Activation of apoptosis pathways by anticancer drugs

Tangeretin inhibits hepatocellular carcinoma proliferation and migration by promoting autophagy-related BECLIN1

Background: Hepatocellular carcinoma (HCC) is a particularly prevalent type of liver cancer and is one of the deadliest malignancies in Asia. Tangeretin is a biological compound extracted from traditional Chinese herbs and has been shown to have potential antitumour properties; however, its mechanism remains largely unknown. Therefore, we sought to determine the role of Tangeretin in HepG2 cells subjected to antitumour treatment. Materials and methods: Cell proliferation was quantified using CCK-8, EdU and colony formation assays, and cell migration was quantified using transwell migration and wound healing assays. Protein expression was assessed using Western blot analysis. Small interfering RNA was used to interfer protein expression. Immunoprecipitation was performed to detect the protein-protein interactions. Results: Tangeretin decreased cell proliferation and increased G2/M arrest. Tangeretin decreased cell migration. Tangeretin increased the LC3II/LC3I ratio and decreased p62 expression in HepG2 cells. Furthermore, the knockdown of BECLIN1 expression in HepG2 cells partially converted the Tangeretin-induced inhibition of proliferation, migration and autophagy. In addition, Tangeretin activated the JNK1/Bcl-2 pathway and disturbed the interaction between Bcl-2 and BECLIN1. Together, our findings demonstrate that Tangeretin inhibited the proliferation and migration of HepG2 cells through JNK/Bcl-2/BECLIN1 pathway-mediated autophagy. Conclusion: Our study contributes to the understanding of the inhibitory mechanism of Tangeretin on HCC development.

VDAC1 at the crossroads of cell metabolism, apoptosis and cell stress

This review presents current knowledge related to VDAC1 as a multi-functional mitochondrial protein acting on both sides of the coin, regulating cell life and death, and highlighting these functions in relation to disease. It is now recognized that VDAC1 plays a crucial role in regulating the metabolic and energetic functions of mitochondria. The location of VDAC1 at the outer mitochondrial membrane (OMM) allows the control of metabolic cross-talk between mitochondria and the rest of the cell and also enables interaction of VDAC1 with proteins involved in metabolic and survival pathways. Along with regulating cellular energy production and metabolism, VDAC1 is also involved in the process of mitochondria-mediated apoptosis by mediating the release of apoptotic proteins and interacting with anti-apoptotic proteins. VDAC1 functions in the release of apoptotic proteins located in the mitochondrial intermembrane space via oligomerization to form a large channel that allows passage of cytochrome c and AIF and their release to the cytosol, subsequently resulting in apoptotic cell death. VDAC1 also regulates apoptosis via interactions with apoptosis regulatory proteins, such as hexokinase, Bcl2 and Bcl-xL, some of which are also highly expressed in many cancers. This review also provides insight into VDAC1 function in Ca²⁺ homeostasis, oxidative stress, and presents VDAC1 as a hub protein interacting with over 100 proteins. Such interactions enable VDAC1 to mediate and regulate the integration of mitochondrial functions with cellular activities. VDAC1 can thus be considered as standing at the crossroads between mitochondrial metabolite transport and apoptosis and hence represents an emerging cancer drug target.

Pristimerin demonstrates anticancer potential in colorectal cancer cells by inducing G1 phase arrest and apoptosis and suppressing various pro-survival signaling proteins

Pristimerin is a naturally occurring triterpenoid that has a cytotoxic effect on several cancer cell lines. However, the cytotoxic effects of pristimerin as well as its molecular mechanisms of action against colorectal cancer have never been explored. In the present study, we investigated the anticancer potential of pristimerin, and examined the different signaling pathways affected by its action in three colon cancer cell lines namely HCT-116, COLO-205 and SW-620. Pristimerin was found to possess potent cytotoxic and proliferation inhibitory effects against these cell lines. Cell cycle analysis revealed G1 phase arrest, which was strongly associated with decreased expression of cyclin D1 and cyclin-dependent kinases (cdk4 and cdk6) with concomitant induction of p21. Pristimerin also induced apoptosis in a dose-dependent manner. Cell plasma membrane alterations studied by Annexin V/PI double staining, loss of mitochondrial membrane potential (ΔΨm), measurements of caspase activities and the inhibitory effect of Z-VAD-FMK (a caspase inhibitor) confirmed the apoptotic effect of pristimerin. Moreover, western blot data showed that apoptotic induction was associated with activated caspase-3 and -8, PARP-1 cleavage and modulation of the expression levels of Bcl-2 family proteins. Additionally, pristimerin treatment downregulated the phosphorylated forms of EGFR and HER2 proteins, and subsequently caused a decrease in the phosphorylated forms of Erk1/2, Akt, mTOR and NF-κB proteins. Taken together, these results suggest that pristimerin may have potential as a new targeting therapeutic strategy for the treatment of colon cancer.

