Detecting cell-in-cell structures in human tumor samples by E-cadherin/CD68/CD45 triple staining

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 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.

Tumor malignancy by genetic transfer between cells forming cell-in-cell structures

Cell-in-cell structures (CICs) refer to a type of unique structure with one or more cells within another one, whose biological outcomes are poorly understood. The present study aims to investigate the effects of CICs formation on tumor progression. Using genetically marked hepatocellular cancer cell lines, we explored the possibility that tumor cells might acquire genetic information and malignant phenotypes from parental cells undergoing CICs formation. The present study showed that the derivatives, isolated from CICs formed between two subpopulations by flow cytometry sorting, were found to inherit aggressive features from the parental cells, manifested with increased abilities in both proliferation and invasiveness. Consistently, the CICs clones expressed a lower level of E-cadherin and a higher level of Vimentin, ZEB-1, Fibronectin, MMP9, MMP2 and Snail as compared with the parental cells, indicating epithelial-mesenchymal transition. Remarkably, the new derivatives exhibited significantly enhanced tumorigenicity in the xenograft mouse models. Moreover, whole exome sequencing analysis identified a group of potential genes which were involved in CIC-mediated genetic transfer. These results are consistent with a role of genetic transfer by CICs formation in genomic instability and malignancy of tumor cells, which suggest that the formation of CICs may promote genetic transfer and gain of malignancy during tumor progression.

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.

Metabolism-Based Molecular Subtyping Endows Effective Ketogenic Therapy in p53-Mutant Colon Cancer

Although targeting cancer metabolism is a promising therapeutic strategy, clinical success depends on accurate molecular and metabolic subtyping. Here, this study reports two metabolism-based molecular subtypes associated with the ketogenic treatment of colon cancer: glycolytic (glycolysis⁺ /ketolysis^- ) and ketolytic (glycolysis⁺ /ketolysis⁺ ), which are manifested by distinct profiles of metabolic enzymes and mitochondrial dysfunction, and by different responses to ketone-containing interventions in vitro and in vivo. Notably, the glycolytic subtype is able to be transformed into the ketolytic subtype in p53-mutated tumors upon glucose limitation, rendering resistance to ketogenic therapy associated with upregulation of ketolytic enzymes, such as OXCT1 by mutant p53. The allosteric activator of mutant p53 effectively blocks the rewired molecular expression and the reprogrammed metabolism, leading to the suppression of tumor growth. The findings highlight the utility of metabolic subtyping to guide ketogenic therapy in colon cancer and identify mutant p53 as a synthetic lethality target for ketogenic treatment.

Heterotypic neutrophil-in-tumor structure: A novel pathological feature first discovered in the tissues of OPSCC

Objective

To reveal a novel pathological feature: heterotypic neutrophil-in-tumor structure (hNiT) first discovered in patients with oropharyngeal squamous cell carcinoma (OPSCC), to analyze the prognostic role of hNiT in OPSCC patients and to explore the role of p16 in the formation of hNiT structures.

Methods

Clinically, 197 patients were enrolled. Clinicopathological information was extracted and analyzed. All pathologic sections made from primary tumors were re-evaluated by immunohistochemistry and immunostaining. In vitro, we cocultured OPSCC cell line SCC-15 with neutrophils to form hNiT structures, which were then subject to fluorescence staining. By RNAi and overexpression techniques, we investigated the role of CDKN2A in the formation of hNiTs. We validated the two techniques by qPCR and Western Blot.

Results

The hNiT as a novel pathological feature was first discovered in the tissues of OPSCC. The FNiT was significantly associated with tumor stage, disease stage, p16 and tumor grade. A total of 119 patients died of the disease, and the 5-year disease-specific survival (DSS) rate was 36%. The median survival time was 52.6 months. In patients with an FNiT<0.5%, the 5-year DSS rate was 40%; in patients with an FNiT>=0.5%, the 5-year DSS was 28%, and the difference was significant (p=0.001). Cox model analysis showed that FNiT along with disease stage, p16 and tumor grade was an independent prognostic factor for DSS. Immunostaining results of p16 expression showed hNiT formation was negatively correlated to p16 in OPSCC as well as in the hNiT formation assays in vitro indicated by fluorescent staining. Function assays of CDKN2A implied that reduce CDKN2A promoted the formation of hNiT while elevated CDKN2A impeded the hNiT formation.

Conclusion

The hNiT as a novel pathological feature is associated with the adverse prognosis of OPSCC patients with p16 inhibiting the formation of hNiT structures.

