α-PD-L1 mAb enhances the abscopal effect of hypo-fractionated radiation by attenuating PD-L1 expression and inducing CD8+ T-cell infiltration

Impacts of combining PD-L1 inhibitor and radiotherapy on the tumour immune microenvironment in a mouse model of esophageal squamous cell carcinoma

BACKGROUND

The combination of radiation with immune checkpoint inhibitors (ICIs) has been demonstrated to display synergistic effects in solid cancers. Nevertheless, the anti-tumor effect of combining radiation with programmed cell death 1 ligand 1 (PD-L1) inhibitor in esophageal squamous cell carcinoma (ESCC) has remained unclear. Therefore, the objectives of our study were to evaluate the anti-tumor effects of PD-L1 inhibitors combined with radiotherapy in a mouse model of ESCC and to depict the immune landscape within the tumor microenvironment (TME).

METHODS

Murine ESCC cells (mEC25) were injected subcutaneously into the right flanks of C57BL/6 mice. Tumor-bearing mice were exposed to different treatments: IgG antibody (control), anti-PD-L1 antibody, radiation, or radiation + anti-PD-L1 antibody. Tumor growth and survival time of mice were monitored. Tumour immune microenvironment was assessed by flow cytometry, including CD4+T cells, CD8+T cells, regulatory T cells (Tregs), tumor-associated macrophages (TAMs), myeloid-derived suppressor cells (MDSCs), and the activation and exhaustion of CD8+T cell. In addition, transcriptomic analysis was used to examine the changes in immune gene expression in the TME.

RESULTS

Radiotherapy combined with anti-PD-L1 inhibitors (radioimmunotherapy) synergistically enhanced anti-tumor immune response, leading to decreased tumor growth and prolonged survival of tumor-bearing mice. The radioimmunotherapy increased the infiltration of CD8+ T cells, the ratio of CD8+ T cells to Tregs, the population of central memory CD8+ T cells (TCM), interferon-gamma (IFN-γ) secretion of tumor-infiltrating CD8+ T cells, and reduced the accumulation of M2-type TAMs and Tregs in the TME in mouse model. In addition, the radioimmunotherapy induced anti-tumor immune response in the spleen and tumor-draining lymph node (TDLN). Moreover, transcriptomic analysis suggested that the radioimmunotherapy promoted the activation of immune regulatory pathways and increased the expression of cytokines such as CXCL9 and CXCL10, thus creating an immunoinflammatory tumor microenvironment.

CONCLUSIONS

Our research revealed that anti-PD-L1 inhibitors combined with radiotherapy caused systemic anti-tumor immunity by reshaping the immune microenvironment in a mouse model of ESCC.

Combination of radiotherapy and PD-L1 blockade induces abscopal responses in EGFR-mutated lung cancer through activating CD8+ T cells

Patients with EGFR-mutated non-small cell lung cancer (NSCLC) respond poorly to immune checkpoint inhibitors (ICIs). It has been reported that the number of CD8+T cells is reduced in EGFR-mutated NSCLC. However, the extent of heterogeneity and effector function of distinct populations of CD8+T cells has not been investigated intensively. In addition, studies investigating whether a combination of radiotherapy and ICIs can improve the efficacy of ICIs in EGFR-mutated lung cancer are lacking. Single-cell RNA sequencing (scRNA-seq) was used to investigate the heterogeneity of CD8+T cell populations in EGFR-mutated NSCLC. The STING pathway was explored after hypofractionated radiation of EGFR-mutated and wild-type cells. Mice bearing LLC-19del and LLC-EGFR tumors were treated with radiotherapy plus anti-PD-L1. The scRNA-seq data showed the percentage of progenitor exhausted CD8+T cells was lower in EGFR-mutated NSCLC. In addition, CD8+T cells in EGFR-mutated NSCLC were enriched in oxidative phosphorylation. In EGFR-mutated and wild-type cells, 8 Gy × 3 increased the expression of chemokines that recruit T cells and activate the cGAS-STING pathway. In the LLC-19del and LLC-EGFR mouse model, the combination of radiation and anti-PD-L1 significantly inhibited the growth of abscopal tumors. The enhanced abscopal effect was associated with systemic CD8+T cell infiltration. This study provided an intensive understanding of the heterogeneity and effector functions of CD8+T cells in EGFR-mutated NSCLC. We showed that the combination of hypofractionated radiation and anti-PD-L1 significantly enhanced the abscopal responses in both EGFR-mutated and wild-type lung cancer by activating CD8+T cells in mice.

