Cannibalism of live lymphocytes by human metastatic but not primary melanoma cells

Beyond typical histology of BAP1-inactivated melanocytoma

BAP1-inactivated melanocytoma (BIM) is a novel subgroup of melanocytic neoplasm listed in the 5th edition of WHO classification of skin tumor. BIM is characterized by two molecular alterations, including a mitogenic driver mutation (usually BRAF gene) and the loss of function of BAP1, a tumor suppressor gene located on chromosome 3p21, which encodes for BRCA1-associated protein (BAP1). The latter represents a nuclear-localized deubiquitinase involved in several cellular processes including cell cycle regulation, chromatin remodeling, DNA damage response, differentiation, senescence and cell death. BIMs are histologically characterized by a population of large epithelioid melanocytes with well-demarcated cytoplasmic borders and copious eosinophilic cytoplasm, demonstrating loss of BAP1 nuclear expression by immunohistochemistry. Recently, we have published a series of 50 cases, extending the morphological spectrum of the neoplasm and highlighting some new microscopic features. In the current article, we focus on some new histological features, attempting to explain and link them to certain mechanisms of tumor development, including senescence, endoreplication, endocycling, asymmetric cytokinesis, entosis and others. In light of the morphological and molecular findings observed in BIM, we postulated that this entity unmasks a fine mechanism of tumor in which both clonal/stochastic and hierarchical model can be unified.

Cell-in-cell phenomena across the tree of life

Cells in obligately multicellular organisms by definition have aligned fitness interests, minimum conflict, and cannot reproduce independently. However, some cells eat other cells within the same body, sometimes called cell cannibalism. Such cell-in-cell events have not been thoroughly discussed in the framework of major transitions to multicellularity. We performed a systematic screening of 508 articles, from which we chose 115 relevant articles in a search for cell-in-cell events across the tree of life, the age of cell-in-cell-related genes, and whether cell-in-cell events are associated with normal multicellular development or cancer. Cell-in-cell events are found across the tree of life, from some unicellular to many multicellular organisms, including non-neoplastic and neoplastic tissue. Additionally, out of the 38 cell-in-cell-related genes found in the literature, 14 genes were over 2.2 billion years old, i.e., older than the common ancestor of some facultatively multicellular taxa. All of this suggests that cell-in-cell events may have originated before the origins of obligate multicellularity. Thus, our results show that cell-in-cell events exist in obligate multicellular organisms, but are not a defining feature of them. The idea of eradicating cell-in-cell events from obligate multicellular organisms as a way of treating cancer, without considering that cell-in-cell events are also part of normal development, should be abandoned.

Cell death by phagocytosis

Cells can die as a consequence of being phagocytosed by other cells - a form of cell death that has been called phagotrophy, cell cannibalism, programmed cell removal and primary phagocytosis. However, these are all different manifestations of cell death by phagocytosis (termed 'phagoptosis' for short). The engulfed cells die as a result of cytotoxic oxidants, peptides and degradative enzymes within acidic phagolysosomes. Cell death by phagocytosis was discovered by Metchnikov in the 1880s, but was neglected until recently. It is now known to contribute to developmental cell death in nematodes, Drosophila and mammals, and is central to innate and adaptive immunity against pathogens. Cell death by phagocytosis mediates physiological turnover of erythrocytes and other leucocytes, making it the most abundant form of cell death in the mammalian body. Immunity against cancer is also partly mediated by macrophage phagocytosis of cancer cells, but cancer cells can also phagocytose host cells and other cancer cells in order to survive. Recent evidence indicates neurodegeneration and other neuropathologies can be mediated by microglial phagocytosis of stressed neurons. Thus, despite cell death by phagocytosis being poorly recognized, it is one of the oldest, commonest and most important forms of cell death.

Hyperactive Rac stimulates cannibalism of living target cells and enhances CAR-M-mediated cancer cell killing

The 21kD GTPase Rac is an evolutionarily ancient regulator of cell shape and behavior. Rac2 is predominantly expressed in hematopoietic cells where it is essential for survival and motility. The hyperactivating mutation Rac2E62K also causes human immunodeficiency, although the mechanism remains unexplained. Here, we report that in Drosophila, hyperactivating Rac stimulates ovarian cells to cannibalize neighboring cells, destroying the tissue. We then show that hyperactive Rac2E62K stimulates human HL60-derived macrophage-like cells to engulf and kill living T cell leukemia cells. Primary mouse Rac2+/E62K bone-marrow-derived macrophages also cannibalize primary Rac2+/E62K T cells due to a combination of macrophage hyperactivity and T cell hypersensitivity to engulfment. Additionally, Rac2+/E62K macrophages non-autonomously stimulate wild-type macrophages to engulf T cells. Rac2E62K also enhances engulfment of target cancer cells by chimeric antigen receptor-expressing macrophages (CAR-M) in a CAR-dependent manner. We propose that Rac-mediated cell cannibalism may contribute to Rac2+/E62K human immunodeficiency and enhance CAR-M cancer immunotherapy.

Activated Src kinase promotes cell cannibalism in Drosophila

Src family kinases (SFKs) are evolutionarily conserved proteins acting downstream of receptors and regulating cellular processes including proliferation, adhesion, and migration. Elevated SFK expression and activity correlate with progression of a variety of cancers. Here, using the Drosophila melanogaster border cells as a model, we report that localized activation of a Src kinase promotes an unusual behavior: engulfment of one cell by another. By modulating Src expression and activity in the border cell cluster, we found that increased Src kinase activity, either by mutation or loss of a negative regulator, is sufficient to drive one cell to engulf another living cell. We elucidate a molecular mechanism that requires integrins, the kinases SHARK and FAK, and Rho family GTPases, but not the engulfment receptor Draper. We propose that cell cannibalism is a result of aberrant phagocytosis, where cells with dysregulated Src activity fail to differentiate between living and dead or self versus non-self, thus driving this malignant behavior.

Non-Professional Phagocytosis Increases in Melanoma Cells and Tissues with Increasing E-Cadherin Expression

Non-professional phagocytosis in cancer has been increasingly studied in recent decades. In malignant melanoma metastasis, cell-in-cell structures have been described as a sign of cell cannibalism. To date, only low rates of cell-in-cell structures have been described in patients with malignant melanoma. To investigate these findings further, we examined twelve primary melanoma cell lines in both adherent and suspended co-incubation for evidence of engulfment. In addition, 88 malignant melanoma biopsies and 16 healthy tissue samples were evaluated. E-cadherin levels were determined in the cell lines and tissues. All primary melanoma cell lines were capable of phagocytosis, and phagocytosis increased when cells were in suspension during co-incubation. Cell-in-cell structures were also detected in most of the tissue samples. Early T stages and increasingly advanced N and M stages have correspondingly lower rates of cell-in-cell structures. Non-professional phagocytosis was also present in normal skin tissue. Non-professional phagocytosis appears to be a ubiquitous mechanism in malignant melanoma. The absence of phagocytosis in metastases may be one reason for the high rate of metastasis in malignant melanoma.

Cell-in-cell: a potential biomarker of prognosis and a novel mechanism of drug resistance in cancer

The cell-in-cell (CIC) phenomenon has received increasing attention over recent years because of its wide existence in multiple cancer tissues. The mechanism of CIC formation is considerably complex as it involves interactions between two cells. Although the molecular mechanisms of CIC formation have been extensively investigated, the process of CIC formation remains ambiguous. Currently, CIC is classified into four subtypes based on different cell types and inducing factors, and the underlying mechanisms for each subtype are distinct. Here, we investigated the subtypes of CIC and their major mechanisms involved in cancer development. To determine the clinical significance of CIC, we reviewed several clinical studies on CIC and found that CIC could serve as a diagnostic and prognostic biomarker. The implications of CIC on the clinical management of cancers also remain largely unknown. To clarify this aspect, in the present review, we highlight the findings of recent investigations on the causal link between CIC and cancer treatment. We also indicate the existing issues that need to be resolved urgently to provide a potential direction for future research on CIC.

