Rapamycin-Loaded Lipid Nanocapsules Induce Selective Inhibition of the mTORC1-Signaling Pathway in Glioblastoma Cells

Abstract

Inhibition of the PI3K/Akt/mTOR signaling pathway represents a potential issue for the treatment of cancer, including glioblastoma. As such, rapamycin that inhibits the mechanistic target of rapamycin (mTOR), the downstream effector of this signaling pathway, is of great interest. However, clinical development of rapamycin has floundered due to the lack of a suitable formulation of delivery systems. In the present study, a novel method for the formulation of safe rapamycin nanocarriers is investigated. A phase inversion process was adapted to prepare lipid nanocapsules (LNCs) loaded with the lipophilic and temperature sensitive rapamycin. Rapamycin-loaded LNCs (LNC-rapa) are ~110 nm in diameter with a low polydispersity index (<0.05) and the zeta potential of about −5 mV. The encapsulation efficiency, determined by spectrophotometry conjugated with filtration/exclusion, was found to be about 69%, which represents 0.6 wt% of loading capacity. Western blot analysis showed that LNC-rapa do not act synergistically with X-ray beam radiation in U87MG glioblastoma model in vitro. Nevertheless, it demonstrated the selective inhibition of the phosphorylation of mTORC1 signaling pathway on Ser2448 at a concentration of 1 μM rapamycin in serum-free medium. Interestingly, cells cultivated in normoxia (21% O2) seem to be more sensitive to mTOR inhibition by rapamycin than those cultivated in hypoxia (0.4% O2). Finally, we also established that mTOR phosphorylation inhibition by LNC-rapa induced a negative feedback through the activation of Akt phosphorylation. This phenomenon was more noticeable after stabilization of HIF-1α in hypoxia.

PTEN‐PI3K pathway alterations in advanced prostate cancer and clinical implications

“…Tolerability of many of the agents tested at clinically effective doses is achieved based on avoiding continuous target engagement—either through short half‐life (such as for samotolisib) or through intermittent dosing (such as the 4 days on/3 days off dosing schedule of capivasertib). On‐target toxicity of these agents could be mitigated by increasing drug exposure in tumor tissues relative to normal tissues—one strategy to accomplish this is to encapsulate inhibitors of PI3K, 107‐109 AKT, 110 or mTOR 111 in nanoparticles that traffic to and deposit their payload specifically in tumor tissues. Another approach to decreasing on‐target toxicity of PI3K pathway inhibitors is to increase selectivity for mutant forms of the drug target.…”

A receptor-mediated landscape of druggable and targeted nanomaterials for gliomas

“… Orthotopic xenograft model Enhanced of anti-tumor immunity through T cells, inhibition of signaling pathways and targeting and penetrability to BBB promoted by type-1 peptides. [ 108 ] Nanocapsules Lipoid ®, Solutol ®,Labrafac® WL1349, rapamycin Inhibition of phosphorylation of mTORC1 signaling pathway Particle size: 110 ​nm; PDI: 0.05; zeta: 5 ​mV; Rapamycin EE: 69% ∗ Selective inhibition in vitro (U 87 ​MG cell) of the phosphorylation of mTORC1 signaling pathway [ 109 ] Polymeric nanoparticles PLGA, PVA, P80, rapamycin Optimizing nanoparticles containing the mammalian target of rapamycin (mTOR) inhibitor Particle size: 247 ​nm; PDI: 0.103; zeta: -11.76 ​mV; Rapamycin EE: 28.21% ∗ The in vitro results demonstrated the ability of the coating to enhance the internalization of nanoparticles into glioma cells (C6 lineage). [ 110 ] Albumin nanoparticles LY2157299, celastrol Inhibition of mTORC1 and TGF-β/SMAD2 signaling pathways.…”

“…In the presence of 8Gy, pAkt protein expression is reduced. These results may express resistance to rapamycin due to the multiplicity of signals downstream of mTOR inhibition [ 119 ]. The loading of rapamycin, the first mTOR inhibitor, into nanoparticles improves its bioavailability and aqueous solubility, but its use is still limited by resistance in GBM.…”

“…The loading of rapamycin, the first mTOR inhibitor, into nanoparticles improves its bioavailability and aqueous solubility, but its use is still limited by resistance in GBM. The co-delivery of rapamycin with other drugs in nanosystems is an efficient strategy to solve the problems related to monotherapy and improve its efficacy in the treatment of cancer, including GBM [ 47 , 103 , 119 ].…”

Mesoporous polydopamine nanoparticles for sustained release of rapamycin and reactive oxygen species scavenging to synergistically accelerate neurogenesis after spinal cord injury

“…21 The oral bioavailability of Rapa is less than 15%, which severely hinders its applications. 22 In addition, Rapa undergoes degradation in aqueous solutions and may lose its pharmacological activity. 23 Therefore, it is necessary to design a drug carrier to improve the solubility and pharmacokinetic properties of Rapa.…”