FRINK Linked Data Fragments server

Matches in SemOpenAlex for { <https://semopenalex.org/work/W1997305864> ?p ?o ?g. }

• W1997305864 endingPage "533" @default.
• W1997305864 startingPage "524" @default.
• W1997305864 abstract "Restoration of apoptosis is an important therapeutic strategy for cancer, but bystander effects may be crucial to treatment success. We examined the involvement of bystander effects in the outcome of pro-apoptotic treatments and investigated the role of macrophages. Using a murine N202 breast cancer chamber model and intravital microscopy, we observed bystander apoptosis in vivo in mixed spheroids consisting of bystander N202 cells plus modified N202 cells overexpressing the p14ARF N-terminal region, which promotes p53-mediated apoptosis. The effect was not observed in cocultures in vitro, and could not be transferred through conditioned medium from modified N202 cells. However, if macrophages were also included in the N202 co-cultures, bystander apoptosis was restored, and correlated with elevated surface expression of phosphatidyl serine, a macrophage recognition molecule, on the modified N202 cells. Bystander killing was not observed in cocultures of N202 cells plus macrophages plus cisplatin-treated or 5-fluorouracil-treated N202 cells, where apoptosis induction in the target cell population was inefficient, suggesting that specific activation of macrophages by apoptotic tumor cells was required. The results suggest that pro-apoptotic therapies benefit both from the intrinsic vulnerability of cancer cells to apoptosis and from an innate immune response that amplifies the therapeutic effect. Restoration of apoptosis is an important therapeutic strategy for cancer, but bystander effects may be crucial to treatment success. We examined the involvement of bystander effects in the outcome of pro-apoptotic treatments and investigated the role of macrophages. Using a murine N202 breast cancer chamber model and intravital microscopy, we observed bystander apoptosis in vivo in mixed spheroids consisting of bystander N202 cells plus modified N202 cells overexpressing the p14ARF N-terminal region, which promotes p53-mediated apoptosis. The effect was not observed in cocultures in vitro, and could not be transferred through conditioned medium from modified N202 cells. However, if macrophages were also included in the N202 co-cultures, bystander apoptosis was restored, and correlated with elevated surface expression of phosphatidyl serine, a macrophage recognition molecule, on the modified N202 cells. Bystander killing was not observed in cocultures of N202 cells plus macrophages plus cisplatin-treated or 5-fluorouracil-treated N202 cells, where apoptosis induction in the target cell population was inefficient, suggesting that specific activation of macrophages by apoptotic tumor cells was required. The results suggest that pro-apoptotic therapies benefit both from the intrinsic vulnerability of cancer cells to apoptosis and from an innate immune response that amplifies the therapeutic effect. There is a growing interest in the process of apoptosis as a target for anticancer strategies. Loss of apoptotic pathways is likely to be essential for the development of cancer, as most cancer-associated cellular abnormalities such as oncogene activation and DNA damage will trigger apoptosis if these pathways are intact.1Hanahan D Weinberg RA The hallmarks of cancer.Cell. 2000; 100: 57-70Abstract Full Text Full Text PDF PubMed Scopus (22047) Google Scholar Restoration of apoptosis would therefore be highly suppressive of all or most cancers. In addition, apoptotic cells undergo membrane changes that promote their recognition and engulfment by macrophages.2Fadeel B Programmed cell clearance.Cell Mol Life Sci. 2003; 60: 2575-2585Crossref PubMed Scopus (85) Google Scholar, 3Fadeel B Orrenius S Apoptosis: a basic biological phenomenon with wide-ranging implications in human disease.J Intern Med. 2005; 258: 479-517Crossref PubMed Scopus (503) Google Scholar, 4Fadeel B Orrenius S Pervaiz S Buried alive: a novel approach to cancer treatment.FASEB J. 2004; 18: 1-4Crossref PubMed Scopus (14) Google Scholar, 5Lauber K Blumenthal SG Waibel M Wesselborg S Clearance of apoptotic cells: getting rid of the corpses.Mol Cell. 2004; 14: 277-287Abstract Full Text Full Text PDF PubMed Scopus (472) Google Scholar Because of this, apoptotic cell death, unlike non-apoptotic forms of cell death, does not result in the release of cellular debris into the tumor microenvironment, an event that can trigger an inflammatory response that leads to further tissue damage.6Savill J Fadok V Corpse clearance defines the meaning of cell death.Nature. 