Background: Lack of Schlafen family member 11 (SLFN11) expression has been recently identified as a dominant genomic determinant of response to DNA damaging agents in numerous cancer types. Thus, strategies aimed at increasing SLFN11 could be used to restore chemosensitivity of refractory cancers. As oncogenic downregulation is often driven by methylation of the promotor region, we explore the demethylation effect of 5-aza-2-deoxycytidine (decitabine), on the SLFN11 gene methylation. Since SLFN11 has been reported as an interferon inducible gene, and interferon is secreted during an active anti-tumor immune response, we investigated the in vitro effect of IFN-g; on SLFN11 expression in breast cancer cell lines. A second broader approach to show cross talk between immune cells and SLFN11 expression is indirect co-culture of breast cancer cells with activated PBMCs and evaluate if this can drive SLFN11 upregulation. Finally, as a definitive and specific way to modulate SLFN11 expression we implemented SLFN11 dCas9 (dead CRISPR associated protein 9) systems to specifically increase or decrease SLFN11 expression. Results: We first confirmed a correlation previously reported between methylation of SLFN11 promoter and its expression across multiple cell lines. We showed in-vitro that decitabine and IFN-g; could increase moderately the expression of SLFN11 in both BT-549 and T47D cell lines, but not in strongly methylated cell lines such as MDA-MB-231. Though, in-vitro, the co-culture of the same cell lines with CD8-CD25 activated PBMC failed to increase SLFN11 expression. On the one hand, the use of a CRISPR-dCas9 UNISAM system could increase SLFN11 expression significantly (up to 5-fold), stably and specifically in BT-549 and T47D cancer cell lines. Though, this system also failed to force a strong expression of SLFN11 in cell lines with robust SLFN11 promoter methylation such as MDA-MB-231. On the other hand, the use of CRISPR-dCas9 KRAB could significantly reduce the expression of SLFN11 in BT-549 and T47D. We then used the modified cell lines to confirm the alteration in chemo sensitivity of those cells to treatment with DNA Damaging Agents (DDAs) such as Cisplatin and Epirubicin or DNA Damage Response (DDRs) drugs like Olaparib. RNAseq was used to elucidate the mechanisms of action affected by the alteration in SLFN11 expression. Conclusion: To our knowledge this is the first report of the stable non-lethal increase of SLFN11 expression in a cancer cell line. Our results show that induction of SLFN11 expression can enhance DDA and DDR sensitivity in breast cancer cells and dCas9 systems may represent a novel approach to increase SLFN11 and achieve higher sensitivity to chemotherapeutic agents, improving outcome or decreasing required drug concentrations. SLFN11-targeting therapies might be explored pre-clinically to develop personalized approaches.

Diabetes induced hyperglycemia increases the risk of cardiovascular complications as it impacts vascular endothelial cells causing vascular dysfunction. Endothelial progenitor cells (EPCs) have been suggested to participate in the repair of vascular endothelial cells once they are impacted by hyperglycemia in diabetic patients. This research aims to test the EPC subtype blood outgrowth endothelial cells (BOECs) and their ability to survive and function under chronic hyperglycemic conditions. For that, we studied BOECs viability, response to shear stress, angiogenesis ability, and barrier function under normoglycemic (5.5mM) and hyperglycemic (25mM) conditions. The results have shown significant effects of chronic hyperglycemic conditions on cell proliferation (n=3, p<0.05), and migration (n=3, p<0.05) which were decreased when compared to control. Cells responses to shear stress were not affected under these conditions. There was a trend towards an increase in permeability as indicated by barrier function assays. The decrease in those endothelial cell functions might impact the repair mechanisms needed in diabetic patients to protect from vascular complications. Further investigations are required to establish therapeutic targets to improve EPCs repair function.

Type 2 diabetes mullites (T2DM) results in different cardiovascular complications. The main cause of these complications is endothelial dysfunction, which affects the endothelium physiologically and pathologically. The chronic hyperglycemia introduced by T2DM impacts the pivotal enzyme endothelial nitric oxide synthase (eNOS) in terms of phosphorylation and dimerization, which initiates oxidative stress and reduces the bioavailability of the vasodilator nitric oxide. To overcome endothelial dysfunction, endothelial progenitor cells (EPCs) contribute to vascular repair due to their regenerative characteristics. The effects of hyperglycemia on EPCs are understudied. Thus, this study aims to investigate the effects of hyperglycemia on the eNOS/Akt signaling pathway and reactive oxygen species (ROS) formation. Cells were treated with normal glucose (NG, 5.5mM) and high glucose (HG, 25mM) media for 3 & 6 days, and the effect on eNOS and Akt phosphorylation were assessed using western blot. ROS was assessed using CellROX stain following 1 and 3 days of treatment. Results showed that both acute and chronic hyperglycemia showed a trend towards decrease in phosphorylation of eNOS and Akt. In addition, ROS formation was increased following 24hr compared to NG. Further investigations are needed to enhance the capability of BOECs to serve as therapeutic tools in T2DM.