Immunopathology of apoptosis--introduction and overview

Cancer and Apoptosis

Cancer is an uncontrolled growth of normal cells due to unchecked regulatory mechanisms working inside the rapidly dividing cells. In this complex cancer disease treatment, various strategies are utilized to get rid of cancer cells effectively. The different methods combine approaches used to treat cancer, such as radiotherapy, surgery, and chemotherapy. Chemotherapy is among the most effective ways, along with radiotherapy and surgical removal of cancer tissue. Effective chemotherapy based on modification of conventional drugs along with various molecular therapeutic targets, which involve different inhibitors that work in a specific manner in inhibiting particular events activated in cancer cells-the understanding of molecular signaling pathways holds key in the development of targeted therapeutics. After the fundamental signaling pathway studies, a single signaling pathway targeting approach or multiple targeting could display remarkable results in cancer therapeutics. The signal approach includes the signal pathway target. However, a double targeted pathway could effectively aid in inhibiting cell growth or metastasis either due to triggering natural suicidal mechanism (apoptosis) activation. The particular environment of cells regulates cell growth and differentiation. Various proteins in the extracellular matrix (ECM) regulate the process of cancer initiation or progression. The ECM collagens, elastins proteins, fibronectins, and laminins might reduce the effectiveness of treatment therapy, reflecting them as an essential target. Any dysregulation in the composition of ECM reflects the regulatory ineffectiveness in a particular area. These have an association with poor prognosis, cell propagation, and metastasis, along drug resistance.Regulation in physiological processes associated with developmental process and maintaining the homeostasis. The pathogenesis of cancer might be connected to dysregulation in cell death programs, including autophagy, necrosis, and the most desirable cell death mechanism called apoptosis: programmed cell death, the highly regulatory mechanism of natural cell death involved in tissue development. The apoptosis involves characteristic feather of cell death which includes specific morphological change along with biochemical alteration. It includes tightly regulated irreversible events, i.e., phosphatidylserine externalization and DNA fragmentation, mainly via the intrinsic and extrinsic pathways. Targeting apoptosis in the development of therapeutics could be the ultimate process in treating cancer via chemotherapy. During apoptosis, cell death occurs without causing much damage or inflammation in neighboring cells. Various pro-apoptosis and anti-apoptosis proteins involved in the regulation of apoptosis could act as a remarkable target. The apoptosis inactivation is the critical dysregulatory process in the majority of cancer types. There is an increase in research development regarding apoptosis-targeted therapeutics. A understanding of apoptotic signaling pathways, a fundamental knowledge, aids in developing particular inhibitors for anti-apoptotic and activator of pro-apoptotic proteins.In both apoptosis pathways (extrinsic and intrinsic), pro-apoptotic and anti-apoptotic proteins act as potential regulators in cell division and growth. The pro-apoptotic proteins Bax trigger the activation of the intrinsic pathway, an excellent target for developing therapeutics, and are currently in clinical trials. Similarly, the inhibitor of the anti-apoptotic proteins is also on track in the drug development process. The considerable importance of apoptosis-based anticancer drugs is also due to improving the drug sensitivity via reversing the resistive mechanisms in cancer cells. The dysregulatory or inactivated apoptosis mechanism involve Bcl-2 family proteins which include both pro-apoptotic members downregulation and anti-apoptotic upregulation, various inhibitors of apoptosis as inhibitory proteins (IAPs), cell cycle dysregulation, dysregulatory repair system, cell progression pathway activation of NF-κB, tumor suppressor (p53) regulation, and death receptors (DRs) of the extrinsic pathway.