2000; 407: 784-788Crossref PubMed Scopus (1271) Google Scholar Restoration of apoptosis as a therapeutic strategy, therefore, could provide a highly physiological approach to tumor suppression by exploiting the intrinsic fragility of the cancer cell to apoptotic cell death, and by recruiting the participation of the innate immune system to clear apoptotic cells. The possible recruitment of macrophages by apoptotic treatments could provide a mechanism for bystander killing as well, a mechanism that may not be available with treatments that induce non-apoptotic cell death. Once they have been activated by contact with apoptotic tumor cells, macrophages might be able to recognize and engulf non-apoptotic bystander tumor cells. Activated macrophages have been shown to specifically recognize and destroy neoplastic cells,7Fidler IJ Recognition and destruction of target cells by tumoricidal macrophages.Isr J Med Sci. 1978; 14: 177-191PubMed Google Scholar and liposome-encapsulated macrophage activators have been shown to have antitumor activity in tumor-bearing mice,8Tanguay S Bucana CD Wilson MR Fidler IJ von Eschenbach AC Killion JJ In vivo modulation of macrophage tumoricidal activity by oral administration of the liposome-encapsulated macrophage activator CGP 19835A.Cancer Res. 1994; 54: 5882-5888PubMed Google Scholar and in patients with cancer.9Killion JJ Fidler IJ Therapy of cancer metastasis by tumoricidal activation of tissue macrophages using liposome-encapsulated immunomodulators.Pharmacol Ther. 1998; 78: 141-154Crossref PubMed Scopus (52) Google Scholar Macrophages are known to infiltrate tumors and to play both pro- and antitumor roles.10Lewis C Murdoch C Macrophage responses to hypoxia: implications for tumor progression and anti-cancer therapies.Am J Pathol. 2005; 167: 627-635Abstract Full Text Full Text PDF PubMed Scopus (336) Google Scholar, 11Ohno S Ohno Y Suzuki N Karnei T Koike K Inagawa H et al.Correlation of histological localization of tumor-associated macrophages with clinicopathological features in endometrial cancer.Anticancer Res. 2004; 24: 3335-3342PubMed Google Scholar Those macrophages that infiltrate cancer cell “nests” and are in close contact with cancer cells are likely to play antitumor roles, as their presence has been shown to be associated with a favorable prognosis.11Ohno S Ohno Y Suzuki N Karnei T Koike K Inagawa H et al.Correlation of histological localization of tumor-associated macrophages with clinicopathological features in endometrial cancer.Anticancer Res. 2004; 24: 3335-3342PubMed Google Scholar In this study, we have sought to clarify the involvement of bystander effects, and the possible role of tumor-associated macrophages, in the outcome of pro-apoptotic therapies. As most cancer therapies, including gene therapy to restore apoptosis, do not reach all of the cells within a tumor, bystander mechanisms, if properly recruited, could be critical to the therapeutic outcome. We have used intravital fluorescence microscopy to examine the in vivo behavior of tumor spheroids of N202 breast cancer cells, in which a fraction of the cells has been modified to trigger p53-mediated apoptosis. We provide direct visual evidence for bystander killing in vivo and show that macrophages, activated by close contact with apoptotic tumor cells, but not tumor cells undergoing non-apoptotic cell death in response to chemotherapy, are possible mediators of this effect. N202 cells express endogenous wild-type p53 and undergo p53-mediated apoptosis in response to ectopic expression of p14ARF,12Huang Y Tyler T Saadatmandi N Lee C Borgstrom P Gjerset RA Enhanced tumor suppression by a p14ARF/p53 bicistronic adenovirus through increased p53 protein translation and stability.Cancer Res. 2003; 63: 3646-3653PubMed Google Scholar a key positive regulator of p53 stability and function.13Kamijo T Weber JD Zambetti G Zindy F Roussel MF Sherr CJ Functional and physical interactions of the ARF tumor suppressor with p53 and Mdm2.Proc Natl Acad Sci USA. 1998; 95: 8292-8297Crossref PubMed Scopus (785) Google Scholar, 14Zhang Y Xiong Y Yarbrough WG ARF promotes MDM2 degradation and stabilizes p53: ARF-INK4a locus deletion impairs both the Rb and p53 tumor suppression pathways.Cell. 1998; 92: 725-734Abstract Full Text Full Text PDF PubMed Scopus (1393) Google Scholar The N-terminal, exon 1β-encoded domain of p14ARF has been shown to be sufficient for stabilization of the p53 protein and activation of the p53 pathway.15Midgley CA Desterro JM Saville MK Howard S Sparks A Hay RT et al.An N-terminal p14ARF peptide blocks Mdm2-dependent ubiquitination in vitro and can activate p53 in vivo.Oncogene. 