Ultrastructural features of tumor-associated mast cells in parasympathetic paragangliomas (chemodectomas) of the neck

The mechanisms of the pathogenesis of neck paraganglioma (PGL) and the possible role of mast cells (MCs) in its development and metastasis are still poorly understood. We analyzed MCs' morphologic characterization, activation, and the properties of their cytoplasmic/released granules in PGLs, using light and transmission electron microscopy. Paragangliomas showed a large tumor-associated MC population both in the connective tissue layers of the tumor and between the tumor cells. Notably, MCs were presented by a high expression of specific proteases, size variation, polymorphism, and variable ultrastructural phenotype of granules. A massive number of granules were released surrounding the degranulated MCs while the integrity of MC membrane was maintained. Granules were electron-dense with or without a membrane, ranging from 0.2 to 0.8 μm in diameter. MC plasmalemma was not found at the site of MC-collagen fibrils contact, whereas the secretome and fibrils were directly contacted. We observed direct and mediator-based interactions between MCs and paraganglioma cells. The latter preserved their membrane integrity when MC granules were not in proximity. The effects of the MC secretome on the paraganglioma microenvironment demonstrated its pathogenetic role in tumor progression and allow its application to new diagnostic criteria and the development of protocols for personalized therapy. RESEARCH HIGHLIGHTS: Ultrastructural analysis reveals novel regulatory effects of mast cells via diverse secretory pathways on the pathogenesis of parasympathetic paraganglioma, including fibrous extracellular matrix remodeling and mediator-based interactions between MCs and cells of the tumor microenvironment.

Procedurally Targeted Delivery of Antitumor Drugs Using FAPα-Responsive TPGS Dimer-Based Flower-like Polymeric Micelles

To overcome the intestinal epithelium barrier and achieve a better antitumor effect, the procedurally targeting flower-like nanomicelles for oral delivery of antitumor drugs were designed based on FAPα-responsive TPGS1000 dimer (TPGS-Gly-Pro-TPGS) and L-carnitine linked poly(2-ethyl-2-oxazoline)-b-poly(D, l-lactide) (Car-PEOz-b-PLA). As expected, compared with unmodified polymeric micelles (TT-PMs) composed of TPGS-Gly-Pro-TPGS, L-carnitine conjugated polymeric micelles (CTT-PMs) formed from both TPGS-Gly-Pro-TPGS and Car-PEOz-b-PLA with favorable stability in simulated gastrointestinal fluid and FAPα-dependent release capability exhibited remarkably enhanced cellular uptake and transmembrane transport through OCTN2 mediation confirmed by fluorescence immunoassay, which was intuitively evidenced by stronger fluorescence within epithelial cells, and the basal side of small intestinal epithelium of mice being given intragastric administration of DiI-labeled micelles. The transport of CTT-PMs across the intestinal epithelium in an intact form was mediated by clathrin along the intracellular transport pathway of endosome-lysosome-ER-Golgi apparatus. Furthermore, both the increased uptake by FAPα-positive U87MG cells and unchangeable uptake by FAPα-negative C6 cells for coumarin-6 (C-6)/CTT-PMs compared with C-6/TT-PMs evidenced the targeting ability of CTT-PMs to FAPα-positive tumor cells. Both OCTN2-mediation and FAPα-responsiveness were beneficial for polymeric micelles to improve the delivery and therapeutic efficiency of antitumor agents, which was further supported by the remarkable enhancement in in vivo antitumor efficacy via promoting apoptosis of tumor cells for paclitaxel (PTX)-loaded CTT-PMs (PTX/CTT-PMs) with low toxicity compared with PTX/TT-PMs. Our findings offered an alternative design strategy for procedurally targeted delivery of chemotherapeutics by an oral route.

The Role of Different Immunocompetent Cell Populations in the Pathogenesis of Head and Neck Cancer-Regulatory Mechanisms of Pro- and Anti-Cancer Activity and Their Impact on Immunotherapy