Heterotypic cell-in-cell structures between cancer and NK cells is associated with enhanced anti-cancer drug resistance

The heterotypic CIC structures formed of cancer and immune cells have been observed in tumor tissues. We aimed to assess the feasibility of using heterotypic CICs as a functional biomarker to predict NK susceptibility and drug resistance. The heterotypic CIC-forming cancer cells showed a lower response to NK cytotoxicity and higher proliferative ability than non-CIC cancer cells. After treatment with anticancer drugs, cancer cells that formed heterotypic CICs showed a higher resistance to anticancer drugs than non-CIC cancer cells. We also observed the formation of more CIC structures in cancer cells treated with anticancer drugs than in the non-treated group. Our results confirm the association between heterotypic CIC structures and anticancer drug resistance in CICs formed from NK and cancer cells. These results suggest a mechanism underlying immune evasion in heterotypic CIC cancer cells and provide insights into the anticancer drug resistance of cancer cells.

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Conformation of heterotypic CIC structures formed between cancer and NK cells

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Heterotypic CICs exhibit a higher proliferative ability than non-CIC cells

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Heterotypic CICs are associated with NK susceptibility

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Heterotypic CICs are involved in anticancer drug resistance

Long-range enhancement of N501Y-endowed mouse infectivity of SARS-CoV-2 by the non-RBD mutations of Ins215KLRS and H655Y

Background

Rodents, such as mice, are vulnerable targets, and potential intermediate hosts, of SARS-CoV-2 variants of concern, including Alpha, Beta, Gamma, and Omicron. N501Y in the receptor-binding domain (RBD) of Spike protein is the key mutation dictating the mouse infectivity, on which the neighboring mutations within RBD have profound impacts. However, the impacts of mutations outside RBD on N501Y-mediated mouse infectivity remain to be explored.

Results

Herein, we report that two non-RBD mutations derived from mouse-adapted strain, Ins215KLRS in the N-terminal domain (NTD) and H655Y in the subdomain linking S1 to S2, enhance mouse infectivity in the presence of N501Y mutation, either alone or together. This is associated with increased interaction of Spike with mouse ACE2 and mutations-induced local conformation changes in Spike protein. Mechanistically, the H655Y mutation disrupts interaction with N657, resulting in a less tight loop that wraps the furin-cleavage finger; and the insertion of 215KLRS in NTD increases its intramolecular interaction with a peptide chain that interfaced with the RBD-proximal region of the neighboring protomer, leading to a more flexible RBD that facilitates receptor binding. Moreover, the Omicron Spike that contains Ins214EPE and H655Y mutations confer mouse infectivity > 50 times over the N501Y mutant, which could be effectively suppressed by mutating them back to wild type.

Conclusions

Collectively, our study sheds light on the cooperation between distant Spike mutations in promoting virus infectivity, which may undermine the high infectiousness of Omicron variants towards mice.

Supplementary information

The online version contains supplementary material available at 10.1186/s13062-022-00325-x.

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.

Senescence as a dictator of patient outcomes and therapeutic efficacies in human gastric cancer

Senescence is believed to be a pivotal player in the onset and progression of tumors as well as cancer therapy. However, the guiding roles of senescence in clinical outcomes and therapy selection for patients with cancer remain obscure, largely due to the absence of a feasible senescence signature. Here, by integrative analysis of single cell and bulk transcriptome data from multiple datasets of gastric cancer patients, we uncovered senescence as a veiled tumor feature characterized by senescence gene signature enriched, unexpectedly, in the noncancerous cells, and further identified two distinct senescence-associated subtypes based on the unsupervised clustering. Patients with the senescence subtype had higher tumor mutation loads and better prognosis as compared with the aggressive subtype. By the machine learning, we constructed a scoring system termed as senescore based on six signature genes: ADH1B, IL1A, SERPINE1, SPARC, EZH2, and TNFAIP2. Higher senescore demonstrated robustly predictive capability for longer overall and recurrence-free survival in 2290 gastric cancer samples, which was independently validated by the multiplex staining analysis of gastric cancer samples on the tissue microarray. Remarkably, the senescore signature served as a reliable predictor of chemotherapeutic and immunotherapeutic efficacies, with high-senescore patients benefited from immunotherapy, while low-senescore patients were responsive to chemotherapy. Collectively, we report senescence as a heretofore unrecognized hallmark of gastric cancer that impacts patient outcomes and therapeutic efficacy.