2000; 19: 2312-2323Crossref PubMed Scopus (230) Google Scholar When we treated N202 cells with a replication-defective adenoviral vector (Ad1β) encoding the ARF N-terminal region, we observed suppression of 72 h in vitro cell viability (Figure 1a), accompanied by an accumulation of p53 protein and induction of the p53-downstream targets, p21, mdm2, and bax, evaluated by Western analysis 48 h post vector treatment (Figure 1b). We also observed an elevation of the bax to bcl2 ratio (characteristic of cells undergoing p53-mediated apoptosis) (Figure 1b) and an increased fraction of cells (18%) with a sub-G1 DNA content (characteristic of apoptotic cells), evaluated by flow cytometry of propidium iodide (PI)-stained cells 48 h post vector treatment (Figure 1c). We used an N202 tumor model to examine how apoptotic N202 cells affected the in vivo behavior of non-apoptotic bystander N202 cells. Mixed tumor spheroids composed of Ad1β-treated or control (AdLuc)-treated N202 cells (designated N202-Ad1β and N202-AdLuc, respectively) together with untreated bystander N202 cells were implanted into dorsal skin-fold chambers in nude mice as described in Materials and Methods and examined by fluorescence intravital microscopy. Spheroids were prepared such that vector-treated cells comprised 50 or 25% of the total starting cell mass. Vector-treated and bystander cell populations were distinguished by different fluorescence markers. Bystander cells (designated “N202-H2B/GFP”) expressed a histone H2B/green fluorescent protein (GFP) fusion protein that localized to the nucleus and enabled us to visualize apoptotic and mitotic nuclear events in this population. The vector-treated cell populations were labeled with the Rhodamine dye, 5-(and-6)-(((4-chloromethyl) benzoyl) amino) tetramethylrhodamine (CMTMR), which distributed throughout the cell. Control chambers were implanted with spheroids composed entirely of untreated N202-H2B/GFP cells. For each spheroid type, three animals were used. Representative chambers containing spheroids composed of 50% vector-treated cells are shown in Figure 2a at 3 days post-implantation. As expected, based on the results shown in Figure 1, N202-AdLuc cells remained viable and formed a solid tumor cell mass that displayed a diffuse fluorescence intensity consistent with packed healthy cells (Figure 2a, top left), whereas N202-Ad1β cells displayed evidence of cell death, revealed by the appearance of isolated, collapsed, densely staining bodies of dead or dying cells (Figure 2a, top right). Arrows indicate typical dead or dying cells. The panels in the bottom row of Figure 2a show the behavior of the respective bystander populations in these same fields. When bystander N202-H2B/GFP cells were present by themselves in control spheroids (Figure 2, bottom left), or when they were present in mixed spheroids with 50% N202-AdLuc cells (Figure 2, bottom middle), they remained viable and gave rise to a solid tumor mass that displayed a diffuse GFP fluorescence characteristic of packed healthy cells. AdLuc-treatment, therefore, had no in vivo toxicity to either target cells or bystander cells and did not trigger a host response to viral proteins in this system. In contrast, when bystander N202-H2B/GFP cells were mixed with N202-Ad1β cells, they underwent apoptosis, characterized by the appearance of bright condensed nuclei, a feature of the early stages of apoptosis (Figure 2a, bottom right). Arrows indicate typical examples of apoptotic bystander cells. Figure 2c plots the average quantitative changes in the integrated fluorescence intensity (proportional to cell number) of bystander cells (black bars) and vector-treated cells (open bars) on day 3 post implantation relative to day 1, in the three experimental animals per group. When N202-H2B/GFP bystander cells were present by themselves in control spheroids (Figure 2c, black bar a), or when they were present in mixed spheroids with 