Prognostic relevance of programmed cell death protein 1/programmed death-ligand 1 pathway in thymic malignancies with combined immunohistochemical and biomolecular approach

Depiction of the Genetic Alterations and Molecular Landscapes of Thymic Epithelial Tumors: A Systematic Review and Meta-Analysis

Thymic epithelial tumors (TETs), consisting of thymomas, thymic carcinomas (TCs), and thymic neuroendocrine tumors, are rare diseases. Surgery remains the prime option in resectable and early-stage TETs, while chemotherapy, targeted therapy, and immunotherapy are also potential treatment modalities. However, the inadequate comprehension of the molecular landscape of TETs impedes the exploitation of such therapies. Hence, we conducted a meta-analysis which includes 21 studies reporting on genomic alterations in TETs and 14 studies reporting on PD-L1 expression levels, respectively. The pooled estimated rates of the most frequently mutated genes and PD-L1 expression levels were analyzed using the R software. We uncovered that the pooled estimated overall mutation rate is 0.65 ([0.49; 0.81]), and the top three genes with highest mutation frequency in thymomas and TCs are GTF2I (0.4263 [0.3590; 0.4936]), TP53 (0.1101 [0.0000; 0.2586]), and RAS (0.0341 [0.0104; 0.0710]), and TP53 (0.1797 [0.0732; 0.3203]), CDKN2A (0.0608 [0.0139; 0.1378]), and TET2 (0.0318 [0.0087; 0.0639]), respectively. A uniform GTF2I mutational rate in thymomas and TP53 mutational rate in thymic squamous cell carcinomas (TSCCs) are also observed. The pooled estimated expression level of PD-L1 is 0.71 ([0.59-0.81]). This systematic review provides an overview of the gene alteration landscape and PD-L1 expression levels in TETs, discovers several potential confounding factors that may contribute to the high heterogeneity, and facilitates deeper investigations into the elucidation of the molecular landscape of TETs.

Immunotherapy in thymic epithelial tumors: tissue predictive biomarkers for immune checkpoint inhibitors

Thymic epithelial tumors (TETs) are rare malignant neoplasms arising in the thymus gland. Nevertheless, TETs, including thymomas (TMs), thymic carcinomas (TCs), and thymic neuroendocrine neoplasms (TNENs), are the most common mediastinal malignancies overall. A multidisciplinary approach is required for the appropriate diagnostic and therapeutic management of TETs. To date, the main therapeutic strategies are largely depended on the stage of the tumor and they include surgery with or without neoadjuvant or adjuvant therapy, represented by platinum-based chemotherapy, radiotherapy or chemoradiotherapy. Immune checkpoint inhibitors (ICIs) are ongoing under evaluation in the advanced or metastatic diseases despite the challenges related to the very low tumor mutation burden (TMB) and the high incidence of immune-related adverse events in TETs. In this regard, predictive impact of tissue biomarkers expression such as programmed cell death ligand-1 (PD-L1), and other emerging biomarkers, as well as their optimal and shared interpretation are currently under evaluation in order to predict response rates to ICIs in TETs.

Molecular and Functional Key Features and Oncogenic Drivers in Thymic Carcinomas

Thymic epithelial tumors, comprising thymic carcinomas and thymomas, are rare neoplasms. They differ in histology, prognosis, and association with autoimmune diseases such as myasthenia gravis. Thymomas, but not thymic carcinomas, often harbor GTF2I mutations. Mutations of CDKN2A, TP53, and CDKN2B are the most common thymic carcinomas. The acquisition of mutations in genes that control chromatin modifications and epigenetic regulation occurs in the advanced stages of thymic carcinomas. Anti-angiogenic drugs and immune checkpoint inhibitors targeting the PD-1/PD-L1 axis have shown promising results for the treatment of unresectable tumors. Since thymic carcinomas are frankly aggressive tumors, this report presents insights into their oncogenic drivers, categorized under the established hallmarks of cancer.

Immunotherapy of thymic epithelial tumors: molecular understandings and clinical perspectives

Immunotherapy has emerged to play a rapidly expanding role in the treatment of cancers. Currently, many clinical trials of therapeutic agents are on ongoing with majority of immune checkpoint inhibitors (ICIs) especially programmed death receptor 1 (PD-1) and its ligand 1 (PD-L1) inhibitors. PD-1 and PD-L1, two main immune checkpoints, are expressed at high levels in thymic epithelial tumors (TETs) and could be predictors of the progression and immunotherapeutic efficacy of TETs. However, despite inspiring efficacy reported in clinical trials and clinical practice, significantly higher incidence of immune-related adverse events (irAEs) than other tumors bring challenges to the administration of ICIs in TETs. To develop safe and effective immunotherapeutic patterns in TETs, understanding the clinical properties of patients, the cellular and molecular mechanisms of immunotherapy and irAEs occurrence are crucial. In this review, the progress of both basic and clinical research on immune checkpoints in TETs, the evidence of therapeutic efficacy and irAEs based on PD-1 /PD-L1 inhibitors in TETs treatment are discussed. Additionally, we highlighted the possible mechanisms underlying irAEs, prevention and management strategies, the insufficiency of current research and some worthy research insights. High PD-1/PD-L1 expression in TETs provides a rationale for ICI use. Completed clinical trials have shown an encouraging efficacy of ICIs, despite the high rate of irAEs. A deeper mechanism understanding at molecular level how ICIs function in TETs and why irAEs occur will help maximize the immunotherapeutic efficacy while minimizing irAEs risks in TET treatment to improve patient prognosis.