Lithium chloride increases sensitivity to photon irradiation treatment in primary mesenchymal colon cancer cells

Colorectal cancer (CRC) is the third most prevalent type of cancer worldwide. It is also the second most common cause of cancer-associated mortality; it accounted for about 9.2% of all cancer deaths in 2018, most of which were due to resistance to therapy. The main treatment for CRC is surgery, generally associated with chemotherapy, radiation therapy and combination therapy. However, while chemo-radiotherapy kills differentiated cancer cells, mesenchymal stem-like cells are resistant to this treatment, and this can give rise to therapy-resistant tumors. Our previous study isolated T88 primary colon cancer cells from a patient with sporadic colon cancer. These cells exhibited mesenchymal and epithelial features, high levels of epithelial-to-mesenchymal transition transcription factors, and stemness markers. In addition, it was revealed that lithium chloride (LiCl), a specific glycogen synthase kinase (GSK)-3β inhibitor, induced both the mesenchymal-to-epithelial transition and differentiation, and also reduced cell migration, stemness features and cell plasticity in these primary colon cancer cells. The aim of the present study was to investigate the effect of LiCl treatment on the viability of primary colon cancer cells exposed to 7 Gy delivered by high-energy photon beams, which corresponds to 6 megavolts of energy. To achieve this aim, the viability of irradiated T88 cells was compared with that of irradiated T88 cells pre-treated with LiCl. As expected, it was observed that LiCl sensitized primary colon cancer cells to high-energy photon irradiation treatment. Notably, the decrease in cell viability was greater with combined therapy than with irradiation alone. To explore the molecular basis of this response, the effect of LiCl on the expression of Bax, p53 and Survivin, which are proteins involved in the apoptotic mechanism and in death escape, was analyzed. The present study revealed that LiCl upregulated the expression of pro-apoptotic proteins and downregulated the expression of proteins involved in survival. These effects were enhanced by high-energy photon irradiation, suggesting that LiCl could be used to sensitize colon cancer cells to radiation therapy.

Immunosuppressive Effect of Polycyclic Aromatic Hydrocarbons by Induction of Apoptosis of pre-B Lymphocytes of Bone Marrow

Polycyclic aromatic hydrocarbons (PAH) are ubiquitous environmental pollutants, distinguished by genotoxic, hepatotoxic, nephrotoxic and immunotoxic effects. Especially secondary toxicity after bioactivation by microsomal monooxygenases (dependent on cytochromes P450) is characteristic of them. The immunotoxic effect is the result of very global impact on immunological reactivity of an organism and immunosuppression by induction of apoptosis of pre-B lymphocytes represents one of its particular forms. It has been proved that the effect of PAH is caused mostly by the following mechanisms: enzymatic induction by the way of activation of AhR (Aromatic hydrocarbon Receptor); alteration of cellular DNA; development of oxidative stress; increase in the concentration of intercellular calcium and decline of activity of NF-κB (Nuclear Factor – kappa B). Most sensitive to these changes are particularly B-lymphocytic precursors and pre-B lymphocytes. Intensity of entire manifestations is also considerably dependent on the presence and intensity of mechanisms of active or passive resistance of cells.

Clonal hematopoiesis

Cancer results from multistep pathogenesis, yet the pre-malignant states that precede the development of many hematologic malignancies have been difficult to identify. Recent genomic studies of blood DNA from tens of thousands of people have revealed the presence of remarkably common, age-associated somatic mutations in genes associated with hematologic malignancies. These somatic mutations drive the expansion from a single founding cell to a detectable hematopoietic clone. Owing to the admixed nature of blood that provides a sampling of blood cell production throughout the body, clonal hematopoiesis is a rare view into the biology of pre-malignancy and the direct effects of pre-cancerous lesions on organ dysfunction. Indeed, clonal hematopoiesis is associated not only with increased risk of hematologic malignancy, but also with cardiovascular disease and overall mortality. Here we review rapid advances in the genetic understanding of clonal hematopoiesis and nascent evidence implicating clonal hematopoiesis in malignant and non-malignant age-related disease.

Putting the pieces together: How is the mitochondrial pathway of apoptosis regulated in cancer and chemotherapy?

