METHODS: Expression of TRAIL and TRAIL receptor in response to insulin and glucose was determined by polymerase chain reaction. Transcriptional activity was assessed using wild-type and site-specific mutations of the TRAIL promoter. Chromatin immunoprecipitation studies were performed. VSMC proliferation and apoptosis was measured.
RESULTS: Insulin and glucose exposure to VSMC for 24 h stimulated TRAIL mRNA expression. This was also evident at the transcriptional level. Both insulin- and glucose-inducible TRAIL transcriptional activity was blocked by dominant-negative specificity protein-1 (Sp1) overexpression. There are five functional Sp1-binding elements (Sp1-1, Sp1-2, Sp-5/6 and Sp1-7) on the TRAIL promoter. Insulin required the Sp1-1 and Sp1-2 sites, but glucose needed all Sp1-binding sites to induce transcription. Furthermore, insulin (but not glucose) was able to promote VSMC proliferation over time, associated with increased decoy receptor-2 (DcR2) expression. In contrast, chronic 5-day exposure of VSMC to 1 µg/mL insulin repressed TRAIL and DcR2 expression, and reduced Sp1 enrichment on the TRAIL promoter. This was associated with increased cell death.
CONCLUSIONS: The findings of the present study provide a new mechanistic insight into how TRAIL is regulated by insulin. This may have significant implications at different stages of diabetes-associated cardiovascular disease. Thus, TRAIL may offer a novel therapeutic solution to combat insulin-induced vascular pathologies.
BACKGROUND: Breast cancer is a heterogeneous disease involving complex mechanisms. TRAIL is a potential anticancer candidate for targeted treatment due to its selective killing effects on neoplastic cells. Nonetheless, resistance occurs in many cancers either intrinsically or after multiple treatments.
OBJECTIVE: Therefore, this research investigated whether the combination of Trichostatin A (TSA) and Zebularine (Zeb) (TZ) followed by TRAIL (TZT) could sensitize the human breast adenocarcinoma cells towards apoptosis.
METHODS: The breast adenocarcinoma cells, MDA-MB-231, MCF-7 and E-MDA-MB-231 (E-cadherin re-expressed MDA-MB-231) were treated with TSA, Zeb, TZ, TRAIL and TZT. The cells were subjected to hematoxylin and eosin (H & E) staining and FITC-Annexin V/Propidium Iodide apoptosis detection prior to proteome profiling.
RESULTS: Based on morphological observation, apoptosis was induced in all cells treated with all treatment regimens though it was more evident for the TZT-treated cells. In the apoptosis detection analysis, TZ increased early apoptosis significantly in MDA-MB-231 and MCF-7 while TRAIL induced late apoptosis significantly in E-MDA-MB-231. Based on the proteome profiling on MDA-MB-231, TRAIL R2 and Fas expression was increased. For E-MDA-MB- 231, down-regulation of catalase, paraoxonase-2 (PON2), clusterin, an inhibitor of apoptosis proteins (IAPs) and cell stress proteins validated the notion that E-cadherin re-expression enhances TZT anti-cancer efficacy. Similar trend was observed in MCF-7 whereby TZT treatment down-regulated the anti-apoptotic catalase and PON2, increased the proapoptotic, B cell lymphoma 2 (Bcl-2)-associated agonist of cell death (Bad) and Bcl-2-associated X (Bax), second mitochondria-derived activator of caspase (SMAC) and HtrA serine peptidase 2 (HTRA2) as well as TRAIL receptors (TRAIL R1 and TRAIL R2).
CONCLUSION: TZ treatment serves as an efficient treatment regimen for MDA-MB-231 and MCF-7, while TRAIL serves as a better treatment option for E-MDA-MB-231. Therefore, future studies on E-cadherin's positive regulatory role in TRAIL-induced apoptosis are warranted.
Methods: A conditioned medium of umbilical cord-derived MSCs (UCMSC-CM) was generated by culturing the cells on serum-free αMEM for 24 h. Following this, human GBM T98G cells were treated with UCMSC-CM for 24 h. Quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR) was then performed to measure the mRNA expression of survivin, caspase-9, TNF-related apoptosis-inducing ligand (TRAIL), DR4 and DcR1.
Results: mRNA expression of caspase-9 in CM-treated T98G cells increased 1.6-fold (P = 0.017), whereas mRNA expression of survivin increased 3.5-fold (P = 0.002). On the other hand, TRAIL protein expression was upregulated (1.2-fold), whereas mRNA expression was downregulated (0.4-fold), in CM-treated cells. Moreover, there was an increase in the mRNA expression of both DR4 (3.5-fold) and DcR1 (1,368.5-fold) in CM-treated cells.
Conclusion: The UCMSC-CM was able to regulate the expression of molecules involved in GBM cell apoptotic pathways. However, the expression of anti-apoptotic molecules was more upregulated than that of pro-apoptotic molecules.