The biology of apoptosis

Preliminary evidence for the presence of programmed cell death in pressure injuries

Pressure injuries (PIs) are a common healthcare problem worldwide and are considered to be the most expensive chronic wounds after arterial ulcers. Although the gross factors including ischemia-reperfusion (I/R) have been identified in the etiology of PIs, the precise cellular and molecular mechanisms contributing to PIs development remain unclear. Various forms of programmed cell death including apoptosis, autophagy, pyroptosis, necroptosis and ferroptosis have been identified in PIs. In this paper, we present a detailed overview on various forms of cell death; discuss the recent advances in the roles of cell death in the occurrence and development of PIs and found much of the evidence is novel and based on animal experiments. Herein, we also state critical evaluation of the existing data and future perspective in the field. A better understanding of the programmed cell death mechanism in PIs may have important implications in driving the development of new preventive and therapeutic strategies.

Naringenin reduces oxidative stress and necroptosis, apoptosis, and pyroptosis in random-pattern skin flaps by enhancing autophagy

BACKGROUND

Random skin flap grafting is one of the most commonly used techniques in plastic and orthopedic surgery. However, necrosis resulting from ischemia and ischemia-reperfusion injury in the distal part of the flap can severely limit the clinical application of the flap. Studies have revealed that naringenin reduces pyroptosis, apoptosis, and necroptosis, inhibits oxidative stress, and promotes autophagy. In this study, the effects of Naringenin on flap viability and its underlying mechanism were evaluated.

METHODS

Mice with random skin flaps were randomly allocated to control, Naringenin, and Naringenin + 3-methyladenine groups. On postoperative day 7, flap tissues were collected to estimate angiogenesis, necroptosis, apoptosis, pyroptosis, oxidative stress, and autophagy via hematoxylin and eosin staining, immunofluorescence, and immunohistochemistry.

RESULTS

The results revealed that naringenin promoted the viability of the random flaps as well as angiogenesis, while inhibiting oxidative stress and decreasing pyroptosis, apoptosis, and necroptosis. These effects were reversed by the autophagy inhibitor 3-methyladenine.

CONCLUSIONS

The findings indicated that naringenin treatment could promote flap survival by inhibiting pyroptosis, apoptosis, necroptosis, and alleviating oxidative stress, caused by the activation of autophagy.

Apoptosis Inhibitor 5: A Multifaceted Regulator of Cell Fate

Apoptosis, or programmed cell death, is a fundamental process that maintains tissue homeostasis, eliminates damaged or infected cells, and plays a crucial role in various biological phenomena. The deregulation of apoptosis is involved in many human diseases, including cancer. One of the emerging players in the intricate regulatory network of apoptosis is apoptosis inhibitor 5 (API5), also called AAC-11 (anti-apoptosis clone 11) or FIF (fibroblast growth factor-2 interacting factor). While it may not have yet the same level of notoriety as some other cancer-associated proteins, API5 has garnered increasing attention in the cancer field in recent years, as elevated API5 levels are often associated with aggressive tumor behavior, resistance to therapy, and poor patient prognosis. This review aims to shed light on the multifaceted functions and regulatory mechanisms of API5 in cell fate decisions as well as its interest as therapeutic target in cancer.

Resveratrol Promotes Proliferation, Antioxidant Properties, and Progesterone Production in Yak (Bos grunniens) Granulosa Cells

Resveratrol (RES) is a class of natural polyphenolic compounds known for its strong anti-apoptotic and antioxidant properties. Granulosa cells (GCs) are one of the important components of ovarian follicles and play crucial roles in follicular development of follicles in the ovary. Here, we explored the effects of RES on the proliferation and functions of yak GCs. Firstly, we evaluated the effect of RES dose and time in culture on the viability of GCs, and then the optimum treatment protocol (10 μM RES, 36 h) was selected to analyze the effects of RES on the proliferation, cell cycle, apoptosis, malondialdehyde (MDA), glutathione (GSH), reactive oxygen species (ROS) accumulation, lipid droplet content, ATP production, and steroidogenesis of GCs, as well as the expression of related genes. The results show that RES treatment significantly (1) increased cell viability and proliferation and inhibited cell apoptosis by upregulating BCL-2 and SIRT1 genes and downregulating BAX, CASP3, P53, and KU70 genes; (2) increased the proportion of GCs in the S phase and upregulated CCND1, PCNA, CDK4, and CDK5 genes; (3) reduced ROS accumulation and MDA content and increased GSH content, as well as upregulating the relative expression levels of CAT, SOD2, and GPX1 genes; (4) decreased lipid droplet content and increased ATP production; (5) promoted progesterone (P4) secretion and the expression of P4 synthesis-related genes (StAR, HSD3B1, and CYP11A1); and (6) inhibited E2 secretion and CYP19A1 expression. These findings suggest that RES at 10 μM increases the proliferation and antioxidant properties, inhibits apoptosis, and promotes ATP production, lipid droplet consumption, and P4 secretion of yak GCs.

The WHO claims estrogens are 'carcinogenic': is this true?

Estrogens are in the list of carcinogenic chemicals from the World Health Organization (WHO). However, estrogens require additional factors such as stromal factors or progestogens to increase the ratio of proliferation/apoptosis for initiation of replication errors and consequent mutations to occur. These mutations require at least 5-10 years to develop into clinically detectable cancer, whereby this review is focused on breast cancer. The US National Cancer Institute highlighted a second mechanism of carcinogenicity: certain estrogen metabolites are capable of inducing DNA damage, even in low concentration. They can be assessed in the tissue and circulation. However, those deleterious reactions require excessive unrestricted oxidative cell stress, for example in industrial areas with heavy pollution. We have shown that this can be avoided using transdermal instead of oral estradiol treatment, especially important in smokers. The spectrum of metabolites is also influenced by other exogenous factors such as nutrition, physical activity and certain diseases. Reduction of breast cancer risk as demonstrated in the Women's Health Initiative (WHI) was explained by pro-apoptotic estrogen effects working after a certain 'time gap'. In addition, certain estrogen metabolites are carcinoprotective, if no genetic polymorphisms would impair their beneficial activities. Thus, since additional factors are required for both main pathways of carcinogenicity and because estrogens can even have carcinoprotective effects, we cannot agree with the statement from the WHO.

Preliminary evidence for the presence of multiple forms of cell death in diabetes cardiomyopathy

Diabetic mellitus (DM) is a common degenerative chronic metabolic disease often accompanied by severe cardiovascular complications (DCCs) as major causes of death in diabetic patients with diabetic cardiomyopathy (DCM) as the most common DCC. The metabolic disturbance in DCM generates the conditions/substrates and inducers/triggers and activates the signaling molecules and death executioners leading to cardiomyocyte death which accelerates the development of DCM and the degeneration of DCM to heart failure. Various forms of programmed active cell death including apoptosis, pyroptosis, autophagic cell death, autosis, necroptosis, ferroptosis and entosis have been identified and characterized in many types of cardiac disease. Evidence has also been obtained for the presence of multiple forms of cell death in DCM. Most importantly, published animal experiments have demonstrated that suppression of cardiomyocyte death of any forms yields tremendous protective effects on DCM. Herein, we provide the most updated data on the subject of cell death in DCM, critical analysis of published results focusing on the pathophysiological roles of cell death, and pertinent perspectives of future studies.