50% N202-AdLuc cells (Figure 2c, black bar b), their average number remained high. In contrast, in mixed spheroids with 25 or 50% N202-Ad1β cells (Figure 2c, black bars c and d, respectively), the average bystander cell number dropped to about 60 and 50% of day 1 values, respectively. A significant difference in average bystander cell number was observed between spheroids composed of 50% Adluc and 50% Ad1β-treated cells (Figure 2c, black bar d versus b, P<0.05). As shown by the open bars in Figure 2c, the average integrated CMTMR fluorescence intensity of N202-Ad1β cells also decreased on day 3 post implantation relative to day 1 in both types of mixed spheroids (open bars c and d). Figure 2d plots the quantitative changes in numbers of apoptotic bodies in the bystander cell population (black bars) or condensed dead cells in the vector-treated cell population (open bars), on day 3 post implantation in the various spheroid types. Numbers were obtained by counting two representative fields per chamber and averaging over the three animals per group. As shown in Figure 2d (black bars c and d), mixed spheroids containing N202-Ad1β cells showed elevated numbers of apoptotic bystander cells. Mixed spheroids containing 50% N202-Ad1β cells (black bar d) had significantly more apoptotic bystander cells than the mixed spheroids containing 50% N202-AdLuc cells (back bar b) with P<0.05. Within the N202-Ad1β cell population itself, the number of collapsed or pyknotic figures characteristic of cell death was elevated in both 50 and 25% mixed spheroid types relative to mixed spheroids containing N202-AdLuc cells (open bars, Figure 2d). Because suppression of neovascularization by p53-transduced tumor cells may contribute to bystander killing in some systems,16Nishizaki M Fujiwara T Tanida T Hizuta A Nishimori H Tokino T et al.Recombinant adenovirus expressing wild-type p53 is antiangiogenic: a proposed mechanism for bystander effect.Clin Cancer Res. 1999; 5: 1015-1023PubMed Google Scholar we compared the appearance of the tumor vasculature by transillumination in chambers implanted with mixed spheroids containing 50% Ad-Luc-treated cells or 50% Ad1β-treated cells (Figure 2b). Consistent with our previous observations,12Huang Y Tyler T Saadatmandi N Lee C Borgstrom P Gjerset RA Enhanced tumor suppression by a p14ARF/p53 bicistronic adenovirus through increased p53 protein translation and stability.Cancer Res. 2003; 63: 3646-3653PubMed Google Scholar we saw little evidence for neovascularization on day 3 post implantation, in either control chambers (50% AdLuc-treated cells, Figure 2b, top panel) or in chambers containing 50% Ad1β-treated cells (Figure 2b, bottom panel), although bystander effects were seen to be pronounced at this time point (Figure 2a). The observations are consistent with the RT–PCR results in Figure 2e, where expression of vascular endothelial cell growth factor and thrombospondin-1, two genes involved in positive and negative regulation of vascularization, respectively, and regulated by p53 in some systems,16Nishizaki M Fujiwara T Tanida T Hizuta A Nishimori H Tokino T et al.Recombinant adenovirus expressing wild-type p53 is antiangiogenic: a proposed mechanism for bystander effect.Clin Cancer Res. 1999; 5: 1015-1023PubMed Google Scholar, 17Dameron KM Volpert OV Tainsky MA Bouck N Control of angiogenesis in fibroblasts by p53 regulation of thrombospondin-1.Science. 1994; 265: 1582-1584Crossref PubMed Scopus (1315) Google Scholar were found to be similar 48 h following treatment of N202 cells with AdLuc or Ad1β. As shown in both top and bottom panels of Figure 2b, we observed at most the formation of tortuous or budding vessels, two events that precede the formation of neovasculature. These results argue against a host-mediated bystander effect involving changes in tumor vascularization. We carried out in vitro experiments to determine whether apoptosis induction results in production of a secreted factor that could directly inhibit adjacent tumor cell growth and viability. Cell culture supernatants were collected from N202 cells 48 h after treatment with 200 PFU/cell of Ad1β or AdLuc, and assayed for inhibitory activity in 96-well assays. Although Ad1β-treated cells began to display an apoptotic population by 48 h (see Figure 1b), the results plotted in Figure 3a fail to reveal an inhibitory activity in cell culture supernatants from Ad1β-treated cells. To determine