ERK inhibition in glioblastoma is associated with autophagy activation and tumorigenesis suppression

Abstract

Purpose Autophagy-dependent tumorigenic growth is one of the most commonly reported molecular mechanisms in glioblastoma (GBM) progression. However, the mechanistic correlation between autophagy and GBM is still largely unexplored, especially the roles of autophagy-related genes involved in GBM oncogenesis. In this study, we aimed to explore the genetic alterations that interact with both autophagic activity and GBM tumorigenesis, and to investigate the molecular mechanisms of autophagy involved in GBM cell death and survival. Method For this purpose, we systematically explored the alterations of autophagic molecules at the genome level in human GBM samples through deep RNA sequencing. The effect of genetic and pharmacologic inhibition of ERK on GBM growth in vitro and in vivo was researched. An image-based tracking analysis of LC3 using mCherry-eGFP-LC3 plasmid, and transmission electron microscopy were utilized to monitor autophagic flux. Immunoblot analysis was used to measure the related proteins. Results MAPK ERK expression was identified as one of the most probable autophagy-related transcriptional responses during GBM growth. The genetic and pharmacologic inhibition of ERK in vivo and in vitro led to cell death, demonstrating its critical role for GBM proliferation and survival. To our surprise, autophagic activities were excessively activated and resulted in cytodestructive effects on GBM cells upon ERK inhibitor treatment. Furthermore, based on the observation of downregulation of mTOR signaling, we speculated the ERK inhibitor-induced GBM cells death might depend on mTORmediated pathway, leading to autophagy dysregulation. Accordingly, the in vivo and in vitro experiments revealed that the mTOR inhibitor rapamycin further increased cell mortality and exhibited enhanced antitumor effect on GBM cells when co-treated with the ERK inhibitor. Conclusion Our data creatively demonstrated that the autophagy-related regulator ERK maintains autophagic activity during GBM tumorigenesis via mTOR signaling pathway. The pharmacologic inhibition of both mTOR and ERK signaling exhibited synergistic therapeutic effect on GBM growth in vivo and in vitro, which has certain novelty and may provide a potential therapeutic approach for GBM treatment in the future. KeywordsAutophagy • Glioblastoma • Extracellular signal regulated kinase • Mammalian target of rapamycin * Jian Yin

Combination of DNA Damage, Autophagy, and ERK Inhibition: Novel Evodiamine-Inspired Multi-Action Pt(IV) Prodrugs with High-Efficiency and Low-Toxicity Antitumor Activity

“…The levels of intracellular ROS (Figure a,b) and tumor suppressor p53 were significantly elevated, while loss of MMP (Figure c,d) and decreased the expression of B-cell lymphoma 2 (Bcl-2) (Figure a,b), further verified that 4 and 10 significantly induced intrinsic (loss of ΔΨm) apoptotic signaling. In addition, it has been proved that the interplay between the ERK pathway and autophagy can regulate tumor progression . Once the cancer cells are exposed to the autophagic stimuli, the ERK signaling shall be downregulated by the upstream pathways, causing mTOR complex decomposition and beclin-1 and ULK1 upregulation, followed by autophagy initiation .…”

“…18 Once the cancer cells are exposed to the autophagic stimuli, the ERK signaling shall be downregulated by the upstream pathways, causing mTOR complex decomposition and beclin-1 and ULK1 upregulation, followed by autophagy initiation. 18 When the ERK signaling pathway is over-suppressed, autophagy might be hyperactivated, which is cytodestructive and catastrophic for cell survival. In the present study, the EVO−Pt(IV) compounds were found to increase autophagy by increasing the expression of ULK1, beclin-1, and LC3-II and suppressing p62 expression, suggesting the cytodestructive role of autophagy induction upon the suppression of ERK signaling produced by 4 and 10.…”

“…The extracellular signal-regulated protein kinase (ERK), a member of the MAPK family, is the only activator that regulates both cytosolic and nuclear transcription factors, thus promoting cell proliferation, survival, and differentiation, which has been considered as an Achilles’ heel of the MAPK pathway in cancer cells. − Furthermore, the interplay between ERK and other pathways has been proved crucial for determining cell fate, which may lead to apoptosis or autophagy . Autophagy, for example, is a process in which lysosomes degrade the cytoplasm contents in eukaryotic cells, and excessive autophagic activity serves as a pro-death mechanism in cancer cells . Once the cancer cells are exposed to the autophagic stimuli, the ERK signaling shall be downregulated by the upstream pathways, causing mammalian target of rapamycin (mTOR) compound decomposition and beclin-1 and ULK1 upregulation, followed by autophagy initiation .…”

“…17 Autophagy, for example, is a process in which lysosomes degrade the cytoplasm contents in eukaryotic cells, and excessive autophagic activity serves as a pro-death mechanism in cancer cells. 18 Once the cancer cells are exposed to the autophagic stimuli, the ERK signaling shall be downregulated by the upstream pathways, causing mammalian target of rapamycin (mTOR) compound decomposition and beclin-1 and ULK1 upregulation, followed by autophagy initiation. 18 When the ERK signaling pathway is over-suppressed, autophagy might be hyperactivated, which further results in autophagic cell death.…”

Ciclopirox drives growth arrest and autophagic cell death through STAT3 in gastric cancer cells

“…Phosphorylation of STAT3 at Tyr705 is critical for its homodimerization, nuclear localization, and transactivation, which can promote tumor cell proliferation via enhancing cell cycle-related protein expression [ 21 , 22 ]. While phosphorylation of STAT3 at Ser727 is mediated by extracellular regulated protein kinases (ERK), inhibition of ERK effectively triggers autophagic cell death via an mTOR-dependent pathway in GBM cells [ 23 , 24 ]. Therefore, phosphorylation of the Ser727 and Tyr705 residues is critical for STAT3 in promoting tumorigenesis.…”