Celastrol induces ubiquitin-dependent degradation of mTOR in breast cancer cells

Abstract

BackgroundCelastrol is a major active component of the thunder god vine (Tripterygium wilfordii) used in traditional Chinese medicine to treat chronic inflammatory and autoimmune diseases. Celastrol inhibits PI3K–Akt–mTOR signaling, which is frequently dysregulated in tumors and critical for tumor-cell proliferation and survival, but the underlying mechanisms are still not fully understood. In the present study, we investigated detailed mechanisms of celastrol inhibition of mTOR signaling in breast cancer cells.MethodsFirst, we evaluated the effect of celastrol on breast cancer-cell growth using MTT assays. Second, we examined the effects of celastrol on mTOR phosphorylation and expression using Western blot. Furthermore, we investigated the cause of mTOR downregulation by celastrol using immunoprecipitation assays. In addition, we evaluated the effect of celastrol on an MDA-MB231 cell-derived xenograft model.ResultsCelastrol suppressed breast cancer cell growth in vitro and in vivo. Celastrol inhibited mTOR phosphorylation and induced mTOR ubiquitination, resulting in its proteasomal degradation. Mechanistically, we found that mTOR is a client of Hsp90–Cdc37 chaperone complex, and celastrol disrupts mTOR interaction with chaperone Hsp90 while promoting mTOR association with cochaperone Cdc37.ConclusionOur study reveals that celastrol suppresses mTOR signaling, at least in part through regulating its association with chaperones and inducing its ubiquitination.

Celastrol Inhibits Migration and Invasion of Triple-Negative Breast Cancer Cells by Suppressing Interleukin-6 via Downregulating Nuclear Factor-κB (NF-κB)

“…The purity of celastrol (Sigma) was ≥98% and it was dissolved in DMSO (Sigma). Cells were incubated with various doses of celastrol (0.1, 0.5, 1, 2, and 5 μM) for 24 h based on methods described in previous reports [ 6 , 15 ]. The high doses (2 and 5 μM) and low doses (0.1, 0.5, and 1 μM) of celastrol were differentiated according to the influence on cell viability.…”

“…Celastrol has been reported to play anti-cancer roles and may be a potential therapeutic candidate in breast cancer. For example, Li et al reported that celastrol inhibits breast cancer cell growth by suppressing the mTOR pathway in vitro and in vivo [ 6 ]. Jang et al showed celastrol suppresses growth of breast cancer cells by regulating estrogen receptor α [ 7 ].…”

Exosome-Based Delivery of Natural Products in Cancer Therapy

“…CEL is a plant-derived triterpenoid and has anticancer effect against a wide variety of cancers ( Li et al, 2018 , 2019 ; Jiang et al, 2019 ). It can induce apoptosis of vincristine-multidrug-resistant oral cancer cells via JNK1/2 signaling pathway ( Lin et al, 2019 ).…”

Biosynthesis, total synthesis, structural modifications, bioactivity, and mechanism of action of the quinone‐methide triterpenoid celastrol

“…Furthermore, celastrol can induce cell‐cycle arrest at the G0/G1 phase, which is a novel effect based on thiol‐related Hsp90 inhibition 5,31 . Later, Li et al 113 observed that celastrol is an inhibitor of mTOR, which could disturb its association with Hsp90 while conversely enhancing its interaction with Cdc37.…”