Regulation of endothelial Fas expression as a mechanism of promotion of vascular integrity by mural cells in tumors

Integration of Pan-Cancer Single-Cell and Spatial Transcriptomics Reveals Stromal Cell Features and Therapeutic Targets in Tumor Microenvironment

Stromal cells are physiologically essential components of the tumor microenvironment (TME) that mediates tumor development and therapeutic resistance. Development of a logical and unified system for stromal cell type identification and characterization of corresponding functional properties could help design antitumor strategies that target stromal cells. Here, we performed a pan-cancer analysis of 214,972 nonimmune stromal cells using single-cell RNA sequencing from 258 patients across 16 cancer types and analyzed spatial transcriptomics from 16 patients across seven cancer types, including six patients receiving anti-PD-1 treatment. This analysis uncovered distinct features of 39 stromal subsets across cancer types, including various functional modules, spatial locations, and clinical and therapeutic relevance. Tumor-associated PGF+ endothelial tip cells with elevated epithelial-mesenchymal transition features were enriched in immune-depleted TME and associated with poor prognosis. Fibrogenic and vascular pericytes (PC) derived from FABP4+ progenitors were two distinct tumor-associated PC subpopulations that strongly interacted with PGF+ tips, resulting in excess extracellular matrix (ECM) abundance and dysfunctional vasculature. Importantly, ECM-related cancer-associated fibroblasts enriched at the tumor boundary acted as a barrier to exclude immune cells, interacted with malignant cells to promote tumor progression, and regulated exhausted CD8+ T cells via immune checkpoint ligand-receptors (e.g., LGALS9/TIM-3) to promote immune escape. In addition, an interactive web-based tool (http://www.scpanstroma.yelab.site/) was developed for accessing, visualizing, and analyzing stromal data. Taken together, this study provides a systematic view of the highly heterogeneous stromal populations across cancer types and suggests future avenues for designing therapies to overcome the tumor-promoting functions of stromal cells.

SIGNIFICANCE

Comprehensive characterization of tumor-associated nonimmune stromal cells provides a robust resource for dissecting tumor microenvironment complexity and guiding stroma-targeted therapy development across multiple human cancer types.

Coordinated linear and rotational movements of endothelial cells compartmentalized by VE-cadherin drive angiogenic sprouting

Angiogenesis is a sequential process to extend new blood vessels from preexisting ones by sprouting and branching. During angiogenesis, endothelial cells (ECs) exhibit inhomogeneous multicellular behaviors referred to as "cell mixing," in which ECs repetitively exchange their relative positions, but the underlying mechanism remains elusive. Here we identified the coordinated linear and rotational movements potentiated by cell-cell contact as drivers of sprouting angiogenesis using in vitro and in silico approaches. VE-cadherin confers the coordinated linear motility that facilitated forward sprout elongation, although it is dispensable for rotational movement, which was synchronous without VE-cadherin. Mathematical modeling recapitulated the EC motility in the two-cell state and angiogenic morphogenesis with the effects of VE-cadherin-knockout. Finally, we found that VE-cadherin-dependent EC compartmentalization potentiated branch elongations, and confirmed this by mathematical simulation. Collectively, we propose a way to understand angiogenesis, based on unique EC behavioral properties that are partially dependent on VE-cadherin function.

Targeted therapy for intervertebral disc degeneration: inhibiting apoptosis is a promising treatment strategy

Intervertebral disc (IVD) degeneration (IDD) is a multifactorial pathological process associated with low back pain (LBP). The pathogenesis is complicated, and the main pathological changes are IVD cell apoptosis and extracellular matrix (ECM) degradation. Apoptotic cell loss leads to ECM degradation, which plays an essential role in IDD pathogenesis. Apoptosis regulation may be a potential attractive therapeutic strategy for IDD. Previous studies have shown that IVD cell apoptosis is mainly induced by the death receptor pathway, mitochondrial pathway, and endoplasmic reticulum stress (ERS) pathway. This article mainly summarizes the factors that induce IDD and apoptosis, the relationship between the three apoptotic pathways and IDD, and potential therapeutic strategies. Preliminary animal and cell experiments show that targeting apoptotic pathway genes or drug inhibition can effectively inhibit IVD cell apoptosis and slow IDD progression. Targeted apoptotic pathway inhibition may be an effective strategy to alleviate IDD at the gene level. This manuscript provides new insights and ideas for IDD therapy.