Optimized CAR-T therapy based on spatiotemporal changes and chemotactic mechanisms of MDSCs induced by hypofractionated radiotherapy

Poor intratumoral infiltration is the major challenge for chimeric antigen receptor (CAR)-T cell therapy in solid tumors. Hypofractionated radiotherapy (HFRT) has been reported to induce immune cell infiltration and reshape the tumor immune microenvironment. Here, we showed that HFRT (5 × 5 Gy) mediated an early accumulation of intratumoral myeloid-derived suppressor cells (MDSCs) and decreased infiltration of T cells in the tumor microenvironment (TME) of immunocompetent mice bearing triple-negative breast cancer (TNBC) or colon cancer, which was further confirmed in tumors from patients. RNA sequencing (RNA-seq) and cytokine profiling analysis revealed that HFRT induced the activation and proliferation of tumor-infiltrated MDSCs, which was mediated by the interactions of multiple chemokines and chemokine receptors. Further investigation showed that when combined with HFRT, CXCR2 blockade significantly inhibited MDSCs trafficking to tumors and effectively enhanced the intratumoral infiltration and treatment efficacy of CAR-T cells. Our study demonstrates that MDSCs blockade combined with HFRT is promising for CAR-T cell therapy optimization in solid tumors.

Effect of triple therapy with low-dose total body irradiation and hypo-fractionated radiation plus anti-programmed cell death protein 1 blockade on abscopal antitumor immune responses in breast cancer

Immunostimulatory effects of radiotherapy can be synergistically augmented with immune checkpoint blockade to act both on irradiated tumor lesions and distant, non-irradiated tumor sites. Our hypothesis was that low-dose total body irradiation (L-TBI) combined with hypo-fractionated radiotherapy (H-RT) and anti-programmed cell death protein 1 (aPD-1) checkpoint blockade would enhance the systemic immune response. We tested the efficacy of this triple therapy (L-TBI + H-RT + aPD-1) in BALB/c mice with bilateral breast cancer xenografts. The L-TBI dose was 0.1 Gy. The primary tumor was treated with H-RT (8 Gy × 3). The PD-1 monoclonal antibody was injected intraperitoneally, and the secondary tumors not receiving H-RT were monitored for response. The triple therapy significantly delayed both primary and secondary tumor growths, improved survival rates, and reduced the number of lung metastasis lesions. It increased the activated dendritic and CD8⁺ T cell populations and reduced the infiltration of myeloid-derived suppressor cells in the secondary tumor microenvironment relative to other groups. Thus, L-TBI could be a potential therapeutic modality, and when combined with H-RT and aPD-1, the therapeutic effect could be enhanced significantly.

Flow cytometry-assisted quantification of immune cells infiltrating irradiated tumors in mice

The immunomodulatory properties of local hypofractionated radiotherapy are known to promote the generation of anti-tumor immune responses. Such responses are largely due to the infiltration of cytotoxic lymphocytes (TILs) into the tumors that are able to destroy malignant lesions. In this context, characterizing the tumor immune microenvironment following radiotherapy is crucial for the study of its mechanism of action. Flow cytometry-based analyses are frequently used to elucidate changes in the tumor immune microenvironment. The use of a fluorochrome-conjugated antibody panel is currently a standard technique to assess the number and phenotype of immune cell populations infiltrating the tumors. Here, we describe a method to isolate and quantify TILs based on flow-cytometry in mammary carcinoma-bearing mice that undergo a local hypofractionated radiotherapy regimen consisting of 3 consecutive doses of 8 Gy. With some adaptations, this protocol can be successfully applied to a diverse range of transplantable and inducible solid mouse tumors of different origins.

