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.

Homotypic Entosis as a Potential Novel Diagnostic Marker in Breast Cancer.

Homotypic entotic figures, which are a form of "cell-in-cell" structures, are considered a potential novel independent prognostic marker in various cancers. Nevertheless, the knowledge concerning the biological role of this phenomenon is still unclear. Since breast cancer cells are remarkably entosis-competent, we aimed to investigate and compare the frequency of entoses in a primary breast tumor and in its lymph node metastasis. Moreover, as there are limited data on defined molecular markers of entosis, we investigated entosis in correlation with classical breast cancer biomarkers used in routine pathomorphological diagnostics (HER2, ER, PR, and Ki67). In the study, a cohort of entosis-positive breast cancer samples paired into primary lesions and lymph node metastases was used. The inclusion criteria were a diagnosis of NOS cancer, lymph node metastases, the presence of entotic figures in the primary lesion, and/or lymph node metastases. In a selected, double-negative, HER2-positive NOS breast cancer case, entoses were characterized by a correlation between an epithelial-mesenchymal transition and proliferation markers. We observed that in the investigated cohort entotic figures were positively correlated with Ki67 and HER2, but not with ER or PR markers. Moreover, for the first time, we identified Ki67-positive mitotic inner entotic cells in clinical carcinoma samples. Our study performed on primary and secondary breast cancer specimens indicated that entotic figures, when examined by routine HE histological staining, present potential diagnostic value, since they correlate with two classical prognostic factors of breast cancer.

New gold (III) cyanide complex TGS 121 induces ER stress, proteasome inhibition and death of Ras-hyperactivated cells.

Metal-based agents in cancer therapy, like cisplatin and its derivates, have established clinical applications but also can induce serious side effects. Thus, metallotherapeutic alternatives for platinum derivatives are developed and intensively studied. Platinum is replaced by several transition metals including gold. Especially gold (III) complexes can have the same square-planar structure and are isoelectric with platinum (II). Hence, they are developed as potential anti-cancer drugs. Thus, our group projected and developed a group of novel cyanide-based gold (III) complexes. Within this work, we aimed to characterize the safety and effectivity of one of them, TGS 121. TGS 121 in our preliminary work was selective for Ras-hyperactivated cells. Here we studied the effects of the novel complex in cancerous Ras-3 T3 and non-cancerous NIH-3 T3 cells. The complex TGS 121 turned out to be non-toxic for NIH-3 T3 cells and to induce death and alternations in Ras-hyperactivated cells. We found induction of ER stress, mitochondria swelling, proteasome inhibition, and cell cycle block. Moreover, TGS 121 inhibited cell migration and induced the accumulation of perinuclear organelles that was secondary to proteasome inhibition. Results presented in this report suggest that stable gold-cyanide TGS 121 complex is non-toxic, with a targeted mechanism of action and it is promising in anticancer drug discovery.

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.

Novel podophyllotoxin and benzothiazole derivative induces transitional morphological and functional changes in HaCaT cells.

Podophyllotoxin (PPT) is an antimitotic drug used topically in the treatment of anogenital warts. Due to its toxicity it cannot be administered systemically as an anticancer agent. However, modified PPT derivatives such as etoposide and teniposide are used clinically as systemic agents. Thus, we invented novel PPT derivative KL3 that was synthesized by photocyclization. Earlier we have shown that KL3 has an anticancer effect in various cell lines. Here we compared the toxicity of KL3 vs PPT on non-cancerous normal human keratinocytes (HaCaT) and peripheral blood mononuclear cells (PBMC) showing that KL3 is less toxic than PPT to non-cancerous cells. At concentrations that neither induced cell death, nor affected cell cycle, KL3 in HaCaT cells evoked transient ultrastructural features of ER stress, swelling of mitochondria and elongation of cytoplasmic processes. Those changes partially reversed with prolonged incubation while features of autophagy were induced. PPT in equivalent concentrations induced HaCaT cell death by cell cycle arrest, intrinsic apoptosis and finally disintegration of cell membranes followed by secondary necrosis. In conclusion, we show that the KL3 derivative of PPT in contrast to PPT allows repair of normal keratinocytes and triggers mechanisms that restore non-tumor cell homeostasis.

Entosis: From Cell Biology to Clinical Cancer Pathology.

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.