Cypermethrin induces Sertoli cell apoptosis through mitochondrial pathway associated with calcium

Cypermethrin, one kind of pyrethroid pesticides, has been shown to act as endocrine-disrupting chemicals (EDCs). The purpose of this study was to explore the roles of Sertoli cell apoptosis through mitochondrial pathway associated with calcium (Ca²⁺) in cypermethrin-induced male reproductive toxicology. The mouse Sertoli cells TM4 were cultured with 0 μM, 10 μM, 20 μM, 40 μM and 80 μM of cypermethrin. We used flow cytometry, Fluo-4 AM, western blot and JC-1 Assay Kit to examine apoptosis, intracellular Ca²⁺, expressions of mitochondrial apoptotic pathway-related proteins and mitochondrial membrane potential. We found cypermethrin increased apoptosis rate of TM4 cells significantly and with a significant increase in intracellular Ca²⁺ concentration. Cypermethrin significantly decreased the protein expressions of cytosolic B-cell lymphoma-2 (Bcl-2) and mitochondrial cytochrome c (Cyt-c). The protein expressions of cytosolic Bcl-2-associated x (Bax), Cyt-c, cleaved caspase-3, calmodulin (CaM), Ca²⁺/CaM-dependent protein kinases II (CaMKII) and phosphorylated CaMKII were increased significantly in cypermethrin-exposed TM4 cells. Cypermethrin decreased mitochondrial membrane potential significantly. Then, Bcl-2 family and Ca²⁺/CaM/CaMKII pathway participate in cypermethrin-induced homeostasis. Ca²⁺ overload activates mitochondrial pathway by increasing permeability of mitochondrial membrane and decreasing mitochondrial membrane potential. We suggest cypermethrin induces Sertoli cell apoptosis involving mitochondrial pathway associated with Ca²⁺ regulated by Bcl-2 family and Ca²⁺/CaM/CaMKII pathway. The study provides a new insight into mechanisms involved in cypermethrin-induced male reproductive toxicology.

Evolution and Structure of API5 and Its Roles in Anti-Apoptosis

Apoptosis, also named programmed cell death, is a highly conserved physiological mechanism. Apoptosis plays crucial roles in many life processes, such as tissue development, organ formation, homeostasis maintenance, resistance against external aggression, and immune responses. Apoptosis is regulated by many genes, among which Apoptosis Inhibitor-5 (API5) is an effective inhibitor, though the structure of API5 is completely different from the other known Inhibitors of Apoptosis Proteins (IAPs). Due to its high expression in many types of tumors, API5 has received extensive attention, and may be an effective target for cancer treatment. In order to comprehensively and systematically understand the biological roles of API5, we summarized the evolution and structure of API5 and its roles in anti-apoptosis in this review.

Amelioration of Combination of Paclitaxel and Di Allyl Sulfide on the Alterations of Bcl2, P53 and Apoptosis Changes Against 7,12 Di Methyl Benz (A) Anthracene Induced Skin Cancer in Experimental Animals

The purpose of this study was to investigate the Bcl2, P⁵³ and apoptosis changes against skin cancer in experimental animals. Skin cancer is the most common form of human cancer. It is estimated that over 1 million new cases occur annually. The annual rates of all forms of skin cancer are increasing each year, representing a growing public concern. It has also been estimated that nearly half of all Americans who live to age 65 are likely to develop skin cancer at least once. Skin cancer was induced in rats by Di Methyl Benz (a) Anthracene at the dosage of DMBA (5 µg) per animal, three times a week for 28 weeks after conformation of skin cancer treated with Paclitaxel and Di allyl sulfide for 30 days. The levels of Bcl2 gene expression were significantly decreased and P⁵³gene expression were markedly increased in Paclitaxel and Di allyl sulfide treated animals when compared with cancer bearing animals. The treatment with combination of Paclitaxel and Di allyl sulfide effectively reduced Bcl2 protein expression and also increased P⁵³gene expression. Moreover, the levels of Bcl2 and P⁵³ a good indicators of restoring the skin architecture, were also reversed in skin damage subjects after treatment with the herbal compounds preparation. So, from the obtained results it is concluded that a combination of Paclitaxel and Di allyl sulfide is capable of restoring the skin architecture and can also increase the apoptosis activities in skin cancer rats.

Shadow Cell Differentiation: A Comparative Analysis of Modes of Cell Death with Apoptosis and Epidermal/Trichilemmal Keratinization

Shadow cells are characterized by an eosinophilic cytoplasm and a ghost-like nuclear contour; the cell shape is preserved, in spite of nuclear disappearance. Shadow cell nests (SCNs) are frequently observed in pilomatricoma (PMX), where the transitional cells immediately adjacent to SCNs often have a crescent-shaped nucleus showing fragmentation similar to that of apoptotic bodies. They show nuclear accumulation of beta-catenin and DNA double strand breaks (as revealed by in situ 3′-tailing reaction or immunohistochemistry for single-stranded DNA [ssDNA]), while they are negative for cleaved caspase-3 or cleaved lamin A, suggesting that shadow cell differentiation (SCD) is a caspase-independent programmed cell death. SCD can be differentiated from epidermal keratinization (EK) and trichilemmal keratinization (TK) based on the expression pattern of beta-catenin, ssDNA, and caspase-14/CD138. SCD is observed not only in PMX, but also sometimes in basal cell carcinomas, gonadal teratomas, and various extra-cutaneous carcinomas. In particular, SCNs are found in 24$ of endometrial adenoacanthoma and are derived from squamoid morules. This establishes a link between basaloid cells in PMX and squamoid morules in endometrial adenoacanthomas as common precursors of shadow cells. Overall, it is suggested that SCD is different from, but partly similar to, apoptosis and that SCD and EK/TK should be differentiated from the standpoint of cell death/differentiation.

IREN, a novel EF-hand motif-containing nuclease, functions in the degradation of nuclear DNA during the hypersensitive response cell death in rice

The hypersensitive response (HR), a type of programmed cell death that is accompanied by DNA degradation and loss of plasma membrane integrity, is a common feature of plant immune responses. We previously reported that transcription of IREN which encodes a novel EF-hand containing plant nuclease is controlled by OsNAC4, a key positive regulator of HR cell death. Transient overexpression of IREN in rice protoplasts also led to rapid DNA fragmentation, while suppression of IREN using RNA interference showed remarkable decrease of DNA fragmentation during HR cell death. Maximum DNA degradation associated with the recombinant IREN was observed in the presence of Ca(2+) and Mg(2+) or Ca(2+) and Mn(2+). Interestingly, DNA degradation mediated by the recombinant IREN was completely abolished by Zn(2+), even when Ca(2+), Mg(2+), or Mn(2+) were present in the reaction buffer. These data indicate that IREN functions in the degradation of nuclear DNA during HR cell death.

The Effect of Hypoxic Preconditioning on Induced Schwann Cells under Hypoxic Conditions

OBJECT

Our objective was to explore the protective effects of hypoxic preconditioning on induced Schwann cells exposed to an environment with low concentrations of oxygen. It has been observed that hypoxic preconditioning of induced Schwann cells can promote axonal regeneration under low oxygen conditions.

METHOD

Rat bone marrow mesenchymal stem cells (MSCs) were differentiated into Schwann cells and divided into a normal oxygen control group, a hypoxia-preconditioning group and a hypoxia group. The ultrastructure of each of these groups of cells was observed by electron microscopy. In addition, flow cytometry was used to measure changes in mitochondrial membrane potential. Annexin V-FITC/PI staining was used to detect apoptosis, and Western blots were used to detect the expression of Bcl-2/Bax. Fluorescence microscopic observations of axonal growth in NG-108 cells under hypoxic conditions were also performed.