Research Progress on Radiotherapy Combined with Immunotherapy for Associated Pneumonitis During Treatment of Non-Small Cell Lung Cancer

Radiation pneumonitis is a common and serious complication of radiotherapy for thoracic tumours. Although radiotherapy technology is constantly improving, the incidence of radiation pneumonitis is still not low, and severe cases can be life-threatening. Once radiation pneumonitis develops into radiation fibrosis (RF), it will have irreversible consequences, so it is particularly important to prevent the occurrence and development of radiation pneumonitis. Immune checkpoint inhibitors (ICIs) have rapidly altered the treatment landscape for multiple tumour types, providing unprecedented survival in some patients, especially for the treatment of non-small cell lung cancer (NSCLC). However, in addition to its remarkable curative effect, ICls may cause immune-related adverse events. The incidence of checkpoint inhibitor pneumonitis (CIP) is 3% to 5%, and its mortality rate is 10% to 17%. In addition, the incidence of CIP in NSCLC is higher than in other tumour types, reaching 7%–13%. With the increasing use of immune checkpoint inhibitors (ICls) and thoracic radiotherapy in the treatment of patients with NSCLC, ICIs may induce delayed radiation pneumonitis in patients previously treated with radiation therapy, or radiation activation of the systemic immune system increases the toxicity of adverse reactions, which may lead to increased pulmonary toxicity and the incidence of pneumonitis. In this paper, the data about the occurrence of radiation pneumonitis, immune pneumonitis, and combined treatment and the latest related research results will be reviewed.

Next-generation engineered nanogold for multimodal cancer therapy and imaging: a clinical perspectives

Cancer is one of the significant threats to human life. Although various latest technologies are currently available to treat cancer, it still accounts for millions of death each year worldwide. Thus, creating a need for more developed and novel technologies to combat this deadly condition. Nanoparticles-based cancer therapeutics have offered a promising approach to treat cancer effectively while minimizing adverse events. Among various nanoparticles, nanogold (AuNPs) are biocompatible and have proved their efficiency in treating cancer because they can reach tumors via enhanced permeability and retention effect. The size and shape of the AuNPs are responsible for their diverse therapeutic behavior. Thus, to modulate their therapeutic values, the AuNPs can be synthesized in various shapes, such as spheres, cages, flowers, shells, prisms, rods, clusters, etc. Also, attaching AuNPs with single or multiple targeting agents can facilitate the active targeting of AuNPs to the tumor tissue. The AuNPs have been much explored for photothermal therapy (PTT) to treat cancer. In addition to PTT, AuNPs-based nanoplatforms have been investigated for combinational multimodal therapies in the last few years, including photodynamic therapy, chemotherapy, radiotherapy, immunotherapy, etc., to ablate cancer cells. Thus, the present review focuses on the recent advancements in the functionalization of AuNPs-based nanoconstructs for cancer imaging and therapy using combinatorial multimodal approaches to treat various cancers.

Local Destruction of Tumors and Systemic Immune Effects

Current immune-based therapies signify a major advancement in cancer therapy; yet, they are not effective in the majority of patients. Physically based local destruction techniques have been shown to induce immunologic effects and are increasingly used in order to improve the outcome of immunotherapies. The various local destruction methods have different modes of action and there is considerable variation between the different techniques with respect to the ability and frequency to create a systemic anti-tumor immunologic effect. Since the abscopal effect is considered to be the best indicator of a relevant immunologic effect, the present review focused on the tissue changes associated with this effect in order to find determinants for a strong immunologic response, both when local destruction is used alone and combined with immunotherapy. In addition to the T cell-inflammation that was induced by all methods, the analysis indicated that it was important for an optimal outcome that the released antigens were not destroyed, tumor cell death was necrotic and tumor tissue perfusion was at least partially preserved allowing for antigen presentation, immune cell trafficking and reduction of hypoxia. Local treatment with controlled low level hyperthermia met these requisites and was especially prone to result in abscopal immune activity on its own.