Cell-in-Cell Structures in Gastrointestinal Tumors: Biological Relevance and Clinical Applications

This review summarizes information about cell-in-cell (CIC) structures with a focus on gastrointestinal tumors. The phenomenon when one cell lives in another one has attracted an attention of researchers over the past decades. We briefly discuss types of CIC structures and mechanisms of its formation, as well as the biological basis and consequences of the cell-engulfing process. Numerous clinico-histopathological studies demonstrate the significance of these structures as prognostic factors, mainly correlated with negative prognosis. The presence of CIC structures has been identified in all gastrointestinal tumors. However, the majority of studies concern pancreatic cancer. In this field, in addition to the assessment of the prognostic markers, the attempts to manipulate the ability of cells to form CISs have been done in order to stimulate the death of the inner cell. Number of CIC structures also correlates with genetic features for some gastrointestinal tu-mors. The role of CIC structures in the responses of tumors to therapies, both chemotherapy and immunotherapy, seems to be the most poorly studied. However, there is some evidence of involvement of CIC structures in treatment failure. Here, we summarized the current literature on CIC structures in cancer with a focus on gastrointestinal tumors and specified future perspectives for investigation.

Cell-in-Cell Structures in Gastrointestinal Tumors: Biological Relevance and Clinical Applications

This review summarizes information about cell-in-cell (CIC) structures with a focus on gastrointestinal tumors. The phenomenon when one cell lives in another one has attracted an attention of researchers over the past decades. We briefly discuss types of CIC structures and mechanisms of its formation, as well as the biological basis and consequences of the cell-engulfing process. Numerous clinico-histopathological studies demonstrate the significance of these structures as prognostic factors, mainly correlated with negative prognosis. The presence of CIC structures has been identified in all gastrointestinal tumors. However, the majority of studies concern pancreatic cancer. In this field, in addition to the assessment of the prognostic markers, the attempts to manipulate the ability of cells to form CISs have been done in order to stimulate the death of the inner cell. Number of CIC structures also correlates with genetic features for some gastrointestinal tu-mors. The role of CIC structures in the responses of tumors to therapies, both chemotherapy and immunotherapy, seems to be the most poorly studied. However, there is some evidence of involvement of CIC structures in treatment failure. Here, we summarized the current literature on CIC structures in cancer with a focus on gastrointestinal tumors and specified future perspectives for investigation.

Ez-Metastasizing: The Crucial Roles of Ezrin in Metastasis

Ezrin is the cytoskeletal organizer and functions in the modulation of membrane-cytoskeleton interaction, maintenance of cell shape and structure, and regulation of cell-cell adhesion and movement, as well as cell survival. Ezrin plays a critical role in regulating tumor metastasis through interaction with other binding proteins. Notably, Ezrin has been reported to interact with immune cells, allowing tumor cells to escape immune attack in metastasis. Here, we review the main functions of Ezrin, the mechanisms through which it acts, its role in tumor metastasis, and its potential as a therapeutic target.

The Role of Nucleases Cleaving TLR3, TLR7/8 and TLR9 Ligands, Dicer RNase and miRNA/piRNA Proteins in Functional Adaptation to the Immune Escape and Xenophagy of Prostate Cancer Tissue

The prototypic sensors for the induction of innate and adaptive immune responses are the Toll-like receptors (TLRs). Unusually high expression of TLRs in prostate carcinoma (PC), associated with less differentiated, more aggressive and more propagating forms of PC, changed the previous paradigm about the role of TLRs strictly in immune defense system. Our data reveal an entirely novel role of nucleic acids-sensing Toll-like receptors (NA-TLRs) in functional adaptation of malignant cells for supply and digestion of surrounding metabolic substrates from dead cells as specific mechanism of cancer cells survival, by corresponding ligands accelerated degradation and purine/pyrimidine salvage pathway. The spectrophotometric measurement protocols used for the determination of the activity of RNases and DNase II have been optimized in our laboratory as well as the enzyme-linked immunosorbent method for the determination of NF-κB p65 in prostate tissue samples. The protocols used to determine Dicer RNase, AGO2, TARBP2 and PIWIL4 were based on enzyme-linked immunosorbent assay. The amount of pre-existing acid-soluble oligonucleotides was measured and expressed as coefficient of absorbance. The activities of acid DNase II and RNase T2, and the activities of nucleases cleaving TLR3, TLR7/8 and TLR9 ligands (Poly I:C, poly U and unmethylated CpG), increased several times in PC, compared to the corresponding tumor adjacent and control tissue, exerting very high sensitivity and specificity of above 90%. Consequently higher levels of hypoxanthine and NF-κB p65 were reported in PC, whereas the opposite results were observed for miRNA biogenesis enzyme (Dicer RNase), miRNA processing protein (TARB2), miRNA-induced silencing complex protein (Argonaute-AGO) and PIWI-interacting RNAs silence transposon. Considering the crucial role of purine and pyrimidine nucleotides as energy carriers, subunits of nucleic acids and nucleotide cofactors, future explorations will be aimed to design novel anti-cancer immune strategies based on a specific acid endolysosomal nuclease inhibition.

Cell-In-Cell Structures in Early Breast Cancer Are Prognostically Valuable

Cell-in-cell (CIC) structures in breast cancer have so far been studied in a small inhomogeneous patient population, suggesting the prognostic importance of CIC. In the present study, we focused on CIC in early hormone-sensitive breast cancer. With in vitro co-culture experiments, we compared the homotypic phagocytic capacity of two breast cancer cell lines to that of primary human fibroblasts. Afterward, we studied 601 tissue specimens from 147 patients participating in an institutional accelerated partial breast irradiation (APBI) phase II trial. Both breast cancer cell lines performed non-professional phagocytosis at a higher rate than primary human fibroblasts. In this study cohort, 93.2% of the patients had T1 tumours, and 6.8% had T2 tumours. CIC was found in 61.2% of the patients, with a CIC rate ranging from <1/mm² to 556.5/mm² with a mean of 30.9/mm² ± 68.4/mm². CIC structures were prognostically favourable for local recurrence-free survival and disease-free survival. Regarding metastasis-free survival, CIC-positive patients had an unfavourable prognosis. Subgroup analysis indicated a correlation between a high proliferation index and high CIC rates. CIC had the highest prognostic value in young breast cancer patients (p = 0.004). With this study, we provide further evidence of CIC as a prognostic marker in breast cancer.

Cell pairing for biological analysis in microfluidic devices

Cell pairing at the single-cell level usually allows a few cells to contact or seal in a single chamber and provides high-resolution imaging. It is pivotal for biological research, including understanding basic cell functions, creating cancer treatment technologies, developing drugs, and more. Laboratory chips based on microfluidics have been widely used to trap, immobilize, and analyze cells due to their high efficiency, high throughput, and good biocompatibility properties. Cell pairing technology in microfluidic devices provides spatiotemporal research on cellular interactions and a highly controlled approach for cell heterogeneity studies. In the last few decades, many researchers have emphasized cell pairing research based on microfluidics. They designed various microfluidic device structures for different biological applications. Herein, we describe the current physical methods of microfluidic devices to trap cell pairs. We emphatically summarize the practical applications of cell pairing in microfluidic devices, including cell fusion, cell immunity, gap junction intercellular communication, cell co-culture, and other applications. Finally, we review the advances and existing challenges of the presented devices and then discuss the possible development directions to promote medical and biological research.

Cytoskeletal and Cytoskeleton-Associated Proteins: Key Regulators of Cancer Stem Cell Properties

Cancer stem cells (CSCs) are a subpopulation of cancer cells possessing stemness characteristics that are closely associated with tumor proliferation, recurrence and resistance to therapy. Recent studies have shown that different cytoskeletal components and remodeling processes have a profound impact on the behavior of CSCs. In this review, we outline the different cytoskeletal components regulating the properties of CSCs and discuss current and ongoing therapeutic strategies targeting the cytoskeleton. Given the many challenges currently faced in targeted cancer therapy, a deeper comprehension of the molecular events involved in the interaction of the cytoskeleton and CSCs will help us identify more effective therapeutic strategies to eliminate CSCs and ultimately improve patient survival.