RESULTS

The hypoxia-preconditioning group maintained mitochondrial cell membrane and crista integrity, and these cells exhibited less edema than the hypoxia group. In addition, the cells in the hypoxia-preconditioning group were found to be in early stages of apoptosis, whereas cells from the hypoxia group were in the later stages of apoptosis. The hypoxia-preconditioning group also had higher levels of Bcl-2/Bax expression and longer NG-108 cell axons than were observed in the hypoxia group.

CONCLUSION

Hypoxic preconditioning can improve the physiological state of Schwann cells in a severe hypoxia environment and improve the ability to promote neurite outgrowth.

A novel cytosporone 3-Heptyl-4,6-dihydroxy-3H-isobenzofuran-1-one: synthesis; toxicological, apoptotic and immunomodulatory properties; and potentiation of mutagenic damage

BACKGROUND

A large number of studies are attempting to identify alternative products from natural sources or synthesized compounds that effectively interact with cancer cells without causing adverse effects on healthy cells. Resorcinolic lipids are a class of bioactive compounds that possess anticancer activity and are able to interact with the lipid bilayer. Therefore, the objective of this study was to synthesize a novel resorcinolic lipid and test its biological proprieties.

METHODS

We aimed to synthesize a novel resorcinolic lipid belonging to the class of cytosporones, AMS049 (3-Heptyl-4,6-dihydroxy-3H-isobenzofuran-1-one) and to evaluate the toxicity of two concentrations of this lipid (7.5 and 10 mg/kg) by determining its genotoxic, mutagenic, immunomodulatory, and apoptotic effects, as well as any biochemical and histopathological alterations in mice treated with cyclophosphamide. The results were analyzed by ANOVA followed by the Tukey test A . level of significance of p < 0.05 was adopted.

RESULTS

The new cytosporone AMS049 was synthesized in only three steps and in satisfactory yields. The results indicate that the compound is neither genotoxic nor mutagenic and does not alter biochemical parameters. The histological alterations observed in the liver and kidneys did not compromise the function of these organs. Histology of the spleen suggested immunomodulation, although no changes were observed in splenic phagocytosis or differential blood cell count. The results also show that AMS049 potentiates the mutagenic effect of the chemotherapy drug cyclophosphamide and that the combination induces apoptosis.

CONCLUSION

These facts indicate a potential therapeutic application of this novel cytosporone as an important chemotherapeutic adjuvant.

Hidden disease susceptibility and sexual dimorphism in the heterozygous knockout of Cyp51 from cholesterol synthesis

We examined the genotype-phenotype interactions of Cyp51+/- mice carrying one functional allele of lanosterol 14α-demethylase from cholesterol biosynthesis. No distinct developmental or morphological abnormalities were observed by routine visual inspection of Cyp51+/- and Cyp51+/+ mice and fertility was similar. We further collected a large data-set from female and male Cyp51+/- mice and controls fed for 16 weeks with three diets and applied linear regression modeling. We used 3 predictor variables (genotype, sex, diet), and 39 response variables corresponding to the organ characteristics (7), plasma parameters (7), and hepatic gene expression (25). We observed significant differences between Cyp51+/- and wild-type mice in organ characteristics and blood lipid profile. Hepatomegaly was observed in Cyp51+/- males, together with elevated total and low-density lipoprotein cholesterol. Cyp51+/- females fed high-fat, high-cholesterol diet were leaner and had elevated plasma corticosterone compared to controls. We observed elevated hepatocyte apoptosis, mitosis and lipid infiltration in heterozygous knockouts of both sexes. The Cyp51+/- females had a modified lipid storage homeostasis protecting them from weight-gain when fed high-fat high-cholesterol diet. Malfunction of one Cyp51 allele therefore initiates disease pathways towards cholesterol-linked liver pathologies and sex-dependent response to dietary challenge.

Clinicopathological and prognostic significance of p53, Ki-67, and Bcl-2 expression in Tunisian gastric adenocarcinomas

Gastric carcinoma (GC) is a highly aggressive malignancy with poor prognosis. It is widely accepted that malignancy results from abnormal cell growth due to dysregulation of the balance between cell proliferation and apoptosis. Our study aimed to investigate the clinicopathological and prognostic significance of p53, Ki-67, and Bcl-2 in Tunisian GC patients by immunohistochemistry. It was observed that the older patients showed p53 overexpression compared with the younger patients (p<0.05). There was higher p53 expression in the intestinal-type compared with the diffuse-type (p<0.05), and in well/moderate differentiated than in poor differentiated tumors. The expression of Ki-67 was positively associated with tumor size and venous invasion (p<0.05). Bcl2 expression occurred in male patients and correlated with depth of invasion (p=0.02). A Kaplan-Meier analysis indicated an inverse correlation between p53 and Ki-67 expression and the overall survival. Multivariate analysis revealed that the tumor site, Ki-67 and p53 expression were independent prognostic factors for gastric carcinomas (p<0.05). Finally, combined expression of p53, Ki-67 and Bcl-2 showed that the group of patients with tumors p53+/Ki-67+/Bcl2- had aggressive behavior and poor prognosis (p log rank=0.000). In summary, our data indicated that the expression of p53, Ki-67, and Bcl-2 may provide useful information for identifying patients with aggressive behavior and poor prognosis of GC.

Survivin depletion inhibits tumor growth and enhances chemosensitivity in hepatocellular carcinoma

Survivin is a member of the inhibitor of apoptosis family, which has been suggested to be crucial in the control of cell division and inhibition of apoptosis. Expression of this protein has been observed in transformed cell lines and human tumor tissues, including those from colorectal cancer, but not in terminally differentiated adult tissues. Survivin mRNA expression has frequently been detected in hepatocellular carcinoma (HCC) and its protein expression has been demonstrated to be highly correlated with proliferation index rather than apoptotic index. The present study aimed to analyze the effect of survivin on the tumorigenicity and chemosensitivity of HCC via the establishment of an HCC cell line (PLC/PRF/5) with the stable knockdown of the survivin gene (PLC‑k3). This cell line displayed significantly lower rates of survival and proliferation in assays of cell viability and proliferation, respectively, compared with those of the control cell line (PLC‑v). In addition, PLC‑k3 cells were more sensitive to cisplatin treatment, resulting in S phase arrest. These findings were further confirmed by an in vivo experiment. The data of the present study suggest that survivin is critical in promoting cell proliferation but not in inhibition of apoptosis, and enhances the chemosensitivity of HCC. Thus, the suppression of survivin expression in combination with cisplatin may contribute to the development of more effective treatments for HCC.

