Visfatin-induced upregulation of lipogenesis via EGFR/AKT/GSK3β pathway promotes breast cancer cell growth

Breast cancer (BC) incidence and associated mortality have increased in tandem with the growth in obesity among the females worldwide. An adipokine, visfatin, has been shown to potentially impact glucose, lipid, and protein metabolism, and promote cancer growth however, the mechanism underlying the effect of visfatin on lipid metabolism dysregulation contributing to BC cell survival, proliferation, and metastasis has not been elucidated. Herein, we have investigated the role of visfatin on the induction of Sterol regulatory element binding protein (SREBP-1) and its upstream and downstream mediators in MCF-7 breast cancer cells. The survival and proliferation was investigated using MTT and Trypan blue assays, cytosolic lipid accumulation was observed using Nile red staining, mRNA and protein expressions were examined using RT-qPCR and western blotting, respectively, and cell cycle analysis was performed using fluorescence-activated cell sorting. Our results indicate that visfatin increased the survival and proliferation of MCF-7 cells in a time- and dose-dependent manner and augmented lipid buildup via activation of SREBP-1 and its associated downstream lipid synthesizing enzymes, at both mRNA and protein levels in MCF-7 cells. Inhibiting SREBP-1 using fatostatin or silencing with siRNA abrogated excessive lipid deposition by suppressing the expression of genes related to lipid synthesis pathway. Further, in-silico study showed high affinity binding of visfatin with epidermal growth factor receptor (EGFR), which was confirmed in an in-vitro study where visfatin increased the phosphorylation of EGFR at tyrosine residue and activated its downstream proteins via phosphorylation of AKT and GSK3β in MCF-7 cells. Inhibition of GSK3β by phosphorylation led to increased activity of SREBP-1 and associated downstream proteins. In summary, SREBP-1 may be a critical player in visfatin-induced lipid synthesis and accumulation in BC cells via activation of EGFR/AKT/GSK3β pathway leading to increased cell survival and proliferation of BC cells.

Polycaprolactone-collagen nanofibers loaded with dexamethasone and simvastatin as an osteoinductive and immunocompatible scaffold for bone regeneration applications

Physiological inflammation has been shown to promote bone regeneration; however, prolonged inflammation impedes the osteogenesis and bone repair process. To overcome the latter we aimed to develop a dual drug delivering nanofibrous scaffold to promote osteogenic differentiation of mesenchymal stromal cells (MSCs) and modulate the pro-inflammatory response of macrophages. The polycaprolactone (PCL)-collagen nanofibrous delivery system incorporating dexamethasone and simvastatin was fabricated by electrospinning process. The morphological analysis and mRNA, as well as protein expression of proinflammatory and anti-inflammatory cytokines in human monocytes (U937 cells), demonstrated the immunocompatibility effect of dual drug-releasing nanofibrous scaffolds. Nitric oxide estimation also demonstrated the anti-inflammatory effect of dual drug releasing scaffolds. The scaffolds demonstrated the osteogenic differentiation of adipose-derived MSCs by enhancing the alkaline phosphatase (ALP) activity and mineral deposition after 17 days of cell culture. The increased expression of Runt-related transcription factor-2 (RUNX-2) and osteocalcin at mRNA and protein levels supported the osteogenic potential of dual drug-loaded fibrous scaffolds. Hence, the results indicate that our fabricated nanofibrous scaffolds exhibit immunomodulatory properties and could be employed for bone regeneration applications after further in-vivo validation.