whether a bystander effect might require cell contact, we carried out an in vitro cocultivation experiment similar to the in vivo experiment with mixed spheroids described in Figure 2. Following vector treatment of cells we plated 1:1 mixtures of untreated cells (N202-H2B/GFP) plus vector-treated cells (CMTMR-stained N202-AdLuc or N202-Ad1β) in 24-well plates at 105 cells/well, a density that provides about 60% confluency. As shown in Figure 3b, on day 2 following plating, untreated N202-H2B/GFP cells remained viable and continued dividing in both mixed populations (see mitotic figure “Mi”, Figure 3b, bottom row, right panel) and apoptotic nuclei were rare (estimated to represent about 2±1% and 2.5±0.7% of the bystander cell population in the mixtures with N202-AdLuc and N202-Ad1β cells, respectively). CMTMR-stained N202-AdLuc cells also remained viable and adherent on day 2 following plating (Figure 3b, top row, middle panel). However, CMTMR-stained N202-Ad1β cells began to die and detach on day 2 following plating (Figure 3b, bottom row, middle panel). N202-Ad1β cells were largely floating cells by 4 days post-treatment (not shown). Thus, under conditions where Ad1β treatment triggered apoptosis in target cells, no bystander killing was observed in vitro. Taken together, these data argue against a cell autonomous mechanism of bystander killing by Ad1β-modified cells in vivo that would involve either a secreted inhibitory factor, or the transfer of an inhibitory factor or signal through direct cell–cell contact. Tumor-associated macrophages recruited from circulating monocytes are integral components of spontaneous human and mouse tumors growing in their natural setting. Importantly, the lack of encapsulation in syngeneic systems such as the N202 system used here, like most spontaneous human and mouse tumors,18Hakansson L Adell G Boeryd B Sjogren F Sjodahl R Infiltration of mononuclear inflammatory cells into primary colorectal carcinomas: an immunohistological analysis.Br J Cancer. 1997; 75: 374-380Crossref PubMed Scopus (43) Google Scholar, 19Kelly PM Davison RS Bliss E McGee JO Macrophages in human breast disease: a quantitative immunohistochemical study.Br J Cancer. 1988; 57: 174-177Crossref PubMed Scopus (136) Google Scholar, 20Moon DC Nakayama J Urabe A Terao H Kinoshita N Hori Y Immunohistochemical characterization of cellular infiltrates in epidermal tumors induced by two-stage and complete chemical carcinogenesis in mouse skin.J Dermatol. 1992; 19: 146-152Crossref PubMed Scopus (10) Google Scholar, 21Strutton GM Gemmell E Seymour GJ Walsh MD Lavin MF Gardiner RA An immunohistological examination of inflammatory cell infiltration in primary testicular seminomas.Aust NZJ Surg. 1989; 59: 169-172Crossref PubMed Scopus (4) Google Scholar allows for macrophage infiltration. We find that tumor-associated macrophages can account for some 40% of the tumor mass (unpublished observations). As shown in Figure 4, macrophage infiltration into N202 spheroids occurred as early as day 3 following spheroid implantation. We have previously observed in mice reconstituted with bone marrow from GFP-transgenic mice, that macrophages are the earliest host cells to infiltrate tumors growing in chambers, appearing within two days of spheroid implantation. This is well before the infiltration of other host cells, including natural killer cells, which occurs after some 7–14 days (P Borgstrom, unpublished observations). Macrophages are therefore a candidate as the mediator of bystander killing. We carried out an in vitro cocultivation experiment similar to the one described in Figure 3, except that monocyte/macrophages, recovered from mouse bone marrow, were included in the cocultures. N202 cells were treated with AdLuc or Ad1β, mixed 1:1 with untreated N202-H2B/GFP cells and plated on monolayers of macrophages. GFP fluorescence was examined 2 days later. As a control for intrinsic cytotoxic activity of macrophages, we cultivated macrophages with N202-H2B/GFP cells in the absence of vector-treated N202 cells. As shown in Figure 5, macrophages were not intrinsically toxic to N202-H2B/GFP cells (Figure 5a) or to N202-H2B/GFP cells mixed 1:1 with Ad-Luc-treated cells (Figure 5b), consistent with other studies.9Killion JJ Fidler IJ Therapy of cancer metastasis by tumoricidal activation of tissue macrophages using liposome-encapsulated immunomodulators.Pharmacol Ther. 1998; 78: 141-154Crossref