Saponin B, a novel cytostatic compound purified from Anemone taipaiensis, induces apoptosis in a human glioblastoma cell line

Glioblastoma multiforme (GBM) is one of the most common malignant brain tumors. Saponin B, a novel compound isolated from the medicinal plant, Anemone taipaiensis, has been found to have a strong time- and dose-dependent cytostatic effect on human glioma cells and to suppress the growth of U87MG GBM cells. In this study, we investigated whether saponin B induces the apoptosis of glioblastoma cells and examined the underlying mechanism(s) of action of saponin B. Saponin B significantly suppressed U87MG cell proliferation. Flow cytometric analysis of DNA in the U87MG cells confirmed that saponin B blocked the cell cycle at the S phase. Furthermore, treatment of the U87MG cells with saponin B induced chromatin condensation and led to the formation of apoptotic bodies, as observed under a fluorescence microscope, and Annexin V/PI assay further suggested that phosphatidylserine (PS) externalization was apparent at higher drug concentrations. Treatment with saponin B activated the receptor-mediated pathway of apoptosis, as western blot analysis revealed the activation of Fas-l. Saponin B increased the Bax and caspase-3 ratio and decreased the protein expression of Bcl-2. The results from the present study demonstrate that the novel compound, saponin B, effectively induces the apoptosis of GBM cells and inhibits glioma cell growth and survival. Therefore, saponin B may be a potential candidate for the development of novel cancer therapeutics with antitumor activity against gliomas.

TaAbc1, a member of Abc1-like family involved in hypersensitive response against the stripe rust fungal pathogen in wheat

To search for genes involved in wheat (Triticum aestivum L.) defense response to the infection of stripe rust pathogen Puccinia striiformis f. sp. tritici (Pst), we identified and cloned a new wheat gene similar to the genes in the Abc1-like gene family. The new gene, designated as TaAbc1, encodes a 717-amino acid, 80.35 kD protein. The TaAbc1 protein contains two conserved domains shared by Abc1-like proteins, two trans-membrane domains at the C-terminal, and a 36-amino acid chloroplast targeting presequence at the N-terminal. Characterization of TaAbc1 expression revealed that gene expression was tissue-specific and could be up-regulated by biotic agents (e.g., stripe rust pathogen) and/or by an abiotic stress like wounding. High-fold induction was associated with the hypersensitive response (HR) triggered only by avirulent stripe rust pathotypes, suggesting that TaAbc1 is a rust-pathotype specific HR-mediator. Down-regulating TaAbc1 reduced HR but not the overall resistance level in Suwon11 to CYR23, suggesting TaAbc1 was involved in HR against stripe rust, but overall host resistance is not HR-dependent.

TaMCA4, a novel wheat metacaspase gene functions in programmed cell death induced by the fungal pathogen Puccinia striiformis f. sp. tritici

Programmed cell death (PCD) is a physiological process to remove redundant or harmful cells, for the development of multicellular organisms, or for restricting the spread of pathogens (hypersensitive response). Metacaspases are cysteine-dependent proteases which play an essential role in PCD. Triticum aestivum metacaspase 4 (TaMCA4) is a type II metacaspase gene cloned from 'Suwon11' wheat, with typical structural features such as peptidase C14 caspase domain and a long linker sequence between the two subunits. Transient expression of TaMCA4 in tobacco leaves failed to induce PCD directly but enhanced cell death triggered by a mouse Bax gene or a candidate effector gene from Puccinia striiformis f. sp. tritici. Enhancement of PCD was also observed in wheat leaves co-bombarded with TaMCA4. When challenged with the avirulent race of P. striiformis f. sp. tritici, the expression level of TaMCA4 in wheat leaves was sharply upregulated, whereas the transcript level was not significantly induced by the virulent race. Moreover, knocking down TaMCA4 expression by virus-induced gene silencing enhanced the susceptibility of Suwon11 to the avirulent race of P. striiformis f. sp. tritici and reduced the necrotic area at infection sites.

Dental pulp stem cells, niches, and notch signaling in tooth injury

Stem cells guarantee tissue repair and regeneration throughout life. The decision between cell self-renewal and differentiation is influenced by a specialized microenvironment called the 'stem cell niche'. In the tooth, stem cell niches are formed at specific anatomic locations of the dental pulp. The microenvironment of these niches regulates how dental pulp stem cell populations participate in tissue maintenance, repair, and regeneration. Signaling molecules such as Notch proteins are important regulators of stem cell function, with various capacities to induce proliferation or differentiation. Dental injuries often lead to odontoblast apoptosis, which triggers activation of dental pulp stem cells followed by their proliferation, migration, and differentiation into odontoblast-like cells, which elaborate a reparative dentin. Better knowledge of the regulation of dental pulp stem cells within their niches in pathological conditions will aid in the development of novel treatments for dental tissue repair and regeneration.

TaDAD2, a negative regulator of programmed cell death, is important for the interaction between wheat and the stripe rust fungus

Defender against cell death (DAD) genes are known to function as negative regulators of cell death in animals. In plants, DAD orthologs are conserved but their role in cell death regulation is not well understood. Here, we report the characterization of the TaDAD2 gene in wheat. The predicted amino acid sequence of TaDAD2 contains typical structural features of DAD proteins, including a signal peptide, three transmembrane regions, and a subunit of oligosaccharyltransferase. Transcripts of TaDAD2 were detected in wheat leaves, culms, roots, florets, and spikelets. The expression level of TaDAD2 was reduced in the initial contact with the stripe rust fungus, subsequently induced and peaked at 18 h postinoculation (hpi), gradually reduced at 24 to 48 hpi, and restored to control level at 72 to 120 hpi. In addition, TaDAD2 exhibited positive transcriptional responses to abiotic stresses after the initial reduction at 1 hpi. Overexpression of TaDAD2 in tobacco leaves inhibited cell death. Furthermore, knocking down TaDAD2 expression by virus-induced gene silencing enhanced the susceptibility of wheat cv. Suwon11 to avirulent race CYR23 and reduced necrotic area at the infection sites. These results indicate that TaDAD2 may function as a suppressor of cell death in the early stages of wheat-stripe rust fungus interaction. However, it is dispensable for or plays an opposite role in hypersensitive response or cell death triggered by an avirulent race of stripe rust fungus at late-infection stages.

Programmed cell death of tobacco BY-2 cells induced by still culture conditions is affected by the age of the culture under agitation

Evans Blue staining indicated that actively growing tobacco BY-2 cells in the exponential phase died more rapidly than quiescent cells in the stationary phase when the cells cultured under agitation were placed under still conditions. Fifty percent cell death was induced at about 18, 26, 80 and 140 h for early, mid, late exponential- and stationary-phase cells, respectively. Actively growing cells became TUNEL (transferase-mediated dUTP nick end labelling)-positive more rapidly than quiescent cells, suggesting that the cell death evaluated by Evans Blue is accompanied by DNA cleavages. Electrophoresis of genomic DNA showed a typical 'DNA laddering' pattern formed by multiples of about 200 bp internucleosomal units. Chromatin condensation was first detected at least within 24 h by light microscopy, and then cell shrinkage followed. These findings suggest that the death of BY-2 cells induced by still conditions is PCD (programmed cell death).

Risk of breast cancer during hormone replacement therapy: mechanisms

Regarding estrogen replacement therapy, two main mechanisms have to be considered for it to be discussed as a potential carcinogen in the breast, and also considering the World Health Organization definition of estrogens and estrogen/progestogen combinations as “carcinogenic”: (i) the proliferative/apoptotic effects on already pre-existing estrogen-sensitive cancer cells and (ii) the production of possible genotoxic estrogen metabolites. By addition of the progestogen component, as is usual in non-hysterectomized women, both mechanisms can lead to an increased risk compared to estrogenonly therapy. The detailed mechanisms underlying the development of the benign breast epithelial cell into clinically relevant breast cancer cells are very complicated. Based on these mechanisms, the following simplified summary of the main steps explains that: (i) an increased risk cannot be excluded, (ii) especially when estrogens are combined with progestogens, but (iii) there are differences between the preparations used in therapy; (iv) the risk seems to be very rare, needing very special cellular and extracellular conditions, (v) and could even be decreased in special situations of estrogen therapy. It is concluded that when critically reviewed, an increased risk of breast cancer during hormone replacement therapy cannot be excluded in very rare cases. Definitive mechanistic evidence for a possible causal relationship with carcinogenesis still remains open.

