Rationale: Angiogenesis is a fundamental process of tumorigenesis, growth, invasion and metastatic spread. Extracellular vesicles, especially exosomes, released by primary tumors promote angiogenesis and cancer progression. However, the mechanism underlying the pro-angiogenic potency of cancer cell-derived exosomes remains poorly understood. Methods: Exosomes were isolated from breast cancer cells with high metastatic potential (HM) and low metastatic potential (LM). The pro-angiogenic effects of these exosomes were evaluated by in vitro tube formation assays, wound healing assays, rat arterial ring budding assays and in vivo Matrigel plug assays. Subsequently, RNA sequencing, shRNA-mediated gene knockdown, overexpression of different EPHA2 mutants, and small-molecule inhibitors were used to analyze the angiogenesis-promoting effect of exosomal EPHA2 and its potential downstream mechanism. Finally, xenograft tumor models were established using tumor cells expressing different levels of EPHA2 to mimic the secretion of exosomes by tumor cells in vivo, and the metastasis of cancer cells were monitored using the IVIS Spectrum imaging system and Computed Tomography. Results: Herein, we demonstrated that exosomes produced by HM breast cancer cells can promote angiogenesis and metastasis. EPHA2 was rich in HM-derived exosomes and conferred the pro-angiogenic effect. Exosomal EPHA2 can be transferred from HM breast cancer cells to endothelial cells. Moreover, it can stimulate the migration and tube-forming abilities of endothelial cells in vitro and promote angiogenesis and tumor metastasis in vivo. Mechanistically, exosomal EPHA2 activates the AMPK signaling via the ligand Ephrin A1-dependent canonical forward signaling pathway. Moreover, inhibition of the AMPK signaling impairs exosomal EPHA2-mediated pro-angiogenic effects. Conclusion: Our findings identify a novel mechanism of exosomal EPHA2-mediated intercellular communication from breast cancer cells to endothelial cells in the tumor microenvironment to provoke angiogenesis and metastasis. Targeting the exosomal EPHA2-AMPK signaling may serve as a potential strategy for breast cancer therapy.

Exosomal EPHA2 derived from highly metastatic breast cancer cells promotes angiogenesis by activating the AMPK signaling pathway through Ephrin A1-EPHA2 forward signaling

Simple Summary Despite tremendous treatment efforts, cancer is still one of the leading causes of death, with approximately 10 million deaths in 2020. In the last decade, immunotherapy entered the stage of clinical practice and was added to the established regimen, i.e., surgery, chemo- and radiation therapy, to fight this deadly disease. Cancer immunotherapies, including immune checkpoint inhibitors, target malignant cancer cells and immune cells in the tumor micro-environment. Among those cells are T cells and antigen-presenting cells, which can efficiently control tumors via both cell-cell interactions and by secretion of inflammatory cytokines. The presence of specific cytokines in the tumor microenvironment has been shown to induce senescence in tumor cells. Subsequently, tumor cells acquire a senescence-associated secretory phenotype that strongly modulates anti-tumor responses. This review describes the mechanisms of cytokine-induced senescence in the tumor microenvironment and highlights their relevance for therapeutic perspectives. Abstract In contrast to surgical excision, chemotherapy or radiation therapy, immune checkpoint blockade therapies primarily influence cells in the tumor microenvironment, especially the tumor-associated lymphocytes and antigen-presenting cells. Besides complete remission of tumor lesions, in some patients, early tumor regression is followed by a consolidation phase where residing tumors remain dormant. Whereas the cytotoxic mechanisms of the regression phase (i.e., apoptosis, necrosis, necroptosis, and immune cell-mediated cell death) have been extensively described, the mechanisms underlying the dormant state are still a matter of debate. Here, we propose immune-mediated induction of senescence in cancers as one important player. Senescence can be achieved by tumor-associated antigen-specific T helper 1 cells, cytokines or antibodies targeting immune checkpoints. This concept differs from cytotoxic treatment, which often targets the genetic makeup of cancer cells. The immune system’s ability to establish “defensive walls” around tumors also places the tumor microenvironment into the fight against cancer. Those “defensive walls” isolate the tumor cells instead of increasing the selective pressure. They also keep the tumor cells in a non-proliferating state, thereby correcting the derailed tissue homeostasis. In conclusion, strengthening the senescence surveillance of tumors by the immune cells of the microenvironment is a future goal to dampen this life-threatening disease.

