Immunotherapy prospects in the treatment of lung cancer and mesothelioma

Lymphopenia predicts response to stereotactic radiosurgery in lung cancer patients with brain metastases

BACKGROUND

Stereotactic radiosurgery (SRS) can enhance immune activation and improve disease control through stimulation of anti-tumor immunity. However, patients with cancer receiving chemotherapy are often immunosuppressed, which may impact the efficacy of SRS. Here we investigate the relationship between systemic lymphopenia and response to SRS in patients with brain-metastatic lung cancer.

METHODS

We reviewed 125 patients with lung cancer brain metastases treated with SRS between January 2014 and May 2017. Complete blood counts from the time of SRS were reviewed, and lymphopenia was defined as absolute lymphocyte count < 1×10⁹ cells/L. Kaplan-Meier survival analysis and cox proportional-hazards models were used to evaluate risks of progression and death.

RESULTS

The median age was 65 years (range 43-86), with 54% female patients. Lymphopenia was present in 60 patients. In univariate analysis, lymphopenic patients had significantly shorter PFS (HR = 2.995, p < 0.0001) and OS (HR = 3.928, p < 0.0001). When accounting for age, gender, smoking history, ECOG score, surgery, and tumor histology in a multivariate model, lymphopenia remained significantly predictive of worse PFS (HR = 1.912, p = 0.002) and OS (HR = 2.257, p < 0.001). Patients who received immunotherapy within 3 months of SRS demonstrated significantly shorter PFS (HR = 3.578, p = 0.006) and OS (HR = 6.409, p = 0.001) if lymphopenic.

CONCLUSIONS

Brain-metastatic lung cancer patients with lymphopenia treated with SRS had significantly worse PFS and OS. The effect of lymphopenia was even more pronounced in patients receiving immunotherapy. These data demonstrate the significant impact of deficient immunity on disease control and survival. Lymphopenic patients may benefit from interventions to improve immune function prior to SRS for brain metastases.

Distribution of PD-L1 expression and its relationship with clinicopathological variables: an audit from 1071 cases of surgically resected non-small cell lung cancer

BACKGROUND

Programmed death ligand 1 (PD-L1) was reported to predict the response of immunotherapy; however, the association between PD-L1 expression and clinicopathologic characteristics has yet to be elucidated in non-small cell lung cancer (NSCLCs).

MATERIALS AND METHODS

We reviewed PDL1 expression investigated by immunohistochemical analysis using FFPE tissue in a total of 1071 cases of primary or metastatic NSCLC tissues analyzed between 2015-2017, and evaluated the association between PD-L1 expression and the clinicopathologic characteristics.

RESULTS

PD-L1 expression was observed in 361 (33.7%) cases with positive staining in at least 1% tumor cells and 116 (10.8%) cases had positive staining in ≥50% tumor cells. The PD-L1 positive prevalence was significantly higher in squamous cell carcinoma (SCC) than in adenocarcinoma (AD). In the AD subgroup, PD-L1 expression on tumors was higher in males and smokers, and with high histologic grade, relative high T, N, M status, advanced AJCC stage, and in ALK rearrangement patients. However, EGFR mutated patients showed relatively lower PD-L1 expression than wild type patients.

CONCLUSION

This study revealed the unique distribution of PD-L1 expression with clinicopathologic features in East Asian NSCLCs in a single, large cohort of patients. Since immunohistochemistry of the PD-L1 protein (PD-L1 IHC) is the only clinically approved predictive biomarker for anti-PD-1/-PD-L1 therapy currently, our outcomes could help to stratify patients to ensure selection of those who would most benefit from PD-1/PD- L1 inhibitor therapy.

Blood immune cell biomarkers in lung cancer

Characterization of host immune cell parameters prior to treatment is expected to identify biomarkers predictive of clinical outcome as well as to elucidate why some patients fail to respond to immunotherapy. We monitored blood immune cells from 58 patients with non-small- cell lung cancer (NSCLC) undergoing surgery of the primary tumor and from 50 age-matched healthy volunteers. Complete leukocyte blood count, the number of circulating dendritic cells (DC), HLA-DR^low monocytes and several lymphocytic subpopulations were determined by eight-color flow cytometry. Furthermore, the prognostic value of the immune cell parameters investigated was evaluated by patients' survival analysis. Compared to the control group, blood of NSCLC patients contained more neutrophils resulting in a higher neutrophil-to-lymphocyte ratio (NLR), but a lower number of blood DC, in particular of plasmacytoid DC (pDC), natural killer (NK) cells and naive CD4⁺ and CD8⁺ T cells. Furthermore, a higher frequency of CD4⁺ regulatory T cells (Treg) and HLA-DR^low monocytes was detected, and smoking had a significant impact on these values. HLA-DR^low monocytes were positively correlated to the number of neutrophils, monocytes and NLR, but negatively associated with the number of pDC and naive CD4⁺ T cells. The frequency of Treg, HLA-DR^low monocytes and naive CD4⁺ and CD8⁺ T cells as well as the ratios of CD4/HLA-DR^low monocytes and HLA-DR^low monocytes/pDC correlated with patient's overall survival. Next to Treg, HLA-DR^low monocytes and naive T cells represent prognostic markers for NSCLC patients and might be useful for monitoring of patients' responses to immunotherapies in future studies.