Homotypic cell-in-cell structures as an adverse prognostic predictor of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most common malignant liver tumors. A homotypic cell-in-cell structure (hoCIC) refers to one or more cells internalized into the same type as their neighbors, which predominantly occurs in multiple tumors. The objective of this study was to investigate the prognostic value of hoCICs in HCC and its relationship with other clinicopathological features. By immunostaining analysis of a panel of HCC tissues, we found that hoCICs were prevalent in tumor tissues (54/90) but not in para-tumor tissues (17/90). The presence of hoCICs in tumor tissues was closely associated with E-cadherin expression. The presence of CICs was identified as significantly associated with poor survival rates of patients with HCC, comparable to traditional clinicopathological parameters, such as histological grade [hazard ratio (HR) = 0.734, p = 0.320]. Multivariate Cox regression analysis further confirmed that CICs were an independent risk factor for poor survival (HR = 1.902, p = 0.047). In addition, hoCICs were the predominant contributor in a nomogram model constructed for survival prediction at 1, 3, and 5 years [the areas under the curve (AUCs) were 0.760, 0.733, and 0.794, respectively]. Stratification analysis indicated that hoCICs tend to selectively affect patients with high-grade disease (HR = 2.477, p = 0.009) and at the early TNM stage (HR = 2.351, p = 0.05). Thus, hoCICs predict poor survival of patients with HCC, particularly those with higher grades and at an early stage.

Causes, consequences and clinical significance of aneuploidy across melanoma subtypes

Aneuploidy, the state of the cell in which the number of whole chromosomes or chromosome arms becomes imbalanced, has been recognized as playing a pivotal role in tumor evolution for over 100 years. In melanoma, the extent of aneuploidy, as well as the chromosomal regions that are affected differ across subtypes, indicative of distinct drivers of disease. Multiple studies have suggested a role for aneuploidy in diagnosis and prognosis of melanomas, as well as in the context of immunotherapy response. A number of key constituents of the cell cycle have been implicated in aneuploidy acquisition in melanoma, including several driver mutations. Here, we review the state of the art on aneuploidy in different melanoma subtypes, discuss the potential drivers, mechanisms underlying aneuploidy acquisition as well as its value in patient diagnosis, prognosis and response to immunotherapy treatment.

Proposal to Consider Chemical/Physical Microenvironment as a New Therapeutic Off-Target Approach

The molecular revolution could lead drug discovery from chance observation to the rational design of new classes of drugs that could simultaneously be more effective and less toxic. Unfortunately, we are witnessing some failure in this sense, and the causes of the crisis involve a wide range of epistemological and scientific aspects. In pharmacology, one key point is the crisis of the paradigm the “magic bullet”, which is to design therapies based on specific molecular targets. Drug repurposing is one of the proposed ways out of the crisis and is based on the off-target effects of known drugs. Here, we propose the microenvironment as the ideal place to direct the off-targeting of known drugs. While it has been extensively investigated in tumors, the generation of a harsh microenvironment is also a phenotype of the vast majority of chronic diseases. The hostile microenvironment, on the one hand, reduces the efficacy of both chemical and biological drugs; on the other hand, it dictates a sort of “Darwinian” selection of those cells armed to survive in such hostile conditions. This opens the way to the consideration of the microenvironment as a convenient target for pharmacological action, with a clear example in proton pump inhibitors.

Cell-in-Cell: From Cell Biology to Translational Medicine

Cell-in-cell structures (CICs) refer to cytoplasmic internalization of a cell by another cell, which are found throughout various biological systems and have been a part of scientific dogma for a long time. However, neither the mechanisms underlying this phenomenon nor their possible roles in disease development have resulted in major breakthroughs until recent years. In view of the ubiquity of CICs in inflammatory tissue and tumors, it is tempting to think that these specific structures could be associated with clinical diagnosis and treatment and thus would become a new hotspot for translational medicine. Translational medicine is a new concept in the field of international biomedical research that appeared in the last 20 years, which transforms basic research into clinical application. With the growing interest in this field, this review addresses recent research on CICs and their potential clinical implications in cytomorphological diagnosis and the pathology of human diseases, while discussing as yet unanswered questions. We also put forward future directions to reduce the gap in our knowledge caused by our currently limited understanding of CICs.

Hydrodynamic dissection of Stentor coeruleus in a microfluidic cross junction

Stentor coeruleus, a single-cell ciliated protozoan, is a model organism for wound healing and regeneration studies. Despite Stentor's large size (up to 2 mm in extended state), microdissection of Stentor remains challenging. In this work, we describe a hydrodynamic cell splitter, consisting of a microfluidic cross junction, capable of splitting Stentor cells in a non-contact manner at a high throughput of ∼500 cells per minute under continuous operation. Introduction of asymmetry in the flow field at the cross junction leads to asymmetric splitting of the cells to generate cell fragments as small as ∼8.5 times the original cell size. Characterization of cell fragment viability shows reduced 5-day survival as fragment size decreases and as the extent of hydrodynamic stress imposed on the fragments increases. Our results suggest that cell fragment size and composition, as well as mechanical stress, play important roles in the long-term repair of Stentor cells and warrant further investigations. Nevertheless, the hydrodynamic splitter can be useful for studying phenomena immediately after cell splitting, such as the closure of wounds in the plasma membrane which occurs on the order of 100-1000 seconds in Stentor.

Construction of a novel model based on cell-in-cell-related genes and validation of KRT7 as a biomarker for predicting survival and immune microenvironment in pancreatic cancer

Background

Pancreatic cancer (PC) is a highly malignant tumor featured with high intra-tumoral heterogeneity and poor prognosis. Cell-in-cell (CIC) structures have been reported in multiple cancers, and their presence is associated with disease progression. Nonetheless, the prognostic values and biological functions of CIC-related genes in PC remain poorly understood.

Methods

The sequencing data, as well as corresponding clinicopathological information of PC were collected from public databases. Random forest screening, least absolute shrinkage, and selection operator (LASSO) regression and multivariate Cox regression analysis were performed to construct a prognostic model. The effectiveness and robustness of the model were evaluated using receiver operating characteristic (ROC) curves, survival analysis and establishing the nomogram model. Functional enrichment analyses were conducted to annotate the biological functions. The immune infiltration levels were evaluated by ESTIMATE and CIBERSORT algorithms. The expression of KRT7 (Keratin 7) was validated by quantitative real-time PCR (qRT-PCR), western blotting and immunohistochemistry (IHC) staining. The CIC formation, cell clusters, cell proliferation, migration and invasion assays were applied to investigate the effects of silencing the expression of KRT7.

Results

A prognostic model based on four CIC-related genes was constructed to stratify the patients into the low- and high-risk subgroups. The high-risk group had a poorer prognosis, higher tumor mutation burden and lower immune cell infiltration than the low-risk group. Functional enrichment analyses showed that numerous terms and pathways associated with invasion and metastasis were enriched in the high-risk group. KRT7, as the most paramount risk gene in the prognostic model, was significantly associated with a worse prognosis of PC in TCGA dataset and our own cohort. High expression of KRT7 might be responsible for the immunosuppression in the PC microenvironment. KRT7 knockdown was significantly suppressed the abilities of CIC formation, cell cluster, cell proliferation, migration, and invasion in PC cell lines.

Conclusions

Our prognostic model based on four CIC-related genes has a significant potential in predicting the prognosis and immune microenvironment of PC, which indicates that targeting CIC processes could be a therapeutic option with great interests. Further studies are needed to reveal the underlying molecular mechanisms and biological implications of CIC phenomenon and related genes in PC progression.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-022-09983-6.

AIM-CICs: an automatic identification method for cell-in-cell structures based on convolutional neural network

Edited by Luonan Chen Whereas biochemical markers are available for most types of cell death, current studies on non-autonomous cell death by entosis rely strictly on the identification of cell-in-cell structures (CICs), a unique morphological readout that can only be quantified manually at present. Moreover, the manual CIC quantification is generally over-simplified as CIC counts, which represents a major hurdle against profound mechanistic investigations. In this study, we take advantage of artificial intelligence technology to develop an automatic identification method for CICs (AIM-CICs), which performs comprehensive CIC analysis in an automated and efficient way. The AIM-CICs, developed on the algorithm of convolutional neural network, can not only differentiate between CICs and non-CICs (the area under the receiver operating characteristic curve (AUC) > 0.99), but also accurately categorize CICs into five subclasses based on CIC stages and cell number involved (AUC > 0.97 for all subclasses). The application of AIM-CICs would systemically fuel research on CIC-mediated cell death, such as high-throughput screening.