Involvement of mitochondrial permeability transition pore opening in alpha-bisabolol induced apoptosis

Alpha-bisabolol is a natural monocyclic sesquiterpene alcohol. It has been used in cosmetics for hundreds of years because of its perceived skin-healing properties. Alpha-bisabolol is known to have anti-irritant, anti-inflammatory and antimicrobial properties. In precedent studies, we described how alpha-bisabolol exerts a selective pro-apoptotic action towards transformed cells [Cavalieri E et al. (2004) Biochem Biophys Res Commun 315, 589-594] and its uptake is mediated by lipid rafts on the plasma membrane [Darra E et al. (2008) Arch Biochem Biophys 476, 113-123]. In this study, we hypothesize that the intracellular target of alpha-bisabolol may be the mitochondrial permeability transition pore (mPTP). To evaluate this hypothesis, we used one transformed cell line (human glioma T67) in comparison with a nontransformed one (human fibroblasts). We assessed the effect of a specific mPTP inhibitor (cyclosporine A) on the toxic action of alpha-bisabolol. Results show that the alpha-bisabolol-induced decrease in oxygen consumption is abolished by the addition of cyclosporine A in T67 cells, indicating that alpha-bisabolol may target mPTP. The central role of mitochondria was also demonstrated by using galactose to force cells to a more aerobic metabolism. In this condition, we observed higher alpha-bisabolol toxicity. Furthermore, we studied the effect of alpha-bisabolol on isolated rat liver mitochondria. This study expands the notion of the specific action of alpha-bisabolol on transformed cells and suggests that it may act by disturbing the structure and function of the mPTP. Alpha-bisabolol toxicity is clearly related to its cellular uptake, which is higher in transformed cell lines.

Potential role of apoptosis and apoptotic regulatory proteins in colorectal neoplasia: correlations with clinico-pathological parameters and survival

An imbalance between apoptotic and proliferative processes is believed to underlie colorectal neoplasia. We evaluated the expression of bcl-2, p53, mdm2 proteins, and apoptosis in colorectal neoplasms, as well as their correlation with clinico-pathological parameters, using image analysis. Biopsies from 46 colorectal cancers, 121 adenomas, and 25 controls were studied using monoclonal antibodies against p53, bcl-2, mdm2 and the terminal deoxynucleotidyl-transferase-mediated dUTP nick end labeling (TUNEL) method for apoptosis. P53 and bcl2 protein expression was higher in adenomas >or=1 cm (P < 0.03) and tubulovillous-villous adenomas (P < 0.03), and correlated with dysplasia (P < 0.03). In Cox regression analysis, Dukes' stage was the most significant independent prognostic indicator of a worse survival (P < 0.019), whereas when stage was eliminated, bcl-2 expression was also a powerful predictor for bad prognosis (P = 0.02). In conclusion, both bcl-2 and p53 immunohistochemical profiles may be useful adjuncts in detecting adenomas with a malignant potential, whereas bcl-2 could be used in combination with Dukes' stage as a predictor of prognosis in colorectal cancer.

Apoptotic pathways in tumor progression and therapy

Apoptosis is a cell suicide program that plays a critical role in development and tissue homeostasis. The ability of cancer cells to evade this programmed cell death (PCD) is a major characteristic that enables their uncontrolled growth. The efficiency of chemotherapy in killing such cells depends on the successful induction of apoptosis, since defects in apoptosis signaling are a major cause of drug resistance. Over the past decades, much progress has been made in our understanding of apoptotic signaling pathways and their dysregulation in cancer progression and therapy. These advances have provided new molecular targets for proapoptotic cancer therapies that have recently been used in drug development. While most of those therapies are still at the preclinical stage, some of them have shown much promise in the clinic. Here, we review our current knowledge of apoptosis regulation in cancer progression and therapy, as well as the new molecular targeted molecules that are being developed to reinstate cancer cell death.

Apoptosis in developmental and repair-related human tooth remodeling: a view from the inside

Apoptosis is a key phenomenon in the regulation of the life span of odontoblasts, which are responsible for dentin matrix production of the teeth. The mechanism controlling odontoblasts loss in developing, normal, and injured human teeth is largely unknown. A possible correlation between apoptosis and dental pulp volume reduction was examined. Histomorphometric analysis was performed on intact 10 to 14 year-old premolars to follow dentin deposition and evaluate the total number of odontoblasts. Apoptosis in growing healthy teeth as well as in mature irritated human teeth was determined using a modified TUNEL technique and an anti-caspase-3 antibody. In intact growing teeth, the sequential rearrangement of odontoblasts into a multi-layer structure during tooth crown formation was correlated with an apoptotic wave that leads to the massive elimination of odontoblasts. These data suggest that apoptosis, coincident with dentin deposition changes, plays a role in tooth maturation and homeostasis. Massive apoptotic events were observed after dentin irritation. In carious and injured teeth, apoptosis was detected in cells surrounding the lesion sites, as well as in mono-nucleated cells nearby the injury. These results indicate that apoptosis is a part of the mechanism that regulate human dental pulp chamber remodeling during tooth development and pathology.

Influence of apoptosis and cell cycle regulator proteins on chemotherapy response and survival in stage IIIA/IIIB NSCLC patients

BACKGROUND

Prognosis for non-small cell lung cancer (NSCLC) patients is very poor. Prediction of the response to treatment in individual patients may be possible using molecular biological alterations such as clinical biomarkers. We investigated the predictive value of apoptosis and cell cycle regulator proteins for neoadjuvant chemotherapy response in stage IIIA/IIIB NSCLC patients.

METHODS

We evaluated p53, bcl-2, p21WAF1/CIP1, p27Kip1, and Ki67 immunohistochemical expression and apoptotic index in mediastinal lymph node metastases from 23 IIIA and 10 IIIB NSCLC patients before treatment with neoadjuvant platinum-based chemotherapy. Univariate analysis was performed to evaluate the relationship between protein expression and survival or time to progression (TTP).

RESULTS

Median follow-up was 25 months (range, 4-112), median TTP was 11 months (range, 0-112), and median overall survival was 22 months (range, 4-112). Of 32 assessable patients, 18 (56%) had stable disease, 12 (38%) had a PR, and two (6%) had progressive disease. Of the 22 patients assessable for pN2 following chemotherapy, 16 (77%) were positive. Univariate analysis showed that shorter TTP correlated with progressive disease (p = 0.000), positive pN2 after chemotherapy (p = 0.026), high Ki67 (p = 0.022), and high p21WAF1/CIP1 (p = 0.038).

CONCLUSION

Our results suggest that in IIIA/IIIB NSCLC patients, a high level of p21WAF1 expression in mediastinal lymph node metastases before neoadjuvant platinum-based chemotherapy is associated with a poor outcome. Our results suggest that expression of p21WAF1, which plays a role in preventing apoptosis, may be significant when selecting chemotherapy for NSCLC patients.