Bromodomain inhibition exerts its therapeutic potential in malignant pleural mesothelioma by promoting immunogenic cell death and changing the tumor immune-environment

Systemic treatment of malignant pleural mesothelioma (MPM) is moderately active for the intrinsic pharmacological resistance of MPM cell and its ability to induce an immune suppressive environment. Here we showed that the expression of bromodomain (BRD) proteins BRD2, BRD4 and BRD9 was significantly higher in human primary MPM cells compared to normal mesothelial cells (HMC). Nanomolar concentrations of bromodomain inhibitors (BBIs) JQ1 or OTX015 impaired patient-derived MPM cell proliferation and induced cell-cycle arrest without affecting apoptosis. Importantly, BBIs primed MPM cells for immunogenic cell death, by increasing extracellular release of ATP and HMGB1, and by promoting membrane exposure of calreticulin and ERp57. Accordingly, BBIs activated dendritic cell (DC)-mediated phagocytosis and expansion of CD8⁺ T-lymphocyte clones endorsed with antitumor cytotoxic activity. BBIs reduced the expression of the immune checkpoint ligand PD-L1 in MPM cells; while both CD8⁺ and CD4⁺ T-lymphocytes co-cultured with JQ1-treated MPM cells decreased PD-1 expression, suggesting a disruption of the immune-suppressive PD-L1/PD-1 axis. Additionally, BBIs reduced the expansion of myeloid-derived suppressor cells (MDSC) induced by MPM cells. Finally, a preclinical model of MPM confirmed that the anti-tumor efficacy of JQ1 was largely due to its ability to restore an immune-active environment, by increasing intra-tumor DC and CD8⁺ T-lymphocytes, and decreasing MDSC. Thereby, we propose that, among novel drugs, BBIs should be investigated for MPM treatment for their combined activity on both tumor cells and surrounding immune-environment.

Novel insights into mesothelioma biology and implications for therapy

Malignant mesothelioma is a universally lethal cancer that is increasing in incidence worldwide. There is a dearth of effective therapies, with only one treatment (pemetrexed and cisplatin combination chemotherapy) approved in the past 13 years. However, the past 5 years have witnessed an exponential growth in our understanding of mesothelioma pathobiology, which is set to revolutionize therapeutic strategies. From a genomic standpoint, mesothelioma is characterized by a preponderance of tumour suppressor alterations, for which novel therapies are currently in development. Other promising antitumour agents include inhibitors against angiogenesis, mesothelin and immune checkpoints, which are at various phases of clinical trial testing.

Association of mutant EGFR L858R and exon 19 concentration in circulating cell-free DNA using droplet digital PCR with response to EGFR-TKIs in NSCLC

The present study aimed to determine the diagnostic concordance of plasma epidermal growth factor receptor (EGFR) mutation using droplet digital polymerase chain reaction (ddPCR) with tumor tissue samples and the predictive clinical significance of plasma EGFR mutation concentration. Plasma DNA samples from patients with non-small cell lung cancer (NSCLC) were analyzed for EGFR exon 21 codon 858 (L858R) mutation, deletion of exon 19 (ex19del) and exon 20 codon 790 (T790M) mutation using ddPCR. Firstly, the mutations in the plasma samples were compared with the matched tumor samples to determine the concordance. Secondly, image examination follow-ups were analyzed to assess the association between plasma EGFR mutation concentration and patients' response to EGFR-tyrosine kinase inhibitors (TKIs). A total of 51 patients with NSCLC were enrolled, including 48 newly diagnosed patients. Compared with tumor tissue samples, the sensitivity and specificity of ddPCR were 76.19% (16/21) and 96.55% (28/29) for mutant L858R, and 88.89% (8/9) and 100% (41/41) for ex19del, respectively. No patient exhibited the T790M mutation in the tumor tissue or plasma samples. Furthermore, 5 patients with the L858R mutation and 4 patients with ex19del in plasma and tumor tissue samples had been followed up with image examination for ≥3 months following EGFR-TKI treatment. The baseline mutant EGFR concentrations were positively correlated with a reduction in tumor burden (Spearman's r=0.7000, P=0.0358). When analyzed separately, ex19del concentrations (Spearman's r=1.0000, P<0.0001) were also positively correlated with the reduction, while mutant L858R concentrations were not (Spearman's r=0.7000, P=0.1881). In the present study, detection of plasma EGFR mutations using ddPCR exhibited sufficient concordance with tumor tissue sample results. Baseline plasma mutant EGFR and ex19del concentrations were significantly and positively correlated with response to EGFR-TKIs.