SARS-CoV-2 spike protein dictates syncytium-mediated lymphocyte elimination

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus is highly contagious and causes lymphocytopenia, but the underlying mechanisms are poorly understood. We demonstrate here that heterotypic cell-in-cell structures with lymphocytes inside multinucleate syncytia are prevalent in the lung tissues of coronavirus disease 2019 (COVID-19) patients. These unique cellular structures are a direct result of SARS-CoV-2 infection, as the expression of the SARS-CoV-2 spike glycoprotein is sufficient to induce a rapid (~45.1 nm/s) membrane fusion to produce syncytium, which could readily internalize multiple lines of lymphocytes to form typical cell-in-cell structures, remarkably leading to the death of internalized cells. This membrane fusion is dictated by a bi-arginine motif within the polybasic S1/S2 cleavage site, which is frequently present in the surface glycoprotein of most highly contagious viruses. Moreover, candidate anti-viral drugs could efficiently inhibit spike glycoprotein processing, membrane fusion, and cell-in-cell formation. Together, we delineate a molecular and cellular rationale for SARS-CoV-2 pathogenesis and identify novel targets for COVID-19 therapy.

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.

Mechanical Ring Interfaces between Adherens Junction and Contractile Actomyosin to Coordinate Entotic Cell-in-Cell Formation

Entosis is a cell-in-cell (CIC)-mediated death program. Contractile actomyosin (CA) and the adherens junction (AJ) are two core elements essential for entotic CIC formation, but the molecular structures interfacing them remain poorly understood. Here, we report the characterization of a ring-like structure interfacing between the peripheries of invading and engulfing cells. The ring-like structure is a multi-molecular complex consisting of adhesive and cytoskeletal proteins, in which the mechanical sensor vinculin is highly enriched. The vinculin-enriched structure senses mechanical force imposed on cells, as indicated by fluorescence resonance energy transfer (FRET) analysis, and is thus termed the mechanical ring (MR). The MR actively interacts with CA and the AJ to help establish and maintain polarized actomyosin that drives cell internalization. Vinculin depletion leads to compromised MR formation, CA depolarization, and subsequent CIC failure. In summary, we suggest that the vinculin-enriched MR, in addition to CA and AJ, is another core element essential for entosis.

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.

PCDH7 Inhibits the Formation of Homotypic Cell-in-Cell Structure

Though homotypic cell-in-cell (hoCIC) structures are implicated in the development and progression of multiple human tumors, the molecular mechanisms underlying their formation remain poorly understood. We found that the expression of Protocadherin-7 (PCDH7), an integral membrane protein, was negatively associated with the formation of hoCIC structures. Overexpression of PCDH7 efficiently inhibits, while its depletion significantly enhances, hoCIC formation, which was attributed to its regulation on intercellular adhesion and contractile actomyosin as well. Via directly interacting with and inactivating PP1α, a protein phosphatase that dephosphorylates pMLC2, PCDH7 increases the level of pMLC2 leading to enhanced actomyosin at the intercellular region and compromised hoCIC formation. Remarkably, PCDH7 enhanced anchorage-independent cell growth in a hoCIC-dependent manner. Together, we identified PCDH7 as the first trans-membrane protein that inhibits hoCIC formation to promote tumor growth.

High Frequency of Cell-in-Cell Formation in Heterogeneous Human Breast Cancer Tissue in a Patient With Poor Prognosis: A Case Report and Literature Review

Cell cannibalism is a unique pathological phenomenon that has been observed at low frequency in a variety of human tumor samples (<0.5%), including breast cancer. Cannibalistic cells typically form cell-in-cell (CIC) structures characterized by enclosure of one cell or more by another, mediating a novel type of cell death "entosis," which was proposed as the type IV cell death. A large number of CIC structures are generally associated with malignant transformation and progression, and they are believed to be primed by and form among heterogeneous cells. However, there is currently no in vivo evidence from human tumor samples. In this case report, covering a 37-year-old female breast cancer patient, we observed considerable heterogeneity and proliferative activity (>70% Ki-67 positivity) in her breast cancer cells, accompanied by high frequency of CIC formation (~6%) and poor prognosis. We consider this a typical example of cell cannibalism, supporting a role of heterogeneity in cell-in-cell formation and malignant progression. It may serve as a pretest basis for further investigations of cell-in-cell biology and breast cancer treatment.

