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Ingested apoptotic cells are localized to the phagolysosome. (A-D) Transmission electron microscopy after the co-culture of Ca9-22 cells with apoptotic Ca9-22 cells for 16 h. Scale bars, 5 μm (A and C) and 1 μm (B and D). AC, apoptotic cells; L, lysosomes, P, phagosome; F, filopodia. Arrowhead in panel C indicates bundles of actin filaments. Arrow in panel D indicates lysosomes fused with the phagosome.
Source publication
Apoptotic cell death frequently occurs in human cancer tissues including oral squamous cell carcinoma (SCC), wherein apoptotic tumor cells are phagocytosed not only by macrophages but also by neighboring tumor cells. We previously reported that the engulfment of apoptotic SCC cells by neighboring SCC cells frequently occurs at the invading front. T...
Contexts in source publication
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... (Fig. 2G, arrow), indicating that they were incorporated into phagolysosomes, in which acidification occurs to degrade the contents. Electron microscopy also revealed that apoptotic cells were incorporated into the phagosomes of the phagocytosing cells, which showed extended filopodia and an increased number of lysosomes within their cytoplasm ( Fig. 3A and B). Meanwhile, the incorporated apoptotic cells had already begun to exhibit a state of secondary necrosis because their cell membranes had collapsed. Actin filaments were assembled in bundles around the phagosomes containing apoptotic cells (Fig. 3C, arrowhead) and lysosomes appeared to be fused with the phagosomes (Fig. 3D, ...
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... which showed extended filopodia and an increased number of lysosomes within their cytoplasm ( Fig. 3A and B). Meanwhile, the incorporated apoptotic cells had already begun to exhibit a state of secondary necrosis because their cell membranes had collapsed. Actin filaments were assembled in bundles around the phagosomes containing apoptotic cells (Fig. 3C, arrowhead) and lysosomes appeared to be fused with the phagosomes (Fig. 3D, ...
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... their cytoplasm ( Fig. 3A and B). Meanwhile, the incorporated apoptotic cells had already begun to exhibit a state of secondary necrosis because their cell membranes had collapsed. Actin filaments were assembled in bundles around the phagosomes containing apoptotic cells (Fig. 3C, arrowhead) and lysosomes appeared to be fused with the phagosomes (Fig. 3D, ...
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... addition, we performed an in vitro phagocytosis assay using cells transiently transfected with pcDNA3-EGFP-Rac1-T17N. The expression of the EGFP-tagged dominant-negative Rac1 mutant (Rac1T17N) was confirmed by fluorescence microscopy and western blotting ( Supplementary Fig. 3A and B). The EGFP-Rac1T17N was mainly detected along the cell membrane, which was similar to wild-type Rac1, although the transfection efficiency was less than 30%. ...
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... EGFP-Rac1T17N was mainly detected along the cell membrane, which was similar to wild-type Rac1, although the transfection efficiency was less than 30%. The cells expressing EGFP-Rac1T17N showed a decrease in apoptotic cell phagocytosis, compared to the control cells expressing GFP ( Supplementary Fig. 3C and Fig. 4E), although this was to a lesser extent than NSC23766. ...
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Mesenchymal stem cells (MSCs) are commonly isolated from bone marrow and adipose tissue. Depending on the tissue of origin, MSCs have different characteristics and physiological effects. In various cancer studies, MSCs have been found to have either tumor-promoting or tumor-inhibiting action. This study investigated the effect of adipose tissue-MSC...
Citations
... Cultivation on type I collagen led to RAC1 activation in Ca9-19 and KO cells but not in SCCKN or ZA cells. Although it has already been shown that integrin-mediated cell adhesion results in tyrosine phosphorylation of intracellular proteins and subsequent activation of mitogen-activated protein kinase, phosphatidylinositol-4,5-bisphosphate 3-kinase, and G protein of the low-molecular-weight RHO family, there are few reports of type I collagen-induced RAC1 activation in oral SCC cells (39,40). Furthermore, no activation of RAC1 was observed in SCCKN and ZA cells, and the reasons for this are unclear and require further investigation. ...