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Cytokine-Induced Senescence in the Tumor Microenvironment and Its Effects on Anti-Tumor Immune Responses

As one of the core aging processes, cellular senescence is associated with tumorigenesis, growth, and immune modulation in cancers. Nevertheless, the prognosis of senescence‐associated genes (SAGs) signature in head and neck squamous cell carcinoma (HNSCC) remains to be further evaluated.

https://onlinelibrary.wiley.com/doi/pdfdirect/10.1002/jcla.24555

Identification of several senescence‐associated genes signature in head and neck squamous cell carcinoma

Lung squamous cell carcinoma (LUSC) is the second most common histopathological subtype of lung cancer, and smoking is the leading cause of this type of cancer. However, the critical factors that directly affect the survival rate and sensitivity to immunotherapy of smoking LUSC patients are still unknown. Previous studies have highlighted the role of N6-methyladenosine (m6A) RNA modification, the most common epigenetic modification in eukaryotic species, together with immune-related long non-coding RNAs (lncRNAs) in promoting the development and progression of tumors. Thus, elucidating m6A-modified immune lncRNAs in LUSC patients with smoking history is vital. In this study, we described the expression and mutation features of the 24 m6A-related regulators in the smoking-associated LUSC cohort from The Cancer Genome Atlas (TCGA) database. Then, two distinct subtypes based on the expression levels of the prognostic m6A-regulated immune lncRNAs were defined, and differentially expressed genes (DEGs) between the subtypes were identified. The distributions of clinical characteristics and the tumor microenvironment (TME) between clusters were analyzed. Finally, we established a lncRNA-associated risk model and exhaustively clarified the clinical features, prognosis, immune landscape, and drug sensitivity on the basis of this scoring system. Our findings give insight into potential mechanisms of LUSC tumorigenesis and development and provide new ideas in offering LUSC patients with individual and effective immunotherapies.

Comprehensive analysis of molecular features, prognostic values, and immune landscape association of m6A-regulated immune-related lncRNAs in smoking-associated lung squamous cell carcinoma

The complex interaction between cancer cells and the immune microenvironment is a central regulator of tumor growth and the treatment response. Chemotherapy-induced senescence is accompanied by the senescence-associated secretion phenotype (SASP). However, the mechanisms underlying the regulation of the SASP remain the most poorly understood element of senescence. Here, we show that nuclear erythroid factor 2-like factor 2 (Nrf2), a master antioxidative transcription factor, accumulates upon doxorubicin-induced senescence. This is due to the increased cytoplasmic Inhibitor of Apoptosis Stimulating Protein of P53, iASPP, which binds with Keap1, interrupting Keap1/Nrf2 interaction and promoting Nrf2 stabilization and activation. Activated Nrf2 transactivates a novel target gene of SASP factor, macrophage colony-stimulating factor (M-CSF), which subsequently acts on macrophages and induces polarization from M1 to M2 via a paracrine mechanism. Genetic inhibition of iASPP-Nrf2 suppresses the growth of apoptosis-resistant xenografts, with further analysis revealing that M-CSF/M-CSFR-regulated macrophage polarization is critical for the functional outcomes delineated above. Overall, our data uncover a novel function of iASPP-Nrf2 in skewing the immune microenvironment under treatment-induced senescence. Targeting the iASPP-Nrf2 axis could be a powerful strategy for the implementation of new chemotherapy-based therapeutic opportunities. 

https://www.nature.com/articles/s41419-022-04611-4.pdf

Hanxin Liu

Papers

Tumor microenvironment and cellular senescence: Understanding therapeutic resistance and harnessing strategies