Ai X, Cai Y, Chu Q, Han C, Lu Y, Qin S, Wu L, Xie C, Yuan Z, Zhong W, Zhu X, Chang JY, Zhu Z. [Combination of Radiation Therapy and Immunotherapy for Non-small Cell Lung Cancer: Peer Exchange on Frontier Academic Topics]

肺癌是目前导致全球和中国癌症患者死亡的主要瘤种。多年来，常规的肿瘤治疗方法，如手术、化疗和放疗一直主导着非小细胞肺癌（non-small cell lung cancer, NSCLC）治疗领域。临床实践中引入免疫疗法使肺癌的治疗与其他实体瘤一样发生了根本性转变。最新临床前和临床数据表明，放疗可以通过诱导免疫原性细胞死亡和重新编程肿瘤微环境促进抗肿瘤免疫反应。研究者开始重新审视放疗作为免疫治疗的联合疗法，导致研究其潜在协同作用的临床试验数量呈指数级增长。放疗联合免疫治疗的临床试验引起了医疗界的广泛关注，会议邀请专家交流前沿及争议学术问题：①放疗联合免疫检查点抑制剂治疗NSCLC最新进展；②放疗联合免疫治疗是否显著增加毒性；③免疫检查点抑制剂治疗后出现的混合反应及局部治疗的干预价值；④放疗联合免疫治疗脑转移瘤的机制和进展。

Is a higher estimated dose of radiation to immune cells predictive of survival in patients with locally advanced non-small cell lung cancer treated with thoracic radiotherapy?

BACKGROUND AND PURPOSE

In previous studies, the estimated dose of radiation to immune cells (EDRIC) showed a correlation with overall survival (OS) of patients with locally advanced non-small cell lung cancer (LA-NSCLC) who received thoracic radiotherapy. However, several factors such as gross tumor volume (GTV) and lymph node (N) stage may impact EDRIC. The purpose of this study was to identify the factors influencing EDRIC and to further assess the prognostic relevance of EDRIC.

MATERIALS AND METHODS

We retrospectively analyzed 201 patients with LA-NSCLC who received radiotherapy between 2012 and 2017. EDRIC was calculated based on the model developed by Jin et al. Kaplan-Meier method and Cox proportional hazards regression were used to analyze the correlation of potential factors with OS, local progression-free survival (LPFS), and distant metastasis-free survival (DMFS). Spearman's rank correlation was used to assess the correlation between variables.

RESULTS

Both GTV and N stage showed a positive correlation with EDRIC (r = 0.347, P < 0.001 and r = 0.249, P < 0.001, respectively). EDRIC was independently associated with DMFS (HR 1.185, P < 0.001). GTV was associated with OS (HR 1.006, P < 0.001), LPFS (HR 1.003, P = 0.017), and DMFS (HR 1.003, P = 0.032). While using GTV as a stratification factor in Kaplan-Meier analysis, EDRIC showed a trend of negative correlation with OS in GTV ≤ 66.6 cm³ group (P = 0.061).

CONCLUSION

EDRIC was an independent prognostic factor for metastasis and it was affected by GTV and N stage. However, the effect of EDRIC on OS was influenced by GTV.

Immunotherapy as sensitizer for local radiotherapy

The purpose of this report was to systematically review the radiation enhancement factor (REF) effects of immunotherapy on radiotherapy (RT) to the local tumor in comparison with other traditional radiation sensitizers such as cisplatin. PubMed and Medline databases were searched until February 2019. Reports with abscopal effect in the results were excluded. Graphs of the selected papers were digitized using Plot Digitizer (Sourceforge.net) in order to calculate the tumor growth delay (TGD) caused by immunotherapy. To enable comparison between different studies,the TGD were used to define the REF between RT versus the RT/immunotherapy combination. Thirty-two preclinical papers, and nine clinical series were selected. Different mouse models were exposed to RT doses ranging from 1 to 10 fractions of 1.8 to 20 Gray (Gy) per fraction. Endpoints were heterogeneous, ranging from regression to complete local response. No randomized clinical studies were identified. The median preclinical REF effect of different immunotherapy was varying from 1.7 to 9.1. There was no relationship observed either with subclasses of immunotherapy orRT doses. In the clinical studies, RT doses ranged from 1 to 37 fractions of 1.8 to 24 Gy per fraction. Most clinical trials used ipilimumab and interleukin-2. Local control rate in the clinical series ranged from 66% to 100%. A strong REF of immunotherapy (1.7 to 9.1) was observed, this being higher than traditionally sensitizers such as cisplatin (1.1). This result implies that for the same RT dose, a higher local control was achieved with a combination of immunotherapy and RT in preclinical settings. This study therefore supports the use of combined RT and immunotherapy to improve local tumor control in clinical settings without exacerbation of toxicities.

