A near atomic structure of the active human apoptosome.

In response to cell death signals, an active apoptosome is assembled from Apaf-1 and procaspase-9 (pc-9). Here we report a near atomic structure of the active human apoptosome determined by cryo-electron microscopy. The resulting model gives insights into cytochrome c binding, nucleotide exchange and conformational changes that drive assembly. During activation an acentric disk is formed on the central hub of the apoptosome. This disk contains four Apaf-1/pc-9 CARD pairs arranged in a shallow spiral with the fourth pc-9 CARD at lower occupancy. On average, Apaf-1 CARDs recruit 3 to 5 pc-9 molecules to the apoptosome and one catalytic domain may be parked on the hub, when an odd number of zymogens are bound. This suggests a stoichiometry of one or at most, two pc-9 dimers per active apoptosome. Thus, our structure provides a molecular framework to understand the role of the apoptosome in programmed cell death and disease.

Predictive value of APAF-1 and COX-2 expression in pathologic complete response to neoadjuvant chemoradiotherapy for patients with locally advanced rectal adenocarcinoma.

PURPOSE: To investigate predictive value of APAF-1 and COX-2 expression in pathologic complete response (pCR) for patients with rectal adenocarcinoma (RAC) who were treated with neoadjuvant chemoradiotherapy (neo-CRT) followed by total mesorectal excision (TME).   MATERIALS AND METHODS: Immunohistochemistry assay was used to detect expression of APAF-1 and COX-2 in paraffin-wax embedded tissues obtained before neo-CRT for patients with RAC. A 5-point tumor-regression grade (TRG) based on the ratio of residual tumor to fibrosis according to Dworak's scoring system was used to assess neo-CRT response. The relationship between expression of APAF-1 and COX-2 genes and pCR was explored. RESULTS: pCR (TRG4) was observed in 23 patients (28.0%). pCR were more likely to be achieved for those with APAF-1 over-expression or lower expression of COX-2. pCR rate in patients with combination of high APAF-1 and low COX-2 expression was 56.0%, significantly higher than those with other combination of APAF1 and COX-2 expression. Multivariate analysis showed that over-expression of APAF-1 and suppressed expression of COX-2 were independent predictive factors for pCR. CONCLUSION: Immunohistochemical evaluation of APAF-1 and COX-2 expression on pretreatment specimen may be used to predict pCR to neo-CRT in patients with RAC. The potential of the markers in monitoring pCR patient merits further investigation.

Retrotransposon insertions in the clonal evolution of pancreatic ductal adenocarcinoma.

Pancreatic ductal adenocarcinoma (PDAC) is typically diagnosed after the disease has metastasized; it is among the most lethal forms of cancer. We recently described aberrant expression of an open reading frame 1 protein, ORF1p, encoded by long interspersed element-1 (LINE-1; L1) retrotransposon, in PDAC. To test whether LINE-1 expression leads to somatic insertions of this mobile DNA, we used a targeted method to sequence LINE-1 insertion sites in matched PDAC and normal samples. We found evidence of 465 somatic LINE-1 insertions in 20 PDAC genomes, which were absent from corresponding normal samples. In cases in which matched normal tissue, primary PDAC and metastatic disease sites were available, insertions were found in primary and metastatic tissues in differing proportions. Two adenocarcinomas secondarily involving the pancreas, but originating in the stomach and duodenum, acquired insertions with a similar discordance between primary and metastatic sites. Together, our findings show that LINE-1 contributes to the genetic evolution of PDAC and suggest that somatic insertions are acquired discontinuously in gastrointestinal neoplasms.

5-Aza-2'-Deoxycytidine and CDDP Synergistically Induce Apoptosis in Renal Carcinoma Cells via Enhancing the APAF-1 Activity.

