A case of infundibular cyst with neutrophil cannibalism by squamous cells in a dog

A 6-years and 6-months-old, neutered male mongrel dog had a skin mass between the left eye and nose. Fine needle aspiration biopsy of the mass revealed giant epithelial cells containing many neutrophils in the cytoplasm. The mass was excised and histopathologically diagnosed as an infundibular cyst with giant epithelial-like cells containing neutrophils in part of the lumen. The giant cells were immunopositive for cytokeratin and immunonegative for vimentin. Cell cannibalism is a cell engulfing phenomenon in which a cell incorporates either the same or a different type of cell and the incorporated cells are degenerate or necrotic. In this case, epithelial cells in the lumen of the cyst incorporated neutrophils, which corresponds to neutrophil cannibalism by squamous epithelial cells.

Mapping Cell-in-Cell Structures in Oral Squamous Cell Carcinoma

Cell-in-cell (CIC) structures contribute to tumor aggressiveness and poor prognosis in oral squamous cell carcinoma (OSCC). In vitro 3D models may contribute to the understanding of the underlying molecular mechanisms of these events. We employed a spheroid model to study the CIC structures in OSCC. Spheroids were obtained from OSCC (HSC3) and cancer-associated fibroblast (CAF) lines using the Nanoshuttle-PLTM bioprinting system (Greiner Bio-One). Spheroid form, size, and reproducibility were evaluated over time (EvosTM XL; ImageJ version 1.8). Slides were assembled, stained (hematoxylin and eosin), and scanned (Axio Imager Z2/VSLIDE) using the OlyVIA System (Olympus Life Science) and ImageJ software (NIH) for cellular morphology and tumor zone formation (hypoxia and/or proliferative zones) analysis. CIC occurrence, complexity, and morphology were assessed considering the spheroid regions. Well-formed spheroids were observed within 6 h of incubation, showing the morphological aspects of the tumor microenvironment, such as hypoxic (core) and proliferative zone (periphery) formation. CIC structures were found in both homotypic and heterotypic groups, predominantly in the proliferative zone of the mixed HSC3/CAF spheroids. "Complex cannibalism" events were also noted. These results showcase the potential of this model in further studies on CIC morphology, formation, and relationship with tumor prognosis.

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.

Hemophagocytic syndrome in a cat with Mycoplasma haemofelis infection

A six-year-old, castrated male domestic shorthair cat was presented for a week-long history of lethargy, acute anorexia, and adipsia. On presentation, the cat was weak with pale mucous membranes, open-mouth breathing, and mild popliteal lymphadenomegaly. Routine bloodwork revealed bicytopenia due to marked non-regenerative anemia and moderate thrombocytopenia; erythrocyte clumping was apparent on the blood smear, but no agglutination was noted on a saline dispersion test. Abdominal and thoracic imaging showed marked splenomegaly and multiple mildly enlarged lymph nodes. Aspirates from the bone marrow and spleen contained many erythrophagocytic macrophages and occasional lymphocytes containing engulfed erythrocytes. The macrophages also occasionally contained phagocytosed erythroid precursors, platelets, and leukocytes. A diagnosis of hemophagocytic syndrome was made based on the presence of bicytopenia and increased numbers of hemophagocytic macrophages in the spleen and bone marrow. Though no organisms were observed, Mycoplasma spp. infection was suspected and confirmed via PCR. To the authors' knowledge, this is the first report of a hemophagocytic syndrome in a cat with Mycoplasma haemofelis. Lymphocyte engulfment of erythrocytes has been previously reported in a cat with M. haemofelis infection. Both hemophagocytic syndrome and engulfment of erythrocytes by lymphocytes should prompt testing for Mycoplasma spp. even with a lack of evident parasitemia.

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.

High neutrophil incorporation rate of ascitic fluid cytology as an indicator of cancerous ascites

