Induction of entosis in prostate cancer cells by nintedanib and its therapeutic implications

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 structure in cancer: evading strategies from anti-cancer therapies

One of the regulated forms of cell death is the cell-in-cell (CIC) structure, in which a surviving cell is engulfed by another cell, a mechanism that causes the death of the engulfed cell by an adjacent cell. Several investigators have previously shown that the presence of CICs is an independent risk factor significantly associated with decreased survival in patients with various types of cancer. In this review, we summarize the role of CIC in the tumor microenvironment (TME), including changes and crosstalk of molecules and proteins in the surrounding CIC, and the role of these factors in contributing to therapeutic resistance acquisition. Moreover, CIC structure formation is influenced by the modulation of TME, which may lead to changes in cellular properties. Future use of CIC as a clinical diagnostic tool will require a better understanding of the effects of chemotherapy on CIC, biomarkers for each CIC formation process, and the development of automated CIC detection methods in tissue sections of tumor specimens.

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.

V. J, Pal S, Nair BG, Kar R, Mishra N. Paraptosis: a unique cell death mode for targeting cancer

Programmed cell death (PCD) is the universal process that maintains cellular homeostasis and regulates all living systems' development, health and disease. Out of all, apoptosis is one of the major PCDs that was found to play a crucial role in many disease conditions, including cancer. The cancer cells acquire the ability to escape apoptotic cell death, thereby increasing their resistance towards current therapies. This issue has led to the need to search for alternate forms of programmed cell death mechanisms. Paraptosis is an alternative cell death pathway characterized by vacuolation and damage to the endoplasmic reticulum and mitochondria. Many natural compounds and metallic complexes have been reported to induce paraptosis in cancer cell lines. Since the morphological and biochemical features of paraptosis are much different from apoptosis and other alternate PCDs, it is crucial to understand the different modulators governing it. In this review, we have highlighted the factors that trigger paraptosis and the role of specific modulators in mediating this alternative cell death pathway. Recent findings include the role of paraptosis in inducing anti-tumour T-cell immunity and other immunogenic responses against cancer. A significant role played by paraptosis in cancer has also scaled its importance in knowing its mechanism. The study of paraptosis in xenograft mice, zebrafish model, 3D cultures, and novel paraptosis-based prognostic model for low-grade glioma patients have led to the broad aspect and its potential involvement in the field of cancer therapy. The co-occurrence of different modes of cell death with photodynamic therapy and other combinatorial treatments in the tumour microenvironment are also summarized here. Finally, the growth, challenges, and future perspectives of paraptosis research in cancer are discussed in this review. Understanding this unique PCD pathway would help to develop potential therapy and combat chemo-resistance in various cancer.

Cell Death by Entosis: Triggers, Molecular Mechanisms and Clinical Significance

Entosis—a homotypic insertion of one cell into another, resulting in a death of the invading cell—has been described in many reports, but crucial aspects of its molecular mechanisms and clinical significance still remain controversial. While actomyosin contractility of the invading cell is very well established as a driving force in the initial phase, and autophagy induced in the outer cell is determined as the main mechanism of degradation of the inner cell, many details remain unresolved. The multitude of triggering factors and crisscrossing molecular pathways described in entosis regulation make interpretations difficult. The question of the physiological role of entosis also remains unanswered. In this review, we summarize the knowledge of molecular mechanisms and clinical data concerning entosis accumulated so far, highlighting both coherent explanations and controversies.

Androgen deprivation‑induced OPHN1 amplification promotes castration‑resistant prostate cancer

