Tumor mechanisms of resistance to immune attack

Mechanisms of HIF-driven immunosuppression in tumour microenvironment

Hypoxia arises due to insufficient oxygen delivery to rapidly proliferating tumour cells that outpace the available blood supply. It is a characteristic feature of most solid tumour microenvironments and plays a critical role in regulating anti-tumour immunity, enhancing tumoral heterogeneity, and promoting therapeutic resistance and poor clinical outcomes. Hypoxia-inducible factors (HIFs) are the major hypoxia-responsive transcription factors that are activated under low oxygenation conditions and have been identified to drive multifunctional roles in tumour immune evasion. The HIF signalling network serves as an attractive target for targeted therapeutic approaches. This review aims to provide a comprehensive overview of the most crucial mechanisms by which HIF controls the expression of immunosuppressive molecules and immune checkpoints, disrupts cancer immunogenicity, and induces immunotherapeutic resistance.

Recent Advances in Delivery Systems for Genetic and Other Novel Vaccines

Vaccination is one of the most successful and cost-effective prophylactic measures against diseases, especially infectious diseases including smallpox and polio. However, the development of effective prophylactic or therapeutic vaccines for other diseases such as cancer remains challenging. This is often due to the imprecise control of vaccine activity in vivo which leads to insufficient/inappropriate immune responses or short immune memory. The development of new vaccine types in recent decades has created the potential for improving the protective potency against these diseases. Genetic and subunit vaccines are two major categories of these emerging vaccines. Owing to their nature, they rely heavily on delivery systems with various functions, such as effective cargo protection, immunogenicity enhancement, targeted delivery, sustained release of antigens, selective activation of humoral and/or cellular immune responses against specific antigens, and reduced adverse effects. Therefore, vaccine delivery systems may significantly affect the final outcome of genetic and other novel vaccines and are vital for their development. This review introduces these studies based on their research emphasis on functional design or administration route optimization, presents recent progress, and discusses features of new vaccine delivery systems, providing an overview of this field.

The Research Progress of Antiangiogenic Therapy, Immune Therapy and Tumor Microenvironment

Anti-angiogenesis therapy, a promising strategy against cancer progression, is limited by drug-resistance, which could be attributed to changes within the tumor microenvironment. Studies have increasingly shown that combining anti-angiogenesis drugs with immunotherapy synergistically inhibits tumor growth and progression. Combination of anti-angiogenesis therapy and immunotherapy are well-established therapeutic options among solid tumors, such as non-small cell lung cancer, hepatic cell carcinoma, and renal cell carcinoma. However, this combination has achieved an unsatisfactory effect among some tumors, such as breast cancer, glioblastoma, and pancreatic ductal adenocarcinoma. Therefore, resistance to anti-angiogenesis agents, as well as a lack of biomarkers, remains a challenge. In this review, the current anti-angiogenesis therapies and corresponding drug-resistance, the relationship between tumor microenvironment and immunotherapy, and the latest progress on the combination of both therapeutic modalities are discussed. The aim of this review is to discuss whether the combination of anti-angiogenesis therapy and immunotherapy can exert synergistic antitumor effects, which can provide a basis to exploring new targets and developing more advanced strategies.

A review on the role of CAFs and CAF-derived exosomes in progression and metastasis of digestive system cancers

Cancers evolve as a result of the accelerated proliferation of cancer cells in a complicated, enriched, and active microenvironment. Tumor microenvironment (TME) components are the master regulators of any step of cancer development. The tumor microenvironment is composed of many cellular and noncellular components that contribute to the evolution of cancer cells. Cancer-associated fibroblasts (CAFs) are activated fibroblasts in the TME that implicate in tumor progression and metastasis dissemination through secretion of oncogenic factors which are carried to the secondary metastatic sites through exosomes. In this review, we aimed to assess the role of CAF-derived exosomes in TME construction and pre-metastatic niche formation in different cancers of the digestive system in order to better understand some important mechanisms of metastasis and provide possible targets for clinical intervention. This review article is divided into two thematic parts explaining the general mechanisms of pre-metastatic niche formation and metastasis and the role of CAF-derived exosomes in different digestive system cancers including colorectal, gastric, esophageal, pancreatic, and liver cancers.

Clinical significance of checkpoint regulator "Programmed death ligand-1 (PD-L1)" expression in meningioma: review of the current status

Introduction

Meningioma is the most common primary brain tumor. Most meningiomas are benign; however, a subset of these tumors can be aggressive, presenting with early or multiple tumor recurrences that are refractory to neurosurgical resection and radiotherapy. There is no standard systemic therapy for these patients, and post-surgical management of these patients is usually complicated due to lack of accurate prediction for tumor progression.

Methods

In this review, we summarise the crucial immunosuppressive role of checkpoint regulators, including PD-1 and PD-L1 interacting in the tumor microenvironment, which has led to efforts aimed at targeting this axis.

Results

Since their discovery, checkpoint inhibitors have significantly improved the outcome in many types of cancers. Currently, targeted therapy for PD-1 and PD-L1 proteins are being tested in several ongoing clinical trials for brain tumors such as glioblastoma. More recently, there have been some reports implicating increased PD-L1 expression in high-grade (WHO grades II and III) meningiomas. Several clinical trials are underway to assess the efficacy of checkpoint inhibitors in the therapeutic management of patients with aggressive meningiomas. Here, we review the immune suppressive microenvironment in meningiomas, and then focus on clinical and pathological characterization and tumor heterogeneity with respect to PD-L1 expression as well as challenges associated with the assessment of PD-L1 expression in meningioma.