The cell‑in‑cell phenomenon (CiCP) involves the incorporation of a viable cell by other cells (host cells) and includes two concepts: Emperipolesis and cell cannibalism. The former involves the incorporation of hematopoietic cells as the incorporated cells, while the latter involves cell incorporation by tumor cells as host cells. A total of 239 peritoneal cavity fluid cytology specimens were evaluated for CiCP and the number of singly detectable nuclei (SDN) were measured by examining virtual slide image files. The rates of CiCP‑positive cases (RCPCs) and CiCP emergence rate (CER)/SDN were significantly higher in ascites samples than in peritoneal washing samples (P<0.0001 and P=0.0026, respectively), although the numbers of SDN were not significantly different between the groups (P=0.8063). Both the RCPCs and CER/SDN were significantly higher in tumor‑positive specimens than in tumor‑negative specimens (P=0.0220 and P=0.0312, respectively), although the numbers of SDN were not significantly different between the samples (P=0.2471). Most of the incorporated cells were lymphocytes and the host cells were macrophages; however, the rate of neutrophil incorporation (NI) by host cells in the total CiCP cells in a sample was significantly higher in tumor‑positive specimens than in tumor‑negative specimens (P=0.0288). NI was mainly performed via emperipolesis by macrophages, with only six examples not by macrophages observed among all CiCP samples. The threshold NI rate/total CiCP (NI/CiCP) between tumor‑positive and tumor‑negative groups was 11.1% (P=0.0115). Using this threshold, the peripheral blood leukocyte count was significantly higher in the high‑NI/CiCP group than in the low‑NI/CiCP group (P=0.0022). The present findings revealed novel aspects of less frequently observed CiCP in ascitic fluid cytology by utilizing combined manual and computer assisted image analysis evaluation of samples. Notably, the present study indicated the importance of increased NI as an indicator of cancerous ascites.

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.

Entosis Controls a Developmental Cell Clearance in C. elegans

Metazoan cell death mechanisms are diverse and include numerous non-apoptotic programs. One program called entosis involves the invasion of live cells into their neighbors and is known to occur in cancers. Here, we identify a developmental function for entosis: to clear the male-specific linker cell in C. elegans. The linker cell leads migration to shape the gonad and is removed to facilitate fusion of the gonad to the cloaca. We find that the linker cell is cleared in a manner involving cell-cell adhesions and cell-autonomous control of uptake through linker cell actin. Linker cell entosis generates a lobe structure that is deposited at the site of gonad-to-cloaca fusion and is removed during mating. Inhibition of lobe scission inhibits linker cell death, demonstrating that the linker cell invades its host while alive. Our findings demonstrate a developmental function for entosis: to eliminate a migrating cell and facilitate gonad-to-cloaca fusion, which is required for fertility.

Cancer cell cannibalism and the SASP: Ripples in the murky waters of tumor dormancy

Relapse in cancer patients following an apparent cure and a prolonged latency period, known as tumor dormancy, remains an unrelenting clinical crisis. Here, I expand on our recent findings that potentially link cancer cell cannibalism of bone marrow-derived mesenchymal stem/stromal cells (BM-MSCs) to the senescence-associated secretory phenotype (SASP) and tumor dormancy.

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

Although Cell-in-cell structures (CICs) had been documented in human tumors for decades, it is unclear what types of CICs were formed largely due to low resolution of traditional way such as H&E staining. In this work, we employed immunofluorescent method to stain a panel of human tumor samples simultaneously with antibodies against E-cadherin for Epithelium, CD68 for Macrophage and CD45 for Leukocytes, which we termed as "EML method" based on the cells detected. Detail analysis revealed four types of CICs, with tumor cells or macrophage engulfing tumor cells or leukocytes respectively. Interestingly, tumor cells seem to be dominant over macrophage (93% vs 7%) as the engulfer cells in all CICs detected, whereas the overall amount of internalized tumor cells is comparable to that of internalized CD45+ leukocytes (57% vs 43%). The CICs profiles vary from tumor to tumor, which may indicate different malignant stages and/or inflammatory conditions. Given the potential impacts different types of CICs might have on tumor growth, we therefore recommend EML analysis of tumor samples to clarify the correlation of CICs subtypes with clinical prognosis in future researches.

Competition between human cells by entosis

Human carcinomas are comprised of complex mixtures of tumor cells that are known to compete indirectly for nutrients and growth factors. Whether tumor cells could also compete directly, for example by elimination of rivals, is not known. Here we show that human cells can directly compete by a mechanism of engulfment called entosis. By entosis, cells are engulfed, or cannibalized while alive, and subsequently undergo cell death. We find that the identity of engulfing ("winner") and engulfed ("loser") cells is dictated by mechanical deformability controlled by RhoA and actomyosin, where tumor cells with high deformability preferentially engulf and outcompete neighboring cells with low deformability in heterogeneous populations. We further find that activated Kras and Rac signaling impart winner status to cells by downregulating contractile myosin, allowing for the internalization of neighboring cells that eventually undergo cell death. Finally, we compute the energy landscape of cell-in-cell formation, demonstrating that a mechanical differential between winner and loser cells is required for entosis to proceed. These data define a mechanism of competition in mammalian cells that occurs in human tumors.