In order to solve a jigsaw puzzle, one must first have the complete picture to logically connect the pieces. However, in cancer biology, we are still gaining an understanding of all the signaling pathways that promote tumorigenesis and how these pathways can be pharmacologically manipulated by conventional and targeted therapies. Despite not having complete knowledge of the mechanisms that cause cancer, the signaling networks responsible for cancer are becoming clearer, and this information is serving as a solid foundation for the development of rationally designed therapies. One goal of chemotherapy is to induce cancer cell death through the mitochondrial pathway of apoptosis. Within this review, we present the pathways that govern the cellular decision to undergo apoptosis as three distinct, yet connected puzzle pieces: (1) How do oncogene and tumor suppressor pathways regulate apoptosis upstream of mitochondria? (2) How does the B-cell lymphoma 2 (BCL-2) family influence tumorigenesis and chemotherapeutic responses? (3) How is post-mitochondrial outer membrane permeabilization (MOMP) regulation of cell death relevant in cancer? When these pieces are united, it is possible to appreciate how cancer signaling directly impacts upon the fundamental cellular mechanisms of apoptosis and potentially reveals novel pharmacological targets within these pathways that may enhance chemotherapeutic success.

Apoptosis and molecular targeting therapy in cancer

Apoptosis is the programmed cell death which maintains the healthy survival/death balance in metazoan cells. Defect in apoptosis can cause cancer or autoimmunity, while enhanced apoptosis may cause degenerative diseases. The apoptotic signals contribute into safeguarding the genomic integrity while defective apoptosis may promote carcinogenesis. The apoptotic signals are complicated and they are regulated at several levels. The signals of carcinogenesis modulate the central control points of the apoptotic pathways, including inhibitor of apoptosis (IAP) proteins and FLICE-inhibitory protein (c-FLIP). The tumor cells may use some of several molecular mechanisms to suppress apoptosis and acquire resistance to apoptotic agents, for example, by the expression of antiapoptotic proteins such as Bcl-2 or by the downregulation or mutation of proapoptotic proteins such as BAX. In this review, we provide the main regulatory molecules that govern the main basic mechanisms, extrinsic and intrinsic, of apoptosis in normal cells. We discuss how carcinogenesis could be developed via defective apoptotic pathways or their convergence. We listed some molecules which could be targeted to stimulate apoptosis in different cancers. Together, we briefly discuss the development of some promising cancer treatment strategies which target apoptotic inhibitors including Bcl-2 family proteins, IAPs, and c-FLIP for apoptosis induction.

Compensatory functions of histone deacetylase 1 (HDAC1) and HDAC2 regulate transcription and apoptosis during mouse oocyte development

Dramatic changes in chromatin structure and histone modification occur during oocyte growth, as well as a global cessation of transcription. The role of histone modifications in these processes is poorly understood. We report the effect of conditionally deleting Hdac1 and Hdac2 on oocyte development. Deleting either gene has little or no effect on oocyte development, whereas deleting both genes results in follicle development arrest at the secondary follicle stage. This developmental arrest is accompanied by substantial perturbation of the transcriptome and a global reduction in transcription even though histone acetylation is markedly increased. There is no apparent change in histone repressive marks, but there is a pronounced decrease in histone H3K4 methylation, an activating mark. The decrease in H3K4 methylation is likely a result of increased expression of Kdm5b because RNAi-mediated targeting of Kdm5b in double-mutant oocytes results in an increase in H3K4 methylation. An increase in TRP53 acetylation also occurs in mutant oocytes and may contribute to the observed increased incidence of apoptosis. Taken together, these results suggest seminal roles of acetylation of histone and nonhistone proteins in oocyte development.