BACKGROUND: It has been reported that the hypermethylation of APAF-1, DAPK-1 and other tumor suppressive genes (TSGs) correlates with progression of renal cell carcinoma and exerts prognostic and diagnostic relevance in renal cell carcinoma. A recent study has confirmed that demethylation regulates the TSGs expression and proliferation of various types of cancer cells. The present study was to recognize a potential anti-tumor effect of 5-aza-2'-deoxycytidine (DAC), a demethylation agent. METHODS: We evaluated the DNA demethylation by DAC in human renal carcinoma cells and determined the synergism of the demethylation with the toxicity of Cisplatin (CDDP), which is a commonly utilized anti-tumor agent for renal carcinoma. RESULTS: It was demonstrated that DAC promoted a significant global genomic demethylation and improved APAF-1 expression at both mRNA and protein levels. The DAC treatment deteriorated the CDDP-induced viability decreasing Caki or ACHN cells and synergized the apoptosis induction of CDDP in ACHN cells. The treatment with both DAC and CDDP promoted a significantly higher level of renal carcinoma cell apoptosis than singular DAC or CDDP treatment. The APAF-1 knockdown significantly inhibited the synergism of DAC with the CDDP-induced apoptosis in ACHN cells. CONCLUSIONS: The present study confirmed that DAC demethylated the CpGs, particularly APAF-1 in renal carcinoma cells, and that the demethylation synergized the cytotoxity of CDDP in renal carcinoma cells via enhancing the CDDP-induced apoptosis.

Influence of polychemotherapy on the morphology of metastases and kidney of resistant RLS-bearing mice.

AIM: Polychemotherapy (PCT), widely used for the antitumor treatment has a pronounced toxic effect on the organism, and its cytostatic effect sometimes is canceled by multidrug resistance of a neoplasia. Comprehension of the nature and development of pathological changes caused by the PCT during the treatment of cancer is very important to improve the efficiency of the therapy and to clarify the mechanisms of tumor-host interactions. This study was aimed to examine PCT impact on kidney cells and tissues in mice with transplanted resistant lymphosacroma (RLS) and to analyze morphology of metastases of the tumor in kidney during PCT. MATERIALS AND METHODS: Male mice CBA/LacSto (55 animals) were intramuscularly implanted in the right hind paw by 105 cells/ml of tumor RLS (a diffuse large B-cell lymphosarcoma) with multi-drug resistance (MDR) phenotype. Mice received combination of cyclophosphamide (50 mg/kg), oncovin (0.1 mg/kg), hydroxydaunorubicin (4 mg/kg), and prednisone (5 mg/kg) accordingly to CHOP scheme each 7 days after inoculation of the tumor. The kidneys were sampled on days 1, 3 and 7 after each series of injection of PCT preparations and processed for light and electron microscopy, immunohistochemical analysis of Ki-67 and Apaf-1 proteins also was performed. RESULTS: Tumor RLS produced metastases comprised of small cells in the kidneys of mice after 8 days post inoculation. Application of PCT resulted in destruction of small-cell metastases and development of many large-cell metastases in kidney. Application of PCT induced the development of prominent damage of nephron cells, primarily in S3 segments of proximal tubules. Even one series of PCT caused reduction of basal plasma folds in these cells and alteration of mitochondria. Damage of proximal tubules and involvement of distal tubules, renal bodies and interstitial tissue in the pathologic process, increased during the experiment. This work presents the description of morphological changes in kidney as well as of the tumor metastases under PCT influence. CONCLUSION: The obtained data should be considered while designing of remedies for recovery of internal organs functions after antitumor PCT.

Design and development of a whole-cell luminescent biosensor for detection of early-stage of apoptosis.

We present here a novel whole-cell biosensor to detect early-stages of apoptosis based on Apaf-1 oligomerization and apoptosome formation using the split luciferase strategy. The amino-fragment (1-416 amino acids) and carboxy-fragment (395-550 amino acids) of firefly luciferase were fused to amino-terminal of Apaf-1. The cotransfected HEK cells were then treated with doxorubicin for induction of apoptosis. The performance of our biosensor for monitoring of programmed cell death over 24h was investigated by measuring bioluminescence activities. We observed a significant increase (≈ 15 fold) in luminescence signal compared to control cells 4h after apoptosis induction. It reached a maximum activity over 10h (≈ 155 fold). Moreover, juxtapositioning of Apaf-1 monomer and apoptosome formation occur about 5h earlier than the appearance of significant caspase3/7 activity upon induction of apoptosis by doxorubicin. The time-response curve of split luciferase shows a sigmoidal pattern which indicates cooperativity in oligomerization of Apaf-1 upon binding of cytochrome c. This biosensor can be used as a new platform, based on the protein fragment complementation strategy for assessing potential chemotherapeutic drugs as well as a sensitive and dynamic system in the time- and dose-dependent studies of apoptosis.