Predictive significance of T cell subset changes during ex vivo generation of adoptive cellular therapy products for the treatment of advanced non-small cell lung cancer

Adoptive T cell immunotherapy with cytokine-induced killer cells (CIKs) has been demonstrated to prolong the survival of patients with advanced non-small cell lung cancer (NSCLC). The aim of the present study was to evaluate whether the expansion of effector T cells and the decrease of regulatory T cells (Tregs) that occurred during the ex vivo generation of DC-CIKs were associated with improved clinical outcome in patients who received treatment. CIKs were generated ex vivo over a 28-day period from the peripheral blood apheresis product of 163 patients with advanced cancer (including 30 with NSCLC). CIKs were also generated from an additional cohort of 65 patients with NSCLC over a 15-day period. The progression-free survival (PFS) and overall survival (OS) time of patients treated with CIKs was determined by reviewing the patients' medical records. The number of CIKs gradually increased during the culture period and peaked at day 15, followed by a slight decline until day 28. Similarly, the percentages of T cell subtypes associated with anti-tumor activity (CD3⁺, CD3⁺CD4⁺, CD3⁺CD8⁺ and CD8⁺CD28⁺) peaked at day 15. Although the percentage of CD4⁺CD25⁺CD127⁺ Tregs increased by day 7, a decrease was subsequently observed. Among the 95 patients with NSCLC, those with a post/pre-culture ratio of CD8⁺CD28⁺ T lymphocytes >2.2 had significantly better PFS and OS compared with those with ratios ≤2.2. Those with a post/pre-culture CD4⁺CD25⁺CD127⁺ Treg ratio ≤0.6 had significantly better OS and PFS compared with those with ratios >0.6. The peak expansion of CIKs from peripheral blood mononuclear cells occurred at day 15 of ex vivo culture. PFS and OS were associated with post/pre-culture CD8⁺CD28⁺ T lymphocyte ratio >2.2 and post/pre-culture CD4⁺CD25⁺CD127⁺ Treg ratio <0.6 in the CIKs of patients with advanced NSCLC treated with adoptive T cell immunotherapy. Further efforts are underway to optimize the DC-CIK infusion for cancer immunotherapy.

Subtype-Based Prognostic Analysis of Cell-in-Cell Structures in Early Breast Cancer

Though current pathological methods are greatly improved, they provide rather limited functional information. Cell-in-cell structures (CICs), arising from active cell–cell interaction, are functional surrogates of complicated cell behaviors within heterogeneous cancers. In light of this, we performed the subtype-based CIC profiling in human breast cancers by the “EML” multiplex staining method, and accessed their values as prognostic factors by Cox univariate, multivariate, and nomogram analysis. CICs were detected in cancer specimens but not in normal breast tissues. A total of five types of CICs were identified with one homotypic subtype (91%) and four heterotypic subtypes (9%). Overall CICs (oCICs) significantly associated with patient overall survival (OS) (P = 0.011) as an independent protective factor (HR = 0.423, 95% CI, 0.227–0.785; P = 0.006). Remarkably, three CICs subtypes (TiT, TiM, and MiT) were also independent prognostic factors. Among them, higher TiT, from homotypic cannibalism between tumor cells, predicted longer patient survival (HR = 0.529, 95% CI, 0.288–0.973; P = 0.04) in a way similar to that of oCICs and that (HR = 0.524, 95% CI, 0.286–0.962; P = 0.037) of heterotypic TiM (tumor cell inside macrophage); conversely, the presence of MiT (macrophage inside tumor cell) predicted a death hazard of 2.608 (95% CI, 1.344–5.063; P = 0.05). Moreover, each CIC subtype tended to preferentially affect different categories of breast cancer, with TiT (P < 0.0001) and oCICs (P = 0.008) targeting luminal B (Her2⁺), TiM (P = 0.011) targeting HR⁻ (Her2⁺/HR⁻ and TNBC), and MiT targeting luminal A (P = 0.017) and luminal B (Her⁻) (P = 0.006). Furthermore, nomogram analysis suggested that CICs impacted patient outcomes in contributions comparable (for oCICs, TiT, and TiM), or even superior (for MiT), to TNM stage and breast cancer subtype, and incorporating CICs improved nomogram performance. Together, we propose CICs profiling as a valuable way for prognostic analysis of breast cancer and that CICs and their subtypes, such as MiT, may serve as a type of novel functional markers assisting clinical practices.