Molecular cloning and responsive expression to injury stimulus of a defender against cell death 1 (DAD1) gene from bay scallops Argopecten irradians

Apoptosis is an active process of cell death, which is an integral part of growth and development in multicellular organisms. The defender against cell death 1 (DAD1), the regulatory protein to inhibit the apoptosis process, was first cloned from the bay scallop Argopecten irradians by randomly sequencing a whole tissue cDNA library and rapid amplification of cDNA end (RACE). The full-length cDNA of the A. irradians DAD1 was 607 bp, consist of a 5'-terminal untranslated region (UTR) of 63 bp, a 3'-terminal UTR of 205 bp with a canonical polyadenylation signal sequence AATAAA and a poly (A) tail, and an open reading frame of 339 bp. The deduced amino acid sequence of the A. irradians DAD1 showed 75.5% identity to Araneus ventricosus, 74.5% to Drosophila melanogaster, and 73.6% to Homo sapiens, Sus scrofa, Mesocricetus auratus, Rattus norvegicus and Mus musculus. Excluding the Saccharomyces cerevisiae DAD1 homologue, all animal DAD1 including A. irradians DAD1 homologue formed a subgroup and all plant DAD1 proteins formed another subgroup in the phylogenetic analysis. The A. irradians DAD1 was expressed in all examined tissues including adductor muscle, mantle, gills, digestive gland, gonad and hemolymph, suggesting that A. irradians DAD1 is expressed in most body tissues. Furthermore, the mRNA expression levels of A. irradians DAD1 gene of hemolymph were particularly high after injury, suggesting that the gene is responsive to injury stimuli.

Cell suicide and caspases

Programmed cell death or apoptosis is a well regulated physiological form of cellular autodestruction. It plays an essential role in embryonic development, homeostasis, remodeling, surveillance, and host defense mechanisms. Conversely dysregulation of apoptosis, resulting in either too less or excessive cell death is implicated in pathogenesis of stroke, myocardial infarction, neurodegenerative diseases, cancer and autoimmmune disorders. Apoptosis is coordinated by a family of cysteine proteinases called caspases, which dismantle the cell by targeting panoply of proteins. The mammalian caspase family contains 14 members, a subset participates in cellular demise and the remaining are involved in the processing of pro-inflammatory cytokines. We have tried to develop a simplified picture of basic apoptotic mechanisms on the basis of recent insights into the area.

Photochemical damage of the retina

Visual perception occurs when radiation with a wavelength between 400 and 760 nm reaches the retina. The retina has evolved to capture photons efficiently and initiate visual transduction. The retina, however, is vulnerable to damage by light, a vulnerability that has long been recognized. Photochemical damage has been widely studied, because it can cause retinal damage within the intensity range of natural light. Photochemical lesions are primarily located in the outer layers at the central region of the retina. Two classes of photochemical damage have been recognized: Class I damage, which is characterized by the rhodopsin action spectrum, is believed to be mediated by visual pigments, with the primary lesions located in the photoreceptors; whereas Class II damage is generally confined to the retinal pigment epithelium. The action spectrum peaks in the short wavelength region, providing the basis for the concept of blue light hazard. Several factors can modify the susceptibility of the retina to photochemical damage. Photochemical mechanisms, in particular mechanisms that arise from illumination with blue light, are responsible for solar retinitis and for iatrogenic retinal insult from ophthalmological instruments. Further, blue light may play a role in the pathogenesis of age-related macular degeneration. Laboratory studies have suggested that photochemical damage includes oxidative events. Retinal cells die by apoptosis in response to photic injury, and the process of cell death is operated by diverse damaging mechanisms. Modern molecular biology techniques help to study in-depth the basic mechanism of photochemical damage of the retina and to develop strategies of neuroprotection.

Immunohistochemical expression of activated caspase-3 as a marker of apoptosis in glomeruli of human lupus nephritis

BACKGROUND

The role of apoptosis in lupus nephritis (LN) is still controversial. One of the key events in the process of apoptosis is activation of caspase-3. Studies of experimental models suggested that activated caspase-3 is a reliable indicator of apoptotic rate, with a favorable comparison against terminal transferase-mediated DNA nick-end labeling (TUNEL) assay. Our aim is to study apoptosis in various forms of LN and its relationship to histomorphological changes and selected laboratory findings by using activated caspase-3 as a novel marker of apoptosis.

METHODS

We investigated glomerular cell apoptosis in 51 biopsy specimens from patients with LN classified according to the International Society of Nephrology/Renal Pathology Society classification by using the TUNEL method and immunohistochemistry against activated caspase-3. In addition, activity and chronicity indices were calculated and anti-Ki-67 antibody was used to estimate proliferative activity.

RESULTS

Activated caspase-3-positive cells were present in glomeruli of 88.2% of cases, observed in the glomerular tuft and cellular and fibrocellular crescents. In the glomerular tuft, they were found mainly in segments with active inflammatory lesions. There was good correlation between apoptotic index assessed by using activated caspase-3 immunolabeling and the TUNEL method (r = 0.72; P < 0.01). We observed a significant positive correlation between apoptotic index and LN class (P < 0.001). Apoptotic index correlated significantly with activity index, proliferation index, and daily protein excretion (P < 0.001), but not chronicity index, creatinine concentration, or anti-DNA antibody-binding activity in serum.

CONCLUSION

Apoptotic rate is greater in severe active glomerular lesions in human LN, suggesting that apoptosis may be involved in augmenting inflammation in human LN.

Activation of different pathways of apoptosis by air pollution particulate matter (PM2.5) in human epithelial lung cells (L132) in culture

Epidemiological studies have associated the increase of respiratory and cardiovascular mortality and morbidity with high levels of air pollution particulate matter (PM). However, the underlying mechanisms of actions by which PM induce adverse health effects are still unclear. We have recently undertaken an extensive investigation of the adverse health effects of air pollution PM(2.5), and shown that in vitro short-term exposure to PM(2.5) induced oxidative stress and inflammation in human lung epithelial cells (L132). Hence, it was convenient to complete the physical and chemical characterization of PM and to investigate whether in vitro short-term exposure to PM could be imply in the activation of apoptosis. Accordingly, we found that 92.15% of PM were equal or smaller than 2.5 microm and their specific surface area was 1m(2)/g. Inorganic (i.e. Fe, Al, Ca, Na, K, Mg, Pb, etc.) and organic (i.e. polycyclic aromatic hydrocarbons) chemicals were found in PM, suggesting that much of them derived from wind-borne dust from the industrial complex and the heavy motor vehicle traffic. In other respects, we showed that PM exposure induced apoptosis by activating not only the tumor necrosis factor-alpha (TNF-alpha)-induced pathway (i.e. TNF-alpha secretion, caspase-8 and -3 activation), but also the mitochondrial pathway (i.e. 8-hydroxy-2'-desoxyguanosine formation, cytochrome c release from mitochondria, caspase-9 and -3 activation). Moreover, changes in the transcription rates of p53, bcl-2, and bax genes, on the one hand, and DNA fragmentation, on the other hand, were reported in PM-exposed proliferating L132 cells, revealing the occurrence of apoptotic events. Taken together, these findings suggested that in vitro short-term exposure to PM(2.5) induced apoptosis in L132 cells.