Cell-in-Cell Events in Oral Squamous Cell Carcinoma

For over a century, cells within other cells have been detected by pathologists as common histopathological findings in tumors, being generally identified as “cell-in-cell” structures. Despite their characteristic morphology, these structures can originate from various processes, such as cannibalism, entosis and emperipolesis. However, only in the last few decades has more attention been given to these events due to their importance in tumor development. In cancers such as oral squamous cell carcinoma, cell-in-cell events have been linked to aggressiveness, metastasis, and therapeutic resistance. This review aims to summarize relevant information about the occurrence of various cell-in-cell phenomena in the context of oral squamous cell carcinoma, addressing their causes and consequences in cancer. The lack of a standard terminology in diagnosing these events makes it difficult to classify the existing cases and to map the behavior and impacts of these structures. Despite being frequently reported in oral squamous cell carcinoma and other cancers, their impacts on carcinogenesis aren’t fully understood. Cell-in-cell formation is seen as a survival mechanism in the face of a lack of nutritional availability, an acid microenvironment and potential harm from immune cell defense. In this deadly form of competition, cells that engulf other cells establish themselves as winners, taking over as the predominant and more malignant cell population. Understanding the link between these structures and more aggressive behavior in oral squamous cell carcinoma is of paramount importance for their incorporation as part of a therapeutic strategy.

Ezrin gone rogue in cancer progression and metastasis: An enticing therapeutic target

Cancer metastasis is the primary cause of morbidity and mortality in cancer as it remains the most complicated, devastating, and enigmatic aspect of cancer. Several decades of extensive research have identified several key players closely associated with metastasis. Among these players, cytoskeletal linker Ezrin (the founding member of the ERM (Ezrin-Radixin-Moesin) family) was identified as a critical promoter of metastasis in pediatric cancers in the early 21st century. Ezrin was discovered 40 years ago as a aminor component of intestinal epithelial microvillus core protein, which is enriched in actin-containing cell surface structures. It controls gastric acid secretion and plays diverse physiological roles including maintaining cell polarity, regulating cell adhesion, cell motility and morphogenesis. Extensive research for more than two decades evinces that Ezrin is frequently dysregulated in several human cancers. Overexpression, altered subcellular localization and/or aberrant activation of Ezrin are closely associated with higher metastatic incidence and patient mortality, thereby justifying Ezrin as a valuable prognostic biomarker in cancer. Ezrin plays multifaceted role in multiple aspects of cancer, with its significant contribution in the complex metastatic cascade, through reorganizing the cytoskeleton and deregulating various cellular signaling pathways. Current preclinical studies using genetic and/or pharmacological approaches reveal that inactivation of Ezrin results in significant inhibition of Ezrin-mediated tumor growth and metastasis as well as increase in the sensitivity of cancer cells to various chemotherapeutic drugs. In this review, we discuss the recent advances illuminating the molecular mechanisms responsible for Ezrin dysregulation in cancer and its pleiotropic role in cancer progression and metastasis. We also highlight its potential as a prognostic biomarker and therapeutic target in various cancers. More importantly, we put forward some potential questions, which we strongly believe, will stimulate both basic and translational research to better understand Ezrin-mediated malignancy, ultimately leading to the development of Ezrin-targeted cancer therapy for the betterment of human life.

Cell-in-cell structure mediates in-cell killing suppressed by CD44

Penetration of immune cells into tumor cells was believed to be immune-suppressive via cell-in-cell (CIC) mediated death of the internalized immune cells. We unexpectedly found that CIC formation largely led to the death of the host tumor cells, but not the internalized immune cells, manifesting typical features of death executed by NK cells; we named this “in-cell killing” which displays the efficacy superior to the canonical way of “kiss-killing” from outside. By profiling isogenic cells, CD44 on tumor cells was identified as a negative regulator of “in-cell killing” via inhibiting CIC formation. CD44 functions to antagonize NK cell internalization by reducing N-cadherin-mediated intercellular adhesion and by enhancing Rho GTPase-regulated cellular stiffness as well. Remarkably, antibody-mediated blockade of CD44 signaling potentiated the suppressive effects of NK cells on tumor growth associated with increased heterotypic CIC formation. Together, we identified CIC-mediated “in-cell killing” as a promising strategy for cancer immunotherapy.

Expression of Hv1 proton channels in myeloid-derived suppressor cells (MDSC) and its potential role in T cell regulation

Immunosuppression by myeloid-derived suppressor cells (MDSC), especially near tumor surfaces, involves the extracellular production of reactive oxygen species (ROS). ROS generation in MDSC occurs during the oxidation of NADPH to NADP+, which NOX2 catalyzes. ROS react with the T cell receptor complex, abolishing the antigen presentation, which blocks the immune system elimination of the tumor cells. Extrusion of protons from MDSC by voltage-gated proton channel (H_v1) sustains ROS production. Here, we demonstrate the expression of H_v1 in mouse MDSC. In this way, H_v1 present in MDSC becomes a potential cancer therapeutic target since its inhibition seems to diminish immunosuppression activity in the tumoral microenvironment, allowing cancer cells to be attacked by the immune system.

Myeloid-derived suppressor cells (MDSC) are a heterogeneous cell population with high immunosuppressive activity that proliferates in infections, inflammation, and tumor microenvironments. In tumors, MDSC exert immunosuppression mainly by producing reactive oxygen species (ROS), a process triggered by the NADPH oxidase 2 (NOX2) activity. NOX2 is functionally coupled with the H_v1 proton channel in certain immune cells to support sustained free-radical production. However, a functional expression of the H_v1 channel in MDSC has not yet been reported. Here, we demonstrate that mouse MDSC express functional H_v1 proton channel by immunofluorescence microscopy, flow cytometry, and Western blot, besides performing a biophysical characterization of its macroscopic currents via patch-clamp technique. Our results show that the immunosuppression by MDSC is conditional to their ability to decrease the proton concentration elevated by the NOX2 activity, rendering H_v1 a potential drug target for cancer treatment.

Cancer Immunoediting: Elimination, Equilibrium, and Immune Escape in Solid Tumors

Emphasizing the dynamic processes between cancer and host immune system, the initially discovered concept of cancer immunosurveillance has been replaced by the current concept of cancer immunoediting consisting of three phases: elimination, equilibrium, and escape. Solid tumors composed of both cancer and host stromal cells are an example how the three phases of cancer immunoediting functionally evolve and how tumor shaped by the host immune system gets finally resistant phenotype. The elimination, equilibrium, and escape have been described in this chapter in details, including the role of immune surveillance, cancer dormancy, disruption of the antigen-presenting machinery, tumor-infiltrating immune cells, resistance to apoptosis, as well as the function of tumor stroma, microvesicles, exosomes, and inflammation.

Cell Communication Network factor 4 promotes tumor-induced immunosuppression in melanoma

Cell Communication Network factor 4 (CCN4/WISP1) is a matricellular protein secreted by cancer cells that promotes metastasis by inducing the epithelial-mesenchymal transition. While metastasis limits survival, limited anti-tumor immunity also associates with poor patient outcomes with recent work linking these two clinical correlates. Motivated by increased CCN4 correlating with dampened anti-tumor immunity in primary melanoma, we test for a direct causal link by knocking out CCN4 (CCN4 KO) in the B16F0 and YUMM1.7 mouse melanoma models. Tumor growth is reduced when CCN4 KO melanoma cells are implanted in immunocompetent but not in immunodeficient mice. Correspondingly, CD45⁺ tumor-infiltrating leukocytes are significantly increased in CCN4 KO tumors, with increased natural killer and CD8⁺ T cells and reduced myeloid-derived suppressor cells (MDSC). Among mechanisms linked to local immunosuppression, CCN4 suppresses IFN-gamma release by CD8⁺ T cells and enhances tumor secretion of MDSC-attracting chemokines like CCL2 and CXCL1. Finally, CCN4 KO potentiates the anti-tumor effect of immune checkpoint blockade (ICB) therapy. Overall, our results suggest that CCN4 promotes tumor-induced immunosuppression and is a potential target for therapeutic combinations with ICB.

