13** (+/- 2.4), 11**(+/-2.1), and 6** (+/- 1.3) respectively. Complete regression of both of the tumors were shown in 20% of mice in both SQ and orthotopic RT-GTVsv groups. Significant high infiltration of CD8+ cytotoxic T cells were also observed in both treated and untreated tumors of both PTV and GTVsv cohorts, 10 days after the treatment given. This study proffers a new MRT strategy for treating aggressive metastatic prostate cancer, leveraging the abscopal effect more efficaciously by treating only a GTV/sv which further reduces the radiation induced toxicity. This strategy may spare peripheral APCs cells, which are crucial in driving the immune-mediated abscopal effect.

Hypofractionated Radiation Therapy Induces an Immune-Mediated Abscopal Effect When Combined with Anti-PD-1 Antibody

Anti tumor check-point immunotherapy could be synergized with local RT.However, various fraction regimens may lead to different immune response.In this study, we tested the immune response under different RT fraction regimens and chose the best fraction regimen to combine with anti-PD-1 immunotherapy. 4T1 murine breast tumor cells were implanted on left and right thigh of BALB/C mice as primary and secondary tumor. Five different fraction SBRT(24Gy×1,8Gy×3,8Gy×1-2Gy×8 or 2Gy×12f) were delivered on primary tumor.Immune response was detected in bilateral tumors, bilateral regional drainage lymph nodes, and spleen, including CD4+T cells, CD8+T cells, CD8+IFN-γ+T cells, and myeloid-derived suppressor cell (MDSC). Then, the best fraction regimen RT was chosen to combine with human anti-PD-1 mAb(HR301210),on humanPD-1 gene knocked-in mice. Relative local and systematic immune response was also detected. No obvious abscopal effect was observed under different fraction RT alone. Though each of the RT regimens achieved growth delay of the irradiated tumor but not the contralateral tumor, we found 24Gy×1 and 8Gy×3 fraction regimens delayed the primary tumor growth more evident than 8Gy×1-2Gy×8 and 2Gy×12f fraction regimens(P＜0.05 and P＜0.05). Hypofractionated radiotherapy(HRT) regimens including 24Gy×1 and 8Gy×3 achieved significantly higher CD8+ tumor infiltrating lymphocytes (TILs)(P＜0.001 and P＜0.05) in bilateral tumors, higher CD4+TILs (P＜0.001 and P＜0.001) in regional drainage lymph nodes of the primary tumor,higher CD4+T cells(P>0.05 and P＜0.05) and CD8 + IFN-γ + T cells (P>0.05 and P>0.05) in the spleen, and lower MDSC (P＜0.001and P＜0.001) in the spleenon 5 days after RT. However, the tendency of immune response stimulation at 48 hours RT was not as obvious as 5 days after RT. We only found CD4+T cells in regional drainage lymph nodes of the primary tumor were evidently higher of all RT groups than control group. In the next study, on day 20 after MC38 colorectal cancer cells injection, we observed primary tumor regression（P＜0.001) and remarkable contralateral tumor regression（P＜0.001)outside the radiation field in 8Gy×3 combined with PD-1-blocking mAb group, the so-called abscopal effect, whichnot occurred in other three groups.So far, we observed that different treatment regimens lead to different immune response. In systemic immune response, compared with single RT or single IT, RT combined with IT increased CD4+T cells（P＜0.05) and CD8+T cells（P＜0.05), decreased MDSC（P＜0.05) in spleen.In local immune response, the tendancy was not as obvious as systemic immune response.More detailed results from ongoing works remain to be further analyzed. Antitumor immune response could be activated by HRTbetter than CRT, which were mostly mediated by CD4+, CD8+T cells and MDSCs.Evident abscopal effect was found after combining SBRT withanti-PD-1 mAb.

