Homotypic Entosis as a Potential Novel Diagnostic Marker in Breast Cancer

Homotypic cell-in-cell structure as a novel prognostic predictor in non-small cell lung cancer and frequently localized at the invasive front

Homotypic cell-in-cell structures (hoCICs) are associated with tumor proliferation, invasion, and metastasis and is considered a promising prognostic marker in various cancers. However, the role of hoCICs in non-small cell lung cancer (NSCLC) remains unclear. Tumor tissue sections were obtained from 411 NSCLC patients. We analyzed the relationship between clinicopathological variables and the number of hoCICs. LASSO and multivariate Cox regression analysis were employed to identify prognostic factors for NSCLC. The impact of hoCICs on overall survival (OS) and disease-free survival (DFS) was assessed using the Kaplan-Meier curves and log-rank test. Prognostic models for OS and DFS were developed and validated using the C-index, time-dependent area under the curve (AUC), net reclassification improvement (NRI), integrated discrimination improvement (IDI), calibration curves and decision curve analysis (DCA). Among the cohort, 56% of patients had hoCICs while 44% did not. Notably, hoCICs were primarily found at the tumor invasion front. Male gender, smoking, squamous cell carcinoma, low differentiation, tumor size ≥ 3 cm, advanced TNM stage, lymph node metastasis, pleural invasion, vascular invasion, necrosis, P53 mutation, and high expression of Ki-67 were identified as relative risk factors for hoCICs. Furthermore, hoCICs was found to be a significant prognostic factor for both OS and DFS, with higher frequencies of hoCICs correlating with poorer outcomes. We constructed nomograms for predicting 1-, 3-, and 5-year OS and DFS based on hoCICs, and the calibration curves showed good agreement between the predicted and actual outcomes. The results of the C-index, time-dependent AUC, NRI, IDI, and DCA analyses demonstrated that incorporating hoCICs into the prognostic model significantly enhanced its predictive power and clinical applicability. HoCICs indicated independent perdictive value for OS and DFS in patients with NSCLC. Furthermore, the frequent localization of hoCICs at the tumor invasion front suggested a strong association between hoCICs and tumor invasion as well as metastasis.

Forms of Non-Apoptotic Cell Death and Their Role in Gliomas-Presentation of the Current State of Knowledge

In addition to necrosis and apoptosis, the two forms of cell death that have been known for many decades, other non-apoptotic forms of cell death have been discovered, many of which also play a role in tumors. Starting with the description of autophagy more than 60 years ago, newer forms of cell death have become important for the biology of tumors, such as ferroptosis, pyroptosis, necroptosis, and paraptosis. In this review, all non-apoptotic and oncologically relevant forms of programmed cell death are presented, starting with their first descriptions, their molecular characteristics, and their role and their interactions in cell physiology and pathophysiology. Based on these descriptions, the current state of knowledge about their alterations and their role in gliomas will be presented. In addition, current efforts to therapeutically influence the molecular components of these forms of cell death will be discussed. Although research into their exact role in gliomas is still at a rather early stage, our review clarifies that all these non-apoptotic forms of cell death show significant alterations in gliomas and that important insight into understanding them has already been gained.

Entosis: the core mechanism and crosstalk with other cell death programs

Cell death pathways play critical roles in organism development and homeostasis as well as in the pathogenesis of various diseases. While studies over the last decade have elucidated numerous different forms of cell death that can eliminate cells in various contexts, how certain mechanisms impact physiology is still not well understood. Moreover, recent studies have shown that multiple forms cell death can occur in a cell population, with different forms of death eliminating individual cells. Here, we aim to describe the known molecular mechanisms of entosis, a non-apoptotic cell engulfment process, and discuss signaling mechanisms that control its induction as well as its possible crosstalk with other cell death mechanisms.

Mechanisms and significance of entosis for tumour growth and progression

To date, numerous mechanisms have been identified in which one cell engulfs another, resulting in the creation of 'cell-in-cell' (CIC) structures, which subsequently cause cell death. One of the mechanisms of formation of these structures is entosis, which is presumably associated with possible carcinogenesis and tumour progression. The peculiarity of the process is that entotic cells themselves actively invade the host cell, and afterwards have several possible variants of fate. Entotic formations are structures where one cell is engulfed by another cell, creating a cell-in-cell structure. The nucleus of the outer cell has a crescent shape, while the inner cell is surrounded by a large entotic vacuole. These characteristics differentiate entosis from cell cannibalism. It's worth noting that entotic formations are not necessarily harmful and may even be beneficial in some cases. In this article we will consider the mechanism of entosis and variants of entotic cell death, and also put forward hypothesis about possible variants of participation of this process on the formation and progression of cancer. This article also presents our proposed classification of functional forms of entosis.

Cell-in-Cell-Mediated Entosis Reveals a Progressive Mechanism in Pancreatic Cancer

BACKGROUND & AIMS

Pancreatic ductal adenocarcinoma (PDAC) is a deadly malignancy with high intratumoral heterogeneity. There is a lack of effective therapeutics for PDAC. Entosis, a form of nonapoptotic regulated cell death mediated by cell-in-cell structures (CICs), has been reported in multiple cancers. However, the role of entosis in PDAC progression remains unclear.

METHODS

CICs were evaluated using immunohistochemistry and immunofluorescence staining. The formation of CICs was induced by suspension culture. Through fluorescence-activated cell sorting and single-cell RNA sequencing, entosis-forming cells were collected and their differential gene expression was analyzed. Cell functional assays and mouse models were used to investigate malignant phenotypes. Clinical correlations between entosis and PDAC were established by retrospective analysis.

RESULTS

Entosis was associated with an unfavorable prognosis for patients with PDAC and was more prevalent in liver metastases than in primary tumors. The single-cell RNA sequencing results revealed that several oncogenes were up-regulated in entosis-forming cells compared with parental cells. These highly entotic cells demonstrated higher oncogenic characteristics in vitro and in vivo. NET1, neuroepithelial cell transforming gene 1, is an entosis-related gene that plays a pivotal role in PDAC progression and is correlated with poor outcomes.

CONCLUSIONS

Entosis is correlated with PDAC progression, especially in liver metastasis. NET1 is a newly validated entosis-related gene and a molecular marker of poor outcomes. PDAC cells generate a highly aggressive subpopulation marked by up-regulated NET1 via entosis, which may drive PDAC progression.

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.

Fate of Entosis: From the Beginning to the End in Untreated Advanced Breast Cancer

Homotypic entosis is a phenomenon in which one cancer cell invades a neighboring cancer cell and is closed entirely within its entotic vacuole. The fate of entosis can lead to inner cell death or survival. Recent evidence draws attention to entosis as a novel prognostic marker in breast cancer. Nevertheless, little is known about the quantity and quality of the process of entosis in human cancer specimens. Here, for the first time, we analyze the frequency of entotic figures in a case of NOS (Non-Other Specified) breast cancer with regard to location: the primary tumor, regional lymph node, and distant metastasis. For the identification of entotic figures, cells were stained using hematoxylin/eosin and assessed using criteria proposed by Mackay. The majority of entotic figures (65%) were found in the lymph node, 27% were found in the primary tumor, and 8% were found in the far metastasis. In the far metastases, entotic figures demonstrated an altered, atypic morphology. Interestingly, in all locations, entosis did not show any signs of cell death. Moreover, the slides were stained for E-cadherin or Ki67, and we identified proliferating (Ki67-positive) inner and outer entotic cells. Therefore, we propose additional criteria for the identification of pro-survival entotic structures in diagnostic histopathology.