Conclusion

We conclude with a brief review of ongoing clinical trials using checkpoint inhibitors for the treatment of high-grade and refractory meningiomas.

Interrogating the microenvironmental landscape of tumors with computational image analysis approaches

The tumor microenvironment is an interacting heterogeneous collection of cancer cells, resident as well as infiltrating host cells, secreted factors, and extracellular matrix proteins. With the growing importance of immunotherapies, it has become crucial to be able to characterize the composition and the functional orientation of the microenvironment. The development of novel computational image analysis methodologies may enable the robust quantification and localization of immune and related biomarker-expressing cells within the microenvironment. The aim of the review is to concisely highlight a selection of current and significant contributions pertinent to methodological advances coupled with biomedical or translational applications. A further aim is to concisely present computational advances that, to our knowledge, have currently very limited use for the assessment of the microenvironment but have the potential to enhance image analysis pipelines; on this basis, an example is shown for the detection and segmentation of cells of the microenvironment using a published pipeline and a public dataset. Finally, a general proposal is presented on the conceptual design of automation-optimized computational image analysis workflows in the biomedical and clinical domain.

CD73 Overexpression Promotes Progression and Recurrence of Papillary Thyroid Carcinoma

Simple Summary

This study aimed to evaluate the clinicopathologic significance of CD73 expression in patients with papillary thyroid carcinoma (PTC) and the potential for CD73 to serve as a therapeutic target of PTC. CD73 was highly expressed in PTC, but not in the normal thyroid tissue. Overexpression of CD73 was associated with unfavorable clinicopathologic characteristics and a shorter recurrence-free survival. The expression level of CD73 mRNA was associated with the abundance of Tregs and dendritic cells, depletion of natural killer (NK) cells, and high expression of immune checkpoint genes and epithelial-to-mesenchymal transition-related genes. CD73 inhibitor attenuated PTC cell proliferation, migration, and invasion in vitro, and suppressed PTC xenograft tumor growth in nude mice. These results suggest that CD73 expression is an unfavorable prognostic marker for patients with PTC. CD73 blockade would be an attractive candidate for therapeutic strategies in patients with advanced PTC.

Abstract

CD73 is involved in tumor immune escape and promotes the growth and progression of cancer cells. The functional role of CD73 expression in papillary thyroid carcinoma (PTC) has not yet been established. In 511 patients with PTC, immunohistochemistry for CD73 on tissue microarrays showed that the high expression of CD73 was associated with an aggressive histologic variant (p = 0.002), extrathyroidal extension (p < 0.001), lymph node metastasis (p < 0.001), and BRAF^V600E mutation (p = 0.015). Survival analysis results showed that patients with high CD73 expression had worse recurrence-free survival (p = 0.023). CD73 inhibitors induced G1 cell cycle arrest and apoptosis, inhibited the migration and invasion of PTC cells, and suppressed tumor growth in PTC xenograft nude mice. High expression of CD73 (NT5E) mRNA was associated with unfavorable clinicopathologic characteristics, the abundance of Tregs and dendritic cells, depletion of natural killer (NK) cells, and high expression of immune checkpoint genes and epithelial-to-mesenchymal transition-related genes in The Cancer Genome Atlas (TCGA) dataset. Taken together, CD73 expression promotes tumor progression and predicts low recurrence-free survival. Targeting the CD73–adenosine axis in the tumor microenvironment offers an attractive pathway for therapeutic strategies aimed at advanced PTC.

Novel c-Myc-Targeting Compound N, N-Bis (5-Ethyl-2-Hydroxybenzyl) Methylamine for Mediated c-Myc Ubiquitin-Proteasomal Degradation in Lung Cancer Cells

Aberrant cellular Myc (c-Myc) is a common feature in the majority of human cancers and has been linked to oncogenic malignancies. Here, we developed a novel c-Myc-targeting compound, N, N-bis (5-ethyl-2-hydroxybenzyl) methylamine (EMD), and present evidence demonstrating its effectiveness in targeting c-Myc for degradation in human lung carcinoma. EMD exhibited strong cytotoxicity toward various human lung cancer cell lines, as well as chemotherapeutic-resistant patient-derived lung cancer cells, through apoptosis induction in comparison with chemotherapeutic drugs. The IC₅₀ of EMD against lung cancer cells was approximately 60 µM. Mechanistically, EMD eliminated c-Myc in the cells and initiated caspase-dependent apoptosis cascade. Cycloheximide chase assay revealed that EMD tended to shorten the half-life of c-Myc by approximately half. The cotreatment of EMD with the proteasome inhibitor MG132 reversed its c-Myc-targeting effect, suggesting the involvement of ubiquitin-mediated proteasomal degradation in the process. We further verified that EMD strongly induced the ubiquitination of c-Myc and promoted protein degradation. c-Myc inhibition and apoptosis induction were additionally shown in hematologic malignant K562 cells, indicating the generality of the observed EMD effects. Altogether, we identified EMD as a novel potent compound targeting oncogenic c-Myc that may offer new opportunities for lung cancer treatment. SIGNIFICANCE STATEMENT: The deregulation of c-Myc is frequently associated with cancer progression. This study examined the effect of a new compound, N, N-bis (5-ethyl-2-hydroxybenzyl) methylamine (EMD), in targeting c-Myc in several lung cancer cell lines and drug-resistant primary lung cancer cells. EMD induced dramatic c-Myc degradation through a ubiquitin-proteasomal mechanism. The promising anticancer and c-Myc-targeted activities of EMD support its use in potential new approaches to treat c-Myc-driven cancer.