Anticancer effects of traditional Chinese herbs with phlegm-eliminating properties - An overview

ETHONOPHARMACOLOGICAL RELEVANCE

Cancer is considered to be the second leading cause of human death. It is unsatisfactory that in the past decades, the treatment for cancer has not progressed as fast as it was expected, as only 50% of newly diagnosed patients could be cured even today. The development of cancer is a multifactorial process, involving tumor cells themselves, the interactions between tumor cells and their microenvironments, as well as the interactions between tumor cells and the host's immunity. Focusing on any single goal may bring limited benefits.

AIM AND METHODS OF THE STUDY

Phlegm-eliminating herbs, which can reduce phlegm and eliminate pathological metabolites, are commonly used to treat cancer in China. However, the underlying molecular targets and efficacy of herbal medicines in cancer treatment still remain unclear. In this study, we reviewed the potential anticancer mechanisms of some phlegm-eliminating herbs and their active ingredients from the articles through such scientific databases as MEDLINE, PubMed, and Google Scholar.

RESULTS

We found that the anticancer mechanisms of phlegm-eliminating herbs and ingredients include inducing apoptosis, anti-proliferation, preventing tumor invasion and metastasis, and reducing resistance to chemotherapy. In addition, some phlegm-eliminating herbs and their ingredients have anti-inflammatory and anti-metabolic syndrome effects.

CONCLUSIONS

We suggest that the phlegm-eliminating herbs and ingredients are potential candidates for anticancer treatment and cancer prevention by playing a comprehensive role.

Anticancer activity of flavonol and flavan-3-ol rich extracts from Croton celtidifolius latex

CONTEXT

Croton celtidifolius Baill (Euphorbiaceae) is a tree found in the Atlantic Forest in Southern Brazil, where it is commonly known as "Sangue-de-Dragão". Its red latex is used traditionally for treating ulcers, diabetes and cancer.

OBJECTIVE

To evaluate antitumor activities of Croton celtififolius latex in vitro and in vivo.

MATERIAL AND METHODS

Phytochemical analyses were conducted using HPLC-DAD-MS. Cytotoxic, nuclease and pro-apoptotic properties were determined using the tetrazolium salt assay (MTT), plasmid DNA damage assay and ethidium bromide (EB)/acridine orange methods, respectively, and antitumor activity was determined in the Ehrlich ascites carcinoma (EAC) mouse model.

RESULTS

Phytochemical studies indicated a high phenol content of flavonols (45.67 ± 0.24 and 18.01 ± 0.23 mg/mL of myricetin and quercetin, respectively) and flavan-3-ols (114.12 ± 1.84 and 1527.41 ± 16.42 mg/L of epicatechin and epigallocatechin, respectively) in latex. These compounds reduced MCF-7 and EAC cell viability in the MTT assay (IC50 = 169.0 ± 1.8 and 187.0 ± 2.2 μg/mL, respectively). Latex compounds caused significant DNA fragmentation and increased the number of apoptotic cells (negative control (NC), 12%; latex, 41%) as indicated by differential staining in the EB/acridine orange assay. The in vivo latex treatment at 3.12 mg/kg/day reduced the body weight by 7.57 ± 2.04 g and increased median survival time to 17.5 days when compared to the NC group (13.0 days). In addition, the highest latex concentration inhibited tumor growth by 56%.

DISCUSSION AND CONCLUSION

These results agree with ethno-pharmacological reports showing cytotoxicity and antitumor activity of C. celtidifolius latex. The mechanism of antitumor action may be related to direct DNA fragmentation that reduces survival and induces apoptosis.