Fumarate hydratase-deficient renal cell carcinoma: A tumor with diverse morphology including cannibalism, lymphocytic emperipolesis, and defective autophagy

We report the clinicopathological findings of the first series of 3 patients from Brazil with fumarate hydratase-deficient renal cell carcinoma. The clinicopathological findings disclosed a very aggressive tumor. All 3 patients had solitary tumor at the left side, metastasis and advanced stage at the time of diagnosis; were females with a median age of 40 years; had a history of uterine leiomyomas; and, at follow-up two patients are deceased and one patient alive. The microscopic findings of these 3 patients are in accordance with the literature disclosing a variety of morphologic features being papillary arrangement, eosinophilic cytoplasm, and prominent nucleoli surrounded by clear halo the constant and most frequent findings. Previously not reported in this tumor, we describe presence of cannibalism, lymphocytic emperipolesis, and cytoplasmic vacuoles with eosinophilic inclusions associated with overexpression of p62 in immunohistochemistry which is considered to be evidence of defective autophagy. Lymphocytic emperipolesis was a more frequent finding than cannibalism and immunohistochemistry for p62 was overexpressed only in the 2 patients disclosing cytoplasmic vacuoles with eosinophilic inclusions. The presence, frequency and significance of these novel findings should be checked in large series of this rare and aggressive tumor aiming to associate with clinical behavior and eventually influence the strategy of treatment.

Hypoxia Reduction Sensitizes Refractory Cancers to Immunotherapy

In order to fuel their relentless expansion, cancers must expand their vasculature to augment delivery of oxygen and essential nutrients. The disordered web of irregular vessels that results, however, leaves gaps in oxygen delivery that foster tumor hypoxia. At the same time, tumor cells increase their oxidative metabolism to cope with the energetic demands of proliferation, which further worsens hypoxia due to heightened oxygen consumption. In these hypoxic, nutrient-deprived environments, tumors and suppressive stroma evolve to flourish while antitumor immunity collapses due to a combination of energetic deprivation, toxic metabolites, acidification, and other suppressive signals. Reversal of cancer hypoxia thus has the potential to increase the survival and effector function of tumor-infiltrating T cells, as well as to resensitize tumors to immunotherapy. Early clinical trials combining hypoxia reduction with immune checkpoint blockade have shown promising results in treating patients with advanced, metastatic, and therapeutically refractory cancers. Expected final online publication date for the Annual Review of Medicine, Volume 73 is January 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Classification of Cell-in-Cell Structures: Different Phenomena with Similar Appearance

A phenomenon known for over 100 years named “cell-in-cell” (CIC) is now undergoing its renaissance, mostly due to modern cell visualization techniques. It is no longer an esoteric process studied by a few cell biologists, as there is increasing evidence that CICs may have prognostic and diagnostic value for cancer patients. There are many unresolved questions stemming from the difficulties in studying CICs and the limitations of current molecular techniques. CIC formation involves a dynamic interaction between an outer or engulfing cell and an inner or engulfed cell, which can be of the same (homotypic) or different kind (heterotypic). Either one of those cells appears to be able to initiate this process, which involves signaling through cell–cell adhesion, followed by cytoskeleton activation, leading to the deformation of the cellular membrane and movements of both cells that subsequently result in CICs. This review focuses on the distinction of five known forms of CIC (cell cannibalism, phagoptosis, enclysis, entosis, and emperipolesis), their unique features, characteristics, and underlying molecular mechanisms.

Single-cell analysis of a tumor-derived exosome signature correlates with prognosis and immunotherapy response

Background

Tumor-derived exosomes (TEXs) are involved in tumor progression and the immune modulation process and mediate intercellular communication in the tumor microenvironment. Although exosomes are considered promising liquid biomarkers for disease diagnosis, it is difficult to discriminate TEXs and to develop TEX-based predictive biomarkers.

Methods

In this study, the gene expression profiles and clinical information were collected from The Cancer Genome Atlas (TCGA) database, IMvigor210 cohorts, and six independent Gene Expression Omnibus datasets. A TEXs-associated signature named TEXscore was established to predict overall survival in multiple cancer types and in patients undergoing immune checkpoint blockade therapies.

Results

Based on exosome-associated genes, we first constructed a tumor-derived exosome signature named TEXscore using a principal component analysis algorithm. In single-cell RNA-sequencing data analysis, ascending TEXscore was associated with disease progression and poor clinical outcomes. In the TCGA Pan-Cancer cohort, TEXscore was elevated in tumor samples rather than in normal tissues, thereby serving as a reliable biomarker to distinguish cancer from non-cancer sources. Moreover, high TEXscore was associated with shorter overall survival across 12 cancer types. TEXscore showed great potential in predicting immunotherapy response in melanoma, urothelial cancer, and renal cancer. The immunosuppressive microenvironment characterized by macrophages, cancer-associated fibroblasts, and myeloid-derived suppressor cells was associated with high TEXscore in the TCGA and immunotherapy cohorts. Besides, TEXscore-associated miRNAs and gene mutations were also identified. Further experimental research will facilitate the extending of TEXscore in tumor-associated exosomes.

Conclusions

TEXscore capturing tumor-derived exosome features might be a robust biomarker for prognosis and treatment responses in independent cohorts.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-021-03053-4.

Hybrid Formation and Fusion of Cancer Cells In Vitro and In Vivo

Simple Summary

Cell fusion as a fundamental biological process is required for various physiological processes, including fertilization, placentation, myogenesis, osteoclastogenesis, and wound healing/tissue regeneration. However, cell fusion is also observed during pathophysiological processes like tumor development. Mesenchymal stroma/stem-like cells (MSC) which play an important role within the tumor microenvironment like other cell types such as macrophages can closely interact and hybridize with cancer cells. The formation of cancer hybrid cells can involve various different mechanisms whereby the genomic parts of the hybrid cells require rearrangement to form a new functional hybrid cell. The fusion of cancer cells with neighboring cell types may represent an important mechanism during tumor development since cancer hybrid cells are detectable in various tumor tissues. During this rare event with resulting genomic instability the cancer hybrid cells undergo a post-hybrid selection process (PHSP) to reorganize chromosomes of the two parental nuclei whereby the majority of the hybrid population undergoes cell death. The remaining cancer hybrid cells survive by displaying altered properties within the tumor tissue.

Abstract

The generation of cancer hybrid cells by intra-tumoral cell fusion opens new avenues for tumor plasticity to develop cancer stem cells with altered properties, to escape from immune surveillance, to change metastatic behavior, and to broaden drug responsiveness/resistance. Genomic instability and chromosomal rearrangements in bi- or multinucleated aneuploid cancer hybrid cells contribute to these new functions. However, the significance of cell fusion in tumorigenesis is controversial with respect to the low frequency of cancer cell fusion events and a clonal advantage of surviving cancer hybrid cells following a post-hybrid selection process. This review highlights alternative processes of cancer hybrid cell development such as entosis, emperipolesis, cannibalism, therapy-induced polyploidization/endoreduplication, horizontal or lateral gene transfer, and focusses on the predominant mechanisms of cell fusion. Based upon new properties of cancer hybrid cells the arising clinical consequences of the subsequent tumor heterogeneity after cancer cell fusion represent a major therapeutic challenge.

3D-printing magnesium-polycaprolactone loaded with melatonin inhibits the development of osteosarcoma by regulating cell-in-cell structures

Melatonin has been proposed as a potent anticarcinogen presents a short half-life for osteosarcoma (OS). Cell-in-cell (CIC) structures play a role in the development of malignant tumors by changing the tumor cell energy metabolism. This study developed a melatonin-loaded 3D printed magnesium-polycaprolactone (Mg-PCL) scaffold and investigated its effect and molecular mechanism on CIC in OS. Mg-PCL scaffold was prepared by 3D-printing and its characteristic was determined. The effect and molecular mechanism of Mg-PCL scaffold as well as melatonin-loaded Mg-PCL on OS growth and progression were investigated in vivo and in vitro. We found that melatonin receptor 1 (MT1) and CIC expressions were increased in OS tissues and cells. Melatonin treatment inhibit the key CIC pathway, Rho/ROCK, through the cAMP/PKA signaling pathway, interfering with the mitochondrial physiology of OS cells, and thus playing an anti-invasion and anti-metastasis role in OS. The Mg-PCL-MT could significantly inhibit distant organ metastasis of OS in the in vivo model. Our results showed that melatonin-loaded Mg-PCL scaffolds inhibited the proliferation, invasion and metastasis of OS cells through the CIC pathway. The Mg-PCL-MT could be a potential therapeutics for OS.

Spindle cell squamous cell carcinoma exhibiting prominent neutrophil phagocytosis: a case report

Background

Spindle cell squamous cell carcinoma is an uncommon variant of squamous cell carcinoma; its diagnosis is sometimes challenging because it histopathologically resembles neoplastic or reactive spindle cell lesions of mesenchymal origins. Here, we report a rare case of spindle cell squamous cell carcinoma exhibiting prominent neutrophil phagocytosis.