... Furthermore, milk fat globuleepidermal growth factor-factor VIII-induced activation of RAC1 involved in phagocytosis of apoptotic cells was shown to occur in an integrin αvβ5-dependent manner (45,46). A recent report showed that oral SCC cells phagocytose apoptotic oral SCC cells in a RAC1dependent manner and that phagocytosis promotes SCC cell migration (39). However, as far as we are aware, there have been no reports of integrin β8 being involved in type I collagen-induced activation of RAC1 in oral SCC cells, hence the results of this study are novel. ...
Background/aim:
The interaction of integrin αvβ8 with type I collagen was shown to promote oral squamous cell carcinoma (SCC) cell proliferation via the mitogen-activated protein kinase/extracellular signal-regulated kinase pathway. However, the role of integrin αvβ8 in SCC progression remains poorly understood. In this study, the role of integrin αvβ8 in oral SCC progression was therefore investigated.
Materials and methods:
Integrin αv and β8 protein expression in oral SCC cells was examined by western blotting. Oral SCC cell motility was investigated using modified Boyden chamber assays. Behavior of oral SCC cells was examined in three-dimensional culture using type I collagen gel. Ras homolog family member A (RHOA), Ras-related C3 botulinum toxin substrate 1 (RAC1), and cell division control protein 42 homolog (CDC42) activity of oral SCC cells was analyzed by pull-down assays.
Results:
SCC cells with high integrin αvβ8 expression levels had a high ability to migrate on type I collagen and exhibited enhanced invasion into type I collagen gel. In SCC cells with high integrin αvβ8 expression level, cultivation on type I collagen induced RAC1 activation. Treatment with RAC1 inhibitor reduced type I collagen-induced motility of SCC cells. Down-regulation of integrin β8 by specific antisense oligonucleotide reduced type I collagen-induced RAC1 activation and suppressed cell motility and invasion into type I collagen gel.
Conclusion:
The interaction of integrin αvβ8 with type I collagen facilitates SCC cell motility and invasion via RAC1 activation. Therefore, integrin αvβ8 and RAC1 may represent new targets for inhibiting metastasis and invasion in patients with oral SCC.
... In BC, the degradation and scavenging stage of PCD can be disrupted by various mechanisms such as the overexpression of anti-phagocytic signals or defects in the clearance of apoptotic cells. Understanding the dysregulation of PCD in BC is crucial for developing new therapeutic strategies that can selectively target cancer cells while sparing healthy cells [79,80]. ...
Breast cancer (BC) is a complex and heterogeneous disease, and oxidative stress is a hallmark of BC. Oxidative stress is characterized by an imbalance between the production of reactive oxygen species (ROS) and antioxidant defense mechanisms. ROS has been implicated in BC development and progression by inducing DNA damage, inflammation, and angiogenesis. Antioxidants have been shown to scavenge ROS and protect cells from oxidative damage, thereby regulating signaling pathways involved in cell growth, survival, and death. Plants contain antioxidants like ascorbic acid, tocopherols, carotenoids, and flavonoids, which have been found to regulate stress signaling and PCD in BC. Combining different antioxidants has shown promise in enhancing the effectiveness of BC treatment. Antioxidant nanoparticles, when loaded with antioxidants, can effectively target breast cancer cells and enhance their cellular uptake. Notably, these nanoparticles have shown promising results in inducing PCD and sensitizing breast cancer cells to chemotherapy, even in cases where resistance is observed. This review aims to explore how nanotechnology can modulate stress signaling and PCD in breast cancer. By summarizing current research, it underscores the potential of nanotechnology in enhancing antioxidant properties for the treatment of breast cancer.
... In cancerous tissues, apoptotic cells are commonly cleared by the professional phagocytes expressing TAM receptors, namely dendritic cells and macrophages. However, nonprofessional phagocytes, such as tumour cells, can also engulf and ingest both dying [43,44] and living cells [45]. TAM receptors seem to participate in the non-professional clearance of apoptotic cells in cancer. ...