Asterosaponin 1, a cytostatic compound from the starfish Culcita novaeguineae, functions by inducing apoptosis in human glioblastoma U87MG cells

Malignant glioblastoma is one of the most common malignant tumors in the neurological system. Asterosaponin 1, a new cytostatic agent from the starfish Culcita novaeguineae appear to exhibit various biological activities, including antitumor effect, but the function and mechanism of this new agent on glioblastoma cells has not previously been determined. In the present study, we investigated the proliferation change of human glioblastoma U87MG cells exposed to different concentrations (2.5-20.0 microg/ml) of asterosaponin 1 for a certain time. The results showed that asterosaponin 1 significantly suppressed U87MG cell proliferation in a time- and dose-dependent manner (IC50 =4.3 microg/ml). Flow cytometric analysis of DNA in U87MG cells showed that asterosaponin 1 induces the prominent appearance of a sub-G1 peak in the cell cycle suggestive of apoptosis identical with the result of annexin V/PI assay. Furthermore, U87MG cells treatment with asterosaponin 1 resulted in nuclear condensation with apoptotic bodies observed by both fluorescence and electron microscopy. Agarose gel electrophoresis of DNA from asterosaponin 1-treated cells revealed a typical "ladder" consistent with apoptotic DNA fragmentation. Western-blot staining showed asterosaponin 1 decreased the expression of Bcl-2 protein and increased the expression of Bax protein. The novel findings suggest that the cytostatic actions of asterosaponin 1 toward U87MG cells result from the induction of cell apoptosis. Overall, our data demonstrate that asterosaponin 1 is fully equipped for an efficient apoptotic killing of glioblastoma cells and suggest that this mechanism may play a critical role in anti-tumor chemotherapy.

Comparison of possible carcinogenic estradiol metabolites: Effects on proliferation, apoptosis and metastasis of human breast cancer cells

OBJECTIVES

Certain estradiol metabolites may play a pivotal role in breast carcinogenesis. Of special interest are the metabolites 2-hydroxyestradiol (2-OHE2), which can react anti-carcinogenically, and 4-hydroxyestradiol (4-OHE1) and 16a-hydroxyestrone (16-OHE1), which may have procarcinogenic potential. In the present study, we have compared for the first time the effect of these metabolites and their parent substance 17beta-estradiol (E2) on proliferation, apoptosis, apoptosis markers and markers of metastatic property of human breast cancer cells.

METHODS

MCF-7 cells (human estrogen-receptor positive metastatic breast cancer cell line) were incubated with the estrogens at concentrations of 0.1-100 nM. Cell proliferation rate was measured by the ATP-assay. Apoptosis was measured by cell death assay and the apoptosis markers cytochrome C, Bcl-2, Fasl and p53 were determined in cell lysates by ELISAs. The markers of metastatic property of the cell line, VEGF and MCP-1 were measured in the cell supernatant by ELISAs.

RESULTS

The estrogens E2, 4-OHE2 and 16-OHE1 display a proliferative effect on MCF-7 cells which is accompanied by a down-regulation of apoptosis. Various markers of apoptosis such as Bcl-2, cytochrome C and p53 appear to be involved. No significant effect was found for the metabolite 2-OHE2. VEGF and MCP-1 were up-regulated by E2 and 16-OHE1, whereas 2-OHE2 and 4-OHE2 did not show any effect.

CONCLUSIONS

The most potent estrogen regarding proliferation, apoptosis and metastasis of breast cancer cells seems to be estradiol. However, the estradiol metabolites 4-OHE2 and 16-OHE1 elicit similar properties on cell proliferation, apoptosis and metastasis as compared to estradiol but only at higher concentrations. In contrast 2-OHE2 did not show any significant effect on these parameters. Thus, intracellular estradiol metabolism may determine an individual's risk for breast carcinogenesis.

Immunohistochemical expression of activated caspase-3 in human myocardial infarction

There is mounting evidence that apoptosis is important in the pathogenesis of myocardial infarction (MI). One of the key events in the process of apoptosis is activation of caspase-3. Much attention has been recently paid to caspase inhibition as a potential treatment for ischemic cardiac disease. To predict the long-term effect of such treatment, it is essential to understand the significance of caspase-3 in the evolution of MI. Our aim was therefore to analyze immunohistochemical expression of activated caspase-3 in MI. Our study included autopsy samples of infarcted heart tissue from 50 patients with MI. Immunohistochemistry was performed by a sensitive peroxidase-streptavidin method on formalin-fixed, paraffin-embedded tissue, using monoclonal antibodies against activated (cleaved) caspase-3. We found caspase-3-positive myocytes in 18 MI less than 24 h old and in 3 MI that were presumably 48 h old. Their density (number of labeled myocytes/mm(2)) was greater in patients who received reperfusion treatment (mean 0.160+/-0.373 vs 0.025+/-0.037, p=0.06). In MI older than 48 h, positive reaction was observed in neutrophil granulocytes in the interstitium and, in subacute MI, it was observed in mononuclear inflammatory cells, myofibroblasts, and vascular endothelial cells. Our results suggest that apoptosis of myocytes is an important mode of cell death in the early MI, being enhanced in patients who received reperfusion treatment. After 48 h, apoptosis is an important mechanism of the clearance of neutrophil granulocytes and other inflammatory cells and of scar formation. Treatment with caspase inhibitors therefore will not only affect myocyte loss but will also interfere with the clearance of neutrophils and with the transformation of granulation tissue into a scar.

FAS and FAS-L expression by tumor cells and lymphocytes in breast carcinomas and their lymph node metastases

FAS receptor (FAS, CD95) and FAS ligand (FAS-L, CD95-L) are complementary members of a particular apoptotic pathway that plays a major role in immune regulation. The activation of FAS-L may trigger cytotoxic mechanisms leading to the death of FAS-expressing cells. Tumor cells and tumor-infiltrating lymphocytes (TIL) may express FAS and FAS-L in various proportions, and their interplay may affect tumor behavior. In the present study, we explored the expression of FAS and FAS-L in 28 mammary carcinomas (19 ductal and 9 lobular) and in their lymph node metastases. The expression of these mediators in immunostained sections was graded and evaluated comparatively between normal and neoplastic mammary epithelium, between tumor cells and TILs, and between mammary carcinoma cells and their lymph node metastases. We demonstrated the coexpression of FAS and FAS-L by breast carcinoma cells and TIL, with FAS expressed more strongly by normal epithelial cells and TIL than tumor cells. FAS-L was better stained on tumor cells than on TIL. There was equal or greater expression of FAS and FAS-L in the primary tumors and their TIL than in the metastatic counterparts. Comparing the expression of FAS with that of FAS-L, we recorded FAS equal or stronger than FAS-L in the primary mammary tumors and the reversal of their expression, FAS-L greater than FAS in the lymph node metastases. These results are consistent with reports of studies with other tumors, suggesting that the upregulated FAS-L indicates an increased ability of tumor cells to induce apoptosis in TIL and in the normal tissues invaded. However, it is understood that the FAS/FAS-L system, although essential for apoptosis, is only a contributing factor to the complex process of tumor invasion and antitumor defense.