A role for Epstein-Barr viral BALF1 in facilitating tumor formation and metastasis potential

Epstein-Barr virus (EBV) is a ubiquitous human herpesvirus that triggers transformation and tumorigenesis of latently infected B cells in vitro. BALF1, a Bcl-2-like EBV gene expressed in both latent and lytic stages, was recently characterized in EBV-infected cells; however, the role and function of BALF1 has remained elusive. Here, we demonstrate that BALF1 expression alters cellular morphology. Importantly, BALF1 promotes cellular transformation, with tumorigenicity assays showing larger and substantially greater numbers of tumors in BALF1 transfectant-injected mice compared to mice injected with pcDNA control transfectants. In addition, BALF1 expression increases cell survival under low-serum conditions, an effect that is attributable to suppression of apoptosis, not to promotion of cell-cycle progression. Furthermore, BALF1 transfectants exhibit markedly increased tumor metastasis in vitro and in vivo. Taken together, these findings suggest that BALF1 may be a new tumor marker for EBV diagnosis and provide a new direction for research on treatments of EBV-associated tumors.

CD4+ CCR5+ and CD4+ CCR3+ lymphocyte subset and monocyte apoptosis in patients with acute visceral leishmaniasis

The potential involvement of apoptosis in the pathogenesis of visceral leishmaniasis (VL) was examined by studying spontaneous and Leishmania antigen (LAg)-induced apoptosis using cryopreserved peripheral blood mononuclear cells (PBMC) of Sicilian patients with VL. Results indicate that monocytes and T lymphocytes from acute VL patients show a significantly higher level of apoptosis compared with that observed in healed subjects. The percentage of apoptotic cells was higher in monocytes than in T lymphocytes. T cells involved in programmed cell death (PCD) were mainly of the CD4(+) phenotype. In particular, the T helper 1-type (Th1) subset, as evaluated by chemokine receptor-5 (CCR5) expression, is involved in this process. Cell death in Th1-type uses a CD95-mediated mechanism. Furthermore, Th1-type CCR5(+) cells are prone to cell suicide in an autocrine or paracrine way, as attested by enhanced expression of CD95L in acute VL patients. The reduction in Th1-type cells by apoptosis was confirmed by the decrease in interferon-gamma secretion. In conclusion, apoptosis of monocytes, CD4(+) and CD4(+) CCR5(+) T cells could be involved in the failure of cell mediated immunity that is responsible for severe immune-depression in VL.

Role of mitochondrial membrane permeabilization in apoptosis and cancer

The release of proteins from the intermembrane space of mitochondria is one of the pivotal events in the apoptotic process, which can lead to the activation of caspases and the ultimate demise of the cell. How these proteins exit the mitochondria is still a matter of intense debate. Here, we discuss the possible mechanisms behind the release of apoptogenic proteins, the ways in which cancer cells subvert these mechanisms, and the therapeutic regimens that aim to promote the timely loss of integrity of the outer mitochondrial membrane.

Apoptosis in glioma cells: review and analysis of techniques used for study with focus on the laser scanning cytometer

Traditional approaches to the treatment of brain tumors are based on the hypothesis that tumors arise and grow because of the disordered regulation of cell proliferation. More recently, it has become apparent that tumor growth depends not only on the rate of cell proliferation but also on the rate of apoptosis (programmed cell death). Genomic alterations that occur in malignancy may limit the cell's ability to undergo apoptosis. Many new treatment strategies for gliomas stem from the use of techniques aimed at manipulating apoptosis. Being able to assess the efficacy of experimental treatments with refined techniques and being able to use instruments that can provide accurate measurements of the apoptotic markers will open the door for discovering novel strategies with the potential to induce effective and selective cytotoxicity. We discuss here in detail the major traditional techniques of assessing apoptosis. We provide an overview of cytometric techniques, including flow cytometry (FC), and will compare it with the laser scanning cytometer (LSC). This is a powerful new tool with potential for obtaining a fast and objective analysis of apoptosis through multiple mechanisms, as well as for assessing proliferation and DNA ploidy in solid malignant tumors.