The triterpenoid pristimerin induces U87 glioma cell apoptosis through reactive oxygen species-mediated mitochondrial dysfunction

It has become evident that some of the natural or synthetic triterpenoids are natural proteasome inhibitors that have great potential for use in cancer prevention and treatment. However, the mechanisms for the antitumor activity of triterpenoids remain to be elucidated. In the present study, we investigated the anticancer activities of a natural triterpenoid, pristimerin, and the signaling pathways affected. Pristimerin was found to possess potent cytotoxic effects, inducing apoptosis and inhibiting proliferation in U87 human glioma cells. Hoechst 33258 staining and Annexin V/PI double staining exhibited the typical nuclear features of apoptosis and increased the proportion of apoptotic Annexin V-positive cells in a dose-dependent manner, respectively. Moreover, western blotting assay revealed that this apoptotic induction was associated with activated caspase-9, caspase-3, PARP cleavage and downregulation of Bcl-xl/Bax in a concentration-dependent manner. Pristimerin also increased the generation of reactive oxygen species and induced the subsequent release of cytochrome c from the mitochondria into the cytosol. Additionally, pristimerin downregulated EGFR protein expression and inhibited downstream signaling pathways in U87 cells. Our results suggest that pristimerin may have potential as a new targeting therapeutic strategy in the treatment of EGFR-overexpressing gliomas.

Newly synthesized bis-benzimidazole derivatives exerting anti-tumor activity through induction of apoptosis and autophagy

In this study, a new series of bis-benzimidazole derivatives were designed and synthesized. Most of these new compounds showed significant anti-tumor activity in vitro compared to Hoechst 33258. Among them, the most potent compound 8 had the IC(50) values of 0.56μM for HL60 (Human promyelocytic leukemia cells) tumor cell line and 0.58μM for U937 (Human leukemic monocyte lymphoma cells) tumor cell line. Subsequent toxicity study on human peripheral blood mononuclear cells (PBMC) showed that compound 8 exhibited less toxicity than 5-FU. We also found that apoptosis and autophagy were simultaneously induced by compound 8 in HL60 cells, and inhibition of autophagy by 3-MA decreased compound 8-induced apoptosis, indicating that they acted in synergy to exert tumor cell death.

Effect of Benzothiazole based conjugates in causing apoptosis by Regulating p53, PTEN and MAP Kinase proteins affecting miR-195a and miR-101-1

BACKGROUND

Hepatocellular carcinoma (HCC) accounts for majority of liver cancers and is the leading cause of cancer related death in Asia. Like any other cancer, HCC develops when there is a mutation to the cellular machinery that causes the cell to replicate at a higher rate and results in the loss of apoptosis. Therefore, a delicate balance between the expression of various genes involved in proliferation and apoptosis decide the ultimate fate of the cell to undergo rapid proliferation (cancer) or cell death.

RESULTS

The benzothiazole based compounds exhibited effective cytotoxicity at 4 μM concentration and have shown G1 cell cycle arrest with decrease in levels of G1 cell cycle proteins such as cyclin D1 and Skp2. Involvement of tumour suppressor proteins such as PTEN and p53 was studied. Interestingly these compounds displayed decrease in the phosphorylated forms of AKT, p38 MAPK and ERK1/2 which play a vital role in cell proliferation. Compounds have exhibited strong and significant effect on the expression of micro RNAs such as miR-195a & miR-101-1 which regulate hepatic cell proliferation.

CONCLUSIONS

The cell cycle arrest and apoptotic inducing nature of these compounds was revealed by FACS, BrdU cell proliferation and tunel assays. Compounds affected both tumour suppressor proteins as well as proteins that are involved in active cell proliferation. Micro RNAs whose target is Cyclin D1 such as miR-195a and miR-101-1 that is required for growth of hepatoma cells was drastically affected. These compounds caused apoptosis by activating caspase-3 and PARP.

3β-hydroxylup-20(29)-ene-27,28-dioic acid dimethyl ester, a novel natural product from Plumbago zeylanica inhibits the proliferation and migration of MDA-MB-231 cells