Heterotypic cell-in-cell structures in colon cancer can be regulated by IL-6 and lead to tumor immune escape

Heterotypic CICs (cell-in-cell structures) have been found between tumor cells and various immune cells in a variety of cancer tissues. The frequency of CICs has been found to correlate with tumor malignancy in some studies but not in others. Herein, we examined in depth the CICs observed in colon cancer to determine their potential significance in disease progression. Heterotypic CICs were observed by histochemistry between epithelial cells and lymphocytes in an expanded spectrum of colon tissue from colitis to cancer and in vitro studies were performed using the colonic tumor cell line HCT8 and human peripheral blood lymphocytes. Our data revealed that the CICs formed by colonic epithelial cells and infiltrated lymphocytes not only positively correlated with tumor malignancy but also were upregulated by the inflammatory cytokine IL-6. In addition, we observed that colon cancer cells could initiate autophagy for survival after cytotoxic lymphocyte internalization and that IL-6 could also be involved in this process to promote the death of lymphocytes in CIC structures. Furthermore, certain changes were observed in tumor cells after experiencing CICs. Our findings suggest that CICs formed by colon cancer cells and lymphocytes contribute to tumor escape from immune surveillance, which could be facilitated by IL-6, and might represent a previously undescribed pathway for tumor cells to adapt and evade host immune defense.

Biological relevance of cell-in-cell in cancers

Cell-in-cell (CIC) is a term used to describe the presence of one, usually living, cell inside another cell that is typically considered non-phagocytic. Examples of this include tumour cells inside tumour cells (homotypic), mesenchymal stem cells inside tumour cells (heterotypic) or immune cells inside tumour cells (heterotypic). CIC formation can occur in cell lines and in tissues and it has been most frequently observed during inflammation and in cancers. Over the past 10 years, many researchers have studied CIC structures and a few different models have been proposed through which they can be formed, including entosis, cannibalism and emperipolesis among others. Recently, our laboratory discovered a role for mutant p53 in facilitating the formation of CIC and promoting genomic instability. These data and research by many others have uncovered a variety of molecules involved in CIC formation and have started to give us an idea of why they are formed and how they could contribute to oncogenic processes. In this perspective, we summarise current literature and speculate on the role of CIC in cancer biology.

Cell-in-cell phenomena in cancer

Cell-in-cell structures are reported in numerous cancers, and their presence is an indicator for poor prognosis. Mechanistic studies have identified how cancer cells manage to ingest whole neighbouring cells to form such structures, and the consequences of cell-in-cell formation on cancer progression have been elucidated. In this Opinion article, we discuss how two related cell-in-cell processes, cell cannibalism and entosis, are regulated and how these mechanisms promote cancer progression. We propose that cannibalistic activity is a hallmark of cancer that results in part from selection by metabolic stress and serves to feed aggressive cancer cells.

Early Hyperbaric Oxygen Treatment Attenuates Burn-Induced Neuroinflammation by Inhibiting the Galectin-3-Dependent Toll-Like Receptor-4 Pathway in a Rat Model

Hyperbaric oxygen (HBO) treatment has been proven to decrease neuroinflammation in rats. This study aimed to determine the potential mechanism underlying the anti-inflammatory effects of HBO treatment on burn-induced neuroinflammation in rats. Thirty-six adult male Sprague-Dawley (SD) rats were randomly assigned to the following six groups (n = 6 per group): (1) sham burn with sham HBO treatment; (2) sham burn with HBO treatment; (3) burn with one-week sham HBO treatment; (4) burn with two-week sham HBO treatment; (5) burn with one-week HBO treatment; and (6) burn with two-week HBO treatment. SD rats that received third-degree burn injury were used as a full-thickness burn injury model. Subsequently, we analyzed the expression of proteins involved in the galectin-3 (Gal-3)-dependent Toll-like receptor-4 (TLR-4) pathway through enzyme-linked immunosorbent assay (ELISA), immunohistochemistry (IHC) analysis, and Western blotting. A behavior test was also conducted, which revealed that HBO treatment significantly suppressed mechanical hypersensitivity in the burn with HBO treatment group compared to the burn with sham HBO treatment group (p < 0.05). ELISA results showed that tumor necrosis factor α (TNF-α) and interleukin 1 beta (IL-1β) levels in the dorsal horn of the spinal cord and the skin significantly decreased in the burn with HBO treatment group compared with the burn with sham HBO treatment group (p < 0.05). Western blotting results demonstrated that HBO treatment significantly reduced the expression of Gal-3 and TLR-4 in the dorsal horn of the spinal cord in the burn with HBO treatment group compared with the burn with sham HBO treatment group (p < 0.05). IHC analysis showed that the expression of Gal-3, TLR-4, CD68 and CD45 in the dorsal horn of the spinal cord was significantly lower in the burn with HBO treatment group than in the burn with sham HBO treatment group (p < 0.05), and the expression of CD68 and macrophage migration inhibitory factor (MIF) in the right hind paw skin was significantly lower. The expression of vimentin and fibroblast growth factor in the right hind paw skin was significantly higher after HBO treatment (p < 0.05). This study proved that early HBO treatment relieves neuropathic pain, inhibits the Gal-3-dependent TLR-4 pathway, and suppresses microglia and macrophage activation in a rat model.