Chemically modified tetracyclines induce cytotoxic effects against J774 tumour cell line by activating the apoptotic pathway

Here, we have studied the effects of chemically modified tetracyclines (CMTs) on apoptosis both at the level of the cytoplasmic proteolytic caspase cascade, and on Bcl-2 and c-myc mRNA expression in the J774 macrophage cell line. The results indicate that CMTs induce morphological changes consistent with apoptotic events, as clearly demonstrated both by the acridine orange and ethidium bromide staining, and by TUNEL and fragmentation ELISA assays. Furthermore, the analysis of the cell cycle by flow cytometry shows an evident apoptotic sub-G0G1 peak, without important modifications in the cell cycle distribution. CMTs induce programmed cell death (PCD) in a dose-dependent manner and CMT-8 is the strongest among them. CMT-1 and CMT-8 activate mainly caspase-8 as attested by the inhibitory effects of Z-VAD-fmk and Z-IEDT-fmk on CMT-induced apoptosis. Part of CMT-induced PCD is due to the activation of caspase-9, since it is reduced by the specific caspase-9 inhibitor, Z-LEHD-fmk. Besides, CMTs increase Bcl-2 and c-myc mRNA expression. Collectively, these data indicate that CMTs are potentially anti-tumour agents, since they strongly trigger apoptosis both activating the proteolytic system of the caspase family and modulating genes involved in PCD regulation.

Aging but not dietary restriction alters the activation-induced apoptosis in rat T cells

The aim of this study was to determine if aging or dietary restriction (DR) alters activation-induced cell death, which is known to regulate cell proliferation and eliminate the high number of activated cells during an immune response. Splenic T cells were isolated from young (4-6 months) and old (25-26 months) Fischer 344 rats that had free access to food, ad libitum (AL), and from dietary-restricted (DR) old (25-26 months) rats that beginning at 6 weeks of age were fed 60% (40% food-restricted) of the diet consume by the AL rats. T cells were incubated with anti-CD3 antibody, or staphylococcal enterotoxin B (primary stimulus) for 72-96 h, followed by restimulation with anti-CD3 (secondary stimulus) for 72 h. Activation-induced apoptosis was assessed by DNA fragmentation and the expression of Fas/CD95 receptor and Fas ligand (Fas-L) was measured by flow cytometry. We found that the amount of DNA fragmentation was significantly (P<0.05) higher in the stimulated and restimulated T cells from AL old rats and DR old rats compared to young rats. The increase in DNA fragmentation with age was paralleled by an increase in the proportion of the cells expressing Fas and Fas-L. However, DR had no significant effect on the age-related increase in DNA fragmentation or the expression of Fas or Fas-L. We also measured the levels of Bcl-2 and Bax protein and found that the level of Bcl-2 decreased and Bax increased with age and that DR had no effect on the age-related changes in the level of Bcl-2 or Bax protein. These results demonstrate that aging but not DR alters activation-induced apoptosis in rat T cells.

Association of increased bcl-2 expression with rescue from tumor necrosis factor-alpha-induced cell death in the oligodendrocyte cell line OLN-93

The present study investigated the effects of flupirtine (Katadolon) on tumor necrosis factor (TNF)-alpha-mediated cell death and Bcl-2 expression in the permanent rat oligodendrocyte cell line OLN-93 (OLN cells). TNF-alpha (500 U/ml) induced apoptosis of OLN cells, which was confirmed by DNA fragmentation using an in situ end-labeling technique and ultrastructural analysis. Flupirtine significantly reduced the rate of spontaneous cell death of OLN cells already at low concentrations; TNF-alpha-mediated apoptosis was suppressed only with higher concentrations of flupirtine (100 microM:). Expression of Bcl-2 protein and mRNA in OLN cells was detected by immunocytochemistry, western blot, and RT-PCR. Quantitative analysis of western blots revealed an approximately 2. 5-fold up-regulation of Bcl-2 protein during TNF-alpha treatment. Furthermore, addition of 10 or 100 microM: flupirtine before incubation with TNF-alpha led to an approximately threefold increase of Bcl-2 expression. Exposure of OLN cells to flupirtine alone moderately augmented the expression of Bcl-2 protein. Our data demonstrate that flupirtine up-regulates the expression of Bcl-2 protein in OLN cells; this Bcl-2 induction is associated with a reduced rate of TNF-alpha-induced cell death.