Plumbago zeylanica, a traditional Indian herb is being used for the therapy of rheumatism and has been approved for anti-tumor activity. However, the molecular mechanisms involved in the biological action are not very well understood. In this study, the anti-invasive activities of P. zeylanica methanolic extract (PME) and pure compound 3β-hydroxylup-20(29)-ene-27,28-dioic acid (PZP) isolated from it are investigated in vitro. PME and PZP were noted to have the ability to induce apoptosis as assessed by flow cytometry. Further, the molecular mechanism of apoptosis induced by PME and PZP was found by the loss of mitochondrial membrane potential with the down regulation of Bcl-2, increased expression of Bad, release of cytochrome c, activation of caspase-3 and cleavage of PARP leading to DNA fragmentation. Importantly, both PME and PZP were observed to suppress MDA-MB-231 cells adhesion to the fibronectin-coated substrate and also inhibited the wound healing migration and invasion of MDA-MB-231 cells through the reconstituted extracellular matrix. Gelatin zymography revealed that PME and PZP decreased the secretion of matrix metalloproteinases-2 (MMP-2) and metalloproteinases-9 (MMP-9). Interestingly both PME and PZP exerted an inhibitory effect on the protein levels of p-PI3K, p-Akt, p-JNK, p-ERK1/2, MMP-2, MMP-9, VEGF and HIF-1α that are consistent with the observed anti-metastatic effect. Collectively, these data provide the molecular basis of the anti-proliferative and anti-metastatic effects of PME and PZP.

FAP-associated desmoid invasiveness correlates with in vitro resistance to doxorubicin

Desmoid tumors are locally invasive myofibroblastic lesions that arise predominantly in the abdominal wall or shoulder girdle and are prone to aggressive local recurrences without metastases. We hypothesized the intrinsic invasiveness and drug resistance displayed by cells derived from a familial adenomatous polyposis (FAP)-associated desmoid tumor would surpass the response shown by cells derived from sporadic desmoid tumors. In vitro cell motility and expression of motility-associated genes were quantified using Boyden Chambers and Enzyme-Linked ImmunoSorbent Assays, respectively. Doxorubicin resistance was quantified by Trypan Blue dye exclusion. cDNA microarrays identified genes responsive to doxorubicin. FAP-associated tumor cells were significantly more invasive and refractory to doxorubicin than were cells extracted from sporadic tumors. Pro-MMP1 protein predominated over MMP3 in FAP-associated cell culture supernatants, while MMP3 was the dominant antigen in sporadic tumor cell supernatants. Three genes associated with apoptosis were identified by microarray, two prosurvival genes overexpressed in FAP-associated cell cultures (NTN1, TNFRSF10C) and one proapoptosis gene overexpressed in sporadic tumor cell cultures (FOXL2).

Pyrimethamine (2,4-diamino-5-p-chlorophenyl-6-ethylpyrimidine) induces apoptosis of freshly isolated human T lymphocytes, bypassing CD95/Fas molecule but involving its intrinsic pathway

Pyrimethamine (2,4-diamino-5-p-chlorophenyl-6-ethyl-pyrimidine), a folic acid antagonist, may exert, in addition to antiprotozoan effects, immunomodulating activities, including induction of peripheral blood lymphocyte apoptosis. However, the molecular mechanisms underlying this proapoptotic activity remain to be elucidated. Here we show that pyrimethamine, used at a pharmacologically relevant concentration, induced per se apoptosis of activated lymphocytes via the activation of the caspase-8- and caspase-10-dependent cascade and subsequent mitochondrial depolarization. Importantly, this seems to occur independently from CD95/Fas engagement. The proapoptotic activity of pyrimethamine was further confirmed in a patient with autoimmune lymphoproliferative syndrome, an immune disorder associated with a defect of Fas-induced apoptosis. In this patient, pyrimethamine treatment resulted in a "normalization" of lymphocyte apoptosis with a significant amelioration of laboratory parameters. Altogether, these results suggest a mechanism for pyrimethamine-mediated apoptosis that seems to bypass CD95/Fas engagement but fully overlaps CD95/Fas-induced subcellular pathway. On these bases, a reappraisal of the use of pyrimethamine in immune lymphoproliferative disorders characterized by defects in CD95/Fas-mediated apoptosis should be taken into account.

Pristimerin induces caspase-dependent apoptosis in MDA-MB-231 cells via direct effects on mitochondria