Androgen deprivation therapy (ADT) is used to treat prostate cancer (PCa). However, ADT may increase the expression of androgen receptor (AR) through the amplification of chromosome X. The gene oligophrenin 1 (OPHN1) is located in the same region as the AR gene, which could be amplified by ADT. Thus, the role of OPHN1 in PCa pathology was investigated. The expression status of OPHN1 in PCa was searched in The Cancer Genome Atlas (TCGA) database. Androgen-sensitive cells LNCaP and 22RV1 were cultured under ADT conditions, and then the expression of OPHN1 was evaluated by northern blotting. The expression of OPHN1 was enhanced or knocked down in LNCaP and 22RV1 cells by transfection. Subsequently, the LNCaP and 22RV1 cells were cultured under ADT, and the viability rate, apoptosis, and migration of cells were assessed by MTT, flow cytometry, and Transwell assay respectively. The expression of OPHN1 was also enhanced or knocked down in androgen-insensitive PC3 cells, and then the effects of OPHN1 on the viability, apoptosis, and migration of PC3 cells were assessed. A mouse xenograft model was created by injecting LNCaP cells with OPHN1 overexpression subcutaneously, and the tumor growth rates were monitored. In TCGA database, amplification of the OPHN1 gene was observed in the PCa tumors. ADT increased the expression of OPHN1 in LNCaP and 22RV1 cells (P<0.05). OPHN1 could promote resistance of LNCaP and 22RV1 cells to ADT by promoting cell survival and preventing their apoptosis (P<0.05). In addition, OPHN1 contributed to cell viability (P<0.05) and enhanced the migration ability in LNCaP, 22RV1 and PC3 cells (P<0.05). In the mouse model, the PCa xenograft with OPHN1 overexpression had a higher growth rate and was more resistant to the ADT condition (P<0.05). In summary, ADT induced the overexpression of OPHN1 in PCa, which facilitated PCa cell survival and promoted PCa progression.

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.

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

Background

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

Methods

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

Results

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

Conclusions

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

Entosis: From Cell Biology to Clinical Cancer Pathology

Simple Summary

We review published clinico-histopathological studies establishing entosis an important prognostic and predictor factor in various cancer types. We also propose a new model to study this phenomenon, which involves active entry of one cell into another one. The internalized cell can remain viable and leave the host cell after a long time, potentially leading to cancer recurrence. Entotic figures are cell in cell structures, in which the nucleus of external cell is crescent-shaped, and the inner cell is surrounded by the extensive space entotic vacuole, distinguishing entosis from cell cannibalism. Entosis correlates with cancer worse prognosis in head and neck squamous cell carcinoma, anal carcinoma, lung adenocarcinoma, pancreatic ductal carcinoma, and some breast ductal carcinoma. The BxPC-3 pancreatic cancer cells provide a new, more convenient model for entosis research in comparison to the previously described semidherent MCF7 model. BxPC-3 cells undergo and survive spontaneous entosis in normal adherent culture conditions.

Abstract

Entosis is a phenomenon, in which one cell enters a second one. New clinico-histopathological studies of entosis prompted us to summarize its significance in cancer. It appears that entosis might be a novel, independent prognostic predictor factor in cancer histopathology. We briefly discuss the biological basis of entosis, followed by a summary of published clinico-histopathological studies on entosis significance in cancer prognosis. The correlation of entosis with cancer prognosis in head and neck squamous cell carcinoma, anal carcinoma, lung adenocarcinoma, pancreatic ductal carcinoma and breast ductal carcinoma, is shown. Numerous entotic figures are associated with a more malignant cancer phenotype and poor prognosis in many cancers. We also showed that some anticancer drugs could induce entosis in cell culture, even as an escape mechanism. Thus, entosis is likely beneficial for survival of malignant cells, i.e., an entotic cell can hide from unfavourable factors in another cell and subsequently leave the host cell remaining intact, leading to failure in therapy or cancer recurrence. Finally, we highlight the potential relationship of cell adhesion with entosis in vitro, based on the model of the BxPc3 cells cultured in full adhesive conditions, comparing them to a commonly used MCF7 semiadhesive model of entosis.

Dietary Fucoxanthin Induces Anoikis in Colorectal Adenocarcinoma by Suppressing Integrin Signaling in a Murine Colorectal Cancer Model

Fucoxanthin (Fx), abundantly contained in edible brown algae, is a carotenoid with strong anti-cancer potential. Anoikis is an anchor-dependent apoptosis particularly related to integrin signaling, and a target for cancer preventive strategies. We recently demonstrated that Fx prevented colon cancer in azoxymethane-dextrane sodium sulfate (AOM/DSS) carcinogenic model mice, and that it increased anoikis-like integrin β1^low/-/cleaved caspase-3^high cells in colonic mucosal crypts. However, an induction mechanism of anoikis by Fx in adenocarcinoma tissue remains unresolved. Thus, we investigated anoikis in colonic adenocarcinoma in AOM/DSS mice. Fx administration (30 mg/kg body weight) significantly suppressed the incidence and multiplicity of colonic adenocarcinoma in AOM/DSS mice. A number of anoikis-like integrin β1^low/-/cleaved caspase-3^high cells in colonic adenocarcinoma and mucosal crypts were significantly increased, 8.3- and 3.5-fold in the Fx group compared with those of the control group, respectively. The results indicated the increase of anoikis-like cells occurred more strongly in colonic adenocarcinoma than in colonic mucosal crypts. In addition, integrin β1 expression, and pFAK (Tyr³⁹⁷) and pPaxillin (Tyr³¹) activation in mucosal tissue decreased 0.7-, 0.5- and 0.6-fold by Fx administration, respectively. The results suggest that Fx induces anoikis in colonic adenocarcinoma developed by AOM/DSS treatment through attenuation of integrin signaling.