Case presentation

A 69-year-old Japanese man presented with pain and a polypoid mass on the lower left gingiva. He had received chemoradiotherapy for squamous cell carcinoma of the buccal mucosa 15 years prior to this consultation. In addition, he was treated for mandibular osteonecrosis 6 years after chemoradiotherapy without evidence of cancer recurrence. A biopsy revealed atypical spindle or pleomorphic cells scattered in the edematous and fibrin-rich stroma; however, no malignant squamous components were apparent. These atypical cells frequently contained neutrophils within their cytoplasm that formed cell-in-cell figures. Immunohistochemically, the atypical cells were negative for cytokeratins, epithelial membrane antigen, and E-cadherin, but positive for p63, vimentin, and p53. Although these findings suggested spindle cell squamous cell carcinoma, it was difficult to reach a definitive diagnosis. Based on a clinical diagnosis of a malignant tumor, the patient underwent a hemimandibulectomy. The surgically resected specimen had a typical spindle cell squamous cell carcinoma histology consisting of biphasic spindle cells and conventional squamous cell carcinoma components. Moreover, the surgical specimen also exhibited spindle tumor cells that frequently included neutrophils, around which intense staining for lysosomal-associated membrane protein 1 and cathepsin B was observed. This suggested that the cell-in-cell figures represent active neutrophil phagocytosis by tumor cells, and not emperipolesis.

Conclusion

The presence of neutrophil phagocytosis may be a potent indicator of malignancy.

The Fatty Acid and Protein Profiles of Circulating CD81-Positive Small Extracellular Vesicles Are Associated with Disease Stage in Melanoma Patients

Simple Summary

Early detection of cutaneous melanoma is the key to increasing survival and proper therapeutic adjustment, especially in stages II–IV. We investigated whether the fatty acid (FA) and protein compositions of small extracellular vesicles (sEV) expressing CD81, derived from the plasma of stage 0–I, II and III–IV melanoma patients, could reflect disease stage. Results showed a higher content of FA and differences in C18:0/C18:1 ratio, a marker of cell membrane fluidity, that distinguished patients’ CD81sEV from those of healthy donors (HD). By proteomic analysis (identifier PXD024434) we identified significant increases in CD14, PON1, PON3 and APOA5 in stage II CD81sEV compared to HD. In stage III–IV, CD81sEV’ RAP1B expression was decreased. These stage-related signatures may support the potential of sEV to provide information for early diagnosis, prediction of metastatic behavior, treatment and follow-up of melanoma patients.

Abstract

The early detection of cutaneous melanoma, a potentially lethal cancer with rising incidence, is fundamental to increasing survival and therapeutic adjustment. In stages II–IV especially, additional indications for adjuvant therapy purposes after resection and for treatment of metastatic patients are urgently needed. We investigated whether the fatty acid (FA) and protein compositions of small extracellular vesicles (sEV) derived from the plasma of stage 0–I, II and III–IV melanoma patients (n = 38) could reflect disease stage. The subpopulation of sEV expressing CD81 EV marker (CD81sEV) was captured by an ad hoc immune affinity technique from plasma depleted of large EV. Biological macromolecules were investigated by gas chromatography and mass spectrometry in CD81sEV. A higher content of FA was detectable in patients with respect to healthy donors (HD). Moreover, a higher C18:0/C18:1 ratio, as a marker of cell membrane fluidity, distinguished early (stage 0–I) from late (III–IV) stages’ CD81sEV. Proteomics detected increases in CD14, PON1, PON3 and APOA5 exclusively in stage II CD81sEV, and RAP1B was decreased in stage III–IV CD81sEV, in comparison to HD. Our results suggest that stage dependent alterations in CD81sEV’ FA and protein composition may occur early after disease onset, strengthening the potential of circulating sEV as a source of discriminatory information for early diagnosis, prediction of metastatic behavior and following up of melanoma patients.

LncRNA nuclear-enriched abundant transcript 1 shuttled by prostate cancer cells-secreted exosomes initiates osteoblastic phenotypes in the bone metastatic microenvironment via miR-205-5p/runt-related transcription factor 2/splicing factor proline- and glutamine-rich/polypyrimidine tract-binding protein 2 axis

Prostate cancer (PCa) patients commonly present with osteoblastic-type bone metastasis. Exosomes derived from tumor cells possess biological significance and can mediate intercellular communication in the tumor microenvironment. Long noncoding RNA (lncRNA) nuclear-enriched abundant transcript 1 (NEAT1) is also implicated in the stability in tumorigenesis and the development of PCa, but the underlying mechanism remains elusive. Hence, the current study set out to investigate the physiological mechanisms by which exosomes-encapsulated NEAT1 affects the progression of PCa. First, after isolation, we found PCa cell-derived exosomes induced the osteogenic differentiation of human bone marrow-derived mesenchymal stem cells (hBMSCs). Besides, NEAT1 in PCa cells could be transferred into hBMSCs via exosomes. Further gain- and loss-of-function experimentation revealed that NEAT1 acted as a competing endogenous RNA (ceRNA) of microRNA (miR)-205-5p to upregulate the runt-related transcription factor 2 (RUNX2) levels. Moreover, NEAT1 could promote the RUNX2 expression via the splicing factor proline- and glutamine-rich (SFPQ)/polypyrimidine tract-binding protein 2 (PTBP2) axis. Functional assays uncovered that NEAT1 shuttled by PCa-exosomes facilitated the activity of alkaline phosphatase (ALP) and mineralization of extracellular matrix, and continuously upregulated the levels of RUNX2, ALP, alpha-1 type 1 collagen, and osteocalcin by regulating RUNX2, to induce the osteogenic differentiation of hBMSCs. Furthermore, in vivo experimentation confirmed that upregulated NEAT1 induced osteogenesis. Collectively, our findings indicated that PCa-derived exosomes-loaded NEAT1 upregulated RUNX2 to facilitate the osteogenesis of hBMSCs by competitively binding to miR-205-5p via the SFPQ/PTBP2 axis, therefore providing a potential therapeutic target to treat osteogenesis of hBMSCs in PCa. PCa cells secrete exosomes containing NEAT1, and NEAT1 exerts effects on osteogenic differentiation of hBMSCs in PCa. NEAT1 shuttled by PCa-derived exosomes could be transferred into hBMSCs, where NEAT1 exerted inductive properties in osteogenic differentiation of hBMSCs through the upregulation of RUNX2 by competitively binding to miR-205-5p and regulating SFPQ/PTBP2 in vitro and in vivo.

Cell-in-cell phenomenon: leukocyte engulfment by non-tumorigenic cells and cancer cell lines

BACKGROUND

Research on cell-in-cell (CIC) phenomena, including entosis, emperipolesis and cannibalism, and their biological implications has increased in recent years. Homotypic and heterotypic engulfment of various target cells by numerous types of host cells has been studied in vitro and in tissue sections. This work has identified proteins involved in the mechanism and uncovered evidence for CIC as a potential histopathologic predictive and prognostic marker in cancer. Our experimental study focused on non-professional phagocytosis of leukocytes.

RESULTS

We studied the engulfment of peripheral blood mononuclear cells isolated from healthy donors by counting CIC structures. Two non-tumorigenic cell lines (BEAS-2B, SBLF-9) and two tumour cell lines (BxPC3, ICNI) served as host cells. Immune cells were live-stained and either directly co-incubated or treated with irradiation or with conventional or microwave hyperthermia. Prior to co-incubation, we determined leukocyte viability for each batch via Annexin V-FITC/propidium iodide staining. All host cells engulfed their targets, with uptake rates ranging from 1.0% ± 0.5% in BxPC3 to 8.1% ± 5.0% in BEAS-2B. Engulfment rates of the cancer cell lines BxPC3 and ICNI (1.6% ± 0.2%) were similar to those of the primary fibroblasts SBLF-9 (1.4% ± 0.2%). We found a significant negative correlation between leukocyte viability and cell-in-cell formation rates. The engulfment rate rose when we increased the dose of radiotherapy and prolonged the impact time. Further, microwave hyperthermia induced higher leukocyte uptake than conventional hyperthermia. Using fluorescent immunocytochemistry to descriptively study the proteins involved, we detected ring-like formations of diverse proteins around the leukocytes, consisting, among others, of α-tubulin, integrin, myosin, F-actin, and vinculin. These results suggest the involvement of actomyosin contraction, cell-cell adhesion, and the α-tubulin cytoskeleton in the engulfment process.

