The combination of rapamycin and MAPK inhibitors enhances the growth inhibitory effect on Nara-H cells

Abstract

The inhibition of the mammalian target of rapamycin (mTOR) signaling pathway promotes the initiation of autophagy, and the mitogen-activated protein kinase (MAPK)/extracellular signal-regulated protein kinase (ERK) is well known to induce autophagy. Autophagy is a self-defense mechanism of cancer cells that are subjected to antitumor agents, and blocking autophagy can trigger apoptosis. In the present study, we demonstrate that an mTOR inhibitor, rapamycin, induces autophagy in the Nara-H malignant fibrous histiocytoma (MFH) cell line through the activation of ERK1/2. Rapamycin-induced apoptosis was enhanced following the inhibition of the MEK/ERK pathway. In the Nara-H cells, we examined the effects of rapamycin treatment on cell proliferation and on the phosphorylation of the mTOR pathway components and autophagy by western blot analysis. Furthermore, we examined the effects of rapamycin with or without the MEK inhibitor, U0126, on the induction of apoptosis by using fluorescence microscopy. Rapamycin inhibited Nara-H cell proliferation and decreased the phosphorylation of the mTOR pathway in the Nara-H cells. Rapamycin induced the apoptosis of Nara-H cells, and this apoptosis was enhanced by U0126. Simultaneously, phospho-ERK1/2 was activated by rapamycin. The present study demonstrates that rapamycin induces autophagy in Nara-H cells by activating the MEK/ERK signaling pathway, and the rapamycin-induced apoptosis can be enhanced by the MEK inhibitor, U0126. These results suggest that self-protective mechanisms involving mTOR inhibitors in Nara-H cells are prevented by the inhibition of the MEK/ERK pathway. The combination of an mTOR inhibitor (e.g., rapamycin) and an MEK inhibitor (e.g., U0126) may offer effective treatment for MFH, as this combination effectively activates apoptotic pathways.

Autophagy upregulates (pro)renin receptor expression via reduction of P62/SQSTM1 and activation of ERK1/2 signaling pathway in podocytes

“…To our knowledge this is the first report demonstrating the role of ERK in autophagy-mediated increase in PRR expression. Previous studies showed that rapamycin increased ERK phosphorylation at 24 h (5,27). Knockout of p62 in mice enhanced ERK activation (18).…”

“…P62, also known as sequestosome-1, is a protein that targets specific cargoes and is required for the formation and the degradation of autophagolysosomes by proteases. Inhibition of the V-AT-Pase by bafilomycin, and therefore blockade of the degradation of autophagolysosomal contents by lysosomal proteases, results in the accumulation of p62 (27). Thus, p62 can be used as a biomarker for the status of autophagic activity (4).…”

BAY 11-7085 induces glucocorticoid receptor activation and autophagy that collaborate with apoptosis to induce human synovial fibroblast cell death

“…Recently, it was shown that ERK activation could regulate expression levels of LC3B and SQSTM1/p62 [ 26 ]. ERK activity is also needed for autophagy in the Nara-H malignant fibrous histiocytoma cell line and in these cells rapamycin induces autophagy, through p-ERK, as well as apoptosis [ 27 ]. In these cells, upon UO126 treatment, apoptosis is enhanced, while autophagy is diminished.…”

Autophagy Induction by Endothelial-Monocyte Activating Polypeptide II Contributes to the Inhibition of Malignant Biological Behaviors by the Combination of EMAP II with Rapamycin in Human Glioblastoma

“…Rapamycin, an mTOR inhibitor, is widely used in the experimental and clinical researches for anti-neoplastic drugs ( Nakamura et al, 2014 ; Wang et al, 2014 ). The mTOR inhibitors have been used in the clinical trial for several tumors, among them are rapamycin analogs temsirolimus and everolimus which have been used to treat some tumors ( Leung et al, 2011 ; Fasolo and Sessa, 2012 ; Voss et al, 2014 ).…”