Death receptor signals to mitochondria

Apoptosis is the best-characterized form of programmed cell death (PCD) and is of fundamental importance in tissue homeostasis. In mammalian systems, there are two major pathways that are involved in the initiation of apoptosis: the "extrinsic" death receptor pathway and the "intrinsic" mitochondrial pathway. Although these pathways act independently to initiate the death machinery in some cellular systems, in many cell types, including numerous tumor cells, there is delicate coordination and cross talk between the extrinsic and intrinsic pathways, which leads to the activation of the executioner caspase cascade. Additionally, there appears to be a fine balance between the caspase-mediated arm of death receptor signaling that engages mitochondria and the caspase-independent arm that promotes vacuole proliferation in many cells. Here, we review our current knowledge about the layers of complexity that are posed by the interactions between death receptor-induced pathways and how they influence mitochondria to regulate cellular life and death decisions.

Survivin expression in hepatocellular carcinoma: correlation with proliferation, prognostic parameters, and outcome

Survivin is a novel inhibitor of apoptosis. It is detected in fetal and neoplastic adult tissue, but not in normal tissues. Several recent studies have shown that survivin not only inhibits apoptosis, but also accelerates cancer cell proliferative activity. Expression of the protein may be of prognostic significance and therapeutic relevance in many cancers. We investigated survivin expression in hepatocellular carcinoma, correlating results with proliferation (MIB-1), prognostic factors, and outcome. Paraffin-embedded sections of 72 hepatocellular carcinoma were immunostained for survivin and MIB-1 using tissue microarray technology. Expression was evaluated in nuclei and cytoplasm as intensity (0-3+), and percentage of positive cells scored on a four-tiered system with less than 10%=negative; 10-25%=1; 26-50%=2; 51-75%=3; and 76-100%=4. Frequency of nuclear survivin expression was 43%. There was a significant correlation between nuclear survivin expression and nuclear grade (P=0.0271), microvascular invasion (P=0.0064), mitotic rate (P=0.0017), and MIB-1 (P=0.0001), as well as local recurrence (P=0.0487), and disease-free survival (P=0.0098). Histologic grade (P=0.0544) and stage (P=0.0548) tended to correlate with survivin expression, which did not correlate with cirrhosis, tumor necrosis, multiple tumors, metastatic disease, or overall survival. Survivin expression correlates with poor prognostic parameters (high nuclear and histologic grade, microvascular invasion, increased proliferation (mitotic count, MIB-1)), local recurrence, and shorter disease-free survival, but does not correlate with overall survival. An important role is suggested for survivin in progression, recurrence, and treatment of hepatocellular carcinoma.

Addition of anticancer agents enhances freezing-induced prostate cancer cell death: implications of mitochondrial involvement

Recent evidence suggests that the successful treatment of prostate cancer may require adjuvant therapies. Accordingly, a better understanding of the molecular mechanisms involved in current treatments may lead to enhanced efficacy by providing a basis for adjuvant therapies. In this study, we demonstrate that the combination of sub-lethal concentrations of chemotherapeutic agents prior to freezing (-15 degrees C) in a prostate cancer cell (PC-3) model results in enhanced efficacy over either treatment alone. Morphological analysis revealed that necrosis appeared to be the prevalent mode of cell death following adjuvant (in vitro) modeling, yet molecular analysis indicated that freezing and chemotherapy differentially activated apoptotic cascades through modulating opposing members of the Bcl-2 protein family. Freezing results in a time-dependent increase of the antiapoptotic Bcl-2 protein, while chemotherapy results in an increase of the pro-apoptotic Bax protein. Anti-apoptotic Bcl-2 protein levels increase over 3-fold following exposure to freezing. 5-Fluorouracil (5-FU) causes pro-apoptotic Bax levels to increase 2-fold during the drug exposure. The increase in Bax was also apparent following the combination of 5-FU/freezing, while Bcl-2 levels were maintained at or below control levels. This led to a shift in the Bcl-2 to Bax ratio to a pro-death tendency. Other effective cryo/chemo combinations were also found to provide similar effects. The combination of cisplatin/freezing resulted in a 4-fold increase in the ratio of Bax to Bcl-2 when compared to controls, which represented a 2-fold increase over the 5-FU/freezing-combination model. This increase may contribute to the continued reduction in cell number observed during the 13-day recovery period. Additionally, the addition of an apoptotic caspase inhibitor was not able to protect cultures from cell death following combination treatment. In conclusion, the data suggest that both Bcl-2 and Bax may, not only, play an important role in the efficacy of the cryo/chemo combination, but also the balance between the two may determine the role and extent of system destruction.

Interactions of the allogeneic effector leukemic T cell line, TALL-104, with human malignant brain tumors

TALL-104 is a human leukemic T cell line that expresses markers characteristic of both cytotoxic T lymphocytes and natural killer cells. TALL-104 cells are potent tumor killers, and the use of lethally irradiated TALL-104 as cellular therapy for a variety of tumors has been explored. We investigated the interactions of TALL-104 cells with human brain tumor cells. TALL-104 cells mediated increased lysis of a panel of brain tumor cells at low effector-to-target ratios over time. We obtained evidence that TALL-104 cells injured glioma cells by both apoptotic and necrotic pathways. A 7-amino actinomycin D flow cytometry assay revealed that the percentages of both apoptotic and necrotic glioma cells increased after TALL-104 cell/glioma cell coincubations. Fluorescent microscopy studies and a quantitative morphologic assay confirmed that TALL-104 cell/glioma cell interactions resulted in tumor cell apoptosis. Cytokines are secreted when TALL-104 cells are coincubated with brain tumor cells; however, morphologic analysis assays revealed that the soluble factors contained within clarified supernates obtained from 4 h coincubates added back to brain tumor cell cultures did not trigger the glioma apoptosis. TALL-104 cells do not express Fas ligand, even upon coincubation with glioma targets, which suggests that the Fas/Fas ligand apoptotic pathway is not likely responsible for the cell injury observed. We obtained evidence that cell injury is calcium dependent and that lytic granule exocytosis is triggered by contact of TALL-104 cells with human glioma cells, suggesting that this pathway mediates glioma cell apoptosis and necrosis.

Diepoxybutane induces caspase and p53-mediated apoptosis in human lymphoblasts

Diepoxybutane (DEB) is the most potent metabolite of the environmental chemical 1,3-butadiene (BD), which is prevalent in petrochemical industrial areas. BD is a known mutagen and human carcinogen, and possesses multiorgan systems toxicity that includes bone marrow depletion, spleen, and thymus atrophy. Toxic effects of BD are mediated through its epoxy metabolites. In working towards elucidating the cellular and molecular mechanisms of BD toxicity, we investigated the ability of DEB to induce apoptosis in human lymphoblasts. DEB induced a concentration and exposure time-dependent apoptosis, which accounted for the DEB-induced loss of cell viability observed in TK6 lymphoblasts. The DEB-induced apoptosis was inhibited by inhibitors of caspases 3 and 9. The role of p53 in mediating the DEB-induced apoptosis was also investigated. DEB induced elevated p53 levels in direct correlation to the extent of DEB-induced apoptosis, as the concentration of DEB increased up to 5 microM. The extent of DEB-induced apoptosis was dramatically higher in TK6 lymphoblasts as compared to the genetically paired p53-deficient NH32 lymphoblasts under the same experimental conditions. Our results confirm and extend observations on the occurrence of apoptosis in DEB exposed cells, and demonstrate for the first time the elevation of p53 levels in human lymphoblasts in response to DEB exposure. In addition, our results demonstrate for the first time that DEB-induced apoptosis is mediated by caspases 3 and 9, as well as the p53 protein. It is possible that DEB-induced apoptosis may explain BD-induced bone marrow depletion, spleen and thymus atrophy in BD-exposed animals.