PubMed Scopus (52) Google Scholar However, when N202-H2B/GFP cells were mixed 1:1 with Ad1β-treated N202 cells, followed by cultivation in the presence of macrophages, extensive apoptosis of the N202-H2B/GFP bystander cells was observed two days later, as seen by the presence of condensed nuclei and nuclei with a heterogeneous fluorescence intensity, indicating condensed, fragmented chromatin typical of an apoptotic nucleus (Figure 5c, arrows indicating Apoptosis, Ap). Figure 5f plots the quantitative changes in apoptotic bodies (apoptotic index=number of apoptotic bodies/number of cells), averaged over three fields for each condition, each field having an area of 0.16 mm2. Bystander killing could not be reproduced by transferring culture supernatants from cocultures of macrophages plus Ad1β-treated N202 cells to N202-H2B/GFP cells (data not shown), indicating either that the effect is transmitted by an unstable product or that it acts only over a short range and requires close contact between macrophages and the tumor cell populations. The effect is not unique to N202 cells. We carried out a series of coculture experiments similar to Figure 5a–c on human MCF-7 breast cancer cells, modified to express histone H2B/GFP (Figure 5i–k). When MCF-7-H2B/GFP cells were mixed 1:1 with Ad1β-treated MCF-7 cells, followed by cocultivation in the presence of macrophages, extensive apoptosis of the MCF-7-H2B/GFP bystander cells was observed 2 days later (Figure 5k). The results provide evidence that a rapidly acting macrophage-mediated bystander effect is triggered in the presence of apoptotic tumor cells. To determine whether the cytotoxic activity of macrophages could also be triggered by chemotherapy-treated tumor cells, we treated N202 cells with the DNA crosslinking chemotherapeutic agent, cisplatin, for 1 h at 40 μM or with the antineoplastic antimetabolite, 5-fluorouracil (5-FU), at 100 μM overnight, before mixing them with N202-H2B/GFP cells and macrophages. The doses of cisplatin and 5-FU were chosen based on the results of the 72-h viability assay shown in Figure 5g, which indicated that the reduction in overall cell viability following each of these treatments was similar to that seen after treatment with 200 PFU/cell Ad1β for 4 h (see Figure 1a). Despite the fact that the three treatments had similar effects on overall cell viability, there was little evidence for bystander cell apoptosis when N202-H2B/GFP cells were mixed 1:1 with cisplatin- or 5-FU-treated cells and cocultivated for 48 h with macrophages. In both cases, nuclei displayed a uniform size and homogeneous fluorescence intensity (Figure 5d and e). To better understand the basis for the differential bystander responses associated with Ad1β treatment and chemotherapy treatment, we compared the mode of cell killing by these treatments. Fluorescence-activated cell sorting analysis of PI-stained cells showed that the cell-cycle distributions of cells 48 h after cisplatin treatment or 5-FU treatment (Figure 5 h) differed from that observed after Ad1β treatment (Figure 1b), suggesting that the mechanisms of cytotoxicity for these treatments were different. Although Ad1β treatment was associated with an accumulation of nearly 20% of cells with sub-G1-phase DNA content characteristic of early stage apoptotic cells (Figure 1b), cisplatin and 5-FU treatment were associated with only about 10 and 8%, respectively, of apoptotic cells (Figure 5h). Untreated N202 cells or AdLuc-treated cells displayed some 2–6% of cells with a sub-G1-phase DNA content (Figures 1b and 5h). Despite the differences in the fraction of apoptotic cells appearing after cisplatin, 5-FU, and Ad1β treatments, overall cell death assayed by trypan blue exclusion, which measures cellular membrane breakdown characteristic of late-stage apoptosis and non-apoptotic cell death, was virtually the same for the two treatments. Forty-eight hours following cisplatin treatment, some 15±1% of cisplatin-treated cells and 16±1% of 5-FU-treated cells stained positive with trypan blue, compared to some 12±2% of Ad1β-treated cells and 3±1% of AdLuc-treated cells. Thus, while cisplatin, 5-FU, and Ad1β produced a similar overall level of cell death in the target cell population, the contribution of apoptosis to that outcome was less for cisplatin and 5-FU than for Ad1β. These results are consistent with a growing body of evidence that non-apoptotic cell death plays an important role in cell death triggered by radiation and many chemotherapeutic agents22Barry MA Behnke CA Eastman A Activation of programmed cell death (apoptosis) by cisplatin, other anticancer drugs, toxins and hyperthermia.Biochem Pharmacol. 