Semispecific TPPII inhibitor Ala-Ala-Phe-chloromethylketone (AAF-cmk) displays cytotoxic activity by induction of apoptosis, autophagy and protein aggregation in U937 cells.

INTRODUCTION: The main component of extralysosomal proteolysis is the ubiquitin-proteasome system (UPS), which is supplemented by tripeptidyl peptidase II (TPPII). That system is a target for anticancer strategies by using proteasome inhibitors. Data from several studies on leukemic cells share evidence for the beneficial and potential role of TPPII in cell survivability. Therefore, the aim of this work was to analyze the effect of AAF-cmk, a membrane permeable semi-specific TPPII inhibitor, on human monocytic leukemic cells U937 for translational research. MATERIAL AND METHODS: We studied the viability of U937 cells incubated with AAF-cmk using tetrazolium salt reduction assay (MTT) and apoptosis induction by assessing caspase activation by Western blotting and Annexin V binding assays. Transmission electron microscopy (TEM), a gold standard for apoptosis and autophagy detection, was used to assess the ultrastructure of U937 cells. RESULTS: Incubation of cells with AAF-cmk reduced their viability and induced apoptosis by intrinsic pathway. In groups treated with AAF-cmk, activation of caspases 9 and 3 was observed and caspase inhibition by zVDA restored cell viability. TEM revealed the presence of ultrastructural features of apoptosis and authophagy. Moreover, we identified two types of protein aggregates. The first one was found in close proximity to the endoplasmic reticulum (ER) and corresponds to Aggresome-Like Structure (ALIS); however, the second novel type of aggregate was not related to ER elements, but rather to free cytosolic ribosomes. This type did not correspond to the aggresome neither in localization nor the structure, thus we referred these aggregates as ALiSNER (Aggresome-Like Structure Not Associated With the ER). CONCLUSIONS: Our results provide novel and important findings about the role of TPPII in protein homeostasis and cell survival. Since semispecific TPPII inhibitor AAF-cmk displays cytotoxic activity against leukemic U937 cells in vitro it can be considered as a potential anticancer agent.

Biodistribution and Efficacy Studies of the Proteasome Inhibitor BSc2118 in a Mouse Melanoma Model.

Inhibition of the proteasome offers many therapeutic possibilities in inflammation as well as in neoplastic diseases. However, clinical use of proteasome inhibitors is limited by the development of resistance or severe side effects. In our study we characterized the anti-tumor properties of the novel proteasome inhibitor BSc2118. The sensitivity of tumor lines to BSc2118 was analyzed in comparison to bortezomib using crystal violet staining in order to assess cell viability. The In Vivo distribution of BSc2118 in mouse tissues was tracked by a fluorescent-modified form of BSc2118 (BSc2118-FL) and visualized by confocal microscopy. Inhibition of the 20S proteasome was monitored both in cultured cell lines and in mice, respectively. Finally, safety and efficacy of BSc2118 was evaluated in a mouse melanoma model. BSc2118 inhibits proliferation of different tumor cell lines with a similar potency as compared with bortezomib. Systemic administration of BSc2118 in mice is well tolerated, even when given in a dose of 60 mg/kg body weight. After systemic injection of BSc2118 or bortezomib similar proteasome inhibition patterns are observed within the murine organs. Detection of BSc2118-FL revealed correlation of distribution pattern of BSc2118 with inhibition of proteasomal activity in cells or mouse tissues. Finally, administration of BSc2118 in a mouse melanoma model shows significant local anti-tumor effects. Concluding, BSc2118 represents a novel low-toxic agent that might be alternatively used for known proteasome inhibitors in anti-cancer treatment.

AAF-cmk sensitizes tumor cells to trail-mediated apoptosis.

TRAIL is a member of the tumor necrosis factor (TNF) superfamily. This cytokine is cytotoxic for a high proportion of tumor cells, but could be also toxic for normal cells. There is a need to find other agents able to potentiate the antitumor effects of this cytokine. In our study, we found that Ala-Ala-Phe-chloromethylketone (AAF-cmk) augmented cytotoxic activity of TRAIL or TNF against human leukemic cells. Flow cytometry studies and electron microscopy revealed that apoptosis was primarily responsible for this potentiation. Altogether, our studies indicate that AAF-cmk might effectively sensitize human leukemia cells to apoptosis induced by TRAIL and TNF.