Case Report: Toxic epidermal necrolysis associated with sintilimab in a patient with relapsed thymic carcinoma

Immune checkpoint inhibitors (ICIs) such as anti-programmed death 1 (PD-1) receptor monoclonal antibody has been shown to be effective in patients with relapsed thymic carcinoma. However, immune-related adverse events (irAE) are increasingly recognized. There is a paucity of clinical data, especially in elderly patients. A patient in his late 80s with a history of thymic carcinoma was treated with sintilimab, an anti-PD1 antibody. After one week of administration, the patient developed diffuse rash. After two cycles of sintilimab, there was rapid progression of the rash with gradual development of blisters and skin detachment. Sintilimab was immediately discontinued, and skin biopsy was performed. The histopathological findings were consistent with the diagnosis of toxic epidermal necrolysis (TEN), which was considered as an irAE. Intravenous methylprednisolone was initially administered, followed by oral prednisone. The patient showed dramatic improvement within 72 hours of initiation of treatment. Unfortunately, the patient died of severe pneumonia three months later. We report a case of TEN, a rare toxicity induced by anti-PD-1 sintilimab in an elderly patient with thymic carcinoma. Since TEN is a life-threatening condition, early recognition and management of this complication is a key imperative.

Effect of tacrolimus on soluble costimulatory molecules in patients with refractory myasthenia gravis

OBJECTIVES

To investigate the expression and possible role of soluble costimulatory molecules in the treatment of refractory myasthenia gravis.

METHODS

Thirty-two patients with refractory myasthenia gravis were enrolled into this study and given tacrolimus 3 mg/day. At the beginning of treatment and 12 months follow-up period, clinical data were collected and recorded. The clinical classification of myasthenia gravis Foundation (MGFA) was performed. The MGFA-quantitative myasthenia gravis score (MGFA-QMGS), manual muscle test (MMT), MG activity of daily living (MG-ADL) and the activity of daily living (MG-ADL), the 15-item myasthenia gravis quality of life (MG QOL-15) and the dose change of prednisone were used to evaluate the efficacy. The expression levels of soluble costimulatory molecules and their ligands (sPD-1/sPD-L1, sICOS/sICOSL, sCD40/sCD40L), soluble CD25 and IL-2 in serum were determined by enzyme-linked immunosorbent assay (ELISA).

RESULTS

We observed that oral administration of 3 mg tacrolimus daily for 1 year can significantly improve the clinical symptoms of patients with refractory myasthenia gravis, which is characterized by a significant reduction in clinical scores, such as QMG, MMT, ADL, MGQOL-15, and a reduction daily oral prednisolone (PSL) dose (P < 0.0001).We also found that the levels of plasma sPD-1, sCD40, IL-2 in refractory MG patients increased significantly, and those decreased significantly 12 months after tacrolimus treatment (P < 0.05). The level of sCD25 was negatively correlated with clinical severity scores (P < 0.05). After tacrolimus treatment, the level of sPD-L1 increased although there was no significant difference.

CONCLUSION

Tacrolimus could relieve the symptoms of refractory MG and significantly decrease the levels of plasma sPD-1, sICOSL, sCD40, sCD25 and IL-2. Soluble costimulatory molecules might be potential biomarkers for MG and tacrolimus treatment.

Unraveling the Immune Microenvironment of Thymic Epithelial Tumors: Implications for Autoimmunity and Treatment

Thymic Epithelial Tumors (TETs) represent a rare tumor family, originating from the epithelial component of the thymus gland. Clinicopathologically, they are segregated into six major subtypes, associated with distinct histological features and clinical outcomes. Their emergence and evolution are accompanied by the generation of a complex tumor microenvironment (TME), dominated by phenotypically and functionally divergent immune cellular subsets, in different maturation states and in analogies that vary significantly among different subtypes. These heterogenous leukocyte populations exert either immune-permissive and tumor-suppressive functions or vice versa, and the dynamic equilibrium established among them either dictates the tumor immune milieu towards an immune-tolerance state or enables the development of a productive spontaneous tumoricidal response. The immunologically “hot” microenvironment, defining a significant proportion of TETs, makes them a promising candidate for the implementation of immune checkpoint inhibitors (ICIs). A number of phase I and II clinical trials have already demonstrated significant, type-specific clinical efficacy of PD-L1 inhibitors, even though substantial limitations in their utilization derive from their immune-mediated adverse effects. Moreover, the completed clinical studies involved relatively restricted patient samples and an expansion in the enrolled cohorts is required, so that more trustworthy conclusions regarding the benefit from ICIs in TETs can be extracted.