Oncolytic peptide LTX-315 induces an immune-mediated abscopal effect in a rat sarcoma model

ABSTRACTLTX 315 is an oncolytic peptide with potent immunological properties. In the present study, we demonstrate that intratumoral treatment with LTX-315 resulted in a complete regression and systemic immune response in a rat fibrosarcoma model. The treatment was T-cell dependent, and also resulted in an abscopal effect as demonstrated by the regression of distal non-treated lesions. Significant infiltration of CD8+ T cells was observed in both treated and non-treated lesions, as shown by immunohistochemical and flow cytometric analysis. LTX-315 rapidly killed the cells in vitro with a lytic mode of action followed by the subsequent release of Danger-Associated Molecular Pattern (DAMP) molecules such as HMGB1, ATP and Cytochrome c. Together, our data demonstrate that LTX-315 represents a new approach to cancer immunotherapy, which has the potential as a novel immunotherapeutic agent.

Addition of anti-neu antibody to local irradiation can improve tumor-bearing BALB/c mouse survival through immune-mediated mechanisms.

This study investigated the therapeutic effects of combined local irradiation and anti-HER2/neu antibody in a mixed tumor mouse model comprised of a nonmetastatic neu-positive tumor and a metastatic neu-negative tumor. While local irradiation alone could control the primary tumor in a dose-dependent manner, it did not improve mouse survival. Combined treatment comprised of local irradiation and anti-neu antibody of tumor-bearing BALB/c mice significantly improved mouse survival (P < 0.5), even though the tumor growth was similar to that of the irradiated-alone group. The combined treatment significantly reduced metastatic tumor masses in the lung and increased immune cell infiltration in primary tumor tissues. However, immune deficient nude mice with tumors did not exhibit prolonged survival in response to the combined treatment. Collectively, these results show that combined local irradiation and anti-neu antibody can elicit an immune-mediated abscopal effect to extend survival. Although the mechanism for abscopal effects induced by the combined treatment of radiation and anti-HER2/neu antibody was not elucidated, to our knowledge this is the first published study to describe the abscopal effect induced by the combination of local irradiation and the anti-HER2/neu antibody.

Ionizing Radiation With An Endoplasmic Reticulum Stress-inducer Promotes Calreticulin Redistribution: A Marker Of Immunogenic Cell Death

Danger signals induced by ionizing radiation (IR) may contribute to an immune-mediated response at the irradiated tumor site, thereby negating the immunosuppressive microenvironment of established tumors. We previously demonstrated that fractionated IR induces an immune-mediated abscopal effect, when combined with CTLA-4 antibodies in vivo. However, the initiating molecular mechanisms behind this effect are not well understood. Recently, Guido Kroemer's group at Villejuif demonstrated that endoplasmic reticulum (ER) stress can restore the immunogenicity of tumors treated with oxaliplatin, via the surface expression of calreticulin (CRT), an ER resident protein and potent dendritic cell “eat me” signal.

Fractionated but Not Single-Dose Radiotherapy Induces an Immune-Mediated Abscopal Effect when Combined with Anti–CTLA-4 Antibody

This study tested the hypothesis that the type of dose fractionation regimen determines the ability of radiotherapy to synergize with anti-CTLA-4 antibody. TSA mouse breast carcinoma cells were injected s.c. into syngeneic mice at two separate sites, defined as a "primary" site that was irradiated and a "secondary" site outside the radiotherapy field. When both tumors were palpable, mice were randomly assigned to eight groups receiving no radiotherapy or three distinct regimens of radiotherapy (20 Gy x 1, 8 Gy x 3, or 6 Gy x 5 fractions in consecutive days) in combination or not with 9H10 monoclonal antibody against CTLA-4. Mice were followed for tumor growth/regression. Similar experiments were conducted in the MCA38 mouse colon carcinoma model. In either of the two models tested, treatment with 9H10 alone had no detectable effect. Each of the radiotherapy regimens caused comparable growth delay of the primary tumors but had no effect on the secondary tumors outside the radiation field. Conversely, the combination of 9H10 and either fractionated radiotherapy regimens achieved enhanced tumor response at the primary site (P < 0.0001). Moreover, an abscopal effect, defined as a significant growth inhibition of the tumor outside the field, occurred only in mice treated with the combination of 9H10 and fractionated radiotherapy (P < 0.01). The frequency of CD8+ T cells showing tumor-specific IFN-gamma production was proportional to the inhibition of the secondary tumor. Fractionated but not single-dose radiotherapy induces an abscopal effect when in combination with anti-CTLA-4 antibody in two preclinical carcinoma models.