APAF-1 is related to an undifferentiated state in the testicular germ cell tumor pathway.

Apoptotic protease activating factor-1 (APAF-1) is a key regulator gene of apoptosis, located downstream from p53. Loss of APAF-1 expression is associated with chemorefractory malignant melanoma and neuronal cell differentiation. In order to make clear the function of APAF-1 in the carcinogenesis of germ cell tumors, we evaluated the expression levels of APAF-1 and several apoptosis and differentiation markers by immunohistochemistry in formalin-fixed paraffin-embedded samples from 43 cases of testicular germ cell tumor (TGCT) and six specimens of normal testis tissue. Expression of cleaved caspase-3, Oct-3/4, and Ki-67 were also examined by immunohistochemistry to evaluate apoptotic reactivity, tumor differentiation, and proliferation activity, respectively. APAF-1 was downregulated in two TGCT cell lines by siRNA transfection, and subsequent expression of the Ki-67 and Oct-3/4 genes and differentiation markers of three embryonic germ layers including keratin16 (KRT16) for ectoderm, vimentin (VIM) for mesoderm and GATA4 for endoderm were then tested. No significant relationship was found between APAF-1 expression and apoptotic activity in TGCTs. Expression of APAF-1, Oct-3/4, and Ki-67 was significantly higher in seminomas than in non-seminomas. In TGCTs, higher APAF-1 expression was correlated with higher proliferation (high Ki-67) and a lower degree of differentiation (high Oct-3/4). Interestingly, the expression of APAF-1 gradually decreased in accordance with tumor differentiation (seminoma and embryonal carcinoma > teratoma). Downregulation of APAF-1 in TGCT cell lines resulted in a decrease of Ki-67 and Oct-3/4 and an increase of VIM and KRT16 gene expression. These data show that higher expression of APAF-1 is related to an undifferentiated state in the TGCT pathway.

Origanum vulgare induces apoptosis in human colon cancer caco2 cells.

Oregano spice is widely used in the Mediterranean diet, which is associated with a low risk for colon cancer. Although the medicinal benefits of oregano, such as the anti-inflammatory and antimicrobial activities, are well known; nonetheless, only few data are available on its effect in cancer prevention, especially concerning the mechanism of action. Here, we investigated the effect of Origanum vulgare ethanolic extracts on redox balance, cell proliferation, and cell death in colon adenocarcinoma Caco2 cells. Oregano extract leads to growth arrest and cell death in a dose- and time-dependent manner. Changes in glutathione content, as well as the increase in its oxidized form, may be involved in oregano-triggered death. Both extrinsic and intrinsic apoptotic pathways appear to be activated by spice extract. Our findings suggest that oregano amounts found in the Mediterranean diet can exert proapoptotic effects, which are selective for cancer cells. Moreover, whole extract, instead of a specific component, can be responsible for the observed cytotoxic effects.

Apoptosis signaling proteins as prognostic biomarkers in colorectal cancer: a review.

Colorectal cancer is a leading cause of cancer related mortality in the Western world. In recent years, combination 5-fluorouracil based adjuvant chemotherapy as first line treatment of this disease has led to improved disease free and overall survival. However drug resistance, both innate and acquired, remains an obstacle in the effective treatment of this disease. Apoptotic pathways are frequently altered in both tumor progression and drug resistance; therefore proteins associated with this pathway may have potential as prognostic biomarkers for this disease. Identification of clinical biomarkers that are able to identify patients who are more likely to respond to specific chemotherapy will lead to more personalized, effective, and less toxic therapy. This review focuses on the current status of apoptosis related proteins as biomarkers for colorectal cancer and discusses the possible application of systems approaches in this context.

Propofol reduces nitric oxide-induced apoptosis in testicular ischemia-reperfusion injury by downregulating the expression of inducible nitric oxide synthase.