Impact of gefitinib in early stage treatment on circulating cytokines and lymphocytes for patients with advanced non-small cell lung cancer

Objectives

The impact of epidermal growth factor receptor (EGFR) tyrosine-kinase inhibitors (TKIs) on the human immune system remains undefined. This study illustrates the immunomodulatory effect of gefitinib in patients with advanced non-small cell lung cancer (NSCLC) and its relevant prognostic significance.

Patients and methods

Peripheral blood samples were collected from 54 patients at baseline and after 4 weeks of gefitinib treatment. Circulating lymphocyte populations and cytokine levels were measured. Pilot investigation of the impact of gefitinib on programmed cell death ligand-1 (PD-L1) expression was conducted by immunohistochemistry (IHC).

Results and conclusion

A significant increase of peripheral natural killer cells and interferon-gamma (INF-γ) after 4 weeks of gefitinib treatment (P=0.005 and 0.02, respectively). In addition, circulating interleukin (IL)-6 was significantly decreased, especially in patients sensitive to gefitinib (P<0.001). Higher levels of IL-6 at baseline independently correlated with poorer progression-free survival. Experiments with NSCLC specimens illustrated that PD-L1 expression were downregulated after 4 weeks of gefitinib treatment. In summary, it was found that gefitinib treatment can alter circulating cytokines and lymphocytes. Dynamic changes of circulating lymphocytes, cytokines, and even PD-L1 IHC expression around gefitinib treatment support the specific immunomodulatory effect of this agent for advanced NSCLC.

Monocytic myeloid-derived suppressor cells as a potent suppressor of tumor immunity in non-small cell lung cancer

Immunotherapy is a promising therapeutic option for patients with non-small cell lung cancer (NSCLC) who do not qualify for surgery. In patients with advanced NSCLC, systemic immune suppression is frequently observed, therefore, researchers are investigating the tumor microenvironment for less invasive and more effective methods of treating lung cancer. Monocytic myeloid-derived suppressor cells (Mo-MDSCs) are potent suppressors of tumor immunity; therefore, this population may significantly impede the application of immunotherapy to treat cancer. The present study evaluated the distribution of Mo-MDSCs and monocytes/macrophages in the peripheral blood, lymph nodes and tumor tissue of patients with NSCLC. Furthermore, the profiles of cytokines produced by these cell populations, including interleukin (IL)-1β, IL-12/23p40, IL-10, transforming growth factor-β (TGF-β) and tumor necrosis factor (TNF), were compared. The cell populations and the expression of cytokines were assessed by flow cytometry after 4 h in culture with mitogens and Brefeldin A. Mo-MDSCs were more numerous than monocytes/macrophages in all tissues and their prevalence was highest in the peripheral blood; they expressed higher levels of TGF-β than monocytes/macrophages in all tissues and expression of TGF-β produced by Mo-MDSCs was higher in the blood than in lymph nodes and tumor tissues. A higher percentage of monocytes/macrophages was observed in lymph nodes and tumor tissues than in blood. CD14⁺HLA-DR⁺ cells also produced more IL-10 in lymph nodes than Mo-MDSCs and more IL-1β and TNF in all tissues. A higher prevalence of cluster of differentiation 14⁺ human leukocyte antigen-D related⁺ cells secreting IL-1β, TNF and IL-12/23p40 was observed in peripheral blood. Thus, the results of the current study support the statement that Mo-MDSCs and monocytes/macrophages participate in NSCLC induced immunosuppression, and is consistent with previous research into associations between the TGF-β signaling pathway and tumor cell invasion, motility and metastasis. The study also demonstrated that Mo-MDSCs promote tumor growth through their immunosuppressive activity. In addition, the profile of cytokines expressed by monocytes/macrophages suggests that this cell population may be associated with metastasis formation and angiogenesis promotion in patients with NSCLC.

Biologic therapy and gene therapy in the multimodality treatment of malignant pleural mesothelioma

The last years have witnessed an abrupt paradigm shift in cancer treatment owing to the discoveries concerning the relationships between the immune system and neoplastic cells. In the field of malignant mesothelioma, which, despite painstaking efforts, remains an incurable form of cancer, the researchers' attention has been seized by a variety of new biologic approaches, including both viral gene therapy and active immunotherapy. The former is meant to induce programmed cell death by introducing a specific gene in the target cell, this gene encoding a specific protein with anticancer activity. Active immunotherapy, on the other hand, tires to induce an active response of the immune system, whose surveillance may be easily dodged by cancer cells. In fact, this mechanism seems to play an important role in the development, growth and diffusion of malignant mesothelioma which easily manages to hinder the immune response. A thorough understanding of the relationships existing between mesothelioma and immune system is the basis for the success of those immune therapies, which are showing promising results in the preclinical setting, especially when combined with other approaches, such as cytoreductive surgery.