Pristimerin, a naturally occurring triterpenoid, has been shown to cause cytotoxicity in several cancer cell lines. However, the mechanism for the cytotoxic effect of pristimerin was never explored. In the present study, human breast cancer MDA-MB-231 cells treated with pristimerin (1 and 3 micromol/L) showed rapid induction of apoptosis, as indicated by caspase activation, DNA fragmentation, and morphologic changes. Pretreatment of a pan-caspase inhibitor benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone (z-VAD-fmk) completely prevented pristimerin-induced apoptosis. Treatment of tumor cells with pristimerin resulted in a rapid release of cytochrome c from mitochondria, which preceded caspase activation and the decrease of mitochondrial membrane potential. In addition, neither benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone nor permeability transition pore inhibitor cyclosporin A markedly prevented pristimerin-induced mitochondrial cytochrome c release. Pristimerin did not significantly alter the protein level of Bcl-2 family members (Bcl-2, Bcl-X(L), and Bax), nor did it induce Bax translocation. Moreover, Bcl-2 overexpression fails to prevent pristimerin-induced apoptosis. The generation of reactive oxygen species in MDA-MB-231 cells was also not affected by pristimerin. In a cell-free system, pristimerin induced cytochrome c release from isolated mitochondria. Taken together, these results suggested that pristimerin is a novel mitochondria-targeted compound and may be further evaluated as a chemotherapeutic agent for human cancer.

Synergistic effects of chemotherapeutic drugs in lymphoma cells are associated with down-regulation of inhibitor of apoptosis proteins (IAPs), prostate-apoptosis-response-gene 4 (Par-4), death-associated protein (Daxx) and with enforced caspase activation

Cytotoxic drugs mediate apoptotic tumor cell death by influencing key regulator proteins of programmed cell death. In clinical practice cytotoxic drug combinations are desired to potentiate tumor cell kill and to minimize side effects. Nevertheless, the molecular mechanisms underlying synergistic and antagonistic effects on tumor cells are still poorly understood. In order to elucidate these molecular mechanisms we established models of synergistic and antagonistic drug combinations within the same lymphoma cell lines. By combination index method we demonstrated that bendamustine in combination with either doxorubicin or mitoxantrone caused antagonistic effects on disruption of mitochondrial membrane potential as well as on the rate of apoptosis. In contrast the combination of bendamustine with cladribine acted synergistically on these parameters. By using the IC(50) (dosages causing 50% rate of apoptosis) the synergistic effect of the combination of bendamustine and cladribine was associated with an enhanced mitochondrial release of cytochrome c and Smac/DIABLO, by down-regulation of x-linked inhibitor of apoptosis (XIAP), cIAP1, Par-4 and Daxx as well as by a significantly increased activation of caspases-3, -6, -7, -8 and -9. At the same rate of apoptosis (IC(50)), the antagonistic combinations did not increase the release of cytochrome c or Smac/DIABLO, nor down-regulate the expression of XIAP, cIAP1, Par-4 and Daxx, nor increase the activation of caspases. The role of down-regulation of IAPs and of enforced caspase activation for synergism in this model was supported by the observation, that broad spectrum inhibition of caspases re-established expression of XIAP. Our study is the first to outline the molecular alterations caused by synergistic and antagonistic drug combinations within the same lymphoma cell model. The above described mechanisms were already assessable at a point where the effects of synergistic or antagonistic combinations could not yet be discriminated quantitatively by the level of apoptosis rate of the lymphoma cells.

Deguelin inhibits the growth of colon cancer cells through the induction of apoptosis and cell cycle arrest

As previously demonstrated, deguelin [(7aS, BaS)-13, 13a-dihydro-9,10-dimethoxy-3,3-dimethyl-3H-bis[1]benzo-pyrano[3,4-b:6',5'-e]pyran-7(7aH)-one mediates anti-proliferative properties in a variety of cell types. In the present study, deguelin was found to suppress the growth of HT-29 colon cancer cells with an IC(50) of 4.32 x 10(-8) M. The cells were arrested in the G1-S-phase of the cycle. Investigations of G1/S regulatory proteins by Western blot analyses showed an upregulation of p27, and decreased expression levels of cyclin E and CDK4. Furthermore, by 24 h, exposure to deguelin resulted in an increase in the hypophosphorylated form of Rb. Since hypophosphorylated pRb binds to and inactivates E2F1, additional studies were performed and downregulation of E2F1 was observed after 24 h of treatment with deguelin. These results are consistent with the observation that deguelin arrested cells in the G1-S- phase. In addition, based on ethidium bromide/acridine orange staining, detection of digoxigenin-labelled genomic 3'-OH DNA ends, and DNA laddering, it was found that deguelin exerts its growth inhibitory effects via the induction of apoptosis. Based on these data, the potential of deguelin to serve as a cancer chemotherapeutic agent for colon cancer may be suggested.

