Necrosis Factor-related Apoptosis-inducing Ligand Signaling Research Articles

Enhancing the Effect of Tumor Necrosis Factor-Related Apoptosis-Inducing Ligand Signaling and Arginine Deprivation in Melanoma

Melanoma as a very aggressive type of cancer is still in urgent need of improved treatment. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and arginine deiminase (ADI-PEG20) are two of many suggested drugs for treating melanoma. Both have shown anti-tumor activities without harming normal cells. However, resistance to both drugs has also been noted. Studies on the mechanism of action of and resistance to these drugs provide multiple targets that can be utilized to increase the efficacy and overcome the resistance. As a result, combination strategies have been proposed for these drug candidates with various other agents, and achieved enhanced or synergistic anti-tumor effect. The combination of TRAIL and ADI-PEG20 as one example can greatly enhance the cytotoxicity to melanoma cells including those resistant to the single component of this combination. It is found that combination treatment generally can alter the expression of the components of cell signaling in melanoma cells to favor cell death. In this paper, the signaling of TRAIL and ADI-PEG20-induced arginine deprivation including the main mechanism of resistance to these drugs and exemplary combination strategies is discussed. Finally, factors hampering the clinical application of both drugs, current and future development to overcome these hurdles are briefly discussed.

SPAG6 silencing induces apoptosis in the myelodysplastic syndrome cell line SKM‑1 via the PTEN/PI3K/AKT signaling pathway in vitro and in vivo.

Apoptosis is a multi-step mechanism of cell self‑destruction for maintaining cellular homeostatic balance. Accumulating evidence indicates that abnormal apoptosis promotes the evolution and progression of myelodysplastic syndromes (MDS). As a novel cancer-testis antigen, sperm‑associated antigen6 (SPAG6) has been reported to regulate apoptosis through the tumor necrosis factor-related apoptosis-inducing ligand signaling pathway in the MDS cell line SKM‑1. However, the mechanism of the intrinsic cell death pathway for apoptosis induction by SPAG6 silencing is unclear. In the present study, the invitro effects of SPAG6 silencing were investigated in SKM‑1 cells through extensive biochemical and molecular approaches. Western blotting and reverse transcription-quantitative polymerase chain reaction were used to detect the expression of SPAG6 and activation of PTEN/PI3K/AKT signal pathway. Additionally, SKM‑1 cells transduced with SPAG6 short hairpin RNA (shRNA) lentivirus were treated with the phosphatidylionositol 3-kinase (PI3K) inhibitor LY294002 or pan caspase inhibitor z‑VAD‑fmk and the apoptosis rates were measured by flow cytometry, and the expressions of associated proteins were examined by western blot analysis. A mouse xenograft model was also used to further evaluate the effects of SPAG6 knockdown on inducing tumor apoptosis invivo. Lentivirus-mediated knockdown of SPAG6 in SKM‑1 cells increased phosphatase and tensin homolog (PTEN) expression and reduced protein kinaseB (AKT) phosphorylation, which in turn resulted in cell apoptosis as evidenced by induced myeloid leukaemia cell differentiation protein Mcl‑1 downregulation, cytochromec release and increased caspase‑9 expression. Consistently, the PI3K inhibitor LY294002 synergistically enhanced apoptosis of SKM‑1 cells when co-administered with SPAG6 shRNA lentivirus. Furthermore, treatment with the pan caspase inhibitor z‑VAD‑fmk failed to prevent PTEN activation upon SPAG6 knockdown, suggesting that SPAG6-regulated PTEN expression was caspase activation-independent. In addition, SPAG6 knockdown was associated with DNMT1 downregulation, implying that SPAG6 may indirectly control PTEN expression via DNA methylation. Furthermore, tumor tissues from nonobese diabetic/severe combined immunodeficient mice inoculated with SPAG6-shRNA lentivirus pre-infected SKM‑1 cells exhibited significantly elevated apoptosis in the extrinsic and intrinsic pathways. These results demonstrate that SPAG6 silencing induces PTEN expression to regulate apoptosis though the PI3K/AKT pathway, indicating that SPAG6 may be a potential therapeutic target for MDS.

MicroRNA expression profiles in testicular biopsies of patients with impaired spermatogenesis.