The efficacy and safety of immunotherapy in thymic epithelial tumors: more effective, more risky: a systematic review

Background

Thymic epithelial tumors (TETs) are rare malignant neoplasms originating from thymic epithelial cells. The current treatment for localized TETs is surgical removal. However, 20-30% of thymomas and 70-80% of thymic carcinomas are unresectable, recurrent, or metastatic at the time of detection. The standard therapy for these patients is chemotherapy, but the effect is limited. With a deeper understanding of tumor immunity, immunotherapy for various cancers has rapidly developed. Antibodies against cytotoxic T-lymphocyte antigen-4, programmed death-1, and programmed death-ligand 1 have been approved for the treatment of many solid tumors. Compared with traditional treatments, these immune checkpoint inhibitors (ICIs) have better efficacy and lower toxicity. Recently, ICIs have been used more enthusiastically in the treatment of TETs. However, due to the unique biological characteristics of the thymus, immunotherapy usually causes severe immune-related adverse events (irAEs). Most previous studies on immunotherapy in TETs had small sample sizes and reported diverse conclusions.

Methods

We collected relevant studies in PubMed during the last five years and analyzed the available data to discuss the efficacy and safety of ICIs in TETs.

Results

According to 14 previous studies in the past five years, all TETs showed expression of programmed death-ligand 1, while thymic carcinomas showed 100% expression. The best median progression-free survival (mPFS) among the five studies was 6.5 months, and the best median overall survival (mOS) was 24.9 months. In addition, the most common irAEs were myasthenic symptoms, liver enzyme elevation, and elevated creatine phosphokinase levels.

Conclusions

ICIs can be used in TET treatment, especially for thymic carcinomas, in the absence of standard second-line treatment. However, more attention should be paid to irAEs.

The Expression of PD-L1 and B7-H4 in Thymic Epithelial Tumor and Its Relationship With Tumor Immune-Infiltrating Cells

Background

PD-L1 and B7-H4 have been reported to be expressed in various malignancies and are considered as promising prognostic factors and potential immunotherapy targets.

Methods

We analyzed the correlation between the expression of PD-L1 and B7-H4 transcriptomes and clinicopathological characteristics in 121 TET patients from The Cancer Genome Atlas (TCGA) database. The immune-infiltration levels in the TET microenvironment were estimated using ssGSEA and quanTiseq algorithms. We collected 80 TET cases from 2008 to 2015. PD-L1、B7-H4、FOXP3 and CD163 protein expression in tumor tissues were detected by immunohistochemistry.

Results

TCGA database showed PD-L1 mRNA levels can predict the OS (P = 0.018) and DFS (P = 0.033) of TET patients. B7-H4 mRNA levels were positively related to the World Health Organization (WHO) pathological classification (P = 0.003) but not correlated with patient prognosis. Immune infiltration analysis showed PD-L1 is positively correlated with Tregs and M2 macrophages, B7-H4 is positively correlated with Tregs. Patients with high PD-L1 and Tregs or M2 macrophages, high B7-H4 and Tregs had a worse prognosis. Immunohistochemistry showed PD-L1 expression was positively correlated with the WHO pathological classification and Masaoka stage (P = 0.025, 0.003) and high PD-L1 expression can predict the poor OS of patients (P = 0.043); B7-H4 was also positively correlated with WHO pathological classification and Masaoka stage (P = 0.036, 0.049). However, B7-H4 expression did not correlate with patient prognosis. Evaluation of co-expression patterns showed TET patients with a high-grade WHO pathological classification harbored a 44.4% co-expression of PD-L1 and B7-H4. In addition, we found the expression level of PD-L1 is positively correlated with FOXP3 and CD163 (P = 0.004, P = 0.029) and B7-H4 is positively correlated with FOXP3 (P = 0.037). High PD-L1 combined with High FOXP3 and High CD163, High B7-H4 combined with High FOXP3 can be used to predict the poor prognosis of TET patients (P = 0.026, 0.031, 0.028, respectively).

Conclusion

PD-L1 and B7-H4 were related to the aggressiveness of TET and their expression level can indicate the suppressive immune microenvironment. Combined with FOXP3 and CD163, PD-L1 and B7-H4 can indicate a poor prognosis of TET.

The Effect and Safety of Anti-PD-1 Single/Combination Therapy in Refractory Thymic Carcinoma: A Case-Series Study

Immunotherapy provided with checkpoint inhibitors such as the programmed cell death-1 (PD-1) receptor or its ligand-1 (PD-L1) protein has been shown to be effective for treating several types of cancer, and was recently approved for use in treating malignant melanoma, advanced non-small cell lung cancer (NSCLC), urothelial carcinoma, head and neck squamous cell carcinoma, liver cancer, and additional forms of cancer. However, there is little evidence concerning its effectiveness in treating thymic squamous cell carcinoma (TSCC). Here, we report two cases of refractory TSCC that were treated with PD-1 single/combination therapy in a clinical setting. The patients exhibited variable responses to therapy without any serious adverse events. In summary, our findings show that immunotherapy provided with an immuno-checkpoint inhibitor in combination with chemotherapy/anti-angiogenesis therapy can improve the treatment response of patients with refractory TSCC. Anti-PD-1 single/combination therapy may be used as a strategy for treating advanced refractory TC.