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Background: Autophagy is a major cellular process by which cytoplasmic components such as damaged organelles and misfolded proteins are recycled. Although low levels of autophagy occur in cells under basal conditions, certain cellular stresses including nutrient depletion, DNA damage, and oxidative stress are known to robustly induce autophagy. Krüppel-like factor 4 (KLF4) is a zinc-finger transcription factor activated during oxidative stress to maintain genomic stability. Both autophagy and KLF4 play important roles in response to stress and function in tumor suppression. Methods: To explore the role of KLF4 on autophagy in mouse embryonic fibroblasts (MEFs), we compared wild-type with Klf4 deficient cells. To determine the levels of autophagy, we starved MEFs for different times with Earle's balanced salts solution (EBSS). Rapamycin was used to manipulate mTOR activity and autophagy. The percentage of cells with γ-H2AX foci, a marker for DNA damage, and punctate pattern of GFP-LC3 were counted by confocal microscopy. The effects of the drug treatments, Klf4 overexpression, or Klf4 transient silencing on autophagy were analyzed using Western blot. Trypan Blue assay and flow cytometry were used to study cell viability and apoptosis, respectively. qPCR was also used to assay basal and the effects of Klf4 overexpression on Atg7 expression levels. Results: Here our data suggested that Klf4-/- MEFs exhibited impaired autophagy, which sensitized them to cell death under nutrient deprivation. Secondly, DNA damage in Klf4-null MEFs increased after treatment with EBSS and was correlated with increased apoptosis. Thirdly, we found that Klf4-/- MEFs showed hyperactive mTOR activity. Furthermore, we demonstrated that rapamycin reduced the increased level of mTOR in Klf4-/- MEFs, but did not restore the level of autophagy. Finally, re-expression of Klf4 in Klf4 deficient MEFs resulted in increased levels of LC3II, a marker for autophagy, and Atg7 expression level when compared to GFP-control transfected Klf4-/- MEFs. Conclusion: Taken together, our results strongly suggest that KLF4 plays a critical role in the regulation of autophagy and suppression of mTOR activity. In addition, we showed that rapamycin decreased the level of mTOR in Klf4-/- MEFs, but did not restore autophagy. This suggests that KLF4 regulates autophagy through both mTOR-dependent and independent mechanisms. Furthermore, for the first time, our findings provide novel insights into the mechanism by which KLF4 perhaps prevents DNA damage and apoptosis through activation of autophagy. [ABSTRACT FROM AUTHOR]

The GORE EXCLUDER iliac branch endoprosthesis (IBE; W.L. Gore & Associates, Flagstaff, Ariz) is designed to preserve internal iliac artery (IIA) patency during endovascular treatment of aneurysms involving the common iliac artery. The device is intended to conform to iliac tortuosity, which may decrease adverse iliac events (AIE). The objective of this study was to evaluate risk factors for AIE after IBE implantation. This was a post hoc analysis of the prospective, multicenter GORE 12-04 IBE pivotal trial. Patients with preoperative and postoperative axial imaging were included, with analysis based on each treated iliac system. An independent core laboratory performed all scan measurements, including iliac diameters, lengths, and tortuosity. Conformability was analyzed by the changes in tortuosity after IBE deployment, with less change indicating greater conformation. The end point was AIE, defined as ipsilateral radiographic or clinical complications. Critical nonconformation was defined as a threshold change in tortuosity associated with a significant increase in AIE. We included 98 patients with 101 treated iliac systems. There were eight AIE (8%; six IIA component occlusions, one iliac branch component occlusion, and one EIA dissection requiring reintervention). Patients with AIE had smaller IIA diameters and less IBE conformability. After multivariable logistic regression analysis, an IIA diameter of less than 10 mm and a change in total iliac tortuosity beyond –15% were independently associated with AIE (odds ratio, 12 [interquartile range, 1.4-110] and odds ratio, 8.2 [interquartile range, 1.5-46], respectively), and the latter was used to define critical nonconformation. Critical nonconformation occurred in 11% of treated systems, and was associated with a high rate of AIE (36% vs 4%; P =.004). Endograft conformation is a novel device property and technical outcome that, along with a larger IIA diameter, is associated with freedom from AIE after IBE deployment. An evaluation of these risk factors may better inform the management of patients with iliac aneurysmal disease. Further research on endograft conformation and patient outcomes is warranted, particularly for those with challenging anatomy undergoing complex procedures. [ABSTRACT FROM AUTHOR]