Alliance with EPR Effect: Combined Strategies to Improve the EPR Effect in the Tumor Microenvironment

The use of nanomedicine for cancer treatment takes advantage of its preferential accumulation in tumors owing to the enhanced permeability and retention (EPR) effect. The development of cancer nanomedicine has promised highly effective treatment options unprecedented by standard therapeutics. However, the therapeutic efficacy of passively targeted nanomedicine is not always satisfactory because it is largely influenced by the heterogeneity of the intensity of the EPR effect exhibited within a tumor, at different stages of a tumor, and among individual tumors. In addition, limited data on EPR effectiveness in human hinders further clinical translation of nanomedicine. This unsatisfactory therapeutic outcome in mice and humans necessitates novel approaches to improve the EPR effect. This review focuses on current attempts at overcoming the limitations of traditional EPR-dependent nanomedicine by incorporating supplementary strategies, such as additional molecular targeting, physical alteration, or physiological remodeling of the tumor microenvironment. This review will provide valuable insight to researchers who seek to overcome the limitations of relying on the EPR effect alone in cancer nanomedicine and go "beyond the EPR effect".

Cysteine Glutathionylation Acts as a Redox Switch in Endothelial Cells

Oxidative post-translational modifications (oxPTM) of receptors, enzymes, ion channels and transcription factors play an important role in cell signaling. oxPTMs are a key way in which oxidative stress can influence cell behavior during diverse pathological settings such as cardiovascular diseases (CVD), cancer, neurodegeneration and inflammatory response. In addition, changes in oxPTM are likely to be ways in which low level reactive oxygen and nitrogen species (RONS) may contribute to redox signaling, exerting changes in physiological responses including angiogenesis, cardiac remodeling and embryogenesis. Among oxPTM, S-glutathionylation of reactive cysteines emerges as an important regulator of vascular homeostasis by modulating endothelial cell (EC) responses to their local redox environment. This review summarizes the latest findings of S-glutathionylated proteins in major EC pathways, and the functional consequences on vascular pathophysiology. This review highlights the diversity of molecules affected by S-glutathionylation, and the complex consequences on EC function, thereby demonstrating an intricate dual role of RONS-induced S-glutathionylation in maintaining vascular homeostasis and participating in various pathological processes.

Stromal barriers to nanomedicine penetration in the pancreatic tumor microenvironment

Pancreatic cancer is known for its dismal prognosis despite efforts to improve therapeutic outcome. Recently, cancer nanomedicine, application of nanotechnology to cancer diagnosis and treatment, has gained interest for treatment of pancreatic cancer. The enhanced permeability and retention (EPR) effect that promotes selective accumulation of nanometer‐sized molecules within tumors is the theoretical rationale of treatment. However, it is clear that EPR may be insufficient in pancreatic cancer as a result of stromal barriers within the tumor microenvironment (TME). These limit intratumoral accumulation of macromolecules. The TME and stromal barriers inside it consist of various stromal cell types which interact both with each other and with tumor cells. We are only beginning to understand the complexities of the stromal barriers within the TME and its functional consequences for nanomedicine. Understanding the complex crosstalk between barrier stromal cells is challenging because of the difficulty of modeling pancreatic cancer TME. Here we provide an overview of stromal barriers within the TME. We also describe the preclinical models, both in vivo and in vitro, developed to study them. We furthermore discuss the critical gaps in our understanding, and how we might formulate a better strategy for using nanomedicine against pancreatic cancer.

Regulation of endothelial Fas expression as a mechanism of promotion of vascular integrity by mural cells in tumors

Angiogenesis is a multi‐step process that culminates in vascular maturation whereby nascent vessels stabilize to become functional, and mural cells play an essential role in this process. Recent studies have shown that mural cells in tumors also promote and maintain vascular integrity, with wide‐reaching clinical implications including the regulation of tumor growth, metastases, and drug delivery. Various regulatory signaling pathways have been hitherto implicated, but whether regulation of Fas‐dependent apoptotic mechanisms is involved has not yet been fully investigated. We first compared endothelial FAS staining in human pancreatic ductal adenocarcinomas and colon carcinomas and show that the latter, characterized by lower mural cell coverage of tumor vasculature, demonstrated higher expression of FAS than the former. Next, in an in vitro coculture system of MS‐1 and 10T1/2 cells as endothelial and mural cells respectively, we show that mural cells decreased endothelial Fas expression. Then, in an in vivo model in which C26 colon carcinoma cells were inoculated together with MS‐1 cells alone or with the further addition of 10T1/2 cells, we demonstrate that mural cells prevented hemorrhage. Finally, knockdown of endothelial Fas sufficiently recapitulated the protection against hemorrhage seen with the addition of mural cells. These results together suggest that regulation of endothelial Fas signaling is involved in the promotion of vascular integrity by mural cells in tumors.