Characterizing parathyroid carcinomas and atypical neoplasms based on the expression of programmed death-ligand 1 expression and the presence of tumor-infiltrating lymphocytes and macrophages

BACKGROUND

Four distinct tumor microenvironments have been proposed based on the expression of programmed death-ligand 1 and the presence of tumor-infiltrating lymphocytes: immunotype I (adaptive resistance, tumor-infiltrating lymphocytes+ and programmed death-ligand 1+); immunotype II (immunologic ignorance, tumor-infiltrating lymphocytes- and programmed death-ligand 1-); immunotype III (intrinsic induction; tumor-infiltrating lymphocytes- and programmed death-ligand 1+); and immunotype IV (tolerance, tumor-infiltrating lymphocytes+ and programmed death-ligand 1-). These subtypes may predict tumor response to immunotherapy. We hypothesized that parathyroid neoplasms may have tumor immunogenic expression that can later be used to guide treatment.

METHODS

We assessed retrospectively the immunohistochemical expression of programmed death-ligand 1 and the presence of tumor-infiltrating lymphocytes (CD3+ and CD8+) and macrophages (CD68+) in parathyroid carcinomas and in atypical parathyroid neoplasms treated at the M. D. Anderson Cancer Center from 1996 to 2016. Using intratumoral digital image analysis, the programmed death-ligand 1 H score was calculated with a standardized formula for predominant staining. The tumor-infiltrating lymphocytes per square millimeter of intratumoral areas were quantified.

RESULTS

Within 30 specimens (17 parathyroid carcinomas and 13 atypical parathyroid neoplasms), there was no difference in the median programmed death-ligand 1 H score between the two groups (P = .57). Four parathyroid carcinoma cases had programmed death-ligand 1 H scores ≥1 associated with CD3+ and CD8+ tumor cell density; 2 of them had distant metastases. Parathyroid carcinomas had a lesser median CD3+ density (P = .04) and a lesser median CD8+ density (P =.07) than did atypical parathyroid neoplasms. Median CD68+ density did not differ between groups (P = .22).

CONCLUSION

Parathyroid carcinomas tended to have immune-ignorant and immune-tolerant microenvironments within the neoplasm (immunotypes II and IV). Of the parathyroid carcinoma microenvironments, 17 had patterns of programmed death-ligand 1 and tumor-infiltrating lymphocytes expression (immunotype I), suggesting possible benefit from immunotherapy. In addition, both parathyroid carcinomas and parathyroid neoplasms expressed CD68+. Further exploration of these potential biomarkers as a target in cancer therapies is needed.

CDKN2A inhibits formation of homotypic cell-in-cell structures

Cell-in-cell (CIC) structures, characterized by enclosure of one or more cells within another cell, were extensively documented in human cancers. Although elevated CIC formation was found in cancers with CDKN2A inactivation, a causal link between them remains to be established. We reported here that inhibiting CDKN2A expression effectively promoted homotypic CIC formation, whereas ectopic overexpression of p16INK4a or p14ARF, two proteins encoded by CDKN2A gene, significantly suppressed CIC formation in MCF7 cells. The regulation of CIC formation by CDKN2A was tightly correlated with subcellular redistribution of E-cadherin, F-actin rearrangement and reduced phosphorylation of myosin light chain 2 (p-MLC2), consistent with which, CDKN2A expression imparted cells winner/outer identity in competition assay. Moreover, CIC formation negatively correlates with p16INK4a expression in human breast cancers. Thus, our work identifies CDKN2A as the first tumor suppressor whose inactivation promotes homotypic CIC formation in human cancer cells.

A fully human anti-CD47 blocking antibody with therapeutic potential for cancer

CD47/SIRPα interaction serves as an immune checkpoint for macrophage-mediated phagocytosis. Mouse anti-CD47 blocking antibodies had demonstrated potent efficacy in the treatment of both leukemic and solid tumors in preclinical experimentations, and therefore had moved forward rapidly into clinical trials. However, a fully human blocking antibody, which meets clinical purpose better, has not been reported for CD47 up to date. In this study, we reported the isolation of a fully human anti-CD47 blocking antibody, ZF1, from a phage display library. ZF1 displayed high specificity and affinity for CD47 protein, which were comparable to those for humanized anti-CD47 blocking antibody B6H12. Importantly, ZF1 treatment could induce robust, or even stronger than B6H12, phagocytosis of leukemic cancer cells by macrophage in vitro, and protect BALB/c nude mice from cancer killing by engrafted leukemic cells (CCRF and U937) to a similar extent as B6H12 did. Thus, these data provide primary early pre-clinical support for the development of ZF1 as a fully human blocking antibody to treat human leukemia by targeting CD47 molecule.