Effect of Low-Dose Radiation Therapy on Abscopal Responses to Hypofractionated Radiation Therapy and Anti-PD1 in Mice and Patients With Non-Small Cell Lung Cancer

PURPOSE

Hypofractionated radiation therapy (HFRT) can induce antitumor T cell responses, particularly in combination with immune checkpoint inhibitors (ICI), but abscopal effects are often precluded by insufficient T cell infiltration of distant, nonirradiated tumors. Additional noncytotoxic, low-dose radiation therapy (LDRT) of distant tumors may enhance the abscopal response, but clinical evidence and preclinical studies for this scenario are lacking.

METHODS AND MATERIALS

We investigated whether triple treatment consisting of HFRT, ICI, and LDRT could achieve better systemic antitumor response in bilateral mouse tumor models and in patients with stage IV non-small cell lung cancer.

RESULTS

Our analyses of bilateral mouse tumor models show that HFRT treatment of the primary tumor combined with LDRT treatment of the abscopal tumor and anti-PD1 therapy enhances the abscopal response compared with HFRT/anti-PD1, HFRT/LDRT, or LDRT/anti-PD1 double treatments; complete cure was observed in more than half of the mice treated with triple therapy. The enhanced abscopal effect was associated with increased infiltration of CD8+ effector T cells and upregulated expression of T cell-attracting chemokines. Of 9 patients with metastatic non-small cell lung cancer who were treated with this triple therapy, 3 and 2 patients showed partial responses and stable disease, respectively. Among 9 relatively large (175.7 ± 42.3 cm³) LDRT lesions, 6 lesions decreased by 28% in size, on average.

CONCLUSIONS

Our study demonstrates preclinically that LDRT of established metastases significantly enhances the abscopal response to HFRT plus ICI. It also shows that additional LDRT was well tolerated by patients and that this treatment profile is effective and worth further study.

Pure abscopal effect of radiotherapy in a salivary gland carcinoma: Case report, literature review, and a search for new approaches

We report the case of an 84-year-old woman with poorly differentiated non-small cell carcinoma of the right parotid who presented with headache, was found to have a primary right parotid gland cancer as well as metastatic disease, and underwent palliative radiotherapy to the primary site. The patient received no chemotherapy or immunotherapy, but both the primary site and several non-irradiated foci in the lungs regressed or completely resolved. The patient remained free of disease for about one year before progression. The case is a rare instance of abscopal regression of metastatic disease in the absence of pharmacologic immunomodulation. A literature review surveys the history of the abscopal effect of radiation therapy, attempts to understand the mechanisms of its successes and failures, and points to new approaches that can inform and improve the outcomes of radioimmunotherapy.

Monitoring abscopal responses to radiation in mice

Focal radiation therapy has the potential to generate systemic tumor-targeting immune responses so potent as to eradicate anatomically distant, non-irradiated malignant lesions, a phenomenon commonly referred to as "the abscopal response." In cancer patients, bona fide abscopal responses are rare, although the recent introduction of immune checkpoint blockers into the clinical practice has significantly increased their incidence. In rodents, abscopal responses can be conveniently modeled by establishing two, slightly asynchronous and anatomically distant subcutaneous tumors in syngeneic immunocompetent hosts, provided that the therapeutic partners of radiation potentially included in the regimen of choice do not mediate systemic anticancer effects per se. Here, we describe such method to monitor abscopal responses based on mammary carcinoma TSA cells implanted in syngeneic immunocompetent BALB/c mice. With minor variations, the same technique can be conveniently applied to a variety of transplantable mouse tumors.