The TAM proteins TYRO3, AXL, and MER are receptor tyrosine kinases implicated in the clearance of apoptotic debris and negative regulation of innate immune responses. AXL contributes to immunosuppression by terminating the Toll-like receptor signaling in dendritic cells, and suppressing natural killer cell activity. In recent years, AXL has been intensively studied in the context of cancer. Both molecules, the receptor, and its ligand GAS6, are commonly expressed in cancer cells, as well as stromal and infiltrating immune cells. In cancer cells, the activation of AXL signaling stimulates cell survival and increases migratory and invasive potential. In cells of the tumour microenvironment, AXL pathway potentiates immune evasion. AXL has been broadly implicated in the epithelial-mesenchymal plasticity of cancer cells, a key factor in drug resistance and metastasis. Several antibody-based and small molecule AXL inhibitors have been developed and used in preclinical studies. AXL inhibition in various mouse cancer models reduced metastatic spread and improved the survival of the animals. AXL inhibitors are currently being tested in several clinical trials as monotherapy or in combination with other drugs. Here, we give a brief overview of AXL structure and regulation and discuss the normal physiological functions of TAM receptors, focusing on AXL. We present a theory of how epithelial cancers exploit AXL signaling to resist cytotoxic insults, in order to disseminate and relapse.
... These tumors also upregulate the expression of several Rho GTPase network components such as Rac2, Rhoh, Rhoj, Vav1, Dock2 and Elmo1 [71]. Apart from these processes, RAC1 contributes to the engulfment of apoptotic SCC cancer cells by epithelial nonprofessional phagocytes [72]. Inhibition of RAC1 also improves the sensitivity of head and neck SCCs to ionizing radiation and cisplatin treatment [73,74]. ...
Skin cancers are the most common cancers worldwide. Among them, melanoma, basal cell carcinoma of the skin and cutaneous squamous cell carcinoma are the three major subtypes. These cancers are characterized by different genetic perturbations even though they are similarly caused by a lifelong exposure to the sun. The main oncogenic drivers of skin cancer initiation have been known for a while, yet it remains unclear what are the molecular events that mediate their oncogenic functions and that contribute to their progression. Moreover, patients with aggressive skin cancers have been known to develop resistance to currently available treatment, which is urging us to identify new therapeutic opportunities based on a better understanding of skin cancer biology. More recently, the contribution of cytoskeletal dynamics and Rho GTPase signaling networks to the progression of skin cancers has been highlighted by several studies. In this review, we underline the various perturbations in the activity and regulation of Rho GTPase network components that contribute to skin cancer development, and we explore the emerging therapeutic opportunities that are surfacing from these studies.
... Furthermore, recently, a relationship between the cell-in-cell phenomenon and malignancy has been shown; for example, cell-in-cell formation by entosis causes aneuploidy in human breast tumors [11]. We previously demonstrated that the phagocytosis of apoptotic oral SCC cells by neighboring SCC cells is mediated by activation of Rasrelated C3 botulinum toxin substrate 1 (Rac1) and promotes cell migration [12]. ...
... The phagocytosis of neutrophils by tumor cells is not a well-understood phenomenon; its biological significance and underlying mechanisms remain unclear. Malignant tumor cells have been shown to possess phagocytic activity against neighboring tumor cells [5,12] as well as other types of cells, including neutrophils [7][8][9]. To date, phagocytized neutrophils have been observed in gastric adenocarcinoma [7,20], salivary duct carcinoma of the parotid gland [21], and even in cytological specimens from diverse malignant tumors, including laryngeal SCC [22]. ...
... Spindle cell components are considered a result of EMT [13], which is induced by the Rac1 pathway [23]. Therefore, Rac1 activation may be an underlying mechanism of neutrophil phagocytosis, as well as of apoptotic cell phagocytosis by tumor cells [12]. In addition, the frequency of phagocytosis by tumor cells is higher in moderately differentiated oral SCC than well-differentiated ones [24], and unlike primary melanoma cells, metastatic melanoma cells have a phagocytic ability [8]. ...
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.