CD68 and interleukin 13, prospective immune markers for esophageal squamous cell carcinoma prognosis prediction

Purpose

Oncology immunity was reported to play a key role in cancer development and progression, so we investigated the prediction role of several immune markers in esophageal squamous cell carcinoma (ESCC) patients after operation in this study.

Patients and Methods

66 primary ESCC tumor tissues and four sets of tissue microarrays including 705 primary ESCC tumor tissues from four centers were collected and analyzed. Expressions of several immune markers in ESCC tumor tissue were detected with immunohistochemistry staining. Their distribution densities were analyzed with InForm^™ 2.0.1 software. All statistic analyses were performed with SPSS16.0 and Stata version 10.0.

Results

Survival analyses assessed by Kaplan-Meier plots and log-rank tests demonstrated that densities of CD68 and interleukin 13 (IL-13) in tumor stroma were positively correlated with the overall survival of ESCC patients after operation (p < 0.01 for CD68, p < 0.001 for IL-13). Further, a model based on tumor stroma densities of CD68 and IL-13 was constructed and it could significantly classify patients with poor or good prognosis. This model could further identify high-risk group and low-risk group at the same Tumor lymph Nodes Metastases (TNM) stage. Lastly, a more accuracy model based on TNM stage, densities of CD68 and IL-13 was constructed to predict the prognosis of ESCC patient after operation.

Conclusion

Combining the TNM staging system and densities of CD68 and IL-13 could substantially improve the prognosis prediction accuracy of ESCC patient after operation, which might be an excellent tool for selecting patients for individualized therapy in future.

Intratumoral and peritumoral expression of CD68 and CD206 in hepatocellular carcinoma and their prognostic value

The aims of the present study were to determine whether the changes in density and location of CD68-positive and CD206-positive macrophages contribute to progression of hepatocellular carcinoma (HCC) and to evaluate prognostic values of these cells in post-surgical patients. A retrospective study involving 268 HCC patients was conducted. CD68-positive and CD206-positive macrophage infiltration in HCC tissues and adjacent tissues was examined by immunohistochemistry (IHC) and the relationship between the clinicopathological features and prognosis was analyzed. Receiver operating characteristics (ROC) curve was used to calculate diagnostic accuracy. There was an increase in CD68-positive and CD206-positive macrophage infiltration in adjacent tumor tissues compared with tumor tissues. ROC curve identified their optimal diagnostic cut-off values. The survival analysis showed that increased CD68 expression in adjacent tissues conferred superior overall survival (OS) and disease-free survival (DFS), while increase of CD206 in tumor yielded inferior OS and DFS. Cox regression analysis suggested both CD68-positive macrophages in adjacent area and intratumor CD206-positive macrophages as independent prognostic biomarkers for post-surgical HCC patients. Finally, a combination of CD68/CD206 and HBV-positive further improved prognostic stratification, especially in DFS. These results provide the first evidence for region- and subset-dependent involvement of CD68 and CD206 cells in HCC progression. A combination of CD68/CD206 density and HBV-positivity improves further predictive value for post-operative recurrence of HCC. Quantification of CD68/CD206 macrophages and their distribution can be exploited for better postsurgical management of HCC patients. These findings provide a basis for developing novel treatment strategies aimed at re-educating macrophages in tumor microenvironment.

Dendritic Cell/Cytokine-Induced Killer Cell Immunotherapy Combined with S-1 in Patients with Advanced Pancreatic Cancer: A Prospective Study

Purpose: Advanced pancreatic cancer has remained challenging to treat effectively. This study aimed to investigate the clinical effects and safety of immunotherapy with dendritic cells and cytokine-induced killer cells (DC-CIK) administered with the chemotherapy (CT) S-1 in this malignancy.Experimental Design: Consecutive patients (n = 47) with advanced pancreatic cancer were treated with either DC-CIK + S-1, DC-CIK alone, S-1 alone, or best supportive care.Results: DC-CIK plus S-1 produced significantly longer median OS and PFS (212 and 136 days) compared with DC-CIK (128 and 85 days), CT (141 and 92 days), or supportive care only (52 and 43 days; P < 0.001). After adjusting for competing risk factors, DC-CIK combined with S-1 and receipt of 2 or more cycles of DC-CIK treatment remained independent predictors of disease-free and overall survival (P < 0.05). Phenotypic analysis of PBMCs demonstrated that the CD3⁺, CD3⁺/CD4⁺, and CD8⁺/CD28⁺ T-cell subsets were elevated (P < 0.05), while the CD3⁺/CD8⁺, CD3⁺/CD16⁺/CD56⁺ and CD4⁺/CD25⁺ cell subsets were significantly decreased after DC-CIK cell therapy (P < 0.05). There were no grade 3 or 4 toxicities. In addition, the mutational frequency in cell-free tumor DNA (cfDNA) declined in 4 of 14 patients who received DC-CIK, and was associated with a more favorable survival.Conclusions: Treatment of advanced pancreatic cancer with combined DC-CIK infusions and S-1 was safe, resulted in favorable PFS and OS, and modulated the peripheral blood immune repertoire. Clin Cancer Res; 23(17); 5066-73. ©2017 AACR.