CONCLUSIONS

Both non-tumorigenic and cancer cells can form heterotypic CIC structures by engulfing leukocytes. Decreased viability and changes caused by microwave and X-ray irradiation trigger non-professional phagocytosis.

Associative Conditioning Is a Robust Systemic Behavior in Unicellular Organisms: An Interspecies Comparison

The capacity to learn new efficient systemic behavior is a fundamental issue of contemporary biology. We have recently observed, in a preliminary analysis, the emergence of conditioned behavior in some individual amoebae cells. In these experiments, cells were able to acquire new migratory patterns and remember them for long periods of their cellular cycle, forgetting them later on. Here, following a similar conceptual framework of Pavlov's experiments, we have exhaustively studied the migration trajectories of more than 2000 individual cells belonging to three different species: Amoeba proteus, Metamoeba leningradensis, and Amoeba borokensis. Fundamentally, we have analyzed several relevant properties of conditioned cells, such as the intensity of the responses, the directionality persistence, the total distance traveled, the directionality ratio, the average speed, and the persistence times. We have observed that cells belonging to these three species can modify the systemic response to a specific stimulus by associative conditioning. Our main analysis shows that such new behavior is very robust and presents a similar structure of migration patterns in the three species, which was characterized by the presence of conditioning for long periods, remarkable straightness in their trajectories and strong directional persistence. Our experimental and quantitative results, compared with other studies on complex cellular responses in bacteria, protozoa, fungus-like organisms and metazoans that we discus here, allow us to conclude that cellular associative conditioning might be a widespread characteristic of unicellular organisms. This new systemic behavior could be essential to understand some key principles involved in increasing the cellular adaptive fitness to microenvironments.

Metabolic features of cancer cells impact immunosurveillance

Background

Tumors rewire their metabolism to achieve robust anabolism and resistance against therapeutic interventions like cisplatin treatment. For example, a prolonged exposure to cisplatin causes downregulation of pyridoxal kinase (PDXK), the enzyme that generates the active vitamin B6, and upregulation of poly ADP-ribose (PAR) polymerase-1 (PARP1) activity that requires a supply of nicotinamide (vitamin B3) adenine dinucleotide. We investigated the impact of the levels of PDXK and PAR on the local immunosurveillance (ie, density of the antigen presenting cells and adaptive immune response by CD8 T lymphocytes) in two different tumor types.

Methods

Tumors from patients with locally advanced cervical carcinoma (LACC) and non-small cell lung cancer (NSCLC) were stained for PAR, PDXK, dendritic cell lysosomal associated membrane glycoprotein (DC-LAMP) and CD8 T cell infiltration. Their correlations and prognostic impact were assessed. Cisplatin-resistant NSCLC cell clones isolated from Lewis-lung cancer (LLC) cells were evaluated for PAR levels by immunoblot. Parental (PAR^low) and cisplatin-resistant (PAR^high) clones were subcutaneously injected into the flank of C57BL/6 mice. Tumors were harvested to evaluate their immune infiltration by flow cytometry.

Results

The infiltration of tumors by CD8 T and DC-LAMP⁺ cells was associated with a favorable overall survival in patients with LACC (p=0.006 and p=0.008, respectively) and NSCLC (p<0.001 for both CD8 T and DC-LAMP cells). We observed a positive correlation between PDXK expression and the infiltration by DC-LAMP (R=0.44, p=0.02 in LACC, R=0.14, p=0.057 in NSCLC), and a negative correlation between PAR levels and CD8 T lymphocytes (R=−0.39, p=0.034 in LACC, R=−0.18, p=0.017 in NSCLC). PARP1 is constitutively hyperactivated in cisplatin-resistant LLC cells manifesting elevated intracellular levels of poly(ADP-ribosyl)ated proteins (PAR^high). Tumors formed by such cancer cells injected into immunocompetent mice were scarcely infiltrated by CD8 T (p=0.028) and antigen presenting cells (p=0.086).

Conclusions

Oncometabolic features can impact local immunosurveillance, providing new functional links between cisplatin resistance and therapeutic failure.

Advances in the study of cancer metastasis and calcium signaling as potential therapeutic targets

Metastasis is still the primary cause of cancer-related mortality. However, the underlying mechanisms of cancer metastasis are not yet fully understood. Currently, the epithelial-mesenchymal transition, metabolic remodeling, cancer cell intercommunication and the tumor microenvironment including diverse stromal cells, are reported to affect the metastatic process of cancer cells. Calcium ions (Ca²⁺) are ubiquitous second messengers that manipulate cancer metastasis by affecting signaling pathways. Diverse transporter/pump/channel-mediated Ca²⁺ currents form Ca²⁺ oscillations that can be decoded by Ca²⁺-binding proteins, which are promising prognostic biomarkers and therapeutic targets of cancer metastasis. This paper presents a review of the advances in research on the mechanisms underlying cancer metastasis and the roles of Ca²⁺-related signals in these events.

Cellular cannibalism and consequent thrombocytopenia in a patient with bone marrow metastasis of malignant pleural mesothelioma: A case report

Cellular cannibalism is a tumor activity where a cell is engulfed by another cell. This process promotes tumor cell survival under unfavorable conditions. The current report describes an extremely rare case of thrombocytopenia resulting from cellular cannibalism in a patient with bone marrow metastasis due to malignant pleural mesothelioma (MPM). A 77-year-old male presented with hemothorax and thrombocytopenia. He was diagnosed with MPM of the sarcomatoid cell type. However, his disease progressed rapidly and he died 11 days after admission. Bone marrow aspiration revealed metastatic MPM cells that had engulfed other blood cells. Accordingly, the observed thrombocytopenia was attributed to cellular cannibalism by metastatic MPM tumor cells. To the best of our knowledge, this is the first reported case of thrombocytopenia due to cellular cannibalism in a patient with this type of malignancy (MPM). The results suggested that although MPM rarely metastasizes to the bone marrow, bone marrow aspiration could be useful in such cases.

Subtype-Based Analysis of Cell-in-Cell Structures in Esophageal Squamous Cell Carcinoma

Cell-in-cell (CIC) structures are defined as the special structures with one or more cells enclosed inside another one. Increasing data indicated that CIC structures were functional surrogates of complicated cell behaviors and prognosis predictor in heterogeneous cancers. However, the CIC structure profiling and its prognostic value have not been reported in human esophageal squamous cell Carcinoma (ESCC). We conducted the analysis of subtyped CIC-based profiling in ESCC using "epithelium-macrophage-leukocyte" (EML) multiplex staining and examined the prognostic value of CIC structure profiling through Kaplan-Meier plotting and Cox regression model. Totally, five CIC structure subtypes were identified in ESCC tissue and the majority of them was homotypic CIC (hoCIC) with tumor cells inside tumor cells (TiT). By univariate and multivariate analyses, TiT was shown to be an independent prognostic factor for resectable ESCC, and patients with higher density of TiT tended to have longer post-operational survival time. Furthermore, in subpopulation analysis stratified by TNM stage, high TiT density was associated with longer overall survival (OS) in patients of TNM stages III and IV as compared with patients with low TiT density (mean OS: 51 vs 15 months, P = 0.04) and T3 stage (mean OS: 57 vs 17 months, P=0.024). Together, we reported the first CIC structure profiling in ESCC and explored the prognostic value of subtyped CIC structures, which supported the notion that functional pathology with CIC structure profiling is an emerging prognostic factor for human cancers, such as ESCC.

New hypotheses for cancer generation and progression

Since Nixon famously declared war on cancer in 1971, trillions of dollars have been spent on cancer research but the life expectancy for most forms of cancer is still poor. There are many reasons for the partial success of cancer translational research. One of these can be the predominance of certain paradigms that potentially narrowed the vision in interpreting cancer. The main paradigm to explain carcinogenesis is based on DNA mutations, which is well interpreted by the somatic mutation theory (SMT). However, a different theory claims that cancer is instead a tissue disease as proposed by the Tissue Organization Field Theory (TOFT). Here, we propose new hypotheses to explain the origin and pathogenesis of cancer. In this perspective, the systemic-evolutionary theory of cancer (SETOC) is discussed as well as how the microenvironment affects the adaptation of transformed cells and the reversion to a unicellular-like or embryo-like phenotype.