... However, several other studies report that MFG-E8 is a multifunctional molecule shown to be released by a variety of cell types such as macrophages, immature dendrocytes, myoepithelial, endothelial, retinal, intestinal epithelial cells (Ceriani et al., 1983;Raymond et al., 2009;Zhou et al., 2018;Chopra et al., 2020). It was also found to be expressed at high levels in many tumor types (Carmon et al., 2002;Neutzner et al., 2007;Ko et al., 2020;Yamazaki et al., 2020). Hitherto, the most critical described function of MFG-E8 is to regulate immune homeostasis through the phagocytosis of apoptotic cells by signaling through α v β 3−5 integrins linking phosphatidylserine at the surface of membrane vesicles (Oshima et al., 2002) of apoptotic cells (Hanayama et al., 2002;Lotfan et al., 2018;Peterman et al., 2019). ...
The mammary gland is a unique apocrine gland made up of a branching network of ducts that end in alveoli. It is an ideal system to study the molecular mechanisms associated with cell proliferation, differentiation, and oncogenesis. MFG-E8, also known as Lactadherin, is a vital glycoprotein related to the milk fat globule membrane and initially identified to get secreted in bovine milk. Our previous report suggests that a high level of MFG-E8 is indicative of high milk yield in dairy animals. Here, we showed that MFG-E8 controls the cell growth and morphology of epithelial cells through a network of regulatory transcription factors. To understand the comprehensive action, we downregulated its expression in MECs by MFG-E8 specific shRNA. We generated a knockdown proteome profile of differentially expressed proteins through a quantitative iTRAQ experiment on a high-resolution mass spectrometer (Q-TOF). The downregulation of MFG-E8 resulted in reduced phagocytosis and cell migration ability, whereas it also leads to more lifespan to knockdown vis-a-vis healthy cells, which is confirmed through BrdU, MTT, and Caspase 3/7. The bioinformatics analysis revealed that MFG-E8 knockdown perturbs a large number of intracellular signaling, eventually leading to cessation in cell growth. Based on the directed network analysis, we found that MFG-E8 is activated by CX3CL1, TP63, and CSF2 and leads to the activation of SOCS3 and CCL2 for the regulation of cell proliferation. We further proved that the depletion of MFG-E8 resulted in activated cytoskeletal remodeling by MFG-E8 knockdown, which results in the activation of three independent pathways ZP4/JAK-STAT5, DOCK1/STAT3, and PIP3/AKT/mTOR. Overall, this study suggests that MFG-E8 expression in mammary epithelial cells is an indication of intracellular deterioration in cell health. To date, to the best of our knowledge, this is the first study that explores the downstream targets of MFG-E8 involved in the regulation of mammary epithelial cell health.
... Previous studies have demonstrated that RAC1 is involved in the cell migration and survival in oral cancers [34][35][36]. Our observations have reported that resveratrol inhibited cell proliferation and induced apoptosis in CAL-27 cells by suppressing the expression of RAC1. ...
This study examined whether activation of zinc finger protein 750/Ras-related C3 botulinum toxin substrate 1 (ZNF750/RAC1) signaling pathway may be involved in the ability of resveratrol to inhibit malignant progression of CAL-27 oral squamous cell carcinoma cells. CAL-27 cells were treated with resveratrol and transfected with plasmids expressing a ZNF750 mimic or ZNF750 inhibitor. Cell proliferation and apoptosis were assessed. Western blotting was used to examine the effects of resveratrol on levels of angiogenin, vascular endothelial growth factor (VEGF), prolyl hydroxylase 2 (PHD2), G protein signal-regulated protein 5 (RGS5), integrin A5 (ITGA5), integrin B1 (ITGB1), CD44, RAC1, and ZNF750. Quantitative PCR was used to examine the effects on mRNA levels of platelet-derived growth factor (PDGFB), tumor vascular marker CD105, and cell adhesion molecules ITGA5, ITGB1, and CD44. Resveratrol downregulated angiogenin, VEGF, RGS5, CD105, and the cell adhesion molecules ITGA5, ITGB1, and CD44 expressions to inhibit the vascular normalization, metastasis, adhesion, and migration of CAL-27 cells. Conversely, it upregulated ZNF750, PHD2, and PDGFB to suppress the malignant progression of CAL-27 cells. We further observed that these changes were associated with reduced proliferation, reduced colony formation, and increased apoptosis in cancer cells. ZNF750 silencing partly reversed these effects of resveratrol on the proliferation and apoptosis of CAL-27 cells. Additionally, RAC1 agonist also weakened these impacts of resveratrol on the growth of CAL-27 cells. The ability of resveratrol to suppress the progression of oral squamous cell carcinoma may involve activation of the ZNF750/RAC1 signaling pathway and modification of the tumor vascular microenvironment.