Head and neck squamous cell carcinoma (HNSCC) is one of the most aggressive and heterogeneous groups of human neoplasms. HNSCC is characterized by high morbidity, accounting for 3% of all cancers, and high mortality with ~1.5% of all cancer deaths. It was the most common cancer worldwide in 2020, according to the latest GLOBOCAN data, representing the seventh most prevalent human malignancy. Despite great advances in surgical techniques and the application of modern combinations and cytotoxic therapies, HNSCC remains a leading cause of death worldwide with a low overall survival rate not exceeding 40-60% of the patient population. The most common causes of death in patients are its frequent nodal metastases and local neoplastic recurrences, as well as the relatively low response to treatment and severe drug resistance. Much evidence suggests that the tumour microenvironment (TME), tumour infiltrating lymphocytes (TILs) and circulating various subpopulations of immunocompetent cells, such regulatory T cells (CD4+CD25+Foxp3+Tregs), cytotoxic CD3+CD8+ T cells (CTLs) and CD3+CD4+ T helper type 1/2/9/17 (Th1/Th2/Th9/Th17) lymphocytes, T follicular helper cells (Tfh) and CD56dim/CD16bright activated natural killer cells (NK), carcinoma-associated fibroblasts (CAFs), myeloid-derived suppressor cells (MDSCs), tumour-associated neutrophils (N1/N2 TANs), as well as tumour-associated macrophages (M1/M2 phenotype TAMs) can affect initiation, progression and spread of HNSCC and determine the response to immunotherapy. Rapid advances in the field of immuno-oncology and the constantly growing knowledge of the immunosuppressive mechanisms and effects of tumour cancer have allowed for the use of effective and personalized immunotherapy as a first-line therapeutic procedure or an essential component of a combination therapy for primary, relapsed and metastatic HNSCC. This review presents the latest reports and molecular studies regarding the anti-tumour role of selected subpopulations of immunocompetent cells in the pathogenesis of HNSCC, including HPV+ve (HPV+) and HPV-ve (HPV-) tumours. The article focuses on the crucial regulatory mechanisms of pro- and anti-tumour activity, key genetic or epigenetic changes that favour tumour immune escape, and the strategies that the tumour employs to avoid recognition by immunocompetent cells, as well as resistance mechanisms to T and NK cell-based immunotherapy in HNSCC. The present review also provides an overview of the pre- and clinical early trials (I/II phase) and phase-III clinical trials published in this arena, which highlight the unprecedented effectiveness and limitations of immunotherapy in HNSCC, and the emerging issues facing the field of HNSCC immuno-oncology.

Cell-specific expression of the FAP gene is regulated by enhancer elements

Fibroblast activation protein (FAP) is an integral membrane serine protease that acts as both dipeptidyl peptidase and collagenase. In recent years, FAP has attracted considerable attention due to its specific upregulation in multiple types of tumor cell populations, including cancer cells in various cancer types, making FAP a potential target for therapy. However, relatively few papers pay attention to the mechanisms driving the cell-specific expression of the FAP gene. We found no correlation between the activities of the two FAP promoter variants (short and long) and the endogenous FAP mRNA expression level in several cell lines with different FAP expression levels. This suggested that other mechanisms may be responsible for specific transcriptional regulation of the FAP gene. We analyzed the distribution of known epigenetic and structural chromatin marks in FAP-positive and FAP-negative cell lines and identified two potential enhancer-like elements (E1 and E2) in the FAP gene locus. We confirmed the specific enrichment of H3K27ac in the putative enhancer regions in FAP-expressing cells. Both the elements exhibited enhancer activity independently of each other in the functional test by increasing the activity of the FAP promoter variants to a greater extent in FAP-expressing cell lines than in FAP-negative cell lines. The transcription factors AP-1, CEBPB, and STAT3 may be involved in FAP activation in the tumors. We hypothesized the existence of a positive feedback loop between FAP and STAT3, which may have implications for developing new approaches in cancer therapy.

Research Progress on Dipeptidyl Peptidase Family: Structure, Function and Xenobiotic Metabolism

Prolyl-specific peptidases or proteases, including Dipeptidyl Peptidase 2, 4, 6, 8, 9, 10, Fibroblast Activation Protein, prolyl endopeptidase and prolyl carboxypeptidase, belong to the dipeptidyl peptidase family. In human physiology and anatomy, they have homology amino acid sequences, similarities in structure, but play distinct functions and roles. Some of them also play important roles in the metabolism of drugs containing endogenous peptides, xenobiotics containing peptides, and exogenous peptides. The major functions of these peptidases in both the metabolism of human health and bioactive peptides are of significant importance in the development of effective inhibitors to control the metabolism of endogenous bioactive peptides. The structural characteristics, distribution of tissue, endogenous substrates, and biological functions were summarized in this review. Furthermore, the xenobiotics metabolism of the dipeptidyl peptidase family is illustrated. All the evidence and information summarized in this review would be very useful for researchers to extend the understanding of the proteins of these families and offer advice and assistance in physiology and pathology studies.