Polyploidy formation in cancer cells: How a Trojan horse is born

Ploidy increase has been shown to occur in different type of tumors and participate in tumor initiation and resistance to the treatment. Polyploid giant cancer cells (PGCCs) are cells with multiple nuclei or a single giant nucleus containing multiple complete sets of chromosomes. The mechanism leading to formation of PGCCs may depend on: endoreplication, mitotic slippage, cytokinesis failure, cell fusion or cell cannibalism. Polyploidy formation might be triggered in response to various genotoxic stresses including: chemotherapeutics, radiation, hypoxia, oxidative stress or environmental factors like: air pollution, UV light or hyperthermia. A fundamental feature of polyploid cancer cells is the generation of progeny during the reversal of the polyploid state (depolyploidization) that may show high aggressiveness resulting in the formation of resistant disease and tumor recurrence. Therefore, we propose that modern anti-cancer therapies should be designed taking under consideration polyploidization/ depolyploidization processes, which confer the polyploidization a hidden potential similar to a Trojan horse delayed aggressiveness. Various mechanisms and stress factors leading to polyploidy formation in cancer cells are discussed in this review.

Intratumoral Hypoxia and Mechanisms of Immune Evasion Mediated by Hypoxia-Inducible Factors

Activation of the innate and adaptive immune systems represents a promising strategy for defeating cancer. However, during tumor progression, cancer cells battle to shift the balance from immune activation to immunosuppression. Critical sites of this battle are regions of intratumoral hypoxia, and a major driving force for immunosuppression is the activity of hypoxia-inducible factors, which regulate the transcription of large batteries of genes in both cancer and stromal cells that block the infiltration and activity of cytotoxic T lymphocytes and natural killer cells, while stimulating the infiltration and activity of regulatory T cells, myeloid-derived suppressor cells, and tumor-associated macrophages. Targeting hypoxia-inducible factors or their target gene products may restore anticancer immunity and improve the response to immunotherapies.

Increase in non-professional phagocytosis during the progression of cell cycle

Homotypic or heterotypic internalization of another, either living or necrotic cell is currently in the center of research interest. The active invasion of a living cell called entosis and cannibalism of cells by rapidly proliferating cancers are prominent examples. Additionally, normal healthy tissue cells are capable of non-professional phagocytosis. This project studied the relationship between non-professional phagocytosis, individual proliferation and cell cycle progression. Three mesenchymal and two epithelial normal tissue cell lines were studied for homotypic non-professional phagocytosis. Homotypic dead cells were co-incubated with adherent growing living cell layers. Living cells were synchronized by mitotic shake-off as well as Aphidicolin-treatment and phagocytotic activity was analyzed by immunostaining. Cell cycle phases were evaluated by flow cytometry. Mesenchymal and epithelial normal tissue cells were capable of internalizing dead cells. Epithelial cells had much higher non-professional phagocytotic rates than mesenchymal cells. Cells throughout the entire cell cycle were able to phagocytose. The phagocytotic rate significantly increased with progressing cell cycle phases. Mitotic cells regularly phagocytosed dead cells, this was verified by Nocodazole and Colcemid treatment. Taken together, our findings indicate the ability of human tissue cells to phagocytose necrotic neighboring cells in confluent cell layers. The origin of the cell line influences the rate of cell-in-cell structure formation. The higher cell-in-cell structure rates during cell cycle progression might be influenced by cytoskeletal reorganization during this period or indicate an evolutionary anchorage of the process. Recycling of nutrients during cell growth might also be an explanation.

Role of tumor cell senescence in non-professional phagocytosis and cell-in-cell structure formation

Background

Non-professional phagocytosis is usually triggered by stimuli such as necrotic cell death. In tumor therapy, the tumors often disappear slowly and only long time after the end of therapy. Here, tumor therapy inactivates the cells by inducing senescence. Therefore, study focused whether senescence is a stimulus for non-professional phagocytosis or whether senescent cells themselves phagocytize non-professionally.

Results

Senescence was induced in cell lines by camptothecin and a phagocytosis assay was performed. In tissue of a cohort of 192 rectal cancer patients senescence and non-professional phagocytosis was studied by anti-histone H3K9me3 and anti-E-cadherin staining. Senescent fibroblasts and pancreas carcinoma cells phagocytize necrotic cells but are not phagocytized. In the tissue of rectal carcinoma, senescent cells can phagocytize and can be phagocytized. A high number of senescent cells and, at the same time, high numbers of non-professional phagocytizing cells in the rectal carcinoma tissue lead to an extremely unfavorable prognosis regarding overall survival.

Conclusion

Senescent cells can be non-professionally phagocytized and at the same time they can non-professionally phagocytize in vivo. In vitro experiments indicate that it is unlikely that senescence is a strong trigger for non-professional phagocytosis. Combined high rates of non-professional phagocytosis and high rates of senescence are an extremely poor prognostic factor for overall survival.

Role of Heterotypic Neutrophil-in-Tumor Structure in the Prognosis of Patients With Buccal Mucosa Squamous Cell Carcinoma

Objective

To analyze the role of frequency of heterotypic neutrophil-in-tumor structure (FNiT) in the prognosis of patients with buccal mucosa squamous cell carcinoma (BMSCC).

Methods

In vitro, we cocultured BMSCC cell line-H157 with neutrophils to form heterotypic neutrophil-in-tumor structures, which were then subject to fluorescence staining. Clinically, 145 patients were retrospectively enrolled. Associations between FNiT and clinicopathological variables including age, sex, smoking history, drinking history, betel nut chewing, tumor stage, node stage, metastasis, disease stage, lymphovascular invasion, extranodal extension, perineural invasion, and tumor grade were analyzed by chi-square test, and the main endpoints of interest were recurrence-free survival (RFS) and disease-specific survival (DSS) which were analyzed by the Kaplan-Meier method and Cox model.

Results

Fluorescent staining results of typical heterotypic neutrophil-in-tumor structure showed that well-differentiated H157 cells had a stronger ability to internalize more neutrophils than poorly-differentiated H157 cells, with the latter often internalizing only one neutrophil or nothing. The mean FNiT was 4.2‰, with a range from 2.3‰ to 7.8‰. A total of 80 patients relapsed and 84 patients died of the disease. The 5-year RFS and DSS rate was 42% and 42%, respectively. Patients with an FNiT≥4.2‰ had a significantly higher risk for locoregional recurrence and cancer-caused death than those with an FNiT<4.2‰ (p=0.001 and p<0.001, respectively). The FNiT alone was independently significant in predicting poor RFS, and the FNiT along with tumor grade was an independent predictor for DSS.

Conclusion

The FNiT as a novel predictor is significantly negatively associated with both the RFS and DSS of patients with BMSCC.

Cell-in-cell phenomenon associates with aggressive characteristics and cancer-related mortality in early oral tongue cancer

Background

Cell-in-cell structures (caused by cell cannibalistic activity) have been related to prognosis of many cancers. This is the first multi-institutional study to assess the prognostic impact of cell-in-cell structures in a large cohort of early oral tongue squamous cell carcinomas (OTSCC).

Methods

A total of 308 cases from five Finnish University Hospitals and from the A.C. Camargo Cancer Center, São Paulo, Brazil, were included in this study. Cell-in-cell structures were evaluated on surgical postoperative sections that stained with hematoxylin and eosin staining.

Results

We found that cell-in-cell structures associated with cancer-related mortality in univariable analysis with a hazard ratio (HR) of 2.99 (95%CI 1.52–5.88; P = 0.001). This association was confirmed in multivariable analysis (HR 2.22, 95%CI 1.12–4.44; P = 0.024). In addition, statistically significant associations were observed between the cell-in-cell structures and other adverse histopathologic characteristics including deep invasion (P <  0.001), high index of tumor budding (P = 0.007), worst pattern of invasion (P <  0.001), perineural invasion (P = 0.01), and stroma-rich pattern (P = 0.001).

Conclusions

Our findings demonstrate a significant relationship between cell-in-cell formation and aggressive characteristics of early OTSCC. Cell-in-cell structures have a distinct impact as a novel prognostic indicator in early OTSCC and they can be easily assessed during routine pathology practice.