Cell-in-cell structures are more potent predictors of outcome than senescence or apoptosis in head and neck squamous cell carcinomas

Background

This study sheds light on cell inactivating processes with focus on the phenomenon of cell-in-cell (CIC). Cell-in-cell describes a cell process where one cell is being engulfed by another non-professional phagocyte. We determined frequency and prognostic impact of CIC structures (CICs) as well as of senescent and apoptotic cells in head and neck squamous cell carcinomas (HNSCC).

Methods

These different forms of cell inactivation as well as the proportion of proliferating and tumor cells were assessed in 169 pre-radiochemotherapy biopsies and 32 post-therapy tumor resections by immunohistochemistry of tissue microarrays. Four consecutive cancer sections were stained with antibodies specific for E-cadherin for CIC detection, cleaved caspase-3 for apoptosis, H3K9Me for senescence and Ki67 as a proliferation marker. Positive events were quantified in corresponding tumor areas.

Results

CICs were found in 55.5%, senescent cells in 67.1% and apoptotic cells in 93.3% of samples. While no prognostic impact of apoptotic and senescent cells was observed, CICs turned out to significantly influence overall-survival (p = 0.016) with a lack of CICs being prognostically beneficial. There was no correlation between CICs and apoptosis and 98.9% of CICs were negative for cleaved caspase-3.

Conclusion

CIC formation is a frequent event in HNSCC and a superior predictive marker compared to senescence and apoptosis. Independence of CIC and apoptosis and the adverse prognosis associated with numerous CICs lead to the assumption that CICs might take up necrotic rather than apoptotic cells preventing an adequate antitumoral immune response that would otherwise be initiated by necrotic cells through damage-associated molecular pattern molecules.

Electronic supplementary material

The online version of this article (doi:10.1186/s13014-016-0746-z) contains supplementary material, which is available to authorized users.

Cell-in-cell phenomenon: A New Paradigm in Life Sciences

Cell-in-cell, a phenomenon characterized by one or more viable cells entering actively into another cell, was observed more than a century and has only attracted more attention in recent years and is becoming a new hot topic in the biological field, owing its biological significance in evolutionary as well as physiological and pathological relevance in development, homeostasis and diseases. In this paper we focus on the diversity, evolutionary conservatism and clinical implication of cell-in-cell as well as latest opinions on the research strategies. Based on the findings from our laboratory and other research groups three working models of cell-in-cell are also proposed.

Mechanisms and consequences of entosis

Multiple mechanisms have emerged where the engulfment of whole live cells, leading to the formation of what are called 'cell-in-cell' structures, induces cell death. Entosis is one such mechanism that drives cell-in-cell formation during carcinogenesis and development. Curiously, entotic cells participate actively in their own engulfment, by invading into their hosts, and are then killed non-cell-autonomously. Here we review the mechanisms of entosis and entotic cell death and the consequences of entosis on cell populations.

Impaired formation of homotypic cell-in-cell structures in human tumor cells lacking alpha-catenin expression

Although cell-in-cell structures (CICs) could be detected in a wide range of human tumors, homotypic CICs formed between tumor cells occur at low rate for most of them. We recently reported that tumor cells lacking expression of E- and P-cadherin were incapable of forming homotypic CICs by entosis, and re-expression of E- or P-cadherin was sufficient to induce CICs formation in these tumor cells. In this work, we found that homotypic CICs formation was impaired in some tumor cells expressing high level of E-cadherin due to loss expression of alpha-catenin (α-catenin), a molecular linker between cadherin-mediated adherens junctions and F-actin. Expression of α-catenin in these tumor cells restored cell-cell adhesion and promoted CICs formation in a ROCK kinase-dependent way. Thus, our work identified α-catenin as another molecule in addition to E- and P-cadherin that were targeted to inactivate homotypic CICs formation in human tumor cells.