Cell death mechanisms in eukaryotes

Like the organism they constitute, the cells also die in different ways. The death can be predetermined, programmed, and cleanly executed, as in the case of apoptosis, or it can be traumatic, inflammatory, and sudden as many types of necrosis exemplify. Nevertheless, there are a number of cell deaths-some of them bearing a resemblance to apoptosis and/or necrosis, and many, distinct from each-that serve a multitude of roles in either supporting or disrupting the homoeostasis. Apoptosis is coordinated by death ligands, caspases, b-cell lymphoma-2 (Bcl-2) family proteins, and their downstream effectors. Events that can lead to apoptosis include mitotic catastrophe and anoikis. Necrosis, although it has been considered an abrupt and uncoordinated cell death, has many molecular events associated with it. There are cell death mechanisms that share some standard features with necrosis. These include methuosis, necroptosis, NETosis, pyronecrosis, and pyroptosis. Autophagy, generally a catabolic pathway that operates to ensure cell survival, can also kill the cell through mechanisms such as autosis. Other cell-death mechanisms include entosis, ferroptosis, lysosome-dependent cell death, and parthanatos.

Cell-in-Cell Phenomenon and Its Relationship With Tumor Microenvironment and Tumor Progression: A Review

The term cell-in-cell, morphologically, refers to the presence of one cell within another. This phenomenon can occur in tumors but also among non-tumor cells. The cell-in-cell phenomenon was first observed 100 years ago, and it has since been found in a variety of tumor types. Recently, increasing attention has been paid to this phenomenon and the underlying mechanism has gradually been elucidated. There are three main related process: cannibalism, emperipolesis, and entosis. These processes are affected by many factors, including the tumor microenvironment, mitosis, and genetic factors. There is considerable evidence to suggest that the cell-in-cell phenomenon is associated with the prognosis of cancers, and it promotes tumor progression in most situations. Notably, in pancreatic cancer, the cell-in-cell phenomenon is associated with reduced metastasis, which is the opposite of what happens in other tumor types. Thus, it can also inhibit tumor progression. Studies show that cell-in-cell structure formation is affected by the tumor microenvironment, and that it may lead to changes in cellular characteristics. In this review, we summarize the different cell-in-cell processes and discuss their role in tumor progression and how they are regulated by different mechanisms.

The Jun N-terminal kinases signaling pathway plays a "seesaw" role in ovarian carcinoma: a molecular aspect

Ovarian cancer is the most common gynecological malignancy that causes cancer-related deaths in women today; this being the case, developing an understanding of ovarian cancer has become one of the major driving forces behind cancer research overall. Moreover, such research over the last 20 years has shown that the Jun N-terminal kinase (JNK) signaling pathway plays an important role in regulating cell death, survival, growth and proliferation in the mitogen-activated protein kinases (MAPK) signaling pathway, an important pathway in the formation of cancer. Furthermore, the JNK signaling pathway is often regulated by an abnormal activation in human tumors and is frequently reported in the literature for its effect on the progression of ovarian cancer. Although the FDA has approved some JNK inhibitors for melanoma, the agency has not approved JNK inhibitors for ovarian cancer. However, there are some experimental data on inhibitors and activators of the JNK signaling pathway in ovarian cancer, but related clinical trials need to be further improved. Although the Jun N-terminal kinase (JNK) signaling pathway is implicated in the formation of cancer in general, research has also indicated that it has a role in suppressing cancer as well. Here, we summarize this seemingly contradictory role of the JNK signaling pathway in ovarian cancer, that ‘seesaws’ between promoting and suppressing cancer, as well as summarizing the application of several JNK pathway inhibitors in cancer in general, and ovarian cancer in particular.