Spermatogenesis is a complex process that involves thousands of genes whose expression during different stages is strictly regulated. Small non-coding microRNAs play an important role in the posttranscriptional regulation of mRNA processing during spermatogenesis. Using Agilent SurePrint v16 microRNA 8×60K microarray kit, we investigated the microRNA expression profiles of 24 formalin-fixed paraffin-embedded testicular biopsies from patients with hypospermatogenesis (n=10), hypospermatogenesis and azoospermia factor c region on the Y chromosome (AZFc) deletion (n=3), Sertoli cell-only syndrome (n=3) and maturation arrest (n=2), in comparison with subjects with normal spermatogenesis (n=6). After adjusting for multiple testing, six deregulated miRNAs were detected in the patients with AZFc deletion, 30 in maturation arrest group, 52 in Sertoli cell-only syndrome group of patients, and none in the group of patients with hypospermatogenesis. Some of the deregulated microRNAs were shared between groups, resulting in 58 unique differentially expressed microRNAs. The expression of five microRNAs (hsa-miR-34b, hsa-miR-449b, hsa-miR-517c, hsa-miR-181c, and hsa-miR-605) was validated by qRT-PCR in a total of 74 samples. Using mRNA expression profiles of subjects with matching histopathological patterns of impaired spermatogenesis from publically available Gene Expression Omnibus data sets, we have performed integrated mRNA-microRNA regulatory network analysis. Pathway analysis revealed significantly enriched set of genes for tumor necrosis factor-related apoptosis-inducing ligand signaling pathway, previously shown to be involved in regulation of apoptosis in normal functioning testis. Our results should be considered as preliminary as we have analyzed only a small number of patients in each studied group. Further studies with larger number of patients with impaired spermatogenesis as well as more targeted approaches with parallel microRNA and mRNA expression profiling in isolated subpopulations of somatic or germ cells from different stages of spermatogenesis are needed to clarify the role of the microRNAs in the process of spermatogenesis.

Phosphorylated Galectin-3 Mediates Tumor Necrosis Factor-related Apoptosis-inducing Ligand Signaling by Regulating Phosphatase and Tensin Homologue Deleted on Chromosome 10 in Human Breast Carcinoma Cells

Galectin-3 (GAL3), a beta-galactoside-binding lectin, confers chemoresistance to a wide variety of cancer cell types. It may exhibit anti- or pro-apoptotic activity depending on the nature of the stimulus. We report here that introducing phosphorylated galectin-3 (P-GAL3) into GAL3-null, tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-resistant human breast carcinoma cells promotes TRAIL-induced apoptotic cell death by stimulating the phosphorylation/inactivation of the pro-apoptotic molecule Bad resulting in the inhibition of mitochondrial depolarization and the release of cytochrome c. Exposure of the transfectant cells to TRAIL leads to the recruitment of the initiator capase-8 followed by activation of the effector caspase-9, independent of cytochrome c, and subsequently the processing of the executioner caspase-3. P-GAL3 and phosphatase and tensin homologue deleted on chromosome 10 (PTEN) were coordinately expressed, with concomitant dephosphorylation of Akt in TRAIL-sensitive cells. In contrast, overexpression of phospho-mutant GAL3 (incapable of phosphorylation) failed to elicit similar responses. Depletion of PTEN using small interference RNAs reinstated Akt phosphorylation and conferred TRAIL resistance. In addition phosphatidylinositol 3-kinase inhibitors rendered the phospho-mutant GAL3-resistant cells sensitive to TRAIL. These findings suggest a pivotal role for P-GAL3 in promoting TRAIL sensitivity through activation of a nonclassic apoptotic pathway and identify P-GAL3 as a novel regulator of PTEN.

Roles of Tumor Necrosis Factor-Related Apoptosis-Inducing Ligand Signaling Pathway in Granulosa Cell Apoptosis During Atresia in Pig Ovaries

To reveal the molecular mechanism of selective follicular atresia in porcine ovaries, we investigated the changes in the expression of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and its receptor (DR4) proteins and TRAIL mRNA in granulosa cells during follicular atresia. Immunohistochemical, Western immunoblotting and reverse transcription-polymerase chain reaction analyses (RT-PCR) revealed that significant increases in TRAIL protein and mRNA levels but not DR4 protein were changed during atresia. The RT-PCR product was confirmed to be porcine TRAIL by the cDNA sequence determination. An in vitro apoptosis inducing assay using cultured granulosa cells prepared from healthy follicles showed that TRAIL could activate caspase-3 and induce apoptotic cell death in the cells. The present findings confirm that TRAIL induces apoptosis in granulosa cells during atresia in porcine ovaries.