Early growth response-1 is a regulator of DR5-induced apoptosis in colon cancer cells

BACKGROUND: Tumour necrosis factor-related apoptosis-inducing ligand (TRAIL) induces tumour cell apoptosis by binding to death receptor 4 (DR4) and DR5. DR4 and DR5 activation however can also induce inflammatory and pro-survival signalling. It is not known how these different cellular responses are regulated and what the individual role of DR4 vs DR5 is in these processes.METHODS: DNA microarray study was carried out to identify genes differentially expressed after DR4 and DR5 activation. RT-PCR and western blotting was used to examine the expression of early growth response gene-1 (Egr-1) and the proteins of the TRAIL signalling pathway. The function of Egr-1 was studied by siRNA-mediated knockdown and overexpression of a dominant-negative version of Egr-1.RESULTS: We show that the immediate early gene, Egr-1, regulates TRAIL sensitivity. Egr-1 is constitutively expressed in colon cancer cells and further induced upon activation of DR4 or DR5. Our results also show that DR4 mediates a type II, mitochondrion-dependent apoptotic pathway, whereas DR5 induces a mitochondrion-independent, type I apoptosis in HCT15 colon carcinoma cells. Egr-1 drives c-FLIP expression and the short splice variant of c-FLIP (c-FLIPS) specifically inhibits DR5 activation.CONCLUSION: Selective knockdown of c-FLIPS sensitises cells to DR5-induced but not DR4-induced apoptosis and Egr-1 exerts an effect as an inhibitor of the DR5-induced apoptotic pathway, possibly by regulating the expression of c-FLIPS. British Journal of Cancer (2010) 102, 754-764. doi:10.1038/sj.bjc.6605545 www.bjcancer.com Published online 19 January 2010 (C) 2010 Cancer Research U

Automated Segmentation of Tissues Using CT and MRI: A Systematic Review

© 2019 The Association of University Radiologists Rationale and Objectives: The automated segmentation of organs and tissues throughout the body using computed tomography and magnetic resonance imaging has been rapidly increasing. Research into many medical conditions has benefited greatly from these approaches by allowing the development of more rapid and reproducible quantitative imaging markers. These markers have been used to help diagnose disease, determine prognosis, select patients for therapy, and follow responses to therapy. Because some of these tools are now transitioning from research environments to clinical practice, it is important for radiologists to become familiar with various methods used for automated segmentation. Materials and Methods: The Radiology Research Alliance of the Association of University Radiologists convened an Automated Segmentation Task Force to conduct a systematic review of the peer-reviewed literature on this topic. Results: The systematic review presented here includes 408 studies and discusses various approaches to automated segmentation using computed tomography and magnetic resonance imaging for neurologic, thoracic, abdominal, musculoskeletal, and breast imaging applications. Conclusion: These insights should help prepare radiologists to better evaluate automated segmentation tools and apply them not only to research, but eventually to clinical practice

Adenovirus E2F1 Overexpression Sensitizes LNCaP and PC3 Prostate Tumor Cells to Radiation In Vivo

PURPOSE: We previously showed that E2F1 overexpression radiosensitizes prostate cancer cells in-vitro. Here, we demonstrate the radiosensitization efficacy of Ad-E2F1 in growing LNCaP (orthotopically) and PC3 (subcutaneously) nude mice xenograft tumors. METHODS AND MATERIALS: Adenoviral E2F1 was injected intra-tumorally in LNCaP (3×10(8) PFU) and PC3 (5×10(8) PFU) tumors treated with or without radiation. Tumor volumes (TV) were measured by MRI in LNCaP tumors, calipers in PC3 tumors and serum PSA levels by ELISA in LNCaP tumors. Apoptosis was measured by TUNEL staining and key proteins involved in cell death signaling were analyzed by Western blot. RESULTS: Intracellular overexpression of Ad-E2F1 had significant effect in the regression of TV and reducing the PSA relative to adenoviral luciferase (Ad-Luc) control. The in-vivo regressing effect of Ad-E2F1 on LNCaP tumor growth was significant (PSA-34 ng/ml/TV-142 mm(3)) compared to Ad-Luc control (PSA-59 ng/ml/TV-218 mm(3); p<0.05). This effect was significantly enhanced by radiation therapy (PSA-16 ng/ml/TV-55 mm(3) compared to Ad-Luc/PSA-42 ng/ml/TV-174 mm(3); p<0.05). For PC3 tumors, the greatest effect was observed with Ad-E2F1 alone, there was little or no effect when RT was combined. However, addition of RT enhanced the level of in-situ apoptosis in PC3 tumors. Molecularly, Ad-E2F1 in a combination setting abrogated radiation induced BCL-2 protein and was associated with an increase in activated BAX, together caused a potent radiosensitizing effect irrespective of p53 and AR functional status. CONCLUSIONS: We show here for the first time that ectopic overexpression of E2F1 in-vivo using an adenoviral vector significantly inhibits orthotopic p53(wild-type) LNCaP and subcutaneous p53(null) PC3 tumors in nude mice. Furthermore, we demonstrate that E2F1 strongly sensitizes LNCaP tumors to RT. These findings suggest that E2F1 overexpression can sensitize prostate tumor cells in-vivo independent of p53 or androgen receptor status