BACKGROUND: The aim of the present study was to investigate the underlying mechanisms in the preventive effects of intravenous anesthetics on testicular ischemia-reperfusion injury. METHODS: Forty male Wistar Albino rats were randomly assigned to four groups of 10 rats each. Anesthesia was induced and maintained with thiopental in groups 1 and 2 and with propofol in groups 3 and 4. Groups 2 and 4 received left testicular ischemia (torsion) for 1 h and reperfusion (detorsion) for 24 h. Groups 1 and 3 (control groups) had no testicular torsion and detorsion. At 24 h of reperfusion, animals were killed and ipsilateral testes were removed for determination of tissue nitric oxide (NO) levels and immunohistochemical evaluation of endothelial nitric oxide synthase (eNOS), inducible NOS (iNOS), and apoptosis protease-activating factor 1 (APAF-1). RESULTS: Between groups 1 and 3, there were no differences in tissue NO levels and eNOS, iNOS, and APAF-1 expressions. iNOS and APAF-1 expressions were markedly increased in group 2, but these parameters were at the mild to moderate level in group 4 at 24 h of reperfusion. Also, elevated expression of iNOS was accompanied by a high NO production in group 2 compared with group 4. Although eNOS expressions were increased in both the groups (groups 2 and 4), there were no significant differences between these groups. CONCLUSIONS: Propofol as an anesthetic agent may attenuate germ cell-specific apoptosis and decrease NO biosynthases through downregulation of iNOS expression in an animal model of testicular torsion and detorsion.

A close link between Fas, p53 and Apaf-1 in chronic myeloid leukemia.

In chronic myeloid leukemia (CML) proliferation is increased and resistance to apoptosis has been proposed as a mechanism accounting for myeloid cell expansion. There is still controversy on whether apoptosis plays an important role in the regulation of myelopoiesis. This study aims to investigate whether apoptosis-related proteins play a role in the evolution of CML and to identify, the relationship between Fas, p53 and apoptosis protease activating factor (Apaf-1) in CML. We found increased p53 and Apaf-1 messenger ribonucleic acid (mRNA) in patients with CML. However, one patient, who had a p53 point mutation, showed a massive elevation of p53 mRNA during blast crisis yet, conversely, a considerable reduction in Apaf-1 mRNA and Fas mRNA. Our results show an in-vivo linkage between Fas, p53 and Apaf-1 transcription regulation. This suggests that key genes involved in apoptosis are also involved in CML disease progression.

Role of APAF-1, E-cadherin and peritumoral lymphocytic infiltration in tumour budding in colorectal cancer.

Tumour budding or dedifferentiation at the invasive margin of colorectal cancer (CRC) is an important prognostic marker and linked mechanistically to dysregulation of Wnt pathway signalling. Since budding is observed in only 40% of CRCs, we hypothesized that Wnt pathway dysregulation may be a necessary but insufficient explanation for budding and that buds may be destroyed selectively by tumour immune mechanisms. Twenty potential markers of tumour budding were evaluated in tissue microarrays (TMAs) obtained from the main tumour body of 1164 DNA mismatch repair-proficient CRCs and the findings were correlated with tumour budding, lymphocytic infiltration and survival. Loss of expression of E-cadherin and APAF-1 were independent predictors of budding (sensitivity 70.3% and specificity 48.2% when one or the other was lost). Peritumoral lymphocytes (PTLs) were observed more frequently in CRCs with loss of either E-cadherin or APAF-1 that were budding-negative. PTLs and tumour-infiltrating lymphocytes (TILs) were strongly correlated. The absence of TILs increased the adverse prognostic impact of E-cadherin and APAF-1 loss. Co-occurrence of E-cadherin loss, APAF-1 loss and low TIL counts in CRCs was an independent prognostic factor. The findings were verified in whole tissue sections from 88 CRCs with known KRAS mutation status (which was not associated with budding). Loss of E-cadherin and APAF-1 within the main body of CRCs are independent predictors of tumour budding. The prognostic benefit of lymphocytic infiltration may be explained by the immune destruction of budding cells.