1990; 40: 2353-2362Crossref PubMed Scopus (911) Google Scholar, 23Brown JM Attardi LD The role of apoptosis in cancer development and treatment response.Nat Rev Cancer. 2005; 5: 231-237Crossref PubMed Google Scholar, 24Gudkov AV Komarova EA The role of p53 in determining sensitivity to radiotherapy.Nat Rev Cancer. 2003; 3: 117-129Crossref PubMed Scopus (461) Google Scholar, 25Ormerod MG Orr RM Peacock JH The role of apoptosis in cell killing by cisplatin: a flow cytometric study.Br J Cancer. 1994; 69: 93-100Crossref PubMed Scopus (140) Google Scholar, 26Sorenson CM Eastman A Mechanism of cis-diamminedichloroplatinum(II)-induced cytotoxicity: role of G2 arrest and DNA double-strand breaks.Cancer Res. 1988; 48: 4484-4488PubMed Google Scholar and suggested that the mode of tumor cell death could be a factor in triggering a bystander effect. Treatments that maximize apoptotic cell death and minimize non-apoptotic cell death would be most likely to recruit a cytotoxic macrophage response that could help to clear bystander cells. We postulated that the antitumor effect of macrophages might therefore be triggered by direct contact with apoptotic tumor cells, possibly brought about by the increased surface expression on the apoptotic tumor cell of a recognition molecule for macrophages. Various macrophage recognition molecules have been described,2Fadeel B Programmed cell clearance.Cell Mol Life Sci. 2003; 60: 2575-2585Crossref PubMed Scopus (85) Google Scholar, 3Fadeel B Orrenius S Apoptosis: a basic biological phenomenon with wide-ranging implications in human disease.J Intern Med. 2005; 258: 479-517Crossref PubMed Scopus (503) Google Scholar, 4Fadeel B Orrenius S Pervaiz S Buried alive: a novel approach to cancer treatment.FASEB J. 2004; 18: 1-4Crossref PubMed Scopus (14) Google Scholar, 5Lauber K Blumenthal SG Waibel M Wesselborg S Clearance of apoptotic cells: getting rid of the corpses.Mol Cell. 2004; 14: 277-287Abstract Full Text Full Text PDF PubMed Scopus (472) Google Scholar of which phosphatidyl serine (PS) is one of the best characterized.27Fadok VA de Cathelineau A Daleke DL Henson PM Bratton DL Loss of phospholipid asymmetry and surface exposure of phosphatidylserine is required for phagocytosis of apoptotic cells by macrophages and fibroblasts.J Biol Chem. 2001; 276: 1071-1077Crossref PubMed Scopus (523) Google Scholar PS is not normally exposed on the outer surface of the cell, but during the early stages of apoptosis, alterations occur in the plasma membrane of the cell that result in a translocation of PS from the inner leaflet of the intact membrane to the outer surface. The increased surface exposure of PS on apoptotic cells can be detected by immunofluorescence staining with Annexin V, a high-affinity binding protein for PS. We used fluorescein isothiocyanate-Annexin V immunofluorescence analysis to evaluate PS surface exposure on untreated N202 cells, and on N202 cells shortly after exposure to various treatments. Exclusion of the DNA stain, PI, was used to distinguish necrotic cells, which lose membrane integrity and stain positive for PI (orange), from live cells and early stage apoptotic cells, both of which maintain intact membranes and exclude PI. As shown in Figure 6, we observed very weak Annexin V st" @default.
• W1997305864 created "2016-06-24" @default.
• W1997305864 creator A5040449061 @default.
• W1997305864 creator A5042828349 @default.
• W1997305864 creator A5077667025 @default.
• W1997305864 creator A5091100858 @default.
• W1997305864 date "2007-03-01" @default.
• W1997305864 modified "2023-10-13" @default.
• W1997305864 title "Macrophage-mediated Bystander Effect Triggered by Tumor Cell Apoptosis" @default.
• W1997305864 cites W1497435349 @default.
• W1997305864 cites W1515730558 @default.
• W1997305864 cites W1583459471 @default.
• W1997305864 cites W1595815978 @default.
• W1997305864 cites W1782545213 @default.
• W1997305864 cites W1945679349 @default.
• W1997305864 cites W1970484905 @default.
• W1997305864 cites W1979724073 @default.
• W1997305864 cites W1982691186 @default.
• W1997305864 cites W1983751803 @default.
• W1997305864 cites W1984033923 @default.
• W1997305864 cites W1985271970 @default.