... Yamazaki et al. demonstrate in oral squamous cell carcinoma that RAC1 mediates the phagocytosis of neighboring apoptotic cells via the actin cytoskeleton lamellipodia formation, promoting tumor progression and therapeutic resistance. The authors note that MFG-E8 accumulates near apoptotic cells and activates RAC1 through an integrin αvβ5-dependent mechanism [50]. In a similar light, Liu et al. implicate RAC1 as a mediator of endocytosis for IDH1-mutated glioma cells. ...
Acting as molecular switches, all three members of the Guanosine triphosphate (GTP)-ase-family, Ras-related C3 botulinum toxin substrate (RAC), Rho, and Cdc42 contribute to various processes of oncogenic transformations in several solid tumors. We have reviewed the distribution of patterns regarding the frequency of Ras-related C3 botulinum toxin substrate 1 (RAC1)-alteration(s) and their modes of actions in various cancers. The RAC1 hyperactivation/copy-number gain is one of the frequently observed features in various solid tumors. We argued that RAC1 plays a critical role in the progression of tumors and the development of resistance to various therapeutic modalities applied in the clinic. With this perspective, here we interrogated multiple functions of RAC1 in solid tumors pertaining to the progression of tumors and the development of resistance with a special emphasis on different tumor cell phenotypes, including the inhibition of apoptosis and increase in the proliferation, epithelial-to-mesenchymal transition (EMT), stemness, pro-angiogenic, and metastatic phenotypes. Our review focuses on the role of RAC1 in adult solid-tumors and summarizes the contextual mechanisms of RAC1 involvement in the development of resistance to cancer therapies.
Motivation:
Spatial transcriptomics (ST) can reveal the existence and extent of spatial variation of gene expression in complex tissues. Such analyses could help identify spatially localized processes underlying a tissue's function. Existing tools to detect spatially variable genes assume a constant noise variance across spatial locations. This assumption might miss important biological signals when the variance can change across locations.
Results:
In this paper, we propose NoVaTeST, a framework to identify genes with location-dependent noise variance in ST data. NoVaTeST models gene expression as a function of spatial location and allows the noise to vary spatially. NoVaTeST then statistically compares this model to one with constant noise and detects genes showing significant spatial noise variation. We refer to these genes as "noisy genes". In tumor samples, the noisy genes detected by NoVaTeST are largely independent of the spatially variable genes detected by existing tools that assume constant noise, and provide important biological insights into tumor microenvironments.
Availability and implementation:
An implementation of the NoVaTeST framework in Python along with instructions for running the pipeline is available at https://github.com/abidabrar-bracu/NoVaTeST.
Supplementary information:
Supplementary data are available at Bioinformatics online.
Cancer-associated fibroblasts (CAFs) have important roles in promoting cancer development and progression. We previously reported that high expression of sex-determining region Y (SRY)-box9 (SOX9) in oral squamous cell carcinoma (OSCC) cells was positively correlated with poor prognosis. This study developed three-dimensional (3D) in vitro models co-cultured with OSCC cells and CAFs to examine CAF-mediated cancer migration and invasion in vitro and in vivo. Moreover, we performed an immunohistochemical analysis of alpha-smooth muscle actin and SOX9 expression in surgical specimens from 65 OSCC patients. The results indicated that CAFs promote cancer migration and invasion in migration assays and 3D in vitro models. The invading OSCC cells exhibited significant SOX9 expression and changes in the expression of epithelial–mesenchymal transition (EMT) markers, suggesting that SOX9 promotes EMT. TGF-β1 signalling inhibition reduced SOX9 expression and cancer invasion in vitro and in vivo, indicating that TGF-β1-mediated invasion is dependent on SOX9. In surgical specimens, the presence of CAFs was correlated with SOX9 expression in the invasive cancer nests and had a significant impact on regional recurrence. These findings demonstrate that CAFs promote cancer migration and invasion via the TGF-β/SOX9 axis.