Reversion of autoimmune lymphoproliferative syndrome with an antimalarial drug: preliminary results of a clinical cohort study and molecular observations

Autoimmune lymphoproliferative syndrome (ALPS) is a paediatric disease characterized by lymphoproliferation and autoimmunity. Most patients are known to carry heterozygous mutations of the TNFRSF6 gene leading to diminished Fas-mediated apoptosis and failure of activated lymphocytes to undergo apoptosis. A subgroup of patients without the TNFRSF6 gene mutation has similar defective apoptosis and clinical features. No effective treatment has been reported so far. Glucocorticoids, intravenous immunoglobulin and/or immunosuppressive drugs have usually led to only transient clinical improvement. Seven ALPS patients (two type Ia and five type III) were treated with the antimalarial drug Fansidar. No toxicity was observed. An objective response was seen in six of them and, in two, the treatment was stopped without reappearance of the symptoms. Moreover, a marked decrease in interleukin-10 levels was observed in two patients during the treatment. We found that the drug induced apoptosis in activated lymphocytes through activation of the mitochondrial apoptotic pathway.

Inhibition of tumour cell growth by hyperforin, a novel anticancer drug from St. John's wort that acts by induction of apoptosis

Hyperforin is a plant derived antibiotic from St. John's wort. Here we describe a novel activity of hyperforin, namely its ability to inhibit the growth of tumour cells by induction of apoptosis. Hyperforin inhibited the growth of various human and rat tumour cell lines in vivo, with IC(50) values between 3-15 microM. Treatment of tumour cells with hyperforin resulted in a dose-dependent generation of apoptotic oligonucleosomes, typical DNA-laddering and apoptosis-specific morphological changes. In MT-450 mammary carcinoma cells hyperforin increased the activity of caspase-9 and caspase-3, and hyperforin-mediated apoptosis was blocked by the broad-range caspase inhibitor zVAD.fmk. When added to MT-450 cells, hyperforin, but not paclitaxel, induced a rapid loss of the mitochondrial transmembrane potential Deltapsi(m), and subsequent morphological changes such as homogenization and vacuolization of mitochondria. Monitoring of Deltapsi(m) revealed that the hyperforin-mediated mitochondrial permeability transition can not be prevented by zVAD.fmk. This indicates that mitochondrial permeabilization is a cause rather than a consequence of caspase activation. Moreover, hyperforin was capable of releasing cytochrome c from isolated mitochondria. These findings suggest that hyperforin activates a mitochondria-mediated apoptosis pathway. In vivo, hyperforin inhibited the growth of autologous MT-450 breast carcinoma in immunocompetent Wistar rats to a similar extent as the cytotoxic drug paclitaxel, without any signs of acute toxicity. Owing to the combination of significant antitumour activity, low toxicity in vivo and natural abundance of the compound, hyperforin holds the promise of being an interesting novel antineoplastic agent that deserves further laboratory and in vivo exploration.

Molecular mechanisms of death-receptor-mediated apoptosis

Apoptosis, also called "programmed cell death", can be induced by a variety of stimuli including activation of death receptors by the corresponding death ligands. Death receptors are a subgroup of the tumor necrosis factor (TNF)/nerve growth factor (NGF) receptor superfamily and are characterized by a death domain, which is required for signal transduction. Upon apoptosis induction, caspases, a family of aspartyl-specific cysteine proteases, are activated, which are the main executioners of apoptosis. Finally, specific death substrates are cleaved, resulting in the morphologic features of apoptosis. Depending on the cell type, activation of mitochondria is of central significance for apoptosis induction. This signaling pathway can be modulated by different pro- and anti-apoptotic proteins such as Bax and Bcl-2, which are localized at the mitochondria. Furthermore, apoptosis initiation can be prevented at the death receptor level by FLICE (caspase-8)-inhibitory proteins (FLIPs). Deregulation of apoptosis is associated with diseases like cancer, autoimmunity, and AIDS. Therefore, the elucidation of cell death pathways and the identification of modulators of apoptosis have many therapeutic implications.

CD95's deadly mission in the immune system

Apoptosis in the immune system is a fundamental process regulating lymphocyte maturation, receptor repertoire selection and homeostasis. Thus, death by apoptosis is as essential for the function of lymphocytes as growth and differentiation. This article focuses on death receptor-associated apoptosis and the role of CD95 (Apo-1/Fas)-mediated signalling in T-cell and B-cell development and during the course of an immune response. Gaining an insight into these processes improves our understanding of the pathogenesis of diseases such as cancer, autoimmunity and AIDS, and opens new approaches to rational treatment strategies.