• W1997305864 cites W1997219075 @default.
• W1997305864 cites W2004706142 @default.
• W1997305864 cites W2011129758 @default.
• W1997305864 cites W2017846490 @default.
• W1997305864 cites W2033791403 @default.
• W1997305864 cites W2034269086 @default.
• W1997305864 cites W2040881358 @default.
• W1997305864 cites W2042886160 @default.
• W1997305864 cites W2048203018 @default.
• W1997305864 cites W2054162713 @default.
• W1997305864 cites W2055796980 @default.
• W1997305864 cites W2070461153 @default.
• W1997305864 cites W2083261882 @default.
• W1997305864 cites W2084328313 @default.
• W1997305864 cites W2084470802 @default.
• W1997305864 cites W2089457438 @default.
• W1997305864 cites W2141529421 @default.
• W1997305864 cites W2143177251 @default.
• W1997305864 cites W2149200346 @default.
• W1997305864 cites W2160731222 @default.
• W1997305864 cites W2161550927 @default.
• W1997305864 doi "https://doi.org/10.1038/sj.mt.6300080" @default.
• W1997305864 hasPubMedId "https://pubmed.ncbi.nlm.nih.gov/17228313" @default.
• W1997305864 hasPublicationYear "2007" @default.
• W1997305864 type Work @default.
• W1997305864 sameAs 1997305864 @default.
• W1997305864 citedByCount "9" @default.
• W1997305864 countsByYear W19973058642019 @default.
• W1997305864 countsByYear W19973058642020 @default.
• W1997305864 countsByYear W19973058642022 @default.
• W1997305864 crossrefType "journal-article" @default.
• W1997305864 hasAuthorship W1997305864A5040449061 @default.
• W1997305864 hasAuthorship W1997305864A5042828349 @default.
• W1997305864 hasAuthorship W1997305864A5077667025 @default.
• W1997305864 hasAuthorship W1997305864A5091100858 @default.
• W1997305864 hasBestOaLocation W19973058641 @default.
• W1997305864 hasConcept C185592680 @default.
• W1997305864 hasConcept C190283241 @default.
• W1997305864 hasConcept C19106626 @default.
• W1997305864 hasConcept C202751555 @default.
• W1997305864 hasConcept C203014093 @default.
• W1997305864 hasConcept C2779244956 @default.
• W1997305864 hasConcept C502942594 @default.
• W1997305864 hasConcept C54355233 @default.
• W1997305864 hasConcept C86803240 @default.
• W1997305864 hasConcept C95444343 @default.
• W1997305864 hasConceptScore W1997305864C185592680 @default.
• W1997305864 hasConceptScore W1997305864C190283241 @default.
• W1997305864 hasConceptScore W1997305864C19106626 @default.
• W1997305864 hasConceptScore W1997305864C202751555 @default.
• W1997305864 hasConceptScore W1997305864C203014093 @default.
• W1997305864 hasConceptScore W1997305864C2779244956 @default.
• W1997305864 hasConceptScore W1997305864C502942594 @default.
• W1997305864 hasConceptScore W1997305864C54355233 @default.
• W1997305864 hasConceptScore W1997305864C86803240 @default.
• W1997305864 hasConceptScore W1997305864C95444343 @default.
• W1997305864 hasIssue "3" @default.
• W1997305864 hasLocation W19973058641 @default.
• W1997305864 hasLocation W19973058642 @default.
• W1997305864 hasOpenAccess W1997305864 @default.
• W1997305864 hasPrimaryLocation W19973058641 @default.
• W1997305864 hasRelatedWork W2002247711 @default.
• W1997305864 hasRelatedWork W2002298712 @default.
• W1997305864 hasRelatedWork W2026183590 @default.
• W1997305864 hasRelatedWork W2099247076 @default.
• W1997305864 hasRelatedWork W2106361531 @default.
• W1997305864 hasRelatedWork W2358971709 @default.
• W1997305864 hasRelatedWork W2394370920 @default.
• W1997305864 hasRelatedWork W2805121851 @default.
• W1997305864 hasRelatedWork W3046665064 @default.
• W1997305864 hasRelatedWork W3148021101 @default.
• W1997305864 hasVolume "15" @default.
• W1997305864 isParatext "false" @default.
• W1997305864 isRetracted "false" @default.
• W1997305864 magId "1997305864" @default.
• W1997305864 workType "article" @default.