Possibility for Transcriptional Targeting of Cancer-Associated Fibroblasts-Limitations and Opportunities

Cancer-associated fibroblasts (CAF) are attractive therapeutic targets in the tumor microenvironment. The possibility of using CAFs as a source of therapeutic molecules is a challenging approach in gene therapy. This requires transcriptional targeting of transgene expression by cis-regulatory elements (CRE). Little is known about which CREs can provide selective transgene expression in CAFs. We hypothesized that the promoters of FAP, CXCL12, IGFBP2, CTGF, JAG1, SNAI1, and SPARC genes, the expression of whose is increased in CAFs, could be used for transcriptional targeting. Analysis of the transcription of the corresponding genes revealed that unique transcription in model CAFs was characteristic for the CXCL12 and FAP genes. However, none of the promoters in luciferase reporter constructs show selective activity in these fibroblasts. The CTGF, IGFBP2, JAG1, and SPARC promoters can provide higher transgene expression in fibroblasts than in cancer cells, but the nonspecific viral promoters CMV, SV40, and the recently studied universal PCNA promoter have the same features. The patterns of changes in activity of various promoters relative to each other observed for human cell lines were similar to the patterns of activity for the same promoters both in vivo and in vitro in mouse models. Our results reveal restrictions and features for CAF transcriptional targeting.

Cancer-associated fibroblasts (CAFs) in thyroid papillary carcinoma: molecular networks and interactions

In 1989, Stephen Paget proposed the 'seed and soil' theory of cancer metastasis. This theory has led to previous researchers focusing on the role of a tumour as a cancer seed and antiangiogenesis agents as cancer soil fumigant; for the latter to be effective, it is important for them to be able to distinguish cancer cells from stromal cells. However, antiangiogenesis agents have not produced dramatic survival benefits in vivo. This may be related to their inability to destroy the supporting stroma that promote cancer cell growth. Therefore, in order to effectively arrest cancer cell growth for therapeutic purposes, a paradigm shift is required in our fundamental approach to decipher the molecular events and networks in the stromal environment that cancer cells can thrive and proliferate. The pathogenesis of cancer is a multidimensional process of pathological molecular and cellular pathways, influencing different stromal properties and achieving a mutually negotiated crosstalk between cancer cells and stromal cells. This review summarises the clinical presentation of current knowledge of classical papillary thyroid carcinoma (PTC), emerging molecular diagnostics and future directions of classical PTC research.

[Mast cells in the microenvironment of uveal melanoma]

OBJECTIVE

To study the morphological features of the microenvironment of a tumor nodule in the eyes with uveal melanoma, focusing on mast cells.

MATERIAL AND METHODS

A total of 43 enucleated eyes with uveal melanoma (260 histological specimens) were examined. The patients' age averaged 54±2.7 years. The morphopathological types of tumors were as follows: epithelioid-cell (n=9; 20.9%), spindle-cell type AB (n=15; 34.9%), and mixed-cell (n=19; 44.2%). The tumor prominence was 4.7±1.3 mm; the base diameter was 13.5±3.3 mm. Statistical methods, such as Microsoft Excel, Statistica 10.1, Spearman's rank correlation coefficient (rs), were applied.

RESULTS

Mast cells in the microenvironment of uveal melanoma were present in 18 (41.9%) of the 43 eyes. There was a significantly higher correlation between the mixed-cell type of tumor and the accumulation of mast cells (r_s=0.636). The correlation coefficient (rs) of the number of mast cells with the degree of tumor pigmentation in terms of densely and weakly pigmented forms was 0.571 and 0.717, respectively. Tumor invasion through the sclera was detected in 7 (16.3%) eyes with mast cells (r_s=0.395). Tumor growth in the emissarium in the presence of mast cells was determined in 8 (18.6%) cases (r_s=0.469). Comparison established a correlation between the number of mast cells and the sections of tumor blood vessels (r_s=0.21). Granulated cells were noted in 15 (34.9%) cases; degranulated ones were seen in 3 (7%) cases of the 43 examined eyes. with an ejection of granules around the tumor cells, which may be evidence of their interaction. Granules were ascertained to be released around the tumor cells, which may be suggestive of their interaction.

CONCLUSION

The study of the mast cell population as one of the components of the tumor microenvironment can be used to elaborate novel approaches for the targeted treatment of uveal melanoma, in particular for its impact on tumor angiogenesis, by using mast cell inhibitors. Therefore, it is relevant and promising to conduct further investigation of mast cells in uveal melanoma.